Wikipedia:Reference desk/Archives/Science/2009 September 21

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September 21

Visually sexing non-sexually diamorphic parrots?

Is this possible, if you're familiar with the species? Without waiting for one of them to lay an egg or to see which one is on top during mating, I mean. Are there any subtle features that might not be obvious to most people that you can look for to determine male from female?

There may also be behavioral ways to tell the gender. What species are we talking about ? StuRat (talk) 15:37, 21 September 2009 (UTC)

Methods for parrot gender determination Cuddlyable3 (talk) 17:04, 21 September 2009 (UTC)

Voltage ratings for light bulbs?

I've got a full-spectrum incandescent bulb for warming reptiles bought in the US that has 120V printed on it. I'm in China now and wondering if I can use it. I know from accidental experience that 120V appliances are sent to their graves on 220V, but I'm wondering about light bulbs. As far as I can recall, this is the first bulb I've ever seen that even HAS a voltage rating. Have I just not noticed all this time? Will using it blow-out the filament inside? Or do voltage ratings not really apply to bulbs? The easy solution is to just try it, but these are expensive and extremely hard to find in China so... (thank you) 218.25.32.210 (talk) 00:56, 21 September 2009 (UTC)

I've done it so you don't have to experiment (25 years ago). It will burn very brightly for a few minutes, then ... poof. No more light. The reptiles might get too warm, too, then too cold. Acroterion _(talk) 01:01, 21 September 2009 (UTC)

Thank you! 218.25.32.210 (talk) 01:20, 21 September 2009 (UTC)

And while you may never have noticed, it is quite standard for light bulbs to carry a voltage rating. --Anonymous, 05:00 UTC, September 21, 2009.

If you happen to have two identical 120v bulbs, they will work fine from 240v if connected in series (and at slightly reduced output from 220v), but don't attempt this unless you know what you are doing. These voltages are dangerous. There are step-down transformers available for a safe solution. Other solutions include connecting your single bulb across one half of a resitive load such as a room heater (or two room heaters in series), but only a qualified electrician should attempt this. Dbfirs 07:38, 21 September 2009 (UTC)

As a lightbulb is not very expensive, you should just buy one locally for the correct voltage. Googlemeister (talk) 13:14, 21 September 2009 (UTC)

Is it legal to bring reptiles bought in the US to China ? Cuddlyable3 (talk) 16:56, 21 September 2009 (UTC)

A lightbulb connected to twice the specified voltage might explode, or it might just burn very brightly for a short while before it failed, Two bulbs connected in series ((NOT PARALLEL) to twice the specified voltage should function, but when the filament in one fails, if it shorts or arcs across, the other would be subject to about twice the specified voltage, and then it might explode. The filament supports may be physically different in high and low voltage bulbs, and arrangements for breaking the arc when a filament opens might not work well at much higher voltage. Edison (talk) 23:47, 21 September 2009 (UTC)

How could a lamp filament fail in a way that short circuits the lamp ? How does fairly undramatic fusing at 4x rated heating become an explosion ? Cuddlyable3 (talk) 07:34, 23 September 2009 (UTC)

Furry *green* animals?

It occured to me on the way to work this morning that I can't think of a single fur-bearing animal that's green. Perhaps there's a small monkey species out there or another, but I can think of no grazing animals, and certainly no predators. In the upper latitudes such coloration would be a hindrance in winter, but in the subtropics and tropics I would think that shades of green would be a useful adaptation. There are plenty of green birds, reptiles, and amphibians. What's with the furries? 218.25.32.210 (talk) 01:00, 21 September 2009 (UTC)

You're quite right. Amazingly, this point has received no discussion whatsoever in any of the evolution literature that Google Scholar finds. Looie496 (talk) 01:09, 21 September 2009 (UTC)

(edit conflict)Heh well, does this count? In all seriousness, I don't know of any, and according to Mammal#Integumentary system there are none with either green or blue. If we think about it, though, there's a good reason. You mention adaptation, but what is green that a mammal hangs out around? Leaves are already way off the ground, and out of the way of most predators. If the creature ever went on the ground, a brown or white color would certainly be very favorable so as to blend in, whereas green would hinder them when on the ground. ~ Amory (user • talk • contribs) 01:13, 21 September 2009 (UTC)

I'm guessing you're from the higher latitudes. Growing up in Florida, and having traveled through Central America and northern South America, the underbrush is always exceedingly green. 218.25.32.210 (talk) 01:21, 21 September 2009 (UTC)

There is no such a thing as a green fur pigment. Evolution cannot make one magically appear. Dauto (talk) 01:25, 21 September 2009 (UTC)

Not magically, but why couldn't it occur by random mutation? It is suggested below that it would be harmful, but that seems strange to me - green pigments exist in nature without doing any harm to other types of lifeforms. --Tango (talk) 03:06, 21 September 2009 (UTC)

If you scroll down the page here it gives the simple answer that most animals (not just mammals) simply are unable to synthesize the colors blue or green. It says that the blues and greens seen in birds and amphibians aren't actually blue and green, but are due to "structural effects." That is, air sacs in feathers scatter light that make them appear blue, for example, and frogs use multiple layers. ~ Amory (user • talk • contribs) 13:52, 21 September 2009 (UTC)

AFAIK, birds 'do' green by overlaying the structural effect that creates blue upon a yellow feather. If the yellow pigment isn't present (as in the case of the blue budgerigar mutation), you end up with blue feathers in the areas that would normally be green. --Kurt Shaped Box (talk) 20:38, 21 September 2009 (UTC)

Indeed, which is why a lot of mammals have mottled and patterned fur - it breaks up the view of predators/prey and makes them harder to detect against the multi-colored and discontinuous background. ~ Amory (user • talk • contribs) 02:00, 21 September 2009 (UTC)

Outdent -- but such pigments apparently exist for feathers and skin, which brings me back to the original question - why aren't there (or why can't there be) green fur-bearing animals? 218.25.32.210 (talk) 01:33, 21 September 2009 (UTC)

The Three-toed sloth can have algae growing in their fur, which will give it a greenish color. Probably the closest to green fur you will find. --Jayron32 01:37, 21 September 2009 (UTC)

The link I provided above actually has some information, albeit unsourced. It mentions in passing that there's some evidence that producing a green pigment in fur would actually harm the animal; I can imagine this wouldn't be the case for feathers. Also, most birds that have green not only pretty much spend all their time in the air or high in trees amongst leaves, but are usually along the lines of birds of paradise. Those animals have such an immense source of resources that they have developed seemingly absurd sexual rituals, often involving incredibly bright coloring, that can in fact be a hindrance to them. Mammals (with the exception of human males) tend to be more logical in their choice of mates due to resource conservation. ~ Amory (user • talk • contribs) 01:58, 21 September 2009 (UTC)

The readers should be aware that vast majority of mammals do not possess the trichromatic color vision; only humans, some simians, and, curiously, marsupials do. Most other mammals are dichromats, therefore they can not tell green from some other colors of same perceived brightness. While this does not answer the question per se, this certainly helps explain the obvious lack of evolutionary pressure on the small mammals to turn green. There obviously is a pressure to turn white in winter, but apparently there is little or no pressure to turn green in summer. Indeed, most predators can tell white from non-white, but probably very few can tell green from some shades of grey or brown. Now, I have no idea what kind of color vision the diurnal birds of prey are capable of; I know their retinas are somewhat different from those of the mammals, but I do not know what classes of photoreceptors they have and how many. If they can tell green from grey and brown, then my hypothesis is probably wrong :( --Dr Dima (talk) 09:31, 21 September 2009 (UTC)

