Wikipedia:Reference desk/Archives/Science/2014 October 14

= October 14 =

Sweat transmission of disease
What diseases can be spread by sweat in places like gyms or pools? I don't think many can other than skin infections such as herpes, HPV. What about blood borne viruses such as hepatitis or ebola? — Preceding unsigned comment added by 194.66.246.123 (talk) 09:37, 14 October 2014 (UTC)
 * It's difficult to claim "impossible to transmit" because if someone happens to have an open wound, lots of viruses and bacteria can enter the body that way and have a small chance of multiplying in the bloodstream. For most diseases, experts would say "extremely unlikely", and give evidence (where it exists) that there has been no recorded case of transmission by this means.    D b f i r s   11:34, 14 October 2014 (UTC)
 * Today's Guardian newspaper says this: "What about sweat - for example could I get Ebola from using gym equipment? No. No one who had Ebola and was symptomatic, with intense muscle weakness and a fever in the early stages, would be well enough to go to the gym - and until they are symptomatic, they are not infectious. Sweat, anyway, is probably not a source of large amounts of virus - in fact, the World Health Organisation (WHO) says whole live virus has never been isolated from sweat." --Phil Holmes (talk) 12:39, 14 October 2014 (UTC)
 * Yes, sweat is a source for ebola and is often the route that infects caregivers and body washers in Africa. Corpses that have dried sweat or sweat that has contaminated surfaces is a path of infection.  Other paths are blood, saliva, urine and feces. --DHeyward (talk) 13:42, 14 October 2014 (UTC)
 * Source, please? For both. — Crisco 1492 (talk) 13:55, 14 October 2014 (UTC)
 * WHO on sweat NY times body washing  .  It's not HIV.  It lives longer, in more fluids, and kills quickly.  The problem is that the infection rate is currently exceeding the death rate by 2-3x and it kills within 3 weeks.  That means the infection is doubling every 3 weeks or so.  It infects at the rate as the flu but not as quickly but also more deadly at 50-70%.  The Spanish Flu had the same infection rate (but much quicker) and much less fatality.  HIV is manageable because it takes a long time to die though one person infects more than Ebola.  The Flu infects the same as Ebola but acts more quickly and resolves more quickly.  The math says that unless the infection rate falls below 1, it will inmfect at a sustainable rate as the flu but the incubation period makes it a 3-4 year world cycle instead of an annual cycle.  It's unclear whether seasonal or animal populations will affect it.  If it is like the flu, in 3-4 years it will sweep the world.  --DHeyward (talk) 06:56, 15 October 2014 (UTC)

Allergy can be caused only by proteins?
Or it can be by other things that are not proteins? in this link there someone who told that there is an allergy for nickle. I'm not sure in this issue. 5.28.154.216 (talk) 17:45, 14 October 2014 (UTC) 5.28.154.216 (talk) 14:48, 14 October 2014 (UTC)


 * Allergies can be caused by many substances; Allergic contact dermatitis has nickel in its list. In fact, nickel was named the 2008 Contact Allergen of the Year. --Mark viking (talk) 20:15, 14 October 2014 (UTC)


 * The antibodies that cause an allergic reaction react only to larger molecules, but Ni can degrade proteins in such a way as to make those proteins allergenic. There are also such things as allergies to latex, which is not strictly a protein. I assume you read allergy and immune response? μηδείς (talk) 20:47, 14 October 2014 (UTC)


 * Strike that about latex, since is does contain proteins, and it is to that fraction that the allergic reaction occurs. μηδείς (talk) 17:00, 15 October 2014 (UTC)


 * Allergy can be caused by carbohydrates, see Alpha-gal allergy. Smaller molecules which may act as haptens are also relevant. Nickel has been mentioned. Other examples are isocyanates and various drugs (penicillin etc.). --109.189.65.217 (talk) 21:29, 15 October 2014 (UTC)

Peeing in a toilet
I've peed into a plastic container during medical exams etc, and like most people I note that pee tends to be dark yellow when you haven't had much to drink and lighter if you have.

