Wikipedia:Reference desk/Archives/Science/2011 April 25

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April 25

PBS series about a family using 1980's computer

I saw a few minutes yesterday of a US Public Broadcasting System program (likely originally BBC) in which a British family was forced to use old electronics. They had to choose a 1982 computer, and chose a "BBC computer" over a Sinclair or Commodore. Later, they acquired a VHS player and huge camcorder. What was the series? It seemed almost like a Twilight Zone episode, when they went to the "Computer Museum" (rather than my living room or attic) to get electronics of the 1980's. Edison (talk) 00:53, 25 April 2011 (UTC)

It was probably Electric Dreams (TV series). I still have a BBC computer and a VHS recorder from the 1980s, and I remember using a shoulder-size video camera, though they were too expensive for me to own one. Dbfirs 07:47, 25 April 2011 (UTC) (Apologies for edit conflict with Ny156uk whose apparently earlier reply has mysteriously appeared below mine.) Dbfirs 07:59, 25 April 2011 (UTC)

Is it the series 'Electric dreams' by the BBC? (http://www.bbc.co.uk/electricdreams/) The family spend some time in the 70s, the 80s and then the 90s. We've an article on it Electric Dreams (TV series) ny156uk (talk) 07:43, 25 April 2011 (UTC)

Thanks! Edison (talk) 18:55, 25 April 2011 (UTC)

Do avocados contain cholesterol?

Do Avocados contain cholesterol? Also, why does the label on the bottle of vegatable oil at my local supermarket read "No cholesterol" if vegatable oil doesn't normally contain cholesterol anyways? Which foods DO contain cholesterol? Thank you. 161.165.196.84 (talk) 03:39, 25 April 2011 (UTC)

The short answer is "no". Cholesterol is only present in any reasonable amount in animal tissue. Cholesterol is a molecule that forms part of the cellular membrane in animals. Plants have a different architecture in their cell walls that does not require cholesterol to regulate fluidity, therefore only animal derived foods contain it. Vegetables and vegetable-derived products, such as avocados and vegetable oil do not contain cholesterol. The statement on your vegetable oil bottle may be obvious to an informed consumer like yourself, but nevertheless is put on for marketing to make the product more desirable for buyers. —Preceding unsigned comment added by 160.79.139.10 (talk) 05:01, 25 April 2011 (UTC)

It should also be noted that choloesterol intake does not directly corrolate to blood cholesterol levels. Your body manufactures cholesterol and cholesterol derivatives from all sorts of sources, so its quite possible to subsist on a fully vegetarian diet and have a high cholesterol. People still have that silly "you are what you eat" mentality, so when the doctor says "You need to get your cholesterol down" they think they can simply cut cholesterol out of their diet and that will help. Its way more complex than that. --Jayron32 05:11, 25 April 2011 (UTC)

Understood; It has always been my understanding that the purpose of cholesterol is to act as a sort of temperature buffer (regulating fluidity) in the phospholipid bi-layers of animal cell membranes; so it makes sense that plant products would not contain cholesterol. thank you for the responses and helping me put this debate to rest. Sorry Roberto / Charissa —Preceding unsigned comment added by 161.165.196.84 (talk) 05:30, 25 April 2011 (UTC)

I always thought the main purpose of cholesterol was to serve as a reservoir of raw material for the manufacture of steroids. Hadn't heard of the temperature thing; sounds interesting though. --Trovatore (talk) 05:41, 25 April 2011 (UTC)

Plants have no substantial reservoirs of cholesterol, but do produce lots of steroids, see Phytosterol. I'm pretty sure that the steroids, being terpenes, can all be synthesized from first principles without going through cholesterol directly. --Jayron32 05:56, 25 April 2011 (UTC)

See also Lanosterol, which IS the starting material for steroids. I think cholesterol, being a steroid, is actually synthesized from Lanosterol like the rest of them. --Jayron32 05:58, 25 April 2011 (UTC)

As per Cholesterol#Dietary sources, fat intake, particularly of saturated fat and trans fat, actually plays a larger role in blood cholesterol than consumption of cholesterol itself. Saturated fat is mainly found in animal fats, but there are also a few plant foods containing large amounts of saturated fat, in particular palm oil and its relatives. However, palm oil might not be as bad for you as animal sources of saturated fat; see Palm oil#Comparison with animal saturated fat. Animal fats used to be the only source of dietary trans fats, but they are now also in partially hydrogenated vegetable oils. (Regular liquid vegetable oil hasn't been hydrogenated.) Red Act (talk) 06:13, 25 April 2011 (UTC)

