Wikipedia:Reference desk/Archives/Science/2007 June 24

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[edit] June 24

[edit] Cat Milk

Settle a bet. Is there anyone, somewhere in the world, who harvests and distributes cat milk? (For any purpose whatsoever, including but not limited to human consumption, infant feline consumption, or the hell of it.) Or, if you don't know, do you know where I might find out? Black Carrot 00:18, 24 June 2007 (UTC)

Well here is a site that says it is a delicacy across Europe, presumably that means there is some company that distributes it. 68.231.151.161 02:26, 24 June 2007 (UTC)

That page reads almost like satire to me, I have no idea if it is real or not. For feeding kittens, cat milk formula is widely used [1], though I know of some scientific studies that have used feline milk, the scientists collected it themselves rather than buy it. Rockpocket 02:37, 24 June 2007 (UTC)

I pity the fools who have to herd the cats, and worse, milk them. Clarityfiend 02:40, 24 June 2007 (UTC)

http://www.youtube.com/watch?v=1SmgLtg1Izw — Omegatron 02:51, 24 June 2007 (UTC)

I'm pretty sure that the cat milk website is a joke - "In the dairy industry it has long been observed that cats have double the teats of cows, hence twice the source of pure cat milk." And Pussy Whip? Come on. For feeding kittens, it's usually kitten milk replacer that is used, which has cow milk as its source. I've never heard of any products actually containing cat milk. But as Rockpocket said above, you can find articles on nutritional and disease studies involving cat milk, for instance PMID 17307374. --Joelmills 03:00, 24 June 2007 (UTC)

Just to be sure, I gathered some reference material (a cat whose belly was recently shaved, and whose teats are therefore prominent), and can tell you with some confidence that your standard-issue housecat has 4, same as a cow. —Tamfang 05:35, 24 June 2007 (UTC)

No, cats have 8 nipples. --67.174.1.215 15:42, 24 June 2007 (UTC)

No, but in Mexico they harvest, make and distribute chihuahua cheese. There's a herd you don't want to get onto the wrong side of. Bendž|Ť 05:26, 24 June 2007 (UTC)

Gee thanks, you just brought back traumatic memories of a chihuahua masturbating. I think that leather couch is still ruined -- Phoeba Wright^OBJECTION! 06:55, 24 June 2007 (UTC)

That should probably be capitalized (Chihuahua cheese, not chihuahua cheese). Nimur 06:50, 24 June 2007 (UTC)

Yeah, that first site is really obviously a joke. That aside, so far it sounds like my worthy opponent is in the lead. Her stance was that anyone who wanted to feed their kitten kitty-breastmilk would use a synthetic, and your info seems to be bearing that out. I figured that would be the case, it seems the most practical course. I'm more expecting to find it in exotic food, some kind of weird religious tradition, or maybe just an internet niche market of some kind to people who want it for unspecified purposes. Black Carrot 07:08, 24 June 2007 (UTC)

There are reliable sources for lab cats getting milked [2]. In that study it was simply done by hand. Many years ago I read about researchers who had built a mouse milking machine for some study of nutrition or whatever.It is done sometimes with a syringe [3] [[4]]. Rats also get milked [5]. I am a bit surprised there is not the availability of milk of various mammals, like the meat of exotic and game animals and the eggs of various unlikely species are sold. Some people drink goats' milk, which tastes nothing like cows milk. Beef cattle farmers have told me that beef cows produce milk, but in lower quantities than dairy cattle. On the Wagon Train tv series, one week they tried to milk a buffalo to feed a starving infant, with rather violent results. Then there is the old joke from the Bible wherein it is claimed per (American Standard Version) Genesis 22:23 that it takes 8 men to milk a bear ("These eight did Milcah bear.." Edison 16:04, 25 June 2007 (UTC)

[edit] Lunesta commercial

A common TV commercial for Lunesta states that side effects may include drowsiness. How can drowsiness be a side effect of a sleep medication? 68.231.151.161 02:24, 24 June 2007 (UTC)

You don't want to stay asleep forever. Drowsiness after your intended wakeup time is not desired. --mglg_(talk) 02:35, 24 June 2007 (UTC)

It's like the instructions on the side of boxes of bath salts: "Keep Dry". Gzuckier 14:41, 25 June 2007 (UTC)

[edit] Why do stars look like that?

