Wikipedia:Reference desk/Archives/Science/2008 January 18

= January 18 =

capillary force vaporizer
The capillary force vaporizer is new technology which offers many practical advantages for the military by burning the same fuel used to power Hum-Vees, trucks and aircraft. It was offered as a major breakthrough for backpackers as well and stoves based on the technology were supposed to become inexpensive and replace other types of stove that burned other fuels.

Today, however, stoves based on capillary force vaporizer technology are not only hard to find but expensive and it appears they are also being covered up. Is it possible that these stoves are so efficient and economical to use that they are being made scarce to discourage people who use gas stoves from converting to them, since we are supposed to be headed for renewable fossil fuels like gas and away from non-renewable fuels like oil? —Preceding unsigned comment added by 71.100.12.59 (talk) 01:52, 18 January 2008 (UTC)


 * No. (Well, okay, yes, it's possible.  But it's vanishingly unlikely.) —Steve Summit (talk) 02:06, 18 January 2008 (UTC)
 * Okay then why can't I buy a CFV stove for my kitchen and a CFV furnace for my basement? —Preceding unsigned comment added by 71.100.12.59 (talk) 02:20, 18 January 2008 (UTC)


 * Why don't you call Vapore Inc. (of Richmond, CA) and ask them? —Steve Summit (talk) 02:26, 18 January 2008 (UTC)


 * Is the CFV concept patented or just the products they produce? Could someone implement the concept in another design without infringing on their patent? I belong to a ceramics class. —Preceding unsigned comment added by 71.100.12.59 (talk) 02:56, 18 January 2008 (UTC)


 * According to the Vapore corporate website], yes, the CFV is patented. They also seem to have quite a bit of information there on how it works.


 * The reason they're hard to find may simply be that they are expensive. If their advantages aren't quite as overwhelming as the inevitably-glowing early reports make them out to be, there may be few people clamoring for them, and that plus a high price would be enough to discourage most retailers from carrying them.


 * But, certainly, Vapore could tell you where (if anywhere) retail versions are available; there's contact information at their website. If you're excited by the prospect of the technology, go ahead and buy one (even if it seems expensive), and try it out, and tell the world what you think!  Most new technologies need some early adopters in order to become well-known. —Steve Summit (talk) 00:28, 19 January 2008 (UTC)


 * I see one company, Vapore, using that CFV term. They say their stove uses "White gas (naptha), clean kerosene, clean JP8, clean diesel" whose main source is petroleum.  As to availability, if Vapore is not making the technology public then you'll have to see what companies are making licensed CFV products.  A company which is protecting its property is not "being covered up" by anyone other than itself.  Also, if the technology is patented then the description of the patent is public and is not under cover, so look up their patents.  -- SEWilco (talk) 17:47, 18 January 2008 (UTC)


 * Also, for the record, gas actually comes from oil, but neither of them are fissile. --Sean 20:28, 18 January 2008 (UTC)
 * Gas can come from other sources than oil making it renewable in that sense. I think "fissile" was a mispelling of Fossile. —Preceding unsigned comment added by 71.100.3.254 (talk) 00:12, 20 January 2008 (UTC)

Radiation "build-up" in high-atomic weight materials
I'm trying to understand the concept of "build-up" of broad beam gamma radiation going through a shielding material. I don't understand why it is of any concern - on average, the number of particles and photons deflected towards a detector is going to be equal to the number deflected away from it, so the term "build-up" which implies that the radiation has increased cannot be correct. Seans Potato Business 09:20, 18 January 2008 (UTC)


 * What has changed is the quality of the radiation. When gamma radiation passes through a material, you get a number of effects.  Lower energy radiation is more likely to be scattered or absorbed, so the resulting beam tends to contain gamma ray photons of higher energy (this effect is called beam hardening).  (The total beam energy coming out is lower than the energy coming in, but what's left over is more penetrating.)  This effect is important in diagnostic x-ray machines, which are designed to filter out very low-energy x-rays before they leave the instrument.  (Very 'soft' x-rays won't ever penetrate the patient to contribute to the image; they would get absorbed in the first few millimeters of skin.)


 * Perhaps more important to you – the soft, squishy human being hiding behind your flimsy shield – is Compton scattering. A high energy gamma ray passing through matter can lose energy in a couple of ways.  One of them is to smack into an electron.  The electron gets kicked loose, and the gamma ray photon loses energy equivalent to the electron's ionization energy (plus some kinetic energy).  So, what's an electron with a bunch of kinetic energy?  A beta ray.  Beta rays of a given energy will travel much less distance through solid matter than a gamma ray of the same energy; what this means is that for each unit of distance a beta ray travels, it deposits more energy: a greater radiation dose along a shorter path.  (Technically, one is trading low linear energy transfer (LET) radiation for high LET radiation.)


