:Ask her, and then do what she says. --[[User:Milkbreath|Milkbreath]] 12:36, 18 October 2007 (UTC)
:Ask her, and then do what she says. --[[User:Milkbreath|Milkbreath]] 12:36, 18 October 2007 (UTC)
::''...and be under control once more.'' Why not skip the seduction and move straight to a ball and chain? Ironically, what some refer to their significant others as. [[User:Lanfear's Bane|Lanfear's Bane]] 12:46, 18 October 2007 (UTC)
::''...and be under control once more.'' Why not skip the seduction and move straight to a ball and chain? Ironically, what some refer to their significant others as. [[User:Lanfear's Bane|Lanfear's Bane]] 12:46, 18 October 2007 (UTC)
:::Wikipedians are ''obviously'' not qualified to give relationship advice...please seek the help of a licensed relationship/marriage counselor. OMG! My eyes rolled too far back!! [[User:38.112.225.84|38.112.225.84]] 14:21, 18 October 2007 (UTC)
== Possible to use CGI instead of night vision? ==
== Possible to use CGI instead of night vision? ==
Hi there! As 90% of the Portuguese students I've ingested considerable amounts of alcohol during my universitary course, specially - at least in my case - in the form of stout beer. So, the question is: What are the consequences of alcohol ingestion to the brain? I know Wikipedia has an article on "effects of alcohol consumption" and also that you cannot offer medical advice, let's skip that, ok? I want to hear your opinion. Will I be able to conclude my MsC thesis? If that matters, I'm partially drunk, despite being able to write in English. Cheers! 84.91.226.18 00:39, 12 October 2007 (UTC)[reply]
A man was horribly maimed in a farming accident, and had to have major reconstructive surgery on both his hands. He went to see his surgeon for the final time. "Doctor," says the man excitedly and dramatically holds up his heavily bandaged hands. "Will I be able to play the violin when these bandages come off?" "I don't see why not," the doctor responds. "Odd," says the man. "I never could before."
The odds are, you will be able to conclude your MsC thesis -- if, and only if, you could do so before the stout beer kicked in. - Nunh-huh 01:04, 12 October 2007 (UTC)[reply]
I would say that you will never get your MSc until you learn to spell MSc properly! —Preceding unsigned comment added by 88.109.232.130 (talk) 01:26, 12 October 2007 (UTC)[reply]
It's OK to spell it MsC when it's from a universitary. Cut him a break, it's a second language and he's drunk. Me, I have no excuse... - Nunh-huh 02:40, 12 October 2007 (UTC)[reply]
Really excessive alcohol consumption will in the long run have negative effects. But if you're still a student I assume you're too young for it to have taken enough effect. It is also a matter of what sort of skills you need for it. Memory is affected more than reasoning. The barkeep of my favourite bar in Eindhoven, where I studied, had a 'live fast die young' attitude. Didn't work. He lived pretty 'fast' (which included being drunk every day for pretty much all his life), but he's still alive, about 60 years old now, I guess. He keeps forgetting things, but his mind is still as sharp as it used to be. That is, he can still reason, but there is less in his head to reason with, so to say. DirkvdM 08:16, 12 October 2007 (UTC)[reply]
Party away! Just remember that alcohol has negative health consequences that trend quite clearly with the quantity and temporal nature of its consumption. When it comes to thesis work, don't forget that libations obviously prevent one from working or studying whilst drunk, but can seriously hinder such activities even a couple of days later, depending on hangover severity and sleep deprivation. Also, booze has a way of sapping one's wallet, which can negatively affect the ability to buy healthy, knowledge-supporting meal ingredients or paying rent on a decent apartment.
On the other end, I believe that socialization is an important part of the education process. Late-night pitchers of stout can facilitate useful discussions, collaborations, and life-long personal and professional relationships that can have positive effects on a career.
It's just a matter of moderation... — Scientizzle 20:40, 12 October 2007 (UTC)[reply]
If you drink somuch you can't pay the rent then you've really got a problem. And healthy food (nothing special, just healthy) is generally cheaper, certainly cheaper than junk food (hamburgers, crisps and the like). DirkvdM 09:52, 13 October 2007 (UTC)[reply]
I think you're missing the bigger problem. How are you supposed to finish you thesis when your too busy drinking to do the research and start the writeup? (And when you're not drinking you're too drunk to get any significant work done) Nil Einne 12:25, 13 October 2007 (UTC)[reply]
Well, no, he asked if his previous alcohol consumption will have had an effect on his abilities. Anyway, he says he can write English even when he's drunk (at least, I think that's the point he was making - then again, if he can't make that sufficiently clear, then maybe he couldn't write a decent thesis, but on the other hand, we can't know if that has anything to do with his alcohol consumption ... all very complicated. :) ). DirkvdM 07:27, 14 October 2007 (UTC)[reply]
Cutting vinyl discs
On the old vinyl discs, was there some advantage or technical limitation that made recording engineers produce discs with minimum (or inadequate) stereo separation? —Preceding unsigned comment added by 88.109.232.130 (talk) 01:02, 12 October 2007 (UTC)[reply]
My understanding was that it was a limitation of the cartridge in the replay head that limited the stereo separation quite sharply. Gramophone_record#Shortcomings seems to agree with me. SteveBaker 04:46, 12 October 2007 (UTC)[reply]
One reason is that the stereo recording format was backward-compatable with the earlier monaural format. The mono fromay moced the needle perpendicular to the surface: the groove varied in depth only. The stereo format moved the needle in two orthogonal dimensions, both 45 degrees to the perpendicular. In any actual physical system, this leads to cross-talk. -Arch dude 19:57, 12 October 2007 (UTC)[reply]
time dilations at high g
do particals in sychrotrons experience time dilations because of the high g forces involved, i.e. have longer than expected half lives? basically i have read of large gravitational bodies bending space time and was wondering if artificial gravity causes similar effects.209.204.181.5 05:52, 12 October 2007 (UTC)[reply]
The particles in synchrotrons experience a lot of time dilation due to their speed, as they are generally accelerated to nearly the speed of light. However I am not sure if acceleration due to other sources than gravity produces the same time dilation effects. Einstein used gravity-acceleration equivalence thought experiments before discovering general relativity which suggests that, yes, you'd expect the same effect, but I can't be sure. Cyta 06:56, 12 October 2007 (UTC)[reply]
The time dilation factor is the Lorentz gamma, which is also the ratio of the particle's rest energy to its speed. E.g. the Tevatron accelerates protons (~1 GeV) to energies of around 1 TeV, so the time dilation factor is about 1000 (not that it matters for protons, which don't decay as far as anyone knows). The acceleration, as such, has nothing to do with it, even in the gravitational case. Time dilation is about the geometry of the worldline. For motion in a circular accelerator, it's analogous to the fact that the wire that goes into a spring of a given length is longer than the length of the spring. For gravitational time dilation, it's analogous to the fact that circular arcs subtending a given angle have different lengths depending on their radii. -- BenRG 11:22, 12 October 2007 (UTC)[reply]
How would the [lub dub] of the human heart be represented musically?
If you had to give a drummer a piece of music to represent a healthy heartbeat, how would you do it? What's the beat, is there a taradiddle?
Damn, a taradiddle would be one big-time arrhythmia. Nothing the heart does is that complicated. So the drummer's going to be bored. For a look at notation, see the opening measures of the Mahler Ninth Symphony. The cellos have the heart-beat. Actually, music notation doesn't really convey the info doctors listen for in auscultation very well...it's better to listen to recordings like this one (the most normal found on this site devoted to auscultation. - Nunh-huh 06:38, 12 October 2007 (UTC)[reply]
Why don't we have an article on taradiddle? Now I don't know why that would be an arrhythmia. Anyway, heartbeat is very important in music. The number of beats per minute is very determining for the mood of music because it emulates the heart rate. A normal heart rate at rest is around 80 b/m, so that should sound relaxed (not sure about the actual value - just know the principle). A faster beat should get you more excited. Maybe if the beat actually sounds like a heartbeat, the effect will be even stronger. Just listen to the beginning of Pink Floyd's Dark side of the Moon. There's a second, softer, beat after every beat. Actually, it's a 3/4 beat (or is that a triplet?), with the 'afterbeat' on the second beat. DirkvdM 08:40, 12 October 2007 (UTC)[reply]
Taradiddle would be a dictionary entry, but paradiddle we have... - Nunh-huh 18:58, 12 October 2007 (UTC)[reply]
Dirk says "The number of beats per minute is very determining for the mood of music" — which is certainly true — "because it emulates the heart rate". To this I say, to put it politely, "citation needed". Most people are not aware of their heart rate most of the time, so why would it affect the experience of listening to music? Do people with bradycardia find music more exciting, and people with tachycardia find it less exciting, than people with normal heart rates? --Anonymous, 02:02 UTC, October 13, 2007.
I wondered about that too when I heard it (sorry, can't remember where). But it is rather striking that really fast dance music has the same beat frequency as a heart of someone excited (about 120 b/m and over). DirkvdM 09:57, 13 October 2007 (UTC)[reply]
Buy the music to Heart of Rock and Roll on Huey Lewis' Sports. Delmlsfan 21:34, 12 October 2007 (UTC)[reply]
Although music is abstract, I have always assumed it's an unconscious mimicking of the music of the human voice - pathetic music mimics sobs; jolly music mimics laughter - that sort of thing. I would say too that although we generally don't hear our heartbeat, we are aware of it in other ways, especially when it's racing - so I side with Dirk on this, Anonymous, though it might be my flaky theorising; I can't provide citations. Thanks, everyone, for your interesting and useful answers. The article on the Mahler Ninth is a fantastic bonus, Nunh. Adambrowne666 03:12, 13 October 2007 (UTC)[reply]
OT: Weird. I must have seen this thread unconsciously earlier in my recent changes, because I just woke up from a nap where I dreamt that I pressed so hard on my carotid artery that my blood backed up in my chest and I could hear my heart trying to clear it. Anchoress 03:53, 13 October 2007 (UTC)[reply]
dot and cross product
why we use cos in dot product and sin in cross product? —Preceding unsigned comment added by 202.69.33.15 (talk) 06:43, 12 October 2007 (UTC)[reply]
and ask on the maths desk for a derivation of the cross product .. if you have a vector C that is at right angles to A and B vectors - you can work out for yourself what this vector will be using the dot products C.A=0 and C.B=0 - if you do the maths you should be able to see where the sin comes from - the cross product is the result of solving these two dot products..eg http://hemsidor.torget.se/users/m/mauritz/math/vect/xprodpro.htm (note in this derivation it only goes as far as getting the orthogonal vector - but doesn't show that the magnitude is ab sin(theta) - if you can get this far you should be able to do that? or ask on the maths desk87.102.87.36 12:54, 12 October 2007 (UTC)[reply]
Sorry I can't be clearer on the cross product but I can't find a link to the derivation - you best bet is to derive the cross product for yourself and then look at what the magnitude of the vector is...87.102.87.36 13:20, 12 October 2007 (UTC)[reply]
thank you mr. SteveBaker and mr. Daniel for your response on the q i asked on 6th. that's true that my application matters a lot.
i asked for some beams/rays/waves that reflect from bones. my application is like i'm trying to make a control system for automobiles in which i want these beams/rays to sense the living object in front of and no other object should bother the control system. for that i need some method that will sense bones only and not metal, plastic or concrete... also at these stage for me the cost and size of the method do not matter eventhough it's a non-stationary application... Neel shah556 10:46, 12 October 2007 (UTC)[reply]
Whatever beams you use will have to pass through flesh to get from your transmitter to the bone and back to a receiver. I, for one, wouldn't want that to happen to me. I'm thinking you could use echolocation to find objects in front of the vehicle and then aim a parabolic microphone at each one to listen for a heartbeat. You could electronically filter the incoming sound quite a bit, and use software to identify the repeating pattern of the heartbeat. Sounds crazy, I know, but there just might be a way to make it work. --Milkbreath 12:37, 12 October 2007 (UTC)[reply]
Also, it would be very difficult to distinguish between bone and cement/concrete, as they are pretty much made out of the same thing.Tuckerekcut 13:39, 12 October 2007 (UTC)[reply]
I very much doubt you could to this - I don't think there is any unique human 'signature' that could distinguish flesh and bone from a lot of other natural and man-made substances. SteveBaker 14:00, 12 October 2007 (UTC)[reply]
Why not measure infrared radiation (heat)? You could at least distinguish between living and non-living in that way without too much difficulty based on the shape and size of the thing in question, and I'm betting that non-living things look quite differently in an infrared spectrum. --24.147.86.187 14:34, 12 October 2007 (UTC)[reply]
The good news for your application is that if human beings can do it, at least it's theoretically possible. I'd go for a combination of systems. A simple camera image will give you some information on whether there's a living being in front of the car (based on shape, movement, etc.) An infrared image should give you a lot of information. And of course any setup with multiple cameras or other wave sensors will give you some spatial (3d) information as well. You can then combine this information into a machine learning algorithm, so that the system can learn to identify living things by itself. I think that just a simple camera could get you a pretty accurate result already. I any case, I think there are plenty of options left before you decide to start throwing x-rays around the place. :)
So you want to avoid pedestrians, but crashing into a brick wall doesn't matter? What you need is something that will give the mass of the object and reflect back. Electromagnetic waves won't work, because they only reflect off of electrically conductive objects. I think sonar might work, but I'm not sure. You could also use some way to recognize objects. That way, you detect objects above a certain size, and see if they look like an object on a list of stuff you can safely hit (like a tumble weed). If you don't recognize it, brake. One thought that just occurred to me is to hit it with a pulse of sound and see how much it moves. The problem is that, unless have an extremely precise way to tell acceleration, it would have to be a very loud sound. — Daniel 01:44, 13 October 2007 (UTC)[reply]
?
I need instruction on how to draw the molecular structure of elements —Preceding unsigned comment added by Cali08P (talk • contribs) 13:14, 12 October 2007 (UTC)[reply]
It depends - some elements have a molecular structure, others are not molecules.. Sulphur exists as a molecule, argon doesn't - could you be more specific.
Yes. It's not generally believed to be a genetic matter. SteveBaker 13:55, 12 October 2007 (UTC)[reply]
Of course, if they're conjoined twins, there may be some logistical problems. GeeJo(t)⁄(c) • 16:24, 12 October 2007 (UTC)[reply]
I understand it's not that simple - there's not a single determining factor. There are advocates for nature or nurture as causes, which, alas, has a lot to do with what people want to be true. When a Dutch researcher found indications for a biological cause, the reactions by homosexuals in the Netherlands and the US were opposite. I can't remember which way around that was, but it surprised me to hear that some homosexuals disliked this finding. I supose they interpreted it like they were 'abnormal' (which, literally, is the case of course, but that doesn't make it a bad thing - I consider myself to be quite abnormal and am proud of it :) ). But if it were nurture, then that would suggest that they're just imagining it. Like they're really heterosexual and somehow they deny their nature. Of course, none of this says anything about what the real causes of homosexuality are. DirkvdM 16:57, 12 October 2007 (UTC)[reply]
In the US it is a very complicated identity-politics issue, primarily because "biological vs. non-biological" has been interpreted to mean "inevitable and unchangeable vs. totally arbitrary and easily changeable choice." This is of course a not very scientifically-informed approach to the nature/nurture dichotomy, but it is the way this issue (and many others relating to sexuality and/or genetics) are handled in terms of US politics. --24.147.86.187 17:11, 12 October 2007 (UTC)[reply]
It is not particularly unusual. One study ([ PMID8494487]) that sampled gay individuals who were also twins found "thirty-eight pairs of monozygotic [identical] twins (34 male pairs and 4 female pairs) were found to have a concordance rate of 65.8% for homosexual orientation. Twenty-three pairs of dizygotic [non-identical] twins were found to have a concordance rate of 30.4% for homosexual orientation." That means 13 of the identical twins had one homosexual, with the other being straight. Their conclusion is that this data supports a genetic influence for homosexuality, but obviously not an absolutely determinant one. This conclusion is generally held up by similar studies. [1]Rockpocket 17:20, 12 October 2007 (UTC)[reply]
Fear suppressing drugs?
Are there any drugs that suppress or numb fear? 64.236.121.129 13:46, 12 October 2007 (UTC)[reply]
Alcohol has traditionally been used to suppress fear. DuncanHill 14:17, 12 October 2007 (UTC)[reply]
True, but they probably want something without major effects other than suppressing fear. PCP will suppress fear too, but that effect is coupled with a number of other effects that make it unsuitable for most purposes. --24.147.86.187 15:27, 12 October 2007 (UTC)[reply]
Every drug has side-effects, or, more precisely, has multiple effects. If you desire one of the effects, then the other effects will be 'side-effects'. The suppression of fear by any drug, including alcohol and PCP, can also be quite undesirable, notably in traffic (such as when you are driving a car or others around you are). DirkvdM 17:06, 12 October 2007 (UTC)[reply]
It would be a useful drug to give to soldiers at the front - I bet there's been some research on it Adambrowne666 04:01, 13 October 2007 (UTC)[reply]
They used to dose them with amphetamines for this purpose, didn't they? --Kurt Shaped Box 08:50, 13 October 2007 (UTC)[reply]
Or shell the enemy with marijuana-bombs, so they'll all turn pacifist. :) I recently heard the US army experimented with something like this. DirkvdM 10:01, 13 October 2007 (UTC)[reply]
I'm not so sure that suppressing fear is a good thing in a battlefield situation. You don't want your men rushing into dangerous situations when they'd be better off staying in cover. It's noticable in video games (where people have very little fear because the consequences of death or injury is minor) - if you watch how players behave in the virtual battlefield, it's totally different to how soldiers behave in the real world - and the casualties are always very much higher. SteveBaker 11:45, 13 October 2007 (UTC)[reply]
Simple solution - dose them with PCP at the same time, so that they don't feel the bullets and also get a neat little aggression boost as part of the package... :) --Kurt Shaped Box 19:50, 13 October 2007 (UTC)[reply]
'They' (i.e. the finest minds of US military science) were trying to invent a gas shell that would instantly turn enemy soldiers gay (and presumably drop their guns and immediately start buggering each other) at one point, weren't 'they'? --Kurt Shaped Box 19:45, 13 October 2007 (UTC)[reply]
Sure! Antidepressants such as SSRIs work to increase the availability of serotonin in the brain which makes you feel confident/horny/manic/aggressive etc. —Preceding unsigned comment added by 88.111.61.118 (talk) 23:44, 13 October 2007 (UTC)[reply]
Graduate degree titles
If you are a nursing graduate student, when can you use the title MSN(c) for Master's in Nursing Candidate? —Preceding unsigned comment added by 71.193.119.109 (talk) 15:48, 12 October 2007 (UTC)[reply]
when you have passed the exam? —Preceding unsigned comment added by 88.109.232.130 (talk) 21:54, 12 October 2007 (UTC)[reply]
beta sheets
what is the distance between every second residue on a beta sheet? —Preceding unsigned comment added by 144.173.6.67 (talk) 15:59, 12 October 2007 (UTC)[reply]
I think what you are looking for is at Beta sheet. --JWSchmidt 16:32, 12 October 2007 (UTC)[reply]
LED flickering question.
A lot of commercial vehicles here, and some cars (continental US) now use LED based taillights and marker lights. When I look at them straight-on, they are (when lit) a steady red or amber color, depending on the light. When I'm rapidly moving my eyes or head, say from one side to the other, and an LED light is thus moving across my field of vision, it will appear to flicker, and I'll see a row of lit dots, not a continuous "smear" of light. Why is this? Do the LED units need to switch on-and-off at some rapid rate? Is it some characteristic of the vehicle electrical system? 71.112.9.77 19:10, 12 October 2007 (UTC)[reply]
I've noticed that too. Just a guess: I think that the LEDs are modulated (Pulse-width_modulation?) by flashing so there can be different brightness levels, so the brake lights can get brighter when the brake is applied. -- Diletante 20:20, 12 October 2007 (UTC)[reply]
Exactly correct, and at least some of the designers have picked too damned low a frequency for the PWM. I hope this gets regulated soon.
Neither of the explanations seen here makes sense to me. Taillights may operate at different brightness levels, but marker lights don't, so why wouldn't they be at full "on" all the time? And multiplexed displays are used when the elements need to be individually switchable, which doesn't apply to these kinds of lights either.
The IC that regulates the current flow to the LEDs is still a pulse width modulator, whether we're talking about the tail lights or the marker lights. It's gotten to the point where its cheaper and far more energy-efficient to use an active circuit than a power-consuming resistor. After all, these LEDs used as auto lamps are operating on a substantial amount of current, not the 5-20 mA thta's used for "indicator" LEDs.
If we were talking about LED traffic lights I'd guess that they were strobing at twice the power line frequency, the way fluorescents do, but that doesn't make sense for vehicle lights that would run on DC.
Does anyone have an actual reference on this? --Anonymous, 06:57 UTC, October 13, 2007.
I know this has been asked before with a good answer given, but I can't find it in the archives. 68.231.151.161 01:36, 14 October 2007 (UTC)[reply]
Here is a description of the electronics involved in automotive LED lighting. It seems they regulate the current to the LEDs by switching a MOSFET, so they all strobe all the time. You can't power LEDs right from the battery, even with analog regulation, for several reasons, one of which is the transients you get when stuff switches on or off in the rest of the electrical system. They use a DC-DC converter driver to power the LEDs. --Milkbreath 02:00, 14 October 2007 (UTC)[reply]
Thanks! --Anon, 04:25 UTC, October 14, 2007.
LED brakelights turn on quicker than incandescent bulbs, allowing a following driver to apply his brakes quicker and avoid rear-ending the braking car. That is great. But present LED lights on cars are typically flashed on and off at high speed, above the critical flicker limit, to appear continuously on when you look right at them, but resulting in the scattered afterimages if there are eyemovements (as there normally are), which, like the questioner, I find distracting and annoying. An array of LEDs in a brakelight array could very easily be set up to operate on the 12 volts (or other voltage) supplied from the battery, without the rapid flashing on and off which results in the scattered afterimages. Of course you can power a series connection of LEDs directly from the battery!
If the forward biased voltage drop for one LED is 2 volts, then connect 6 of them in series across the battery! Two or more such series arrays would allow the light to contimue operating if one series array failed. Suitable adjustments could be made for other forward biased voltage drops or supply voltages. No need to annoy everyone else on the road by flashing them 30 (or however many) times per second. (edited to add) The ref supplied by Milkbreath discusses the challenges which may have led to the strobing and afterimage problem. The designers worry about an idiot jumpstarting your car's 12 volt system with a 24 or even 36 volt battery, perhaps with reverse polarity. Crowbar circuits with a fuse could stop that sort of moronic insult to the car's electrical system. Then the designers legitimately worry about keeping constant brightness with varying battery voltage, so that your taillights and other exterior safety lights stay on even when you crank the engine for a prolonged period and the battery voltage gets down to 7 volts. You don't want someone running into your car at night. They also legitimately worry about the transient energy which might get dumped through the LEDs when the battery (a fine voltage clamp itself) is isolated from the electrical system by the ignition being shut off or a fuse blowing. This dictates DC-DC conversion incorporating protective circuitry, but note that said convertor puts out DC. The problem is they apparently found it useful to turn the DC on and off rapidly 30 or 60 times per second or sime such, I would guess. The article cited does not even mention this frequency. Looks fine in the showroom, I guess. No afterimage problem there like there is on the highway at night. If the headlights of cars also switch to ultrabright LEDs and the designers similarly use circuits which switch them on and off rapidly, the multiple afterimage problem will get even worse and more distracting. I have used solid state DC-DC convertors for decades which produce a very steady DC output, even though internally the current is switched rapidly to allow voltage multipliers etc. Edison 02:15, 14 October 2007 (UTC)[reply]
Efficiency might be an important factor. A failure mode of LED chips is overheating. Thus you have to keep the power dissipated below a certain level. At the same time, you want the LEDs to be as bright as possible for a given current.
To use an example, if you have a constant current of 10 ma going through an LED, you will dissipate a certain power. If, instead, you pulse it at 100ma at a 10% duty cycle, you’ll dissipate the same power, to a first approximation. However, the pulses will be a lot brighter.
It so happens that the human eye is a good peak detector. So the pulsed LEDs will appear a lot brighter, while not dissipating any more power. Bunthorne 03:47, 15 October 2007 (UTC)[reply]
I disagree with the claim that the human eye responds to the peak brightness. Bloch's Law says itt integrates pulses that occur at a frequency higher than the critical flicker frequency. Designers of LED lights [2] claim to utilize the Broca-Sulzer effect that for certain durations, flashing the LED on and off may produce an enhanced brightness impression, but apparently the frequency has to be relatively low, producing the cluster of afterimages, and annoying people who notice it. There is no inherent reason that the LED signal lights on cars could not be used in a continuous rather than flashing mode, by giving up this gimmick. Automakers couls spend a few more bucks and produce a more pleasing light. Edison 16:02, 16 October 2007 (UTC)[reply]
I'm not even sure it's a question of price. The LED controller ICs often use an inductor and generally, the higher the frequency, the smaller the inductor. I think it may be as simple as "the problem wasn't apparent when we tested the taillights in the lab". That's why I hope this will be regulated soon.
When Hydrogen Peroxide is doing its thing (oxidising something), is ozone ever a by-product? Anchoress 20:14, 12 October 2007 (UTC)[reply]
Not usually. Ozone is a more oxidized form of oxygen than peroxide is and is less stable. DMacks 21:18, 12 October 2007 (UTC)[reply]
This explores the idea that hydrogen peroxide might be generated from ozone. This article says, "H2O2 catalyzes the decomposition of O3 via the peroxone process". --JWSchmidt 21:19, 12 October 2007 (UTC)[reply]
Ever is a pretty strong word. It is unlikely to do so as shown by the oxidation potential chart in the H2O2 article. See where ozone is more positive than hydrogen peroxide? That means that going from ozone to H2O2 is a favorable reaction and going the other way is unfavorable. But I wouldn't say never. Delmlsfan 21:21, 12 October 2007 (UTC)[reply]
Thanks all for the info and the links!! Anchoress 23:02, 12 October 2007 (UTC)[reply]
It is a low shrub, found in the U.S. mid-Atlantic states. In the spring it has little purple flowers with yellow centers. In the summer the flowers are joined by green berries which ripen to orange and then bright red. Here it is in the autumn, when the flowers are gone.
That looks to me like an ornamental pepper plant. So, I don't think they are berries. If you search for ornamental pepper plant, you'll see many plants that look similar. -- kainaw™ 02:50, 13 October 2007 (UTC)[reply]
I thought it was a pepper of some kind when I saw the picture. The shape of the fruit and the three colors are suggestive. I don't think it's a native plant where I live (southern New Jersey); I think I'd have seen it. I googled on lots of stuff like "capiscum" and "wild pepper" and came up with zilch. --Milkbreath 03:05, 13 October 2007 (UTC)[reply]
After reading the goji article, I'm pretty sure that's what it is. BTW goji is a member of the nightshade family, which also contains peppers. Anchoress 05:10, 13 October 2007 (UTC)[reply]
I think Cacycle wins this one. Thank you very much! I have been wondering about this plant for years. -- Dominus 03:41, 14 October 2007 (UTC)[reply]
Is it abstract or not?
ok, someone last week tried to tell me that physics and chemistry were abstract. To me that doesnt make any sense because something that is abstract is the opposite of "concrete" and i have always been told that science is very concrete?
so could you consider physics and chemistry to be abstract?
