Wikipedia:Reference desk/Archives/Science/2017 September 15

= September 15 =

Extreme(ly foolish) Airbrushing
I want to use a cheap airbrush to spray clothes-washer grade bleach on some clothes dyed using natural colorants. What kind of bleach is a better choice, chlorine-based bleach or peroxide-based bleach?

Chlorine-based bleaches are sold as aqueous solutions. They are very likely easy to spray.

Peroxide-based bleaches are mostly sold as dried powders and must be dissolved in water before use.

I want to "paint" on the clothes using the bleach. I will do it outdoors in the open and wear rubber gloves, eye protective and a breath mask. I just want to know which kind of bleach is relatively friendlier to the airbrush which is made of stainless steel and rubber O-rings. -- Toytoy (talk) 01:34, 15 September 2017 (UTC)
 * An Airbrush is a tool that needs a supply of compressed air. Will you consider instead a cheap plastic spray bottle? I find that a disposable spray handle screws directly onto a large plastic bottle of chlorine bleach. Blooteuth (talk) 11:05, 15 September 2017 (UTC)
 * In the 70s, it seemed common to me to use plastic spray bottles with chlorine bleach to fade out our jeans. Then, many people painted on the faded parts. Bleach is "wet", so it doesn't stick to one spot. It bleeds into the fabric. Further, it isn't about how much bleach you use. It is about how long you leave the bleach on the clothes. 209.149.113.5 (talk) 11:22, 15 September 2017 (UTC)


 * Either bleach will do this, although the perborate (oxygen) bleaches tend to be better at cleaning without damaging dyes, so you might want to use hypochlorites.
 * For an airbrush (I use a lot of airbrushes, and I spray awkward things through them) you can't beat the old Badger 250 design, which is widely copied and comes from China via eBay for about £10. This is the crudest airbrush around, as an external mix brush with no metering needle. It does though have the ability to spray almost anything and is much less fussy about fluid viscosity. Easy to strip and clean too.
 * For your sanity, get a quiet airbrush compressor too, not a garage one. Andy Dingley (talk) 11:27, 15 September 2017 (UTC)
 * I appreciate you're taking precautions but it may not be worth it: . 92.8.176.91 (talk) 12:13, 15 September 2017 (UTC)
 * Quats aren't bleach. Andy Dingley (talk) 12:25, 15 September 2017 (UTC)
 * That article is way over my head but this medical report is headed "Regular Use of Bleach Linked to COPD". 92.8.176.91 (talk) 12:49, 15 September 2017 (UTC)
 * I wouldn't pay much heed to either of those as sources (try running WebMD past WP:MEDRS!) - if someone can post the citation or link for the original paper, that would be appreciated. Andy Dingley (talk) 15:14, 15 September 2017 (UTC)
 * [[User:Andy Dingley, Point taken, the WebMD article does eventually say "The results should be treated with caution as they have yet to be published in a peer-reviewed journal." Both news articles above are very recent. It seems as though the study is not utter rubbish, but I also don't trust either of those sources to not sensationalize or otherwise muck things up. They do both seem to be reporting on the same thing, though neither can be arsed to even give a name of researcher. It seems to be analyzing data pulled from one of these long-term longitudinal studies of nurses, based on surveys etc. Telegraph mentions Harvard, but Harvard has not yet issued any press release as far as I can see. SemanticMantis (talk) 17:20, 15 September 2017 (UTC)
 * I think this paper isn't published until Monday, and it's not easily visible. Presumably there's a press release copy already circulating, but I don't read medicine so haven't seen it. The newspaper reports all seem to be conflating disinfectants and bleaches, in a way that has nothing as yet to support it. Andy Dingley (talk) 17:27, 15 September 2017 (UTC)
 * This comes down to risk/benefit ratio. Splashing about in a chlorinated swimming pool brings one into contact with a very dilute solution of chlorinated phenols, due to the action of sodium hypocrite reacting with organic matter (they often  occur in chlorinated tap water as well).  Phenols are know to be cancer promoters... but the 'risk' of splashing around in non chlorinated water or drinking it is higher -  much higher. My favorite way to avoid chlorinated phenols, is to drink pure spring water only... but even then ! I always take the greatest care ( ask the family) to  sanitized it with a equal amounts of a good Scottish Single Malt. So chlorination is not the only solution and  in many ways,  the old traditional ways are best (IMHO) . Aspro (talk) 15:54, 15 September 2017 (UTC)


 * How about grain alcohol and pure spring water to replenish your vital bodily fluids ? :-) StuRat (talk) 17:20, 15 September 2017 (UTC)


 * Grain alcohol ? Rather wash my mouth out with soap. Aspro (talk) 12:51, 16 September 2017 (UTC)


 * You prefer wood alcohol ??? StuRat (talk) 00:32, 18 September 2017 (UTC)


 * I think he's more concerned about keeping his Essences Pure. In which case, he'd be well served to learn what "spring water" is, and how it's different from mineral water. Andy Dingley (talk) 17:28, 15 September 2017 (UTC)


