User was blocked for a year as User:cuddlyable3 sock and is back here correcting people's misspellings as soon as unblocked--off to see a match, will SPI when I get back
:4)In the 1800's it was finally fully realized that the earth was generating a magnetic field with it's poles close to the axial poles, and that hence the earth itself is analogous to a giant magnetic bar with its south pole near the north axial pole, and vice versa.
:4)In the 1800's it was finally fully realized that the earth was generating a magnetic field with it's poles close to the axial poles, and that hence the earth itself is analogous to a giant magnetic bar with its south pole near the north axial pole, and vice versa.
:[[User:Medeis|μηδείς]] ([[User talk:Medeis|talk]]) 17:35, 24 September 2015 (UTC)
:[[User:Medeis|μηδείς]] ([[User talk:Medeis|talk]]) 17:35, 24 September 2015 (UTC)
:::<small>English grammar note: the [[Apostrophe]] punctuation mark is useful to mark an omitted letter as in the contraction of ''it is'' to ''it's''. English provides a consistent set of posessive ''personal'' pronouns that allow one to write ''my poles, your poles, his poles, her poles, its poles,'' etc. in which no apostrophes are required, and to split arbitrarily any of these pronouns by adding an apostrophe serves no good purpose. (In linguistics the singular [[Grammatical person]] comprises '''I, you, he, she''' and '''it'''.) [[Special:Contributions/84.209.89.214|84.209.89.214]] ([[User talk:84.209.89.214|talk]]) 18:16, 24 September 2015 (UTC)</small>
== what exactly is the sense of this kind of a Tractor [[Road-rail vehicle]]? ==
== what exactly is the sense of this kind of a Tractor [[Road-rail vehicle]]? ==
Revision as of 22:52, 24 September 2015
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.
Why don't people use jetpacks? Because the tech exists, as I understand it.
Are the main problems basically to do with accidentally setting your legs and ass on fire and/or running out of fuel in mid-air and dropping like a stone? Anyone able to explain in layman's terms? Thanks. -84.51.162.182 (talk) 01:39, 20 September 2015 (UTC)[reply]
See risk analysis. Most air-bound travel systems (aside from commercial airlines, which are very safe because of well-established safety protocols and improving control systems) suffer from the problem of providing very little benefit in terms of improved travel times/costs coupled with catastrophic failure modes. In other words, the risk associated with death from failed jet pack isn't worth the marginal improvement in mobility over ground-based methods. --Jayron32 01:43, 20 September 2015 (UTC)[reply]
Considering how much danger hobbyists' drones are causing, imagine how it would be with people themselves flying around. ←Baseball BugsWhat's up, Doc?carrots→ 01:54, 20 September 2015 (UTC)[reply]
I agree that they aren't practical on Earth, but they seem better suited to space. See astronaut propulsion unit. StuRat (talk) 02:59, 20 September 2015 (UTC)[reply]
Most problems have already been mentioned, and most apply to the "Why are there no flying cars" queston, too.
Fuel cost
In currency; the average citizen can't afford flying.
In weight; you can only lift so much (MythBusters came really close to flying with a "helicopter pack" but they didn't actually take off – imagine how much worse a lot of fuel would make the situation) Consequence: you can't fly for long (a minute or two in most cases).
Traffic. While one would think another dimension would provide infinitely more space, that's not true in practice. The point of flying is to land somewhere, so there's a lot of traffic near ground level (although it's less of a problem away from the endpoints). Look at road traffic, and then think about how chaotic airspace would be if all those guys were flying around! Air traffic control is a huge task even if the flying personnel are few and well trained.
Situational awareness. You have to watch an entire hemisphere around you to avoid collisions, and that's if everybody agrees to fly forward, no aerobatics.
Speed and accidents. Jetpacks are quite slow and about as safe as a motorcyclist, if not less. Even collisions at low speeds (about 10m/s, 36kph, 22mph) are severe if not fatal. Next point down the list only adds to it.
Fail-deadly. What happens if your jetpack breaks down, or runs out of fuel, in flight? You don't grind to a halt, you're going down, fast (and then you grind to a halt – messily). What happens if two collide? The same, times two. BTW, in dense traffic patterns, there's quite a risk of running into other flyers on your way down. Atmospheric Kessler syndrome.
To make a long story short, the helicopter is about as close as we can get to a flying car (decent safety and fuel capacity/economy, high unit prices lead to limited numbers which lead to manageable air traffic), and jetpacks or air-cycles are pretty much sci-fi dreams. - ¡Ouch! (hurt me / more pain) 07:11, 21 September 2015 (UTC)[reply]
For an entertaining (and to some degree harrowing) fictional treatment examining the implications of freely available jet pack-like technology (actually anti-gravity harnesses), see Bob Shaw's novel Vertigo aka Terminal Velocity. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 13:34, 21 September 2015 (UTC)[reply]
I should point out that the article says there actually has been a 9-minute jet pack built, allowing someone to actually cross the English Channel with one, which is definitely a lot better than the 30-second curiosities I've read about. Since they say that engineering small, light jet engines is an issue, I suppose that better materials and fabrication technology might allow some further progress on this front. Still... until you can actually go somewhere with one, all the other good arguments not to use them aren't even relevant. Wnt (talk) 23:40, 23 September 2015 (UTC)[reply]
I have to disagree with you there. If they were perfectly safe, they would be popular just for entertainment purposes. At one time, hot air balloons, tethered to the ground, that just went up a few hundred feet and then landed in the same spot, were quite popular at county fairs, etc. StuRat (talk) 23:44, 23 September 2015 (UTC)[reply]
You may have a point there - I was thinking of a slightly different philosophical concept for "use". As entertainment, clearly safety can be improved if it has something similar to self driving car software. Which brings us to propulsion. Electric cars (especially the Tesla brand) have been becoming known for being able to put on bursts of power comparable to gas-powered vehicles. Can you make an all-electric jetpack, powered only by batteries, that releases relatively mild heat? I have this image in my head of the Horsey, a small jetpack given as a present to children, that has a big red button on the front; if it's safe, it lifts the child about six feet in the air, to see over the heads of adults in a crowd, before automatically landing again. Such a thing would need many & various thrusters I suppose, making it less efficient, but still it ought to be good for a few hops before the power runs out. Wnt (talk) 12:40, 24 September 2015 (UTC)[reply]
why does the clock of Ahmed Mohamed has so many cables and looks like a bomb?
I can find only pictures in the internet where is his clock shown in a case and it really looks like some kind of a bomb... But tell me, what can his clock do, what a Rolex doesn´t? I can´t believe that all this cables are only to show the timer at the display. This clock must be able to do something, what a rolex doesn´t. What is it? Has somebody of you seen his clock working?--Hijodetenerife (talk) 21:47, 19 September 2015 (UTC)[reply]
It looks like what you think a bomb should look like, because you've seen pictures of "bombs" with leads sticking out of a timer, connecting it to explosives. This kid has created this clock from a few bits he's thrown together which he found at home. If he'd have found the bits to make a Rolex at home, then no doubt he'd have created a Rolex. Why shouldn't anyone make something out of what you find at home? You can make a oommunications system out of two tin cans and some wet string, you know! --TammyMoet (talk) 09:05, 20 September 2015 (UTC)[reply]
I agree to this. I have also seen in movies always bombs in a suitcase.--Ungerechtfertigter Sperrer (talk) 08:21, 21 September 2015 (UTC)[reply]
How do you mean it has "so many cables"? Here's an image of the clock with the parts labeled. There's a cord that plugs into the wall, a pair of wires from the transformer to the mainboard and a pair of wires to the battery connector. Oh, and a flat cable to the display. It looks like the minimum needed for this type of clock. You do understand that cables need to be in pairs to transmit power?
As for looks like a bomb: it doesn't. If anything it looks like the kind of prop used in movies and TV shows to represent a bomb. [1]Sjö (talk) 09:37, 20 September 2015 (UTC)[reply]
a pair of wires from the transformer to the mainboard - why the hell should a clock really need a mainboard like a Macbook?--Ungerechtfertigter Sperrer (talk) 08:21, 21 September 2015 (UTC)[reply]
You have posted pictures of regular damn bombs from a tank or airplane, Ahmed Mohamed has a suitcase and we all have seen bombs inside of a suitcase: (for example Rush Hour, Speed and all this movies, I can recommend) - a timer and C4. Simple, right? And like this way this clock looks like a bomb, only C4 is missing to be honest. I don´t understand your pictures, is that a joke?--Ungerechtfertigter Sperrer (talk) 08:21, 21 September 2015 (UTC)[reply]
Oh, I see! I posted real pictures of real bombs, whereas your idea of what a bomb looks like is based on fake bombs in fictional movies. My bad for giving an answer that's based on reality and not make-believe.
"And like this way this clock looks like a bomb, only C4 is missing to be honest."
Oh, I see! This clock looks like a bomb, except it doesn't have the one and only essential component of any bomb. Similarly, the Pacific Ocean looks like the Himalayas--only water is missing. Also, a grassland looks like a jungle--only trees are missing. --Bowlhover (talk) 09:13, 21 September 2015 (UTC)[reply]
I also would say, that just C4 is missing, exactly this kind of suitcase bomb I was thinking about, Like this and not this pictures what you have given...--Hijodetenerife (talk) 18:46, 22 September 2015 (UTC)[reply]
Yes, that image is not of a real bomb (here is another page from the same website). Anyway, a fake bomb like the one in your image has something to represent the explosive. That's one of the biggest differences between Mohamed's device and a "movie bomb". Of course, the difference between his device and a real bomb is even bigger as Bowlhover showed. Sjö (talk) 19:57, 22 September 2015 (UTC)[reply]
Disclaimer: The Refdesk doesn't give advice -- no, we can't suggest you take apart your alarm clock, because you might get arrested as a terrorist! Wnt (talk) 11:20, 20 September 2015 (UTC)[reply]
It isn't directly relevant but may be worth mentioning that no one involved in this situation seems to have ever believed that the clock might actually be a bomb. No one called a bomb squad or evacuated the school. -- BenRG (talk) 21:56, 20 September 2015 (UTC)[reply]
Please tell us more! I know only he got arrested in the school but I have really not heard who took the clock and who called the Police. --Ungerechtfertigter Sperrer (talk) 08:21, 21 September 2015 (UTC)[reply]
The charge was a "hoax bomb." They knew it wasn't a bomb but the question is about intent. Most threats including bomb threats are not real but that doesn't mean the provocateur has not committed a crime. Even if he play-dough with wires in it, that wouldn't make it a bomb either but the same reaction (or harsher). "It's a clock with play-dough." This is basically a zero-tolerance policy and applies to all kinds of innocent items. A second-grader was suspended for chewing his pop-tart into a shape of a gun and pointing it at kids. Nobody is afraid of the pop-tart but he still got suspended. And everyone is familiar with "joking" policy at a TSA checkpoint - joke and you don't fly. --DHeyward (talk) 04:30, 21 September 2015 (UTC)[reply]
There is one rather careful analysis out there: here (v.slow right now) - which conclusively demonstrates that the kid did not "invent a clock" or "design a clock" or even "build a clock". What it seems that he did was to take an existing electric alarm clock (a circa 1986 Tandy model PICTURE HERE), remove all of the 'guts' from the case - and dumped them into his lunchbox. The evidence for this is in the silk-screened serial number on the circuit board which matches the Tandy clock - and the obviously identical display. The original clock had a small mains transformer and a 9v battery backup - both clearly visible in the photo of the clock in the lunchbox.
Clearly, this is something that didn't take the kind of intelligence that's gotten MIT "interested in him" or the Whitehouse to invite him to show his "invention" to the president - he's claimed to have designed and built the clock - and evidently managed to fool a lot of people.
This news does rather change the dialog. We no longer have "genius kid is misunderstood". What this now boils down to is whether he intended to try to make his teacher/classmates believe that he'd invented something (when he evidently had not) - or did he really intend it to look like a bomb? We can't know what was in his head...and his fate depends entirely on which of those two things it was. All we really know is that he didn't invest a lot of genius brainpower to do it...any kid with a screwdriver could have done this. If he gets a free pass into MIT for doing this - then all of the people who don't get into MIT should be seriously pissed!
Agree with Steve. See also also another analysis here [2]]. It seems the parents are associated with CAIR, who is an organisation with political goals and this event certainly has had a effect that serves CAIR's general purpose. It also seems that the school and police followed the rulebook precisely, (maybe too precisely to some people's taste). --Lgriot (talk) 14:13, 21 September 2015 (UTC)[reply]
Yes, and my parents are "associated" with the country of China (even though I am not), which generally believes in science and technology. I've also brought electronic projects to school and work before. Therefore, me bringing completely innocuous electronics that look nothing like a bomb must be an influence operation designed to further Chinese goals. The operation would only work in the unlikely case that the one teacher who accidentally discovers my device happens to have no IQ points. --Bowlhover (talk) 17:28, 21 September 2015 (UTC)[reply]
Fair enough, it is very possible that this boy was not being manipulated, at first. But now it certainly does look like CAIR have taken control of the family. I don't know whether CAIR was involved before the event, and his motives for removing an alarm clock from its case and pretend he had build it remain unknown. Anyway, this discussion is not a science question any longer. Should we hat? --Lgriot (talk) 20:49, 21 September 2015 (UTC)[reply]
Breitbart isn't a reliable source which makes the second analysis somewhat questionable. Sjö (talk) 04:42, 22 September 2015 (UTC)[reply]
I think given how politicised this has become, there's a fair chance we will never know what really happened here. But we should also be careful with not overestimating what we do know.
