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November 14

Type of hearing loss with anger at loud sounds

There's a type of hearing loss that is characterized by extreme sensitivity to loud sounds, which is typified by abnormal anger in the patient when subject to loud sounds. I remember it being called something like acquisition deafness; although acquisition is apparently the wrong word. Can anyone identify the name of this type of hearing loss? Thanks. μηδείς (talk) 01:08, 14 November 2013 (UTC)

(Three words I am not looking for are phonophobia, hyperacusis, and misophonia. It was a two-word term, axxxxxxxx deafness.)

Acoustic trauma? It's two words starting with "A", at least. Red Act (talk) 02:44, 14 November 2013 (UTC)

The "anger at loud sounds" bit sounds like one of the symptoms of autism. StuRat (talk) 03:39, 14 November 2013 (UTC)

No, acoustic trauma's not it. Autism isn't even close, unfortunately. It was a type of hearing loss in otherwise "normal" older people that was accompanied by extra sensitivity to loud sounds, to the point of outrage at an unexpected loud sound. It was something I hadn't heard of until I went looking for articles on hearing loss and heard of this specific type. μηδείς (talk) 04:58, 14 November 2013 (UTC)

I've never heard of that as a natural phenomenon, but I can tell you from experience that it commonly happens in older people who wear hearing aids. Looie496 (talk) 15:52, 14 November 2013 (UTC)

It sounds like you're describing loudness recruitment (see: [1], [2], [3]), which is related to/part of Sensorineural hearing loss. I couldn't find the specific term you were looking for, but the only thing I can think of would be "acquired deafness", but that's only an indicator of when, not the what. Presbycusis is age related hearing loss, it could be described as "acquired" and it can/does involve recruitment.Phoenixia1177 (talk) 07:15, 14 November 2013 (UTC)

Yes, that's it! It was loudness recruitment. Wonderful, thanks! μηδείς (talk) 16:02, 14 November 2013 (UTC)

Resolved

Ducks adopt unrelated chicks?

Hi, noticed that a particular species of duck often has hordes of ducklings following the parents around, often as many as 20-24. However checking out the species page i note the clutch size is only about 10 wood duck. Where do the extra chicks come from? I've heard of parents ducks adopting as many chicks as they can since ducklings are largely autonomous in terms of feeding and don't require any extra work while the more foreign ducklings she has the greater the chance of her own surviving a crow/seagull attack.. couldn't find anything after a few quick Google searches on the topic however. ideas? --Benjamint 01:40, 14 November 2013 (UTC)

I could think of additional reasons for adopting other ducklings:

1) Once the adopted ducklings mature, they provide mating opportunities for their own ducklings, and prevent inbreeding.

2) Since they fly in flocks, it's useful to have a larger flock, for better aerodynamic efficiency, etc. StuRat (talk) 03:37, 14 November 2013 (UTC)

Good observation, and question! First, I'll note that brood size varies wildly. Just because 10 is the average number of hatchlings doesn't mean some broods might be much larger. But, various duck species do "adopt" other ducklings which were not originally part of their brood (let's leave "unrelated" out of this, because there's a decent chance that neighboring females of of the same species are related.)

Here's a study of a few other spp., "Causes and functions of brood amalgamation in Barrow's Goldeneye and Bufflehead" [4]. From the abstract,

“ In 3 years of observations there was no significant relationship between brood size and duckling survival. I contend that brood amalgamation in Barrow's Goldeneye and in Bufflehead has not evolved as an adaptation to increase young and (or) female survival but that it is simply an accidental outcome of territorial aggressiveness. ”

--So at least one author thinks it is more of a by-product, and not an adaptive trait. However, different spp. will have different social structures, environment, migratory patterns, predators, and so on, so we can't just generalize to all fowl from a few spp.

Here's another paper looking at Eider brooding behavior [5], which says

“ Thus, the cost of adopting additional

ducklings may be small, and Eadie and Lumdsen (1985) listed three possible ways in which the risk of predation of the female's own young could be reduced through adoption. First, the addition of foreign young would dilute the recipient's brood size. Second, larger groups may more rapidly detect, and confuse, a predator. Third, mortality of the recipient's young may be reduced through the selfish herd effect (Hamilton 1971 ; Nudds 1980). In our study there was no increase or decrease in survival with brood or creche size. Thus, our data are not consistent with the dilution effect hypothesis, and we cannot reject the neutral effect hypothesis

”

(emphasis mine)--So, scientists have looked at possible benefits of brood amalgamation in at least three spp., and haven't found any strong evidence of said benefits, e.g. decrease in predation mortality. I might poke around a bit more, but anyone who's interested (and perhaps has access) can use google scholar's features to see who has cited these works, maybe someone has figured out more about this more recently, or perhaps more specifically to the Australian wood ducks that you've observed. Also, I only skimmed the articles, but both have much more info and discussion that is highly relevant. If anyone wants to read them but can't access, feel free to contact me. SemanticMantis (talk) 17:06, 14 November 2013 (UTC)

Earthling Phone Home!

Clickable image, highlighting medium altitude orbits around Earth, from Low Earth to the lowest High Earth orbit (geostationary orbit and its graveyard orbit, at one ninth of the Moon's orbital distance), with the Van Allen radiation belts and the Earth to scale.

If we disregard all possible national security and flight safety issues, can an astronaut in the ISS or any earth-orbiting spacecraft phone home using the Iridium service? (If the radio signal can penetrate the spacecraft's metal hull).

Most manned spacecrafts, except for Apollo moon rockets, are travelling below Iridium's orbits. They must have very good views of many of these satellites at any moment. Does the speed affect their use of Iridium phones?

What would happen if they use a very powerful GSM cellphone to phone home? Let's say a Russian cosmonaut wants to phone home when the ISS is over the great Russian land (if your country is too small, the ISS flies past your country in less one minute!). His beefed-up signal could be picked up by hundreds of ground stations. However, each station may only hear the signal for a very short time depending on signal strength. How does the GSM handle this situation.

Can an astronaut use his off-the-shelf GPS smart phone, tablet or wrist watch to get his approximate location over earth?

Many spacecrafts use GPS as a way of navigation. They must take altitude into consideration. However, the GPS or Glonass circuits in consumer devices probably assume that you're on the ground or maybe within civilian aviation altitudes. How do these inexpensive gadgets operate if they are 400 km above the earth? -- Toytoy (talk) 01:42, 14 November 2013 (UTC)

Some systems like the GPS receiver may not believe that it could be travelling so fast, and therefore not lock on correctly. For a telephone system the Doppler shift would be large and not acceptable to the operator. So I suspect it would not work. Graeme Bartlett (talk) 10:56, 14 November 2013 (UTC)

Consumer GPS is designed to shut down if it moves too fast and/or too high. This is to prevent garage tinkerers and unfriendly folks from building GPS-enabled intercontinental ballistic missiles. (Also annoys high altitude balloon hobbyists.) I expect (but have no source) that there are military grade GPS chips that are designed to go ballistic - you'd want that if you were an authorized ICBM manufacturer, wouldn't you. 88.112.41.6 (talk) 20:14, 14 November 2013 (UTC)

I believe that no "very powerful" GSM phone would work, because the speed the phone is travelling at would be so fast that the "handshake" between cell masts and the phone would make it impossible, and the phone would be visible to many cells at the same time, which wouldn't work. — Preceding unsigned comment added by 217.158.236.14 (talk) 14:21, 14 November 2013 (UTC)

However Iridium phones are not cell phones, and connect directly with the satellites, not via a ground station. Would this help? Rojomoke (talk) 17:48, 14 November 2013 (UTC)

I'd bet that this would have the same problem as the GPS. The phone has to figure out which satellites are overhead and where they are moving...and I'd bet that the configuration of satellites would change more rapidly than the calculations could be performed...that's true of GPS - but I'm only guessing for Iridium phones. SteveBaker (talk) 17:53, 14 November 2013 (UTC)

(ec) Our Cell site article says that the range of a cell tower is limited (in part) by: "Timing limitations in some technologies (e.g., GSM is limited to 35 km, with 70 km being possible with special equipment)". Which probably means that the tower and the phone are required to exchange some kind of signal with a round-trip time of maybe 1/5th of a millisecond - and that would be flat out impossible with the speed-of-light transit time to the 425 km-high ISS orbit being at least 1.2 milliseconds. So I'm pretty sure GSM won't work - but CDMA/IDEN phones don't have that restriction. Orbital speed might also be a problem - a typical cell is one or two kilometers across and the ISS is moving at 7.65km/sec - that would require it to switch cells maybe 7 times a second. Ironically, it might do better over rural areas where the towers are spaced further apart (maybe up to 60km apart) - which might give the software in phone and cell tower enough time to switch towers.

GPS is much more problematic - the difficulty being that when on the ground, they have to take account of relativity in order to get accurate positioning - they know the speed of the satellites in orbit - so they can do that. However, I'd be quite surprised if they bothered to take account of the speed that the GPS unit itself is travelling...and since the speed of the ISS is so high, I'd assume that would cause intolerable errors. Another issue with GPS is that it has to do protracted searching to find the satellites whenever you turn it on after moving it more than a few miles. With my GPS, it sometimes takes several minutes to get it all sorted out. I suspect that in the ISS, the configuration of visible satellites would change faster than the calculations could keep up and it would never lock on.

So, I'm fairly sure, the answer is "No" for both things...but it's not about radio propagation distances - it's about software performance and subtle issues like that. SteveBaker (talk) 17:51, 14 November 2013 (UTC)

I would think the ISS and orbiting satellites would use reverse GPS. Well known ground reference points, receiver in satellite that picks them up. Multiple radar installations could track very accurately where, what altitude and velocity objects in space where traveling with similar precision to GPS (error might be slightly higher due to length of transit in atmosphere). Bouncing a timed and coordinated signal from one source on earth to a satellite and back to multiple receivers on earth at different, known, locations accomplishes the same thing as GPS. Just need a powerful radar and sensitive receiver.. --DHeyward (talk) 08:32, 15 November 2013 (UTC)

Reverse GPS is a great idea. However, unless you're travelling on a much higher orbit (ISS is about 400 km above the ground), your horizons are quite limited (ISS: a 2300 km radius circle).

http://www.ringbell.co.uk/info/hdist.htm

This means you must install many many many radio beacons on land. And when the ISS is over the Pacific Ocean, it may only see a handful of beacons on some islands.

However, if you're on a much higher orbit, this idea may work! -- Toytoy (talk) 12:56, 15 November 2013 (UTC)

Duel Electric Meter for saving money?

I live in Michigan and have moved into a house that is electric everything and each room (10 in all)has it's own thermostat. I have been told that we can save money by having a duel electric meter put in if our electric company (Consumers Energy) provides this. What exactly is a duel electric meter and how can it help us save electricity? Officerswife (talk) 02:14, 14 November 2013 (UTC)

I don't know what it is but it's likely spelled "dual" as in two of something rather than "duel" as in a sword or gun fight between two people. A Google search confirms that there are such things as a Dual Electric Meter but I haven't been able to figure out what they do. Dismas|^(talk) 02:20, 14 November 2013 (UTC)

This talks about dual rate electricity but it seems to center on the UK, so I'm not sure how much it would apply to your situation. To my knowledge, we only have a single rate charged to us for electricity here in Vermont but Michigan may have two like the article discusses. Dismas|^(talk) 02:25, 14 November 2013 (UTC)

The article cited by Dismas talks about off-peak electricity delvered via the second meter. This can work well, lowering your electricity costs if you have storage hotwater systems and/or storage space heating - you mostly want heating in the evenings, which are off-peak for the power company, anyway. You can aslo run a small oven from the off-peak meter, so that if you like late (or even early) evening snacks, you can cook them on cheap electricity. You may alternatively have a system used by power companies elsewhere. The second meter is set up to charge at a slightly lower tariff, but the power company has the right to turn off the power to it when demand is high. They usually only do this for short periods - under an hour. You need to consider the usage of such power carefully. In hot weather, if your airconditioning is fed from the low tariff meter, it can result in increased electricity charges, as your aircon will go like the clappers to catch up when the power comes back on. 60.230.232.138 (talk) 03:05, 14 November 2013 (UTC)

I live in Michigan, and have dual meters, as our house was once set-up for an upstairs tenant. However, just having two meters alone may actually cost you money, since now you have 2X the flat monthly rate. However, there are so many plans it's difficult to tell, without analyzing your usage patterns:

1) They have "off-peak usage plans", as mentioned above, which typically charge more at peak times and less at off-peak times. That might require a dual-meter.

