Wikipedia:Reference desk/Archives/Science/2014 April 3

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April 3

identifying circuit component

Hello, I'm curious as to what this component is. It is itself unmarked and I couldn't google up neither the schematic symbol (the half circles with the wiggly line) nor what devices have "TH" as their symbol. The device is (or rather, was) a cassette player. Much thanks in advance Asmrulz (talk) 01:28, 3 April 2014 (UTC)

I'm not sure, but it could be a type of resistor. 24.5.122.13 (talk) 01:30, 3 April 2014 (UTC)

The 'wiggly line' symbol is used for resistors in IEEE Standard 315. [1] See also Electronic symbol. The 'TH1' marking however suggests that it might possibly be a thermistor. AndyTheGrump (talk) 01:46, 3 April 2014 (UTC)

Yes, although "RT" is the standard designator for a thermistor, "TH" is also in common use.[2] Red Act (talk) 02:17, 3 April 2014 (UTC)

To me it looks like a ceramic capacitor[3] but I agree with the comments above about the circuit board markings so things seem wrong. I think a thermistor wouldn't look like this – it needs to measure the temperature of something and I don't see how this could. It'd be a funny shaped resistor but you never know.Thincat (talk) 22:43, 3 April 2014 (UTC)

If you do a Google image search for thermistors, you'll see that they very commonly look a lot like ceramic capacitors.[4] And thermistors are quite commonly used as inrush current limiters, in which case they aren't being used to measure the temperature of anything other than just their own temperature. It's a thermistor. Red Act (talk) 00:38, 4 April 2014 (UTC)

Yes, you've persuaded me. Thincat (talk) 08:07, 4 April 2014 (UTC)

Request to check INR definition

Speaking of thrombosis, I've just added a short definition for INR on Wiktionary. I'm not a medical professional, so I'd like to be extra careful and am asking for it to be checked over. Is this definition ok? Please edit it directly if you feel necessary. Sorry if this isn't the right place to ask. —Pengo 01:36, 3 April 2014 (UTC)

References about INR include: Point-of-care international normalized ratio (INR) monitoring devices..., An Unpdate on INR Monitoring and Blood Clotting: INR. The latter states that INR was devised in 1983 as a ratio of prothrombin times

INR = (prothrombintest / prothrombincontrol)^ISI

where ISI is a numerical value representing the responsiveness of any given commercial system relative to the international standard. 84.209.89.214 (talk) 13:58, 3 April 2014 (UTC)

Metabolic question

Why would some cells use more fat, in compare to glucose - to create energy? Please note; this is a very specific physiological question. I don't ask why are many people overweight. thanks. 79.176.81.154 (talk) 04:52, 3 April 2014 (UTC)

Well, glucose provides quick energy, while fat is more for long-term, slowly burned energy. Thus muscles, as in your arms or legs, may do better to use glucose, initially. When the glucose level gets too low, then fat starts to be burnt. StuRat (talk) 16:18, 3 April 2014 (UTC)

Hey Sturat. Please note that I don't ask why glucose is being used before fat, but rather, why does some cells will use more fat than others? thanks. 79.176.81.154 (talk) 16:22, 3 April 2014 (UTC)

Why does the OP think that some cells use more fat than other cells? The all have the same mitochondria – save for red blood cells which have non at all. An individual organ may suffer from mitochondrial dysfunction but I take it, we are talking about the average individual. As StuRat intimated, when the blood supply runs short of glucose and/or oxygen, they have go into anaerobic mode and use fatty acids. --Aspro (talk) 19:18, 3 April 2014 (UTC)

Sorry, I might have badly phrased my question in the first place, please let me ask again: Why would the cells of one person could use more fat, In compare to glucose, than the cells of another person what factors could cause it and what is the name of this phenomenon? sorry& thanks again. 79.176.81.154 (talk) 19:51, 3 April 2014 (UTC)

