Going to Islets of Langerhans is more useful - it tells you PP cells are gamma cells, which secrete pancreatic polypeptide. But it does seem like they get short shrift compared to their more famous siblings, which probably means someone has a chance to discover something really interesting about them. Wnt (talk) 04:32, 4 November 2014 (UTC)

What's special in "Medical" oxygen?

what is the reason for the noting "medical" on the bottles? 213.57.99.33 (talk) 04:32, 4 November 2014 (UTC)

You might be looking to read this: Oxygen therapy --lTopGunl (talk) 04:45, 4 November 2014 (UTC)

Interesting question. This site says there are concentration differences; I'm not all that convinced. There are definitely industrial oxygen concentrators. Chemical oxygen generators exist for emergency situations (those conceivably could contain different chemical impurities, though apparently not to immediately hazardous levels?) An oxygen bar is different from oxygen therapy. The common thread seems to be legal requirements of prescription and medical device regulation. Wnt (talk) 04:57, 4 November 2014 (UTC)

BOC Healthcare says that it's regulated as a medical drug and therefore has to undergo more intensive testing during manufacture and bottling than industrial oxygen. SteveBaker (talk) 05:02, 4 November 2014 (UTC)

The designation "medical" means that the gas can legally be given to patients under medical care. Absence of that designation would mean that the gas is intended for some other use. The exact meaning may depend on what legal jurisdiction you are in, but it indicates a specific combination of:

• purity of the gas used to fill the cylinder
• testing and certification to ensure that the gas is as pure as it should be
• fill procedures (see below)

In some places, there may not actually be any difference in purity between medical oxygen and oxygen sold for industrial use—the supplier may use the same grade of gas, but skip the testing and certification.

Fill procedures for medical-grade oxygen require pumping out the previous contents of the bottle first, to ensure there are no contaminants present. This would not be required when refilling a welding oxygen bottle, for example.

I found this web page informative.--Srleffler (talk) 05:16, 4 November 2014 (UTC)

One important point is that medical-grade oxygen can contain significant amounts of water vapour, which makes it unsuitable for use at low temperatures (such as in aviation or mountaineering). Srleffler's link gives the details. Tevildo (talk) 10:01, 4 November 2014 (UTC)

• Just to clarify the explanations above: the difference may or may not be with the actual gas itself, the difference is in the certification procedure. That is, it is a difference in how well we can trust that the gas in the bottle is suitable for medical purposes; there's nothing stopping a manufacturer from using uncertified (but identical in every other way) medical grade oxygen for other purposes. --Jayron32 17:24, 4 November 2014 (UTC)

The sterilization is relevant here? (I mean in case of the Oxygen bottle. I thought maybe it's for strilization, but I don't know if an organism can live in this conditions)213.57.99.33 (talk) 05:25, 5 November 2014 (UTC)

I recently discovered a case in point: It's common to use oxygen in welding (eg in the oxy-acetylene process) - and it's also commonly used as an "assist gas" when laser cutting sheet metal. In neither case does the oxygen have to be particularly pure. But in the latter case, the sensitive (and hideously expensive) optical parts get wrecked by even the slightest trace of oil. When oxygen is compressed for welding, the compressor that they use employs oil as a lubricant - and traces of that get into the gas. In the welding application, this trace quantity of oil gets burned up without anyone even noticing it - but for laser cutting, they need oxygen that's only ever been pumped with "oilless" compressors to avoid that specific contaminant. You could easily imagine similar-but-different limitations with medical oxygen. SteveBaker (talk) 16:43, 5 November 2014 (UTC)

What are the odds of being struck by lightning?

What are the odds of being struck by lightning?Whereismylunch (talk) 05:27, 4 November 2014 (UTC)

See Lightning strike#Epidemiology. For the US, roughly 1 in 500,000 per year. Dragons flight (talk) 05:47, 4 November 2014 (UTC)

(E/C) About 1 in 700000 or 1 in 3000, depending on the time frame you're looking at. WegianWarrior (talk) 05:50, 4 November 2014 (UTC)

Killed by a bolt, or affected by a strike? I've read stats closer to one in 1,000 per lifetime for the latter. I'll look for a ref if we can get a defined question. μηδείς (talk) 03:17, 5 November 2014 (UTC)

Note that your chances of being struck by lightning will vary dramatically with your location, habits, and occupation. Your chances will be a much higher if you work on cell phone towers for a living (or a dying). StuRat (talk) 12:19, 5 November 2014 (UTC)

This fellow survived being struck by lightning on at least 7 different occasions. Don't miss the "Statistics" section of the article. --174.88.134.249 (talk) 06:53, 6 November 2014 (UTC)

If you're the Empire State Building, your odds are quite good. ←Baseball Bugs carrots→ 11:53, 6 November 2014 (UTC)

Human body as a capacitive sensor

If I understand the principle of capacitive sensor operation correctly, any conductive surface can serve as an extension of a sensor. Does it mean that you can turn your own body into one? If so, how sensitive can it be? Would it be able to detect a handshake or an action of holding a door knob? What about the presence of a person nearby? Also, I wonder if it would be harmful for the human body. — Preceding unsigned comment added by 128.68.216.15 (talk) 11:49, 4 November 2014 (UTC)

I'll first comment that Capacitive sensor is a pretty bad article -- the only people who will be able to understand it are those who already understand it before reading it. Regarding turning your own body into an extension of one, sure, that could be done in principle, but it would be very difficult to distinguish changes in electric field due to touching something from changes in electric field due to changing the posture of your body. Looie496 (talk) 14:12, 4 November 2014 (UTC)

The capacitance of the human body is exploited in that classic musical instrument, the Theramin. It is insanely sensitive to body position...even small flutters of the fingers are enough to alter the sound coming out of the thing. SteveBaker (talk) 14:29, 4 November 2014 (UTC)

Giving the inventor his due, it's actually spelled theremin. --174.88.134.249 (talk) 23:01, 6 November 2014 (UTC)

The same ability is also exploited by those Touch-sensitive lamps. And proving once again that we have an article on everything, see Body capacitance which discusses the principle. --Jayron32 15:35, 4 November 2014 (UTC)

Our article on Touchscreen is more readable. Dbfirs 15:43, 4 November 2014 (UTC)

Fanged deer

Is the fanged deer of Afghanistan or Africa? This seems to contradict this. Bus stop (talk) 12:30, 4 November 2014 (UTC)

The "fanged deer" referred to in the first article is actually the Kashmir musk deer if you view the whole press release, a separate species from the water chevrotain. ~Helicopter Llama~ 12:32, 4 November 2014 (UTC)

See the Tragulidae and the Moschidae, primitive unhorned relative of true deer. μηδείς (talk) 19:09, 6 November 2014 (UTC)

Would an EOD suit really stop bullets?

I'm not 100% sure this is the right section, but there's a trend of games featuring characters wearing bomb disposal suits and being highly resistant to bullets, as well as explosives. Games I can think of include GTA 5, Payday 2, Metal Gear Solid 2, Call of Duty Modern Warfare 2, which provide at the very minimum high resistance to bullets (The characters in Payday 2 take enormous amounts of ammo to take down) to outright invulnerability in the case of Fatman in Metal Gear Solid 2).