2) They have "interruptible service" which promises they will only interrupt it in an "emergency", but my brother had that, and every hot day was considered an emergency, with the result being that he could only use his A/C on days when he didn't need it. This might require dual meters, one for the interruptible "non-critical" portion of the service (used for A/C), and another for the rest.

3) They have "senior plans", where they charge a lower rate for light usage, and a higher rate for higher usage. I see no reason for a dual meter here.

4) They have lower rates for those with whole house electrical heating. If the heating unit is on one meter at the lower rate and the rest of the appliances go on the other meter at the higher rate, that might explain it. I think this is the case you have. Yes, that could reduce your bill. However, even at the lower rate, electrical heating is still far more expensive than gas heating. StuRat (talk) 03:30, 14 November 2013 (UTC)

Electric heating on a separate meter is also my guess - but electric heating is unusual in Michigan (only 8% of homes)[6]. Consumers Energy calls it Heat Plus Metering [7]. Rmhermen (talk) 18:36, 15 November 2013 (UTC)

Do they not have smart meters in Michigan? I have a single meter that is remotely read and has time-of-use rates. I am not sure how having two meters would be used for multi-rate service. Dual meters are used for solar and other grid-tie systems as they measure the power that is put back on the grid. If you house isn't designed to have multiple service entrances, I don't see how splitting up the service is possible or efficient. Is there a penalty for exceeding a certain amount of kWh per month? Is your house underpowered for a heat pump or central heat such that someone is recommending a different heating system on it's own service? StuRat's #4 sounds most likely (and also can't be turned off in winter by law). --DHeyward (talk) 07:20, 14 November 2013 (UTC)

They have "smart meters" designed to broadcast whether we are home or not to nearby thieves, yes. However, they don't broadcast on the Internet, but only to the street, so the meter readers need to go around in a vehicle to take readings. Unfortunately, the portable units they use to read the meters from the street have a seriously underpowered battery, and the utility company requires the employees to return to base to verify that the battery is dead and get a replacement. Rather than deal with this hassle, the employees instead continue to read the meter manually, just as before. :-) StuRat (talk) 08:20, 14 November 2013 (UTC)

Wow. I believe ours use the power-line for data transmission and is updated daily. The meter is addressable and queryable. Everyday, the power company posts usage (down to the hour) on my account. It's not 100% as sometimes it updates at midnight or 4am but it's correct. My meter is supposed to be physically accessible but I created a courtyard with a gate (the Fire Department could get in, but the power company would have complained if they had ever checked in the last 5 years. They phased out the meter readers. The gas company and the water company read by hand with the gas company being the least efficient. --DHeyward (talk) 10:26, 14 November 2013 (UTC)

That's what my Michigan smart meter is like. It actually lets you break it down to the minute if you want to. — Preceding unsigned comment added by 209.131.76.183 (talk) 12:32, 14 November 2013 (UTC)

Solar power systems have become common in Australia due to the stupid Government heavily subsidising the installation, and imposing a tarrif for power fed back to the grid much higher than for power drawn from it. No additional meter is required - they have new technology meters that store the amount of electricity fed back separately from electricity drawn off. But dual tarrif (either off-peak or off-in-high demand) are much older ideas that have required dual meters. 60.230.232.138 (talk) 08:56, 14 November 2013 (UTC)

Net metering (the solar meter) is usually required by the local city/utility code based on fire codes (NFPC/NEC) and also allows the utility to lock it out safely. Even though the inverters are suppose to cut out without a grid and there is both a DC and AC disconnect, removing and locking out the meter is the way the power company controls the service entrance. One of the the codes that makes solar ugly is that it's not allowed to penetrate the roof or a wall until it hits the service entrance disconnect and meter. Because of utility laws, only regulated companies are allowed to sell electricity to consumers (i.e. homeowners can't install a sub-metering system to tenants, but a power company can) so a meter is almost always required between the solar power and the consumer. I always wanted to forego the solar array and use off peak cheap energy to charge deep-cycle batteries and then connect the batteries to the solar inverters during on-peak hours. It's almost as cost effective as the raw cost for solar but they won't give me a tax break to buy the batteries. The break even point is around 12 years for current prices. --DHeyward (talk) 10:26, 14 November 2013 (UTC)

That must be a quirk of DHeywood's power company or of the US National Electrical Code (NEC). Or error by DHeywood. DHeywoods's requirement that the solar invertor output be routed to the meter/service connection point before entering the building cannot be applicable in Australia. We have what are known as "battle-axe" blocks. This is a way of saving money on roads. Each roadside in a battle-axe area has residential or light industrial blocks of land fronting the street, and another lot of blocks behind the roadside blocks. The "behind" or rear blocks get their access via drive-ways running down the side of the road-fronting blocks. Hence the name "battle-axe" as that is what it looks like on the title deed survey drawing. To make life reasonable for the meter readers, all gas, water, and electricity meters are installed at the road/street end of the driveway, and there is typically 100 to 300 m of gas-pipes, water pipes and electric cabling from the meters to the house or factory. If the owner of a battle-axe block installs solar power, the power company replaces the meter (and charges a fee), if the existing meter is an old type. But nobody installs additional cabling so that the solar can go via the meter - that would be very expensive, involving trenching, the new cable, filling-in, and re-instatement of the driveway surface, macadam, bitumen, or concrete, whatever it may be. Many $1000's. Who wants cabling running across their roof, over the eaves, and down the side of their house anyway? Not sensible. If the cable is correctly sized and fused, fire is extremely unlikely, virtually impossible, and it is much safer concealed inside the structure. Most invertors are not rated for external installation (ie they are not weather-proof and/or cannot tolerate direct sun) - they can be installed outside in porches and the like however, so long as the sun and rain cannot reach them. 60.230.247.177 (talk) 11:41, 14 November 2013 (UTC)

It's a hazard to fireman if they cannot easily disconnect it before entering a structure. It's a hazard to have undisconnected electric service (AC or DC) penetrating the roof or wall. So it stays outside for residential installations. Commercial installations sometimes have a service entrance utility room where everything, including the meter and disconnect, is in a room (the fire department has keys). Short of a blanket or night time, there is no way to stop the string of panels (which are often wired in series to provide upwards of 400VDC) from providing a hazard to firefighters so the DC pieces from the panels to the inverter never penetrate into a living space. Designs usually treat the solar array as a source when doing fault analysis so there are a number of calculations and requirements for disconnect before power from an array can enter the home (in the U.S. for example, the backfeed into the main panel is often done in the breaker position farthest from the other source. This is to limit the current into a fault generated in the middle of the panel. Large solar installations to existing services often require the main breaker be derated as the rest of the equipment would not be fault protected from the maximum setting of the breaker - i.e. a 2,000 amp service has components that are not rated for more than 2,000 amps. If you add a solar array that can supply 200 amps of additional current to a fault, a component may have more that 2,000 amps available to it. The main disconnect breaker has to be derated to account for these types of faults.) Grounding is also an issue with PV systems as what and where to ground is critical as there can always be a short-circuit current (sometimes in the PV panel itself). Most of the residential solar installations just follow the cookbook which is solar meters, mechanical disconnect at the service and no structure penetrations. Rules are covered by NFPA 70 (NEC) section 690 (www.nfpa.org). The electric code is written for fire safety (both for fighting and preventing them as well as protecting public from electrical hazards). Grid tie inverters are service side wiring. I don't know how Australia does it. --DHeyward (talk) 08:15, 15 November 2013 (UTC)

Rotor in a cylinder

Would a rotor generate more lift if it's inside a cylinder instead of spinning in an open space? Intuitively, I imagine that the cylinder will canalize the flow in the right direction. However, it seems a too simple of a solution to remain unimplemented. So, are both scenarios different? OsmanRF34 (talk) 19:02, 14 November 2013 (UTC)

You mean something like a Ducted fan? AndyTheGrump (talk) 20:58, 14 November 2013 (UTC)

Yes, I have something like that in mind, but also for ships. OsmanRF34 (talk) 23:35, 14 November 2013 (UTC)

Ducted propeller, Bow thruster. AndyTheGrump (talk) 23:38, 14 November 2013 (UTC)

Pump-jet and vectored thrust are related. StuRat (talk) 05:00, 15 November 2013 (UTC)

November 15

Using Computers in Space

I asked about using GPS, Iridium and GSM in space. It's quite amusing that our spacemen can hardly enjoy space technologies without using very expensive military grade equipment.

• Radiation hardening

Now what would happen if you send an unshielded modern computer into low earth orbit? Today's ICs are so advanced, material background radiation could easily affect the bits stored in DRAM. Does it mean a computer, unprotected from space radiation, may crash within minutes? -- Toytoy (talk) 04:37, 15 November 2013 (UTC)

Modern semiconductor components employ a wide variety technique to harden against radiation (or rather, single event upset or failures as it could be anything). Keep in mind that background radiation and radiation at elevations as low as 5,000 feet have not changed while device sizes have. Things like triple bit error detection, double bit error correction in memory lines are fairly common algorithms (a 256 bit line in a cache dedicates a certain amount of bits for error correction so reading the line, going through the decoder corrects the error and writes the correct value back so the line is error free again. The ECC bits are no different than the memory bits). Techniques that exist today for the smallest sized transistors can often be sent back a generation as a "hardened" technique. (i.e. parity was an error detection scheme that worked when errors were rare, that was replaced with single bit error correction, double bit detection - now applying the error correction algorythm to feature sizes previously protected with parity is "hardening".). Lead (Pb) used in packaging when BGA and flip-chip started used to be a major ionizing radiation source but it, too, was adapted. So the answer is basically today's ICs run the gamut of hardening. Low-power is also just as much of a concern in satellites so a lot of the tradeoffs is power v. hardening. Also some microprocessors that are advertised with multiple cores also have different modes that are designed to harden them against errors (i.e. a lock-step mode). Think about the radiation as simply a multiple of the radiation at sea level. A Los Alamos massively parallel computer system will have faults generated at random and it is not an insignificant problem and is magnified by simply by being at elevation. It also has to be state of the art. So, it's less about the technology of the components than it is about how the components react together in their environment. Do you use your laptop or iPad on an airplane? That in itself is a large increase in available radiation. --DHeyward (talk) 07:09, 15 November 2013 (UTC)

From our International Space Station article: "The ISS is equipped with approximately 100 IBM and Lenovo ThinkPad model A31 and T61P laptop computers. Each computer is a commercial off-the-shelf purchase which is then modified for safety and operation including updates to connectors, cooling and power to accommodate the station's 28V DC power system and weightless environment. Heat generated by the laptops does not rise, but stagnates surrounding the laptop, so additional forced ventilation is required." Katie R (talk) 12:55, 15 November 2013 (UTC)

The ISS itself is a metal shield. I don't know how thick is the shell. At least it can withstand the 1 ATM air pressure inside the ISS (see International Space Station#Atmospheric control systems). No wonder they have to spend hours in a depressurized chamber breathing pure oxygen before EVA. Life on the ISS is much better than in a space capsule where the air pressure can be very low.

It also explains another question about hard disk. Today's hard disks require air pressure for the disk head to hoover above the disk plates. If the air pressure in the ISS is too low, the computer's hard disks may simply cease to work!