(sense this might be more of an opinion than a definite answer, input from man people would be appreciated)
!NOTE! he was calling it abstract because you cant see it (I.E. you cant see atoms) but to me just because something isn't visible to the naked eye doesn't mean its abstract
also how can you consider a theory to be science/ i thought science was suppose to be based on fact not speculation?
—Preceding unsigned comment added by 71.98.105.119 (talk) 23:19, 12 October 2007 (UTC)[reply]
It's somewhat meaningless to apply abstract/concrete to an entire field of science. Both chemistry and physics can predict and explain very detailed phenomena, which would make them "concrete." However, they can also produce broad predictions about a wide range of phenomena, which would be somewhat abstract. Someguy1221 00:02, 13 October 2007 (UTC)[reply]
It would have probably been more clear to try and press whomever told you this exactly what they meant by the description at the time. "Abstract" has many meanings. Maybe they just meant they dealt with "abstractions"—rough representations—which most thoughtful practitioners would agree with. Perhaps he meant something else. Who knows? Science deals with representations, in any case. The goal is to make these representations match as closely as possible to how things "actually are," but that has always been tough and the ultimate ability for humans to do that has often been questioned. --24.147.86.187 01:08, 13 October 2007 (UTC)[reply]
Science goes from the specific to the general and then back again. It takes many examples (through observation, preferably by experimentation) to create an abstract image of reality, which it can then apply back to specific instances to predict what will happen. So it uses abstraction to describe the specific. DirkvdM 10:05, 13 October 2007 (UTC)[reply]
I didn't read the comment but perhaps what was meant was that in many way, theoretical physics and theoretical chemistry nowadays tends to seem very abstract. Stuff like subparticles may be important, but it can be fairly hard for the average person to see the importance or relevance in real life. While this applies to all areas of science to some extent, I think it's easier for the average person to see the relevance and perhaps even important of even the more theoretical aspects of biology Nil Einne 12:15, 13 October 2007 (UTC)[reply]
Physics and chemistry can be real OR abstract - theoretical models are abstract, doing reactions is real.
In a addition the scientific models used (eg atomic theory etc) can be considered abstractions - so the answer is yes and no.83.100.254.51 14:57, 13 October 2007 (UTC)[reply]
I said that. :) DirkvdM 07:48, 14 October 2007 (UTC)[reply]
Calling something concrete and abstract is often a matter of how familiar you are with that kind of thing. As an example, I remember very well when, on one of the first functional analysis classes, our professor said "Let's take a concrete example: let x be a self-adjoint operator". At that point, we laughed hard, because we didn't think something starting like that could be concrete enough. We were familiar with expressions containing variables which represent complex numbers and simple functions and things like that, so we could think of an expression with such variable as concrete (even if it might look as an abstract expression to someone else). However, we didn't have a grasp of functional analysis at that time so we couldn't imagine an operator as a concrete thing. On the other hand, a did a matured physician who works with such operators every day have heard this, he wouldn't even have winked, for he can accept such things as concrete. – b_jonas 21:26, 16 October 2007 (UTC)[reply]
October 13
Robotic Arms
Has anyone come up with a way to make robotic tentacles? That is, long, everywhere-articluated arms like an octopus or snake? Black Carrot 01:56, 13 October 2007 (UTC)[reply]
I knew I'd forgotten something. I did check Wikipedia itself for it (and ran into some serious stubs). Thanks. 76.185.123.122 03:04, 13 October 2007 (UTC)[reply]
Make that an image-search and you get some intriguing ideas of what one could do with such tentacles. DirkvdM 10:11, 13 October 2007 (UTC)[reply]
On Saturday (in fact, on the very day this question was posed - how curious!) I was at a convention where they had a "satellite link-up" with Stan Lee, and one of the people lined up to ask him a question actually offered to make him a set of Dr Octopus arms. Confusing Manifestation 22:35, 14 October 2007 (UTC)[reply]
Runaway Global Warming
What evidence is there for and against runaway global warming? Don't talk about related, but different, stuff such as the existence of global warming and the effects of humanity on it. Please state weather the evidence is about existentially dangerous or merely catastrophic runaway global warming, or both. Site sources if possible. — Daniel 03:12, 13 October 2007 (UTC)[reply]
We shall have proof of Runaway Global Warming after the fact and never before. 211.28.129.8 09:47, 13 October 2007 (UTC)[reply]
He asked for evidence, not proof. Alas, this sort of thing was not included in the IPCC report because of the low probability (or even inability to calculate a probability). Which is stupid, of course, because risk is a function of probability and seriousness. You're asking about both (good on you). I don't know about the probability, but I can give some considerations concerning the existential risk (the chances that mankind will become extinct, I understand). Such events have taken place many times in Earth's history, and the consequences have indeed been catastrophic. Even to the point that almost all life on Earth died. But with rapid change, it's the least adaptable species that die out. It just happens that mankind's strongest point is adaptability. I think no other (land) species is as widely spread across the globe, so we've already got experience with all sorts of climates. And if we encounter a climate that we're not familiar with, we'll learn. We do that like no other species. Basically, species adapt through evolution, so they need many generations. We can do the same thing within one generation. So mankind will almost certainly not die out. Maybe some 90% will die, but even then there will be 500 million left (more than is normal for a species our size, which is the cause of the problem, but that's a different issue, which you didn't want to hear about :) ). And it won't be any fun for the survivors, but their will to survive will ensure mankind will not die out. DirkvdM 10:31, 13 October 2007 (UTC)[reply]
The effects that might cause "runaway" global warming are the ones that have an element of positive feedback to them, there are three that I can immediately think of:
Increasing global temperatures cause the ice caps and glaciers to melt. Shrinking polar/glacial ice reduces the area of the earth's surface that is white and increases the area that is dark. This in turn reduces the earth's albedo - which causes more absorption of sunlight - and more global warming - and more ice melting. This effect could potentially runaway until there is no more surface ice year-round.
In a similar vein...as the climate warms up, the oceans get warmer. As water warms up, it expands (except at temperatures very close to freezing) - and that causes a rise in sea levels. This inundates some lighter coloured land areas with darker coloured sea water - which also causes the earths albedo to drop - increasing the absorption of sunlight and adding to global temperatures - causing the sea levels to rise still further.
In deep parts of the ocean, there are large deposits of frozen methane. If the ocean temperatures rise too high, these will start to melt. The resulting methane gas will bubble to the surface. Unfortunately, methane is an even more virulent greenhouse gas than CO2 - so releasing more methane traps more sunlight which raises temperatures and in turn releases more methane.
You can argue about other effects such as the disruption of certain ocean currents - but these are more about affecting the weather in certain regions than they are about global warming - they aren't any less devastating - but they aren't likely to make global temperatures change much UNLESS they cause warm water to be carried to places where more ice or methane can melt.
The nasty thing about effects with positive feedback is that even if mankind mended it's ways overnight, if we've inadvertently triggered one of these feedback loops, we may not be able to prevent ultimate catastrophy (although we ought to be able to slow it down). The tricky part is to know at what global temperature each effect will kick in. The fact that the northern polar cap and the glaciers are all melting MUCH faster than we had formerly predicted means that we've almost certainly triggered that problem in the Northern hemisphere. Fortunately, the majority of the ice is at the South pole which doesn't seem to be in a runaway situation yet.
Follow up question: I never heard about methane clathrate back in the dark ages when I was in school. Is it technically correct to talk in terms of natural sources of "frozen methane" on Earth? Methane says the melting point is -296.5 °F. --JWSchmidt 15:27, 13 October 2007 (UTC)[reply]
The stuff was only discovered 'in the wild' fairly recently. Technically, it's not "frozen methane" it's methane dissolved in water ice. However, when the water melts and turns back into liquid water it releases the methane as bubbles - so the effect is the same. This is fairly exotic stuff and it generally only forms at great depths - which explains why we only recently discovered these deposits. Our article suggests that there is a heck of a lot of this stuff out there - and it could even (theoretically) be mined as a source of fossil fuels (except that we're trying to use LESS fossil fuels - not more!) —Preceding unsigned comment added by SteveBaker (talk • contribs) 17:26, 13 October 2007 (UTC)[reply]
Steve, the southern polar cap is also shrinking in size - that is, at the sides, where the ice is on water, so there is the same feedback effect. This is in a way compensated by the fact that the ice gets thicker in the central parts, due to heavier snowfall, so the total amount of ice remains more or less the same. But that's not what counts here. In this case, surface size matters.
Concerning the slowing down of the first two effects (both albedo related), I suggested in a previous thread that we could scatter some reflective stuff like polystyrene on the oceans to replace the ice. That would reflect the light. An alternative would be to capture it with solar panels. These would not only prevent the seas from warming up, but would also provide us with energy, for which we would then not need to burn fossil fuels, so that would give a double positive effect. For the first effect, the panels would not need to be very efficient, so we can use the technology we have now. This would give a big boost to the solar panel industry, which would then have more of the money they lack so much now to develop more efficient and cheap solar panels. A very postiive feedback indeed, I dare say. :)
The third cause, the sudden release of methane, could be truly catastrophic. Methane is a greenhouse gas that is 62 times stronger than CO2, but it has a shorter lifetime. I don't know what the most important of these two factors would be, but it is theorised to be have been a factor in the Permian-Triassic extinction event, which killed off almost all life on Earth. If this release were to take place in our lifetime, then it would not be mainly a problem for later generations. A sudden rise in temperature by several degrees (global average!) would likely cause massive crop failures the world over. Which of course would lead to war the world over. Not WWIII, because alliances will likely break down, but smaller continuous wars all over the world (a worldwide Darfur, so to say), which would probably be a whole lot worse. DirkvdM 08:14, 14 October 2007 (UTC)[reply]
The short lifetime of methane in the upper atmosphere is only partially comforting. When it breaks down you get CO2 and water vapour. Water vapour (at those altitudes) is another gas that's a stronger greenhouse gas than CO2. The amount of these methane clathrate deposits is estimated to be equal to the total amounts of underground natural gas deposits - so even after the stuff decomposes, it would be like putting 500 years worth of CO2 from fossil fuel usage into the upper atmosphere. SteveBaker 15:35, 14 October 2007 (UTC)[reply]
There are many positive and negative feedback loops. Theoretically, you could use them to construct an accurate model, but I very much doubt we know enough to make a very complete one, and thus any we make will probably only be accurate for a short time after it is made, if at all. By studying the Earth's history, it may be possible to find evidence for catastrophic runaway global warming. Specifically, how often have circumstances similar to what we are currently in led to it. Has anyone done so? Whether we can use our own planet as evidence against existentially risky runaway global warming is closely related to the Sleeping Beauty problem. Personally, I think we can. If so, a similar study to the one I mentioned for catastrophic runaway global warming can be done for it. Again, has anyone done so?
By the way, DirkvdM, solar panels absorb much of the light that hits them as heat. This could be helped by making a coating that reflects light too low of a wavelength for the panels to use. AFAIK the painting the roof of houses in warm climates white saves more energy than solar panels make, and reflects more light into the atmosphere. — Daniel 21:49, 14 October 2007 (UTC)[reply]
Interesting idea. But how much ground do human settlements cover? Looking at the Netherlands on Google maps I'd say less than 10%. And the Netherlands is one of the most densely populated countries on Earth. If you zoom in about 2/3 of the way at a random location in the US, you need to search around quite a bit until you find any buildings. And even in densely populated India the buildings cover just a few percent of the ground. The total land surface on Earth is about 150 million km2. So let's assume we're talking about 1 million km2, where maybe 30% extra is reflected. Polar ice cap says "The area covered by sea ice ranges between 9 and 12 million km²". And the albedo difference between ice and water is more like 90%. So painting all (!) houses all over the planet white (yes, that includes your house plus all other buildings in your city) will have a compensating effect of just 1/30 of the melting of all sea ice, which is likely to happen much sooner than this paint job, given the slowness of politics (voters, really). Of course two more factors are that polar caps receive less sunlight and that roof tops cover less than half of a city's surface, which probably balance out against each other.
But any bit helps. There is no single all-encompassing solution, so we have to implement anything that might help. And this seems a very simple and cheap thing to do. So I'm all for it.
In what other ways can we change the albedo? Asphalt has an albedo of almost zero, and streets cover about as much ground as buildings in cities, so those could also be painted white. In cities they're not always in the sun, but in the tropics, the ones that run east-west are. But there are also the streets outside the cities. How much ground do they cover (literally)?
Btw, at first I thought you meant that if you cool a building with paint you need less airco. That'd largely be the southern US then because in most tropical countries most people can't afford airco, although shopping centres in most tropical countries do often have it. I think it would make more of a difference if they didn't turn it up so ridiculously high. What's the radiative forcing effect of cooling a 100,000 m2 building down 5C, compared to the extra energy reflected by the same building if it got a fresh paint job? DirkvdM 07:59, 15 October 2007 (UTC)[reply]
That wasn't supposed to be a way to stop global warming. I'm more saying solar panels wouldn't do a very good job. 67.182.172.17 23:28, 16 October 2007 (UTC)[reply]
Where? Did you forget to log in? DirkvdM 06:09, 18 October 2007 (UTC)[reply]
Human birth defects???
Any and all text related to the subject of human birth defects.
1 Abnormalities related to but not limited to the following, herniated diaphram, herniated stomach.
2 Formentioned organ and conective tissue missplaced within torso cavity resulting in underdeveloped lung or heart tissue.
All other information on human birth defects welcome.
—Preceding unsigned comment added by Terrynisely (talk • contribs) 04:15, 13 October 2007 (UTC)[reply]
Other things then what's been mentioned, e.g. Polydactyly. There are so many possibilities I'm not sure if you'd really want to study them all. It depends also on your definition of a Congenital disorder. For example I noticed Huntington's disease in one of the lists. While I'm not disagreeing, as far as I'm aware it's very rare or never that symptoms are present at birth even if the disorder is. Therefore should we also include any inherited genetic disorder (which would be present at birth)? But of course even this isn't a clear cut issue since there is no boundary between 'normal' and 'disorder'. Nil Einne 11:53, 13 October 2007 (UTC)[reply]
fixed point calculation by utilisation of non stressed axial expansion joints
i would like to know how the force is calculated on the anchor points in a vertical chill water risers used in high rise buildings. all the steps in detail. these risers have expansion joints to take on the expansion and how to calculate on to where these joints can be installed on the pipe. how much should the distance be between the expansion joint and the fixed anchow point at the top and bottom fixed points. —Preceding unsigned comment added by Mohdbilal123 (talk • contribs) 13:17, 13 October 2007 (UTC)[reply]
Well, from first principles, I guess you need to consider the hottest and coldest temperatures of the water in the pipe - look up the thermal expansion coefficient of whatever the pipe is made of - and from that calculate the total amount of expansion that has to be allowed for - then (adding a safety factor) divide that by the number of pipe segments you have. However, I would assume there were standards set for such things - and if such standards exist, those are what you should follow. SteveBaker 13:26, 13 October 2007 (UTC)[reply]
I'd guess that since there are expansion joints - you would want no force on the anchor points (common sense) - therefor you want to know how much expansion the expansion joints need - to get this you need the length between anchors, the thermal expansitivity of the pipe, and the expected temperature range. For safety include extra expansion in the expansion joints for extreme conditions etc.
You can work this out in reverse as well - for a expansion joint that can expand x - calculate how much pipe it can allow to expand under given temperature ranges - so for a total pipe length you can work out how many expansion joints you need.. (Was this relevent?)83.100.254.51 13:33, 13 October 2007 (UTC)[reply]
Oh great, another genius. And how many of those do we have here? *rolls eyes* But anyway, have you tried combining the two terms into one google search? NASCAR Fan24(radio me!) 22:21, 14 October 2007 (UTC)[reply]
In theory, how high could the metabolic rate in humans be raised as a percentage of the average human metabolic rate?
My interest in this comes from an article I read about the powers of characters in the TV show Heroes. One character has rapid spontaneous regeneration ability and the article I read said that she would need an incrediably high metabolism to achive this. I'm aware that the ability to heal this quickly would be physically impossible (it would require constant eating and cardiovascular exercise, leading to indigestion) but I'm curious about how fast human metabolism could be raised.
One problem with any significant amount of increase would be that metabolism produces heat. Increasing heat production would push up your body temperature - and taken to superhero extremes that would not be a healthy thing. This probably explains the skimpy costumes that those guys wear! :-) (Although, not in Heroes).
Oxygen is a rate limiting factor for human energy throughput. There are some numbers at VO2 max suggesting that it is rare for the best athletes to be able to sustain more than 3 times the oxygen uptake of the average person. I guess "in theory" might include genetically engineered humans. According to this dogs can do 3 times better than the best humans, so it might be possible to modify humans genetically and increase the maximum aerobic capacity. --JWSchmidt 15:14, 13 October 2007 (UTC)[reply]
And to back up my earlier point, dogs have a significantly higher body temperature than humans. There is also (across all mammals) a strong correlation between lifespan and body temperature - so increasing your metabolic rate will also (on the average) result in you dying sooner. SteveBaker 17:15, 13 October 2007 (UTC)[reply]
I've been thinking about healing and cell division and even noticed that Wikipedia has "healing factor". I've never seen Heroes, but I've had a chance to consult with my kids and they claim that on that show a character was shown regenerating a toe in a few seconds. For a relatively small amount of tissue repair/regeneration such as this, I do not think that "metabolic rate" is really the issue. There are limits on how quickly individual cells can reproduce and organize themselves. To get around these physical limitations, I think rapid regeneration would require special stores of cells and some kind of special cell migration process. After injury, pre-formed bone, muscle and other cell types would have to be quickly released from storage sites and transported (in the blood?) to the wound where they would have to efficiently assemble into tissues. There is no known mechanism for such assembly of differentiated cells into complex organs and limbs. As described at regeneration, animals that can regenerate structures form stem cell masses that must slowly differentiate and organize into new tissues using the kinds of cell-cell interactions used during normal embryogenesis. So I think you would have to say that some kind of shapeshifting is required, maybe involving some kind of nanorobotics (functional and structural components that are not conventional cells). I'm not an engineer, but it seems to me that if you can imagine some type of sophisticated self-organizing nanobots that can quickly shape themselves into a toe, then I do not see why we would have to assume that such self-assembly would require large amounts of energy....someone with the ability to design such nanobots would probably be able to make their assembly efficient. If you get into needing to rapidly produce (from conventional organic molecular building blocks?) a large mass of such nanobots in a short period of time using conventional metabolic energy sources, then in addition to energy concerns for synthesizing the nanobots, you might have a problem related to limitations on the rate at which storage molecules like glycogen and protein can be broken down and their molecular components released from cells. I end up thinking that it is unrealistic to imagine that "metabolic rate" is the only limiting factor. --JWSchmidt 18:39, 13 October 2007 (UTC)[reply]
I can't quantify how much metabolic rates could be increased as I'm not an expert in biochemistry. What I do know from my limited knowledge in biochemistry is that many (if not most) enzymes that we have operate close to the maximum rate that nature allows. A way to increase the rate in metabolism is to have all metabolic enzymes run at their most optimal rate.
Another way to raise metabolic rates is to have more efficient pathways. Metabolic pathways are very complex; for a particular biological function, some organisms have more efficient pathways in completing that function. (For example, instead of requiring two steps and enzymes to synthesize a product, only one is needed. There are many sorts of evidence of this in nature. Evolutionary mechanisms have forced certain species to develop better pathways.)
And as the questioner mentioned, quick regeneration is impossible without constant eating. With the two things I mentioned about increasing metabolic rates, none of them would matter if there is no increased intake of molecules that contain consumable energy.128.163.113.152 17:50, 16 October 2007 (UTC)[reply]
What is the chemical composition of a typical computer?
Hey. I understand that my question might look pretty weird, but what I want to know is what elements a typical computer would be made out of- specifically, would it contain a majority of organic compounds, or inorganic ones? Any help would be appreciated. Thanks in advance! 68.54.42.126
First, make sure you know the difference between element and compound. Here is a guess at the most common elements a computer is made of: carbon, oxygen, hydrogen, chlorine, aluminum, iron, copper, silicon.
Plenty of other trace ones after these.
Because of the housing, circuit board, and wire insulation, I bet organic compounds would be most prevalent Delmlsfan 17:21, 13 October 2007 (UTC)[reply]
Iron (steel) for the case and transformer, a lesser but similar amount of copper for the wires.
There's some silicon in the chips but also in the glass fibre in the printed circuit board.
Very Small amounts of other elements in the chips eg germanium etc (tiny).
Relatively small amounts of other metals - gold/silver/tantalum etc in wires/contacts/capacitors
The remainder will be 'plastic' - almost certainly hydrocarbons eg polystyrene, ABS, polypropylene etc - a quite large perentage of the mass of the plastic will be filler - this can be chalk, gypsum, silica, feldspar, titania (any inert mineral) or even carbon fibres or other exotic materials.83.100.254.51 17:20, 13 October 2007 (UTC)[reply]
If PVC is used in plastic shielding of cables this means that chlorine will also be present, anything made of teflon (not unknown in cableing and insulation) would introduce fluorine
And the heat sinks are likely to be made of aluminium
Any paint will be carbon based - though the pigment might contain other elements
By mass I'd expect iron to be the major component - next copper, then carbon as plastics, then silicon and oxygen (not sure which is most) plus a similar amount of aluminium if you have large heat sinks (may also be present in filler), followed by hydrogen (in the plastic) and then all the trace elements (gold, boron etc)83.100.254.51 17:27, 13 October 2007 (UTC)[reply]
According to a number of computer recycling websites, there are about 5 pounds of heavy metals like cadmium, arsenic, and mercury in the computer motherboard and CRT monitor. --24.147.86.187 17:28, 13 October 2007 (UTC)[reply]
That sounds wrong - were would these elements be found?83.100.254.51 18:23, 13 October 2007 (UTC)[reply]
If you're including the CRT then you have a lot of glass (Silicon, Oxygen) and Phosphorous in the face-plate - plus a bunch more copper, etc from the circuitry and plastic in the case. I'm not qualified to guess what an LCD panel includes - certainly more plastics, copper and glass - but what is the liquid crystal made from? A plasma display presumably has some of the novel gasses in it...dunno, my knowledge just ran out! SteveBaker 17:37, 13 October 2007 (UTC)[reply]
Forgot to mention all that lead and tin in the solder - quite a lot of this...83.100.254.51 18:28, 13 October 2007 (UTC)[reply]
Plus a disk drive or cd rom (as well as hard disk) will most likely have a cast metal base - these are made out of aluminium/zinc/(possibly magnesium) alloys.83.100.254.51 18:43, 13 October 2007 (UTC)[reply]
Wow, there are quite a few responses! Thanks for the help! 68.54.42.126 —Preceding signed but undated comment was added at 20:07, 13 October 2007 (UTC)[reply]
All those elements just to download porn. Delmlsfan 21:59, 13 October 2007 (UTC)[reply]
For older (pre 2005) computers, there is a fair amount of lead in the solder. Newer computers comply with ROHS and do not have lead in the solder. Quite a bit of tin either way. For CRTs, there is a fair amount of lead in the glass. -Arch dude 00:27, 14 October 2007 (UTC)[reply]
That's an EU law, not a worldwide one, however. Rmhermen 13:44, 15 October 2007 (UTC)[reply]
True, but since the computer market is a worldwide one, it's usually cheaper to make computer parts RoHS-compliant than it is to make different products for the EU and the rest of the world. --Carnildo 21:39, 15 October 2007 (UTC)[reply]
infrared
What is the reason that (absorption of?) wavelengths surrounding 3μm causes the temperature of atoms and molecules to rise? In particular, can you tell me if it is due to a correspondence between wavelength and the dimensions of an atom or molecule? Clem 16:50, 13 October 2007 (UTC)[reply]
Absorption of light of any wavelength causes the temperature to rise - it's just energy. Perhaps your question should be "Why do materials absorb more light in the 10,000nm band than elsewhere in the electromagnetic spectrum?" (I'm not sure that's true either - but it's a better question!) SteveBaker 17:03, 13 October 2007 (UTC)[reply]
Infrared spectroscopy may be of some use here, though it is of some middling quality. Essentially, molecules (not atoms!) have specific vibrational and rotational frequencies, some of which just happen to match the IR band. These "resonant frequencies" explain why the molecules absorb EM radiation of those particular wavelengths. As the energy of the molecules is increased by doing this, the average energy of the system (temperature) increases. Note though that there are many vibrational frequencies outside of the IR range (which is why UV-vis spectroscopy works). GeeJo(t)⁄(c) • 17:11, 13 October 2007 (UTC)[reply]
Is there a graph of resonant frequencies showing various molecules which might reveal how they are grouped or more closely distributed around 10,000nm? And for that matter a graph showing temperature rise on a black body surface for different wavelengths of radiation at the same intensity? Clem 21:25, 13 October 2007 (UTC)[reply]
For the first question, I'm not sure anyone's really looked that deeply into absorptions around that region for the simple reason that everything in the lab is going to be emitting radiation in that band, making it impossible to get any decent resolution. For the second question, a black body absorbs all radiation by definition, so it'd be a fairly dull graph, with E=hv determining the change in energy contribution from the various wavelengths. GeeJo(t)⁄(c) • 22:41, 13 October 2007 (UTC)[reply]
In general any absorbsion of any light wavelength will cause an increase in temperature - the more light - the more the temp rises - 10,000nm isn't particularily special here. —Preceding unsigned comment added by 83.100.254.51 (talk) 17:13, 13 October 2007 (UTC)[reply]
That contradicts visible light having a higher energy level than IR yet not producing the same rise in temperature as IR of the same intensity. Clem 21:28, 13 October 2007 (UTC)[reply]
You seem to be under the misapprehension that IR wavelengths are somehow "more heating" than those of visible light. If you pointed lasers with beams in the visible and IR bands at a black body, I guarantee you that the visible will heat it more quickly. GeeJo(t)⁄(c) • 22:55, 13 October 2007 (UTC)[reply]
ee assay
Does anyone know what an ee assay is? It is simply any assay used to determine the mixture of enantiomers, or is it something more subtle or completely different?
Thank you very much! I don't know how I missed that when I searched. Cheers! Aaadddaaammm 22:22, 14 October 2007 (UTC)[reply]
becoming an alcoholic without alcohol.