Is this realistic? I can't imagine a suit designed to stop overpressure from a bomb blast would be all that great at stopping bullets? 81.138.15.171 (talk) 15:27, 4 November 2014 (UTC)

We have an article on Explosive Ordnance Disposal#EOD_Suits, and a much bigger article at Bomb suit and even Advanced_Bomb_Suit -- It looks like there's plenty of Kevlar, foam and plastic in a suit weighing up to 37 kg. While they don't seem to be designed specifically for bullet resistance, it seems reasonable that they would provide at least as much resistance as a bullet-proof vest, and possibly more. I can't find any references at the moment that specifically talk about bullet resistance, but there is some good general info in this article about a US EOD technician. Looking it all over, I'd think the biggest unreality in the games would be the movement speed and agility of characters wearing these rigs. In real life, they would be highly encumbering. SemanticMantis (talk) 15:47, 4 November 2014 (UTC)

See Bomb suit and bulletproof vest. According to the latter article, "Armor designed primarily to counter explosives is often somewhat less effective against bullets than armor designed for that purpose", "often somewhat less?" Fowler would have had apoplexy. See WP:WEASEL, although the bomb suit would provide a degree of protection. However, it would be virtually impossible to fight in a bomb suit, due to the severe restriction on mobility and the excessive heat build-up in the suit. Tevildo (talk) 15:52, 4 November 2014 (UTC)

Maybe because it could depend on the type of bullet. ←Baseball Bugs carrots→ 15:56, 4 November 2014 (UTC)

(edit conflict) I pasted your question into the Google searchbar and got Ask people anything about their jobs - SWAT Team Commander (Retired), and he says (after claiming not to be an expert): "...typical bomb squad suits are basically giant bullet resistant vests made from the same materials, but that cover the entire body, not just the torso. As such, they are good at stopping flying fragments and shrapnel common to small explosive devices". The Wellington Sears Handbook of Industrial Textiles by Sabit Adanur (p. 387) says that EOD suits have 16 layers of Kevlar, and The Encyclopedia of High-tech Crime and Crime-fighting by Michael Newton (p, 43) says that 16 to 18 layers should "cope with most threats encountered in urban shooting situations". So there you have it. Alansplodge (talk) 16:08, 4 November 2014 (UTC)

(edit conflict) For sure they are designed to somewhat protect the wearer against shrapnel - fast-moving chunks of metal - so it would be surprising if there wasn't at least some protection from bullets. So this is all a matter of degree. But the amount of damage someone can take in a video game is INSANELY high anyway. In real combat, one hit almost anywhere on the body is enough to take someone out of combat...except in rather rare cases. But in video games, you can take a whole lot of hits before you start to even slow down. In the face to that lack of reality - why would you be surprised if various forms of protection are over-rated?

These are video games...they are only realistic up to the point where the game designers decide that gameplay would be more enjoyable if it were less so. If they need a 'boss' to fill out a level, or to make some objective harder to reach - and if they have to stretch the truth a little to make it so by giving bomb disposal suits magical protection against bullets, then they most certainly will. (Trust me - I used to work on 1st person shooters in the video games industry - AND in 1st person shooters for serious military training - and I can assure you that there is little resemblance between the two when it comes to these kinds of matters!) SteveBaker (talk) 16:11, 4 November 2014 (UTC)

What, the U.S. military doesn't have little green boxes with + signs on them stashed around battlefields so their soldiers can instantly heal their wounds? --Jayron32 16:58, 4 November 2014 (UTC)

And we know from these games that no enemy would be so rude as to take them and use them on their own people. SteveBaker (talk) 16:31, 5 November 2014 (UTC)

I suspect they would not stand up against armor-piercing bullets. ←Baseball Bugs carrots→ 16:13, 4 November 2014 (UTC)

Depending on the range. Air resistance gradually robs the bullet of kinetic energy, so there must come a point where the suit would be of some value. SteveBaker (talk) 16:31, 5 November 2014 (UTC)

That's a given. And if you're standing sufficiently far away from a bomb blast, you don't need any special protection. ←Baseball Bugs carrots→ 11:52, 6 November 2014 (UTC)

Stopping bullets with magnetic eddy currents

Magnets are already used in eddy current brakes on trains, roller coasters and power tools. The brakes induce current to circulate in the rails, and the rails a generate an opposing magnetic force. Would it be possible to use this effect to stop bullets made of conductive material? I am pretty sure the bullets would not need to be ferromagnetic.

9×19mm Parabellum has a muzzle velocity of less than 700 Joules. According to our article, the bullet could travel 1 meter in 2.33 ms, so does that mean to stop it within a 1 meter distance would require an average power output of over 300 kW? I know magnetic force declines with the square of distance, so the peak power would be many times higher. I can instantly see how the power requirements make this impractical, as that's a jet engine's power output to stop a pistol bullet. But I still think in theory a magnet of the right specifications could make the bullet stop dead in its tracks, and also heat it up quite a bit.

Am I correct in this belief? Let's say we want to build one of these, what would be the actual requirements of the magnet and power supply used in this "bullet brake"?--79.97.222.210 (talk) 23:17, 4 November 2014 (UTC)

Several of your concerns are really not a problem. Rapidly dissipating that amount of energy inside the bullet would suddenly and dramatically raise its temperature, but that does not prevent the process from happening in a few milliseconds. And just like a car's engine is much larger and with far lower peak power capability than its disc brakes, the jet engine comparison is all but meaningless. The bullet would have to travel through a region with a strong, rapidly spatially alternating magnetic field, e.g. a set of neodymium magnets with opposing poles directed at each other across a gap barely wide enough to allow the bullet to pass, with the poles alternating rapidly along its travel. The bullet would have to be made from a material that had a suitable resistivity and ideally not ferromagnetic. As with any eddy current brakes, this would become ineffective once the bullet's velocity was low, but by then most of the braking would have been done. As to the power supply, there would be none: only solidly mounted magnets mounted in a suitable configuration. —Quondum 03:41, 5 November 2014 (UTC)

If the bullet hits a person, it might still do damage, not due to it's speed but due to it being molten metal at that point. StuRat (talk) 12:13, 5 November 2014 (UTC)

Depends on the setup. If you use a 100m long tube, with a cascade of powerful magnets, it should not be a problem. If you would try a wall of magnets the bullet can hardly be stopped with it. You would need a very high Deceleration force to brake the bullet from around 300 m/s like above example to zero in 2.33 ms. --Kharon (talk) 12:42, 5 November 2014 (UTC)

Have a look at the "Fun with an MRI magnet" YouTube video (can't post the link) of a guy throwing an aluminium ball into the cavity of an MRI machine. It looks as if the repulsive force gets greater as the speed of the object increases, so it might repel a bullet. Of course, the momentum has to go somewhere, so it might destroy the magnet. --Heron (talk) 19:44, 5 November 2014 (UTC)

November 5

7 or 10 listeria species?

