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March 23

Hospitals inhibiting cell phone signal

I was at a hospital and noticed that my cell phone was getting no signal despite the hospital being in a major (population in the millions) city of a modern industrialized country with generally excellent cell phone coverage. I'm aware some hospitals have a rule not to use cell phones over concerns, founded or unfounded, over cell phones having a small possibility of interfering with medical equipment, but a nurse whom I was talking with told me something I found surprising: she claimed that the hospital not only had a rule banning cell phone usage, but that I was getting no signal because the hospital was somehow inhibiting cell phone signals to prevent anyone from circumventing their rule. Also, I did notice that I got a strong signal outside the hospital, but no signal inside the hospital, though this is not decisive evidence.

So does this actually happen, urban hospitals somehow inhibiting cell phone signals? If so, how widespread is this practice? And what technique or technology does the hospital use to accomplish it? (Deliberate siting in a dead zone outside the range of cell towers? Walls of some particular shape or material? Cell phone jammers? Some other method?)

—SeekingAnswers (reply) 09:03, 23 March 2016 (UTC)[reply]

Laws will differ based on jurisdiction, but in the U.S., according to the Federal Communications Commission's website, "Federal law prohibits the operation, marketing, or sale of any type of jamming equipment, including devices that interfere with cellular and Personal Communication Services (PCS), police radar, Global Positioning Systems (GPS), and wireless networking services (Wi-Fi)." - Nunh-huh 09:28, 23 March 2016 (UTC)[reply]

My suggestion: The hospital is built with reinforced concrete and they used "energy saving" windows which are designed using a metall film or mesh. The result is very bad reception. And if the policy is that cell phones shall not be used indoors then no repeaters will be installed. Practical things to check 1) is the reception good just outside the door? or if you open and stand in a window? 2) What kind of windows do they use? It may also be that the operators have commanded their equipment to drop cell phones in that sector. Ferrofield (talk) 20:32, 26 March 2016 (UTC)[reply]

A cell phone jammer would be totally self-defeating in a hospital, since it releases exactly the kind of interference that the hospital wants to avoid. Smurrayinchester 09:29, 23 March 2016 (UTC)[reply]

There' no evidence cell phones cause that sort of problem. Interestingly in Britain they tried to bring in some special phones for the emergency services - and they were shown to cause interference! Also they had bad coverage so were a bad idea. I'd have thought there should be some way to have call interception so only emergency service or other authorized calls are allowed. Surely it should be possible to stop people taking their phones out every three minutes and yapping loudly where they shouldn't -- they can go outside first using those appendages called legs if they want to do that. Dmcq (talk) 10:35, 23 March 2016 (UTC)[reply]

If they wanted to really curb the use of cell-phones, they would block them (not actively jam them). Although I doubt this is a huge issue. It appears to be just a case of making the safe bet. --Scicurious (talk) 22:00, 23 March 2016 (UTC)[reply]

How would you block them? That is the question. —SeekingAnswers (reply) 23:48, 23 March 2016 (UTC)[reply]

I have no idea what the reason is, but the observation is credible and it would be interesting to hear more. For example, you might have been under interfering material (some kind of metal shielding for an X-ray station on the next floor up?). Conceivably, a nearby cell phone tower could refuse to continue a connection with you based on triangulation of your position or by spying on GPS in the phone - I don't know if this software exists but it could certainly be written. In that instance I imagine that More Important People Than You would have some special code or their phone numbers on a whitelist or something. Wnt (talk) 11:27, 23 March 2016 (UTC)[reply]

The hospital could be a giant Faraday cage. Use metal sheeting on (or within) the walls and roof and glass windows with a thin metal coating. The latter may be used anyway, as they provide better thermal insulation. I know of a building that was an accidental Faraday cage. The architect liked a metal sheeting exterior. After complaints of no or bad cellphone reception (depending on provider), they considered installing signal repeaters. I don't know whether they actually installed them. I imagine this type of hospital building may have been popular in the Cold War, as it is also immune to EMP. PiusImpavidus (talk) 11:33, 23 March 2016 (UTC)[reply]

Come to think of it, although most serious medical conditions in a private prison are treated with ibuprofen, prisoners are occasionally brought to hospitals for treatment. This implies that a hospital building's primary purpose is to serve as a prison. Cell phones in prison describes some of the sort of software I was hypothesizing; and I think it is obvious that preventing malingering prisoners from violating incommunicado would be ranked far above any possible medical or personal concern you might have. Wnt (talk) 11:42, 23 March 2016 (UTC)[reply]

Your statement makes no sense. You state that occasionally, a prisoner is taken to a hospital to be treated. Then you state that the primary purpose of the hospital is to be a prison. That literally does not follow logically, since the prisoners are in no way the primary population of the hospital... --Jayron 32 13:09, 23 March 2016 (UTC)[reply]

My assumption is that if one prisoner coordinates an escape or calls up and threatens a victim or orders a hit, heads will roll. If tens of thousands of people complain that they couldn't update their relatives on what's happening, heads will not roll. Wnt (talk) 15:05, 23 March 2016 (UTC)[reply]

Wow. In a world full of horses, you really are only capable of seeing zebras. Or unicorns... --Jayron 32 18:35, 23 March 2016 (UTC)[reply]

This BBC report on the subject shows that there are definite problems in real hospital equipment from real cellphones. It goes on to point out that the phone has to be really close to the equipment to have an effect. I think the conclusion is that phones should be turned off inside treatment areas - but should be fine out in the corridors and waiting rooms.

OK - so that's the pragmatic approach - but you could understand (given the importance of the matter) that in an abundance of caution, they simply apply a blanket rule. That same BBC article says that 64% of doctors admitted that they use cellphones in the hospital in violation of the rules...and that NO deaths have ever been attributed to cellphone interference with hospital equipment.

This FCC page says that it's illegal to block or jam cellphones - and doesn't mention an exception for hospitals. But let's suppose there were some kind of exception made:

Clearly (as User:Smurrayinchester points out), jamming the signal would be a stupid idea because the jammer would (by necessity) put out more power in those frequencies than the cellphone itself).
Passively blocking cellphone signals with a Faraday cage around the whole building would actually be counter-productive because the cellphone will gradually increase the power of it's transmissions to the absolute maximum in a failed effort to reach nearby cell towers - so this would be a great way to guarantee the maximum possible radio noise!
More intelligent (and probably cheaper/easier/more practical) would be to put the faraday cage around the treatment areas to at least shield radio noise from corridors and such - but since we already know that the phone has to be within a few feet of the sensitive equipment, that would also be pointless since the only problematic devices are those INSIDE the treatment areas.

So I VERY much doubt that this hospital was intentionally either jamming or blocking your cellphone. Being in the middle of a large steel and concrete building - possibly on the margins of reception for some other reason - might be enough to produce the effect you're seeing - but I very much doubt that the hospital authorities had done this deliberately. Large/heavy equipment such as body scanners and X-ray equipment could have blocked the signal - and it's plausible that some kind of electromagnetic emissions from such devices was unintentionally interfering with your phone. Either way, moving a hundred yards from that spot ought to have gotten your better reception. Did you actually try that? SteveBaker (talk) 14:16, 23 March 2016 (UTC)[reply]

Re: "Either way, moving a hundred yards from that spot ought to have gotten your better reception. Did you actually try that?": I didn't stay in a single spot. After hearing what the nurse told me, I got curious and went all over the hospital, and even to different buildings of the multi-building hospital. My cell phone normally has no trouble getting a signal inside large buildings, but at this hospital, I couldn't get a signal anywhere inside the hospital buildings, but could outside. —SeekingAnswers (reply) 17:34, 23 March 2016 (UTC)[reply]

The cell phones in prison article links this product, which apparently is not a cell phone jammer. On the other hand, I found this report of cell phones blocked in a hospital in Ireland due to an adjacent prison with cell phone jamming. Wnt (talk) 15:13, 23 March 2016 (UTC)[reply]

I am not sure that a jammer or Faraday cage would prevent a cellphone from interfering with nearby equipment. Would the phone still transmit (perhaps in short, infrequent bursts) as it looks for a nearby tower? Or would it simply listen for the tower and not transmit a reply until it finds one? --Guy Macon (talk) 15:22, 23 March 2016 (UTC)[reply]

Depends. Sometimes it drops into analog modes which will drain the battery quickly. But I find it strange that this topic has gone on so long only because my closest hospital has built in WiFi for the rooms. Now if your in the MRI room or the Xray room, no cell phones are allowed. The cardiac monitors to the nurses station are wireless now as well. I'm sure they don't want you wearing a cell phone while hooked up to the monitor. They even had cell phone charging stations in the ER waiting room. What they really don't want is employees spending the day on social media instead of patient care. Day care centers have stricter policies than the hospitals. Hospitals (at least in the US) want repeat business so ERs and Maternity wards are the nicest and most accommodating places. --DHeyward (talk) 16:06, 23 March 2016 (UTC)[reply]

This is tangential, but no modern cell phones have an "analog mode". Analog signalling for cell phones was part of 1G systems, which no modern phones support and which have been taken out of service I think everywhere. What will drain the battery is the phone boosting its transmission power if it can't connect to a tower, to try to connect to towers that might be farther away. --71.110.8.102 (talk) 01:30, 24 March 2016 (UTC)[reply]

