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October 27

Does an inguinal orchiectomy result in the removal of the *entire* vas deferens?

Basically, this one person on this forum here:

http://forums.eunuch.org/showthread.php?27751-Is-it-possible-for-a-doctor-who-performs-an-orchi-to-remove-the-entire-vas-deferens

--told me that an inguinal orchiectomy results in the removal of the *entire* vas deferens.

Indeed, is this information accurately? Does an inguinal orchiectomy result in the removal of the *entire* vas deferens all of the way up to the seminal vesicle (in addition to the removal of the testicles and epididymis, obviously)?

Any thoughts on this? Futurist110 (talk) 00:44, 27 October 2016 (UTC)[reply]

Ask the surgeon who is going to perform the procedure. Beyond that, see WP:NOTAFORUM, WP:CRYSTAL, and WP:DISCLAIMER. μηδείς (talk) 01:06, 27 October 2016 (UTC)[reply]
Wikipedia has an article titled Inguinal orchiectomy which describes the procedure sufficiently to answer your question. --Jayron32 01:36, 27 October 2016 (UTC)[reply]
Given that the spermatic cord, which contains the vas deferens, has to be tied in two places, and cut between them, it is inevitable that there will be a short section left. To cut it right at the end would leave nothing to tie - which would risk internal bleeding as it also contains the blood vessels which serve the testes. Wymspen (talk) 09:19, 28 October 2016 (UTC)[reply]
As noted in Vasectomy, oftentimes one or both ends of the tubes will be cauterized. ←Baseball Bugs What's up, Doc? carrots→ 16:08, 28 October 2016 (UTC)[reply]
In an orchiectomy the whole spermatic cord is cut, including the blood vessels - not just the vas deferens. There is therefore a much greater risk of bleeding. Wymspen (talk) 11:24, 30 October 2016 (UTC)[reply]

October 28

Why did old TV screens dwindle to a tiny dot when switched off?

And why was this dot in the centre of the screen specifically? Equinox ◑ 13:35, 28 October 2016 (UTC)[reply]

Because the scanning coils no longer scanned. The the few electrons (cathode rays) being produced by the still hot emitter (gun), thus took a straight path to the centre of the screen.--Aspro (talk) 13:59, 28 October 2016 (UTC)[reply]
Some relevant diagrams at cathode ray tube. SemanticMantis (talk) 14:33, 28 October 2016 (UTC)[reply]
A CRT screen works by creating an electron beam pointed toward the center of the screen, which is then deflected by electromagnetics to create each dot. The electromagnets turn off right away when the TV turns off, and the residual electron stream thus hits the center. StuRat (talk) 16:24, 28 October 2016 (UTC)[reply]
Not quite instantly. The picture could be seen visibly shrinking to a dot, and the dot might wander around slightly for a bit until the scanning waveforms died out completely. By the way, the picture on CRTs was not made up of dots (I presume StuRat is implying pixels), rather, it is made up of lines and each line carries analogue information. SpinningSpark 21:45, 28 October 2016 (UTC)[reply]
A colour CRT was made of dots. The spots still scanned as lines, but there is a dot mask - literally a metal sheet with holes in - just behind the front glass. The beams then hit spots of coloured phosphors on the back of the glass. The dot mask is needed to stop the closely spaced beams from the three electron guns, one for each colour, from overlapping and blurring the colours. Andy Dingley (talk) 20:53, 30 October 2016 (UTC)[reply]
I am not sure, but I think a cathode ray tube television is just an oscilloscope being fed a fancy signal. Certainly there are some elaborations like using magnetic rather than electrostatic deflection to allow a larger screen, and the colored phosphors laid out in a repeating pattern, but the basic idea seems there. Wnt (talk) 22:39, 28 October 2016 (UTC)[reply]
Not exactly "just an oscilloscope being fed a fancy signal". Based on my limited experience with oscilloscopes, my understanding is that the intensity of the electron beam in those is constant. In a CRT TV, the intensity of the beam is what's varied to produce bright or dark areas on the screen. --69.159.60.36 (talk) 10:38, 29 October 2016 (UTC)[reply]
The electrons are drawn towards the screen by the high positive charge on an anode with a hole in its center for the electrons to go through. The high voltage is generated by a voltage multiplier and without some active way of discharging it will continue to hold its charge for some time. It will discharge eventually through a high resistance but in the meantime there will be a spot on the screen as the cathode will stay warm for a while. Making a mechanism to quickly discharge the anode when the power is turned off is a non-trivial task because of the high voltage. Dmcq (talk) 23:23, 28 October 2016 (UTC)[reply]

Just as an interesting tangent to this question: while everyone knows that computers used CRTs to display text and sometimes graphics for many years, some of the earliest computers (in the late 1940s) had a completely different use for them: they were the main memory of the computer. The idea was that when the electron beam is pointed at a particular part of the glass and then turned off, it takes a while for the charge on that part of the glass to dissipate. You can then tell whether there's a charge there by pointing the beam at it again and seeing how it behaves. If there is, that's a 1-bit and you recharge the spot using the beam. If not, it's a 0-bit and you don't recharge it. A single CRT might have a 32x32 grid of positions, enabling it to store 1,024 bits, or as we would now say, 128 bytes. See Williams tube. Modern main memories are a bit larger! --69.159.60.36 (talk) 10:46, 29 October 2016 (UTC)[reply]

