Wikipedia:Reference desk/Archives/Science/2008 July 14

= July 14 =

colostrum
Cow's colostrum are rich in lg M.If we consume products with these cow colostrum, can it really increase the immune system and boost our health.?218.208.43.111 (talk) 02:00, 14 July 2008 (UTC)Rainy


 * First, it is IgM, not lg M. It is a basic antibody found in B cells.  Ingesting IgM does not magically get it into your blood stream and into your B cells to boost your immune system.  Next, you will probably ask about shooting it straight into your blood stream.  If you did that, your body will recognize it as a foreign invader and kill it off before any hoped for beneficial effect could take place. --  k a i n a w &trade; 02:25, 14 July 2008 (UTC)


 * IgM will be absorbed across the intestine of a nursing calf and could possibly be absorbed by a human also. The problem there is that the IgM antibody will most likely only signal the immune cells found in cows. Antibodies work in a two-stage process, they recognize an antigen but they also have to activate a leukocyte to initiate a comprehensive immune response. I doubt that cattle IgM has evolved to activate human immune cells, so the IgM antibody itself might neutralize a single pathogen, but it would not convey the lasting immune benefit that calves experience. Franamax (talk) 02:46, 14 July 2008 (UTC)
 * Animal Ig can be used to boost immune response (Antivenin) but I don't think that cow's milk Ig is a good immune booster as said by the posters above. However, I think milk can indirectly improve the immune system though as it provides the amino acids that can be used to manufacture Ig's.-- Lenticel ( talk ) 03:06, 14 July 2008 (UTC)
 * As I noted, ingesting of antibodies is not an effective method of use (which I assume the questioner means by "consume"). Antivenin is delivered intravenously (or within range of plenty of capillaries if there is a major rush). --  k a i n a w &trade; 12:08, 14 July 2008 (UTC)
 * Kainaw, the flaw in your reasoning is that for calves, ingestion clearly is an effective method of use, evidenced by the fact that major purpose of colostrum is to boost the immune system of the calf, and calves drink milk rather than shooting up. Clearly, the antibodies are capable of passing the intestinal barrier (caveat - it's possible the immune stimulation is generated within the gut, then passed to the body system by some other method). The question here seems to be whether the IgM antibodies in colostrum have an immune-stimulative effect in the human body, regardless of the method of delivery. Franamax (talk) 12:31, 14 July 2008 (UTC)
 * The article on breast and formula milk I was reading in New Scientist the other day certainly seemed to suggest that most of the immune system stuff in milk works only on the gut population. Very little of that stuff passes into the blood stream. This is based on my reading of it though, not on having any sort of relevant qualification. 79.66.54.186 (talk) 17:34, 14 July 2008 (UTC)
 * The questioner asked about humans, not calves. In humans, antibodies from other animals are not effectively passed through to the blood stream through ingestion.  As the anon pointed out, they aren't even passed effectively from human to human through ingestion - but human to human is a lot more effective than cow to human. --  k a i n a w &trade; 19:13, 14 July 2008 (UTC)
 * Well, I did put that caveat in there. Turns out there's a little more to the story too. A newborn calf is able to directly absorb the antibodies for 24 hours and I found some indications the same is true of human babies. After that, the effects would indeed be confined to the gut itself. Given that, I would go back to saying that the cow antibodies would be able to bind and neutralize antigen but would be unlikely to stimulate the immune system. For any 12-hour-old humans reading this though - yes, colostrum is good for you! Franamax (talk) 19:52, 14 July 2008 (UTC)