How might someone become an alcoholic, if you don't include alcohol or anything that breaks down or combines etc into alcohol. Can you substitute alcohol with something else (non-alcohol) and cause someone to become alcoholic over extended, high-volume ingestion? (This is just one example, another source of alcoholism, such as a pill that affects neural structure or something jsut taken once, would also fit my request). Thank you! —Preceding unsigned comment added by 81.182.100.153 (talk) 22:21, 13 October 2007 (UTC)[reply]
Some research on alcoholism has suggested that there could be specific neurotransmitters involved in alcohol addiction. For example, endorphin activity might be enhanced by ethanol, allowing a receptor antagonist such as naltrexone to possibly inhibit addiction to alcohol (See). Hypothetically, there might be some drug that could be chronically administered which would cause a person to become addicted to that drug and would at the same time predispose the person to alcohol addiction. If you are creating a plot element for a science fiction story, it might be more trendy to invent a polynucleotide analog or a viral vector that would genetically predispose someone to alcoholism. See also: Wikipediholic. --JWSchmidt 15:40, 14 October 2007 (UTC)[reply]
Some people lack the genes to make enzymes needed to break down alcohol. This makes them predisposed to NOT be alcoholics, I suppose. This is documented in Alcohol flush reaction. Personally, I don't believe that alcoholism is a strictly phisiological condition, though. I'm not sure if what you're asking is possible. --Mdwyer 15:54, 14 October 2007 (UTC)[reply]
You'd have to convince them that whatever they're drinking is alcoholic. If they know it isn't, they'll have no way of knowing alcohol will satisfy their craving, and thus they couldn't be considered alcoholic. — Daniel 21:53, 14 October 2007 (UTC)[reply]
Any good spectroscopy textbook will carry table upon table of the things. The only one I can find on Wikipedia itself is for a few organic bonds in the near-IR range at Infrared spectroscopy correlation table. GeeJo(t)⁄(c) • 23:04, 13 October 2007 (UTC)[reply]
There are more detailed versions of the graph you mention out there - were you thinking of organic molecules specifically or anything? - a search for "IR absorbtion bands table" or "ir functional group" turns up thousands (try image search)
There probably are millions - if you need more help please ask.87.102.19.106 04:39, 14 October 2007 (UTC)[reply]
Yes, this seems to be what I'm looking for, one question though, are absorption frequency and resonant frequency the same or do they refer to different phenomenon, and if not, are there graphs for resonant frequency? Clem 14:01, 14 October 2007 (UTC)[reply]
Yes - in terms of IR the absorbtions cause physical vibrations of the molecules at the resonance frequency of the bond - so the absorbance frequency is the same as the natural resonance frequency of a bond. they have the same origin/meaning/frequency87.102.82.26 17:54, 14 October 2007 (UTC)[reply]
OK, then things now add up. A microwave oven works because it operates at whatever the absorbency/resonance frequency of food is so the food heats up. What I'm locking for then is an online graph that extends all the way from zero to the highest frequency known that shows the frequencies at which something (everything from atoms to kettle drum) resonates. Clem 18:30, 14 October 2007 (UTC)[reply]
Yes, that's right - though typically the microwave oven is 'tuned' to water's frequency - or OH (hydroxyl) groups - microwave ovens don't heat up fat as well as water for this reason (though they melt butter well because butter has water in)
No, 2.5GHz microwave ovens aren't tuned to water resonance which is up above 10GHz. Also, while water gas (vapor) does have sharp resonance frequencies, liquid water does not. If a microwave oven was actually tuned to a sharp frequency for water, then the food would be opaque to the radiation, and only a tiny outer layer of the food would be heated. Because the oven's operating frequency is far from any absorption peak, the RF energy passes deep into the food before being absorbed. --128.95.172.173 01:24, 16 October 2007 (UTC)[reply]
second question - I've never seen but would like to see too such a graph.. Can't find one.87.102.82.26 20:44, 14 October 2007 (UTC)[reply]
reduction of multiple state logical equations
If “… we're overrun by really efficient algorithms. “ (SteveBaker 13:40, 8 October 2007 (UTC)) to reduce logical equations to minimum form, which of these algorithms is capable of reducing multiple state equations to minimum form? Clem 22:53, 13 October 2007 (UTC)[reply]
October 14
Maximum limit of kinetic energy?
Hey guys! So i was daydreaming today and i thought if absolute zero exists is there an upper limit to the amount of energy a particle can have? Thank you very much for your time!
A greatly simplified way to think of it is that absolute zero is all mass and no energy. The speed of light is all energy and no mass. So, those are your two opposites. From there, you can get into the particulars that break down the simplicity into a muddy mess of conflicting areas of science. -- kainaw™ 02:51, 14 October 2007 (UTC)[reply]
That's a level of simplification even I would never go to...In short, no. Someguy1221 04:13, 14 October 2007 (UTC)[reply]
But it is true that the speed of light sets an upper limit to kinetic energy, right? DirkvdM 10:11, 14 October 2007 (UTC)[reply]
Short answer, no. And that's exactly the reason for the odd mass increase of the accelerated particle when it approaches the speed of light. You 'add' energy to the particle, since it can't store the extra energy as speed, it stores it as extra mass. --Taraborn 14:21, 14 October 2007 (UTC)[reply]
Not really. Kinetic energy = 1/2mv, so (ignoring common sense) if you had a mass travelling at c, you could simply have another mass slightly greater than double that of the first travelling at half the speed and you'll have a higher kinetic energy. You can set a maximum theoretical kinetic energy for any specific object, but the maximum possible kinetic energy would be the entire mass of the universe travelling at the speed of light, which is a ridiculously large and pointless number. GeeJo(t)⁄(c) • 10:37, 14 October 2007 (UTC)[reply]
Firstly, it's 1/2mv2, secondly, that is a formula of classical mechanics, false in special relativity, and so is invalid for large speeds. In SR, the kinetic energy of a body of rest mass m and speed v is given by
And so, as the speed of a massive body approaches c, its kinetic energy approaches infinity. Thus c does not provide a very interesting upper bound. (note this does not apply for photons, which actually travel at c but have zero rest mass). Algebraist 10:54, 14 October 2007 (UTC)[reply]
<after ec, before seeing Algebraist's response>The relativistic kinetic energy of an object with rest mass m traveling at velocity v (in a given inertial frame of reference) is
This is approximately when v is small compared to c. However, as v approaches c, Ek is unbounded - it has no upper limit. What this means in practice is that no matter how much energy you pump into an object, it will never reach the speed of light. This is sometimes expressed by saying that the energy increases the object's relativistic mass or inertial mass , and so makes it "harder to accelerate". Gandalf61 11:00, 14 October 2007 (UTC)[reply]
Uh oh, I just thought of something. If photons are all energy and no mass, what is their temperature? I mean, if more photons in an area means more energy (and thus higher temperature), what if you could measure the temperature in a photon? Since temperature depends on the amount of photons (particularily heat) in a certain amount of space, what would be the temperature of one photon? If there is no upper limit, would it be infinity? What if you could squueze a huge amount of photons (just photons) into an extremely tiny space, is it possible for the photons to be so crammed that they create their own mass and gravity? Also, if they had no mass, why don't they float away from gravitation? Is there such thing as an antimatter photon? If there was, if one touched a matter photon, wouldn't it create either no energy at all, or only the amount of energy already in the photons, because E=MC2 relies on mass of the object? Thanks. ~AH1(TCU) 20:30, 17 October 2007 (UTC)[reply]
Wow, that's a lot of misconceptions in a row. I'll see how many of them I can dispel. First of all, temperature is a concept of thermodynamics and statistical mechanics, which only makes sense if there are a large number of particles with a certain statistical distribution of energy. One particle does not have a temperature, only an energy. So one photon does not have a temperature, but a large number of photons can have a temperature if they follow a special distribution called Planck's law. For example, the light from an incandescent light bulb has a temperature (it is equal to the temperature of the filament), but the light from a fluorescent lamp does not (because the spectrum is quite different, having discrete spikes for the different phosphors rather than a smooth curve). The light from a fluorescent lamp has a non-thermal distribution, because it is not in thermal equilibrium with itself (which is possible because the photons don't exchange energy with each other).
The thing you describe next is called a geon. It's unknown whether they are stable in theory, and they certainly haven't been observed.
I'm confused why you ask "why don't they float away from gravitation?". If you shine a flashlight into the night sky, the light does "float away from gravitation". Perhaps you're asking why light follows a curved path in a gravitational field? Well, that's not true either. Light follows a geodesic, which is the straightest possible path in the curved spacetime of general relativity.
The photon is its own antiparticle, which simply means the total number of photons is not a conserved quantity. Anyway, photons can't "touch" because light doesn't interact with other light, only with electrically charged particles (photons are uncharged). So photons cannot annihilate with each other. —Keenan Pepper 14:30, 18 October 2007 (UTC)[reply]
Redox reactions
I know that oxidation is loss of electrons and reduction is gain of electrons.
I also know that an oxidant gains electrons whilst a reductant loses electrons.
Yet I am a bit confused about the terms (1)"oxidising strength", (2)"reducing strength", when something is (3)"oxidised", when a molecule (4)"oxidises" something else, when something is (5)"reduced" and when something (6)"reduces" something else.
I think that "oxidising strength" refers to the ability for something to act as an oxidant whilst "reducing strength" refers to the ability for something to act as a reductant. Yet I'm not completely certain.
Could somebody please define clearly the 6 above terms. (You can refer to the words oxidant, reductant, oxidation and reduction in the definition as I am confident with these terms.)
Thank you very much. —Preceding unsigned comment added by D3av (talk • contribs) 09:28, 14 October 2007 (UTC)[reply]
The oxidising strength is the tendency to oxidise - a very strong oxidant may oxidise a weaker oxidant that would usually be reduced in a reaction and not oxidised - the same goes for a concept of reducing strength - you already have the meaning of 3,4,5,687.102.82.26 17:51, 14 October 2007 (UTC)[reply]
The Redox page might be useful…besides being "yet another explanation of the ideas" (sometimes one wording just sinks in better than another), it puts them in context and explains the reactions. Memorizing terms is pretty useless without knowing what they really mean and how they work in the real world. DMacks 18:57, 14 October 2007 (UTC)[reply]
Thanks for the reference. I found what I needed on the Redox page. D3av 11:31, 15 October 2007 (UTC)[reply]
Cyanide Vs. CO
Though Cyanide and CO are both strong ligand, why is there a difference in their mechanism of toxicising the human body? —Preceding unsigned comment added by Curieous (talk • contribs) 13:51, 14 October 2007 (UTC)[reply]
cyanide would almost certainly poison in the same manner as CO, but there is (according to the experts) yet another way in which CN can poison.. If this pathway wasn't available to CN, then cyanide would still be poisonous in the same manner that CO is. (The two compounds CN- and CO are isoelectronic and would be expected to have very similar behaviour
A side question that arises is why doesn't CO poison in the same way in which CN- poisons87.102.82.26 20:35, 14 October 2007 (UTC)[reply]
The short answer is that their chemistry is different, so they affect certain vital systems more effectively than others. Even if the substance affects several vital systems it is the one that causes you to die the fastest that is officially the cause of death. For example, if your head gets cut off, it is lack of oxygen to the brain that kills you the fastest (in seconds) rather than lack of glucose, so the cause of death is lack of oxygen although both separately would have killed you.
The long answer is that the "cause of toxicity" is a combination of which cellular process reaches the failing point the soonest after the substance is introduced to the body (usually one with a low concentration of the substance needed to cause critical failure) coupled with the time it takes to die from that failure. Carbon monoxide and cyanide have sufficient chemical difference so that they affect different vital cellular processes much more effectively thus causing the difference in mechanism of toxicity witnessed. Although the compounds are isoelectronic, the overall charge and the distribution of charge are not identical.
Carbon monoxide is an overall neutral molecule with a slight negative charge on the carbon and a partial positive on the oxygen.
The cyanide ion is overall negatively charged with the Electrostatic potential surface model on the cyanide page suggesting the negative charge is spread around to both atoms of the cyanide with the more-electronegative nitrogen hogging more of the negative charge.
These compounds have different bond lengths and atom sizes.
Enzymes are "finely tuned" for their normal mode of operation, with the side effect that small differences in the chemistry of potential inhibitors can drastically change the magnitude of the inhibition.
Now, to get to the nitty gritty. For the sake of this question I will assume a large fatal concentration of the compounds are being inhaled continuously.
Carbon monoxide poisoning
CO binds to hemoglobin very effectively, so most of it getting into the body will probably stick to hemoglobin and less will be available to muck around with other enzymes. Even if carbon monoxide is binding to many different enzymes in various life supporting pathways, the first pathway that will reach its failure point is the oxygen transport system due to carbon monoxide outcompeting oxygen on the binding site of hemoglobin. Death by lack of oxygen occurs in several minutes so the time until death after the failure point is fairly quick, making it the primary cause of toxicity.
Cyanide poisoning
Cyanide doesn't bind to hemoglobin as efficiently as CO does, so more of it will be available to muck about with other vital enzymes. Cyanide happens to bind very efficiently to the enzyme cytochrome c oxidase, vital to the production of ATP (which is in high demand in the heart and nervous system). It takes much less cyanide to bind to bind a fatal amount of cytochrome c oxidase than a fatal amount of hemoglobin, so even if the majority of cyanide is stuck to the hemoglobin, the system that reaches it's "fatal concentration" first will be the ATP pathway. Death by lack of ATP to the heart/central nervous system is also fairly quick; the article cyanide says several minutes for high doses, similar to the time to death caused by lack of oxygen. Therefore the cause of death and primary means of toxicity for cyanide poisoning is binding to cytochrome c oxidase and causing a failure of the ATP pathway in the heart and nervous system.
Hoped that helped. If anyone has anything to add please do so. Sifakatalk 05:32, 15 October 2007 (UTC)[reply]
If possible I'd like to see equilibrium constants for CN/CO Haemoglobin - it the bit about "Cyanide doesn't bind to hemoglobin as efficiently as CO does" - as having a little chemistry I'd find that suprising - but I was never expert in biological systems..83.100.255.190 10:04, 15 October 2007 (UTC)[reply]
Also at Cytochrome c oxidase ref 1 - says CO also inhibits the enzyme - is it possible that the CO page is wrong/out of date?83.100.255.190 10:07, 15 October 2007 (UTC)[reply]
Would it be truer to say that CO/CN poisoning is in fact due to both pathways? (I'm no biochemist - it's a question.not my 'theory')83.100.255.190 10:27, 15 October 2007 (UTC)[reply]
Just have a look at this excerpt from the CO article:-
Toxic mechanism:-
The precise mechanisms by which toxic effects are induced by CO are not fully understood.
Carbon monoxide binds to hemoglobin (reducing oxygen transportation), myoglobin(decreasing its oxygen storage capacity), and mitochondrial cytochrome oxidase (inhibiting cellular respiration)#
So,may be it justifies the above discussion that though multiple paths are available,the declared path will be the one which is the fastest.
However,the above excerpt says that the mechanism is not fully understood...could someone mention the complications involved in it? --Curieous 08:52, 16 October 2007 (UTC)[reply]
microscopy
when the slide is moved down in what direction does the image move —Preceding unsigned comment added by 99.226.126.42 (talk) 14:43, 14 October 2007 (UTC)[reply]
Think: Which way is the lens moving relative to items on the slide? --Mdwyer 15:49, 14 October 2007 (UTC)[reply]
For the type of microscope often used in school teaching labs, the image is inverted, see this manual, page 26. --JWSchmidt 20:02, 14 October 2007 (UTC)[reply]
When light enters a microscope's objective lens, light from the lower part of the slide will hit the upper part of the lens, travelling upwards. Light from the upper part of the slide will do the same and hit the lens' lower portion. Of course, the same is true of light from all other directions; it will strike the lens in a position opposite to the object's direction.
This will cause the image to be inverted. So, in which direction will an inverted image move if the slide is moved down? --Bowlhover 04:45, 16 October 2007 (UTC)[reply]
Effects of long term usage of asthma medication
I'm just wondering if there are any known adverse effects to long term usage of asthma medication. In particular inhalers such as Duovent. Thanks :) 84.197.59.250 15:16, 14 October 2007 (UTC)[reply]
Take a look at the page for the active ingredients: fenoterol and Ipratropium. Both of those articles are kind of short, so you may want to then feed those names into Google. --Mdwyer 15:47, 14 October 2007 (UTC)[reply]
Long term inhaled steroid use has risks of glaucoma and cataract formation.
While browsing today in WIKIPEDIA, I came across the entry TRANSPORT PHENOMENA. I notice that our book
TRANSPORT PHENOMENA, by Bird, Stewart, and Lightfoot (Wiley, 1960) has been cited. Actually there is
a 2002 edition as well as a 2007 "Revised Edition." These later revisions should really be cited, since
the 1960 edition is now 47 years out of date! R. B. Bird, University of Wisconsin —Preceding unsigned comment added by 128.104.178.123 (talk) 18:03, 14 October 2007 (UTC)[reply]
First of all, this is not the place to grovel about out-of-date information. Secondly, the most likely cause of the 1960 ed. being cited is that no one who contributed to the article has the 2002 or 2007 editions. NASCAR Fan24(radio me!) 18:16, 14 October 2007 (UTC)[reply]
Be nice. And nobody "groveled". I copied the original message to the article's talk page. --Milkbreath 18:19, 14 October 2007 (UTC)[reply]
Guess I did bite them there. I just get mad when people don't use things for their intended functions. To Professor Bird: You may change any out-of-date information in the article. You may want to read WP:CITE to learn how to cite a book. NASCAR Fan24(radio me!) 18:22, 14 October 2007 (UTC)[reply]
Some people in academia are too busy to edit, feel they have a conflict of interest or they are just unfamiliar with the wiki concept. I've had people send me email about page content problems in Wikipedia when they could have just taken a minute and fixed the problem by editing the page. "when people don't use things for their intended functions" <-- See Murphy's law. --JWSchmidt 19:45, 14 October 2007 (UTC)[reply]
There would be an air of impropriety with the author of a book citing his own work on Wikipedia (although in this case, I doubt anyone would object). It makes sense to have someone who is already an active editor of the article make the change. So the best procedure would be to post this kind of note to the talk page of the article (which Milkbreath took care of)...and if that doesn't produce a result, look at the edit history of the article and ask some of the most active editors directly via their talk pages (or email addresses if they provided them). SteveBaker 21:41, 14 October 2007 (UTC)[reply]
Dr. Bird, I would like to apologize on behalf of polite Wikipedians everywhere for the unmerited incivility you were shown above. It's absurd that an obviously-qualified editor offering input should be treated so rudely. --Sean 15:35, 15 October 2007 (UTC)[reply]
I second this apology. Dr. Bird deserves a more detailed explanation and I have a request, so here goes: anyone can edit, but must cite sources. The original editor had access to the earlier edition, but not to the later one, and therefore could cite it: you must not cite a work unless you actually read it and used it. If another editor (such as Dr. Bird himself) has access to the newer edition and is willing to verify that facts in the article are supported by the newer edition, then that editor is welcome to change the article to use the newer edition. Please help us. Thanks. -Arch dude 15:54, 15 October 2007 (UTC)[reply]
Spectroscopy of elements
If spectroscopy of molecules reveals the frequency at which their bonds resonate what is it the spectroscopy of the elements represents, the resonance of the subatomic particles, i.e., protons and neutrons and electrons, within the atom? Clem 18:35, 14 October 2007 (UTC)[reply]
NMR and EPR are types of spectra that analyze resonance of nuclei and electrons, respectively. Careful though…"resonance" applies to a particular kind of interaction, not a particular kind of particle. Ultraviolet-visible spectroscopy is another kind that analyzes resonance of electrons, but it's not related to EPR. DMacks —Preceding signed but undated comment was added at 18:52, 14 October 2007 (UTC)[reply]
exlcuding nmr - all these resonances are at frequencies above that of visible light - the difference between 'resonance' frequencies of electrons is electronic spectroscopy (the term resonance is possible debateable here - depending on what theory you have), the differences between energy states in nuclei is in the x-ray or gamma ray region - again it's debateable whether or not the nuclei are actaully resonating - and depends on what theory you are using..
Note that electronic spectoscopy (the electrons) also depends on the type of molecule the electrons are in - there's also (for lower down electrons) mossbauer spectroscopy and X-ray photoelectron spectroscopy amongst others,not all these spectrosopy are interpreted as being directly from resonances..87.102.82.26 20:50, 14 October 2007 (UTC)[reply]
And you can get crazy and do Raman spectroscopy, which is a measurement of electronic transitions that indicates bond vibrations. This is similar to using IR, which only examines vibrational modes, to see the effect of rotational modes on those vibrations, instead of using Microwave spectroscopy to probe rotational modes more directly. DMacks 22:10, 14 October 2007 (UTC)[reply]
CLASSIFICATION
What would a scientist have to prove to show that the organisim they had discovered was a new species?
What would you expect to see in the organisms within groups that get smaller and smaller.
88.110.21.169 18:38, 14 October 2007 (UTC) Alex McAdam[reply]
I suggest checking out the Species and Species problem articles. As for the organisms in groups that get smaller and smaller -- fortunately, there are a finite number of organisms on Earth, so if you kept dividing organisms into group, you'd at least hit the limit once you created a new group for each organism. -- JSBillings 18:59, 14 October 2007 (UTC)[reply]
Usually a lack of cross breeding with other similar species of organisms is what you need to prove that an organism is a new species. How exactly this is determined may vary between different organisms. 71.226.56.79 22:13, 14 October 2007 (UTC)[reply]
I posted this in a question below but it seems to be important to this one as well. Sometimes the line between species are drawn for reasons other than "can two species interbreed". Even if two organisms can interbreed they may still be considered separate species based on the fact they wouldn't likely interbreed in the wild because they are separated geographically, or because their behaviors are suitably different, etc... See the hybrid page for some examples. Taxonomy has all manner of inconsistencies and politicking. A cross between a Bullock's Oriole and a Baltimore Oriole produces fertile offspring, but the two may be considered separate species or the same species called the Northern Oriole depending on who you talk to. Animal taxonomy is arguably the most straight forward. Plants are probably next but can be a nightmare taxonomically because many "species" can cross rampantly. Fungal taxonomy is all over the place and still developing. Many fungal species have multiple nomenclature synonyms simply because the various reproductive stages of fungi appeared different only to be found to be the same thing later. I don't know enough about protista and bacteria, but I can guess they probably can get rather messy as well. Sifakatalk 02:13, 15 October 2007 (UTC)[reply]
Absolute zero
I just want some input on my reasoning about this topic, or any other speculations that are floating around out there.
Absolute zero is the lack of all energy, right? So if you managed to get an atom down to absolute zero, what would happen to it? Don't electrons have potential energy based on their orbital position? In order to reach absolute zero, would they have to fall into the nucleus? What would happen then?