The OP did say 'diminish' : (intransitive) To disappear gradually. wiktionary even though this takes just a few milliseconds. It is a matter of proportionality. The scanning coils need energy to scan and one can see this if the supply voltage falls – the picture gets smaller, (30 odd years ago in Brazil one could by primitive looking electromechanical voltage regulators, to keep the TV picture the same size as the mains voltage went up and down). Same thing happens to the electron beam but instead of having to illuminate the whole screen, the residue electron only illuminate a small area. Good thing too. If all that energy required to illuminate the whole screen just hit the centre of the screen without being spread out across the whole screen, they burn away the phosphorus coating. I used to come across this sometimes when someone had tried to 'fix' a telly without out ensuring the raster circuits were working first. It left the TV with a dim spot in the centre of the screen and as the c.r.t. was the most expensive thermionic vale in the whole set, it rendered it only good for spare parts. Talking of oscilloscopes, the TV has a built in oscilloscope. It is the screen itself. By looking at (preferably) the test card transmissions one could tell what needed doing. I think it was seeing how a magnet placed upon the screen and deflect that little dot that got me interested as a kid in repairing TV in the first place – together of course with the extra pocket money it started earning me. So , the energy to keep the oscillators and raster scan going, dies pretty quickly but the hot 'gun' still emits enough electron, with at a high enough potential between cathode and anode to excite the phosphorus at the centre of the screen. Final, the CRT acted as big condenser (capacitor). This was evident even if it was removed and on the work bench if one placed one's fingers on the wrong places before discharging the charge through a high resistance and received a big belt from it. Hence, their early use as computer memory tubes. @SpinningSpark. Colour television screens have a mask behind them so to only allow one RGB picture element (PEL) to be illuminated at a time. Take a magnifier glass and look a (say) a Sony Trinitron and they are all little distinct PEL's, so me thinks StuRat is right in that context.--Aspro (talk) 12:00, 29 October 2016 (UTC)[reply]

Reasons for and severity of the dangers of leaving mobile phones on during flights

I have repeatedly been told to shut off the wireless functionality of mobile phones during flights, but do not know why. Why is it hazardous, and how hazardous is it?--Leon (talk) 15:44, 28 October 2016 (UTC)[reply]

Without this rule, you would have many passengers picking up their phones to call home near landing time. Now, mobile phones will increase transmission power if needed, and that's certainly likely to happen when calling from inside a plane. Then imagine 200 people switching on their phones, each phone would transmit at a power of the order of 1 watt, this RF power of all the phones collectively would cause massive interference inside the plane affecting the phone users, so they would keep their phones switched on for longer trying to get in touch with whoever they are calling. So, even if you start with a handful of phone users at any one given time, their mutual interference would cause more simultaneous phone users as the phone calls take a lot longer to be completed. You could thus easily get a total RF power of a few hundred Watts inside the plane.
A phone that is transmitting at some specific frequency that is subjected to huge levels of RF interference will start to produce intermodulation signals. To transmit a signal at some frequency, an oscillator produces a signal at the desired frequency, which is then amplified. But if you subject the device to an RF interference, then this RF signal will mix with the current that is used to amplify the signal from the oscillator, giving rise to spurious signals at different frequencies (at the sums/differences of the original frequencies). Each phone will thus end up transmitting at many different frequencies, it is then possible that the plane's communication or GPS systems will be affected. That would only require a small fraction of the total power of a few hundred watts to be converted to signals at frequencies close to those used by the plane. Count Iblis (talk) 18:01, 28 October 2016 (UTC)[reply]
Sorry, this is a pure speculation. There is no evidence that phones can produce any unusual frequencies because some other phones work nearby. The highly non-linear parametric processes, that you refer to, require such strong electromagnetic fields that phones (together with the plane) will likely melt before this parametric generation becomes significant. Please, stick to verifiable facts. Ruslik_Zero 19:27, 28 October 2016 (UTC)[reply]
Well yes there is evidence, see this paper for instance. Specifically, the research found intermodulation products from mobile phones in the DME and GPS bands, two important aviation navigation aids. Intermodulation due to transmitters receiving an interfering signal through their transmission antenna is a well known and common phenomenon amongst radio engineers. SpinningSpark 21:19, 28 October 2016 (UTC)[reply]

There's another issue besides any possible hazards to the airplane, which is possible problems with the cellular system. Depending on the altitude, a single phone might try to connect simultaneously with a large number of cell towers, and the system might not be able to handle that. --69.159.60.36 (talk) 10:50, 29 October 2016 (UTC)[reply]

Disregard the answers above. Youtube has the right one: Why can't you use phones on airplanes. Hofhof (talk) 14:06, 29 October 2016 (UTC)[reply]

Question about plane waves

On the "Plane waves" page it states that the argument of the wave equation (ω t − k ⋅ r) can be obtained by using the "scalar product" as shown below. But I'm wondering, where did the negative sign come from? Since this section references the four-vectors of special relativity, I think this assumes the use of the standard metric signature (+---) but I don't see that stated and I want to be sure. Also, why is the argument (ω t − k ⋅ r) always subtracted? I think this is because if it were positive (ω t + k ⋅ r) the wave would travel backwards, but this is also not stated so I'm not sure. Thanks.