If an individual exercises to the point that they spend much time utilizing anaerobic metabolism, they will start burning fatty acids -that is the WHY that you ask. A good place to start to understand this, is our article on Anaerobic exercise. This is so complicated, that even your GP may not understand the details. Cells will die if they are staved of energy for too long. The 'factors' that cause anaerobic metabolism is lack of oxygen and glucose. The name of this phenomenon is I think Anaerobic respiration but please don't quote me on this as I am now (according to little up-starts that were born knowing everything) very old.--Aspro (talk) 22:20, 3 April 2014 (UTC)

steady body weight

I've heard that the body "knows" one's normal or recent body weight and that it is able to regulate body processes like metabolism to maintain the weight within a few pounds. First, is this true? If so, what physiological mechanisms are involved? What would be the normal ranges? How long would it take to lose or gain five pounds (for example)? How long before the body settles on a new normal? -Halcatalyst (talk) 13:09, 3 April 2014 (UTC)

It is true if you are physically fit and get enough exercise and eat well. The precise mechanisms are not known (note that it was only recently that it was discovered that fat cells produce hormones that the hypothalamus uses to regulate the metabolic rate, also it will modualte your feeling of hunger). But it's perhaps easier to understand by considering natural selection. Obviously, it is preferable for animals living in the wild to make sure the body weight stays within certain limits and does not drift randomly. Without any feedback mechanisms, the body weight would evolve according to a random walk; on the long term the animal would be in danger of starving to death without there having been any food shortages at all. Count Iblis (talk) 14:28, 3 April 2014 (UTC)

(What you are saying seems reasonable but please provide references if possible) SemanticMantis (talk) 14:47, 3 April 2014 (UTC)

See here and here: "In 1967, a medical researcher, Ethan Sims, carried out an experiment at Vermont state prison in the US. He recruited inmates to eat as much as they could to gain 25% of their body weight, in return for early release from prison.

Some of the volunteers could not reach the target however hard they tried, even though they were eating 10,000 calories a day. Sims's conclusion was that for some, obesity is nearly impossible."

Then this disproves the calories in -calories out = weight gain model" which assumes that "calories out" does not depend on "calories in". So, there exists a feedback mechanisms which may become less efficient in some people. If you eat an unhealthy diet, have way too little exercise and are over the age of 30 then you are more likely to get problems with your weight due to this feedback mechanism starting to fail. In contrast, if you stick to a rigorous exercise program that keeps you extremely fit, you won't gain much weight even if you start to eat 1000 Kcal per day more, simply because your body is then programmed to maintain itself in this excellent state of fitness. Count Iblis (talk) 17:32, 3 April 2014 (UTC)

Also note that some animals in the wild do gain weight, e.g. animals that hibernate, but you can't compare that to obesity. Obesity is a pathological condition. Just compare the physical fitness of a big fat polar bear with a 300 kg extremely obese person. Count Iblis (talk) 17:37, 3 April 2014 (UTC)

• Per Wikipedia's article titled body weight there are several methods of calculating one's ideal body weight. There is the Hamwi method and there is the one used to calculate one's Body mass index. --Jayron32 16:09, 3 April 2014 (UTC)

• As pointed out above, the rate at which your body uses energy is only half the equation, with the rate at which your body obtains energy being the other half. And the rate at which your body obtains energy isn't just dependent on how much you eat, it also depends on your digestion efficiency. For example, eating a huge amount of food at one time forces other food out before it is fully digested.

As far as the rate at which your body uses energy, one effect is that you feel more energetic when you have a higher blood sugar level, so are more likely to perform activities which burn energy. This can even take the effect of tapping your foot as you sit. StuRat (talk) 16:13, 3 April 2014 (UTC)

I don't know about these 'regulated processes' - whatever they are, they don't stop people who eat what they fancy from gradually doubling their body weight over 10 years, and this "regulation" doesn't stop dieting to go back the other way from working...so if these mechanisms exist, they must be at best somewhat ineffectual.

1lb of fat is around 3,750 calories - this is a very important number to know if you're planning a weight change.

