Wikipedia:Reference desk/Archives/Science/2009 June 1

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June 1

Cholesterol Level/Temporal Arteritis

I am a 79 year of age male married and have five children. On September 9, 1995, a biopsy was taken from the artery on the left side of my temple and was diagnosed as Temporal Arteritis. I am presently on 5 mg of prednisone taken daily and a quarterly (ERS) lab work is done by my family doctor. The present rate is 25.

I continue to have high level cholesterol even after a week of fasting on a low cholesterol diet prior to blood work and taken every precaution to get it down. My cholesterol for the last three years are - 11/14/07 = 221, 01/24/08 = 198, 04/13/09 = 197.

Can the inflammation of the main arteries caused by arteritis create an incorrect reading on the lab test for cholesterol? Thank you. —Preceding unsigned comment added by 76.7.97.223 (talk) 00:11, 1 June 2009 (UTC)

We apologize, but we have a policy that prohibits us from answering medical questions such as this on Wikipedia. -- Tcncv (talk) 00:47, 1 June 2009 (UTC)

As Tcncv says, we cannot give medical advise. You need to go and talk to a doctor. If you suspect your doctor may have made a mistake, you can get a second opinion from another doctor. --Tango (talk) 15:15, 1 June 2009 (UTC)

Seeing a blue tint for a minute - overexcited photosensitive ganglion cell activity?

It was a lovely, lazy Sunday afternoon, and I at out on my deck for a few minutes. With the sun beating down, I looked up into the brilliant blue sky and closed my eyes and relaxed for a few minutes. (Maybe have had a 1-2 minute nap.) When I went back inside, things were in a slight blue tint for a minute, maybe less.

What caused this? In checking the articles on vision, I happened upon the photosensitive ganglion cell article, as one of the cells that picks up informationa nd sends it brainward. Was this from overstimulation of these cells? It's a logical hypothesis, from my estimation, becasue not only was I staring totally at the blue sky, but with my eyes closed, would each pupil also be bigger? After all, with them closed I can still see slight differences in light and dark, such as my room light here versus under my desk.

Thanks And, don't worry, I'd never stare directly at the sun - even with my eyes closed. :-).Somebody or his brother (talk) 00:41, 1 June 2009 (UTC)

I am not familiar with the specific seeing-blue-tint phenomenon you describe, but my guess is that it is caused by adaptation and/or bleaching of L and M cones compared to S cones while you were outside, resulting in higher response from S cones compared to L and M. The thing is, human eyelids are not completely opaque, so some light gets through; and the light that gets through is mostly at the long-wavelength end of the visible spectrum. Thus, L and M cones are exposed to light in their respective opsin absorption bands, and adapt to that light; but S cones are not (as they mostly absorb short-wavelength light), so they adapt to the relative "darkness". If you look at a bright red or orange light for a while, objects projected on that area of the retina will look green or blue for some time after that. I guess that what you have experienced is largely the same effect. Now your second question is on photosensitive ganglion cells. Our article on the photosensitive ganglion cells is extremely detailed, considering how little do we actually know about them. They certainly project to suprachiasmatic nucleus, helping to regulate the circadian rhythm; they also likely have an effect on pupillary contraction via the olives. However, I seriously doubt they have such a strong and direct effect on color perception as the phenomenon you describe. I'm not ruling them out 100% as a "suspect" in your phenomenon, but I think there may be far simpler - and more conventional - explanation for your experience, like the one I gave above. All the best, --Dr Dima (talk) 02:14, 1 June 2009 (UTC)

Yes it'd give the same explanation but a bit simpler than Doc. Your eyes get used to the red colour you see with your eyes closed, so then everything else looks really "not red" afterwards. Aaadddaaammm (talk) 10:11, 1 June 2009 (UTC)

Cool, thanks, y'all.Somebody or his brother (talk) 10:40, 1 June 2009 (UTC)

Young's double slit experiment

Dear Wikipedians:

What does "first order image" mean for Young's double slit experiment? I'm having trouble with this terminology, it seems to be made up by my physics teacher, I can't find it anywhere in double-slit experiment.

Thanks,

70.31.158.159 (talk) 02:10, 1 June 2009 (UTC)

Maybe they mean the first diffraction fringe (strongest, central bright area)? Nimur (talk) 07:31, 1 June 2009 (UTC)

No that's the zeroth order fringe. The first order images are the ones sitting next to it on either side...the peaks of intensity...that's how my teacher taught me :-) Rkr1991 (talk) 08:34, 1 June 2009 (UTC)

Thanks!!! I was able to get the right answer with the definition. 70.31.158.159 (talk) 14:46, 1 June 2009 (UTC)

Technicians on planes

I noticed on the AF447 article, that there were 3 technicians onboard. It made me wonder whether there are always technicians onboard, what they actually do, and where they sit. Can anybody help? Thanks United Bob (talk) 13:32, 1 June 2009 (UTC)

