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August 6

Which human ancestors invented fire?

In the course of evolutionary history ,Which human ancestors invented fire?

AmRit GhiMire 'Ranjit' (talk) 00:26, 6 August 2013 (UTC)

Probably Homo erectus: see Control of fire by early humans. AndyTheGrump (talk) 00:30, 6 August 2013 (UTC)

And that would be "discovered how to use fire", not "invented". StuRat (talk) 00:39, 6 August 2013 (UTC)

Roasting, stewing, frying, and baking of food with fire could be considered "inventions," since at the time they were new and useful processes, resulting from happy accidents, or from observation and experimentation. Edison (talk) 14:47, 6 August 2013 (UTC)

There is also a distinction between those who used fire that they found in their environment (from forest fires, lightning, volcanoes, whatever) and those who created the means to make it from scratch. The latter would definitely be an "invention"...and I think that this is what we should probably be discussing here. SteveBaker (talk) 16:25, 6 August 2013 (UTC)

Type of solid

What is the term for a covalent network solid that melts by ionising? For example, -ABABA- → AB⁺ + ABA^-. Plasmic Physics (talk) 04:48, 6 August 2013 (UTC)

Generally, covalent network solids (like diamond, silicon, Bakelite, etc.) melt WITHOUT ionizing. Can you give an example of a covalent solid that ionizes as it melts? 24.23.196.85 (talk) 04:56, 6 August 2013 (UTC)

I'm certain that some of the hyperfluorinated metals exhibits this sort of behavior, though I can't seem to find a good example at the moment. Plasmic Physics (talk) 05:03, 6 August 2013 (UTC)

Metal fluorides are ionic solids, not covalent. 24.23.196.85 (talk) 05:42, 6 August 2013 (UTC)

Not generally, that is an over-simplification taught in secondary schools, just like "the conjugate of a weak base, is a strong acid" which is not strictly true either. See aluminium fluoride for an example of a covalent metal fluoride. Plasmic Physics (talk) 05:51, 6 August 2013 (UTC)

Correct, but AlF₃ breaks up into neutral molecules upon melting, not into ions. 24.23.196.85 (talk) 07:44, 6 August 2013 (UTC)

Indeed. However, I did not give it as an example of the substance in question, but only of a non-ionic metal fluoride. Plasmic Physics (talk) 08:36, 6 August 2013 (UTC)

Do any of the transition metal hexafluorides qualify? And ReF₇? Double sharp (talk) 07:45, 7 August 2013 (UTC)

None of the ones list on WP, or rhenium heptafluoride are covalent networks. Plasmic Physics (talk) 08:04, 7 August 2013 (UTC)

Struck out my question above Brain was not retrieving information properly – oops! Double sharp (talk) 08:43, 7 August 2013 (UTC)

Some sort of homoassociation of the parts? DMacks (talk) 05:56, 6 August 2013 (UTC)

Perhaps. Would it be a two step process, whereby the solid breaks into individual monomeric molecules, followed by their homoassociation? Plasmic Physics (talk) 07:05, 6 August 2013 (UTC)

It will be the other way around -- the solid will first break into neutral molecules, which may then self-ionize (but only to a small extent). 24.23.196.85 (talk) 01:41, 7 August 2013 (UTC)

No offense, but I'm certain that that is the same order as what I used. Plasmic Physics (talk) 02:18, 7 August 2013 (UTC)

Is solid oxonium hydroxide stable under pressure, or does it require an applied electric field? I wonder how the density would be different from ice. Plasmic Physics (talk) 07:14, 6 August 2013 (UTC)

Do you mean hydronium hydroxide (also known as dihydrogen monoxide)? If so, it is stable under pressure, but experiences melting point depression and requires supercooling to remain in solid form (it will melt under pressure otherwise). As for the density, it's the same as that of ice -- for obvious reasons! 24.23.196.85 (talk) 01:32, 7 August 2013 (UTC)

No, I'm not using a pseudonym (yes, pseudo-, not syno-) for molecular water. I'm talking about a legitimate salt of composed of discrete ions. Plasmic Physics (talk) 02:18, 7 August 2013 (UTC)

I ask because I know that an equilibrium shift can occur as a consequence of a change in pressure, I also know that this is only applicable to gases, as solids and liquids are incompressible. However, I also know that that last bit is only true for relatively small changes in pressure. Solids and liquids can actually compress under MPa pressures and higher. So, I wondered if MPa or greater pressures, could indeed shift the K_w away from water. Plasmic Physics (talk) 02:27, 7 August 2013 (UTC)

If you're looking for a solid composed entirely of H₃O⁺ and OH^- ions, you won't find it anywhere -- such a solid cannot exist because of energy considerations. Only in a plasma can water be completely ionized! 24.23.196.85 (talk) 04:11, 7 August 2013 (UTC)

I care to know what these energy considerations are - Gibbs, entropy, enthalpy, etc. (FYI I thought that the water decomposes into the elements before becoming a gas plasma.) Plasmic Physics (talk) 04:18, 7 August 2013 (UTC)

In lay terms, it takes so much energy to ionize the water molecules and separate the resulting ion pairs that the water (ice) will vaporize first regardless of applied pressure. I thought you, of all people, would know this? 24.23.196.85 (talk) 02:20, 10 August 2013 (UTC)

American plague

European diseases killed many native americans, why did not american diseases kill the europeans? — Preceding unsigned comment added by 128.214.48.186 (talk) 09:59, 6 August 2013 (UTC)

The Straight Dope tacked this thoroughly. 184.147.136.32 (talk) 11:28, 6 August 2013 (UTC)

This was discussed a couple of weeks ago - see Wikipedia:Reference desk/Archives/Science/2013 July 13#Natives. Clarityfiend (talk) 13:16, 6 August 2013 (UTC)

European diseases may not be the whole story. Count Iblis (talk) 13:49, 6 August 2013 (UTC)

In the Jamestown colony, most of the settlers died their first year. Lack of food was a cause, but they also died from malaria, dysentery and "fevers." The local germs may have been strains they had not encountered back in Britain. The river water may have been nasty, but so were many rivers in England. The local natives were likely not only living in healthier locations, but probably had more natural resistance to the local pathogens. Edison (talk) 14:39, 6 August 2013 (UTC)

Jared Diamond wrote perhaps the definitive work on this exact subject (at least as far as material that is accessible to a wide audience), if you're looking to understand the subject in detail. I recommend the book in any event as a must-read, but here's the long and the short of it - animal domestication. Most infectious diseases pass into the human population for the first time as a result of zoonosis and as Eurasians had been living in close proximity with their domesticated species for many thousands of years by the point of time in question, they had built a healthy collection of diseases, but also had steadily built immunities to the same, limiting their virulence. Native Americans, by comparison, had only a handful of domesticated species (only a very small portion of all species on the planet possess a social nature and other features which make them good candidates for steady and lasting domestication through the methods that are available to a non-technologically advanced people), which were not very well dispersed geographically and as such had not developed nearly as extensive a collection of diseases/immunities. Unfortunately for these peoples, they also lacked the immunities necessary to protect them against the diseases brought with Europeans, and even the pathogens that had relatively mild effects on their Eurasian hosts of this era could in some cases prove deadly to their new American hosts, to say nothing of a disease like small pox, which spread well in advance of the Europeans themselves. Snow (talk) 00:27, 7 August 2013 (UTC)

Another factor was that indigenous Americans, having had little experience with deadly epidemics, did not have cultural coping techniques like quarantine. They learned, to be sure, and survival rates went up when practices like quarantine were enforced. But at first the natural reaction was exactly the kind of thing that exacerbates epidemics. This is beside the point of why did not "american diseases kill the europeans?" Folks like Jared Diamond have tackled that quite well. Pfly (talk) 10:37, 8 August 2013 (UTC)

DNA questions

1. How many codons are there in a base pair?
2. What is the size in megabytes of the human genome?

--Czech is Cyrillized (talk) 23:46, 6 August 2013 (UTC)

One codon equals three base pairs, so there is 1/3 of a codon per base pair. Estimates of the number of base pairs in the human genome vary a bit due to technical reasons, but the most recent value I've seen is around 6.3 billion (in women, with two X chromosomes rather than an X and a Y). Since each base pair contains two bits of information, that yields slightly under 1.6 GB of information. Looie496 (talk) 00:11, 7 August 2013 (UTC)

You can download each chromosome (or those for any of 50 or 60 other species) here. If you grab the "GBK" file, you can unzip it and watch a sea of A's, G's, C's and T's scroll by. I was able to download the full set within a minute or so...and with compression - the whole thing fits comfortably onto a double-sided CD-ROM. You don't even need a DVD, let alone a BluRay disk. It's kinda humbling actually.  :-) SteveBaker (talk) 02:36, 7 August 2013 (UTC)

Because of this compactness I've always thought of the human genome as a good demonstration of the power of procedural generation (yes, I realise that the analogy isn't exact). Equisetum (talk | contributions) 19:12, 8 August 2013 (UTC)

August 7

Creating a Faraday cage without matter.

Greetings!

I've been studying the concept of Faraday cages and how they contain energies from certain frequencies of the electromagnetic spectrum. I have a question, though, as to how this relates to the properties of visible light apropos human sight. To wit, certain materials—such as the acrylic used to make a woman's swimsuit—remain impermeable to wavelengths longer than 400 nanometers, even when wet. (Otherwise, why would she even wear it?)

I clearly understand the concept as it relates to matter. Nevertheless, I cannot help but wonder: Could one achieve a similar effect with energy, or some other immaterial substance? Namely, is there any method known to science that can create an immaterial, two-dimensional barrier though which Gamma Rays, X-Rays, and Ultra Violet can pass, but not Visible Light (or, for that matter, Infrared, Microwaves, or Radio)?

If so, how would somebody go about doing so, and what would the risks and implications (if any) would such a device entail? Thank you.Pine (talk) 03:47, 7 August 2013 (UTC)

Gravity perhaps? I'm visualizing an array of microsized blackholes in a vacuum. If the curvature of space-time can that be calibrated, it should allow only certain frequencies to pass. As for how to create such a device, I have no answer. Plasmic Physics (talk) 03:58, 7 August 2013 (UTC)

Pine, you seem confused about a couple of things. A faraday cage works by surrounding the protected area with electrical conduction paths (typically either wire mesh or conductive sheets). It works by forcing the electric field within to be such that no voltage can be measured or defined between any point on a object within, and any point on the inside of the shield. For any frequency not zero, subject to some practical limitations, faraday shields cancel out any external magnetic field because such fields will cause a circulating current in the faraday cage, which will set up another magnetic field equal and opposite.

Things that are not transparent, such as swimsuit cloth, are NOT faraday cages. Such things work by attentuation - as the electromagnetic waves (light) penetrate into the material, the interact with the material molecules and are converted to heat. Another example of attenuation is the absorption of light in pure water. The greater the distance into the water, the dimmer the light gets. This has nothing to do with faraday cage operation - pure water does not conduct electricity.