Losing 5lbs really requires eating 5x3750 calories less than is required to maintain your body weight...over whatever period of time you intend. There are two approaches to that, either reduce your calorie intake by that much - or make your body need that many more calories (eg, by exercising), and not giving it them. Exercise doesn't let you lose weight without getting hungry or without some amount of willpower.

It's generally accepted that losing more than 1lb per week is difficult and perhaps, arguably, dangerous. So I would plan to cut around 500 calories per day from your food intake for 5 weeks. 500 calories is roughly the difference between a small, normal meal and a salad - or between a big fast-food item and a small, sensible meal.

Going the exercise route is tougher than you might expect. There are many web sites to help with estimating this - I use http://www.myfitnesspal.com/exercise/lookup - you enter the exercise you'd like to take...lets say..."Swimming laps, freestyle, leisurely pace"...and enter your weight...lets say...180lbs...and the time...lets say 30 minutes per day. That'll consume 286 calories per day...so if all you do is go swimming every day, you'll only drop a half pound per week...but it'll get you there eventually. If you can exercise harder than that - then you'll drop weight faster - but it's easy to do exercises that convert fat into muscle and don't actually drop much weight off. Of course, after you exercise, you may be more hungry - and if you eat more because of that, then you're probably undoing the calorie burn. It's obviously healthy to engage in lots of exercise - but as a weight loss program, I think it sucks, every time I've tried it, I actually put on weight.

In any diet, people seem to lose a lot more in the first week, then plateau out a bit over the next week before settling into a more steady rate of loss...and many people give up during that second week plateau - claiming that their diet has 'failed'. So whatever you do, stick with it for a solid month before deciding how well it worked.

I've also tried a very low calorie diet (around 1,000 cal per day) and with that I can lose 2lb per week...I have a sedentary job and take less exercise than I should - and my body needs maybe 2000 cal per day. My crash diet is only 1000 cal/day - so over a week I'm 7000 short - which is about 2lbs...so the math works! But it's horrible to do - I feel hungry all the time and the amount of willpower needed to stick with it is hard to muster! However, the usual claim that this somehow flips your body into "starvation mode" seems to be unsubstantiated - and although its said everywhere, nobody seems to be able to point to a scientific study to say for how long you can diet and how many calories worth of loss will cause this "flip" to happen - or how long after returning to a normal diet it flips back again. Some sources have dire warnings over missing even a single meal - and others say that you should merely take a break from your diet every six months to avoid it! They can't both be right - and writers of diets are notoriously unscientific bullshitters! I stuck to the 1000/day diet (skip lunch, no snacks, no sugar) for 2 months, and it worked really well...and the weight has stayed off since...but it was *HORRIBLE*. So plan for 1lb/week.

To add 5lbs, just do the reverse. Eat around 500 calories per day more...or exercise 500 calories per day less...and you should add about a pound every week. Of course whether you can make those pounds be muscle or fat is a much harder thing to manage.

How well this change 'sticks' over time is much harder to know...and that's probably where this 'regulation' thing cuts in. Arguably, it never settles on a new normal - and it doesn't take many extra snacks each week to start slowly putting the fat back on again. After all, that's probably how you gained the extra weight in the first place...so slowly, you hardly noticed.

While tracking weight change, you should weigh yourself every morning, after you pee/poop and before you eat or drink anything. That gives you the most reliable reading from one day to the next. Bathroom scales are horribly inaccurate so if your weight dances up or down by 1 lb or even 2lb - don't worry about it. Plot a graph and over a week, you'll see an obvious trend line.

I always recommend "The Hacker Diet" to anyone with half a brain - it explains how all of this works and why...and it is the "source" for most of what I said above. It's the only diet book I've seen that actually explains why things work in verifiable, scientific terms.

SteveBaker (talk) 16:53, 3 April 2014 (UTC)

There also seems to be the reverse of starvation mode, a "fat storage mode", where you body decides it has enough calories coming in that it might as well store some of it for a later famine. Eating a low calorie diet every other day, or every third day, seems to be enough to prevent that.