Bond Energy & EN
How is bond energy affected by the electronegativity difference between the 2 atoms? Here it says the more polar the bond, the stronger it is. But why is this so? 125.238.241.210 (talk) 07:30, 14 July 2008 (UTC)
 * A more polar bond means the atoms being bonded have a partial charge (a polar-covalent bond is somewhere in between covalent and ionic). So in addition to the covalent bond itself, you have an electrostatic attraction between the slightly cationic and slightly anionic atoms. See also chemical bond. DMacks (talk) 11:17, 14 July 2008 (UTC)

economics
what is meant by perfect competition? give examples —Preceding unsigned comment added by 117.193.36.7 (talk) 11:26, 14 July 2008 (UTC)
 * I tweaked your spelling a bit, hope that's OK.
 * Is this a homework question? You can start by reading our article on perfect competition, if you have further questions, bring 'em on! Franamax (talk) 11:40, 14 July 2008 (UTC)

Gyroscopic Precession
So, my crackpot question is whether it is feasible to use gyroscopic precession as a method of propulsion. My main idea involves three wheels: one large one and two smaller ones, fixed rigidly to the first. Imagine two saucers fixed side by side to a large dinner plate, such that the outer edge of the saucers were lined up to the outer edge of the plate, and the inner edge of the saucers were lined up with the center of the plate:

(00) <- More or less like this, never mind the crudeness of the diagram. The point of this alignment is that if you rotate both the saucers and the plate counter clockwise (for example), and then observe one particular spot on the edge of one of the saucers, the net momentum of that spot will change depending on its position with respect to the outer edge of the plate.

Assume each object is rotated such that, measured separately, the outer edge would maintain a (completely arbitrarily selected) speed of "1". At the point where the outer edge of the saucer is lined up with the outer edge of the plate, the *net* speed should be very nearly "2" - as the rotation of the plate will be added to the rotation of the saucer. But as that point rotates around to the place closest to the center of the plate, it will now be travelling against the rotation of the plate - for a net speed slowing to very nearly zero.

And now, to do something useful, perhaps: Instead of having our plates and saucers all aligned on the same plane of rotation, we tilt the saucers up at a 45 degree angle. From the side, it might look something like this:

_\_/_ <- assuming we were trapped in a horrible ASCII world it might, anyway. The point in doing this, is that the edges closest and farthest from the center of the plate will still be travelling parallel to the rotation of the plate. My "outermost" saucer edge (now also "uppermost") - will still be travelling at a speed of approximately "2", and my "innermost" edge (now also "lowermost") - will be travelling at a speed of approximately "0".

The other predicted effect is that the saucers, by virtue of being constantly forced by the plate's rotation out of their own planes of rotation, will exert a constant and linear force via gyroscopic precession. Being as how momentum has now been maximized at the outer edge, and minimized at the inner edge - this force should be asymmetric in nature, providing a unidirectional "push" as it were rather than simple torque. The "down" phase will exhibit very little precession effect, due to possessing very little angular momentum, leaving only (mostly) the precession effects of the "up" phase significantly affecting the whole system.

I will be the first to admit if I have overlooked some profound and perhaps hilariously obvious fact which invalidates my scheme. But I would be most greatful if someone could point it out to me, so that we may both share the laugh! :)

24.89.139.202 (talk) 12:33, 14 July 2008 (UTC)
 * I can't quite follow you, but just so we're clear, you're trying to violate Conservation of linear momentum with gyroscopes? APL (talk) 16:04, 14 July 2008 (UTC)


 * Yes, that's about the size of it. :)  —Preceding unsigned comment added by 24.89.139.202 (talk) 22:44, 15 July 2008 (UTC)

Question about contantness of physical laws
how can we say that advanced technology gives us conclusive evidence of past events? —Preceding unsigned comment added by 221.135.192.89 (talk) 13:59, 14 July 2008 (UTC)


 * Nothing's conclusive, it's just a question of what is most likely based on the evidence we have. In most cases, inconstancy in various physical laws (say, the strength of gravity) would have real implications for how we observe the world today. --98.217.8.46 (talk) 14:19, 14 July 2008 (UTC)
 * Conclusive just means "sufficient to draw a conclusion". Plenty of scientific evidence is conclusive. None is 100% certain, though. --Tango (talk) 17:26, 14 July 2008 (UTC)