For curiosity's sake... justice 18:41, 14 October 2007 (UTC)[reply]
Thermodynamicists say it isn't possible to reach absolute zero. Xn4 18:48, 14 October 2007 (UTC)[reply]
Our absolute zero page has info about this topic. One important issue is that "Absolute zero is the lack of all energy" is a convenient and short explanation for the general public, but it's not the precise and correct definition. As you note, there is a non-zero minimum for various potential energy components. DMacks 18:49, 14 October 2007 (UTC)[reply]
Theoretically though, for you to reach absolute zero the electrons couldn't stay in their orbitals because of potential energy. If they hit the nucleus, what would happen? Also, I'm assuming that in real life, if we can never reach absolute zero, it's an like an exponential function- always getting closer to whatever number, but never quite reaching it? justice 19:08, 14 October 2007 (UTC)[reply]
Again, I point you to the absolute zero page, which states "It is the point at which particles have a minimum energy, determined by quantum mechanical effects, which is called the zero-point energy.". They don't stop moving and they don't have zero potential energy. DMacks 19:12, 14 October 2007 (UTC)[reply]
Yes, a necessary result of quantum mechanics is that you can never get rid of zero-point energy. Someguy1221 19:19, 14 October 2007 (UTC)[reply]
There is a certain elegant symmetry here - Einstein says we can't reach infinite kinetic energy - and the third law of thermodynamics says that we can't reach zero kinetic energy either. Nature seems to love having exponential tails to avoid having mathematical discontinuities. SteveBaker 21:31, 14 October 2007 (UTC)[reply]
The third law applies to statistical ensembles of particles. Individual particles within an ensemble may well obtain a state of minimum possible kinetic energy, such as happens to the majority of particles in a Bose-Einstein condensate. Dragons flight 23:15, 14 October 2007 (UTC)[reply]
It's also worth noting that ending up with zero energy could have weird implications for what it means for fundamental particles to "exist". What happens to light if it has no energy? Light is defined (in part) by its wave-like properties — would it even make sense to talk about it as existing if it had no energy, no motion? I'm no physicist but I imagine similar issues come up when you are talking about matter as well, given the deep connection between energy and matter. --24.147.86.187 22:25, 14 October 2007 (UTC)[reply]
I was going to ask about that. So nothing, as best we understand it, would exist without energy? If it had no energy, the matter would be... destroyed? justice 22:55, 14 October 2007 (UTC)[reply]
No, no, no! Not "Zero Energy" - we're talking about temperature - which is "Kinetic Energy" - mass times velocity squared. When the velocity of an atom drops to zero (so you get absolute zero temperature), it still has mass - so it still has energy of the E=m.c2 variety - it's just kinetic energy that hit zero because that's mass multiplied by velocity and when velocity is zero, the kinetic energy is zero no matter what the mass is. I agree with User:Dragons flight too - single atoms can have zero kinetic energy. SteveBaker 15:06, 15 October 2007 (UTC)[reply]
Why there are apparently relatively few STDs? I think there "ought" to be hundreds of well known STDs. I mean, fluid exchange during sex is a jackpot for microcritters to evolve to take advantage of. Could it be that these missing STDs are really there but are wrongly presumed to be genetically heritable diseases, defects,(or even advantageous traits!?) since they would commonly run in families?-Rich Peterson —Preceding unsigned comment added by 130.86.14.86 (talk) 20:53, 30 September 2007 (UTC)
(I put this on the STD discussion page a while back, but that isn't the right place for it, according to Wikipedia policy)130.86.14.90 20:02, 14 October 2007 (UTC)[reply]
You're running on some pretty strong assumptions there. Genetic defects are not diseases, as they are... well, not diseases. They're flaws in the DNA that cause abnormal conditions in the body's development, not body parts being attacked by a specific organism. Second, why should there be "hundreds of well known STDs." Sexual fluids are actually a less efficient method of spreading disease than blood or airborne transmission. There's nothing inherently special about sexual fluids that should be a "jackpot" for diseases. -- Kesh 20:09, 14 October 2007 (UTC)[reply]
I know what a genetic defect is.What I'm proposing is that some things thought to be genetic defects are actually diseases transmitted semen.I am interested in what you say about sexual fluids not being as efficient, perhaps you're right. Can you explain your reasoning or refer me to a source? Thanks, Rich Peterson—Preceding unsigned comment added by 130.86.14.90 (talk • contribs) 22:56, October 14, 2007
Please read disease. A disease is a foreign organism that enters the body and damages it in some way. Genetic defects are inherent in the DNA of the child. How are you proposing that a disease could A) stick around in the mother's body long enough to infect the fetus, yet B) be undetected in the mother OR the fetus, C) not harm the mother and D) continue to affect the child throughout its development? -- Kesh 23:03, 14 October 2007 (UTC)[reply]
I think you may be inadvertently defining a possibility out of existence, by use of the word "disease". In answer to A and B and C, it's not too different to what most parasites struggle and adapt to do over time, though some may not be hidden but are perceived to be genetic defects, rather than stowaways in fluids for gene transmission. Thanks for your comments.--Rich Peterson
At this point, I'm not even sure what you're proposing. The causes of genetic defects are in the DNA of the child, inherited from the parent. An STD is a disease, a microorganism. The two are not even similar. The mechanics behind both are rather well understood, so I don't see how a disease can "masquerade" as an inherited defect. -- Kesh 23:35, 14 October 2007 (UTC)[reply]
I agree with part of what you say if you mean a disease's strategy is to 'masquerade" as a genetic defect--that surely wouldn't happen as often. I mean perceived by us in our ignorance, not an intentional masquerade. What "is rather well understood" may or not be just a portion which is "rather well understood." For example, there is no telling for sure that the the two that "are not even similar" don't have a large, and unknown, range of intermediates.--Thanks, thats's all for today for me.-Rich Peterson —Preceding unsigned comment added by 130.86.14.90 (talk) 00:13, 15 October 2007 (UTC)[reply]
At that point though, you're venturing into philosophy territory. That there may be things we do not know is obvious. However, going from that to saying "diseases are causing these defects" is a huge leap of faith. There's nothing whatsoever to support it in science. -- Kesh 00:19, 15 October 2007 (UTC)[reply]
I don't think sex is a good way for a disease to transmit itself at all. Humans are relatively monogamous and typically have sex just a few times a week - mostly with the same partner. A common cold virus is transmitted between complete strangers via nothing more than a handshake, a cough or a sneeze - with an opportunity to transmit itself dozens and dozens of times per day. SteveBaker 21:27, 14 October 2007 (UTC)[reply]
Careful Steve, humans are not that monogamous. If you've ever had a partner who has had at least one other partner, you are part of the great sexual network. I do agree though, airborne is the best way for a pathogen to go. Returning to the original question, STDs aren't super easy to pass to your kids (it depends on the STD of course, but AIDs for example, is preventable to about a 15%-25% transmission rate in the West), and mistaking them for genetic defects seems pretty far fetched. Also, remember that diseases "should" evolve to become less noticeable and less virulent, so there are probably "STDs" that we don't even classify as diseases anymore. --Cody Pope 21:39, 14 October 2007 (UTC)[reply]
--I think "so there are probably ""STDs" that we don't even classify as diseases anymore" supports my proposal. I did suggest an STD could even be advantageous as an extreme case of what, as you say, tends to happen-diseases evolve to become less noticeable and less virulent. Thanks for your comments.--Rich Peterson
Sheesh! I said "relatively monogamous" and "typically" - just how careful do I have to be? The point is that it's pretty much impossible to have sex with someone without passing on a cold. So it's pretty much certain that a disease that can transmit itself through the air is going to have more potential contacts to spread to than an STD. The spread of AIDS is pathetically slow compared to whichever cold or flu strain is unleashed in a given year. Even in the countries where AIDS has spread the furthest, you're only looking at 10 to 20% of the population over 20 or more years. A strong flu strain can spread to a similar percentage of the population in a couple of months. SteveBaker 22:07, 14 October 2007 (UTC)[reply]
Hey, I attacked "relatively" not "typically" -- man you do need to be more careful :). But mostly I completely agree with you. --Cody Pope 22:22, 14 October 2007 (UTC)[reply]
Compare that to how often you've breathed the same air as someone. I'm not certain, but I'd be willing to bet that most people also share drinks more often then they have sex. In addition, I'm pretty certain that almost all diseases can be transmitted that way, and STDs are the ones that can only be transmitted blood to blood. — Daniel 22:00, 14 October 2007 (UTC)[reply]
Hmm, I was agreeing with Steve's observation that airborne is way more common/easy, but disagreeing with him saying that we're all monogamous -- so I'm not sure how we disagreed. Plus, I really just wanted to say "great sexual network" :). Moreover, "almost all diseases can be transmitted that way" is an odd statement (where "that way"=airborne?). Ebola is transmitted through fluid exchange (non-sexual and sexual alike) and it's certainly not classified as an STD. A lot of parasites need a vehicle that isn't air. As well as malaria, non-parasitic dysentery, TB (airborne momentarily, sure but only if someone just sneezed in your face, the bacteria isn't transmissible through sharing water glasses washed dishes though) and others. Take African sleeping sickness, it is usually passed by a fly, but can theotrically be passed via fluid exchange etc. Saying anything transmitted via fluid exchange is an STD doesn't work. --Cody Pope 22:13, 14 October 2007 (UTC) (I would add that people with Ebola almost never have sex). --Cody Pope 22:25, 14 October 2007 (UTC)[reply]
I just don't see your point about efficiency or effectiveness of transmission. First, there's quite a lot of different germs that transmit by air etc, far more than the few hundred for sexual transmission I'm proposing. Second, even if very few germs were transmitted by semen, say a few eons ago, there would be lots of time for them to speciate--some adapting to become less virulent, and every once in a while a few "choosing" the greater virulence strategy.-Regards and thanks to all for your thoughtful comments.--Rich Peterson
The point is that it's simply not as effective a method of transmission. Speciation tends to favor the best methods of continuing the species which, for diseases, means they tend to favor the more reliable/easier methods of spreading. Thus, more airborne diseases than fluid-borne ones. -- Kesh 23:44, 14 October 2007 (UTC)[reply]
Yes, but I don't mean to suggest there should be more fluid-borne than airborne diseases, I don't know. I only suggest there are MANY fluid-borne ones, more than we suspect. Also, a species transmitted by a fluid would be reasonably likely to have at least some of its daughter species use the fluid route.--Rich Peterson —Preceding unsigned comment added by 130.86.14.90 (talk) 00:00, 15 October 2007 (UTC)[reply]
You've still not explained why there should be more than we are currently aware of. -- Kesh 00:03, 15 October 2007 (UTC)[reply]
Ok, to summarize, if I understand the conversation so far, Rich argues that there should be more STDs since sex is a good vehicle for transmission and others are saying that sure sex is a great mode, but airborne is way better (where "better" means faster). Now, Rich also argues that it is possible that we have misidentified STDs as Genetic defects, since they could be passed to children by parents and might only present in development. Is that about it? First, airborne is faster and thus ideal for anything that wants to reproduce quickly. Second, sure, I agree that it is possible for us to misidentify a disease as a defect under the conditions that: a. it can be passed from mother to child, b. it is unknown to science, and c. it causes some developmental problem. But, I also contend that given the level of modern medicine this is highly unlikely, since, "a." only happens about 15-25% of the time (for HIV at least), "b." is untestable, and "c." is probably not happening given that many if not most developmental problems have identifiable causes. Tangentially, my problem with the question is more about the limited definition of "STD". Take a look at HPV for example: "of about 13 so-called 'high-risk' sexually transmitted HPVs". There are over 100 HPV forms, and only about 13 are considered STDs. Now all of them can be transmitted by sex (skin contact really). The common cold can be transmitted by sex (kissing and coital fluid exchange). Ebola can be transmitted by sex (any fluid exchange really, touching soars etc). So our working definition of STDs doesn't seem super effective when you're discussing the evolution of diseases and their radiation. We could simple say that Rich's "lost" STDs are all those virus/pathogens/bacteria that can be transmitted via sex but are most often not (or at least not associated with sex in the traditional sense). So to summarize: fluid exchange is not the jackpot it could be, since it is slow. STDs being misidentified as genetic defects is possible but improbable. And if you just change the definition of STD you get a whole bunch of speciation in your new group. --Cody Pope 04:30, 15 October 2007 (UTC)[reply]
On HPVs, actually only 13 are "high-risk STDs", that doesn't mean that none of the others are STDs. The article says, "A group of about 30-40 HPVs is typically transmitted through sexual contact", thus about 30-40% are STDs. A "high-risk STD" is one that includes a risk of death, as noted in the Cancer section that says, "About a dozen HPV types [...] are called 'high-risk' types because they can lead to [various forms of cancer]." The section on HPV caused genital warts (which is an STD) notes that they are not "high risk" because they don't cause cancer. The reason why so few are "high-risk" is not because STDs are hard to contract, but because they increase the odds of killing off the host, which is a maladaptive trait compared to the more benign versions of HPVs. -- HiEv 17:41, 15 October 2007 (UTC)[reply]
Actually, this is a pretty good question. To start off with, there are already quite a few STDs, with over 100 species of Human papillomavirus (HPV) identified so far alone. Besides that, the fact is that there are probably many more STDs that we're not aware of, but they're not noticed due to being fairly benign. If a bacteria or virus is transmitted, but there are no symptoms, then people aren't likely to look for it or try to figure out how it was transmitted.
Also, there are diseases that seem to run in families, so we assume that there is a genetic component to the disease, however this could be in error. Researchers are still searching for genes responsible for some apparently genetic diseases. However, what appears to be a genetic condition might actually be due to an environmental cause, such as exposure to a certain germ. If a virus, for example, had evolved to be able to infect a foetus in the womb then it might cause some early developmental changes that affect later growth. For example, while often thought to be genetic, some suspect that one of the causes of schizophrenia could be due to prenatal exposure to infection by the parasitic protozoa Toxoplasma gondii.
Still, there are many problems with this, such as the difficulty in infecting the foetus (as seen above in the AIDS numbers) without killing it, the long dormancy period that would be required from birth to sexual maturity, the fact that negatively affecting the future host reduces its ability to spread, the length of time it would take to evolve to be able to cause a positive adaptation in its future host, and an explanation as to why it would stick to some families and not spread more randomly among the population as other STDs do.
So, yes, there probably are more STDs, but for the most part it's unlikely they're ones worth worrying about, and it's very unlikely, though not impossible, that they're the cause of any apparently heritable conditions. It sounds like it might be worth investigating scientifically, but currently I wouldn't put the odds in favor of it being true. -- HiEv 17:18, 15 October 2007 (UTC)[reply]
It depends how you are defining STD. Is an STD something that is only transmissible by sex (or a sex-like act such as a blood transfusion), or is an STD something that is transmissible by many means, including by sex? By the latter definition, almost every disease is an STD. You can catch flu by having sex with someone -- it's just that you could just as easily have kept your pants on and caught it. --M@rēino 21:02, 17 October 2007 (UTC)[reply]
I'd say an STD is something that is primarily transmitted due to sexual contact. After all, there are ways to get any transmissible disease without sex. For example, you can get AIDS from a blood transfusion. So if you say an STD is a disease only transmissible by sex then there are no STDs. -- HiEv 14:06, 18 October 2007 (UTC)[reply]
Mitochondrial genome size
Everyone seems to know that the mitochondrial DNA in humans is 16569bp long. This comes from a 1981 paper that sequenced it. My question is: there's gotta be some variation in this number - does anyone know how much give and take there is in humans? Aaadddaaammm 22:19, 14 October 2007 (UTC)[reply]
I didn't know the size of the mitochondrial genome if it makes you feel better. :P I am positive it would vary as is it subject to the same (or more as mitochondrial DNA copying machinery is slightly less fullproof than nuclear DNA copying machinery) random duplication and deletion events as the nuclear DNA. That number is probably good for an average. Sifakatalk 02:17, 15 October 2007 (UTC)[reply]
species
Does the inability of one species to impregnate another species serve as the dividing line for species or does it include the ability to impregnate but with the result of offspring so deformed they are not able to live? Clem 22:32, 14 October 2007 (UTC)[reply]
Neither. For instance, horses and donkeys can interbreed, but create infertile mules. They are still considered separate species, as their offspring cannot breed, even though said offspring are not deformed. Most modern biologists look at more than that, though, as genetics and bodily structure play into the definition of species quite a bit. It's not as simple as who they can breed with. -- Kesh 22:35, 14 October 2007 (UTC)[reply]
Generally, both genders of any offspring between the two have to be themselves fertile. Mules aren't. Of ligers and tigons, only the females are. Not sure about grolars, but then they're a lot rarer. GeeJo(t)⁄(c) • 22:42, 14 October 2007 (UTC)[reply]
I don't know about grizzly bears in particular but as Ursid hybrid mentions, some brown bears are more related to polar bears then they are each other which is something I've also read before in scientific papers. It also appears to suggest that both sexes are fertile which isn't surprising although not guaranteed by the DNA studies (polar bears could have some specific difference other then their colour which prevents them successfully interbreeding) Nil Einne 11:52, 15 October 2007 (UTC)[reply]
Sometimes the line between species are drawn for reasons other than "can two species interbreed". Even if two organisms can interbreed they may still be considered separate species based on the fact they wouldn't likely interbreed in the wild because they are separated geographically, or because their behaviors are suitably different, etc... See the hybrid page for some examples. Taxonomy has all manner of inconsistencies and politicking. A cross between a Bullock's Oriole and a Baltimore Oriole produces fertile offspring, but the two may be considered separate species or the same species called the Northern Oriole depending on who you talk to. Animal taxonomy is arguably the most straight forward. Plants are probably next but can be a nightmare taxonomically because many "species" can cross rampantly. Fungal taxonomy is all over the place and still developing. Many fungal species have multiple nomenclature synonyms simply because the various reproductive stages of fungi appeared different only to be found to be the same thing later. I don't know enough about protista and bacteria, but I can guess they probably can get rather messy as well. Sifakatalk 01:54, 15 October 2007 (UTC)[reply]
Yeah - you can cross a Lion with a Tiger and get a Tigon or a Liger (yes, really!) - but nobody would consider Lions and Tigers to be the same species - we "know" they are different because they look different, they behave totally differently (tigers are lone hunters, lions are pack animals, tigers love to swim, lions don't), they sound quite different (lion roars and tiger roars sound way different) - you can easily tell the difference between a male and female lion by the mane - no such clear difference exists with tigers...stripes...you name it. For sure we don't want to call lions and tigers by the same name. On the other hand, we do want to call all dogs "Dogs" - even though they look/behave/sound more different than lions and tigers do, they actually are closer genetically than lions and tigers.
The problem is that we have this big pile of taxonomic data with lots and lots of history to it - and we're loath to toss it all out, even though it's evident that the whole thing is a big blurry mess of genetics. The inability to interbreed could be due to just one teeny-tiny genetic incompatibility - or it could be that there are thousands of genetic differences that none-the-less do not prevent interbreeding. Then we have the 'mule' situation where the offspring of two different kinds of animal is infertile, or the situation with tigons and ligars where the female offspring are fertile, but the males are not, or the situation with Great Danes and Shi-Tsu dogs where the offspring are all fertile but will probably have weird health problems of other kinds. Using that 'interbreeding' criteria as a way to name things is an old, outdated idea.
But to come up with an entire new taxonomy based on genetic differences measured directly by number of different genes would require huge amounts of effort, thousands of textbooks been rewritten, endless wrangling over who gets to name what 'new' species with what name and which name to call the result of two sub-species being grouped together. This is a horrible mess - but in the end, it really doesn't matter all that much...it's just a matter of terminology.
I bet taxonomists could play a fun six degrees of Kevin Bacon sort of game where you try to link two distant species by breedable species in between, in the style of a ring species. I wonder what the longest such chain among extant creatures is? --Sean 15:26, 15 October 2007 (UTC)[reply]
October 15
race
If the distinction between species is so ambiguous how are modern races distinguished, especially with so much inbreeding? Clem 02:19, 15 October 2007 (UTC)[reply]
Many scientists feel that race has no scientific basis at all. Dragons flight 02:27, 15 October 2007 (UTC)[reply]
The short answer is not easily. There are massive committees dedicated to this sort of thing. For animals it's the International Commission on Zoological Nomenclature (ICZN) which creates the International Code of Zoological Nomenclature, effectively the rules of how to name things when disputes arise. For plants it's the International Code of Botanical Nomenclature. Narrowing the question, for most non-microscopic sexually reproducing animal species the division between species is typically decided based on whether or not the animals frequently interbreed in the wild or not. Mammals may be considered separate species even though they can technically interbreed if they are geographically separated. As a rule of thumb, biological nomenclature for a particular group of organisms is designed so that it can be fairly easy to apply. Dragon flight raised the issue above that labeling a group of organisms a species attempts to impose a black and white concept on the grey world of biology with varying results. While ideally we would like to be able to classify every organism with a consistent definition, we can't at this point. There are tons of cases where it is currently difficult to observe or expensive to exhaustively test whether or not an organism interbreeds with related species or reproduces asexually so the typical criteria don't apply, or whole bunches of other reasons. In these cases, the concept of "species" is based off of observable morphological characteristics which appear to "set apart" a group of organisms from similar organisms. In parts of mycology this method is frequently used; fungal species are determined by differences in spore characteristics, hosts, range, disease symptoms, and whatnot so that populations of very similar organisms are lumped together to form a "species." Sifakatalk 02:33, 15 October 2007 (UTC)[reply]
Note that human races were considered ill-defined even before the species problem really came to a head. You can find discussions about the lack of human races being real biological distinctions going back into the 19th century at least. In any case there is nobody today who thinks that human races are different species. It has occasionally been a belief floated by various scientists in the 19th century but even then it was considered spurious by many (including Darwin). --24.147.86.187 02:50, 15 October 2007 (UTC)[reply]
According to the article subspecies the International Code of Zoological Nomenclature calls human races "infrasubspecific entities." Sifakatalk 03:10, 15 October 2007 (UTC)[reply]
Next time I want to piss someone off, I'll call them an infrasubspecific entity. Might be interesting to see how they react. :) Or unhealthy. :( DirkvdM 18:10, 15 October 2007 (UTC)[reply]
This is really another one of those "what's in a name?" questions that we shouldn't be too concerned about. It's clear that humans inherit their skin colour and hair type and various other physiological features from their parents. In that sense the races 'breed true'. But on the other hand, we can interbreed between races quite freely and successfully too - so you can't describe the various racial types as separate "species". Between one end of the scale and the other - it's just a matter of what name you decide to use - and that's as much a matter of political correctness as it is science. This is equivalent to asking whether Pluto is a planet or not - biologists need to put a stake in the ground and define their terminology (just as the astronomers did) - but it doesn't "mean" anything in any important way. Sadly, people will make just as big a fuss over whatever they decide as they did over Pluto's demotion to "minor planet" status...and it's just as big a waste of breath to discuss it. SteveBaker 14:02, 15 October 2007 (UTC)[reply]
Problem is, if others like to waste their breath so much, the ones who know can't stand by and say nothing. After all, why did you answer this question? :) DirkvdM 18:10, 15 October 2007 (UTC)[reply]
Why don't flat-chested women use estrogen to grow larger breasts instead of getting implants? Doesn't estrogen work to grow breasts on males? --124.254.77.148 09:08, 15 October 2007 (UTC)[reply]
Well it can cause males to develop breasts but this is different from causing breasts to grow larger. Lanfear's Bane 10:59, 15 October 2007 (UTC)[reply]
Hormones are the bio-chemical equivalent of cluster bombs: you can't just apply the œstrogen to one part of the body - it would spread, causing havoc through the rest of the body; it could screw up the menstrual cycle, digestive processes and even induce cancer. Plus, œstrogen can cause the body to burn fat and kill muscle tissue, causing a net reduction in size. Laïka 11:30, 15 October 2007 (UTC)[reply]
Pregnant women grow larger breasts (and it's often a permanent change) - I wonder what hormonal brew does that? But as you say - the number of side-effects would be pretty horrific, so it's not something you'd really want to do. SteveBaker 13:53, 15 October 2007 (UTC)[reply]
The worst side-effect of that being a parasitic growth that drops out after nine months and then feeds off you for eighteen years or more. Sometimes. Lanfear's Bane 14:52, 15 October 2007 (UTC)[reply]
Worst still, the parasite somehow latches onto the father as well. (And 18 years is a severe under-estimate.) SteveBaker 15:42, 15 October 2007 (UTC)[reply]
They do! Many women report that taking birth control pills causes their breasts to get a little bigger. --Sean 15:21, 15 October 2007 (UTC)[reply]
As I recall, there are a few published studies of the effect of estrogen supplementation on breast size in women and they do not indicate that estrogen supplements have much effect on breast volume in most normal women. Most women have normal levels of estrogen and adding more estrogen will have little effect to increase breast size. There are probably some doctors who will help normal women try topically applied estrogen for a few months, without promising any results. Rarely, women who have low estrogen (genetically, for example, see aromatase; or otherwise) will have a spectrum of problems and breast size is not likely to be their main concern. During pregnancy there are multiple hormones and growth factors that can influence breast size including progesterone, IGFs, prolactin and poorly-characterized factors that influence weight gain and patterns of adipose tissue growth. Hormone/growth factor levels are not the whole story; there is genetic variation in how tissues respond to these signaling molecules. --JWSchmidt 15:54, 15 October 2007 (UTC)[reply]
Oh. Well, maybe when women get on the pill they also start wearing tighter sweaters, which has led to these false reports. :) --Sean 17:16, 15 October 2007 (UTC)[reply]
Combined estrogen and progesterone will stimulate mammary gland tissue growth inside the breasts of many women, which is mainly of concern for associate increased risk of breast cancer. Is a possible small increase in breast size worth an increased risk of breast cancer? Orally administered estrogen supplements increase the risk for stroke and other blood clotting problems. I think a doctor who gives women prescriptions for oral estrogen or an orally administered estrogen+progesterone supplement in order to try to increase breast size would be a likely target for legal action. I suspect most doctors feel it is not ethical to give women drugs that have serious side effects while trying to deal with something like small breast size, which is not really a medical problem. --JWSchmidt 17:43, 15 October 2007 (UTC)[reply]
As far as medical ethics go, I note that doctors routinely operate on perfectly healthy women for breast enlargement surgery. Both anesthesia and major surgery carry the risk of serious complications, but are still widely available. --Sean 19:29, 15 October 2007 (UTC)[reply]
Medical uses of breast implants, estrogen and progesterone are all regulated by the FDA. Breast implants are approved for breast size augmentation. To my knowledge, estrogen and progesterone supplements have not been approved by the FDA for use in attempts to increase breast size, but I might have missed it. --JWSchmidt 20:14, 15 October 2007 (UTC)[reply]
I didn't mean to imply that they were. I was just noting that doctors are not ethically above doing other potentially risky procedures for something that is, as you say, not really a medical problem. --Sean 21:03, 15 October 2007 (UTC)[reply]
I probably should not have left it at "not really a medical problem". In our society there can be psychological problems arising from breast size (even in the normal range), so it has been possible do document psychological benefits for some women from breast size augmentation. In terms of medical ethics, there should be some balance of the benefits against the risks. If there is an FDA-approved medical procedure and a doctor makes sure that the patient knows the available risk/benefit information then they are on fairly safe ground. --JWSchmidt 22:28, 15 October 2007 (UTC)[reply]
(outdent) As I understand it, once a medication is approved by the FDA for one purpose, doctors are (as a general rule) free to prescribe it for any purpose. (Do we have an article on off-label prescriptions?) I do seem to recall hearing recently of an exception to this general rule; I don't recall what it was.
Yes, I imagine doctors who do this would be taking risks from a malpractice standpoint. They'd probably want the patient to sign an informed consent form at the very least. --Trovatore 22:34, 15 October 2007 (UTC)[reply]
I know some doctors are very comfortable with topically applied estrogen and the breasts are one body location that is sometimes recommended for application of estrogen-containing creams. I'm not aware of FDA approval of estrogen for breast enlargement, but I think some doctors would be comfortable with letting their patients try it for a short time: this would probably qualify as an example of off-label use. --JWSchmidt 23:17, 15 October 2007 (UTC)[reply]
This study of topical estrogen therapy for labial fusion had a patient who demonstrated breast enlargement as a side effect (but that was only one out of a cohort of twenty). Rockpocket 23:37, 15 October 2007 (UTC)[reply]
Besides all the other points made, not all women want large breasts, nor do all men find them attractive. -- Kesh —Preceding comment was added at 23:38, 16 October 2007 (UTC)[reply]
Kinetic energy, part 2
The previous questions about kinetic energy and absolute zero touched on a topic that wasn't specifically answered. If you have an electron - just a plain electron - how much energy can you add to it without changing it? It must remain an electron - just a high energy electron. Is there any limit? If you converted all the mass in the entire universe to energy and applied it to the electron, would it still be an electron? I believe this is what the original kinetic energy question was getting at, but was not answered. -- kainaw™ 12:34, 15 October 2007 (UTC)[reply]
Yes as far as I know you can keep adding kinetic energy to an electron - under non-relatavistic thinking as well as under relatavity theories..87.102.47.243 13:12, 15 October 2007 (UTC) The difference between the theories is that as an electron gets approaching infinite energy in relativistic theories it has approaching the c as a velocity (ie 3x10^8m/s), whereas in non relativistic theories it has approachin infinite velocity.[reply]
Again as far as I know (and I'm sure someone will take this up) - no electron has ever been found to simply disintegrate due to instrinsic high energys87.102.47.243 13:15, 15 October 2007 (UTC)[reply]
Certainly the electron cannot disintegrate due to too much kinetic energy because kinetic energy is a relative thing. Relativity allows us to consider things from the point of view of the electron - and from it's point of view it's dead stationary - why would it spontaneously disintegrate? From our point of view, yes, we can keep pumping energy into it and it will go faster and faster - but even with the entire energy of the universe pumped into that one solitary remaining electron, it'll still only be going 99.99...9% of the speed of light (there would be quite a lot of '9's in that '...' bit - I can't be bothered to work out how many!). This experiment has been done to quite high fractions of 'c' in various high energy physics labs - I don't think any of them have claimed any spontaneous disintegrations in the process - if they did, it would surely be big news. SteveBaker 13:51, 15 October 2007 (UTC)[reply]
oops I walked into that one (fun!) - I'm going to pretend that I meant no electron has ever been found to disintergrate due to a high energy collision - actually I'd like to know if this is true? anyone?83.100.252.179 18:20, 15 October 2007 (UTC)[reply]
The electron, by my quick calculation, would be moving at , so about 160 9s in your ellipsis (and then a 5 after your last 9). --Tardis 23:16, 15 October 2007 (UTC)[reply]
Sorry, I should have mentioned that I rounded to 159 places of decimals. I predict we will be using the results of your calculations in future ref desk answers! Thanks! SteveBaker 02:26, 16 October 2007 (UTC)[reply]
Possibly to make a hybrid/tribrid car that captures wind energy?
