:Yes, you ''are'' referring to sidereal day vs. solar day. The reason we don't notice is that all timekeeping in everyday life is based on the solar day. Sidereal days are only important if you're interested in observing the stars, planets, etc. --[[Special:Contributions/69.159.60.147|69.159.60.147]] ([[User talk:69.159.60.147|talk]]) 06:10, 30 September 2017 (UTC)
:Yes, you ''are'' referring to sidereal day vs. solar day. The reason we don't notice is that all timekeeping in everyday life is based on the solar day. Sidereal days are only important if you're interested in observing the stars, planets, etc. --[[Special:Contributions/69.159.60.147|69.159.60.147]] ([[User talk:69.159.60.147|talk]]) 06:10, 30 September 2017 (UTC)
::When you say "sunrise is lagged behind approximately by 1 min" I think you mean 1 ''degree''. The sun's position along the ecliptic (orbit) can be expressed in degrees or time measured eastward from the vernal equinox ([[Right Ascension]]). This is tabulated in almanacs - you can see the daily change here [http://books.google.co.uk/books?id=zPINAAAAQAAJ&pg=PA2]. [[Special:Contributions/82.14.24.95|82.14.24.95]] ([[User talk:82.14.24.95|talk]]) 11:55, 30 September 2017 (UTC)
Revision as of 11:56, 30 September 2017
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.
[1] is a homework question. I don't understand it. If the air inside the pot counters the atmospheric pressure, then all we need for water to boil is when the water vapor cancels out the weight of the lid, which is 4*gravitational constant. Area of lid is pi/100, which gives me a needed water vapor of 1.249 kPa, which according to a water vapor pressure table is achieved when water is just 7 degrees Celsius. This doesn't make sense.
Alternatively, according to the professor, we are to solve the problem by cancelling out the atmospheric pressure and lid weight with the water vapor pressure. Then the required water vapor pressure is 102 kPa. I don't know how to find the temperature of water from this, but I assume it'll be just under 101 degrees Celsius. This number makes more sense, but I don't believe the logic. I don't see how we can ignore air inside the pot. Imagine Reason (talk) 11:50, 26 September 2017 (UTC)[reply]
Didn't we have this same homework question just a week ago?
Oh, the water vapor needs to counter the air inside the pan as well. But how do I go from water vapor pressure to water temperature? I don't see such a table in my book. Imagine Reason (talk) 12:03, 26 September 2017 (UTC)[reply]
There are two ways. An engineer would look up the equilibrium temperature of steam and water for a particular pressure in a book of steam tables. A scientist would probably be expected to calculate it (which is easy, look for the Antoine equation at the heading of the table), or in an exam you might be expected to derive it, which is harder - start with Clausius–Clapeyron relation. Andy Dingley (talk) 12:44, 26 September 2017 (UTC)[reply]
Weights to compensate for weight loss
Suppose someone who's a little overweight is steadily losing weight, while maintaining a constant (and significant) level of physical activity. It seems obvious that, as weight declines, the physical activity itself becomes less strenuous, possibly making it difficult for the person to maintain the same level of strength, especially in the legs, and also reducing caloric output.
Have there been any good studies comparing different ways of compensating for this, through, say, ankle, wrist, or waist weights, worn throughout the day or at least while walking for exercise? For example, is one option more effective at maintaining leg strength or caloric output? Is one option safer than another in terms of effect on joints or tendons? --Trovatore (talk) 18:08, 26 September 2017 (UTC)[reply]
One problem you're going to have is distributing the weight evenly. You would need a full fat suit (but weighted) to do that, and this would block air flow to the skin, interfering with thermal self-regulation, etc. StuRat (talk) 18:13, 26 September 2017 (UTC)[reply]
Well now, I asked a specific question about the outcome of studies. I didn't ask whether it is possible to replicate the exact conditions that the person experienced when heavier. --Trovatore (talk) 18:16, 26 September 2017 (UTC)[reply]
It has been done (no, I don't have refs offhand) and that specific effect is negligible, because it's dwarfed by the other effect of exercise, that of converting fat to muscle mass. As is known only too well, many people don't lose weight by increasing exercise, they may even put it on - but they don't mind, because they recognise that they're still "looking better" as a result.
So the effect of "the exercise becoming easier" (as a number of Joules) is negligible, or even negative. But the body does become more efficient at carrying out this exercise, and that's the predominant effect. So yes, the overall effect you describe is there (and any trainer will increase the training schedule as the subject becomes fitter) but not for the reason you describe, and not compensated for by the simple "ballasting" you put forward.