@71.110.8.102: - Meh, I have an old phone. But seriously, SMS is one of the oldest formats used in pagers ans uses the AT modem command set. Certainly later GSM and 4G LTE have made it digital but I still believe the U.S. with Verizon and others that avoided GSM initially still have some analog service in rural areas and for compatibility a TDMA phone can drop into analog mode. I haven't looked in a while but see if any of those carriers still support TDMA (Qualcomm took over the market with 4G CDMA and FRS is all but gone but I think some of phones still support analog for SMS even if they can't make a call). Pagers still exist. If your phone works in the U.S. but not Europe or Japan, I think it still has analog communication capability. China went CDMA but I think they avoided paying Qualcomm. CDMA licensing dominates Qualcomm earnings. --DHeyward (talk) 07:43, 24 March 2016 (UTC)[reply]

Our Advanced Mobile Phone System and History of mobile phones article suggests all analog or digital AMPS was shut down in the US by 2008. As for pagers, our article suggests there are a whole host of different systems used both local and wide and that these systems are usually distinct from mobile phone systems (which is an advantage for numerous reasons). It's not clear to me if any of them are analog, but neither that article nor our Short Message Service article suggests SMS was ever used for pagers (the SMS originated with GSM not with analog networks). SMS may be used for message submission and partly analog systems may have been used to submit SMS (e.g. Telelocator Alphanumeric Protocol) but those are different issues. Getting back to pagers, our article suggests FLEX protocol is the most common one used in the US nowadays at least for wide networks and it seems to be digital. Nil Einne (talk) 18:41, 24 March 2016 (UTC)[reply]

It's quite possible the hospital may have taken counter-measures that are counter-productive. The person(s) they assigned the task of ensuring that cell phones can't be used in the hospital may not even be aware of the reason. I like to use the example of speed bumps, which are designed to slow traffic down, to make roads safer. However, when you combine people who see them swerving to avoid them and those who don't see them losing control of their car when they hit them at high speed, they may very well make the roads less safe. StuRat (talk) 17:54, 23 March 2016 (UTC)[reply]

No matter where I stand in my apartment, my smartphone registers a low level signal (only two bars), but if I initiate a call, the level immediately increases to maximum (all bars). This implies that the cellphone towers transmit at low level when idle, but increase power when actually interacting with a device. It might be interesting if the OP had initiated a call while inside the hospital - it may have been successful. Most users simply start a call without looking at the level; by checking it he may have been unnecessarily discouraged. Akld guy (talk) 21:24, 23 March 2016 (UTC)[reply]

I would expect that cell phones would then adjust the signal meter depending on if it's during a call or not. Perhaps yours has poor software. StuRat (talk) 23:38, 23 March 2016 (UTC)[reply]

I do not understand your response. It does not seem to bear any relationship to my suggestion that the cellphone tower increases power. Are you saying that my cellphone should misrepresent the signal level that it receives? This is a 6-month-old Samsung 5 with all available updates installed. Please clarify what you meant. Akld guy (talk) 02:18, 24 March 2016 (UTC)[reply]

The cell phone knows if it is currently making a call or not. If it's customary for cell towers to increase power during a call, then the cell phone manufacturers would adjust for that in the signal bar, say by showing twice as many bars, when the phone was not in use. This would make customers happier, since they would see more bars. (Of course, they wouldn't want them to always see full strength bars, as then they would be pissed when they couldn't make a call, and call customer service and complain that their phone was broken.) Think of a voltmeter which has different settings with different sensitivities displayed on the meter. StuRat (talk) 02:28, 24 March 2016 (UTC)[reply]

Utter nonsense, sorry. You're asking me to believe that a cellphone that hadn't initiated a call via a celltower could predict the full-power output of that tower? Not only that, but whatever level it predicted would be a misrepresentation. C'monnn. Akld guy (talk) 02:54, 24 March 2016 (UTC)[reply]

If there is some standard practice, like cell towers boosting to twice the strength during calls, then the cell phone makers would know that and use it. And it's not misrepresentation, since there are no units listed on the bars. The usual interpretation is that it's a percentage of max. If you have 5 bars possible, then 4 bars is 80% of max, etc. So, if they know what the max cell tower output is under each scenario (during a call or not), 4 bars should be 80% of that max. StuRat (talk) 16:28, 24 March 2016 (UTC)[reply]

Your last sentence implies that you're assuming that maximum cell tower power always equates to all bars lit. No more, no less. Well duh, signals can be so strong that they're right off the scale at more than 5 bars, which of course displays can't show because they're limited to 5 bars. Do you have any experience with radio receiver LCD S meters as I do? You're presenting hypothetical situations based on OR theories about cellphone makers misrepresenting signal levels to their customers. Provide some evidence that they manipulate levels. Akld guy (talk) 20:57, 24 March 2016 (UTC)[reply]

I've been in our local hospital many times and I can get a signal in only a few areas. I thought that it was probably due to all of the steel used in the construction or all of the electronic equipment, but I don't know. Bubba73 ^{You talkin' to me?} 01:53, 24 March 2016 (UTC)[reply]

March 24

Is gray matter of CNS - just collection of the bodies?

I'm reading now in a textbook that "Cell bodies are located in the gray matter of the CNS, and their collections are called ganglia in the PNS and nuclei in the CNS." Does it say that the gray matter of CNS is just collection of the bodies and the white matter is the collection of the Dendrites? If it is, what is the reason for the grey color of the bodies? is it because of that the bodies have nuclei?93.126.95.68 (talk) 00:06, 24 March 2016 (UTC)[reply]

The difference in color between gray matter and white matter is largely that the latter contains myelin whereas the former does not. --Jayron 32 00:13, 24 March 2016 (UTC)[reply]

A big reason is neuromelanin - see [1]. Indeed, there is a substantia nigra in the brain ... yes, we have all been slandered with a racial epithet. :) Also a locus coeruleus. The source I cite suggests all these wonderful colors are about protecting the brain from free radicals and metals. Quite possibly they're right. But melanin's highly complex structure reminds me of an earlier era when strands of sugars bound to four nitrogenous bases in random order were assumed to have some modest structural role ... I wouldn't rule out the possibility of a big surprise here. Wnt (talk) 00:18, 24 March 2016 (UTC)[reply]

Thank you for your comments. What about the text that I brought? What does it mean to say? 93.126.95.68 (talk) 00:38, 24 March 2016 (UTC)[reply]

It says basically that Grey matter is where the cell bodies of the neurons are located. Concentrations of gray matter are called ganglia in the peripheral nervous system and nuclei in the central nervous system. If you read those articles, you'll learn more about those terms. --Jayron 32 01:30, 24 March 2016 (UTC)[reply]

The answers about are pretty much correct. However, I must quibble with the idea that "cell bodies are in gray matter, dendrites in white". This is only the case for neuronal cell bodies, and even then not exclusively so. There are plenty of oligodendrocytic, astrocytic, microglial and endothelial cell bodies in the white matter. Also, whilst neurolaminin is indeed important in giving the substantia nigra its colour, it is not responsible for the making the grey matter grey (it's more a dirty yellow sort of colour in fresh brain anyway, the white matter is indeed fairly white in my experience). Fgf10 (talk) 08:18, 24 March 2016 (UTC)[reply]

Is it known which substance (ingredient) in cow milk causes to sleepiness?

93.126.95.68 (talk) 01:35, 24 March 2016 (UTC)[reply]

This source claims that any protein-rich food should induce drowsiness, so milk can do so, but not exclusively milk. --Jayron 32 01:45, 24 March 2016 (UTC)[reply]

Is that also true for turkey? Or is it just because we eat too much of it at one sitting? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:47, 24 March 2016 (UTC)[reply]

Yes, overeating definitely causes sleepiness, as does the excess protein and tryptophan. StuRat (talk) 01:50, 24 March 2016 (UTC)[reply]

Mother Nature's way of directing your body's focus toward digestion? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:55, 24 March 2016 (UTC)[reply]

Basically yes. While tryptophan can cause sleepiness, and tryptophan (as an amino acid) is present in the proteins of milk and turkey (and lots of other foods), the sleep-inducing effects of tryptophan cannot be induced by turkey or milk alone. I believe the source I cited notes that one would need to eat a stomach rupturing 40 pounds of turkey meat to get enough tryptophan to induce drowsiness. Protein-rich foods are themselves enough to induce drowsiness, according to same. --Jayron 32 02:02, 24 March 2016 (UTC)[reply]

Yep, like a snake who swallowed a pig. StuRat (talk) 02:02, 24 March 2016 (UTC)[reply]

Isn't it supposed to be warm milk ? That suggests it's a psychological thing, since warm milk is associated with being a baby, much like the white noise of the womb, and the fetal position, things also sometimes used to make you "sleep like a baby". StuRat (talk) 01:54, 24 March 2016 (UTC)[reply]

Google "warm milk and sleep" and many claim it's a myth. However, it also says milk contains tryptophan, as with turkey. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:57, 24 March 2016 (UTC)[reply]

See source above. While enough tryptophan can, of its own accord, induce sleep, you cannot get enough of it through either milk or turkey, or really any foodstuff, to do so. --Jayron 32 02:04, 24 March 2016 (UTC)[reply]