So when I pee into the toilet, and my pee is dark yellow (visibly dark yellow during the flow), why doesn't the water in the toilet dilute the colour of the urine? It seems to be just as yellow when it mixes with the water as when its flowing. Shouldn't the water dilute it and make it less yellow?36.225.87.98 (talk) 15:02, 14 October 2014 (UTC)


 * The absorbance of many chemicals is in a narrow frequency band. Light of just that color is removed all but completely, while light of other colors never gets removed no matter how much is added.  Of course, there's always a shoulder where more means darker, but the effect can be subtle.  I didn't quickly find an absorption spectrum of urobilin online, though it is probably here, unless you count a ... very early version.  (There may be aspects of the relation with urobilinogen and pH that I haven't appreciated) Wnt (talk) 15:21, 14 October 2014 (UTC)


 * A bowl of water reflects and refracts light. Pee is only yellow because its light is. In a way, it glows. Shine a small red light into your toilet, same deal. More red. InedibleHulk (talk) 15:54, 14 October 2014 (UTC)


 * Also note that a stream of urine is very thin, so even though it is darker, looking through such a small amount makes it look lighter, especially with a white background like a typical toilet bowl. The urine/water mix in the bowl is lighter, but you're looking through a lot more of it, and since you're looking at the light reflected off the bottom of the bowl, it actually passes through the water/urine mix twice.  StuRat (talk) 16:09, 14 October 2014 (UTC)


 * has some spectroscopic information about uribilin, including possible pH and solvent effects. DMacks (talk) 17:57, 14 October 2014 (UTC)


 * Of course there's also the question of the colour of a stream of bat's p!$$. 1m50s inμηδείς (talk) 18:17, 14 October 2014 (UTC)

Volcanism on the Moon! Consequences for colonization
This is really surprising (other references added at Moon): there are apparently 70 volcanoes that have been active on the Moon in fairly recent geologic times. The activity was found on the near side of the Moon, which apparently is warmer due to radioactive elements. There remain a few things I'm not clear on...

(1) Does the presence of this volcanism pretty much guarantee there are substantial amounts of water and gasses (especially CO2) trapped deep below the lunar surface, that would have separated from the magma proper?

(1b) The Moon, after all, is partly derived from the one planet where we know life exists. Could life exist in such spaces, or if absent, thrive if introduced?

(2) How do we know the "deep crust" of one side of the Moon is "several hundred degrees warmer" than the deep crust on the other?

(3) Can we get similar data for the shallow crust - specifically, do we know if there are any regions near the volcanoes where temperatures a short distance underground might be nice and comfortable? Also, our article doesn't give the data for what the temperature of the Lunar soil is once you get down beneath the day-night temperature variations.

(4) Are the volcanoes suitable for getting geothermal energy using known methods from Iceland, or new methods?

(5) If you get inventive and start drilling into magma pools, could you harvest interesting resources that might be hard to find on the Moon otherwise?

(6) Is there any chance of volcanic activity "fairly near to" the lunar polar craters where ice deposits exist? (Obviously the warmth is not directly compatible with the coldest spots in the solar system, so some commute is allowed!)

Wnt (talk) 15:08, 14 October 2014 (UTC)


 * (1b), whether it's Titan, Enceladus, Europa or whatever other current candidate bodies for ET life, exobiologists always come back to a few sources of inspiration: the dark cold lakes below the arctic ice caps are now thought to house entire ecosystems that do not derive their energy from sunlight, though there is of course still much unknown. The other favorite is the life at hydrothermal vents. Though things like Riftia get a lot of attention, they are highly derived worms. However, they depend on chemoautotrophic endosymbionts. These archaea are thought to be rather old, and can also be free-living, and take their nutrients from sulfides (?) that come out of the vents. All this is to say, sure, it is not unreasonable to think there are some extremophiles on earth that could thrive in certain local regions of the moon. All you'd need is some heat close enough to the ice to melt it, and some mechanism to churn things and cycle nutrients. If you want to get creative, throw in a little panspermia and recall that even "advanced" animals like water bears can survive in the cold vacuum of space...
 * All this is not to say any of this is likely, just that it is conceptually possible, based on what we know of terrestrial nutrient cycles and metabolic pathways of extant critters. SemanticMantis (talk) 15:51, 14 October 2014 (UTC)
 * Well, I'm not clear on the geological point of whether magma means water has to be around. I'm thinking water/gas emerge from super pressurized magma, yet get caught under some kind of dome and remain pressurized instead of escaping to space.  Except that obviously a salt dome doesn't exist on the Moon, lacking among other things sedimentary rock, not to mention evaporites.  I scarcely know the geology of the Earth, let alone this. Wnt (talk) 16:09, 14 October 2014 (UTC)
 * I don't know if magma has to entail water, but my reading of Lunar_water is that there is most likely some water there... SemanticMantis (talk) 16:51, 14 October 2014 (UTC)