There's also the question of why someone is training. It's probably not (in this case) to increase strength, but rather endurance. So the increase to make with improved fitness may be in duration, not load. Andy Dingley (talk) 19:02, 26 September 2017 (UTC)[reply]
Sorry, I was less than completely clear. The hypothesis I want you to assume is an active person with a stable level of activity, who has started losing weight as a result of reduced caloric intake. --Trovatore (talk) 19:18, 26 September 2017 (UTC)[reply]
In which case they're not exercising, so it doesn't matter. If they're exercising enough to count (presumably walking, step aerobics or similar, if their own body mass is so relevant) then we'd see the increased muscle effects too. Andy Dingley (talk) 20:34, 26 September 2017 (UTC)[reply]
I still don't seem to have gotten the point across. The hypothesis is that the person does significant exercise, but the same amount as before the weight loss started. --Trovatore (talk) 20:58, 26 September 2017 (UTC)[reply]
According to recent studies, changing your level of exercise has little to no effect on the number of calories your body uses [2]. Herman Pontzer found that the hunter-gatherer Hadza people, who are incredibly active compared to Westerners, have a similar daily energy expenditure to people living modern sedentary livestyles. So even if changing body weight has a slight effect on your body's energy budget, it likely has no measurable effect on caloric usage. However it may be relevant for other outcomes of exercise such as muscle strength or cardiovascular health. CodeTalker (talk) 23:19, 26 September 2017 (UTC)[reply]
This is an issue for arm strength but not for leg strength. For leg muscles this isn't an issue because to be in good physical shape you need to run at about 70% of maximum effort and as you lose weight you'll end up running faster if you exercise for the same amount of time. We're not limited to walking at a slow pace and small distances. But in case of our arms this is different. Exercises like pull-ups can get significantly less effective if you lose weight, and here a common method is to attach weights to your body to make these exercise heavier. Note here that our arm muscles are a lot weaker than our leg muscles, so much so that doing just a few push-ups is too much for many people, while a push-up is a lot less exertion than getting up from your chair. An arm muscle exercise equivalent to getting up from your chair is a handstand pushup. This is why in a gym you'll see people doing this, but you'll not see anyone running on treadmills while wearing heavy backpacks. Count Iblis (talk) 23:41, 26 September 2017 (UTC)[reply]
Based on my experience, I put on 1 or 2 kgs in the winter and pullups are harder than in the summer. Also, my hands don't work as well in the colder weather, which also makes the exercise more difficult. This results in less per set in winter and it takes longer to reach my target number (60-70 in case you're interested). It has been like that for the 33 years of going to the gym. --TrogWoolley (talk) 12:28, 27 September 2017 (UTC)[reply]
Shade balls
Why using shade balls when it's possible to just cover the reservoirs and ponds with a single large tent-like sheet from sun-screening material? Also, potentially the balls may enter some sort of weak chemical reaction with the water, unlike the large tent. Thanks. 212.180.235.46 (talk) 20:14, 26 September 2017 (UTC)[reply]
I tried keeping a large tent over my car in storage in the backyard, and it was a nightmare. No matter how I secured it, it always tore loose in high winds. And this "large tent" was 10×20 feet. With a much larger one it would be far more expensive and difficult to control. (If you meant that the tent should float on the water, then water currents, as opposed to wind, might damage it. Also, if you block oxygen from getting into the water, then anaerobic organisms could grow in it.) StuRat (talk) 20:25, 26 September 2017 (UTC)[reply]
They're cheap, simple to install and aren't visible in their height. Wide span covers are difficult to construct and expensive. An arched cover is tall (and expensive), a flat and less obvious cover is even more expensive. Andy Dingley (talk) 20:28, 26 September 2017 (UTC)[reply]
Googling "floating cover" gives some examples that come close to what 212.180 described. To illustrate the expenses and give one cost comparison, for covering the Los Angeles Reservoir (175 acres / 0.7 km2): "$250 million -- to install a floating cover" v. "At 36 cents a pop, the 96 million plastic balls covering the surface have a lifespan of 10 years and require almost no maintenance aside from occasional rotation". So, $34.456 million for the shade balls. Floating covers, however, "provide more of a complete barrier from both sunlight and airborne contaminants", and thus the title of the article containing this info is actually "Los Angeles to Replace ‘Shade Balls’ with Floating Covers". ---Sluzzelintalk00:55, 27 September 2017 (UTC)[reply]
Whenever I hear that a system which works fine is being replaced by a new, more expensive system, I suspect that the brother-in-law of the person who decided on the replacement will get rich as a result. StuRat (talk) 04:51, 27 September 2017 (UTC)[reply]
The Future Structure article Sluzzelin cited explained that the smaller reservoirs still being left in production could be more completely protected from from avian pollution and photogenic bromide --> bromate synthesis by floating covers. The inference being that shade balls aren't an optimal solution for those reservoirs, but are the only workable one for the 175-acre Los Angeles Reservoir, which will still be protected by shade balls. loupgarous (talk) 01:14, 29 September 2017 (UTC)[reply]
Microbiology questions.