I'm confused because in the beginning of the article is written that "Listeria is a genus of bacteria that contains seven species:", and later in this article itself:" The genus Listeria currently contains ten species: L. fleischmannii, L. grayi, L. innocua, L. ivanovii, L. marthii, L. monocytogenes, L. rocourtiae, L. seeligeri, L. weihenstephanensis and L. welshimeri.". so what's right? 213.57.99.33 (talk) 03:50, 5 November 2014 (UTC)

Another one: "the overt form of the disease has a mortality rate of about 20 percent" while in this article itself says: "The case fatality rate for those with a severe form of infection may approach 25%". it looks like as if many people the article without reading the previous things. 213.57.99.33 (talk) 03:55, 5 November 2014 (UTC)

Without getting into the specifics of this article; this may be the case of people (likely multiple different editors) adding information from multiple sources and different times. I would not be entirely surprised that different sources would disagree on exactly how many species of Listeria there were, or that different studies would come out with different data as to mortality/fatality rates (especially where the sources may not even be measuring comparable things). --Jayron32 04:00, 5 November 2014 (UTC)

If all the sources are reliable, the solution is to say there are 7-10 species with a 20-25% fatality rate. As for why they can't agree on the number of species, there could either be disagreement on whether 3 are listeria, or whether those 3 are separate species or just strains of other listeria species. StuRat (talk) 12:08, 5 November 2014 (UTC)

This all seems reasonable. I'll remind the OP that Misplaced Pages:Wikipedia_is_not_a_reliable_source, and this kind of thing is to be expected, especially in biology/taxonomy, where there are few universally "correct" answers. Even textbooks have this kind of issue, but they are written by experts who know when to leave out details, or know what study is most relevant for the current topic. SemanticMantis (talk) 15:52, 5 November 2014 (UTC)

Why does infusion bag need an expiration date?

I would like to understand why does "infusion bags" need an expiration date. What does it say when the date comes? it says this is a time it has a high potential to be contaminated? the same question about Oxygen tanks that have an expiration date. 213.57.99.33 (talk) 05:25, 5 November 2014 (UTC)

I suppose the assumption is that you expect those things to be "sterile", uncontaminated, fresh, etc with a HIGH degree of certainty. Under ideal conditions, I guess you'd expect the oxygen in a sealed tank to remain uncontaminated "oxygen" for a very, very long time, but there are seals, gaskets, perhaps lubricants, which do not last indefinitely. tanks can get knocked around, dropped, bags get handled, bent, folded... To be certain the item you have is "good" it should be below a certain age. Vespine (talk) 05:53, 5 November 2014 (UTC)

Also, plastic infusion bags may contain chemicals which slowly leak into the contents. The longer they sit, the more leaching occurs. And the manufacturers probably only test them to a certain age, so can't say one way or the other if they are good past that age. StuRat (talk) 12:05, 5 November 2014 (UTC)

It's commonly the case with medical supplies that the legal requirement to specify how long the product is good for is onerous for the manufacturers to test. If I come out with some new infusion bag, if I want to stick a 10 year expiration sticker on it - then I have to prove to the FDA that it'll still be OK in 10 years - and it could easily take me 10 years of testing to prove that...even if I know that the plastics it's made from should last for 1,000 years. Since I'll go bankrupt if I have to sit around for 10 years testing without being able to sell a single infusion bag, I'm much more likely to test for 1 year and put a 1 year sticker on it...even though the product might easily last 100 years.

The FDA created this rule in 1976 - and they weren't trying to be very subtle about it. So *all* drugs, *all* supplies and *all* medical devices are required to have an expiration date, even if they are some simple mechanical item or something that seems to be obviously safe - like a gas cylinder. This is why cotton balls used in hospitals cost twenty times what cotton balls sold to the general public for makeup removal cost...and have an expiration date of a few years - even though they are the exact same product you use at home with no expiration date.

There was a case some time ago (see ) when the US military had a small mountain of drugs that they'd stockpiled in case of some hypothetical emergency - which were due to expire quite soon, or which had already expired. The cost of dumping all of those drugs lead them to actually test their viability and they found that 15 years after the expiration date, 90% of the kinds of drugs they had were still just as good as the day they were purchased...so they extended the expiration dates. But it's rare for organizations to have such gigantic stock-piles of unused drugs (or infusion bags or whatever), so the cost of re-testing them by far exceeds the cost of tossing them out and replacing them. So in general, tons of completely usable, safe, materials are dumped just because nobody can afford to keep testing them.

SteveBaker (talk) 16:22, 5 November 2014 (UTC)

Wouldn’t disagree with anything Steve said yet to add only that infusion bags can become contaminated over time by the plasticisers used in plastic that the bag is made from. See the section PVC and DEHP in medical products: --Aspro (talk) 22:16, 6 November 2014 (UTC)

the Oxygen in the tanks is in liquid or gas condition?

213.57.99.33 (talk) 08:40, 5 November 2014 (UTC)

The critical point of oxygen is -118.56°C (ref Wolfram Alpha). Thus it needs to be kept below that temperature to be liquefied. LOX (liquid oxygen) is used for rockets, but not generally for other purposes. CS Miller (talk) 12:23, 5 November 2014 (UTC)

supercritical oxygen could be thought of as a liquid if it is condensed to the density to be expected of liquid oxygen; but it would still (even under those conditions) more closely resemble a gas, as the molecules will still have enough kinetic energy to overcome the bonding energy necessary to hold the molecules in a true "liquid" phase. That's the molecular definition of a supercritical fluid: the temperature at which the kinetic energy of the molecules is greater than the energy needed to hold the molecules together. --Jayron32 13:42, 5 November 2014 (UTC)

Liquid at 200-300 bar. --Kharon (talk) 12:24, 5 November 2014 (UTC)

Man turns mobile off whilst committing crime?

I've taken the liberty of moving this to Misplaced Pages:Reference desk/Humanities#Man turns mobile off whilst committing crime?, which discusses legal and social matters. Wnt (talk) 13:31, 5 November 2014 (UTC)

Note: if you are actually interested in how precisely companies can determine when a cell phone was off, I'd probably recommend the Computing refdesk, but be clearer when you ask that you're interested in technical capabilities rather than admissibility. Wnt (talk) 13:38, 5 November 2014 (UTC)

How common are capacitors that can hold a charge for several days?

Are there any household machines (or anything that private people use) that use these? The wash-machine maybe, the car? How much electricity can they be charged with?--Senteni (talk) 18:36, 5 November 2014 (UTC)

I can't answer with numbers, but proper safety practice calls for adding Bleeder resistors. Ariel. (talk) 19:54, 5 November 2014 (UTC)

Old televisions (CRT type) have large capacitors. Rmhermen (talk) 22:17, 5 November 2014 (UTC)

There are few (if any) modern household appliances that do this - mostly because it's potentially dangerous. I have a couple of laser cutters that have capacitors that retain enough charge after a couple of hours to produce a three inch spark at a few thousand volts...these are hardly "household" appliances but plenty of hobbyists have them. so they fit the "anything that private people use" category.