Is it possible to make a car with air intakes, that capture wind energy while the car moves? Like the air flow spins a fan inside the intake, which converts that into electricity which is stored in a battery. 64.236.121.129 13:36, 15 October 2007 (UTC)[reply]
No - that's definitely not a good idea. The energy you'd extract from the wind would merely show up as increased drag on the car. So the energy your little wind turbines would extract would be dwarfed by the extra drag they'd impose. There is no such thing as a free lunch! If your idea worked then you could build a perpetual motion machine by fixing a windmill onto a cart, and using the windmill (through some gear wheels or something) to drive the wheels of the cart - give it a little push and it would run forever. Since perpetual motion is not allowed (the first law of thermodynamics is a harsh mistress) - we know this can't work. Some older aircraft used little turbine blades out on the wing somewhere to generate electricity - but this was so that they still had a source of electricity if the engine died - they were a net energy loss though, eating kinetic energy (by slowing the aircraft down) at a considerably higher rate than the electrical energy they'd generate. SteveBaker 13:42, 15 October 2007 (UTC)[reply]
A vertically mounted turbine (rotate about the vertical) - could capture side winds - but the benefits would be minor - and the downsides (low bridges etc) major..87.102.47.243 13:48, 15 October 2007 (UTC) I don't believe such things can be very efficient easily anyway.87.102.47.243 13:52, 15 October 2007 (UTC)[reply]
Sure, you can make a wind-powered vehicle - it's called a 'yacht'! Notice how few yachts use windmills rather than sails! There is a reason for that! However, I have seen things like this A fuel-saving system for ships relies on kites and Giant Sails that could power ships - but they aren't extracting energy from the slipstream air caused by the motion of the vehicle (as our OP suggests) - because that's not possible. SteveBaker 15:31, 15 October 2007 (UTC)[reply]
A supercharger pumps cold air into the engine to extract chemical energy by optimizing the fuel-air ratio. This is not usually considered wind energy. It probably adds extra drag, but the energy boost outweighs the drag. Nimur 14:43, 15 October 2007 (UTC)[reply]
That's completely the opposite thing! Our OP is talking about extracting energy from the wind using a turbine - you are talking about something that consumes energy to create an air flow (more like a jet engine than a windmill). Superchargers are driven by a belt off the main drive shaft - and turbochargers extract energy from the cars exhaust flow to pump air into the engine. Also, it's not so much that they optimise the air/fuel ratio - a decently designed carburettor can do that without supercharging or turbocharging - the point of a super/turbocharger is that with increased airflow you can inject more fuel and keep the SAME optimum ratio - and thereby either get more power from the same engine - or the same power from a smaller engine. Neither superchargers nor turbochargers directly affect drag - although it is common to add a hood scoop to feed air directly into these beasts, because the pump is sucking air into the duct, it actually creates a small amount of negative drag (but it's pretty negligable!). In the case of a turbocharger, you are actually taking some of the energy out of the exhaust flow to drive the thing - so I suppose you reduce the tiny amount of extra thrust that you car gets from the 'jet' of exhaust fumes being pushed out the back...but again, it's totally negligable compared to the extra power it enables the engine to deliver. As usual though, there is no such thing as a free lunch and these gadgets almost always make the fuel consumption of the car worse, not better. SteveBaker 15:31, 15 October 2007 (UTC)[reply]
Commercial aircraft have an emergency generator of this type that deploys if all of the engines fail. It increases the drag, but it provides enough power for the essential flight systems. These units deployed in at least two situations when an airliner flew through a volcanic cloud and lost all engines. -Arch dude 15:41, 15 October 2007 (UTC)[reply]
Yes, that plane did use its ram air turbine. --Anonymous, 21:55 UTC, October 15.
Hmmm, I wanted to make a lame joke about how we could interbrid different technologies, but it turns out tribrid is an existing word. (Note how I sneaked in the joke anyway. :) ) Anyway, with a strong sidewind, it might still help if the car had sort of a sail or wing shape. However, given the usual speed of a car, it would have to be a pretty strong side-wind to have a noticeable effect. And if the wind comes from the other side, the car would have to shapeshift. Not a good idea, it seems. DirkvdM 18:21, 15 October 2007 (UTC)[reply]
–15:00, 15 October 2007 (UTC)15:00, 15 October 2007 (UTC)~~ca person falls on the ground in front of me,i check his ABC (airway, breething, circulation) and find out that he has no pulse nor breething, hence i start doing CPR trying to revive him. now while i do this can the person start bleeding. basically my question is , can there be bleeding without pulse on?82.148.96.68 15:04, 15 October 2007 (UTC)cuby[reply]
If the person still has a decent blood pressure - yes. However, if their blood pressure has fallen too far - then the only blood that'll flow out is under gravity - so maybe yes, maybe no, depending on where the wound is. SteveBaker 15:11, 15 October 2007 (UTC)[reply]
Also you are compressing their chest and forcing air into their lungs, pressure may force blood out from any wounds. Lanfear's Bane 15:15, 15 October 2007 (UTC)[reply]
Well, the problem with Mr Freeze's gun is where all that water comes from. I suppose you could make a mixture of water and something that would evaporate very quickly when released into the air that would pull the energy out of the water and freeze it. But you'd have to carry a gigantic tank of water around with you - and I can't imagine any way around that. If he were just freezing the water that was already there - then there is no mystery because a CO2 fire extinguisher or a can of freezer spray can really do that (albeit on a small scale). But he seems to be able to create ice anywhere - even when there is no water around - and there is much more water created than would fit into that tiny gun+backpack. I think the myth is that he's freezing the water vapour in the air - but there isn't anywhere near enough of that to do the job. So basically, "No". SteveBaker 15:39, 15 October 2007 (UTC)[reply]
Yep - same problem. It's all very well being able to freeze things - but if there isn't anything there to freeze, you're out of luck! I suppose he might be freezing the air itself - but that's an altogether more difficult proposition! SteveBaker 16:10, 15 October 2007 (UTC)[reply]
.129, I hope these answers haven't left you "COLD"! --Sean 17:25, 15 October 2007 (UTC)[reply]
Sometimes you just gotta take the heat. 64.236.121.129 17:37, 15 October 2007 (UTC)[reply]
Cool puns, guys. risk 19:28, 15 October 2007 (UTC)[reply]
Maybe use hydrogen to power a refrigerator and use the resultant water as the water supply? But then you have to carry hydrogen tanks instead. --antilivedT | C | G 05:01, 16 October 2007 (UTC)[reply]
That's funny. But seriously, if you haven't seen the movie Frozone claims to use the moisture in the air, which is why his powers didn't work in that building fire. Besides, what about liquid nitrogen? It worked on the Termintator...and my friend's wart. XD --JDitto 18:56, 17 October 2007 (UTC)[reply]
Hydrogen Alpha Images of the Sun
I am a student trying to find hydrogen alpha pictures of the sun. I need to access archives and find one every day for the past week at roughly the same time. I tried the soho website, but their archive section is very confusing. Any help would be greatly appreciated. —Preceding unsigned comment added by 128.255.107.249 (talk) 17:35, 15 October 2007 (UTC)[reply]
The Sun in H-alpha light Why don't you use Google's Image search? Google for "hydrogen alpha sun" and you'll get plenty of nice pics. There is also one here is to the right. 85.127.181.53 21:50, 15 October 2007 (UTC)[reply]
That looks about right according to the two lines in my Atlas of the Heavens. --Milkbreath 18:57, 15 October 2007 (UTC)[reply]
Radio Transmissions
If I had a remote control car, would there be a way to extend the radio transmissions to go very far and for the signal to not have so many interuptions, i.e it could go into a sewer or a cave and still receive my signals from a distance? Could it work off of a satellite or is there a way to strengthen the radio signals? —Preceding unsigned comment added by 63.110.180.29 (talk) 21:08, 15 October 2007 (UTC)[reply]
I guess you could hook the radio controller up to a more powerful transmitter with a larger aerial? You'd need one that could transmit the same frequencies, and you'd probably violate several laws doing so. Radio waves don't penetrate solid objects very well, so it's unlikely you could get it to work underground. It's probably conceivable to transmit a signal to a satellite and have it beamed down again, but you'd end up with noticable lag in the cars' response. Exxolon 23:03, 15 October 2007 (UTC)[reply]
To get radio signals in tunnels special leaky coax antennas are used to carry the signal into the underground space and make it available all through. You too could use this technology in your sewer or cave, but in fact you may be better off with a roll of optic fibre or wire that unrolls as the car goes forward, and you can drive by wire.
To extend over satellite you will need a fancy antenna on the car, and there is no way to make this work in a cave. Graeme Bartlett —Preceding comment was added at 00:39, 16 October 2007 (UTC)[reply]
It's just a matter of power - as a 'thought experiment' - it you really had to, you could equip a satellite with enough power to send a signal that a toy car could pick up 5 feet underground. Soil attenuates radio waves but it's not a sudden cut-off. It would probably have to be a VERY large satellite with one heck of a big transmitter though. But for more sane applications, you can certainly boost the range. When you want to double the effective range of a radio transmitter, you have to quadruple the transmitter power. So let's suppose your car's standard transmitter worked out to maybe a kilometer - to run your car (out in the open) from geostationary orbit (35,786 km) your satellite would have to have a transmitter maybe 35786*35786 times more powerful than the one you have now. That's about 1.3 billion times more powerful! To get through a few feet of dirt afterwards would push the power requirements to truly ridiculous levels. However, that's assuming that (like your regular transmitter) it sends radio waves out in all directions equally. If it only had to send a narrow beam down towards the toy car - it would need a lot less. NASA have used 'ground penetrating radar' systems in satellites that can see down through several meters of martian soil - and in that case they have not only send a radio signal that far - but detect the return 'bounce' too. Those probably don't run on the frequency that your car uses - and that probably makes a difference too. So it's "possible" - but definitely not "easy".
In terms of a practical answer to running your car at longer distances, it's certainly possible to boost the power - but there is a reason they don't do that. Because they sell lots of toy cars (and boats and who-knows-what-else) that use the same range of frequencies, if the signals at the transmitter are too strong, then someone driving one of these things two streets away would interfere with your car - and that would make matters worse, not better. For this reason, radio control transmitters operate at power levels that are strictly limited by law. The best way to get good range from your transmitter is to ensure that the antenna is always fully extended - and if the car has one of those 'dangly wire' antennas - thread it through a drinking straw and hot-glue that onto your car to make that antenna stick up vertically as far as it will go. Don't coil it up! Holding your transmitter antenna vertically will then get you the best possible range. SteveBaker 02:15, 16 October 2007 (UTC)[reply]
At some point, the power levels you're using to get the signal through the ground leave the realm of "radio signals" and enter the realm of "directed-energy weapon". The energy in the radio waves doesn't just magically vanish as the signal is attenuated by the ground -- some of it gets reflected, while more of it gets absorbed. --Carnildo 21:34, 16 October 2007 (UTC)[reply]
Growing a mushroom on the skin
Don't laugh.
Dermatophytes are fungi, and they are terrible. Amanita muscaria is also a fungus, but it is pretty. Would it be possible to cultivate a fly amanita on one's skin? Would it be safe to do so? HYENASTE 21:59, 15 October 2007 (UTC)[reply]
It is not possible, the diet of the fungi is too different. Perhaps you could live off a diet of human skin, but I think you would not survive long on a diet of mulch and tree roots. These different fungi have the same issue. Graeme Bartlett 00:35, 16 October 2007 (UTC)[reply]
There is no way to grow a saprophyticAmanita muscaria on one's living skin because it is not adapted to deal with the human body's defenses. You couldn't even grow it on a decomposed flesh either because Amanitas are adapted towards decaying plant matter. So definitely not. Any fungus growing on your skin is going to be decomposing it, ushering in all manner of infection and putridity, so it wouldn't be safe or the least bit attractive either. Lastly, sorry I did laugh. The mental image of mushroom people I conjured up was way too surreal for me not to. 71.226.56.79 15:43, 16 October 2007 (UTC) (This is User:Sifaka who is unable to sign in)[reply]
The moon and stars
In what ways are the stars and moon similar? —Preceding unsigned comment added by 24.126.168.23 (talk) 21:59, 15 October 2007 (UTC)[reply]
Um, they appear in the night sky? Have you tried looking at our articles on moon and star? I suspect you'll find more that's different than in common, but if you can ask a more specific question we might be able to help better. Confusing Manifestation 22:32, 15 October 2007 (UTC)[reply]
They can be used to tell the time of the year, or in lunar calendars the date in the month. Graeme Bartlett 00:34, 16 October 2007 (UTC)[reply]
There is really very little that the stars and the moon have UNIQUELY in common - I mean, they are both made out of atoms (well, except for neutron stars) - they are both kinda-sorta more or less round (but so are golf balls and we don't ask about what makes a golf ball similar to a star). Both stars and moon can be seen in the daylight sky (if you have the right equipment) - and technically, there is one star in particular (the one that we call "the sun") that isn't ever visible at night. The moon isn't even always visible at night - about half the time it's only visible in daylight. And what's wrong with planets, asteroids, comets and dust clouds? Those are a lot more similar to the moon than stars are - why aren't they participating in this arbitary listing of objects? It's really hard to come up with any property that's similar between stars and moon that are not also common with almost everything else in the known universe! "star" and "moon" both have four letters? SteveBaker 01:53, 16 October 2007 (UTC)[reply]
Well, think about it this way, stars are formed from nebula dust. A moon is formed when, a large clump forms in the nebula dust surrounding the new star, and as the clump forms, more nebula dust gathers and rotates and around that clump, and you've got a moon. However, The Earth's moon is believed to have formed when a planetoid struck the Earth, ejecting materiel both from it and the Earth, gathering into a ball. Well, I guess you could say they're both made from nebula dust. Well that's our present theory anyway, but it may have a few bugs. For example, if stars are formed from nebula dust, there wouldn't be that much nebula in the galaxy at any one time, so perhaps some of it was made from galactic dust. Well, I con't really give much of an exact answer here. Hope this helps. ~AH1(TCU) 20:40, 17 October 2007 (UTC)[reply]
Pulling wire and the 4th dimension
In a house, if you connect 2 electrical boxes together, you can't hang the wire through the air, but you have to pull through the walls. So if I have 2 boxes that are 10m away, I could be dealing with 1, 2, or 3 dimensions.
A:
I have 1 wall and 1 dimension.
I have to make perpendicular turns in 0 nonparallel planes.
I use a maximum of sqrt1*10m = 10m of wire.
B:
I have 2 walls and 2 dimensions.
I have to make perpendicular turns in 1 (nonparallel) plane.
I use a maximum of sqrt2*10m = 14.1m of wire.
C:
I have 3 planes and 3 dimensions.
I have to make perpendicular turns in 2 nonparallel planes.
I use a maximum of sqrt3*10m = 17.1m of wire.
E:
I have 4 planes and 4 dimensions.
I have to make perpendicular turns in 3 nonparallel planes.
I use a maximum of sqrt4*10m= 20m of wire.
But in 4 dimensions, it appears I can end up exactly where I started, although I have to take the time to whip through the 3 planes. Is this correct; does it show that the 4th dimension is time? HYENASTE 23:31, 15 October 2007 (UTC)[reply]
In 4 dimensions you are right, you could run the cable there and back. I don't think this has anything to do with time though! just that sqrt(4) = 2.
This certainly doesn't prove anything special about 4 dimensions. It's just a numerical coincidence. Do the same thought experiment while thinking about the amount of 2D wallpaper you need to cover all of the walls and ceilings - you'll get a completely different set of coincidences. SteveBaker 01:36, 16 October 2007 (UTC)[reply]
Sadly, I am very confused by the question. Edison 04:57, 16 October 2007 (UTC)[reply]
Simply put - in four dimensions you don't end up were you started - if you start at (0,0,0,0) you end up at (10,10,10,10) - because dimensions are orthogonal ie at right angles (the fourth dimension the same) - you don't end up doubling back on yourself..87.102.12.235 13:15, 16 October 2007 (UTC)[reply]
October 16
Why lengthwise instead of widthwise
But even before the A380 takes to the skies on a commercial basis, Airbus chief operating officer John Leahy is talking of stretching the giant lengthways.
My question is why do they want to stretch it lengthwise instead of widthwise. There is a limit of how long you can stretch it lengthwise but no limit on widthwise. 202.168.50.40 00:26, 16 October 2007 (UTC)[reply]
There will be many issues, sich as facilities designed for the planes, such as how wide is the runway, the gate space for the plane. A fatter shape will have more air resistance, more so than a longer one, after all an arrow is long and thin. Graeme Bartlett 00:45, 16 October 2007 (UTC)[reply]
In terms of redesign, longer is less effort too - just stick in another section identical to the ones you used before. If you make it wider, the wings have to be further apart - the entire cockpit shape changes - the center fuel tank design would change, tha flare down to the tail would block more airflow over the tailplane. There would be issues with how food service could reach through to the new rows of seats...it would be a 'start from scratch' kind of a thing from an engineering perspective. Making it longer is very little engineering effort by comparison. SteveBaker 01:29, 16 October 2007 (UTC)[reply]
Indeed. Lengthwise stretching (for ships as well as aircraft) is simple from an engineering perspective - just keep building the hull a little while longer than normal - but widthwise stretching requires new design, new stesting, new machinery... Shimgray | talk | 17:31, 17 October 2007 (UTC)[reply]
...and now I've got the picture of a Limousine stuck in my head... by this one is stretched the other way. It seems like a good example, though. Lengthened vehicles work, but I couldn't fit a double-wide vehicle down my driveway, let alone in my garage. --Mdwyer 02:18, 18 October 2007 (UTC)[reply]
Body mass index
Where can I find a correlation between BMI, age and death? In other words do people who have a lower BMI live longer and if so how much longer per lower BMI? Clem 02:18, 16 October 2007 (UTC)[reply]
Is it the case that, sadly, fat people die young? Edison —Preceding comment was added at 04:55, 16 October 2007 (UTC)[reply]
Indeed, haven't you heard the famous saying: "Live Fat, Die Young"...(and leave a good-looking, albeit rather heavy, corpse?) Facts and figures from other studies can be found here, damningly, one study quoted found "the risk of mortality increased with increasing BMI at all ages and for all categories of death." Rockpocket 06:55, 16 October 2007 (UTC)[reply]
Is homosexuality a STD
Is homosexuality a sexually transmitted disease? Let me explain what I meant. Assume that there is a unknown STD. Let's called it H. Let assume that people with H shows no symptoms.
Now suppose, a woman contracted H from another person. Then the woman became pregnant. Because of the disease H, the fetus is "deprived" of certain chemicals. When the baby is born, the baby becomes a homosexual person.
So scientifically, how should a scientist prove or disproves this assertion?202.168.50.40 05:29, 16 October 2007 (UTC)[reply]
I'm no scientist, but I'd say homosexuality - and heterosexuality, for that matter - are STDs only in the same way that life itself is an STD. Homosexuality isn't a disease at all, ergo it isn't an STD. -- JackofOz 05:40, 16 October 2007 (UTC)[reply]
Well hypothetically, a scientist with such an hypothesis could test several things:
Are mothers that had many sexual partners more likely to have homosexual children?
Are mothers that had one homosexual child more likely to have additional homosexual children?
Since the prevelance of H would presumably vary across different populations, one could look for large variations in homosexuality across populations, especially for isolated populations. (Though this could be hard to distinguish from cultural variations.)
Look for physiological indicators in mother or child that are associated with homosexuality.
For the record, I think it is quite unlikely that homosexuality is a disease. Dragons flight 05:53, 16 October 2007 (UTC)[reply]
I am a scientist and your hypothesis doesn't make a much sense. If that were the case, then twins would always be gay or straight, but never one of each. Moreover, parents who had just one sexual partner would never (or rarely) have gay children. It is possible, I suppose, that some form of STD could result in a uterine environment that, in turn, increased the probability one's child is homosexual, but even that would be tractable by statistical analysis. Sexuality, like most aspects of human behaviour, will not be wholely explained by such simple hypotheses. Its clear that a complex interaction of genes and environment (probably both uterine and post partum) are responsible for defining our sexuality. Rockpocket 06:13, 16 October 2007 (UTC)[reply]
(edit conflict) Isn't this a matter of definition, and attitude, rather than scientific discovery or statistical analysis? Homosexuality used to be technically classified as a disease in DSM4; nowadays it's not. The only thing that changed was the attitude of the scientific/psychiatric/medical community to homosexuality and to gay people. Which is why psychiatrists etc who claim to be able to "cure the disease" are in some jurisdictions at risk of being disbarred on the grounds of professional malpractice. -- JackofOz 06:22, 16 October 2007 (UTC)[reply]
Incidentally, by the same rationale, its equally likely (i.e. not very) that heterosexual children could be the result of an STD. Homosexual children may be the minority among us, born unaffected by the disease... Rockpocket 06:47, 16 October 2007 (UTC)[reply]
Life is a sexually transmitted disease. Cyta 06:57, 16 October 2007 (UTC)[reply]
With a 100% mortality rate. Cyta 06:58, 16 October 2007 (UTC)[reply]
Hmm .. I think I already made that point. :) -- JackofOz 07:24, 16 October 2007 (UTC)[reply]
Shamelessly cut and paste from the web:
First: If one twin is gay, what's the likelihood of the other being gay?
Well, the most widely used numbers are cited from a 1991 study by Northwestern University psychologist Michael Bailey and psychiatrist Richard Pillard of Boston University School of Medicine in which identical and fraternal twins were studied. At least one twin in each pair was gay. The study found that 52 percent of the identical twins were both gay as opposed to only 22 percent for fraternal twins. In other words, there is a 52 percent chance that if one identical twin is gay, both are; and a 22 percent chance both fraternal twins are gay if one is gay.
so if STD H is the cause of homosexuality then we would expect both twins to be gay all the time211.28.130.81 08:36, 16 October 2007 (UTC)[reply]
How many people were investigated in this study. I'd be happy to say that 52% of the identical twins would have the same sexual preference, but if the test subject population is small, drawing any conclusion as to what that preference is would be dangerous. Also, how was homosexual defined by the researchers? - Mgm|(talk) 09:22, 16 October 2007 (UTC)[reply]
"we would expect both twins to be gay all the time" <-- Why? For many genetically-influenced traits there is low penetrance and for many infectious agents there is low infectivity and variability in the course of the infection. --JWSchmidt 14:05, 16 October 2007 (UTC)[reply]
Because the OP made the claim that this hypothetical STD would cause homosexuality due to a change in the womb environment. Your suggestion (which is more likely) would be a situation where a STD would increase the probability of having a homosexual child. The difference is key, I think, in attributing "cause" to the development of such characteristics. Rockpocket 16:55, 16 October 2007 (UTC)[reply]
photon momentum and mirror .
A mirror is a device that change the momentum of incident photons; but it's own momentum remain unchanged , how is this possible ? —Preceding unsigned comment added by Shamiul (talk • contribs) 06:07, 16 October 2007 (UTC)[reply]
False assumption. Momentum is conserved, and the mirror's momentum must change (or at least transfer that impulse to another body), but the magnitude of this change is generally imperceptibly small, just as the momentum of photons is nearly imperceptible in most situations. Dragons flight 06:17, 16 October 2007 (UTC)[reply]
How non-charged particles are accelerated in particle accelerator .
Charged particles like electron,proton may be accelerated using voltage difference . How non-charged particles like neutrinos or neutron are accelerated in particle accelerator ? —Preceding unsigned comment added by Shamiul (talk • contribs) 06:49, 16 October 2007 (UTC)[reply]
They are normally not accelerated. They come from something that already has a source of energy, they may be decay products of an accelerated charged particle, or taken from a nuclear reactor where they are already emitted with some energy, and you just select those in a particular direction. This is tricky, hence why particle accelerators use charged particles. Neutron/neutrin experiments are not normally considered particle accelerators. Maybe see Neutron source and Neutrino#Neutrino_sources. Cyta 07:03, 16 October 2007 (UTC)[reply]
An analogy for the fuel cell?
Having read and re-read the entry on the Fuel cell and studied the diagram, I'm still searching for a way to explain - using a widely understandable analogy - how a hydrogen fuel cell works (in a hydrogen car, for example). I need to reduce its function to an explanation that doesn't feature a set of terms that would also require explanation, such as anode, cathode etc. Naturally this is for a lay audience. My problem is that I don't have a background in science and really am only learning about much of this myself.
Any suggestions? Wolfgangus 08:04, 16 October 2007 (UTC)[reply]
http://simple.wikipedia.org/wiki/Hydrogen says "A fuel cell combines Hydrogen thru a catalyst with an Oxygen molecule releasing an electron as electricity." And http://simple.wikipedia.org/wiki/Catalyst says "A catalyst is something that makes a chemical reaction go faster." But I suppose you want more than that. Alas there is no fuel cell article there - hopefully, answers here will lead to one. DirkvdM 08:17, 16 October 2007 (UTC)[reply]
Wow, I didn't know that wiki existed. It's like wikipedia for idiots. 64.236.121.129 13:10, 16 October 2007 (UTC)[reply]
Alright, here's an attempt.
Water is a molecule that consists of one oxygen atom and two hydrogen atoms. It takes energy to split the two and when they are recombined energy is released. A fuel cell does the latter. Hydrogen (the energy source) and oxygen (which can come in the form of plain air) are fed into it, separated by a membrane that will only let positively charged hydrogen (H+) through to the oxygen (O). At the hydrogen side, a platinum plate helps the electrons of the hydrogen atoms to split off. The now positively charged hydrogen atoms pass through the membrane, while the electrons enter an electric circuit. This produces the electricity required. At the other end of the electrical circuit, it connects to the oxygen side, where the electrons then combine with the positively charged hydrogen and the oxygen to form water (which then comes out the exhaust pipe). These three (H+, O and electrons) 'want' to combine and thus 'pull' the electrons through the electric circuit, thus creating the desired energy.
I'm not sure if that is all strictly correct - I just now learned the workings of a fuel cell through the diagram. But I think it's roughly correct. Is this more like what you were looking for? DirkvdM 08:35, 16 October 2007 (UTC)[reply]
Oh, sorry, you were asking for an analogy. I should read questions a bit more carefully in the future. DirkvdM 08:41, 16 October 2007 (UTC)[reply]
Actually, DirkvdM, while yes, I was seeking an analogy, I might be able to make one from your explanation - specifically from your word choice, "want". That word might give the process just enough character for me to build on. So I do appreciate your help. Wolfgangus 15:12, 16 October 2007 (UTC)[reply]
I don't think there is a suitable analogy - however the hydrogen/oxygen fuel cell is electrolysis of water in reverse - (which is a school topic) - you should be able to find lots of resources on electrolysis of water.. explain that.. then say "the fuel cell instead of using H20 and energy to make O and H uses O and H to make H2O and energy !" ...87.102.12.235 15:43, 16 October 2007 (UTC)[reply]
Beta decay .
Beta decay is a phenomenon where a neutron in an unstable atomic nucleus is converted to proton releasing energy(gamma ray) . After beta-decay process is completed the atomic neuclious contain one more proton which should make the atomic nucleus more unstable because protons in an atom repeal each-other , but neutrons in a nucleus do not repeal each-other . So is'nt a neuclious much stable before beta-decay rather than after beta-decay . Please supply me detailed explanation of this confusing topic ; you are wellcome to write down interactive and interesting web address containing this topic . Thank you all . —Preceding unsigned comment added by Shamiul (talk • contribs) 08:55, 16 October 2007 (UTC)[reply]
I'm not an expert, but I'll try to give you some info. Have a look at the nuclear force which is a force acting at the subatomic level which binds neutrons and protons. From that article "At short distances, the nuclear force is stronger than the Coulomb force; it can overcome the Coulomb repulsion of protons inside the nucleus." Nucleons have energy levels within the nucleus which can be approximately predicted using the Shell model. Just as atoms favor certain electron orbital configurations, nuclei favor certain "nuclear" orbital configurations. Adding a proton might stabilize a nucleus by filling up a "nuclear orbital." You might also be interested in magic numbers, certain numbers of protons an neutrons that tend to stabilize a nucleus greatly. Sifakatalk 04:20, 17 October 2007 (UTC)[reply]
TV animals
Have there been studies on the influence on animal behaviour of watching TV (apes, cats dogs,.)? When offered the opportunity, are apes interested in TV at all? Keria 09:12, 16 October 2007 (UTC)[reply]
I've seen many reports of non-human apes watching TV, for example Hiasl. Some dogs and cats can notice things on TV, but not all. A published study with chimps. --JWSchmidt 14:29, 16 October 2007 (UTC)[reply]
I did an externship at a pharmaceutical lab when I was in school, and part of the required "enrichment time" for the macaques was TV time. The monkeys seemed to have a preference for cartoons, and they would all sit at the front of their cages watching. The only thing that fascinated them more was the occasional escape. --Joelmills 14:55, 16 October 2007 (UTC)[reply]
You didn't let them watch MacGuyver, did you?! --Mdwyer 20:30, 16 October 2007 (UTC)[reply]
My dogs certainly notice things on TV. But it's never the pictures - firstly, their eyesight isn't that good - and secondly there is a strong possibility that the colours of TV don't look right to dogs (who can see some colour - contrary to urban legend). They definitely hear the sounds of other dogs though - and they'll sometimes prick up their ears and turn to look in that direction when they hear dog barks or (especially) the whining of a dog or puppy in distress. If I play a home movie, they'll prick up their ears and get VERY excited if they hear voices they recognise or each other's barks coming from the TV.