You are aware that hydrogenating removes a double bond? That is you saturate the fat. 95.112.225.249 (talk) 09:07, 25 April 2011 (UTC)

Not if it has more than one double bond, hence partially hydrogenated. --Jayron32 12:59, 25 April 2011 (UTC)

blood type

If the mother is type B and the father is Type AB is it possible to have a type A baby? If both parents are type B is it possible to have a type A baby? — Preceding unsigned comment added by Everlalin (talk • contribs) 09:51, 25 April 2011 (UTC)

Yes for the first question, no for the second. See ABO blood group system. As with everything that has to do with biology, there might be very rare exceptions to the rules. Type B has either double genes for B or one for B, one for O. AB always has both A and B genes. Type A has either double A or A and O. So if the mother has genes B and O and the father A and B there is a 1 in 4 chance that the child will have A and O genes and as the O genes don't express anything that is measured by the tests the resulting blood type will be A. If both parents lack the A gene it is impossible for the child to have one. 95.112.225.249 (talk) 10:24, 25 April 2011 (UTC)

Before anyone makes any conclusions such as diagnosing a "nonpaternity event," he should also note that occasionally the blood type for an individual is reported incorrectly. In a case where both parents are reported to be or or thought to be type B, one might be in fact something else. Even if someone with incorrectly reported blood type received a transfusion in an operation, there are variations in which it would not have caused a serious reaction (like 60% of the time, on average), so the incorrect report would not have been caught (for other mismatches there would be fatal results). Edison (talk) 18:53, 25 April 2011 (UTC)

Some other weird aberrations include the Bombay phenotype and random deletions.^[1] Though admittedly it is far-fetched, though not quite impossible, to picture a way to witch an A out of a BxB mating. I think genetic mosaicism is the most likely example. I remember a news story about a woman genetically "proven" not to have given birth to her baby, and taken into custody, but I can't find the link now. Wnt (talk) 00:29, 27 April 2011 (UTC)

Does Diet Coke cause cancer?

People have told me not to drink Diet Coke or any diet sodas because they contain aspartame which causes cancer, is there any truth to this? --112.213.139.29 (talk) 10:47, 25 April 2011 (UTC)

We have an article about aspartame, where you can read all about this ingredient, and follow further to the Aspartame controversy article about health concerns. Both of these appear to be well-referenced from many reliable sources (rather than just "I heard...") to explain the concerns and currently available research and conclusions. Also, there are diet sodas that use other artificial sweeteners instead, so you can easily avoid this ingredient rather than the broader category of products that might contain it. DMacks (talk) 10:50, 25 April 2011 (UTC)

Pretty much everything you can imagine has been reported to cause cancer in one study or another. There is no way you can avoid them all. See Carcinogen for some details. --Tango (talk) 11:02, 25 April 2011 (UTC)

You may be interested in the Daily Mail Oncological Ontology Project.--Shantavira|^{feed me} 11:31, 25 April 2011 (UTC)

But some chemicals have stronger correlations than others, obviously. (Or put more precisely, all cancer-causing agents are probabilistic — some increase your risk factor more than others.) That's what the OP is most likely concerned about. There are quite a lot of studies on aspartame in particular, which are discussed in the article. --Mr.98 (talk) 11:35, 25 April 2011 (UTC)

I think that when looking into chemical controversies, the first thing to put into context is the patent expiration date. In the case of aspartame that was December 14, 1992, at which time the price fell from $70 per pound to $20-$35 per pound.^[2] When the same or other companies have new patented products to compete on the market, such a cheap competitor is clearly a major problem.

Now by comparison to other chemicals, the situation with aspartame was adjudicated with great integrity. By contrast, the FDA had just made up a new power to ban the herb stevia in 1991, requiring congressional action (DSHEA) four years afterward.

Also consider Accutane, which upon its patent expiration in 2002 was found to be so teratogenic that special restrictions had to be placed on it. Then the FDA, finding that the original manufacturer had abused its first program, decreed that once generics would become available, it was necessary to impose iPLEDGE, a program so draconian and lunatic that, for example, men had to promise not to become pregnant.

For a similar example, consider Oxycontin, which in slow-release form was patented as a "less addictive opiate". This turned out to be bogus advertising, and the manufacturer was hit up with an unprecedented $600 million fine (for its $1.2 billion annual profit on the drug). After that they introduced a new "safer" form and have ten more years on that patent.

