Wikipedia:Reference desk/Archives/Science/2008 March 5

Science desk
< March 4	<< Feb | March | Apr >>	March 6 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 5

Avoiding the Nazi Swastika

While I was researching PETN looking for more efficient ways for the atoms and their connections to be drawn I became aware of the potential to draw this molecule in the pattern of a Nazi Swastika and that was before I read that the molecule was invented in Germany and patented by the German government and that the Homeland of the Nazis was Germany. Are there any other molecules that can be redrawn as a Nazi Swastika and if so what are they? Just curious in an odd sort of way.

Is this really science related? Wisdom89 _{(T / ^C)} 00:26, 5 March 2008 (UTC)

More so that art related.

It kinda looks like a swastika in a 2d diagram as shown in the article. But in reality, the 3d structure of the middle carbon is different. Looking straight from above, you wouldn't see the "swastika". The middle part will look like a plus sign. If you look at it sideways, or from the plane of the molecule, the middle part looks like a seesaw. The point is that the swastika is invisible in the 3d structure.128.163.116.74 (talk) 01:19, 5 March 2008 (UTC)

Chemists have a way of describing this - you are looking for a molecule with C_4h symmetry.. (point group) - because of its 3 dimensional structure PETN doesn't actually have this symmetry.87.102.85.28 (talk) 15:09, 5 March 2008 (UTC)

Tetraethyl lead could be drawn as a swastika , but as above in 3D it doesn't have this structure.87.102.85.28 (talk) 16:03, 5 March 2008 (UTC)

Lots of metal-centered things do have square-planar geometry though...just gotta find the right ligand/metal combination. Maybe tetraethyl platinum, or Pt(OH)₄? DMacks (talk) 18:01, 5 March 2008 (UTC)

Pt(OH)₄ sounds promising since hydrogen/oxgygen bonding interactions would tend to cause the H's to point towards the O's in the plane of the molecule, does it exist?87.102.85.28 (talk) 18:14, 5 March 2008 (UTC)

Pt(OH)₄ exists both as a neutral Pt(IV) compound and apparently also as the Pt(II) dianion. Lots of known chemistry, but I can't find structural data. Many uses involve adding additional ligands and many 4-small-legand complexes of Pt are square-planar, so my SWAG is square-planar at Pt. I hadn't thought of the H-bonding helping the arms stay in the correct orientation, good idea! DMacks (talk) 18:38, 5 March 2008 (UTC)

rodents with large binocular field of view

Hi everyone. A simple question, but the search yielded nothing for some reason. The question is: are there any rodent species with a decent binocular field of view (FOV)? Most rodents have eyes set far off to the sides of the skull, hence the FOV of both eyes overlap only over a small angle (a few degrees AFAIK) in front of the animal. That, of course, makes sense: rodents have a large number of predators to watch out for, and therefore large coverage, even monocular, is more important than binocular vision. Still, do you know which rodent or lagomorph species have a relatively large binocular frontal FOV? Thanks in advance. --Dr Dima (talk) 06:44, 5 March 2008 (UTC)

Ferrets? They have eyes close to the front. —Preceding unsigned comment added by 84.68.70.170 (talk) 01:15, 6 March 2008 (UTC)

Ferrets aren't rodents. They're carnivores, who eat rodents, among other things. Mattopaedia (talk) 02:36, 6 March 2008 (UTC)

If it had this binocularity, would it still be a rodent? Julia Rossi (talk) 07:08, 6 March 2008 (UTC)

Yes, Julia, I think it would. AFAIK, defining features of Rodentia are the particular anatomy and physiology of teeth, jaws, and palate. A small binocular frontal FOV is not a defining feature of rodents, as it also occurs in Lagomorpha. Still, thank you for an interesting thought. --Dr Dima (talk) 20:00, 6 March 2008 (UTC)

relative calcium absorption into bones compared to teeth

I've read somewhere that 99% (or some other very high percentage) of calcium absorbed into your body is in your teeth, while only 1% goes to your bones. Can anyone verify this? Mitchell Cain (talk) 08:26, 5 March 2008 (UTC)

