Wikipedia:Reference desk/Archives/Science/2015 November 28

= November 28 =

How do pneumatic quick exhaust valves work?
How do pneumatic quick exhaust valves like these ones work internally? I think I understand how they're connected externally and what its functionalities are, but I'm curious as to its internal operations. If I understand correctly, air can flow from the In port to the Out port, and from the Out port to the Exhaust port. However it's not possible to flow from In to Exhaust, nor Out to In. Does this mean there are 1 or 2 one-way valves inside each QEVs? 731Butai (talk) 09:09, 28 November 2015 (UTC)
 * This document from the same site shows how the valves work. See also pop valve. Tevildo (talk) 10:28, 28 November 2015 (UTC)

Human biochemistry
Am I correct in thinking that everything that happens in the human body is just a series of chemical reactions? 2A02:C7D:B901:CC00:1C60:49B4:ABF9:45E4 (talk) 12:48, 28 November 2015 (UTC)


 * Not everything. Consider urination - an almost purely physical process, yet oh so relieving. Wnt (talk) 12:52, 28 November 2015 (UTC)
 * The contraction of the muscles that opens and closes the valves that allow urination are no less biochemical in cause than any, and the signals to your brain that allow one to experience the sensation of relief are as well. Though the OP's realization is rather trite.  All chemistry reduces to quantum mechanics anyways.  It doesn't mean knowing that is useful to understanding the human body.  The more interesting and informative studies come in the emergent behaviors that cannot be studied or explained at the lower levels Jayron 32 13:22, 28 November 2015 (UTC)
 * Ah, reductionism! This seems appropriate. 99.235.223.170 (talk) 15:53, 28 November 2015 (UTC) Hey, didn't xkcd used to have a native search function?
 * Yes. Reductionism.  According to August Comte, sociology (his own word) is reducible to psychology, psychology is reducible to biology, biology is reducible to chemistry, chemistry is reducible to physics, and physics is reducible to mathematics.  That all appeared to be true in Comte's time, only that the reduction wasn't feasible in Comte's time.  Unfortunately or fortunately, the problem is that physics isn't reducible to physics.  Robert McClenon (talk) 17:59, 28 November 2015 (UTC)


 * No, the word "just" is a problem. See emergence and supervenience, as well as  and . μηδείς (talk) 01:54, 29 November 2015 (UTC)
 * No. I meant that physics isn't reducible to physics, because quantum physics is just weird.  Robert McClenon (talk) 13:16, 29 November 2015 (UTC)


 * did you mean to end with biology is not reducible to physics? If so I agree, and Ernst Mayr goes int that in depth in What Makes Biology Unique?: Considerations on the Autonomy of a Scientific Discipline.


 * A better explanation for the OP: Imagine that before you go to bed you ask your husband to leave a note to remind you to drink your orange juice in the morning. But instead of leaving a note, he puts an overturned juice glass at your spot at the table.  Or he lays the carton of orange juice on its side in the fridge, the top end pointing toward the door, and a little smiley face in red ink on the cap.  In the morning, whether he left a note, he left an overturned glass, or he left the cartoon in the fridge in an odd way, you would remember to drink the juice.


 * I read the Stanford entry on Supervenience I linked to above; unfortunately it won't be scrutable to anyone without a degree in philosophy, if even then. To make the issue clearer, emergence holds that higher levels of order cannot be satisfactorily explained merely by reference to constituents at lower levels.  You can't explain why a tennis ball bounces and an egg doesn't by referring to quantum mechanics; you can't explain what it feels like to see red by reference only to organic chemistry; you can't explain the unconstitutionality of a law by reference to its mass and velocity.


 * Supervenience recognizes the converse. Although one may not be able to reduce the explanation of guilt for a murder to a description of atoms and their velocity, one can say that there couldn't be an actual difference in the moral state of being (guilt) unless there were at least some sort of difference on the physical level.  Two physically identical parallel universes cannot exist where the same person is innocent in one and guilty in another.  Differences in ideas, for example, depend on biological and thus chemical differences, even if the correlation is not one to one.


 * Consider, for example, getting your blood sugar checked at the doctor. Today your blood glucose level is 200, yesterday it was 100.  All other things being equal, there must be twice as much free glucose in solution in your blood today than there was when it was tested yesterday.  But lets say every glucose atom in your blood miraculously happened to rotate 75 degrees, and then you were tested again.  On the physical level there would be a definite difference, but on a medical level there would be no difference whatsoever, your tested blood sugar level would be identical, and its affects on your eyes and kidneys would be identical, regardless of the physical rotation of the chemicals.