That statement has now been removed from the article, so it may not have been accurate. I don't believe it is routine to have technicians on board, but some planes do carry a Flight engineer, who sits on the flight deck with the pilot and co-pilot. Modern planes don't generally have engineers. I doubt an Airbus A330, like the one involved in this incident, had one. --Tango (talk) 14:10, 1 June 2009 (UTC)

Indeed - flight engineers are pretty rare these days - what they used to do was to monitor the engines for vibration and/or temperature problems - and also track fuel consumption, shift fuel from one tank to another if one engine was consuming more than the others - that kind of thing. Other airline staff such as technicians frequently fly with an aircraft as passengers in order that they can do some maintenance during the next stop-over or something...I suspect that's what happened in this case. It's hard to read anything meaningful into it though. SteveBaker (talk) 17:47, 1 June 2009 (UTC)

Yes, they could have been Deadheading (an unfortunate term, in context). --Tango (talk) 18:11, 1 June 2009 (UTC)

Output Formula question

output for per man per shift formulaSathyavolu sar (talk) 13:35, 1 June 2009 (UTC)

i want to know about the formula for "output per man per shift" in a mass production manufacturing industry

can any body help

Sathyavolu sar (talk) 05:30, 1 June 2009 (UTC)

I have moved your question to a new section so it can be answered. Since you are probably new to Wikipedia, I have also taken the liberty of copying your talk-page message to this location where it will probably be better answered.

Have you looked at the man-hour article? Nimur (talk) 14:46, 1 June 2009 (UTC)

Take the total amount produced and divide it by the total number of shifts (that is the average shifts per person, times the number of people). --Tango (talk) 15:13, 1 June 2009 (UTC)

Adderall vs. recreational speed

Does Adderall differ from the amphetamine pills that are standard among recreational users? If so, how? NeonMerlin 14:07, 1 June 2009 (UTC)

A major issue with all illegal pharmaceuticals is the lack of quality control. For refined drugs (heroin, cocaine) the chief issue is concentration (alloyed with dangers from harmful adulterants and from poor hygiene). Synthesised drugs (ecstasy, lsd, pcp, amphetamine) have additional issues with purity. It's really quite difficult to make exactly the drug desired, without inadvertently making lots of similar compounds as well. Getting that justright is a core business of major pharma companies; bunging stuff out the door is a core business of some gangsters in an industrial park in The Hague. Adderal is a specifically chosen cocktail of related amphetamines, picked to support a desired psychopharmaceutical outcome. By contrast, if someone is buying "amphetamine" from some bloke in a club somewhere, he'll likely be getting pills with a diverse range of related substances, in unknown concentrations and proportions. Moreover, as the Adderall article notes, it's dispensed in a pill which has been engineered to control its release, whereas the illegal pill hasn't been. That all said, related compounds often have very similar effects, so most of the bad things that illegal "amphetamine" pills can do to you are also dangers of their prescribed brethren. Hopper Mine (talk) 17:20, 1 June 2009 (UTC)

Adderall is a mix of two mirror-image molecules of amphetamine, dexamphetamine and levoamphetamine. Some recreational pills may be mixed, some may be dexamphetamine, some may be methamphetamine which is a different compound. As Hopper Mine pointed out, illicit drugs can virtually contain anything e.g. caffeine, benign or even toxic compounds. - cyclosarin (talk) 07:41, 7 June 2009 (UTC)

Inorganic chemistry

How metal exess defect responsable for violet colour of KCl due to exess k and pink colour due to exess Li ?Rikichowdhury (talk) 15:58, 1 June 2009 (UTC)

Wow. I am not sure I understand your question at all. KCl and LiCl are white solids and/or clear solutions. The colors only become apparent during flame ionization or gas-phase eletrical ionization, as in a Geissler tube. Could you elaborate on your question so that we can answer it better? --Jayron32.talk.contribs 18:34, 1 June 2009 (UTC)

Are you talking about something like KCl_0.99? How do you make this? You could make K deficient KCl due to radioactive decay, if you could find some billion year old KCl. Graeme Bartlett (talk) 01:40, 2 June 2009 (UTC)

I definitely remember studying about it during my school days. It has something to do with that one unpaired excess electron which the excess K provides. It absorbs energy (from incident light rays) and goes up to higher levels, and we see the complimentary color of the wavelength absorbed. I am actually quite amazed that we don't have a page on this (or maybe i looked in all the wrong places), but the fact remains that if you heat (white) KCl with excess potassium vapour, your compound turns purple. The same thing also holds for LiCl. Rkr1991 (talk) 04:38, 2 June 2009 (UTC)

Inorganic chemistry

Two compound NaCl and AlCl3 . Here NaCl is ionic crystal and AlCl3 is covalent in natuer .But when we use highly polar solvent AlCl3 treatet as ionic why ?Supriyochowdhury (talk) 16:04, 1 June 2009 (UTC)