 * This effect is used with great benefit in clinical external-beam radiotherapy. Modern linear accelerators can generate x-rays with peak photon energies of greater than 20 MeV; these beams will deliver their maximum dose several centimeters deep in a patient's body.  (I've done testing of clinical linear accelerators; for testing the collimation and alignment of 20 MV x-rays I would put a sheet of film under a four or five-centimeter slab of plastic to 'build up' the dose that the film saw.  If one forgot the plastic, the film would be fogged only slightly by the x-rays.  TenOfAllTrades(talk) 15:38, 18 January 2008 (UTC)

Cloning
In the precess of cloning genetic material, does the resulting clone contain within its cells nucleuses the introns which would otherwise have been found in the orignal subject? Weasly (talk) 16:33, 18 January 2008 (UTC)


 * I'm no biologist, but you already asked this. Consensus was yes for the common use of the word "clone", no for Molecular cloning which I'm pretty sure is a completely different process. APL (talk) 17:25, 18 January 2008 (UTC)


 * Completely different processes. Clones like, Dolly (sheep), have an entire nucleus transferred into another cell. Therefore this type of clone (the one understood colloquially as a "clone") has everything, introns & all.
 * Coles created from a cDNA library, such as most molecular clones used to study individual proteins and such, generally lack introns because cDNA is usually derived from mature mRNA.
 * Read Cloning for more info. &mdash; Scientizzle 17:48, 18 January 2008 (UTC)

easy stable magnetic levitation
im building a project (non school)and a part of it is to levitate a circular plastic plate 3" across with magnets imbeded in it on a large plate magnet a few feet large but before investing in a large magnet i would like to find out if a stable enough levitation is achivable on a plate with magnets spread apart enough or maybe some better magnet configuration,

ive read about using a diamagnetic material between the magnets to cut the magnetic field but i dont know much about this

my goal is only to have 1 or 2 milimeters of levitations at most

thanks for the help —Preceding unsigned comment added by 69.70.41.10 (talk) 17:20, 18 January 2008 (UTC)


 * Did you try a miniature test with paper/plastic plate with a few cheap magnets? See also magnetic levitation.  Also, what is "a large plate magnet"?  Magnets tend to be long, not thin (magnetic poles on ends, not on sides).  -- SEWilco (talk) 17:28, 18 January 2008 (UTC)


 * You won't be able to balance out the forces with standard magnets. (Though you may get infuriatingly close.) Diamagnetic_levitation looks like it may be possible for your project. APL (talk) 17:45, 18 January 2008 (UTC)

to SEWilco the full sized magnet i will need will be the about size of a diner table (around 2` by 4` but not decided yet) and i dont know if its possible to make a magnet of that shape with 1 pole being on the top side but if it is it would probably be the easyest way of doing it ,

of course i could place a lot of smaller magnet side by side but that would be a lot of work and over time i dont know if the magnets would degrade from interfering with each other

i avent been able to gather materials and any large enough magnet to make a model yet or enough small ones yet (i am working at it tough)

i have also been thinking of an electro magnet but i dont know enough about electricity and am woried about electrocutions

to APL

my idea was to try to get a very small levitation on a few magnets held by plastic spread as far as possible to try to get the most stability i can, also the best form of diamagnetic levitation ive seen in the article would be with pyrolitic graphyte but that seems very expensive and i dont know if it could levitate 20+ grams of plastic —Preceding unsigned comment added by 69.70.41.10 (talk) 18:12, 18 January 2008 (UTC)
 * Sadly, as APL writes, it has been proven impossible for simple permanent magnets to remain stationary and levitated in a static magnetic field (see Earnshaw's theorem). However, there are some tricks to getting around that problem.  I think diamagnetic levitation will be difficult to pull off on the scale you are thinking of, unless you have easy access to superconducting materials (which would allow you to harness the Meissner effect).  I think your best bet will be to use spin stabilized magnetic levitation.  However, even this is a pretty tricky prospect.  Using electromagnets and feedback control are another possibility to get around Earnshaw's troublesome limitations, but that would require rather advanced knowledge of electromagnetic theory and electrical engineering.    --Bmk (talk) 19:29, 18 January 2008 (UTC)

i was thinking, what would happen if you put an inverted magnet in the center of the other levitating magnets , since it would be atracted by the magnet underneat coudnt that help stabilizing the whole thing by making it closer to the oposing magnetic field ? —Preceding unsigned comment added by 72.0.206.235 (talk) 23:28, 18 January 2008 (UTC)


 * It's mathematicly impossible to achieve a stable balance like the poster wants. Anything that "helps" will just frustrate him because no matter how close he gets it will never be exactly right.
 * Perhaps an Air Hockey table would be more in line with the original poster's needs? APL (talk) 05:32, 19 January 2008 (UTC)