Besides the too small amount of tryptophan to cause drowsiness, I wonder if the problem is also that it does not reach the brain when taken orally. Llaanngg (talk) 18:58, 24 March 2016 (UTC)[reply]

Presumably because different things work for different people. As far as finding one universal sleep aid, well, propofol might work, but Micheal Jackson found that's not a wise choice. StuRat (talk) 02:02, 24 March 2016 (UTC)[reply]

Milk is also rather high in sugar content. Hyperglycemia. I used to drink several gallons a week. I gave it up when I was diagnosed as diabetic. Nowadays when I do have a sip it tastes as sweet as fruit juice. μηδείς (talk) 02:32, 24 March 2016 (UTC)[reply]

There is an article analyzing the link between food and drowsiness. Llaanngg (talk) 19:00, 24 March 2016 (UTC)[reply]

The article on "specific impulse" seems to mix up force and mass (physics)

In the article on Specific impulse. It specifies that "If mass (kilogram or slug) is used as the unit of propellant, then specific impulse has units of velocity." this statement may be correct. But! "If weight (newton or pound) is used instead, then specific impulse has units of time (seconds).". Weight is supposed to have unit in mass not force? I suspect there's some serious mixup here. Anyone care to scrutinize this from a physics standpoint ? Ferrofield (talk) 04:01, 24 March 2016 (UTC)[reply]

It's correct. Thrust is force (mass * length/time^2)). If mass is used, the rate of consumption is mass/time. Divide and you get (length/time) which is velocity. Weight, though, is also force (a kilogram is mass, a pound is force - knowing weight is not mass is critical here). (force/(force/time)) = time. It's a measure of efficiency. You are either measuring how quickly the rocket is getting lighter for a given thrust to weight ratio or you are measuring how far the rocket has moved for a given amount of time. --DHeyward (talk) 07:10, 24 March 2016 (UTC)[reply]

Shouldn't it say "If force [N] is used instead, then the specific impulse has units of time (seconds)." ? Ferrofield (talk) 15:25, 24 March 2016 (UTC)[reply]

In physics, weight is a force. Weight can be measured in pounds, which are a unit of force.

In many other contexts, we know that the weight is measured on Earth, so we can easily translate between weight and mass: these two parameters are related by the g (little g) standard gravitational constant.

When people are sloppy, they interchange mass and weight freely. But in our article on specific impulse, we are being precise: weight is a measurement of force. "Pounds" are a unit of force, not a unit of mass.

Some people choose to clarify this distinction by separately defining two different units: Pound (force) and Pound (mass) - but they're really just formalizing a sloppy conversion. To make matters even worse (!) - even if the author intends to distinguish between "pounds force" and "pounds mass", and diligently works to ensure correctness, in common speech many English speakers elide the qualifier and simply say "pound", yielding a linguistic collision.

In our Wikipedia article on specific impulse, and most of our other physics articles, we totally avoid this confusion by using pounds to refer only to force. If you want to use an imperial unit of mass, use the slug (mass). Alternately, you can use SI units.

Nimur (talk) 16:32, 24 March 2016 (UTC)[reply]

You could use "force" but it would be more confusing, I think. People understand intuitively "Thrust to weight ratio." That's a dimensionless term since thrust is Newtons and weight is Newtons (or "pounds"). The "impulse" is thrust to weight ratio with the added "and thrust to weight ratio improves because the rocket is expelling part of its weight in Newtons/sec)." The dimensions work out but what's missing and might be confusing is it's an integral approaching an ideal Dirac delta function. Ideally, a rocket would have infinite thrust and expel all it's fuel in 0 seconds so it doesn't have to lift the fuel. That 0/0 equation has an integral solution. The difference in using mass (slug/kilogram} or weight (pound/Newton) lets the engineer calculate lift efficiency. Using mass, a moon rocket can be compared to an earth rocket as it will be the same efficiency, but using weight shows the difference in the the amount of burn necessary. An identical rocket motor expels mass at the same rate on the moon as it does on earth and has the same thrust but not the same weight. The rocket weighs less on the moon so the thrust to weight ratio is better - that means less burn time and less fuel (i.e. "seconds" of burn). When calculating efficiency and capability, both metrics are useful/needed but you can't lose sight that it's an integral and units aren't independent of the fuel, mass of the rocket or thrust. --DHeyward (talk) 16:56, 24 March 2016 (UTC)[reply]

Tiny nitpick: an identical rocket on the moon has about one atmosphere less back-pressure on the exhaust system - which has a nontrivial effect on the exhaust mass rate and the flow expansion characteristics. To really get into the details, we'd have to do some "rocket science" - but anyone who looks at, say, the iconic bell nozzle of the Apollo Service Module Service Propulsion System - and compares the bell nozzle shape to, say, the F-1 engine, you can almost intuitively feel that one of those engines was designed to exhaust into vacuum, and one was designed to eject exhaust at sea level. For any particular ambient backpressure, there is a particular nozzle expansion shape that will encourage laminar flow for optimal energy and momentum extraction, even at the same Isp. Nimur (talk) 17:44, 24 March 2016 (UTC)[reply]

Must admit that on first reading, the article did not make complete sense to me either. So,what may help too, is a sentence or two explaining that the velocity of the exhaust is dependant on the total molecular weight (molecular mass) of the combustion products. Which is why Hydrogen & Oxygen is favoured for the higher speeds required for obit insertion and of interplanetary probes. In practical engines, the unit of mass ejected has little to do with the resulting velocity. One could construct a whooping big engine that ejects a ton of lead oxide per second but stays firmly on the launch pad or a smaller engine with the same starting wet weight that ejects a ton of super heated H2O per second and brakes the sound barrier within seconds of being launched. Therfore , this article would benefit I think, from an explanation that all fuels are not equal and that very much affects SPI per unit mass. As a thought experiment: imagine one is sitting just outside the airlock on the ISS with two balloons. One is full of hydrogen and the other (smaller) balloon is filled with the same mass of gas but of CO2. There is no air resistance to worry about. Let go of both necks at the same time. Which balloon will zoom away fastest? The math is the same and the starting mass is the same but it is the velocity of the exhaust that makes the difference to the SPI. This molecular mass bit, the article fails to include explicitly for clarity. Other than that, I think that the article is pretty comprehensive and well structured.--Aspro (talk) 20:31, 24 March 2016 (UTC)[reply]

Wouldn't "If force (newton or pound-force) is used instead, then the specific impulse has units of time (seconds)." be more correct? Currently it seems to use weight as a substitute for force and a lot of loosely specified imperial units. Ferrofield (talk) 02:21, 26 March 2016 (UTC)[reply]

A reflection on black hole event horizon (physics)

A black hole event horizon is supposed to be the final end of interaction of anything falling into it with the outside world, besides hawking radiation and preservation of information. Now suppose the gravity exerted by the black hole is measured externally and an object less massive than the black hole falls into it. Will the gravity of the black hole plus an object outside of it become less in magnitude when the external objects falls into it? Such that the event horizon has the ability to chop gravitational interaction? Ferrofield (talk) 05:06, 24 March 2016 (UTC)[reply]

No, the mass of whatever falls into a black hole adds to the mass of the black hole. -- BenRG (talk) 09:13, 24 March 2016 (UTC)[reply]

Indeed, the mass (and therefore the gravitational force), the electrical charge and the spin of the incoming object all add to whatever the black hole had before it 'consumed' it. Conservation laws do apply to black holes. SteveBaker (talk) 13:02, 24 March 2016 (UTC)[reply]

So light which is an electromagnetic phenomena with the propagation of 3*10^8 m/s can't break free. But gravity with the same wave nature and propagation of 3*10^8 m/s goes straight through. Kind of like the black hole where selective about which wave types it permits to escape. It's like it's permeable for some type of waves and not others. Perhaps there are other wave types yet undiscovered that would enable one to see what's inside? (if 2800 light years won't degrade the resolution too much) Ferrofield (talk) 15:17, 24 March 2016 (UTC)[reply]

Um, stop right there. Your statement " gravity with the same wave nature and propagation" isn't necessarily an established way to think of gravity. Gravity has not been properly explained by the standard model and thus analogies between gravity and other standard model forces (like electromagnetism) and their gauge bosons like photons or light are not valid. You simply can't treat gravity like light and ask what a black hole does to gravity. While the standard model did not exist at the time of Einstein, he DID have an intuitive sense that gravity as a force did not work like other forces, which is why he treated gravity as a pseudoforce and developed general relativity to explain the phenomenon of gravity without having to resort to treating gravity like light or other phenomena, which causes all sorts of problems. --Jayron 32 15:58, 24 March 2016 (UTC)[reply]

Also best keep apart gravity itself and that ripple called "gravity wave" (caused by some interaction of bodies of huge mass) which is more precise a ripple in time or time-space, not a ripple in gravity!! --Kharon (talk) 17:03, 24 March 2016 (UTC)[reply]

The equivalence principle implies that you can treat gravity in more or less the same way as electromagnetism for this purpose (at least for a small object falling into a large hole). The Standard Model's gauge forces are actually similar to gravity; mathematically they are like general relativity applied to compact extra dimensions. And electric and gravitational charge are both preserved, so there is no difference that needs explaining here. -- BenRG (talk) 18:26, 24 March 2016 (UTC)[reply]