Your understanding of "ionic" and "covalent" is somewhat flawed. Don't think of the two as two sides of a coin, but rather as two ends of a continuum. All bonds basically consist of positive charged nuclei attracted to a negative charged electron cloud consisting of the "bonding electrons". The difference between an ionic or covalent bond is the location of the bonding electron cloud. Consider these extremes:

covalent bond

ionic bond

The deal is, that almost all compounds exist somewhere between these two extremes. Most of the time, the bonding cloud is not localized exactly in the middle, but it is also rare to find it centered on one of the two nuclei. The center of electron density in all compounds will lie somewhere between the midpoint of the bond length and the center of the more electronegative atom. Aluminum Chloride lies almost exactly 50% between the right and left picture; the bonding in aluminum chloride is covalent enough that it has a relatively low melting point, but it is ionic enough for water to seperate the aluminum from the chloride during the solvation process. It would not be unique in this regard; the strong acids like hydrochloric acid and nitric acid behave much the same way; HCl is a gas at room temperature but it ionizes 100% in water. --Jayron32.talk.contribs 18:29, 1 June 2009 (UTC)

In short, no compound is purely ionic, or purely covalent. There is always a balance. In the case of AlCl₃, it is covalent because of the large positive charge of the metalk cation and relatively bis anion (Fajans' rules). However, in polar solvents, this bond is easily broken, and you get the charged ions, because of the large difference in electronegativity between the atoms. The positively charged Al ion is surrounded by the negative part of the solvent (OH^- if the solvent is water) and the negatively charged Cl ion is surrounded by the positive part of the solvent(H⁺ if the solvent is water). This leads to a stabilization called the solvation enthalpy. If this enthalpy is able to compensate the enthalpy required to break the Al-Cl covalent bond, then the compound is solvated, which is what happens here Rkr1991 (talk) 04:32, 2 June 2009 (UTC)

human body

what is the function of the gall bladder —Preceding unsigned comment added by Javedesmail (talk • contribs) 17:56, 1 June 2009 (UTC)

All you have to do is type "gall bladder" into the search box on the left side of the screen, and it will take you to the gall bladder article. Friday (talk) 18:01, 1 June 2009 (UTC)

Does crumpling a piece of paper increase its density?

Help me settle an argument. Please source this well. Lesath (talk) 19:50, 1 June 2009 (UTC)

No. Depending on how you define it, the density either stays the same or decreases. If you are referring to the density of the paper itself, crumpling it has no significant impact at all. If you are referring to bulk density (the mass divided by the volume it actually takes up), then it decreases - you can fit more uncrumpled pieces of paper in a given box than crumpled ones. --Tango (talk) 20:17, 1 June 2009 (UTC)

We don't have pages. What you may be hunting for is the compressive strength that crumpled paper displays. There are formulas that you can use in package design to calculate the amount of crumpling and the increase in compressive strength. (Corrugated fiberboard needs a section there, pages for BCT and ECT are missing.) For packaging there is another important factor and that is that cumpled paper does not only have compressive strength, but elasticity too. Mechanically crumpled paper has more predictable results than manually crumpled paper. It is used by industry in packaging [1] [2] [3] [4]71.236.26.74 (talk) 01:49, 2 June 2009 (UTC)

Paper is made up of microscopic fibres with spaces between them (see photos), and compressing it would certainly reduce the spaces and increase the density (by close inspection you can see that papers often have a slight hairiness). Whether crumpling up a sheet in your hand would compress the fibres enough to significantly reduce the volume, I'm not so sure. The question of how to measure the volume of a hairy thing is not simple either. --Maltelauridsbrigge (talk) 13:54, 2 June 2009 (UTC)

I don't think crumpling a piece of paper has any bearing on its density. Its configuration changes, but I don't think that its density changes at all. Density is a factor of the material. Changing the configuration of a material such as a sheet of paper has little bearing on the material's density, in my opinion. Bus stop (talk) 14:07, 2 June 2009 (UTC)

Damaged parrot mandible

The upper mandible of this parrot was damaged in an accident, causing it to be much shorter than the lower one - a condition which makes it impossible to feed itself. It has been suggested that the lower mandible be cut back in the hope that the upper would then regrow. Can anyone advise? Rotational (talk) 20:06, 1 June 2009 (UTC)

You really need to talk to your avian veterinarian about that. The reference desk does not provide medical advice. I will say that I have seen and read about birds with prosthetic beaks in the past, though... --Kurt Shaped Box (talk) 20:15, 1 June 2009 (UTC)

I agree that you need to talk to your avian veterinarian, but I disagree that this condition makes it impossible for your parrot to feed itself. I have a green cheek conure with this exact injury. His upper beak will never grow back as the damage was too severe. Every couple of weeks, I use a dremel tool to file his lower beak down so that it doesn't overgrow the top beak and he eats just fine. In fact, he eats exactly the same foods that he ate before the injury. If your bird is having trouble eating, then I would suggest purchasing a coffee grinder to grind his food into a course powder that will make it easier for him to eat. If you can not do the filing yourself, your vet can do it. It is amazing how well any creature can adapt to their situations.