There will be helium-filled hard disks within a year or two. These helium-filled disks will be totally sealed. I guess they may work in space. -- Toytoy (talk) 13:09, 15 November 2013 (UTC)

Solid state drives are a more conventional solution to computers at high altitudes. They're expensive for the everyday consumer, but the cost would be utterly negligible compared to anything else on the ISS. --Bowlhover (talk) 16:25, 15 November 2013 (UTC)

Solid state drives are quite new. Before they were cheap enough, I guess they used specially-made high-altitude hard drives (in case of a loss of air). And life in space can be boring. They need much disk space for them to store Hollywood movies (who gives copyright a damn). I don't think the MPAA can send a lawyer to the ISS to check their disk drives. No wonder their computers are infected with a virus[8]! -- Toytoy (talk) 02:42, 16 November 2013 (UTC)

They weigh less too, so they probably cost less overall when you include what it costs to get them up there. Katie R (talk) 16:45, 15 November 2013 (UTC)

Why m.s-1 instead of m/s?

Why most physics related stuff uses m.s-1 instead of m/s, which is more intuitive and more people use it in everyday lives? — Preceding unsigned comment added by 101.255.36.219 (talk) 11:36, 15 November 2013 (UTC)

(I wrote an answer but I think it might have been incorrect. Please disregard it, sorry!)80.254.147.164 (talk) 12:11, 15 November 2013 (UTC)

s^-1 = 1/s.

As a result, m/s = m ⋅ s^-1.

I think it is a good idea that you use multiplication signs exclusively in a formula instead of using multiplication and division signs here and there. A mixture of two signs may result in more calculation errors. -- Toytoy (talk) 13:16, 15 November 2013 (UTC)

m.s-1 does not mean (m ⋅ s)-1. It means m ⋅s^-1. -- Toytoy (talk) 13:18, 15 November 2013 (UTC)

In everyday use, it seems to me that m/s is far more frequently used than m·s⁻¹, said metres per second (the article does not say anything about this). You could regards the slash notation as being more "intuitive" (really just more familiar to most people, as "per") than the notation for the inverse. In physics and other disciplines, where many combinations of units occurs, use of the raised −1 forms part of a more regular, and hence more more convenient, system of denoting units, where powers are combined with division and parentheses are not necessary, e.g. kg/(m·s²) would be written kg·m⁻¹·s^–2. —Quondum 15:22, 15 November 2013 (UTC)

One possible reason is consistency with other expressions in an article. Lets say an article contained the expression m∙s⁻¹∙cy⁻¹ to make it clear which units were in the denominator of the fraction. The same superscript might be used throughout the article to indicate division. Jc3s5h (talk) 16:00, 15 November 2013 (UTC)

Another issue is publication technology. Nowadays, we can, with some effort, write $m/s$, or ${\frac {m}{s}}$, and likewise m·s^(-1), or $m\cdot s^{-1}$. Not that long ago, many of these forms would require special typesetting when publishing a book, and that cost more money. Also, even though modern journals and book publishers can easily do things like this: ${\frac {\frac {a_{x}}{b_{y}}}{\frac {c^{z}}{d^{w}}}}$, they usually prefer inline forms, because large unwieldy expressions make the whole page look bad (see e.g. right there). There are several technologies supporting all this, including LaTeX, MathJax, Mathml, and many others.

Finally, things like OCR get all messed up on fancy math, and it also looks bad on axes labels for graphs. So, the lesson is, we "pretty print" when it aides understanding of complex expressions, but use old fashioned methods when they suffice. SemanticMantis (talk) 16:14, 15 November 2013 (UTC)

When you start getting more complex equations/units. e.g. acceleration is m.s-2 . Pascal is N.m-2 , Newton is kg.m.s-2 once we start combining units it is easier to add and subtract powers, hence pascal becomes kg.m-1.s-2 i.e. it is making it easier to work with units.Martin451 02:02, 18 November 2013 (UTC)

Is there a scientific explanation as to why gay kids are bullied?

Is there a scientific (psychological/neurological) explanation as to why gay kids are bullied? Is childhood homophobia a social contagion, observational conditioning, social transmission of information, operant conditioning, etc. or all of the above? 140.254.136.168 (talk) 18:00, 15 November 2013 (UTC)

No and yes, and you should read bullying and child sexuality. If you have a specific question you want answered, you can ask it, or check the Ohio State University library. This is not the place for open-ended discussions, especially not when your edit history shows you rarely follow up on the myriad questions you create here. μηδείς (talk) 19:11, 15 November 2013 (UTC)

Medeis, this being the Science desk, a question asking about the existence of a scientific explanation of something seems quite valid. It's not really open-ended. If it drifts off into something other than scientific explanation, it can (and should) be hatted. HiLo48 (talk) 21:23, 15 November 2013 (UTC)

This editor is a troll. He posts endless provocative questions with no obvious interest in the answers. It seems feeding trolls is an addiction around here. μηδείς (talk) 22:35, 15 November 2013 (UTC)

Have you reported the troll? Anyway, I still think this particular question is a reasonable one. Maybe the troll is changing. HiLo48 (talk) 23:28, 15 November 2013 (UTC)

It's an IP-hopper along a particular subnet, so reporting would be futile. They won't do a rangeblock on such a large range, and checkusers won't do anything about IP's. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:38, 15 November 2013 (UTC)

(ec) I don't think there's anything unique about homophobia, as kids are also bullied because of their race, language, weight, appearance (such as wearing glasses), etc. Bullies just look for any difference and use that as a justification for their behavior. I suppose it's a combo of asserting dominance and favoring their own group, which can both have evolutionary advantages. StuRat (talk) 19:13, 15 November 2013 (UTC)

You're onto it. The issue is not really why some particular group is targeted for no apparent reason, but rather why anyone is targeted for no apparent reason. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:41, 15 November 2013 (UTC)

The external links on Kinsey Institute for Research in Sex, Gender, and Reproduction should also help you find some references, or put you in touch with some experts that can help guide your search. Katie R (talk) 19:21, 15 November 2013 (UTC)

I have a theory that linguistic issues are involved in anti-gay feelings among kids today. (Though not the only aspect.) The first meaning of the word gay that children learn is that of being something that someone doesn't like. At a quite young age they will hear someone say "That's gay" or "This school is gay" or similar, long before they have any knowledge of the sexual meaning. So, it's a word with negative connotations from the moment they first hear it. When they discover that it also means homosexual and find out more about what that means, it must be impossible initially to separate the negative connotation from the newly discovered, sexual meaning. HiLo48 (talk) 21:58, 15 November 2013 (UTC)

In my adolescent years, the term "queer" was used exactly the same way. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:39, 15 November 2013 (UTC)

Where I grew up "butch" always meant lacking a perfumed deodorant. The pig farm on the edge of town and the dumpsters behind McDonald's were always called "butch" for that reason. It was hard as an adult for me to accept that spikey haired Lesbians and leather-queens might not necessarily smell bad. μηδείς (talk) 00:23, 16 November 2013 (UTC)

Well, in my childhood in Gloucestershire, we always sang "God Save the Queen", and that made me think I had to pray for the effeminate male patrons when I started frequenting gay bars in my 20's. μηδείς (talk) 00:23, 16 November 2013 (UTC)

Given their frequent targeting for abuse, that was not inappropriate. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:24, 16 November 2013 (UTC)

"Queer" originally meant "strange" or "not normal". J B S Haldane is famous for the quotation "The universe is not only queerer than we imagine, it is queerer than we can imagine" - and he wasn't referring to its homosexuality! --TammyMoet (talk) 16:42, 16 November 2013 (UTC)

It hasn't stopped meaning that. According to Etymology On Line: "queer (adj.) c.1500, "strange, peculiar, eccentric," from Scottish, perhaps from Low German (Brunswick dialect) queer "oblique, off-center," related to German quer "oblique, perverse, odd," from Old High German twerh "oblique," from PIE root *terkw- "to turn, twist, wind" (see thwart (adv.))" "Sense of "homosexual" first recorded 1922; the noun in this sense is 1935..." Apparently there are actually a few people still alive from the era when the "gay" meaning hadn't yet been published. μηδείς (talk) 20:04, 16 November 2013 (UTC)

Lots of people. The Flintstones theme song from the 1960's said "...we'll have a gay old time !", in the end, and somehow I doubt if they meant it that way. StuRat (talk) 20:35, 16 November 2013 (UTC)

I am unfamiliar with the "queer old time" version. μηδείς (talk) 21:31, 16 November 2013 (UTC)

As a high school teacher, when I hear the word "gay" used by teenagers (with whatever meaning), I often throw in the line "Which of the three meanings of gay do you intend in that sentence?" Forcing them to think about three distinct meanings usually stops any sense of bullying or just plain rudeness that was going on, at least in the short term. HiLo48 (talk) 21:06, 16 November 2013 (UTC)

Yes, I've said something similar in those circumstances. Wiktionary has more than three senses, and my local dialect has another gay (no village jokes please), often spelt "gey", regularly used just for emphasis. ( ... and, Medeis, I can recall first hearing (and being puzzled by, in the 1950s) the word gay used in a sense other than Wiktionary's "dated" senses, then I can recall first hearing the more recent "lame, uncool, stupid" sense. ) This must be one of the mast rapidly changing words in English. Dbfirs 21:32, 16 November 2013 (UTC)

South Park has had fun with some of the different meanings of gay, like the musical group "Getting gay, with kids". StuRat (talk) 22:20, 16 November 2013 (UTC)

The term "gay" meaning "homosexual" has been around for quite a few generations, but it didn't really start to go mainstream until the late 1960s or so. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:21, 16 November 2013 (UTC)

Aside from the "gay old time" in the Flintstones theme, another old-fashioned usage is in "Deck the Halls", with the line "don we now our gay apparel", which I saw parodied in the late 60s in a cartoon panel showing a guy cross-dressing while singing that line. Then there was the line from Bringing Up Baby in a scene where Cary Grant has to don some women's clothing. Someone asks him why he's dressed like that, and he says, "I just went gay all of a sudden!" ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:26, 16 November 2013 (UTC)

Australians can buy a Gaytime. HiLo48 (talk) 04:37, 17 November 2013 (UTC)

My favourite is the song "Girls Were Made to Love and Kiss" from the 1925 operetta Paganini by Franz Lehár, made famous by Richard Tauber. It's indisputably about heterosexual romantic love, yet read how the English words supplied by A. P. Herbert in 1937 go:

• Girls were made to love and kiss / And who am I to interfere with this? ? Is it well? Who can tell? / But I know the good God made them so - so far, so good. Then comes this:
• Am I ashamed to follow Nature's way? / Shall I be blamed if God has made me gay? / Does it pay? Who can say? / I'm a man, and kiss them when I can. It continues:
• Yet I have suffered in Love's great deeps / I know the passion that never sleeps / I know the longing, the wronging of hearts / The hope that flatters and shatters and smarts / I suffer still but I sleep at nights / Man cannot always be on the heights / And now the aching and breaking is done / Flirting is jolly, it's folly, but fun.