This paper states that 99% of the body's total calcium is in bone (but I suspect they are using "bone" to mean "bones and teeth", as prior animal studies use the figure 99% for bones & teeth). I don't find a reliable source differentiating teeth vs bones (but this retailer of calcium says teeth contain 1% of total body calcium, which seems reasonable: the calcium content of tooth and bone are similar (by weight), and all your teeth taken together weigh considerably less than all your bones taken together.) So I suspect that either you misunderstood what you read, or it was just plain wrong. - Nunh-huh 10:01, 5 March 2008 (UTC)

Another way of looking at it is that the human body is about 1.5% calcium by weight, so a 150-lb person would have about 2¼ pounds of teeth in her head, which seems rather high. --Sean 14:30, 5 March 2008 (UTC)

Physics

Can Kgf be used as a unit for Force in place of Newton. To be specific if I say that an aircraft wieghs 6000 kgf, does it mean 6000 N or 6000 x 9.81 N? Shary249900 (talk) 13:52, 5 March 2008 (UTC)

The latter is closer to correct. 6000 kgf = 9.80665 m/s² x 6000 kg = 543999 N. See kgf. jeffjon (talk) 14:04, 5 March 2008 (UTC)

Free protons? Free neutrons?

Free electrons are described as electricity. What would free protons and free neutrons be described as? 64.236.121.129 (talk) 15:37, 5 March 2008 (UTC)

How about dangerous?

Seriously though, a free proton is an ion of Hydrogen, that is a Hydrogen atom that's lost its electron. You can get neutron radiation, but other than that neutrons don't tend to hang around on their own. They decay into protons. —Preceding unsigned comment added by AlmostReadytoFly (talk • contribs) 15:55, 5 March 2008 (UTC) Damn! SineBot doesn't give you much chance! AlmostReadytoFly (talk) 15:56, 5 March 2008 (UTC)

Did you really think you could beat a robot? 206.252.74.48 (talk) 16:22, 5 March 2008 (UTC)

(ec) While electric currents definitely do involve electrons (well, usually), the situation is much more complex than a bunch of free electrons wandering down a wire. Signals in a metallic wire travel much faster (close to the speed of light) than the individual electrons that carry the current (drift velocity about a millimeter per second). (See also speed of electricity). The very same electrons that are 'free' in the sense of being able to move in a conduction band down the length of a wire don't just fall out the end of the cable when you unplug it—they're bound.

A 'free' electron – one not bound to other matter – might be called a cathode ray in some contexts, or a negative beta particle in others. Really though, a 'free electron' wandering about with relatively small kinetic energy is usually described as just that—a 'free electron'.

As an aside, when I saw the section header on this question my first thought was that there was some sort of giveaway of particles going on. Cheers! TenOfAllTrades(talk) 16:27, 5 March 2008 (UTC)

Whereas I thought someone was scrounging :P AlmostReadytoFly (talk) 16:32, 5 March 2008 (UTC)

There used to be a donut shop near UC Berkeley called the "Neutron Bakery" (no doubt a name left over from an earlier period of nuclear enthusiasm). I tried to convince the then-current owner once that they should give away some donuts for "no charge" but they didn't get it. Sigh. --98.217.18.109 (talk) 17:03, 5 March 2008 (UTC)

I absolutely hate it when a great joke falls through like that. You have my deepest sympathy. 206.252.74.48 (talk) 19:46, 5 March 2008 (UTC)

I mean free protons and free neutrons. Not binded together. A Hydrogen atom that lost an electron still has a proton and a neutron. I'm talking about free protons and free neutrons, unbinded. 64.236.121.129 (talk) 16:26, 5 March 2008 (UTC)

No it doesn't usually. A Deuterium atom (which is a type of Hydrogen atom) has a proton, a neutron and an electron, but most Hydrogen has only a proton and an electron. If it loses the electron, all you have is a free proton. AlmostReadytoFly (talk) 16:32, 5 March 2008 (UTC)

Your standard hydrogen ion is just a proton, as above. Deuterium (a comparatively rare isotope) is the proton+neutron combo. 199.209.144.218 (talk) 16:30, 5 March 2008 (UTC)

