Allow members of one Google group to post (but not be members of) another group

Question: At my school we have a group for each class in the school, where the owner is the class teacher, and the students are members. We also have a group for all of the teachers. I want any teacher to be able to post to any of the class groups, but not to be a member of all class groups. Is there any way to do this other than opening the permissions to allow anyone in the school to post to the class groups?
Comment: This question has been bumped by Community User 7 times. It doesn't include enough details, and there have been several changes in Google Groups and the Google accounts for schools. If you are still looking for an answer, please update the question and include more details like the type of accounts that you are using.
Answer: (My answer is not tested with GAFE.)
To achieve the desired functionality, subscribe each teacher to each class group, but with "delivery setting" set to "no email."
This next idea is just fantasy -- I wonder if you could subscribe the name of the teachers group, and also set it to "no email"?


Does the force on the bottom piece of a hummingbird feeder depend on the height of the water in the reservoir?

Question: Intuitively I would think that the more nectar you put into the reservoir the more weight it will put on the bottom piece (the tray that holds the open pool of nectar that the birds can feed out of). While I was trying to think about this I thought about doing some free body diagrams. The reservoir would have a force acting upwards on it from the hanger, and a downwards force from the sheer from the stored nectar. The bottom piece would have an upwards force from where it threads onto the reservoir and I can't really figure out how to do the downwards force. I'm thinking if I could calculate the pressure all along the interface between the pan and the nectar that would do it..
Comment: Make sure that your FBD includes the air pressure pushing the column from above.
Comment: Short answer : Yes.  (re BowlOfRed's comment : if the column of nectar is not open to the atmosphere, the pressure pushing it from above will be less than the surrounding air pressure.)
Comment: As the humming birds feed the level in the tray drops till there is air flowing up into the reservoir and liquid flowing out. But then the liquid pulling down tries to make a "Torricellian vacuum" (I got that term from here https://en.wikipedia.org/wiki/Barometer while trying to do some more research on this). If you assume there is no air in there to begin with (they filled it 100%) that pressure is zero and you effectively have a vacuum (ignore the vapors coming off the liquid), and as the birds feed the pressure would slowly go to atmospheric.
Answer: The force the fluid does on the bottom piece does not depend on the height of the water column of the reservoir. It does depend on the height $h$ of the water column in the plate.

This can be easily seen by the fact the water is static so the pressure at any horizontal plane is the same. The pressures in $a$ and $b$ are the same. The force of the water on the plate is $F=pA=\rho g h A$, where $\rho$ is the water density and $A$ is the area of the plate.
It is definitely counterintuitive so I had to go get an empty bottle of wine and a plate to check it. As long as the bottle does not touch the plate, the latter weights the same no matter if the bottle is full or almost empty.
Comment: The description of your experiment gave me another way to think about it! If you are holding the wine bottle up and you feel the weight of the entire column of liquid in the bottle, then the plate probably doesn't feel that weight other wise the weight would get counted twice, and probably screw up some conservation law. So to get an intuition pull a glass out of the sink upside down and if it feels like it's as heavy as the water it is pulling up...


Is it acceptable to put programming code as proof in paper?

Question: I used statistical language R to fit probability distribution to acquired data. Instead of doing it by hand I relied on code. I wrote something like "probability density function was computed using programming language R (for more details see appendix A)". And appendix A has exact code to compute this. I also put reference to R package documentation. Is it bad to rely external tools for proof?
Comment: What do papers in your target journal usually do? Do that.
Comment: I don't see how R will *proof* you anything. It might do statistical calculations for you, and if those are used in your paper I'd append the code in the appendix (if there is room).
Comment: IMO programs proves nothing, as programs can have bugs which mimic "correct" answers. Alternatively, the (subliminal) desire of the author to have a program produce "correct" answers can cause the author to write a program which produces the "correct" answer, irregardless of the "correctness" of the paper.
Answer: From what I can guess about the context, I would avoid putting the code in your paper unless:

the code is really short (say no more than half a column);
the code is interesting in itself;
and you know that your average reader understands the language R.

Otherwise, it would probably better to omit the code altogether and write, in a note, something like:

To those interested, the authors can provide the R code employed to compute the probability density functions described in this work.
Comment: Rather than "can provide", though, point to a URL where the code is already up....
Comment: You're probably right. 2 and 3 are false in my case.
Answer: It's very common to include code when code was used. That being said, it's not clear whether you should think of this as "proof" of something in a rigorous mathematical sense, or whether is constitutes evidence in your argument. How accepted this is will depend on the community you are trying to convince.
Comment: @pusheax, how can it be **exact** proof if it was done with floating-point arithmetic in R? At best it approximates the PDF numerically.
Comment: I do think of this as **exact** proof that PDF is correctly chosen. Because this language is open source, anyone can see what I did in a few sentences of code. This constitutes proof as much as saying according to Theorem so and so. I just do not want to clutter paper with excessive statements. And I think that no one does that among my peers - that's why I asked.
Comment: exact proof that it's the best fit among several chosen distributions. But I see your point about FP arithmetic. I could have a case with two PDFs being close to data but I had not.
Answer: It is fine to put it in your appendix / supplemental info, but it's not really necessary.  Computing something as simple as a PDF should be easy for anyone.  It's along the lines of including your work to convert from atomic units to Joules.  However, enough people have forgotten to normalize correctly so there's nothing bad about including it.
Answer: You can put the source code in the appendix but it is not necessary.
1). For it to really matter that there is code in the appendix the read would need to have a basic understanding of programming to at least get the general idea.Other wise as soon as they see something like randomCode = NSString.format"string here"; they are so lost they'll skip over it.
2).If the length of the code is short and doesn't take up much space then even if the reader doesn't understand it you could use it as a "Hey this is the code" and not take up too much space for something the reader may have no understanding of. If the code is lengthy and takes up too much room (this is all dependent of the overall length of all of the other content) then even if the reader is a code junkie it's just too much.
3). You could post the code or at least parts of it and then explain what it actually means for example "This algorithm above is what takes all of the students grades and compiles them from a numeric value into a letter grade.