Saying the child "pretend he had build it remain unknown", is not sufficiently supported by the evidence. "pretend" implies there was intentional disinformation, yet as even Dawkins has acknowledged, we are referring to a 14 year old child and even though it may be a little odd for a 14 year old with a good level of English to call the clock an invention or saying he built it when it appears he mostly disassembled an existing clock, we don't know what was meant my these statements. Also, AFAIK, we don't know, and may never know, precisely what was said, for example, to the engineering teacher about the clock, and it seems a little strong IMO to say he "pretend"ed he built it based on statements given after the shitstorm, even if it happens he did knowingly mislead after being overwhelmed by the attention.
Also, we should remember that whatever the politics of the parents, we can't assume their actions are mostly a result of any political leanings, as opposed to an obvious desire to protect their kids (whether or not their actions are good or achieve that).
P.S. Given how litigious things can be in the US, am I the only one surprised neither teacher apparently made a fuss over there being potentially exposed live wires on this device which the kid was apparently plugging in to show people? Well it's possible the engineering teacher did say have concerns about this, I'm not sure if we know precisely why they said the clock should be kept in the backpack.
Although the most surprising thing to me was to learn that it's apparently somewhat common in the US, unlike what's shown in TV shows which admitedly are normally set in New York or perhaps California, that the police can detain a child and question them about their alleged offending without an adult or someone to represent the interests of the child present. [3][4]. Seems a little odd to make such a big deal about the Mirandi Warning, but not worry about whether the person is likely to understand it all. As far as I know, in NZ it's generally expected an adult will be present to help the child [5].
Admitedly there was dispute over whether a parent was specifically asked for which I believe normally should be granted, and other aspects over how this was handled [6] although I appreciate this is complicated by the fact police can't release all details due to confidentiality requirements. I'm presuming of course there was the intention that the questioning would potentially lead to a charge, and also as BenRG and others have said, no one believe there was an imminent threat.
@Nil Einne: I am not sure which is worse: that he was trying to mislead when he said "invention" or that, at 14 year old, he doesn't know the meaning of the word "invention". Is it a worst insult to be called dishonest or very stupid?--Lgriot (talk) 15:18, 24 September 2015 (UTC) [reply]
@Nil Einne: I have to say the same thing crossed my mind - as a matter purely of school policy, I'd have thought there'd be some kind of "live wires" clause. I mean, if a kid came into school carrying a yanked-out electrical cord with a plug at one end and two bare wires at the other, a teacher might rightly be concerned what might happen. And admittedly, the criminalization of even the most elementary kid stuff in the U.S. creates a position where such a thing - terribly - can become a police matter. However, that is always wrong, whether it is a fistfight or a threat or anything else, and where discipline is concerned, part of a well-run school is that those who show competence and have a reason should be allowed to bring things that have a mild level of danger associated with them. Indeed, American schools used to be known for their rifle teams, which the students would take into the bus properly stowed unloaded in cases; though perhaps that is a bad example since the kids could end up harming their hearing. Wnt (talk) 12:48, 24 September 2015 (UTC)[reply]
It is worth noting that the police / local government declared they were not going to prosecute the kid the morning after this hit the news. Their statement essentially acknowledged that Ahmed had never intended any harm (intend to create fear is one of the required elements for a "hoax bomb" charge). Dragons flight (talk) 21:09, 21 September 2015 (UTC)[reply]
An electromagnet consists of a coil through which a current passes. This can be made more effective by putting a metal core in the coil. But what if you use a magnet for a core? Would that make any sense? And could you then (partially) de-activate the magnet by passing a 'counter-current' through the coil? Probably a useless thought, but I was just wondering. DirkvdM (talk) 10:26, 20 September 2015 (UTC)[reply]
This is the basic principle of the self-keeping relay - no article, but see Relay, and search for the term more generally. Tevildo (talk) 10:56, 20 September 2015 (UTC)[reply]
Ah, interesting. I was indeed thinking about a switch. Knowing very little about electricity, I came up with this, but thought it was too silly. Still, it intrigued me, so I asked. Turns out it's not silly at all. Thanks. DirkvdM (talk) 15:59, 20 September 2015 (UTC)[reply]
Wouldn't you know it; someone asked a question about something I spent twenty years studying and repairing. Alas, I can't find online an explanation as clear as the training materials that taught me in the 1970s, though this BSTJ article covers it for engineers who already have the engineering background of both relays and the somewhat related magnetic core memory technology. But yes, millions of these "ferreed" and "remreed" magnetic crosspoints were built, and they worked, simplifying terribly, by applying a brief current pulse in the coils surrounding the crosspoint. Each of the millions of crosspoints was a tiny and very simple magnetic latching relay. Hmm; ought we make redirects? Jim.henderson (talk) 13:18, 24 September 2015 (UTC)[reply]
Note that the link in the title redirects to "magnetic water treatment", which I don't think is the same thing. Here's a link to what I mean:
[7], which appears to be a production model, not the theoretical magnetic model. It boasts it can take the excess minerals out of hard water without adding salt. So, does it use a positively charged plate and a negative plate ? If so, wouldn't the plates need to be frequently replaced, and wouldn't hydrogen and oxygen also be produced by the electrolysis of water ? StuRat (talk) 14:23, 20 September 2015 (UTC)[reply]
If you ignore the marketing junk, at about 1:50 the video in your link suggests the device uses sonic waves to stop calcium adhering to pipes and appliances.
I have doubts that the device works anywhere near as good as the video claims (if at all), particularly all the claims about the water feeling "silkier" and reducing eczema, skin feeling smoother etc, but I don't see where it "boasts it can take the excess minerals out of hard water without adding salt".
On the contrary, the video seems to imply the calcium and magnesium ions aren't removed, it specifically mentions them being "healthy" and the device being an alternative to water softening (point blank).
The text also compares it to water softeners and "non-intrusive to the water" (whatever that's supposed to mean, but I guess anything reducing the calcium and magnesium ion concentration could be consider intrusive).
The closest seems to be "solves hard water problems without the need for chemicals, salt or maintenance", but that says "problems", which seems to imply it's supposed to solve the problems caused by hard water, rather than hard water being a problem that needs to be solved (i.e. it's making the hard water soft).
Wow, sounds like a total scam. I'm surprised it would be sold at a reputable big box store. I just took "silkier" to be marketing talk for "fewer minerals", as soft water could be described that way ("greasier" or "slimier" might be less charitable ways to describe it). StuRat (talk) 15:10, 20 September 2015 (UTC)[reply]
Walmart sells homeopathic 'medicines', Target sells homeopathic 'medicines' for your pets (good luck with the placebo effect there!). Our local HEB supermarket sells those foot pads that "draw toxins out of your body through the soles of your feet". Home depot offers free water test kits where the water isn't tested at all, but instead they use your zip code to give you a generic result and collect your name and address so they can spam you with water softener adverts from now until eternity. Where exactly are you finding these 'reputable' big box stores?!? SteveBaker (talk) 13:24, 21 September 2015 (UTC)[reply]
I found [8] which talks about several different types of these products, confirming my suspicion they're all basically scams. While it doesn't talk about the Scale Blaster in particular, it does talk about Scalewatcher which appears to advertise a similar principle of using sonic waves.
There are also ones claiming to use an EM wave. And of course all the magnetic ones our article talks about, which have been scamming people since 1998 [9] and probably long before. Most sources do talk about these magnetic ones which seems to be most common and definite bullshit (the alleged wonders of magnetic crap are so common, I was fairly sure of this before even reading even our article).
I had a strong feeling the Scaleblaster was the same, but it's useful to establish how the device is claiming to work (if they do claim a method), otherwise supporters and salespeople will just claim "sure the magnetic ones are bullshit, but our ones...".
Notably, the science part of their website just repeats the same crap as in their video with no evidence of studies or anything supporting even the basic claim of sonic waves reducing adhesion [10]. (There's also IMO a strong implication the calcium is semi permanently alternated to be non-adhesive ala homepathy etc, rather than just a temporary effect in water that is significantly affected by the sonic waves.)
This is perhaps one area where ScaleBlaster are "smarter" than Scalewatcher. Unlike Scalewatcher who claim to work by Magnetohydrodynamics, Scale Blaster just mention sonic waves and reducing adhesion, which sounds bullshit but there's no principle people can easily check to confirm it is. They also avoided such obvious junk as "The signal consists of a frequency modulated (FM) wave form within the audio frequency (AF) bandwidth. This inaudible sonic frequency signal...".
I would certainly bet money against this being legit; nonetheless, I can think of a hypothesis by which such an approach might make sense. Suppose your source of hard water contains some small crystal nuclei - in other words, it is heavy in calcium-magnesium, but there's some little flecks of Ca/MgCO3 in it. Then if you could use sound to break up all the flecks, it is possible (definitely not certain) that this would hinder the growth and adhesion of calcium deposits, because the crystals would grow more slowly. Caveat being that a metal surface might nucleate crystals all on its own; I have no idea whether stray mini nuclei in solution have anything to do with it at all. But even if I see this theory written up in a water conditioning project, I'm just going to assume they're chiselers plagiarizing me, unless I see some pretty impressive data in a real scientific journal to back up their claims. Wnt (talk) 15:49, 20 September 2015 (UTC)[reply]
@ User:StuRat and the others posting here. The advertisement did not boast it can take the excess minerals out of hard water. It states and I quote: “prevents lime scale deposits in household pipes” ( not a 100% in the real world I will grant you but better than nothing). These devices have been used in industry for years and industry does not go in for the pseudo-science that some here are suggesting Water purification using magnetic assistance: A review. The little red & black terminals on that box go to a coil wound around the pipe. The magnetic field interferes with nucleation that normally allows crystallization of calcium carbonate (scale). So that the foreman can see that the device is still working, the coils are wound around a non-metallic plastic transparent pipe. The internal surface of the pipe going into the coils gets coated with crud and the out flow surface stays cleaner. Does any one think that the night-watchman keeps cleaning out the out-flow when everybody has gone home for the evening – I think not! In yesteryears these conditioners ran on thermionic tubes which made them very expensive and out of the reach of the ordinary John Doe. Now they are cheap and affordable. Whether the aforesaid example works as advertised I don't know but it is not pseudo-science.--Aspro (talk) 17:14, 20 September 2015 (UTC)[reply]
I think we already established that the device doesn't claim to remove excess minerals for hard water. However we also established the unlike some devices, this device does not claim to use "magnetic assistance", it claims to use sonic waves.
Note that it also doesn't claim to simple reduce scaling by a small percentage, it claims to eliminate it as your own quote shows. Or more clearly "Lime scale will no longer form in the pipes or on equipment that comes in contact with hard water. This results in the lowering of the saturation level of hard water, so that new lime scale is prevented and any existing scale is removed."
Scaleblaster evidently do make some magnetic devices for industrial use. But the possible effectiveness of some industrial magnetic devices for a specific purpose i.e. reducing scaling, tells us nothing about the effectiveness of a device which doesn't even use magnetic fields, and for other purposes.
The claim of the magnetic devices reducing scale may very well not be pseudoscience, but the other claims do appear to be, that's why many sources rightfully call them so. Beyond the two I included above ([11][12]), there's also [13][14][15][16][17][18][19] and many more. (This isn't that different from acknowledging that increased vitamin C consumption whether via supplements or fresh fruits will have some benefits from people who are deficient, but claims like it will cure cancer are largely pseudoscience.)
In fact, if you take a careful read of those sources, not all of them are really talking about the other purported effects. There's quite strong scepticism about whether the basic claim namely in reducing scaling really happens much even with the magnetic devices. The sources mention problems with some of the published science such as poor controls (e.g. failing to establish that it's actually the magnetic field, instead of something about the redesign required to install the device or construction of the device which the water passes through that reduces scaling), as well as the fact that the number of published science on negative results tends to outweight the positive.
One other big problem with the field already discussed is the tendency of manufacturers to come up with highly exaggerated claims of effectiveness, and bullshit other myriad benefits particularly for residential devices. As well as manufacturer's absurd claims of how their devices work rather than simply saying they don't know, but here's the high quality published evidence they do. Funnily your own source says "Owing to several parameters responsible for de-scaling, the superiority of one mode of operation over another is therefore difficult to predict". But of course if someone claims their device works, they should be able to come up with some evidence of how well their device works and predictions don't matter any more. There should be some industrial standard or several if some devices are more effective in differing circumstances, even if just defacto ones for how to compare the effectiveness of these devices, but apparently there isn't.
