Wikipedia:Reference desk/Archives/Science/2013 October 2

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October 2

Can human live for a long period under a gravity of 2g?

--163.125.83.8 (talk) 08:43, 2 October 2013 (UTC)

Probably not without special measures, like a suit that contracts and relaxes to help pump the blood. Otherwise bed sores would result. I also wonder about the psychological issues from being "weighed down" like that for long. That would have to be depressing. StuRat (talk) 10:02, 2 October 2013 (UTC)

I don't think that last comment bears any weight regarding the outcome of this discussion. Plasmic Physics (talk) 12:21, 2 October 2013 (UTC)

You don't think a person's psychological state has any effect on their life expectancy ? StuRat (talk) 16:20, 2 October 2013 (UTC)

No, my reply was in regard to your pun (alternate definition of "depressed"); and was in fact a pun in its own right. Plasmic Physics (talk) 22:09, 2 October 2013 (UTC)

Ah, OK, I see we are amassing quite a few puns. :-) StuRat (talk) 22:16, 2 October 2013 (UTC)

Answer2

Related topics are the Hypergravity and Gravitational biology. Rats are aging faster in slightly higher gravity, according their higher metabolism. The term of life not changed significantly. Next to the previous answer I think the effect are the same if the body hight had been doubled in normal gravity. More stress for the heart and vein problems like Varicose veins going to be higher. --hu:Rodrigo (talk) 10:48, 2 October 2013 (UTC)

Also see G-force#Human tolerance of g-force. Duoduoduo (talk) 17:52, 2 October 2013 (UTC)

There are certainly people who weighed 120 pounds at age 20 and 240 pounds at age 45. Their skeleton and muscles have to deal with much the same burden (though there are clearly differences) as if the 120 pound person had been placed in a gravitational field of twice gravity. Plus they are older. Yet, they function in the workplace and in leisure pursuits, though with some limitations. There are certainly some medical issues, but they can live independently to 70 or older. I would not be surprised if a healthy 20 year old could tolerate 2 G for many days or even months. Edison (talk) 20:36, 2 October 2013 (UTC)

Yeah, but how will the body's ability to adapt be affected by an dramatically increased rate of change in gravitational acceleration? Over-weight people don't become thus over-night. Plasmic Physics (talk) 00:17, 3 October 2013 (UTC)

I think I mean with some buffer period to adjust to gravity change, just like adapting to pressure change in scuba diving.--58.250.108.53 (talk) 09:07, 3 October 2013 (UTC)

According to [1] humans were exposed to some level of hypergravity for several weeks during the 1960s in Downey, California --- but no publicly accessible results from the experiment are known. Maybe it's time for a FOIA on behalf of Wikipedia...? Wnt (talk) 23:15, 2 October 2013 (UTC)

Magistral blood vessels

What are the magistral blood vessels of the human body? I found in a publication title [2] and mentioned in several google citate. Can somebody describe? (The original question arrived to the Hungarian Reference desk ([3]) , but looks this is an English medical jargon. --hu:Rodrigo (talk) 09:09, 2 October 2013 (UTC)

Magistral means "master" blood vessels. Magistral blood vessels are the vessels that must have continuing blood flow for CNS function and life to continue. Stopping blood flow in peripheral vessels affects only the part of the body served by that vessel. Magistral vessels include carotid arties, vertebral arteries, jugular vein etc. Magistral vessels show little branching and in consequence have a consistent diameter. Use search terms "definition of magistral vessels in Google." 60.230.209.212 (talk) 10:50, 2 October 2013 (UTC)

Rabies as a behavior-altering parasite

Rabies is categorized under "Category:Mind-altering parasites". Behavior-altering parasites and parasitoids alter the behavior of the host in a way that helps transmission of the disease. But rabies in humans presents in two different forms, depending on the location of neuronal infection. "Furious rabies" is exhibited when the virus replicates in the limbic system while "dumb rabies" is experienced when the virus replicates in the neocortex (source). Both forms are seen in animals as well (source). My main question is: did the virus evolve to cause aggressive behavior, or are species that become aggressive when infected simply better at spreading the disease, which led to them becoming the main hosts for the virus? Also, is the behaviour simply a result of the destruction of the CNS, or does it change the brain functions in other ways? Ssscienccce (talk) 12:18, 2 October 2013 (UTC)

I thought it disabled the higher parts (both figuratively and literally) of the brain first, leaving the brain stem for last, which is the seat of aggression. Thus you are left with uncontrolled aggression.