Sun limb - how to make sense of the direction

I understand that the edge of the sum is called a limb, but I don't understand why the upper left is called the Northeastern Limb.

Note the new solar prominence and sunspot identified as being on the northeastern limb.

Space Weather 1 June 2009

I get the north - why the east?Sphilbrick (talk) 21:14, 1 June 2009 (UTC)

Imagine facing the south; east would then be to your left. Look up to the sky and east would still be to your left, but north would be "up"--so east is to the left of north. In the heavens, the directions are mirror-reversed simply because one looks up towards the sky and down towards the ground. --Bowlhover (talk) 22:15, 1 June 2009 (UTC)

They can't call it "upper left" because that would depend on where on the Earth you were. What's the top for a viewer at the North Pole would be the bottom for a view at the South Pole (they are, in effect, standing upside-down relative to the person at the North Pole), for people at intermediate latitudes there is a gradual change in orientation. With the Sun, you don't notice this much, but with the Moon it is far more obvious - when I look out the window here with a latitude of about 55 deg N, a crescent moon looks like it is roughly upright. Near the equator it would look like it was lying down. That same happens with the Sun, there is just no way of telling unless you can see sunspots or similar. For that reason, they need a more universal way of naming the directions, so they use compass points in the manner described by Bowlhover. --Tango (talk) 22:34, 1 June 2009 (UTC)

It isn't making sense yet. Obviously, I know they couldn't call it "upper left" I was just clarifying which item on the image I meant. It's also obvious why they can't call it top or bottom, but prefer North and South. Is it simply a convention that East and West directions are reversed in space? The claim that East is to your right when facing north and looking down, so we want that same direction to be East on the sky behind you sounds clever, but I would think it would be cited somewhere - I've looked and I can't find one, which may just mean my search skills aren't up to par. I think the choice is arbitrary, and I'd like to know why they chose the opposite of the intuitive choice. Sphilbrick (talk) 23:07, 1 June 2009 (UTC)

It's not arbitrary, and it was intuitive when it was chosen. Remember that Astronomy is thousands of years old, dating back to long before it was accepted that the Sun and other celestial objects were independent spherical bodies in space, with easts, and wests, and axial rotations of their own. Originally they were though to be minor features on the Earth's sky (itself possibly a revolving solid sphere, hence "firmament"). The convention arose of the eastern side (limb) of the Moon, say, being the one nearest the eastern horizon of the Earth, because an Earth-centred point of view was the only one that seemed important.

We still usually use this convention when describing things as seen from the surface of the Earth, but now we know that the Sun, Moon and planets are worlds in their own right, we also know that if we're describing, say, Mars from a Mars-centered viewpoint, East and West will be reversed (such that on Mars the Sun will still rise in the East). This can occasionally cause confusion, and now that we've actually visited the Moon, modern Moon maps often show East and West opposite to the way they're marked on older, pre-spaceflight maps. 87.81.230.195 (talk) 02:07, 2 June 2009 (UTC)

Imagine looking in the usual way at a globe that represents planet Earth. Obviously, it North is at the top, then East is to the right. Now put yourself inside the globe and look outwards. While North is still upwards, East is now to the left. But that is exactly the situation when we look up at the sky, the "celestial sphere". --Wrongfilter (talk) 10:14, 2 June 2009 (UTC)

I’m not yet persuaded that the decision wasn’t arbitrary. For example, even the choice of north could be chosen in more than one way. Once one has (arbitrarily) assigned north on the Earth, the question arises how to assign north on other planets. We start by saying it is on the axis on rotation, but that still leaves two possibilities. We could choose the end that lies in the same side of the ecliptic as the north of the earth, or w could invoke a right-hand rule to determine north. Note that these two rules do not give the same answer for all bodies in the solar system – the decision to use the right hand rule was an arbitrary choice, albeit a choice that can be defended.

Once north is selected, south is forced, but east is not. So we have to make a choice. Again, we could pick from more than one rule. One possible rule is – orient so north is on top, and choose east so that it is on the right, just as one would do looking at earth. Apparently that rule wasn’t chosen. As wrongfilter suggests, imagine yourself inside the earth, and choose the direction that is closest to the direction you would look is you looked to the east on earth. A rule, to be sure, but a different rule (and one I suspect gives the wrong answer for Uranus).

However, as 87…points out, we don’t use that rule for all celestial bodies, we use it only for those we haven’t visited. I checked some moon maps, and with north on top, east is to the right. Ditto for Mars. Well, have we visited Mars? Humans haven’t been there, but we’ve sent equipment. But if the rule for determining east is use the rule based upon the view from inside the earth, except for bodies we have visited, then why does it apply to the sun? After all we have sent a probe to the sun.