What are the acceptable methods to thaw food items?

Question: What are the proper ways to thaw foods?   Are there any advantages or disadvantages to them?
Answer: There are four methods for thawing frozen foods which are recognized as safe:

In a refrigerator
In the microwave
Under cool running water
As part of the cooking process

These four methods all meet the criteria that they minimize the amount of time the food spends in the danger zone (40-140 F, 4-60 C) where bacteria can grow.
The pros and cons of the following often-recommended methods are also reviewed:

Leaving food on the counter overnight
Thawing in a bowl (or sink) of water
On a metal pan or with a "miracle thaw" device

In the refrigerator
Thawing food in the refrigerator is slow; it can take a day to thaw several pounds (a kilogram or two), and even more time for larger foods like a whole frozen turkey.
The advantage is that the refrigerator is at a safe temperature, and bacterial growth is already inhibited, so there is little risk.
This is probably the preferred method for many foods, if you have the time.
In the microwave
Thawing in the microwave is fast, but it has several disadvantages:

It requires a lot of attention, turning or rotating the food to get even coverage from the microwaves; for items like ground beef, you might even need to scrape off the thawed portions and continue defrosting the frozen portion.
It is easy to accidently go to far and start cooking the food, especially if it has an odd shape or small pointier parts sticking out (like wings on a chicken).

For this reason, microwave thawing is best done only for foods like soup or stew, where you can stir them and if one part boils a small amount while another part is frozen, no harm is done.
Under cool running water
This one is most surprising, but it is true:  the fastest way to thaw food safely is under cool running water (at or below 70 F / 21 C), like the cold water from your tap.
The reason is that that water has an extremely high capacity for carrying heat, and the forced convection from running water ensures that it transfers heat from the food item as rapidly as possible.  In the Good Eats episode What's Up Duck, Alton Brown thawed several frozen ice duck sculptures by various methods.   The one under cool running water was almost completely melted, even when the one in the oven at 200 F was still fairly recognizably bird shaped.
It is important that the water be running, to ensure strong convection.  You can do this by setting the food in the sink under a very small stream of water.
If the food should not get wet, you can put it in a zip-type bag or similar to keep it dry.  Try to remove as much air as possible, to get the best contact between the water and the food (through the bag).
This is the best method for forced, rapid thawing (at least when microwaving is not appropriate or inconvenient), but it is probably less convenient that the refrigerator method.   You also have to monitor the food, and remove it when it is thawed, or it will come to the ambient temperature of the water, which is probably in the danger zone.
As part of the cooking process
Some foods can be cooked starting from the frozen state, thawing and then cooking in one operation.
Among the ones most suitable for this are are smaller or thinner items, such as:

Cookie dough lumps
Hamburgers
Chicken parts
Pizza
Stew meat
Frozen, chopped vegetables
Frozen stock (at least in smaller quantities)

Bad idea: on the Counter overnight
This is a bad idea, especially for meats and other highly perishable items.   You have no control over the temperature the surface of the food will reach, and it may begin to spoil at the surface before the center is thawed.
Bad idea: In a bowl (or sink) of cold water
Again, a bad idea.  Without the convection, the thawing speed is reduced.  There is also no source of newer, cooler water, so the temperature of the water itself will rise.
Some parts of the food may reach dangerous temperatures before it is fully thawed.  Also, if you don't check the food frequently, the temperature can get into dangerous territories, facilitating spoilage.
Risky: On a cast iron, stainless steel or other metal pan, or a "miracle thaw" device
This method is most often used with thin foods like steaks or frozen hamburgers.
Physics are with you, as the specific heat capacity and conductivity of the metal are very high (higher even than water).  The large surface area of the metal acts like a radiator or heat sink in reverse, conducting heat away from the food more rapidly than air alone would.
This method is not approved by health codes for commercial use, and carries some risks.  You need to monitor the food closely, and cook it or move it into the refrigerator as soon as it is thawed.  Failure to do so will allow the food to spoil, and the conductivity of your metal will become your enemy, more quickly bringing the food to ambient temperature.
While this method is not officially sanctioned, you may choose to assess its risks for yourself.

See also:

USDA Food Safety Fact Sheet
How do I know if food left at room temperature is still safe to eat?
Comment: USDA recommends cool running water means below 21 C
Comment: please, define 'cool running water', as having a water heater allows to vary the stream temperature in like 15..60C.
Comment: Bypass the water heater; use the cold faucet.
Answer: After managing restaurants, where chicken was a staple, frozen chicken does very well, under a small stream of running water, thawing safely.  If you thaw in refrigerator,  put your chicken on bottom shelf, avoids cross contamination with other items


Is there any reason why vacuum is like it is?