1. 10% bleach, 70% ethanol, 70% isopropanol, and 3% hydrogen peroxide, they are all better at killing gram-positive bacteria than gram-negative bacteria. What are some things that kill gram-negative bacteria better than gram-positive? I asked a microbio professor, who says "whatever kills lipid A and LPS better." So, Wikipedia shows both of those are stuff found in gram-negative bacteria. So my new question is, what's something that can destroy lipid A and LPS?
2. Can there be a bacteria that produces endospores, and be gram-negative and aerobic?
3. Are there any benefits to having obligate anaerobes in our intestines, such as Clostridium? It's beneficial to have E. coli in our intestines because E. coli prevents anaerobes like Clostridium from taking over, so.
4. We have chemicals that kill viruses and bacteria, and bacteria only. For example, O3 is a chemical that kills bacteria but does not kill viruses. But are there any chemicals that kill viruses but not bacteria?
5. This 1 I have the answer to, but I'll take feedback. There are bacteria that kill bacteria, viruses that kill other viruses, and viruses that kill bacteria. However, there isn't any bacteria that kill viruses. Is it because we haven't found any yet, or also because we don't think it's very easy for them to. Thanks. 12.239.13.143 (talk) 20:36, 26 September 2017 (UTC).[reply]
3.: "Anaerobic metabolism of peptides and proteins (putrefaction) by the microflora also produces short-chain fatty acids." And "anaerobic bacteria [in human gut flora ] outnumber aerobic bacteria by a factor of 100–1000." From here [3], a relatively recent and freely accessible scholarly review article. I'm no expert, but if the anaerobes outnumber the others by such a factor in healthy humans, I'd suppose they have some benefit. Also consider asking a question every day or two, rather than five at once. We'll be here all week, and these five questions span a lot of ground ;) SemanticMantis (talk) 21:25, 26 September 2017 (UTC)[reply]
3: Gut flora mentions several beneficial effects of some Clostridia species. Any bacterial species can become harmful if the gut flora's balance is disrupted and one species is able to "take over".
This seems like a question with a very wide scope. If this matter can be used as fuel, sure, the energy costs, benefits, efficiency will of course vary depending on the materials, available other materials and technologies used. Also taken into consideration could be the transformations matter can have over time (oil comes from organic material for instance, which can be used as energy source to produce light)... —PaleoNeonate – 07:16, 27 September 2017 (UTC)[reply]
"No mass is lost" is true for alll practical purposes but technically incorrect. "Too little mass is lost to measure" would be correct. Every time energy is emitted, mass is lost. This is detailed in our article about Mass–energy equivalence. It takes a lot of light to equal a very small mass. The Grand Coulee Dam's turbines put out roughly 7 gigawatts per hour. The output of the dam for four hours reduces the mass of the Columbia River by roughly one gram. This mass is sent away through the power lines in the form of electrical energy, and some of it goes to electrical devices such as lights or computer monitors where it is converted to light. When the light from your computer monitor hits the walls of the room you are in, the walls become a tiny bit warmer and a very tiny bit heavier. (warmer object weight more. spinning balls weigh more. charged batteries weigh more. A jar of pickles on the top shelf weighs more...) Also see Conservation of energy and Conservation of mass. --Guy Macon (talk) 12:35, 27 September 2017 (UTC)[reply]
I'm not sure that a jar of pickles on the top shelf does weigh more than it does at floor level :) The increase in weight due to added gravitational potential energy is mg2h/c2, but the *decrease* in weight due to the decrease in g with height is approximately 2mgh/R where R is the radius of the Earth (this assumes h << R). Taking g = 10 m/s2, c = 3 x 108 m/s and R = 6.3 x 106 m, we have mg2h/c2 is approximately 10-16 mgh, whereas 2mgh/R is approximately 3 x 10-7 mgh. So decrease in weight due to lower g >> increase in weight due to higher E. Gandalf61 (talk) 16:06, 27 September 2017 (UTC)[reply]
(Guy slaps himself with a wet trout). Of course. Rookie mistake, saying "weighs" when I should have said "masses". The gain in mass from the added kinetic energy is tiny compared to the fact that gravity pulls less at higher altitudes. I haven't done the calculations but I am guessing that both are tiny compared to a speck of dust landing on the pickle jar or the barometric pressure changing and affecting the buoyancy of the jar. Thanks for the correction. --Guy Macon (talk) 03:50, 28 September 2017 (UTC)[reply]
Distortionless enhancement by polarization transfer is a type of 13C-NMR that works by shining two different frequencies of radio waves at a sample. One interacts with protons, one interacts with 13C nuclei. Somehow this causes the 13C nuclei eventually to get a detectable amount of energy by virtue of changing the orientation of their spin relative to the magnetic field, in a way that is affected by how many protons they were bound to. Somehow it works out that a pulse of 0.5 pi-halved units makes all of them show a positive phase, then 1 makes only C-H show up, then 1.5 makes CH2 negative and the others positive. Every review will explain that this works. But ... how the heck does that make any sense? Any explanations welcome, even on the "simpler" aspects of how the polarization transfer really works. Wnt (talk) 11:08, 27 September 2017 (UTC)[reply]