I’m looking for a coherent rule – I’ll even accept that we arbitrarily made a decision and stuck with it, but I’d like to see a source – I don’t see that this is addressed in Wikipedia, and I haven’t found it elsewhere yet. Sphilbrick (talk) 12:24, 2 June 2009 (UTC)

Outdent – incidentally, I accept that it make sense to label sky in the way wrongfilter suggests – so sky maps, with north on top have east of the left. This makes perfect sense, because we can think of ourselves being inside a sphere looking at the inside of a larger sphere. Mirror real makes sense it that case - if someone says Castor and Pollux are in the east, it seems natural to look toward the east to find them. The convention for the celestial sphere makes perfect sense to me. What I am questioning is why the same rule is applied to the sun. From our point of view, we are outside the sun, looking at it from the outside, not the inside. Same for the moon and Mars. In the case of the moon and Mars, we locate east at pi/2 clockwise from north. In the case of the sun, we locate east at pi/2 counterclockwise from north. clearly arbitrary – my question is what was the thinking behind the convention? Sphilbrick (talk) 12:48, 2 June 2009 (UTC)

A consistent system would be for planets and stars to have their own compass directions, with east to the right when north is up, the same as earth, and for it also to be possible to talk about their "limbs" which are oriented to the celestial sphere and therefore have east and west reversed (and might not have north the same way up). I'm only guessing, but I think this might be the way it works. See this page I just dug up: http://www.sidleach.com/mars_081703_21.htm "South is up in this image, and the eastern limb of Mars is to the right." Presumably the eastern limb of mars is different from mars's east, and the same could apply to the sun if we ever talk about the sun's east (I don't know if anyone does). 81.131.66.245 (talk) 19:45, 2 June 2009 (UTC)

Much observation of any celestial body still takes place on Earth, using telescopes. In that case, it would make sense to use the same system of east/west as the rest of the sky to avoid confusion. If you look at amateur astronomy maps of the Moon or Mars, you'll see that they also have east 90 degrees counterclosewise from north. --Bowlhover (talk) 11:33, 3 June 2009 (UTC)

A complication is that astronomical telescopes usually show an inverted image, because this requires the least amount of lens glass (or number of mirror surfaces) in the optical train, thus maximising the brightness of the image and minimising its degredation, given that no lens or mirror is perfect. When such images are photographed and printed, there is endless scope (sorry!) for - deliberately or accidentally - further changing the orientation of the picture. Everyone in the astronomical community (amateur and professional) is well aware of this and double-checks alleged orientations against reality when it matters, but mistakes or ambiguities in published pictures may well mislead the layperson.

Further to Sphilbrick and Bowlhover's remarks above, I've just checked the 2 editions of Norton's Star Atlas I have to hand. In the 1946 edition, the "Sketch Map of the Moon (As seen in an inverting telescope)" marks South at the top and East on the right, with Mare Crisium near the North West (lower left) limb; in the 1973 edition, the (much superior) "Map of the Moon (. . . based on a drawing published in 1926 . . .)" marks South at the top and East on the left, with Crisium near the North East (lower left) limb. In Patrick Moore & Garry Hunt's Atlas of the Solar System (1990 edition), the multi-page lunar maps designate North at the top and East on the right. with Crisium near the North East (upper right) limb. 87.81.230.195 (talk) 20:33, 3 June 2009 (UTC)

Turing test

Is it possible for a human to fail the Turing test? —Preceding unsigned comment added by 81.76.42.229 (talk) 21:29, 1 June 2009 (UTC)

Certainly, but false negatives aren't a result of interest. Anyone could respond to a tester in such a way as to be indistinguishable from a computer program. — Lomn 21:46, 1 June 2009 (UTC)

An autistic person (or Rush Limbaugh) could easily give nonsensical responses. Clarityfiend (talk) 21:50, 1 June 2009 (UTC)

More than that, I could (as a Turing testee) bring the source code to a chat bot and manually interpret it to determine my test responses. It is comparatively trivial for a human to not only fail the Turing test but to be completely indistinguishable from a known computer. — Lomn 02:19, 2 June 2009 (UTC)

You would have to interpret it in real time, though, and that's not so easy. -- BenRG (talk) 14:31, 2 June 2009 (UTC)

Purple, 7, the east. -Arch dude (talk) 22:30, 1 June 2009 (UTC)

Yes it happens sometimes e.g. [5]. Dmcq (talk) 22:32, 1 June 2009 (UTC)

What makes you believe is it possible for a human to fail the Turing test? --Sean 13:16, 2 June 2009 (UTC)

How do you feel about Purple, 7, the east? Nimur (talk) 15:02, 2 June 2009 (UTC)

Oh... believe is it possible for a human to fail the Turing test? SteveBaker (talk) 02:53, 3 June 2009 (UTC)