All manner of substances are available that attenuate visible, light, xrays etc. For xrays metals are commonly used. Lead is very effective. In medical xray rooms, good thick concrete walls are used to protect the operators.

What do you mean by "immaterial"? If you mean blocking radiation by use of more radiation, it cannot work, as energy can neither be created nor destroyed - only converted from one form to another - as in the converstion of light or radio waves into heat. Such conversion requires the use of physical matter. Faraday cages are by definition made of matter, which supplies the electrically conductive paths. If you mean "force fields" a la Star Trek, that's just science fiction nonsense.

1.122.160.132 (talk) 04:18, 7 August 2013 (UTC)

I noticed those confusions as well, however, I ignored the bulk of the query and only focused on the question actual at the very end. With regards to 'immaterial', I think that the OP is referring to 'not of matter'. Plasmic Physics (talk) 04:23, 7 August 2013 (UTC)

You're right, I am confused.

Somebody told me that the protective mesh on the door of a microwave oven acts as a Faraday cage allowing visible light (400 nm to 700 nm) to pass through, but not the microwaves themselves (12 cm, or so). i.e. One can see his food being cooked, without himself being cooked in the process.

Yes, by 'immaterial,' I mean something not of matter that would produce a similar effect, but would also block out the visible spectrum.

Does this violate the laws of thermodynamics? Or can it theoretically happen? Pine (talk) 04:35, 7 August 2013 (UTC)

No, nor really. If you take my above gravitational solution into account, you can deflect or absorb the unwanted frequencies. When microsized blackholes evaporate, they release only x-rays and γ-rays. Plasmic Physics (talk) 05:22, 7 August 2013 (UTC)

No reason to continue this discussion, Keit/Ratbone etc is a banned editor per WP:RESTRICT Nil Einne (talk) 08:38, 9 August 2013 (UTC)
The following discussion has been closed. Please do not modify it.
While one could argue about semantics, it is correct to say that the mesh in the door of a microwave oven acts as a sort of faraday shield in reverse, working with the magnetically doped door seal (positioned within just the right dimensioned metal parts) and the inner metal surface of the oven to keep the microwaves safely inside. (A true faraday shield is an enclosing electrically conductive surface that keeps outside energy getting inside.) The mesh is a good electrical conductor, and the microwaves set up circulating currents in it, causing the microwave enegery impinging on the mesh to be reflected back into the oven. The key to understanding this is that the microwave energy is reflected back in, not converted into heat as it passes through. To eliminate radiated energy from a given region without the use of matter to do the conversion or reflection is not possible. It would indeed violate an important thermodynamic principle: As I said above, energy can neither be created nor destroyed, but only converted from one form to another - the so called First Law of Thermodynamics. 1.122.207.51 (talk) 06:05, 7 August 2013 (UTC) Blackholes do not destroy energy, so no it does not. Plasmic Physics (talk) 07:21, 7 August 2013 (UTC)

KDKA's weakened radio signal

When my father was a child, he says KDKA (AM) was audible throughout the Eastern United States at night. The article Greg Brown (broadcaster) agrees it was audible ~175 miles away. Finally, I can confirm it too: as recently as 2004, I picked it up clearly in South Carolina.

But it is no more! Even in different parts of Central Pennsylvania, I can no longer hear it. Not even a small flicker even fades in. And it can't hold a candle up to the easily audible WBZ (AM) and KYW (AM).

What happened? I can't find anything written about a signal reduction. Magog the Ogre (t • c) 04:53, 7 August 2013 (UTC)

All three staions have similar frequency and power output, so in general, coverage should be about the same. What is your location now? Perhaps you are closer to WBZ than you are to KDKA.

In general though, AM distance reception is not what it was in earlier decades. The technology of modern solid state receivers with synthesised or digital tuning results in poor intermodulation performance - this results is weak signals being overiden by what appears to be white noise. Transistor radios made up to the 1980's and tuning with variable capacitors can be a lot better in this regard. Well designed tube radios better again. As well as that, with the increased use of electrical appliances of all kinds, there is more noise to drown weak signals out nowadays.

Local geology can affect reception. AM travels well over water and can be affected by monazite etc. HV powerlines also affect it.

Lastly, an anecdote: I once worked in a similar 50 kW AM "clear channel" station. Over a few years, more and more complaints arrived from distant (300 to 700 km) listeners that our signal was dropping. Eventually we realised that some villain was sneaking in to the unattended transmitter site and bit by bit digging up the copper earth mat and stealing it (a buried mesh of thick copper wire extending over several acres. As well as causing power loss in the ground, it altered the intended direction of radiation.

1.122.207.51 (talk) 06:23, 7 August 2013 (UTC)

I am in central Pennsylvania. I travel within parts of central Pennsylvania. Magog the Ogre (t • c) 05:05, 8 August 2013 (UTC)

Interesting. KDKA transmits from Alison Park, at the extreme western end of Pennsylvania. KYW transmitts from Lafayette Hill, at the extreme eastern end. WBZ transmitts from Hull in Mssachusets, much futher from you than either KDKA or KYW. However KYW has a directional antenna. I was unable to find out on the web the preferred direction, but westerly would seem likely. So all three should be equally good or equally bad for you. Perhaps you could email the station engineers for their view. If you use the form provided under "Contact" in KDKA's website, be sure to put in the first line "For Station Engineer" - you'll get a good answer then, and not one from some PR or sales person.1.122.190.3 (talk) 09:14, 8 August 2013 (UTC)

In the United States, we can get such information from the FCC, including their extensive collection of online databases. For example, you can use the online AM Broadcast Station database to find data and diagrams, including antenna radiation pattern for the KYW licensee (and even a graphical plot plus detailed information about both antenna masts). Nimur (talk) 17:15, 8 August 2013 (UTC)

Melting and boiling points of the heavy alkali metals

Caesium has melting point 28.44 °C; francium has melting point ~27 °C; ununennium is predicted (see the article's infobox) to have a melting point of 22–24 °C. Why are they so close to each other? (The lighter alkali metals have a more normal trend.) Can anyone offer a (relativistic) explanation?

The boiling points also behave similarly: Cs 671 °C, Fr predicted to be 677 °C(!), Uue predicted to be 655–669 °C.

(A lessened effect seems to occur in group 2; Ubn may at the high extreme have a melting point higher than Ba and Ra (why?), but everything else conforms to normal periodic trends.)

Standard Double sharp disclaimer: Please give sources if possible, because I want to include this into an article (in this case, alkali metal). Double sharp (talk) 07:43, 7 August 2013 (UTC)

The 1978 Bonchev full-text (cited as the source for the data in the ununennium infobox) is available here (note Table 1 and figures 6 and 7). The properties of Cs and Fr are quite similar to each other, and the predicted properties of Uue are extrapolated based on a variety of parameters derived from empirical data, which are periodic. They are not based on first principles/relativistic considerations. -- Scray (talk) 22:29, 7 August 2013 (UTC)

Interesting. And yet Fricke (1971) [1], which is relativistic (I think), also gives a melting point of 0–30 °C and a boiling point of 630 °C for Uue. The lower value of 0 °C is all right, but is there any mechanism that would give the higher value of 30 °C? Double sharp (talk) 11:38, 8 August 2013 (UTC)

Note that the francium value is certainly theoretical rather than empirical, because a macroscopic amount of francium has never been collected in one place, and if you did, it would give off so much heat from radioactive decay that it would essentially instantly explode, with the radiation killing anyone nearby. So even the meaning of a melting point for francium is a bit obscure. I suppose it means something like "if by pure chance, one chance in $10^{10^{\textrm {largevalue}}}$, it so happened that not too many francium atoms in your sample decayed in the interval of observation, but the laws of probability worked otherwise as expected except for that, this is the melting point you'd see". --Trovatore (talk) 21:38, 8 August 2013 (UTC)

Why has no one ever tried to deposit a francium vapour onto a cooled surface to form a nanolayer, which is then slowly heated to test francium's melting point. Plasmic Physics (talk) 23:54, 8 August 2013 (UTC)

Well, I can't tell you for sure why (or even that) no one has ever tried that. But I can tell you that the largest amount of francium that our article mentions being collected in one place is 300,000 atoms, which works out to about 10^−16 grams. If you think you can measure the melting point of that, even in a monolayer, go ahead and write a grant proposal. How much can you learn about the melting point of a 3D material from a monolayer, which is effectively 2D? Doesn't strike me as the same thing. --Trovatore (talk) 00:16, 9 August 2013 (UTC)

OK. FYI: nano- and mono- are not the same thing, a nanolayer can consist of any number of layers with a cumulative thickness of less than a micron. Plasmic Physics (talk) 00:20, 9 August 2013 (UTC)

I think you're vastly underestimating the difficulty of assembling and manipulating a macroscopic quantity of francium—even a microscopic macroscopic quantity. The largest quantity ever collected has been about 300,000 atoms, and that only in the vapor phase. If you made a solid cube out of it, it would be less than 70 atoms on a side–and it would be vigorously heated by more than 2000 radioactive decay events every second. And even if you were able to measure a melting point using such a small quantity of material, it wouldn't be 'correct' anyway. Melting points are depressed sometimes by very significant amounts when you deal with very small particles; see melting-point depression. Essentially, the unusual or quirky behavior of the atoms at the surface or edges dominate the 'bulk' material behavior that you're trying to measure, resulting in a very sensitively size-dependent melting temperature. TenOfAllTrades(talk) 00:21, 9 August 2013 (UTC)

That is why I suggested a nanolayer and not a nanodot. Is it not possible to use the depressed melting point data to improve current estimates of the bulk melting point? Plasmic Physics (talk) 00:44, 9 August 2013 (UTC)

You'd have to correct for self-heating from the radiation. (In fact this is probably part of the reason why the Fr melting point is so close to the Cs melting point). I've seen a value of 23 °C given for Fr before; presumably some corrections were applied to the value after the experiment there. (Is the 27 °C value even experimental? The very fact that it is so close to the Cs value suggests to me that it is.) Double sharp (talk) 06:55, 9 August 2013 (UTC)

Relative motion..

A driver was sent to traffic court for speeding. The evidence against the driver was that a policeman observed the driver's car alongside a second car at a certain moment, and the policeman had already clocked the second car as going faster than the speed limit. The driver argued, "The second car was passing me. I was not speeding." The judge ruled against driver because, in the judge's words, "If two car were side by side, you were both speeding." In this case, how to argue the case in term of physics in the favour of accused driver?

AmRit GhiMire 'Ranjit' (talk) 14:15, 7 August 2013 (UTC)

This sounds like a homework question aimed at testing your understanding of concepts and the articulation thereof, and unwarranted deductions based on flawed interpretation of wording. On the other hand, my experience of the legal system makes this kind of abuse of logic (often deliberate on the part of the practitioners manipulating the outcome, being protected by the shear weightiness of the process of fighting it) pretty standard in the application of "justice". — Quondum 14:24, 7 August 2013 (UTC)

As stated, the judges' decision is clearly wrong. You could be parked, stationary with another car passing you at the instant the policeman observed you. Your statement of the story is that the policeman observed the action "at a certain moment"...ie, over a period of zero elapsed time. Since the measurement of speed requires knowing the distance travelled over time, (even if it's distance travelled relative to another car) - having a zero-time snapshot tells you nothing whatever. If that were literally true then he has no clue how fast you were moving.

