::<small>[[Magnetostriction]], incidentally. Worth a redirect as a likely misspelling? [[User:Tevildo|Tevildo]] ([[User talk:Tevildo|talk]]) 18:28, 14 October 2016 (UTC)
::<small>[[Magnetostriction]], incidentally. Worth a redirect as a likely misspelling? [[User:Tevildo|Tevildo]] ([[User talk:Tevildo|talk]]) 18:28, 14 October 2016 (UTC)
:::Thank you for the correction. [[User:AllBestFaith|AllBestFaith]] ([[User talk:AllBestFaith|talk]]) 19:36, 14 October 2016 (UTC)</small>
:::Thank you for the correction. [[User:AllBestFaith|AllBestFaith]] ([[User talk:AllBestFaith|talk]]) 19:36, 14 October 2016 (UTC)</small>
{{cot|The article [[Electric current]] explains the rôle of electrons as the [[Charge carrier|charge carriers]] in metals. [[User:AllBestFaith|AllBestFaith]] ([[User talk:AllBestFaith|talk]]) 19:56, 14 October 2016 (UTC)}}
*I think the common misconception as "electricity is the flow of electrons" is what is at heart of the misunderstandings here. Such misunderstandings come from MANY common misunderstanding of electrons as little, discretely identifiable little hard balls of negative change, bouncing around like ping pong balls. I'm not sure that level of misunderstanding is capable of being rectified in this scope of this discussion, so let's ignore it, and use the "little balls" model (wrong as it is) to show that even if we were to assume it correct, ''electricity is still not the movement of electrons''. Electricity is the ''flow of energy through an electric field''. Not a single one of the electrons actually has to carry the energy individually from one place to another. Even if we think of electrons (quite wrongly, but lets keep it for now) as little rigid balls; those little rigid balls don't travel down a wire as though they were marbles being rolled down a tube. Direct current is NOT all of the balls rolling down the tube in one direction, and alternating current is NOT all the little balls shaking back and forth, though some simplified models try to show it that way. Instead we should think about electrical energy being passed through a medium in the same manner that energy gets passed though the stationary ball in the [[roquet]] move in the game of [[croquet]]. See [https://www.youtube.com/watch?v=rD9pdzKwstQ this video] if you're unfamiliar. Notice how the red ball ''doesn't go anywhere'' and yet is able to transmit a bunch of energy to the blue ball. Electricity is like that: the electrons don't go anywhere in either AC or DC. They just "pass the energy" down the chain. Of course, that's still a very wrong way to think of electrons and electricity, but it's [[lie-to-children|right enough]] to get us to reach the correct conclusion that ''electrons don't move''. --[[User:Jayron32|<span style="color:#009">Jayron</span>]][[User talk:Jayron32|<b style="color:#090">''32''</b>]] 18:49, 14 October 2016 (UTC)
*I think the common misconception as "electricity is the flow of electrons" is what is at heart of the misunderstandings here. Such misunderstandings come from MANY common misunderstanding of electrons as little, discretely identifiable little hard balls of negative change, bouncing around like ping pong balls. I'm not sure that level of misunderstanding is capable of being rectified in this scope of this discussion, so let's ignore it, and use the "little balls" model (wrong as it is) to show that even if we were to assume it correct, ''electricity is still not the movement of electrons''. Electricity is the ''flow of energy through an electric field''. Not a single one of the electrons actually has to carry the energy individually from one place to another. Even if we think of electrons (quite wrongly, but lets keep it for now) as little rigid balls; those little rigid balls don't travel down a wire as though they were marbles being rolled down a tube. Direct current is NOT all of the balls rolling down the tube in one direction, and alternating current is NOT all the little balls shaking back and forth, though some simplified models try to show it that way. Instead we should think about electrical energy being passed through a medium in the same manner that energy gets passed though the stationary ball in the [[roquet]] move in the game of [[croquet]]. See [https://www.youtube.com/watch?v=rD9pdzKwstQ this video] if you're unfamiliar. Notice how the red ball ''doesn't go anywhere'' and yet is able to transmit a bunch of energy to the blue ball. Electricity is like that: the electrons don't go anywhere in either AC or DC. They just "pass the energy" down the chain. Of course, that's still a very wrong way to think of electrons and electricity, but it's [[lie-to-children|right enough]] to get us to reach the correct conclusion that ''electrons don't move''. --[[User:Jayron32|<span style="color:#009">Jayron</span>]][[User talk:Jayron32|<b style="color:#090">''32''</b>]] 18:49, 14 October 2016 (UTC)
{{cob}}
== The science behind how "Metanium" cream works ==
== The science behind how "Metanium" cream works ==
Revision as of 19:57, 14 October 2016
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
Where in the world did you find it? When did you collect it? What type of area was it growing in? The answers to these questions can help. If you don't get an answer here, you might try at reddit's What's this plant. SemanticMantis (talk) 14:15, 10 October 2016 (UTC)[reply]
I'm pretty sure it's Dioscorea bulbifera, the Air potato. The same leaf shape and veins and flower bud arrangement can be found with a Google image search. -Modocc (talk) 14:18, 10 October 2016 (UTC)[reply]
Yes thanks its the same dioscorea.i found it in my garden.i found it in Orissa,india.
Many thanks modocc — Preceding unsigned comment added by Sameerdubey.sbp (talk • contribs) 01:09, 11 October 2016 (UTC)[reply]
How long should a clock radio last on a UPS?
Our electricity was out for a long time because of hurricane Mathew. I have a clock radio that runs on A/C and it says that it uses 3 watts. I put it on a UPS rated at 780 watts or 1300 VA. The battery capacity is 187 volt-amp-hours. There is a chart saying that it should provide 300 watts for 20 minutes. Since the clock radio uses 3 watts, I was figuring that it would last 2000 minutes, or over 33 hours. There is a counter on the UPS showing how many minutes of life it has with the current load and that was showing less than 6 hours. The UPS was nearly fully charged when I started using the radio and it is new - I bought it this year. Why was it lasting so much less than my calculation? Bubba73You talkin' to me? 07:39, 10 October 2016 (UTC)[reply]
The inverter will have its own power requirements, probably 5-10 watts, even if it is merely switched on and not powering anything. Greglocock (talk) 09:26, 10 October 2016 (UTC)[reply]
If the inverter uses on the high end of that 5-10 watts, that explains it. Bubba73You talkin' to me? 15:26, 10 October 2016 (UTC)[reply]
The UPS manufacture should take into account the inverter drain and publish the available power deliverable. That said, the inverter is going to consume some linear power regardless of the drain (OK I know that not exactly right but talking base-load here) . Most UPS's are used for short brownouts and thus prolong longtime power outages may mess up the long-term calculations based on the manufactures data sheets.. This (I think) backs up the previous comment by Greglocock . The other thing to remember, is even if the UPS is fresh out of the box. Those storage batteries may not be able to hold their indicated charge. You could consider a cheap purchase (or steal, borrow, etc,) some wire wound resistors to act as a dump for the UPS's full rated power for the purpose of which it was advertised for. Should the UPS still fall short, then return it under warranty. --Aspro (talk) 12:10, 10 October 2016 (UTC)[reply]
A clock with a cord always seemed like a truly terrible idea. By comparison, the all too clever folks at ISIS use the Nokia 105, which is cheap enough to afford in the Third World and is alleged to be able to stand by for 35 days on a single charge, and includes an AM radio. Wnt (talk) 14:36, 10 October 2016 (UTC)[reply]
The OP may be referring to a much loved and cherished Clock Radio Alarm of a style like they don't make anymore. Sure, he could get a modern, boring, equivalent that cuts to battery upon a power failure and a RRC chip to ensure that if he goes camping (off mains 60Hz grid) it will still wake him up with an accuracy of a couple of milliseconds.. But that is not what the OP is asking.--Aspro (talk) 16:14, 10 October 2016 (UTC)[reply]
Well, the way ISIS customizes them, one of those cheap little cell phones can wake you up many blocks away. :) :( Wnt (talk) 10:34, 11 October 2016 (UTC)[reply]
Yes, the clock radio I have is one I've had for a long time. - probably since 1991. Bubba73You talkin' to me? 16:58, 10 October 2016 (UTC)[reply]
Aw. That's assume. They just don't make them like that any more! The modern ones are of poor build quality and all made in China now. Think yours, may have one of the National Semiconductor MM5314N series of clock chips inside (all made in the US), so consider passing it on to a grandchild as a family heirloom.--Aspro (talk) 17:59, 10 October 2016 (UTC) [reply]
I don't know about the chips, but it is a Sony. I wish it had digital tuning. Bubba73You talkin' to me? 19:36, 10 October 2016 (UTC)[reply]
Phase-locked loop digital tuning was only just being introduced at that time. My transceiver had it but is cost about £400 back then. Mind you my 1957 Pontiac Star Chief had a self-seeking radio. But there again, in bed, one doesn’t tend to move out of one local broadcast station area and into another. So there was no point in include this feature in a bed-side alarm clock. Also, even though it is a Sony, it still probably has this chip series as they were ubiquitous back then. They were duel standard. Outside North America, within a country with a 50 Hz main frequency one just shorted out pin 16 on the chip, on returning home, one simply broke the short. Unscrew the box and I bet, it has a MM5 n n n n n chip like one of these: [1] . Digital tuning … 60 years before, one had to fiddle for ages with the cat's whisker before even getting the chance to tune in. Oh, those were the halcyon days...--Aspro (talk) 21:07, 10 October 2016 (UTC)[reply]
I have two reasons for wanting digital tuning: (1) tune in more accurately to the station. Even though the one I have come on automatically is a local station, it isn't picked up very well in the house. I have to turn the radio a certain way to get it to come in at all. (It broadcasts with only 7,000 watts.) (2) during the power outage when stations were dropping off the air, I kept having to search for stations that were broadcasting information. It would have been a lot easier to find them if the tuner could scan. Bubba73You talkin' to me? 02:56, 11 October 2016 (UTC)[reply]