 * Return to the orange juice example. You remembering to drink the juice is in no way strictly explained by a reduction to some necessary physical state.  There is no law of physics that says an upside down juice glass on your spot at the table will make you drink orange juice.  Not only could the glass just be there because the cabinets will be taken down by the contractor, so all the plates and dishes are on the table; there could have been an infinite number of ways for him to cause you to remember to drink the juice, an orange in you slipper, a message in tooth paste in one of whichever languages you speak on the bathroom mirror.  What happens cannot "just" be tied to or explained by the physical differences, even though there must be some physical difference to remind you. μηδείς (talk) 04:40, 29 November 2015 (UTC)


 * I don't pretend to understand that reply by Medeis and am disappointed that the Mayr reference is not an essay, merely an ad for a book. But I digress. I would have thought that besides chemical reactions in the body, there are also nervous impulses, which are not chemical in any way, or are they? Akld guy (talk) 05:41, 29 November 2015 (UTC)
 * why aren't nervous impulses a series of chemical reactions? They seem like it to me.  Aren't these series of reactions called pathways?  2A02:C7D:B901:CC00:9597:AF2C:2F79:8F40 (talk) 17:54, 29 November 2015 (UTC)


 * Apparenttly Cambridge has made the entirety of Mayr's work available on line in PDF form, here. Talking about my putting an "ad" for his book as a link is a bit funny, considering Ernst Mayr was a central figure in the modern synthesis, a noted field researcher, theoretician, and philosopher and historian of (biological) science.  He was referred to as the "Dean of Evolutionary Biology" during the latter part of the 20th century.  Chapters 2, 3, and especially 4 on reductionism are especially relevant.  They are short, cogent, and accessible to the educated layman.


 * If the OP's question is, is there some other force at work in the body at the electro-molecular level, besides just normal chemical processes, the answer is no, and the theory that there are such unique forces is one Mayr also addresses, called vitalism. μηδείς (talk) 18:31, 29 November 2015 (UTC)
 * OP may also have a look at Reference_desk/Archives/Science/2015_March_9. Brandmeistertalk  19:26, 29 November 2015 (UTC)

Other species throwing a football...
Are any of the other great apes capable of throwing a football (American, the pointy one) of a significant distance? Are there other animals outside the primates capable of doing so? (Elephant's trunk?) I'm sort of trying to figure out what an american version of "Bedknobs and Broomsticks" would look like and was trying to imagine who other than humans would be throwing the ball. (Yes, given the original, a continuous action game would be better, but the only continuous action game played by Americans more than "Soccer" is Hockey which has even more problems.Naraht (talk) 13:38, 28 November 2015 (UTC)
 * Wouldn't basketball be a continuous action sport? Rmhermen (talk) 17:01, 28 November 2015 (UTC)
 * Not to soccer-heavy nations. They really. hate. stopping the clock. Sagittarian Milky Way (talk) 20:58, 28 November 2015 (UTC)


 * The human arm is uniquely adapted for throwing and clubbing and the human hand is the only one that can make a fist. I do knot know the skill of elephants in throwing, but suspect that if they could, people would be making money off it. μηδείς (talk) 17:20, 28 November 2015 (UTC)
 * Looking at the articles, it appears that the best of the apes in throwing is the Chimp and that the average wild chimp would do worse than your average 40 year old couch potato at throwing a round ball. The motion to get a spiral on a football would be even more difficult. (and difficult to train an ape to do) And an elephant isn't putting a spiral on it either.Naraht (talk) 23:28, 29 November 2015 (UTC)
 * Just a quick note which is not really related to the OP but relates to elephants. I have worked on the behaviour of elephants in zoos.  Elephants are highly inquisitive and investigate anything new in, or near, their enclosures.  If they can not investigate it directly, they often throw things at it.  As part of my research, I set up video cameras in their night-time enclosure.  I arrived there the following day to find the cameras covered in the most readily available ammunition - their faeces.  The elephants had been extremely accurate in their turd-tossing.  Unfortunately, my scientific curiosity was a little lacking that day and I neglected to observe whether a spiral action had been imparted. DrChrissy (talk) 23:44, 29 November 2015 (UTC)
 * For a spiral action, the feces would have to be shaped in a very specific way. I'd much rather have an Elephant as the running back anyway. Though I wonder if they would be able to catch passes out of the backfield, how able are they to catch thrown objects?Naraht (talk) 04:13, 30 November 2015 (UTC)