After the first verse he seems to have had something else on his mind than girls. I have no idea how true Herbert's translation was to the original German words. -- Jack of Oz ^{[pleasantries]} 07:42, 18 November 2013 (UTC)

This has totally sidetracked, but might as well mention "Oh, Boy! (song)" :) Wnt (talk) 08:10, 18 November 2013 (UTC)

I think the OP would get better results at the Humanities desk, because I get the feeling people here aren't taking bullying as a serious science, whether it could be or not. My assumption is that a certain amount of genuine ideological hostility drives it, but I wouldn't even know where to look to see if anyone has tried to relate the incidence of people in the population openly hateful of a group to the incidence of bullying in schools. My feeling is that bullying is a fundamentally adult phenomenon, no matter how much people associate it with children - that children who bully do so because school authorities are more afraid to go after them than they are to pick on the victim themselves, and that the patterns of bullying therefore largely reflect the social bullying that goes on in the adult community. Wnt (talk) 08:10, 18 November 2013 (UTC)

The question is trolling. Define "scientific explanation". Is he looking for a gene that codes for an anti-gay protein? Define gay. Is he saying football players who sodomize weaklings and threaten them not to tell are gay, and get bullied? Is he saying that effeminate and nerdy kids who seem like easy victims are in inherently different classes? By gay, does he mean boys who get manipedis and summer in Provincetown while snorting amyl nitrate? Does he mean spikey-haired girls who sell advertising for Theater Week? Note the OP lost interest in this thread the moment he posted it. μηδείς (talk) 19:59, 19 November 2013 (UTC)

Capillary electrophoresis

In typical capillary electrophoresis, why does decreasing the pH of the running buffer result in longer retention times? Does it has something to do with electroosmotic flow? --FutureTrillionaire (talk) 18:58, 15 November 2013 (UTC)

I assume so, you only get electroosmotic flow when the capillary wall becomes charged, which happens when the SiOH groups become ionized (SiO^-). Higher pH means more SiOH groups are ionized, so more electroosmotic flow. Lower pH gives less EOF, longer retention times... http://chemwiki.ucdavis.edu/Analytical_Chemistry/Instrumental_Analysis/Capillary_Electrophoresis Ssscienccce (talk) 11:29, 16 November 2013 (UTC)

If the charge of the analyte is pH dependent, that might also be a factor. (+)H₃N-Protein\Chemist-CO₂(-) 17:29, 18 November 2013 (UTC)

Ethology and Behavioral ecology

Dear Wikipedia Hello, My question is simple. What is the difference between Ethology and Behavioral Ecology?

Sincerely, Kooz (talk) 21:09, 15 November 2013 (UTC)

Ethology is animal behavior, while behavioral ecology is why that behavior evolved. StuRat (talk) 05:59, 16 November 2013 (UTC)

November 16

Fear of abortion

trolling
The following discussion has been closed. Please do not modify it.
What would the name be, and would it be considered a mental disorder if it incited someone to act violently? -- CensoredScribe (talk · contribs) The name would be "Fear of abortion". Not every concept needs other words to describe it. Often, the words that already exist are sufficient. --Jayron32 01:03, 16 November 2013 (UTC) If what incited someone to act violently? And who's asking? μηδείς (talk) 01:15, 16 November 2013 (UTC) It was CensoredScribe. And I suppose it could be "abortionphobia", if there were such a thing. I've never heard of anyone who "feared" abortion. Some favor abortion rights, some oppose, some are neutral. If he's talking about what characters like Eric Rudolph did, that's not abortionphobia - it's just plain terrorism. ←Baseball Bugs What's up, Doc? carrots→ 01:43, 16 November 2013 (UTC) Fear of Genocide? We acted pretty violently to stop the Nazis. --DHeyward (talk) 03:07, 16 November 2013 (UTC) DH is right. Forced abortion? Induced abortion? Spontaneous abortion? If the OP wants a reasonable answer he should clarify himself. μηδείς (talk) 03:12, 16 November 2013 (UTC) "Incited someone to act violently" isn't the deciding factor. Something can be a mental disorder without any violence, and not all the things incite violence are considered mental disorders. There are many things called "fear of…" or "…phobia" are not mental disorders, as our article Phobia mentions. You need to clarify if you mean the clinical or the non-clinical meaning of the term.Sjö (talk) 09:55, 16 November 2013 (UTC) Somebody wise said that more evil has been done in the world because of the love of a leader than because of the hatred of an enemy. An anti-abortionist acting violently over that issue is most likely showing an over-the-top love of his Christian god, whose earthly spokesperson told him that abortion was a bad thing that must be prevented (at all costs). HiLo48 (talk) 10:24, 16 November 2013 (UTC) Or not. --DHeyward (talk) 10:38, 16 November 2013 (UTC) That's a bit of a distorted way of looking at things, most people wouldn't call that genuine love. It'd be like saying that a jealous husband who beats his wife does it out of an over the top love for her. It's not that you can't contort the phrase to make that technically work, but without specifying a bunch of "I mean this by this" 's, it sounds like you're saying something very different than what you are, and which isn't actually accurate.Phoenixia1177 (talk) 11:07, 16 November 2013 (UTC) I did say "over the top love". It was meant to describe something irrational. HiLo48 (talk) 11:27, 16 November 2013 (UTC) True, I apologize. I've seen a lot of statements like the one you made (on both sides of the fence) used to distort issues, so I'ma bit bitchy about them. Sorry, I honestly didn't intend for that to come off as it did:-).Phoenixia1177 (talk) 11:32, 16 November 2013 (UTC) That does not suggest "fear", it's more like "righteous indignation". The idea of "fearing" abortion only makes sense in terms of the embryo or fetus (who doesn't know what's happening anyway); and the mother contemplating an abortion but being fearful of the procedure. Neither of those scenarios suggests consequent murder-and-mayhem by the respective parties. ←Baseball Bugs What's up, Doc? carrots→ 16:25, 16 November 2013 (UTC) The prejudiced legal tactic of 'homosexual panic', and subsequently the inept word 'homophobia', has engendered many abuses of the English language, in which ideological hatred and irrational fear are confounded. 'Islamophobia', for example. To continue this sorry trend, one need only look up abortion in Greek (the older the Greek, the better) and attach -o-phobia. Looking up on the web I came up with two of the big ones, then finally went to a decent source: http://www.lexilogos.com/english/greek_ancient_dictionary.htm . This gets stuff like ἄμβλωμα / ἄμβλωσις , ἀπόφθαρμα , ἔμβρημα , ἐξάμβλωμα . A drug to produce abortion is φθορεῖον , and procuring abortion is διαμβλώττω . It would help of course to narrow down the 'phobia' desired - is it the fear of a pregnant woman that someone will hold her down or poison her, or is it (as I suspect) the fear by someone of having it legally practiced in a community? (Or, more specifically, the fear of a husband having his child taken without his consent, contrary to the Code of Assura?) In any case, one need merely transliterate the various roots, which I shall most inexpertly, missing many nuances, do as amblōma / amblōsis , amophtharma, embrema, examblōma; phthoreion, diamblōttō. Searching I didn't find amblosophobia, amblomophobia, amophtharmophobia, embremophobia, examblomophobia, phoreiophobia, or diamblottophiba (also tried -osso-). I could very readily have missed some variation, but my guess is that you have an open field here to pick whichever one you like the best, and in ten years people may be using it to sound 'educated', and in 20 to avoid appearing politically incorrect. Wnt (talk) 17:42, 16 November 2013 (UTC) Spot on, Wnt. We've had this same "what do you call the insanity of (insert socially conservative position here)" before, recently in regard to homophobia and islamophobia. Perhaps someone can suggest a term for leftist political trolling at the wikipedia ref desks. μηδείς (talk) 20:00, 16 November 2013 (UTC) Leftist? Now, there's a seemingly simple but appallingly misused word! HiLo48 (talk) 20:50, 16 November 2013 (UTC) Says the raving Leftist. μηδείς (talk) 21:28, 16 November 2013 (UTC) Define raving. HiLo48 (talk) 21:44, 16 November 2013 (UTC) Simple, lol. By definition all Leftists are raving. The political trolling per se is the problem though. We just so rarely get things like this it can be monotonous. μηδείς (talk) 03:36, 17 November 2013 (UTC) The thing is, though, that while attaching "-phobia" to "homo" and "Islam-o" carries a measure of political bias, there are people who are actually afraid of homosexuals and/or Muslims. When have you ever heard of someone being "afraid" of abortion? ←Baseball Bugs What's up, Doc? carrots→ 23:17, 16 November 2013 (UTC) It is hard to believe that there is not a feature horror film, based on some corresponding story of a few pages from H.P. Lovecraft, entitled The Abortionist. "My senses swirled about me as I giddily stumbled into that final chamber, and my unbelieving eyes absorbed the truth of Gosnell's dark rituals. My gaze darted from the minute and carefully preserved faces of the dead to the pulsing entrails of the living, but infinitely more disturbing was the thing -- how dare I speak of it? -- the proud result of all Gosnell's experiments, which looked up from its orgiastic feeding of primordial life-force to behold me with eyes, such eyes, perfect youth and vigor, infinite age and malice! Wnt (talk) 00:54, 17 November 2013 (UTC) I don't follow. Who is it, in that quote, who's "fearing" abortion? ←Baseball Bugs What's up, Doc? carrots→ 00:57, 17 November 2013 (UTC) A patient at Arkham Asylum, I should suppose. If people are afraid of cemeteries, of houses where people died, why not abortion clinics? :) Wnt (talk) 01:03, 17 November 2013 (UTC) The OP asked about fear of abortion, not fear of clinics. It would be nice if he would come back here and explain just what he was trying to ask. ←Baseball Bugs What's up, Doc? carrots→ 01:15, 17 November 2013 (UTC) That would be a first. Trolling is even less fun than humor when you have to explain it. μηδείς (talk) 03:40, 17 November 2013 (UTC) And Islamophobics are afraid of turbans -- more often than not, the guy they pick out of a crowd to beat up is a Sikh... Wnt (talk) 01:41, 17 November 2013 (UTC) Kind of the way acrophobics beat up cliffs and skyscrapers? The term you want is ignorant bigot, Wnt.μηδείς (talk) 03:40, 17 November 2013 (UTC) Well, as I suggested above, I don't see these 'phobias' as true phobias. While people can be afraid of any number of things based on prejudice, that fear is based on the prejudice and rational deduction from that premise rather than the other way around. Wnt (talk) 04:26, 17 November 2013 (UTC) Whether "true phobia" or not, I would still like to see Censored Scribe define exactly what he means by "fear of abortion". ←Baseball Bugs What's up, Doc? carrots→ 14:09, 17 November 2013 (UTC) The OP has posted a number of times to other pages since the post here. I have asked him to explain what "fear of abortion" is supposed to mean. If we don't get an answer by his next post, I recommend the entire thread be boxed or deleted as trolling. ←Baseball Bugs What's up, Doc? carrots→ 14:13, 17 November 2013 (UTC) Mental illness is not required for being a phobic - being stupid is often sufficient. ←Baseball Bugs What's up, Doc? carrots→ 03:15, 17 November 2013 (UTC)

spaceship water shielding

I just watched the film Europa Report, which I had heard was remarkably scientifically accurate (for being a science fiction movie). During one scene, a crew member ejects what they call "water shielding". It's never shown what it is, but it apparently was very heavy. Is this a real thing, or a sci-fi invention? --209.203.125.162 (talk) 01:51, 16 November 2013 (UTC)

Neutron can be very dangerous.

You need water. There must be a water storage on a spaceship. A water molecule is one oxygen plus two hydrogen atoms (one neutron + one electron). Hydrogen is really good at stopping neutron. A water shield is a water tank made to shield astronauts from dangerous cosmic radiation. I think it's also a good idea to use food (contains water), fuel (especially liquid hydrogen) and anything that can be used to protect astronauts to create a wall between a spaceman and the space. -- Toytoy (talk) 02:33, 16 November 2013 (UTC)

Ummmm, what? That hydrogen thing. Uhhh, no. Just no. --03:10, 16 November 2013 (UTC)

These all mention water shields: [9], [10], [11], and [12]. The idea is as above, using water to shield the crew from radiation.Phoenixia1177 (talk) 07:36, 16 November 2013 (UTC)

Our article on Radiation protection mentions the use of water as shielding a couple of times. Someguy1221 (talk) 08:05, 16 November 2013 (UTC)

If they could go to Europa then robots could easily have got ice from comets for shielding, and anyway I'd hope they'd use robots on Europa before sending people!. Until then though I'm a bit sorry they just destroy satellites at the end of their life rather than moving them all together into a single mass in a higher orbit to use as shielding or as raw materials for future missions. Dmcq (talk) 10:58, 16 November 2013 (UTC)

On a space trip, water can be used for shielding a human crew from radiation during solar flares. Water as such is not a magic substance that is particularly good for a shield; any substantial mass of matter will do. In scenarios such as going to Mars water and food are often mentioned as radiation shields because you'll have those things for drinking and eating anyway. You could bring along a big block of lead but that doesn't have the dual use that a tank of water has. I'm not sure why you'd eject the water though because after you use it for radiation shielding it's still good for drinking, bathing, growing plants, flushing your toilet, etc. 88.112.41.6 (talk) 20:57, 16 November 2013 (UTC)

Europa Report#Plot says: "The crew agrees to leave in order to bring their discovery back to Earth, but the engines malfunction. As the ship hurtles back to Europa's surface, Xu unbuckles from his seat to remove water shielding to reduce the impact speed." So the plan was presumably to keep the water for the home trip. PrimeHunter (talk) 11:35, 17 November 2013 (UTC)

If neutrons are what you're shielding against, then wouldn't something like beryllium, boron or cadmium make a better shield than water? 24.23.196.85 (talk) 02:22, 17 November 2013 (UTC)

In a nuclear war, you need water to shield you from neutron.