Question: I wonder whether there is any explanation for e.g. magnetic permeability of the vacuum. Is it just as it is, so that we take its properties as a given constant, or will we ever be able to find a reason for its properties?
Comment: related: [Are the permittivity and permeability of free space associated with the zero point energy field?](https://physics.stackexchange.com/q/305728/84967).
Comment: see also my answer here https://physics.stackexchange.com/q/420618/
Answer: The vacuum's permeability and permittivity take the values they have by the definition of our units. While the metre's definition in terms of the second fixes $c^2=1/(\mu_0\varepsilon_0)$ in SI units, the definition of the  Ampere implies $\mu_0=4\pi\times 10^{-7}\text{NA}^{-2}$.
Comment: I feel, this just turns the question around. I mean, here c is the magic constant which has to be just taken as given property to calculate µ0.
Answer: Assume a 2-dimensional space (maybe square) and suppose you have two charges pinned down at diagonally opposite corners of the square and the square is filled with a certain material. The electric force felt by one of the charges due to the other charge will strongly depend on the material. Simply put, permittivity of the material is a property which decides how much force a charge will feel and this force changes if you change the material (hence permittivity). So the vacuum case is similar. It's the vacuum that decides how much force those charges will feel. You have the same reasoning for permeability too.
One of the best properties of the vacuum is that it is isotropic unlike certain materials which can have different permittivity and permeability values for different directions. Such materials are called anisotropic and the permittivity and permeability values now become tensors rather than just scalar numbers.
Answer: The value of the magnetic permeability can be seen as being fixed by special relativity. Maxwell's equations, describing electromagnetic phenomena, fall naturally from SR. And in these equations, the speed of light $c=(\varepsilon_0 \mu_0)^{-1/2}$ is one empirical constant (related to our choice of time-units). The other constant is the permittivity of the vacuum, $\varepsilon_0$. So the permeability $\mu_0$ is not independent, and is rather determined by speed of light and the permittivity, or in other words its value is necessitated by SR and the permittivity.
The question now becomes whether we can similarly fix the value of the vacuum permittivity $\varepsilon_0$. Well, it's related to the way electrons influence each other, so really it can be reduced to things like coupling constants in the Standard Model.
But then the question becomes - can we explain those? Can we explain the coupling constants? And the answer to this seems to be that currently we can't, but it increasingly appears that our universe if part of a multiverse which means that there is nothing to explain. The multiverse contains universes with all coupling constant values, and we live in a part of it that has these values.
One then wonders whether the equations describing the multiverse are necessary. And again one reaches these same two options: either the equations are basic, and have no explanation, or else the multiverse encompasses all possible realities, so they need no explanation. The latter is Max Tegmark's "Mathematical Universe Hypothesis". It still leaves unexplained why the multiverse should take on this all-encompassing structure. (And, of course, is nothing but wild conjecture at this point.)
Ultimately, explanations are based on more fundamental theories. We can climb down a level, but either the whole structure is infinite or we'll reach the bottom-most theory at some point (we'll reach a brute fact, that has no explanation). Neither options seems palatable, and there is no solution for this conundrum that I know of.


Detecting drops from the same process

Question: Is it possible for a class implementing DropTargetListener, to detect whether the stuff being dragged comes from the same process of from elsewere?
Answer: If you check the DataFlavor of the drop event, you can look to see if it contains a DataFlavor of javaJVMLocalObjectMimeType.  As long as your app always provides that DataFlavor, then you'll know the source of the event was your app.
If that doesn't work for you, you could create a marker mime type and DataFlavor that your app can attach to any of it's drag sources.
Answer: In general no. Marker DataFlavor is possible. In general, in DnD there is no need to know if I'm in or out. If I can convert data into way I can handle, then it is OK. Else I'm not interested.

Detecting drops from the same process


On adjective days, when to use の

Question: Given the two sentences,
寒い日は温泉に行きます。雪の日は温泉に行きます。
Why does "on cold days" not need the の, but "on snowy days" it does? It appears most other adjectives also require the の, with the exceptions I've so far found being hot and cold.
Comment: Do you know how to recognize the difference between a noun and verb in Japanese?
Comment: @A.Ellett Honestly no other than some very basic things like るverbs, but that's something I'm starting to work towards. So far I've been basically just WK for kanji, and Duo/other apps for vocab and basic sentence structure examples, but none of that really explains these types of differences (which became very obvious as soon as it was explained).
Answer: In the sentences  寒い日は温泉に行きます and 雪の日は温泉に行きます, the words 寒い and 雪 are different parts of speech.   Hence the differ structure used.
寒い means cold and is an adjective.
雪 is a noun. It means snow, not snowy.  In order to say a snowy day, you basically say "day of snow" 雪の日.
You can see this same structure in other phrases: 雨の日, a rainy day (more literally, a day of rain).
With adjectives, you do not put の between the adjective and the noun.  暑い is an adjective meaning hot.  暑い日 is a hot day.
If you said 暑いの日, this would be ungrammatical.
Comment: Thanks, that makes a ton of sense. I was getting too hung up on the translation to English being given as "rainy day" or "snowy day", I was thinking of it as an adjective even though I know the kanji itself is a noun.
Comment: In English we indeed sometimes say "snow day" which is even more confusing!
Comment: @Fattie Indeed. But usually a "snow day" refers not so much to a snowy day as it does to a day when you cancel something: like school or close a business because the streets are impassable or something.  Depending on where you are in the country (thinking States and Canada) that could just mean slick roads to a full blown blizzard.
Comment: quite true, @A.Ellett

On adjective days, when to use の


What is it called when a cockroach eats another dead cockroach?