As SteveBaker said, electric charge (which is the electromagnetic equivalent of mass) is also preserved. It doesn't disappear. There is no difference between gravity and electromagnetism/light in this regard. There are various ways of thinking about this. One way is that the field is an entity unto itself which can't disappear for geometric reasons, much like you can't untie a knot in a rope if you don't have access to the ends. Another way is that you never actually see the object cross the event horizon; it's always just outside, where it can still "emit" the field for you to detect. -- BenRG (talk) 18:26, 24 March 2016 (UTC)[reply]

Yeah, the question of how the gravity escapes the black hole is a long-standing one. One thing I wonder -- if you look at something falling into the event horizon, it is said that it is always hypothetically visible since there is always the chance of some absurdly red-shifted photon finally outrunning the infalling space (???) of the event horizon and getting out. But you can't see it because the photon emission is minimal. However, from our frame of reference the mass of an infalling object, travelling at almost the speed of light, should grow without limit, right? And that tremendous and super-fast-moving mass ought to emit some kind of gravitomagnetic radiation, shouldn't it? Which leaves me thinking someone who knows a hell of a lot more physics than I do could work out some kind of limit calculation for how much the gravitomagnetic emission vs. the redshifting comes out to be. If you can redshift gravity that is. Am I just gibbering? :) Wnt (talk) 23:39, 24 March 2016 (UTC)[reply]

If the sun would disappear in an instant. How long would it take for us to know? I suspect the propagation delay is 3x10^8 m/s. So whatever it is, it has some properties that can be explored. Say if one can design a device that can sense really small gravity changes and have high angular resolution. And have this sent to orbit close by a black hole. Perhaps one would discover something about what happens on the inside. Ferrofield (talk) 21:43, 25 March 2016 (UTC)[reply]

Egg white whipping with contaminants

Can egg white be whipped into a foam if it already contains sugar and cocoa powder or will these prevent that? ----Seans Potato Business 07:59, 24 March 2016 (UTC)[reply]

Contamination from copper seems to help with whipping eggs, and the foaming is a result of denaturing and air insertion. I can't imagine sugar and cocoa powder preventing denaturing of the egg whites. It might affect the form of the foam, but that's just a guess. Ian.thomson (talk) 08:21, 24 March 2016 (UTC)[reply]

Those things make whipping more difficult if they are added at the very start, but I don't think they will prevent it. Note though that even a little bit of fat can make it impossible to whip egg whites. Looie496 (talk) 14:30, 24 March 2016 (UTC)[reply]

This suggests to me that one needs to look into if certain substances will bind to or interact with the substances in the egg white in a way that prevents denaturing or stable bubble walls. Ferrofield (talk) 15:21, 24 March 2016 (UTC)[reply]

Sugar improves the stability of whipped egg white - Meringue#Chemistry actually discusses this issue in some detail although the section lacks sources. Roger (Dodger67) (talk) 16:15, 24 March 2016 (UTC)[reply]

Entropy. Statistical mechanics. Information ~ Energy

Question	Remark
In this source [exergy.se/ftp/exergetics.pdf, pages 70-77] author writes: Assume a system of N unique particles. The number of allowed states Ω of the system is exponentially depending on N. Let the probability of the j:th state be Pj and the sum of the probabilities of all states to be 1, i.e. the system is in at least one state $\sum _{j=1}^{\Omega }P_{j}=1$ The entropy of the system is then defined from statistical mechanics as $S=-k\sum _{j=1}^{\Omega }P_{j}\ln {P_{j}}$ ... Let us exemplify by a system of N different particles with 2 possible states each, e.g. 0 or 1. Then we have $\Omega =2^{N}$ . If there are no other restrictions then all $P_{j}^{0}$ must be $2^{-N}$ , see the Table below. Is it correct? We know form Boltzmann's entropy formula that $W={\tfrac {N!}{\prod \limits _{i}{}N_{i}!}}$ , where $N=\sum _{i}N_{i}$ . Taking the logarithm of W, we have $\log W=\log N!-\sum _{i}\log N_{i}!$ . Applying Stirling’s theorem, we obtain $\log W=N\log N-N-(\sum _{i}N_{i}\log N_{i}-\sum _{i}N_{i})=N\log N-\sum _{i}N_{i}\log N_{i}$ $=\sum _{i}N_{i}\log N-\sum _{i}N_{i}\log N_{i}=\sum _{i}N_{i}(\log N-\log N_{i})=\sum _{i}N_{i}(\log {\tfrac {N}{N_{i}}})$ $=N\sum _{i}{\tfrac {N_{i}}{N}}(\log {\tfrac {N}{N_{i}}})=-N\sum _{i}{\tfrac {N_{i}}{N}}\log {\tfrac {N_{i}}{N}}$ . Let $p_{i}={\tfrac {N_{i}}{N}},{\text{ for }}i=1,2,...,m$ . Then $\log W=N(-\sum _{i}p_{i}\log p_{i})$ and $S=k\log W=kN(-\sum _{i}p_{i}\log p_{i})$ . So first, we must add factor $N$ (BTW in wiki articles also $N$ is absent). Second, $m$ is a number of existing states among all particles, not all possible states. So we count only system states, which consist of same set of particle states. E.g. we have 5 particles of which 2 are in state 0 and 3 are in 1. E.g. we have system 00111. Now we can consider only 00111, 01011, 01101, 01110, 10011, 10101, 10110, 11001, 11010, 11100. We cannot compose 00000 or 11111. In this example we have $m=2,N=5,N_{1}=2,N_{2}=3,W=10.$ So why author believes $\Omega =2^{N}$ and counts $j=1,2,...,\Omega$ ??? Is it correct?	Boltzmann's entropy formula [ http://exergy.se/ftp/exergetics.pdf , pages 70-77]

37.53.37.94 (talk) 20:07, 24 March 2016 (UTC)[reply]

The author doesn't believe this: he defines it. He has explicitly stated that his hypothetical system has N independent variables that may each take only one of two possible states. This is definitional or axiomatic - he constructed the problem so that he could work out the math that follows from it.

This formulation is nearly identical to what shows up in my textbook on thermodynamics, Stowe's Introduction to Thermodynamics and Statistical Mechanics. It's a pretty standard formulation, because it's a simple way to work the math.

I've never heard of this particular author - so I'm not going to vouch for the entirety of everything else he's written: in particular, his unique terminology "exergy" is not commonly used in other books on statistical physics. Reading through some more of his material, I'll say this: his book is clearly the work of a non-native English speaker, and it doesn't look like he had a very good editor. I would not use his book as your primary reference for anything, let alone for information on standard formulations of thermodynamics - even if some parts of his book are correct, there are plenty of much better resources. I can personally vouch for several other great books on statistical mechanics if you're interested; and we have a list of references in our article on thermodynamics.

Nimur (talk) 20:10, 24 March 2016 (UTC)[reply]

Exergy wasn't taught in the physics classes I remember either, but it has been around a while and I have encountered it in the wild before. I'm too lazy to try and verify if he is using the terminology in the same way that others have used it. Dragons flight (talk) 19:50, 25 March 2016 (UTC)[reply]

But with this formulation he calculates entropy wrong way. He must take

j=1,2,...,m

. If particle states are 0 and 1 ,

j=1,2

.37.53.37.94 (talk) 20:53, 24 March 2016 (UTC)[reply]

in particular, his unique terminology "exergy" is not commonly used in other books on statistical physics -- This is book not on statistical physics. This book about exergy. And this word is not unique [see http://www.collinsdictionary.com/dictionary/english/exergy ]. Quality of the book isn't the subject. I've leafed through your book and it does not contain info I'm looking for. In your book you write

\Omega =\omega ^{N}

too. So your book also does not agree with wiki article Boltzmann's entropy formula. E.g. let system have 5 non-distinguishable atoms of helium. Every particle can be in state 0 or 1. Two atoms are in state 0, Three atoms are in state 1. How will you calculate number of system states

W

, which is used in formula

S=k\log W

? And why? 37.53.37.94 (talk) 04:47, 25 March 2016 (UTC)[reply]

Question	Remark
And 2nd question. Can human generate information (and so energy) by brain activity: thinking and processing? For me it's important to distinguish both these types of activity. I know that from knowledge of particles' speed we can generate energy (Maxwell demon). But it is not brain activity, but measurements. And I also know brain is processing huge amount of data. But I feel brain does the job only for own purposes (human survival). If we are talking about processing, then decoding also is present. So we can use Shannon information. But I can't assemble the puzzle. Brain decodes information (e.g. from eyes) and then answers. To minimize processing it can use instincts, learning (it's much harder as connected with statistics collection to estimate probabilities). If neither instincts nor learned patterns fit, then brain thinks.

