Wikipedia:Reference desk/Archives/Science/2017 May 15

= May 15 =

Meaning of "above" in geology
I know by the law of superposition in geology that generally younger rocks lie above older ones. Reading Moine Supergroup I see the phrase "tectonically above" used twice and, although I can't find anywhere a definition, I suspect this means that the rocks physically above have been forced there and are, in fact, older. Am I understanding this properly? Would you ever say "tectonically above" if the higher strata were younger – both situations occur in the area of the Moine Thrust Belt? In the article "structurally above" is used twice and I think I can infer from the article that this phrase has the same meaning as "tectonically above". Is this right? When the word "above" is used without qualification in a geological context does it have a definite meaning to a geologist? I'm wondering whether "above" is ever used to mean "younger". Thincat (talk) 08:29, 15 May 2017 (UTC)


 * You're correct in your assumption - this is tectonic stratigraphy. Thrust faulting has the general effect of placing older rocks on younger rocks. We would use the term tectonically or structurally above (they are synonyms) when the upper sequence lies physically above a lower sequence with a tectonic (faulted) contact, rather than a normal stratigraphic contact. Mikenorton (talk) 10:55, 15 May 2017 (UTC)
 * Good, thank you. That seems clear now. Thincat (talk) 12:45, 15 May 2017 (UTC)

Induction and Convention of thermoelement
Does induction and convention of thermoelements are depends on their geometry? What geometry of thermoelements is more profitable, it is a complex geometry or simple geometry?--109.252.29.219 (talk) 15:30, 15 May 2017 (UTC)


 * We have articles about conduction and Convection which are two major types of Heat transfer. Both depend on the geometry of the body and its surroundings. Conduction can be calculated using the Thermal conductivity of material(s) in the path of heat flow. Convection is much harder to calculate since it involves movement of air whose flow may be laminar or turbulent. You may be interested in reading about the Heating element used in an electric heater. Blooteuth (talk) 14:06, 16 May 2017 (UTC)


 * Generally agree, but note that convection requires the movement of any fluid (usually a gas, liquid, or plasma), due to a thermal gradient, not necessarily air. Also note that the third major form of heat transfer, radiation, is also dependent on the shapes of the radiating and receiving bodies. StuRat (talk) 20:16, 16 May 2017 (UTC)

Is possible induction and convection cooling?--109.252.29.219 (talk) 09:34, 18 May 2017 (UTC)


 * Yes, since "cooling" is just looking at "heating" from the opposite direction. So, when you put a hot object in contact with a cold one, the hot one cools while the cold one warms (conduction).  If there's a fluid between them, the same thing happens, but it's called convection.  Radiation will also occur to cool one object and warm the other, even when not in contact and without a fluid between them. StuRat (talk) 23:32, 19 May 2017 (UTC)


 * It can be an absolute cyclone?--109.252.29.219 (talk) 12:20, 18 May 2017 (UTC)


 * Yes, a hurricane/cyclone is a massive type of convection process that cools the ocean and heats air sucked down from the upper atmosphere. StuRat (talk) 23:36, 19 May 2017 (UTC)

Autopsies in the absence of a coroner's investigation
Back in this question about the death of Margaret Thatcher, I noted that as I saw it, there would be no reason for an autopsy in the absence of a coroner's investigation. I further noted that any such autopsy would require the consent of the next-of-kin; only a coroner can order an autopsy without their consent. user:Nunh-huh, whilst agreeing to my second point (autopsies, unless ordered by a coroner, require consent from the next of kin), said that "autopsies are certainly not reserved for the edification of coroners".

My question is: take, for random example, the United Kingdom. Half a million people die there every year. Obviously, if the death warrants a coroner's investigation (it's somehow possibly unnatural or untimely), an autopsy makes logical sense.

But in which of these half a million cases which do not involve the coroner, would an autopsy still be considered? Obviously, the next of kin would need to consent. But who would be making the request to perform the autopsy? And what criteria would they be using to decide which of those half a million bodies they should be dissecting?

(My question is a general one, in no way particular to Thatcher; it's simply that the debate happened in the discussion of Thatcher's death). Eliyohub (talk) 17:23, 15 May 2017 (UTC)


 * Just as an example: 80 year old dies at home, coroner releases the body, attending physician has no basis on which to conclude cause of death, or suspects an undiagnosed hereditary illness that may affect living grandchildren and advises an autopsy. Or a patient on a drug study dies and the cause of death is not certain. Or the lawyers want to sue for malpractice and want evidence. Anyone with an interest in knowing what killed someone might suggest an autopsy. Is this somehow mysterious? - Nunh-huh 18:53, 15 May 2017 (UTC)


 * Have a look here. Summary: Before the coroner is considered, the attending doctor has to decide whether they can certify cause of death and release the body.  If the circumstances demand, they must inform the coroner (so you have these steps back to front).  The coroner can decide whether the cause of death is obvious, and if it isn't can order a post-mortem.Phil Holmes (talk) 08:02, 16 May 2017 (UTC)