And to your other question, rabies probably both evolved to cause aggressiveness and those species more prone to be aggressive are more likely to become hosts. In the case of humans, we may also become aggressive in end-stage rabies, but we seldom bite each other, as we really aren't built for that method of attack, so rabies doesn't tend to spread from human to human well, and thus rabies is rare in humans. StuRat (talk) 12:27, 2 October 2013 (UTC)

But how sure are we that the virus evolved to cause aggressiveness? Alzheimer patients can become violent, aggression is one of the most common consequences of traumatic brain injury (source), clearly that's not because of evolutionary advantage in transmitting the disease (although, in the case of traumatic brain damage ;-)...); encephalitis, hypoglycemia, lead poisoning can also cause aggression. How do we know that it's not simply a logical consequence of the infection attacking the brain? Saying that "it is modifying the behavior of its host to facilitate its transmission" implies that if you would use one host's saliva to infect the next host and repeat that for enough generations, or if you selected for "dumb rabies", you eventually end up with a strain that doesn't cause aggression. I'm basically asking if there is evidence for the claim or whether it is simply assumed because it makes sense. Ssscienccce (talk) 20:14, 2 October 2013 (UTC)

I think it's just assumed, as the evidence would be earlier non-aggressive strains which died out thousands or millions of years ago. Perhaps we will one day be able to find fossilized rabies DNA and figure out that those strains didn't cause aggression. StuRat (talk) 22:29, 2 October 2013 (UTC)

Rabies virus reports that all extant rabies viruses appear to have evolved within the last 1500 years. Makes you wonder what those ancient Greek and Roman writers were talking about... Ssscienccce (talk) 01:08, 3 October 2013 (UTC)

And I notice it says: "Consequently, the emergence of rabies may have been contemporaneous with the extreme weather events of 535–536 and/or the 1883 eruption of Krakatoa." What?! how can it be either 535 or 1883???

They probably meant Krakatoa's 535 eruption. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 09:33, 3 October 2013 (UTC)

Rabies was called Hydrophobia due to behavioral symptoms presented when the infected tries to drink water. This panic and shaking is thought to facilitate transmission of rabies among Ungulates congregating at the watering hole.--Digrpat (talk) 21:44, 2 October 2013 (UTC)

Wait, viruses are parasites? Is that a usual usage of that term? --Trovatore (talk) 21:53, 2 October 2013 (UTC)

I think that's correct, in that they make their living from the host, but do not contribute to the survival of the host (with perhaps some rare exceptions where they contribute useful DNA). This is precisely the relationship of, say, a tapeworm (except that their rare contribution to the survival of the host might be if the host was suffering from obesity). StuRat (talk) 22:22, 2 October 2013 (UTC)

Well, parasites are living organisms........ :) Wnt (talk) 23:03, 2 October 2013 (UTC)

Yes, viruses are obligate intercellular parasites. They have no metabolism of their own. See Nature. μηδείς (talk) 00:38, 3 October 2013 (UTC)

Going by the parasite article, it appears that some people use the word macroparasite to cover the meaning I understand for "parasite". I'm not completely sold on this linguistic change; it appears to make virtually all pathogens "parasites", so you wonder why you really need a separate word. Sometimes WP articles are edited by people who have a particular way of talking that may not entirely reflect all of scholarly usage — does anyone know how completely this new meaning of "parasite" has been adopted? --Trovatore (talk) 01:05, 3 October 2013 (UTC)

The use of the word "parasite" started before the microscope, so the people at the time had no idea that many diseases were caused by microbes. Had they known this when the word originated, then surely they would have been included in the original usage of the word, as there is no reason to classify them differently, based on size alone. StuRat (talk) 11:28, 3 October 2013 (UTC)

If you read the article, you'll see that the (allegedly modern) distinction is not in fact about size, though it correlates with size. --Trovatore (talk) 18:46, 3 October 2013 (UTC)

I think of this as not very serious, basically semantics. If a virus is counted as a parasite, can it be a nonliving parasite (some sources appear to say yes). But is a prion a parasite? The thing is what it is, whatever we call it. Wnt (talk) 00:43, 4 October 2013 (UTC)

Always weird when people use the word "semantics" to mean "something that's not very important". Semantics is the science of meaning. It's unutterably important.