OK, I did a little reading and it looks like birds do have a very good color vision. However (at least in a starling) the sensitivity peaks of the different classes of cones are all far apart in wavelengths, while in humans the L and M cone sensitivity peaks are close. This suggests that birds can see some colors that we can't (in near UV, for example), but probably can not tell shades of red from shades of green very well. The latter requires the L and M cone sensitivity peaks to be close to each-other -- like it is in humans -- in order to enhance the selectivity over a relatively narrow spectral band between 560 and 600 nm. So my hypothesis may be right after all. --Dr Dima (talk) 09:56, 21 September 2009 (UTC)

The animals that tend to have good color vision are the ones that depend upon being able to tell whether fruit is ripe by sight alone. Those are not carnivores - so the prey of carnivores don't need green fur. But in any case, camoflage isn't so much about being the right color as in breaking up the shape of the animal. Think about animals like Zebra and Tigers - they have those big, bold, high-contrast stripes - which you'd think would stick out like a sore thumb. But they don't. Those patterns break up the shape of the animal and make it surprisingly hard to see. SteveBaker (talk) 13:32, 21 September 2009 (UTC)

This link backs up your theory about vision playing a role as well. ~ Amory (user • talk • contribs) 13:52, 21 September 2009 (UTC)

A couple thoughts. First, humans and some other mammals can have green eyes, so we are able to make that pigment. It's just a matter of making it in our skin rather than our eyes. And while I agree that solid green wouldn't be the best camo, perhaps green and brown stripes or mottling would be good, such as the clothes and face paint soldiers sometimes use. Next point: since the Q was about green furry animals, not just mammals, I'd include fuzzy green caterpillars. StuRat (talk) 15:02, 21 September 2009 (UTC)

Green eyes have no green pigment on them. Dauto (talk) 17:47, 21 September 2009 (UTC)

But does that matter ? If we can produce eyes that appear to be green, it can't be all that much of a stretch to imagine that we could do the same on our skin or hair. StuRat (talk) 02:02, 25 September 2009 (UTC)

To answer the OP, the Green Monkey and the Squirrel Monkey come immediately to mind - the Green Monkey isn't really _that_ green, but the Squirrel Monkey is. :) Tevildo (talk) 19:21, 21 September 2009 (UTC)

It's possible to get green mammals, you just have to cheat. - cyclosarin (talk) 13:43, 25 September 2009 (UTC)

Bunches of doctors in an emergency room...

I was looking at some pictures of emergency patients getting operated on and I noticed there were somewhere around six to seven people working with the same patient at once. What are they all doing? I am asking for a likely role breakdown for doctors/nurses/clinicians tending to the patient. (e.x. one lead surgeon, two assisting him in holding tissue away from where the main surgeon is working, one to fiddle with the IV, three residents watching to learn... something like that) Do this many doctors work on a single person for non-emergency surgery too? 66.57.240.8 (talk) 05:15, 21 September 2009 (UTC)

Well, of course, it depends on the particular surgery and the setting (large teaching hospital, small community hospital), etc., but typical roles would include the following:

1. anesthesiologist or nurse anesthetist - provide anesthesia and monitor vital signs and respiratory status
2. attending surgeon - to perform the surgery proper, supervise resident
3. surgical resident(s) - learning, may open or close incision, or perform other parts of the surgery
4. medical student(s) - learning, may run errands to lab etc.
5. scrub nurse - gives instruments to surgeon, maintains sterile operating field, keeps track of instruments and sponges, etc.
6. circulating nurse - provides supplies to scrub nurse, labels & sends pathological specimens, other tasks not requiring sterility

-Nunh-huh 06:24, 21 September 2009 (UTC)

Nurse quickly, give me suction!

And the scrub nurse can't have any kids...because she's sterile. :) DRosenbach ^{(Talk | Contribs)} 17:11, 21 September 2009 (UTC)

And the head nurse isn't likely to get pregnant either, but for an entirely different reason. :-) StuRat (talk) 20:12, 21 September 2009 (UTC)

Are you talking about an emergency room or an operating theatre? They are different things. What you may be describing as surgery may actually be resuscitation - that's what is done when a trauma patient is first brought to the ER. --Tango (talk) 20:46, 21 September 2009 (UTC)

I was looking at a bunch of different pictures from Flickr and several of them still have a lot of staff in the room when it is pretty clear that the patient is not being resuscitated. (I'm assuming that the surgeon would not be fiddling with the person's innards with forceps or tubes or whatever they are holding while resuscitating someone.) In several of the photos, the rooms were also pretty small which makes me think they are ERs and not theaters. Part of the reason I asked was because I was curious if having so many doctors crammed into one rather small room was normal and what they all were doing. I was wondering if I was mistaken in thinking that for most surgeries only three or four people were actually needed at most once the patient was stable (i.e. not being resuscitated). Thank you Nunh-huh for your detailed answer by the way. 66.57.240.8 (talk) 23:45, 21 September 2009 (UTC)

An interesting story here. Bus stop (talk) 17:19, 23 September 2009 (UTC)

an adiabatic enclosure, 2 mol of Cu...

I'm trying to get this concept. So there's one mol of Cu at 0 C, and one mol of Cu at 100 C, in thermal contact. They are both in an "adiabatic enclosure". AFAIK there is no phase transition, but their equilibrium temperatures are not 50 C. I'm trying to figure out why this is. So since it's adiabatic, I take it no energy is being lost to the environment or anything and the energy gets transferred to some other mode besides kinetic energy. (The Cp given is 33.64 + 6.28×10^-3 T J/mole K.)

This is an entropy issue I think -- it occurs to me that the volume of the two mols of Cu will change at different rates w/respect to each other, and as a result, one mol of Cu will have more energy stored in the form of internal potential energy (seen as difference in volume) than the other, so the equilibrium temperature will be below 50 C. Is there any way to calculate this equilibrium temperature? John Riemann Soong (talk) 05:36, 21 September 2009 (UTC)

Is the 'T' in the formula for Cp temperature? If the heat capacity is temperature dependent, then the temperature won't be linear in the amount of heat energy. In this case the equilibriums temperature would be over 50 C, although the amount over would be pretty negligible. Rckrone (talk) 07:31, 21 September 2009 (UTC)

Hmmm, the nonlinear part of heat capacity is because of potential energy, right? Okay, is the equilibrium temperature higher because the entropy of the system has increased? Where does the additional enthalpy come from? John Riemann Soong (talk) 07:39, 21 September 2009 (UTC)

OOHHHHH I think I get it now. I was thinking differential volume expansion (does that factor in Cp?) and work being done by the heat transfer, but in heat transfer from hot to cold, S always increases. I wasn't really thinking about Debye heat capacity and such, but I realise it probably kicks in for copper. So let's get an extreme-ish case -- 1 K helium and say, 100K helium (let's choose a suitable pressure where we can ignore phase transitions). Basically, for a system with very little disorder, transferring a fixed amount of heat from a system with much more disorder will increase the disorder of the first system by a lot more than it would decrease the disorder of the much-disordered system? And thus, disorder as a whole increases, increasing temperature? John Riemann Soong (talk) 08:23, 21 September 2009 (UTC)