Our article mentions the flash unit on a disposable camera as containing a potentially lethal capacitor...those things are becoming rare - but you still probably still find them in people's homes.

Supercapacitors can store immense charges - but they start to blur the line with rechargeable batteries, which, in a sense are just capacitors too. SteveBaker (talk) 23:58, 5 November 2014 (UTC)

Just to help us get a feel for it, can you quantify the size of your capacitors? Are we talking a few Farads, or many? SemanticMantis (talk) 15:22, 6 November 2014 (UTC)

• If the two ends of a capacitor are very well insulated from each other, its ability to hold charge is determined by its leakage rate. I believe that most ordinary capacitors are capable of holding a charge for days without major loss. Low-leakage capacitors can hold a charge for months. The maximum charge that a capacitor can hold is determined by its dielectric breakdown point, which depends on the quality of construction. Looie496 (talk) 16:25, 6 November 2014 (UTC)

understanding the waveform representation

If an oscillogram depicts a wave around the x axis, and there are values that are positive and negative for the y-axis. The y-axis represents frequency, but how can the frequency be negative? And don't we need multiple values at the same time on the y-axis for all frequencies? Think https://en.wikipedia.org/Praat#mediaviewer/File:Spectrogram_-_mot%C3%A1ngo_mwa_basod%C3%A1.png --Senteni (talk) 19:57, 5 November 2014 (UTC)

An oscilligram depicts amplitude vs. time (not frequency vs. time). Typically, there is some sensitive element that responds to sound waves (such as a microphone transducer), and the y-axis is proportional to the back and forth fluctuations in that element caused by passing sound waves. Dragons flight (talk) 20:04, 5 November 2014 (UTC)

On the image in question, the upper trace is an oscillogram (with positive and negative y-axis values), and the lower trace is a spectrogram (with only positive y-values). Tevildo (talk) 20:12, 5 November 2014 (UTC)

That's a confusing plot to say the least. The upper window appears to be the time history of the sound waveform, in black. As such it will oscillate around 0 Pa. I suspect the vertical blue lines represent the occurence of peaks in the time history, the interval of which is plotted as its reciprocal in the blue curve in the lower plot. The lower plot is what I'd call a spectogram, a 2d representation with frequency on the y axis, time on the x axis, and intensity of that frequency and time represented by grey scale. I do not understand the left and right hand y axis notations, the red dots appear to be some sort of peak picking algorithm. Greglocock (talk) 22:38, 5 November 2014 (UTC)

It's not confusing if you are familiar with spectrograms. I would go so far as to call this a "standard" plot format for certain types of digital signal processing. Nimur (talk) 22:34, 5 November 2014 (UTC)

Oh yes, try explaining to an engineer why there are two y axis scales and no explanation as to which data uses which one! Greglocock (talk) 22:38, 5 November 2014 (UTC)

Regarding the plot arrangement: there are two plots. One who is familiar with waveform analysis will very quickly visually identify that the two plots correspond to a waveform and a spectrogram. One who is unfamiliar would do well to read the caption.

Regarding the colors: the image has a caption:

• light blue line = pitch (as documented)
• dark blue lines = pulses
• red dots = formants (as documented)

Here is a link to the Praat software tool official website.

Here's a tutorial, Praat Sound Window, from UNC's computational linguistics program.

Nimur (talk) 22:44, 5 November 2014 (UTC)

Black Holes, Dark Matter, General Relativity

Why aren't dark matter, black holes and general relativity labeled as pseudoscience? All three concepts fit the description of pseudoscience very well. We do not need to delete these articles, just label them correctly. Wavyinfinity (talk) 21:28, 5 November 2014 (UTC)

Who says they're pseudoscience? ←Baseball Bugs carrots→ 21:35, 5 November 2014 (UTC)

Because e.g. black holes are not pseudoscience. Our article defines: "Pseudoscience is a claim, belief or practice which is falsely presented as scientific, but does not adhere to a valid scientific method, lacks supporting scientific evidence or plausibility, cannot be reliably tested, or otherwise lacks scientific status."

Black holes are considered plausible by the astrophysics community. They have plenty of scientific evidence for their existence and most published results about them conform to the scientific method. We even have a whole section on Black_hole#Observational_evidence. The same goes for dark matter and general relativity (they are topics in science, not pseudoscience), which I think you'd know if you'd read the articles carefully. I'm assuming good faith here, but you should know that your question sounds a bit like trolling. SemanticMantis (talk) 21:37, 5 November 2014 (UTC)

(edit conflict)No, they don't fit the description you claim, because they are attempts to explain observations. Science starts with evidence and develops theory to explain it. (I agree that sometimes speculative science puts forward a theory that goes beyond the available evidence, but it then looks for evidence to confirm or refute the extended theory.) Have you read the articles that you link? (Do you believe in infinity? ) Dbfirs 21:38, 5 November 2014 (UTC)

Read the essay on the user's page and it will be clearer where he's coming from . ←Baseball Bugs carrots→ 21:41, 5 November 2014 (UTC)

The definition of pseudoscience (at least according to Wiktionary) is:

"Any body of knowledge purported to be scientific or supported by science but which fails to comply with the scientific method."

(Other dictionaries define it similarly)

So:

1. Do these fields of study "purport to be scientific"? Well, yes...duh!
2. Do they "comply with the scientific method"? Yes, they do. They propose hypotheses, they make predictions that are (at least in principle) testable, they don't make unfalsifiable claims, they perform experiments and/or observations in an effort to prove (or disprove) those predictions. They publish results in peer-reviewed mainstream journals. Experiments and/or observations are repeated independently where possible. This is "THE SCIENTIFIC METHOD" at it's finest.

Now, it's very possible that any or all of these things might turn out to be false. But that's not the acid test of pseudoscience.

Pseudoscience is something like Homeopathy where they make scientific claims (in this case that diluting some active ingredient to the point where there is none left leaves a stable 'imprint' in the water - and that the resulting water can cure illnesses) - but they do not create working hypotheses, they do not perform experiments (like a double-blind drug trial would do), they don't do peer reviews and publish results in mainstream journals. They are making clearly testable scientific claims yet NOT following the scientific method...so they are pseudosciences.

A religion, on the other hand does NOT make scientifically testable claims (their claims are generally non-falsifiable) - so the scientific method is inapplicable, even in principle - so they are not pseudoscience.

Pseudoscience is NOT the same thing as bad science or unproven science or disproven science. So even if you believe that black holes do not exist - that doesn't make the field of study "pseudoscience".

Cold fusion is a good case in point. It was claimed to occur, they tried to do experiments to prove it, the experiments were written up, peer reviewed and published, efforts to repeat the experiments failed - and now it's (generally) believed to be false. But it's definitely science and not pseudoscience because they followed the scientific method. Our article correctly labels it as "pathological science" - but not pseudoscience.

Misplaced Pages has very clear rules about pseudoscience and how it's determined and labelled - and the things you mention are not remotely it.

If you want a target to attack, you might try Freudian psychoanalysis (for example) - which makes scientific claims and has historically failed to do serious experimentation to back up those claims.