However, the lack of appropriate smell cues coming from the TV seems to tell them that this is just some weird irrelevence because they rapidly lose interest and ignore subsequent dog noises coming from the TV. Even the sound the TV produces doesn't have the high 'ultrasound' frequencies that dogs can hear (Dogs can hear up to 45kHz - a typical TV set only manages around 15kHz) - so it must sound severely muffled to them.
There is a pattern here. Dogs live in a world primarily perceived through smell, secondarily through sound and only lastly through sight. For them, TV's are pretty hopeless contraptions! No smell, really low quality audio and (possibly) very unrealistic colours. It's not surprising they aren't interested in watching. SteveBaker 22:14, 16 October 2007 (UTC)[reply]
Declining caffein
Someone told me that the content of caffein decreased if you left tea to brew for too long. Is there any truth in this? Keria 09:14, 16 October 2007 (UTC)[reply]
I think leaving tea to brew for too long would release more tannin which means a lower percentage would be caffein. I'm not sure if caffein degrades if left for too long. The molecule seems pretty sturdy. - Mgm|(talk) 09:19, 16 October 2007 (UTC)[reply]
If you leave it brewing too long, the tea tastes terrible. Which means you get less caffiene, as you won't drink it! -- Kesh 23:43, 16 October 2007 (UTC)[reply]
Hydrogen sulfide oxidizing enzyme
Which human enzyme catalyzes the oxidation of hydrogen sulfide (the Wikipedia article says that there are enzymes doing that)? I cannot find it at OMIM. Icek 09:54, 16 October 2007 (UTC)[reply]
I get PV=4/3 Ekinetic (or 3PV/4=Ekinetic) , but the ideal gas page gives the internal energy as 3PV/2.
1.Is PV=4/3 Ekinetic correct
2.If so what's the the extra 3PV/4 in the internal energy of a monatomic gas ( 3PV/2Internal-3PV/4kinetic = 3PV/4extra )
3.If (1.) is wrong - Help!87.102.12.235 13:23, 16 October 2007 (UTC)
[reply]
Let's just say I spotted my mistake - to those that would have helped - a speculative thanks
And a rhetorical 'You are welcome' to you too. (Actually I couldn't have helped, but lets ignore that fact :P ) Lanfear's Bane 13:47, 16 October 2007 (UTC)[reply]
Effect of human population growth on global warming
Hi all,
I have been to the climate change and global warming section of wiki. I didn't see anything about the effect of human population growth on global warming. E.g. more humans = more humans breathing out CO2 = increase in one of the greenhouse gases. Is this contribution by humans so insignificant that it does not warrant a mention?
Also, what about the effect of billions of 36.6 oC people on this planet? Surely all those lovely warm bodies exuding heat should heat up the air around us over time?
Can anyone justify why this is so... or add something regarding this on one of these pages? I have looked on the internet and the only reference I found was way too full of jargon for me to make head or tail of it.
Maybe the amount of carbon dioxide a person breathes out is negligable compared to the amount of carbon dioxide pumped out by transport and powerstations and animal farms to supply the "needs" of that same person. I personally agree that increasing human population increases global warming, but this comes mostly from the actions/consumption of that person, more than their breathing/body heat. --SeansPotato Business 14:20, 16 October 2007 (UTC)[reply]
Exactly. Expired CO2 through respiration or body heat is nothing compared to the amount of greenhouse gases or heat produced for energy and food purposes. --24.147.86.187 16:31, 16 October 2007 (UTC)[reply]
As Sean says, it is the knock-on effects of a growing population that significantly influences global warming, rather than the people themselves. For example, more people need more space to live, leading to deforestation. Also, more people need more food. More food mean more crops and livestock. Have a read of Livestock's Long Shadow to understand the effect of that on global warming. Rockpocket 16:47, 16 October 2007 (UTC)[reply]
Living creatures have no net effect on the amount of CO2 in the atmosphere. For every molecule of CO2 breathed out by a human or other animal, there is a food plant somewhere that will take that molecule and turn it into sugar and oxygen. --Carnildo 21:41, 16 October 2007 (UTC)[reply]
Sorry - but all of the previous respondants (except Carnildo who beat me to it with an edit conflict) have utterly missed the point. (They aren't wrong - they just missed the crucial thing!)
The CO2 you breathe out comes from the breakdown of carbon compounds in your body. The carbon in your body came from the food you've been eating. The carbon in the food either came from a plant - or from the meat or milk or eggs of something that ate a plant (or something that ate something that ate....a plant). So all of that carbon basically came from plants. How did the plant get the carbon? Well, it absorbed it as CO2 through its leaves and used photosynthesis to turn it into sugars and starches. So - in the grand scheme of things, humans (and all other animals) are 'carbon-neutral'. By eating big plants and replacing them with little ones - we're effectively removing CO2 from the air - then cycling it through this big chemistry set and pushing the exact same amount of CO2 out again. Every single microgram of CO2 that every single human produces was fairly recently sucked out of the air by a plant somewhere. The more of us there are, the more plants we eat - the more small plants are growing into big plants and consuming CO2. Everything balances (well...almost...see the bit at the end).
The difference with cars and coal fired power stations and other problematic things is that we fuel them by digging up coal and oil that's been locked away for millions of years. Since the coal and oil isn't being replaced at anything like the rate we're digging it up, we're putting CO2 into the atmosphere WITHOUT locking a corresponding amount away again. A wood-burning power plant - based on renewable/sustainable forestry techniques - or a car that ran on ethanol made from saw-grass that could be grown sustainably - would be no problem at all for global warming.
There is a teeny-tiny caveat that messes up an otherwise beautiful picture. There is no nice way to say this...the problem is: farting. The deal is that some of the carbon we ingest turns into methane - which we fart out. Methane is a much nastier greenhouse gas than CO2. So a very, very tiny percentage of the CO2 that we (indirectly) consume gets turned into a nastier form than CO2 by the time we're done with it. Having said that, there is little or no evidence that the tiny amounts involved are in any way a problem for the planet. However, one big concern for global warming is our farming of cows. Cows fart a LOT more than we do - and we humans have dramatically increased the number of cows in the world. Cow farts are a serious part of global warming - and there are (believe it or not) bunches of scientists out there wondering whether we can genetically engineer cows that don't fart as much - and a bunch of technologists wondering whether we can capture the methane that cows produce and use it to generate electricity - and in the process, turn it back into CO2 so that the grand cycle of CO2-plant-cow-fart-methane-CO2 can be completed.
Indeed, Steve. You will notice I previously mentioned the effect of livestock on global warming and, hence, did not "utterly miss the point". Rockpocket 01:16, 17 October 2007 (UTC)[reply]
The critical point you missed (and to directly answer the OP's question) was to explaining that the human metabolism is carbon-neutral. SteveBaker 14:33, 17 October 2007 (UTC)[reply]
The question reminds me of the one that goes something like, "How much lighter would the Earth be if humans hadn`t evolved?" lol Dave 64.230.233.222 02:04, 17 October 2007 (UTC)[reply]
The problem isn't that the scenarios aren't plausible, the problem is that they are very difficult to quantify. The carbon cycle is dominated by forces much larger than anthropogenic contributions so the effect of man on CO2 is a very small forcing function that acts over decades. Since 1750 the net effect of all the oil we burned and methane we've releases is 1.6 Watts/square metere (IPCC) being retained on the surface. This is slightly more than the 1.3 W/square metre variation in the 11 year sunspot cycle and a small fraction of the 1366 W/sq metre from the sun. Sunspots and global warming are not related, but the order of magnitude is good for comparison of the type of measurement we are trying to make. It is very difficult to extract a forcing effect from such a small effect and predict it's long term behaviour with accuracy especially when our accurate temperature record is so short compared to the multitude of natural cycles of varying duration. We also don't really know how components of the carbon cycle will react to man-made CO2 entering the system with rising temperatures. The ocean and rain forest are complicated and dynamic systems. --DHeyward 07:08, 17 October 2007 (UTC)[reply]
Well, one effect is that CO2 is absorbed by the oceans. As a result they become acidic. Notice that this is not future tense - the oceans have already absorbed a large part of the CO2. If they hadn't, the global warming would have been considerably bigger. So so far they've been buying us some time. But they can only absorb a certain amount of CO2, one factor for which is the temperature. So, as the oceans warm up, they can not hold as much CO2 (I think - not entirely sure if I remember this correctly). So somewhere in the future (some of) that CO2 will get released again. So even if we would completely stop pouring still more CO2 into the atmosphere, the concentration is likely to still increase. DirkvdM 06:19, 18 October 2007 (UTC)[reply]
Really, really good ones. A metal is a metal is a metal, super is just an adjective. The only references I can find to supermetals (all one word) are proper nouns (company names), in reference to music (super metal), ficticious (Lodestar) or hyperbole (this cheese-fibre biscuit-reinforced steel is supermetal!). Lanfear's Bane 15:00, 16 October 2007 (UTC)[reply]
Supermetals usually refer to metals that excel in one or more particular properties. I've usually heard "superalloys" in the context of the metals from which gas turbine and jet engine turbine blades are fabricated.
For a gas (in a piston or something) (ideal monatomic) - at constant temperature - in contact with an infinite resovoir at the same temperature..
If I compress the gas slowly to half it's volume so that it is able to equilibriate with the resevoir then then work done is
(1.) Work(gas) = PVln2 (please comment if wrong)
(P=Pressure, V=Volume, N=number of molecules/atoms , n=number of moles)
And the entropy change (of the gas in the piston) is
(2.) ΔS = -Nk ln2 (since the volume has halved and assuming the number of ways to arrange the gas molecules is proportional to VN therfor Waysafter / Waysbefore = (V/2)N/VN = 0.5N and ΔS =k ln Waysafter/Waysbefore = k ln 0.5N = kN ln 0.5 = -Nk ln2
(please comment if wrong)
(The entropy change of the resevoir will be infinitely increase - since it is of infinte size and gets some energy)
Assuming I got 1. and 2. right
TΔSpiston = NkT ln2
and N=Ln (L=avogadros constant and n=moles) so
TΔSpiston= nLkT ln2
and kT=R (the gas constant)
TΔSpiston= nLkT ln2 = nRT ln2
I also have Work(gas) = PVln2 (from 1.)
Which means that the TΔS of the piston gas is equivalent to the work that was done - my question is is this supposed to be significant? or is it coincicidence - or is it a definition (in part) of boltzmann entropy?87.102.12.235 14:28, 16 October 2007 (UTC)[reply]
Generically, for a reversible isothermal processes, heat flow (Q) = work (W) = TΔS. Dragons flight 22:32, 16 October 2007 (UTC)[reply]
The problem is that I get ΔS = ΔEk ln N for the entropy change of a ideal gas increasing in energy by ΔE (with N atoms) - using S=k ln W2/W1 - but this doesn't fit as well with the ΔE=-TΔS formulation - how can I go about reconsiling these two?87.102.12.235 14:38, 16 October 2007 (UTC)[reply]
I don't understand what you are trying to say here. Dragons flight 22:32, 16 October 2007 (UTC)[reply]
Probably not clear - what I'm asking is more obvious in a question below - I'm trying to use theorectical statistical entropies (ie from non experimental mathematical models) in the thermodynamic definition of entropy - one of the pages states that the two have been shown to be equivalent (using boltzmanns relationship S=k ln W) - but when I try this I only get equivalence on certain cases.. The example of changing the volume of a ideal gas (at constant T) works well. But other cases such as the when the temperature change show no match at all... The equation "ΔS = ΔEk ln N" was statistically obtained - I've clarified my question below relating to the integral STdT and whether or not it makes sense to use it..87.102.12.215 14:08, 17 October 2007 (UTC)[reply]
require information on CoMFA (Comparative Molecular Field Analysis)
please send the information about CoMFA —Preceding unsigned comment added by Satyaprasad2007 (talk • contribs) 15:18, 16 October 2007 (UTC)[reply]
If I have two bodies A and B at two different temperatures Ta Tb that are isolated or insulated from everything else.. and then I join them so that they eventually attain the same temperature..
1.What 'measure of energy' should I be using for this process - is it G (gibbs energy)
and
2.What ways are known to calculated the entropy change for the temperature equilibriation process? (assume if you want that it's a very simple system if that help)?87.102.12.235 15:53, 16 October 2007 (UTC)[reply]
Can't you just measure the temperatures? Isn't temperature a measure of heat energy? You would just need to know their specific heat values? Don't worry, the real scientists will be with you in a short while :) --SeansPotato Business 16:15, 16 October 2007 (UTC)[reply]
What do you know about the system? Do you know the masses? What else? Or are you looking for some sort of general equation? (I struggle with thermodynamics, but I'm sure there'll be others...) Skittle 16:32, 16 October 2007 (UTC)[reply]
It's sort of irrelevent to the question but you can assume that the heat capacities are the same and there is the same amount of both... Couldn't you both have not answered? (smiles horribly...)87.102.12.235 17:08, 16 October 2007 (UTC)[reply]
I was trying to make sure your answer was sufficiently clear that it could be quickly, thoroughly answered by the first person who could, hopefully getting you your answer quicker. After all, you'd be annoyed if someone who could have answered gave you the answer to a different question to what you had intended, then went offline leaving you waiting hours longer than necessary. Skittle 21:03, 16 October 2007 (UTC)[reply]
Assuming no mechanical work is going to be done on the system, you would look at the internal energy, U and find the temperature T such that Ua(Ta) + Ub(Tb) = Ua(T) + Ub(T), where Ua and Ub are internal energy functions for A and B respectively. For simple gases, you often have things like U = 3/2*N*k*T where N is the number of particles, and k is Boltzmann's constant, but for arbitrary materials U can be a more complicated function.
The change in entropy calculation is discussed in Entropy (classical thermodynamics). In the simplest case, e.g. equal masses of the same material with constant heat capacity, C, then T = (Ta + Tb)/2 and
What about the common formula ΔG=ΔH-TΔS can I use that here in the form ΔG=ΔH-ʃSTdT ( ΔH=0 ? ) to calculate if ΔG is negative (and hence if the process occurs)
I was really thinking about a theoretical treatment so I'd be using a derived estimate for S (or maybe C) at a given temperature.87.102.12.235 18:29, 16 October 2007 (UTC)[reply]
Specifically if I have an equation for S at a given temperature is ΔG=ΔH-ʃSTdT workable (and if it is wrong please explain why.. thanks) 87.102.12.235 18:41, 16 October 2007 (UTC)[reply]
In the above example if T1=T2 then the entropy change is zero - but if the masses are initially separated (thermally) and then allowed to exchange energy (even though T remains the same) by removal of the thermal barrier this causes an increase in entropy (statistically - and possibly depending on your point of view..) (this can be considered like a sort of phase change - depending on your point of view) How does classius's definition of entropy deal with phase changes of the example I gave above in general?87.102.66.248 21:09, 16 October 2007 (UTC)[reply]
NOTE: I think I've resolved this - if I make atoms distinguishable but energy indistinguishable as particles then boltzmanns S=k lnW is ok - otherwise not. Anyway if anyone can answer my bolded question above I'd still appreciate it, and if anyoen can tell me more or help out I'd still appreciate that too.87.102.12.215 15:21, 17 October 2007 (UTC)[reply]
24 hr urine - checking that we got a full sample
Apparently from creatinine clearance, we can infer whether or not the full 24 hr urine was collected. You can take the concentration of creatine in the blood, the amount in the urine, and divide the amount by the concentration, to determine the GFR necessary to provide this amount in the urine, assuming 100% transfer from glomerulus to urine. Now sure, if you know for a fact that there is nothing wrong with the kidney, an apparently low GFR, could simply be due to a reduced amount of creatinine in urine, directly resulting from the patient not voiding into their container D:< but how is it possible to tell from this test alone, that it is infact, not due to an abnormally low GFR? This whole test seems kinda useless to me, if an actual low GFR could be written off as a failure to collect the full 24 hrs worth of urine. --SeansPotato Business 16:11, 16 October 2007 (UTC)[reply]
I haven't thought through this extensively, but it's commonly understood (at least at the hospital I'm training at) that 24-hour urine collections are fraught with errors, including the one you mention. In practice, GFR isn't measured using creatinine clearance; instead, the steady-state plasma concentration of creatinine (along with age, gender, etc.) is plugged into something like the MDRD equation (no page!?). Similar approximations are used in the measurement of urinary protein to avoid having to collect a 24-hour urine sample. In that case, a spot urine test is done and the ratio of urinary protein to urinary creatinine is taken to approximate urinary protein (in grams) per 24 hour period. The point is exactly what you've realized: the utility of the 24-hour urine sample in determining GFR (and other values) is waning. --David Iberri (talk) 21:02, 16 October 2007 (UTC)[reply]
Tongue
Is a healthy human tongue supposed to be completely smooth, or would you expect to find bumps towards the back of the tongue? If not, what do the bumps mean? 172.206.176.138 16:21, 16 October 2007 (UTC)[reply]
If you're asking for advice about your own health, you should be warned that there's a very good reason why we say "Do not ask for medical advice" (or used to, until we had to make it broader). Anyone with sufficient medical training to give you a good answer to this question will not do so, because they know it would be unethical and dangerous (for example, they can't see or feel what you mean by 'bumps', nor can they see your medical history or examine anything else about you). The only people who will attempt to give you an answer as to what the bumps mean will not be trained or qualified to do so, as well as having all the problems a doctor would have in this situation. So they will offer even worse advice than the doctor would have thought was dangerous and unethical! If this is about yourself, or someone you know, get to a real, physical doctor and show them what you mean :) That's the only way you'll get a reliable answer. Skittle 16:28, 16 October 2007 (UTC)[reply]
I'm a biology student and this is part of an assignment of mine. I've tried looking around the web, but as yet I've found nothing written in a level of English that I can understand and so Wikipedia now seems like my best option. 172.206.176.138 16:40, 16 October 2007 (UTC)[reply]
However, when the tongue is infected, (not a common occurence), the condition is called glossitis and is characterised by a smoother than normal tongue. Richard Avery 17:34, 16 October 2007 (UTC)[reply]
As purely anecdotal evidence, I have had bumps on the back of my tongue for as long as I can remember, in exactly the way described in circumvallate papillae. --24.147.86.187 18:02, 16 October 2007 (UTC)[reply]
Lack of oxygen and sleepiness
Today I had a meeting in a room with "bad air" (no circulation) and we all got very tired and sleepy. However, usual recommendations for a good night's sleep is that the sleeping room is well aired. Wouldn't it be easier for sleepless people to fall asleep in a room that is badly aired? Lova Falk 17:24, 16 October 2007 (UTC)[reply]
I imagine it would be easier to fall unconscious, but that doesn't necessarily mean restful sleep. You might get some enlightenment from the article on sleep apnea. --Mdwyer 20:28, 16 October 2007 (UTC)[reply]
Not to mention Carbon dioxide. It's unlikely to build up too quickly, but poor circulation can't help. -- Kesh 23:44, 16 October 2007 (UTC)[reply]
Technically I think it would be easier to fall asleep in a "badly aired" room. However, I think the point of the advice you cited is not to help people fall asleep, but to make sure nothing happens to them while they are sleeping. You can add a good amount of carbon monoxide to a room, go lay down, and you'll fall asleep within no time, but you also won't wake up. Mrdeath5493 04:41, 17 October 2007 (UTC)[reply]
As Kesh said, carbon dioxide is probably the key, but the general heating of the room and boredom probably provides the rest of the explanation. Next time, may I suggest buzzword bingo as a remedy? Or clandestinely edit Wikipedia...
:) Thanks! Lova Falk 11:31, 18 October 2007 (UTC)[reply]
LASIK
"LASIK" stands for "Laser-assisted in situ keratomileusis". Since they feel it neccessary to mention that the process is in situ, this implies that there is a process where they don't work on your eye in place -- that they pop the eyeball out, reshape the lens, and put it back in. What's this process? --67.185.172.158 18:59, 16 October 2007 (UTC)[reply]
Um, just because they point out that they are doing something doesn't mean that the converse exists. Especially when you are talking about a name that happens to make a cool-sounding acronym. In any case, see keratomileusis for discussions of how it was done before lasers. --24.147.86.187 19:44, 16 October 2007 (UTC)[reply]
medicine online
Is there any serious university in the US or UK offer medicine online? At least the first two years. —Preceding unsigned comment added by 88.0.101.106 (talk) 19:28, 16 October 2007 (UTC)[reply]
Not to my knowledge. What would be the purpose of providing two years of medical school online? Generally speaking, the medical profession is not keen on the idea of many people becoming only half-versed in medicine. Entering medical students are generally warned to not provide medical advice until after completing their degree. The patient experience gained in the clinical years (third and fourth years of a four-year M.D. degree) are crucial. Andrewjuren(talk) 22:03, 16 October 2007 (UTC)[reply]
A study in medicine is also pretty useless if you don't have any practical experience in a laboratory or with patients. - Mgm|(talk) 08:52, 17 October 2007 (UTC)[reply]
I just thought that I could do online the two years until the usmed step 1 and then go to the practical experience...Actually there are some 'schools' offering online programs, but they are clearly not serious. —Preceding unsigned comment added by 88.0.101.106 (talk) 12:18, 17 October 2007 (UTC)[reply]
How to minimise my exposure to halogens in my food and water?
I no longer wish to be subjected to forced halogenation by government agencies against my individual will. How can I remove all fluourine and chlorine compounds from my water supply and the iodine from my salt, leaving only the untainted product behind? —Preceding unsigned comment added by 62.136.234.82 (talk) 21:44, 16 October 2007 (UTC)[reply]
If you can, you could dig a well for your water, it'd probably be easier to just go to the source rather than try to remove fluorine and chlorine. You'll find that Kosher salt is iodine free. -- JSBillings 22:42, 16 October 2007 (UTC)[reply]
Buy your water from a difference source, or buy expensive filtering systems that can remove it. The former is probably cheaper than the latter, especially if you are only talking about drinking water. As for salt, simply don't purchase iodized salt—there are lots of non-iodized varieties out there (i.e. sea salt or kosher salt) and purchasing them is surely easier and less expensive than trying to remove the iodine from the salt. Note that I think being paranoid about these sorts of public health measures is a bit silly, but hey, it's your choice, right? --24.147.86.187 22:35, 16 October 2007 (UTC)[reply]
Nethertheless you needs chloride and iodine in your diet to survive. Don't try to reduce these to zero. Well water will almost certainly contain chloride, and some fluoride dissolved from the rocks. Graeme Bartlett 23:25, 16 October 2007 (UTC)[reply]
Don't worry, if he ever eats out of the house he'd bound to pick up enough. There's a futility to trying to remove things like iodized salt from your diet when almost all salt you consume outside the house is probably going to be iodized anyway. --24.147.86.187 01:02, 17 October 2007 (UTC)[reply]
Don't go near the seashore. There are a lot of aerosols that come off the water. There's bound to be iodine in them. And I would guess a few naturally produced chlorinated organics as well. Delmlsfan 02:44, 17 October 2007 (UTC)[reply]
Firstly, well water is highly fluorinated. Secondly, avoiding iodine is not a good idea. The reason iodine comes in salt is because long ago iodine deficiency was common; This caused public health issues such as goiters and cretinism. About removing chlorine... That doesn't make sense. Chlorine is one of two atoms that combine to make table salt. So if you buy Kosher salt to avoid iodine (which is stupid in and of itself) then you'll still be ingesting chloride from the salt. My thoughts: Judging by the content and tone of your question, I believe you have a niacin deficiency. Mrdeath5493 04:37, 17 October 2007 (UTC)[reply]
I think the poster was saying that they wanted food products without having any additives - I assume your description of a niacin defficiency was intended as a joke. Mostly though you were a little insulting - what vitamin deficiency to you attribute to that?87.102.12.215 14:24, 17 October 2007 (UTC)[reply]
In my experience, most table salt in the UK (which is where the OP appears to come from), is not iodized (some shops like Lidl sell iodized salt as default, but this is because it is the same salt they sell in Germany, where it has to be iodized). I would suspect that sea salt would contain significant amounts of iodine, as well as various other impurities (sewage, dead fish, etc) which are not present in the purified rock salt usually sold for table use. However, as the OP wishes to avoid chlorine compounds, then he will not be using any salt at all, and will die a slow and painful death as a result of electrolyte depletion. Water filters aren't that expenxive nowadays (I use one, because the water in Brighton tastes foul, and cannot be used to make a decent cup of tea). OP cold move to an area without fluoridated water if a filter would not be practicable. DuncanHill 12:37, 17 October 2007 (UTC)[reply]
In the US, restaurant salt is typically not iodized (because some people have mdeical iodine restrictions), and everywhere sea salt actually contains much less iodine than iodized table salt. Seafood has lots of iodine, but the salt doesn't. --Tardis 19:58, 17 October 2007 (UTC)[reply]
Radio Transmissions and Camera Transmissions
This question relates to the other question previously posted. Is it difficult to get a closed circuit camera signals if it were in a cave or sewer or underground? Would there be a way to boost those signals or does the ground and other interferences cut off the signal? —Preceding unsigned comment added by 67.121.107.157 (talk) 21:49, 16 October 2007 (UTC)[reply]
The closed-circuit television system itself is irrelevant to the question. If you have a wire-based transmission (which is the case for most CCTV installations), then the environment is of little consequence. If wireless, then yes, transmission is impeded to various degrees. A more powerful transmitter and a higher-gain antenna are two means of boosting wireless reception. The broadcast frequency is also a significant factor. — Lomn 22:56, 16 October 2007 (UTC)[reply]
So, if it is wireless and you boost wireless reception and a more powerful transmitter and a higher gain antenna then it is possible to still get transmissions if it were underground and the receiving end was above ground or down in a sewer, there would still be a way to receive signals? —Preceding unsigned comment added by 67.121.107.157 (talk) 23:23, 16 October 2007 (UTC)[reply]
Maybe. There are too many variables to give a definitive answer (e.g. how deep, what material, what transmitter, what antenna...). For instance, FM radio tends to do fine through basic road tunnels and steep valleys and such whereas AM radio doesn't, with the only distinction being frequency. — Lomn 04:14, 17 October 2007 (UTC)[reply]
What makes FM car radio work better than AM in tunnels and such is not the frequency but the method of modulation. In AM, the whole carrier is modulated, and in FM, the carrier's frequency is modulated. This means that in AM the strength of the signal available to the audio amplifier in your radio falls off with the strength of the radio wave at the antenna and will get down into the noise pretty quickly. In FM, the audio is more or less encoded in a frequency shift, so that practically any signal at all at the antenna will deliver full audio. This is a simplified version of what really happens, to be sure, but close enough for jazz.