Lymphocytes

how we can separate lymphocytes from blood sampleAnkita.roshni (talk) 05:37, 21 September 2009 (UTC)

By googling 'separating lymphocytes' I got many results. This[1] was the first, which you may find helpful. 86.4.186.107 (talk) 06:05, 21 September 2009 (UTC)

The standard laboratory method for isolating lymphocytes, is by ficoll centrifugation, as described in our article. You then get a mixture of lymphocytes and monocytes, called peripheral blood mononuclear cells. If you start out with anticoagulated blood, there will be platelets in the mixture as well. If you start out with defibrinated blood, there will be few platelets, and also fewer monocytes. Defibrinated blood is produced by shaking blood containing no anticoagulant in a bottle filled with glass beads. If you need to remove monocytes, specialized centrifugation techniques exist, or you may take advantage of the tendency of monocytes to adhere to plastic, e.g. in a petri dish. Other methods for isolating lymphocytes include fluorescence-activated cell sorting and immunomagnetic separation. The standard method for removing lymphocytes (and other white blood cells) from red cell or platelet concentrates for transfusion, is by filtration. --NorwegianBlue ^talk 08:30, 21 September 2009 (UTC)

Combustion

Is combustion always with oxygen? From the combustion article it appears not, but everywhere I've looked the definition is a reaction with oxygen. What's the actual definition? --wj32 ^t/c 08:04, 21 September 2009 (UTC)

You could probably combust something with anything electronegative like a halogen like chlorine, but note that oxygen is the most abundant atmospheric electron acceptor, whereas diatomic nitrogen is quite stable and not very electrophilic. In fact, oxygen is prolly the most abundant oxidiser because all the more reactive ones don't survive as long at ambient temperatures, while you need a little more "oomph" to get something to combust with oxygen. The idea of combustion essentially is that the item being combusted is being oxidised, and the oxidiser is getting reduced. John Riemann Soong (talk) 08:39, 21 September 2009 (UTC)

So... the oxygen-only definition is wrong (technically)? --wj32 ^t/c 08:42, 21 September 2009 (UTC)

Well it works most of the time. And if you're doing some chemical process where you're halogenating something or making some exotic acid, then you could say, "yeah I'm combusting it in fluorine"... I suppose to distinguish "combustion" and "oxidation", one would say that the primary method of combustion is via free radical formation and propagation and homolytic cleavage, whereas with ambient oxidation it doesn't always this way. John Riemann Soong (talk) 08:51, 21 September 2009 (UTC)

OH -- one more important point. Oxygen is unique among most oxidisers in that it is a diradical, usually found in triplet oxygen state. Hence the emphasis on radical formation -- diatomic oxygen cannot participate in many classic reactions in organic chemistry, like nucleophilic lone pair donation, or electrophilic electron acceptance, since diatomic oxygen's highest energy electrons are not paired ... and O2's lowest LUMOs (in the not fully occupied orbital sense) are half-occupied by one electron each.

Other electronegative species (like chlorine) generally react via electrophilicity/nucleophilicity-driven mechanisms which involve the movement of electron "pairs". These species react via radical mechanisms at room temperature only under special conditions (like a radical catalyst, due to light, peroxide, etc.). So that's why chlorine, although is less electronegative than oxygen on the Pauling scale (chlorine is the electron donor to oxygen in perchlorate), is far more reactive and electrophilic at room temperature. Diradicals react best with other radicals and it happens to be that most of the biosphere, most of the time, is made up of non-radical substances -- unless you of course suddenly turn up the heat (like in a forest fire) and suddenly start breaking molecular bonds homolytically to get your radicals. Chlorine, not being a radical, reacts readily with "normal" electron donors.

So I guess the refinement of the definition is that combustion is "free radical oxidation". Oxygen is the most abundant free radical oxidiser out there. There are of course derivatives like peroxides, perchlorates and other oxygen-containing things. And then there are probably free radical oxidisers that don't involve oxygen atoms, but they are considerably less abundant. John Riemann Soong (talk) 09:02, 21 September 2009 (UTC)

Gunpowder uses potassium nitrate instead of molecular oxygen as the oxidiser. Dauto (talk) 11:58, 21 September 2009 (UTC)

I'm not sure the precise technical definition as distinct from other sorts of oxidation. May be speed (iron rusting vs on fire) or the presence of some sort of flame? Magnesium (and other active metals I assume) burn with a bright flame under a pure carbon-dioxide atmosphere. I don't know whether that involves free-radical (probably). And thermite is another mixture that contains its own oxidizer agent. DMacks (talk) 13:29, 21 September 2009 (UTC)

Likewise, Magnesium will burn in pure carbon dioxide, which while possibly not "technically" a combustion (since it does not involve oxygen) still amounts to burning to any reasonable person. See this video for a demonstration. --Jayron32 13:29, 21 September 2009 (UTC)

The mystery of the defunct scientific journal

I have sought an article from a journal entitled 'Current Research in Molecular Therapeutic' (ISSN: 1367-6275). The article, printed in 1998, is not listed on PubMed. I contacted the author and was sent a copy in PDF format. The author himself was not sure why the article never appeared on PubMed. Could it be that the journal did not meet PubMed's standards for inclusion and has since gone out of publication? There is only a little evidence on the Internet that it even existed. ----Seans Potato Business 11:04, 21 September 2009 (UTC)

I've been poking around, and so far can't find any references to publications in Curr. Res. Mol. Therapeut. that aren't from 1998. To be fair, I haven't been digging very deep, but it's possible that the journal didn't last long enough to meet the longevity requirements for review and inclusion in Medline/PubMed: Journal selection FAQ. Moreover, if the editors/publisher anticipated winding up the journal after a few issues, they might not have bothered to submit their journal for Medline indexing, or continued to shepherd their application through the Medline process. The Medline FAQ indicates that about three-quarters of submitted journals aren't selected for indexing; a two-year waiting period is imposed before a reapplication is permitted. Again, if the journal missed the cutoff on its first evaluation, it may not have survived long enough to apply again. TenOfAllTrades(talk) 13:47, 21 September 2009 (UTC)

One possibility is that this was a fake journal. Often somebody hawking some product will set up a fake journal so they can claim they are endorsed by the scientific community. What was the article in question ? StuRat (talk) 14:46, 21 September 2009 (UTC)

The odd title lends immediate (weak) support to StuRat's idea. Comet Tuttle (talk) 16:49, 21 September 2009 (UTC)

The grammatically correct title would be http://www.google.co.uk/search?hl=en&q=%22current+research+in+molecular+therapeutics%22&btnG=Search&meta= with an S ...83.100.251.196 (talk) 17:09, 21 September 2009 (UTC)

The current publisher seems to be "Nature America Inc." does that help?83.100.251.196 (talk) 17:13, 21 September 2009 (UTC)

That does sound rather suspicious. Looking through those Ghits, it looks like they got a reputable scientist willing to sell out her reputation to endorse a questionable product. If so, the "journal" may have only lasted long enough to endorse all the products of the parent company. Once this was done, it no longer served any purpose. StuRat (talk) 20:24, 21 September 2009 (UTC)