SteveBaker (talk) 23:37, 5 November 2014 (UTC)

It's nice that you all are trying here, but I feel the need to bring forth this rather reliably true aphorism: You cannot reason a person out of a position they did not arrive at via reason. The entire question above, and their entire main Misplaced Pages page screams "Science is hard and stuff, and it's easier to reject the things I don't understand than to either a) understand it or b) trust the people that do". It does no good to argue with people this far out of touch with reality. At best we can remind the rest of the world how silly they are. But people like this are a lost cause. --Jayron32 00:23, 6 November 2014 (UTC)

Given the following quote on the user's page, the full screen of discussion here is somewhat amusing:

"1. Hit and Run tactics. Post things on public forums like Einstein was an idiot, Stephen Hawking is a pawn for the mathematical priests of establishment. Do not respond to the replies, just post these things and then do something else with your time. You must insert ideas that can not be said otherwise because they are taboo. These taboo statements are incredibly dangerous to establishment."

MChesterMC (talk) 09:23, 6 November 2014 (UTC)

"The establishment", sure. It would be interesting to see a public opinion poll as to what percentage of the public either knows or cares about this subject. ←Baseball Bugs carrots→ 11:51, 6 November 2014 (UTC)

I suggest you take greater caution in the future. I'm not going to report you, but your topic ban seems very broad "everything related to astrophysics or cosmology" User talk:Wavyinfinity#Arbitration enforcement topic ban: Pseudoscience so it can likely be said to apply to the RD, particularly since, as many including the topic closer have suggested, you appear to be either trolling or soapboxing/POV pushing rather than asking a genuine question even if it's not clear you're trying to harm wikipedia by advocating for changing articles. I presume you know it's very broad, since you were blocked for fooling around with a wikiproject . Nil Einne (talk) 18:01, 6 November 2014 (UTC)

How would Freud Interpret This Dream?

Just out of curiosity i always wanted to know how sigmund freud would interpret this dream, with his theory of dream analysis.The dream itself is something like this a man walks down a flight of stairs following a trail of blood to find his father lying in a pool of blood. This has always been something i wanted to know. Help from my fellow wikipedians would be greatly appreciated, THANKS. — Preceding unsigned comment added by 173.52.22.58 (talk) 22:45, 5 November 2014 (UTC)

We can never know what a dead person would think, but you can read about what he did think!

The Interpretation of Dreams (1900) is available at no cost in German from Project Gutenberg, and in English from other websites. Several other translations are listed in our article. Another of his works, Dream Psychology (1920) is available in English from Project Gutenberg.

I read The Interpretation of Dreams a long time ago. Reading Freud's own writing proved to me to be the most damning cases against Freudian psychology as a scientific enterprise. Nimur (talk) 22:52, 5 November 2014 (UTC)

If someone else's interpretation can help you, walking down stairs "might suggest being in control of a changing situation." Bleeding (from the same source) "could mean hurtful remarks, for instance being told we are not loved." Seeing a dead parent is "either the beginning of independence from parent or repression of the emotions they engendered in us."

In my absolutely unprofessional opinion, you murdered your father and mostly forgot about it. Also, your house is haunted. InedibleHulk (talk) 23:03, November 5, 2014 (UTC)

The dream is about anxiety. Now, donate 5 dollars to your favorite charity, in my name. ←Baseball Bugs carrots→ 23:11, 5 November 2014 (UTC)

• Of course we can't know what Freud would have said, but it isn't hard to guess. The fundamental tenet of Freud's theory was that all dreams consist of wish fulfilment. What sort of wish is being fulfilled in that dream? Well, another basic tenet of Freudian theory is that every male child has an Oedipal desire for his mother and therefore is jealous of his father. So this one is pretty easy. (My personal view is that the idea of dreams as wish fulfilment has some validity, but doesn't apply to all dreams and in any case Freud's use of it was utter bullshit.) Looie496 (talk) 16:12, 6 November 2014 (UTC)
  • I always figured Freud was into that, and assumed everyone else was too. ←Baseball Bugs carrots→ 16:29, 6 November 2014 (UTC)

Can an healthy man use a medical oxygen for breathing?

I've heard that using of a medical oxygen when it's not needed, is harmful. That's right and based on a reliable source? 213.57.99.33 (talk) 23:18, 5 November 2014 (UTC)

I think this is bordering on medical advice - and we're not allowed to provide that here on the ref desk. SteveBaker (talk) 23:22, 5 November 2014 (UTC)

The OP should consult Google, which I expect would have many references (albeit many of them bad information). ←Baseball Bugs carrots→ 23:26, 5 November 2014 (UTC)

No, the OP should consult a doctor. SteveBaker (talk) 23:38, 5 November 2014 (UTC)

Oh, please. The OP is seeking information, not advice, and even if advice were sought, we are at liberty to provide information not related to a specific case. Aside from pointing out that medical oxygen is essentially pure oxygen, the oxygen toxicity article linked by InedibleHulk below is probably a good place to start. Essentially, unless unusual conditions exist or where ambient pressure is elevated above that at sea level, there is no reason to suggest that breathing pure oxygen, especially over a limited period, would be harmful to the majority of individuals. —Quondum 00:09, 6 November 2014 (UTC)

I'm pretty sure we're allowed to say oxygen toxicity exists. InedibleHulk (talk) 23:46, November 5, 2014 (UTC)

Thank you. I've found this article: Oxygen therapy, and it refers this issue. (By the way, it's so interesting to understand why this information is bordering on medical advice - when it's in the article.213.57.99.33 (talk) 23:51, 5 November 2014 (UTC)

The issue is that what's in the article has been massaged over the years by many editors to be good, well sourced content. What gets written here is not in the same class. Anyone can write anything they think of here. Not to be trusted. (Not even my comments.) HiLo48 (talk) 00:01, 6 November 2014 (UTC)

Though if we refer people to that good, well-sourced content, it's not us they're trusting. If they even need to be trusting in the first place. The question didn't suggest "I'm considering taking oxygen I don't need. What should I do?" to me. Just looking for a source to verify whether it's generally harmful. Almost every question here can be taken with suspicions about the asker's reasons, but if they're not provided, I assume generic curiosity. Telling people to consult a doctor is medical and often financial advice, even if the assumption that they need one is correct. InedibleHulk (talk) 00:24, November 6, 2014 (UTC)

Hyperventilating with pure oxygen is necessary if you need to hold your breath for a long time. Count Iblis (talk) 04:29, 6 November 2014 (UTC)

• If the OP is a medical volunteer he should also ask his supervisor whether he should be researching such questions here. I had a friend training as an EMT in college who lost his job because he listed a patient's body temperature as 95F when tradition required it be rounded to the nearest even number. Should you suddenly come out with "but I was told on wikipedia that..." you may find yourself summarily dismissed. μηδείς (talk) 17:12, 6 November 2014 (UTC)

Our article on oxygen toxicity covers the main points that I'm aware of as a former clinical data analyst and biomedical engineering technologist. Further than that, I agree we oughtn't to be giving advice on when and how oxygen ought to be used to questioners. We don't know what their health status or their reasons for asking are, and any information beyond sourced material in the oxygen toxicity article falls under the general medical advice prohibition here.