Regarding:

In special relativity, one can utilize an even more compact expression by using four-vectors: 

   The four-position R = ( c t , r ) 
   The four-wavevector K = ( ω c , k ) 
   The scalar product K ⋅ R = ω t − k ⋅ r — Preceding unsigned comment added by Dugclaws (talk • contribs) 17:16, 28 October 2016 (UTC)[reply]
Yes, correct, the expression is for a forward travelling wave if k is in the same direction as r. For the version of the equations which use a scalar k rather than a vector, a plus sign would indicate a wave travelling backwards. This kind of notation is used for analyzing transmission lines for instance, where the wave is restricted to travelling in only one of two directions. However, when using a vector k a backward travelling wave can be represented by pointing k in the opposite direction to r (or it can be pointed in any other direction at all). There is thus no need to have two different forms of the equation if vectors are used. SpinningSpark 21:35, 28 October 2016 (UTC)[reply]

Largest fragrant flower

What is the largest fragrant flower in the world (in terms of diameter, flower weight or both)? I mean with pleasant smell, unlike Rafflesia, etc. Thanks in advance. --93.174.25.12 (talk) 17:39, 28 October 2016 (UTC)[reply]

Besides Rafflesia, Amorphophallus titanum also has huge flowers (I'm pretty sure the name means "giant floppy dick", which brings me no end of giggles), but also apparently stinks of decomposing flesh. Reading through a few "listicles" of large and unusual flowers suggests the largest "non-rotting-dick-smelling flower" in the world may be the common sunflower, or Helianthus annuus; some of the domesticated breeds have very large flowers, this image search here turns up sunflowers whose central pod, not including the outer ray petals, exceed 16 inches (40 centimeters). It, of course, depends on how one defines a "flower", the term in common speech differs greatly from the botanical definition. See flower and Plant reproductive morphology for some of the background. --Jayron32 18:15, 28 October 2016 (UTC)[reply]
The sunflower, however, does not smell, not to mention it's not fragrant. 93.174.25.12 (talk) 19:10, 28 October 2016 (UTC)[reply]
I can smell them. --Jayron32 21:01, 28 October 2016 (UTC)[reply]
I think "giant misshapen penis" is probably a better translation to modern English. A-morphos - without clear shape. SemanticMantis (talk) 20:08, 28 October 2016 (UTC)[reply]
Except wikt:amorphous doesn't mean misshapen, just "does not hold a regular shape" Hence, floppy. --Jayron32 21:07, 28 October 2016 (UTC)[reply]
Ok, you are free to translate however you like, I was merely offering an alternative. A. titanum are not floppy, by the way, they are rather firm in fact, due to turgor pressure. Perhaps "unshapen" is a better word for 'amorphus', but translation is always a bit subjective. SemanticMantis (talk) 21:34, 28 October 2016 (UTC)[reply]
I think a more relevant point is both wiktionary which says "without form, shapeless, deformed" and our article "without form, misshapen" seem to imply misshapen or deformed is a resonable (I won't say better) translation. Whether this is correct or not I cannot say. And I assume we are talking about translation here, if the word is from the Ancient Greek ἄμορφος ‎(ámorphos) rather than the English amorphous, we potentially should be going by the Ancient Greek rather than the modern English meaning which may not be entirely the same (i.e. a form of false friends). Although scientific names can be complicated, as people may be thinking of the English word, look for a Latin, Greek or whatever alternative etc rather than studying the meaning of the Greek or Latin word that well. Then again, Amorphophallus was first scientifically described and I assume named in 1878 by an Italian botanist. Nil Einne (talk) 09:31, 29 October 2016 (UTC)[reply]
No, obviously, it's glassy rather than crystalline. —Tamfang (talk) 20:17, 29 October 2016 (UTC)[reply]
Also yes, to clarify, sun flowers have rather large inflorescences, but rather small flowers. The Asteraceae and a few other families an especially uncommon/derived inflorescence, called a Pseudanthium. SemanticMantis (talk) 20:59, 28 October 2016 (UTC)[reply]
When I stated "it depends on how one defines a "flower", the term in common speech differs greatly from the botanical definition" what I meant by that was "it depends on how one defines a "flower", the term in common speech differs greatly from the botanical definition." Just in case that was unclear. — Preceding unsigned comment added by Jayron32 (talk • contribs) 21:03, 28 October 2016 (UTC)[reply]
And the concept of nested quotation marks continues its slow death. —Tamfang (talk) 20:19, 29 October 2016 (UTC)[reply]
Some water lilies are about the size of that sunflower (um no my imagination getting the better of me Victoria cruziana) grow to about 25cm and they do have a light pleasant scent. Plus I think one can get a lotus growing to about the same size as a water lily flower. Dmcq (talk) 19:21, 28 October 2016 (UTC)[reply]
Individual Cattleya warscewiczii orchid flowers can reach 11" across [1], and there are usually several (up to 10) of them per spike (inflorescence). Several Cattleya hybrids are also in the same ballpark of size. By weight - I need to look up the literature, but Stanhopea tigrina flowers are quite massive (albeit short-lived). Several other orchids (e.g. Angraecum sesquipedale) have flower parts that are very long, and have a pleasant smell, but I'm not sure that's what the OP is asking. Dr Dima (talk) 23:32, 28 October 2016 (UTC)[reply]
note to self: I need to fix a bunch of our orchid pages, they are ridiculously lacking in content. I'll try to do this over the weekend, unless life happens. Dr Dima (talk) 23:36, 28 October 2016 (UTC) [reply]
OK, I fixed our Cattleya warscewiczii article. On to the next one... Dr Dima (talk) 05:11, 30 October 2016 (UTC)[reply]
How about Magnolia grandiflora? The article says the flowers are up to 12 inches in diameter, and I know they are fragrant. -Arch dude (talk) 16:29, 29 October 2016 (UTC)[reply]