Inclusion in PubMed and inclusion in Medline are not the same.[2] It's easy to get a journal listed in PubMed, just have a half-decent editorial board and don't look like a total fly-by-night operation. Medline is a whole other ball game. You need consistently good publication levels for about 18 months, and each journal goes through a vetting procedure. If it fails to get indexed it needs to wait two years before reapplying. Fences&Windows 03:23, 23 September 2009 (UTC)

Ha, this was a tricky one to figure out. Apparently there is a company called "Current Drugs Ltd" (recently acquired by Thompson Reuters) that does research on drug development, creating reports that they sell to corporate clients. This Google Scholar search will show you a whole bunch of them. "Current Research in Molecular Therapeutics" is the title of a report they published in 1998. I'm not absolutely certain of what I just wrote but I think it is probably close to correct. In any case, an article that appeared there would not be a valid source for Wikipedia. Looie496 (talk) 00:13, 22 September 2009 (UTC)

Current Drugs Ltd. was then part of the Current Science Group,[3] now the Science Navigation Group. Current Research in Molecular Therapeutics may be related to Current Opinion in Molecular Therapeutics, which was launched in late 1998.[4] It could be a typo, an early title, or an abortive journal, but assuming it is a "fake journal" isn't correct. Fences&Windows 03:19, 23 September 2009 (UTC)

Why don't I sneeze when I'm asleep?

Why is it that, when I have a cold, I don't sneeze or cough while asleep? (I know there are instances when we do, but the symptoms are always at least reduced.) Does it come of the mechanism that paralyses us so we don't act out our dreams? If so, it seems odd, because as far as I can tell, the paralysis stops voluntary movements, not involuntary ones, and I imagine big convulsive sneezes are involuntary...

I wonder if there's a way we can harness whatever causes this to reduce the symptoms of a cold...

thanks Adambrowne666 (talk) 11:20, 21 September 2009 (UTC)

How do you know you don't sneeze in your sleep? Also, while sneezing is semi-involuntary, it may also controled by the somatic nervous system and NOT the autonomic nervous system, and so any control over your conscious movements while asleep would also likely regulate sleeping. --Jayron32 13:24, 21 September 2009 (UTC)

We should also talk about why we sneeze and why it might be suppressed during sleep. The purpose of a sneeze is to clear the airways of irritants or blockages. While awake this works well. However, when asleep, excessive sneezing may interfere with sleep, and thus may cause more harm than good. So, the sneeze response is somewhat repressed, but not totally. If someone blew pepper up your nose while you were asleep, you would wake up sneezing. In this case the harm done by sleeping all night with such an irritant in your airways would be greater than the harm done by waking up. Of course, this system does fail at times, as when we have allergies or asthma. In such cases the response to a minor irritant (or none at all) is all out of proportion. StuRat (talk) 14:30, 21 September 2009 (UTC)

We are able to sleep when there is no apparent danger or immediate demand for activity. While we sleep the body needs only to maintain breathing at a low level since there is only a small constant muscle activity. In contrast, when awake the body needs a higher intake of oxygen to give the ability to react quickly to sudden dangers and to make necessary efforts. It actively resists anything that impairs breathing such as bronchial or nasal congestion by a sneeze or cough reaction. Cuddlyable3 (talk) 15:09, 21 September 2009 (UTC)

The sneeze article mentions this, search for the word "sleep". Googling for sneeze sleep reveals e.g. this and this. 88.112.60.134 (talk) 19:38, 21 September 2009 (UTC)

Well then. So what would be the effect of artificially relaxing the part of the brain responsible for the sneeze reflex as a way of reducing sneezes? Adambrowne666 (talk) 08:32, 22 September 2009 (UTC)

I doubt if it would work, as the chemical which suppresses sneezes likely also represses all other voluntary movements. So, not being able to walk would be a rather serious downside. But, if it was a separate chemical, it could still be harmful by allowing irritants to remain in the air passages, leading to inflammation, infection, etc. On the other hand, it could be useful in reducing the spread of airborne diseases, like the flu and colds. In that case it would have a similar logic with vaccines, since they protect both the person who takes them and those around them, but the person who takes them assumes all the risk. StuRat (talk) 14:12, 22 September 2009 (UTC)

trauma

I am in Africa Botswana and was recently involved in a car accident with my girlfriend, the accident left her traumatised such that she is afraid to get in a car ! The part where we are doesnt have counseling services so how do i help her get through this????

You need to contact a medical professional or counselor. You need to contact a psychologist working in Botswana, and not random strangers on the internet, whose advice may or may not be reliable. this search in Google lists some psychologists... -Jayron32 13:20, 21 September 2009 (UTC)

The questioner said they have no access to counselling services, Jayron. Adambrowne666 (talk) 08:36, 22 September 2009 (UTC)

Try to get in touch with your insurance company. Hopefully you have some kind of travel insurance (either you bought it conciously or you have it, for example, through a credit card you paid with). Ask them if they can provide any help over the phone, if they can refer you to someone, or if they have any other advice. Jørgen (talk) 20:42, 22 September 2009 (UTC)

If she is religious, perhaps a minister at her place of worship could talk this through with her? They probably have a lot of experience in lending a sympathetic ear. 81.155.57.153 (talk) 16:14, 5 May 2010 (UTC)

Virial Theorem & Quantum Mechanics

Hi all -

I'm looking at a proof of the virial theorem and trying to work out where a term disappears to, and was wondering if anyone could explain it for me. (I've done all of the question except the very last line of the last step!)

The Hamiltonian operator for a particle in one dimension is H = T +U where T = p²/2m, and U is any potential.

Show that the expectation value "{T}" is positive in any (normalized) state. By considering {H} show that the energy of the lowest bound state (assuming there is one) has energy above the minimum of U.

Suppose ψ is an eigenstate of H with energy E. Show that, for any operator A, and in the state ψ, {[H,A]} = 0.

By taking A = x,show that {p}=0. Now let U(x) = kxⁿ for constants k and n; by taking A = xp, derive the virial theorem

2{T} = n{U}.

(p is the momentum operator, [a,b] is the commutator ab-ba, and {_} is the expectation, throughout the question.)

Now by fiddling around with [H,xp] I've managed to get to:

${\frac {p^{2}}{2m}}+{\frac {Uxp}{2}}={\frac {nU}{2}}\,\Rightarrow \,2\{T\}\,+\,\{Uxp\}=n\{U\}$

for the given 'U', at which point the {Uxp} is meant to disappear, but there's no explanation in the proof - but why? Is it because {p}=0? If so, why does that imply {Uxp}=0? Since there's no explanation in an otherwise detailed proof, I'd assume it's fairly obvious with little calculation.

I don't need much explanation but just a rough idea of why the expectation of kxⁿ⁺¹p should be 0, e.g. a symmetry argument, would be brilliant.