But if this is what the claim hinges on then it's a ridiculously fabricated situation - nobody could see an event like this in a literal instant.

In reality - a policeman doesn't get an instant, zero-millisecond snapshot picture of the event. He'd easily be able to tell whether the two cars were or were not going at the same speed from a one or two second glance...and if we trust his testimony then both drivers were indeed speeding and the judge made the right call. If we don't trust the police officer's testimony then all bets are off and we have no way to know whether the accused was speeding or not.

The only other possible inference (and one that this contrived story may be trying to elicit from you) is that the two cars might have been driving around a tight bend in the road - with the accused driver on the inside of the curve and the speeding car on the outside. Both cars could then remain side-by-side with the car on the outside of the curve traversing a longer distance than the one on the inside. Thus the outside car could be exceeding the speed limit while the inside car was not.

But that's one hell of a stretch. In any practical situation, the difference in speed would have to be tiny - probably less than the threshold of error that the police would allow for in using a speed gun. I don't buy it - if that's it, then in any practical situation, the driver is guilty as hell!

SteveBaker (talk) 16:58, 7 August 2013 (UTC)

If I were the driver's lawyer, I would argue that the policeman's account of the relative speed of the two cars is not reliable, because his attention was focused on the first car. I would also look for anything in the law that required a radar speed record, and if there were such, I would argue that, even if the policeman's account is reliable, it is not codified in the law that the policeman is allowed to make inferences (even valid ones) from the speed of one car and its relative speed to another car. That's not really an answer to a science question, but it might be an answer to the original question in some other context. --Trovatore (talk) 21:50, 8 August 2013 (UTC)

Why no industrial scale production of human breast milk using transgenetic cows?

More than 25 years ago I thought that by now we would be living in a World where genetic modification of animals would have led to many applications. While you could expect that some predictions would turn out too difficult to realize, (e.g. genetically engineered pigs to grow human organs has faced problems due to retrovirusses), it's rather strange that almost nothing has changed in the food industry. So, what is preventing us to make progress with genetic modification of animals? Count Iblis (talk) 19:42, 7 August 2013 (UTC)

How do you propose getting human milk from a cow? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:04, 7 August 2013 (UTC)

It's difficult enough convincing the population that tiny modifications in the genes of cereals are safe to eat, so can you imagine the reaction of mothers asked to feed their babies milk from cows with human udders? Research is continuing, but slowly. Dbfirs 21:18, 7 August 2013 (UTC)

It's not so much the udder, it's human nutrients in human milk which are alleged to be better for baby than cow's milk is, provided the mother is producing adequate and good milk, which not every woman can. So it would require engineering cows to alter the chemistry of their milk to simulate human milk. Given that some of the benefit of human milk is alleged to be the ingestion of antibodies which the mother has in her system, it would be a very tall order to make a cow produce that. They would be better off focusing on what the negatives are with cows' milk, and trying to fix that. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:58, 8 August 2013 (UTC)

I believe (sorry, can't track down references right now) that I have also read about research showing that the mother's milk changes composition over time as the baby's needs change, and can react to things such as an infant's illness or stress as well. Obviously those are benefits an artificial milk will never produce, but I suppose it would still be a big step up from formula - many mothers pump and freeze milk because their schedules (or their baby) don't allow for a regular nursing schedule. But like Dbfirs points out, it will likely be a very long time till people accept cows with human genes. Human insulin is produced on a large scale by genetically modified bacteria, but our article on Humulin doesn't really make it clear if there are definitely human genes added to the bacteria. 209.131.76.183 (talk) 11:36, 8 August 2013 (UTC)

Researchers have worked on exactly this project, as of 2011. www.cbsnews.com/8301-504763_162-20071923-10391704.html I have limited internet access at work so I cannot provide more links, but googling 'cow human gene' and similar terms will be productive. 198.190.231.15 (talk) 13:42, 8 August 2013 (UTC)

• Our article on genetically modified organisms contains the following paragraph:

In 2011, Chinese scientists generated dairy cows genetically engineered with genes for human beings to produce milk that would be the same as human breast milk.[56] This could potentially benefit mothers who cannot produce breast milk but want their children to have breast milk rather than formula. Aside from milk production, the researchers claim these transgenic cows to be identical to regular cows.[57] Two months later scientists from Argentina presented Rosita, a transgenic cow incorporating two human genes, to produce milk with similar properties as human breast milk.[58] In 2012, researchers from New Zealand also developed a genetically engineered cow that produced allergy-free milk.

So clearly people are working on that sort of thing, but all the progress has been very recent. Looie496 (talk) 14:08, 8 August 2013 (UTC)

Note that these advances involve changing to human style lysozyme and lactoferrin and removing beta-lactoglobulin. They make the milk "more human-like" but by no means human. Basic parameters like the overall fat content are different. It is no easy task to change everything, hard even to tell if you've missed something. Also, I worry about putting human-style immune functions (the lysozyme and lactoferrin) into an otherwise bovine context - you might get infections that don't bother the cow, but adapt to defeat the human antibacterial measures, and do bother the humans. But that is IMHO. Wnt (talk) 15:02, 8 August 2013 (UTC)

Most abundant organic polymers

According to the respective articles, the #1 abundant organic polymer is cellulose and #2 is lignin (which apparently employs 30% of non-fossil organic carbon). Is there a longer list available (say, a top 10), particularly one with estimates for the global mass and the % of non-fossil organic carbon employed? List of most abundant organic polymers would be an interesting article... ManyQuestionsFewAnswers (talk) 22:27, 7 August 2013 (UTC)

There are chitin (fungi, protostomes) and keratin (vertebrates). You seem to be aiming for long-chain structural polymers. μηδείς (talk) 23:43, 7 August 2013 (UTC)

I suspect keratin is nowhere near as abundant given that vertebrates form a relatively small % of biomass, but I could be wrong. My not particularly well-informed guess would be that several hemicelluloses would be higher on the list. There are other polysaccharides (e.g. pectin), as well as polypeptides (presumably the most abundant being RuBisCO) and nucleic acids, which I suspect would rank lower. But I'd love to see some hard data. ManyQuestionsFewAnswers (talk) 01:27, 8 August 2013 (UTC)

August 8

Water-soluble material ?

Is there a water-soluble material which is not soluble in a solution of sodium hypochlorite (chlorine bleach) dissolved in methanol (alcohol) ? It can be only slightly water soluble, but can't be at all soluble in alcohol or bleach. If so, what is it/are they ? If not, why not ?

Also, mixing chlorine bleach with ammonia is dangerous, as it produces chlorine gas. Is there any such danger from mixing it with methanol, or any other dangers ? StuRat (talk) 06:39, 8 August 2013 (UTC)

Well chlorine + ethanol produces chloroform, heat and then chlorine gas once hot, so don't do this. Ammonia and chlorine can make chloramine or hydrazine, neither a good idea. I don't think that methanol and bleach are a good combo either! Graeme Bartlett (talk) 11:16, 8 August 2013 (UTC)

I see. Can bleach be safely diluted in anything else besides water ? StuRat (talk) 16:23, 8 August 2013 (UTC)

What's your goal here? Might be many possible solutions to "what you're trying to accomplish" other than as you've phrased it, and also your application may limit the solutions (ha!) that might answer your general question. DMacks (talk) 17:20, 8 August 2013 (UTC)

It's to solve a problem with using bleach in the washing machine. I like that it's inexpensive, whitens, and sterilizes clothes, but don't like that if it splashes on your clothes they are ruined and if it splashes in your eyes you are in serious trouble, and breathing it is bad for your lungs. So, my idea is to have a small quantity contained inside a water soluble wrapper, which then dissolves during agitation, eliminating any possibility of it splashing, and hopefully only creating bleach fumes after you are out of range. StuRat (talk) 04:54, 9 August 2013 (UTC)

Well you could have it as a solid powder, perhaps diluted with a harmless things like sodium sulfate. Then you could coat little balls of that in a slightly soluble coat of something. Splash should not be a problem, just when it dissolves it will be concentrated at first. Graeme Bartlett (talk) 11:58, 9 August 2013 (UTC)

NaOCl doesn't solidify well (at least not stably, safely, cheaply, and usefully:). But there are lots of other types of bleaches that do. Calcium hypochlorite is commonly used as a granular solid alternative to sodium-hypochlorite solutions, but takes a while to dissolve. I vaguely remember that it has different pH effects, but the swimming pools where I worked had such high bather loads and other environmental situations, we was hard to notice the OCl^– source difference as having other effects. There are also stabilized forms of NaOCl that are solid (pre-reacted with isocyanuric acid), and also other sources of the key ion (via chloramine-T)--lots of waste mass and probably not likely as economical. The idea you're proposing is akin to microencapsulation (probably easier to do QA and handle than a single portion of a liquid, maybe we could call that "macroencapsulation"?). There are already such products available (or at least patented and discussed if you google it). DMacks (talk) 15:37, 9 August 2013 (UTC)

Thanks. Sounds like calcium hypochlorite clumps might be the way to go. How much would be equivalent to a cup of bleach (6% sodium hypochlorite) ? And how long would it take to dissolve in the agitation of a washing machine ?StuRat (talk) 06:34, 10 August 2013 (UTC)

Cancer

Is cancer partly genetic as some families don't have many cancer sufferers compared to others? — Preceding unsigned comment added by Clover345 (talk • contribs) 09:35, 8 August 2013 (UTC)

Definitely, and many of the genes responsible have been identified, such as the BRCA mutation. Diet, exercise and environmental exposure to carcinogens are other major factors which affect cancer rates. StuRat (talk) 10:27, 8 August 2013 (UTC)

Do you have any source about exercise as a carcinogen factor? 79.156.170.130 (talk) 12:27, 8 August 2013 (UTC)

It is lack of exercise that is the factor: see Cancer#Diet and exercise. AndyTheGrump (talk) 12:34, 8 August 2013 (UTC)

LOL, yes, I would have thought that was obvious, but have appended to my original response to make it clear. StuRat (talk) 16:19, 8 August 2013 (UTC)

structure of element 171

See Fricke [2] (relativistic). It's probably a solid at STP, right? Seeing as I have so far failed to find any reliable sources on the possible structure, can someone give their predictions here (with thoroughly citable reasoning? – especially polyatomic vs. diatomic.) Thanks. Double sharp (talk) 11:40, 8 August 2013 (UTC)

It is impossible to answer, current theory predicts that it should not even exist. Due to the requirement of electrons to have a speed exceeding the speed of light. What you're asking is comparable to asking "If balloons were conscious beings, what would they say?" Are you sure that you're referring to unseptunium, or do you mean ununseptium? as that would change everything. Plasmic Physics (talk) 04:05, 9 August 2013 (UTC)

I do mean 171, but would not mind also receiving info about 117. Element 137 is not really a problem; if you take into account that the nucleus is not a point, then you only get problems at 173 (see Periodic table#Element with the highest possible atomic number). Even then the problems might not cause and end to the periodic table.