Question: I have a question on a cockroach eating another cockroach, because I was in a toilet where I killed a cockroach after few minutes there are another cockroach appear eating the dead cockroach, I am not a cockroach researcher, but my curiosity came out from no where and wanted to know about the word that describe it. We called cannibalism for human, what about cockroach? Roachebalism?
Comment: I'm just glad I didn't encounter this question before dinner.
Comment: Hahahaha yeah hope don't disgust you haha
Answer: It appears that it is also called cannibalism:

Cannibalism is the act or practice of humans eating the flesh or internal organs of other human beings. A person who practices cannibalism is called a cannibal. The expression cannibalism has been extended into zoology to mean one individual of a species consuming all or part of another individual of the same species as food, including sexual cannibalism.

In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food.
  (Wikipedia)

It seems like animal cannibalism is in usage, to distinguish it from human cannibalism. In particular, you can use the animal name as in [animal name] cannibalism:

CHICKEN

You've heard of the expression "pecking order," right? Well, chickens within a flock have a certain social hierarchy, and they establish that hierarchy with .. pecking. Literally, pecking.
With beaks. Sharp beaks.
This behavior results in drawn blood and torn skin ... and even worse. It can turn into chicken cannibalism. And since chickens have a tendency to imitate each other, once one member of the flock goes all Hannibal Lecter on its neighbors, the rest will follow.
  (Animal Planet)

So cockroach cannibalism seems possible too.
Comment: I heard an academic on the radio recently, distinguishing between eating the live of one's own kind and eating the dead of one's own kind. Cannibalism was the former, i.e. killing the victims in order to consume them, rather than eating the already dead. Those who ate the dead in order to stay alive themselves resorted to *necrophagia* not *cannibalism*, by her lights.


QGIS 2.12.3 Crashes on buffering line vectors

Question: I'm using QGIS 2.12.3 and I'm trying to create a buffer of 100 mt around a line vector using the Vector - Geoprocessing Buffer tool, but qgis crashes at every try. I've already checked that the RS of the vector is the same of the project.
Can anybody give some hint to solve this problem and create the buffer?
Comment: Does it still crash if you use the buffer tools from the _Processing Toolbox_?
Comment: which CRS are you using?
Comment: @Joseph It doesn't crash, but it returns this in the log:

QgsFeature.setGeometry(QgsGeometry): argument 1 has unexpected type 'NoneType'
Comment: @iant I'm using WGS84 UTM32N EPSG:32632
Comment: I tried buffering a simple line vector and it works perfectly... is it possible that the error depends on a multipath vector or on an error made in the creation of the line vector?
Comment: Could you also check the geometry validity of your vector?
Answer: QGIS has issues with geographic coordinates, you should use Save As and pick a projected CRS such as 27700 british national grid. If that didn't solve it then...
I just had the same problem with a "bad" line vector layer. Hope it's not too late but after trying several workarounds, what I've done was using the MMQGIS plugin > modify > convert geometry type. The resulting layer was perfectly fine


What are the benefits and disadvantages of the Global Trust and Eden Initiative factions?

Question: I always play as the Eden Initiative. Am I missing out on anything by not playing Global Trust?
Comment: Go with the tycoons for quick cash, and when you reach 1 executive, unlock the Eden for your farms.
Thats what I did.
Answer: The Global Trust tends to use much more efficient buildings for resource acquisition and powering structures, but at a cost of having a detrimental effect to the environment.
The most obvious one players will notice is the ability to mine iron and coal far more efficiently than the Eden Initiative. Their buildings tend to take up more space however, and generate a significantly worse impact on the ecosystem.
As your cities level up, you'll find that not only can Global Trust generate much more in resources, they also tend to generate a lot more funds than the Eden Initiative (they have Casinos).
You should decide carefully which pros and cons you feel better suited to playing with when deciding which faction to choose.
Eco-friendly, but weak in resources?
Or industrious, but polluting?
Either way you play it, both sides have their pros and cons to balance each other out. They can be equally as difficult to work with.
Comment: One can put blueprints for the dam or the big eco-devices tl clunteract the bad effects of being a tycoon. I never had a bad eco system or energy needs for the first few citizen levels
Answer: The short answer is 'not really'. The fundamental mechanics are the same, and I'd say the complexity of each faction's supply chain is about equal. Playing either faction feels about the same, aside from a few small differences which IMO the game doesn't really do enough to emphasize... aside from making Tycoon islands look very brown.
A number of Tycoon and Eco techs compliment each other, so you're limiting yourself if you avoid Tycoons altogether (particularly on continuous+large games). Tycoon resource extraction tends to be more compact, so you can squeeze more out of your land early on, but at the cost of more eco damage. Tycoons also generate more cash, but this is offset by the fact that eco farms can be made a lot more productive because the Eco tech can push an island's eco score very high, allowing farms to overproduce.
Playing a different faction probably won't rekindle your interest in the game if its fading, but I'd definitely recommended mixing it up if you're still looking forward to spending a lot of time with it.
Answer: Global Trust is much easier to manage as you don't need to worry about ecobalance. Eden on the other hand has a penalty of "low ecobalance lowers population happiness" which means lower profit. IMO Global Trust is much easier to play compared to Eden since you have less things to worry about, but in late game high ecobalance can get you overclocked farm builds which can save a lot of space for more pops.
Also, Eden unlocks shield generators which can come in handy in late game when everyone is building missile launch pads.
Answer: well tycoons are bad polluters only until you unlock engineers, then you've the deacidification station which pops in up to +90 eco and takes 60 energy (= 1 coal power plant) and are really small so you can squeeze them in those tiny spots you wouldn't use anyways (also they don't need to be connected)
tycons > eden (provided you can sustain deacidification stations)
Answer: Well... I play only as an Eco. Eco does not mine any resource directly, but trade for them. Advance your city before you do that, though. The general idea is to use the other players' technology, produce their products and undersell them. When you feel that you're overproducing something, you can start building other faction's buildings and houses.
When I play Eco I use only one island for populating. Everything else is for farming and production. This gets you more space for houses.
Comment: Eco DO mine resources, and I don't think it matters how you settle islands, as that has nothing to do with the question.


