Wikipedia:Reference desk/Archives/Science/2016 September 8

= September 8 =

additional info on automotive MIL or "check engine light"
After reading the wiki page for Malfunction indicator lamp and doing a google search I was unable to find the information that I'm looking for. (hence why I'm here). When a vehicle has the check engine light on, regardless of the problem causing the MIL lamp, the vehicle gets worse gas mileage and/or power to the wheels. Why is this? The only thing I could surmise is that since the computer has detected a problem the vehicle will run on default variables to prevent further strain on the vehicle and/or for safety. However I am unable to find any additional info on this matter. 199.19.248.107 (talk) 00:04, 8 September 2016 (UTC)
 * One of the most common reason the "check engine light" activates (other than a loose fuel cap) is a failure in the oxygen sensor system (either a malfunctioning sensor or an electrical short/loose wire). See Oxygen sensor for details. In short, the sensor(s) provide(s) feedback on the condition of exhaust gases and the computer makes necessary compensatory changes to other systems, such as fuel injection, based on that feedback. If an O2 sensor (or any or the myriad other sensors the computer monitors) isn't working properly, the computer will be making those adjustments based on faulty information which negatively affects gas mileage and engine performance. Note: depending on the make and model of the vehicle, there can be many other reasons for the "check engine light" and if gas mileage is affected, it will be for similar reasons. Take your vehicle to a professional to diagnose it or, if you are good with tools, you can use a handheld scanner (OBD-II PIDs to diagnose it yourself.--William Thweatt TalkContribs 00:29, 8 September 2016 (UTC)


 * Older vehicles (before OBD II) which have a disgnostic connector sometimes are easy to read out. Sometimes with LED and pre-resistor and counting the long and short flashes. Some other vehicles, do a special Operation while turning the key, but do not start. The MIL will also appear when other sensors do not work propperly. Sometimes the engine will not run or start caused by this issue. The the oxigen sensor died, the catalytic converter may get damaged and the fuel consumption increases. Also the emissions become worse due missing control, cause not valid sgnal from the oxigen sensor. Newer vehicles have two oxigen sensors installed, before and behind the catalytic converter. Use the OBD II to see which one causes the problem. Oxigen sensors are affected by temperature and weater conditions. Sometimes they can not be removed without destroying it. Just only gently thighten the new one, not the have the problem again. -- Hans Haase (有问题吗) 14:05, 11 September 2016 (UTC)

Elevated levels of amino acids as evidence?
In the just-aired season 1 episode 12 of the murder mystery television series American Gothic, the following dialogue (this is an exact transcript) occurs between a forensic scientist and a police detective regarding a dollhouse that they believe has been touched by an unidentified accomplice to murder:


 * Forensic scientist: "The prints in the dollhouse didn't match anyone in the system, but they did have elevated levels of amino acids."
 * Police detective: "Meaning?"
 * Forensic scientist: "The accomplice is female."

This dialogue confused me. Are the writers of this TV series just making stuff up that has no basis in fact, or are elevated levels of amino acids really evidence indicative of a female? If so, how/why?

—SeekingAnswers (reply) 06:55, 8 September 2016 (UTC)


 * Apparently this is real.   In 2015, a chemist reported that they could distinguish male from female with ~99% accuracy by looking at the amino acid content of the prints.  It seems that women generally have about twice as many amino acids in their sweat.  As a recent discovery, I doubt it has been routinely used in forensics as of yet, and probably deserves further scrutiny to see if it really works as well as he claims.  Dragons flight (talk) 07:06, 8 September 2016 (UTC)


 * Clarification: Flight means "twice the level of amino acids", not "twice as many" (which would refer to how many different amino acids occur). --69.159.61.86 (talk) 14:06, 8 September 2016 (UTC)


 * In my world, "twice as many amino acids" would mean twice the total concentration of amino acids, and has no direct bearing on the variety of amino acids. Of course, your experience might be different.  Dragons flight (talk) 15:04, 8 September 2016 (UTC)


 * Partly blocked by a paywall, but this article suggests that the technique is still in its early days and isn't currently a standard forensic method. Smurrayinchester 08:31, 8 September 2016 (UTC)