(Naturally, please assume there is some unknown metastable isotope, or else it's a rather pointless question) Double sharp (talk) 04:31, 9 August 2013 (UTC)

It is still difficult to predict, considering that we don't know how the periodic table is structured beyond the seventh period - the rate of change in trends with respect to period may contain an unknown point of inflexion. Plasmic Physics (talk) 05:40, 9 August 2013 (UTC)

The article says that 171⁻ should be a hard base like Cl⁻ and that 171 should have an electron affinity of 3.0 eV. Does that help in predicting? Double sharp (talk) 06:51, 9 August 2013 (UTC)

I that sounds highly dubious considering the decreasing stability of the halide ions with respect to the period. Astatine is already the more stable in the 1+ state than in 1- state. PS I can't open the link. Plasmic Physics (talk) 07:22, 9 August 2013 (UTC)

relativistic effect! np_1/2np_3/2 subshells are destabilized, but the 9th period fills 9s 9p_1/2 (1st two electrons of p) 8p_3/2 (last four electrons of p), which is apparently stabilized to the point that it behaves like the 2p or 3p subshell. (summarizing the rationale in the link for you) Double sharp (talk) 08:01, 9 August 2013 (UTC)

Ok, so the trend does an about face, like what I've mentioned at 05:40? In that case, it would depend on how strong that stabilising effect is. Plasmic Physics (talk) 10:18, 9 August 2013 (UTC)

I'm just pulling this out of a hat, but I predict that it will be a highly reactive, grey-coloured, monoatomic, volatile metal, in which the 3+ state is most stable followed by the 1- and 1+ states. Possibly forming a variety of coloured suboxides. Possibly having an electronegativity between that of sodium and lithium. Plasmic Physics (talk) 12:20, 9 August 2013 (UTC)

reading his description, would personally not call it a metal... Double sharp (talk) 12:55, 9 August 2013 (UTC)

Perhaps a weak metal like aluminium, or maybe a poor metal like thallium? Plasmic Physics (talk) 13:05, 9 August 2013 (UTC)

Yet if he's right and the trend does do an about face, then I have some difficulty seeing how M⁻ (M = metal) could be a base like Cl⁻...also he calls H(171) a hydrogen halide, which implies to me that it would be more like iodine (given the similar electronegativity). What would that imply? Double sharp (talk) 13:18, 9 August 2013 (UTC)

I reckon it would not be so dramatic, it would probably be between iodine and astatine (closer to astatine), possibly with a 70 degree Celsius melting point? Plasmic Physics (talk) 13:32, 9 August 2013 (UTC)

OK, and structure-wise? (iodine is only just diatomic, could this have a polyatomic structure? diatomic At could also be stabilized in solid form due to intralayer bonding just like I, so 171 could plausibly be diatomic, but I can see it not happening too!) Double sharp (talk) 06:27, 10 August 2013 (UTC)

also interested: electronegativity? band structure? packing efficiency? Goldhammer-Herzfeld criterion? (bcos I wanna see if it's going to be a metalloid or a nonmetal, although I suppose if he calls it a halogen then it's probably nonmetallic enough to be called a nonmetal like iodine or astatine) Double sharp (talk) 06:38, 10 August 2013 (UTC)

The social structure of ants, bees etc. and the evolutionary explanation to their sexual reproduction

Colonies of ants, bees etc. have a single individual (the queen) that procreates. Is there a name to this social structure? I guess it would be related (but not identical) to eusociality.

Also, these organisms have sexual reproduction, but I can't think of any evolutionary justification to it. As far as I understand the Red Queen hypothesis doesn't apply because the queen and the male that impregnates her are siblings. What's the explanation?

Thanks, 84.109.248.221 (talk) 11:57, 8 August 2013 (UTC)

See kin selection and evolution of eusociality. Also, you might find "Darwin's special difficulty: the evolution of “neuter insects” and current theory" interesting. Sean.hoyland - talk 12:05, 8 August 2013 (UTC)

When only a single queen is present, the colony is called monogynous, and when many fertile queens are present, the colony is polygynous. These habits do not clearly break along the pre-social to eusocial continuum, and some species have colonies of both types. Note that a queen is not usually inseminated by a sibling male. Many species (e.g. honeybees, fire ants, etc) have massive nuptial flights, where all the drones and virgin queens go out at once to play. The evolution of eusociality is an ongoing topic of research, but it is commonly agreed that Haplodiploidy has plaid a role in the social insects. However, haplodiploidy is not a necessary condition, as there are eusocial, monogynous mammals (naked mole rats), and haplodiploid solitary wasps. The classic text on all things social insect is The Insect Societies, by E. O. Wilson, [3], and I highly recommend it to any interested parties. SemanticMantis (talk) 13:30, 8 August 2013 (UTC)

Are all flames produced by fire?

Can flames be produced through any other source? Like when an atomic bomb goes off and you see the fireball, are those flames being produced through simple heating of the atmosphere via the nuclear products or is something actually burning (redox) that produces those flames? ScienceApe (talk) 15:16, 8 August 2013 (UTC)

Air can be heated to incandescence without a chemical combustion reaction. If you accept the definition of flame provided in the leader to our article, though, the word "flame" refers to that type of incandescent air related to fire (that is, ordinary chemical combustion). So, this is really just a question of how you want to use the word.

As far as I know, Atomic Fireballs are flavored with cinnamon, and have neither flame nor fire. Nimur (talk) 15:58, 8 August 2013 (UTC)

Though if you want to get pedantic, the cinnamon plant grew with much help from the Calvin cycle, which involves small heat-producing reactions. Also, unless advertising lies, many cinnamon candies cause smoke to emit from the ears and flames from the mouth. InedibleHulk (talk) 08:49, August 9, 2013 (UTC)

Incandescence by definition involves the emission of visible light. Heating air to incandescence? I don't think so. To emit light, a substance must be an effective black body radiator for light. All the gasses in air, Nitrogen, oxygen, argon, etc) are fully transparent. Flames from burning hydrocarbons emit visible light mostly because they contain carbon, which is one of the best black body radiators (not transparent) known. The fireball following atomic bomb detonation contains all manner of compounds from the earth thrown up by the blast, some set alight, some just heated enought to emit as black bodies without combustion. The explosion itself emits visible light directly. You can heat the gasses of air hot enough to ionise them (well above black body incandescence temperature), which will produce light, but then you no longer have air. It's a bit like saying let's heat water to incandescence. You won't have water any more longer before you get hot enough for ionisation. It will split into H2 and O2 longer before, and further into monoatomic hydrogen and oxygen at lower theperatures. And ionisation always involves emision at specific wavelengths, unlike black body radiation, which is essentially random noise (all wavelengths). 1.122.236.146 (talk) 16:20, 8 August 2013 (UTC)

1.122.236.146_(Geolocate), you're seriously suggesting that atmospheric air can not incandesce when heated, because it's transparent at room temperature? Although that's an interesting piece of thought-experiment science-fiction, it's totally false. Air - including nitrogen - incandesces when heated, and emits visible light whenever its temperature is high enough. You might want to re-read black-body radiation and incandescence. Nimur (talk) 16:30, 8 August 2013 (UTC)

Yeah - and if you doubt it - I guarantee that you've seen it with your own eyes. The air glows during a lightning strike. There are no other substances introduced into the path of the lightning bolt - so it must be the air that's glowing. Indeed the air forms a plasma with a core temperature around 50,000 K, causing it to glow with a blue-white color.

The problem with our OP's question is that the terms "Fire" and "Flame" are inextricably entangled and confused - and not very well defined in scientific terms. Is the sun "on fire"? Are there "flames" coming out of the surface? What about molten steel? Are electrical sparks a kind of flame?

Our dictionaries fail us at these times - so answering a question that's a bout mere words in a scientific manner is kinda silly. Put it this way - there are certainly ways in which gaseous and finely divided airborne particulate substances can be made to glow brightly in the absence of any vigorous oxidation processes. If the former is "flame" and the latter "fire" - then yes. SteveBaker (talk) 20:08, 8 August 2013 (UTC)

Nimur and Steve, you didn't read carefully what I wrote. You missed the distinction between incandescense and spectral emission. Gasses such as N2, O2, Ar, Co2, are fully transparent at ALL temperatures at which they can exist. The dissociated forms N, and O are also fully transparent at all temperatures for which they can exist. Re lighning strike emission, you said it yourself: Ionisation occurs - it is not N2, O2, and Ar etc when it glows. It's not even N and O. The emission from ionisation is spectral and not black body. This spectral emission is not from air, not black body, and not flame or fire. It's true that many terms in chemistry are not standardised and precise as terms in other sciences are. However, it is generally undertstood that flame is the visible gaseous part of a fire, caused by and exothermic reaction. My answer above works with this definition. See the Wikipedia article on flame, especially the first sentence, which Nimur was clearly aware off, even though he stated incorrectly that air can be heated to incandescence. Incandescence IS by definition that emission that is thermal radiation (noise) and is not spectral - you can check this yourself. Saying air can be heated to incandescence is much like saying aluminium can be heated to incandescence. You can certainly ionise Al and make it emit spectral lines, but you can't make it glow with heat like iron does. 1.122.175.140 (talk) 01:25, 9 August 2013 (UTC)

Adding heat is a method to ionize atoms in some materials. And whenever ionization happens, spectral emission might also happen. But those spectral emission lines superimpose on top of a blackbody emission curve. All materials emit thermal radiation; and the spectrum of thermal radiation is characterized as a blackbody spectrum. Hot materials - even "inert" substances like noble gases and non-reactive metals - emit visible light. Why do you believe that aluminum can't emit blackbody radiation in the visible spectrum? First of all, aluminum doesn't vaporize or ionize until it gets much hotter than necessary to emit visible light. And even still - supposing a different material does vaporize or ionize - those effects don't cancel out the blackbody emission. At best, ionization causes spectral emission lines that superimpose on top of the continuous thermal radiation spectrum. A good example is the solar spectrum: the sun, as a highly ionized plasma, emits light at visible and other wavelengths - and its spectrum contains discrete lines imposed on top of a continuous blackbody pattern. Nimur (talk) 04:00, 9 August 2013 (UTC)

