Wikipedia:Reference desk/Archives/Science/2016 July 31

= July 31 =

Origin of Russian Anthrax
I was reading a recent news story and was wondering whether the anthrax was "natural" in origin, like similar outbreaks in the US and the UK(see Anthrax), or whether it's another leak of bio-weapson like the Sverdlovsk anthrax leak. The news story doesn't specify. Crudiv1 (talk) 00:20, 31 July 2016 (UTC)
 * It specified. "The concern among experts is that global warming thawed a diseased animal carcass at least 75 years old, buried in the melting permafrost, so unleashing the disease." --Tagishsimon (talk) 00:29, 31 July 2016 (UTC)
 * Yes, I read that, but it doesn't rule out the bio-weapons case since the animal could have contracted the disease from an unintentional lab leak or it could have been infected intentionally as test case like in on Gruinard Island.Crudiv1 (talk) 03:27, 31 July 2016 (UTC)


 * here is another article. Bear in mind that the Yamal Peninsula is ground zero for global warming - last winter it was the spot that was 11.5 C warmer than normal (see ) and since then, as the news link mentions, they've had a summer heat wave with 95 degree Fahrenheit temperatures as opposed to a normal high of 77.  The Arctic is warming faster than anywhere else, and Yamal is warming much more than some other parts of the Arctic.  The other thing not mentioned in the first link is that there were 1500 live reindeer infected with anthrax, providing a plausible intermediate step to the humans.  Because the cases were not "confirmed", I'll go out on a limb and guess they're gastrointestinal cases from eating infected meat rather than inhalation cases that would trip my paranoia. Wnt (talk) 10:27, 31 July 2016 (UTC)

FTIR machines
I've finally found an FTIR machine which is inexpensive enough (and small enough) for me to buy, but I was surprised to see a disclaimer on the product page saying that "The sale of this item may be subject to regulation by the FDA..." and so on. Is that true? Are sales of FTIR machines really regulated by the FDA, or did they just put this out to be on the safe side? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 03:12, 31 July 2016 (UTC)


 * In the section on the use of these, there is a phrase "examining the homogeneity of pharmaceutical tablets" - I suspect something like that would come under the authority of the FDA.You can also get more information by putting FTIR into the search box on the FDA home page - quite a lot of things come up, which I don't have time to read through. Wymspen (talk) 11:46, 31 July 2016 (UTC)


 * From the official FDA website, "What does FDA regulate? Sale of a device may be regulated by FDA if the seller claims the device is for medical or diagnostic use - and that could be one application of some FTIR machines.  (Along the same lines: if you're selling popsicle sticks in an art-and-craft store, you probably won't draw much FDA regulatory attention - but if you sell popsicle sticks for use as a tongue depressor... then you are in clear territory where FDA can and will regulate your sale, even if other applications of ostensibly the same product would fall outside their jurisdiction).
 * FDA may also regulate a device if it emits electromagnetic radiation - and many FTIR machines make use of a laser, so that could count.
 * There are many other reasons why FDA or other regulators might have authority to oversee such a product, too. If you aren't sure, and the answer actually matters, you ought to contact an attorney.  You can also talk to the vendor - if they are reputable.  They can help provide guidance to keep both the seller and the purchaser in clear compliance with all the rules.  Nimur (talk) 15:51, 31 July 2016 (UTC)


 * Thanks -- I've asked at the FDA site itself and they will answer by Tuesday. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 04:02, 1 August 2016 (UTC)

Blood group
Hi all,

I've had several blood tests and it always showed I'm O+. Yesterday I went to donate blood and they made a quick check by taking a drop of blood from my finger tip. That's the time the nurse told me I was A. How come they can make such a mistake? She checked twice and she couldn't believe me when I said I was O+. Btw the blood tests were made by home in France and also in Dubai, the blood donation was made is a poor hospital in the Philippines. That might explain things but still, I don't get how they can make such a mistake that could kill someone! 203.111.224.94 (talk) —Preceding undated comment added 03:29, 31 July 2016 (UTC)

Blood group
Hi all,

I went to donate blood in a poor hospital in the Philippines. Before that, they took a drop of blood to check my blood group. The lady told me I was A. I am actually O+ (I checked it several times back home in France and also in Dubai for my previous company). The nurse wouldn't believe me. I was just wondering how they cannot find out what is the real blood group? Does this mistake often happens? 122.53.58.54 (talk) 06:26, 31 July 2016 (UTC)
 * It is difficult to answer this question without seeing actual papers. Ruslik_ Zero 07:46, 31 July 2016 (UTC)
 * We can't diagnose anybody, but I should point out in general that the ABO blood group system is not as simple as in a biology textbook. There are weak A alleles that straddle the boundary with O - see the article for the reference.  I would not be surprised if borderline cases are treated differently when donating vs. receiving blood as a matter of safety.  Wnt (talk) 10:31, 31 July 2016 (UTC)