37.53.37.94 (talk) 21:12, 24 March 2016 (UTC)[reply]

Here's some questions for you to consider: Is there more information in one-minute of white noise or one minute of the Crab canon? Or what about a one-minute of me speaking this comment? Shannon would say white noise has far more information, but that doesn't necessarily match up with our intuitive notion of information. As for generation: can a farm consisting of sheep, pigs, and cattle generate information? Note that one of the most popular Diversity_indexes used is in fact just Shannon's entropy, more on that here [2]. So if we calculate the Shannon diversity of a given paddock, it will change on a day-to-day basis based on the which animals are there, and we could perhaps claim that the animals are creating information, sort of Maxwell's livestock as an analog to Maxwell's demon. My point is that it's pretty easy to compute some H and say "there's this much entropy/information in this system", but the interpretation of that claim is subtle and often depends on many other implicit assumptions and models. SemanticMantis (talk) 14:26, 25 March 2016 (UTC)[reply]

March 25

Amplitude stabilisation of sinusoidal electronic oscillators

Im looking for refs concerning the theory of stabilisation of sinusoidal oscillators using non linear semiconductor components. Any offers?--178.111.96.35 (talk) 01:15, 25 March 2016 (UTC)[reply]

HP200A has several references. --Guy Macon (talk) 05:08, 25 March 2016 (UTC)[reply]

Fast Amplitude Stabilizing of an RC Oscillator Wein bridge oscillator with incandescent lamp stabilization LC Oscillator has stable amplitude High-Purity Sinewave Oscillators with Amplitude Stabilisation. AllBestFaith (talk) 10:58, 25 March 2016 (UTC)[reply]

How to block out female pin headers

I brought a JTAG programming cable but the the key-way pin of the header isn't properly "blocked out". The end in question is a 1.27mm pitch female header. What's the name for the part used to "block out" certain female header pins? Alternatively a link to Digikey for the right part would help too. Johnson&Johnson&Son (talk) 06:31, 25 March 2016 (UTC)[reply]

See Pin header#Polarizer key. AllBestFaith (talk) 11:06, 25 March 2016 (UTC)[reply]

Thanks. Is there any place that actually sells 1.27mm pitch polarizer keys? I tried Digikey and couldn't find any there and they pretty much have the biggest selection. Johnson&Johnson&Son (talk) 12:56, 25 March 2016 (UTC)[reply]

Sorry if this is way off: Here [3] is a rack of 24 pins, perhaps one of them would suit your needs. SemanticMantis (talk) 14:11, 25 March 2016 (UTC)[reply]

Here is a range of headers but for blocking one hole of a female header, consider gluing a male pin in place. AllBestFaith (talk) 14:13, 25 March 2016 (UTC)[reply]

The male pin would be conductive though unfortunately. I guess I'll use that as a last resort. It's weird though, both the male and female headers are so widely available, and yet a supposedly common accessory like the polarizer key is so hard to find.Johnson&Johnson&Son (talk) 14:31, 25 March 2016 (UTC)[reply]

Yeah - don't use anything conductive. If I don't have a proper blocking pin to hand, I generally put a squirt of glue in there with a hot-glue-gun. Don't squirt too much in there because it can ooze out and block other pins too - but a tiny amount does the job perfectly. SteveBaker (talk) 14:45, 25 March 2016 (UTC)[reply]

I see the value of being extra careful, but isn't the point that the block is just to make it impossible to plug something in the wrong way? E.g. if plugged in correctly nothing should be touching that socket, so it shouldn't matter much if it's blocked with a conductive pin or glue. Maybe I've gotten something terribly wrong and backwards, but clarification would be appreciated. SemanticMantis (talk) 16:03, 25 March 2016 (UTC)[reply]

The idea is that you cut off one of the pins on the male connector (typically at one end of the block) and fill in the corresponding hole on the female connector. If you try to insert the connector with a 180 degree rotation by mistake, then the blocked hole hits an un-cut pin and you can't push them together. Hence blocking one pin suffices to prevent the cable being plugged in backwards. You can use the same kind of trick when you have two or more identical-looking connectors to make sure that the correct cable is plugged into the socket. Cutting and blocking multiple pins in different places along the header allows for some considerable control over which connectors go onto which headers as well as ensuring they aren't plugged in backwards. SteveBaker (talk) 19:59, 25 March 2016 (UTC)[reply]

What is needed is a cock header. Something that probably doesnt exist atm but cuould do with inventing.--178.111.96.35 (talk) 00:12, 26 March 2016 (UTC)[reply]

WP:WHAAOE. See Urethral sounding. Tevildo (talk) 00:15, 26 March 2016 (UTC)[reply]

File:Salt Lake.JPG

Greetings, does someone know what File:Salt Lake.JPG is a photo of?Jo-Jo Eumerus (talk, contributions) 15:15, 25 March 2016 (UTC)[reply]

The uploader was User:Mountainloverk2, who sadly has not edited in 8 years. I don't see anything that can be used to identify the picture to more specific than a body of water in a dry landscape. The plant life appears to be part of the American West in some way, but there's nothing in the picture to nail it down specifically. If it is a real salt lake in the American West, it could be part of the massive endorheic basin which occupies much of the west. See Great Basin. I do note that the landscape looks roughly like the landscape in some pictures in that article. That giant area is far too vague to be useful in determining the location of the body of water, and there's other similar desert areas in the American West or Mexico in which this would fit as well. --Jayron 32 15:25, 25 March 2016 (UTC)[reply]

And I'm probably wrong, because the uploader also uploaded a whole slew of pictures from locations in Pakistan such as File:Crossing Khanwal Luck.Jpg from I think Khanewal District, all around the same time as this picture. So, maybe Khanewal District? No idea though, certainly nothing to nail it down closer than that. --Jayron 32 15:29, 25 March 2016 (UTC)[reply]

I bit on this one and noticed that there is an EXIF date for August 14, 2006, which is matched only by File:Nawabshah1.JPG. See Nawabshah. Since this is a "digitized on" date I'm not sure it's even weak proof the two were taken close together. I do see that searching for salt lakes in Sindh pulls up vaguely similar-looking terrain, to my bleary eyes, e.g. [4]. Wnt (talk) 16:52, 25 March 2016 (UTC)[reply]

Seems fairly plausible; I'll change it to that.Jo-Jo Eumerus (talk, contributions) 11:49, 26 March 2016 (UTC)[reply]

@Jo-Jo Eumerus: Well, for Wikipedia we're supposed to have sourced data, not just guess. Unfortunately for our purposes it remains just a salt lake somewhere. It can't be that hard to find other free-licensed pictures of salt lakes somewhere. Wnt (talk) 23:00, 26 March 2016 (UTC)[reply]

Old cod liver oil capsules useless?

Am I right in my interpretation of this article that cod liver oil capsules which are over a year out-of-date have probably oxidised and become useless?

Yes, and not only useless, but potentially harmful. One trick is to open one (over the sink) and smell it. If it smells bad, it is bad. StuRat (talk) 02:01, 26 March 2016 (UTC)[reply]

Actually it smells alright. Wouldn't the encapsulation protect the oil against oxidation? --78.148.107.251 (talk) 13:50, 27 March 2016 (UTC)[reply]

Slow it down, yes, but these capsules are a year past the expiration date. That's a long time. StuRat (talk) 13:55, 27 March 2016 (UTC)[reply]

There are antioxidants in there too! And they pass the smell test! --78.148.107.251 (talk) 20:31, 27 March 2016 (UTC)[reply]

Doesn't all cod liver oil smell bad? Dbfirs 07:58, 26 March 2016 (UTC)[reply]

I suppose it depends on your preferences, but fresh fish definitely smells better than spoiled fish. StuRat (talk) 16:14, 26 March 2016 (UTC)[reply]

You're best off discarding any consumable thing that's way past its expiration date. — Preceding unsigned comment added by Baseball Bugs (talk • contribs) 02:45, 26 March 2016 (UTC)[reply]

Isolated neutron--how many neutrinos go thru it, or at least strike it, per second, at least on Earth with the average flux here?

I've heard that zillions of neutrinos go through our bodies every second. I don't know if a neutrino can pass through a neutron, I would like to know. Anyway, what is the average number of collisions and/or passages thru per second? How many per 15 minutes? (I'm wondering if the were actually around 1 per hour, chance could distort the measurement of neutron half-life, provided the neutrino could somehow initiate neutron decay. Thanks, Rich Peterson155.97.8.213 (talk) 20:52, 25 March 2016 (UTC)[reply]

Well 10¹⁵ solar neutrinos pass through every square meter in one second. A neutron is about 10^-18 meters across so it covers about 10^-36 square meters. So it'll take on average 10²¹ seconds for a neutron to be hit by a neutrino - the age of the universe is around 10¹⁸ - so there is about a one in a thousand chance for a particular neutron here on earth to EVER be hit by a solar neutrino. Of course there are a lot of neutrons out there - so this does happen - but it's not happening enough to make much of a dent in the neutron half-life. SteveBaker (talk) 21:13, 25 March 2016 (UTC)[reply]

Your neutron diameter is way off. According to the article it has a mean square radius of 0.8×10⁻¹⁵ m, which corresponds to a cross-sectional area of 2×10⁻³⁰ m². So it's more like one neutrino every 20 million years (using the flux value from Solar neutrino#Observed data, which is close to yours). But individual neutrinos are probably not localized enough to definitely pass through or not pass through a neutron, so it might be better to say there's a constant neutrino flux through every neutron that adds up to 1 particle every 20 million years. Also, that's the number that pass through the neutron, not the number that hit it (i.e., interact with it). For the latter you'd have to use the interaction cross section instead of the size of the neutrino (see below). -- BenRG (talk) 02:01, 26 March 2016 (UTC)[reply]

good answer155.97.8.213 (talk) 00:05, 26 March 2016 (UTC)[reply]

Neutrinos don't "pass through" neutrons. Neutrinos pass through ordinary matter most of the time because neutrinos only interact through the weak interaction and gravity. Gravity is so weak that it has basically no effect at the atomic level. The weak interaction has an extremely short range. If a neutrino gets close enough to a neutron or another weakly interacting particle, they will interact. But neutrinos usually go right through the Earth without noticing because atoms are mostly empty space, so they rarely get close enough to any particle to interact. It's like firing a BB gun and trying to hit an individual grain of sand. When neutrinos do strike a particle, they interact and produce other particles, which we can detect in neutrino detectors. This just happens so rarely that we need to build huge detectors to get a decent detection rate. Remember, everything at the quantum level is tiny and weird. Our ape brains aren't intuitively programmed to understand it. --71.110.8.102 (talk) 21:19, 25 March 2016 (UTC)[reply]

Neutrinos do pass through neutrons. The cross-sectional area of a neutron is ~10⁻²⁶ cm², and according to this page, the cross section for neutrino-neutron interaction is around 10⁻³⁸ cm²/GeV. So a neutrino will pass through about a trillion/(energy in GeV) neutrons before interacting with one. -- BenRG (talk) 02:01, 26 March 2016 (UTC)[reply]

thanks155.97.8.213 (talk) 00:05, 26 March 2016 (UTC)[reply]

What is the relation between axon and its etymology?