I don't think it is unreasonable to conclude that proving a compound unsafe at the end of its patent term is as important to the pharmaceutical company as proving it safe when it is introduced. (And often not so difficult for those who know all the little details glossed over in the original studies) Wnt (talk) 19:52, 25 April 2011 (UTC)

Laser pump design

In electrically pumped TEA lasers, what consideration is given to the efficient matching of the source and load impedances? I mean, do designers of this type of laser ever think about efficiently matching, or is this not possible? What is the effictive load impedance of the discharge etc? Also, why do the designs waste half of the energy by shorting out one of the capacitor plates with a spark gap and therby losing half the stored energy? This seems most inefficient.--79.66.81.54 (talk) 10:56, 25 April 2011 (UTC)

If you're referring to the circuit designs linked from Professor Csele's webpage above, that was a "homemade TEA laser," (albeit, made by a professional laser physicist). An industrially designed LASER from one of the major vendors will probably have a team of power electronics engineers specifically dedicated to optimizing the power supply. A major problem in lasers, particularly of the sort you've been investigating, is thermal loss in the gain medium due to poor quantum efficiency; the power supply should be tuned to deliver a pulse duration and intensity that is suitable for the statistics of the gain medium. The chemical and physical properties of the gain medium will determine its electrical impedance, and cannot be easily summarized, even as a complex impedance. See active laser medium for details. It's not unlike asking for the impedance of a transistor or a vacuum tube; the device is active and has multiple ports, so the system as a whole requires a more elaborate treatment. Other common power supply efficiency can be analyzed as well, such as power factor correction, albeit that the load impedance is very very very nonlinear/non-uniform/non-ideal. In an ordinary experimental setup, it's up to the physicist to determine if that thermal energy loss interferes with his/her measurement, or affects his electric bill in any meaningful way. Nimur (talk) 14:31, 25 April 2011 (UTC)

Can a dish washer dissolve rubber compeletely?

I had a rubber band for home canning the like of which you can see here in my dish washer and can't find the least trace of it now, not even tiny bits spread around in an ugly way and sticking to everything else, as sometimes happens with other things. Is it possible that it has been completely dissolved? 95.112.225.249 (talk) 14:33, 25 April 2011 (UTC)

It's unlikely that the temperatures of the dishwasher could melt the rubber; nor that any chemical in the detergents would dissolve rubber completely. However, the combination of heat and detergent sounds like a great scenario to denature the rubber - it probably loses its elasticity, becomes crumbly, and the pieces easily flow down the drain. We have discussion of the chemistry behind natural rubber elasticity at our article. Nimur (talk) 14:38, 25 April 2011 (UTC)

I am astonished. So you could make a kind of fridge that uses rubber instead of a gas? My late rubber band would be originally designed to withstand boiling temperatures whereas the dish washer nominally gets only up to 70C°. 95.112.225.249 (talk) 14:49, 25 April 2011 (UTC)

It's true that rubber has interesting thermoelastic properties, and the thermodynamics of elasticity has been heavily studied by physicists and material scientists. I don't think you could make a practical refrigerator out of it; we have several articles related to refrigerator thermodynamics, start with heat pump and refrigeration cycle for an overview. Numerous lab demos exist to show the effect of temperature on elasticity; it's harder (but not impossible) to show the effect of elastic expansion on temperature. Nimur (talk) 16:27, 25 April 2011 (UTC)

From the section natural rubber elasticity you gave I can see that you can "wring out" the heat energy from rubber by stretching it like water from a sponge. This is what normally happens in the condenser step of the refrigerator cycle. So I imagine it is easy to put up a cycle where rubber is stretched and, loosing degrees of freedom, gains temperature and looses heat energy by exchange with the environment. When relaxed again, it gains degrees of freedom, the heat capacity goes up and it takes heat energy from the environment. I cannot believe I'm the first one to think of it. Either there is some flaw in my reasoning or there must be some rubber-fridge already. 95.112.225.249 (talk) 22:10, 25 April 2011 (UTC)

You may be interested in thermoplastic. Also, some descriptions of kevlar attribute the armor's "bullet-stopping" capability to the thermal properties of the fibers. While it is possible to transform bulk kinetic energy into thermal energy, and therefore transfer heat, a practical refrigerator needs a medium with a high heat capacity; the quantity of thermal energy you can transfer using only elastic deformation of a polymer is very small, compared to a conventional refrigerant. Nimur (talk) 22:57, 25 April 2011 (UTC)