 * As always, AD is pedantically on the button by pointing out that Spring & Mineral are not always considered interchangeable. However,  “Spring water can be considered mineral water if it naturally contains the required amount of trace minerals.”  Mineral Water Vs. Spring Water. Which is a  comparison that I would agree with,  providing both contain the minerals. Unfortunately, many a good water now comes in plastic bottles which can leach phthalates over time. These chemicals can cause frogs etc., to exhibit both male and female characteristics, which why phthalates have been nicknamed gender-benders. Fortunately, Haggis survive by just licking the morning  dew. Which is presumably why, I haven’t seen any that have ram like attributes  and the growing of horns– but I constantly live in fear of what people  on vacation may feed them. The left-overs from a McDonald’s family meal is not a haggis's normal diet. Lastly, who granted  McDonald's the right to use the clan name of  McDonald and trademark it ? Clan Chief  McDonald didn't – he said so! Anyway AD, you're leading us off at a tangent to the OP's question. Also, I don't think I would be better served, if even if I had my own sommelier ;¬) Aspro (talk) 12:51, 16 September 2017 (UTC)
 * I'm in the UK (maybe Europe). Here we have a legal and labelling difference between spring and mineral water. "Spring" water ain't all that. Andy Dingley (talk) 09:32, 18 September 2017 (UTC)


 * Your neighbors might complain about bleach fumes. I suggest you consider hydrogen peroxide.  It's inexpensive enough and far less toxic.  It also flows quite well.  It may have less bleaching power, depending on the strength.  At high concentrations, it's flammable and even explosive, but you won't find that concentration available in stores, where 3% is typical, and that 97% water will keep it non-flammable.  If that doesn't bleach enough, you can find somewhat higher concentrations sold online.  StuRat (talk) 13:34, 15 September 2017 (UTC)


 * The OP hasn’t mentioned the nature of the stains. Bleaches of any variety are not always efficacious, especially with natural dyed fabrics. Other cheap alternatives are often better,  Also, cheaper  than an air brush but just as effective in this application is one of the many Spray Atomizer Bottles at around £1 to £2. Example : . Aspro (talk) 14:27, 15 September 2017 (UTC)


 * I don't believe the OP wants to clean the clothes, but rather create something like a tie-dyed look by randomly bleaching out the color in spots. StuRat (talk) 17:22, 15 September 2017 (UTC)


 * Maybe this article could be expanded?  Apart from the dangers of swimming pools, here's a detailed study on the dangers of domestic cleaning chemicals: . 92.8.216.51 (talk) 16:25, 15 September 2017 (UTC)

Tileable "scatter" patterns for texture generation in a CGI context.
Hi,

This is on the Science Desk but is here rather than the Mathematics desk because it relates to image generation. In the context of a simulation and CGI generation suite, it is possible to generate textures to represent fine details that cannot for various reasons be implemented as geometry.

Does anyone have a reference to a paper or article (most likely a SIGGRAPH report) that gives a method for generating seamless texture artwork approximating a field of vegetation or crop when viewed from above or moderate distance, utilizing random scatter patterns based on an observed colour distribution over a number of sampled images from the real world? ShakespeareFan00 (talk) 12:32, 15 September 2017 (UTC)


 * Think you may have better luck asking this on a Wikimedia Commons help desk, whose editors  are more into images. There are applications like MegaScatter but I don't know if this is what you mean. Aspro (talk) 15:06, 15 September 2017 (UTC)


 * Well I found sort of the converse: using hierachical Bayesian methods to analyze textures in photographs of weeds and crops . Might give you some insight on how to generate such a thing. SemanticMantis (talk) 16:40, 15 September 2017 (UTC)


 * Oh, here you go, this is much close I think:  Use google scholar to track down other work by Deussen, the common author on those papers, also you can use Scholar to skim through later works that cite these. Thanks for the interesting question, I knew a bit about this stuff but I'm pretty blown away by some of the figures in those papers SemanticMantis (talk) 16:46, 15 September 2017 (UTC)

Space probe selfies
In a similar refdesk question some time ago someone answered that artistic renditions of space probes are because it's impossible to take a photo of them on a mission in deep space (e.g. for Cassini-Huygens, etc.). So what's the problem with installing an additional camera on them for selfies or shooting with an already existing onboard camera, like it was done for selfies from Curiosity Mars rover? 212.180.235.46 (talk) 16:39, 15 September 2017 (UTC)


 * Certainly possible, but anything you put on a space probe costs millions of dollars, and/or replaces some valuable instrument(s). It's hard to justify spending taxpayer money to do that, just for selfies.  I suppose there could be an argument made for it, that it would allow them to spot potential problems like a micrometeorite hit, but the chance that a problem could actually be spotted and then fixed in this way is next to zero. StuRat (talk) 17:12, 15 September 2017 (UTC)