But if you mean it's just about word choice, sure, I agree. That's what my first remark was explicitly about. --Trovatore (talk) 00:53, 4 October 2013 (UTC)

No, a prion is not a parasite. It is a molecular toxin that catalyzes a chemical-conformational change in similar existing molecules. It does not reproduce itself or need to be reproduced. Viruses do need to be reproduced, which the host cell does for them. This is rather obvious and settled science, or it was when I got my bachelors in bio several decades ago, and per Nature and every text on generally biology and virolgy I have seen. Not to be rude, but it's not something any OP should take seriously coming as an armchair argument between laymen not giving sources. μηδείς (talk) 01:31, 4 October 2013 (UTC)

PrP^Sc does increase in level over the lifetime of an infected animal. [4] The raw materials (more PrP) come from the host cell. Whether the reaction that creates it is conformational or chemical seems of little relevance. You start off with a stolen infected instrument and a few basement captives, and within a few decades you're ready to start a 'zombie' apocalypse - it seems like replication. But the real point is that all these things - life, replication, parasitism - are ideas we try to use to describe the universe in a neat little framework, like wallpapering a tree, which might at times lead to slippage, folds, confusion. Wnt (talk) 04:15, 4 October 2013 (UTC)

Prions are proteins, they neither replicate themselves nor influence the cell's genetic output. They work as a catalyst on newly produced proteins as the cells produce them, which is the reason for increase over time. An interesting analogy is Kurt Vonnegut's ice-nine in his novel Cat's Cradle which was written before the prion phenomenon was fully understood. μηδείς (talk) 20:08, 4 October 2013 (UTC)

‎chemicals (affect of sleep on brain chemicals involved in memory)

Resolved

The dream article states; "Certain brain chemicals necessary for converting short-term memories into long-term ones are suppressed during REM sleep." No reference is given. Assuming this statement is true, what chemicals are being suppressed? 82.44.76.14 (talk) 12:59, 2 October 2013 (UTC)

Rapid eye movement sleep mentions norepinephrine, serotonin and histamine. Whether these are the ones meant in the dream article, I don't know Ssscienccce (talk) 13:45, 2 October 2013 (UTC)

Yes, all of those are suppressed during REM sleep, but norepinephrine is the one for which there is strong evidence that it is involved in converting short-term memory traces to long-term traces. There is quite a large literature on this topic -- see for example http://www.molecularbrain.com/content/3/1/15. Looie496 (talk) 15:00, 2 October 2013 (UTC)

Ok, thanks. 82.44.76.14 (talk) 18:21, 2 October 2013 (UTC)

How much alcoholic content is in church wine in Orthodox churches?

In Orthodox churches, it is known that little baptized infants take communion. Although they may not take in solid food, they may consume the "blood of Christ". How much alcoholic content does the "blood of Christ" have? 164.107.102.255 (talk) 17:19, 2 October 2013 (UTC)

Here is the contact page for a winery that produces wines for Orthodox religious services. You could ask them what the alcohol content of their wine is. However, Orthodox religious practice calls for chalice wine to be cut with hot water, so the alcohol content of the resulting mixture would be considerably lower than that of the wine in the bottle. Red Act (talk) 18:41, 2 October 2013 (UTC)

When I used to go to church (CofE) they used dark grape juice. --TrogWoolley (talk) 19:27, 2 October 2013 (UTC)

My CofE church used to have a Priest-in-charge who was a wine buff and provided some rather nice port for the purpose. Alansplodge (talk) 07:34, 4 October 2013 (UTC)