Assuming the saliva produces a good DNA sample, current (since 2009) tests are more than 90% accurate in detecting if a person has blue eye color. Detecting brown eye color is not over 90% accurate as well. I assume that if you demonstrate that a person does not have brown or blue eye color, you are left with green. The blue-brown tests are down to using only 6 positions on the human genome. So, your sample needs to have all 6 of those positions undamaged. 209.149.113.5 (talk) 11:53, 27 September 2017 (UTC)[reply]
It also assumes the color is constant. I've hazel eyes which are mostly brownish now but on occasion they've been quite green. Nothing to do with envy or anything else I know of :) Dmcq (talk) 16:58, 27 September 2017 (UTC)[reply]
Brown covers amber (amber is brown with extra collagen). Blue covers grey (gray is blue with extra collagen). Hazel is a mix of brown and green. As for consistency of eye color - it can change. My eyes permanently changed from brown to blue when I was in my early 20s. 209.149.113.5 (talk) 12:24, 28 September 2017 (UTC)[reply]
Preserving meat in boiling water
I was boiling some meat and boiled it far longer than I meant to. There was nothing wrong with the result. Could meat be preserved by boiling it indefinitely? Could I still eat a piece of meat after boiling it for a year? — Preceding unsigned comment added by 85.76.43.174 (talk • contribs)
Hiroo Onoda's autobiography, about how he spent more than 30 years in a jungle on Lubang Island, describes his techniques for keeping beef by boiling it. He even has a few drawings of Dakota pits, in case you want to boil the beef on the down-low.
“
When we shot a cow, we cut the meat up, skewered it and dried it over a fire at night. During the ten days required for this, we ate boiled beef. Piled on pieces of wood, the liver and other innards were cooked in a makeshift steamer. Small pieces of meat were boiled in a pot until the water was gone. To keep it from getting moldy, it was reheated every day.
He also describes a lot of gastrointestinal distress, and other systematic problems related to bad food:
“
For the first three days, we would have fresh meat, broiled or stewed, two times a day. Presumable because of the meat's high calory count, as I ate, my body temperature climbed until I felt hot to the soles of my feet. It was hard to breathe when walking and impossible to climb a tree. My head would always feel a little giddy. I found that if I drank the milk of green coconuts as a vegetable substitute when I ate meat, my temperature would soon return to normal.
”
“
On the fourth day we piled as much meat as possible in a pot and boiled it. By heating this up once every day and a half or two days after that, we kept it from spoiling, and the flavor held up for a week or ten days. While we were eating the boiled meat, we dried what was left for future consumption. We called this dried meat "smoked beef." ...From one cow, we could make about 250 slices of smoked beef. By eating only one slice apiece each day, we could make the meat last for about four months.
Also see perpetual stew. Note that, as stated above, it isn't necessary to boil it continuously, but only periodically, to keep it from spoiling. Boiling continuously will cause the structure to break down more quickly, making it mushy. Bones, on the other hand, could use far more boiling to become soft enough to eat. Also note that boiling continuously, especially with the lid off, will concentrate whatever impurities were in the water, which must be constantly replenished. That likely includes salt, but also perhaps copper, lead, etc. The materials the pot is made from will also tend to find their way into the stew, so pewter and maybe aluminum should be avoided. StuRat (talk) 18:02, 27 September 2017 (UTC)[reply]
A bit of yes and no here: “boiling” think was used in the old generic sense to mean reheating as one doesn't boil meat. What is important is the critical control point for the foods being cooked. Once cooked they can be kept 63 deg C or above until served. Even so, this is not perpetual. In the 19th century some quacks still thought that life spontaneously evolved because they 'scientifically' demonstrated that if one boiled a broth then sealed the glass vessel, the broth still went on to turn into something horrid. Eventually we came understand, that some bacteria survive boiling temperatures. Perpetual stews (when done as one's grandmother and her grand mother did before) ensure that the pH is too low for pathogenic bacteria to thrive in. They are not only safe but delicious. It gets even more complicated when one gets to putrefied flesh. Fish don't need any artificial heat to turn the flesh into fish source. Yet 99% of the readers here have probably enjoyed purified juices with their meal without knowing it. Aspro (talk) 19:46, 27 September 2017 (UTC)[reply]
"Could meat be preserved by boiling it indefinitely?" Short answer NO. If you boiled the water indefinitely the meat in it will be what's the word, deconstructed into basic components. The proteins will be broken and what you have left is not "meat" but I don't know what it is. The best way I can put it is basic components. From the article in cooking, it says "When proteins are heated they become denatured (unfolded) and change texture." 110.22.20.252 (talk) 07:19, 28 September 2017 (UTC)[reply]
At first the proteins might just be broken down to amino acids, which are still nutritious. But, yes, eventually they would be broken down further, into something non-nutritious. There are other processes which cause decomposition besides microbes. Food in cans breaks down eventually, even though sterile. These processes would likely be accelerated at higher temps. Rancidification is one such process. StuRat (talk) 03:10, 30 September 2017 (UTC)[reply]