So even though certain magnetic treatments may reduce scaling in certain circumstances, there's a good chance even many of the industrial ones don't actually work much. Let alone the residential devices not all of which even claim to use magnetic fields (like the one discussed here which just to repeat for the final time, claims to use sonic waves).
? where did StuRat's example claim to use sonic waves ? ScaleBlaster-Deluxe. That’s the sort of misdirection that pesudo-skeptics love to use. Oh, and bye the way, thanks for all your links to other psudo-skeptic sites. Comming now to some of your Quote: One other big problem with the field already discussed is the tendency of manufacturers to come up with highly exaggerated claims of effectiveness. Now My Question: Have you ever achieved the milage per gallon form your automobile that the manufactures claim? Which pot or kettle are you calling black? Quote: This isn't that different from acknowledging that increased vitamin C consumption whether via supplements or fresh fruits will have some benefits from people who are deficient, but claims like it will cure cancer are largely pseudoscience. Refer you to Reductio ad Hitlerum. Your playing the "playing the Nazi card" by referring to something unconnected. Quote:The sources mention problems with some of the published science such as poor controls. But of course if someone claims their device works, they should be able to come up with some evidence of how well their device works On this point Nil Einne may have come up with something that save us tax payers a lot of money. Military aircraft are fitted out with very, very expensive ejector and parachute systems. However, these have never been subjected to any good randomized controlled trials. Therefore, the military contractors (based on the thinking in the posts above) are probable ripping us (the tax payer off) and we should have them all removed until the self appointed psudo-skeptics are satisfied that they work as advertised. Would any of pseudo-sceptics like to volunteer to be the dummies in the aircraft without exit systems or would they about-face and claim they are really an unrepresentative cohort – all of a sudden. --Aspro (talk) 13:01, 21 September 2015 (UTC)[reply]
We do use ultrasound for cleaning things like jewelry - so it doesn't seem immediately impossible that ultrasound might clean the calcium deposits from your pipes. Which is something that a hypothetical scammer might rely on you to remember.
However, the issue is with attenuation and reflections. The amount of power they use would have to be low enough to avoid cavitation in the water - because that would erode your pipes, which would be a seriously bad problem. It appears that this would limit them to using no more than 10 watts per square centimeter of pipe cross-section. Attenuation gets to be more of a problem with higher frequencies - so it seems likely that they'd want to pick a frequency that's just high enough to avoid bothering people and pets. I couldn't find a number for attenuation in water - but several papers concerning the attenuation of ultrasound in the human body should give us a 'ballpark' figure - which is 0.5 dB/cm/MHz. So at 1MHz, you get 0.5dB per centimeter. I'd bet that most houses have pipe runs over 10 meters, so there must be around 500 dB of attenuation in some parts of the house...if just 10 watts go into the pipe to avoid cavitation, then at the far end of the pipe, there's negligible energy left to do any cleaning.
Even if there were enough energy somehow - then we'd have to think about how our pipes are made. Most pipes these days are soldered copper. The very worst thing for destroying solder joints is vibration. How would those solder joints stand up to ultrasound that's powerful enough to remove calcium? How will the rubber/plastic washers in your faucets and toilets survive?
We might maybe hypothesize that the pipes act like some kind of wave-guide to prevent some of the sound attenuation - but what about when the pipe opens out into your hot water tank?
Also, sound waves suffer interference - with all of the 'dead ends' in the pipes because of faucets and toilet fittings that are currently turned off - the sound waves would reflect back down the pipes...what effect would that have? For sure you'd get 'dead' zones where the sound waves were cancelling out and your pipes would still get blocked.
Cavitation is only a problem on a surface where the energy during the implosion is high enough to pit the material. The device mentioned does not use sonic but a magnetic field so this reply is moot.--Aspro (talk) 13:55, 21 September 2015 (UTC)[reply]
Above here, we're talking acoustics - not magnetics. With non-magnetic water flowing through non-magnetic pipes and leaving non-magnetic deposits...it's kinda hard to see how magnetism would do a darned thing...unless you have a strong enough field for paramagnetic effects to happen (and you don't have that much field strength, for sure). With an acoustic actuator, the copper pipes are the surface that the cavitation would occur at if the power was sufficiently high - and they would erode as a result. SteveBaker (talk) 20:15, 21 September 2015 (UTC)[reply]
The OP's question is about "magnetic water treatment”. I don't know about what the above and you're talking about either, so keep it to yourself ;¬) --Aspro (talk) 20:48, 21 September 2015 (UTC)[reply]
September 21
What is the lifespan of leukocites?
I read on the book Basic "Medical Laboratory Techniques" (p.100) that "Leukocytes have varied life spans, from a few days to several years." Is that right? When I read our article I saw that is years for a memory cells. What does it mean "years"? years can be 2 as well as 80. I would like to get information about this issue. Thank you. — Preceding unsigned comment added by 37.73.202.15 (talk) 01:57, 21 September 2015 (UTC)[reply]
That much variation makes me think they have no fixed lifespan, but rather survive until something kills them. So, if this is the case, there might be no maximum lifespan, other than the maximum lifespan of the organism (and I suppose they might get around that as the result of transfusions). StuRat (talk) 03:51, 21 September 2015 (UTC)[reply]
One study reported lifespans of at least 17 years and half-life of 11 months for effector CD4+ T cells. They looked at HIV infected cells, don't know if the virus may have effected the life-span... Ssscienccce (talk) 10:54, 21 September 2015 (UTC)[reply]
If my understanding is correct, memory B cells and memory T cells are where active immunity is "stored", so that implies they can live at least as long as the organism they're a part of, since immunity can be lifelong. --71.119.131.184 (talk) 18:27, 21 September 2015 (UTC)[reply]
Not if they can reproduce to form two daughter cells with the same "memory". StuRat (talk) 22:32, 21 September 2015 (UTC)[reply]
That's true, but I believe they only divide when stimulated, either directly by antigen, or indirectly by other immune cells. If not activated, they just sit around in the body. This is why you can lose immunity, because eventually all the memory cells for a particular antigen may die or become senescent. Again, I think this is correct based on what I've read, but I'm not an expert. --71.119.131.184 (talk) 00:03, 22 September 2015 (UTC)[reply]
Diagnosis of schizophrenia (critique of the diagnosis)
There was a article with a name similar to the above that disappeared from the Wikipedia several months ago. It was an article critical of this psychiatric diagnosis, and deservedly so, since there is a substantial amount of scientific evidence and scholarly writing to put the construct in doubt. I would like to know what happened to the article (if it was deleted, if it was renamed) and the process involved.Spinheel01 (talk) 04:03, 21 September 2015 (UTC)[reply]
Thank you for responding. Those two articles are completely different from the missing one and that is my concern. The missing article, which cited numerous peer-reviewed publications, presented a critical view of the psychiatric diagnosis and the DSM in general. If this page is gone, proponents of the prevailing biomedical approach will have successfully purged the alternative perspective from Wikipedia. I thought this type of bias and censorship is exactly what Wikipedia, as an open encyclopedia, was designed to prevent. Spinheel01 (talk) 14:01, 21 September 2015 (UTC)[reply]
Not every opinion someone holds is Wikipedia-worthy. Wikipedia has rules such as WP:FRINGE and WP:MEDRS upon what's allowed as medical claim. This is "The free encyclopedia that anyone can edit." It isn't an "anything goes" forum for crank science (see WP:ABIAS). Tgeorgescu (talk) 22:20, 21 September 2015 (UTC)[reply]
I don't think it is controversial or fringe to argue that schizophrenia is a social construct. What counts as AIDS and what counts as pre-AIDS HIV is partly arbitrary but that doesn't mean AIDS isn't any less real or deadly. The disease epilepsy is also a catch-all diagnosis for many different unrelated things but it is still real. Sexual orientation is hard to define and is a human invention, not any less real. Of course we can debate things like Szasz and the right to be different when it comes to schizophrenia but that's unrelated. Andrea Carter (at your service | my good deeds) 23:30, 23 September 2015 (UTC)[reply]
There is, as you point out, a difference between socially constructed and bogus. It is true that the criteria for diagnosing schizophrenia were arrived at through medical consensus, which is a social process, but that does not mean that the diagnosis would be bogus nor that treating schizophrenia would not help patients. Tgeorgescu (talk) 14:39, 24 September 2015 (UTC)[reply]
I have reviewed the Wikipedia rules cited above and I reject the claim that the article in question should have been removed based on these criteria. First of all, the material referenced numerous articles that were published in established, peer-reviewed journals or books printed by reputable publishers, including university-affiliated presses. Second, much of the information reported was secondary research culled from original articles published in prestigious, mainstream psychiatric journals (e.g., American Journal of Psychiatry, Archives of General Psychiatry). This secondary research collected findings that revealed the weak and almost nonexistent scientific evidence to support a biomedical model of behavioral or mental disorders and the frequent failure of drug treatments for these problems. Most psychiatrists are dimly aware of these shortcomings, but this information is rarely made available to patients and the public. The accusation of "crank science" is merely a ploy to dismiss and censor research revealing the serious flaws in this belief system.
However, I have been distracted from my original question: Was the article in question deleted, and if so, who deleted the article and under whose authority? Can this action be appealed and reversed? At the present moment, Wikipedia only represents the prevailing biomedical perspective, which is currently undergoing intense criticism from social and behavioral scientists, mental health professionals, and former mental health service consumers both in United States and internationally. Wikipedia is at risk of falling out of touch with an important social movement and common public knowledge.Spinheel01 (talk) 03:06, 22 September 2015 (UTC)[reply]
To even know why the article was deleted, and how/whether that decision could be appealed, we first need to know where the page was located. If you could remember anything about the page such as its exact title or who wrote it, that may help tracking it down. Unfortunately there is a technical flaw with the MediaWiki software that Wikipedia is built on, which prevents searching the database of deleted pages. Any editor can pull up the deletion log of a page if they know its title, and as an administrator I can pull up such a page's former content, but no one can search for a term and have returned a list of deleted pages that use that term in the body or title. Someguy1221 (talk) 03:15, 22 September 2015 (UTC)[reply]
Search of deleted articles is here: https://en.wikipedia.org/wiki/Special:Log/delete but needs exact name. and browsing through the list of deletions doesn't seem a realistic option, must be 2 or more per minute, by the looks of it..
If you came across the article from an outside link, on a blog for example, that link would tell you the name. :I've searched the WikiProject Medicine for "schizophrenia", but no mention of an article deletion.
Options depend on how sure you are it can't be one of the others where the content is removed. If not sure, you could check the history of the pages. Ssscienccce (talk) 04:29, 22 September 2015 (UTC)[reply]
This is very helpful information. I appreciate your assistance. I will begin searching through these links for the lost article. Thanks again!64.13.120.128 (talk) 03:37, 24 September 2015 (UTC)[reply]
Maximum feasible speed for a space ship
What speeds are realistic for a space ship, and how much would these speeds dilate time? --Llaanngg (talk) 04:05, 21 September 2015 (UTC)[reply]
You are asking about theoretical limits, not the limitations of current technology, right ? If so, a spaceship that shoots matter out at the speed of light should itself be able to move close to the speed of light. The necessity of saving some mass for deceleration and stopping at the other end would mean it couldn't use quite so much of it's mass in the initial acceleration, so that would limit it's maximum speed. And, if a return trip is intended without picking up any more mass to use as propellant, then that would limit the max speed even more.
As for time dilation, keep in mind that it could take months or years to accelerate and decelerate at each end, especially if you want to keep it down to one g for human health reasons. So, the time dilation then would be minimal. Indeed, the passengers might spend more time in those two phases than in the much longer (distance-wise) cruising phase. StuRat (talk) 04:28, 21 September 2015 (UTC)[reply]
... and, of course, from the point of view of the occupants of the space ship, the speed does not affect time at all. In fact, when they are moving close to the speed of light relative to their starting planet, they observe their own time as normal, and that planet's time as slowed down. Effects in Special Relativity are symmetrical, though that fact doesn't contradict the reality of the twins paradox. Dbfirs 07:13, 21 September 2015 (UTC)[reply]
(ec) However, the time dilation near the midpoint can still be quite substantial. I read somewhere that a least-time flight to Proxima Centauri (that is, accelerate at 1g for the first half, then decelerate at 1g) would take about 6 subjective years but more than 7 as seen from Earth. A radio signal from Proxima Centauri would return to Earth just short of 12 years after launch. No twin-paradox-grade weirdness yet, but far from minimal either.
If you went to Vega (25LY), the subjective trip time would be shorter than the objective light-speed delay. - ¡Ouch! (hurt me / more pain) 07:28, 21 September 2015 (UTC)[reply]
If the problem is realistic speeds - then we have to get into the rocket-science part. A ship that's capable of accelerating/decelerating at one g for years by throwing propellant out the back is going to need a lot of mass to throw out the back ("reaction mass") and a lot of energy to throw it with ("fuel"). In a typical rocket design today, the energy comes from the fuel and the reaction mass is just the waste product from that combustion - but there are other possibilities - you could, for example, imagine a rocket that used water as the reaction mass and solar panels to collect the energy to boil the water and use the steam to propel the ship forwards. That's not going to be an efficient design - but it simply illustrates the possibilities.