What is the relation between axon and its etymology? according to what I read, the meaning of "axon" is axis in Greek. My question is what is the relation between axis to the part of the neuron which is called axon. 93.126.95.68 (talk) 22:54, 25 March 2016 (UTC)[reply]

The entire nerve is an "axon". An axis on a graph is a line - perhaps "axon" refers to the line-like shape of a nerve. DrChrissy ^(talk) 23:05, 25 March 2016 (UTC)[reply]

Thank you93.126.95.68 (talk) 23:29, 25 March 2016 (UTC)[reply]

In other, uh, words, while both words are derived from the same Greek root word, their meanings in modern English differ: cf. axis and axon. --71.110.8.102 (talk) 01:30, 26 March 2016 (UTC)[reply]

The axon was definitely discovered by Camillo Golgi, probably in the late 1870s or early 1880s, but I can find no evidence he ever called it an axon. Merriam Webster's dictionary says the word "axon" was first used to describe a part of a neuron sometime in the 1890s, which could plausibly make the name an invention of Santiago Ramon y Cajal, though I have been unable to find the first publication to use the word. I'm able to find a publication titled "Neuron" in 1896 by one Aloysius Kelly that defines an axon as the "axis-cylinder", and just a year later, everyone seems to be throwing around the word "axon" as if you are expected to know what it means. Someguy1221 (talk) 04:36, 26 March 2016 (UTC)[reply]

The OED is similarly vague. The word "axon" appears in 1842 in R. Dunglison's Medical Lexicon, and Wilder used the word in the New York Medical Journal of August 1884, but these cites seem to be for the axis of the body or the spinal column, rather than for the neuron usage. Dbfirs 07:48, 26 March 2016 (UTC)[reply]

what is meta-sympathetic system?

I always knew about the sympathetic and para sympathetic systems, and today I was told about the meta-sympathetic system, but I didn't understand well the man who told me about it and I didn't find enough or reliable information about this system, and if it's accepted in the scientific world or it's arguable. 93.126.95.68 (talk) 23:29, 25 March 2016 (UTC)[reply]

"Metasympathetic nervous system" seems to be a phrase peculiar to a handful of Russian scientists. Based on this translated abstract, it is something entirely different from the sympathetic and parasympathetic systems, but I have no access to their paper (not that I'd be able to read it unless it's translated into English). It's a bit unlikely that there is a feature of anatomy only Russians are aware of, so this has to be either something English-speaking scientists give a totally different name, or a pile of bullshit. Maybe someone can find their paper and let us know. Someguy1221 (talk) 04:39, 26 March 2016 (UTC)[reply]

Yes, it makes sense. 1) Indeed, the man is Russian scientist but his English wasn't so clear for me. 2) The most of the result about it i PubMed are from Russian. 3) your suggesting for the two possibilities are absolutely reasonable, and in any case I don't think that this term is studied in the universities in US for example. The classical method is to teach about 2 systems only (sympathetic and Para-sympathetic). Anyway, It will be useful to see article about this topic. 93.126.95.68 (talk) 05:19, 26 March 2016 (UTC)[reply]

This article is in English [5] although I haven't tried to read it yet. This also is nominally in English [6] and there's also these slides [7] and this has some brief mention [8]. Nil Einne (talk) 07:17, 26 March 2016 (UTC)[reply]

Is it saying that the brain feels pain like other organs? (I've no medical expertise, so I'm asking that as a question rather than an opinion.) Dbfirs 07:38, 26 March 2016 (UTC)[reply]

The autonomic nervous system is responsible for body reflexes and has two branches:

the sympathetic nervous system: serves quick responses "fight or flight".
the parasympathetic nervous system: serves slower damped responses "feed or breed, rest and digest".

The OP's question about a possible third category "metasympathetic system" has also been asked at Stack Exchange. It is suggested that the motor activities of the heart, ureters, intestine and stomach that are truly autonomous fit this third category, sources: Nozdrachev AD (Russian), The Metasympathetic System of the Brain. Their conclusion that "the brain, like other organs, has its own metasympathetic nervous system" is not simply equivalent to "feeling pain" since it is talking about unconscious reflex. AllBestFaith (talk) 14:25, 26 March 2016 (UTC)[reply]

Some presentations [9] and articles [10] seem to equate the metasympathetic and enteric nervous system, though according to [11] the enteric nervous system is just the enteric portion of the metasympathetic nervous system. One reference from 1953 [12] mentions the term but it is obscure journal/no abstract. The term stayed in Italy, without intervening publication, to 1974, after which it packed up and moved to Russia [13] in a journal that I think Nozdrachev's group also used. My guess is that this group finds it a more meaningful way to define a third autonomous nervous system than the enteric nervous system, but everyone else just wants to use a term other people understand. Wnt (talk) 15:23, 26 March 2016 (UTC)[reply]

The article [15] quoted above also says: "the brain is an ordinary hollow organ." Might be true for a large portion of mankind. :-) --AboutFace 22 (talk) 17:52, 26 March 2016 (UTC)[reply]

"OH, HOLLOW! HOLLOW! HOLLOW!"

What time the poet hath hymned
The writhing maid, lithe-limbed,
Quivering on amaranthine asphodel,
How can he paint her woes,
Knowing, as well he knows,
That all can be set right with calomel?

When from the poet's plinth
The amorous colocynth
Yearns for the aloe, faint with rapturous thrills,
How can he hymn their throes
Knowing, as well he knows,
That they are only uncompounded pills?

Is it, and can it be,
Nature hath this decree,
Nothing poetic in the world shall dwell?
Or that in all her works
Something poetic lurks,
Even in colocynth and calomel?
I cannot tell.

Bunthorne's "wail of the poet's heart on discovering that everything is commonplace" from Patience by W. S. Gilbert. AllBestFaith (talk) 19:07, 26 March 2016 (UTC)[reply]

Vogons or no vogons, the neural tube is a hollow structure (indeed, a specialized sort of ectoderm, with much in common with the skin), and the hollow center remains in the form of the ventricular system even in the adult (which can become all too hollow in the case of hydrocephalus). Wnt (talk) 22:58, 26 March 2016 (UTC)[reply]

March 26

Information ~ Energy. Maxwell's demon. Szilard

Question	Remark
Szilard says that measurement of 1 particle speed (is speed more than average = yes/no question = 1 bit) is accompanied by entropy increase of $k\log 2$ . Is this entropy increase of Universe or what? E.g. demon converts work to heat and makes maesurement: $W=Q$ ; Then he tries to convert back heat to work : $Q=W'+kT\ln 2,W'<W$ ; How much work can demon obtain using information about speed? Can it be equal to $kT\ln 2$ ?	[ http://www.weizmann.ac.il/complex/tlusty/courses/InfoInBio/Papers/Szilard1929.pdf ]
As we know, $k\ln 2$ is lower boundary for entropy increase during measurement. If entropy increase is more than $k\ln 2$ , can we obtain entropy decrease via information more than $k\ln 2$ ?	Entropy in thermodynamics and information theory Maxwell's demon

37.53.37.94 (talk) 16:22, 26 March 2016 (UTC)[reply]

SI status of the litre

Is the litre somehow not an official SI unit? I've always taken it to be a core part of the SI, but the intro to tonne says:

Although not part of the SI per se, the tonne is "accepted for use with" SI units and prefixes by the International Committee for Weights and Measures, along with several other units like the bar, litre and day.