Besides inadequate dietary intake, are there any other causes of Pantothenic acid deficiency? The article is rather vague. Also, what is the treatment protocol for Pantothenic acid deficiency in a hospital setting? Thanks for your time. 116.58.233.152 (talk) 19:06, 27 September 2017 (UTC)[reply]
Don't take this as gospel but people with ME who find their guts play them up (i.e. unable to absorb essential vitamins) often end up noticing that their feet feel hot. Supplementation with Pantothenic Acid relieves the symptoms. No idea if this also occurs in Beriberi but one can imagine it does for the gross similarities not observed with with pure thiamine deficiencies. Aspro (talk) 20:07, 27 September 2017 (UTC)[reply]
Part of the problem is that the enzymes that that are being synthesized have redundant parts, making the biochemical pathways more complex than they needs to be, making us susceptible to diseases that affect these pathways. As pointed out here this is a likely consequence of the enzymes being relics from the the RNA world. Count Iblis (talk) 00:08, 28 September 2017 (UTC)[reply]
Plainest color
In general, white looks like the plainest color. But on a computer screen, black looks like the plainest color. What special properties do computer screens have?? Georgia guy (talk) 22:55, 27 September 2017 (UTC)[reply]
In the case where the monitor uses LCD (see Thin-film-transistor liquid-crystal display for details), pixels are made of multiple subpixels which can sometimes be perceived. Other technologies also have their own artifacts; the black color is usually produced by non-activated regions or using a separate more uniform layer. —PaleoNeonate – 23:42, 27 September 2017 (UTC)[reply]
The point is that color are qualia. I can't even define "red" in a satisfactory way that would have meaning without referencing something red; aesthetic opinions about colors and how they make the OP feel are entirely undefined, and there's no meaningful way to explain why he decides to feel certain ways about colors. --Jayron3201:05, 29 September 2017 (UTC)[reply]
I suspect that the difference is between reflected light and emitted light. Most surfaces reflect light, while computer screens emit light (some have backlights the emit light, and an intermediate layer that absorbs light, but that detail's not relevant here). StuRat (talk) 00:53, 28 September 2017 (UTC)[reply]
Left: An additive colour scheme, as used in computer displays. Right: A subtractive colour scheme, as used in printing. To add a bit to this: reflected light (like light reflecting off paper or a painted wall) has "subtractive colour" - the light starts as white, and certain frequencies get absorbed by the material they reflect off, and if all the frequencies are absorbed you get black. Emitted light (like light from a computer screen) has "additive colour" - the absence is black, and as you add frequencies of light it becomes white. Smurrayinchester08:26, 28 September 2017 (UTC)[reply]
There is little difference between subtractive colour on a reflective device and additive colour for a luminescent device – that's the point of them. They both emit light according to the additive model. Andy Dingley (talk) 09:33, 28 September 2017 (UTC)[reply]
Rate of drinking water affects the urging to urinate
I claim that drinking water real slowly, taking hours to drink the whole glass of water, doesn't make me feel more urging to urinate, while drinking faster would more likely feel more urging to urinate within an hour or so. Is it true that the rate of drinking water affects the amount of water ending up as urine and therefore the degree of increase of urge? PlanetStar23:03, 27 September 2017 (UTC)[reply]
Sure. The sooner you drink a given ounce of water, the sooner it is absorbed into your bloodstream, the sooner it is removed by your kidneys and the sooner it ends up in your bladder. So, if you slowly drink water, it will slowly accumulate in your bladder, and if you quickly drink it, it will quickly accumulate there.
In addition to this effect, note that the kidneys will remove less water than you drink, if you are dehydrated, until you are properly hydrated. So, slowly drinking water when dehydrated will produce very little urine at all. Also, water leaves the body in other ways, such as sweat and respiration, so if you drink water slowly enough, it may largely be disposed of in these ways, with little left for urine. StuRat (talk) 00:46, 28 September 2017 (UTC)[reply]
If you drink water quickly then you will produce urine quickly. However, the total volume of water that ends up as urine is not affected by how fast you drink it. Rather, water in must equal water out. The kidneys achieve homeostasis by reacting against changes in blood solute concentration and blood pressure. Drinking pure water dilutes the blood and increases blood pressure. C0617470r (talk) 07:43, 28 September 2017 (UTC)[reply]
Depending on climate there can be an "insensible loss" of water by breathing; also, in dry climates sweating can at times be far less noticeable. Together, a person can need far more water in a desert, even when not noticeably sweating, than in a humid area; so if the same amount were consumed over a long period, most of the water would be lost by these mechanisms and anti-diuretic hormone would still keep the urine production low. Wnt (talk) 10:39, 29 September 2017 (UTC)[reply]
Cold water stomach gurgles
frankly dangerous medical speculation about user's own symptoms
The following discussion has been closed. Please do not modify it.