It occurs to me that the OP seemed to be asking how safe medical oxygen was compared to, say, oxygen intended for SCUBA mix or welding oxygen. The same hazards listed in our article on oxygen toxicity apply regardless of whether the oxygen is USP (prepared according to the specs in the United States Pharmacopeia for medical use), non-medical oxygen for SCUBA or other nonmedical life support applications, or industrial oxygen (except that additional hazards may exist when industrial (welding) oxygen is used owing to impurities. loupgarous (talk) 01:02, 7 November 2014 (UTC)

Both oughtn't and ought not have become rare in North America. Oughtn't in particular may not be understood  :) Count Iblis (talk) 19:47, 7 November 2014 (UTC)

November 6

filling an oxygen in the bottles from three others continuously

I've noticed when the First-Aid-responders fill their small tanks, they fill the oxygen by three big tanks. It says, they take one small tank (2 liter approximately) and connect it to one big tank and open the tap, after a minute they close the tap they pass the small tank to another tank big one for a minute, and eventually they do the same processes with another big one tank (third time...) I'm volunteer student, and I would like to understand what happen here... 213.57.99.33 (talk) 00:08, 6 November 2014 (UTC)

My supposition is that this arrangement results in a higher final pressure for all the small tanks than if the three big tanks were simply connected in parallel, or used individually. The first big tank loses the most pressure, but the pre-pressurisation of the small tank to whatever its pressure is results in the second big tank losing much less and retaining a higher pressure, and the repetition on the second tank preserves most of the pressure in the final topping-up tank. —Quondum 00:25, 6 November 2014 (UTC)

(edit conflict) Can you point to any images or documents that show this behavior? The process you describe is probably specific to the equipment being used, so I doubt we'll be able to give any kind of a definite answer without more context. Dragons flight (talk) 00:27, 6 November 2014 (UTC)

Here's a nice article from Praxair (one of the largest commercial suppliers of gas products in the United States): An Inside Look. I know from personal experience: it is really complicated to fill a tank with cryogenic liquid/gas like Liquid Oxygen! There are a lot of safety procedures and a lot of practical problems. For example, do you tap from the top or the bottom of the tank? The answer depends on what you are doing. As you fill, the temperatures and pressures in the supply- and the destination vessel are changing - gas always flows from high pressure to low pressure. If there's a gas pressure head, it will drive the liquid to flow in the same direction - even working against gravity! If you aren't carefully watching the pressure, you might be using the small tank to fill the big tank! Be sure to follow safe procedures when you are working with oxygen (... it is a strong oxidizer)! Nimur (talk) 00:39, 6 November 2014 (UTC)

(EC) It sounds like you're referring to a Cascade storage system used for transfilling. Note that images e.g. you can see may be a bit confusing (and I didn't find the explanation in our article very good and most search results are just vendors). It looks like all the tanks are connected together and there is only one output valve you connect to, which may suggest you're using them all at once. However as can be seen in this video , you only open one of the large tanks at a time, moving from low pressure to high pressure which seems to be similar to what you were describing (well you didn't know/mention pressure differentials).

The reasons appear similar to what Quondum said, and as described in the video and also to some extent here . You basically start with a low pressure tank, fill the bottle to equilbrium, and then close it and move on to the next higher pressure one until you reach the desired pressure. That way you can end up with a relatively high pressure in the last larger bottle (which you may not use at all, if your earlier ones are high enough).

Once the last/highest pressure larger bottle is below the minimum pressure needed for you final fill or alternatively if the first/lowest pressure is so low it's rarely useful (like if the tanks you're filling would generally be at a higher pressure), you can just remove the lowest pressure bottle (to be an empty to be filled. And replace it with a full bottle, now the new last tank. You renumber the bottles rather than moving them around, I presume because it's safer and easier.

So you don't end up with a lot of low pressure bottles that are below the minimum needed but still have a fair amount of oxygen (or whatever), in other words, you get more from each large bottle for a given pressure. I'm not sure but there may also be an advantage in possibly reduced temperatures changes, a lower pressure differential and easier monitoring for safety reasons.

The disadvantage may be , although I'm not sure that using a single bottle will help in any way. It may be the alternative the commentators in that link are thinking of is professionally/externally filling the small bottles rather than using a cascading storage system to fill the small bottles by someone for who it isn't their primary job.

BTW, it's somewhat unclear to me if in your example the larger bottles are all connected together (although I note you seem to have added the same video below). As mentioned, this appears to be the norm in such systems (based on the images and vendors) and there would seem to be advantages (namely you aren't moving and reattaching the smaller bottle so much which would seem to be an avenue for mistakes) but I guess it's possible for cost or other reasons, in your example they aren't. I presume they otherwise work similar.

P.S. In terms of numbers, if you only ever use 3 in this set-up before you need to replace the lowest pressure one, then I guess there's probably no advantage to adding 4 more to get 7. Unless for some reason you prefer to keep the "empty" ones in situ and simply unnumber or whatever and don't use them until they are replaced in bulk. Which is possible, since they are probably quite heavy and there are likely additional safety precautions. Nil Einne (talk) 01:28, 6 November 2014 (UTC)

It's kind of what we see in this video (but we have only three big tanks, here there is 7 I think). I must to say, that the three big tanks that I'm talking about they are the same thing: oxigen. (it's written on) 213.57.99.33 (talk) 01:02, 6 November 2014 (UTC)

That cascade storage system article makes a lot of sense. Basically, I assume that the site wouldn't want to return every oxygen container to be refilled the moment its pressure drops below whatever they're filling the little containers up to. Not when you can still use the depleted containers to fill little containers that are nearly empty... the rest follows logically. To me this seems very similar in concept to a countercurrent exchange. Wnt (talk) 02:52, 6 November 2014 (UTC)

This is a really neat analogy. With enough bottles in the cascade, one would expect that energy put into the compressed gas in the small cylinders is transferred from the cascade with efficiency approaching 100% (asymptotically); also, the cooling due to decompression will be asymptotically zero. —Quondum 14:08, 6 November 2014 (UTC)

The relation between Pulmonary embolism and birth

From time to time we hear about women who get PE (Pulmonary Embolism) as a result of birth. My question is what is the relation between the two. And why does the birth raise the risk of getting it? 213.57.99.33 (talk) 01:13, 6 November 2014 (UTC)

In this freely-available, high-quality article describing the risk factors for venous thromboembolism (e.g. PE), the authors note that the risk starts rising in the first trimester, and is primarily attributable to changes in the blood levels of clotting (and natural anticoagulant) factors. They argue teleologically that the shift to increased tendency for clotting might protect against hemorrhage, a major cause of death during pregnancy. -- Scray (talk) 02:02, 6 November 2014 (UTC)

Thank you deeply! now it makes sense. 213.57.99.33 (talk) 02:14, 6 November 2014 (UTC)