Quote from Lessons from a Restricted Turing Test: "Ms. Cynthia Clay, the Shakespeare aficionado, was thrice misclassified as a computer. At least one of the judges made her classification on the premise that '[no] human would have that amount of knowledge about Shakespeare.'" -- BenRG (talk) 14:31, 2 June 2009 (UTC)

I could not resist in linking this famous comic strip :) [6] ... aaaand, this one too :) [7] --131.188.3.21 (talk) 22:58, 4 June 2009 (UTC)

Easiest cell to extract DNA from

For humans, which cell would be the easiest to extract DNA from? I don't just mean getting the DNA, the cell has to be accessible as well. Any help would be appreciated. --The Dark Side (talk) 22:22, 1 June 2009 (UTC)

You can get DNA from saliva, or from hair, and I believe from skin, blood, and basically anything that makes up a human. Take your pick. --KageTora - (영호 (影虎)) (talk) 22:50, 1 June 2009 (UTC)

But is any one easier to use than the others? --The Dark Side (talk) 22:56, 1 June 2009 (UTC)

Ok, imagine the story of Goldilocks, and imagine an alternative ending where she left before the bears came home. They could find out who it was who ate the porridge, broke the chair, and slept in the beds just by the forensic evidence (assuming she wasn't a first-time offender). From the spoon she used to eat the porridge, there maybe some residual saliva, which could be used to extract DNA. It would also help if she licked the spoon clean, and even more so if she licked the bowl clean. When she sat on the chair that broke, she would have fallen, and possibly cut herself on the broken chair (not mentioned in the original story, but this is an alternative). This would be a perfect source of DNA. Failing that, when she slept in Baby Bear's bed, it's pretty well a sure thing that some of her hair would be on the pillow, and considering baby bears don't usually have long blonde hair, they would be easy to spot. Another source of DNA in the bag. The FBI would be round her house in a shot! --KageTora - (영호 (影虎)) (talk) 23:15, 1 June 2009 (UTC)

Okay, I understand that it's easy to collect cells. What I'm really after is the ease with which the DNA can be extracted. This would probably have to take into account the cell membrane and the features that differentiate the various human cells. --The Dark Side (talk) 23:55, 1 June 2009 (UTC)

Extracting DNA from any recently living nucleated cell is so trivial that its essentially moot to decide which cells one is extracting from. Forensic scientists don't even differentiate it that way. A single microscopic sample may contain DNA from dozens of different kinds of cells from the same individual. For example, take a blood stain. The sample obviously contains DNA from white blood cells, but it also likely contains skin cells (of which there are many different types, vertically striated, from the same cut even!), subcutaneous fat cells, muscle cells, and from any number of other sources. With tools like polymerase chain reaction any DNA sample can be amplified to a useful amount, so it really doesn;t matter where it comes from. --Jayron32.talk.contribs 04:29, 2 June 2009 (UTC)

And that is exactly what I was implying, but said in a more scientific way. --KageTora - (영호 (影虎)) (talk) 10:08, 2 June 2009 (UTC)

A buccal swab (swabbing the inside of the cheek) is the most prevalent way of DNA sampling, assuming you haven't already drawn blood for some other purpose. -- 128.104.112.106 (talk) 20:23, 2 June 2009 (UTC)

Indeed, a buccal swab (can't believe we don't have an article yet) is probably the least invasive method that is most widely used. It isn't as "good" as blood, but its a hell of a lot easier to sample. In a job I used to do, I would extract DNA from both blood (a few ml) and buccal swabs on a daily basis. I must have done many hundreds, if not thousands, of both. The number of nucleated cells in a 1ml of blood outnumbers the best buccal swabs, so you would get much more DNA from blood. The quality of the DNA would also be better as the blood environment is more consistent than the mouth. We found that the quality of DNA from buccal swabs varied greatly depending on what was eaten immediately prior to the swab. Particularly problematic was when a kid ate an apple just prior to swabbing. Then DNA would always be crap. We never formally tested by this, but our assumption was that the acidity of the apple was to blame. Rockpocket 01:28, 3 June 2009 (UTC)

I remember reading that it is easy to extract human DNA in a home experiment suitible for schoolchildren, but do not remember how its done, except that it requires a beaker and a glass rod. 78.144.244.22 (talk) 22:31, 2 June 2009 (UTC)

Untreated Cancer

Horrible subject, this, but I've been thinking. What happens if cancer goes completely untreated? Of course, death is the usual consequence, but I am asking about what happens in the body leading up to that. Also, I know there are many different places in the body that can become cancerous, and so they will all exhibit differing symptoms from onset until the end, so this may be a difficult question to answer. I am interested in this because in the "modern developed world" we have cancer treatments, while in older eras there were none (or at least, none as we have now). To complicate matters more, there seem to have been many studies that suggest that untreated cancer victims tend to live longer than those who are treated (sorry, no reliable links). Another question is, do animals get cancer? I'm sure they do, but how is this treated, if at all? Thanks. And please do not post links with pictures of what it looks like, as I am a tad squeamish. :) --KageTora - (영호 (影虎)) (talk) 22:48, 1 June 2009 (UTC)

"there seem to have been many studies that suggest that untreated cancer victims tend to live longer than those who are treated" — if there aren't any reliable links, I would be inclined to suggest it is because such studies don't exist.