There are free protons in the solar wind. But we don't encounter free protons and free neutrons in "everyday life", because their presence is an indication that there are some high energy nuclear processes happening - it takes much more energy to dislodge a nucleon from a nucleus than it does to free an orbital electron. If you find free protons or neutrons flying around, you should probably stand well back. Gandalf61 (talk) 16:40, 5 March 2008 (UTC)

So a free proton is just ionized hydrogen? Ok. What about free neutrons? 64.236.121.129 (talk) 16:56, 5 March 2008 (UTC)

Neutron radiation, as mentioned above. They decay into protons. AlmostReadytoFly (talk) 16:59, 5 March 2008 (UTC)

Yup, as denoted H+ - that's essentially what a proton is. Wisdom89 _{(T / ^C)} 17:49, 5 March 2008 (UTC)

You have to be careful when using H+ because most of the time it is used when in H+ is in water where it is actuall more like H3O+ or H3O+.(H2O)3 or other funky complexes that aren't really fully understood, H+ is just an easy way of treating protons that are loosely bound. Certainly though if you heated HCl gas up you would get free protons. --Shniken1 (talk) 22:43, 5 March 2008 (UTC)

Oh also there is research that I've heard of that uses carbon nanotubes to transport protons to be used as electricity. The direction of Electric charge is actually defined as the direction a positive charge would travel not a negative charge (electron), this because it was defined before the electron was discovered.--Shniken1 (talk) 22:48, 5 March 2008 (UTC)

The sweet taste of deuterium

Does heavy water taste differently from ordinary water? ----Seans Potato Business 18:13, 5 March 2008 (UTC)

I'm not sure about the taste, but I know it can kill you if you drink it. 64.236.121.129 (talk) 18:16, 5 March 2008 (UTC)

That's not exactly true. I just drank it as part of a crazy experiment for which knowledge of my body composition is required. It tasted sweet, but I wonder if that's something else I'm tasting... ----Seans Potato Business 18:18, 5 March 2008 (UTC)

Drinking too much is toxic. 64.236.121.129 (talk) 18:24, 5 March 2008 (UTC)

Heavy water#Toxicity_in_humans says "for a poisoning, large amounts of heavy water would need to be ingested without significant normal water intake for many days to produce any noticeable toxic effects", so it's only really toxic under highly improbably circumstances. Regular water is too, for that matter. --Sean 18:39, 5 March 2008 (UTC)

Well, I think it's a little different. It says on that article that heavy water given to rats to drink for a week, died. If you drink it on a regular basis, it's toxic. You really want to mess with something that might kill you? 64.236.121.129 (talk) 18:46, 5 March 2008 (UTC)

Such experimentation is fairly common. Inhaling helium or sulfur hexafluoride to change the pitch of one's voice is fairly common, even among those who understand the risks, because the associated risk mitigation is also well-understood. Not that I personally am gung-ho to start slurping deuterium, mind you. — Lomn 18:54, 5 March 2008 (UTC)

In all fairness, Helium is non-toxic. It's only dangerous if it displaces oxygen. 64.236.121.129 (talk) 19:09, 5 March 2008 (UTC)

Risk is risk. Do you put toxicity into a special category of risk? If so, why? --Trovatore (talk) 19:25, 5 March 2008 (UTC)

Categories are made by scientists on these matters. 64.236.121.129 (talk) 19:41, 5 March 2008 (UTC)

Discussing risk is entirely a matter of severity, dependent on magnitude and time of exposure. The issue of risk is by no means binary (i.e. toxic vs. non-toxic), and such models are only presented as guidelines so the average Joe doesn't have to figure it out. Bottom line, too much of anything will kill you; too little of some things will also kill you. Once we know the time/concentration needed to cause illness, continuing to argue over the meaning of "toxic" is utterly pointless. Someguy1221 (talk) 19:46, 5 March 2008 (UTC)

How does this contradict what I said? 64.236.121.129 (talk) 21:25, 5 March 2008 (UTC)

"If you drink it on a regular basis, it's toxic. You really want to mess with something that might kill you?" Someguy1221 (talk) 23:53, 5 March 2008 (UTC)

Risk is risk? Won't the actuaries be surprised! --Sean 20:54, 5 March 2008 (UTC)