Thanks a lot! Spamalert101 (talk) 13:51, 21 September 2009 (UTC)

I think you’ve made a mistake in computing the commutator. I get [H,xp] = -iħ(p²/m–knxⁿ) = -iħ(2T-nU), from which the result follows immediately. If you calculate the commutator correctly, the kxⁿ⁺¹p term that comes from (kxⁿ)(xp) cancels out the -kxⁿ⁺¹p term that’s one of the two terms that comes from the -(xp)(kxⁿ) term. Red Act (talk) 11:20, 22 September 2009 (UTC)

Extreme Trees

Where can you find the northernmost and southernmost trees (not mosses, grasses, etc) in the world? What species are they? My first thought was evergreen but surely there is a hardier stock than that! TheFutureAwaits (talk) 14:39, 21 September 2009 (UTC)

The Arctic willow grows up to N80, but it is more a shrub then a tree. Granted, at extreme elevation, an 80 year old tree might only be 1 ft tall. If being in the extreme north also has that effect, it would not be trivial to differentiate shrubs and trees since they would probably be the same size. As far as south goes, Tierra Del Fuego has beavers, so I would presume they have trees. There could be islands further south then that with trees. Googlemeister (talk) 16:01, 21 September 2009 (UTC)

Northermost tree: 72°30'N at Ary-Mas (102°27' E) on the Central Siberian Plateau, see Tree line. Southermost tree: Look around 55°58'S 67°16' W Cape Horn on Tierra del Fuego because there are no trees on Antarctica. Cuddlyable3 (talk) 16:10, 21 September 2009 (UTC)

Ah, found it. Dahurian Larch TheFutureAwaits (talk) 16:11, 21 September 2009 (UTC)

Star Trek Voyager & Beaming Stuff Aboard

On Star Trek: Voyager, they seem to routinely lock on to things on other ships and beam them aboard. Wouldn't this be a more effective way of destroying an enemy ship than the proton torpedoes they use to just make the ship rock and the people on board fall against the walls? If they could just beam the engine of the enemy ship (or other essential parts) and put them somewhere else, wouldn't that completely disable the ship once and for all with minimal effort? Or do proton torpedoes just look better? --KageTora - SPQW - (影虎) (talk) 15:22, 21 September 2009 (UTC)

The pretense, as I recall, is that they can't beam stuff through the shields. Generally, though, it's that torpedoes look better. Additionally, transporter-based battles would be remarkably dull: who can beam out the opponent's power system first? OK, you win. — Lomn 15:42, 21 September 2009 (UTC)

I think the OP means photon torpedoes because proton torpedoes are only used by aliens disguised as actors in latex masks. Beaming people around is handy for plot development. Someone put effort into making the stardust fade effect so why not use it in every episode as often as possible? BTW the ship doesn't really rock, they shake the camera and the people just pretend to fall against the walls. Cuddlyable3 (talk) 15:54, 21 September 2009 (UTC)

Also, there is probably some kind of maximum size of object that can be beemed. Otherwise, why not just beem the whole ship into the nearest star, planet, moon, asteroid whatever. Googlemeister (talk) 15:56, 21 September 2009 (UTC)

They actually tried that in one episode using an alien transporter - it turned out not to be compatible with their hardware (something to do with anti-neutrinos). --Tango (talk) 16:24, 21 September 2009 (UTC)

Indeed, they usually have to use conventional weapons to disable the shields before they can transport anything. Once they have done that, it only takes one photon torpedo to destroy the ship, so why bother with the transporter? --Tango (talk) 16:24, 21 September 2009 (UTC)

In Stargate Atlantis they use beamining technology to beam nuclear devices aboard Wraith hive ships to destroy them, until the Wraith learn to use a "jamming frequency". I've always wondered why they didn't simply beam a whole part of the ship out instead of wasting a valuable nuclear explosive - they've been shown to beam objects the size of skyscrapers (well, they've been shown to beam actual skyscrapers) before. On a slightly less tangental note, in Star Trek, beamining tech could easily be used to harmlessly cripple an enemy ship who is, perhaps, only partially disabled (remove, say, the weapons array, or a small yet vital component of the warp drive). I agree...They don't seem to use it as often as they should. Vimescarrot (talk) 16:46, 21 September 2009 (UTC)

If there is anything I learned from Stargate, it's that each and every problem can be solved with a sufficiently big explosion somewhere. Why would you break that basic law of that universe? --Stephan Schulz (talk) 22:56, 21 September 2009 (UTC)

A major reason to bother with the transporter is the preserving of life, presumably a Federation priority; and a second is improved salvage ability, though that would probably be only for museum purposes. Comet Tuttle (talk) 16:48, 21 September 2009 (UTC)

It's basically down to the shield factor. To use Star Trek transporters against an enemy ship you first have to get their shields down, then you have to drop your own shields too - which of course renders you vulnerable to the enemy's transporters or any remaining conventional weapons they may have. Also as far as I'm aware the transporters are specifically calibrated to make it hard to beam out parts of objects for safety reasons - you don't want to chop people in half by accident. Exxolon (talk) 21:16, 21 September 2009 (UTC)

As for actual science, I see no reason why we can't eventually develop a transporter, provided a scanner and transmitter is at one end and a receiver and replicator at the other end. Such a transporter should have an unlimited range, as far as you can send a signal. On the other hand, I see no possible way to do a transport without the devices at each end. How exactly would that work ? So, unless the enemy was kind enough to give you access to their transportation equipment, such sabotage wouldn't work. I suppose there could be a code they use to gain remote access to it, and you could break the code; that might make for a more realistic plot.

A weapon system I always thought they should use is antimatter missiles that drop out of warp drive right on the target. I believe I saw them in one episode. I seriously doubt if any ship-to-ship or face-to-face combat would occur then, it rarely even occurs now, as our offensive weapons are far more effective than any defenses we have. In the future, what "shield" could stand up against, say, black holes launched at the enemy ? StuRat (talk) 23:01, 21 September 2009 (UTC)

As a practical matter, transporting even inert objects would be problematic, and transporting living things would likely kill them. Maybe those details could be worked out. But before anyone gets too confident about matter transportation, find a copy of The Fly (1958 film), where matter transport worked... sort of.

It's a little known fact that at the end of the film, David Hedison is saved by one last matter transport, and finds himself on the bridge of the Seaview. :) →Baseball Bugs ^{What's up, Doc?} carrots 23:20, 21 September 2009 (UTC)

As I recall from The Physics of Star Trek, there are two main problems with transporting a human. The first is data - in order to store sufficient information about all the unique particles in a unique human body to successfully be able to reassemble it from scratch, at the time of writing's storage limits (which have not improved that much) you would need a hard drive approximately 150 million miles across. The second is the Heisenberg Uncertainty Principle which posits "it is impossible to measure simultaneously both position and velocity of a microscopic particle with any degree of accuracy or certainty." - Star Trek transporters actually have "Heisenberg Compensators" to deal with this problem! Exxolon (talk) 00:03, 22 September 2009 (UTC)

Neither of those is the problem. The problem is the physical disassembly and reassembly. It just can't be done. -- BenRG (talk) 00:24, 22 September 2009 (UTC)

Well if I recall the passage I read was assuming that the principle problem of matter-energy-matter conversion was solvable and was looking at the ancillary problem. To put the hard drive problem into perspective - if you centred the centre of the hard drive platter at the centre of the Sun, the outer edge of the disk would be beyond the orbit of Mars! Exxolon (talk) 00:45, 22 September 2009 (UTC)

With modern hard drives, I reckon we're down to about half way to Mercury! We're getting there! --Tango (talk) 00:56, 22 September 2009 (UTC)

I do not see living people ever able to be transported, because there is very very little room for error but something inert, like furniture could if you could get the scanning time down and some great data compression algorithms. Who really cares if a couple of the molecules are off by 30um? It will still be a functional bookcase or table. Googlemeister (talk) 13:19, 22 September 2009 (UTC)

BenRG touches on the main objection to transporting humans in the way Star Trek envisages it. Think about what it does - it scans you, disassembles you, send the information about you to another location, and reassembles you. Note the disassembling bit. You're dead, ripped into pieces, and then a copy of you is reconstructed elsewhere. Nice for the copy, not so great for you. See Second Chances (Star Trek: The Next Generation). Apparently the physics just doesn't work either.[5] Fences&Windows 02:53, 23 September 2009 (UTC)

The concept of converting the atoms to energy, transmitting them, and then changing them back into atoms at the other end always seemed silly to me. All you need to transmit is the pattern (information). The copy can be assembled from stockpiles of various atoms at the target location. As for the old object, just destroy it in whatever way is most convenient (and less painful, if it's alive).