So to get a constant one g acceleration for years is a painful problem. If you just tried to use current rocket technology, you get into this horrible spiral where you need X amount of fuel to push the rocket - but you need more fuel to propel the fuel along with it, and yet more fuel to propel that fuel. It turns out that even for relatively modest goals (getting out of earth orbit and travelling to the moon - coasting for most of the way) - you need that gigantic Saturn V launcher just to take the lightest imaginable, teeny-tiny capsule and lander. That approach would barely give you a one g acceleration for a few hours...certainly not for years. So conventional rockets are off the table.
To get around that spiraling fuel demand problem, you have to understand that the faster you can push the reaction mass out the back of the rocket, the less reaction mass you need. So to sustain constant acceleration, you need to be pushing the reaction mass out as fast as you possibly can - faster than a conventional rocket can...but that still takes crazy amounts of energy. If you're going to avoid the "needing more fuel to accelerate the fuel" trap - you need to either resort to 'exotic' fuels like antimatter - or you need to provide the energy from outside of the ship...and that means using solar panels - or big lasers placed in orbit and fueled by lots of nuclear reactors or something. This is all tremendously difficult to achieve. Whether it passes your "realistical" test depends on your tolerance for doesn't-yet-exist-but-might-not-be-impossible technologies.
One of the more practical designs is to use an 'ion drive' which propels the reaction mass out the back of the craft at close to light-speed - this drastically reduces the amount of reaction mass you need to carry - but doesn't help with the energy source issues. Ion drives have very low accelerations - but are very energy/mass-efficient, so they can accelerate gently for very long periods of time using solar panels for energy and thereby eventually reach exceedingly high speeds...but once you get too far from the sun, the issue of providing enough energy is what kills you.
Another approach is solar sails - in this case, the space craft doesn't keep the reaction mass on board or the energy source - both come from sunlight (or perhaps massive orbital lasers). Light has mass (although not very much) so if you shine light onto a humungous mirror mounted onto the spacecraft, then the reflected light becomes the reaction mass to propel the ship. Using sunlight to do this through most of the solar system would require an insanely large mirror (the "solar sail") - but as you start to leave the solar system, the power delivered by the sun gets less and less - and the size of sail you'd need would soon be completely unreasonable.
One of the more crazy (but not entirely implausible) approaches is to build a space ship with an insanely thick curved metal plate at the back end - and to explode nuclear bombs against the plate to push the ship forwards. See Project Orion (nuclear propulsion) for details. This design has been studied very carefully - and it would be entirely possible to build such a thing if we had the motivation to do so. The problem with this design is that it's not very human-friendly - especially when it's launching! It could be made to produce 100g accelerations(!) - and get up into the fraction-of-the-speed-of-light realms rather quickly - but the crew wouldn't survive the experience. But by setting off a nuclear bomb every three seconds for ten days to produce a constant 1g acceleration, they could get to the nearest star within 133 years and reach 3% of light speed after the first ten days of acceleration. Such a ship would cost 300 billion dollars to build and launch...which is expensive - but plausible - Americans spend four times that much on health care every year, and if we built it over ten years (or with help from the other governments of the world) - we'd hardly notice the cost.
A similar design, but with matter/antimatter annihilation explosions could theoretically reach 80% of the speed of light...but we have no means to make, or store, anything like the amount of antimatter needed - so this is on the intersection of the "possible by the laws of physics" - and "impossible using practical technology" issues - and it's unlikely that it's ever going to be a practical engineering possibility.
I think it's safe to say that we have no known/reasonable way to propel humans to the nearest star and get there without dying of old age...but project Orion comes closest.
In my opinion, we could possibly get a lightweight probe to nearby stars within reasonable time/budget using an "Orion"-like spacecraft and allowing 100g accelerations. It seems more feasible to me to develop light-weight artificially intelligent robots that can tolerate crazy accelerations than to ever get an actual human there.
Why is it theoretically impossible to produce and store large amounts of antimatter ? I understand the risk of a breach in the (magnetic ?) containment field, but we could build an automated production facility out by Pluto to negate that risk. (Of course, this technology would be centuries away.) StuRat (talk) 18:52, 21 September 2015 (UTC)[reply]
We currently don't have methods to make antimatter at rates that would let us power a lightbulb, so even putative methods for storing large quantities of antimatter safely cannot yet be tested. Someguy1221 (talk) 03:32, 22 September 2015 (UTC)[reply]
You're talking about practical tests, while I just asked about theory. StuRat (talk) 16:29, 22 September 2015 (UTC)[reply]
I was aware, but simply trying to point out that theory aside, we can't test our theories, so they are useless. Though perhaps that doesn't bother you. Someguy1221 (talk) 03:59, 23 September 2015 (UTC)[reply]
Are you sure that's true? According to our article on antimatter weapons, it would take CERN about 2 million years to produce half a gram of antimatter at current production rates, which would be enough for a weapon equaling Hiroshima bomb. Our article on TNT equivalency says that the Hiroshima bomb had an energy of 63 TJ. If we divide that by 2 million, that supposedly means that CERN is producing enough antimatter to produce about 32 MJ of energy per year. While this is not even a drop in the bucket compared to world energy consumption (something like 5.598 × 1020 joules), it still seems like enough for at least a lightbulb. --OuroborosCobra (talk) 18:32, 22 September 2015 (UTC)[reply]
That's about 1 watt of power. The weakest incandescent light I'm aware of runs on 4 watts, which is obviously far weaker than your typical 60-100 watt lightbulb. Perhaps you could run a small LED. Someguy1221 (talk) 03:59, 23 September 2015 (UTC)[reply]
@SteveBaker: Can you really nuke even an "insanely thick" metal plate 2.5 million times and have something left? How do you dump the heat of part of a nuclear bomb in 3 seconds (steady state), without having your blackbody at the temperature of a pulsar? Is there any material that wouldn't be blasted to smithereens by the cumulative neutron flux? Wnt (talk) 19:12, 21 September 2015 (UTC)[reply]
Yes! Evidently...according to a bunch of very, very clever people who researched this to death in at least three different studies! See Project Orion (nuclear propulsion) for the US version of it and Project Daedalus for the British effort at a similar design. It's not a joke - it's a very serious consideration. You can certainly be 100% sure they thought of the more obvious objections, such as the plate being vaporized! There are actually some really complex calculations about how much time must be left for the plate to cool off between explosions, and how big the shock-absorbers have to be to protect the crew from the alternation of high-g acceleration and free-fall every 3 seconds! Those are actually the things that limit the rate at which the bombs can be set off. Anyway - if you haven't heard of it before - you should definitely read the articles. SteveBaker (talk) 20:09, 21 September 2015 (UTC)[reply]
Even with nuclear power, you can't keep 1g of acceleration for very long (at least, not enough to achieve the 90-something percent where relativistic effects keep the crew much younger than their families left behind on Earth). Therefore, it's not that important if it starts at 100g or 1g - the limiting factor is the delta v, and a longer acceleration phase won't hurt much. The mass of the shock absorbers would probably a more significant limiting factor than the fact that it takes you weeks, rather than hours, to get up to top speed. (It would be more important if you had a less damaging thruster capable of >1g, because you could use that as a lift-off stage.)
Moot point, though: The mass savings with an unmanned mission (smaller payload, no need for atmospheric containment, life support etc) would probably outweigh both of the above combined. - ¡Ouch! (hurt me / more pain) 11:20, 22 September 2015 (UTC)[reply]
Indeed, practical considerations limit the speed that can be reached by most propulsion systems.
Rocket mass ratios versus final velocity calculated from the rocket equation.
The rocket equation shows that the required mass ratio (m0=initial mass with fuel; m1=final mass) grows exponentially with , making velocities much larger than exhaust velocity prohibitively expensive. Slowing down (unless external forces are used) requires the same mass ratio for a given speed, effectively squaring the mass ratio required. If it requires a mass ratio of 1000 to reach a velocity, reaching it and slowing down again will require a mass ratio of one million.
Note that the rocket equation only specifies the propellant mass required, not the energy needed to propel the mass, or the engine and fuel mass needed to produce that energy. The most mass efficient engines theoretically possible, anti-matter propulsion engines, would reach no more than about 20% efficiency, the rest of the energy is lost in radiation and heat.
A 2003 paper by the Jet Propulsion laboratory discusses how such a spacecraft would theoretically be built. The result is a cylinder 600 km (400 mile) long with a diameter of 20 meters (65 feet). Most space is taken up by the 515 km long radiator, operating at 1200°C (2200°F), needed to cool the engine. How exactly the heat from the engine, caused by gamma radiation produced in the propulsion process, could be transferred to the radiator is unclear. A quick calculation shows that with the assumed energy flux of 210000 TW (more than the total solar energy hitting the earth: 137000 TW), the required temperature gradient in the Tungsten radiation shield for such a heat flux would be more than 106 °C or °K per nanometer, a physical impossibility.
Production of the anti-matter needed, assuming the predicted maximum efficiency possible, would require 177 billion years with current human energy output.
"Realistic" space travel would exclude relativistic speeds, it seems. Ssscienccce (talk) 16:09, 21 September 2015 (UTC)[reply]
With periodic in-flight refueling, the greater time for acceleration required by human star travel at 1g is not a problem. The ship would simply utilize fuel and propellant from a fleet of robotic projectile/tankers that are each coilgunned from the solar system to increasing speeds in order for them to match the ship's speed at their rendezvous points. Ideally, the coilguns are also established near destination points to service the deceleration of client ships, otherwise it takes a long time for the slowest tankers to reach the ships from their departure point and have to be sent prior to a ship's departure. Unlike when carrying large quantities of fuel, the mass-energy requirement for the ship's deceleration is then identical to its acceleration. Absorption or deflection of interstellar dust would become important at some point, but there is no theoretical limitation or even practical limitation that I'm aware of to the ship's speed other than the vacuum velocity of light. As for the amount of time dilation, that does depend on the ship's speed in accordance with the equation
Also see our article on Space travel using constant acceleration, especially this section on the trip with respect to the ship's reference frame: according to which it takes 3.6 years to our nearest star and less than 24 years to visit other parts of our galaxy. :-) P.S. I advocated this coilgun-assisted in-flight refueling approach before, perhaps not as well, here and years ago on the BBC's chat pages though I'm surprised that this article does not explicitly mention it under its feasibility section. -Modocc (talk) 16:53, 22 September 2015 (UTC)[reply]
It's not just dust. The interstellar medium becomes hard radiation once you get to a certain speed. I don't know that it's an insoluble problem, but it's certainly not an easy one. --Trovatore (talk) 22:39, 22 September 2015 (UTC)[reply]
citation or reference to the chemical equation
Only my second time to ask a question for further information so may do this all wrong, but
Question. Could author of the statement, chemical reaction, cite a reference or addition detail to the chemical equation?
C5H10O5 → C5H4O2 + 3 H2O
from the article on Furfural, looking for additional information, specific conditions for the reaction
Also any additional information for the conversion to Furfuryl alcoholChem4Engr (talk) 05:56, 21 September 2015 (UTC)[reply]
I added a ref to the furfural article for this content, taken from the xylose article about he reactant mentioned in it. DMacks (talk) 06:50, 21 September 2015 (UTC)[reply]
Why do waterproof clothing fabrics have a "hydrostatic head"? Why can't they just be actually waterproof like a plastic bag? --129.215.47.59 (talk) 11:59, 21 September 2015 (UTC)[reply]
Thanks. I gather it's to allow evaporation of sweat. I'd rather rely on vents since I'm pretty sure the majority of moisture on my body when I peel off my "waterproofs" is rain. --129.215.47.59 (talk) 13:19, 21 September 2015 (UTC)[reply]
I wouldn't be so sure. Skin puts out lots of moisture, even when you don't think you are sweating. It just normally evaporates before you can notice it. StuRat (talk) 00:29, 22 September 2015 (UTC)[reply]
Disposal of medication
When medication is handed in at a pharmacy for disposal, does it all just go into a furnace or does it get sent different ways depending on knowledge about the content? Could the same thing be achieved by putting it in a biohazard bag at a life science lab? --129.215.47.59 (talk) 11:59, 21 September 2015 (UTC)[reply]
Old medicines handed in at pharmacies are probably incinerated; this seems to be the preferred method in the US:
Currently, high temperature incineration at properly permitted facilities is the standard for disposal of waste pharmaceuticals from hospitals, pharmacies, and drug company manufacturers. High temperature incineration completely destroys the chemical activity of the pharmaceuticals.source
Do the cheapest dish and laundry detergents offer the best value or is it better to get the next thing up? I figure people scientifically-inclined may be less amenable to persuasion by marketing and consider the chemical contents of the products they're buying. For example the cheapest washing up liquid is lower viscosity but I don't suppose that necessarily mean it's less concentrated if the regular store-brand has a thickening agent.— Preceding unsigned comment added by Seans Potato Business (talk • contribs)
I'm afraid the purpose of this desk is not to give our opinions on our favorite detergent brands. If you are looking for good, tested product comparisons, let me suggest Consumer Reports, which has a reputation for scientific testing of products, and likely has done tests on the products you're looking at. --Jayron32 14:36, 21 September 2015 (UTC)[reply]
@Jayron32 it might be clumsily worded but I'd be inclined to consider this a legitimate question (the OP isn't naming specific brands). It could be paraphrased more neutrally as "do liquid soaps of different viscosities have different cleaning properties?". For laundry detergents, the main issues would be bio vs non-bio, which have different cleaning and dermatological properties; plus, some brands include a softening agent and some don't. For liquid soaps, thicker is always going to be better when it comes to washing dishes or hands, as you want the detergent to remain in contact with the surface rather than running down the plug. ‑ iridescent 15:33, 21 September 2015 (UTC)[reply]
Did I not direct the OP to a possible source to find the information they seek? Is that not the purpose of the reference desk? --Jayron32 15:44, 21 September 2015 (UTC)[reply]
Well, you directed him to a US publication which will have minimal relevance to someone in Maastricht (even when the brand names are the same, US cleaning products tend to bear little resemblance to their European equivalents, since the regulatory framework is different). I'm not sure that's really what he was looking for. ‑ iridescent 15:57, 21 September 2015 (UTC)[reply]
In that case This testing lab mentions they do their tests in The Netherlands, so that would be a good lead. --Jayron32 16:02, 21 September 2015 (UTC)[reply]
(EC) I mostly agree with Jayron32. BTW, I'm also uncertain how thicker dishwashing detergent is guaranteed to be better when you're simply diluting it as often happens with some methods of washing.