Largest inflorescence (branched) is the talipot palm which does have an odor. The Titan arum is the largest unbranched inflorescence. Rafflesia arnoldii is the largest single flower. EvergreenFir (talk) 17:14, 29 October 2016 (UTC)[reply]

October 29

component type ID

what is this diode(?) ? On the PCB, the designator is SGxxx and the symbol is like this: o---><---o
Thanks everyone in advance! Asmrulz (talk) 03:37, 29 October 2016 (UTC)[reply]

The colour band numbering suggests 53±2%. If it was a diode you would put "1N" on the front. 1N532, but since the red is offset it looks more like a tolerance. THis may not be a diode. Graeme Bartlett (talk) 04:01, 29 October 2016 (UTC)[reply]
It might be a transient-voltage-suppression diode. Though at first I thought it looked like a fuse: http://www.slimlab.net/mirror/fusecolours/fusecolours.htm but the colours don't decode to anything. Graeme Bartlett (talk) 04:29, 29 October 2016 (UTC)[reply]
I don't think this looks much like a diode. The internal structure looks much more like a resistor, although the clear glass packaging would be unusual. If it is a resistor, I don't think the offset red band is a tolerance, resistor colour codes are a minimum of three bands and this has only three. More likely the offset is to indicate which end to read it from. I would also read the centre band as brown rather than orange; 53 is not a preferred number whereas 51 is on the E24 series. That would make its value 5.1kΩ. Have you tried measuring it?
I have seen diodes colour coded in this way, for instance the common 1N4148 diode is marked with Y-BN-Y-S colour bands by some manufacturers, and the "1N" is just implied. However, 1N512 is a large diode with a threaded stud. SpinningSpark 09:29, 29 October 2016 (UTC)[reply]
It feels plastic-y and doesn't measure as anything (open loop) in either direction Asmrulz (talk) 10:08, 29 October 2016 (UTC)[reply]
If that's the case it would not be a fuse, diode or resistor. (but could be a blown fuse.) transient-voltage-suppression diode is still possible as it will only conduct when the voltage is high. Graeme Bartlett (talk) 12:56, 29 October 2016 (UTC)[reply]
The pictured component is a spark gap surge protector. [2] AllBestFaith (talk) 12:58, 29 October 2016 (UTC)[reply]
Yup, put a coil across it, is arcing. Thanks everyone Asmrulz (talk) 14:07, 29 October 2016 (UTC)[reply]

Best substance to absorb moisture from a damp item upon contact

I am looking for a substance that will absorb moisture directly from a damp item upon contact. I have been looking into desiccants (specifically activated carbon because of it's easy regeneration properties and additional odor removal characteristics) as well as super absorbent polymers. However, the only evidence I can find regarding desiccant moisture absorption is dealing with removal of moisture in the air and the SAPs absorbing liquid that has been directly poured onto the polymer.

Is there a material out there that can remove moisture from a damp item? Preferably a material that can be reused and can maintain it's absorption properties if contained in a non-woven/fabric covering. — Preceding unsigned comment added by 146.88.42.76 (talk) 04:51, 29 October 2016 (UTC)[reply]

Powdered calcium chloride can do this, but it's not reusable. 2601:646:8E01:7E0B:411:FA40:3178:507F (talk) 06:36, 29 October 2016 (UTC)[reply]
  • Are you concerned about transfer of the dessicant to the item? Calcium chloride would be a problem there.
I would look at fuller's earth. This is cheaply available as cat litter (the grey mineral cat litter) and can be powdered further in a coffee grinder (cheap whirling blades type). It's inert, absorbent and can be regenerated by oven drying.
I'd also consider using a towel. This is already "its own fabric covering" and can be applied and removed cleanly and easily. Well laundered (older) cotton towels are fairly fibre free, and microfibre fabrics work well too. Andy Dingley (talk) 09:24, 29 October 2016 (UTC)[reply]
Sawdust or fine wood chippings, possibly, if it's dried out after use.--TammyMoet (talk) 10:38, 29 October 2016 (UTC)[reply]
Vermiculite is often used as an absorbent. --Jayron32 10:47, 29 October 2016 (UTC)[reply]
It would help if you inform us of what the item was. For instance, once having finished the wet process of making gunpowder one uses distilled alcohols for fast desiccation before the nitrate can form large crystals. If you have been looking at polymers, you will ready know about how to rejuvenate silica-gel in order to use it again. Then there is vacuum freeze drying and many other techniques. However, there is not one method that suits all cases. --Aspro (talk) 12:20, 29 October 2016 (UTC)[reply]
Indeed. Fuller's earth will work great on some items, while ShamWow may be more effective on others. Drying cabinet may be the best bet for other things. SemanticMantis (talk) 15:27, 29 October 2016 (UTC)[reply]
Disposable diapers are designed for contact moisture removal. If the moisture is clean water only, the diaper can be dried and reused, but it may be more cost-effective to just throw it away. If you have ever fished a diaper out of the toilet after baby throws it in there as a experiment, you know how much water a diaper can hold -Arch dude (talk) 16:22, 29 October 2016 (UTC)[reply]
The "magic" in this case is courtesy of sodium polyacrylate which can absorb several hundred times its own mass of water. Roger (Dodger67) (talk) 15:27, 30 October 2016 (UTC)[reply]
After reading the diaper article, I now see that some diaper products are designed to be slightly less than optimal at removing moisture from the skin, so baby will feel a small amount of discomfort to hasten potty training. You should avoid these products, perhaps by using diaper for newborns or using a different product like a tampon. -Arch dude (talk) 01:40, 31 October 2016 (UTC)[reply]