Take a look at Image:NGC602.jpg. Many of the stars have a halo around it, and the cross-hair like thingie. Why? Thanks. Xiner (talk) 03:42, 24 June 2007 (UTC)

See Diffraction spike Paul venter 06:06, 25 June 2007 (UTC)

Lens aberration. Every defect and aberration that a lens has will be revealed in an astrophoto. These include spherical aberrations, chromatic aberrations, coma, astigmatism, curvature of field, and vignetting. I believe it's the chromatic aberration that is responsible for the halos. - Nunh-huh 03:56, 24 June 2007 (UTC)

The "cross-hair-like thingie" is due to diffraction by the struts that hold the telescope's secondary mirror. See the diagram at Newtonian telescope. The telescope used for your image used four struts to hold its secondary mirror, hence the four-fold symmetry of the diffraction effects. --mglg_(talk) 04:34, 24 June 2007 (UTC)

Photographers like to stimulate the cross-hair effect with cross screen filters. Bendž|Ť 05:21, 24 June 2007 (UTC)

Sometimes the effect is even added to astronomical images in post-production to add aesthetic appeal. I am sort of disappointed by the artistic liberties that have become commonplace in astronomical photography; it is one thing to make a pretty picture, but it is another to pass it off as a scientific image. Nimur 07:37, 24 June 2007 (UTC)

Please, provide sources to your claims. It seems highly unlikely that artifacts would be added to pictures just to make them pretty. Oh, and please, don't confuse channel mixing with photo manipulation. — Kieff | Talk 09:11, 24 June 2007 (UTC)

Here's the first that comes to mind... this goes well beyond false color - [6], all created from this source image from Cassini.

Deep space objects get even more post-processing. Nimur 10:40, 24 June 2007 (UTC)

No - that example isn't one of exaggeration for aesthetic reasons - read the article that goes along with the photos! It quite clearly says that by exaggerating the contrast they could find details in the data that were not obvious in the unenhanced image: "In such views, imaging scientists have noticed color variations across the diffuse rings that imply active processes sort the particles in the ring according to their sizes.". Image processing is absolutely necessary - and a quite valid scientific approach to finding more information from the available data. It may be that this is sometimes done for aesthetic reasons (after all, don't astronomers have the right to make pretty posters to hang on their walls too?) - but this is categorically not an example of that. SteveBaker 13:22, 24 June 2007 (UTC)

Perhaps this example was less than stellar. I'm not opposed to image processing, but I think there is a threshold that can be crossed, when more information is due to the post-processing than due to the source measurement. But this is a complaint which can be levied across the board against all of experimental science - "massaging the data" until it looks the way it "should." I'm probably making gross generalizations; most scientists use good technique and have integrity with respect to their data. So, I'll rescind my previous comments. Nimur 02:04, 25 June 2007 (UTC)

Calling the jpeg the source isn't altogether accurate of course... the source image would look similar to it by our eyesight and as far as the monitor could render the colours. I know nothing about digital photography, but isn't it possible that there was hidden data in the form of infrared and ultraviolet that had to be compressed into the visible spectrum? The labelled colours are, afterall simply blue and red with nought in between. Bendž|Ť 21:20, 24 June 2007 (UTC)

I strongly object to User:Nimur's characterisation of how science processes images. Certainly in astronomy - and in many other sciences too - there is no such thing as the "real" image that you can see with your eyes. All we really have is a series of spatially separated numbers representing the count of the numbers of photons hitting the detector within some waveband. Turning those into a picture for human eyes to view is for the most part an entirely arbitary process. To accuse the scientist of "massaging" the data is ridiculous. You can't see in the infrared (or whatever waveband it was) - you can't see things that faint (and certainly not in full colour). Unless you want a completely black picture, you'll never see what your eyes might have 'really' seen. You have to accept a heavy amount of numerical work on the data. Firstly we have to map the photon counts in the detectors into a range of brightnesses that you can see - then we have to shift the frequencies we measured into human frequency ranges. Worse than that - our eyes can only see about three or so orders of magnitude of brightness - and computer monitors and printers can only display a couple of orders of magnitude. If the sensors are detecting five orders of magnitude - then if you do a simple 1:1 mapping then you'll miss much of the subtlety in the data. It's all entirely arbitary - all of it. You are in no position to say what is a 'legitimate' image enhancement and what is 'over manipulation' - there never was a 'true' or 'real' image in the first place. It's purely a matter of the math of how you get this range of brightnesses and frequencies into the human range of perception. SteveBaker 02:55, 25 June 2007 (UTC)