 * Primates do fling feces with an underhand toss, but not an overhand throw. Only humans do the latter. μηδείς (talk) 21:02, 2 December 2015 (UTC)

Medical career paths
Do doctors find high competition at every stage of progression in their career compared to other careers due to the very structured nature of their careers? And I'm guessing limited options compared to other careers? 176.24.25.109 (talk) 18:15, 28 November 2015 (UTC)


 * That will depend very much on the country in which they are progressing their career. In the UK there is fairly strong competition.  Have you read this and this and this ?   D b f i r s   16:43, 29 November 2015 (UTC)

How do people get enough exercise if their jobs force them to sit all day?
If a person works a regular 9-5 workweek but also has to work on-call, and the job has very little physical activity beyond minor movements of the arms and legs, then how does that person get enough exercise? Are obesity and obesity-related illnesses inevitable? 71.79.234.132 (talk) 21:08, 28 November 2015 (UTC)
 * Many large companies offer exercise facilities. And being on call doesn't mean you have to sit around. ←Baseball Bugs What's up, Doc? carrots→ 22:28, 28 November 2015 (UTC)


 * See User talk:Jimbo Wales/Archive 146 (October 2013)
 * and User talk:Jimbo Wales/Archive 152 (December 2013).
 * —Wavelength (talk) 23:53, 28 November 2015 (UTC)
 * Find a walking desk. I built one using a secondhand treadmill for 120 bucks, at which I can use my computer and do conference calls while strolling along, slowly. Otherwise, yes you'll die early, even if you don't get fat. Other solutions involve getting up early and swimming intensively for an hour before work, etc. Greglocock (talk) 00:31, 29 November 2015 (UTC)


 * I ride to work on a bicycle, which means that I'm riding about fifty to sixty miles every week at a minimum! On average, it takes me fewer minutes to bike to work than it takes to drive to work - so I'm actually saving time and getting exercise at the same time. Besides, I get to spend about an extra hour outdoors each day (or night, depending on the season!).  This is called "active commuting" by the CDC; essentially, if you structure your work/life so that you actively commute, you guarantee yourself a non-sedentary lifestyle, no matter how your work environment is set up.  I would like to think that anyone who is committed to making the effort could probably do the same, but of course it depends on your individual circumstances.  The sedentary lifestyles that are commonly promoted by office-environments are a real problem that has been widely recognized by epidemiologists and public health professionals: we have an entire article on diseases of affluence.
 * According to this 2010 study, Commute Times, Food Retail Gaps, and Body Mass Index in North Carolina Counties, your car commute time correlates strongly with your Body Mass Index; there is a full discussion of the compounding factors that you should also consider. The commute-time correlation is strong across many different types of workers - not all whose jobs involve desk-work!  When you spend all those hours in a car each week, you have less time for exercising; you're more inclined to rush your food choices; and more inclined to be overweight.  But, above all, chances are very high that you aren't commuting by bike or any other active method - to the detriment of your own health!
 * A sedentary lifestyle is not inevitable - but it takes real physical and mental effort to resist the ultra-convenient options that are available to professional workers in wealthy, developed nations.
 * Nimur (talk) 01:58, 29 November 2015 (UTC)
 * Using the stairs may be more economical than taking the elevator, especially when you are just travelling through one story. If you get weekends and you want to travel to a specific location in your neighborhood, then you may bike or walk or run to that location. Choosing tap water instead of distilled water may be healthier too. 71.79.234.132 (talk) 13:40, 29 November 2015 (UTC)


 * You don't need a lot of time to incorporate something like the 7-Minute Scientific Workout into your life.Denidi (talk) 14:40, 29 November 2015 (UTC)

Forty years ago I had a sit down job 4 miles (6.5 km) from home. I got bored with walking home at night, so began jogging. Eventually I was flat-out running the first two thirds, slowing to a fast walk in the last bit to cool down. I was never before, and never since, in such good condition. After five years I was again working near home, walking while doing my duties, walking home for lunch. That made me fat, so I took up bicycling to the suburbs, which was more fun than running. Jim.henderson (talk) 14:14, 30 November 2015 (UTC)