This is not to say that there are no trials which show some individual treatments are ineffective — some drugs and therapies don't work as well as animal models or biological theory might suggest, and the only way to know for sure is to do clinical trials. Further, there are some cases where watchful waiting (monitoring, without immediate treatment) is considered an appropriate response to a cancer diagnosis. Finally, opting for treatment does (potentially) expose a patient to immediate risks in return for the potential later reward. Let's say a surgical intervention cures 90% of patients, but 10% die on the table. One could say that the latter 10% did significantly worse than they would have had they not been treated — but it probably wouldn't be justifiable not to offer treatment. TenOfAllTrades(talk) 00:01, 2 June 2009 (UTC)

Animals do get cancer. In the wild that quickly puts them in the "gets eaten" category, so it's not a top animal channel item. Rats and mice serve as models for cancer studies. There are viruses that cause cancer [e.g. Feline leukemia virus or HPV}. Dogs are listed as having quite a variety of cancers, including one that is transmitted through sexual contact. A new form of cancer in cats is injection site carcinoma (no page??). It is ironically caused at sites of inoculations that are supposed to protect our feline friends from diseases. Vaccinations are now moved to legs, so that amputation becomes an option. Radiation treatment and chemotherapy are costly, so some owners opt to have their animal put down. Some of the criticism of cancer treatments is that tumors get identified and removed/treated aggressively that would have gone into remission or never developed if left to themselves. [8] [9] [10]Clinical study results are hard to come by because of the dire results if the tumor remains untreated and mestastasizes instead of going into remission. We have no way of predicting outcomes. AFAIK it is not disputed that there are cases when the immune system manages to cope with cancerous tumors.(e.g.Phoebe Snetsinger) Another complaint is that biopsies used in diagnosis cause some tumors to mestastasize which would not have done so otherwise. Some cases have been described, but clinical studies hinge on the same problem as above. [11]71.236.26.74 (talk) 01:05, 2 June 2009 (UTC)

Cosmological units

Why does cosmology use such odd units (parsecs, lightyears, solar masses, etc) instead of the SI units like almost all the rest of science? And why are there so many different distance units in use? It seems to be not uncommon to be discussing kilometers, parsecs, lightyears and astronomical units at once. For example, conventionally, Hubble's constant is given in (km/s)/Mpc, which seems insane to me -- would s^-1 have not sufficed? —Preceding unsigned comment added by 79.72.180.91 (talk) 23:02, 1 June 2009 (UTC)

Probably because the numbers would be astronomically large in SI units. It is easier to grasp the mass of a star in terms of solar mass than kilograms or a long distance in light years rather than meters. Bubba73 (talk), 23:19, 1 June 2009 (UTC)

Are there lots of people writing and reading about cosmology who do not understand numbers like 10³¹? Why should one area of science stick with non-SI units? Edison (talk) 23:44, 1 June 2009 (UTC)

The parsec stems directly from one method used to measure the relative distances of stars from the Solar System. It's easier to determine that one star is, say, 2 parsecs away while another is 4 than it is to calculate exactly how far a parsec is, so - especially when you're comparing lots of similar measurements - it saves some trivial and unnecessary maths to leave parsecs unconverted. Parsec is short for 'parallax second', and 1 parsec is the distance (about 3.26 light years) an object would be if the revolution of the Earth about the Sun over 6 months caused it to exhibit an apparent (parallax) shift in position angle of 2 arc seconds; or conversely, it's the distance at which a length of 1 Astronomical Unit (see below) would subtend an angle of 1 second.

Astronomical Units similarly derive directly from comparative methods used to measure the sizes of orbits in the Solar System relative to Earth's (whose orbit is 1 AU in radius, 2 AU in diameter). Again, historically we could measure these sizes relative to each other more accurately than we could measure the actual distances involved.

A light year, as you know Bob, is the distance light travels in one year. Apart from giving usefully low numbers (nearest star 4.2 ly, diameter of Milky Way about 100,000 ly, nearest major external galaxy about 2,000,000 ly), it's a useful reminder that we're seeing something x ly away as it was x years ago.

Hubble's constant is, again, left in the form in which it gets measured, in part because it isn't a pure distance, but rather a consequence of the way the Universe is expanding whose fine details are still subject to some uncertainty.

Of course, it's not a distance at all, but a rate. I knew that really. Doh!. 87.81.230.195 (talk) 20:15, 2 June 2009 (UTC)

These (and other) methods of distance determination do not (yet) give precisely interconvertable results, just as different methods of age determination in archaeology (say C14 and thermoluminescence) give answers that have to be carefully calibrated rather than ones that can be taken at face value. Converting them all to SI would mask these uncertainties.