A hypothetical idea

Suppose a universe has four spatial dimensions, but gravitational force is not proportional to acceleration, but to jerk. Would there be stable orbits? 93.142.81.244 (talk) 18:16, 29 October 2016 (UTC)[reply]

See Anthropic principle#Spacetime and the linked articles for our coverage of this issue. Tevildo (talk) 18:29, 29 October 2016 (UTC)[reply]
But there the force of gravitation is still mass × acceleration, so the gravitational acceleration is constant. I'm talking about mass × jerk, where the Δacceleration would be constant. For example, suppose a jerk of j = 1 m/s3 is applied to a standing body. After five seconds, a = jt = 5 m/s2, v = jt2/2 = 12.5 m/s, s = jt3/6 ≈ 21 m. I wonder if that could solve the instability of orbits. I suppose this is useless in our own universe, where acceleration is constant but I wonder if anyone has tried this? 93.142.81.244 (talk) 18:43, 29 October 2016 (UTC)[reply]
The initial problem with that idea is that Newton's first law would become "if the net force acting on an object is zero, then the acceleration of the object is constant", so the speed of all bodies in free space would tend to become infinite. Tevildo (talk) 09:41, 30 October 2016 (UTC)[reply]

Do athletes live longer?

Another thing that has been bugging me. Exercise is supposed to be healthy and increase our lifespan, and who exercises more than the athletes? But the thing is, when you exercise you breathe in more air, which contains lots of O2. Similarly, if you drink more water, which is also something that athletes do and is supposed to be healthy, you drive extra oxygen atoms through your body. Shouldn't all that oxidation kill us faster? 93.142.81.244 (talk) 18:30, 29 October 2016 (UTC)[reply]

One leading cause of death is heart failure (alongside cancer). Sport can considerably help here. Add to it that other pretty common causes of death are diabetes and simple falls. Sport also reduces the incidence of this. If you are active, you also have a lower chance of developing dementia.
Do not assume though that the more sport you do the healthier you are. Professional athletes might have a shorter lifespan compared to reasonable active people who bike, walk, play soccer, and lift moderate weights. Going to the extreme can also be pretty bad. Sumo wrestlers might have a lifespan 10 years below average, for example. Llaanngg (talk) 18:37, 29 October 2016 (UTC)[reply]
Well, I'd expect injuries from full contact fighting sports to overwhelm any benefits. 93.142.81.244 (talk) 18:50, 29 October 2016 (UTC)[reply]
Well, that was a useless pile of personal opinion. Changes to life expectancy due to athleticism has been studied quite a bit. For example here is a meta-study that examines 54 primary studies regarding the life expectancy of athletes. It goes into some detail and has a sizable bibliography for your perusal. This article discusses some of the factors that probably lead to the greater lifespan. And here's an easy-to-read newspaper article that relates the basics of a smaller study involving Tour de France competitors. If you're interested in the negative health effects of oxygen, our article at oxidative stress is a pretty good start. Presumably, the health benefits outweigh the problems, but I didn't immediately find anything the discussed that particular topic directly. Matt Deres (talk) 18:57, 29 October 2016 (UTC)[reply]
Personal opinion? Amazingly what I said, although did not have more than one source can be corroborated even by your sources: "Physical activity reduces many major mortality risk factors including arterial hypertension, diabetes mellitus type 2, dyslipidemia, coronary heart disease, stroke"Llaanngg (talk) 19:19, 29 October 2016 (UTC)[reply]
Yes, a lot of damage is caused by metabolism, but almost all that damage has to be repaired, otherwise we would not live very long (if you shut off the self repair mechanisms in a healthy teenager, that teenager would look like a 100 year old within a few years and then die). So, longevity comes down to how well the body is capable of repairing itself. This has a strong genetic component, which explains why many super centenarians (people who have lived beyond the age of 110) actually did not stick to healthy lifestyles (most people do not stick to healthy lifestyles, the super centenarians are a self-selected group out of the pool containing everyone who happen to have good genes for self-repair). E.g., Calment smoked cigarettes from the age of 21 (1896) to 117 (1992). So, the huge damage done by smoking which would have caused most people to not reach their maximum possible age, did not significantly affect her, because the repair mechanisms at work in her body repaired the damage done by smoking much better than in most other people, without that mechanism at work in her body she would not have reached anywhere near her record breaking age, even if she had lived according to the most healthy lifestyle you can imagine.
Now, if you exercise a lot, then you will do a lot more damage to your body. But note that the reason why exercise improves physical fitness is due to the body repairing itself. After damage has been done the body will not simply restore itself in its previous state it will go beyond that making itself stronger than it was before. A system that has to maintain itself would not be stable if the extra repairs in response to more damage done, would not lead to it becoming a bit stronger. Damage done via exercise is extra damage on top of all the processes in the body that lead to decay. The body is constantly at work to counter these processes. Exercise will stimulate the self-repair mechanisms, the ramped up metabolism will do more damage, but the net effect of all processes taken together is that your body becomes stronger and fitter. Longevity will increase provided you stick to your exercise routine well into old age. Genes that in people destined to become super centenarians are always switched on by default, may be switched off in normal people by default, but they can be switched on if you exercise a lot. While the variant of these genes may be different in non-super centenarians making them less effective, it will still be a huge benefit to switch them on. So, it's best to stick to Jack LaLanne's routine and keep on exercising. Count Iblis (talk) 19:02, 29 October 2016 (UTC)[reply]
Nitpick Count Iblis said: "if you shut off the self repair mechanisms in a healthy teenager, that teenager would look like a 100 year old within a few years and then die"
I'm afraid that is a gross overestimation of the survival time in such a situation. Death would occur in a matter of hours at most, not years. Just one such mechanism; the constant replacement of the stomach lining, if stopped would cause the stomach acid to dissolve the stomach and then move on to the rest of the viscera, but by then the victim would already have bled out and died. Roger (Dodger67) (talk) 15:44, 30 October 2016 (UTC)[reply]
To focus purely on one thing in the OP: drinking more water doesn't really "drive extra oxygen atoms through your body". It is technically true, since water molecules contain oxygen atoms, but your body doesn't split water molecules apart to get at the hydrogen and oxygen. Respiration actually produces water. Plants, and other photosynthetic organisms, are the ones that take up water to use it as an electron donor, yielding oxygen as a waste product. The reason you need to drink water is to replenish excreted water. --47.138.165.200 (talk) 21:47, 29 October 2016 (UTC)[reply]
Thinking further about this... does this mean that respiration is an antioxidative process? 93.142.81.244 (talk) 00:46, 30 October 2016 (UTC)[reply]
There isn't really such a thing as an "antioxidative process". Aerobic metabolism is a redox process, which involves oxidizing "fuel" like sugars and fatty acids and reducing oxygen. This inevitably generates reactive oxygen species as a byproduct, which is why aerobic organisms have antioxidants, to counteract this. --47.138.165.200 (talk) 06:52, 31 October 2016 (UTC)[reply]