See the problem. 7000 watts is actually quite strong and a external dipole aerial (even a cheap one that just tapes onto the wall above) works wonders for good reception. From memory though, I don't think these Sony Radios had any thing other than an internal ferrite rod. Not even a telescopic antenna. If it does, that’s easy, just hook the dipole aerial up-to that (unscrew it first and feed into the socket) . Failing that, the only other solution for a stronger signal would be to drill into the case and pass the the external aerial feed though. But at the minimum, you will need a capacitor or even a balun to match the arial to the radio. However, that dispenses with the need to turn the radio this way and that to get a strong signal. The other thing is: if your local station is broadcasting to mainly automobile audiences. The transmitters are probably vertically polarized. Domestics radios have their ferrite horizontal, so you might try standing it on edge for a stronger signal.--Aspro (talk) 13:57, 11 October 2016 (UTC)[reply]
The Sony clock radio has no external antenna and no screws for a dipole antenna. The station's transmitter is less than 10 miles away, but I can pick up stations 70 miles away better (probably a lot more powerful). We have a lot of electronic stuff in our house which may interfere with the reception. It is FM, BTW. Bubba73You talkin' to me? 16:20, 11 October 2016 (UTC)[reply]
Are you thinking of the right phone? The article you linked to mentions use for making IEDs, but doesn't say anything about including an AM radio and a search also finds nothing. An AM radio is extremely rare in a mobile phone primarily I think because of antenna difficulties. By comparison FM radios are somewhat common in phones, both smart phones and classical phones, especially those targetting the developing market. Smart phones commonly rely on the earphone cord for the antenna as do some classical phones although some have a built in antenna that is sufficient. However I suspect the FM radio isn't a big selling point for IED makers. While nominally you could use that perhaps as a backup trigger AFAIK most simply rely on the mobile phone network for trigger. Nil Einne (talk) 03:08, 11 October 2016 (UTC)[reply]
BTW, the two fluorescent lights I tried on the UPS didn't work right, probably because that the output is a stepped approximation to the sine wave. Would an LED work on such a UPS? Bubba73You talkin' to me? 15:33, 10 October 2016 (UTC)[reply]
USP's of the type referred to, are designed to power computers. Computers have smoothing capacitors in the internal power supply to smooth out spikes. So not surprised if your tubes “didn't work right”. If the tubes didn't work right, then it can be assumed that LED's (depending on their drivers) may also strobe. Solution: Place a electrolytic capacitor before the LED (or LED chain) and a resistor after.--Aspro (talk) 16:14, 10 October 2016 (UTC)[reply]
As the above, a UPS is really just to stop your computer suddenly and unexpectedly losing power (and data) during a power "interruption" or a brown out, it's not really a complete power "replacement" device. If you do have a full power outage, a UPS gives you enough time to startup a backup generator OR at least perform a graceful shutdown, it's not really designed to just keep running your computer "as normal". Vespine (talk) 22:22, 10 October 2016 (UTC)[reply]
Yes, I know, I've used them for years. I shut all of the computers down as soon as the power went out. I have five UPSs that I used for the radio and charging devices. We drained the three smallest ones. I used up about half of the battery on the largest one. Bubba73You talkin' to me? 23:15, 10 October 2016 (UTC)[reply]
Is this your camping kit or did you actually have a blackout? Vespine (talk) 03:21, 11 October 2016 (UTC)[reply]
We were without electricity for 47 hours because of Hurricane Mathew (starting 6 hours before it hit). I was trying to keep the radio going to get news reports and get some lights. (I have a battery-powered radio with a telescoping antenna, but it would not turn on, even though the batteries are good.) Bubba73You talkin' to me? 20:44, 11 October 2016 (UTC)[reply]
In most common installation scenarios UPS are intended to be used like that. However UPSes installed for alarms and home fibre connections are often intended to be used for most power failures and many people don't even have any provision for generators. (When it comes to home fibre connections, depending on the country I think many people don't even have UPSes.) However this is more commonly for the more routine (power cuts lasting several hours rather than those extremely rare events (at least in the developed world) lasting several days. Of course you commonly don't really need a UPS, a quick acting battery backup will do at least for the fibre system but it's often easier just to use a UPS of some times. (Alarms systems may not like any loss of power.) Ideally a DC to DC may be better, but some do use 240V UPSes. I believe some roadside telecommunications cabinet also rely on UPSes or battery backups (more commonly the former although sometimes a UPS may simply be called a battery backup even if it designed like a UPS) exclusively as they lack a connection for power to the telecommunications exchange and while it may be possible, it's generally fairly unlikely except in special circumstances that anyone is going to attach a generator to each cabinet. Nil Einne (talk) 03:35, 11 October 2016 (UTC)[reply]
Sounds like its time to think out side the box. Depending on a UPS is like putting all ones eggs in one basket. Don't know what your financial situation is like but LED lanterns are inexpensive today and last for days. An auto battery with a inexpensive DC-to-DC converter bought from (say) eBay will keep a cheap (£4.00) Raspberry Pi (that can maintain internet connection) going for days and days, plus a cheap FM/MW transistor radio with a proper arial. The car battery will also (via the DC-to-DC converter) recharge your phone many times. Start preparing now and you will be prepared before Hurricane Nicole and Otto hits, (Otto hasn't got going yet but it may be coming your way when it does).--Aspro (talk) 23:39, 11 October 2016 (UTC)[reply]
As a user of the Raspberry Pi, I must question your advice that it can be powered for days and days from a car battery. The RPi draws (at 5 Volts) in the vicinity of 1 Amp, but usually not more, when idling or when doing tasks (it doesn't vary much). It's quite a power hog and not at all like microprocessor chips that draw milliamps. In 24 hours, continuous use would virtually flatten a fully charged car battery. If you mean that it could last days and days if turned on briefly to check emails every few hours and be switched off during the intervals, you should have said so. You also haven't mentioned how the car battery will power the associated monitor and keyboard, since they are peripherals that aren't part of the RPi package. Akld guy (talk) 20:35, 12 October 2016 (UTC)[reply]
Ah, you have obviously had the benefit of a high fluting education better than mine. Yet, in simple terms, in the ancient mathematics I was taught, a 70 amp-hours auto battery will power such a devise for at least 48 hours continuously, i.e., plural -days in normal use. But perhaps you expect to leave your TV and everything on 24/7, in which case -the reply is not applicable to you. One must credit the OP with having a bit of common-sense to understand what I meant and do a dry run before Otto hits. Nice to know your using a RP however.--Aspro (talk) 19:47, 13 October 2016 (UTC)[reply]
I don't like the sarcasm, and you still haven't answered how the car battery will power the associated monitor and keyboard which will draw far more than the RPi. Akld guy (talk) 23:38, 13 October 2016 (UTC)[reply]
Level (logarithmic quantity)
Level (logarithmic quantity)Abandera61 (talk) 10:01, 10 October 2016 (UTC)[reply]
According to me , and at first sight, Formulas in "Units of Level" are not correct.
For "root power" or "Field" quantities is:
Lf = ln( F / F(0)) , which means: ln( F / F(0))Np = 10*log(10)( F / F(0)) dB.
Not:
Lf = ln( F / F(0))Np = 2*log(10)( F / F(0))B = 20*log(10)( F / F(0))dB.
And for "Power" quantities is:
Lp = 1/2*ln( P / P(0)) , which means: ln( P / P(0))Np = 20*log(10)( P / P(0)) dB.
Not:
Lp = 1/2*ln( P / P(0))Np = log(10)( P / P(0)) B = 10*log(10)( P / P(0)) dB.
Want to know , if I can edit the page , after further checks, and if it can affect other articles automatically.
hope to have put "Abandera61 (talk) 10:01, 10 October 2016 (UTC)" in the right way,
best regards
alessandro[reply]
Thank You
Alessandro Bandera
Abandera61 (talk) 13:56, 10 October 2016 (UTC)[reply]
Do the sparks from car welding robots have any effect on the car or robot?
The robot presumably is tougher than thin car metal but drops of molten metal must keep freezing on the robot for years. Sagittarian Milky Way (talk) 18:16, 10 October 2016 (UTC)[reply]
Robots spot weld body shells, so no molten metal spilling all over the place. Not even sparks. Similar to blacksmith hammer welding. They just get dusted in iron oxide.--Aspro (talk) 20:13, 10 October 2016 (UTC)[reply]
Note that sparks, having a high surface-area-to-volume ratio, cool quickly as they shoot through the air, so they are not molten when they land, they are solid. StuRat (talk) 21:17, 10 October 2016 (UTC)[reply]
I worked in a tool shop for a while that had a manual welding "production line" with several people using MIG welder pretty much all day. Those definitely DID constantly spit out little balls of metal, and yes there were little balls of metal everywhere, but they are so small and most of the time if they build up to more than one "layer" on anything (jig, frame, table, etc) they just brush off. I think very very rarely, someone would get a grinder out if some build up happened in an inconvenient place. Vespine (talk) 21:57, 10 October 2016 (UTC)[reply]
Spatter builds up, but doesn't fly all that far (it's dense). So anywhere exposed to it is usually covered by something non-metallic to which it won't stick. For wire-feed welding, spatter does build up around the gas shield nozzle and has to be cleaned off periodically. It can also be a problem around fume extraction vents (if the atmosphere is kept human-friendly), where the airflow can be enough to draw light spatter into it, where it accumulates.