 * Well, I was assuming he meant "sufficient to draw a totally certain conclusion". Which just doesn't happen in science or anything else where you are talking about rigorous methodology. --98.217.8.46 (talk) 17:36, 14 July 2008 (UTC)


 * Argument from ignorance is interesting. -hydnjo talk 20:06, 14 July 2008 (UTC)

bones transformation
hi...i just want ti know which part of the has seven (7) bones while you are still a baby and becoming three (3) as you grow up? I really appreciate the help. —Preceding unsigned comment added by 212.43.3.2 (talk) 17:51, 14 July 2008 (UTC)


 * I presume you mean which part of the human body. If you think about it the answer will pop into your head.  That is a very strong hint by the way.  Jdrewitt (talk) 18:17, 14 July 2008 (UTC)


 * And, if that last answer doesn't suture needs, perhaps a better hint will follow soon. StuRat (talk) 22:27, 14 July 2008 (UTC)

I simply do not have the brains to work this one out. — CycloneNimrod Talk? 22:42, 14 July 2008 (UTC)


 * This help desk is a fontanelle of information! Scray (talk) 01:02, 16 July 2008 (UTC)

50 - 75 - 83 - 91 - 96 - 98 - 99% - clone
Putting the ethics aside and as a tought experiment, imagine someone traveling through the future stopping every 20 years to impragnate his own daughter. Would the end result (after, say, 100 generations) be someone with an almost identical genome or do other factors come into play. How much do random mutations mess it up? What kind of genetic traits would it push forward? What would be the genetic dangers there? 190.190.224.115 (talk) 20:27, 14 July 2008 (UTC)


 * (light-hearted aside: Oh, we so badly need a template to handle questions like this, warning that the reference desk does not give advice on time-travel related incest or ancestoricide, complete with stern paradox warning sign icon. :)  -- Finlay McWalter | Talk 20:36, 14 July 2008 (UTC)
 * How 'bout this then? Franamax (talk) 21:33, 14 July 2008 (UTC)
 * How 'bout this then? Franamax (talk) 21:33, 14 July 2008 (UTC)


 * Genetic dangers would be those associated with severe inbreeding. It's not genetically any different than a person reproducing and then impregnating their daughter and then the granddaughter. If someone was really dedicated to the idea and got started early enough they could easily impregnate their great-granddaughter too, or even more, if they started around age 13 and reproduced every time the "daughter" was 13. Yuck. It wouldn't end up with an identical genome, you'd just see the side effects of lots and lots of recessive genes. As for what genes it would encourage; no way to know that ahead of time. Historically inbreeding has encourage a wide variety of deleterious genes in humans. --98.217.8.46 (talk) 20:41, 14 July 2008 (UTC)
 * I agree you wouldn't end up with an identical genome, since each daughter would get a different combination of the father's genes, but I think you would get an ever greater proportion of alleles coming from the father, since the only other source of genetic information (the man's original mate) would be further and further back in the family tree, thus contributing ever less of the genome, and the rest has to come from the father's genome. To reach 99% coming from the father, you would need 7 generations of daughters. By that point, almost any gene for which the father was homozygous, the daughter would be identical. For heterozygous genes, the daughter could be identical or could be homozygous with two copies of either of the alleles present in the father. I'm not sure what the odds of each option is, but I suspect it's uniform, so 50% chance of being identical and 25% of each of the homozygous cases. --Tango (talk) 22:59, 14 July 2008 (UTC)