Thanks, guys. I guess it's more complicated than I thought. 93.142.81.244 (talk) 22:43, 29 October 2016 (UTC)[reply]

A thing to keep in mind in general (touched on in some of the responses above) is that athletes (in the American English sense of the word) are people who compete. Sometimes (actually, very often) competitive sport has exigencies that don't match up well with personal fitness.
This is a peeve of mine with regard to high-school athletics in the United States, especially football. High-school football forces the school day to start very early, so that the team can run practices afterwards. Any time it is questioned, the first arrow from the defenders' quiver is that American kids are fat and unhealthy and need physical education.
And that part is certainly true. What's not clear at all is that football is at all a good way to make them more fit. Getting smacked on the head is not an intuitive way to improve your physical health. --Trovatore (talk) 22:57, 29 October 2016 (UTC)[reply]
Aside for anyone who was confused by my "American English" comment: It seems that in Commonwealth English, "athletics" is not competitive sport in general, but one particular competitive sport, the one that on this side of the pond we call "track and field". So in England, say, a student who plays rugby or cricket does not count as an "athlete". --Trovatore (talk) 23:06, 29 October 2016 (UTC) [reply]
Yeah, I meant athlete as a competitive sports player, not just Usain Bolt etc. 93.142.81.244 (talk) 00:46, 30 October 2016 (UTC)[reply]
Also, in American English, football means American football, which is a rougher game than association football. Robert McClenon (talk) 00:54, 30 October 2016 (UTC)[reply]
@Trovatore: I would be very suspicious of this explanation for the early school day. My guess (and it's just a guess) is that parents want to see kids safely off to the school bus, or at the very least awake and dressed, before they head out the door to work. Kids being what they are, if they come home at 3 and the parent comes home at 5, they may get in a little trouble... but if the parent leaves at 8 and the kids are supposed to get on the bus at 10, there's no telling what would happen. Wnt (talk) 13:12, 30 October 2016 (UTC)[reply]
Some factors to consider:
1) Some sports cause regular concussions, like boxing and American football, so those can shorten lifespans.
2) Some sports require consuming large numbers of calories, which can cause a problem when the player retires, and needs to immediately downsize their diet or become obese. StuRat (talk) 02:25, 30 October 2016 (UTC)[reply]

Is the a/c ventilation system ever big enough so that a person can move through it?

How big can the ventilation system of a/c be? Or is this just a reality bending for movies? --Llaanngg (talk) 18:30, 29 October 2016 (UTC)[reply]