Perhaps most importantly, it seems the OP is missing a big factor, they have to define cheapest. (Edit: And note; they mentioned "less concentrated".) For everything cheapest would have to be per some unit, since it makes no sense to talk about a $1 bottle of soap with 500 ml as being cheaper than a $2 bottle of the exact same soap with 1.5 L if you're looking for cost effectiveness.
But, particularly for laundry detergents, your unit probably shouldn't be volume or weight. I don't know about where the OP lives, but here in NZ manufacturer recommend volumes for washing can vary quite significantly. (For liquid detergents they normal use the cap, for powders a scoop but how much these can fit vary, and some even use two for a normal load.) Most, but not all, manufacturers publish "number of washes" figures on their containers which would be likely be the best way to define cheapest presuming you follow the manufacturers recommendations. (Edit: For those that don't, it's obviously possible to derive these figures empirically if you buy the product. And perhaps in other countries, it's the norm to specify the volume or weight you're supposed to use, which happens here occasionally as well although only generally with those that publish a "number of washes" figure.)
Now, the amount to use can vary depending on wash size and how heavily soiled the clothes are, and some but not all also recommend differing amounts depending on whether a toploader or front loader is used. So these factors will need to be considered too. Although most recommendations are fairly non descript, e.g. they say "large load" or "normal load" with no real explaination what they mean by this (e.g. 5kg of cotton clothes), and I don't think there's any standard for this.
One big complicating factor and the one Jayron32 touches on is that besides everything else, performance can vary. Your national Consumer Institute or similar may publish reports comparing performance (probably based on following the manufacturer's recommendations). Note that performance data tends to be complicated, it will often depend on the wash temperature, the type of soiling, the type of washing machine, the fabric of the clothes and probably other factors, it will often be the case that there's no universal winner. Alternatively, if you find your detergent doesn't work well, or you find you need to use significantly more than recommended but don't with another detergent, this should be taken in to account. Ultimately, how much you actually use and how well it works is what matters, not more abstract factors which may be quite removed from these.
I Agree that Consumer organizations would be the best source of information, their tests show that price is not a good indicator for quality; often the products scoring best on "value for money" include both cheap and more expensive ones, and the same is true for those scoring worst. See for example here and here. I wonder if game theory or survival strategies seen in evolution could explain the relative lack of correlation between price and quality...
Picking the second cheapest might not be a good strategy in general (wine in restaurants comes to mind). Ssscienccce (talk) 18:53, 21 September 2015 (UTC)[reply]
Some marketing practices to watch out for:
1) The "concentration game". In the US, at least, there is no requirement that they describe the concentration of the active ingredient(s). So, they will come out with "triple concentrated" formula, and charge twice the old price. That seems like a good buy, so you go for it. Then, after a while, the "3X concentration" label disappears. If you call them to ask if this means it's no longer triple concentrated, they will tell you, truthfully, that it still is. But, once people stop calling, then they start reducing the concentration until they get back down to the original strength, and everyone is still paying double for it. Powdered detergents can't play with the amount of water they add, but they could still use cheaper fillers, like salt.
2) Just like other products, the size keeps getting smaller. This you could notice, if you read the label carefully every time, but most people don't. Then they might come out with a "super size" which is the original size, but at a higher price.
3) Sales, on the other hand, can be a good way to go on laundry detergent, as they can offer substantial discounts, and it's unlikely any will actually ruin your clothes or dishes. When one goes on sale, you might buy one unit, try it, and, if it works, buy more while it's still on sale.
4) You can actually have detergent that's too thick, in that it won't easily dissolve in water.
I've also used failed shampoo (shampoo that I bought then didn't like) as general purpose detergent, most often as body soap (I don't worry if my armpit hair lacks luster). Better than tossing it out.
For laundry I've taken to using just a small quantity of bleach, and no detergent. It's much less expensive, as I get bleach for US$1 a gallon. All my clothes seem to survive bleaching, except, for some strange reason, my socks. They fade dramatically if bleached, while the rest of my clothes might fade a bit, but not noticeably more than they would with detergent alone. And, most importantly, bleach seems to kill mildew, while normal detergent does not. I save up a load of socks and wash them with detergent. StuRat (talk) 18:32, 21 September 2015 (UTC)[reply]
If the OP does not live in a very hard-water area, he might find that ordinary cheap sodium carbonate works just as well. It does not benefit from multi -million dollars marketing (which cost money and so gets added the the retail price), because no supplier can brand it as their own invention. Also, for those that don't have access to main swage but just a septic tank, it doesn't mess up the bacterial break -down like what detergent do and so negates costly maintenance. So it can be much less expensive whilst also cleaning ones cloths. Also, it is hypoallergenic, so less costly visits to the quack for problems whose causes he can't put his finger on nor find a cure for. For those that live in prosperous cities, why wash your cloths. Do what everyone else does, throw your dirty cloths away and keep buying new ones.. That’s what my grandchildren do... “ but Grandpapa! I have already worn that dress once, I just can not let my friends me wearing the same dress twice – please buy me this one – it has a designer label that non of my other frends can afford – but you can, huh, my very very dearest Grandpa “--Aspro (talk) 20:25, 21 September 2015 (UTC)--Aspro (talk) 20:12, 21 September 2015 (UTC)[reply]
Here is where we should look to Hollywood stars as our example, since they each get married multiple times, presumably to get more wear out of those wedding dresses. :-) StuRat (talk) 22:03, 21 September 2015 (UTC) [reply]
One thing to keep in mind when using machines (dish washer or laundry) is that many are designed specifically for tablets or powder or liquid or gel and these are not always interchangeable. In particular, I've been told that using liquids or gels can cause build-up. Make sure you check with your manufacturer before switching cleaners. 99.235.223.170 (talk) 23:53, 21 September 2015 (UTC)[reply]
September 22
How many people have died due to Volkswagen's defeat devices?
Based on [20][21], I'd like to come up with a figure for how many people have been killed by the software that allowed Volkswagens to sense when they are being tested for emissions and producing lower levels only at that time. This involves:
A) What are the total number of air pollution deaths caused by nitrogen oxides? (as I understand it, some are caused by particulates, ozone, etc. - so I see figures for overall mortality like 55,000 in the U.S. and 30,000 in Britain (which don't seem very reconcilable to start) but so far I've only seen partial answers for NOx e.g. [22].
B) What portion of the total nitrogen oxide production can be attributed to the cheating software? (I am seeing figures like 10 times too much for each car, but I don't know how much is emitted per car and how much that is for X million cars, versus the total emission) Note that the calculation has to be bottom-up rather than assumed from a market share where the others are all honest, because there are already reports of other brands possibly doing the same thing.
Of course, if someone can simply cite a direct analysis, that would be even better! Wnt (talk) 13:18, 22 September 2015 (UTC)[reply]
I tried estimating this earlier. I got that the 480,000 US cars emitted roughly 17 kilotons more NOx than allowed by regulations (assuming emissions 40-fold above regulations and US average miles travelled), which is a drop in the bucket given that US annual emissions are 11100 kilotons (EPA for 2013). For the US, mortality is dominated by particulate matter (90%) and most of the remainder is due to ozone. NOx itself is probably a very small factor in mortality, though NOx does react to promote ozone and particulate formation, and it could be difficult to figure out that indirect effect. Though, given that it is only a 0.1% increase in total emissions and it is only a minor player in mortality, the net effect is likely much less than 0.1% increase in air pollution mortality. The only likely exception to this is if these cars happen to be geographically concentrated in a way that is not proportional to other NOx sources, and for that I don't really know. Dragons flight (talk) 13:56, 22 September 2015 (UTC)[reply]
Correction FWIW, the cars mask the emissions with urea when being tested; they do not suddenly produce lower emissions.DrChrissy(talk) 13:24, 22 September 2015 (UTC)[reply]
Urea reacts with NOx emissions to convert it to harmless substances. See selective catalytic reduction. That's real reduction in tail pipe emissions, which is what we ultimately care about, and not just masking. Of course it does no good if the car turns off the urea system, as VW was apparently doing. Dragons flight (talk) 13:56, 22 September 2015 (UTC)[reply]
Ah, I see. Thanks for correcting my correction.DrChrissy(talk) 14:59, 22 September 2015 (UTC)[reply]
It's a tough calculation. It's clear that the very large numbers for the emissions are only happening in certain driving patterns - so the numbers being kicked around are likely the peak emission rate. The average (which is what we really care about) is probably much lower. But I don't think sufficient study has been done on this to really know the full effects of this deception over a range of different cars and a range of different driving patterns.
There an argument that diesel engined cars are more fuel-efficient than gasoline engines - which results in lower overall emissions - you might argue that if Volkswagen had not done this, more people would have bought gasoline-powered cars and that would have made things worse overall...or you might argue that more people would have bought hybrids had there not been fuel-efficient diesels and that would have made things better overall. That's an almost impossible question to answer.
More complication comes from the fact that this trick was done to improve fuel economy...which it undoubtedly did - and with huge success. So what we have here is a car that produces less CO2 than it would have done if it followed the EPA rules and burned more fuel - but simultaneously produces more NOx than it should have done. So your calculation of lives lost to excess NOx should also include lives saved due to reduction in CO2, sulfur and other pollutants typically generated by diesel engines. That's a much tougher calculation because the vast majority of deaths attributable to CO2 emissions probably won't happen for a few more decades as the effects of global climate change kick in - we simply don't know how many will die as a result.
Suffice to say that whatever calculations you might come up with from total deaths due to NOx (etc) divided by the percentage of excess NOx caused by Volkswagen - you will miss those two important factors, and that renders your results meaningless.
Personally, I don't condone what Volkswagen did - but don't think it's at all clear that Volkswagen will have caused any deaths at all - especially if you look sufficient years into the future so that the effects of CO2 emissions can be included into the calculations. I've always believed that the EPA restrictions on diesel engines (and especially on diesel FUEL) are ill-conceived because they principally relate to large trucks - and their emissions patterns are totally different. The world would undoubtedly be better if more people could be persuaded to drive small diesel engined cars. Those cars are extremely popular in Europe - but much less so in the USA because of inappropriate EPA restrictions for small diesel engines.
Are you sure the trick was done primarily to improve fuel economy? When I research the slightly related question on RDC, I saw various other suggestions like it being done to increase power (which may or may not improve fuel economy) or simply that it was done to reduce the need for maintenance. The sources I provided on RDC discusses this a bit. Nil Einne (talk) 14:44, 22 September 2015 (UTC)[reply]
From what I've been reading, the trick definitely improves both power and fuel economy. Whether it was intended to do just one of those things - and the other was just a fortuitous side-effect - is anyone's guess. In retrospect, people should perhaps have wondered how the car was getting so much better MPG in practical day-to-day driving than they were getting when the EPA measured their MPG on the test track. We don't know whether Volkswagen management made their software guys do this and then swore them to secrecy - or whether the software team - or maybe just one programmer - did it without telling anyone. We don't know whether that software was written in-house or by some outside contractor (I happen to know that the engine management software for the MINI Cooper wasn't written by either MINI or their parent BMW company - so it could easily have been out-sourced). Assigning either motive or blame is difficult at this point. What's clear is that TDI Diesel owners are going to be mightily pissed when they have to have their software replaced and suddenly get less acceleration and worse gas mileage out of cars they've owned for a year or three! If they refuse to go for the recall in sufficient numbers then the EPA are going to have a hard time knowing how to handle emissions inspections in the future. SteveBaker (talk) 19:40, 22 September 2015 (UTC)[reply]
Concentration of odorant in natural gas
Natural gas§Safety§§Use says: "In order to assist in detecting leaks, a minute amount of odorant is added to the otherwise colorless and almost odorless gas used by consumers." How much is "a minute amount"? In other words, what is the typical concentration of odorant in the final mix piped to consumers?