Did sommeone just misunderstand something about the litre, or is it really not an SI-official unit? Nyttend (talk) 17:45, 26 March 2016 (UTC)[reply]

I think some wires got crossed: litres (or liters - the exact same unit, spelled in American English), are an SI unit, but they are not an SI base unit. The distinction is purely a matter of the difference between an SI derived unit and an SI base unit. Nimur (talk) 18:10, 26 March 2016 (UTC)[reply]

On the other hand, after consultation with a few references linked from our numerous articles, such as this NIST Special Publication SP-330 The International System of Units, it seems that many authoritative sources consider the liter to be "outside" the SI system! I guess this really depends on who you ask - and here in the USA, the National Institute of Standards and Technology is the end-all and be-all authority for standardization of units of measurement - so I guess I will respectfully defer to their opinion! Nimur (talk) 18:18, 26 March 2016 (UTC)[reply]

More important, the document that Nimur linked to is the standard that defines what is and is not an SI unit. (It's the US edition of it, so it uses some different spellings than other countries, but the spelling of units is not standardized and anyway the document includes footnotes on such issues.) The liter is indeed not an SI unit; you find this table 6 on page 32 (37th page of the PDF). --69.159.61.172 (talk) 18:48, 26 March 2016 (UTC)[reply]

See Non-SI units mentioned in the SI. AllBestFaith (talk) 18:58, 26 March 2016 (UTC)[reply]

It's roughly the metric analog to the "quart". So, being actually useful, it's shunned by the standards gods. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:46, 26 March 2016 (UTC)[reply]

The main problem with the litre is that the value (not merely the definition) of the unit has changed over the years, which makes it undesirable for use as a scientific unit. Tevildo (talk) 20:26, 26 March 2016 (UTC)[reply]

It seems to work fine for sodapop sales. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:35, 26 March 2016 (UTC)[reply]

Presynaptic cell must be neuron or it can be also miocyte for example?

93.126.95.68 (talk) 22:31, 26 March 2016 (UTC)[reply]

Well, to call something a synapse it usually has to have an axon ... however, as that article explains, you can (occasionally) have dendro- and somato- synapses as well, i.e. from the dendrites and cell body. That article also explains that traditionally only neuron on neuron contacts are called synapses and neuron-on-something-else contacts are called "junctions". If you take the loosest possible definition, possibly you could argue cardiac myocytes make synapses with each other, but I would say that's an error because the intercalated discs that connect them use gap junctions to make direct contact. What makes a synapse a synapse is that one cell releases a transmitter that is interpreted by another in an intelligent way, rather than acting as a simple short circuit hardwiring the two together. There may be something that comes closer to what you want but I'm not thinking of it. Wnt (talk) 23:11, 26 March 2016 (UTC)[reply]

Thank you for your comment. When you open Campbell biology book (10th edition, p.1062) you see that postsynaptic can be a muscle, a neuron or a gland cell: "Each branched end of an axon transmits information to another cell at a junction called a synapse. The part of each axon branch that forms this specialized junction is a synaptic terminal. At most synapses, chemical messengers called neurotransmitters pass information from the transmitting neuron to the receiving cell. In describing a synapse, we refer to the transmitting neuron as the presynaptic cell and the neuron, muscle, or gland cell that receives the signal as the postsynaptic cell." 93.126.95.68 (talk) 01:26, 27 March 2016 (UTC)[reply]

Nerves (usually via axons) can go to a lot of funny things ... like melanocytes. [14] But your question above asked for a non-neuron as the presynaptic cell, which is harder to think of. Wnt (talk) 01:59, 27 March 2016 (UTC)[reply]

March 27

What is the meaning of AKA in the context of the nervous system anatomy?

What is the meaning of the letters AKA in the context of the nervous system anatomy or physiology? (except of "also known as"). 93.126.95.68 (talk) 00:42, 27 March 2016 (UTC)[reply]

AKA is Alcoholic ketoacidosis in the field of endocrinology, fwiw. Do you have any more context, or a pointer to an example?--Tagishsimon (talk) 00:50, 27 March 2016 (UTC)[reply]

To be honest I just heard my teacher say it when he gave us an introduction on the nervous system. He explained something about it but I unfortunately I forgot it. and I don't find where I wrote it, if any. I sent message to my teacher in a request to remind me it. Thank you93.126.95.68 (talk) 01:22, 27 March 2016 (UTC)[reply]

He may have just meant the basic aka - also known as -. Graeme Bartlett (talk) 10:36, 27 March 2016 (UTC)[reply]

What does it mean "specialized population of neurons"?

What does it mean "specialized population of neurons"? the full context is (from the Campbell textbook): "In all but the simplest animals, specialized populations of neurons handle each stage of information processing. • Sensory neurons, like those in the snail’s siphon, transmit information about external stimuli such as light, touch, or smell, or internal conditions such as blood pressure or muscle tension. • Neurons in the brain or ganglia integrate (analyze and interpret) the sensory input, taking into account the immediate context and the animal’s experience. The vast majority of neurons in the brain are interneurons, which form the local circuits connecting neurons in the brain. • Neurons that extend out of the processing centers trigger output in the form of muscle or gland activity. For example, motor neurons transmit signals to muscle cells, causing them to contract." By the way, Does it say that each acting occurs due to these three stages? If it does, I wonder because when we think about something and then decide to act (e.g. to take something from the table) actually we pass just two stages, because we don't really use sensory neurons for the information processing.93.126.95.68 (talk) 01:42, 27 March 2016 (UTC)[reply]

In this context "population" just means "a distinct group of". Action does arguably involve the three groups mentioned. In your example of taking something from the table, the sensory inputs you ignore might well be sight (you have to see the table and the object, and if you're blind, then touch), but also proprioception - where is your hand, your arm, etc; how well are they responding to actions initiated in support of your objective? --Tagishsimon (talk) 01:47, 27 March 2016 (UTC)[reply]

thank you for your comment, it helped me. I didn't ignore of the sight, because I meant to case that you don't saw it at the same moment. for instance, if you are reading a book and suddenly you feel that you're hungry then you decide to go the kitchen and to open the refrigerator. Does it says that you saw it before? and why does the text limit it to a distinct group of neurons? do exist other types of neurons which don't pass these three stages? 93.126.95.68 (talk) 01:55, 27 March 2016 (UTC)[reply]

In this instance they are probably referring to neurons with different specialized morphology. See retina - two of the figures show the different layers and different types of connectivity in each layer, though I've seen far far better illustrations. However, I think that the statement as written could refer to something else, which is when you have an initially homogeneous set of neurons with the same apparent cellular identity and different ones are recruited to different tasks - like which ones react to a particular word or touch to a particular spot on the body. In that case the connectivity is also different, of course, but the differences may be much more subtle, not morphologically recognizable. Wnt (talk) 02:05, 27 March 2016 (UTC)[reply]

Reading through Nervous tissue may assist you. That article shows a number of different ways of grouping nerve tissue. The list you gave, above, is a functional classification - which must be seen for what it is - a very broad and very simple means of introducing and describing subdivisions of the nervous system. I'm not sure it is very useful to spend time looking for actions which can be performed using only two of the three in the classification system. And, clearly, it is possible to break down the functional classification further, into sub-classifictions. Or to reach for one of the other classifications mentioned in the Nervous tissue article. --Tagishsimon (talk) 02:28, 27 March 2016 (UTC)[reply]

Military applications of wafersats

I was surprised to read a claim [15] that it is possible to send instrument probes to Alpha Centauri and other stars within 10 light years using a laser light sail approach. One thing that they don't seem to discuss at all: the lack of spread of the beam. It isn't that clear to me how long the probe accelerates for before the beam spreads out too much to be caught by the sail, but they seem to describe sails just meters across being beamed at for some appreciable portion of a light year.

If this is true, then these probes seem like the basis of some rather devastating space weapons. For example, the probes - tiny things, grams in weight, probably cubesat material - might be deployed in low Earth orbit, using more rigid reflectors than described. A laser of the type used for probe propulsion can then be bounced off them to set fire to thousands of widely separated remote wilderness sites in a short span of time, or burn right into a giant tank of natural gas (I mean, they talk about a reflector capable of withstanding 10⁵ suns of brightness!), or I suppose to lock onto some VIP caught out in the open. This isn't the first time I've seen hints of such capabilities (the AF 2020 report was another), but I've also seen claims that you can't collimate a laser beam well enough to pull it off. So .... can you? What is the feasibility here, for either application? Wnt (talk) 02:22, 27 March 2016 (UTC)[reply]

Military Industry has been trying to make this work since befor 1984. See Strategic Defense Initiative. Over the years every now and then someone claims to finaly have a working experimental model, presents something alike, but then every time you never read about it again. --Kharon (talk) 11:26, 27 March 2016 (UTC)[reply]

There is a huge difference in range due to air. Air contains dust and perhaps water droplets, both of which spread the beam out and/or absorb it. Space also contains dust, but at a much, much lower density (can somebody put some numbers on this ?). Also, temperature differences in layers of air can defract the beam. This is why stars sometimes appear to "twinkle". StuRat (talk) 13:51, 27 March 2016 (UTC)[reply]

Transparent enough that you can see Deneb right in the middle of the Milky Way through several thousand light years of the galactic disc. 10 light years would be like a 300th root of the Earth to Deneb light transmission percent would it not? Unless the 10 light years are dustier than average but it would still be very very transparent. Sagittarian Milky Way (talk) 16:01, 27 March 2016 (UTC)[reply]

Nephron can be considered also as a cell?