The original post on this subject was at the Humanities Ref. Desk which is more suitable for this continuation than the Science Ref. Desk. Blooteuth (talk) 14:11, 16 May 2017 (UTC)]


 * From my readings in the medical literature (a medical writer reads a lot of "the literature" as his physician clients do in order to document things clearly in light of existing knowledge about a condition), I can say autopsies are indeed performed in the United Kingdom outside of coroners' inquests, to increase knowledge of conditions where more knowledge of their direct effects on the body is useful in the treatment of the living. They are also sometimes (not always) done after a patient has died while receiving a new or investigational drug or other investigational therapy. Drug regulatory agencies require that in some cases. loupgarous (talk) 23:01, 17 May 2017 (UTC)

== Feynman Lectures. Exercises PDF. Exercise 4-2 JPG.==

I have tried to solve as Feynman suggested: png. But when I use another virtual displacement png, I get wrong answer. Why? For x and y weights we can put the pulleys as far as needed to make displacements infinitesimal.

Username160611000000 (talk) 19:12, 15 May 2017 (UTC) And 2nd question: As I see, virtual work method doesn't show the direction of the forces, in contrast to force component method. Is it correct?

Username160611000000 (talk) 19:50, 15 May 2017 (UTC)

If one eats fruits and veggies without washing them or cooking them, then what is the likelihood of dying by acute illnesses and plant toxicity?
Or is that an easy way to commit suicide? Is getting an Entamoeba histolytica or Giardia intestinalis infection still possible in a relatively wealthy, developed country? 50.4.236.254 (talk) 23:44, 15 May 2017 (UTC)


 * E. coli exposure is essentially ubiquitous in manure-fertilized vegetables, but not all strains of E. coli are deadly, and some don't cause illness at all. Further, most infections resolve spontaneously, and the death rate is under 5%. I imagine it would probably be higher if you refused treatment, but then many of the deaths are in vulnerable populations to begin with (children, the elderly). But good luck knowing what kind of fertilizer your food was grown on, and even then, it seems you're more likely to get an upset tummy than die. Entamoeba histolytica seems like a damn hard one to get infected with in a first-world country. Most people in developed countries that carry it got infected while traveling in a developing country . The same is true of Giardia intestinalis, but new infections do occur in developed nations from person-to-person transmission . Someguy1221 (talk) 00:01, 16 May 2017 (UTC)


 * This is far to broad to be worth cognitive effort. Please stop posting every thought you have, and narrow your questions down to specifically answerable ones.  Do you seriously expect us to list ever plant toxin and food-born pathogen? μηδείς (talk) 00:15, 16 May 2017 (UTC)
 * Seconded. -- Jayron 32 01:42, 16 May 2017 (UTC)
 * Hmmm... Someguy1221 seems to have provided a sufficient answer. 50.4.236.254 (talk) 01:56, 16 May 2017 (UTC)
 * Someguy's mentioned not a single plant toxin, and three pathogens spread by fecal contamination that have nothing to do with plants per se. But if you are satisfied, mark it resolved. μηδείς (talk) 00:09, 17 May 2017 (UTC)
 * It seems more like a half-answer to me. At least I know that acute illnesses are more salient than plant toxicity. 50.4.236.254 (talk) 01:24, 17 May 2017 (UTC)
 * I somehow don't doubt that permanently dying by cyanide poisoning from improperly prepared cassava is worse than diarrhea. μηδείς (talk) 12:53, 17 May 2017 (UTC)
 * "Worse" is subjective. If one's intention is to die through mental disorientation than to die by upset stomach on top of mental disorientation, then death by cyanide poisoning (from eating cassava, cherry pits, apple seeds) may be the better option. 50.4.236.254 (talk) 23:29, 17 May 2017 (UTC)
 * Outbreaks of Giardia lamblia have occurred in Sydney, Australia, Oslo and Bergen, Norway through the water supply, so washing the veg during those brief outbreaks could have raised your chances of getting a nice dose of Giardia. Just sayin'. loupgarous (talk) 10:40, 16 May 2017 (UTC)
 * There are several peer-reviewed reports in the medical literature of chlorine-resistant cryptosporidium spread through water supplies in the industrialized world, several in the United States (Oregon, Milwaukee, and Arizona, among other places). Then again, crypto exposure was traced in at least one case (the Baker City, Oregon outbreak) to run-off from cattle pastures (stools from humans infected were positive for a subtype of Cryptosporidium parvum common in cattle, according to CDC researchers), which raises the specter of "organic" produce from acreage fertilized by cow manure possibly bringing a little crypto along for the ride to your market.  As far as "easy ways to commit suicide", only if you're immunocompromised, and even then it's a crapshoot (no pun intended this close to a mention of cryptosporidium). loupgarous (talk) 22:26, 17 May 2017 (UTC)


 * See also Ergotism. Count Iblis (talk) 04:33, 18 May 2017 (UTC)