Do you have any figures at hand? (I admit I'm too tired and lazy right now to search for myself9. The key figures would be the heat capacity of the rubber when stretched compared to when relaxed. I don't see how any melting points or glass temperatures would come in. 95.112.225.249 (talk) 23:11, 25 April 2011 (UTC)

No, I don't have any hard numbers; but if you don't have the physical intuition to see why a rubber band stores very little heat as it expands, compared to a refrigerant, what makes you think you've got the physical intuition to interpret a numeric measure of heat capacity? At the end of the day, the universe does what it should, irrespective of any equation we wrote to model it numerically. Nimur (talk) 03:23, 26 April 2011 (UTC)

Nimur's words with Voltaire's Pangloss express the Leibnizian optimism of Pangloss about the Universe. The OP may inspect the door seal on their dishwasher that I wager is made of Neoprene, a synthetic rubber that hopefully has not perished as unvulcanized caoutchouc is prone to do. Cuddlyable3 (talk) 08:54, 26 April 2011 (UTC)

Pharmacology - Dose Effect Curves

A standard pharmacology experiment is to place a piece of smooth muscle into an organ bath, that contains a concentration of drug and to measure the contraction / relaxation of the drug.

Can then plot a dose effect curve for the results at different concentrations and use this to work out the maximum response that a drug can produce and the EC50 value.

My question is... Since the concentration of the drug in the organ bath is completely different from the concentration of drug at the receptors, what is the point of this experiment? Is not the drug concentration at which a 50% maximal response obtained then completely arbitrary? Or can the results of this experiment only be used to compare other drugs in exact some situations?

Hope that makes sense!

Thanks :) — Preceding unsigned comment added by 138.38.187.77 (talk • contribs)

Trees and/or plants affected by white-tailed deer and invasive species in Maryland

I'm looking to research a plant or tree whose future is potentially compromised by both overgrazing of the white-tailed deer population and the presence of invasive species, specifically in the state of Maryland. Any suggestions, links or reading recommendations would be greatly appreciated. — Preceding unsigned comment added by Marie Poling 03 (talk • contribs) 19:05, 25 April 2011 (UTC)

Have you tried using Google Scholar to start your research? --Jayron32 19:08, 25 April 2011 (UTC)

Also try the invasive species listing for Maryland. ~AH1 ^(discuss!) 21:16, 25 April 2011 (UTC)

motional electric field

http://www.rexresearch.com/hooper/horizon.htm#intro 'During World War II the writer, working on an invention for a "drift and ground speed meter for aircraft", arrived at a plan for utilizing the vertical component of the earth's magnetic field. If the voltage induced between the ends of two oriented linear conductors traveling horizontally across the vertical component could be measured within an aircraft, a self-contained meter, independent of ground instrumentalities, would be forthcoming. The plan was reviewed by the U.S. Bureau of Standards, and its workability confirmed under a certain restriction. It was stated that the device would be inoperable within a conducting cavity such as a metal-clad aircraft. Our textbbooks have taught us that when a linear conductor moves with a velocity V across a magnetic flux of intensity B, an electric field of vector intensity VxB is induced within the wire and gives rise to a voltage at its terminals. This electromagnetically induced electric field, often called a motional electric field, we have been taught, would be electrostatic in character, that is, identical and indistinguishable from an electric field arising from charges of electricity. We know that radio tubes, silvered on the inside, shield the interior from stray electrostatic fields. In the same way, it was explained, such a drift and ground speed meter within a metal-clad aircraft would be shielded from the electric field induced in a conductor by motion across the vertical component of the earth's magnetic field. This explanation was a jolt to the writer. How could we know, without experimental evidence, that such would be the case? This presented a great challenge! Some of the foremost thinkers in physics were consulted. It was discovered that there was no experimental evidence to support the popular belief held by physicists that the motionally induced V x B field was electrostatic in its fundamental character and therefore subject to shielding. It will be shown how, step by step, the writer has been guided over a period of 20 years to experimental means which at last reveal experimentally, beyond all doubt, the beautiful unique properties of the motional electric field. It is not electrostatic! Its immunity to shielding, magnetic or electrostatic, is the exciting property which it shares with the gravitational field and thereby indicates their kinship. By a general theorem in electric field theory we know that a non-uniform B x V field must also act attractively on matter! Thus the motional electric field has acquired a status which makes it quite unique.'