Anti-spatter spray is an aerosol (usually a silicone) which can also be used to make surfaces non-adherent to spatter. Andy Dingley (talk) 22:18, 10 October 2016 (UTC)[reply]
How is that inferred? We can say a body's mass is consistent with the presence of such a core, but it's also consistent with a bigger core of ice. Can its moment of inertia be measured? —Tamfang (talk) 00:41, 11 October 2016 (UTC)[reply]
I don't fully understand the math behind it, but many observations feed into the model. Specifically: surface spectroscopy, mass, radius, gravitational dipole moment, gravitational quadrupole moment, and modeling of the behavior of different materials under high temperature/pressure. As far as I can tell from reading papers on Uranus' core that I don't fully understand, you can't make a model agree with all of this without having a rocky core. Someguy1221 (talk) 00:57, 11 October 2016 (UTC)[reply]
Also I dare say evolution of the solar system might have a few things to say about what is likely and unlikely to be found at the center of a gas giant. I strongly suspect there are very good reasons why no one expects to find solid ice in the middle of any planet, let alone a gas giant. Vespine (talk) 03:06, 11 October 2016 (UTC)[reply]
Yes, there are reasons to think most planetary cores are primarily iron and nickel. Iron and nickel are the most common "heavy" elements in the universe because their nuclei are the most stable. Denser elements tend to sink to the center of a planet, so iron and nickel, along with any denser elements, "want" to sink to the core. --47.138.165.200 (talk) 10:34, 11 October 2016 (UTC)[reply]
But, Uranus is rather unique in that there is much evidence of a major collision in the early formation. It is further away than models show it should be. It is rotating on its side. It radiates almost no heat. That last one fits with a collision that would have kicked out most of the rocky or metallic core, leaving a sparse icy ball behind. The magnetic field, which was traditionally thought to be solely created by cores may not come from the core. It is off by about 60 degrees, but so is Neptune's. Therefore, the theory that it comes from movement in the core may be wrong. It may come from another source. In the end, our current models and expectations make us believe that Uranus has a rocky/metallic core. However, it is strange and as we learn more about it, we may very well discover that it has a core of loosely compressed ice. 209.149.113.4 (talk) 14:07, 11 October 2016 (UTC)[reply]
I don't see how you'd get a core of ice. The successful models of Uranus inner structure all assume a core density of ~10g/cc, which as far as I know is way higher than you could achieve with water/ammonia ice, even under extreme pressure. Someguy1221 (talk) 21:51, 11 October 2016 (UTC)[reply]
I would have loved to prove you wrong, but [2] says that you need pressures in the ballpark of 100 GPa (one million times the atmospheric pressure) to even reach 2g/cm^3 in water. So yeah, 10 sounds hard. TigraanClick here to contact me 08:05, 12 October 2016 (UTC)[reply]
The "we may very well" is used to indicate that the following statement is unlikely. However, it is used in this case because currently accepted models of the core of Uranus indicate that the inner core of rock/metal is very small and very cold. The outer core (mantle) is vary large made of ice. The interesting part isn't that it is made of ice. The really interesting part is that this ice exists in high pressure and high temperature (relatively - you have to note that Uranus is much colder than any of the other planets). So, the icy mantle of Uranus is a very unique and unexpected feature - if it actually exists. 209.149.113.4 (talk) 17:53, 12 October 2016 (UTC)[reply]
October 11
Nights are loud
Why are background noises from cars louder at night than during the day? It is because nights are quieter as there aren't as many people outside. When people are outside making sounds like voices, machines, etc.; those sounds are effective at blocking background noises from cars, but don't travel as far, that's a reason why days are often quieter, that's my opinion. Upon hearing cars loudly at night, I can picture the outdoor as a giant dome! At the time of this writing, I had a window opened next to me at night and heard those background noises somewhat loudly. PlanetStar 02:28, 11 October 2016 (UTC)[reply]
I think you definitely have at least "part" of the answer. Our ears are very good at attenuating sounds and a clue is that decibels are a logarithmic scale. This means you roughly need ten times the sound energy to make something sound twice as loud. Without "loud" sounds to drown them out, you can hear the quiet sounds a lot better. I've noticed pretty much the same effect when I listen to music or a podcast on the train, I don't listen to it loud, just a comfortable level like someone speaking to me, when the doors open and I step out of the train it easily gets drowned out by the noises outside of the train in particular as the train takes off. Even though without headphones at all the train doesn't actually sound that loud at all, subjectively one at a time the train sounds doesn't seem nearly loud enough to drown out what's coming out of my headphones, but in actual fact when you have both sounds at the same time, I have to increase the volume substantially on my headphones to be able to hear over the sounds of the train. Vespine (talk) 02:57, 11 October 2016 (UTC)[reply]
There is also another effect called sound refraction, when there is a layer of cold air above or below a layer of hot air, (which typically happens at night as the earth cools and the warm air rises, but also happens on hot days when the earth heats up but the air above is still cool) sounds do actually travel further and therefore would seem louder from farther than normal. So cars on a road nearby could be heard from further away, for example. Vespine (talk) 03:02, 11 October 2016 (UTC)[reply]
In my above opinion, quieter IS louder would be a paradox. Sound behaves like light that there is refraction you mentioned as well as reflection. There is also sound fog, sound glare, and even colors of sound. So sound have all the characteristics that light has, except that sound does not travel in outer space like light. Also hearing background car sounds is often louder on rainy days. Sometimes though, car noises are only slightly audible at night, possibly due to minimal air temperature differences by layer, don't you think? PlanetStar 04:39, 11 October 2016 (UTC)[reply]
Maybe cars just make more noise when moving on a wet road? PiusImpavidus (talk) 10:02, 11 October 2016 (UTC)[reply]
That's certainly true in my experience. Also wet surfaces reflect sound more easily, and so transfer sound farther. SemanticMantis (talk) 13:04, 11 October 2016 (UTC)[reply]
[citation needed]The first part is believable, after all, splashing water makes a lot of noise. But I don't buy that wet roads reflect sound better than dry roads. Please provide a source for that. StuRat (talk) 22:21, 11 October 2016 (UTC)[reply]
I have no problem proving sources upon polite request. You could learn from my example. Here are two references that support my claim that wet surfaces generally have higher reflectivity in the audible range [3][4]. It's also true that wet surfaces reflect radar better [5][6]. I hope you are as responsive and successful at providing citations to support your own claims in the future. SemanticMantis (talk) 01:54, 13 October 2016 (UTC)[reply]
The first ref is about wet sand, loess (sediment), and clay, not roads, and the closest comparison, with dry and wet compacted clay, actually shows more absorption of sound when wet. The 2nd ref is behind a paywall, but nothing in the abstract suggests that it supports your assertion. The two refs of reflectivity of radar are completely irrelevant. If you have some actual proof that wet roads reflect SOUND better, please provide quotes and page numbers, not just irrelevant refs. And when people ask nicely, I tend to give USEFUL refs, but you started by being extremely sarcastic, rather than asking for a ref politely. StuRat (talk) 13:07, 13 October 2016 (UTC)[reply]
Thanks for providing references. Keep in mind that your own impoliteness tends to breed impoliteness from others. ←Baseball BugsWhat's up, Doc?carrots→ 07:17, 13 October 2016 (UTC)[reply]
He's very adamant about demanding sourcing, but "in his experience" is apparently adequate sourcing for... his experience. ←Baseball BugsWhat's up, Doc?carrots→ 00:07, 13 October 2016 (UTC)[reply]
According to you, that's a personal attack. Stop trying to be "clever" and WP:pointy and start being useful, or, failing that, at least stop being so disruptive. SemanticMantis (talk) 01:50, 13 October 2016 (UTC
It's often very evident that it's currently raining or has been raining, as you can hear the splashing as the cars plow through the layer of water on the roadway. Whether the roadway is otherwise "reflecting" more sound than a dry road could be hard to measure. ←Baseball BugsWhat's up, Doc?carrots→ 07:33, 12 October 2016 (UTC)[reply]
I believe for awhile that we hear sounds more loudly in the dark than in the light because light interacts with sound. I looked up in Yahoo Answers and reported to be true. The darkness of night may have minutely contributed to cars heard more loudly than during the light of day. PlanetStar 04:39, 11 October 2016 (UTC)[reply]
I'm going to assume good faith here but the above answers are nonsense. Sound and light do not interact at all, one is a physical propagation of vibrations through a medium (like air) and the other is electromagnetic radiation. That yahoo answer is preposterous, I very strongly suspect it's only got "up votes" by people who think it's "so ridiculous it's funny", not because anyone has verified it as true. It would be trivially easy to prove, does the sound of ANYTHING change when a cloud blocks out the sun? Clouds block 50%-80% of the photons reaching the earth but nothing gets quieter louder when a cloud goes overhead. Vespine (talk) 06:13, 11 October 2016 (UTC)[reply]
Also, color of sound is purely a metaphor, you can just as validly call it "flavor of sound" it does not mean you can literally "taste it" with your tongue. Vespine (talk) 06:20, 11 October 2016 (UTC)[reply]
Sound and light are both waves. Both are described by the physics equations for wave propagation, which describe how waves are reflected or refracted when their speed changes depending on the medium where they move. That's about all they have in common. Light is an electromagnetic wave, sound a pressure wave.
There are indeed reasons why sound seems louder at night. In the dark you see less, so you pay more attention to what you hear. At night, the air close to the ground cools. This leads to a warm layer on top of the surface layer, known as an inversion, and this warm layer refracts sound back to the ground. And at night, there's less background noise. PiusImpavidus (talk) 10:02, 11 October 2016 (UTC)[reply]
1) One obvious reason is that you have a window open at night, and presumably not during the day.
2) Another could be rush hour, with more cars on the road from around 5 or 6 AM, which could still be called "night".
3) As for the effect of darkness, that brings lower temperatures, and potentially fog. Both effect sound propagation. I think sound travels better in cold air, but high frequencies are blocked by fog (hence low frequency fog horns). So, if cars make more low frequency sounds, they may then stand out better, due to a lack of competing high frequency sounds. StuRat (talk) 12:42, 11 October 2016 (UTC)[reply]
Speed of sound as a function of temperature in dry air, especially for Stu."I think sound travels better in cold air" Why do you think that? [citation needed]SemanticMantis (talk) 15:44, 11 October 2016 (UTC)[reply]
[7] says, on page 156: "...the maximum value of absorption increases with increasing temperature". Therefore, sound is absorbed less at lower temps. StuRat (talk) 22:17, 11 October 2016 (UTC)[reply]
Here are a few research papers on noise pollution that you might be interested in [8][9]. SemanticMantis (talk) 13:04, 11 October 2016 (UTC)[reply]
See Psychoacoustics, especially the subsection titled "Auditory masking" and the article titled Auditory masking. To wit "Auditory masking occurs when the perception of one sound is affected by the presence of another sound." Also very relevant is the article titled Loudness, again to quote the relevant part "loudness is a subjective measure, often confused with physical measures of sound strength such as sound pressure, sound pressure level (in decibels), sound intensity or sound power." --Jayron32 13:20, 11 October 2016 (UTC)[reply]
The speed of sound link isn't relevant, but the second link is. Also note that my foghorn link does state that low frequencies travel better through fog. StuRat (talk) 15:09, 11 October 2016 (UTC)[reply]
not references or answers
Shall I box this up as a non-answer? Speed of sound most certainly talks about effects of temperature. Maybe you're having some problems with reading comprehension, in addition to having problems with scientific facts and references? SemanticMantis (talk) 15:43, 11 October 2016 (UTC)[reply]
"Sounds travels better" could mean speed, in which case it goes up with temperature (at constant pressure though, methinks), or attenuation factor, in which case it goes down with temperature (at least for some non-irrealistic range).