Light confinement in homojunction laser diode

Question: Why is light confined to the depletion region in a simple homojunction Fabry-Perot laser diode, like the one schematically illustrated below? Does this region for some reason have a higher refractive index even though, it too, is GaAs? If so, Why? I cannot find anything on this. Thank you
Answer: In laser diodes there are basically two ways of optical confinement

index guiding
There the laser has a refractive index profile and the optical wave is confined because of this. This may be because the refractive index of the active region is different  and/or because there is a ridge for the other lateral dimension.
gain guiding
Here it is used that the gain is inhomgeneous and the light wave is only amplified there. This does not remove scattering/diffraction, but the gain might be high enough to achieve lasing. Due to Kramers Kronig this may go along with some index guiding as well (because if there is gain, there is also a refractive index change even if it is the same material).

Modern laser diodes are mostly index guided.
Comment: So, if the active region of the device pictured was just the depletion region of a GaAs p-n junction, the pictured device would not actually work? Even in the ideal case?
Comment: I am sure it can work and think the first semiconductor laser was of this kind. Quantum well lasers were invented later.
Comment: Why is light confined in the depletion region of such a device?


Consistency of an unusual estimator for a binomial parameter

Question: I have a random sample $X_1, \ldots, X_n$ from a $\operatorname{Bi}(N,p)$ population. How do I show that the estimator $$\hat{p} = \frac{\bar{X}}{\max(X_1,\ldots,X_n)}$$
is consistent? The normal way I would approach such a question is to take the expectation and variance of the estimator and use that $\operatorname{MSE}(\hat{p})=\operatorname{Var}(\hat{p}) + \operatorname{Bias}(\hat{p})^2$, but for a ratio of random variables this would be incredibly messy. Is there an easier alternative?
Answer: If $Y_n\stackrel{p}{\to}Y$ and $Z_n\stackrel{p}{\to}Z$ then $Y_nZ_n\stackrel{p}{\to}YZ$.
So you might do it by proving that $\overline{X}_n\stackrel{p}{\to}np$ and $\left[\max(X_1,\dots,X_n)\right]^{-1}\stackrel{p}{\to}n^{-1}$.
Comment: Are you sure about the first statement that convergence of $Y_n$ and $Z_n$ implies convergence of $Y_n Z_n$? IMHO, it is true only when one of them is degenerate r.v. (constant. aka, Slutsky theorem).
Comment: @V.Vancak The Slutsky theorem concerns convergence in *distribution* (not in probability). Have a look at [this answer](https://math.stackexchange.com/a/2739582/75923).
Comment: Thanks for the clarification. Will look closely at the linked answer a little later.


Gravity in vector

Question: We know that gravity is a force. But what is it's direction? Can it be expressed by vector and how can we do that? This question can also be asked for Coulomb's Law.
Comment: *"We know that gravity is a force."* - Newtonian gravity is a force, but General Relativity is the currently accepted theory of gravitation.
Answer: Imagine you have only two masses in the universe $M$ and $m$, then the gravitational force that $m$ feels due to $M$ is indeed a vector that points towards $M$. This is called a central force, and as you point out Coulomb's force also behaves like that.
If you add another mass $M'$ into the picture the problem becomes more complex, in the sense that $m$ will feel now two forces: one pointing towards $M$ (${\bf F}$) and the other one pointing to $M'$ (${\bf F}'$). The resulting force ${\bf F} + {\bf F}'$ is also a vector but not necessarily point in any particular direction
Comment: How can a vector "not point in any particular direction?" Having a particular magnitude and a particular direction is pretty much what _defines_ a vector.
Comment: @jameslarge Sure, what I meant is that it does not point in either the direction of $M$ or $M'$
Answer: If we use the centre of the earth as origin, we have
$$\mathbf{F}=-\frac{GM_{\oplus}m}{r^3}\mathbf{r} \tag{$r>R_{\oplus}$}$$
where $\mathbf{r}=(x,y,z)$ and $\displaystyle \left| \frac{\mathbf{r}}{r^3} \right|=\frac{1}{r^2}$.
At the surface of the earth,
$$g=\frac{GM_{\oplus}}{R_{\oplus}^2} \approx 9.8 \text{ m s}^{-2}$$
where $M_{\oplus}$ and $R_{\oplus}$ is the mass and radius of the earth respectively.

We assume the earth and the test mass have spherical symmetry in their densities.