Seasoning a cast iron skillet
We've been using olive oil to coat our cast iron skillets after cleaning them. Last night we got some PAM olive oil cooking spray. The ingredients on the can only list extra virgin olive oil, lecithin from soybeans, water, and propellant. Would this be okay to season the skillets? Any idea how much water is in the Pam and if it would be enough to have an effect on the cast iron? And finally, what do they use as a propellant? Dismas |(talk) 19:15, 18 January 2008 (UTC)


 * Seasoning (cast iron) does not mention PAM and its water content. Aerosol spray mentions that some cooking sprays use nitrous oxide and carbon dioxide as propellants but PAM is not specifically mentioned.  -- SEWilco (talk) 20:22, 18 January 2008 (UTC)


 * Olive oil, and especially extra-virgin olive oil, would be an unusual choice for seasoning cast iron, as far as I know. Extra-virgin olive oil has a strong flavor, is expensive, is relatively prone to rancidity, and has a low smoke point.  All of these factors would discourage me from using it for seasoning.  I've always read that you should use neutral vegetable oil (e.g. canola oil) or vegetable shortening (e.g. Crisco).  I use Crisco myself, with good results.  -- Coneslayer (talk) 20:29, 18 January 2008 (UTC)


 * The anodized non-stick pans that I have specifically warn against using any spray oils. Something about the propellants defeating the non-stick materials. I don't know whether that would also hinder their seasoning ability on cast iron, but I'd agree with Coneslayer and avoid it. jeﬀjon (talk) 21:28, 18 January 2008 (UTC)


 * I would definitely concur with Coneslayer's take on this. Having cooked with cast iron skillets, pans and Dutch ovens for years, I would never think of using any of the lighter oils to season them. Now, don't get me wrong, I absolutely adore cooking with olive oil, especially the expensive extra extra virgin kind. I also like to use Pam spray on things such as my waffle iron. But I would absolutely never use either olive oil or Pam to season my cast iron cookware. I am not sure whether you are a vegetarian, but if not, I'd say the best thing would be to buy some good old-fashioned pork lard to season your cookware. You may never use it for anything else, but for seasoning cast iron, pork lard is the best. However, if you want to take Coneslayer's advice you may also use Crisco (shortening) and get pretty good results. Happy cooking! I love my cast iron cookware! -- Saukkomies 14:47, 18 January 2008 (UTC)

Tempature
What is the average human body tempature?--76.28.67.224 (talk) 19:38, 18 January 2008 (UTC)
 * See normal human body temperature. Algebraist 19:42, 18 January 2008 (UTC)

Biogas
So I'm watching a program on the BBC and it's talking about biogass application in rural China. The program paints the whole process in a very favourable light. Going through the Wiki Articles, I've gotten an idea how it's done but I dont see many criticisms in regards to it. What are the cons to this type of renewable energy? What type of emissions are produced and are they harmful to the environment? If the cons are few, why is this not being adopted as a method to cheaply produce energy and more third world nations? Also what are the start up costs to this? Sorry for all the questions, but I'm very interested in this technology.

Thanks 70.49.119.82 (talk)Jeff —Preceding comment was added at 20:56, 18 January 2008 (UTC)


 * Actually, since the 1960s Biogas has been used quite extensively in "Third World Countries". Not as much as it should, most likely, but there have been many biogas generators set up all over the place. India is one of the major Biogas nations, for instance, and many villages in India have used Biogas for quite some years. There's a Biogas Wiki that you may wish to explore for further info here. -- Saukkomies 16:55, 18 January 2008 (UTC)
 * The older Biogas plants use bacteria to make methane, burned to make CO2 and water. Some cons. These plants need an interested person to manage them. The raw ingredients are often smelly. The end products are always smelly. In many cultures dealing with smelly things automatically makes you looked down upon, even if you do useful work.Polypipe Wrangler (talk) 11:47, 24 January 2008 (UTC)

Twisted trees!
I cannot seem to explain why some trees I see in harsh climates (i.e. Patagonia) have a twisted, spiral set of outer growth layers. I have not seen whether the bark follows this pattern or not. It is important to note that some trees that display this feature are directly next to some that do not! Any ideas? Need any more info? Thanks! —Preceding unsigned comment added by 200.47.63.6 (talk) 21:55, 18 January 2008 (UTC)


 * Krummholz may help. Delmlsfan (talk) 02:59, 19 January 2008 (UTC)

Common cold aid
Rest is recommended along with plenty of liquids as an aid to fighting the common cold. Have any studies been conducted to determine the effect of stress (or lack of rest) and the amount and rate of water consumed on maintaining/fighting a cold and the severity of the symptoms and if these at maximum possible dose would qualify as a remedy for the common cold? —Preceding unsigned comment added by 71.100.12.59 (talk) 22:40, 18 January 2008 (UTC)