As for underground radio, it seems to me that it can't be done. The ground is, well, ground, and radio waves are produced with respect to ground. There is a ground wave that will run along the surface to an extent, more with lower frequencies, so that if you want to send and receive from inside a cave to a spot at the cave's entrance, you might get something by using a strong low-frequency transmitter at each end.
If you really want to go nuts with it, try ELF. --Milkbreath 13:00, 17 October 2007 (UTC)[reply]
Hornworms
Do Hornworms develop under water? —Preceding unsigned comment added by 75.44.152.111 (talk) 22:40, 16 October 2007 (UTC)[reply]
what happens when i add silver to a solution of potassium nitrate?
thanks —Preceding unsigned comment added by Karkaputto (talk • contribs) 00:54, 17 October 2007 (UTC)[reply]
The chunk of metal sinks to the bottom, because its density is much greater than the (presumably aqueous) KNO3 solution? Or is there something you didn't explain clearly here? DMacks 03:19, 17 October 2007 (UTC)[reply]
While silver nitrate is quite soluble, potassium is a much stronger reducing agent, and so won't be displaced the silver. In short, nothing. Someguy1221 03:27, 17 October 2007 (UTC)[reply]
I am certain that the nitrate will oxidize the silver (but with what results is my question), so that is a moot point--Karkaputto 03:52, 17 October 2007 (UTC)[reply]
Make the solution highly acidic and nitrate will dissolve the silver very happily. Someguy1221 04:05, 17 October 2007 (UTC)[reply]
unfortunately, that is not my situation--Karkaputto 13:55, 17 October 2007 (UTC)[reply]
You need a table of elctrode potentials for nitrate reductions (and adjust to neutral conditions) (Ag > Ag+ -.8V see Table_of_standard_electrode_potentials) then find reductions of nitrate that have potentials at a higher value (note if using standard elecrode potentials the value will be reduced since in your solution [H+] << 1 .Does any of that need more explaining?
However I guess that even if a reaction could occur - it will most likely be very slow (acid usually speeds things up) - most reductions of nitrate need H+ to proceed so if a reaction does occur the solution will become basic - further complicating things..87.102.123.108 19:42, 17 October 2007 (UTC)[reply]
The barrier for nitrate oxidizing is high because the only way to go is to nitrogen N2 and this is complicated. You need an relative high activation energy and this is not possible in reasonable time in water at room temperature--Stone 13:54, 17 October 2007 (UTC)[reply]
I cant think of a reaction between Silver and nitrate in the absence of acid, in the presence of acid silver will be oxidised by thee nitric acid formed.87.102.123.108 19:29, 17 October 2007 (UTC)[reply]
Light for plants
Can plants grow under normal light bulbs (household lights) or do they need to have sunlight? Hyper Girl 10:14, 17 October 2007 (UTC)[reply]
They only use certain frequencies (which couple energy best to the chlorophyll molecules), but they will grow under practically any source of light that we'd deem as "white"; it's just a question of efficiency -- sunlight is free while artificial light costs various amounts depending on its source.
Also, sunlight is immensely brighter than artificial light. We tend not to notice that because our vision system is easily able to adjust to the brightness or dimness of the lighting - but plants really do notice that because light is what "powers" them. However, it's certainly possible to grow plants in artificial lighting - people who engage in illicit Indoor Cannabis cultivation use massive amounts of halogen lighting (the article talks about 1000 Watt bulbs) to give the plants what they need. So a typical 40 Watt table lamp isn't going to cut it because the plant is only getting 4% of the energy it needs. (Our coverage of Cannabis (drug) cultivation techniques is truly alarmingly comprehensive! It's a real "How To" kind of a guide with lots of sub-pages and an entire WikiProject all of it's own!) SteveBaker 14:14, 17 October 2007 (UTC)[reply]
Cannibis cultivators are reputed to use metal halide lighting, not tungsten-halogen.
Actually the old (not warm white - but cool white) fluorescent tubes have sufficient colour temp (enough blue and red light) for some plants to survive. An incadescent bulb won't help much - not enough blue.. Hopefully someone will come along and tell us about plants that have evolved to survive in low light conditions ivy perhaps - anything with very dark leaves is a good sign..87.102.12.215 15:41, 17 October 2007 (UTC)[reply]
I guess the plants that live on rainforest floors (where very little sunlight filters through) would be a good choice. Lots of those are carniverous...and I presume there is a reason for that! SteveBaker 20:15, 17 October 2007 (UTC)[reply]
I thought being carnivorous (for a plant) was more to do with the lack of nutrients in the soil than the energy? Skittle 23:05, 17 October 2007 (UTC)[reply]
Carniverous plants tend to grow in nitrogen-poor environments and have their nitrogen fix delivered to them.
Note that indoor cannabis growing doesn't have to be illicit. I did some of that and of course researched it. Ed Rosenthal's excellent Marijuana Growers Handbook has some quite extensive info on this, but I can't find the book now (probably lent it out to some dopehead :) ). What I can tell you is that two 58 W Fluorescent lamps were enough for two good harvests per year (for a total of about 50 g, precisely enough to cover my 'needs'). This came from about four or five plants (per harvest) on half a square metre of soil. So about 50 W should be enough to let a plant grow. Note, though, that cannabis is a very tough plant and that the lamps were very strategically placed. They weren't used to light the room, so most of the light went to the plants. Also note that I did this because the only alternative I had was the windowsill, which puts to the northwest, so the plants only got some direct sunlight for a few hours in the evening (if any). The lamps did much better. Then again, I didn't put them in as much soil on the sill, so I don't know how big of a factor that was. Ok, the real reason for growing under lamps was that I couldn't look out into the street anymore. Was a shame for the tourists on the boats passing by going "Wow, look at that - marijuana growing in broad daylight." (note the pun). DirkvdM 06:56, 18 October 2007 (UTC)[reply]
I can't speak for cannibis growth, but I can assure you that some pretty mighty rubber trees and jade plants grow fine under 4x40W of "cool white" fluorescent lighting; I did that for years.
In reference to an earlier question about black contact lenses, can one die the color of their eyes? Would something like food coloring be harmful to put into the eye? Obviously pen ink might, but are there any alternatives? Thanks and bunch Picture of a cloud 10:19, 17 October 2007 (UTC)[reply]
My mother would tell you not to put anything in your eyes. She would also advise against putting things in your ears or up your nose. Don't run with scissors, either. --Milkbreath 10:57, 17 October 2007 (UTC)[reply]
Mums are always out to stop kids having fun. Mine (well my nanna - she brought me up) told me not to play with fire or throw stones at stuff too. Gawd, what else is there to do when you're that age and have no money? :) --Kurt Shaped Box 11:03, 17 October 2007 (UTC)[reply]
N.B. Nothing in your ears smaller than your elbow please.
Even if there was a dye that would stain the iris but not the lens, how would you get it in there? The coloured part is down underneath the cornea and is washed in the aqueous humor. Any kind of dye that you could inject in there would tend to dissolve in the aqueous humor - and that would really mess up your vision. The answer has got to be a big "No". SteveBaker 14:04, 17 October 2007 (UTC)[reply]
I'm reasonably sure that some sort of yellow die is used to test Intraocular pressure, but it apparently wears off pretty quickly. I've never come out of the doctor's office looking like a kidney patient... --Mdwyer 19:04, 17 October 2007 (UTC)[reply]
Some treatments for glaucoma, such as prostaglandin analogs, are known to change the eye colour in maybe 10% of patients. These combat glaucoma by increasing drainage of intraocular fluid, thereby lowering pressure. It was thought that prostaglandin acts on eye colour by mimicking a natural hormone that mediates melanin production. However recent research suggests that this hormone does not regulate uveal melanin after all, leaving the mechanism of action a bit of a mystery. Note, however, that this isn't a dye, but a bioactive compound. There are lots of dyes that will stain the eye, including indocyanine green, trypan blue, gentian violet, and methylene blue. However these are temporary, would severely disrupt your vision, and are mainly used for medical purposes during surgery. They are generally also non specific, so would leave you looking very weird for a time. Please don't put any substance in your eye - certainly not a dye - unless instructed to do so by a professional. It would, if you'll excuse the pun, end in tears. Rockpocket 00:31, 18 October 2007 (UTC)[reply]
Yes, that sounds familiar. A relative used to have a rabbit that had something wrong with its eyes - some sort of chronic condition. Every couple of weeks, the veterinarian would drip a yellow/orange dye into each of its eyes to see how it was getting on. It would come back with the whites of its eyes stained whatever colour the dye had been. IIRC (it was a long time ago now), it wore off fairly quickly. --Kurt Shaped Box 01:14, 18 October 2007 (UTC)[reply]
I've just been reading this thread over at the misc. desk and it reminded me of something that the local amateur wildlife rehabber once mentioned to me WRT gulls (the large ones, at least). Apparently, they have an *extraordinary* resistance to Botulinum toxin and can tolerate a dose that would kill a human with no apparent ill effects. Even the birds that do come down with botulism paralysis and end up with him are very often save-able (provided that the lungs are not affected), by simply keeping them warm and forcing them to drink enough fluids (his own formula) to flush the toxins out of their systems - then they just get right back up. Next time he gets one brought in, he's going to let me go round to watch the process and help out.
So, anyone have any more info on the mechanism by which gulls have managed to develop such a high tolerance to the bad stuff? I find this kind of thing absolutely fascinating. --Kurt Shaped Box 11:00, 17 October 2007 (UTC)[reply]
The mechanism by which they developed it is easy - evolution - gulls that had some kind of resistance to the nasty consequences of their ikky diets survived - those that didn't died. Hence they evolved. What mechanism they developed to do that...I have no clue. According to our article, Botulinum toxin blocks the release of acetylcholine from nerve endings thus arresting their function, and there is an anti-toxin that's "derived from Horses" (how?). Perhaps whatever this natural anti-toxin is - it's produced naturally by Horses...and perhaps also by Gulls? But I really don't know. Another possibility is that somehow the gull doesn't let the toxin reach it's important nerve endings. After all, humans don't get sick from Botox injections - and Botox is just a nice, sanitized shorthand for "BOtulism TOXin". SteveBaker 13:57, 17 October 2007 (UTC)[reply]
carbon resistor
1.How can i interpret a carbon resistor with 2 gold bands.plz give one example?Roar2lion 12:06, 17 October 2007 (UTC)
2.how can i interpret a resistor with 5 colour bands.which type is it of?Roar2lion 12:06, 17 October 2007 (UTC)[reply]
All your homework questions are answered in the article on resistors. Lanfear's Bane 12:17, 17 October 2007 (UTC)[reply]
(edit conflict) Here is a picture that explains color coding for resistors better than any words of mine could. If you still have questions after looking at that, please do ask here. --Milkbreath 12:26, 17 October 2007 (UTC)[reply]
In brief, remember that gold is used in two different contexts. It can be the "multiplier" (where it means x0.1) or it can mean the "tolerance" where it means 5%.
If you wanted the strongest material ( for building/construction material, armor, etc), what would you want maximized/minimized ideally? For example, ductility should be maximized, tensile strength should be maximized, brittleness should be minimized, melting point should be high, heat conduction should be low, etc. Those are some I can think of, what else? 64.236.121.129 13:20, 17 October 2007 (UTC)[reply]
It's not that simple - the properties you desire depend on what you are using it for. You need a totally different material for (say) the foundations of a bridge pier than you need for the cables holding up the roadway. One needs to be strong in compression - the other strong in tension. Since no material is good at both - you end up with two different sets of needs for two different applications. There are times when high stiffness is required - there are other times when flexibility is needed. I don't think there is a meaningful answer to your question. SteveBaker 13:43, 17 October 2007 (UTC)[reply]
Steel is perfectly happy in both tension and compression, it just doesn't tend to be the most economical material for carrying many compressive loads.
Hmm, I'm talking hypothetically. I'm not looking for any particular real world examples. Like for example, we use reinforced concrete in buildings because it has high compression strength, low heat conduction, among others. But if there was a material that possessed all those attributes while also having high tension strength, it would be even better.
So I'm talking hypothetically. You mention where high stiffness is needed, and other times flexibility (I'm assuming you mean ductility) is needed. But an ideal material would have a strong resistance to stress before deforming, but when it does deform, it is highly ductile. Ignore the fact that such materials don't exist. Ideally, what should be maximized/minimized. 64.236.121.129 14:36, 17 October 2007 (UTC)[reply]
I get that - the answer is - all the measures of strength should be maximise eg tensile strength, yield or breaking strength, compressive strength, and also toughness.. you'll also want high melting point and the effect of temperature on strength should be minimised. Intersetingly ductility isn't a measure of strength - a very ductile material would be very weak.87.102.12.215 14:47, 17 October 2007 (UTC)[reply]
Thank you, but I think you are mistaken on a ductile material being weak. Of course you want the material to maximize strength while subjected to stress, but all materials will be unable to hold up against stress at a certain point so at that point it has two options. It can either fracture, or it can deform. Ideally, you want it to deform rather than fracture. If it always fractures past its initial maximum holding strength, that means it's brittle, which is undesireable. A highly ductile material will undergo elastic and plastic deformation before it completely fractures. Ideally, a material should maximize all the strengths you mention, while also being high ductile.
Yes and no. a ductile material will deform though.. not good - that's why I prefer toughness as a measure rather than ductilty.87.102.123.108 17:34, 17 October 2007 (UTC)[reply]
ie a material could be tough, non ductile and non brittle..87.102.123.108 17:39, 17 October 2007 (UTC)[reply]
Plus if your material is starting to undego plastic deformation - it's broken - and you would need to go back to the drawing board as an engineer!87.102.123.108 17:43, 17 October 2007 (UTC)[reply]
I suppose you also want this hypothetical material to have minimal weight and minimal cost as well ? I imagine carbon fiber reinforced plastic is going to be a strong contender in all dimensions apart from cost - so if you constructed a whole building from it, it would be enormously expensive, as well as overengineered. For bulk use ECC might be a better choice. Gandalf61 16:07, 17 October 2007 (UTC)[reply]
There also are the articles Fracture_mechanics which may help you reverse engineer a perfect material87.102.123.108 17:48, 17 October 2007 (UTC)[reply]
But surely there are lots of conflicting goals. There are bound to be some applications for construction materials where rigidity is valued - and others where flexibility is key. You can't have both - so there can't be a single perfect construction material. To take an extreme example - suppose nanotechnology is someday able to deliver arbitarily large structures made of diamond for the same cost as lumps of coal. This is (virtually) the hardest material known to mankind - it would be cheap, life would be good...until someone wants to hang a shelf inside the building and no drill known to mankind can cut a hole in the darned stuff! So sometimes we WANT a hard material - sometimes that's the last thing we need. You'll always need a range of materials with different properties - so there can never be a single "best" - not even hypothetically. —Preceding unsigned comment added by SteveBaker (talk • contribs) 20:12, 17 October 2007 (UTC)[reply]
Except I wasn't asking for the "best". What is best, is subjective to what the task is. As for your first point, you CAN have something strong and ductile. There's nothing in physics that doesn't allow this. 64.236.121.129 13:30, 18 October 2007 (UTC)[reply]
Is it possible to kill someone with the technique above? --WonderFran 15:09, 17 October 2007 (UTC)[reply]
No, as Bill is dead and I doubt Beatrix or Pai Mei will teach you. Lanfear's Bane 15:20, 17 October 2007 (UTC)[reply]
Pai Mei is also dead, IIRC. Algebraist 15:49, 17 October 2007 (UTC)[reply]
A good point, my bad. Poisoned fish heads. Lanfear's Bane 15:58, 17 October 2007 (UTC)[reply]
Beatrix also gave up fighting to live with BB. It dies with her. —Preceding unsigned comment added by 128.101.53.151 (talk) 00:08, 18 October 2007 (UTC)[reply]
Use of human excrement as manure in farming
A farm near to where I live in Grafton, Wiltshire has just started to use Human excrement as a manure on two of it's crop fields. Is this a prevalent practice? Does it come from a sewage treatment plant and has it been processed in some way? Is there any difference between the use of human and animal excrement in manure and are there any chemical properties of human excrement that would make it an ideal growing aid? Nanonic 15:09, 17 October 2007 (UTC)[reply]
In my part of the world, it's common to spread the sludge that remains after sewage processing on agricultural fields, but it is not permitted to spread it on crops meant for human consumption. --Sean 17:08, 17 October 2007 (UTC)[reply]
I read (and therefore it's Original Research) of a family who spread human manure on their front lawn, only to find that tomatoes began growing there, as the seeds had not been filtered out of the manure. Corvus cornix 20:23, 17 October 2007 (UTC)[reply]
Hi. I heard that in some countries, they use human feces or urine (or both) in their crops. however, I've never heard of this being used in farming, as mass-production of human waste is ... eww. However, they might use it in their gardens where they are growing vegetables. As I am not so sure about this, I think you should check with someone else before you start putting human feces in your crops. If I remember correctly, urine contains ammonia, which could be used as an anti-acidizer, which also contains the element nitrogen, which is found in many fertilizers. Again, check with someone else before you actually start doing so. Hope this helps. ~AH1(TCU) 20:50, 17 October 2007 (UTC)[reply]
If you do this, be careful to keep any pets or livestock away. Human manure is more likely to contain diseases that can infect humans than animal manure is. --M@rēino 21:36, 17 October 2007 (UTC)[reply]
Manure generally wants to be composted before use anyway. --Sean 00:37, 18 October 2007 (UTC)[reply]
He isn't planning to do this - his neighbours are doing it.
Anyway, three thoughts on this. First, human excrement can carry and thus transmit human diseases (eg cholera spreads this way), so I suppose it would certainly need special treatment for that. The humanure article only briefly mentions this (the article could do with some expansion). Second, what happens to human excrement if it is not recycled like this? Does it all go through the sewers to the oceans, thus slowly depriving the land of nutrients and feeding mass cultures of algae or something in the oceans? Third, excrement is the leftover from food after the body has depleted it of all the stuff that that body needs. So wouldn't human excrement be very bad manure for human foodcrops? DirkvdM 07:15, 18 October 2007 (UTC)[reply]
Dirk, as to your third question -- there's two factors at work. First off, excrement is the leftover after the body depletes it of most, not all, of the stuff that the body needs. The better-fed the animal, the richer the manure -- I remember reading a fascinating piece a while back (sorry, can't remember the source) claiming that human excrement had become larger in the last century or so b/c we now eat more, and that in particular the protein content had gone way up. Second off, good manure supplies the nutrients that the plant needs. For inorganic material like minerals, that tends to be the same thing as what the human needs because life is very bad at making its own inorganic molecules, but both plants and animals are skilled at chemically converting most organic material into the molecules that they need. --M@rēino 14:00, 18 October 2007 (UTC)[reply]
Activation energy
When two particles collide, in order to react do they both need the actication energy or would it suffice for their combined or average energy to be greater than the activation energy, i.e. if one particle has an energy siginficantly greater than the activation energy and the other has an energy only just below the activation energy? asyndeton 15:29, 17 October 2007 (UTC)[reply]
Almost certainly the sum of both energies. (though sometimes the situation can be complex - requiring the 'atom' to be in a specific energy state to react - rather than just having Energy > x )87.102.12.215 15:37, 17 October 2007 (UTC)[reply]
Mobile phone on the moon
The earthward face of the moon is in line of sight of mobile phone transmitters. So would a phone work on the moon, or are the signals just way too small? -- SGBailey 15:39, 17 October 2007 (UTC)[reply]
Normaly they do not work in airplanes so the moon is simply a few miles too far. They also only collect and transmit horizontally!--Stone 15:51, 17 October 2007 (UTC)[reply]
I'd argue that, and agree with it. A GSM phone would NOT work on the moon due to limitations in Timing advance. A CDMA phone would probably not work on the moon due to the low power and antenna limitations. An analog phone might have the power, but the signal from the moon would engage EVERY cell tower it could see, which would just mangle the whole system. (THAT, incidently, it why you can't use a phone in an airplane. It has little to do with safety. Your phone is only licensed to be used on the ground.) Stone's comment about antenna is also apt -- most modern cell towers use antennas that put beams near the groun of the service area. Radio waves going up to space would be wasted, so they are damped. Finally, see EME (communications) to learn about proper ways to reach the moon with radio signals. --Mdwyer 17:30, 17 October 2007 (UTC)[reply]
Radio signals drop off in intensity with the square of the range. Your nearest cell tower is usually no more than about 15km away - the moon is 400,000km away - 27,000 times as far. So your cellphone signal would be 730 million times fainter than it would be at your longest distance here on earth. No...it's NOT going to work! SteveBaker 19:59, 17 October 2007 (UTC)[reply]
Follow-up question -- would an Iridium phone work, or are the satellites positioned to only detect earth-based signals? --M@rēino 21:41, 17 October 2007 (UTC)[reply]
Same problem - the Iridium satellites are in a very low orbit (just 780km) and there are lots of them - so you're still only going to be a thousand or perhaps two thousand kilometers away from the nearest one. At 400,000km, the moon is still 200 to 400 times as far away as the nearest satellite - which means that (because of that inverse square law problem) you need a transmitter that's 40,000 to 160,000 times more powerful than the one in your Iridium phone. (And of course the transmitter in the satellite would have to be similarly more powerful - and it's not!). There are probably lots and lots of other reasons why it wouldn't work - but signal strength alone is a killer problem - so we need look no further. SteveBaker 22:42, 17 October 2007 (UTC)[reply]
Again, take a look at EME (communications). It says that even with current technology, it takes 100 watts and large directional antennas to bounce off the moon. That assumes an out-and-back bounce, of course, but it certainly lends a lot to Steve's explanation. Also, the Iridium sats will have the same antenna-pattern problem as the ground-based stations, except with even tighter patterns. The satellite flare page suggests that the Iridium antennas are "door sized" -- and that just to reach 780km! --Mdwyer 02:12, 18 October 2007 (UTC)[reply]
Sacrificing mice
When the time comes, what methods are used to kill laboratory mice? --SeansPotato Business 16:09, 17 October 2007 (UTC)[reply]
The method doubtless varies depending on what you're hoping to analyze ex-post-mouso. You don't want the killing method to perturb the data (add stress hormones, etc.).
Atlant —Preceding comment was added at 16:42, 17 October 2007 (UTC)[reply]
Thoracic puncture, exsanguination, decapitation, cervical dislocation, CO2…lots of possibilities, which is important as Atlant notes, to avoid interfering with whatever you hope to study after dispatching them. See also [6]. DMacks 16:52, 17 October 2007 (UTC)[reply]
I once had a girlfriend who was a biochemist. When I visited her lab, she proudly showed me the guillotine they used for decapitating live mice. In some cases they used the CO2 method instead...it depended on what they wanted to measure. Urgh! SteveBaker 19:54, 17 October 2007 (UTC)[reply]
Just curious: How did that relationship end? Well, I take it? :) --Mdwyer 02:05, 18 October 2007 (UTC)[reply]
In some countries, the UK for example, the manner in which one kills mice is regulated by law, specifically Schedule 1 of the Animals (Scientific Procedures) Act 1986[7] . In other countries there is no legal restriction, though local IACUCs may restrict the use of some methods. Other methods include an overdose of anesthetic or, in the case of baby mice, decapitation with a pair of scissors. It can be quite disturbing decapitating newborns in that manner (especially when they keep crawling for a while after their head has been removed). Rockpocket 00:00, 18 October 2007 (UTC)[reply]
Other documented methods scientists have used include, "dissolving mice in acid, spinning them in centrifuges, blowing them up in vacuum chambers, and forcing them to navigate exit-free mazes" One scientist "Dr. Thomas Huber, author of the 1996 study Mouse Elasticity And Kinetic Rebound In High-Acceleration Collisions" found a novel method: "...when I have the time, I like to send them flying into walls." [8] (note to ALF, this is a parody and no mice were harmed in its creation) Rockpocket 00:11, 18 October 2007 (UTC)[reply]
Man - you can see why the animal rights campaigners freak out over things like this. I know that most of it is necessary - but it certainly sounds harsh when taken out of context and listed. Newspeek-like terms such as 'Sacrificing' and 'Homogenizer' probably don't help either... --Kurt Shaped Box 09:53, 18 October 2007 (UTC)[reply]
Heat-deactivated FCS and deliberate hypotonic lysis
We discussed an article about the involvement of C/EBPa in granulocyte differentiation. In the method, they used 10% heat-deactivated fetal calf serum; since I thought the whole idea behind FCS was that its growth factors can stimulate the growth of cells, what is the point in using heat-deactivated FCS?
They also say that "normal murine marrow cells were obtained from the femurs of mice after hypotonic lysis and enrichment for lineage-negative hematopoetic precursor cells using the standard StemSep protocol" - what is the purpose of the hypotonic lysis? Is this part of the enrichment process? Are certain cells perhaps more susceptible to hypotonic lysis than others? --SeansPotato Business 16:31, 17 October 2007 (UTC)[reply]
Most remotes have two Infrared LEDs to transmit the codes to the receiver on the controlled device. Why two instead of just one? —Preceding unsigned comment added by 160.42.234.85 (talk) 17:00, 17 October 2007 (UTC)[reply]
I can make a guess: Once would be the pattern. A single led throws a circular spot of light. Two of them would throw a wider oval of light, making it easier to aim. --Mdwyer 17:24, 17 October 2007 (UTC)[reply]
I don't think this is right - most I'm aware of only have one LED - see this image ..?87.102.123.108 17:29, 17 October 2007 (UTC)[reply]
Most only have one LED, but I have seen ones with multiple LEDs. Here's another theory: A universal remote might need to have two different LEDs to make two different wavelengths of IR light for different receivers. --Mdwyer 18:52, 17 October 2007 (UTC)[reply]
I googled this before posting the question here, and couldn't find anything explicitly answering the question, but I got the idea it might be for increased range because two would be brighter, but then why not just use a brighter one to begin with, so I dunno. —Preceding unsigned comment added by 160.42.234.85 (talk) 18:43, 17 October 2007 (UTC)[reply]
Mdwyer has it correct: better remote controls use two LEDs for the wider "throw pattern" that is produced. Alternatively, the two LEDs can each be focused more narrowly allowing greater range for the same "pattern width".
Most modern video cameras see far enough into the InfraRed to see the flashes from a TV remote in a darkened room. You could do an experiment to see what's going on. If they are indeed widening the throw pattern (which would certainly be my guess) - then you should be able to aim the thing off to one side of the camera and only see one of them flash when you push a button (use one of the 'continuous' functions like volume because they keep flashing as long as you hold the button down). Then if you aim directly at the camera, it should be possible to see both of them flashing together. (It might be that from off to the side, you see one brightly lit and the other very dimly lit...it's hard to predict) SteveBaker 19:51, 17 October 2007 (UTC)[reply]
Cell phone cameras work great for seeing infrared remotes. Sancho 22:26, 17 October 2007 (UTC)[reply]
Good advice, both of you! Also, Radio Shack used to sell a cute little "Infrared test strip" that could reveal infrared light and so could also be used to reveal the pattern of infrared light emitted by a remote control. It wasn't strictly a phosphor but instead had to be charged from visible light first; a little infrared than triggered the emission of the stored energy. I don't know the technical name for that effect (but would welcome it if someone else did!) but it was obviously a form of stimulated emission.
you know how you can see double for whatever reason (maybe a blunt trauma to the head). can the same thing happen with your two ears, to where they aren't coordinated and you hear one sound source as two? Why not?