It seems to me that drinking cold water would usually make my stomach gurgle more readily and more often than warm water. It could be because as cold water warms up in the stomach it produces bubbles as warm water don't hold air as well as cold water. But at some other times drinking hot water would be the most effective when there's something in the intestine blocking the flow of water because the hot water has greater power to go through and dissolve the blockage more easily than what cold water does. Is my belief correct that cold water would make the stomach gurgle more easily in the empty stomach? PlanetStar23:03, 27 September 2017 (UTC)[reply]
The alimentary canal is not a simple piece of plumbing. Any liquid drunk, whether hot or cold, will exchange heat with the body and reach normal internal temperature within a very short time, long before it could reach the intestines. What nature of "blockage" do you think could exist, that would be dissolved by additional water but not by normal digestive juices? (That additional fluid intake will help constipation by softening dry stools, or slowing their formation, is not disputed.) {The poster formerly known as 87.81.230.195} 2.217.210.199 (talk) 23:51, 27 September 2017 (UTC)[reply]
A blockage is an undigested food that would eventually be digested or excreted out as waste that it can be managed by water. Often as soon as I lay my belly down right after drinking water, gurgles would start. As cold water warms in the body it release bubbles; the colder the water I drink, the more quickly and more bubbles water releases as colder water warms up faster at the start while taking longer to warm up, therefore producing more intense and longer lasting gurgles. That's my theory. PlanetStar00:29, 28 September 2017 (UTC)[reply]
There are quite a few ways to die from a self-diagnosed "blockage" of the alimentary canal, including tumors, torsions, diverticulitis and so forth. Having had 2/3 of my colon removed and told I had a 60% chance of survival, please see a doctor if you need to discuss your symptoms. WP:DISCLAIMER. μηδείς (talk) 03:02, 28 September 2017 (UTC)[reply]
Intestinal obstruction is a medical emergency which will cause death within a few hours without immediate surgery. Chronic Type 2 diabetes is something rather different which no longer requires destructive surgery - a lining has been developed which coats the alimentary canal and prevents absorption. 92.8.220.234 (talk) 13:06, 28 September 2017 (UTC)[reply]
I have heard that the the neutrons and protons in the nucleus are sometimes combined into alpha particles. But the article seems to imply that bosons don't feel the nuclear force, or at least not as well as fermions do. Is this why alpha decay happens, because the nucleus doesn't have the nuclear force to hang on to it?144.35.45.70 (talk) 02:50, 29 September 2017 (UTC)[reply]
An Alpha Particle is simply an ionizedhelium atom. Alpha decay is the expulsion of a helium nucleus from an unstable heavy element, called "decay" for historical reasons, but not really decay into a different type of particle in the same way as lone neutron decay into a proton, an electron, an antineutrino and a gamma ray. μηδείς (talk)
I think the OP is thinking too hard about the nucleus really looking like a cluster of colored balls all glued together, as classic pictures in most textbooks show it. The nucleus does't look like that. Insofar as it looks like anything, it looks like a fuzzy sphere, not unlike an atom would look if you could look at it (that is, if vision at that scale has any meaning, which is a debate for another day). The fuzziness may be denser than the fuzziness of the electron cloud, but it's still basically an impervious cloudy structure. When we say that the nucleus undergoes alpha decay, we say that it emits a helium nucleus, which is to say that a new nucleus is formed, that of helium, and the remaining nucleus has lost a mass and charge equivalent to that helium nucleus (ignoring, for the sake of this discussion, binding energy/mass, etc) That doesn't mean, however, that if you looked at that original nucleus, you could identify discrete neutrons and protons, or that those discrete particles "broke off" in any meaningful way. If you think about alpha decay like that, you run into real problems using the same explanation for beta decay. After all, where is the electron in the nucleus? The classic lie to children explanation is that a neutron in the nucleus turns into a proton by emitting an electron. Which is only sort-of correct, and works because it makes the picture easier to understand. The next question you may be asking is "where in the nucleus was that electron". Was it in the neutron? No, classically, neutrons conists of three quarks, none of which are electrons. Well, maybe electrons are themselves made of quarks, or gluons, or some other particle we know to be in there? No, near as all models can tell, electrons are fundamental particles which means they don't have any finer structure, they aren't made of parts. So, if the electron didn't exist in the nucleus, and there are no parts of electrons in a nucleus with which it could be built, what then? By what mechanism does beta decay happen? The answer is shut up and calculate. By which to say, quantum mechanics does not behave by the same rules as newtonian mechanics, so stop trying to make it work that way. To say that protons and neutrons exist in a nucleus is true, but only in the sense that they are a useful model to explain concepts like nuclear decay and atomic mass and charge and stuff like that. When you start treating them as objects unto themselves as though they were little lego bricks you could just pluck off and build new things out of, you start to introduce things into your model which do not match reality. If your model is that bad at matching reality, throw away the parts of the model that don't work. And the part of the model where we expect these particles to behave like little hard balls is the part which we need to abandon. --Jayron3216:29, 29 September 2017 (UTC)[reply]