No reason to continue this discussion, Keit/Ratbone etc is a banned editor per WP:RESTRICT Nil Einne (talk) 08:38, 9 August 2013 (UTC)
The following discussion has been closed. Please do not modify it.
Ok, let's take all your points, one by one, and examinine them in the context of ScienceApe's question, and in the context of my responses to you and Steve above. Adding heat is a method to ionise atoms: Yes, of course. 100% correct, and nothing I said is in contradiction to that. If you heat some air enough to ionise the atoms, you no longer have air. You have instead the component atoms in ionised form, with all manner of completely different properties. Whenever ionisation happens, spectral emission might also happen: No real problem here. Strictly speaking, it will happen, but some or all of the lines may not occur in the visible range, depending on the electron orbital structure. Spectral emision lines superimpose on black body emission: Yes, of course. Nothing I said is in contradiction to that either. All materials emit thermal radiation with a spectrum characterised as blackbody radiation. Strictly speaking, all materials DO emit black body radiation. However, and this where you've gone astray, the emission from any real substance is always less than the theoretical blackbody emission curve. Carbon is an example of a very good black body emitter. Over a wide range of temperatures, its emission vs wavelength curve approximates the theoretical black body curve very closely. Aluminium is an example of a not very good black body radiator. Its emission vs wavelength curve shows very markedly reduced output in the visible spectrum, and reduced emission at infrared. As any welder or foundry worker can tell you, you simply can't get aluminium to visibly glow by heating it. In contrast, iron, which is a good black body emittor at moderate temperatures and above, glows readily. This is important in both arc welding and oxy-acetylene welding. Note that aluminium melts at 933 K; steels at 1100 to 1500 K or so; visible black body light starts at around 800 depending on ambient lighting. So, according to you, when aluminium melts, it should be glowing. It certainly does not. Welders are taught how to assess the temperature of hot steel quite accurately by its emission colour (deep red thru to yellow at metal working temperatures). You just can't do this with aluminium - we use tricks like wiping it with a thin pine stick, wiping it with soap and noting how quick the soap turns bown, and the like. There is a "trick" for making any substance into a dramatically better black body radiator though - form it into a cavity radiator. This is a way to improve emissivity by increasing the colour density per unit area, and is often used as a simple temperature indicator in furnaces and kilns. Aluminium doesn't vaporise or ionise until it is much hotter than necessary for black body radition: Well, since it vaporises at ~ 2800 K, and visible radiation from an ideal black body starts as a dull red at around 800 K depending on masking of ambient lighting, that is on the face of it true. Trouble is, aluminium is NOT anywhere near an ideal black body radiator. It's not black, it's shiny and white. — Preceding unsigned comment added by 1.122.206.136 (talk) 08:16, 9 August 2013 (UTC) Vaporisation and ionisation do not cancel out (stop??) black body radiation: This has no impact on what I said before. It is sort of right. In practice, transparency and colour of a substance is often different in the gas form than in the liquid or solid form though. Where this is the case, efficiency as a black body radiator is affected, more so at certain wavelengths. The rest of your points are a re-iteration of the points I've gone through. You have it all pretty right, but you have assumed that all substances are perfect black body radiators. They are not. Real substances show overall emission less than 100% of the perfect back body, and real substances are good (not perfect) at some parts of the EM spectrum and poor at other parts. The black body emission curve is the limiting case that nothing real can exceed. Substances that are dark coloured and non transparent are good black body emittors in the visible spectrum. Conversely, substances that are fully transparent to the eye (and thus by definition are not coloured) are poor black body emittors in the visible spectrum. They may, of course, and most often will be, good black body emittors at non-visible wavelengths. Nothing I said before violetes this. Why do I believe that aluminium won't glow with heat? Two reasons: 1) years of experience that includes welding and casting Al and its alloys; 2) Kirchoff's Law of Thermal Radiation. Essentially, this is a Law of Reciprocity. Substances than absorb poorly at a given band of wavelengths are poor emittors at those same wavelengths. If there is zero absorbtion (ie substance is transparent) then it cannot thermally emit. — Preceding unsigned comment added by 1.122.206.136 (talk) 07:22, 9 August 2013 (UTC) 1.122.206.136 (talk) 06:24, 9 August 2013 (UTC) Not attempting to refute your point, just curious: What about glass? It's near transparent, but still glows when heated. MChesterMC (talk) 08:21, 9 August 2013 (UTC)

You can get flames by burning various substances in chlorine gas, so an oxygen atmosphere is not necessary. μηδείς (talk) 22:00, 8 August 2013 (UTC)

And apparently, Kiet/Rabone has discovered another way to produce flames...but not without getting fire. SteveBaker (talk) 14:30, 9 August 2013 (UTC)

I avoided answering this because I don't know how transparent gas really is, but there has to be some limit. There are molecular orbitals and higher molecular orbitals, so there have to be some emissions/absorptions, right? (Looking this up quickly it looks like [4] page 9 gives a whole range of frequencies in the visual spectrum. I'd wonder how I see through it at all now... Wnt (talk) 17:49, 9 August 2013 (UTC)

The link you supplied seems to be defunct - it's just a blank page. However, it seems from your wording, and the link address, that you are talking about spectral emission/absorption. When we talk about something being transparent, we are not talking about no spectral emission/absorption. We are talking about no broadband black body emission/absorption. A fully transparent substance can emit spectral lines even though it is transparent, but it cannot act as a black body and emit a broad band. A non fully transparent substance can emit both broad band and spectral lines, as Nimur has pointed out. In a sense, a gas only absorbing specific spectral lines is not fully transparent as then those specific frequencies/wavelengths are not passing right through it. However, the eye will not detect it unless the ambient illumination comprises only those precise wavelengths. Under white light or near-white light the substance will appear fully transparent, and will be classified as such. 124.182.50.53 (talk) 02:53, 10 August 2013 (UTC)

mathematical proof to evolution

Should it be possible, in principle, to proof mathematically that mechanisms like natural selection, sexual selection etc, combined with mutation rate like the rate found in nature, can create the diversity and complexity of life as we see it? did researches tried to construct such proofs? thanks, 94.159.164.161 (talk) 19:27, 8 August 2013 (UTC)

Evolution is certainly a "self-evident" logical consequence of systems that

1. Replicate themselves on the basis of a design embedded as a part of themselves.
2. Compete for limited resources of some kind - without which they cannot replicate.
3. Have occasional errors in the replication process.

If those three conditions are satisfied, then there is no way that evolution cannot occur because:

1. The errors will result in some differences in the design of some individuals relative to their parents.
2. The competition for resources will result in the numbers of accidentally improved designs increasing.
3. Result in a gradual improvement in the design.

Turning that into the language of mathematics ought not to be difficult.

Life (as we know it) uses DNA as the "embedded design", has to compete for nutrition and possibly other things, and DNA is subject to random mutations and transcription errors. Hence life evolves. QED.

Very minimal computer-based systems (See: Artificial life) bearing just those three basic characteristics have been shown to evolve every bit as strongly as "real" living things and Genetic algorithms are routinely used by software engineers to solve certain sorts of programming problems using an "evolutionary" approach.

SteveBaker (talk) 19:51, 8 August 2013 (UTC)

See "Fine-tuned Universe".—Wavelength (talk) 20:11, 8 August 2013 (UTC)

No, don't see Fine-tuned Universe since it has nothing to do with the question.

See Evolutionary dynamics and Evolutionary game theory instead.

Dauto (talk) 20:32, 8 August 2013 (UTC)

• There isn't really any need for a mathematical proof. To people who understand genetics, it is completely obvious that evolution will occur if enough time is allowed. The problem is that people who have doubts about evolution hardly ever have any knowledge of genetics, so it isn't obvious to them. Looie496 (talk) 21:16, 8 August 2013 (UTC)

You may be right in this case, because you'd only be proving things about a model anyway, not about the real world of biology. But, in general, "obviousness" is no reason not to prove things mathematically. For instance, certain "obvious" facts are actually wrong, and other "obvious" results are very rather difficult to prove, e.g. the Jordan curve theorem. In that case, the value of the proof is not only that it gives us certainty of the result, but the methods developed for that proof are also useful to prove other, less obvious things. SemanticMantis (talk) 21:24, 8 August 2013 (UTC)

• No. The premise is a corollary of reductionism, that everything (and its' explanations) reduces to the laws of physics expressed in a few equations and the original state of the universe. But There are loads of concepts which in no way can be reduced to the laws of physics: in This is Biology, Ernst Mayr gives an off-the-cuff list of two dozen concepts like ecological niche, sympatric speciation, and sexual selection which are emergent and cannot be reduced to any chemical description or physical laws. See [[5]]. To even pretend that one could, from bare premises, predict a pouched mammal that eats only Eucalyptus leaves or the existence of such organisms as Vampyroteuthis is intellectual hubris. μηδείς (talk) 21:54, 8 August 2013 (UTC)

But if you have some emergent phenomena then these are (to some degree) independent of the underlying model, then it is possible (in principle) to predict these phenomena. The issue is simply that a higher level description in terms of the emergent phenomena captures the relevant dynamics of the system. So, if a lion is chasing a wildebeest, the dynamics of this system is appropriately described at the level of these animals. You could describe everything in terms of atoms, but to make the lion and wildebeest visible, you have to integrate out the lower level dynamics, and then invoke the definition of the higher level concepts in terms of the lower level description. For some systems one can actually perform such calculations within some appropriate approximation, such methods are known as "renormalization group methods".

These methods have been particularly successful in explaining the thermodynamic propreties of substances near the critical point where phase transitions happen. These thermodynamic properties do not exist at the level of atoms (they are emergent phenomena), yet one can explain them starting form a model about the atoms and their interactions. It was always believed to be impossible to do so (because the thermodynanic properties only become well defined in a regime that is infinitely far removed from the scale that your model applies to, so it seems that it would require an infinite computational effort to compute them), until Wilson showed in the early 1970s that one can in fact quite easily compute the quantites of interest.

So, I would not give up on the idea of deriving biological behavior that is to some degree universal from the underlying laws of physics. Count Iblis (talk) 23:37, 8 August 2013 (UTC)

The whole purpose of the concept of emergence is precisely to deal with higher level phenomena which are not able to be described or hence predicted from lower level phenomena. I strongly recommend reading Mayr, who formulated the biological species concept (another phenomenon which is based on the interactions of populations and cannot be predicted from physics or chemistry) and who as the "Dean of biology" was the voice of 20th century consensus. Mayr criticised S J Gould, but far less than he did reductionists like Richard Dawkins. Gould's emphasis on radical biological contingency reveals another concept that argues against such physiochemical prediction. Read Gould's description of the lone German Shepard dog which over a period of six weeks almost sent the Kiwi bird into extinction. 'Bully for Brontosaurus PDF'. That's hardly something that can be explained or described in terms of masses and velocities of C, H, N, O, Mg, & P. μηδείς (talk) 00:56, 9 August 2013 (UTC)

See http://www.darwinismrefuted.com/molecular_biology_04.html

—Wavelength (talk) 01:32, 9 August 2013 (UTC)

See our article on the self-published author of that website, Adnan Oktar. μηδείς (talk) 01:44, 9 August 2013 (UTC)

Thank you for directing me to that article. I had not previously investigated the website to find out its author. At the bottom of http://www.darwinismrefuted.com, the expression "About the Author" is a link to http://www.harunyahya.com/bilgi/yazarHakkinda, titled "About the Author".