IIRC, Mythbusters once did an episode about it. It turned out to be impractical even if possible, because anyone moving inside it made a lot of noise, and sound travels very well through metal tubing. 93.142.81.244 (talk) 18:48, 29 October 2016 (UTC)[reply]
Specifically, see MythBusters (2006 season)#Episode 54 – "Crimes and Myth-Demeanors 1". --76.71.5.45 (talk) 04:41, 30 October 2016 (UTC)[reply]
Yes, the idea of sneaking past somebody in the HVAC system is absurd. Also, in No Country for Old Men, a bag of money was slid in and out of the duct-work, which would also have alerted everyone in the motel. However, hearing something in the duct-work and knowing exactly where it is are two different things. It would be hard to locate the source of the sound, precisely because sound caries so well to each of the vents. This might work well in a horror movie, if the baddie was in the HVAC system, but nobody could tell exactly where it was, to run from it. StuRat (talk) 15:00, 30 October 2016 (UTC)[reply]
Quite apart from the noise aspect, all of the ventilation ducting I've ever seen (which may not be a representative sample) would, both of itself and in the structures supporting it, be too weak to support the weight of a person crawling through it. {The poster foremrly known as 87.81.230.195} 90.211.130.104 (talk) 05:17, 30 October 2016 (UTC)[reply]
I would love to see someone in Hollywood do this one properly. The ventilation duct to the sinister top secret spy base should quickly reach a comfortable height for walking. There should be little colored lines on the floor for you to follow with labels so that you can find the vaccine, aliens, self destruct mechanism, head honcho office. A few times you'd pass other bands of heroes, kids armed with wrenches or some James Bond on a rocket skateboard following their own lines, and a few groups of high-tech janitors in cleansuits burnishing the sides of the duct to keep it cinema-grade clean. You might find this air duct somewhere off the grand spiral staircase that connects the mezzanine of a 747 with the cargo hold below and the computer rooms on the top floor. Wnt (talk) 13:08, 30 October 2016 (UTC)[reply]
As an architect, I've seen ductwork up to maybe 5 feet high in a big room with a big air handler, but that tends to be right before or after the main HVAC unit and it rapidly diminishes to two feet max as it branches out, and it's often vertical, with smaller branches running out at each floor. Then there's the air speed - a duct that size is moving lots of air, pushed by a multi-horsepower motor that would tend to move large obstructions along with the air - and a row of turning vanes at every change of direction, balancing dampers, zone dampers ... In an office space the ducts are always much smaller because there's economic pressure to minimize the wasted space above the ceiling. Bruce Willis would have a hard time with such ducts, assuming the whole thing doesn't fall out of the ceiling or the colossal amount of noise he makes doesn't give him away. Bruce is also too big to fit through the distribution registers. Acroterion (talk) 14:38, 30 October 2016 (UTC)[reply]
Also, ducts are dirty as Wnt notes. A further note to Hollywood - when the hero activates the sprinkler system ,only one sprinkler comes on at a time in a normal sprinkler system, the one that gets hot. It spews filthy, greasy black rusty water, because the sprinkler pipes are steel and are rarely flushed after they're installed. The threading is cut using cutting oil, which remains in the system.
In jails, even though the heads are tamper-resistant, somebody occasionally sets one off. The cell has to be scrubbed and re-painted (and the inmate scrubbed too, though not painted). As a jail maintenance guy told me, the inmate said "I won't be doing that again!" Acroterion (talk) 14:54, 30 October 2016 (UTC)[reply]
Can't fit through the A/C duct? Take the Jefferies tube! Seriously, though TV Tropes has an intersting writup on this topic.[3] --Guy Macon (talk) 15:49, 30 October 2016 (UTC)[reply]
That's a good essay. As in lots of movie things, "where's all that light coming from?" is an obvious question too. Acroterion (talk) 17:48, 30 October 2016 (UTC)[reply]
@Acroterion: What you say about the sprinkler system is absolutely true, but I do have to wonder why. I mean, it's not like they really only get set off in a fire - there's always some undergrad with a frisbee or an unsung vandal looking to do damage for the hell of it, or the good folks at Prank University just call one of the people who ought to know better on the phone and get them to do it for them. It would seem to make sense to spare the extra twenty minutes and flush the damn things out. Wnt (talk) 22:54, 30 October 2016 (UTC)[reply]
They do usually get drained down a couple of times during construction and now and then the fire marshal opens the test port to make sure the alarm works or it's drained for alterations, but there's really no means of actually flushing the system from one end to the other, since it's normally open on only one end. Draining clears out construction debris, but the oil from pipe manufacture and thread sticks around, and the pipe oxidizes a little. Ideally the system reaches an equilibrium and you don't want to introduce oxygenated water on a regular basis. Adding multiple flush points adds cost to a system that's supposed to be affordable protection, and it's usually hard enough in design to find a place to put the main drain where its discharge won't dump dirty water in a public place, much less in several places. The hydraulic calculations are fussy and the designers avoid adding complications. Acroterion (talk) 23:11, 30 October 2016 (UTC)[reply]
Plastic piping is commonly used in residential applications and the water isn't especially dirty. Plastic piping is starting to appear in commercial work but isn't approved everywhere. Acroterion (talk) 01:44, 31 October 2016 (UTC)[reply]
But wouldn't plastic piping be a problem in a fire scenario, because it would melt or even burn and thereby take out the sprinkler system precisely when it's needed most? 2601:646:8E01:7E0B:998F:4012:900C:F798 (talk) 05:06, 31 October 2016 (UTC)[reply]
There are lots of different kinds of plastic. The correct kinds—I've only seen PEX used in this scenario—are listed if they meet "UL 1821: Thermoplastic Sprinkler Pipe and Fittings for Fire Protection Service" (see also "NFPA 13D: Residential Fire Sprinkler Applications"). DMacks (talk) 05:39, 31 October 2016 (UTC)[reply]

October 30

Glass frit filters

Is it possible to obtain a glass frit filter plate alone, without the funnel? Or alternatively, is it possible to remove the filter plate from the funnel without irreparably damaging the item (i.e. in such a way that it would be possible to put the plate back in again as before)? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 06:15, 30 October 2016 (UTC)[reply]

What's wrong with this [4] & [5] or I think [6] & [7] too? Nil Einne (talk) 12:43, 30 October 2016 (UTC)[reply]
Cool! That's precisely what I was looking for! 2601:646:8E01:7E0B:998F:4012:900C:F798 (talk) 21:32, 30 October 2016 (UTC)[reply]