SteveBaker, that is the difference between an "photograph" and all of the other things we call plots, charts, contour maps, data visualizations, etc. But I have already rescinded my comments as overgeneralizations. I understand your point about "arbitrary" visualization. More effort should be made to convince the general public that "this isn't what it would look like if you were looking at this object with your eyes." Nimur 06:07, 25 June 2007 (UTC)

Alright, so it was just a benign generalisation. I'd like to know of a single case where a scientist has used "more information due to the post-processing than due to the source measurement" without being defrocked of his labcoat. This instance is from an academic paper where a "planets may look smaller/darker/duller/less-inspiring-to-E.T.-ologists than they appear" disclaimer would be insulting. If it's in an elementary science textbook, they do just that. Bendž|Ť 13:29, 25 June 2007 (UTC)

This is an interesting discussion. I really think astronomical visualisation techniques and principles deserve an article! JH-man 08:39, 27 June 2007 (UTC)

It's not just astronomy though - all sorts of scientific visualisations require enhancement technologies...and are potentially the subject of abuse if not treated correctly. Think about a "photograph" taken with an electron microscope for example - there is no light coming from the object being photographed - and the machine has to convert the image formed by the electrons into an image we can see and understand - and the processes involved can be identical to the kinds of things we do to data captured with a telescope. In that case, it's pretty obvious how to display the data - so any 'manipulation' of it might come in for these kinds of criticism (unnecessarily so IMHO). But imagine taking the raw data from an X-ray diffraction machine and visualising the crystal structure from the raw data! In that case, the 'enhancement' isn't just shifting colours and brightness ranges around - it's a full-scale reconstruction. So I don't think we need an astronomy-specific article - we need something about scientific data visualisation in general...and we have that in Scientific visualization, Visualization (graphic) and Knowledge visualization. SteveBaker 15:27, 27 June 2007 (UTC)

[edit] Kaiser Permanente's origens

Did the modern Kaiser Permanente entity begin in Richmond, California? (PLEEEASE let me know on my talk page if youve answered or answer there too hugs) ^{Cholga is a SUPERSTAR}¡Talk2Cholga!_{Sexy Contribs} 03:48, 24 June 2007 (UTC)

Yes. See Kaiser Permanente. —Tamfang 05:27, 24 June 2007 (UTC)

Per User talk:Tamfang, Cholga's real question appears to be: how can I persuade another editor that this info belongs in the Richmond article, if the mention in Kaiser Permanente is insufficient? —Tamfang 06:48, 24 June 2007 (UTC)

Well, Kaiser says it started in Richmond, and so does this site, though I'm not sure about its reliability. Corvus cornix 18:38, 25 June 2007 (UTC)

[edit] The evolution of annoying fish bones

Several mammals, such as Grizzly bears, prey on fish. Could this evolutionary pressure push certain bony fish towards having more bones, or sharper, peskier bones? Which earlier studies have looked into this speculation? Best, Lior 05:53, 24 June 2007 (UTC)

It's possible that fish might evolve that way. The question would be whether the losses due to bear predation were more damaging to the fish than the wasted energy or other disadvantages of having more annoying bones. If so, then it's possible that they could evolve that way (and in fact, the present shape of their bones is very likely to reflect the best balance between annoying the bears and getting on with life). SteveBaker 13:14, 24 June 2007 (UTC)

Note that the bear must have a way of guessing the shape of the bones without killing the fish, or else this evolutionary development could only occur as group selection which is generally less effective than selection on smaller units like individuals or genes. Icek 14:27, 24 June 2007 (UTC)