—Wavelength (talk) 02:48, 9 August 2013 (UTC)

The OP's question is in the same vein as one asked some weeks or months ago, about whether you could predict the evolution of a language. The answer to both questions is, no, you can't, because no model can take into account all the random factors that influence entities in the universe. As a simple example, consider hurricane landfall predictions. They don't tell you where it's going to land, they give you probabilities. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:30, 9 August 2013 (UTC)

Conway's Game of Life has emergent patterns though the individual cells have specific rules. If you played out the game with many moles of automata for billions of years, maybe, though no H. sapiens could ever keep track or follow the calculations, you'd see Dilbert contemplating free will. 75.75.42.89 (talk) 03:45, 9 August 2013 (UTC)

Life shows amazing emergent properties, and it is (in theory) Turing-complete. But it not a good analogue to evolution, since it is fully deterministic. You would need to introduce some small randomness to promote "real" evolution. --Stephan Schulz (talk) 03:57, 9 August 2013 (UTC)

It's not just "in theory" that Life is Turing-complete. Someone built an actual, working, Turing engine within the game: http://rendell-attic.org/gol/tm.htm SteveBaker (talk) 14:11, 9 August 2013 (UTC)

Do the emergent properties instantly disappear when you introduce automata rules that factor in some small randomness (e.g., if the cell above you is black, and a random number generated is greater than 0.8, do X)? 75.75.42.89 (talk) 11:00, 9 August 2013 (UTC)

No. There are stochastic cellular automatas (although our article is rather brief), and they show similar emergent behaviour. Here is a hunter-prey model based on a stochastic cellular automaton. It's a rather small grid and simple ruleset, but it already shows interesting behaviour. --Stephan Schulz (talk) 11:24, 9 August 2013 (UTC)

Even without true randomness, you could produce evolution in Conways' game of life by having devices that pseudo-randomly shot out objects (like maybe a "glider") that would act like a cosmic ray in the real world to disrupt some self-replicating system and induce mutation.

Here is (roughly) one way to do that:

• Because Life is "turing-complete" you could use this Turing machine to run an arbitrary computer program. (The "Church-Turing thesis" says that this is possible because all Turing-complete machines are equivalent).
• Hence we can write Pseudorandom number generators with sequences of arbitary length - including lengths that are longer than the life of the simulated universe.
• Self-replicating structures do exist in Life (for example this one - which replicates itself every 34 million generations (that's actually kinda fast for such things!). Nobody thinks this is the best possible replicator because it's the first one that anyone ever came up with - so there is certainly room for improvement.
• The replicator uses an "instruction tape" structure - which is (in effect) it's DNA.
• We could presumably use the output of the turing machine to pseudo-randomly shoot gliders at the tape structure to modify it.
• This would cause mutations of the original structure as it replicates itself.
• Most of the time, this would cause the generated replicator to fail.
• But given enough time, a viable - but somewhat different replicator would come out of that.
• Most of the time, those would be worse at replicating than the original one.
• But given enough time, a better replicator would eventually emerge.
• However, for evolution to occur, there has to be some kind of limited resource to compete over - or else the less-efficient replicators won't die out.
• The difficult part of "Life" is that the only resource that objects can compete for is space - and even that is infinite in an idealized version of the game. However, there is a "speed of light" limitation in Life - the maximum speed that any object can move is limited. Hence, from a single replicator and a single source of disruption there is a rapidly growing - but still finite - amount of space available for our replicators to grow into...that is space that they can compete over. But there is no equivalent of "mass" or "energy" in a life simulator. That's going to make evolution happen a bit weirdly...but it can still happen.

But if a system as simple as "Life" can exhibit evolution, then surely there can be no doubt that our universe, with it's vastly richer set of "rules", can also do so...particularly because we know that it's possible to implement Conway's game of life inside our universe.

SteveBaker (talk) 14:06, 9 August 2013 (UTC)

It may not prove evolution, but Homer Simpson (after an accident left him briefly intelligent) disproved God. Take it with a grain of salt, perhaps. InedibleHulk (talk) 11:05, August 9, 2013 (UTC)

And then, as a fitting punishment, God returned Homer to his former condition. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:28, 9 August 2013 (UTC)

That was Moe's work. "You know when your dog's having a bad dream? That's who I pray to." InedibleHulk (talk) 18:04, August 9, 2013 (UTC)

Is there some sort of proof a random element is either necessary for or indeed would lead to evolution in the sense of natural selection? I find both claims horribly dubious, and have to laugh at the return to Epicurus's clinamen. μηδείς (talk) 00:35, 10 August 2013 (UTC)

Randomness is what provides the material for natural selection to work on. It's "Evolution through random mutation and natural selection" - natural selection is the non-random part. Yes, you need some source of randomness to inject information into the system (unless you assume an open system with some kind of input from the outside - but in that case, see infinite regression). You don't need to go back to Epicurus. Quantum mechanics is enough. --Stephan Schulz (talk) 04:40, 10 August 2013 (UTC)

No, randomness there simply means without regard to some predetermined end, like mutations that don't all occur with the predetermined goal of turning dinosaurs into birds. Such mutations have no preset goal in mind--in that way they are random. But their cause could be regular--every 1,000th base pair might mutate to the next base on the right handed side, A>C>G>T>A starting with the date of the year the proto-chicken's born on. What causes the mutation need not be random for its effect on the chicken to be random. μηδείς (talk) 05:15, 10 August 2013 (UTC)

Well, that depends on what you use as the state for your deterministic system of mutations. The strength of random mutation is that different identical copies of the genome undergo different changes, thus exploring a much larger space of possibilities. If you systematically mutate the genome, starting with a single individual, then all generation X members will have the same genetic markup. Moreover, you might get stuck in a local fitness maximum much easier - since there is only one possible mutation, if that one does not improve fitness, you are stuck. If you do what Steve is suggesting (having a sufficiently large number of pseudo-random numbers and use them to drive evolution), then yes, you can be deterministic. But then the information you need is already in the pseudo-random sequence - see Information theory. --Stephan Schulz (talk) 14:58, 10 August 2013 (UTC)

What is needed is some means for the DNA of the offspring to have some probability of being different from either of the parents...a mutation. It is true that without some kind of relatively unpredictable mutation, all creatures on Earth would be genetically identical...and if that's the case then there is no evolution.

But that variation could still occur in an entirely deterministic universe. A deterministic universe could still shower the earth with cosmic rays, some of which would cause mutations - and so long as they originated in a sufficiently complicated manner - their actions would be indistinguishable from random mutations. All that's really needed is that all parts of the DNA strand can be changed by the process and that the change isn't 100% consistent from one generation to the next.

Any mathematically chaotic system can produce enough randomness to do that. Weather patterns, for example, are essentially unpredictable - even in a deterministic universe. If a single-celled animal's DNA mutated every time it survived being struck by lightning - then that would suffice for evolution to take place.

In computer simulations of evolution, we have no source of truly random numbers (the computer program is deterministic) - but we can use a Pseudorandom number generator (PRNG) to generate numbers that appear to be random until the sequence eventually repeats. We could, for example, use a million bit PRNG with a repetition period of around 2^999,999 and use the output of that to determine which C,A,G or T in the DNA should be switched to a different letter whenever a bacterium reproduced. With a few billion letters to choose between, you'd have enough randomness to produce one mutation every second for the life of the universe and you'd never see the same mutation happen twice.

It's trivial to produce an entirely deterministic system that would continue to exhibit evolution for more than the life of our universe. SteveBaker (talk) 15:16, 10 August 2013 (UTC)

August 9

Stages

Is this sentence scientifically correct? "First we are gametes, then zygotes, then embryos, and then fetuses." Pass a Method talk 00:24, 9 August 2013 (UTC)

The sequence is correct, but gametes are haploid organisms, and no gamete is genetically identical with any person, all of whom are diploid organisms. See also alternation of generations in plants for comparison. μηδείς (talk) 01:39, 9 August 2013 (UTC)

You could say we start out as two gametes, but that's only retroactive to them having merged. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:26, 9 August 2013 (UTC)

Gamete Jim, I'm a doctor, not a zygote. Clarityfiend (talk) 02:56, 9 August 2013 (UTC)

There also is the problem of "we". If you talk about personal identity, you (may?) need a consciousness, which means that we only slowly form during development, and certainly don't exist at the zygote level (unless you assume some religious perspective). --Stephan Schulz (talk) 09:44, 9 August 2013 (UTC)

I can't speak for the OP, but I'm talking strictly biology. If you want to take it ever farther back, you'd have to look at what precedes the gametes, i.e. the process that creates them. Then you could say we start out as molecules within our parents' reproductive systems. And so on, clear back to the first strand of DNA that ever existed. I'm reminded of one of my favorite Carl Sagan quotes, from Cosmos: "If you wish to make an apple pie from scratch, you must first invent the universe." ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:25, 9 August 2013 (UTC)

I take your point. Another way of looking at the question of "when does life begin?": Though some governments and religions like to quibble over the details of pregnancy and fetuses, the biological answer is ~3.5 billion years ago. SemanticMantis (talk) 15:00, 9 August 2013 (UTC)

If a zygote is a person that can be made of two cells, why can't two gametes be a person, either before or after fusion? Indeed a zygote might work out to be a pair of identical twins... Wnt (talk) 17:42, 9 August 2013 (UTC)

Technically the zygote is only the single fertilized egg cell. Before fusion gametes are two discrete haploid organisms incapable of mitosis on their own or any function we attribute to persons. (I may be misunderstanding you, because I am otherwise surprised by your question, given the amount of medical questions you answer.) μηδείς (talk) 18:07, 9 August 2013 (UTC)

It's a little like looking at a pile of bricks and calling it a building before it's actually built. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:15, 9 August 2013 (UTC)

Whey protein

Why is there research showing that whey protein decreases cancer risk and also research showing it increases it. This is contradictory. Clover345 (talk) 10:08, 9 August 2013 (UTC)

I am not surprised - the idea that scientific research always produces clean, easily interpreted and consistent results is an over simplifcation. There are many reasons why valid studies could produces apparently contradictory results. Maybe there was some important difference in the groups being studied or the study methods that was not accounted for (dosage, age, gender, diet, lifestyle etc. etc.). Maybe there was some external factor that was not controlled for. Maybe the baseline risk was underestimated or overestimated. Maybe the results in one or both of the studies were due to random coincidence. The appearance of contradictory results suggests that we do not yet have a complete or accurate model of the interaction between whey protein and cancer risk, and so further research is required. Gandalf61 (talk) 10:53, 9 August 2013 (UTC)

With foods that claim to improve health in one manner or another, there is a serious issue with companies who sell such things as "Nutritional supplements" (which are largely unregulated by the FDA) - they need to make their product look beneficial, and very often fund dubious research to produce that goal.

Since you didn't link to the paper(s) that you saw, we can't know whether that's the case here and this might be very carefully done and accurate research - but I strongly suggest you look back at the favorable papers and ask yourself whether they were funded in this manner - whether the journals they were published in are peer-reviewed, whether the researchers involved only produce favorable reports about food supplements and so forth.