What are your thoughts on the article how the electric field should be shielded? and the fact that we do not know that the the motionally induced V X B field was electrostatic in its nature and the fact that the non uniform B x V field must attractively on matter is this true from the article? How has not modern traditional science not seen this? — Preceding unsigned comment added by Lufc88 (talk • contribs) 20:38, 25 April 2011 (UTC)

Bluntly, you've stumbled on the self-published work of a crank who thinks he's discovered some sort of new fundamental theory of electromagnetism, and wants to use it to build gravity-cancelling devices. TenOfAllTrades(talk) 22:02, 25 April 2011 (UTC)

The Earth's magnetic field indeed penetrates an aluminium-clad aircraft but you will find it does not penetrate a thick iron-walled sphere. I don't know why you wish to shield an electric field but a Faraday cage is a means. The linked article notes that Faraday cages cannot block static and slowly varying magnetic fields, such as Earth's magnetic field (a compass will still work inside), and they are only partially effective in blocking electromagnetic radiation. I apologise that the OP's initial link was TLDR for me and I still need convincing that a "non-uniform B x V field must [act?] attractively on matter". Does that cause radio transmitter antennas to collect dust? Cuddlyable3 (talk) 08:37, 26 April 2011 (UTC)

The linked article really isn't worth reading all of. I only read a bit of it myself, but in what I did read, the author was racking up points on crackpot index items 11, 17, and 18, at least, which just isn't a good sign. Red Act (talk) 13:07, 26 April 2011 (UTC)

oh right any one else got any thoughts on this Lufc88 (talk) 16:13, 26 April 2011 (UTC) Lufc 88

NNRTIs and Hep B

Are any NNRTIs used to treat Hepatitis B infection? The drugs used to prevent Hep B replication only appear to be of the NRTI class. I've had a look on each NNRTI page but they all seem to be used to treat HIV. Trying to search for it on Google only seems to bring up a side-effect of NNRTI usage as hepatitis... So even judging from that, it does seem unlikely they would be used but maybe someone knows better than I do. Thanks! 86.185.188.62 (talk) 21:13, 25 April 2011 (UTC)

I never bothered to learn about HBV, so I started with Hepatitis B and Hepatitis B virus. The latter article describes only four genes, of which three don't sound like they have known enzymatic activity. So I focused on Hepatitis B virus DNA polymerase. Specifically, I typed into Google "Hepatitis B virus DNA polymerase inhibitor". Unfortunately, no direct hits. The non-quoted phrase hits cover all sorts of nucleotide inhibitors - I looked at one page of hits. Among these I ran across description of IFN alfa-2b as a treatment, but not curative.^[3] That isn't what I'd call NNRTI though. So I tried the phrase without quotes and added quoted term "non-nucleoside". This gave some 34 hits, including [4]: this includes foscarnet as a "non-nucleotide inhibitor", but it's a product analogue (pyrophosphate). In my mind that doesn't count either. To quote (Google serves up pages from this $439.95 book, written 2007):

"As described above, nucleoside analogues can inhibit cellular as well as viral enzymes, and viruses can mutate to resist to these drugs. As a result, efforts have been made to discover compounds that might inhibit viral polymerases by other mechanisms. The first of these to be approved for clinical use was foscarnet (phosphonoformic acid [PFA]), whose structure is shown in Figure 14.6. Although it is not orally available and intravenous administration is required, it is nephrotoxic; it is approved for treatment of severe HSV, VZV, and HCMV infections that are resistant to front-line drugs.

Foscarnet is an analogue of pyrophosphate, which is a product of polymerization of nucleic acids. Unlike the nucleoside analogues described above, it does not require activation by either cell or viral enzymes but rather inhibits Pol directly. Inhibition is not competitive with deoxynucleoside triphosphates. Rather, it appears that foscarnet acts as a product analogue, evidently by binding to the site normally occupied by pyrophosphate and preventing normal pyrophosphate release so the polymerase cannot complete the catalytic cycle (97,248). Selectivity arises from the viral Pol being more sensitive than cellular enzymes, which is confirmed by the existence of foscarnet-resistant pol mutants (82,96,114). Resistance is caused by an altered polymerase that is less susceptible to foscarnet inhibition.