Of course, you both knew it - but StuRat wouldn't explain, and SemanticMantis would pretend not to have understood, because it is so much funnier to be confrontational. TigraanClick here to contact me 16:24, 11 October 2016 (UTC)[reply]
I'm not sure I know what you're talking about. I have never pretended not to understand anything on these pages. I make it a point to provide as little as possible other than the references I cite. I admit my (now removed) sarcastic confrontation was not ideal. However, since I cannot delete Stu's misleading and incorrect posts, and he adamantly refuses to properly cite references, I have little recourse other than posting correct information, and challenging his guesswork. SemanticMantis (talk) 16:51, 11 October 2016 (UTC)[reply]
I was hoping you were just pretending not to understand, but, just in case you really don't understand, I will patiently explain. This Q is about why cars seem louder at night. Loudness is volume, and attenuation of that volume is therefore the issue here. Loudness is not related to the speed at which sound travels (unless you are talking about sonic booms). Frequency and wavelength are related to the speed at which sound travels, but this Q is not about that.
As for references, my fog horn ref was good one, and I've added another good one, while you had some good refs, some bad refs, and some missing refs, so don't get all "holier than thou" on me. StuRat (talk) 22:05, 11 October 2016 (UTC)[reply]
I'll stop criticizing you when you learn how to properly reference your claims. I'm fucking thrilled that you managed to find a decent ref to support your claim above. Good job. Next time, do it without being asked, and you'll be on the path to being useful here. SemanticMantis (talk) 13:38, 12 October 2016 (UTC)[reply]
I did provide a useful ref, the fog horn one. You provided at least one USELESS ref, about the speed of sound, wasting the OP's time, and failed to provide any ref for your claim that wet roads reflect sound better. Stop criticizing others and try to do better with your own refs. StuRat (talk) 16:45, 12 October 2016 (UTC)[reply]
This is not exactly rocket science. Atmospheric conditions could be a factor, but keep in mind that what you can hear often depends on what other noises there are. Vespine's original answer pretty well explains that part of it. As a simple example, when you're driving in your car with your radio at what seems like an optimal level, if you stop the car and turn off the engine, the radio will seem louder, even though you have not increased the volume of it. Why? Because the engine noise is no longer there. Another practical example is attending a game in a domed stadium filled to capacity with spectators. When your team scores, the crowd's roar is very loud and that's about all you can hear. But when there's nothing going on, you can hear a lot more of the "quieter" sounds that Vespine points out. ←Baseball BugsWhat's up, Doc?carrots→ 06:40, 12 October 2016 (UTC)[reply]
I believe the OP is not necessarily claiming car sounds are objectively louder at night but seeks an explanation why they seem (subjectively) louder. Consequently it may be unnecessary to look for explanations based on the physics of Sound or on human hearing physiology. Under the article heading Neural adaptation we have a short section Neural adaptation#Auditory that may be relevant to the OP (though it is not as detailed as the one devoted to visual adaptation.). There are articles on preoccupation of general attention in some specific abnormalities e.g. BDD (own appearance), Egomania (own importance), Hypochondriasis (own sickness), etc., but no article about preoccupation in healthy people by multiple distractions that may be present in greater strength during the day than during the night. Such daytime distraction might decrease the sensitivity of hearing and this idea seems straightforward to test by controlled experiment.AllBestFaith (talk) 00:44, 13 October 2016 (UTC)[reply]
Vespine's explanation pretty well covers it. If there are fewer other sounds, the sounds you hear will tend to seem louder. ←Baseball BugsWhat's up, Doc?carrots→ 07:20, 13 October 2016 (UTC)[reply]
Hearing fewer other sounds would make the other sounds already present seem louder. That is similar to what I mentioned in my first comment of this section. PlanetStar 23:45, 13 October 2016 (UTC)[reply]
Assuming Vespine's answer about sound refraction, sounds not just from cars and other vehicles in the background can be heard more loudly at night, but of any sound. For example, we could hear the music playing from down the street more loudly at night than during the day, even though the source is at same distance and same volume. PlanetStar 23:45, 13 October 2016 (UTC)[reply]
What plants are these (the ones in the foreground)?
(regarding the first image) A variety of Dracaena fragrans Massangeana? The shading of the leaves looks different in that article, but see here for example ---Sluzzelintalk 02:37, 11 October 2016 (UTC)[reply]
Hi I remember asking a question about mind uploading a few weeks back. If mind uploading were not possible, would there be other possible ways for humans to become immortal?Uncle dan is home (talk) 08:12, 11 October 2016 (UTC)[reply]
We have an article on immortality which includes some notable theories. Why don't you start there, and then let us know if you have any more specific questions. Someguy1221 (talk) 08:16, 11 October 2016 (UTC)[reply]
Immortality is a philosophical problem, not a physical one. The atoms that make up the body endure. The fundamental essence of consciousness (Atman) is arguably universal and immortal. Even the information learned in a lifetime accumulates in some sense, whether transmitted recognizably as text or whether it disperses and affects future events in unpredictable ways. Even particular aspects of the genome are long-lived - though the precise combination of genes may not occur again, the individual alleles likely remain present in the gene pool for a very long time. And this is even before we broach such issues as parallel universes and whether they contain copies of ourselves, or the related quantum immortality. And then there are creepy misgivings regarding qualia, such as Nietschze's notion of "eternal return". Now all these things are uncertain, but is it certain that who you were five minutes ago was you, rather than just a memory? Let alone a robotic effigy or an imperfectly cell-printed copy! So outside the very narrow sense of trying to put off disease a little longer, the fundamental issue of what the human being is and whether or how long he remains is a far voyage beyond all we understand. Wnt (talk) 10:30, 11 October 2016 (UTC)[reply]
Woody Allen was once asked if he wanted to achieve immortality through his film work. He said, "I would rather achieve immortality by not dying." ←Baseball BugsWhat's up, Doc?carrots→ 10:50, 11 October 2016 (UTC)[reply]
Plus I'd want good health! Not as a Struldbrug. :) Dmcq (talk) 11:55, 11 October 2016 (UTC)[reply]
Wave some philosophy at it. When you're dead, you don't exist. At the moment of death, you're dead. Therefore, you never experience the moment of death; hence, you never die. Q.E.D. :) Wnt (talk) 12:34, 11 October 2016 (UTC)[reply]
There's the possibility of some type of suspended animation, like being frozen. Of course, there's not much point in living forever if you aren't aware of any of it. But the hope is that eventually mind uploading will be possible, then you could be revived and live again. Other life extension techniques, like replacing failing organs with those cloned from your own stem cells, may also keep you alive until that time. StuRat (talk) 12:29, 11 October 2016 (UTC)[reply]
@StuRat: The issue with "mind uploading" is that you're in a lump of live neurons doing action potentials, and your "alter ego" is in a bunch of integrated circuits carved into silicon. How can the essence of yourself be in that thing, but not be in some five-year-old who lives in Ethiopia? Yeah, yeah, I know, you taught it some lines. I know some folks who can quote every line in Monty Python and get the accents right, does that mean the actors have uploaded their minds to them? Wnt (talk) 16:09, 13 October 2016 (UTC)[reply]
Sometimes the actors are no different than the character, so what's important to one's identity and ego would be a period of integration. If one can create a cyborg AI for which experiences can be transferred from organic form to the other and vice versa, then one will come to identify with both even if the transistor copy version is imperfect and so one may eventually not "mind" making a complete transition to a hardwired life because you will have, in critical ways, remembered experiencing both forms of consciousness during the transition. --Modocc (talk) 18:15, 13 October 2016 (UTC)[reply]
Are you worried that your ants are aging too slowly ? :-) StuRat (talk) 15:12, 11 October 2016 (UTC) [reply]
There are only a finite number of physically distinguishable states your brain can be in. This means that an immortal brain would eventually have to experience the same things over and over again, ad infinitum. Anything that this brain experiences will involve only a finite recollection of a "past" (which in most cases will be an artifact of false memories). The more you try to evade these limitations by using a system that can access larger and larger number of states, the more different persons with different experiences you'll end up producing. Count Iblis (talk) 17:19, 11 October 2016 (UTC)[reply]
@Count Iblis Would your hypothesized immortal brain discover a repetition in the decimal expansion of Transcendental numbers such as π and e or in an inward zooming animation of the Mandelbrot set ? AllBestFaith (talk) 15:15, 12 October 2016 (UTC)[reply]
Not a full repetition as these are irrational numbers, but the Mandelbrot set does contain exact copies of itself. Count Iblis (talk) 17:38, 12 October 2016 (UTC)[reply]
There is no finite number of repetitions of a digit that will not eventually occur in the expansion of a transcendental number. Your hypothetical immortal-but-capacity-limited brain will be unable to decide whether very long-cycle repetitions it sees are infinite or finite patterns. Scientific method for us mortals relies on experiments that are sufficiently replicable, where sufficiency is a criterium related to an intellectual's life resource. Example: I have seen the demonstration that a lead ball and a feather fall at the same rates in a vacuum a couple of times and I regard that demonstration as such conclusive evidence for Newton's laws for falling bodies that I regard them as indisputable, and won't "waste" my time repeating the ball and feather test whose result is to mortal me highly predictable. In contrast, the immortal brain lacks the option of dismissing any result as too unlikely to happen to seriously consider, hence if it is honest about its own finite capacity, it can suffer the uncomfortable awareness of inability to discover (know) anything scientifically.
While some fractals are exactly self-similar such as the Koch snowflake, a deep animation[13] of the Mandelbrot fractal (warning: big file 146 MB, chosen for beauty) suggests the supply of fresh contexts for the reappearing kernel is inexhaustible. Perhaps you will draw on the argument that images digitized in a finite number of bits inevitably repeat after 2bits images. AllBestFaith (talk) 18:59, 13 October 2016 (UTC)[reply]
@Count Iblis: AI is not limited to our brains, but, in any case, our universe would need to be eternal and with my modeling of its underlying physics I have reason to believe that it is. --Modocc (talk) 18:31, 13 October 2016 (UTC)[reply]
can radiation from outer space cure cancer?
If you had cancer, could you treat it by going into outer space, which I've heard is full of high levels of radiation.
NOTE: I am not asking if this is a sensible, feasible, cost-effective or risk-free way to cure cancer. Just wondering if it could cure cancer.--Captain Breakfast (talk) 16:22, 11 October 2016 (UTC)[reply]
Radiation is such a vast, complex idea, you can't make general statements about "radiation" as though it were some tiny little thing that always does the same thing. It's like asking "Is eating good"? Eating what? When? How much? --Jayron32 16:35, 11 October 2016 (UTC)[reply]
Okay. Thank you for your exteremely helpful comment. Radiation is not "some tiny little thing that always does the same thing." Glad we cleared that up. Can any of the kinds of radiation you would be exposed to in outer space cure cancer?--Captain Breakfast (talk) 16:41, 11 October 2016 (UTC)[reply]
Jayron32 is helpfully pointing out that this topic is incredibly broad. It might take weeks of reading background science to bring you up to the point where you are phrasing your question in a way that a scientist could actually answer. But here at the reference desk, we aren't here to provide you with a definitive "yes" or "no" to your question: our role is just to point you in the right direction towards great encyclopedic resources.