 * If, as a donor, you are O, but get classified as B, that won't threaten the life of anyone. I'd rather worry about the other way round. That is, you could be O, but get classified as B.Hofhof (talk) 12:22, 31 July 2016 (UTC)


 * Note that per Hofhof and Wnt's points, even if there was some mistake (which is uncertain), for the nurse to refuse to accept that you were O would be correct if the tests say you are B (for example). The concerning thing would be if you are B (for example) but she diagnoses you as O and refuses to accept you are B. In that case it's likely she should either need to accept you are B or since there's some doubt over the test maybe tell you thanks but no thanks.Nil Einne (talk) 14:17, 31 July 2016 (UTC)


 * I believe the comment "Actually, it's not that simple" applies here also, but I am no expert. I suggest that the original poster should consult a doctor who can diagnose whether they have a rare blood type (as Wnt hints at), and that we should close this thread. --69.159.9.219 (talk) 21:22, 31 July 2016 (UTC)


 * Having a weak A isn't a disease; it's just one of the many phenomena that can confuse people overseeing blood donation.  and  are typical references to it.  What's interesting about it is that a person with weak A activity can have weak anti-A agglutination activity, even as their antigens can provoke anti-A agglutination activity in others.  There's a certain natural level of anti-self antibody activity throughout anyone's body, but my gut feeling is that the product of the activities here is too high for it to be that simple.  I would guess that there is some statistical property of the sugars - maybe if they are uncommon enough, you never see two within range of one antibody or something, and that's what the weak A's can form protective antibodies against - but I don't know. Wnt (talk) 12:41, 1 August 2016 (UTC)
 * Also note that if the OP had this blood type, (s)he is already taking the appropriate precaution by believing (s)he is type O. There are no bags of "weak A" blood waiting at the hospital, and type O will work even on someone with strong A.  What the blood bank does with any donated blood is their problem; they certainly cannot take the donors at their word for what blood type they are anyway, so it is of little if any use to tell them.  Had there been repeated tests of an A blood type from past blood donations and then one came back as type O right before the OP would be receiving blood in an emergency, this obviously would be a scarier situation, since one lab tech might have missed the weak agglutination.  But it's too late for history to go that way now ... it just should remind us that transfusing blood is no joke, and the people doing it had better be paying attention. Wnt (talk) 12:54, 1 August 2016 (UTC)
 * Which is why I suggested that expert information would be useful. --69.159.9.219 (talk) 16:51, 1 August 2016 (UTC)
 * I can't speak for why the OP would be told conflicting information about their blood type (my best guess would nursing operator error) but they should rest assured the mistake would likely not kill anyone. Transfusion is not done with just matching the ABO status, and blood is typically cross-matched before it is transfused. Cannolis (talk) 00:21, 2 August 2016 (UTC)


 * Could a chimera test differently at different times ? StuRat (talk) 20:36, 2 August 2016 (UTC)
 * Nothing is impossible in biology, but it's hard to imagine how a chimera would have one genotype of hematopoietic stem cells active at one time and then have a different genotype active at another. This is definitely in a category of things I'd have to see to believe. Wnt (talk) 23:35, 2 August 2016 (UTC)


 * Per our Chimera (genetics) article, it's usually the case that any particular cell-line is almost entirely one of the two rather than being a mix. But also per our article, there are human cases where the blood was a mixture of two types. But blood-type testing is usually by serology, not just carefully checking one or two cells, and blood moves around and mixes a lot in the body. I don't think it's likely that different macroscopic blood samples from a person would be likely to give different type-test results. DMacks (talk) 02:50, 3 August 2016 (UTC)
 * But see John Schneeberger for an interesting forensic case. DMacks (talk) 19:50, 3 August 2016 (UTC)


 * Well, a rubber tube of someone else's blood scarcely counts as a chimera in my opinion. There actually are some scenarios I can think of for changing blood type... they're probably about as likely as the chance that there's an undiscovered population of wild horses with a single long horn centered on their foreheads somewhere in the wilds of Europe.  Which is to say, not impossible but not very likely.
 * For example: suppose a parent with one or two B alleles experiences a transposition event that leaves a new transposon sitting on the DNA next to one of those alleles in their developing gonad.  Well, the body has a sort of antispam mechanism called heterochromatin that might wrap up the region and keep it from being transcribed, turning that B allele into effectively an O allele.  Sometimes this process is less than 100% reliable, leading to variegation.  So suppose one of the alleles that is particularly affected by gene silencing gets passed on to a child.  Well, almost surely there are some random events to reveal at least a low level of activity before the child develops an immune system and it's all for nothing, but just suppose there is some extra stimulus required, a certain transcription factor only in adults, an environmental chemical that activates some site or gene near the heterochromatin, too much fatty food or environmental toxins strip some of the histone markings, or the child grows up and catches a retrovirus that interacts with the transposon and opens up the DNA around it.  Well, then the B gene gets active and the now-adult person's immune system probably destroy the affected cells and no one is any the wiser.  But maybe the process starts so slow, in a broad population of cells, that it slowly induces immunological tolerance, like someone with peanut allergies very gradually and cautiously working himself up to surviving a stray nut.  In that case, conceivably, the B antigen gradually becomes more and more detectable in the blood, and the anti-B antiserum gradually gets weaker and weaker, until the person gets to the point that you can say he was born O and now he's a B.  Now to be sure, I don't expect to see this, but ... it's biology.  Expect the unexpected! Wnt (talk) 22:59, 3 August 2016 (UTC)