But the Church of England is part of the Anglican communion, which is a totally different branch of Christianity from Orthodox churches, which is what the question is asking about. The composition of sacramental wine differs widely between the various branches of Christianity that use sacramental wine. Even the OP's specification of "Orthodox churches" is rather vague; I presume "Orthodox churches" refers to Eastern Orthodox churches, not one of the Oriental Orthodox churches. However, the Eastern Orthodox churches are comprised of 14 or 15 autonomous subbranches, some of which are comprised of sub-sub-branches (see Eastern Orthodox Church#Eastern Orthodox churches in communion, so I'd be very hesitant to assume that all of those churches use the same practices pertaining to their sacramental wine. Red Act (talk) 21:34, 2 October 2013 (UTC)

The wine given weekly where I was baptized under the Eastern Rite was real wine, but I don't know if it was cut. I suspect it was, since Roman Catholic wine is not supposed to be full strength. We have a few Russians here, someone should be along shortly. μηδείς (talk) 00:35, 3 October 2013 (UTC)

The phrase Eastern Rite has a half dozen different meanings. Since you also use the term Roman Catholic, I presume you're referring to one of the 20 or so Eastern Catholic Churches, and using the term Roman Catholic in its broader sense of all the churches that are subject to the pope, as opposed to its narrower sense of referring to the Latin Church in distinction from the Eastern Catholic churches? It's unclear to me that the Eastern Orthodox churches' practices as to sacramental wine would be any more similar to that of the Eastern Catholic churches than to that of the Church of England. Both splits involved were long ago; the East–West Schism began in 1054, whereas the Church of England split from the Catholic Church in the mid-1500's. Red Act (talk) 05:42, 3 October 2013 (UTC)

The Church to which I am referring was Eastern Orthodox until a schism before WWII at which time it became subject to the pope. The church has icons, a typical Russian altar, the Chrysostum mass is chanted, incense is used, communion is given in both species. Except for using the Gregorian calendar I am unaware of any changes. In any case, I can't say if the wine is diluted--just that it is indeed wine. μηδείς (talk) 17:56, 3 October 2013 (UTC)

Just to point out that the purpose of watering-down the Communion wine is to represent the water and blood that is reported to have flowed from Christ's side when it was pierced with a spear at the Crucifixion. Alansplodge (talk) 07:37, 4 October 2013 (UTC)

Hmmmm... there is a peculiar beauty to the symbolism that the Holy Grail, filled with commingled blood, sweat, urine, faeces, the dust and filth of the streets of Jerusalem, becomes the very symbol of purity; but I'm surprised to think that the Communion water would represent Christ's urine. But could there be another origin? Namely the Romans traditionally drank wine (or vinegar, which always confused me) mixed with water, and so this would presumably be authentic to how the Last Supper would have been done. Wnt (talk) 14:31, 4 October 2013 (UTC)

Who, other than you, has mentioned urine and faeces here? I think you may be seriously misunderstanding what Alan has said. AlexTiefling (talk) 15:05, 4 October 2013 (UTC)

Thank you Alex - this is mainstream Christianity not Arthurian Legend. I was talking about Saint John's Gospel, Chapter 19: "(v.33) But when they came to Jesus, and saw that he was dead already, they brake not his legs: (v.34) But one of the soldiers with a spear pierced his side, and forthwith came there out blood and water. (v.35) And he that saw it bare record, and his record is true: and he knoweth that he saith true, that ye might believe."

A reference for my assertion is Saint Thomas Aquinas: "Water ought to be mingled with the wine which is offered in this sacrament. First of all, on account of its institution: for it is believed with probability that our Lord instituted this sacrament in wine tempered with water according to the custom of that country: hence it is written (Proverbs 9:5): 'Drink the wine which I have mixed for you.' Secondly, because it harmonizes with the representation of our Lord's Passion: hence Pope Alexander I says (Ep. 1 ad omnes orth.): 'In the Lord's chalice neither wine only nor water only ought to be offered, but both mixed because we read that both flowed from His side in the Passion.'" [5] Alansplodge (talk) 19:57, 4 October 2013 (UTC)

Just to mention Aquinas dates to about 200 years after the East-West schism, not that he can't be referring to an older common tradition here. μηδείς (talk) 20:01, 4 October 2013 (UTC)

Quite right, but he quotes Alexander I who predates the Great Schism by more than almost a thousand years. Alansplodge (talk) 20:05, 4 October 2013 (UTC)

Pretty smart guy. μηδείς (talk) 20:09, 4 October 2013 (UTC)