Because foscarnet is not a nucleoside analogue HSV tk mutants and HCMV UL97 mutants are not resistant to it. Although foscarnet inhibits DNA polymerase by a mechanism that differs substantially from the nucleoside analogs, many pol mutants that are resistant to nucleoside analogs are resistant to foscarnet. Moreover, most foscarnet-resistant mutants are resistant to one or more nucleoside analogs (116). Thus, for some patients with serious herpesvirus infections, no viable treatment options are available. This should be an impetus to further drug development."^[5]

Now searching "foscarnet hepatitis B" on PubMed,^[6] I don't find any recent papers mentioning it, which I would think would happen if someone were testing a new non-nucleoside inhibitor for the viral polymerase. But I haven't searched those other funny proteins with other functions yet. At the most fundamental level, HBV doesn't look like it has a protease, so it doesn't have HIV protease inhibitor like drugs as an option. I hope that by tracing my steps here, I've shown those interested how to continue researching these things over time as drug development progresses. Wnt (talk) 23:35, 25 April 2011 (UTC)

Hmmm, taking another look, it seems like HBx now has a known function as a transcriptional activator (It's not a transcription factor that binds DNA directly^[7] - it just changes the effect of something like E2F).^[8] It sounds like it makes the liver cell more vulnerable to apoptosis from other causes (such as transient ischemia).^[9] But according to PMID 21468663 the bastard little protein actually protects expressing cells from death by etoposide, reducing the effectiveness of this as an anti-cancer treatment. (But not cisplatin) And if that's not enough, it interferes with DNA repair.^{[ PMID 21375739]} According to PMID 21490166, it predisposes the liver to hepatocellular carcinoma more when a particular mutation, HBx5, is present. It is actually essential to the HBV life cycle.^{PMID 21376091}

Now transcriptional factor activity is conceptually a sort of vast neural network of cellular decision-making, and there are many ways to try to counteract an effect. One I found in the search was PMID 19172229 (2010), concerning a Phase II clinical trial to test PXD101 (belinostat), a histone deacetylase inhibitor, in inoperable hepatitis B hepatocellular carcinoma. As you can see this has been a really quick and dirty search; hopefully there is more I missed, and more on the way. Wnt (talk) 00:02, 26 April 2011 (UTC)

(response to OP, further indented to avoid confusion with post above) For NRTIs (which are nucleoside/nucleotide RT substrate analogs), there are shared binding determinants because both HIV RT and HBV Pol have reverse transcriptase activity, resulting in substantial active site homology. NNRTIs bind at sites removed from the active site; therefore, there's little reason to expect that NNRTIs developed for HIV would be active against HBV - here is an example: PMID 10377169. With over a billion people infected with HBV, and many of those infected with both HIV and HBV, you can be assured that the pharma companies are looking for such activity for two reasons: (i) market, and (ii) safety issues of inadvertent HBV treatment when treating HIV - due to issues of resistance and HBV flares when HIV treatment is stopped PMID 18447614. -- Scray (talk) 00:40, 26 April 2011 (UTC)

the kinetics of 3H + 2H ---> 4He + n

How do I calculate the final kinetic energies of each particle, if Q is 17.7 MeV and final momentum is zero? This apparently should be a really really easy two-body problem, but all the google guides on collisions out there assume your masses don't change mass and release energy. John Riemann Soong (talk) 22:22, 25 April 2011 (UTC)

The equations are simple: E₁+E₂=E₃+E₄ with E_i= (c₀²+1/2 v_i²)m_i and v₁m₁ + v₂m₂=0. When I said the equations are simple I didn't mean to say it is easy to resolve them, not at my given local time of day. But I don't see any higher maths involved either.95.112.225.249 (talk) 22:51, 25 April 2011 (UTC)

The solution given above assumes non-relativistic speeds which may or may not be the case. If that's indeed the case, than the solution is really trivial. use the second equation to express one of the final velocities in terms of the other and substitute it on the first equation, which will then have only one unknown and will be easy to solve. Dauto (talk) 23:20, 25 April 2011 (UTC)

I'm afraid that with neutrons of that energy we are on the brink of leaving the range of Newtonian mechanics. Neutron temperature#Fast neutrons. 93.132.131.100 (talk) 23:41, 25 April 2011 (UTC)

Nah... The neutron mass is about 50 times larger than that energy. Newtonian mechanics should still give a reasonable approximation. Dauto (talk) 04:33, 26 April 2011 (UTC)