Would they? What do they think risk is, if not risk? Silly banter aside, the point is that when comparing small risks, the fact that one of them is from toxicity rather than, say, asphyxiation, or car crashes, or whatever, does not make it autmatically more objectionable. --Trovatore (talk) 20:58, 5 March 2008 (UTC)

There is little in the scientific literature on the taste of heavy water, but a few publications exist. There is a public account from Time magazine (4 February 1935) describing Klaus Hansen of the University of Oslo as the first person to consume concentrated heavy water. He consumed "two teaspoons" of heavy water, and reported the experience thus [1]:

"I lifted the beaker to my lips. Immediately I felt a burning dry sensation in my mouth and then I could feel nothing. First my mind became excited and impressed with a feeling of crisis.

I had some shock. Then I said to myself, 'Be quiet—you are simply going through a minor experience.' Then it was all over. I could see, hear, breathe, feel and walk just as before."

The guy was probably just nervous, however. In a letter to Nature (15 March 1935) Harold Urey (recipient of the 1934 Nobel in Chemistry for demonstrating the existence of heavy water) reported on his own experiment. It involved two subjects who each tasted one cubic centimeter of distilled water and an equal volume of heavy water. This test was blinded—a third person outside the room prepared the samples. The final conclusion was that "pure deuterium oxide has the same taste as ordinary distilled water."

A 1976 paper in Experimental Biology and Medicine (CP Richter, "A study of taste and smell of heavy water (99.8%) in rats", 152(4):677-684) describes the odor of heavy water as "faint" in its abstract ([2]), but the full article isn't online. (The abstract also states that "Rats did not taste heavy water", but it is unclear from the context whether it means that the rats were incapable of tasting a difference, or that they chose not to drink heavy water because of a perceived odor.) TenOfAllTrades(talk) 19:18, 5 March 2008 (UTC)

(ec)According to Effects of Heavy Water on Living Cells, Science, Vol. 86, No. 2243, p. 587-588, December 24, 1937, heavy water "seems to exhibit to some people mild and varying differences in taste from ordinary water. He gives a citation to this of K. Hansen, Klin. Wochenschr., 14: 1489, 1935. I'm not quite up to hunting down that citation, but it's something...Someguy1221 (talk) 19:21, 5 March 2008 (UTC)

Helium is actually dangerous because it displaces CO2, which prompts the body to breathe. You will not feel like you need to breathe but you do need to. Heavy water is only toxic when it displaces normal water in cells where it can change the folding of proteins due to weaker hydrogen bonding. (There may be some adverse effects by replacing the extracellular fluid with heavy water but these would be minor in comparison and/or I cannot think of any ATM). But back on topic, I cannot see a reason (other than psychological) that heavy water would taste different--Shniken1 (talk) 22:37, 5 March 2008 (UTC)

To be fair, heavy water could taste different for the same reason that it is toxic at high concentrations. The extra neutron doubles the mass of the hydrogen nucleus, which affects the kinetics of biochemical reactions. In principle I could see exposure to concentrated heavy water affecting the (normally water-equilibrated) taste receptors on the tongue, and generating a response that way. TenOfAllTrades(talk) 01:00, 6 March 2008 (UTC)

One could imagine that heavy water taste identically to normal water but that the difference in the hydrogen bond affect chemical reactions where water take place or the binding of water to other molecules. That way, it could affect taste but only if mixed with something else. But this is just an idea. —Preceding unsigned comment added by 129.241.215.226 (talk) 08:26, 6 March 2008 (UTC)

I have learned that was I drank was 99% heavy water with nothing else added and it tasted very much different. Given samples of regular water and heavy water, I could differentiate between them both every time. Of course this is original research, so I can't fix the article on this basis (which claims absence of difference of taste). You should know however, that I assert that this statement is incorrect. In case it matters, it made me extremely dizzy (I needed to drink 200 mls) and I didn't like it. --Seans Potato Business 20:39, 6 March 2008 (UTC)

Did you know it was heavy water? Taste is probably the most suggestible of the senses. I had this impressed on me in college when I told a girl which Sweet Tarts I liked best and worst, and she challenged me to tell one from another without looking at them. Couldn't do it at all. But I still like the green and purple ones best. --Trovatore (talk) 20:41, 6 March 2008 (UTC)