Pope Alexander or me? Alansplodge (talk) 00:48, 5 October 2013 (UTC)

The intended ambiguity was between yourself and Aquinas, actually. μηδείς (talk) 01:42, 5 October 2013 (UTC)

I'll take that as a compliment. Thank you. Alansplodge (talk) 07:41, 5 October 2013 (UTC)

Yes, I find subtle ones are better. μηδείς (talk) 04:51, 7 October 2013 (UTC)

I had assumed it was a similar usage to "make water", but looking into this, it seems like there is more of a range of opinion than I thought, with some sources identifying the "water" as ascites. ([6] includes some references) It would not be out of the range of possible intent, though, since the whole purpose of the crucifixion process was to attempt to inflict humiliation. Wnt (talk) 23:27, 4 October 2013 (UTC)

Do any ancient Egyptian drugs cause amnesia?

The odyssey describes a potion of Egyptian nepenthe being drunk by Helen of Troy/Sparta and causing her to forget any sorrowful memories. What ancient Egyptian substance, if any could have such an effect? — Preceding unsigned comment added by CensoredScribe (talk • contribs) 17:39, 2 October 2013 (UTC)

According to this abstract in PubMed, nepenthe can't be identified with any well-known substance known to actually exist in ancient Egypt that would cause drug-induced amnesia. Red Act (talk) 18:14, 2 October 2013 (UTC)

However, there is a number of plants in the Mediterranean region that have known psychoactive effects. For example: Peganum harmala, Acacia (and List of Acacia species known to contain psychoactive alkaloids), Ephedra, and so on. --Dr Dima (talk) 18:37, 2 October 2013 (UTC)

The article Nepenthe cites the actual snippet of text from the Odyssey. Note that the text calls this drug a "pharmikon" that "chases away sorrow" (nepenthes) i.e. the term is a description, not a name of a drug. It is a very vague description compared to, say, the very exact description of the flower used by Medea to make men invulnerable to pain. I have to think, therefore, that Homer, or at least his intended audience, had no knowledge of a drug that would cause this effect. Nonetheless, it apparently came from Polydamna, wife of a "Lord Thōn", and it is conceivable that further historical research (say, to find out what crops he grew and traded on the Mediterranean market) might tell something of the secret. As antidepressants were certainly possible, I would suspect that the story is true (though likely exaggerated or distorted), even if one scientific study failed to identify it. Wnt (talk) 19:57, 2 October 2013 (UTC)

As a description of opium that's not too bad. It doesn't exactly take away sorrowful memories, but it takes away their sorrowfulness. Looie496 (talk) 03:07, 3 October 2013 (UTC)

Well, the source Red Act posted didn't think so... I should point out also that opium was so widely used, even in the ancient world, that I'd have expected it to be recognizable - it was used for at least as long before Homer as it has been after him. Wnt (talk) 08:16, 3 October 2013 (UTC)

redox buffer? Acids and bases have buffers, why not oxidizing and reducing agents?

I was reading wikipedia article on oxidation and it said out there were parallels between acid-base reactions and oxidation-reduction reactions. So I'm wondering if there's a parallel to buffer solutions for redox reactions. Thanks.-Rich Peterson76.218.104.120 (talk) 19:42, 2 October 2013 (UTC)

See Mineral redox buffer. 24.23.196.85 (talk) 23:30, 2 October 2013 (UTC)

thanks, just what i needed!76.218.104.120 (talk) 07:59, 4 October 2013 (UTC)

Interesting question. I found one formulation for an aqueous redox buffer: 150 mM Tris-HCl pH 8.0, 1 mM EDTA, 10 mM reduced glutathione, 1 mM oxidised glutathione.[7] In this the glutathione is the key ingredient, and indeed it has this role in the cell -- but I don't usually see it described as a redox buffer, but merely as an "antioxidant", just as the article says. But on consideration it definitely exists in two forms in equilibrium and so is fulfilling the buffer role. Wnt (talk) 14:22, 4 October 2013 (UTC)

thanks, that's good,too.76.218.104.120 (talk) 21:36, 6 October 2013 (UTC)

parallel and series cct

hello, i am struggling in determining the total resistance for this circuit -> here the way i see it is Rt= R1 + R2 // R3 + R4 // R5 but i dont think its correct.205.211.50.163 (talk) 19:45, 2 October 2013 (UTC)