The Columb's law version is
$$\mathbf{F}=\frac{Q_1 Q_2}{4\pi \epsilon_0 r^3}\mathbf{r}$$
assuming point charges or negligible electrostatic induction.
See another answer with electrostatic induction here.
Comment: Nice answer.  But you're missing a factor of $R_{\oplus}$ in your definition of $g$, which should read: $g=\frac{GM_{\oplus}}{R_{\oplus}^2} \approx 9.8 \text{ m s}^{-2}$
Comment: You might want to spell out what **r** is.
Answer: As a first statement, I like to begin by stating that gravity is always towards the mass (e.g. always attractive). In other words, if mass A pulls on mass B, I would state that the direction of the gravitational force is towards mass A. If you set up coordinate system, you may then put this in by hand. (The same line of reasoning applies to the coulomb force, except now the direction of the force may be either toward or away depending on the signs of the charges.)
If we wish to be more formal, we can set up a spherical coordinate system centred on mass A. The direction of the gravitational force on mass B will always be in the $-\hat{r}$ direction, where $\vec{r}$ is a vector that describes the location of mass B.
Comment: Chung Tak....why is there a negative sign in Your formula for gravitation?and an extra r?I could not understand this.
Comment: @AsifIqubal --> in my formula for gravity?
Comment: Yes whoever wrote the answer.I didn't understand why you did that?
Comment: I didn't explicitly write a formula for gravity (there are 3 separate answers to this question).

I wrote a negative sign because if we work in spherical coordinates and place a large mass at the origin, the force of gravity on a (small) test particle due to the large mass will always be pointing toward the origin (hence in the $-\vec{r}$ direction).

Gravity in vector


Is it possible to connect two monitors on a laptop, one through HDMI and the other through DisplayPort?

Question: For example the Alienware m17x offers 3 connections, HDMI, DisplayPort, and VGA. Is it possible to connect two independent external monitors, one through the DisplayPort and one through the HDMI port?
Comment: That's actually an interesting question. Have you tried it already? For my Intel GMA it doesn't work. It is a dual head GPU because it can connect to two screens (to the laptop display and the VGA or DVI port). For anything different you would need a triple/quad head GPU, two GPUs or at least the possibility to switch from the Laptop screen to one of the external connectors.
Comment: My current laptop only supports hdmi/vga. I'm looking to replace it with one that will support two digital outputs, hdmi, dvi, displayport, etc. I just can't find any reliable information on how well they will work together...
Answer: Simple answer is yes so long as your drivers support it. It would certainly be possible if you were using a usb displayport adapter I'm just not sure whatever chipset your running would support different output to 3 connections (assuming you want to extend your desktop not just have it cloned on multiple screens)


Reinstall windows on peppermint

Question: Someone I know who has windows 7 was put on peppermint but after using it they decided they didn't like it and wanted to go back to windows. Is it possible to re-install windows on a peppermint computer and how?
Answer: It's definitely possible, and it's essentialy the same as installing Windows on a brand new computer - you get a Windows installation USB drive, boot from it (plug it in, then restart the computer), and go through the wizard.
 There are plenty of guides to do this (Microsoft's official https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/install-windows-from-a-usb-flash-drive).
There's also one for Windows7: https://www.microsoft.com/en-us/software-download/windows7
Just be sure to copy your important personal files from the peppermint, because Windows will most likely do a clean install, wiping the drive clean.
Comment: Thanks, @Liudvikas  Akelis, but I want to install windows 7 not windows 10. Also, is it possible to install it from a CD and not a USB stick?
Comment: Thanks for the upvotes, but I'm really just googling things for you at this point
Comment: Hi @LiudvikasAkelis , The person who wants to install windows doesn't have their product key. What should I do now? The guy that installed peppermint also said windows was still there.
Comment: Right. Usually when people install Linux alongside Windows (rather than writing over), they will leave an option for switching in the bootloader. If that's the case, you will see that option during boot (when computer turns on, before loading the operating system). There will be some sort of menu with Windows as an option.
If you are unable to find such menu during boot, that doesn't necessarily mean that Windows isn't there. However, at that point you really need hands-on help (any moderately seasoned IT person), but that kind of personal support is kinda beyond the scope of this site :/
Comment: Is there a stackexchange site where i could get that kind of support???
Answer: Yes its possible,follow the below steps:
Step 1.Take out all your backup from the pc, so that you wont lose any data.
Step 2.Run GParted or any other application to clean your disk related to peppermint.
Step 3.Install the windows version that you like.