Proper medical professionals rarely talk about curing cancer; they use words like "treatment," "prevention," "remediation," "remission." Even our encyclopedia editors have decided that cure for cancer ought to redirect to our article on cancer research - because this is how well-informed individuals actually speak about cancer.
So - where do you want to begin? Jayron32's advice was much briefer than mine - but he's making the exact same point: your question, as it is worded, cannot be answered with scientific rigor.
Radiation therapy works by focusing a beam of ionizing radiation onto a localized area of cancer, to kill the cancer cells. The radiation must be carefully directed so that it hits the intended target (the cancer) without affecting very much of the surrounding noncancerous tissue. Exposing the entire body to radiation at a level that would kill cancer cells would most likely kill the patient, by killing large amounts of normally functioning cells. Exposing the body to lower, non-lethal, levels of radiation would be more likely to cause cancer than to cure it. CodeTalker (talk) 16:44, 11 October 2016 (UTC)[reply]
(edit conflict) Radiation can kill cell, even cancerous ones. Dead cells don't reproduce. So yes, it "can".
Now, either the probability of that happening without killing the patient is ridiculously small, or radiotherapists with access to precise levels of radiation and focusing the rays at some places are desperately incompetent.
What Jayron32 said is actually very relevant, because (to take his example) your answer amounts to "glad that we cleared up that the safety of food depends on its type" - if you ask an imprecise question, people are not going to assume you are an expert in the subject. In addition to "it depends on radiation", I would add "it depends on cancer", because there are plenty of "cancers" out there and some of them are completely different. TigraanClick here to contact me 16:53, 11 October 2016 (UTC)[reply]
"Treat" also implies survival of the patient generally. A shotgun cures cancer quite effectively otherwise. Likewise radiation - it may well stop the cancer, the tricky bit is not making the side-effects worse than the initial disease. Marvel Comics are not a competent guide to medical physics and the therapeutic uses of radiation, even when administered via the spider-bite mechanism. Chemotherapy is already a matter of deliberately poisoning the patient and hoping that the cancer is slightly more poisoned than the rest of the patient. We have some hope that the next generation of cancer treatments will be more self-targeted themselves.
Historically radiotherapy has largely been a matter of three dimensional geometry and cooking the patient along a line through their body, repeating treatments at different angles to repeatedly dose the cancer site whilst irradiating other parts only once. This relies on radiation as narrow collimated beams, and accurate positioning relative to the patient. Neither of these would arise from the "cook in space" approach. Andy Dingley (talk) 17:17, 11 October 2016 (UTC)[reply]
Adding to what the others have said, there are many ways radiation is used in oncology. Its almost always used to cook the cancer more than the tissue we don't want to kill. The typical question is how you concentrate the radiation. Chemotherapy generally assumes that tumors get more blood flow that healthy tissue so adding a bit of radioactive material to the blood will hurt the tumor more than the rest of the body. Beams of radiation (Cyberknife) where you fire from many directions at one point are another way to get the local concentration. Yet another way is via radioactive seals (brachytherapy) placed near/around the tumor. This is common for prostate surgery. Springee (talk) 17:57, 11 October 2016 (UTC)[reply]
Nothing personal, but your terminology is incorrect. Chemotherapy refers to the use of cytotoxic drugs. Administering radioisotopes is known as radioisotope therapy. Also chemotherapy isn't really based on tumors having increased blood flow, though that does help. Rather, it's based on the tendency of cancer cells to divide rapidly. Most chemotherapy drugs interfere with cell replication, and thus affect rapidly-dividing cells more. This also accounts for their most common side effects. --47.138.165.200 (talk) 19:44, 11 October 2016 (UTC)[reply]
Total body irradiation generally involves 10-12 Gray given in "fractions" so the patient can recover from shorter term effects in between. Honestly I have not bothered to learn the exact protocol which sounds like some kind of semi-fictional horror story about the Dark Ages. The Apollo astronauts received 0.86 Gray during the outbound transit through the Van Allen belts, according to [14]; the inbound was much less though, presumably since they could use the atmosphere to slow down more at the end? So it seems plausible that a nice leisurely orbit through the Van Allen belts can deliver the same total radiation dose in as many fractions as desired, though the profile of how long each treatment takes will be forced to be longer. I don't know if that matters. I would presume there is no FDA approval or Cochrane review about doing total body irradiation using a space capsule, so there is a certain level of guesswork here. :) One good thing is that potentially the capsule may have been very well disinfected prior to launch, making recovery safer from infection. The astronaut might shield his lungs per the current irradiation protocol, and of course you'd best shield the bone marrow to be transplanted afterward! You might cure leukemia with something like this. Wnt (talk) 20:24, 11 October 2016 (UTC)[reply]
Feynman Lectures. Lecture 30. 30–1The resultant amplitude due to n equal oscillators [15]
I'm trying to check formulae 30.1 and 30.2 in Mathcad:
PNG xmcd
So according the image we see that two formulae give different graphs. But it looks like the derivation of 30.2 is correct. How is it possible?
@Username160611000000: It looks to me like one is finding R and one is finding AR. If I had to take a guess, I'd say AR is the amplitude of R, perhaps the absolute value? In any case, I notice AR (the second) hits its low points everywhere R (the first) passes through zero. Catch is, the graph makes it look like AR goes slightly negative, so I should see if that's real or not. (As it happens I just rehabilitated the copy of R I have here, so if I get a chance I'll put it to the test) Wnt (talk) 16:18, 13 October 2016 (UTC)[reply]
Thank you. Now I see that R is a projection of AR on X-axis (or x-component of the vector AR). Besides the angle OQT (Fig. 30–1) is not always equal to nφ , sometimes it is equal to (2π - nφ). When I found y-component and length of the vector, it became equal to modulus:
What matches the density of air compressed by a factor of one trillion? — Melab±1☎ 21:35, 11 October 2016 (UTC)[reply]
The density of air at ordinary temperatures and pressures is around 1.2 kg/m3, or about 830 times less dense than liquid water. Something a trillion times more dense than air would be about 1.2 billion times more dense than water, which is denser than the core of the sun (150x that of water). In fact, the only place in the universe you find material this dense is inside a neutron star. Someguy1221 (talk) 21:58, 11 October 2016 (UTC)[reply]
October 12
New Earth Like Planets
General question, The knew possible earth like planet reported in the news could be covered in water, with the current scientific methodology if this is so could we also assume it would have an oxygen rich environment or can water exist in fluid form with out producing any oxygen? 5.175.72.42 (talk) 09:19, 12 October 2016 (UTC)[reply]
We can't assume it has oxygen rich environment just because it has water. Our atmosphere is oxygen rich because early life on earth produced lots of oxygen. Fuortu (talk) 10:06, 12 October 2016 (UTC)[reply]
See Great Oxygenation Event. The Earth's atmosphere contained very little oxygen for the first quarter of its existence (despite the presence of the oceans). Tevildo (talk) 18:00, 12 October 2016 (UTC)[reply]
Is it possible through current scientific methods to see the makeup of the environment...as we do with in our solar system or is the exo-planet to far away? an aded question i know sorry. — Preceding unsigned comment added by 5.175.72.42 (talk) 11:14, 12 October 2016 (UTC)[reply]
An oxygen atmospherecan be abiogenic, if hydrogen is stripped away from the planet by solar wind. With the flare activity of young red dwarfs, this doesn't seem implausible. See Habitability of red dwarf systems for a mention of this. Here is the original paper: [16] Note it is simulation of a range of possibilities and doesn't actually say much. Wnt (talk) 11:45, 12 October 2016 (UTC)[reply]
We can often estimate an exoplanet's mass and orbit size by observing the motions of its host star. That, plus the brightness of its host star is enough to get a rough idea about its surface temperature (if one assumes it is a rocky planet). That gives us a clue about whether it might possibly be habitable for earth-like life. If the planet happens to pass directly in front of the star from our point of view, it is also possible to estimate the composition of the atmosphere by the nature of the small changes observed in the star's light during the time the planet is passing in front. Most planets don't happen to have orbits that pass in front of their host star. As far as I know there is no feasible way right now to learn about an exoplanet's composition if it doesn't happen to pass in front of host star. Dragons flight (talk) 12:09, 12 October 2016 (UTC)[reply]
Regenerating a li-ion battery?
Is it possible to regenerate a li-ion battery that has degraded due to normal use (that is, several cycles of charging and discharging)? I suppose the wikihow solution of putting the battery in the freezer does not help. However, is there an industrial scale refurbishing of old batteries? Maybe not for small smartphone batteries, but for hybrid/electric vehicles. --Llaanngg (talk) 10:23, 12 October 2016 (UTC)[reply]
Battery recycling generally involves taking the battery apart, melting down the components to separate out the valuable metals, and then using the resulting materials to build new batteries. At industrial scales, such recycling is often cheaper than buying freshly mined raw materials. However, that's not really a "refurbishment". As far as I know there is no simple process to restore the longevity of a li-ion battery. They degrade due to chemical and physical changes in the battery itself and I am unaware of any method of reversing those processes that doesn't involve scraping the battery. Dragons flight (talk) 12:17, 12 October 2016 (UTC)[reply]
(ec) The article Li-Ion#Battery life describes a variety of different ways that these batteries can degrade and there is no way to reverse them all. It is true that their life is longer if kept at low temperature and if a battery management system prevents operation outside each cell's safe operating area (max-charge, min-charge, safe temperature range). Experiments in reviving Li-Ion batteries by methods that have been suggested, such as "zapping crystal dendrites away with an electric welder" (that has been proposed to treat Nicad batteries that have an unrelated chemistry) are too dangerous due to the documented liability of Li-Ion batteries to explode. Thus the only option is to replace degraded Li-Ion battery cells with newly manufactured ones. Ideally old Li-Ion batteries should be recycled to recover their elements including iron, copper, nickel and cobalt but not much has been invested into recycling Li-ion batteries due to costs, complexities and low yield. AllBestFaith (talk) 14:28, 12 October 2016 (UTC)[reply]
"Several" discharge cycles should have no effect on the battery; it should take several hundred cycles at least for any noticeable loss of charging capacity. If you were being literal, and you have a battery that is new, it's defective and you should return it if it's under warranty. --47.138.165.200 (talk) 19:43, 12 October 2016 (UTC)[reply]
With "several" I meant enough wear and tear under normal circumstances to reduce its capacity, but nothing that would be covered by a warranty. Llaanngg (talk) 17:12, 13 October 2016 (UTC)[reply]
What's the Maximum cruise speed for Boeing 767 at 5000 ft?