An object made of certain uniform materials could be transported now. A stereolithography (STL) machine makes a 3D object out of a type of plastic, and laminated object manufacturing (LOM) creates a type of wooden object. So, all that's needed is to scan such an object, transmit the dimensions to a remote STL or LOM machine, and create it there. There will be some error in the process, and it will take minutes or hours to complete, but the result should be close enough to the original to be recognizable. StuRat (talk) 13:42, 22 September 2009 (UTC)

That's not transporting it's remote duplicating. Try that with a person and the clone arrives dead with no internal momentum, and the original asks When will something happen? Cuddlyable3 (talk) 07:21, 23 September 2009 (UTC)

They are one and the same. As for restarting the heart, that's a relatively simple matter compared with teleportation. StuRat (talk) 12:27, 23 September 2009 (UTC)

Remote duplication is exactly what the Star Trek teleporter does. Except it kills the original. Fences&Windows 18:42, 23 September 2009 (UTC)

Seemingly forgotten in all this is that Roddenberry invented the matter transporter simply as a plot device to get people from one place to another quickly without having to take a shuttle every time. He also used other far-fetched ideas, such as backwards time travel, which is impossible also, but undeniably makes for interesting storylines. →Baseball Bugs ^{What's up, Doc?} carrots 09:34, 23 September 2009 (UTC)

Backwards time travel may be possible, as long as it's not into your own time line, where it leads to paradoxes. The infinite universes hypothesis (redlink ?) has some serious support, and that means there are also an infinite number of universes exactly like ours. There's no reason you couldn't go back in time in one of those (or appear to do so, if you find a universe which is delayed by the required amount from ours). StuRat (talk) 12:27, 23 September 2009 (UTC)

Pendulum's bob

Does is make any difference for the swinging of a pendulum if we put water inside a hollow bob (physics) instead of other solid material with the same mass?--Quest09 (talk) 16:14, 21 September 2009 (UTC)

No difference to the swing frequency (added) provided the water fills the bob. Turbulence will not occur. Assume you do not burst the bob by freezing or boiling the water Cuddlyable3 (talk) 16:23, 21 September 2009 (UTC)

If there was some water and some air in the bob then you would get movement of the water, which would result in less constant motion, I guess. There may also be a damping effect due to friction of the water with the sides of the bob. --Tango (talk) 16:26, 21 September 2009 (UTC)

Water motion creates a dampening effect, not just turbulence, correct? I remember seeing a documentary on some skyscraper which used drums half-filled with water to dampen the swaying of the buildings (the same concept as motion of a pendulum). -- kainaw™ 16:37, 21 September 2009 (UTC)

Once in motion the water does not move.its all part of being a pendulum83.100.251.196 (talk) 20:15, 21 September 2009 (UTC)

The water in the filled bob rotates. The pendulum swing is damped (pun!) by the mechanical energy loss that goes to heat the water. Vanes could be added inside the bob to prevent this. Cuddlyable3 (talk) 20:22, 21 September 2009 (UTC)

no, the acceleration of the pendulum means that the water inside is stationary with respect to the bucket.83.100.251.196 (talk) 20:43, 21 September 2009 (UTC)

I don't think that is true. At the peak on either side the pendulum is stationary, so the water will just fall down. Down is in a different direction on each side (relative to the pendulum). --Tango (talk) 21:27, 21 September 2009 (UTC)

At the peak the body is accelerating (down) - as the water sloshes down so does the container - result no net motion relative. Try calculating forces and acceleration on the water - same as the container. Same motion.83.100.251.196 (talk) 23:35, 21 September 2009 (UTC)

It isn't true that the forces on the water are the same as those on the container. First of all, the whole container experiences a uniform force from the arm of the pendulum since it's a rigid body, but the water doesn't. Different parts of its volume are affected differently by the normal forces of the walls of the container and since the water isn't rigid, that'll cause the shape to deform. But even if that weren't the case, for example if we replaced the water with a rigid frictionless weight, we still wouldn't have a normal pendulum. The bob and the weight would still experience different forces, since the direction of the force that the bob exerts on the weight depends on the weight's relative position, and so is not necessarily in the direction of the pendulum arm. What we'd have is something like the double pendulum. Notably the double pendulum does have some normal modes that behave nicely like what you're talking about, but usually the motion is chaotic. Rckrone (talk) 05:31, 22 September 2009 (UTC)

If you consider the spherical shells (around the pivot point) of water - it seems to me that each shell experiences uniform force (increasing with radial distance from the pivot) - so that makes me think that the pressure in the water increases with radial distance (just like in a standing column), and that there is no net tangential force on an part of a shell (relative to it's neighboring molecules in the same shell).. Assuming the 'bukcet' doesn't buckle I'm still not convinced that there will be any motion, but I'll have to give it more thought. (the actual pressure @ depth does change over the pendulum period - but I don't see a point when the forces cause motion in the water)83.100.251.196 (talk) 11:11, 22 September 2009 (UTC)

Correcction due to the width of the bucket in the direction of oscillation the equipressure surfaces will not be perfectly spherical - but I still don't have any 'inversion' or reason for motion.83.100.251.196 (talk) 11:14, 22 September 2009 (UTC)

Ah the top surface will 'hollow'! this would cause shearing in the body of liquid (not turbulence I think) - this would inevitably dissipate some energy83.100.251.196 (talk) 11:16, 22 September 2009 (UTC)

wait a minute no shear, just a non-flat surface - cant anyone actually answer this definitively without arm waving? :)

Well, so if the bob were half-filled with water and half-filled with air, the pendulum would swing less and not be simply less predictable, right? And, if we could avoid turbulence, would it still make a difference? --Quest09 (talk) 16:39, 21 September 2009 (UTC)

Are we approaching tuned mass damper territory?

No difference under pendulum motion - the liquid undergos the same forces as the rest of the pendulum - thus is stationary with respect to the vessel which holds it. There won't even be any turbulence.83.100.251.196 (talk) 20:15, 21 September 2009 (UTC)

A container filled with water and subject to angular acceleration (like a pendulum bob) will have the water rotate. This could be seen if a sealed glass container with bits of paper suspended in the water were suddenly turned one way or the other. The water nearest the sides of the container would, due to friction with the sides, start to turn with the container, more than the water in the center. When the rotation is reversed (as in a pendulum bob starting to swing the other way), there will be turbulence and it will then start to follow the sides in the other direction. This is besides any sloshing around in a partially filled container. This work should affect the movement of the pendulum slightly, but slight effects on period could be important in a timekeeping device. Edison (talk) 23:39, 21 September 2009 (UTC)

Right, except that there would only be turbulence if the rotation were fast enough. I don't know for sure, but I bet you'd find that the friction created by the water rotation would cause the pendulum to slow down noticeably quicker. Looie496 (talk) 23:49, 21 September 2009 (UTC)

I do not agree that that there would be no turbulence with "slow" rotation, whatever "slow" means in terms of a pendulum, just less than with greater angular acceleration. If the pendulum were very long, the period would be quite long, but there would still be some turbulence. (I must be off to file a research grant for a snow globe full of water and floaty bits and a very long pendulum.) Edison (talk) 01:13, 22 September 2009 (UTC)

"Turbulence" has a very specific meaning in fluid dynamics - I'm fairly sure there would be motion in the water, but it wouldn't necessarily be turbulent. (It depends on Reynolds numbers and other things I don't understand!) --Tango (talk) 01:19, 22 September 2009 (UTC)

Could the actual motion be estimate using that fact that pendulums of different lengths have different time periods (an extension of the double pendulum idea suggested above by Rckrone) ?