I think we can be a bit more generous to the OP. An alpha particle is indeed a type of boson, because it has a net spin that is an integer. In principle bosons can be packed at arbitrary density, but as our boson article explains (or at least tries to explain), other factors may come into play that prevent that from happening. Such is the case with alpha particles: the strong forces that their components feel prevent them from coming too close together. Looie496 (talk) 17:00, 29 September 2017 (UTC)[reply]
That's true, but as you note the concept of boson has limited utility here. There are lots of nuclei one could construct which are boson; it's trivial as any even-nucleon nucleus (such as C-12 or a deuteron) is also a boson. However, since the composite particles (protons and neutrons) that make up the nucleus are fermions, one gets the unreasonable task of deciding which is more important to consider when describing the properties of such a nucleus. You do get wierd physics when boson nuclei interact (such as in a Bose–Einstein condensate). --Jayron3217:35, 29 September 2017 (UTC)[reply]
I fell in love with the Atomic orbital concept once i learned to understand it, because it also works so well in explaining molecular bindings and their resulting geometry and function aka chemistry. Id say its also a very good approach to understand nuclear physics. So i would recommend to ignore the quarks and focus on that instead to learn how matter "works". --Kharon (talk) 16:59, 29 September 2017 (UTC)[reply]
Do large doses of Pantothenic Acid (say, 500mg a day) cause Biotin deficiency in humans? I've read conflicting reports that they compete for the same absorption mechanism and so an excess of either can cause a deficiency in the other. But I've also read that they require each other for the other to be absorbed and used. I'm confused and can't seem to find a straight answer to this question. Thanks for your time. OrvilleVoyager (talk) 17:20, 29 September 2017 (UTC)[reply]
I see no studies on PubMed for humans. I do see studies on rats, mice, and bulls. The only one with a very conclusive result involved increasing both Pantothenic Acid and Biotin while reducing Folic Acid. The result was an increase in cancer risk. As of 2008, my nutrition textbook states that there have been no conclusive studies on Pantothenic Acid or Biotin supplements. Instead, B-complex vitamins are used, which include both. 209.149.113.5 (talk) 18:56, 29 September 2017 (UTC)[reply]
"Large doses of pantothenic acid do not cause symptoms, other than (possibly) diarrhea. There are no known toxic symptoms from biotin." Source: https://medlineplus.gov/ency/article/002410.htm
I am wondering why anyone would take large doses of Pantothenic Acid supplements without taking any Biotin supplements. Most people just take a B Complex supplement, which contains both. Also, large doses of either do nothing except create expensive urine. --Guy Macon (talk) 19:48, 29 September 2017 (UTC)[reply]
Design engineers
Many site and project engineers have to be reactive, for example if a problem arises on site or an incident occurs. Is design engineeeing less reactive? Or is it possible the design engineer could also be called in if something goes wrong on site? 94.10.178.193 (talk) 20:01, 29 September 2017 (UTC)[reply]
Both. For instance the Millennium Bridge at first swayed from side to side due to well understood resonance. It was much easier then for the design team (using real data) to then add dampening correction. This would have been difficult and more expensive to do at the conceptual stage before the bridge had been built. Architects tend to be conservative, even when creating something new. The counter lever roof on the original Wembly stadium was new on that scale but the principles had already been proven on a smaller scale. Even the largest domed-roof is only a cement version of an Igloo. A sky scraper using new construction techniques on Manhater Island was found to be unsafe, but its short comings were rectified, negating the neead to demoish it. Yet, as always some architects get is wrong... Ronan Point and Tacoma Narrows Bridge etc. Aspro (talk) 20:58, 29 September 2017 (UTC)[reply]
Design engineers are usually called in as second or third level support when a problem arises with a product after it is in use. This is nearly universal practice with software products, and also with complex or custom physical products. -Arch dude (talk) 02:46, 30 September 2017 (UTC)[reply]
As a design engineer in a car company I spent hours each week working on problems on the assembly line with my parts, and would also get involved in recalls and technical service bulletins. Greglocock (talk) 07:15, 30 September 2017 (UTC)[reply]
are neurons specific to a single neurotransmitter?