Deriving the subjective arrow of time from entropy
I've been reading through the arrow of time articles, and I've run into a conceptual problem that I didn't see an answer for. I understand the principle that the physical arrow of time, at least above the scale of quantum mechanics and below the scale of cosmology, seems to be entirely a matter of the steady increase in entropy over time. I don't see an explanation of how that would determine the subjective/psychological arrow of time. Why does the steady rise in entropy, which should be a pretty smooth process with little distinction between the near past and near future, produce a subjective experience of time in which there is a perfectly hard line between the past and the future? Specifically, what series of steps would get you from entropy as a physical principle, to a brain in which memories are only formed of events from the entropic past? I came up with a possible solution, and I would like to get feedback on whether it makes sense, or if there is some other obvious explanation that I missed. Taking an action potential in a neuron as the fundamental step of information processing in the nervous system, it seems like it could be viewed as a mechanism for converting entropy into time-irreversible computation. Ignoring the complicated processes for amplifying and propagating an action potential, it is kicked off when channels across a membrane between an area of high sodium concentration and an area of low sodium concentration are opened, allowing the passive diffusion of sodium down the concentration gradient. When enough sodium ions have crossed that the charge passes a threshold, that kicks off the rest of the action potential. So in a world where entropy in fluids of a sufficient volume reliably increases, kicking off an action potential is reliably time-irreversible. In the case of sensory neurons, this allows the transformation of external events that are mostly time-reversible, such as the deformation of a surface or the absorption of a photon, into time-irreversible internal neural events. For instance, in the case of a mechanoreceptor, deforming and then straightening a membrane is time-reversible, ignoring the small amount of heat created. But deforming a membrane which has holes in it that allow segregated fluids to mix, and then straightening it, is time-irreversible, and can kick off a series of events that flow in only one direction in time. As a result of that, regardless of what goes on outside the body, our brains and subjective experiences can only contain information about sensory events that occurred in the strict entropic past, up to the time resolution of a small diffusion event. In terms of the purpose of this process, maybe it protects us from the random noise of events occuring and then de-occuring on small time scales. Black Carrot (talk) 04:29, 31 July 2016 (UTC)
 * This causal description of irreversible psycho/neurological events is eerily coherent with the Buddhist doctrine of causality: everything we perceive is a result of "dependent origination" that is irreversible, but to the devotee could be rendered void by enlightenment about the fundamental emptiness in all phenomena and experiences. AllBestFaith (talk) 14:45, 31 July 2016 (UTC)
 * I'm more looking for a scientific explanation for the phenomenon. Black Carrot (talk) 16:35, 31 July 2016 (UTC)
 * I believe Tenzin Gyatso the spiritual head of Tibetan Buddhism, who seeks common ground between science and Buddhism, has expressed that "If science should demonstrate that Buddhism is in error about something then Buddhism must change." AllBestFaith (talk) 17:04, 31 July 2016 (UTC)
 * This has to do with the link between entropy and information. To describe a generic past state requires less information than a generic future state. This means that when some (in principle) reversible dynamics of a physical systems works as an information processing device, then in the forward time direction (as defined by the entropy increase) there is no problem, but in the opposite direction, you need to invoke conspirational initial conditions to explain the output. Count Iblis (talk) 18:09, 31 July 2016 (UTC)
 * I sort of get how that works, but it seems hand-waving to me. I'm comfortable with that level of detail in describing simple systems like ideal gasses, because I see how someone could have gone through the math to verify it, but I'm not confident that the same type of justification is available in a more complicated case like this. How can we verify that the sort of information processing the brain is doing is the kind of thing that that rule would apply to, and how can we verify that the scale of the system and the amount of entropy involved are appropriate to draw that conclusion? Linked from the arrow of time articles are examples of small (micron-scale) systems that experimentally aren't well-behaved on short time scales, so it does make a difference. Black Carrot (talk) 20:31, 31 July 2016 (UTC)
 * The firing of even a single neuron seems more irreversible than a bump of Brownian motion. Sagittarian Milky Way (talk) 06:34, 1 August 2016 (UTC)
 * I guess? I'm not sure what you mean. Black Carrot (talk) 03:32, 2 August 2016 (UTC)