Reinstall windows on peppermint


Installing Apache Mesos on CentOS or RHEL

Question: I tried to install the latest release tarball of Mesos on CentOS 6.4 with no luck. It ended up in all sorts of failures in trying to find jvm & jni bindings. Is there any instructions on how to install Mesos on RHEL or CentOS ?
Comment: You might want to check out the [mesosphere getting started for rpm based installations](http://mesosphere.io/docs/mesosphere/getting-started/rpm-install/).
Comment: It's been a while since you have posted that question but so newcomers, there are some installation instructions here: http://mesos.apache.org/gettingstarted/ for Ubuntu 14.04, Mac OS X Yosemite & El Capitan, CentOS 6.6 and CentOS 7.1. It can be a good start even if you don't have those OS versions.
Answer: I couldn't find any instructions around so I thought I would troubleshoot all through my way and thought of documenting it here so it can save your time.
First things first, load your CentOS box with essential build tools to get started
<code>$ sudo yum groupinstall "Development tools"
</code>
Get Java and python dependencies installed
<code>$ sudo yum install java-1.6.0-openjdk.x86_64  java-1.6.0-openjdk-devel.x86_64 python python-devel libcurl libcurl-devel
</code>
Get the latest Mesos tarball
<code>$ wget http://mirror.nus.edu.sg/apache/mesos/0.13.0/mesos-0.13.0.tar.gz
$ tar -xzvf mesos-0.13.0.tar.gz
$ cd mesos-0.13.0
</code>
Before you can build Mesos, you need to set correct JAVA binding paths
<code>$ export  JAVA_HOME=/usr
$ export  JAVA_LDFLAGS="-L/usr/lib/jvm/java-1.6.0/jre/lib/amd64/server -R/usr/lib/jvm/java-1.6.0/jre/lib/amd64/server -ljvm"
$ export  JAVA_CPPFLAGS="-I/usr/lib/jvm/java-1.6.0/include -I/usr/lib/jvm/java-1.6.0/include/linux"
$ export LD_LIBRARY_PATH=/usr/lib/jvm/java-1.6.0/jre/lib/amd64/server:$LD_LIBRARY_PATH
</code>
Configure and build it
<code>$ ./configure
$ make
</code>
After you have built Mesos, it is advisable that you build and run the tests, this will make sure that what you have installed meets all the requirements
<code>$ make check
</code>
If the checks are successful, You are just one step away from installing it in your system installation paths
<code>$ make install
</code>
To learn how to use Mesos , go here http://mesos.apache.org/gettingstarted/
I hope you found this useful and saved your time troubleshooting it.
Comment: Having the same problems on Ubuntu.  Have you been able to get an external slave to connect to the master?


Create a Table with 3 different variables from 2 Lists and 1 Table

Question: I am new to Mathematica. I learned how to join 2 lists to make (x,y) type of representation using Transpose@{X,Y}. Now my problem is that I have to make a table of 3 variables. I have one set of data with 63 points, another one with 64, and I have third one which is a huge table recording third type of data at 64 rows and 63 columns, related to the first two types. Now I want to make a plot (ListContourPlot) where X and Y will create a surface from first 2 data (as last data doesn't know what are X and Y), and on Z axis will be related to the 3rd dataset values at each of the (x,y) values. Sorry for ambiguous explanation. Thank you in advance.
Comment: Code and data are much less ambiguous than natural langauge text. It would help if you posted a sample of your data. Please don't post the entire 64x63 matrix. Pare down your lists to a maximum of 5 (or whatever is both readable and sufficiently illustrative) in any dimension.
Comment: I added a picture of what I would like to achieve. So that 64x63 matrix (in this case 5x4) is z-points. I have a separate list of x and y points (as shown on example in the picture). Each of these 3 sets is saved in separate files that I imported into Mathematica. And then I am trying to create a table which looks like the picture.
Comment: Okay, I see a matrix of data now. What we need next is how to find the (x,y) values. Presumably this is what your other lists are, but I'd like to see that to confirm and understand.
Comment: This will also be much easier if you add the data as copy-paste-able code. Go through the introductory tour to find out how to do that on this site.
Comment: Have you imported the data successfully? If not, that's a separate step that we can help with, but if you've imported the data into Mathematica, that's the data that I want to see.
Answer: Let's assume that the x-coordinates are in a list called xs. Similarly for a list called ys. Let's say data is len(xs) by len(ys) and holds the z values. We need to get some data in the right shape for ListContourPlot. We can pair up the xs and ys like this:
Outer[List, xs, ys]

To get the data in a compatible shape for Join (there are other options, but this works), we need to add a layer of List:
Map[List, data, {-1}]

Now we can join them:
plotData = Join[Outer[List, xs, ys], Map[List, data, {-1}], 3]

Now we want just a list of points in 3D space:
Flatten[plotData, 1]

This can be fed into ListContourPlot:
ListContourPlot[Flatten[plotData, 1]]


MySQL connection logs backtrack

Question: Is there a way to backtrack who connects to MySQL server? Aside from show processlist;? I want to see who connects last day. Thank you.
Answer: There are multiple audit logging products available. If you are using Percona or MariaDB flavour of MySQL you have the option of their plugin. If you are using Oracle MySQL you can pay for their enterprise version of audit plugin (as part of Enterprise Edition). There is also an audit plugin from McAfee that will fill this requirement and is generally available cross-alternative and from 5.1+. These products permit you to log both logins and queries. Finally there's a plugin to track logins only from a community contributor. Links to all below.
http://www.percona.com/doc/percona-server/5.5/management/audit_log_plugin.html
https://mariadb.com/kb/en/mariadb/documentation/plugins/mariadb-audit-plugin/
http://dev.mysql.com/doc/refman/5.5/en/audit-log-plugin.html
http://code.openark.org/blog/mysql/introducing-audit_login-simple-mysql-login-logfile-based-auditing