 * 4) I think geothermal energy would be difficult to use on the Moon. Typically lots of water is used to produce steam, and water is likely to be in short supply on the moon, and the little you have needs to be slated for human consumption.  Solar energy might work well on the Moon for short-term energy needs, with no clouds or atmosphere to reduce the sunlight.  However, solar panels might break down over time due to the harsh environment, or be covered with Moon dust.  StuRat (talk) 16:23, 14 October 2014 (UTC)
 * Provided the water is properly recycled, it seems a worthwhile investment. Especially if more water can be from associated natural or man-made vents where gasses escape. Wnt (talk) 17:27, 14 October 2014 (UTC)
 * Solar cells should work fine on the moon for a very long time. They work well enough for long-term space missions. Moon dust should settle very slowly on them - what would make it rise to begin with? --Stephan Schulz (talk) 18:17, 14 October 2014 (UTC)


 * Dust is a likely explanation for the degraded performance of the lunar reflectors, see here:

"Dust is perhaps the most likely candidate for the observed degradation. Astronaut accounts from the surface and from lunar orbit, as well as a horizon glow seen by Surveyor 7, suggest the presence of levitated dust—possibly to altitudes in excess of 100 km, for which a lofting mechanism has been suggested by Stubbs, Vondrak, and Farrell (2006). The dust monitor placed on the lunar surface by the Apollo 17 mission measured large fluxes of dust in the east-west direction around the time of lunar sunrise and sunset— consistent with the electrostatic charging mechanisms described by Farrell et al. (2007). The main difficulty with the dust explanation is that electrostatic charging alone is not strong enough to liberate dust grains from surface adhesion. But mechanical disturbance seeded by micrometeorite and impact ejecta activity may be enough to free the already-charged grains. Whether or not dust is responsible, the supposed health of the reflector arrays has been used to argue that dust dynamics on the surface of the moon are of minimal importance. Our observations of the reduced reflector performance invalidate the invocation of reflector health in this argument." Count Iblis (talk) 18:35, 14 October 2014 (UTC)

Does China still have sparrows?
It's well known that during Mao's Four Pests Campaign, people killed off most of the Eurasian tree sparrows in China, with devastating consequences for agriculture. But I never see any followup: is China still bereft of sparrows, or have their numbers recovered? Wikipedia's article on them mentions that "thousands" of Passer montanus dilutus are present in eastern China during autumn, but "thousands" might be a small number in context. --Lazar Taxon (talk) 17:35, 14 October 2014 (UTC)


 * First thing to recall is that the Eurasian sparrow (Passer montanus) is a human commensal species; they love our cities. In most of their range, they are denser in human settlements than in "wild" habitat. I don't have time to search through all the citations included, but these three papers all talk a bit about sparrow populations in China  . Reading the abstracts indicates there are plenty of sparrows around, but you'll probably have to dig through the citations to find good pre- Mao population estimates. Regardless of that comparison, I'm confident the sparrow population is not currently threatened or endangered in China. SemanticMantis (talk) 19:19, 14 October 2014 (UTC)


 * It's payback for the Norway rat from the far, near and middle east - but not Norway.  --DHeyward (talk) 07:06, 15 October 2014 (UTC)


 * Anecdotally, yes. They're one of the most common birds I remember seeing in China's cities.  --Bowlhover (talk) 08:07, 15 October 2014 (UTC)

Soil compaction
Normally, soil is compacted to maximise it's dry density and increase its strength. Moisture content can be increased to do this until the optimum moisture content is reached. But what happens if the soul becomes too saturated? Then does it lose its strength? — Preceding unsigned comment added by 82.132.245.233 (talk) 18:16, 14 October 2014 (UTC)
 * Check out Mud. ←Baseball Bugs What's up, Doc? carrots→ 18:29, 14 October 2014 (UTC)