 * There may be a factual basis to a report I heard from a factory supervisor at a British company that employed women to construct wartime radio equipment. Fine coil windings showed corrosion if they had been wound by certain women at certain times of the month. It is known that hormonal activity in PMS can cause skin symptoms such as cyclic acne possibly due to overactive Sebaceous glands. AllBestFaith (talk) 14:23, 8 September 2016 (UTC)


 * It seems to me that there is a problem with using the percentage of amino acids, by volume or mass, in sweat, to identify gender. That is, the original total volume or mass of the sweat is unknown, as presumably most of it has evaporated by the time the test is done.  However, if some component that does not evaporate, such as salt, can be measured, that might give an indication of the original total volume, but only if that component is produced in sweat at a relatively constant level.  Somehow I doubt if this is true of salt, as presumably sweat contains more salt when you have a higher blood sodium level.  Is any other component in sweat a suitable gauge, being a constant percentage of sweat and not being volatile ?


 * Also, does this difference between males and females apply before puberty and after menopause ? StuRat (talk) 15:14, 8 September 2016 (UTC)


 * "Increase of salt intake, at least within the limits obtaining in these experiments, has no constant effect on the excretion of chloride in the sweat." That took me two seconds to find the article and two minutes of skimming to get to the important bit.  SemanticMantis (talk) 16:06, 8 September 2016 (UTC)


 * Please stop posting your uninformed guesses on the reference desk, it's not helpful. Actually, it's worse than not helpful, it actively harms our reputation, because your bullshit guesswork appears on almost every question, and it makes our service look shitty. SemanticMantis (talk) 16:06, 8 September 2016 (UTC)


 * As the original asker of the question, I disagree and have unhid your collapsing of StuRat's response. StuRat raised a couple of interesting questions related to the topic and added to the discussion. Administrators'_noticeboard/Archive283 was decided overwhelmingly against sanctions for StuRat. There's no need to attack StuRat for his response or to hide it, particularly here in this case, wherein it is clear that he is asking questions about how certain parts of the technique would work rather than stating something authoritative. If you disagree with some part of an idea he raises, just explain why and move on. What really "looked shitty" above was not StuRat's answer, but your attack on him for raising legitimate questions in good faith.


 * Also, the quote in your response ("increase of salt intake, at least within the limits obtaining in these experiments, has no constant effect on the excretion of chloride in the sweat") does not actually rebut StuRat's point, which was about how to determine what is an "elevated" percentage of amino acid if the original volume or mass of sweat is unknown.


 * —SeekingAnswers (reply) 20:22, 8 September 2016 (UTC)


 * Thanks, SA. Let's avoid this unnecessary drama and remain focused on the actual Q.  This site  says "The amount of sodium in sweat averages about 500 mg sodium/lb sweat (and ranges from 220 to 1,100 mg)."  With that type of range, regardless of the cause, it sounds like a poorly suited gauge for the total amount of sweat.  Can anyone else find a suitable gauge ? StuRat (talk) 21:48, 8 September 2016 (UTC)


 * Feel free to unhide, but that's no personal attack. I can say all day, every day that StuRat rarely if ever posts useful references, and you should probably not not listen to him unless he's talking about Fortran or has cited a reference. It's not a very flattering statement, but it is not a personal attack. Rather, it is a statement about references, and lack thereof. Maybe you are interested in his uninformed critiques of published scientific research that he hasn't even read, but I'm not, I find it extremely distracting from the question you asked. I thought Stu might have learned something from that ANI incident, but apparently it was the wrong lesson. Unless he's providing references and any hint that he's done more than ponder for ten seconds, I can and will state that he's making shit up, whenever I want ;) SemanticMantis (talk) 21:58, 8 September 2016 (UTC)


 * You are stating your opinion that I am "making shit up", and your opinion is neither an answer to the Q nor a specific rebuttal of any claim I made. As such, it doesn't belong here, it belongs on whichever talk page you choose.  Otherwise, we will end up arguing back and forth here, instead of trying to answer the Q.  That's bad form. StuRat (talk) 00:04, 11 September 2016 (UTC)


 * In regard to your question "Can anyone else find a suitable gauge ?": I think this is a total red herring, I think based off of a misunderstanding of the cited science papers. If you'd like to know how and why they think this test is effective at determining the sex of the person via a fingerprint, you should read the research papers. These have been vetted by established scientists in the field, and they do a better job of explaining it than I can. If you can't obtain a copy, I'll happily send you one if you contact me over email. SemanticMantis (talk) 22:58, 8 September 2016 (UTC)