I think I can 'derive' shearing motion in the water as the top water level surface changes (see above Ah and above) - if you know what reynualds numbers are you know more than me, maybe you could look at it^^ and say if it sounds reasonable.83.100.251.196 (talk) 11:27, 22 September 2009 (UTC)

I know the words "Reynolds number" and that it has something to do with determining when a flow becomes turbulent, that's about a far as I go! --Tango (talk) 13:21, 22 September 2009 (UTC)

Just googling... There appear to be specific classes of water dampers for pendulums such as "sloshing" and "tuned column" dampers. -- kainaw™ 23:45, 21 September 2009 (UTC)

A tuned liquid column damper isn't quite the same thing as a swinging pendulum- here's a simple picture [6] , a tuned mass damper is also not a simple pendulum.83.100.251.196 (talk) 11:03, 22 September 2009 (UTC)

My 2-year old wanted to play and I thought this was easier to simply try instead of guess at. It is rather simple: Hang a rod from a hook on the back porch railing. Fasten a cup to the bottom of the rod. Test it - does it swing without flopping around and hitting things? Yes. It acts like a nice pendulum. Pour a tiny bit of water in the cup. No noticeable change in the action of the pendulum - but the water does slosh around a lot. Fill the cup half full. The pendulum doesn't swing anymore. It goes to one side, then has extremely noticeable resistance attempting to reach the same elevation on the return swing. After a few swing, went into another motion. The water kept sloshing around, causing motion in the pendulum. Then, fill the cup almost full. The water sloshes out and it ends up half full and acts as it did previously. If anyone else wants to do this experiment, please let me know if your results are different. -- kainaw™ 19:20, 22 September 2009 (UTC)

It would be good to try that last experiment with a lid to stop the water sloshing out. --Tango (talk) 03:40, 23 September 2009 (UTC)

Is that cup fastened rigidly to the rod or is it hinged at the fastening point ? Cuddlyable3 (talk) 07:15, 23 September 2009 (UTC)

I will have to switch cups to put a lid on it. I may try this afternoon when I get back from work. As for hinging - the cup was fastened to the rod on top and on bottom, so it couldn't swing separately. I didn't want to create two pendulums, which I already know have a very odd swinging pattern. -- kainaw™ 13:00, 23 September 2009 (UTC)

I couldn't get it completely full because all of my cups with lids have a wider diameter on top than on bottom. So, the cup is tilted on the rod. I got is almost full with a lid on it. The pendulum doesn't slow down much as it swings. I did 5 tries with no water and 5 tries with it almost full. They are about the same. The almost full of water version shows loss of momentum after a minute, but not what you'd notice if you weren't measuring it. -- kainaw™ 23:43, 23 September 2009 (UTC)

Turning into another creature

In the movie, District 9, Wilkus accidently consumes an alien fluid and slowly is transforming into one. I know it doesn't exist, however what would have to happen on a cellular level in order for this to happen? Also, what would happen if you took, say, frog DNA and tried to change my DNA cells with it? Forgive my absolute ignorance on this subject. --Reticuli88 (talk) 17:43, 21 September 2009 (UTC)

My level of knowlege on this subject is very limited, but I will give my own speculation on the subject. I also don't believe there's any major research on transformation of living creatures like this. If it were to happen though, you would suffer severe adverse effects as your body's cells are slowly replaced with those of a (very likely) genetically incompatible creature. I imagine that you would be in incredible pain and feel incredibly sick while this is taking place. This is assuming that you can survive as even human to human transplants (with only a TINY amount of genetic difference) requires anti-rejection drugs to be taken continuously. In some ways, you could think of it as a cancer that covers your entire body where incompatible cells are reproducing alongside, and replacing existing human cells. Granted, once again, this is pure speculation based on my limited knowlege of cellular biology. Caltsar (talk) 18:11, 21 September 2009 (UTC)

Think of the body as a collection of cells with one DNA that are specialized to particular purposes and structures. Now imagine the difficulty of spreading new cells with new DNA throughout the body, while simultaneously replacing existing structures and cell-types. It's bad form to speculate about future potentialities, but I would say, "probably not." We can imagine being able to change an entire body's DNA in the future by means of viruses that would modify existing cells, and even that sounds very hard (your body's immune system would likely say "ack, that's not me!"). One would imagine doing this as part of gene therapy—to get your body to stop producing an incorrect hormone, for example. But to simultaneously change body size and structure? It seems a little far-fetched to me. Certainly if one is imagining not only going between species, but species with no shared evolutionary history (e.g. an alien). --98.217.14.211 (talk) 20:07, 21 September 2009 (UTC)

There is nothing called a DNA cell. DNA is the coded double-string of molecules that make up chromosomes in living cells. See the Wikipedia article Introduction to genetics for explanation. Trying to replace your DNA with frog DNA would cause your human cells to reject the intruder, just as they are doing all the time to cells that get damaged by radiation or infection. Cuddlyable3 (talk) 20:11, 21 September 2009 (UTC)

(EC) Unless the alien DNA is encapsulated by some sort of vector which allows penetration to the nucleus, and also contains enzymes which destroy the original DNA, it won't work. We consume DNA all the time in our food, I believe it is just broken down into nucleotides which can be recombined to our own DNA. --Mark PEA (talk) 20:12, 21 September 2009 (UTC)

When thinking about the logistics behind this kind of thing, remember that your bones are basically mineralized deposits; they're not changing for anyone without a whole lot of effort. In the movies, I suppose it doesn't matter because every alien happens to look exactly like a human with a blob of putty on their forehead, but it's the kind of thing you'll need to work out while working on your frog-men. ;-) I loved ST:The Next Generation, but their episode where the crew all starts "de-evolving" just bugged the hell out of me. I'm sure it was news to biologists to learn that spiders are in the family tree... how would the switch from endoskeleton to exoskeleton even work? Matt Deres (talk) 20:32, 21 September 2009 (UTC)

I can imagine a simpler way such a transformation could occur, if the parasitic organism simply eats the host from the inside out. The fungus that takes over the body of an ant works in this way. While, in this case, the exoskeleton remains intact and in "ant form", it's not too much harder to imagine that an organism could digest the existing skeleton and create a new one to it's own liking, and then create organs, a brain, etc. However, note that much of the digested host would be needed for energy, so the final organism would likely be much smaller than the host, unless it ate additional food. I'd also expect all this transition to take far longer than it does in the typical sci-fi thriller, where it can happen in seconds, minutes, or hours. I'd expect it to take weeks, months, or even years. StuRat (talk) 22:44, 21 September 2009 (UTC)