And what's happening when the plane pass the cruise speed? 37.142.197.179 (talk) 12:51, 12 October 2016 (UTC)[reply]
Wikipedia has a general article on Cruise (aeronautics) which covers some of the general concepts, such as how optimum cruise speed is arrived at. That may help some with your second question. --Jayron32 13:01, 12 October 2016 (UTC)[reply]
The normal cruising height for a large jet is above 30,000 feet. At 5,000 feet the plane will have difficulty reaching its normal cruising speed. Wymspen (talk) 13:24, 12 October 2016 (UTC)[reply]
14 C.F.R. §91.117 (a) Aircraft Speed states: "Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.)." (These rules apply in the United States, but generally, almost all other nations have similar or stricter requirements).
If you happened to be near San Francisco this week, you might have seen a United Airlines 747-400 operating low and slow - here's a video of Saturday's show. The aircraft maneuvered below 5000 feet MSL at speeds between 145 mph and 300 mph (with special approval from the FAA).
A large airliner like a 747 or 767 is not designed to operate efficiently at cruise configuration at 5000 feet MSL - but it is capable of flying in that configuration.
In normal cruise flight, a 767 is operating at or below VNO. That means its flaps are up, its gear is up, and its multiple engines are configured for long-term, efficient flight; and it is not making any abrupt control surface deflections.
Had the pilots of El Al Flight 1862 known what was going on, they would have had a shot at a survivable outcome by dumping more fuel and then attempting a landing at a speed of around 200 knots. Count Iblis (talk) 17:34, 12 October 2016 (UTC)[reply]
Sorry, but... [citation needed] ? Do you make this claim because a reliable source - like the post-crash investigation report - indicated that the accident would have been survivable if the pilot(s) had done something differently? Because... if not, you probably shouldn't repeat that kind of a ludicrous claim on our encyclopedia, especially if you aren't an expert in the detailed analysis of 747 accidents.
After a major aviation accident that involves such great loss-of-life, experts study the event in great detail and publish their findings. If it is determined that different pilot-decision-makingcould have saved lives, that type of important detail gets published, and usually gets incorporated into training material. I do not believe any reputable accident-investigator believes that El Al Flight 1862 could have been made survivable if the pilots had made different decisions.
A detailed analysis of crew decision making is included in Chapter 2.5 of the Nederlands Aviation Safety Board AIRCRAFT ACCIDENT REPORT 92-11, available in English from archive.org. There is no mention whatsoever that Count Iblis' proposal - which does not even comply with the emergency-operations procedures for a 747 - could possibly have made the situation work out any better. Specifically quoting the accident report: "the possibility for a safe landing was highly improbable, if not virtually impossible" - even if the pilots had done something differently. That's the official, published opinion from a team of aviation experts - who specifically studied the accident - and know far more than you and I about 747 operations.
This is Wikipedia - the free encyclopedia that anyone can edit - but we have a standard for sourcing our claims. Just like you can't make up random numbers and facts about general science and post them in our articles, you should not post procedures, airspeeds, or analyses, if you don't know them and can't cite sources for them.
See here: "The analysis indicates that the accident aircraft was recoverable from a technical point of view. However, the required procedures to perform such a recovery are not part of current industry training practices for complex in-flight emergencies or handling qualities in degraded modes. It is therefore understandable that a successful recovery of the aircraft was highly improbable." Count Iblis (talk) 19:10, 12 October 2016 (UTC)[reply]
Thank you for citing a source. At least we can now attribute the claim, irrespective of my personal opinions about that claim.
The author of the conference-paper you cited, M.H. Smaili, has his entire thesis available at this link, hosted by Netherlands Aerospace Centre: NLR-TP-2003-392 Flight data reconstruction and simulation of the 1992 Amsterdam Bijlmermeer airplane accident. It is worth consideration. I read most of the 40-some pages, and it is true that the author of that paper does recommend your idea, including a fuel jettison and a "high-speed landing or ditch at 200/210 KIAS", and also acknowledges that this recommendation is in contravention of the ordinary emergency operating procedure.
Even still, the source you cite is a student's thesis (abridged into a conference-paper presentation). Here's my two cents: pilots should not turn to students for advice on how to fly damaged aircraft. Even very smart people - who work out math very carefully, and perform elaborate simulation - are not necessarily qualified to provide advice or instruction on the safe operation of an aircraft in any condition. The author even admits that the procedure he recommends deviates from the procedure that industry-experts recommend. For example: here are a few bits of techno-babble that you might have lost in the details: "Weight reduction was achieved by simulation of fuel jettison up to a remaining quantity for about 20 minutes of flight." "Further speed reduction below approximately 220 KIAS at flaps 1 resulted in a loss of go-around capabilities." Are you - or the author - qualified to evaluate that statement to determine the impact of those consequences? Do you believe that you could make the judgement-call between one statistically-unsafe outcome, and another, different, statistically-unsafe outcome? (For example: do you know whether it is safe to jettison fuel on a Boeing 747 when the cockpit instruments are indicating an engine fire? Do you know whether there is enough precision to dump the correct amount of fuel when an aircraft is damaged in this way? What if you inflame the fire and blow up a wing? What if you jettison all your fuel and lose all propulsion? You just made your catastrophic emergency into an even worse catastrophic emergency!) This is exactly why pilots are highly trained to follow standard procedures, even during catastrophic emergencies.
In this case, I would defer to the accident report, which found that safe control of the aircraft was a virtual impossibility.
Here's a life-tip: Go Fly. During the pre-flight brief, ask your flight instructor to demonstrate an emergency-procedure during your first flight. It will change the way you think about aviation safety. Because, at some random time during the flight, probably while you are out sight-seeing and having a great time, the instructor will simulate an emergency and do something with a small airplane that will scare the lights out of you. Surprise! You're a mile from earth and don't have an engine! How will you react?
Demonstrating, and practicing, and preparing, for emergency operation is a very normal part of flying and flight training. Just a few weeks ago, I practiced something like five or ten emergency-landings. You can even listen to me having a pleasant conversation with our air traffic controller as I repeatedly kill the engine. This stuff has to be beaten into your head during practice flights so that you do it right when you're in a real actual emergency. Don't panic. Follow the checklist. Definitely don't try anything new.
Here it says that butterflies are "able to remember the solution to a puzzle that they were taught how to solve when they were a caterpillar". How can you teach a caterpillar how to solve a puzzle? How can you even teach ANYTHING to an animal as inferior as a caterpillar? --Qnowledge (talk) 16:13, 12 October 2016 (UTC)[reply]
Insect nervous systems may be quite primitive, but that doesn't mean they don't have a capacity for learning. This source may be helpful. NorthBySouthBaranof (talk) 16:21, 12 October 2016 (UTC)[reply]
Note that the "puzzle" could be quite basic, like remembering that the red leaves are bitter and the green leaves are good. StuRat (talk) 16:39, 12 October 2016 (UTC)[reply]
These scientists. When volunteering to help at a reference desk, it's a good idea to look for references before posting. It can be hard, so I'll tell you how I did it. I remember reading the work, but forgot who published it and where. So I went to google and typed /caterpillar learn butterfly/ [17]. The top hit is this Wired article [18], and a quick skim of that gave me an author name, Weiss. Now it's just another click over to google scholar, where I typed /weiss caterpillar learn/ [19], where the mentioned PLoS ONE article is the second hit. That's how you can help provide references on the reference desk. It took me longer to type this up (~3 minutes) than it did to find the answer for OP (<1 minute), but I hope that helps. SemanticMantis (talk) 17:42, 12 October 2016 (UTC)[reply]
The famous recent work on butterfliesLepidopterans remembering what was learnt as a caterpillar is Blackiston et al. (2008) "Retention of Memory through Metamorphosis: Can a Moth Remember What It Learned As a Caterpillar?" [20] It explains in the abstract:
“
Fifth instar Manduca sexta caterpillars received an electrical shock associatively paired with a specific odor in order to create a conditioned odor aversion, and were assayed for learning in a Y choice apparatus as larvae and again as adult moths.