I've been trying to self educate myself about the brain, neurons, etc. My background is computer science and I have a decent understanding of artificial neural networks. One question I'm not sure about that seems rather important is: how specific is a neuron to a neurotransmitter? I.e., does each neuron only respond to and/or take input from a single neurotransmitter, or can neurons respond to neurotransmitters in different ways (e.g., dopamine might excite neuron x but serotonin inhibit it). This seems to me to be an important differentiator between ANNs and actual neural networks. Are there other major differences (or would that take a book to respond to)? Thanks. --MadScientistX11 (talk) 22:24, 29 September 2017 (UTC)[reply]
Almost every type of neuron responds to a wide variety of neurotransmitters. In fact, almost every type of neuron releases multiple neurotransmitters. The only real restriction is Dale's principle, which says that a neuron releases the same set of neurotransmitters at all of its output synapses -- and even that has exceptions. You're right that simple ANNs don't capture this aspect of real neurons. There are more sophisticated types of ANNs that do, as described in our biological neuron model article, but they are of more interest to biologists than computer scientists. Looie496 (talk) 23:03, 29 September 2017 (UTC)[reply]
Looie's got it right, and you also have to consider that a specific neuron can accept stimuli from scores of other neurons that themselves react to different neurotransmitters. We are at the beginning of understanding the brain. Cannabinoids were only recognized as neurotransmitters in the last decades of the last century.
How much higher in energy is the excited state of oxirane, wherein the molecule can be considered an ethylene complex of an oxygen atom, than the ground state? Plasmic Physics (talk) 00:03, 30 September 2017 (UTC)[reply]
That's only body temperature, but what about environmental temperature? I'd say that it would be pretty close to the point at which you start to choke from the fluid in your lungs. However, what if you had respiratory gear that controlled the temperature of the air that you inhale? Plasmic Physics (talk) 03:00, 30 September 2017 (UTC)[reply]
You'll need to be able to define the Q more precisely to get a precise answer. Some factors:
1) Humidity. The lower the humidity the hotter temps we can survive, due to evaporative cooling from sweat.
2) Wind. Wind can actually make things worse at high temps, as it blows away the air near the body which has been cooled (by the conduction with the body and evaporative cooling) and replaces it with hot air.
3) Time. Obviously high temps are more survivable for short time periods.
4) Body mass. A larger body will take longer to heat up than a small one, due to the square-cube law.
5) Sunlight versus shade. In sunlight, clothing matters a lot, and loose-fitting white clothes may be best.
In relation to body mass: it's not as simple, because thinner bodies will also tend to more efficiently dissipate heat. If it is still possible of course (if the environment does not transfer more heat to the body than the body can transfer it to the environment including by sweat). Large bodies tend to cope better with cold. Also of interest which was not mentioned would be heat shock. —PaleoNeonate – 06:15, 30 September 2017 (UTC)[reply]
Question about the SUNRISE and SUNSET on equator of Earth?
Planet earth not only rotates about its axis but also orbits around the sun once every 365.25 days. Ignore the obliquity of the earth's axis which is more related to the seasons. Days and nights on the equator of the earth are nearly the same; 12 hours each say e.g., Seri Lanka.
For simplicity, lets days and nights are 12 hours each on the equator of the earth throughout the year.
• SUNRISE in the autumn equinox and SUNSET in spring equinox on his RHS
• SUNSET in the autumn equinox and SUNRISE in spring equinox on his LHS
Thus Bird’s eye view shows a difference of 12 hours when SUNRISE in the autumn equinox takes the position of SUNSET in spring equinox on earth - vice versa and the same is applied to summer and winter solstice. Sunrise and sunset take their original positions when the earth completes its orbit around the sun.
This means, each day, sunrise is lagged behind approximately by 1 min and 24 hours in one year (12 hours in six months as explained above)
I think you are referring to sidereal day vs. solar day. A real day is 23 hours, 56 minutes and 4.something seconds. The reason this is not noticed is because right is winter constellations and left is summer constellations and this is how you'd tell. (technically a sidereal day is not exactly one rotation, a stellar day is but it takes 26,000 years for the two to be off by 1 day). Sagittarian Milky Way (talk) 04:31, 30 September 2017 (UTC)[reply]
No, I am not referring to sidereal day vs solar day as days and nights in my questions are still remain the same but lagging behind every moment when the earth changes its position in its orbit around the sun.
Yes, you are referring to sidereal day vs. solar day. The reason we don't notice is that all timekeeping in everyday life is based on the solar day. Sidereal days are only important if you're interested in observing the stars, planets, etc. --69.159.60.147 (talk) 06:10, 30 September 2017 (UTC)[reply]
When you say "sunrise is lagged behind approximately by 1 min" I think you mean 1 degree. The sun's position along the ecliptic (orbit) can be expressed in degrees or time measured eastward from the vernal equinox (Right Ascension). This is tabulated in almanacs - you can see the daily change here [7]. 82.14.24.95 (talk) 11:55, 30 September 2017 (UTC)[reply]
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