Chapter IV Leak DetectionPDF of the Texas Railroad Commission's simplified description of federal pipeline safety regulations says: "Gas is intentionally odorized so that the average person can perceive it at a concentration well below the explosive range. That odorant concentration is generally between 0.5 to 1.0 percent by volume or as local applicable codes dictate." which is much less "minute" that I would have expected, and I wonder if whoever worked up the simplified description was confused by a requirement that the odor be detectable when a leak yields a natural gas concentration of 0.5 to 1.0 percent by volume. (See 49 CFR 192.625 - Odorization of gas (a): "A combustible gas in a distribution line must contain a natural odorant or be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with a normal sense of smell.") -- ToE 13:24, 22 September 2015 (UTC)[reply]
Methyl mercaptan, the odorant usually used, has an odor threshold of 0.002 ppm (parts per million) or 2 ppb (parts per billio (see here That means that 2 mL of methyl mercaptan distributed in a volume of 1,000,000 liters is detectable. If gas was doped with 1 percent methyl mercaptan, that's one part per hundred, so the gas leak would be detectable at 200 ppb, or 0.2 ppm, or 2 mL of gas per 10,000 liters. --Jayron32 14:12, 22 September 2015 (UTC)[reply]
The kind used in America, at least, is strong but a lot less noxious than cigarette smoke, for example. — Preceding unsigned comment added by Baseball Bugs (talk • contribs) 05:01, 23 September 2015 (UTC)[reply]
North and south pole
Why is the North Magnetic Pole a south pole and vice versa? GeoffreyT2000 (talk) 14:02, 22 September 2015 (UTC)[reply]
If by "why" you mean why the names are opposite their magnetic nature, see Magnet#Pole_naming conventions. If you mean why the poles at these locations actually have the magnetic nature they do, Earth's magnetic field talks about the origin of the effect and that it does change over time. DMacks (talk) 14:12, 22 September 2015 (UTC)[reply]
André-Marie Ampère, inspired by Oersted's discovery published 1820 that electric current visibly affected magnet needles, established rigourously in 1822 that magnetism is produced by "electricity in motion". In his words: if an observer has a current flowing from his feet to his head then a needle placed in front of him would have its north-seeking pole deflected to his left. Today we express this in Ampère's right hand screw rule and consider that all magnetism, even that of permanent magnets, is due to circulating currents, see Magnetization. Such currents produce a directed magnetic field (an isolated north or south pole cannot be realized). The Earth itself is a big electromagnet where the so-called North magnetic pole is by electrodynamics a south pole - the apparent paradox arises because of the convention to identify the north-seeking pole of every magnet as "North" regardless of whether it might actually be useful as a compass needle. These days we celebrate Monsieur Ampère in our unit of current which he first defined together with electric tension (voltage) some years before Ohm's law was published 1826-27. 84.209.89.214 (talk) 18:22, 22 September 2015 (UTC)[reply]
1) The direction of "north" developed, at least in the Indo-European languages, from the name given to where your left arm points when you hold out your arms to the side facing the dawn. The word northcomes from the PIE root *ner-.
2) It was eventually discovered that the earth rotates about an axis, and we now call the points where the axis intersects the surface the North and South Poles. It was discovered well before Columbus that a permanently magnetized free-floating bar would tend to align north-south. Mariners realized that if they marked the ends of the bar, they could use it to identify north versus the south, even during cloudy weather or under strange stars.
3) Eventually it was realized that the north and south magnetic poles did not exactly correspond to the axial poles. It was further realized how magnetism works, and the "north" end of a magnet or magnetic field is attracted to the south end of another magnet or magnetic field.
4)In the 1800's it was finally fully realized that the earth was generating a magnetic field with it's poles close to the axial poles, and that hence the earth itself is analogous to a giant magnetic bar with its south pole near the north axial pole, and vice versa.
what exactly is the sense of this kind of a Tractor Road-rail vehicle?
Like this ? This kind of road-rail vehicle is so popular you can buy it in H0 scale for your model train... I don´t understand what does a Tractor have to do on the rails... It would use more fuel than a simple Train.. --Hijodetenerife (talk) 18:40, 22 September 2015 (UTC)[reply]
It may be used as a rail car mover, which is cheaper and easier than a switcher locomotive. It may be used for construction.
The thing about rail transport is that there are tons of specialized equipment; and all this neat special-purpose gear exists because trains weigh tons. If you want to move a rail car thirty feet across the yard, you can hardly get out and push! You either need a full-blown locomotive - which means spending the time and money to get a locomotive, or else you need to use specialized gear. If you need to repair a piece of equipment out on the line, the only way to get there might be along the railway, so a hybrid road/rail vehicle might be the best way to get there.
The vehicle in the photograph linked above is a Fortschritt (East German) rail tractor. It has an article in the German Wikipedia, Zugtraktor ZT 300. "Einige Traktoren wurden zu Zweiwege-Traktoren umgerüstet und als Rangiergeräte vor allem in DDR-Kleinbetrieben mit Bahnanschluss eingesetzt. Neben den erforderlichen Signaleinrichtungen (Spitzen- und Zugschlusssignal) waren diese Traktoren mit hydraulisch absenkbaren Spurkränzen ausgestattet." (That is, they were modified for use in East Germany for rail yard switching at smaller depots by adding the rail wheels, suspension, and legally-required rail lighting beacons).
But they need more fuel and a regular tractor is driving outside the streets for plants.. I don´t know why a tractor should be abused to drive freight car´s or wagons.. There are yet other Road-rail vehicle which can do this. --Hijodetenerife (talk) 04:01, 23 September 2015 (UTC)[reply]
I would translate "Kleinbetrieben mit Bahnanschluss" as "small businesses connected to the railway" rather than "smaller depots" (although it is a bit ambiguous), which helps answer your question. Yes, there are more efficient ways to move wagons... but East Germany was not a terrifically rich country, and its industries struggled to match the advances that West Germany made during the Wirtschaftswunder. You could buy your factory a dedicated freight tractor and a dedicated shunter locomotive, but you would need to pay for, maintain and train your staff on two totally different specialized vehicles. You can get almost the same benefit much cheaper by just sticking railway wheels on a mass-produced agricultural tractor. Smurrayinchester 10:59, 23 September 2015 (UTC)[reply]
My guess: Most tractor types can be fitted with a variety of implements and have levers or switches to raise and lower such attachments. So adding the flanged steel wheels only requires a rigid or hinged attachment, the mechanism to raise and lower them is already in place. Why buy an expensive rail car mover when you can adapt an old tractor to do the same job. Also, rail tracks don't usually have roads next to them, a tractor would have excellent off-rail performance on rough terrain, loose soil, etc..
The fuel efficiency is not a factor, they are only used to move railroad cars over limited distances. The advantage is that it can move off the track, so you don't need a network of tracks and switches to get it to the place where it's needed. A factory will typically have a range of freight cars on site, both loaded and empty cars used for raw materials and finished products, waiting to be loaded, unloaded or taken away. Even with loops and switches, using a ("track-bound") locomotive to move one freight car could require moving a lot of other cars just to get the locomotive to the right location. Ssscienccce (talk) 15:57, 23 September 2015 (UTC)[reply]
September 23
Wavelengths from Outer Space
What are the shortest and longest wavelengths that can be meausred (by telescopes, etc.) from outer space? In other words, what is the spectrum of the measurable wavelength from outer space? 80.246.136.222 (talk) 05:17, 23 September 2015 (UTC)[reply]
The shortest wavelengths that we can measure from space are cosmic gamma rays – the High Energy Stereoscopic System can see gamma rays with an energy of over 100 TeV, which is equivalent to a frequency of 2.4×1028 Hz, or a wavelength of 1.24×10-20 m. Ultra low frequency light is harder to measure from outer space, since there are huge amounts of Earth-based noise at these frequencies. The Demeter satellite can see as low as 10 Hz, but that's pointed at the Earth itself. This paper suggests that the lowest frequency/longest wavelength that can be used in radio astronomy is currently 30 MHz (10 metres). There are (very early) plans to go further, but they would need to be space-based (since the atmosphere blocks low frequencies) and would have to be an array (since it's very difficult to put an antenna large enough on a single spacecraft). Smurrayinchester 10:44, 23 September 2015 (UTC)[reply]
If we interpret "outer space" to include Earth's magnetosphere, then very low frequency radio is commonly detected from that region. Among the many signals are whistler mode waves; dawn chorus (as the magnetosphere warms up from solar radiation, each time it comes out of Earth's shadow); and low frequency hiss. These waves are in the range from 1 kHz to 100 kHz; and even lower frequency (longer wavelength) signals can be detected if you have the right equipment. Perhaps the most notable is 7.83 Hz, an ultra-low frequency radio signal we find on Earth a lot, because it happens to be the characteristic frequency of one light-speed trip around our planet! In other words, the wavelength is approximately equal to one Earth circumference.
From my understanding, dysmorphophobia is an undesirable manifestation of the OCD neurotype. Why is it considered separate from OCD? Can you be both "properly" obsessive-compulsive and have BDD? Andrea Carter (at your service | my good deeds) 23:10, 23 September 2015 (UTC)[reply]
OK - so the relevant article is Body dysmorphic disorder. It says "BDD is categorized in the obsessive–compulsive spectrum.". Our article on Obsessive–compulsive spectrum says: "recently there is a growing support for proposals to narrow down this spectrum to only include body dysmorphic disorder, hypochondriasis, tic disorders, and trichotillomania". So as far as I can tell, your assertion that it's considered "separate" from Obsessive–compulsive spectrum simply isn't correct. OCD is a 'spectrum' condition, from people who are just mildly obsessive - to people who are totally debilitated by the condition, and the symptoms of OCD vary between individuals and may or may not include BDD. So I can't agree with the premise of your question. If someone suffers from BDD, they are (per medical definitions) fully OCD. SteveBaker (talk) 03:18, 24 September 2015 (UTC)[reply]
I read the question as being about the difference between OCD, not OCD spectrum, and BDD. OCD spectrum is a group of disorders, with OCD being one of them.
According to this, people with BDD tend to have poorer insight (understanding that recurrent intrusive thoughts they have are irrational) than people with OCD. And "BDD compulsions may have a greater emotional regulation function, rather than anxiety reduction as with OCD". Those differences would affect treatment selection and effectiveness. Other article here, mentioning that significantly more BDD patients are classified as delusional. A small magnetic resonance imaging study found opposite differences in OCD vs BDD patients compared to a healthy control group (leftward vs rightward shift in caudate asymmetry and greater vs reduced white matter volume).
This study looked at comorbidity between the two: Lifetime comorbidity rates of BDD–OCD are almost three times higher in samples with a primary diagnosis of BDD than those with primary OCD. There are studies of people diagnosed with comorbid BDD/OCD, so having both at the same time is possible. Ssscienccce (talk) 04:30, 24 September 2015 (UTC)[reply]
I am aware of the idea of the obsessive-compulsive spectrum and that BDD is included in it. I was talking about why consider it separate from OCD itself. So people with BDD and OCDers have difference in neurology and psychology but similarities in behavior? Also, OCD is not just a spectrum, it is extremely diverse within the OCDer themself. Ergo, the same person can have periods of no symptoms and periods of severe symptoms and things in between. Andrea Carter (at your service | my good deeds) 17:45, 24 September 2015 (UTC)[reply]
The spectrum is the group of diseases that have certain features in common with OCD. I was wrong btw to include OCD, the OC spectrum disorders are the ones different from OCD: body dysmorphic disorder, hypochondriasis, tic disorders, and trichotillomania; at least that is the definition that the OC spectrum disorders workgroup for DSM-V used.
Before DSM-V, OCD and the spectrum disorders weren't even in the same category: DSM-IV put OCD under anxiety disorders, BDD under somatoform disorders. ICD-10 places BDD (F45.22) under Hypochondriacal disorders (F45.2) which is classified under Somatoform disorders (F45), while OCD is separate (F42).
DSM-V groups OCD and the OCSDs together under OCRDs (OCD and related disorders), but they are still considered separate conditions; BDD is not a symptom of OCD.
"DSM-V contains a number of changes with respect to obsessive-compulsive disorder and related conditions (OCRDs): the chapter includes obsessive-compulsive disorder (OCD), body dysmorphic disorder (BDD), and trichotillomania (hair-pulling disorder). Second, the chapter includes several new conditions, including hoarding disorder and excoriation (skin-picking) disorder.