That kind of double-check is always a good thing to do with any scientific paper - but in the special case of reports that claim beneficial health outcomes from processed food products, you have to have your "bullshit" meter dialled up to 11.

SteveBaker (talk) 13:37, 9 August 2013 (UTC)

The old saying still applies: "Follow the money." If someone claims something about something, first find out what they have to gain by someone buying that something. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:59, 9 August 2013 (UTC)

• Yes, along the same lines as what Gandalf61 said. Without reference to the accuracy of any specific study it is totally logical to assume that under certain circumstances adding whey protein to a persons diet may either raise or lower the risk of certain cancers. Also the composition of different whey protein products varies depending on factors such as heat treatment which may destroy certain beneficial components such as immunoglobulins. 122.109.123.252 (talk) 16:52, 9 August 2013 (UTC)

Placebo and nocebo effect

Are placebo and nocebo effects linked to stress? Could it be that the reason placebo pills work is because it puts the mind at ease and relieves stress? If so, could other psychological effects affect physical health? For example, could the simple thought of pain going away cure it just as a placebo would? And could the opposite also be said? Clover345 (talk) 14:57, 9 August 2013 (UTC)

The mechanism is discussed in Placebo#Mechanism_of_the_effect and Neural top down control of physiology. SteveBaker (talk) 16:36, 9 August 2013 (UTC)

Yes, stress could be a factor. Also, for subjective measures, like "how much pain do you feel", people can experience the same amount of neural activity, measured objectively, as less pain. Placebos are less effective when objective measures are applied. StuRat (talk) 06:20, 10 August 2013 (UTC)

Reading that section in the article on the placebo effect, I think it misses something that I've observed. A friend of mine who is into alternative medicine for his complaints sometimes tells me how well he has been helped. But if you listen to his complete story, you can't help but notice the following effect. Suppose that you have some illness and you are inclined to reduce your physical activities, not eat as much as a result, stay in bed longer etc. etc. However, because you are now getting pills, you are more optimistic, so you decide to do more during the day. Then, for certain complaints simply being a bit more active compared to behaving like you are ill, can have apositive effect, apart from simply reducing stress. Count Iblis (talk) 13:33, 10 August 2013 (UTC)

How long after eating does "take with meal" not apply

I hope this doesn't fall under the guise of "medical advice", because I'm just curious about digestion. I notice some vitamins and medications instruct the person to "take with meals". What's the time window for that period? How long after eating would be considered too late to take something "with meals"? What biochemical actions (relative to ingested pills) take place "with meals"? --157.254.178.141 (talk) 17:21, 9 August 2013 (UTC)

On average, the stomach takes about 1 hour to empty its' contents into the small intestine. Reasons to take with meals include better absorption of the drug (as with vitamins) or avoiding upset from an irritating drug. If this is a prescription drug you can call your pharmacist, they enjoy answering such questions. If its' over the counter there will be a toll-free customer service number to call. μηδείς (talk) 17:57, 9 August 2013 (UTC)

No apostrophe is needed after its to indicate possessive. See [6]. Edison (talk) 20:51, 9 August 2013 (UTC)

Channeling Cuddlyable3??? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:13, 9 August 2013 (UTC)

Shes' been' making' some' sort' of' weird' point' for' quite' some' time' now'. See' below' @ whats' and' OPs' . -- Jack of Oz ^{[pleasantries]} 23:46, 9 August 2013 (UTC)

It's certainly a dangerous path to tread. We've already determined that spelling/grammar/punctuation complaints constitute "disruptive editing" here on the Ref Desks. The fate of Cuddlyable3 and his oh-so-cuddly socks clearly demonstrates that one should not go there. SteveBaker (talk) 14:53, 10 August 2013 (UTC)

Maybe one of you can link to the original discussion which got CuddlyAble3 blocked? It seems to have been before my time. Tis hard to believe a misplaced apostrophe alone was the cause. Thanks. μηδείς (talk) 20:33, 10 August 2013 (UTC)

Dog reproduction

Hi. My aunt's bitch just gave birth to a litter and she gave me two puppies, a boy and a girl. I was wondering: if I raise them at home and keep them away from any other dogs, once they get to reproductive age, will they mate with each other? Thanks. 24.92.93.248 (talk) 17:43, 9 August 2013 (UTC)

Yes. I am not sure where one would look for a source, but yes. μηδείς (talk) 17:59, 9 August 2013 (UTC)

I would want to see a reference for that. In many species, individuals avoid mating with other individuals that they spend a lot of time with when young. I can't spot any information directly about dogs, though. Looie496 (talk) 18:07, 9 August 2013 (UTC)

Animal_sexual_behavior#Mammals says that incest is common in foxes - referenced to a document that relates to DNA investigations. Incest#Animals says that "Many mammal species including humanity's closest primate relatives tend to avoid close inbreeding, especially if there are alternative partners available." - suggesting that animals will actively seek to mate outside the litter if they can - but if not, then incest is OK. If you think about it without viewing the behavior through human morality, that's the most evolutionary sound approach. Faced with the choice of not passing on DNA to the next generation at all - or risking some small reduction in genetic variation in the next generation - the evolutionarily "correct" answer is to do exactly as our article suggests. So, in the absence of any other evidence - I'd answer this question with a pretty solid "YES!" SteveBaker (talk) 18:20, 9 August 2013 (UTC)

Here are two refs that that discuss inbreeding avoidance in canines: one for African wild dogs, here [7], and one for Ethiopian wolf, here [8]. Both seem to conclude that there are inbreeding-avoidance mechanisms at work, in line with Looie's comments above. But who knows how domestication messes with these instincts? Here's at least one vet who says that littermates will mate [9]. I suspect that the answer is that littermates of domestic dogs would tend to not mate with eachother, if other mates are available. But, if the only option is a sibling, they'll likely go for it. Really, unless they have some plans of being a dog breeder, the OP should spay and neuter their pets. SemanticMantis (talk) 18:27, 9 August 2013 (UTC)

The OP has specified that the dogs will be kept together away from other dogs. In that case there will be no other dogs for them to prefer, and they will settle for whats' available. μηδείς (talk) 18:31, 9 August 2013 (UTC)

When a female dog goes into heat, she and potential partners have an amazing ability to go over, under, or through barriers set up by humans. "Keeping them away from other dogs" is a strategy which would require exceptional diligence to prevent breeding with "other dogs." omnia vincit amor. Edison (talk) 20:48, 9 August 2013 (UTC)

That's quite true, I can attest from various litters I've midwived. But the OPs' entitled to his premises. μηδείς (talk) 22:03, 9 August 2013 (UTC)

At first glance I thought LC had moved to Wisconsin. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:12, 9 August 2013 (UTC)

Relative velocity?

For example if an object floats in space, covering several thousands kms per hour relative to Earth, but only several kms/h relative to itself, is it called relative velocity or something else? (in other words, when that object travels somewhat slowly relative to itself, but covers lots of territory relative to Earth)--93.174.25.12 (talk) 21:35, 9 August 2013 (UTC)

An object always has zero velocity relative to itself. SpinningSpark 21:40, 9 August 2013 (UTC)

[ec] The object would appear motionless relative to itself. All speeds are relative (that is, it needs another point of reference to determine what the speed is, and that apparent speed can change based on a variety of factors. If you were in a car travelling 60, a vehicle coming towards you at the same speed relative to the road appears to you to be moving faster than one passing you at 65, which would be passing relative to you at only 5) If you mean that the acceleration is comparatively slow, that's a different thing. It sounds confusing because on human scales, it is confusing. Mingmingla (talk) 21:52, 9 August 2013 (UTC)

As Einstein pointed out - all motion has to be measured relative to something else. Here on earth, it's easy to forget that and just measure all velocities relative to the earth. So when that cop accuses you of driving faster than 70mph - you should be able to say "But officer, I was travelling at only 10mph relative to that truck just behind me" and thereby be let off getting a ticket. (Please don't try that!) Sadly, that doesn't happen because we all naturally assume the earth itself as the basis for "absolute" velocity measurements. However, that's just a local convention - it's not backed by any particular laws of physics. We read that the Apollo Lunar Rover was driven at up to 8mph...but that was relative to the moon. Taken relative to the Earth, it was zipping along at 2,200 mph.

So our human perception of "absolute speed" depends on some kind of spoken or unspoken "reference frame". For your object that's just floating out in space - there is no "obvious" object to use as a reference - so it's meaningless to talk about speed. If you say "relative to itself" - then the answer must be zero because an object can't move away from itself. Unless you're either implicitly or explicitly saying "relative to earth" or "relative to the sun" or "relative to that empty coke can that the astronaut just tossed out of the window" - you can't say anything meaningful about the velocity of your object out there in space.

SteveBaker (talk) 14:45, 10 August 2013 (UTC)

triple / triangle of life in emergency

In Israel there is an emergency term (generally used by resque teams or paramedics) which is called: "triangle of life" (משולש החיים). This term refers to three important sistems of the body: blood sistem, nervous sistem,breathing sistem. When one of them does not work, it endangeres the life and it can be caouse of death. My question is: Is there a same term in English? and Is there a same term in the other countries? I'm intrested to know what is the origin of this term` maybe its origin is in Israel and maybe not [I have red in Wiki about another thing which called "triangle of life", it referes to another issue entirely.] Thank you. מוטיבציה (talk) 22:03, 9 August 2013 (UTC)

This reminds me of the ABC's of medicine, which is commonly taught in first-responder courses in the United States. Here, it stands for "airway, breathing, circulation". Not quite the same as the triangle of life, but reminiscent. Someguy1221 (talk) 22:24, 9 August 2013 (UTC)

Hospital doctors refer to "vital signs". The primary vital signs are temperature, blood pressure, pulse, breathing rate. Any primary sign below certain limits means that you are clinically dead or dying, and immediate action is required. The secondary vital signs are sensitivity to pain and the reaction of the pupil to light. Lack of these signs does not mean that you are dead or dying, but you are seriously ill or injured, and corrective action is required ASAP. 124.182.50.53 (talk) 01:48, 10 August 2013 (UTC)

Vital signs. Someguy1221 (talk) 03:13, 10 August 2013 (UTC)

In the USA, the term ABC for EMTs and Paramedics is sometimes expanded to ABCDE, which stand for airway, breathing, circulation, disability (that is, what is the main thing wrong with the patient that is readily visible) and expose (that is, remove any clothing necessary to accurately access the patient). Jc3s5h (talk) 02:29, 10 August 2013 (UTC)

ABC it's another thing which used also in Israel. I did not mean about the ABC (Airway, Breathing and Ches Compressions, no Circulation. circulation is in the protocol of trauma life support,there, there is ABCDE that the letter C is circulation. That's a freqence mistake to say circulation instead of chest compression in CPR). By the way, the schema is not yet ABC but CAB, according to updates of AHA- American Heart Association, that Israel emergency goes according to it. I meant in my question to triangle of life, not to ABC. and according to the answers I can guess that this term is not used in other countries in this meaning. מוטיבציה (talk) 09:58, 10 August 2013 (UTC)

August 10

Magnetic lines of force

Why do iron fillings align themselves along the magnetic lines of force of a bar magnet, even if lines of force are imaginary? Publisher54321 (talk) 08:16, 10 August 2013 (UTC)

I believe the filings conduct the magnetic field better than the air, so this tends to cause them to clump together, aligned in the direction of the magnetic field, since the magnetic field is stronger by other iron filings than away from them. StuRat (talk) 08:37, 10 August 2013 (UTC)

Magnetic field lines talks some about it. DMacks (talk) 10:06, 10 August 2013 (UTC)

The linked section seems to do little more than mention the phenomenon. Iron filings themselves become magnetically polarized in a magnetic field – either temporarily or permanently. If an individual filing is considered, this magnetic polarization is dominant along its long axis (if it has one, i.e. is not spherical). The polarisation generates its own magnetic field, which interacts with the overall magnetic field in such a way as to orient the long axis of the filing with the field if it can rotate freely. There is no preferential positioning of a single filing though: it will simply orient itself by the field, and not move, unless there is a magnetic field gradient, in which case it will experience a small force in the direction of the increasing gradient (assuming that its polarization is allowed to align freely). The gradient is generally strongest nearest a dipole source (like a normal bar magnet). This is why the force between two magnets increases so markedly when they get very close together: this is where the gradient of the field of a magnet is highest, and the force increases with the inverse cube of the distance (if I have not misremembered it).