Yeah, along the lines of Icek, there really is no mechanism that would allow such an evolutionary event to occur. A bear would only know what kind of bones exist in the fish after/while eating it. At which point, it has already been selected against, regardless of its bone structure. And also, group selection doesn't happen, and is no longer viewed as a possible mode of evolution. --Cody.Pope 15:16, 24 June 2007 (UTC)

Thank you for your fascinating answers. According to your explanation, I fail to grasp how Hebeloma crustuliniforme could have developed its nauseating properties. This mushroom has to be consumed, at least partially, for its naive consumer to feel sick. So how could it be selected for without group selection coming into play? Once I grasp that, the speculative bear hypothesis will be easier to rule out. I guess bears alone do not lay enough pressure over them fish, but let bears represent the total mammalian (or soft-palated) pressure for this matter. By the way, perhaps group selection should be adapted to conform with Cody's last remark. Lior 16:28, 24 June 2007 (UTC)

Erg, learning is what allows for Hebeloma crustuliniforme-like systems to exist. But a bear grabbing fish in a river is a rather hap-hazard endeavor. I was more or less assuming that the act of catching killed the fish and also that the act was random, so that learning couldn't play a huge role. Especially with poisonous animals/plants/fungi, learning plays a big role in avoidance. Also, I haven't looked at group selection, but will when I have the energy. --Cody.Pope 17:05, 24 June 2007 (UTC)

Erg and also, I've looked at the group selection article, it's more or less fine. The thing is is that the cited Wilson paper discusses some extreme social systems, whose evolutionary histories aren't super well understood. When group selection is viewed in systems of high relatedness (like ants or the mole rat), then individual selection can appear to be group selection, when it really isn't (but that's a point of contention). I guess I should amend my comment about group selection to say that the mode is a highly contentious, which is what the article says. --Cody.Pope 17:14, 24 June 2007 (UTC)

As far as I could tell from watching Grizzly Man, Grizzly bears seem to be rather selective fish catchers. Then again, watching the film to this point requires a considerable degree of mental fatigue that precludes fair judgement. I take your answers to imply that fish might only become peskier if their dominant predators can learn that, and that studies on this matter are not widely known. Cheers, Lior 19:03, 24 June 2007 (UTC)

Group selection is just a way of looking at natural selection, but of course, fundamentally, the gene is what is selected for or against. Most damage-inducing predation deterrents work with a warning signal, as there's no use making your grizzley die from tetanus resulting from mouth wounds caused by your pesky rib cage if the rest of you is sitting in its gut. Armour or spikes are more probable solutions as they can be seen and will save your hide. Batesian mimicry is worth a shot if you share your habitat with similar species to you that are poisonous with cautionary bright colours, but don't want to expend resources synthesising poisons yourself. Bendž|Ť 21:46, 24 June 2007 (UTC)

[edit] Electroblotting

Why is the reason for the need to pre-soak the PVDF membrane in methanol before transfer? Is it because methanol aids in the binding of proteins to membrane? If so, how does methanol aid in the binding of proteins to membrane? Or, if not, could you please tell me why?

Thanks alot for your help;)

Could you please offer a little more context? Yechiel Man 17:11, 24 June 2007 (UTC)

Reading from here: "it is there to stop the gel swelling due to heating, and to keep proteins denatured for attachment to the membrane." Someguy1221 20:02, 24 June 2007 (UTC)

[edit] Which city in the U.K are you most likely to find Rats?

Which city in the U.K are you most likely to find Rats? --I.W Iway amway Imagineway Izardway. 11:49, 24 June 2007 (UTC)

There are undoubtedly significant rat populations in every city in the UK - quite possibly in every city in the world. So I guess the question is either: Which cities are most likely to bring you into contact with the rats? Or: Which city has the most rats? Or: Which city has the largest ratio of rats to humans? The second question is probably the same as asking "Which is the largest city in the UK?" - which would be London. For the other two - I have no idea. SteveBaker 13:06, 24 June 2007 (UTC)

I'd say London, since that's where Parliament meets, but perhaps equating rats to politicians would be unfair to my rat brethren. :-) StuRat 01:43, 25 June 2007 (UTC)

[edit] How was matter created in the universe?