I know that the nephron is renal functional unit but I'm asking if we can consider it as a cell? 93.126.95.68 (talk) 03:31, 27 March 2016 (UTC)[reply]

No, a nephron is an assembly of many hundreds or thousands of cells. This page briefly describes the cells found in a nephron. Someguy1221 (talk) 07:55, 27 March 2016 (UTC)[reply]

A simple kidney in small bilaterians consists of a flame cell and tube cell. I think that the collecting aspect of a nephron would hint that the tube cell should be counted as part of its equivalent there, but you could argue the issue. Another question is whether it can be counted as a nephron when there is no loop of Henle (AFAIK). A weirder variant is the nephrocyte - honestly I have no idea what it's doing in the esophagus ( see [16]) but it is said to be homologous to a podocyte. Wnt (talk) 10:33, 27 March 2016 (UTC)[reply]

Effective Strength of a martian "Storm"

Storms on earth can cause many effects - even blow away houses and more. This needs force measured in pressure per square inch. On Mars The resulting mean surface pressure is only 0.6% of that of Earth - so I'd like to know, how much force a martian storm of perhaps 400 km/h can provide at one suare inch (or cm²) to press against objects (and perhaps to move them) - in other words: can such a storm do more that letting a flag flutter? Chiron McAnndra (talk) 14:05, 27 March 2016 (UTC)[reply]

There is a movie showing the Telltale of the Phoenix mars lander moving. I try to find how heavy the thing is but look at the movie first [17] --Stone (talk) 14:31, 27 March 2016 (UTC)[reply]

The small tube with the fibres is in the 10mg range and the length is 2-3 cm. [18] This looks like even on a windy day on Mars you would require a real low weight flag, or do the same cheating like on the moon. --Stone (talk) 14:38, 27 March 2016 (UTC)[reply]

If 400 kph is correct it should be like a 400kph*0.6%**.5 wind on Earth times some adjustment for density (~44 amu vs 29 average particle mass and it's colder so denser) and the force of the wind-driven dust particles. That seems plenty to fly a flag. I don't know how fast the dust moves or how thick it is. When there is no dust storm (which is often) the wind isn't strong enough to pick up any dust by definition so it is pretty weak. Sagittarian Milky Way (talk) 15:47, 27 March 2016 (UTC)[reply]

(ec)Assuming mostly turbulent flow, drag grows quadratically with velocity, but linearly with density. So a 400 km/h storm at 0.6% surface pressure should create roughly the same force as a wind of 30km/h on Earth - that is a "fresh breeze" (Beaufort scale 5 on Earth. Not catastrophic, but certainly noticeable. As a beginner, you don't want to experience that in a Hobie Cat. As a good sailor, its probably where the fun begins ;-). All modulo misunderstanding of the physics and errors in the math.... --Stephan Schulz (talk) 15:52, 27 March 2016 (UTC)[reply]

(ec) Worth noting is that the wind speed in Martian storms is usually vastly overstated. Measured wind speeds on the Red Planet top out around 30 m/s (in round numbers, 60 mph or 100 km/h)— quite a strong wind on Earth, but not extraordinarily so. (Here on Earth, sustained 30 m/s winds would be a tropical storm, not even qualifying as a lowest-grade hurricane.) Note also that wind forces scale with the square of velocity, so cutting the wind speed by three-quarters reduces the force by a factor of 16. TenOfAllTrades(talk) 15:54, 27 March 2016 (UTC)[reply]

Our article on Dynamic pressure can help you get a rough approximation. So at 400km/h or 111m/s and [19] give an air density on Mars of about 0.020 kg/m3. Thus, that gives one q=0.5(0.02)(111)2 = Pa
From there you can get your kg ⋅ m/s2 . So, yes it would feel very windy.--Aspro (talk) 15:56, 27 March 2016 (UTC)[reply]

Such storms would have a much lower impact than what was depicted in The Martian (film). It would also not carry rocks, but only a thin sand that would feel more like smoke. For more details: storms in Mars.--Scicurious (talk) 19:10, 27 March 2016 (UTC)[reply]

Is solder for mechanical joining different from electrical?

Is there a difference in the chemical composition of solder intended for electronics vs mechanical joining of e.g. pipes or other large pieces of metal or are they just different in diameter of wire/pieces? --78.148.107.251 (talk) 16:38, 27 March 2016 (UTC)[reply]

There are different kinds of solder. Please see the Solder article - especially the Solder alloys table. MarnetteD|Talk 16:46, 27 March 2016 (UTC)[reply]

Oh boy! I just want to repair a broken candelabra which I think is bronze plated carbon steel. --78.148.107.251 (talk) 20:33, 27 March 2016 (UTC)[reply]

Brazing or welding are more likely to be used on large pipes or pieces of metal. StuRat (talk) 16:50, 27 March 2016 (UTC)[reply]

They have to be different. Solder in electronic components has to conduct electricity. There are further subdivisions by type of alloy or being leadfree (or not) — Preceding unsigned comment added by Scicurious (talk • contribs) 19:01, 27 March 2016 (UTC)[reply]

The flux used differs also. For electrical work, you will want one that does not need washing off, and will not corrode the surfaces. Graeme Bartlett (talk) 21:29, 27 March 2016 (UTC)[reply]

Deep space telescope

This article mentions a "solar lens focus where the Sun acts as a gravitational lens to magnify distant objects". Einstein predicted a 542 AU focal length but it seems difficult to obtain an image through a "lens" whose deflection angle of light decreases away from the axis, and whose center is blinding. Is it sensible to send a radio- or optical Hubble-like telescope all the way out there to take a look? AllBestFaith (talk) 18:53, 27 March 2016 (UTC)[reply]

At least it still magnifies. You should block out the Sun with something like a coronagraph. Thousand Astronomical Units mission gives some idea of what this kind of mission would be like. Sagittarian Milky Way (talk) 20:14, 27 March 2016 (UTC)[reply]

Cats

If cats are solitary creatures, why do they make good pets in large human households? Surely, if there were solitary they wouldn't allow themselves to be domesticated, show affection to people, etc. I'm not sure the argument that we give them convenience flies that well, because they're perfectly able to fend for themselves. Also, in countries where there are large stray cat populations, like Egypt or Turkey, they seem to work together. Is the solitary and aloof quality associated with cats just a myth, are they closet pack animals? --Andrew 19:30, 27 March 2016 (UTC)[reply]

I don't know what you mean by "solitary creatures." They are more independent than dogs, and also have a shorter domestication history behind. But that does not conflicts with the fact that they simply evolved to be around humans. Just because they could live independently out in the wild does not mean that getting food from an old lady is not their first preference. The question is why humans keep them, since they do not provide any service nowadays. Maybe being small non-threatening furry and cute helps their case. At the beginning it might be that they were convenient back then, since they could catch mice, and mice were near us since we are good at producing grain. --Scicurious (talk) 19:38, 27 March 2016 (UTC)[reply]

Wild cats are solitary. Domesticated cats (including ferals) are not. http://icatcare.org/advice/understanding-your-cat/social-structure-cat-life Iapetus (talk) 20:16, 27 March 2016 (UTC)[reply]

The answer is actually quite simple. It depends on food availability. If food is plentiful, domestic cats will readily tolerate each other, even in large groups. Hence the scenes of many feral cats coming together when they are being fed by well-meaning humans, or individuals owning 20+ cats in their homes. Cats can be highly dangerous in aggressive interactions so it is to their benefit to avoid confrontation and aggression. If they have plenty of food, there is no benefit in fighting. Generally, cats, including domestic cats, are considered to be solitary - I think the only exception is lions, although cheetahs will form sibling alliances.DrChrissy ^(talk) 20:27, 27 March 2016 (UTC)[reply]

I would question the "they do not provide any service nowadays" assertion above. A cat provides companionship with less upkeep needed than even a small dog requires, and they eliminate small vermin from residences. --Guy Macon (talk) 22:02, 27 March 2016 (UTC)[reply]

Mine bring the bloody things in! "Hey Dad - look what I brought you!" ;-) DrChrissy ^(talk) 22:08, 27 March 2016 (UTC)[reply]

What does "non-Gaussian AO situations" mean?

Within the context of statistics and control theory I found this sentence:

"produces estimates that are quite good approximations to the exact conditional mean in non-Gaussian AO situations"

What does "AO" mean? source Ferrofield (talk) 22:10, 27 March 2016 (UTC)[reply]

@@ Line 508: / Line 508: @@
 :::I would question the "they do not provide any service nowadays" assertion above. A cat provides companionship with less upkeep needed than even a small dog requires, and they eliminate small vermin from residences. --[[User:Guy Macon|Guy Macon]] ([[User talk:Guy Macon|talk]]) 22:02, 27 March 2016 (UTC)
 ::::Mine bring the bloody things in!  "Hey Dad - look what I brought you!" ;-) <span style="font-family:Segoe print; color:red; text-shadow:gray 0.2em 0.2em 0.4em;">DrChrissy</span> <sup><span style="font-family:Segoe print; color:red; text-shadow:gray 0.2em 0.2em 0.4em;">[[User talk:DrChrissy|(talk)]]</span></sup> 22:08, 27 March 2016 (UTC)
+== What does "non-Gaussian AO situations" mean? ==
+Within the context of statistics and control theory I found this sentence:
+ "produces estimates that are quite good approximations to the exact conditional mean in non-Gaussian AO situations"
+What does "AO" mean? [https://www.stat.washington.edu/raftery/Research/PDF/martin1987.pdf source] [[User:Ferrofield|Ferrofield]] ([[User talk:Ferrofield|talk]]) 22:10, 27 March 2016 (UTC)