Now I think you may need to shield yourself from gamma ray in deep space. -- Toytoy (talk) 10:36, 17 November 2013 (UTC)

I had a look once at a radioactive pile in a deep pool of water. It had a pretty blue glow all around it. I'd probably be dead now if the water wasn't there. Dmcq (talk) 11:32, 17 November 2013 (UTC)

In the case of radioactive waste storage, the water is there not just to absorb the radiation -- even more importantly, it's there to absorb the heat generated by the radiation, which would otherwise melt or ignite the radioactive waste and disperse radioactive smoke all over the place (as happened at Chernobyl, although in that disaster, the initial dispersion was due to an explosion). And yes, gamma rays are a serious danger in space. 24.23.196.85 (talk) 01:57, 18 November 2013 (UTC)

Heavy water is probably a better candidate for radiation shielding. — Preceding unsigned comment added by 168.178.74.25 (talk) 22:34, 18 November 2013 (UTC)

No, ordinary water is better for neutron shielding -- it absorbs neutrons better (which is why they have to slightly enrich the uranium for light-water PWR and BWR type reactors, but not for the heavy-water CANDU type). As for shielding against gamma rays, both kinds of water are equally ineffective -- gamma-ray shielding requires lead, concrete or heavy armor plate (or a combination of the three). 24.23.196.85 (talk) 07:39, 19 November 2013 (UTC)

It's just you need a much smaller thickness of lead, it depends more on the total mass and lead is much denser than water. A deep pool is quite effective against gamma rays. Dmcq (talk) 12:55, 19 November 2013 (UTC)

If you're concerned at all about weight (as would be the case in any aerospace application), then lead or armor plate would be the best choice. 24.23.196.85 (talk) 21:44, 19 November 2013 (UTC)

You are saying that regular water is better than the heavy water, then how about the Norwegian hydroelectric plant in WWII that produced heavy water for the Nazis? Why did people risk their lives to destroy it and deprive them of this vital material for a nuclear bomb? — Preceding unsigned comment added by 168.178.74.104 (talk) 16:57, 19 November 2013 (UTC)

No, no, no, you got it all bassackwards -- the Nazis used heavy water as the MODERATOR for their reactor, not as SHIELDING! The role of the neutron moderator is not to shield the operator from neutrons -- it's specifically to slow the neutrons down INSIDE the reactor so they have time to react with the uranium (or plutonium) instead of flying out like they would do at the speeds at which they normally fly! And since the moderator's purpose is to help the neutrons react with the uranium, the best moderator is one that would slow the neutrons down effectively WITHOUT absorbing them -- which is what heavy water does, which is why it's better than ordinary water AS A MODERATOR! Whereas if you want SHIELDING, you want to ABSORB neutrons or REFLECT them rather than just slow them down -- which is why ordinary water would be better FOR SHIELDING than heavy water. 24.23.196.85 (talk) 21:44, 19 November 2013 (UTC)

Lecithin

The article says it lowers cholesterol. Is the source good? Thanks. 67.243.4.94 (talk) 02:08, 16 November 2013 (UTC)

If you're concerned about yourself or someone else with high cholestoral, you should follow your doctor's orders on the matter. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:22, 16 November 2013 (UTC)

Since lecithin is a nutritional supplement, not a medicine, advice on when to take it is not medical advice. StuRat (talk) 02:40, 16 November 2013 (UTC)

Is that some sort of legal situation in the USA? It seems to match the bit of text in the article that says "Lecithin is marketed as a dietary supplement. As such, no claims may be made as to its usefulness in treating or preventing a disease or condition." HiLo48 (talk) 02:49, 16 November 2013 (UTC)

Yes, as "nutritional supplements" are exempt from regulation by the FDA. StuRat (talk) 03:42, 16 November 2013 (UTC)

I don't think that's exactly correct. It's a "food" instead of a "drug" and so must comply with food labeling and marketing including special rules for Dietary supplements that's enforced by the FDA (F=Food). Claims about what the food can do is regulated as well but obviously a food group is different than a medication. It cannot claim that it fights disease as that would run afoul of the labeling rules but "cholesterol" is not a disease, rather it's correlated to one. Lowering cholesterol through lecithin, for example, has no known health benefit and another section links lecithin to an increase in TMAO which is also not a disease but linked to one. --DHeyward (talk) 07:24, 16 November 2013 (UTC)

The OP asks "Is the source good?" I'm particularly keen on the source that says "...the expansion of the soybean crushing and soy oil refining industries in Europe after 1908 led to a problem disposing the increasing amounts of fermenting, foul-smelling sludge. German companies then decided to vacuum dry the sludge, patent the process and sell it as "soybean lecithin." Scientists hired to find some use for the substance cooked up more than a thousand new uses by 1939" I think one must always be cautious about an allegedly good-for-you product derived from someone else's waste product. HiLo48 (talk) 02:47, 16 November 2013 (UTC)

This sounds similar to the situation with peanuts, which weren't of much value until George Washington Carver experimented with different uses for them, coming up with peanut butter, peanut oil, and a few other products. StuRat (talk) 03:46, 16 November 2013 (UTC)

Depends on your definition of value - something that goes so well with a beer is of value to me! Equisetum (talk | contributions) 23:03, 18 November 2013 (UTC)

• If the OP's question is whether claims in out articles are well sourced he should either specify the sources he doubts or ask the question at the article's talk page. μηδείς (talk) 03:16, 16 November 2013 (UTC)

Hot water improving cleaning ability

It seems that the warmer the water, the better cleaning ability it has -- especially when used in conjunction with soaps and detergents. How/why does water temperature affect cleaning ability? --209.203.125.162 (talk) 19:29, 16 November 2013 (UTC)

Both the mechanical agitation caused by increasing the heat of the water molecules and any increased rate of reaction of any chemical reactions would improve cleaning and bleaching speeds. μηδείς (talk) 19:48, 16 November 2013 (UTC)

Solubility of oils, fats etc in water generally increases with temperature. AndyTheGrump (talk) 20:00, 16 November 2013 (UTC)

Agreed, and edible fats, in particular, tend to be solid at cold water temperatures and liquid at hot water temperatures. Think of the liquid bacon grease poured off from the frying pan, which then solidifies as it cools. Detergents tend to be far more effective in dissolving liquid fats than solid fats (technically emulsifying the fats in water). StuRat (talk) 20:59, 16 November 2013 (UTC)

How many items of clothing a year do you launder due to their accumulated bacon grease? μηδείς (talk) 21:27, 16 November 2013 (UTC)

That comment makes me guess that you incorrectly refer to liquid dishwashing detergents as "dish soap" and only think detergents are used for laundry. StuRat (talk) 22:09, 16 November 2013 (UTC)

Well, no, but I was only thinking about cleaning cloth, not dishes. μηδείς (talk) 03:31, 17 November 2013 (UTC)

Do you not reckon that you need to wash clothing because of the accumulated sebum arising from skin secretions then? --TammyMoet (talk) 09:38, 17 November 2013 (UTC)

Not primarily, although I can't speak for others. In any case, sebum is not bacon grease, or at least it doesn't taste like it. μηδείς (talk) 18:44, 17 November 2013 (UTC)

A Bib (garment) or an Apron might be made of cloth and might to a degree be impregnated with bacon grease. Such items might require washing though understandably they might not be considered "garments". Bus stop (talk) 18:53, 17 November 2013 (UTC)

So, Stu, you wear a bib regularly? :) 00:43, 18 November 2013 (UTC)

Can I equate "m" from the following two equations?

We get "E/ c^2 = F/ a" after eliminating m from the following two equations.

F = ma & E = mc^2

Which mean F, E, a and c are independent of mass. So is this true if "E/ c^2 = F/ a" is valid equation?162.157.235.1 (talk) 21:45, 16 November 2013 (UTC)EEC

I'd say normally no, since the m in F = ma is just the mass, while the m in E = mc² is the mass converted to energy. I suppose there could be some special cases, though, like if a known force applied to an anti-matter particle achieved a measured acceleration, then this was used to determine the particle's mass, which was then converted to energy by ramming it into normal matter (although this would then double the mass converted to energy, so the formula would need to reflect this). StuRat (talk) 21:48, 16 November 2013 (UTC)

Sure it's valid. Not very interesting, though, since it just says that the ratio of force to acceleration is the object's energy (perhaps rest energy, but the equations are slightly ambiguous; see relativistic mass) divided by the speed of light squared. That's of course just two different statements of mass, so of course they're equal. --Tardis (talk) 00:06, 17 November 2013 (UTC)

See Relativistic mechanics#Force for the mathematics. To over-simplify a little, F = ma only applies if the mass is constant (which it may not be even in a classical system), and, in a relativistic system, the mass (the "m" in E = mc²) will vary with the velocity, so "m" in the two equations isn't the same. Tevildo (talk) 23:20, 16 November 2013 (UTC)

No, the "m" in both cases varies, and is the same. As the mass increases at relativistic speeds, the acceleration reduces (as seen by an observer left behind). So the OP's suggested equation is correct, but one must just keep in mind that E is the relativistic energy (rest-mass energy plus kinetic energy). —Quondum 05:02, 17 November 2013 (UTC)

Yes they are correct, but you are misinterpreting what they mean. E=m (c^2 is a constant) is an identity. They are interchangeable. The total energy (and mass) of an object is the sum of it's rest mass and kinetic energy. Even "massless" particles like photons exhibit gravitational forces equivalent to the E=m identity (energy/mass of a photon is proportional to frequency). As you approach relativistic speeds, the energy division between mass and velocity is observer dependent but the overall energy and gravitational force is not because that does not matter whether it's observed as mass or kinetic energy and the identity will always hold true. The interesting thing is that this applies to everything so a baseball that is thrown has a slightly larger mass when you impart kinetic energy to it. It's tiny but you can use E=mc^2 to find it. --DHeyward (talk) 07:25, 17 November 2013 (UTC)

Careful — I believe that you end up off by a factor of 2 if you try to use a photon's relativistic mass and Newtonian gravity, even in the weak-field approximation. --Tardis (talk) 00:10, 18 November 2013 (UTC)

Yes, one has to be a little careful when one starts speaking of the gravitational effects on and by a system: these are not determined solely by the mass of the system. The gravitational influence of a system is determined by the stress–energy tensor, so the pressure contributes. In the case of photons, this additional effect is on the same scale as the effect of the mass. But the gravitational effect does not form part of this question. —Quondum 00:34, 18 November 2013 (UTC)

First let me point out that even if it made sense to eliminate m from the two equations, that doesn't mean that E, F, and a "independent of mass". The original equations are still valid showing how those things relate to mass. Second point: F=ma isn't a relativistically correct equation. It is a non-relativistic approximation.

Third point: Within that approximation, m stands for rest mass and the E taken from E=mc^2 will be the rest energy. The equation is than correct but is also boring because it adds nothing to the theory and doesn't help solve any problems.