 * I don't think you could expect to achieve more than a 75% match on average. That's because the father and mother each contribute 50% of the genes, but there's nothing to force the combination to exactly complement each other.Say the father has gene pairs aA, bB, cC, and dD.  Even if the mother has identical genes, the offspring would not likely have all the necessary genes to be your "clone".  Using the aA pair as an example crossed with another aA pair, the offspring might end up with aa, aA, Aa, or AA.  Only half have 100% of the necessary genes, while the other half have only 50% of the genes needed to match the father.  Back to four gene pairs: while there is a 1/16 small chance of having 100% gene coverage (such as aA, Bb, cC, dD), there is a 1/4 change of having 87.5% coverage, 3/8 chance of 75% coverage, 1/4 chance of 62.5% coverage, and 1/16 chance of only 50% coverage (such as aa, bb, CC, dd).  With more genes, the change of 100% coverage continues to decrease, but the average coverage remains 75%.  (I've ignored xy genes for now for simplicity.) -- Tcncv (talk) 01:48, 15 July 2008 (UTC)
 * For an exact match, you may well be right. As I said, all you can say is that after several generations most of the genes will come from the father, but not necessarily in the same combinations. For example, consider the father is ab and the mother is cd for a given gene. The options for the first daughter are {ac,ad,bc,bd} with equal chances. Then, for the second daughter, in each of those cases, you get {{aa,ac,ba,bc},{aa,ad,ba,bd},{ab,ac,bb,bc},{ab,ad,bb,bd}}, all having equal chances again. That gives a 50% that both alleles will come from the father. If you do another generation, you'll get an even higher chance of both alleles being from the father (75%, I think). --Tango (talk) 02:15, 15 July 2008 (UTC)


 * If that logic is extended to 100 generations, the chances for any of the pairs {aa,ab,ba,bb} in the daughter would approach 25% each, while the chances of the remaining combinations {ac,ad,bc,bd} would be negligible. Taking ab as equivalent to ba, we would have a 50% chance of "cloning" the gene pair of the father.  Taking aa and bb as each a 50% match to ab, we have a 50% chance of a 50% match.  Together that gives us an average match of 75%.  Given a large number of genes, the great majority of 100the generation offspring would hover be 65% to 85% match range.


 * Interestingly, it doesn't matter whether the 99th mother had gene pairs aa, ab, ba, or bb. The average match for the daughter to the father would be 75%.  (Left as an exercise.)  Note that all this only considers gene pairs with two distinct halves.  It doesn't count genes that start out like aa in the father. -- Tcncv (talk) 05:01, 15 July 2008 (UTC)


 * Note that time travel into the future is not only permissible, it is inevitable. We all travel into the future by one year per year. You can get the same genetic effect by simply freezing enough sperm and then using some for each generation. To avoid the ethical problem and speed up the process, I recommend that you use mice instead of men. -Arch dude (talk) 00:25, 15 July 2008 (UTC)


 * "How much do random mutations mess it up?" Mutations are much more likely to prove fatal than beneficial, so such mutations would likely be quickly eliminated.  Even if a daughter with such a mutation is impregnated, as long as the likelihood of surviving and giving birth is lower with the new gene than without, the next daughter would likely not have the mutation.
 * 100 generations seem much too short of a time for beneficial mutations to appear. If one does appear, it would disappear as soon as the father reproduces with a daughter who does not have the mutation.  --Bowlhover (talk) 07:45, 15 July 2008 (UTC)


 * And much, much more likely than either to not do much at all, in which case they would be preserved. 79.66.54.186 (talk) 11:22, 15 July 2008 (UTC)


 * Does this father have a dud Y chromosome or something? Nil Einne (talk) 14:59, 15 July 2008 (UTC)


 * I'm assuming 190.190.224.115 intended for the father and daughter to breed as many times as necessary to ensure a succeeding generation will exist. --Bowlhover (talk) 15:54, 15 July 2008 (UTC)
 * We have an article about this: Backcrossing. Rockpock  e  t  17:12, 15 July 2008 (UTC)


 * hey, why not go whole hog? All_You_Zombies%E2%80%94 Gzuckier (talk) 20:01, 16 July 2008 (UTC)

Fetus blood type
How soon is it possible to tell a fetus' blood type? Mac Davis (talk) 23:41, 14 July 2008 (UTC)
 * Have a look at our terrible Amniocentesis article. Or better don't. (First thing tommorow, I'm going at it) and this which says it is carried out from 15 weeks. Fribbler (talk) 23:55, 14 July 2008 (UTC)