Medicine

I would like to know about the latest oral iron preparations ( new molecules ) for anaemia that are available in India along with the brand names and names of pharma companies that manufacture them. I also want to know about the latest calcium preparations available in India similarly. Ritamacwan (talk) 18:04, 21 September 2009 (UTC)

Here are thousands of search results for Iron[7] and Calcium[8] preparations. Cuddlyable3 (talk) 19:58, 21 September 2009 (UTC)

ideal gas

is Chlorine (Cl2) an ideal gas at -20F? Googlemeister (talk) 20:44, 21 September 2009 (UTC)

Ideal for what? Poisoning someone? Exxolon (talk) 21:11, 21 September 2009 (UTC)

I assume Googlemeister means ideal gas. DMacks (talk) 21:13, 21 September 2009 (UTC)

My (very old) chemistry book only says: "Ideal gas heat cap: 0.144BTU/lb-°F @ 75F." -- kainaw™ 21:16, 21 September 2009 (UTC)

There's no such thing as an ideal gas. Chlorine boils at -30F, so at -20F it will be close to that - which isn't the best condition for ideal gas properties.

The ideal gas law is an extension of experimentally discovered gas laws. Real fluids at low density and high temperature approximate the behavior of a classical ideal gas. However, at lower temperatures or a higher density, a real fluid deviates strongly from the behavior of an ideal gas, particularly as it condenses from a gas into a liquid or solid. The deviation is expressed as a compressibility factor.

So the compressibility factor aka "Z factor" is what you need (at -20F) to see how far off it is.83.100.251.196 (talk) 23:22, 21 September 2009 (UTC) [9] gives "Compressibility Factor (Z) (1.013 bar and 15 °C (59 °F)) : 0.9867" - that's fairly ideal - it is after all a non-polar molecule. There are even equations for estimating Z-factor (search) - but I don't understand/not familiar with them.83.100.251.196 (talk) 23:31, 21 September 2009 (UTC)

Car steering problem

For a math word problem, I had an idea from a problem with a car I had as a teenager. The steering wobbled a bit when I had the car. Over time, it got worse. Eventually, it pulled hard to the right. I corrected by pulling it left. Then, it pulled hard to the left. I correct by turning right. Then, it pulled hard to the right. So, I junked it. For this word problem, I want to state that a part in the steering has failed at X%. This makes it Y% undrivable. What part in steering would reasonably cause this sort of problem as it degraded? -- kainaw™ 20:49, 21 September 2009 (UTC)

I would guess it was the steering rack - the central part of the rack had worn away so it would only engage to the left or the right. Exxolon (talk) 21:09, 21 September 2009 (UTC)

Not everything can be described in terms of percentages. I don't see how drivability can be quantified like that. --Tango (talk) 21:22, 21 September 2009 (UTC)

On math exams, everything in the world can be quantified to a clear percentage. -- kainaw™ 21:24, 21 September 2009 (UTC)

On badly written maths exams, maybe. I would hope you would write good maths exams... --Tango (talk) 21:28, 21 September 2009 (UTC)

You're describing a form of oversteer. The fault, as noted, is probably with the steering rack, or the mounting of the steering rack (although there are many other potential causes). You can probably make up some sort of algorithm describing the extent to which the input (your turning the wheel) relates to the outcome (the extent of oversteer), and state that within certain parameters the oversteer is acceptable, and outside those parameters, unacceptable. But it does sound as if you'll have to make a great deal of the problem and evidence up. --Tagishsimon (talk) 21:34, 21 September 2009 (UTC)

If there was an ECU operating the hydraulic power steering, any number of electrical, software, or mechanical failures might have been responsible for the trouble Kainaw described. I also vote against using "percentage of steering" because it is an unintuitive concept. Can't you rephrase as, say, "percentage that the steering wheel was rotated", and "percentage that the wheels actually turned"? Those are direct, and I think it's what you were trying to describe in the first place, just worded in a confusing way. Nimur (talk) 15:36, 24 September 2009 (UTC)

housing ideas for wiring in a heated enviroment?

im making a mini hot-plate (from a soldering iron taken apart) that should sit in the center of a glass dome. and i need to know how and what to us to place it there with out the heat being made, melting the wires. i was thinking maybe it put them in a glass up-stim to the mini hot-plate. any advise?

Use wires with high heat tolerance? Googlemeister (talk) 21:00, 21 September 2009 (UTC)

How hot? How long a time? Any other factors to consider for your system (high humidity)? Any physical requirements (permanent vs temporary, must allow repositioning vs can be fixed in one position)? DMacks (talk) 21:10, 21 September 2009 (UTC)

My soldering irons always had wires inside them that were protected from the heat of the iron. Why not use wires like those? -- kainaw™ 21:11, 21 September 2009 (UTC)

Some low wattage soldering irons have mains voltage flowing through an insulated resistance wire in the tip. More powerful soldering guns, which might have trigger selectable power up to 100 watts, have a transformer in the handle which steps low current mains voltage electricity down to very low voltage very high current electricity which flows through the noninsulated metal tip. Electrocution is likely to result if things are constructed from these disassembled devices and no distinction is made. The questioner has posted twice about this and never specified the temperature or purpose of the device. Putting mains voltage on something which gets very hot is a good way for the technical novice to injure someone or start a fire. High enough heat will melt insulation and cause wires to short. Ceramic insulators might crack if it gets hot enough. This projects sounds like a recipe for disaster. An adult with sound knowledge of electricity and the safe design of heating devices, so they comply with ANSI standards and the National Electrical Code (or any country's equivalent) should supervise any such work. Edison (talk) 14:03, 22 September 2009 (UTC)

i thought i mentioned how hot it was going to get. it should get around 320'-360' Degrees F. im not so worryed about the glass, the only thing im not sure about is the wiring. i was thinking of using a lead free solder to hold the plate to the soldering iron. becouse i have no need to get it hotter them 360'F im not worryed about it melting agien. im just not sure how to get it in the center of the glass without damaging the parts and wiring.

Ok to throw fermented waste in my compost?

Hi all,

I have a composted heap that is pretty well balanced with greens and browns, is well aerated, and doesn't smell. I had previously told my neighbor, who has a little air-tight kitchen compost bin, that she was welcome to dump her waste in my compost -- the more the merrier! (No meat etc. though). Well, the other day I guess she did so, because it reeked across the whole yard. When I opened the composter to turn it, I was a little light-headed. I'm guessing that her waste had been piling up for weeks in that air-tight container and had started to ferment.

My question is: is it ok to put fermented waste in my composter, or should I tell her not to bother if it gets over-ripe? The smell, by the way, was gone by the next day.

Thanks! — Sam 76.24.222.22 (talk) 22:51, 21 September 2009 (UTC)

My view: it's fine. A random website confirms this. --Tagishsimon (talk) 22:56, 21 September 2009 (UTC)

That web site is mostly about a specific kind of "fermented composting" using Bokashi, so I'm a little unsure if they're knowledgable about regular composting, but you're right that they do say you can just dump it in your regular compost. There's no reason anyone can think of why the byproducts of the fermenting would be harmful to the bacteria doing to composting, or that different kinds of bacteria might compete? — Sam 76.118.181.97 (talk) 00:31, 22 September 2009 (UTC)