Einsteins General theory states that things cant travel faster than the speed of light. And if they did, "anything" travelling faster than the speed of light will become more massive. Is ths how the first matter was created? And if this is so, when the universe began what was the "anything" it stated with? WAs it light? DId light travelling faster than light become massive enough to be matter? Was it dust? and if so presumable there was no dust at the beginnig of the universe. And if the universe was created in the process of the big bang can we assume that the big bang acelerated faster than the speed of light, and it was that which created the "first" matter?

Would like an answer to this question that doesnt include "dark matter" please. Dark matter seems to be some recently invented nonsense that seems nothing more than a desperate attempt to force the universe to fit into our common sense notion that there must be stuff out there. Im sure there was an established theory of my question before "dark matter" and I'd liek to be reminded of what what was.

Thanks

ASamuel

I don't have good answers for you myself, but you might find these links useful: Quark-gluon plasma, Cosmic inflation. --Allen 15:10, 24 June 2007 (UTC)

Also note that while dark matter may in fact be nonsense, it enjoys significant support by astronomers because every other theory explaining the available observations is worse. --TotoBaggins 15:16, 24 June 2007 (UTC)

One clarification: Our questioner said: "anything" travelling faster than the speed of light will become more massive" - that's not what Einstein said. He said that it's not possible to travel faster than light at all. Things get more massive as they get closer to the speed of light. I think it's dangerous for someone outside of the field of cosmology/astronomy (especially someone who appears to be clueless about relativity) to declare dark matter to be nonsense. Whilst it's not an entirely proven theory, it fits the facts perfectly and there is no evidence to disprove it. The only really viable theories that don't include dark matter require new forces that we have not observed or modifications of the laws of gravity that we don't see in reality. All of the theories are 'out there' - and dark matter is probably the least unbelievable. Let's leave the experts to figure out whether it's true or not. At any rate - I recommend that our questioner read Big bang. SteveBaker 17:15, 24 June 2007 (UTC)

As far as I know it doesn't follow from Einsteins theory that it wouldn't be possible for anything to travel faster than light. Only thing is that anything traveling slower than light cannot be accelerated to or above the speed of light. 84.160.217.154 21:17, 25 June 2007 (UTC)

Oh...groan...the whole tachyon thing. I think that's been pretty carefully busted as a thoery (as our article explains). There are other theories out there that permit them - but we're not talking about them - we're talking about Einstein. According to him, tachyons would experience time and space distortions that follow the Lorentz factor: ${ 1 \over \sqrt{1 - v^2/c^2} }$ - go ahead - plug in any value for v that's greater than c and you'll discover that you're taking the square root of a negative number...the mass, time contraction, distance measures - all become imaginary numbers! You can't have imaginary numbers popping up in the real world - so no going faster than c according to Einstein. SteveBaker 02:16, 26 June 2007 (UTC)

With the same argument you can compute the z coordinate of a sphere by ${ \sqrt{1 - x^2 -y^2} }$ and deny the existence of Australia 84.160.217.154 06:20, 26 June 2007 (UTC)

OMG! That's utter nonsense!! Jeez! If you're going to answer questions on the science desk, you should probably learn a little high school math! What you can prove with the equation for the surface of a sphere $z = { \sqrt{1 - x^2 -y^2} }$ is that no point on the surface of a sphere of radius 1 (which is what that equation describes) can have a coordinate such that (x²+y²)> 1 because that would result in an imaginary z coordinate. But since no point on the surface of an idealised spherical earth violates that constraint, there is no problem. Australia's negative Z coordinate (in the southern hemisphere) is perfectly fine because the square root of a positive number can be either positive or negative - so there is no difficulty whatever. The problem with v>c in the example above is that (1-v²/c²) is NEGATIVE - and you can't take the square root of a negative number without getting an imaginary result - that's totally different from the situation with the equation of a sphere and Australia! Please learn the following facts about square roots: The square root of a positive number can be either positive or negative - but the square root of a negative number is imaginary. Imaginary distances, times and masses are not allowed - so NO!!!! per Einstein, you are not allowed to travel faster than 'c'. Sorry. SteveBaker 15:14, 26 June 2007 (UTC)

Seconded. In fact, read cosmology and all of the linked articles, especially baryogenesis, nucleogenesis and Big Bang nucleosynthesis. I'm afraid if you are looking for a simple answer, you are asking the wrong question ! Gandalf61 18:13, 24 June 2007 (UTC)

[edit] Earth

how did earth get a exact spherical shape and not an irregular shape?