You started off correctly with R1 + R2, but you need to calculate the combined resistance of (R3 + R4) in parallel with R5 using the resistors in parallel formula, then add this result to get the total. See Resistor#Parallel Dbfirs 20:19, 2 October 2013 (UTC)

It's R1+R2+((R3+R4)//R5); Best do it in separate steps: You can replace R1 and R2 with one resistor value R1+R2 , same with R3 and R4, gives R3+R4; then you have two resistors in parallel, R3+R4 and R5, you replace those with the equivalent value (R3+R4)*R5/(R3+R4+R5), and that resistor is in series with R1+R2 so you take the sum which is R1+R2+ (R3+R4)*R5/(R3+R4+R5) Ssscienccce (talk) 20:28, 2 October 2013 (UTC)

The rules are

• If two devices (or parts of a circuit) are connected at both ends, they are in parallel
• If two devices (or parts of a circuit) are connected at one end and there's nothing else connected at the junction, they are in series

Dauto (talk) 23:10, 2 October 2013 (UTC)

Ancestor of human races

Do the human races today have a common ancestor from which the different races evolved? What is the genetic distance between the races, and does that show how long ago did the races diverge. Thank you. — Preceding unsigned comment added by 70.49.46.223 (talk) 23:52, 2 October 2013 (UTC)

Distance between races is not a meaningful figure, so far as I am aware. Most out-of-Africa hypotheses posit the extra-African humans leaving Africa around 75,000 in one wave, which gives an earliest date for their divergence. See Y-chromosome Adam for an estimate of the earliest divergence of modern humans as a whole--the actual date will be more recent if one is looking at races. μηδείς (talk) 00:29, 3 October 2013 (UTC)

Of note, genetics supports the out-of-Africa hypothesis in the sense that, genetically speaking, all non-African populations show a MUCH smaller range of genetic diversity than African populations do. Or to put it yet another way: a Russian and an Aztec would have a closer genetic relationship than two black Africans from different parts of Africa would. That's part of the reason why the concept of "race" has so little genetic or scientific basis: it's a cultural categorization based on superficial characteristics (skin and hair color, eye shape, etc.) and not on actual genetics or ancestry. --Jayron32 01:53, 3 October 2013 (UTC)

"Human races" is a concept with no precise biological definition. See Race (human classification). For this reason, there is no meaningful answer to your question. All humans living today have many common ancestors, one of which is the most recent common ancestor. At no time has there been a single couple from which all humans descended, see also previous thread. If you look at individual genes or chromosomal regions which are inherited as a group, you have the Mitochondrial Eve, whose mitochondria were the most recent ancestors of all human mitochondria living today, and the Y-chromosomal Adam, from whom all Y-chromosomes found in men today descend. Neither the mitochondial Eve nor the Y-chromosomal Adam were alone (nor contemporary), many of their contemporaries were also ancestors of all humans living today. The mitochondrial Eve was the maternal grand-grand-grand....-grandmother of all humans living today, i.e. everyone living today has an unbroken chain of maternal ancestors, that all converge in the mitochondrial eve. Analogously, the Y-chromosomal Adam was our paternal grand-grand-grand....-grandfather. Both lived much longer ago than our most recent ancestor. If you look at the ancestry of individual genes, say the HLA-DQ beta genes of all humans living today, the carrier of their most recent ancestor may not have been human at all, but an ape-like creature (se previous thread). --NorwegianBlue ^talk 09:01, 3 October 2013 (UTC)

The question is answerable however you define human races, assuming the out of africa, and not the multiregional hypothesis of human origins is true. Current models look at a paraphyletic "black" group in Africa, a first wave outside Africa following the Indian Ocean coast to Australia, "Caucasian" and "Oriental" waves moving north out of West and East Asia, and the Amerinds moving out of the Baikal region into the Americas. Whether that model is fully accurate or not, the extra-African branches can be dated to about 75,000 BC and the infra-African branches timed to correspond with the advent of anatomically modern humans. μηδείς (talk) 18:53, 5 October 2013 (UTC)