Solar masses are used because it's more useful and informative to compare the relative masses of other stars to each other and to our Sun's than it is to know their absolute tonnages, which again are far harder to determine (and give insanely large numbers in SI units). The luminosities of stars are also often measured in units of Solar luminosity.

Exactly, and the absolute mass of an astronomical body is hard to pin down because the gravitational constant is not known to great precision. --Bowlhover (talk) 00:26, 3 June 2009 (UTC)

In addition to avoiding often unnecessary conversions, using each of these units in their traditional contexts where likely magnitudes are familiar avoids continually dealing with SI unit quantities containing large exponents, in which it's easy to make unobvious mistakes. Astronomers will cheerfully convert them as necessary to communicate with the lay public (who seem perfectly happy with light years and, often, AUs anyway): if any non-astronomer scientists want measurements in SI units, the conversion factors are readily available and they're quite capable of performing the calculations themselves, and welcome to, ta very much. 87.81.230.195 (talk) 01:27, 2 June 2009 (UTC)

It's not like cosmologists and astronomers are alone in this though. Particle physicists use all sorts of specialised units - Electron volts instead of Joules, an entire system of Plank units that bear no resemblance to SI units. Electrical systems engineers use Kilowatt hours instead of Joules, Aerospace engineers still use 'knots' for airspeed and feet for altitude - despite using metric for almost everything else. Biologists and Atmospheric engineers measure pressures in millimeters of mercury instead of Pascals. Computer scientists abuse the 'k' and 'M' prefixes to mean 1024x and 1048576x respectively. All sorts of people abuse and adapt the system for convenience. If it makes communications clearer - then that's a good thing. It would be a real pain in the ass to have to talk about having 110 m²kg⁻³A⁻¹s electricity coming out of the wall socket. SteveBaker (talk) 02:28, 2 June 2009 (UTC)

And atom masses are measured in atomic units instead of grams, High explosive energy output is measured in tons of TNT instead of joules, food energy is measured with Calories (capital c) which is equivalent to 1kcal istead of joules, there are several different conventions for electromagnetic units, and the cgs system of units is as popular as the SI system of units. The list is quit impressive. There is no rule (neither implicit nor explicit) saying that scientists should use SI units. We are only expected to state the unit system being used clearly. Dauto (talk) 03:24, 2 June 2009 (UTC)

Related question: Why is it that astronomers, who deal with the largest and heaviest things in the universe, generally use CGS units instead of MKS units? I understand it's probably convention, but how did such a bizarre convention come about (as it makes the numbers even more cumbersomely large than they already are)? -RunningOnBrains^{(talk page)} 04:52, 2 June 2009 (UTC)

Historical accident, and in that case it really does not matter much - just add another two to the exponent. Note that most of the non-SI-units in use are units of convenience - lightyears, AU, Parsecs, Electron Volts, u, all have a direct and intuitive connection with the domain of discourse. The SI-units, and many traditional units have lost most of that connection, and are now very abstract and generic. How often do you consider the fact that the meter is approximately a millionth of one quarter of the length of the equator? Or that a mile is 1000 double steps of a Roman legionnaire (well, for frictionless legionnaires of standard weight on the Via Appia, I suppose ;-). --Stephan Schulz (talk) 09:29, 2 June 2009 (UTC)

Assume a spherical legionnaire... —Tamfang (talk) 03:44, 4 June 2009 (UTC)

Well, also remember that the metric system is supposed to be devoid of context. It's not like they created the metric system to measure the equator—they knew the length of the equator and worked backwards, the idea being that anyone could then reconstruct the length if need be. They are meant to be context-free units. Which have their ups and downs, as noted. --98.217.14.211 (talk) 12:38, 2 June 2009 (UTC)

There's a legend that the metre was conceived as the length of a pendulum whose half-period is 1 sec, until someone with colonial experience chimed in with the French equivalent of Afraid that won't do, old chap (gravity, and thus the appropriate pendulum length, varies with latitude). Sadly, one hears that there's no truth in it. —Tamfang (talk) 03:44, 4 June 2009 (UTC)

The use of parsecs, kilocalories, and other special units used above are objectionably non-SI, but still far better than the use by science popularizers such as Science Daily, adapting material from the American Chemical Society, originally published in ACSNano, which says that silver nanoparticles useful in medical treatment are "1/50,000th the diameter of a human hair" without specifying red, blonde or brunette, and from what part of the body. This type of nonsense is like comparing some object in space to so many "city blocks," another widely varying metric. Edison (talk) 15:58, 2 June 2009 (UTC)

See our list of unusual units of measurement and the associated list of humorous units of measurement. My personal favourite is the beard-second. Gandalf61 (talk) 16:32, 2 June 2009 (UTC)