November 17

Biting your tongue

If you bite your tongue or cheek with force, you get a painful area that feels "hard", as if the area swells or something like that. What generally causes this phenomenon (i.e. is it swelling, or something else?), and (if such a term exists) what's the official anatomical/physiological term for an area that's experiencing this phenomenon? Nyttend (talk) 03:23, 17 November 2013 (UTC)

When most parts of the body are subject to trauma (e.g. biting of the tongue, banging the head, trapping a finger) it is normal for two things to happen. Firstly the body has a reaction which involves extra blood being channeled to the injured area, this assists in bringing materials required to repair the area and the removal of any unwanted products of trauma. The other thing that occurs is bleeding within the soft tissue that is damaged. This causes discoloration, swelling and pain in variable amounts dependent on what and how badly the tissue is damaged. These two processes will cause the swelling you feel, the medical term for hardening of the tissue is induration. Richard Avery (talk) 07:49, 17 November 2013 (UTC)

Novel electric unicycle design

Does there exist a design for an electric unicycle, where the rider is positioned at the centre of a wheel, rather than atop it; the engine contains no moving parts; and the unicycle is steered by shifting the centre of mass along the axis of rotation? Plasmic Physics (talk) 03:59, 17 November 2013 (UTC)

I believe you have a monowheel in mind. However, note that there must be moving parts: in your proposed design, even though the center of mass is kept steadily ahead to move it forward, it has to be moving in a circle relative to the outer wheel (as is the rider). (speculation:) Using a weight in this way depends on it being massive in relation to the rider; I suspect it works out to be inefficient to push a weight to where it will move the wheel by force of gravity rather than simply pushing the wheel with the same motor mechanism. Wnt (talk) 04:22, 17 November 2013 (UTC)

Yes, it is a monowheel I'm thinking of. Plasmic Physics (talk) 05:39, 17 November 2013 (UTC)

I suppose you could set up a mag-lev connection between the wheel and the compartment where the rider sits. They would still move relative to each other, but there would be no friction (other than air resistance), since the moving parts are not in contact with each other. The rider could then lean forward to move forward or lean backward to move backward. Leaning to the sides should help to steer. StuRat (talk) 05:15, 17 November 2013 (UTC)

Yes, it is a monowheel that functions on the principle of the linear motor. To ensure that the wheel spins instead of the rider, it could be solved by increasing the difference in the moment of inertia between the wheel and "hub". Plasmic Physics (talk) 05:39, 17 November 2013 (UTC)

I meant that last sentence as a question, not as statement. Plasmic Physics (talk) 07:52, 17 November 2013 (UTC)

Yes, the moment of inertia should effect which rotates faster. I also imagine that the battery, motor, etc., would be under the driver's seat, to bring the center of gravity down. This would help prevent him from turning upside down. At high acceleration, though, it might still be a problem. Driver rotation might also occur when braking or if the vehicle hits something. StuRat (talk) 08:41, 18 November 2013 (UTC)

What if the entire vehicle was structured as a gyroscope? Plasmic Physics (talk) 12:08, 18 November 2013 (UTC)

Dynamo lights become ever brighter with increasing speed?

I made this circuit to light a couple of LEDs (in series) on my bike. The power comes from a bottle dynamo which I think is rated at 6 V and 3 W. My question is: does the light get ever brighter the faster I cycle or does something limit the output of the dynamo? The LEDs can actually handle at least an amp but I'm a pretty lazy cyclist so I'll never even approach that; I just wondered. If the rating is 3W, that must mean the limit for the dynamo is 500 mA; is that a point at which something inside the dynamo could start to melt? --78.148.107.181 (talk) 16:03, 17 November 2013 (UTC)

A bicycle dynamo is not, in fact, a dynamo, but a magneto (generator). However, although we have plenty of articles on magnetos, we don't have one which explains how they work. This paper describes the operation of an ignition magneto - a bicycle dynamo doesn't have the contact breaker or secondary winding, but it's more or less the same otherwise, and the Continental paper does imply that the output increases with speed. That being said, I assume that there will be a point where the rotor is continuously saturated and increasing the speed only increases the frequency. The best thing to do is probably just try it, and put in a voltage regulator if the output looks like it's getting too high. Tevildo (talk) 19:50, 17 November 2013 (UTC)

As speed is increased from zero, the generator voltage will increase proportionately, up to a certain point where the load (the lamps or LEDs) draws a current near the rated output. Beyond that point, two effects come into play that limit the current: a) magnetic saturation of the stator core (Tevildo was on the right track here, but it is the magnets that rotate on the shaft, the windings are on a stator - this avoids needing slip-rings) and, b) pole reluctance. Pole reluctance arises because at high currents the magnetic filed in the stator poles created by the load current opposes the magnet field as the rotor magnet poles rotate into mesh with the stator poles. This effectively lengthens the air gap between the rotor and stator, weakening the generated voltage. The limiting is not a hard or staright line limit - further increase in load or speed will increase the current to a certrain extent. 120.145.133.195 (talk) 00:45, 18 November 2013 (UTC)

So would it then be approaching an asymptotic limit? 24.23.196.85 (talk) 02:00, 18 November 2013 (UTC)

The electricity-producing thing on my old bike was called an 'alternator' when I bought it, so presumably it produces alternating current. To drive LEDs, I would consider adding add a rectifier chip and a capacitor to smooth the ripple, and would tip the bike and spin it to make sure it could not overdrive the LEDs and burn them out. Edison (talk) 01:28, 18 November 2013 (UTC)

Blood glucose result discrepancy

All my fasting glucose tests taken at a medical lab (vein blood) show above 100 mg/dL. However home test (finger prick) results are always ~80 mg/dL, no fasting, before and 1.5 hours after a big meal. How can this be explained? Gil_mo (talk) 16:16, 17 November 2013 (UTC)

I'm afraid that because this bears on your personal medical issues, an answer would constitute medical advice, which we are not permitted to give. Looie496 (talk) 16:53, 17 November 2013 (UTC)

I'm asking this on a general note. Let me rephrase: what could be the explanation for such a discrepancy should it occur for anyone doing the test?Gil_mo (talk) 07:10, 18 November 2013 (UTC)

See Glucose meter, home tests measure whole blood glucose level, lab tests measure plasma glucose level which is generally 10% to 15% higher than the equivalent whole blood value. All the glucose is in the plasma, if you remove the blood cells, the volume decreases but the amount of glucose stays the same, so the amount of glucose per unit of volume rises. Ssscienccce (talk) 11:28, 18 November 2013 (UTC)

Obvious question, are the home testing strips expired? Have they been stored in an airtight container? Have they been stored in excess heat (like a hot car)? I know these can affect the accuracy. Also, many home testing units contain a little bottle of control solution (with a known glucose concentration) that you can test your strips against. --209.203.125.162 (talk) 18:55, 19 November 2013 (UTC)

science (magnification in parallel and series circuits)

magnification is independent in series or parallel circuit.true or false? — Preceding unsigned comment added by Mintoooo (talk • contribs) 17:51, 17 November 2013 (UTC)

The word "magnification" has no meaning for an electrical circuit. If you are going to ask "true or false", you need to use correct terminology. In this case, I can't even figure out what you are trying to ask. Looie496 (talk) 17:57, 17 November 2013 (UTC)

To paraphrase Chico Marx, then, the correct answer to the question is, "No." ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:52, 17 November 2013 (UTC)

banned editor and off-topic discussion
The following discussion has been closed. Please do not modify it.
It would be nice if people would answer questions only if the question is within their competence. Magnification certainly does have meaning in electical circuits containing inductance (L) and capacitance (C), and is of fundamental importance to radio. It is the basis of tuning. Magnification occurs in parallel L and C circuits - at or near the resonance fequency, the current circulating in the L-C circit may be many times greater that the externally supplied current. This phenomena is referred to as magnification. In a series L-C circuit, the voltage across either L or C at and near resonance may be many times greater than the externally applied voltage - this is also referred to as magnification. The degree of magnification depends on the Quality of the inductor and capacitor. Quality here essentially is degree to which resistance is kept out of the inductor and capacitor. For this reason, various companies in Britain, before British industry lost its way, used to sell instruments known as Circuit Magnification Meters. Marconi being the most well known in the industry (Model TF1245A). In the USA, the various manufacturers (eg Hewlett Packard) called them Q-Meters - this name is easier to say and has become the dominant term world-wide. However the correct term for what happens in resonant circuits is still magnification. To answer the OP question, magnification is independent in magnitude regardless of the circuit being series or parallel - however what gets magnified, voltage or current, depends on whther the circuit is series or parallel. Magnification can also occur in circuits containing only resistors and capacitors, and in circuits containing only inductors and resistors. Magnification of either voltage OR current, but not both at the same time, can be arranged by combining current OR voltage in suitable phases. However such circuits are not simple series or parallel arrangements. It can be done becasue the arithmetic sum of voltages in a series RC circuit is greater than the applied voltage, due to differing phase. 120.145.133.195 (talk) 01:00, 18 November 2013 (UTC) Ah Wickwack, it's always such a pleasure to have you around. Looie496 (talk) 05:13, 18 November 2013 (UTC) Unfortunately, he shouldn't have answered, as this is an obvious homework question with the student making no attempt to solve it on their own. StuRat (talk) 05:19, 18 November 2013 (UTC) I am the previous poster 120.145.133.195. It had occurred to me that it might be homework, but it doesn't smell like it. The OP wrote it in quite poor grammar. A question written in a textbook or set by a teacher could well use the term "magnification", but they would not (or should not) word a question as "Magnification independent in series or parallel circuits..." Independent OF what? Independent IN one case and not IN the other?? Quite possibly the OP is a beginning electronics hobbyist or amateur. If so, it was very bad of Looie496 to say that the word magnification had no meaning in electric circuits - rather than helping such a person, it would set them back. That was my reason for posting - to prevent a beginning amatuer from being misled. In any case it's ok to just not answer a homework question, but it is never ok to mislead, intentionally or accidentally. And I am not Wickwack. 58.170.182.209 (talk) 13:38, 18 November 2013 (UTC) Ah, then it's an amazing coincidence that you geolocate to Perth and write in the same style as Wickwack, with the same mannerisms. (I do make mistakes sometimes and am willing to acknowledge them, but it is always hard when they are pointed out in such an unpleasant way -- the typical Wickwack style.) Looie496 (talk) 16:17, 18 November 2013 (UTC) Probably best to let this lie, but there may indeed be more than one cranky old electrical engineer in the Perth area. I'd imagine their styles and tones could come across rather similarly in this medium ;) SemanticMantis (talk) 18:10, 18 November 2013 (UTC) Wickwack and aliases are more known for criticizing other responders for being wrong, regardless of whether he, or the person he criticized, are correct or not. Looie, sorry your pride was hurt. I suggest using this method: "I've never heard of 'magnification' with regard to an electric circuit". This leaves you an out, in case it turns out to be real. And even an expert may not be aware of some obscure terminology used by a small group on the other side of the globe. StuRat (talk) 18:56, 18 November 2013 (UTC)

I added a useful title. StuRat (talk) 06:03, 18 November 2013 (UTC)

We have some scant coverage at LC_circuit#Applications, which uses the "magnification" terminology, and mentions the tuning discussed above. SemanticMantis (talk) 18:10, 18 November 2013 (UTC)

Most likely because the term is most likely and commonly called resonance and specifically electrical resonance. --DHeyward (talk) 05:30, 19 November 2013 (UTC)

Actually, both terms are in use - there is an important difference in meaning. Resonance is what allows magnification to occur. Resonance also causes other phenomena to occur - for instance when a parallel L-C circuit is brought into resonance, a dip (reduction) in the current drawn from the external voltage source occurs, and the phase of the current drawn from the supply is brought into alignment with the supply voltage phase. An analogy is cooking food. Applying heat typically causes several changes - reduction in moisture content, browning, reduction in vitamin content, denaturing of protein, etc. Just as one does not use the term "heating" or "cooking" when one wants to discuss "browning", an electrical engineer does not use the term resonance when he/she means magnification, any more then he/she would say "brought into phase" if he/she meant magnification or resonance. Magnification can be quantified - one can say such-and-such a circuit has a magnification of (say) 96 times. Saying the resonance is 96 times is a nonsence - you can only say things like "off resonance", "near resonant", "resonant" and the like. Further, as I said before, magnification can occur in L-R or C-R circuits, but in these cases there is no resonance in the sense that electrical engineers use the term. 120.145.154.249 (talk) 06:45, 19 November 2013 (UTC)

Never heard "magnification" used in engineering. "peaking", "resonance", "Q", "Q factor", "FWHM", "magnitude", etc. Never heard of "magnification." Some passive filters can peak, but I've never heard it called magnification. It would be an odd term as I believe the maximum is always referenced as 0db. --DHeyward (talk) 07:12, 19 November 2013 (UTC)

Why “g = GM/d^2” prevail over the higher derivatives of position w.r.t time?