For starters, it's not an exact sphere; see Figure of the Earth. For why it's roughly spherical, I think that's in Planetary formation. --Allen 16:14, 24 June 2007 (UTC)

Well, maybe that second link isn't the best. There are several related links about protoplanetary this and that and I'm not sure what's best. But anyway, I think the answer is that a sphere is the shape that any blob of fluid tends to take when the forces of its own gravity dominate other forces. --Allen 16:18, 24 June 2007 (UTC)

Right - and the deviation from an idealised sphere comes about because the earth is spinning - so ceentrifugal force makes it bulge a bit at the equator and is squashed/flattened a little at the poles. SteveBaker 17:02, 24 June 2007 (UTC)

And then, tectonics gives a very minute variation (mountains, valleys, and oceans) on top of the geoid. Cumulatively, these are very small variations of a few kilometers; comparatively, earth radius is roughly 6350 km. Nimur 02:11, 25 June 2007 (UTC)

Yes, these things seems like they're big to us, but on the scale of the Earth they are very small. A nice analogy I've heard is that if put on the same scale, the surface of the Earth would be smoother than a billiard ball. --jjron 05:06, 25 June 2007 (UTC)

I've read that too but I've never quite believed it. Even on such a minute scale, the Himalayas would hardly be that indistinguishable from coastal areas - would they? Maybe indistinguishable by sight, but I doubt by touch. -- JackofOz 12:32, 25 June 2007 (UTC)

Shrinking the earth to a billiard ball is about 200 million to one. At that scale a difference of a kilometer is 5 micrometers (on the order of a speck of dust). I don't know if we can distinguish that. iames 13:32, 25 June 2007 (UTC)

Five micrometers? That's right on the edge of what you can distinguish by touch. The Himalayas will show up as a rough patch on your billiard-ball Earth. --Carnildo 22:48, 26 June 2007 (UTC)

I've never quite believed it, either, but according to our Earth article, it's true. Though the rough patch may be detectable, it won't disqualify the billiard ball from being officially acceptably smooth. —Steve Summit (talk) 12:17, 15 July 2007 (UTC)

In short, gravity. Even rock has a point at which it won't hold more weight above it. For instance, note that Mars, being smaller then the Earth, has bigger mountains before gravity makes them fall down. And that asteriods, or Phobos and Deimos, are small eough to be randomly shaped. Gzuckier 14:47, 25 June 2007 (UTC)

Sure gravity is very important and essentially sets an upper limit, but erosion by wind, water, etc also plays a significant role in this as well. Obviously more significant on Earth than these other places. --jjron 23:40, 25 June 2007 (UTC)

Gravity is the main answer to the question, though. It acts globally to make the planet more or less spherical. Erosion just smooths out some of the bumps and hollows. --Anonymous, June 26, 2007, 21:30 (UTC).

I don't understand the debate between gravity and erosion here. If we're talking about relatively small-scale things like mountains (as opposed to the flattening of the poles and the bulging of the equator), you can't say which effect is in charge. Think about it for a moment: Without bits being knocked off the rocks due to erosion, gravity would have no part to play because the rocks would just sit there in whatever odd shape they were at to start with. Without gravity, erosion could knock bits off the rocks - but they wouldn't settle into hollows to make a more spherical planet, they'd just float off into space somewhere. It's only the two effects taken together that explains the tendency towards a more accurate approximation to a sphere. But on the other hand: Gravity can cause lighter materials to be pushed upwards to make room for heavier ones beneath - so gravity can cause surface irregularities to appear in a previously smooth surface (think about volcanic islands appearing in the middle of the ocean for example)...and erosion doesn't always make things more smooth and spherical either - look at the deep valleys cut by rivers and glaciers in otherwise flat plains. (The Grand Canyon in the USA for example). So there isn't an 'either/or' debate here. You need both of them to attain smoothness - yet both of them are also causing irregularities. SteveBaker 15:15, 27 June 2007 (UTC)

The question was only one sentence, so we sort of have to guess what the original poster had in mind, and I guess the "debate" is really about that. When I saw "irregular shape" mentioned in this context, it made me think of bodies like the smaller asteroids and moons that are not even close to spherical... and this is possible because they don't have much gravity. However, the question also used the word "exact", which does bring to mind the fine-tuning of the shape due to erosion. --Anonymous, June 27, 22:56 (UTC).