As far as the body's self-regulation mechanisms not being very effective, that's only in the presence of the modern Western diet. It works quite well when exposed to the foods we evolved to eat. StuRat (talk) 17:03, 3 April 2014 (UTC)

• The brain largely determines body weight by controlling food intake. The process is very complex and not yet very well understood -- it involves chemicals such as orexin, leptin, and ghrelin. For most people who don't deliberately try to control their weight, the brain mechanisms will eventually cause it to stabilize at some level -- though it might be a lot higher than you like. It's hard to give a range, because it varies from person to person and depends on factors such as the type of food eaten and physical activity. There are some people whose weight-control circuitry is so disfunctional that they are unstable at any level, though. Looie496 (talk) 17:20, 3 April 2014 (UTC)

First author, second author, principal investigator...

Do scientists ever argue about who gets to be first author or principal investigator of the research paper? Say Professor A contacts Professor B to work on a research project, and Professor B agrees. Since it's technically Professor A's idea, Professor A will probably declare himself as "Principal Investigator". Can he also list himself as First Author, if he perceives that Professor B is not contributing most of the work? Now, the two professors may also have a Research Team of minor workers (a graduate research assistant, an undergraduate research assistant, a senior research scientist, and an animal technician). The Research Team does the experimental work, while the professors do the brainer, theoretical work and actually writing the paper. Generally speaking, how do people determine First Authorship and Principal Investigator? 140.254.227.73 (talk) 18:07, 3 April 2014 (UTC)

This (Difference_between_Corresponding_author_and_First_author_and_what_are_all_their_responsibilities) sums it up nicely I think. (+)H₃N-Protein\Chemist-CO₂(-) 19:35, 3 April 2014 (UTC)

Short answer to your initial question: yes, of course scientists argue about author order. They are just people working together, and disputes are bound to come up. That being said, we try to avoid it.

Also, note that principal investigator is a term that's tied to a research proposal and grant funding, not just one specific paper. So the PI is the person who led the development of a successful grant proposal (see second sentence of our article). That part is discussed between coauthors of the proposal long before any papers are published. One the funding body accepts the proposal, the PI and possible CO-PIs are fixed for all work on that project. So keep in mind that projects and funding have PIs, papers just have authors. In situations where no big funding source is at play, I suppose the senior professor could call themselves PI, but that's not really a controlled term for journal articles.

For reference: here's a nice topical peer-reviewed journal article, titled "Author Order and Research Quality." [5]. A key quote:

“ We observe a great deal of heterogeneity in the manner in which author orderings are assigned both across and within academic markets ”

My personal experience is that there is great variation in how author order is determined. You will find different customs within and between national cultures, science/humanities, specific field and research areas, as well as personal preferences.

So, there isn't really an "In general" description of the process, just many customs that vary by culture. SemanticMantis (talk) 20:01, 3 April 2014 (UTC)

more personal obs. for the interested SemanticMantis (talk)

In USA math, alphabetical order is usually the norm. In USA biosciences, I've seen two main approaches. One is that the senior/funding adviser generally goes last, this is most common. So, a typical author order might be Postdoc, main driving force, performs analyses, writes first draft of manuscript Grad student, assists with experiments, participates in writing Other Grad student, wrangles undergrads, designed experiment, possibly wrote protocols. Undergrads may get on author list if they make a big contribution, often just acknowledged at the end. PI, funds the other two, makes sure everything looks ok, willing to stake their name and reputation on it, may not do much of the "grunt work" involved. Another approach is that whoever writes the first draft goes first, and that could be anyone from the PI to some obscure undergrad. Most scientists seem to agree that the group should be very open and explicit from the start about expectations of author order. However, almost any order can happen. I've put undergrads that I've supervised first on papers, just to highlight the fact they were a crucial part of the research. Sometimes technicians only get a brief acknowledgement at the end, sometimes a paper on particle physics has ~200 authors, down to very minor players. Finally, as far as switching author ordering without consent -- big no-no, it could potentially end a career or two. Someone has to be the person that actually performs the submission. There is always (in my experience) as portion where the submitter effectively says "I testify that all authors have approved of this submission." So if the submitter changes the order, that's essentially academic fraud.