The new chapter on OCRDs reflects growing data that OCD differs from the anxiety disorders on a number of diagnostic validators, and that there are important phenomenological and psychobiological overlaps between OCD and a number of related conditions [19]. At the same time, it is important to emphasize that there are both strong overlaps between OCD and the anxiety disorders, and important differences between the OCRDs. " sourceSsscienccce (talk) 20:08, 24 September 2015 (UTC)[reply]
September 24
Animals dying after mating
Why do some animals, such as bees, die after mating? — Preceding unsigned comment added by 24.207.79.50 (talk) 04:07, 24 September 2015 (UTC)[reply]
It is widely believed by evolutionary biologists that most examples of deadly mating habits either have a purpose or once had a purpose. In the case of some species of bee, the male reproductive organ detaches and is left behind inside the queen, with the supposed purpose being to prevent semen from leaking out of the queen's reproductive tract. Death inevitably follows for the drone. See Drone_(bee)#Mating_and_the_drone_reproductive_organ. Someguy1221 (talk) 04:17, 24 September 2015 (UTC)[reply]
It's 'benefit' rather than 'purpose' (which suggests ID) manya (talk) 04:37, 24 September 2015 (UTC).[reply]
This general issue is discussed at Semelparity_and_iteroparity. Many organisms reproduce only once before dying. In plants, this is much more common, e.g. annual plants. The evolutionary and ecological forces that lead this situation are well-studied, but research in to life history theory and evolution of life history traits is still ongoing. Generally, semelparity is considered to be a beneficial tradeoff in some situations where the species can have higher population growth (and higher fecundity) via a semelparous strategy than an iteroparous one. See also r/K selection. SemanticMantis (talk) 14:31, 24 September 2015 (UTC)[reply]
Oh, I should also mention that bees are a bit of a special case - the impacts of haplodiploidy mean that male bees don't have a father, female bees are more related to their sisters than their potential offspring, and all other sorts of weird stuff that has probably strongly influenced their evolution to the current state of eusocial insects with few reproductives and drones that are essentially long-lived sperm. So if you want to understand semelparity more generally, you might be better of thinking of a salmon or an octopus as a more representative species that commonly has a semelparous life history. SemanticMantis (talk) 14:31, 24 September 2015 (UTC)[reply]
The above is all correct, but in brief layman's terms, animals die after mating because their chance of living to a second mating season is so low that they are better off using all the energy they can to mate and produce offspring during the first season rather than hold back and risk not breeding to their full potential now or living to make it to a second breeding season. This goes for animals like ephemeropterans, salmon and drone bees. In some animals, like the antechinus it is theorized the males die rather than compete with their mates for food the females need in order to raise the young. μηδείς (talk) 20:44, 24 September 2015 (UTC)[reply]
Hm. Well, that fits for some critters. But salmon can take anywhere from one to several years to mature before they decide to spawn. Atlantic_salmon discusses a bit of this variation and how it is beneficial. SemanticMantis (talk) 20:50, 24 September 2015 (UTC)[reply]
The issue is that they breed once. At least the ones that go to sea and swim back up stream do--they are better off at that point using all their energy to spawn, since only like one in a million make it back upstream to spawn the first time. There are also precocious parr, which are otherwise immarture males which haven't yet been to see but who mate with returning females, "cheating" the system. μηδείς (talk) 22:29, 24 September 2015 (UTC)[reply]
Besides "putting all available resources into maximizing reproduction, at the expense of future life" (as pointed out in Semelparity_and_iteroparity) by dying the reproducing organism also instantly makes place for his offspring and thus prevents to become an competitor of his offspring for the same resources. --Kharon (talk) 21:55, 24 September 2015 (UTC)[reply]
Yes, like the antechinus as mentioned above an hour ago. μηδείς (talk) 22:29, 24 September 2015 (UTC)[reply]
Waterproof light fixtures
For the upcoming Jewish Succos holiday, I want to put some fluorescent light fixtures in my succah (succah is like a treehouse on the ground, sort of). I had special outdoor encased fixtures, but they broke, and now I can't find any in stores. The various stores around only offer fixtures for indoors or outdoor ones that are hard wired, and I'm no electrician. A guy at the local store suggested using an indoor fluorescent fixture that I attach to a board of wood that extends past the light fixture on all sides to prevent any rain from entering the fixture by extending around the entire periphery, and painting it with waterproof paint. What do you think? DRosenbach(Talk | Contribs) 13:19, 24 September 2015 (UTC)[reply]
You still have the risk of rain drops running along the wood, or of being blown/splashed directly onto the light itself, which is dangerous if the light is of the sort where the bulb is exposed and water can get into the contacts. If it's just something relatively temporary, "site lights" might be your best bet (that's a British website, but hardware stores in any country should have them). These are generally powerful, portable, waterproof and very strong – at the cost of being ugly – but once Succos is over you can also use them in your garage, on camping trips, etc. You can even get ones that hang from the ceiling. Smurrayinchester 14:14, 24 September 2015 (UTC)[reply]
For a short lasting events such as this – the power efficiency of fluorescents does not really matter. I would go with festoon lights. [23]. They look pretty, are weather resistant, and can be used on other occasions to illuminate the yard for barbecues, garden party’s etc. Being of different colours, they mix to produce an acceptable white ambient light. Also the juxtaposition of these different coloured bulbs give a richer light (in high-lights and shadows) than just white bulbs would do alone. P.S. Also purchase an earth leakage trip. This is a must. Do you hear. Also, including a light from a naked flame ( say an oil lamp) can give that little bit of atmosphere to provide a visual reminder to the early beginnings. Or you could go ultra modern and European and use exterior waterproof LED strips that one can run off an automotive battery for days and days on just one charge. 5m Waterproof 3528 LED Warm White Strip Lights with Power supply--Aspro (talk) 18:03, 24 September 2015 (UTC)[reply]
For indoor lighting in a temporary structure the advantages of low voltage Track lighting are:
the only parts that must be kept in a dry, insulated and earthed metal box are the on/off switch and transformer
there is no shock hazard from the cables and/or track that carry low voltage to the lamps, even if they are exposed to moisture
you have a wide choice of low voltage lamps including incandescent (such as car lamps), fluorescent with inverter and various LED lamps. It's only necessary to match their voltage (typically 12V) and total current requirements to the output rating of the mains transformer. LED lamps are the most economical to run but need to have a DC supply which a circuit regulates from the AC output of the transformer.
In case of a mains failure, the low voltage lighting can be kept alight by connecting a vehicle lead-acid battery as backup power supply. 84.209.89.214 (talk) 18:06, 24 September 2015 (UTC)[reply]
If I understand it correctly, it's really a "portable" waterproof fixture with an attached power cord that you want? Maybe ask around for someone who can connect the two? Connecting the fixture would take only a few minutes, the time to open it up, connect three wires, and close it again. You could use a (three-wire) extension cord of suitable length (cutting of the unneeded socket), it would save the trouble of having to attach a plug at the other side (and in my experience, an extension cord from a discount store is usually cheaper than buying a cable and a plug from an electrical supply).
Or you could opt for the alternatives suggested above by other editors. But don't use an indoor fixture outside, that is compromising electrical safety. Probably no ground wire, not waterproof, needs an extension cord, which, if you want to do it safely, would require an "outdoor power cord protect box", etc... Ssscienccce (talk) 18:25, 24 September 2015 (UTC)[reply]
Try LED strings - low voltage, so not really a problem, and some can run on solar power (legit during Succoth I think) which means no actual power cords. And very safe. Collect (talk) 19:49, 24 September 2015 (UTC)[reply]
To clarify my question, I would also like to know the direction of causation: whether salt pans and dry lakes are flat because because the process of drying away of water somehow made them flat, or whether they were already flat and that was why water "sought" them out. —SeekingAnswers (reply) 14:46, 24 September 2015 (UTC)[reply]
Hm, this is of course appropriate, but not the whole story. Why are there hills by my house if gravity and erosion should take them away? Of course the answer is that they are slowly eroding, and there is also uplift in some areas, recent glaciation, and other things that cause topography. I think gravity is important, as is the self leveling of water, but I think a complete explanation must draw on some other factors that I can't think of right now. SemanticMantis (talk) 14:41, 24 September 2015 (UTC)[reply]
Because the material that makes the hills by your house is not the same as the material that makes up salt flats. The cohesive forces holding together different soil and rock types varies widely.--Jayron32 14:52, 24 September 2015 (UTC)[reply]
User:SemanticMantis self-deleted a comment as "non-helpful" wherein he wrote, "Sure, but it's not clear that erosion is the dominant feature in flattening of salt flats. Mikenorton has it as an accreting process rather than an ablative process." I thought it was a helpful comment and makes a valid point. —SeekingAnswers (reply) 15:32, 24 September 2015 (UTC)[reply]
The lack of hills in the areas of salt flats is why there isn't as much erosion. It's not that there were hills, and they salt eroded down into flat areas, so much as the lack of slopes in the area is why water collected in basins and evaporated into flat salt pans. Had there been slopes, the water would not have collected in depths necessary to form salt flats. --Jayron32 15:43, 24 September 2015 (UTC)[reply]
Because "water seeks its own level." Oddly enough, I can't find a WP page that simply addresses this concept and common phrase. It occurs in Pressure#Liquid_pressure, along with lots of math and derivations for why this is the case. SemanticMantis (talk) 14:41, 24 September 2015 (UTC)[reply]
"Water seeking it's own level" is a folk expression which scientists call Hydrostatic equilibrium. --Jayron32 14:53, 24 September 2015 (UTC)[reply]
"Water seeking its own level" and hydrostatic equilibrium explain why the surface of water bodies would be flat; it does not explain why salt pans and dry lakes (the bottom floor) would be. —SeekingAnswers (reply) 15:30, 24 September 2015 (UTC)[reply]
As to causation, water (and the salts that it carries in solution) collects in the topographically low areas that are now salt pans. Repeated cycles of filling and evaporation will produce that flat surface. Mikenorton (talk) 14:56, 24 September 2015 (UTC)[reply]
Sometimes salt formations are flat, sometimes they pile up. EDIT- these are not natural, I made a mistake in grabbing the first pile of salt picture I found.I tried to make an analogy of filling a bowl of salt water, then waiting for the water to evaporate. The problem with that analogy is that it won't always work - depending on the rate of evaporation and the salt concentration, you may get a nice flat surface, or you may get large crystals or mounds, like in the picture at right SemanticMantis (talk) 15:20, 24 September 2015 (UTC)[reply]
Hm, I guess it doesn't say explicitly that they are natural, but the photo does claim to be taken at the world's largest salt flat Salar_de_Uyuni. SemanticMantis (talk) 15:29, 24 September 2015 (UTC)[reply]
From the image description: "Salt is harvested in the traditional method: the salt is scraped into small mounds for water evaporation and easier transportation, dried over fire, and finally enriched with iodine." Smurrayinchester 15:59, 24 September 2015 (UTC)[reply]
D'oh! Thanks. I'll amend the caption, other good pics of natural salt pillars in your links above. SemanticMantis (talk) 16:25, 24 September 2015 (UTC)[reply]
(Edit conflict) To expand a little: rain will fall on the salt pan and dissolve some of the salt (and also carry the insoluble sediments). Gravity will then pull it to the lowest point, where it will pool until it dissolves, leaving the salt behind. By this process, salt and other sediment is transported from the highest points to the lowest, which gradually flattens the pan. That said, salt pans aren't always smooth - Devil's Golf Course is very rough indeed, because rain in Death Valley is virtually unknown and instead crystalisation effects predominate. Smurrayinchester 15:22, 24 September 2015 (UTC)[reply]
Agree. Salt lakes form in endorheic basins, closed drainage basin that retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation. Climate changes with time, I assume that in the past, rain would wash sediment down from the surrounding heights, and over time sediment deposition would cause the bottom of the lake or marshes to become fairly flat. The thickness of the salt layer of the Bonneville Salt Flats for example reaches only 5 feet near the center. Ssscienccce (talk) 15:31, 24 September 2015 (UTC)[reply]
Does the sedimentary pile-up process resulting in flatness, described in the above responses, apply only to salt pans and dry lakes with their repeated cycles of evaporation, or would it apply to bodies of water in general, so that even (non-dry) lakes, seas, and even oceans have flat bottoms? (Are lake, sea, and ocean bottoms generally flat?) Why or why not? —SeekingAnswers (reply) 15:41, 24 September 2015 (UTC)[reply]
Trenches and ridges are the result of tectonic processes, as the plates move together or apart. Ignoring tectonic effects the ocean bed looks like a big step. Near land, you have the flat continental shelf (produced by water flows called turbidity currents), and the ocean you have the also flat, but much deeper abyssal plain, with a big drop between them. Smurrayinchester 15:59, 24 September 2015 (UTC)[reply]
This has been something I've been wondering since I was young, especially since my grasp on physics isn't the best: Say you're traveling in a closed car or other vehicle on a straight stretch of highway at 100 km/h, and you toss a ball straight upwards into the air of your car interior. Why doesn't the ball remain positionally stationary relative to the car, and careen into the car's back window as the car continues traveling forward? ᴅʀᴀᴄᴏʟyᴄʜ - ✉✎ 14:53, 24 September 2015 (UTC)[reply]
Inertia. Its frame of reference is the same as yours. Although you are throwing it upwards, It has the same forward momentum as you and the car have. So, when you throw it up, it is moving forward at the same speed you are. 217.158.236.14 (talk) 14:55, 24 September 2015 (UTC)[reply]
It does remain stationary relative to the car. The car is moving 100 km/h relative to the road, and the ball is too. Thus, they are (horizontally) stationary relative to each other. AlexTiefling (talk) 15:25, 24 September 2015 (UTC)[reply]
Here's a nice cartoon illustration from the UCLA physics dept. [24]SemanticMantis (talk) 15:26, 24 September 2015 (UTC)[reply]
If your car is accelerating as you throw, the ball will probably hit the back window (or the front windscreen if the car is braking harshly, or the side window if cornering). When accelerating, braking or cornering, the car is changing its inertial frame, so the ball no longer remains matched to that frame once it is in the air. An interesting experiment is to take a helium balloon in a vehicle to see how it behaves. Newton's First Law applies to your ball in a car at constant velocity. Dbfirs 15:44, 24 September 2015 (UTC)[reply]
If the car is travelling at constant speed and is tall enough and the ball is thrown upwards hard enough, surely it would eventually hit the rear window. Imagine a car 100 feet tall and you throw the ball so it would attain that height. Air pressure acting on the front surface of the ball will eventually slow its forward motion, so that the rear window catches up to it and collides. That air pressure on the front surface must be offset by the pressure acting on the rear surface due to the window pushing air ahead of it. Nevertheless, at some point on its upward or downward travel, the window and ball must collide. So although the answer is that the forward motion of the ball at the instant it leaves the passenger's hand keeps on carrying it forward, the phenomenon is apparent only because of the limited height to which the ball can be thrown in a conventional car. Akld guy (talk) 21:19, 24 September 2015 (UTC)[reply]
No, it has nothing to do with height. In the reference frame of the constantly moving car there simply is no net force that would push the ball either forward or backward. Just like in everyday life we do not experience the motion of the Earth's rotation (even if we jump really high), the ball inside the car cannot 'feel' in which direction the car is moving. - Lindert (talk) 21:31, 24 September 2015 (UTC)[reply]
(ec) In the hypothetical situation being described in the original question the car is closed. Assuming that there is no air blowing into or out of the car, then the air in the car is moving at the same speed as the car and so there is no "air pressure on the front of the ball" to slow its motion as the air pressure is equal on all sides. Of course if you start to introduce variables such as air blowing through the car then the whole situation is different and you are looking at the effects of air movement rather than inertia. Richerman(talk) 21:35, 24 September 2015 (UTC)[reply]
Yes but no mention was made that the car was a totally closed, sealed car. We were led to believe that this was an ordinary car, which as everyone knows has air leaks even when the windows are closed. You're talking about a hypothetical situation with a sealed unit, something that would exist only in a lab experiment. Akld guy (talk) 21:57, 24 September 2015 (UTC)[reply]
Why is the Baja California Peninsula a desert area?