Yes I did, and I believe that knowledge had nothing to do with it. If someone wants to include me as a subject in a properly controlled scientific experiment and any associated expenses will be covered, then I'd be happy to take part. The taste was very distinctive and not remotely subtle. --Seans Potato Business 22:22, 6 March 2008 (UTC)

I read somewhere that alcohol makes the room appear to spin because it reduces the density of the fluid in the inner ear, and that if you drink heavy water it increases the density and the room spins in the other direction. I was never sure whether to believe it or not, but is that what you meant by dizzy? Eve (talk) 22:48, 6 March 2008 (UTC)

The room was spinning, yes, although I don't know what direction... counter-clockwise? Of course it only seems to spin with my eyes closed, otherwise it spun a bit and went back very quickly over and over. ----Seans Potato Business 17:10, 7 March 2008 (UTC)

Yep! The article on alcohol explains the spinning sensation and eye movement, although doesn't mention the heavy water effect. But it makes sense. Eve (talk) 18:17, 7 March 2008 (UTC)

Have you also tried drinking distilled water? Once you remove the dissolved minerals, the dissolved gases, and similar things from it, ordinary water tastes pretty awful. --Carnildo (talk) 23:09, 6 March 2008 (UTC)

Maybe it was the absence of minerals that made it taste distinctive. I don't know where it came from or how it was treated. Never tasted distilled water before. --Seans Potato Business 17:10, 7 March 2008 (UTC)

Is it true the Wright brothers were mocked?

I heard people made fun of them, and didn't believe that they could achieve what they were trying to build. Is this true? 64.236.121.129 (talk) 18:30, 5 March 2008 (UTC)

Quite so, including well after their first successful flights. Our article on the Wright Brothers notes their efforts to avoid the "circus" of reporters that surrounded early flight attempts. I consider the most interesting example to be that laid out in the "public showing" section, which notes that fully five years after the brothers' original success, the French media still referred to them as "bluffeurs". — Lomn 19:00, 5 March 2008 (UTC)

It was true with many early pioneers of powered flight. Richard Pearse's story in particular is quite a sad one. Grutness...wha? 23:59, 5 March 2008 (UTC)

Color of hemoglobin

What determines the absorption spectra of hemoglobin and its derivatives? Why is HbO bright red and Hb purplish red? --Eleassar ^{my talk} 20:09, 5 March 2008 (UTC)

Here's a little. Hemoglobin#In_history_and_art David D. (Talk) 20:19, 5 March 2008 (UTC)

technically it comes from crystal field theory as the Fe species changes in oxidation state oxidation state the splitting between energy levels changes, changing the optical absorption range, and thus color. 193.60.95.72 (talk) 00:51, 6 March 2008 (UTC)

Not according to the wikipedia article. It says it is the Porphyrin. David D. (Talk) 01:15, 6 March 2008 (UTC)

You haven't 100% understood that, both are true. (Don't answer questions you're not qualified to..)87.102.74.217 (talk) 09:59, 6 March 2008 (UTC)

Huh? I didn't answer the question. I point to the wikipedia article. How about a source for your info and then the article can be improved. David D. (Talk) 10:23, 6 March 2008 (UTC)

easy guys, don't fight. The crystal field theory is modeling the interactions between the Fe ion and the porphyrin. Its not a bare Fe ion floating around... those ARE the ligands interactions that define the color. Furmanj (talk) 18:54, 6 March 2008 (UTC)

Thanks for the replies. --Eleassar ^{my talk} 14:55, 6 March 2008 (UTC)

Nanomedicine

Hi guys... whow do you think the future scenario of nanomedicine is going to be? only the rich and famous having the benefitts? everyone? only the insured? only citizens of the developed countries? will it not be available at all but to a select few who will become supermen of some sort and rule the world?...--Cosmic girl (talk) 22:09, 5 March 2008 (UTC)

I think as with most technology it will be expensive and basic initially - once processing techniques and development comes into play the price will drop, the technology will advance and the consumer base will broaden. I don't expect super(wo)men over-night... maybe 2 nights.Boomshanka (talk) 01:08, 6 March 2008 (UTC)