 * What happens when there is too much water depends on the soil mineral content, grain size, slope, porosity, and many other factors. Soil mechanics gives an overview of this large topic. The specifics relevant to your question are at pore water pressure and bearing capacity. SemanticMantis (talk) 19:10, 14 October 2014 (UTC)


 * I fear my soul has become over-saturated. :-) StuRat (talk) 01:49, 15 October 2014 (UTC)

What are scientific opinions as to which part of the brain experiences qualia?
I do not want pseudoscientific opinion from geologists or sociologists—not a slight, but they are not the experts in the field with which I am concerned. Nor am I after scientific consensus because I am almost certain that there is none. Rather, I am after the opinion of neuroscientists that believe in the existence of qualia (some don't). Have any neuroscientists published their opinions on this matter?--Leon (talk) 19:41, 14 October 2014 (UTC)


 * These links may be of use to you  . SemanticMantis (talk) 19:48, 14 October 2014 (UTC)


 * "Which part of the brain experiences" is a rather reductive question. You might look at The Rediscovery of the Mind by John R. Searle (and his other works, including the Chinese Room argument, as well as Stephen E. Palmer, author of Vision Science and his refutation of Locke's argument that qualia could be reversed without our being able to find it in natural trichromats. μηδείς (talk) 20:38, 14 October 2014 (UTC)
 * Searle is a materialist—he believes that qualia happen in the brain, and that this can be investigated scientifically, so he would approve of the original question. He has no personal opinion about the answer since he's not a neuroscientist. Neither does Palmer, as far as I can tell, so all of this is irrelevant to the original question. -- BenRG (talk) 23:08, 14 October 2014 (UTC)


 * Searle is not a reductionist, so he doesn't identify qualia with any specific part of the brain. He's certainly not a naive materialist. Palmer denies the standard notion that qualia are interchangeable.  Both have plenty of interest to say on the topic.  I'm tempted to say your objections prove the relevance of my comments, but I don't think they actually have anything whatsoever to do with my comments.  In any case, they OP is invited to investigate the sources I have referenced, regardless of your OR. μηδείς (talk) 00:28, 15 October 2014 (UTC)
 * The point is that "consciousness of a person must be reducible to consciousness of cells/molecules/subatomic particles" and "consciousness can't be localized at all" are not the only two options here. Consciousness suggests that the prefrontal cortex might be the seat of consciousness. That's a nontrivial partial answer to the original question, and it isn't at odds with anything that Searle or Palmer has written, to my knowledge -- BenRG (talk) 01:31, 16 October 2014 (UTC)


 * Consciousness and Neural correlates of consciousness are relevant. -- BenRG (talk) 23:08, 14 October 2014 (UTC)


 * This question presupposes the validity of what Daniel Dennett called Cartesian materialism. That article deals pretty directly with the question, and the range of scientific and philosophical opinions about it. Looie496 (talk) 15:56, 17 October 2014 (UTC)

Slow tire leak and tire pressure at speed vs sitting.
I have a very slow leak in one of my car tires, I have to top it off about every ten days. My question is that is there much of a difference in the pressure being applied on the tire, or the air in the tire, while my car is sitting vs while it is travelling at local speeds and vs highway speeds? I can't get over the mental picture of my tire "slamming" into the pavement harder as I go faster, even though this doesn't seem very logical. Thanks. Beach drifter (talk) 23:54, 14 October 2014 (UTC)


 * I would expect air to leak out faster when it's moving. The mechanical compression and decompression of the tire with each rotation is one reason, but the hotter air inside (as a result of friction), which then increases the air pressure, may be an even more important reason.  However, you may only notice the loss of air when the tire cools and the pressure decreases. StuRat (talk) 01:52, 15 October 2014 (UTC)


 * Same problem and I can say that heat affects pressure more than use. The weight of the car doesn't change and pavement is relatively smooth.  Temperature increase from friction as well as sunlight is a much larger effect than terrain.  The warning light turns off during use.  All anecdotal of course.  --DHeyward (talk) 07:10, 15 October 2014 (UTC)
 * Nah, this is for the main part just a result of real leaks. If you exchange your tires the one very slowly leaking will still leak and the other will still not. --Kharon (talk) 12:52, 15 October 2014 (UTC)