How do lungs cleanse themselves from dust buildup

Does all the dust and other particles that come with breathed air build up somewhere in the organism? If so, how do lungs or respiratory pathways cleanse themselves from such deposits? I know that nasal mucus catches some particles, but I don't think it's enough to prevent dust accumulation somewhere in the respiratory system in one's lifetime. Thanks.--93.174.25.12 (talk) 14:15, 30 October 2016 (UTC)[reply]

The two possibilities would be coughing it up and either swallowing it or spewing it from the mouth (see mucociliary clearance), or the body absorbing those particles over time, through the lung walls: [8]. However, in some cases, such as chain smokers, the particles may indeed accumulate faster than they can be removed: [9]. StuRat (talk) 14:20, 30 October 2016 (UTC)[reply]
In humans, we have a process called mucociliary clearance, in which our cilia cells that line our respiratory tract convey foreign particles out of the lung. Once again, our article cites numerous studies with further information on the effects of dust, particulates, and even cigarette smoke.
Nimur (talk) 14:30, 30 October 2016 (UTC)[reply]
Thank you for updating your post with corrections and citations, StuRat. Nimur (talk) 14:51, 30 October 2016 (UTC)[reply]
No corrections, only clarifications and citations. StuRat (talk) 17:23, 30 October 2016 (UTC)[reply]
Adding citations to a post without any [10] is indeed a correction to a majorly flawed post on the reference desk. Sorry this is still a surprise to you, but we do have standards here even if some people regularly don't meet them. Nil Einne (talk) 23:16, 30 October 2016 (UTC)[reply]
No, a correction would be if I removed an incorrect statement. I did no such thing. I clarified, and added citations, just as I said. StuRat (talk) 00:53, 31 October 2016 (UTC)[reply]
[failed verification]? I've read through the Heyder article and find no mention of particles being absorbed through the lung walls. A text search for "wall" yields only "multiwalled carbon nanotubes" and there are no hits for "absorb". There is a single clause mentioning "drug delivery to the systemic circulation", which I suppose would involve a drug molecule (not necessarily a particle) crossing the lung wall. Have I missed something?--Wikimedes (talk) 19:30, 30 October 2016 (UTC)[reply]
I concur - not in citation given. We've made a little progress - it's better than no citation, which was the original post - but I also do not find the statement in the full article that StuRat linked. Nimur (talk) 21:37, 30 October 2016 (UTC)[reply]
I hate to pile on here, but it was only 5 days ago at "Why are evolutionary the testis are located outside of the body?" that StuRat similarly used a source that did not actually contain the content he claimed. @StuRat:, you must realise that using sources in this way is disruptive because other editors are having to repeatedly fact-check your postings. Please try to raise the standard as this is a REFERENCE desk. DrChrissy (talk) 23:41, 30 October 2016 (UTC)[reply]
The linked article is titled "Deposition of Inhaled Particles in the Human Respiratory Tract and Consequences for Regional Targeting in Respiratory Drug Delivery". In that context, it's clear that they are talking about inhaled particles of medication which are absorbed into the lungs. If you're going to nitpick every source to this degree, I might be better off not listing my sources. StuRat (talk) 00:50, 31 October 2016 (UTC)[reply]
There's some discussion here [11] Nil Einne (talk) 14:25, 30 October 2016 (UTC)[reply]
I had thought that asbestos got absorbed through the lungs, but apparently not. This specifies that they may only lodge in the lungs (not that that is a good thing), and that they may get absorbed by the digestive tract if the particles are coughed up and swallowed. Matt Deres (talk) 22:03, 30 October 2016 (UTC)[reply]
The lungs contain alveolar macrophages which engulf anything foreign that makes it into the alveoli. (That article needs a lot of work.) --47.138.165.200 (talk) 02:54, 31 October 2016 (UTC)[reply]

Fetal pain at 13 weeks

Is there any evidence that fetuses are able to feel pain at 13 weeks gestation? I read the story of one former employee of Planned parenthood who said she witnessed a fetus squirming around as it was being aborted.Uncle dan is home (talk) 23:53, 30 October 2016 (UTC)[reply]

Prenatal perception#Prenatal pain seems fairly clear the answer is no. As for later in the pregnancy, if you're having trouble understanding parts of the article, perhaps this will help [12]. I can't seem to find any good sources discussing such videos that you mention in all the junk, hopefully someone else will. But in the interim, consider that when I touch my cat he will respond in vaious ways, even though I try to avoid causing pain and think I succeed most of the time. Point being, even if there is a reflex response let alone a conscious response, it doesn't mean either are because of anything remotely similar to pain. If someone is claiming something is a response to pain, you have to ask them what evidence the have fo the claim. Nil Einne (talk) 00:24, 31 October 2016 (UTC)[reply]

October 31

Balloon descent

How does a large helium balloon (e.g. a blimp or something the size of a hot-air balloon) descend? Hydrogen isn't particularly rare, so you could probably just let off some of it without losing a lot of money, and with a hot-air balloon, you can presumably just stop heating the air, but re-filling the Goodyear Blimp with helium sounds absurdly expensive. <helium balloon descend> on Google is all about party balloons and the like. Nyttend (talk) 03:02, 31 October 2016 (UTC)[reply]

See Ballonet. -- ToE 03:18, 31 October 2016 (UTC)[reply]
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