 * The above comments are a huge waste of time, by people who obviously felt entitled to comment without having looked at the actual research. They aren't measuring the sodium content.  They aren't even measuring sweat.  A fingerprint is not a sweat stain.  A fingerprint is a deposit consisting primarily of lipids transferred from the skin due to casual contact.  The researchers are taking the fingerprint, exposing it to dilute acid and resuspending any water-soluble amino acids that happened to have been deposited along with the lipids.  They find that fingerprints left by female volunteers consistently contained much higher concentrations of these amino acids.  In making this finding they only sampled approximately 3 men and 3 women, all Caucasian, with fingerprints deposited under laboratory conditions (though on a variety of surfaces).  They suggest that the observed difference is due to women generally having about twice as high a concentration of amino acids in their sweat (prior research).  However, the observed signal obtained from volunteer fingerprints was actually more than a factor of two larger for women than men.  They also make an argument, based on the statistical characteristics of the gender differences in sweat (again, prior research), that they ought to be able to distinguish gender in about 99% of cases.  However, they haven't looked at nearly enough fingerprints to demonstrate that directly, nor have they looked at the full variety of confounding effects that might arise from trying to use fingerprints deposited under real world conditions.  Dragons flight (talk) 13:21, 9 September 2016 (UTC)


 * I agree that a sample size of 6 is way too small to draw any valid conclusions. As far as real world conditions, if they are measuring fingerprints, the question still comes up regarding what they are measuring the concentration of amino acids against.  From your description it sounds like they are using lipids as the gauge.  The good news is that those will evaporate far slower than the water component of sweat, but they do still evaporate, and the nature of fingerprints means they will have a large surface area to volume ratio, which will tend to increase evaporation rates.  Temperature would be another big factor.  And, of course, time is another big factor.  So, if they knew the time when the prints were made, and the conditions since then, they might be a able to make a good estimate for the original volume of lipids.  Perhaps if it's been only hours, versus years, they can just ignore the trivial amount of evaporation since then.  Sweat might still be a factor, if the fingerprint is mixed with sweat.  Not sure how that might effect the evaporation rate of the lipids.  And the stress at a murder might well effect all of the various levels.  So, yea, lots of research needed before this would qualify for real-life use.  Also, if they have a fingerprint, that seems to imply they will have some DNA from skin cells, so checking that for X and Y chromosomes seems like the more viable option. StuRat (talk) 14:38, 9 September 2016 (UTC)


 * Why do you keep jumping to conclusions about an article you haven't read? That seems like a really weird way to spend your time. My offer still stands if you want to read about some science, rather than guessing what it might have said. SemanticMantis (talk) 17:24, 9 September 2016 (UTC)

How many people visit Antarctica every year?
How big is the global Antarctic research programme, how many scientists and support staff visit the continent annually (in recent years)? As far as I know the winter "population" is low, only a few hundred in total, but I have no idea how many seasonal or shorter term visitors go each summer. Roger (Dodger67) (talk) 17:21, 8 September 2016 (UTC)
 * Do you even Google, Bro? A simple google search on your question turned up Tourism in Antarctica, a Wikipedia article that notes about 37,000 visited in 2010, This page which breaks down the number of tourists year-by-year based on a bewildering set of data, including nationality, methods of arrival, etc.  This page which quotes numbers as well... -- Jayron 32 17:53, 8 September 2016 (UTC)
 * Nevermind the tourists. I'm looking for the numbers of people who go there to work; to do science and support those who do science. Beside the specific words I used in the question, the fact that this is is the Science Refdesk should be a clue. Roger (Dodger67) (talk) 18:00, 8 September 2016 (UTC)
 * This site claims around 4000 scientist visit seasonally each summer to support ongoing research. This site says about 3700 in the summer, with about 1200 remaining through the winter.  This site says around 3500 each summer.  So it seems that depending on how, and when, you're counting it seems about 3500-4000 summer residents, with about 1200 winter residents, not counting tourists.  I added the word "scientist" to your header in my google search to get that, BTW.  -- Jayron 32 18:07, 8 September 2016 (UTC)