Air permeability of glass

I find it HIGHLY unlikely. The internuclear distance between the silicon and oxygen atoms in SiO₂ (glass, quartz, etc) is about 1.67 angstroms (0.167 nanometers).. Air is basically a mixture of O₂ and N₂. The internuclear distance between oxygen and nitrogen atoms in molecules of O₂ and N₂ is 0.120 nm and 0.110 nm respectively: . So, IF you had a sheet of glass that consisted of a SINGLE atomic layer of silicon dioxide the pore size would JUST be big enough to let a molecule of air slip through OCCASIONALLY, if it hit the EXACT hole at the EXACT right angle, maybe. In glass as thick as that flask, you've got a network many trillions and trillions of atoms thick; there just aren't any pores large enough to let any molecules of the air through, given the tolerances we're talking about here. Ain't no way. Assuming there isn't any other way for the air to leak out, it certainly isn't coming through the glass itself. --Jayron32 12:21, 6 November 2014 (UTC)

Diffusion does occur in solids. Water, in fact, is particularly fast as it actually reacts with silica up to about 1% of its normal density! At high temperatures, the effective diffusion coefficient is high enough that the glass is quite permeable indeed; I get a 6-meter scale length for the diffusion profile after 150 a. However, at room temperature the Arrhenius equation predicts so much slower a process that the scale length is just 3 μm. The diffusion coefficients for air are theoretically larger at high temperatures (above 1500 K, which (coincidentally?) is the glass transition temperature for fused quartz), but because it cannot diffuse chemically, the activation energy is almost twice as large and the room temperature rates are much smaller. It looks like room-temperature nitrogen can cross only about one atomic layer in the glass even over 150 a. --Tardis (talk) 14:53, 6 November 2014 (UTC)

Nice explanations, I think the OP has a good answer now. Related: does anyone think this would be worth adding to our article on Long-term_experiments? On the one hand, we could say the experiment is over, and helped disprove spontaneous generation. On the other hand, we could say that it has only disproven spontaneous generation on a ~150 yr time scale! I see this jar as similar to the Oxford_Electric_Bell (which is also included in the article). The Oxford Bell is similarly not really an active experiment, it's just a neat old science artifact that is still around. SemanticMantis (talk) 16:36, 6 November 2014 (UTC)

• Isn't the much larger electron cloud of Si going to be more important in stopping diffusion than the relative internuclear distances, nucleii being point particles for the purposes of this exercise? Also, N2 and O2 are much bigger molecules than H2O, aren't they? I imagine trying to sneak a pair of apples through a wall of bricks a mile thick. Of course, if the internal surface of the glass oxidizes, could not a charge differential eventually lead to the loss of a few O2 molecules or SiO2 molecules from the outside. Maybe over the length of time the flask will simply shrink as (X)O2 is lost from its outer skin? μηδείς (talk) 18:55, 6 November 2014 (UTC)

  Glass contains no O2 molecules, nor strictly, does it contain any SiO2 molecules. Silicon dioxide (quartz, glass, etc.) is a network solid and does not contain any discrete molecules, as such. The formula SiO2 is merely the ratio of Silicon to Oxygen in lowest terms and does not imply the existence of discrete molecules as such. The actual composition is basically this pattern of atoms repeated billions and billions of times in all dimensions. --Jayron32 02:46, 7 November 2014 (UTC)

Right, and in case anyone doesn't know, the structure in the bottle walls is not precisely that pattern, because glass is an amorphous solid. SemanticMantis (talk) 14:17, 7 November 2014 (UTC)

Sideeffects of Madras Eye

Recently, people who suffered Madras Eye(Conjuctivitus)are found having some sideeffects in addition. The skin of their whole back is reddish with itches. Is this the sideeffect of Madras Eye.117.193.119.71 (talk) 16:31, 6 November 2014 (UTC)

See what Pinkeye has to say about it. Anecdote: I've had it in the past, and my back was unaffected. ←Baseball Bugs carrots→ 16:58, 6 November 2014 (UTC)

Conjunctivitis is a type of disease caused by many different pathogen. The OP should look at Madras Eye and if that doesn't help, google ("Madras Eye" and "Back Rash") if this is a question of curiosity or, if he has a rash, ask a doctor about it. μηδείς (talk) 17:02, 6 November 2014 (UTC)

Also see Hives for the back itches. Ariel. (talk) 12:03, 7 November 2014 (UTC)

Oils and the Trachea

Can some edible large-chain Oils, and especially Mineral-oils "find there way" into the Trachea and "Settle" there? while food is swallowed?, if yes, can it be problematic to Humans&Animals consuming them?, thanks. Ben-Natan (talk) — Preceding undated comment added 17:40, 6 November 2014 (UTC)

This sounds like some sort of bizarre plot to kill Batman in the 1960 TV series. Not a direct answer, but see cough, and aspiration pneumonia. μηδείς (talk) 18:58, 6 November 2014 (UTC)

If I understand correctly, Whenever oils get into the Trachea, the Cough-able Organism would Cough till they come out? (As clued, I don't know if I understand correctly). Ben-Natan (talk) 21:09, 7 November 2014 (UTC)

Kindle region restriction

I've taken the liberty of moving this to WP:Reference desk/Computing#Kindle region restriction. Wnt (talk) 20:42, 6 November 2014 (UTC)

How much oxygen liquid will be in the same tank

If I have 2.4 liter oxigen tank in the room temprature,how much oxygen liquid will be in the same tank in condition of the boiling point? How can I calculate it?5.28.172.180 (talk) 20:52, 6 November 2014 (UTC)

Are you asking how much volume 2.4 liters of liquid oxygen would take up once it has boiled and been brought to room temperature at standard pressure? -- ToE 22:27, 6 November 2014 (UTC)

I think the OP is asking "If we cool the tank from room temperature to the boiling point of oxygen, what will be the volume of the liquid?" To answer this, we need to know the pressure of the oxygen tank at room temperature. From this, we can work out the mass of the oxygen using the ideal gas equation - we know p, V, T and R, and the molar mass of oxygen is 32 g/mol (it's actually 31.9988, but 32 will do for this calculation). The density of liquid oxygen is 1.141 g/cm (from our liquid oxygen article), which enables us to calculate the volume from the mass. Tevildo (talk) 22:45, 6 November 2014 (UTC)

Sorry for my abstruseness. I mean to ask: how much oxygen liquid could enter in the same tank of 2.4 liter oxygen (gas)? 149.78.27.187 (talk) 03:13, 7 November 2014 (UTC)

2.4 litres of liquid oxygen have a mass of 2.738 kg (this just uses the density). It wouldn't be possible to use the oxygen tank to store liquid oxygen, as the tank is not insulated, and the oxygen will boil off. If you want to know how much liquid oxygen is needed to fill the tank with oxygen gas at room temperature, we still need to know the (maximum) pressure. 2.74 kg of oxygen in a 2.4 litre tank at room temperature would require a pressure of about 900 bar, which is much higher than the maximum pressure of a normal oxygen tank. Tevildo (talk) 11:40, 7 November 2014 (UTC)