the trade winds (yellow arrows) which bring weather to the Baja region blow across wide stretches of land, and are also blocked by the Sierra Madre Occidental mountains, lying along the Sea of Cortez/Gulf of California on the Mexican mainland. The Baja peninsula thus does not receive any winds that carry any moisture, as there is almost no fetch to speak of.
The primary winds over Baja are the Trade winds, which blow east-to-west, the opposite as the direction over the U.S.; so Baja is in the rain shadow of the Sierra Madre Occidental mountains. See the map to the right. --Jayron32 16:02, 24 September 2015 (UTC)[reply]
See Orographic lifting for rain shadow. I believe most of the rain comes in the eastern Pacific tropical storm season. --DHeyward (talk) 16:09, 24 September 2015 (UTC)[reply]
Which uses, overall, the least amount of water, almond milk, soy milk, or rice milk?
Have there been any studies made comparing them? Of course it may vary a lot within any one of the three industries, like perhaps one soy milk producer using way more water than another, especially if that producer is in a region with less expensive water, but on average, is one of almond soy, or rice much less water intensive? Furthermore, are there potential production designs that could in the future save more water in that industry than in the other two industries? Thanks.Rich (talk) 16:19, 24 September 2015 (UTC)[reply]
It takes almost 300 liters of water to make 1 liter of soy milk, see table 2 here [25]. A key term to help in other searches is water footprint. You are correct that it will vary within an industry due to production methods. An obvious source of variation is whether the soy is irrigated or produced via rainfed agriculture. In the corn belt of the USA, most of the corn is alternated with soy, and irrigation is relatively rare in that area. However the study linked above seems to have also averaged in the water usage from some irrigated soy. SemanticMantis (talk) 16:28, 24 September 2015 (UTC)[reply]
(edit conflict) Here is a study for Soy Milk. Here is a discussion of Almond production in general, though it does not go into the additional water needed for making almond milk. I can't find anything specifically on rice. Note, that finding good, scientific studies on Almond Milk is a bit trickier, since the popular press has blown up in recent years calling almond milk the devil; and then responses from other parts of the popular press saying almond milk is NOT the devil. Mostly because almonds come from California, and California is under a drought, and almonds use water to grow. --Jayron32 16:29, 24 September 2015 (UTC)[reply]
To avoid wasting time - we both linked the same document for soy, just with different URLs and file names. SemanticMantis (talk) 16:41, 24 September 2015 (UTC)[reply]
Among the many resources, these pages include summaries of scientific studies on water use and its effect on, say, almond tree irrigation efficiency.
Unlike many other crops, California tree farmers can't make the decision to not water their orchards this year - even if the economics of nut prices make the water costs a net financial loss; even if the natural resource experts know the Central Valley has not enough water for this agriculture this year. The orchards will die if they are not watered; and that will cause an economic impact over the span of several decades. So, it is more efficient to opt to keep the trees alive (at an economic loss) and not to plant other, more profitable crops - provided that those other crops' life cycles don't recur over many years. Contrast this with, say, alfalfa: if this year's market is poor, an alfalfa farmer can simply choose not to plant, and not to use any water on a fallow field. They can just pick right back up where they left off next year, (hopefully) when the water is more plentiful.
The point of all this discussion is to emphasize that "water budget" is not as simple as one number. The entire agricultural economy, and the natural resource landscape, is full of complex interdependency.
In general, if your concern is to have the least environmental impact, then the cheapest generic item is the best, since this will normally mean the lower the costs in materials and transportation to produce it and bring it to market. As long as all the costs are all factored into the price (there is no government subsidy or additional penalty) and the item is not one bought for its brand name, whichever has the lowest price should have had the least cost in production. There will always be a bunch of hidden factors, but that's going to be the case no matter how you do your calculations. μηδείς (talk) 20:22, 24 September 2015 (UTC)[reply]
NOx in diesel vs NOx in gasoline engines
Why is NOx production higher for diesel engines/a problem to be dealt with? --Scicurious (talk) 19:03, 24 September 2015 (UTC)[reply]
Diesel engines are designed to operate at significantly higher pressures and temperatures. This is necessary given the characteristics of diesel fuel and allows for greater energy efficiency, but it also has the side effect of creating much more NOx. Dragons flight (talk) 19:12, 24 September 2015 (UTC)[reply]
Infact the effords to reduce CO2 emissions from combustion engines - what todays politics focus on to prevent global warming - have lead to higher NOx emissions. On top this lowered combustion engines performance because exactly a high CO2 emission makes an effective combustion. The clue to the riddle is the simple fact that mono-nitrogen oxides (NOx) are formaly not Greenhouse gas but Carbon dioxide (CO2) is. --Kharon (talk) 21:34, 24 September 2015 (UTC)[reply]
I usually buy peaches and bananas a handful at a time, and find this often means they all ripen and then quickly go bad. I was curious about brewing prison hooch as an experiment. Everything I have read on line says you need actual brewer's yeast as an ingredient, that you need to keep the brew warm, and that you need to use an airtight container which you must burp to expel excess gas. I would like to know:
(1) Is store-bought yeast necessary? The peaches I buy almost always have a rather obvious yeast blush on the day they become ripe. Or am I running the risk of getting mold instead?
(2) How warm does the brew need to be? Would a black bag plastic bag in a sunlit window be good enough if the room averaged, say, 70 degrees?
(3) Would an oversized jug with a pinhole in the lid be good enough as an "airtight" container? I've had friends brew beer and lose half the batch to explosions, and I definitely don't want exploding hooch. I just don't know if the pinhole will interfere with the fermentation, assuming the brew is producing gas.
You do understand that pruno is part of the punishment, right? I hope this is just a chemistry experiment and you're not actually planning to drink the stuff. I guess you could save it for Lent. --Trovatore (talk) 20:42, 24 September 2015 (UTC) [reply]
Sounds like someone has never had the pleasure of sipping some delicious and inexpensive homebrew :P SemanticMantis (talk) 20:52, 24 September 2015 (UTC)
[reply]
Who, me, or Travatore? I have had home made wine (dad added too much sugar) and home brewed beer using both hops and hemp. I am assuming what I will get is something between wine and very cheap vodka, and do intend to drink it but will dilute it with OJ if it's that bad. μηδείς (talk) 22:16, 24 September 2015 (UTC)[reply]
No, you don't need to buy yeast, but there's a reason brewers commonly do - it lets you control what is in there and also initial concentration. Lots of things are traditionally made with Brewing#Spontaneous_fermentation, like sourdough bread, kombucha, sour beers, kimchi, sauerkraut, yogurt, etc. But your brew will likely be more sour than if you didn't let in the things like Brettanomyces and Lactobacillus that will likely show up with spontaneous fermentation. As for temp, low temp is the easiest way to get dangerous things into yogurt or kombucha, but my kombucha goes just fine at ~78F. Not sure how much that applies to hooch. You also might be interested in doing something more like Applejack_(beverage). SemanticMantis (talk) 20:43, 24 September 2015 (UTC)[reply]
As I understand it, leaving even a pinhole will likely let in wild stuff, which may turn out fine, but that's why people usually want air locks. One thing you can do for small batches is cover the lid with a balloon - gives you plenty of time to let it off gas while keeping it airtight. And if you forget about it, the balloon will just pop off, not explode [26]. SemanticMantis (talk)
Starting with fruit and not boiling the mixture before fermenting, there will be all kinds of stuff in it anyway. A big cotton ball in the neck of the jug as an improvised fermentation lock would suffice, I think, for keeping additional organisms and oxygen out. Ssscienccce (talk) 21:45, 24 September 2015 (UTC)[reply]
Good point, I was thinking of critters that could colonize over time in a liquid that might not colonize the outer bit of a peach within a few days. But there is indeed probably more than just yeast at the start, if you're starting with old peaches exposed to air. SemanticMantis (talk) 21:50, 24 September 2015 (UTC)[reply]
Yes, I had thought of the balloon, and am sure I could rig an ess-neck trap for ventilation. I think from what's been said I will go with a pack of brewer's yeast, although I was kind-of hoping to work from "scratch". My understanding is that you know the process is done when the burping stops. μηδείς (talk) 22:21, 24 September 2015 (UTC)[reply]
You should read Yeast in winemaking. As yeast ferments the fruit it produces Co2 and alcohol as waste products. Eventually as the concentration of alcohol increases it kills the yeast, so it more-or-less drowns in its own urine! Wine and beer yeast has been selectively bred to be tolerant enough of alcohol to produce the required concentration before it stops working and to produce the flavours that the consumer finds desirable. Wild yeasts will work but they may become overwhelmed by other organisms before they have multiplied enough to begin the fermentation process, and if they do get going they will be very variable in their tolerance to alcohol and so may stop working before the required concentration has been reached - see Why Should I Use Wine Yeast? When the fermentation is going well it will produce enough Co2 to keep out oxygen and other organisms, but as it slows down towards the end of fermentation it won't - this is when an air lock comes into its own. Fermentation works best at the correct temperature - see: [27] You only get explosions if the fermentation is confined and the Co2 can't escape, such as: if the airlock gets blocked, if the drink has been bottled whilst still fermenting, or if fermentation restarts after the drink has been bottled. Richerman(talk) 22:36, 24 September 2015 (UTC)[reply]
Almost certainly a little different than they were 500 years ago. How much depends on what you care about and how you measure. The yogurt they make is probably pretty much the same. Here [28] is a study that specifically looked at drug resistance in Lactobacillus, and concluded that high spontaneous mutation frequencies were responsible. Even without the strong selective pressure, genetic drift also occurs. This paper [29] discusses the very high genetic variability in Lactobacillus spp. that live in vertebrate guts. SemanticMantis (talk) 21:46, 24 September 2015 (UTC)[reply]
Lactobacillus bulgaricus seems to have undergone important evolutionary changes "recently", and is still evolving rapidly. It has adapted to the dairy milk environment created by man, has lost functions not needed in that environment, and seems to cooperative with S. thermophilus in several ways.
"Several unique features of the L. bulgaricus genome support the hypothesis that the genome is in a phase of rapid evolution. ... has known a recent phase of important size reduction ... an extremely rare feature in bacterial genomes, may be interpreted as a transient stage in genome evolution. The results indicate the adaptation of L. bulgaricus from a plant-associated habitat to the stable protein and lactose-rich milk environment through the loss of superfluous functions and protocooperation with Streptococcus thermophilus." See source for more details. Ssscienccce (talk) 22:23, 24 September 2015 (UTC)[reply]