 * Basically because putting a camera on an arm wouldn't have any practical use for a deep space probe.
 * The mast camera on Curiosity is on the end of a flexible arm because they want to be able to get closeups of rocks and stuff. The fact that they could use the camera to create cool looking selfies didn't even occur to them until it was already on its way to Mars.
 * Here's a great article on the Curiosity Selfies : The story behind Curiosity's self-portraits on Mars (I like the selfie taken by the duplicate robot sitting in a robotics lab at JPL.)
 * On a deep space probe there wouldn't really be a point to putting a camera on the end of a long, flexible arm. It never gets close enough to anything that an arm would be useful. If they want to take a picture of something, they turn the whole probe to face that thing. A long arm would just something that could break, and unneeded weight.
 * Maybe they'll do it some day, if only if they need the hardware for some other thing. I can't find the reference right now, but I believe there are some proposed space telescopes that consist of more than one craft flying in formation. If they build them, maybe those things will photograph each-other. ApLundell (talk) 17:25, 15 September 2017 (UTC)


 * The additional mass is by far the most important disadvantage of adding "selfie" hardware. The incremental cost, power, and complexity (i.e, unreliablity) are also important, but extra mass is a show-stopper. This is especially true for deep-space probes. That mass would be traded against electrical power, or thruster fuel, or antenna size, or initial launcher capacity, or some other critical mission constraint. -Arch dude (talk) 04:12, 16 September 2017 (UTC)


 * In addition to the obvious - that it would serve no real purpose - keep in mind that Cassini launched in 1997, and according to EO, the term "selfie" didn't become a "thing" until at least 2002. In practicality, selfies have been around a lot longer, they just hadn't coined the term yet. But in 1997, it was not really on the radar. ←Baseball Bugs What's up, Doc? carrots→ 05:29, 16 September 2017 (UTC)
 * The "Problem" may be that these are no tourist trips but scientific missions. Nevertheless in general- whats the value in a "selfie"? Visual prove of an potential epic meeting? Are close range detailed images of Saturn, without any obstacles, not most epic already? --Kharon (talk) 06:48, 16 September 2017 (UTC)


 * In the days of film cameras, I used to hear the term "proof of visitation", such as standing in front of the Eiffel Tower just to prove that you were there. The advent of digital technology has probably rendered that concept obsolete, since anyone can easily artificially put themselves into any picture. ←Baseball Bugs What's up, Doc? carrots→ 12:52, 16 September 2017 (UTC)


 * It's not entirely impossible. Cassini carried the Huygens probe with it - in theory, one could have photographed the other as they separated. As it happens, the cameras weren't facing the right way, but Rosetta was able to take a selfie by activating Philae's camera while the two were still connected, and it repaid the favour when Philae separated. Note that the photos aren't great quality - lighting in space is very stark, and spacecraft cameras are usually calibrated to photograph very large, distant objects, not small, close ones (even getting the dark image of a solar panel took a lot of photo editing and edge detection work, to pick out the details in the gloom). Smurrayinchester 11:55, 16 September 2017 (UTC)

Effects of painful stimulus on food intake in rats/mice
I'm interested in any experiments done on rats/mice relating to whether applying a painful stimulus to receive food reduced food intake in the test subject. For example, even with an abundance of available food will the subject eat less if it receives a painful stimulus upon approaching / eating the food? Does the subject eventually get used to the pain and resume normal eating patterns? Are there any such scientific studies that you could link me to? Thanks for your time. — Preceding unsigned comment added by 119.42.87.140 (talk) 19:14, 15 September 2017 (UTC)
 * At a more practical level barbed wire or electric fences work. Greglocock (talk) 20:36, 15 September 2017 (UTC)
 * Read this article. -- Jayron 32 20:43, 15 September 2017 (UTC)


 * The type of conditioning you're looking for is called Positive punishment. (In humans, if it's being done by a doctor it might be called Aversion Therapy.)
 * The wikipedia articles don't answer your precise question, but maybe they'll help in your research. ApLundell (talk) 21:35, 15 September 2017 (UTC)
 * This article notes decreased appetite and weight loss as signs of dental problems In Rodents. Blooteuth (talk) 22:48, 15 September 2017 (UTC)


 * What you are asking about are approach-avoidance conflicts -- however the science on this is pretty complex and our article is not very informative. The bottom line is that, yes, the punishment will probably reduce eating, but a lot of factors come into play, most importantly the strength of the punishment. Looie496 (talk) 02:48, 16 September 2017 (UTC)

Cold-water immersion and heart rate
Does spending time on cold water (full body) reduce average heart rate? I mean not only when we are in water but during the day, in the same way that aerobic exercise reduces our resting heart rate? — Preceding unsigned comment added by 31.4.136.173 (talk) 21:59, 15 September 2017 (UTC)
 * See the article Hypothermia that describes the effects of reducing the Human body temperature below 35°C. Therapeutic hypothermia is a medical treatment occasionally applied to reduce the risk of tissue injury following lack of blood flow. Hypothermia has possible adverse effects and no proven subsequent benefit. Blooteuth (talk) 22:32, 15 September 2017 (UTC)
 * I assume the OP means something along the lines of ice baths or the polar bear plunge and not reducing your body temperature up to a potentially lethal level.--B8-tome (talk) 23:45, 15 September 2017 (UTC)


 * See here. Count Iblis (talk) 01:44, 16 September 2017 (UTC)