In part because because of that "heterogeneity in the manner in which author orderings are assigned", and partly because there can be concerns about authors receiving either insufficient or undue authorship credit, some natural sciences journals encourage (or even require) a 'statement of contributions': a footnote or short manuscript section briefly describing what each named author actually added. (And I don't know of any scientific journal that would refuse to print such a statement.)

Worth noting, as well, is that WHAAOE: academic authorship.

Finally, sometimes you get to be an author just because it makes the paper's citation more fun: Alpher–Bethe–Gamow paper. TenOfAllTrades(talk) 20:46, 3 April 2014 (UTC)

Immunologist Polly Matzinger wrote a 1978 paper in the Journal of Experimental Medicine together with her dog, Galadriel Mirkwood (PMID 78964), story mentioned in the article. Whether the authorship order was the result of an argument or agreed beforehand, the story does not say. --NorwegianBlue ^talk 21:04, 5 April 2014 (UTC)

Is there an example for Boyle's law - from the daily life?

I'm looking for an example for Boyle's law from our daily life. May you help me for? 213.57.121.149 (talk) 21:46, 3 April 2014 (UTC)

Your freezer is a good one.--Aspro (talk) 22:40, 3 April 2014 (UTC)

Boyle's law is obeyed whenever a given amount of gas expands or contracts, provided there is no chemical change or temperature change.

$P\propto {\frac {1}{V}}$

Here is an illustration. 84.209.89.214 (talk) 22:50, 3 April 2014 (UTC)

A concertina. All the best, Rich Farmbrough, 22:46, 3 April 2014 (UTC).

See: Combined gas law.--Aspro (talk) 22:49, 3 April 2014 (UTC)

Breathing. All the best, Rich Farmbrough, 22:59, 3 April 2014 (UTC).

When travelling by plane, don't throw away your empty plastic bottle of mineral water. Just close it tightly when still at cruising altitude. Then observe how the bottle looks after the plane has landed. Count Iblis (talk) 23:54, 3 April 2014 (UTC)

If you squeeze a closed container of air, it gets smaller. That's all Boyle's law says. If you didn't already know how squeezing things works, then I'm not sure we can help you any further. --Jayron32 01:24, 4 April 2014 (UTC)

How does the freezer function as Boyle's low? The same question I have for the concertina. 213.57.121.149 (talk) 23:22, 4 April 2014 (UTC)

You make the concertina smaller, the pressure increases. Air flows out making a sound. You stretch it, pressure decreases. Air flows in making a sound. The airflow (and sound) is simply evidence that the pressure has changed. All the best, Rich Farmbrough, 00:43, 6 April 2014 (UTC).

Leap years in the Igbo calendar

How are these dealt with if at all? And the extra day for each year, is it inserted in the 13th month or is it monthless? Refs would be appreciated, of course. All the best, Rich Farmbrough, 22:41, 3 April 2014 (UTC).

See the article Igbo calendar. The extra day is at the end of the year (afo) and there is no word in the Igbo language for a leap day. A need for leap days arises mainly in advanced societies where printed calendars and almanacs are expected to predict seasons and astronomical events accurately. I suspect that the annual year-counting festival known as Igu Aro is simply declared whenever the traditional time keepers in Igboland, the priests Dibia, say so. 84.209.89.214 (talk) 13:08, 4 April 2014 (UTC)

Thanks! (I did read the article!) I am not to concerned about Igu Aro, which can be delayed, indeed it seems would be if it was thought that the time for planting was not yet nigh. It has been suggested that for equatorial communities the seasons are less important, so the change with respect to the solar year is not important, however the extra day indicates the opposite. Again it is suggested that this was done to match with the Egyptian year, but no RS have been sighted yet.

The Youruba calendar which is very similar does have leap days.

If there's no definitive answer known here, I will make a few off-wiki enquiries.

All the best, Rich Farmbrough, 23:39, 5 April 2014 (UTC).