Although higher derivatives of the position are not discussed by the Newton while formulating “F = GMm/d^2” (where reduction in “d” is lopsided for the falling of small objects on earth) but verily the subtle nuances of such spawning can easily be perceived through arcane reasoning if imagined two identical planets of mammoth masses “M” separated by conspicuous on-center distance “d”. Since both masses "M" are under the influence of gravitational force "F" therefore reduction in “d” would be equal but abrupt on either side of point “c” lucidly if “c” is the mid point of “d" as both F = GM^2/d^2 and "g =GM/d^2" are time varying.

The simultaneous abruptness of such motion starts equally on either side of "c" right at the inception of "g" of each M which sent the aforementioned masses “M” swiftly into different higher types of motion such as gravitational jerk, jounce, crackle, pop, lock, drop etc. This means two objects that fall towards each other are under the influence of higher types of gravitational motion/ higher derivatives of position w.r.t time - Theoretically.162.157.235.1 (talk) 23:24, 17 November 2013 (UTC)EEK

Under Newtonian gravity, there are no higher derivatives of position due to gravity. The acceleration really is a=GM/d^2, and the third, fourth, fifth, etc. derivatives of position are all zero. --Bowlhover (talk) 02:16, 18 November 2013 (UTC)

Not correct in general. If d is not constant then a is not constant either, so higher derovatives of position such as da/dt are not zero. Only exception I can think of is a circular orbit when the magnitudes of d and a are constant (although even then they are not constant when considered as vectors). Gandalf61 (talk) 10:05, 18 November 2013 (UTC)

But this hold true only when the difference in two masses is extremely gigantic. For example it is said that both earth and the Newton's apple (smaller objects) accelerate toward each other gravitationally but apple looks a lot to the earth due to its greater acceleration as compared to the earth toward an apple which is so minuscule to be distinguished. Here in this case the on-center distance “d” reduces totally on one side of the mid point of “d” as earth remains at its position (almost) therefore a=GM/d^2 is noticeable but the picture is totally different according to the equation “F = GM^2/d^2” if both the masses are mammoth as illustrated where on-center distance “d” reduces equally on both sides of the mid point of “d” therefore aren’t the said two objects under the influence of type of gravitational motion which is greater than “a=g=GM/d^2”162.157.235.1 (talk) 04:45, 18 November 2013 (UTC)EEK

The force acting on each object is F=GM^2/d^2. Therefore, by F=Ma (the definition of force), a=GM^2/Md^2 = GM/d^2. Since the acceleration varies with position (and position with time), there will be higher derivatives w.r.t. time, but these just describe how the acceleration changes, it's not correct to say that jerk "prevails over" accelration, instead, each of jerk, acceleration, velocity etc are used to describe how the position of the masses changes. Acceleration just tends to be the most used representation, since higher derivatives tend to be less mathematically useful. Also, in the graviational case, aceleration can always be expressed purely as a function of position, with no initial condition needed for velocity, but higher deivatives will require at least such conditions to be calculated accurately. (da/dt = da/dx . dx/dt = v.da/dx = -2vGM/d^3 in the case where the velocity is parallel to the acceleration). 91.208.124.126 (talk) 09:38, 18 November 2013 (UTC)

Wouldn't the said both identical masses in scenario collided each other earlier than expected in acceleration?74.200.19.65 (talk) 11:20, 19 November 2013 (UTC)EEK

November 18

Climate of Korea

My mental image of the Korean War is that of soldiers spending months and months in snow-filled trenches, freezing off half their extremities as they wait for the weather to get warm enough for combat. The climate section of Geography of South Korea would seem to back up my idea, talking about "Winters are usually long, cold, and dry", but the specific data in Climate of Seoul sounds far warmer and more hospitable than my mental image or the picture created by the first article's climate section. What's going on? What's the true situation? Nyttend (talk) 02:35, 18 November 2013 (UTC)

Well, Seoul is close to the Yellow Sea, and being near a large body of water will tend to warm and moisten things up in winter, if the prevailing wind direction comes in off the water (unless the water freezes over, and I don't think it's far enough north for ocean water to freeze solid there). So, that's my guess as to why it might be warmer than the interior, in winter.

Also, during a war people (both soldiers and refugees) tend to be far more exposed to the environment. So, a temperature which is just fine if you are in a house becomes unbearably cold if you are in a flooded foxhole. StuRat (talk) 04:58, 18 November 2013 (UTC)

Finally, the cold weather was a major factor in the Battle of Chosin Reservoir, which may have been the images that you were thinking of. Not only is this in the far north of North Korea, close to the border with Manchuria, but the reservoir itself is over 1,200 metres (4,000 feet) above sea level and much of the fighting was on higher peaks and passes. The Environmentallapse rate allows you to calculate a reduction in ambient temperature of 6.49 °C per 1,000 metres of altitude, plus whatever windchill you get in a high mountain pass. Alansplodge (talk) 09:24, 18 November 2013 (UTC)

BTW, the figures in the climate table that you linked are certainly cold for a climate described as Humid subtropical. The average winter temperatures are lower than Copenhagen for instance. Alansplodge (talk) 11:43, 18 November 2013 (UTC)

Also, don't forget that the early '50s were at the very end of a short-term global colding trend (which started in the mid-'30s and was at its peak in 1944 -- that was the coldest year of the 20th century), so temperatures worldwide were lower than average. 24.23.196.85 (talk) 07:34, 19 November 2013 (UTC)

Naming Be
₆N
₄, additively

Following 2005 inorganic IUPAC additive nomenclature, is the following a correct name for [Be]=N[Be]N([Be]N=[Be])[Be]N=[Be]?

μ₃-nitrido-1:1':1"κ³N-tris(μ-nitrido-diberyllium)

Plasmic Physics (talk) 02:41, 18 November 2013 (UTC)

Wow. This is not my expertise, but there's some coverage of this at [13] but this is... remarkable. So you have a single nitrido (N) bridging three Be-N-Be units (the μ-nitrido-diberyllium). The κ³ indicates the N is linked three times from N (where else?). I suppose the 1:1':1" is a specification of where it links to. But I don't know if the IUPAC rules really require or allow that kind of precision about where a nitrogen is linked from when there's one atom, or so much detail about the three units it links to when it's just tris()... it all seems so absurd. Wnt (talk) 08:46, 18 November 2013 (UTC)

I'm also using the 2005 Red Book, but I was using IR 9.5.2.1, specifically comments surrounding example 8. Plasmic Physics (talk) 12:00, 18 November 2013 (UTC)

Please help, Heat transfer coefficient of the external fluid flowing steadily over a horizontal plate

I have read the article "Heat transfer coefficient", only found fluid flowing over horizontal plates (not a plate). Can someone give me an equation on the case of one plate. Many thanks :) SongJie@NTU (talk) 14:23, 18 November 2013 (UTC)

If you're referring to Heat transfer coefficient#External flow, Horizontal plates, the equations seem to describe a single plate (in four different scenarios), in spite of the section title. If that doesn't meet your needs, could you be clearer about what your needs are? Looie496 (talk) 16:04, 18 November 2013 (UTC)

How to make adult stem cells totipotent?

Is there a way to make adult stem cells totipotent and therefore provide an alternative non-controversial method of making totipotent stem cells? 164.107.102.191 (talk) 16:48, 18 November 2013 (UTC)

See our article Induced pluripotent stem cell, and these science articles in Science [14] and Nature [15]. It is not entirely clear to me how these are limited from being "totipotent" (e.g. is there some target cell type that they cannot become?), but maybe someone else can help clear that up. SemanticMantis (talk) 18:02, 18 November 2013 (UTC)

At least as concerns mammals, pluripotent cells can differentiate to form any cell lineage of the body, whereas totipotent cells can additionally form placental tissues [16]. For most biomedical research applications I would imagine there would be little difference (i.e. if you don't want to study placental tissue it doesn't matter), and in any case human stem cells generated "traditionally" (i.e. human embryonic stem cells) are pluripotent rather than totipotent. Equisetum (talk | contributions) 22:56, 18 November 2013 (UTC)

physics gravittation

In the derivation for gravitational potential energy, we consider the work done by agent in bringing a particle from infinity is a constant for small displacement dx. but once the particle is in the gravitational field, the gravitational force done by an agent will reverse direction. in that case the work done by the agent is first positive and then becomes negative. do we really consider both the positive as well as the negative work? — Preceding unsigned comment added by 120.62.184.196 (talk) 16:56, 18 November 2013 (UTC)

I don't fully understand your scenario, but if you bring a point into a gravity well close to a planet, you'll get negative work out of it that you can use for kinetic energy, annihilating settlements from space, whatever you'd like. Now if you take it away again, out of the well, do you keep that energy, or do you have to give it back? If you don't count both positive and negative work, does that mean you have a plot of the energy you've extracted/put in that abruptly turns into a flat line at some point? Nature doesn't much like flat lines with sharp corners. So my assumption is that you need to count positive and negative, but depending on exactly what you want to calculate, you might end up defining your number differently. Wnt (talk) 17:14, 18 November 2013 (UTC)

direction of Jupiter spot rotation

which direction does Jupiter spot rotate?--Akbarmohammadzade (talk) 17:32, 18 November 2013 (UTC)

Our article is at Great Red Spot, and says "The GRS rotates anticlockwise, with a period of about six Earth days." SemanticMantis (talk) 18:04, 18 November 2013 (UTC)

Enforced neoteny

As many animals become unsuitable as pets once they reach adolescence, and at the very least need to be castrated/spayed to make them manageable, is there any way to keep them young via drugs ? (Even if such drugs are prohibitively expensive when used for people, they might be offered more cheaply for animals, as many are.) StuRat (talk) 19:45, 18 November 2013 (UTC)

Do you mean freeze the aging process, or do you mean keep the pets small? 140.254.229.160 (talk) 21:15, 18 November 2013 (UTC)

You'd be looking at pituitary and genital surgery to remove the source of growth and sex hormones that cause puberty and increase in size. μηδείς (talk) 22:03, 18 November 2013 (UTC)

That may keep the pets small and infantile, but the pet itself may still age regardless in terms of how the other organs will wear out. 140.254.229.160 (talk) 22:10, 18 November 2013 (UTC)

I very much doubt Stu is asking about how to keep them young as in not old. Rather, the obvious issue is immature versus mature. Immature primates make good pets. Not so much so after puberty, and the same for most other wild animals. μηδείς (talk) 22:17, 18 November 2013 (UTC)

Ideally they would stop aging entirely, but I don't believe that's possible. What might be possible, though, is to prevent them from developing adult traits as they age. Yes, neutering them is one method, but I was asking if any drugs are available which can do this, as well. One option might be to prolong their juvenile state, but eventually stop the drugs and allow them to mature naturally. StuRat (talk) 03:48, 19 November 2013 (UTC)