”
The paper is freely accessible, and include diagrams of the puzzle/challenge setup. SemanticMantis (talk) 17:37, 12 October 2016 (UTC)[reply]
Other examples of memory and learning surviving metamorphosis include -[21][22][23]DrChrissy(talk) 22:43, 12 October 2016 (UTC)[reply]
As described, this does not necessarily have to mean the nervous system carries the memory. Most notably, aversive associations have been reported to be passed on in mice through two generations. [24] I would take a guess that this involves the epigenetic alteration of specific genes closely associated with the odor reception itself, though I don't know that - what I do know is that spermatozoa don't have brains. :) Wnt (talk) 15:45, 13 October 2016 (UTC)[reply]
Yeah, the second generation mouse "memories" together with the trans-pupation "memories" form a captivating picture. You're right that sperm don't have brains, but structural content for the moths could conceivably be preserved in the Imaginal discs. SemanticMantis (talk) 16:28, 13 October 2016 (UTC)[reply]
I have traced the mouse study back to its original source here[25]. Rather oddly, hidden away in the text is a statement that pups born by artificially insemination were not behaviourally tested. This, to my mind, makes their statements dismissing observational learning as weaker than might be perceived. DrChrissy(talk) 17:01, 13 October 2016 (UTC)[reply]
User:DrChrissy Interesting, thanks. Are you suggesting that parents could some how teach pups odor aversion even when not they are exposed to the odor simultaneously? I don't think the mothers were challenged with the odor while pregnant, so that rules out in utero "observation," right? Maybe I should just dig into the design/protocol myself but I'm curious what you're getting at. SemanticMantis (talk) 19:01, 13 October 2016 (UTC)[reply]
Ah - I have just seen that in the cross-fostering study, the pups were fostered On Day 1 postnatally. This means there would have been very, very limited opportunity for observational learning. And you are correct the females were not (deliberately) exposed to the odour while pregnant. DrChrissy(talk) 19:30, 13 October 2016 (UTC)[reply]
Human travel to Mars
How are we going to shield the astronaults brains from radiation?--86.187.174.75 (talk) 17:34, 12 October 2016 (UTC)[reply]
Some good stuff at radiation protection and radiation hardening (though that second one is geared more towards protecting equipment). We don't seem to have a specific article devoted to the subject of protecting astronauts from radiation, but it shows up in a number of other areas. Matt Deres (talk) 17:46, 12 October 2016 (UTC)[reply]
You'll want to shield more than just the brain. Actually, the brain is more radiation-resistant than some other parts of the body, because (especially in adults) it doesn't contain a lot of actively-dividing cells. Human spaceflight and Effect of spaceflight on the human body may be of interest. --47.138.165.200 (talk) 20:13, 12 October 2016 (UTC)[reply]
I'd say start here: [26]. It is possible to take a portion of the radioresistance of tardigrades and put it into human cells, allowing for the possibility of gene therapy or other penetrating treatments getting Dsup to where it could protect the DNA directly. Wnt (talk) 15:48, 13 October 2016 (UTC)[reply]
Purported car that runs on sea water
I came across this recently which appears to boast that their car can run on ordinary sea water. It sounds bogus but I wanted to confirm with the experts here. This is bs right? ScienceApe (talk) 18:53, 12 October 2016 (UTC)[reply]
Yep, total bs, more precisely some mix of pseudoscience, hoax, and fraud. We have a pretty good article on water-fueled cars that explains the problems and some history, Snopes is also always a good place to check for this kind of thing. They don't seem to have a full article but their discussion thread on the topic is here [27]. SemanticMantis (talk) 18:58, 12 October 2016 (UTC)[reply]
(Sorry, I flubbed this one by skimming the source link too quickly and jumping to conclusions. Best to ignore my whole post.) SemanticMantis (talk) 03:16, 13 October 2016 (UTC)[reply]
It not purported to run on seawater, that is merely what the journalist described it as. No, in fact the nanoFlowcell is described by its inventor as running on "bi-ion liquids" which he claims was conceived by NASA decades ago (though I can find no evidence of this). If you read his description, it sounds like a relatively ordinary battery, and the water is simply the solvent for the electrolytes. If you buy his description of how it is supposed to work, the advantage of this over an electric car is that instead of recharging the battery, you simply refill the emptied electrolyte tanks. If it worked, that would certainly be a lot faster than recharging. The one part of the description that sounds extremely fishy is the inventor's claim that one side contains a positive charge, and the other contains a negative charge. Two tanks of water separated by a membrane doesn't seem like an especially good capacitor, so that doesn't seem like a winning design for a car battery. We can give him the benefit of the doubt and assume he's talking about the general way that batteries work, with chemical reactions continuously generating positive charges on one side and negative charges on the other. This description is too vague to violate the laws of physics, but it has other hallmarks of a scam. The biggest red flag is that he is going public with this project while at the same time being extremely secretive about how it works - giving general descriptions but no specifics. In my experience reading about scams, any time someone presents what is basically a magic box that does something revolutionary, but won't let you look inside, it's a scam. And believe me, this car is pretty magical. Battery design is a very hot field, and making a battery light enough to power a car any significant distance is quite a feat. The batteries currently used in electric cars run on some fairly exotic electrolytes in organic solvents or fancy solid substrates, and are the result of decades of research and development. For someone to claim he did it with something he could dissolve in ordinary water is hard to believe. The typical evolution of all of these water-fueled-car scams is to go public with a revolutionary invention, be incredibly vague about how it works so no one can point to a violation of the laws of physics, collect millions of dollars in investments, then disappear into the aether. Someguy1221 (talk) 20:37, 12 October 2016 (UTC)[reply]
I erroneously jumped to the conclusion this was the same old junk. In fact it seems to be merely conceptually similar junk, so thanks for clarifying :) SemanticMantis (talk) 21:24, 12 October 2016 (UTC)[reply]
Flow batteries are commercially available and in use worldwide. Vanadium pentoxide, from memory. Greglocock (talk) 22:12, 12 October 2016 (UTC)[reply]
We apparently haven an article on flow batteries, and apparently a number of laboratories are trying to develop ones suitable for cars. Someguy1221 (talk) 22:19, 12 October 2016 (UTC)[reply]
Any student who took college chemistry and is familiar with the Nernst equation will also hopefully remember the concept of the concentration cell, of which a flow battery is basically a highly engineered version of. --Jayron32 22:39, 12 October 2016 (UTC)[reply]
The "water dust" part sounds pretty fishy to me. I don't know what the secret ionic liquids are, but I bet whatever they are if you dump the residue from 150 liters of them on the road pretty often, the ecologists will have something to say about it. I mean, they don't even like road salt, and if this were as easy as road salt you'd think it would have been invented before. Wnt (talk) 15:53, 13 October 2016 (UTC)[reply]
It is also worth noting that if he were a real scientist, he'd use the damn right terms. I suppose he could be talking about some of the more exotic low-temperature ionic liquids, though most actual chemists I know tend to use the term to refer mostly to molten salts. Unless he means simply an aqueous solution of a salt. I'm pretty sure one of the indicators on the Crackpot index is someone who confuses basic terms from the very science he's purporting to be an expert in. --Jayron32 19:02, 13 October 2016 (UTC)[reply]
Lord, there is a year and a half old Wikipedia article on this dubious Liechtenstein company NanoFlowcell which is asking for investors on its linked to website. Car show flash, and not even close to being enough grit, and perhaps worthy of deletion. --Modocc (talk) 20:08, 13 October 2016 (UTC)[reply]
Acousto-magnetic tags
This is about acoustto-magnetic tags, particularly about the role of the second "magnetically semi-hard metallic strip". According to the wikipedia article its purpose is to offset the magnetic anisotropy within the first strip, which "makes the [first strip] respond much more strongly".
How exactly does the external field make the response stronger and what does "stronger" mean here?
Somewhere else I read that the second strip provides a "bias" which causes the first strip to vibrate at the same frequency as the external pulse frequency (58 kHz) from the detector. Without the "bias" it would oscillate at twice this frequency.
Firstly it's a "switch". By being either magnetised or not, the tag can be turned on or off. This isn't essential for all tags (some are mechanically detached, some are always active but passed around the detector by staff), but it's useful and is used here.
Secondly, it increases the sensitivity of these tags - they may just not be viable devices without. The way it works is that (all?) magnetic devices demonstrate hysteresis: the relation between applied field strength and resultant magnetisation isn't linear or even a simple mapping. However if is increased (by the nearby strip) it shifts the material's behaviour away from the point (the least linear point) to a place where the behaviour between the two is more approximately linear, or at least where the available change in (i.e. how much the reader's field coils can apply) gives a larger and more easily detectable change in . Andy Dingley (talk) 21:08, 12 October 2016 (UTC)[reply]
Thanks that argument with the hysteresis makes sense to me. However, unless I misunderstand magnetic anisotropy, this is not exactly what it says in the article, is it? Also what about the frequency argument, is it correct? bamse (talk) 22:29, 12 October 2016 (UTC)[reply]
The frequency argument is correct but Andy Dingley's hysteresis description (though relevant to magnetic recording) is not relevant to the acousto-magnetic tag.
The sentence "The magnetized strip makes the amorphous strip respond much more strongly to the detectors, because the DC magnetic field given off by the strip offsets the magnetic anisotropy within the amorphous metal." was posted by Oosacker[28] and may be challenged. I find no source for it and instead believe this explanation [29]:
"[The acousto-magnetic tag] requires bias magnet material in addition to active element material. The[magnetorestrictive]material will shrink no matter which direction the magnetic field is placed upon it. If the tag is driven with Frequency, F, it gets smaller as the magnetic field increases and larger as it's driven towards zero. This means that while it is being driven at F, the tag is trying to work at 2F, because at both positive and negative halves of the drive signal, the tag is getting smaller. To get the tag to work at F, a bias field is required. The bias is provided by a semi-hard magnetic element in the label. When magnetized, the bias prevents the active element from ever being in a zero field condition. So for an entire half of the drive signal, the tag shrinks. Then it expands for the other half. This results in an F response.
When you walk through the gate with a tag, the transmitter in the gate energizes the material and causes it to resonate at F. The transmitter then stops. The tag will continue to "ring" at F for a short period of time, and the receiver listens for that frequency. If it hears it, it knows there is a tag and sounds the alarm.
When the AM tag is demagnetized, it is deactivated. When it's magnetized, it is activated. (This is the opposite of how the deactivation of EM tags works.)"
What's the smallest nm node that's inevitable in consumer electronics (as far as we know)?
I guess I could wake up in a holodeck on a Discworld in a universe where matter's infinitely divisible at any time so nothing's inevitable but assume that unlikely shocks to civilization like that or a comet ending humanity or something don't happen. 7nm is still not inevitable yet, right? Is 10nm inevitable? When it gets to the point where manufacturers realize a full node is too hard will they start releasing ever smaller percentage shrinks just so the time between nodes doesn't accelerate astronomically or to try to take the asymptotically decelerating record from company X for awhile? Sagittarian Milky Way (talk) 23:40, 12 October 2016 (UTC)[reply]
We actually have articles on these. The 10 nanometer chip appears to be commercially inevitable. The 7 nanometer chip is more iffy, but major corporations are planning to produce them in bulk in the future. 5 nanometer chips and under are still highly experimental and it doesn't look to me like these will be inevitable until some completely new chip technology has matured, after which we'll have to reassess what's possible. Someguy1221 (talk) 23:59, 12 October 2016 (UTC)[reply]
Do T3 and T4 hormones play role in regulation of the body temperature?
I know that they play role in stimulation of the metabolism rate, growth and development and brain maturation during fetal development. but my question is on the regulation of the body temperature. (I can understand that the metabolism rate relates in such way or another to the temperature) 93.126.88.30 (talk) 00:26, 13 October 2016 (UTC)[reply]
I had high hopes for the article Thermoregulation in humans, but it doesn't seem to go into that kind of detail. I didn't watch this video here: [31]. But the title has some potential to be useful. --Jayron32 02:00, 13 October 2016 (UTC)[reply]
Unfortunately there's no information there. but thank you for your motivation to help. 93.126.88.30 (talk) 17:44, 13 October 2016 (UTC)[reply]
Are follicles the structural units for all types of glands or just thyroid gland?