Each filing, being magnetically polarized, generates its own tiny dipole field, which is superimposed on the surrounding magnetic field. This creates local gradients in the magnetic field such that there are effective forces between proximate filings. A simple way to think of it is that the filings all become aligned magnets due to the external field, an then they act as you'd expect many little magnets to act: they form chains of north-to-south magnets sticking to each other. The striations formed by clustering of adjacent chains is a little trickier, but is probably attributable to irregularities in the chains that causes them to stick together, leaving gaps between clusters, thus forming the striations. — Quondum 12:30, 10 August 2013 (UTC)

To put it more completely yet more concisely: The reason the filings form spaced lines is a) as Quondom said, as each filing become magnetised by the field, it increases the local flux density attracting filings ahead and behind it in a (North-South)-(North-South)-(North-South) chain as opposite poles attract, and b) the field is thus weaker between such chains, this establishing a gradient that makes locations between chains unstable, and because like poles repel. 121.215.72.7 (talk) 13:25, 10 August 2013 (UTC)

Not entirely: the spacing instability depends on non-uniform chains. Several closely (but not necessarily exactly evenly) spaced steel wires, all in and parallel to a uniform magnetic field, will experience no forces between them. In this, there is no field gradient between the wires (although the field strength between wires is reduced compared to no wires). A filing floating between them will also experience almost no force (other than orientation). A very small residual attraction will exist for the filing to the nearest wires though: its polarization will alter the polarization in the nearest parts of the wires, which is to say, with the uniform magnetic field removed the filing will experience the same attractive force to the adjacent wires by interaction with the polarization that it induces in them as a tiny permanent magnet of the same polarization. This depends on the filing not being part of a uniform chain (like another wire). Because the chains are not uniform this is not an accurate description, but it gives a feel for the mechanisms at work. — Quondum 14:10, 10 August 2013 (UTC)

We know that a tangent drawn from any magnetic line of force gives the direction of magnetic field. Suppose I have a figure showing a bar magnet and direction of magnetic field around that magnet. Can I call this arrangement a vector field? I asked this question because I am not able to understand what really a vector field is. Publisher54321 (talk) 14:38, 10 August 2013 (UTC)

How many kinds of blood cells are there?

I have red in the entrey of blood cells that there are three general catgories: Red blood cells (leucocytes), White blood cells (thrombocytes) and platlets (trombocytes). I can understand from the word GENERAL that there are more kinds of blood cells, it says that there are sub-categoies of blood cells. So, how many kinds of blood cells are there in all? (In the Hebrew Wiki there are 10 kinds of blood cells: Two of them are belong to the Red blood cells, and seven of them belong to White blood cells, and one of them is a platelet. these are the kinds: 1.Erythrocytes. 2. Reticulocyte. 3. Neutrophils. 4. Eosinophils. 5. Basophils. 6. Macrophages . 7.lymphocytes . 8. Monocytes. 9. Phagocytes . 10. platlets ). So, is it correct to say that there are 10 kinds of blood cells or there are more or you have another something to say about... Thank you מוטיבציה (talk) 10:22, 10 August 2013 (UTC)

You've got things a bit confused. The usual classification is:

Red blood cells, or erythrocytes. Reticuloctes are young erythrocytes.

White blood cells, or leucocytes. There are three main classes:

Granulocytes, with three subclasses:

Neutophils

Eosinophils

Basophils, which are also called mast cells

when they leave the circulation and enter

the tissues;

Lymphocytes, consisting of three main groups:

B cells

T cells, including

Cytotoxic T cells

Helper T cells

Memory T cells

Regulatory (or suppressor) T cells

Natural killer cells

Monocytes, which are which are called

macrophages when they leave the circulation

and enter the tissues. Together, monocytes

and macrophages are refered to as phagocytes.

Platelets or thrombocytes. Not really cells strictly speaking, but rather cell fragments. We have articles on all the terms used above. Look at them for further information. Dominus Vobisdu (talk) 10:54, 10 August 2013 (UTC)

-

-

-

Well, if I understand you properly, there are 10 kinds of blood cells, here is the acount:

Red blood cells (reticulocytes are young cells)- It's one or two in the acount.

White blood cells incloud three main classes:

granulocytes with three subclasses:

1. :Neutophils. 2.Eosinophils. 3. Basophils (mast cells).It's plus three to acount.

Lymphocytes, consisting of three main groups:

B cells

T cells, including 1.Cytotoxic T cells. 2.Helper T cells. 3.Memory T cells. 4. Regulatory (or suppressor) T cells. 5. Natural killer cells.

Monocytes (macrophages/phagocytes). It's plus six to the acount.

Platlets - It's plus one to the acount.

In all, there are 10 kinds of blood cells. (I did not understand why you don't acount platlets as blood cells). Thank you for the help :) מוטיבציה (talk) 14:25, 10 August 2013 (UTC)

No. Monocytes are not under T lymphocytes. And the answer from your question ranges from three to a big bunch, depending what you mean by "kinds" of blood cells. I already explained why platelets are not cells. They are cell fragments. Dominus Vobisdu (talk) 14:34, 10 August 2013 (UTC)

I made order again in my things, and monocytes no more under lymphcytes. In regard to the platlets, I understnad your things, but I ment that I don't understand why some books and wiki itself call it "cell" (in the hebrew wiki it's called expressly: blood cell), so I wondered if what that you say is it not known to all above mentiond? מוטיבציה (talk) 15:27, 10 August 2013 (UTC)

It is a common misconception for platelets to be called cells; they are cell fragments that lack nuclei, as reflected in our article on the topic. It is appropriate to ask whether the same applies to red blood cells, but the latter are often nucleated (e.g. in infants, people with functional or anatomic asplenia, and other vertebrates) whereas platelets are not nucleated and are produced by pinching off cytoplasm from a megakaryocyte (rather than cell division). -- Scray (talk) 15:51, 10 August 2013 (UTC)

Further, it might be tempting to call anything membrane-bound in the blood a cell, but then what to call exosomes, apoptotic bodies, and enveloped viruses that might be found in the blood? Platelets are better grouped with "cells" than with "plasma", but they are even better described as cell fragments. -- Scray (talk) 15:57, 10 August 2013 (UTC)

Should we assume that the original question refers to human blood cells, or does it embrace the blood cells of all creatures having blood?

—Wavelength (talk) 16:45, 10 August 2013 (UTC)

It's pretty much the same for all vertebrates, at least as far as the main groups and subgroups of blood cells go. The last evolutionary event was the divergence of lymphocytes from monocytes, which might have occured soon after fish evolved, or perhaps soon before, so it is possible that some primitive fish like sharks and lampreys may not have lymphocytes, though I'm not sure. Basophils are perhaps an even younger derivitave of the granulocyte prototype, and whether fish have them or not is not settled. Originally, all the WBC types evolved from a phagocytic ancestor in invertebrates. Dominus Vobisdu (talk) 17:37, 10 August 2013 (UTC)

Main Battle Tank

My question is about Leopard 2 Tank when looking at the image in the picture of the link downward you find that part number 2 is (Main Hydraulic Pump), what is the purpose of this pump and why this pump does not exist in other tanks like M1 Abrams or T-90 -as I expect- http://imageshack.us/a/img811/4895/leopard2wieakoncpecja.png Tank Designer (talk) 11:10, 10 August 2013 (UTC)

Well, the M1 Abrams does have a hydraulic pump, but it's located in the hull rather than the turret. The main purpose of the hydraulic pump, as I understand it, is to move the turret and gun. Looie496 (talk) 14:49, 10 August 2013 (UTC)

Thank you very much but where does the pump exist in T-90 there is no where to place it-as expect only - as yo know it is very cramped from inside 86.108.126.173 (talk) 20:49, 10 August 2013 (UTC)

on difference between serum and plasma?

I have red that the main difference between serum and plasma of the blood is coagulation factors (proteins of cougulation). Serum is without these couglations factors, and plasma is with it. Why is it needed to take out the couglation factors? what is the profit/ adventage/ use in the serume that we can not do with plasma? Thank you. מוטיבציה (talk) 14:58, 10 August 2013 (UTC)

There are many differences between serum and plasma, some of which affect laboratory assays; this is sometimes called matrix effect (a consistent effect on an assay of the matrix from which the sample is taken). Because matrix effects are hard to predict, and lab assays are developed empirically, an important principle is to stick with the matrix (specimen type, e.g. serum or plasma) for which the assay has been validated. Examples of dominant influences on assays include: (i) fibrinogen, present in high concentration in plasma but nearly absent from serum, can interfere with interactions of other proteins; and (ii) anticoagulants such as EDTA used in plasma collection but absent from serum, can interfere with assays that depend on cations like Ca²⁺. If you search for some of these things, you may find some more examples and specific references (I may do the same if others don't). -- Scray (talk) 15:24, 10 August 2013 (UTC)

• some references: review articles PMID 21400551 PMID 17377775 PMID 15915347; example 1 - differential stability in stored serum vs plasma PMID 23570966; example 2 - differential effects of heparin, citrate, and EDTA anticoagulants in plasma PMID 23473258. -- Scray (talk) 18:46, 10 August 2013 (UTC)

String bass v fretless bass guitar

What is the principal reason for the marked difference in tone between a double bass (or an electric double bass) and a fretless bass guitar? The only differences I can think of are the string thickness and length. So how do these factors affect the tone so much and cause the double bass to give a much deeper sounding richer tone?--86.177.63.179 (talk) 18:51, 10 August 2013 (UTC)