Also, am I smart or what. Thank you. —Preceding unsigned comment added by 77.234.80.106 (talk) 17:57, 17 October 2007 (UTC)[reply]
Ignoring your second question for the moment, the eyes and ears aren't really comparable in this way. You see double because your eye muscles lose coordination, and are unable to correctly do Fixational eye movement. The eyes literally *are* seeing two different images. Problems with the ears usually don't show up as audio problems. They usually show up as balance problems. See Ménière's disease for an example. --Mdwyer 18:58, 17 October 2007 (UTC)[reply]
What about some condition that results in somebody hearing a single sound twice, in succession? Has something like this ever been reported? My first guess is that this might happen when taking certain drugs. Sancho 19:08, 17 October 2007 (UTC)[reply]
Nitrous oxide causes a flanging effect on inhalation. In my own personal experience, I would call it echoing. —Preceding unsigned comment added by Mdwyer (talk • contribs) 19:25, 17 October 2007 (UTC)[reply]
The problem is that your ears are on two sides of the head so what ends up happening is that if there's a problem with hearing, it ends up with the perception of the origin of the sound being incorrect. It would have to be a dramatic difference in processing times for the two ears to give a doubled signal. If it were caused by drugs, it would be something happening in the brain rather than a difference in signals from the ears. Donald Hosek 19:20, 17 October 2007 (UTC)[reply]
Yeah, I meant a doubled signal coming from one ear, not from any physical causes at the eardrum, but with the perception in the brain. Sancho 23:51, 17 October 2007 (UTC)[reply]
I don't think it can happen with your ears. With your eyes, you have to point each eye very precisely at the 'target' object so that the two images 'line up' - and your brain calculates the distance to the object by measuring the difference in the angle that the eyes are pointing when everything is properly lined up. When your eyes won't point where they are told to the very great precision needed (perhaps because the muscles are tired) - you see two images.
Your ears don't swivel (you may have noticed that) - you detect the direction the sound is coming from by the relative delay in the sound arriving at the two ears - plus some really complicated stuff to do with how the sound reverberates around inside your skull. There is no way for there to be a 'delay' between the two ears that's consistent with two nearly identical sounds coming from different directions. That's something that it's virtually impossible for us to pick out anyway - let alone by accident. Most hearing 'errors' come down to lack of accurate direction determination.
There was some interesting research done recently that shows that our noses also work in 'stereo' - just like our ears - to enable us to detect where smells are coming from. For the same reason, we don't get double-smelling problems either.
As to your second question, see IQ test. If you do find an answer please come back and tell us what you find out. :) --S.dedalus 23:36, 17 October 2007 (UTC)[reply]
All photos taken yesterday morning in South England. (Bonus points if you know what the plant is. I have no idea) Shimgray | talk | 18:09, 17 October 2007 (UTC)[reply]
The insects are on Ivy flowers, probably English Ivy, Hedera helix.--Eriastrum 21:29, 17 October 2007 (UTC)[reply]
Er, Shimgray, are you sure the third one is a bee? It looks like a fly to me, though I don't know what kind. Flies have only two wings, which is what it looks like in your photo. Hence the name for the order of flies, Diptera.--Eriastrum 21:37, 17 October 2007 (UTC)[reply]
This photo [9] is of a 'dark bee' too - you have to look pretty hard to see that second set of wings! They are a little more obvious in the side-view photo we have at European dark bee - but still - you've gotta agree they aren't exactly prominant. Worse still for the "Not a Bee" theory, the photos clearly orange fur and stripes on the thorax - and I don't think I ever saw a fly that looked like that. I wish we had a photo with a clearer view of the legs - pollen sacs would have clinched the deal. But I have to agree with Shimgray, it's a "European Dark Bee". SteveBaker 22:28, 17 October 2007 (UTC)[reply]
Eh, I think it is a bit ambiguous. The "fur" is not very distinct. There are a number of bee-flies that look very similar; the genus Exoprosopa in particular has a lot of very similar look candidates (lots of photos here). (Like this guy or this guy.) Anyway, if it is a bee, it doesn't look much like the European dark bee to me. --24.147.86.187 22:43, 17 October 2007 (UTC)[reply]
Shimgray, I think you are right on about the second photo. It does indeed look like a house fly--quite possibly good old Musca domestica.--Eriastrum 21:44, 17 October 2007 (UTC)[reply]
The third/fourth pictures are definitely not a bee. The angle of the resting wings are wrong, there is an absence of hair and the abdominal shape is not bee-like. This is a species of hover-fly, (English colloquial name) possibly Rhingia campestris, but it is always difficult to identify exactly from photos and there are many species of hover-flies. Most hover-flies used protective bee or wasp mimicry which naturally can cause some difficulty in initial identification. Very nice photograph. Richard Avery 09:10, 18 October 2007 (UTC)[reply]
An Interesting Event with a Credit Card
There was a lineup in the mall because someone's card didn't work on the machine. However, after the cashier wrapped it in plastic, it worked! (It was swiped with the plastic on!) Can someone tell me the science behind this? Is it something with electromagnetism? Thanks. --JDitto 18:36, 17 October 2007 (UTC)[reply]
I've seen that, too! The reader is using a magnetic tape head to read pulses off the card. The only thing I can think of is that the head is somehow out of alignment with the data track on the card. The plastic might change things just enough to get a good read. Another possibility is that the data on the card is recorded too 'loudly', and the plastic attenuates the signal enough for it to be read. The truth is, I have no idea. :) But I *have* seen it work! --Mdwyer 18:55, 17 October 2007 (UTC)[reply]
I can add a bit of data: the cashier who did that to one of my credit cards actually taped over the magnetic stripe with a piece of what you probably call Scotch tape if you live in North America or Sellotape if you live in England. The tape stayed on there until the card expired and never seemed to cause me any problems. --Anonymous, 23:33 UTC, October 17.
Funny that scotch is used in twoways in the US that are not used in England. Do I detect some animosity between the neighbouring countries? DirkvdM 07:33, 18 October 2007 (UTC)[reply]
What is the second way ? If you ask for a "Scotch" in an English pub you will get a Scotch whisky. The key point to remember is that the adjective "Scotch" should never be applied to people, who are always "Scottish". Gandalf61 10:06, 18 October 2007 (UTC)[reply]
According to [Dr Karl] (an Australian science presenter) the tape or plastic bag trick works because as credit cards get old or are damaged the magnetic strip can get "noisy", that is spurious data appears. The noise is "quieter" than the data, but the magnetic strip reader can see it and so the data is not clearly readable. If you add some space between the card and the reader, though, the quieter noise becomes unreadable, but the data remains readable. The tape or plastic bag add that space. --203.22.236.14 11:46, 18 October 2007 (UTC)[reply]
Steam Freezing?
I recently watched a steampunk sci-fi movie,(Memory isn't functioning...) and at a point in the film this machine started blowing steam
all over a city, the steam was creazing ice/extremely cold tempuratutes because the steam comes out so hot it sucks in all the cold air into itself and freezes, is this a factual phenomena or fiction? —Preceding unsigned comment added by 72.183.196.100 (talk) 20:39, 17 October 2007 (UTC)[reply]
Fiction. The second law of thermodynamics dictates that putting a hot object with a cold object will (with no external intervention) cause the two to equalize temperatures, not further differentiate. — Lomn 21:24, 17 October 2007 (UTC)[reply]
In case there's a misunderstanding, though, blowing steam over very cold surfaces can certainly cause it to freeze out as ice. It's not creating the cold temperature, however. — Lomn 21:26, 17 October 2007 (UTC)[reply]
Maybe the steam was not hot water, but evaporating dry ice? That could be quite cold indeed (sublimation of minus 78.5 °C), and it would look a lot like water steam. --M@rēino 21:45, 17 October 2007 (UTC)[reply]
To be terribly pedantic, the 'steam' caused by dry ice isn't the CO2 released from the dry ice. It is water vapor. The vapor is nowhere near as cold as the dry ice is. There are some other options, though -- liquid gasses are often terribly cold when they are boiling away. For example, liquid butane and flourocarbons found in air duster cans. --Mdwyer 02:02, 18 October 2007 (UTC)[reply]
If by chance the movie was Steamboy, which has great releases of steam freezing parts of London, then the reason, as I understand it, is that the sci-fi "steam ball" was under extreme pressure. Gas released from extreme pressure turns very cold, no? Pfly 07:30, 18 October 2007 (UTC)[reply]
Well, it certainly cools down. That's adiabatic expansion. But if heat is the (sole) reason for the pressure then the net effect will be (close to?) zero. If, however, the compressed gas is at ambient temperature (eg room temperature) then releasing it will cause a cooling. Like with an aerosol spray - try spraying on your hand and feel the cold. Do this over a city and you will get something steamy, except it's not steam but mist - same thing, but under different temperatures. The water in the air condenses because its concentration is too high for that new temperature. DirkvdM 07:42, 18 October 2007 (UTC)[reply]
Virtual Photon
A few questions which my physics teacher wasn't able to answer:
What is the main difference between a virtual photon and a 'real' photon?
Does this make any practical difference to how the virtual photon behaves?
Also, when a virtual photon is exchanged in electrostatic repulsion, does this mean that energy is exchanged between the two (in this example, electrons). I have also read somewhere, that there is some way in which the conservation of mass/energy law is broken Is this true?
Thanks, Aiyda 21:47, 17 October 2007 (UTC)[reply]
Does virtual particle help with your questions? (I should emphasise that I am not familiar with this topic and have not read the article) Algebraist 22:08, 17 October 2007 (UTC)[reply]
A real photon is described as on-shell. It's rest mass is exactly 0. A virtual photon can have a different effective mass, but this means it must be absorbed, it can not travel as a free particle. This is a consequence of a Heisenberg Uncertainty Principle kind of borrowing of energy, but only for a limited time, which in effect limits the range of the force. Energy is exchanged between two electrons if they exchange a photon, yes. The mass/energy relation you refer too is probably that the virtual photon doesn't have 0 mass enforced as in a real photon. Energy is conserved both when the photon is emitted and absorbed, it is not conservation that is broken, but the relation between energy and mass. This is hard to put into words I hope the article does a better job. Cyta 07:47, 18 October 2007 (UTC)
Yes looking at it quickly the article seems quite comprehensive, although I am not sure about the stuff in the intro about some scientists not believing in virtual particles, I have never heard that view anywhere before. Cyta 07:49, 18 October 2007 (UTC)[reply]
Carbon-oxygen backbone polymer
Does a polymer with an alternating carbon-oxygen backbone exist, for example H-[CH2-O]n-CH3? If so, what are they called? These are similar to the silicones, but with carbon in place of silicon. Thanks, AxelBoldt 21:52, 17 October 2007 (UTC)[reply]
The Delrin page has a lot of applications for polyoxymethylene, in case you're interested. Delmlsfan 00:28, 18 October 2007 (UTC)[reply]
October 18
sharks
Do jellyfish stings effect sharks? If so where can I locate this answer with more info? —Preceding unsigned comment added by 63.3.17.130 (talk) 00:06, 18 October 2007 (UTC)[reply]
Kinetic Energy in the Universe
Because all matter in the universe came from the big bang, if we use the velocity of all the mass in the universe just before the bang as a reference frame and all of the matter in the universe, does that mean that the total kinetic energy of the universe is 0? If its true, is this useful to scientists in any way?
Statements like "velocity... just before the Big Bang" hold no meaning, as the laws of physics do not hold at the singularity point. So no, you can't derive "total kinetic energy is zero" from that statement. Besides, "total kinetic energy" is better described as a magnitude than a vector. — Lomn 01:14, 18 October 2007 (UTC)[reply]
Right there are at least three things wrong with that statement. Firtstly, there is no "before" when we are talking about the big bang. Secondly, because kinetic energy is mass times velocity SQUARED, it doesn't have vector component to it. Two particles with the same mass, moving at the same speed in opposite directions don't have "opposite" kinetic energy - they have identical kinetic energy (Suppose they both have a mass of 2 units and velocities of -3 and +3, then m.v2 is 18 for both of them because 32 is 9 and so is -32). Thirdly, kinetic energy isn't conserved - it can be converted back and forth into other forms of energy - so even if there were some sense in which all mass/velocity 'things' summed to zero - it wouldn't still be true now. SteveBaker 04:14, 18 October 2007 (UTC)[reply]
Most Popular Health Topics
I am wondering if there is a way to determine which health topics are accessed most frequently on Wikipedia. Is there a list available to the public that displays the number of times a health page is accessed. If not, is there a way to access the top ten health issues viewed through Wikipedia? —Preceding unsigned comment added by 67.172.250.112 (talk) 00:27, 18 October 2007 (UTC)[reply]
I downloaded the 1500 most popular articles, and grepped for "health" in the category. Results:
Why was Pakistan a grep result if the article has no mention of the word "health"? --Bowlhover 03:30, 18 October 2007 (UTC)[reply]
Sean didn't grep the article - he grepped the names of wikipedia categories mentioned inside it (presumably hoping to find all of the articles that were inside categories relating to health). There is a [Show] section in the Pakistan article that refers to Category:Healthcare in Pakistan. Hence he also inadvertently included articles that LINK to health-related categories without being in any way about health themselves. That probably explains all of the ones that don't seem like they should be there! I didn't say it was a good technique! SteveBaker 04:03, 18 October 2007 (UTC)[reply]
Medicine = poison?
Who was it -- some ancient Greek thinker? - who said all medicines are actually small doses of poison? Thanks, Adambrowne666 00:45, 18 October 2007 (UTC)[reply]
Sounds similar to Homeopathy#Law of similars. Some homeopaths think it makes sense to make treatments out of toxins that cause the symptoms found in disease states. --JWSchmidt 00:56, 18 October 2007 (UTC)[reply]
Makes sense in a way. Antibiotics certainly are poison to the bacteria they are supposed to kill. But the toxicity of something basically lies in its quantity or concentration. Lots of things that the human (or whatever) body needs will be lethal if the dosage is too large. I've even heard a story of someone who swallowed some 'household chemical', and rang the doctor, who advised her to drink loads of water while he was on his way to her. In her panic, she drank so much water that that killed her. Don't know if this is an urban myth, though. Anyway, how much of something you ingest has an effect on the 'balance' in your body. Altering the normal pattern of ingestion may thus be used to treat some disease. That said, a lot of medicines are things that the human body hasn't evolved to deal with (eg because they're synthetic), so any amount could be regarded as poison. DirkvdM 07:54, 18 October 2007 (UTC)[reply]
In a lecture (actually on psychology, not on medicine) I was told the same thing. For a medicine to work, it must affect the body. Anything that affects the body in any way, can be dangerous to the body when the dosage is not right. Lova Falk 11:26, 18 October 2007 (UTC)[reply]
That's bullshit. Something could affect the body in some way, but completely taper off after, say, 1 ounce, so that a pound, or 1,000,000 pounds of it, has the same effect. For example, consider "darknesss" -- having 1 lumen of darkness affects the eyes in a certain way, but going to a million or a billion or a trillion lumens won't adversely affect the body. Likewise, dropping into a pool of water has an affect on the body, but the efffect won't be different if the amount of water in the pool is trillions of gallons. So, just two examples of how it's NOT true that " Anything that affects the body in any way, can be dangerous to the body when the dosage is not right", 1) darkness, 2) external amounts of swimming pool water. —Preceding unsigned comment added by 77.234.80.59 (talk) 12:41, 18 October 2007 (UTC)[reply]
Harnessing biomath
Humans and other animals can innately do some amazing math, such as calculating where a tennis ball coming at you at 100 mph is likely to end up, in a much shorter time than even the Richard Feynmans of the world could calculate it on paper. I'm wondering if there has been any line of research into using that mathematical ability at the conscious level to do equivalent calculations quickly? Thanks. --Sean 00:45, 18 October 2007 (UTC)[reply]
I'm not sure what sort of "equivalent calculations" you're going to find. As I see it, "biomath" is either very specific in scope or very approximate in result. That is, the average person knows about where a tennis ball will end up, but about isn't likely to be of sufficient use to spur serious research. On the other hand, while Roger Federer may be very precise about determining where a tennis ball will end up, he's probably no better than average at, say, gaging a baseball hit to deep center. In this case, you might have a viable calculation, but your pool of equivalent calculations will be quite restricted. — Lomn 01:10, 18 October 2007 (UTC)[reply]
Sean, what you're talking about isn't calculation. Calculation is something done with digital representations of numbers, like "16 feet + 29 feet = 45 feet". The intuitive estimates you're talking about involve analog operations, like "<-- THIS far --> plus <---- THIS far ----> equals <--------- THIS far --------->". It's a completely different way of thinking.
--Anonymous, <--THIS late--->, October 18, 2007.
As I see it, predicting where a ball will end up is based on experience; an experienced tennis player will know what trajectory a ball travelling at a certain speed will follow, after seeing similar situations many times before. I fully agree with Anonymous that this is not math but intuition. A tennis player on the Moon, for example, will not be able to predict trajectories very accurately even if he knows the strength of the Moon's gravity and the effects of a vacuum. --Bowlhover 03:19, 18 October 2007 (UTC)[reply]
There is a sense in which we are innately able to imagine approximate solutions to what would be horribly complex problems if calculated out exactly...but they are very, very approximate. If I ask you to imagine a shelf in your garage or garden shed full of paint cans - and think about what happens if one of the two brackets holding up the shelf were to fail - then in a very tiny fraction of a second - and without any accurate data of any kind - you can envisage the whole business. One end of the shelf slides downwards - the cans start to accellerate down the shelf - they impact the ground one after another - some of the lids come off, paint runs out and forms a big puddle on the floor. You can imagine the sounds of the cans sliding and clanging on the ground - and perhaps even have a reasonable stab at the smell of the paint. That's an AMAZING thing to calculate in such a short time with almost zero data - but is it correct? Does the twisting of the shelf cause the other bracket to fail? Do the paint cans land on top of each other or spread out a little? Do all of the lids come off or just some of them? Exactly how big a puddle does half a litre of a water-based emulsion paint form? You really didn't calculate this - you formed some kind of clever approximate simulation by gluing together bits of past experience. However, it's impressive just how close to reality these things turn out to be. We'd be very hard pressed to write a computer program that could produce such an accurate prediction - even with all of the initial data and all of the physics envolved. And if we did, it might take hours to run. Our brains can do a pretty good job in a small fraction of a second. It's not even that we've seen this exact thing happen before and we remember it. I can make up "what if" thought experiments based on combinations of everyday things you've never seen - and you can come up with a similarly reasonable answer in very short order. SteveBaker 03:53, 18 October 2007 (UTC)[reply]
Funny, my very first physics teacher could go on and on about how awful these fraction-of-a-second predictions were, before you took his class, of course ;-) Someguy1221 04:57, 18 October 2007 (UTC)[reply]
Cotton buds/Q-tips
Is this just a false memory on my part or were cotton buds (aka Q-tips) at one point specifically sold (in the UK at least) for the purpose of scraping earwax out of the depths of the ear canal? Now, they always make it clear on the packaging that they should *not* be used in this manner. --Kurt Shaped Box 01:24, 18 October 2007 (UTC)[reply]
Their original designer Leo Gerstenzang saw his wife wrapping cotton wool around the end of a cocktail stick for the purpose of removing the wax from their babies' ears. Yes. SteveBaker 03:34, 18 October 2007 (UTC)[reply]
Funny, that. What else would people buy them for? And why are they perfectly shaped and proportioned for that purpose? I occasionally use them to clean tape heads, but that's not what I primarily buy them for. DirkvdM 08:03, 18 October 2007 (UTC)[reply]
Exactly. I look at them and I struggle to think of many other advantages that a cotton bud has over your standard cotton wool in the home environment. --Kurt Shaped Box 09:42, 18 October 2007 (UTC)[reply]
All you who answer seem to be men. Cotton buds are perfect for small make-up adjustments. They are also ideal for removing kajal out of your eye (kajal has a nasty habit of slipping into the eye) :) Lova Falk 11:22, 18 October 2007 (UTC)[reply]
They are also handy for touching up small nicks in your rooms' paint, especially at corners. But "cleaning tape heads" was the first alternate use I flashed on too; 'guess I'm getting old. ;-)
They're also good for cleaning the accumulated fluff and scum from mouse rollers. Still, if it wasn't for people buying them to ream their ears out, I doubt that most shops would even bother stocking them. --Kurt Shaped Box 13:04, 18 October 2007 (UTC)[reply]
Come to think of it, I've occasionally used cotton buds to brush eyelashes from my corneas. The loose ones are not so bad - it's the ones that fold down under the eyelid whilst still attached that are the real bastards. --Kurt Shaped Box 13:00, 18 October 2007 (UTC)[reply]
So, besides dripping peroxide in our ears, what's the "safe" way to remove wax from the ear canal? Someguy1221 04:54, 18 October 2007 (UTC)[reply]
I always used to use them, the idea of it being bad for you is a rather recent one. I spent most of my childhood using them... SGGHspeak! 08:37, 18 October 2007 (UTC)[reply]
I suspect we can blame that idea on a corporate liability lawyer somewhere.
TBH, I still do. Scraping out earwax and scratching an itch inside the ear at the same time has got to be one of the best sensations possible - only *just* behind orgasm and the relief you feel when taking a slash after holding it in for three hours. --Kurt Shaped Box 09:36, 18 October 2007 (UTC)[reply]
Kurt, take one bobby pin, snap it in half at the join and discard the 'crinkled' half. You now have a smooth end and a rough hooked end to use as you see fit. Never found anything better. This is not medical advice or indeed advice of any sort, if you perforate your eardrum consult a medical professional and don't mention you are silly enough to do what someone off The Internets recommended. But seriously, it's heaven. Lanfear's Bane 10:29, 18 October 2007 (UTC)[reply]
I use a paperclip (somewhat straightened). --Psud 11:57, 18 October 2007 (UTC)[reply]
I once worked with someone who'd sit at his desk scrubbing out his ear canals with matches (phosphorous end!). That may have been an accident waiting to happen... :) --Kurt Shaped Box 13:06, 18 October 2007 (UTC)[reply]
Sort of back on track, those cotton bud/Q-tips are also perfect for cleaning dirty laser lenses. Dip one end in a bit of rubbing alcohol (spectacle cleaning solution works), rub over the lens, wait to dry a bit, then use the dry end of the bud to polish it up. I originally learned that to get my Playstation 2 working again, but it works on anything (assuming you can take it apart safely to get to the lens). Neil☎ 14:16, 18 October 2007 (UTC)[reply]
Bray-Curtis
What is the Bray-Curtis dendrogram and how does it apply to ecology? —Preceding unsigned comment added by Redrumusic (talk • contribs) 06:17, 18 October 2007 (UTC)[reply]
Hairsplitting
Considering how long the hair of humans can get if it is not cut, I used to wonder if that wasn't inconvenient for our ancient ancestors. My first guess was that their lifestyle would cause the hair to get a 'natural cut'. For example, domesticated animals often need to get their nails or hooves cut, which of course doesn't happen in nature. But a while ago someone remarked that I have split ends. About 15 years ago I stopped using shampoo (as a result of which, as planned, my hair stopped falling out - I was already starting to go bold at the age of 30). At around the same time I stopped having my hair cut. But it didn't grow further than my neck. So might that be the cause? Are having split ends and hair of the length I have the natural state of our hair? Also, do other animals have split ends? The article suggests, as many people do, that it is a bad thing, even a 'medical condition'. I claim the opposite. Split ends are healthy. DirkvdM 10:44, 18 October 2007 (UTC)[reply] ps, I will put a baldness-spell on anyone who whines about this being a medical question. :) DirkvdM
Interesting! How do you keep your hair from looking greasy and dirty? Lova Falk 11:18, 18 October 2007 (UTC)[reply]
1. Just because 'split ends' have a complicated medical name doesn't make it a medical condition (take my word for it)
2. I've heard about split ends but never been able to see them myself..
3. Is it possible that saying "you have split ends" in another way of saying "go and get a haircut!" - a euphemism - a bit like saying "how do you get your skin so shiny looking" can mean "get a bath you greasy ..." - seriously - look a grizzly bears.. they probably have split ends - but pandas dont87.102.3.9 13:10, 18 October 2007 (UTC)[reply]
Help with my marriage (pleasing my wife)
Dear Sir / Madam, I wish to learn some sexual techniques that I will be able to perform to pleasure my wife when we are having the sex. Please help me Mr. Wikipedian, I believe this may be the only way to save my failing marriage. I love my wife very much but I do not think she feels the same. Hopefully once I have seduced her she will think otherwise and be under control once more. Thank you for you speedy help with this request of mine. God bless you. —Preceding unsigned comment added by Visible to the recipient (talk • contribs) 11:43, 18 October 2007 (UTC)[reply]
Ask her, and then do what she says. --Milkbreath 12:36, 18 October 2007 (UTC)[reply]
...and be under control once more. Why not skip the seduction and move straight to a ball and chain? Ironically, what some refer to their significant others as. Lanfear's Bane 12:46, 18 October 2007 (UTC)[reply]
Wikipedians are obviously not qualified to give relationship advice...please seek the help of a licensed relationship/marriage counselor. OMG! My eyes rolled too far back!! 38.112.225.84 14:21, 18 October 2007 (UTC)[reply]
Possible to use CGI instead of night vision?
Lets say, we are many many years into the future. 2530 or something. We have super advanced computers, quantum computers perhaps, or better. We have a tank in the middle of the night, and it's pitch black. Is it possible for the tank to send signals (possibly radar or something) to get terrain information, then use that information to generate computer generated images in real time to give the driver detailed information of what is in front of him? Perhaps it can be combined with information from a satelite to give topographical information as well.
So in other words, can an advanced computer generate in real time, what is in front of the tank, and display it as if it were day time, and use that CGI instead of nightvision? 64.236.121.129 13:36, 18 October 2007 (UTC)[reply]
500 years into the future? We could do it now, including the combination with known topographic data (aircraft use this all the time). However, sending signals continuously like that is the military equivalent of screaming "I AM A TARGET SHOOT AT ME". Night vision goggles, on the other hand, are passive, granting them an enormous tactical advantage. — Lomn 13:44, 18 October 2007 (UTC)[reply]
Well I said 2530 because I wanted the CGI to look very advanced. Close to how you would expect the objects and terrain to look in real life. Hmm, that is true about being a huge target. Maybe such technology would be best on a civilian vehicle then. Something like that could be useful in fog or stormy conditions where lights alone don't help much. 64.236.121.129 13:55, 18 October 2007 (UTC)[reply]
For civilian vehicles, I think it far more likely that automated highway systems will be prevalent. A problem with the fog/storm thing is that radars capable of what you want are subject to similar limitations as the human eye. Millimeter-wave radars, for example, suffer heavily from rain fade. — Lomn 14:13, 18 October 2007 (UTC)[reply]
![[5]](http://www.cdaccess.com/jpg/shared/front/large/eatcatmp.jpg){kind=link}
..?87.102.123.108 17:29, 17 October 2007 (UTC)
![[9]](http://www.mediterrangarten.de/Nordbiene/Mellifera01.jpg){kind=link}