Failure to develop in size and maturity naturally is caused by the lack of a hormone or a receptor for it. We can then possibly supply the missing hormone (not a missing receptor). But we don't usually give a drug to compete with or block a hormone. Such a thing is entirely possible, but were not at the stage where we can target such drugs to knock out certain types of development without possibly incurring serious, if not lethal side effects. At this point, physical removal of the relevant organs is the only practical option. For example, when my grandfather had terminal stage prostate cancer, they castrated him and put him on estrogen, which competes in some effect with testosterone, but would not entirely have masked it. I suggest looking at treatments for this and breast cancer and testicular cancer as well as acromegaly to see if any chemical treatments have the effect you want. μηδείς (talk) 18:10, 19 November 2013 (UTC)

Well, we've enforced neoteny through selective breeding of most out our domestic animals. See e.g. Neoteny#Domestication, Origin_of_the_domestic_dog#Neoteny_in_the_rapid_evolution_of_diverse_dog_breeds, Cat#Sociability, and even Self-domestication#Foxes. If there were currently any reliable way to push this trend further via drugs, rest assured that we would be inundated with advertisements for permanent kittens ;) SemanticMantis (talk) 22:32, 18 November 2013 (UTC)

A boy across the street from me in the 70's was famous for making permanent kittens. Until they stopped buying him replacements. μηδείς (talk) 02:15, 19 November 2013 (UTC)

Castrati used to be common. Had interesting side effects. Different than eunuch --DHeyward (talk) 07:25, 19 November 2013 (UTC)

From Chambers 20th Century Dictionary: Eunuch - means a castrated (ie testicles removed) male, especially one castrated before hormonal development; Castrati - means a male castrated before hormonal development and trained to sing. So no difference except that a castrati can sing, but a eunuch wasn't necessarily, and typically was not, trained to sing. So no real difference. 120.145.154.249 (talk) 15:39, 19 November 2013 (UTC)

What you want is an axolotl, the Peter Pan of the pet world, but not so cuddly. Richard Avery (talk) 15:30, 19 November 2013 (UTC)

Axolotls can apparently be made to metamorphose into adults by giving them iodine, which is sort of the opposite of what Stu is asking for here ... maybe he'd like a functionally immortal pet Turritopsis_dohrnii ? SemanticMantis (talk) 16:34, 19 November 2013 (UTC)

November 19

Tea for sore throat

How does tea with honey and/or lemon help hoarseness if food and drink descend down the esophagus and hoarseness originates in the larynx? DRosenbach ^{(Talk | Contribs)} 02:35, 19 November 2013 (UTC)

The Mayo clinic confirms that honey and lemon tea are both shown to be effective cough suppressants in clinical trials, but does not present a mechanism for how they work; merely noting that honey is shown to suppress coughs in children as effectively as dextromethorphan. --Jayron32 03:13, 19 November 2013 (UTC)

The obvious answer is vapors. For clearing my sinuses, I like to make a "tea" by dissolving menthol-eucalyptus cough drops in boiling water. That tea goes down my esophagus, too, but the vapors clear my sinuses right out. StuRat (talk) 03:43, 19 November 2013 (UTC)

I think every medicine has a "mechanism is unknown" in the PDR references. They can do studies to prove efficacy and limit side-effects but metabolism is so complex that it's generally impossible to have a complete mechanism. Therefore most of it is statistical. Kind of scary if you ask me. (I think they may finally have a complete mechanism for aspirin). Read a PDR on drug mechanism to be completely disheartened. --DHeyward (talk) 07:21, 19 November 2013 (UTC)

Yes, I just commented on this in another Q, how much of western medicine really is just trial-and-error, without knowing why things do what they do. StuRat (talk) 07:41, 19 November 2013 (UTC)

Not to mention being in part snake oil, as we see when pharmaceutical companies are forced to re-run clinical trials under more rigorous protocols. —Quondum 13:28, 19 November 2013 (UTC)

The heat of the tea will act as a painkiller, while the steam will carry the oils of the lemon into the sinuses. Honey is well known for its antibacterial properties. The larynx and associated soft tissues are close enough to the oesphagus to benefit from the heat of the tea. It's not just the larynx that may be inflamed or infected: the pharynx may be as well, or the tonsils or adenoids or the other fleshy parts. --TammyMoet (talk) 13:23, 19 November 2013 (UTC)

Our article on swallowing mentions that true vocal fold closure is the primary laryngopharyngeal protective mechanism to prevent aspiration during swallowing. The article is lacking in sources but see for example here. The epiglottis will fold over and cover the glottis, the upper esophageal sphincter first relaxes to allow the food or drink to pass into the esophagus and then contracts to reduce backflow into the pharynx. For liquids, this process won't be one hundred percent effective, there will always be some liquid sticking to the mucous tissue which may be redistributed when one swallows the next sip. Honey, with it's greater viscosity and stickiness may be able to reach the vocal cords this way. but that's pure speculation on my part. A youtube video showing the vocal cords and the epiglottis during swallowing here, and one showing radiology of someone swallowing barium here. Ssscienccce (talk) 14:37, 19 November 2013 (UTC)

"...clear my sinuses right out," and "... carry the oil of lemon into the sinuses", does that mean the nasal sinuses or the nasal conchae. If it is the former I am interested to know how the active agent enters the sinuses, given that access and egress is through a very small, and tight, meatus surrounded by cilia sweeping outwards. Sorry DR, well off topic, but sometimes one has to question stuff that people say. Richard Avery (talk) 15:25, 19 November 2013 (UTC)

You're quite right to question me Richard, and I'm wary of quoting my sources on here because I've been told off for quoting pseudoscience about aromatherapy before. The essential oil will be vaporised by the heat and carried by the steam into the nasal cavity, and from there into the sinuses at the front of the face, when the steam from the tea is inhaled. --TammyMoet (talk) 20:02, 19 November 2013 (UTC)

Could a dog sense radon or the the effects of radon in a basement?

I know that radon is odorless, at least to us, but i wonder if a dog could smell it, or otherwise detect ionization from the radioactivity or smell the lead byproduct or or other byproducts. thanks!67.177.40.9 (talk) 15:07, 19 November 2013 (UTC)

No, I don't think so.

• Radon itself is a "noble gas" - it doesn't react chemically with anything - which means (I believe) that it truly is odorless and tasteless, even to dogs.
• The radiation also has no "smell" because the sense of smell operates by detecting molecules using chemical reactions.
• I could easily believe that a dog could be trained to pick up some kinds of by-products. Radon changes to Polonium with a half-life of 3.8 days - which over a few minutes turns into lead. I doubt that enough polonium stays around for long enough for a dog to pick it up. But training a dog to sniff out minute quantities of lead ought to be possible.

But there is a horrible snag. The problem is that the dog would need to detect very small quantities of lead - which I'm sure it could do - but there is almost certainly going to be lead from other sources in the area where you're trying to do the measurement. If you want the dog to sniff out radon by-products in someones' basement for example - then if it's sniffing for lead, it's going to find it in the solder joints of copper household piping, in the solder joints of any electronics, in pottery glazes...all over the place!

Since the dog can't tell the difference between lead-from-radon and other sources, it can't detect the byproducts of Radon.

So this hinges on whether it could smell the truly tiny number of short-lived polonium atoms in the few minutes between the radioactive decay of a radon atom and the polonium atom turning into lead. But polonium is almost as unreactive as radon - and also, polonium is found in places that might fool the dog - smoke detectors, for example, contain small amounts of the stuff - but in quantities that would dwarf the amount in the air of a radon-infested basement.

I couldn't find a reference for any of this - but I'm pretty sure the reasoning is sound.

SteveBaker (talk) 16:31, 19 November 2013 (UTC)

A good undergrad-level chemistry question is "given the half-life of the relevant Rn isotope and the amount of radiation detected, what is the concentration of Rn in the air?" Helps focus attention on orders of magnitude...what can a radiation detector or (bio)chemical sensor detect and also sensitive instruments such as mass spectrometry (all the "immediate detection" methods vs requiring long-term collection/concentration steps). DMacks (talk) 17:27, 19 November 2013 (UTC)

Another point to consider is the difference between the sensitivity of a detector and its accuracy. A dog's nose is very sensitive, so dogs are very good at detecting whether something (drugs, explosives, cancer cells) is present in a sample, but the important thing we need to know is how much radon is in the basement, which dogs aren't particularly good at communicating. Tevildo (talk) 18:42, 19 November 2013 (UTC)

Physically, we know it is possible for some devices (Geiger counter) to detect the radon radioactivity. Therefore, there is no physical law that prevents the dog from detecting it with some similar function. It may seem far-fetched, yet it has been suggested at times that people living in areas with high background radiation have some ability to acclimate (radiation hormesis). That is a controversial idea itself, but clearly, if something can acclimate, if its biology is literally reacting to the radiation somehow, then in theory it could sense that and react to it by behavior also. At this point, the only biological answer possible is to do the experiment and see what happens. Wnt (talk) 18:44, 19 November 2013 (UTC)

"Cyclone Cleopatra"

This storm recently killed a number of people in Sardinia. But do cyclones occur in the Mediterranean? Our cyclone article makes no mention of that area. Which type of storm is it? Who is the official name giving body for this storm? Or is this like The Weather Channel naming U.S. winter storms? Rmhermen (talk) 17:05, 19 November 2013 (UTC)

Sort of quasi-cyclones -- see Medicane. Looie496 (talk) 17:28, 19 November 2013 (UTC)

What's a medicane -- is it like our Witch of November? I presume it's not the brand name of a walking stick, or of a medicated candy cane ;-) 24.23.196.85 (talk) 21:30, 19 November 2013 (UTC)

I couldn't find any reference to this kind of thing happening over the Mediterranean - Europe in general seems pretty much devoid of that kind of activity. One exception (which I recall well because I was living right in the middle of it at the time!) is the Great Storm of 1987 - which hit France and southern England - but not the Mediterranean.

According to Hurricane#Naming, hurricanes are named either by the World Meteorological Organization according to a fixed rota of alphabetically consecutive names - or sometimes by national weather offices. Tornadoes are generally named after the place they touch-down - but it's all a bit informal. We have an entire article about Tropical cyclone naming.

That same article says "Tropical cyclone formation is rare within the Mediterranean sea...and as a result there are no official naming lists for these areas.". Evidence, again, the Great Storm of 1987 - which had no 'official' name but is universally known in the UK just as "The Great Storm" and the Burns' Day storm which is named for the birthday of Robert Burns (a Scottish Poet).

European windstorms (which are really "extratropical cyclones" tend to go north of the Mediterranean - mostly missing Europe completely. There is a section in that article that explains the naming system...but it's not a well-organized, or recognized system - and different countries frequently give the same exact storm different names.

SteveBaker (talk) 17:31, 19 November 2013 (UTC)

Well, European windstorms mostly miss continental Europe, but they frequently hit Scandinavia. In the British Isles, they frequently hit Scotland but rarely make it down to England. If they hit England they can do a lot of damage, but in Scotland, as somebody said, they usually just knock the cows over. Looie496 (talk) 17:57, 19 November 2013 (UTC)

3D printed stainless steel?

I saw an advertisement for an artsy bottle opener that said it was "3D printed stainless steel". This seems a little beyond 3D printing technology as I know it. How would this be possible? --209.203.125.162 (talk) 18:48, 19 November 2013 (UTC)

If you Google "3D printed stainless steel" or similar, you'll find lots of services that provide exactly that. Shapeways has a 3D printed stainless steel Klein bottle-shaped bottle opener that shows up on their main page. TenOfAllTrades(talk) 19:34, 19 November 2013 (UTC)

(ec) Doing it properly involves Selective laser melting - alternatively, according to this website, "3D printers deposit small drops of glue onto layers of stainless steel powder, one layer at a time, until the print is complete.... The models then go through an infusion process that replaces the glue with bronze, creating a full metal product." Your bottle opener is probably made by the latter method, but it can be done. Tevildo (talk) 19:35, 19 November 2013 (UTC)