The early responses seemed to form a "hierarchy" or spectrum of (roughly) coarse to fine adjustments to the earth's shape; planetary formation and gravity shape the mass into a sphere; rotational motion squishes it into an oblate spheroid; tectonics and geology encourage mountain ranges and plateaus; and small-scale erosion creates river valleys, glacial canyons, etc. On the most microscopic scale, tiny irregularities can be caused by animal, plant, and human activity. Nimur 00:57, 28 June 2007 (UTC)

[edit] Polyester

How to check carbon content in polyester black fibre by an instrument
We have chemical method which takes too much time
—Preceding unsigned comment added by 59.95.205.125 (talk • contribs) 17:28, 24 June 2007

You probably want a total inorganic carbon machine like this one: [7] Rmhermen 21:58, 24 June 2007 (UTC)

[edit] The cytotoxic T cell that wasn't

For school I and several other students had to analyse the results for a FACS and figure out what the patient was suffering from. Now you could basically make up anything you'd want. So we setteled on immunosupressed and we know the teacher will be happy with it. Something really stumped me though. If my calculations are correct our patient has a very low T cell count (9%) and an even lower Tcyt count (0.8%) (thus the idea that the patient is immunosupressed). But the patiënt has many cells that express CD8 but not CD3. Aren't cytotoxic T-cells supposed to express CD3 and CD8 at the same time?

So my question is: Are there cells that only express CD8? And if not, how can I (for my own sanity) explain the apperantly rather large amount of cells solely expressing CD8 and not CD3?PvT 18:24, 24 June 2007 (UTC)

No need to go off the deep end :)... there are a number of possible explanations. The cumulative effect of loosing CD3 expression would indeed be immunosupression. And, yes, normal CTLs express CD3 and CD8, but in tumor infiltrating T cells, abundant evidence has shown that a down-modulation of TCR-CD3 (specifically the ζ (zeta) chain) occurs, and possibly contributes to suppression antigen-specific T-cell responses against the tumor.[8] Loss of CD3 expression has also been observed during viral infection (like HIV) and in several autoimmune diseases. In all three situations the loss of CD3 expression is not (usually) accompanied by a loss of CD8 expression[9][10] and could explain the large population of CD3-/CD8+ cells you are seeing. It is worth mentioning that, in a normal immune reaction, CD3 is transiently down-regulated during T-cell stimulation, but this wouldn't usually result in a profound loss. --DO11.10 07:05, 30 June 2007 (UTC)

[edit] Circular orbits -- Saturn's rings?

I'm writing a blurb on conic sections for a science museum (in Guatemala City). I want to use orbits as one example. It's easy to find examples of elliptical and hyperbolic orbits, but what about circular ones? I thought maybe I could use Saturn's rings. It seems obvious just from looking at some of the better pictures that some (frictional?) process has all but eliminated any eccentricity from the rings - I'd wager that in general they're as perfectly circular as just about any precision-machined doodad, and that any deviations are more like ripples from the moons than like elliptical eccentricity. Can anyone back me up (or shoot me down) on this? --Homunq 21:38, 24 June 2007 (UTC)

It seems from a bit of Googling that the rings are mostly circular, although the individual particles have elliptical orbits ([11]). Apparently the F Ring and the Titan Ringlet are elliptical exceptions. --Allen 22:37, 24 June 2007 (UTC)

Amazing (but irrelevant) factoid about Saturn's rings: if you scaled the A Ring down to the diameter of a dime, it would only be about 4 hydrogen atoms thick. --TotoBaggins 14:02, 25 June 2007 (UTC)

So how many atoms uncircular would it be? --Homunq 18:07, 25 June 2007 (UTC)