I am reading about the thyroid gland now and the book states: "Thyroid tissue is composed of follicles, which are structural units of the gland". It's not clear if it refers to any gland or to the thyroid only. According to what I read here (follicular cell) it seems to be in thyroid glands only, but I'm not sure about it. 93.126.88.30 (talk) 01:17, 13 October 2016 (UTC)[reply]
Have a look at Endocrine gland, all of them are linked and have a "structure" section. While I admit it's a little ambiguous, I think using "the gland" in the sentence indicates reference to the object, in this case "Thyroid", not "glands" in general. If instead follicular tissue was the substance all glands are made out of, the sentence would make a lot less sense. Vespine (talk) 01:26, 13 October 2016 (UTC)[reply]
Just analyzing the sentence, "units of the gland" means a specific gland, to me, while "units of a gland" or better yet "any gland", would have the more general meaning. StuRat (talk) 14:19, 13 October 2016 (UTC)[reply]
Google's dictionary says a follicle is "a small secretory cavity, sac, or gland, in particular." NOAD's definition is identical. Arnold's Glossary of anatomy [32] has a similarly broad definition, as does Wiktionary [33]. Our own article Follicle_(anatomy) gives the broad sense too. Ovary has follicles. Peyer's_patch is described as a follicle. Lymphatic_system says there are lymphoid follicles in tonsils.
These links show that the term 'follicle' has a general anatomical usage, and it is clear that glands other than thyroid have sub structures called follicles. I would not assert, based on this evidence, that all glands have substructures described as follicles. SemanticMantis (talk) 15:46, 13 October 2016 (UTC)[reply]
Anatomical usage is basically descriptive Latin. wikt:follicle from wikt:folliculus, a small wikt:follis. In common Late Latin, a follicle is a little sac, like the scrotum; in anatomy, the term has since been applied at the end of a microscope. Wnt (talk) 15:59, 13 October 2016 (UTC)[reply]
Just looked at this again and tried some random searches. "Mammary follicle", "Harderian follicle", "parotid follicle" basically strike out. "Pituitary follicle" and "prostatic follicle" hit on stuff. "Sebaceous follicle" is the gland. "Salivary follicle" hits really old literature, comparative anatomy. I'm not sure though how much difference is biological and how much is cultural, basically random chance of who uses what term (also Harderian is pretty obscure, but "lacrimal follicle" picks up only junk hits also). It would take a long time to think this one through properly. Wnt (talk) 22:28, 13 October 2016 (UTC)[reply]
That is consistent with some of my research as well. Another tack is to search each article in List of glands of the human_body to see which use the term. I noted a few that did, many that did not. It's hard to rule out linguistic/cultural trends in science. I don't think we have any actual physiologists or anatomists in the house, but I'd be happy to be proven wrong on that. SemanticMantis (talk) 14:28, 14 October 2016 (UTC)[reply]
Mortality during pregnancy
What happens when a pregnant woman dies during the middle of her pregnancy? What happens when a married man dies during the middle of his wife's pregnancy? GeoffreyT2000 (talk, contribs) 16:48, 13 October 2016 (UTC)[reply]
"What happens?" is very broad. Can you specify what aspects you are interested in? Life insurance may come into play in either scenario. Maternal death is our article about women who die during pregnancy. SemanticMantis (talk) 17:10, 13 October 2016 (UTC)[reply]
See en ventre sa mere for the legal implications in common-law jurisdictions of the second case. Tevildo (talk) 18:11, 13 October 2016 (UTC)[reply]
There is also Posthumous birth although it includes cases where the father isn't married to the mother, sometimes not even alive during conception. And in rare cases of the first, there is Coffin birth. Nil Einne (talk) 07:02, 14 October 2016 (UTC)[reply]
October 14
How long would electrons take to stop accelerating if homes used DC?
Drift velocity not field propagation velocity. Is this why AC has less resistive losses? (the electrons not getting that "fast" in 1/200th 1/100th or 1/240th 1/120th of a second) Sagittarian Milky Way (talk) 00:54, 14 October 2016 (UTC)[reply]
No, the average time between collisions is orders of magnitude shorter than the switching time of AC current. Dragons flight (talk) 01:27, 14 October 2016 (UTC)[reply]
So since the voltage hardly changes in the short time between the first and second collision after the current's on does that mean both collisions are about same speed, at least for the average electron? (luck at dodging atom centers and quantum mechanics and all that) Sagittarian Milky Way (talk) 02:09, 14 October 2016 (UTC)[reply]
As I understand it, the advantage of AC for long-distance transmission is that you can use a higher voltage; therefore you don't need as high a current to transmit the same power. (Power = voltage times current, but resistive power loss = resistance times the square of current).
So you may ask, why can you use a higher voltage? Well, theoretically, you could use just as high a voltage for DC transmission, but then what are you going to do when you want to power a house? Stepping down DC voltage is complicated and costly. For AC it's easy; you just use a transformer. --Trovatore (talk) 01:34, 14 October 2016 (UTC)[reply]
Ah, I did not know your penultimate sentence. I always guessed AC was to keep drift velocities down and they didn't exceed 60Hz to avoid needing gears for the generator. Sagittarian Milky Way (talk) 02:27, 14 October 2016 (UTC)[reply]
If you are interested in those questions, you might also want to give a look at the skin effect, which is the reason why power cables everywhere have the same diameter (well, High-voltage cables are larger, but the extra section is not made of copper). TigraanClick here to contact me 07:40, 14 October 2016 (UTC)[reply]
The Drift velocity of electrons in wires is typically 1570 km/s (related to the Fermi energy concept in quantum mechanics). Please compare the values in bold as they relate to the OP's question. As derived in detail in the linked article[34]:
- 1A DC flowing in a small copper wire changes the electron velocity by 0.000 023 m/s. It's probable that the majority of electrons in a switch when it left the factory never move out of it throughout the life of the switch.
- Going from DC to AC means the change direction reverses 120 (US) or 100 (Europe) a second. Here the original electrons certainly never leave the switch or indeed any metallic conductors.
This may make it clear that electrons never "stop accelerating" and our use of them for electric power distribution has almost negligible effect on their individual paths.
Virtually all electronic equipment in the home, including the computer or phone you are using, uses DC supplies. Homes could be (have been) supplied by DC mains but AC distribution is universally preferred because of its advantages of low-cost voltage conversion by transformers, the possibility to balance generators and loads in a network by phase control, and other minor advantages in avoiding corrosion at connections between dissimilar metals, arc quenching and avoiding permanent magnetization.
The saving in cable weight by using a high voltage (low current) for long-distance distribution applies to both DC and AC. However AC conductors need more insulation to handle 41% higher peak voltage than DC for the same power level.
The choice of AC frequency is a compromise between contradictory requirements.
Lower frequency
Higher frequency
More reliable rotating generators and converters
Smaller transformers for a given power :-)
Negligible skin effect
Skin effect reduces effective cross section of conductors
Negligible power factor loss
Power factor effects require correction and over-dimensioning of generators and network components to handle extra reactive current
Negligible impact of cable capacitance
Cable capacitance hinders long-distance power transmission
Tolerable audio hum from transformers or interference from mains wiring to audio equipment
Increasingly noticeable noise from transformers (see Magnetostriction) and potential for man-made EMI
The main results of standardization are:
Home distribution in Europe and Asia: 50 Hz
Home distribution in USA: 60Hz
Aircraft on-board power distribution: 400 Hz (for low weight)
New long-distance high-power lines: DC (as new HVDC conversion equipment becomes economical). AllBestFaith (talk) 17:42, 14 October 2016 (UTC)[reply]
I think the common misconception as "electricity is the flow of electrons" is what is at heart of the misunderstandings here. Such misunderstandings come from MANY common misunderstanding of electrons as little, discretely identifiable little hard balls of negative change, bouncing around like ping pong balls. I'm not sure that level of misunderstanding is capable of being rectified in this scope of this discussion, so let's ignore it, and use the "little balls" model (wrong as it is) to show that even if we were to assume it correct, electricity is still not the movement of electrons. Electricity is the flow of energy through an electric field. Not a single one of the electrons actually has to carry the energy individually from one place to another. Even if we think of electrons (quite wrongly, but lets keep it for now) as little rigid balls; those little rigid balls don't travel down a wire as though they were marbles being rolled down a tube. Direct current is NOT all of the balls rolling down the tube in one direction, and alternating current is NOT all the little balls shaking back and forth, though some simplified models try to show it that way. Instead we should think about electrical energy being passed through a medium in the same manner that energy gets passed though the stationary ball in the roquet move in the game of croquet. See this video if you're unfamiliar. Notice how the red ball doesn't go anywhere and yet is able to transmit a bunch of energy to the blue ball. Electricity is like that: the electrons don't go anywhere in either AC or DC. They just "pass the energy" down the chain. Of course, that's still a very wrong way to think of electrons and electricity, but it's right enough to get us to reach the correct conclusion that electrons don't move. --Jayron32 18:49, 14 October 2016 (UTC)[reply]
The science behind how "Metanium" cream works
Please could you explain to me how the ingredients in "Metanium" cream actually treat nappy rash. According to this website the cream contains;
I am only interested in the scientific understanding of how the ingredients in this cream treat nappy rash. I believe this question is acceptable on the Reference Desk and does not contravene the medical advice prohibition because I am not asking for any diagnosis or treatment plan. To make absolutely clear, I do not have nappy rash and I am not asking this question in relation to any specific case of nappy rash that has ever existed. This is purely a scientific question.
"A review of the pathophysiology, prevention and treatment of irritant diaper dermatitis" [35] - seems to be a very comprehensive and relatively recent review, including titanium dioxide ointment treatments like the one you mentioned, mechanisms, and many further refs. It is unfortunately paywalled, I can provide a copy to interested readers upon request. Here [36] is a less comprehensive but freely accessible overview of topical agents in neonates. SemanticMantis (talk) 14:20, 14 October 2016 (UTC)[reply]
We currently redirect titanium peroxide to titanium oxide, but this seems invalid, as it apparently contains a true peroxide group. Actually, the combination of this peroxide + the organic chemicals in this mixture leaves me a little bit surprised it doesn't go boom... Wnt (talk) 15:57, 14 October 2016 (UTC)[reply]
What's larger, follicle cell or parafollicle cell?
it's not clear to me if the follicle itself is cell or something which composed of many epithelial cells 93.126.88.30 (talk) 19:27, 14 October 2016 (UTC)[reply]