You may be interested in the concept of molar volume, which allows you to do quick calculations while avoiding explicit use of the ideal gas law. The molar volume for 1 atmosphere of pressure is 24.465 L/mol at 25 °C. One mole of O₂ masses 32 g, so if you divide by the density, 1.141 g/cm, you find that one mole of liquid oxygen takes up only 28.05 cm. If you divide that into the 24,465 cm molar volume you can show that when liquid oxygen boils off and reaches 25 °C at 1 atmosphere of pressure it increases in volume by a factor of 872. Thus you would need a 2094 L balloon to hold the result of boiling off 2.4 L of liquid oxygen. But I think that you are asking about storing that O₂ in a tank instead of a balloon, so as Tevildo says, you need to specify the pressure of that tank, as the higher the pressure the smaller the volume is needed to contain the same amount of gas. From our oxygen tank article: "Oxygen is rarely held at pressures higher than 200 bar / 3000 psi due to the risks of fire triggered by high temperatures caused by adiabatic heating when the gas changes pressure when moving from one vessel to another." 1 atm (standard atmosphere) of pressure is just over one percent more than 1 bar. If we compress our 2094 L of O₂ to 200 atm (2393 psi -- note that 3000 psi is the working pressure of the AL80 scuba tanks commonly used in the United States), then the volume will decrease by a factor of 200 to 10.47 L. (See Boyle's law, one element of the ideal gas law.) Thus you need a 10.47 L, 200 atm working pressure tank to hold the same oxygen as held by a 2.4 L Dewar flask filled with liquid oxygen.

So the take away here is that O₂ at 200 atm takes up 4.36 times as much volume as when liquefied.

( 1 atm / 200 atm ) * (24.465 L/mol) /

In practice, most medical O₂ tanks I have seen are pressurized to 2200 psi which is only 150 atm, but searching online I see that 230 bar (3336 psi or 227 atm) high pressure medical oxygen cylinders are available, so the actual multiple you want will depend on the working pressure of your tank.

Is this what you were looking for? -- ToE 13:53, 7 November 2014 (UTC)

November 7

Sun/Star

Hi everyone!

I would like some help with the following questions please:

1. Does a star’s solar mass increases/decreases as they evolve/age?
2. Is Blue staggers real or fake?
3. After a protostar is formed, what comes next a blue star or an orange star?
4. Pre-main sequence or post-main sequence star, is it the protostar creation period or the protostar itself?
5. Main sequence star, can a blue star fall in the main sequence period… or main sequence is just called an yellow star from ZAMS?
6. Is the following, the true steps a star’s life follows? – protostar (baige colour), Blue star (after its fully formed), yellow star, orange star, red star, white star, neutron star (what colour?), black star (black hole).
7. What is a dead star?
8. What is a black hole? A ‘dead star’ or a ‘black hole’ just like a drain.
9. When was ‘Dark age’ and when was ‘reionaziation’ epoch? Did Reionaization occur during the dark ages?

(Russell.mo (talk) 01:38, 7 November 2014 (UTC))

1. A star's mass decreases over time for several reasons 1) It is giving off a ton of energy in the form of light, and energy is mass. 2) It is also shedding mass directly in the form of solar wind. Early in their life they are gaining mass as they actually form as gravity pulls them together, but eventually they start to lose mass.
2. The only references I can find to blue staggers are the plant Dicentra cucullaria aka Dutchman's Breeches: . They're quite real.
3. You can read more about the life cycle of stars at Stellar evolution.
4. See above
5. See above
6. See above
7. See above
8. See black hole
9. The dark ages can mean many things, I assume you mean the one from astrophysics. You can also read about the reionization epoch at the article titled Reionization.

I hope that helps some. --Jayron32 02:41, 7 November 2014 (UTC)

You deserve the masochist's barnstar for that one, Jayron. μηδείς (talk) 02:43, 7 November 2014 (UTC)

In this context, "Blue staggers" is probably luminous blue variable, and, yes, they do exist. Tevildo (talk) 02:47, 7 November 2014 (UTC)

Or possibly a Blue straggler star. CS Miller (talk) 12:26, 7 November 2014 (UTC)

I've read through point 3, 8, the things I mentioned were unclear that's why I asked... Can some help me understanding by explaining in simple terms please? -- (Russell.mo (talk) 18:45, 7 November 2014 (UTC))

If you could point out passages from the stellar evolution article which are unclear, perhaps we can help make them more clear. The article is fairly well written and quite accessible, but if there are words or statements in that article that you are struggling with, let us know, and we'll try to explain them a bit differently if we can. --Jayron32 21:41, 7 November 2014 (UTC)

Prestressed concrete failure

Is it correct to say that the failure of a prestressed beam is explosive due to the stresses which have built up in the concrete? — Preceding unsigned comment added by 194.66.246.101 (talk) 19:06, 7 November 2014 (UTC)

This is just off the top of my head: As the 'tensional' stress is in the rebars, The failure is not down to the stress in building up in the concrete. High alumna cement (for example) when poorly mixed (too much water) may start to crumble and loose the 'compressive' strength required to hold the rebar stress in place- which is imposed during casting. The compressive stress within the concrete is already imposed in casting and curing, so should not (I think) build up over time. Off the top of my head again: I think that rebars lose about 5% of their strength per decade. Therefore, by my reckoning the stress on the concrete is ever diminishing not building up. Err.. does that make sense. It is not the build up of stress “in the concrete” but the reduction of the concrete’s ability to resist the tension stress imposed on it by the rubars.Also, cracks in the concrete can allow water and atmospheric oxygen to get down to the rubars. This makes them corrode. The corrosion not only weakens the rubars, it also causes them so expand volumetrically, which makes the concrete cocoon spall off. Which will further weaken the structure. Possible leading to an 'explosive' or rapid unscheduled disassembly of the building or structure (in other words - it collapses). This maybe the phenomena of which you maybe inquiring about. --Aspro (talk) 19:49, 7 November 2014 (UTC)

Organic chemistry question

Say, in an organic compound, we have a main chain of nine carbons (-nonane); on the sixth carbon there is a propyl side chain (normal position), while on the fifth carbon there is an isopropyl side chain; would the preferred IUPAC name be "5-isopropyl-6-propylnonane" or "5-s,6-dipropylnonane"? Thanks 74.15.5.210 (talk) 21:41, 7 November 2014 (UTC).

Neither. It would be 4-propyl-5-isopropylnonane. Always number from the end which gives you the lowest numbers for your side chain. --Jayron32 21:45, 7 November 2014 (UTC)

Actually, it might be 5-isopropyl-4-propylnonane. I think you put side chains in alphabetical order. But you would still always number from the short end. You'd never have a 5,6 nonane, because 4.5 nonane is a lower way to name the same molecule, whatever the side chains are. --Jayron32 21:47, 7 November 2014 (UTC)

5-isopropyl-4-propylnonane is correct according to the IUPAC rules for alkanes. Longest chain gets the root name, than side chains in alphabetical order, then lowest (total) numbering. Mihaister (talk) 23:00, 7 November 2014 (UTC)