MySQL connection logs backtrack


Internet Text & Ubuntu Menu Text Color variegated - hard to read

Question: I'm a new user to linux/ubuntu and I have just installed the ubuntu 14.04 version.
The drop-down menu text and the internet texts appear to be orange/red and fade/mix-up randomly.  Sometimes texts 'disappear' completely and are unable to be seen until I click/do something else with the cursor or keyboard. Nothing else is wrong with the text except for the color itself.
For example the beginning of this post starts pink/red fades to dark blue/purple back to red/orange and then starts having interspersed letters of bright yellow and ends with light green text at the right side.
Thank you for helping me out! (:
Answer: As described here https://askubuntu.com/a/606583/448007, the problem seems not to appear by using the old UXA hardware acceleration for for the Intel graphic cards.
Edit the following section of the /etc/X11/xorg.conf file such that AccelMethod is set to "uxa" or create the file if it does not yet exist:
<code>Section "Device"
   Identifier  "Intel Graphics"
   Driver      "intel"
   Option      "AccelMethod"  "uxa"
EndSection
</code>
Reboot or restart X.
The problem went away for me


Closet door minimums

Question: Is there a code for the minimum width of a closet door? I've always assumed it was 24 inches. Or is it determined by the square footage of the closet?
Comment: I have a hall closet with a 12" door.  Not sure there are code requirements for a closet, but could be wrong.  You need a location for code questions.
Answer: The Code only stipulates the size of one door in a residence. It requires one egress door that...

has a 32" clear opening with the door in the 90 degree position (which requires a 36" wide door)
is located at a exterior entrance into the residence opening into a public way or open side yard that opens to a public way
does not open into a garage or carport
is a minimum of 78" high measured from top of threshold to bottom of stop
is side-hinged (no sliding doors allowed)

See 2017 ICC R311.1 and R311.2.
The only other requirement is for sleeping room egress windows, but that's not your question.
Answer: If a closet isn't intended to be occupied bodily by humans it's essentially a cabinet. There are no restrictions on access to such spaces.

Closet door minimums


Delete all files in a folder except the last (most recent) 20

Question: I want to remove all the files from different directories, and want to keep only latest files 20 files.
is this the correct command to do this?
ls -t1 /mnt/dwh/ftp/dwh_ftp_cbs/ARLOGS/ | tail -n +22 | xargs rm -f

Comment: useful tip 1: replace the `rm -f` after `xargs` with `ls -ld` to see what it would delete.   tip 2: if you're using GNU xargs (default on linux), you can use -d'\n' to use newlines as the input delimiter.  this will prevent files with spaces etc in the from causing problems.  tip3: `ls -1` is mostly safe, but be wary of parsing the output of ls, in particular `ls -l`.  tip4: `find` is usually better choice than `ls` for this kind of job.
Answer: In your command there are many disadvantages, for example the processing of the output of ls, it's kind of a catechism. See this article why not to do this.
This approach uses no GNU extensions, and is tested on bash, zsh, ksh93, dash and ash:
for f in * .*; do
  [ -f "$f" ] && printf "%s " $(perl -e 'print((stat("$ARGV[0]"))[9])' -- "$f") && \
  printf "%s\0" "$f";
done | tr '\0\n' '\n\0' | sort -k1nr | \
sed "1,20d;s/'/'\"'\"'/g;s/[^ ]* \(.*\)/rm -f -- '\1';/" | tr '\0' '\n' | sh

This is the weirdest filename I was able to produce, it works with even this:
touch -- '--a'"'"'b"c
d$e\nf\r!g;h^i`j(k)l*m%n=o?p.txt'

Or a filename which tries to "jump out":
touch '\'"'"'echo test '"'"'\'

Comment: It's still GNU specific in that most other `sort` or `sed` implementations will choke on input containing NUL characters. You'd want to do the whole thing in `perl`. Note that `stat` will check the modification time of the target of symlinks, use `lstat` so it be more like `ls -t`. Also it will not support sub-second resolution.
Comment: Also note that the `.` regexp operator in GNU sed won't match bytes not forming valid characters, so you should fix the locale to C.
Answer: With zsh and glob-qualifiers:
print -rl -- *(D.Om[1,-21])

will list all regular files except the last (most recently modified) twenty.
D selects hidden files, . selects only regular files, Om means reverse sort by mtime (so oldest first) and [1,-21] selects from the first  up to the 21st-to-last.
If you're happy with the result replace print -rl with rm:
rm -- *(D.Om[1,-21])

If you have a huge number of files you may have to use zargs to avoid arguments list too long:
autoload zargs
zargs ./*(D.Om[1,-21]) -- rm

Comment: Cool `zsh` solution!
Answer: ls -t1 /mnt/dwh/ftp/dwh_ftp_cbs/ARLOGS/ | tail -n +22 | xargs rm -f

Won't work because the output of ls will only include the files' names, not their full path. It would also skip files whose name starts with a ..
cd /mnt/dwh/ftp/dwh && ls -At1 | tail -n +21 | xargs rm -f --

would solve that, but you'd still have problems with filenames that contain blanks or newline or apostrophe or backslash or double quote characters (and possibly file names with bytes that don't form valid characters in the locale).
(export LC_ALL=C
 cd /mnt/dwh/ftp/dwh && ls -At1 |
   tail -n +21 |
   sed 's/"/\\"/g;s/.*/"&"/' |
   xargs rm -f --
)

would fix most of those, but you'd still have a problem with filenames containing newline characters. The problem is that the output of ls -At1 is not post-processable.
The output of ls -Atd1 ./.* ./* could be post-processed (as those ./ prefixes indicate where each filename starts in the output, but not easily), but you run the risk of reaching the limit on the number of arguments passed to a command by passing the list of filenames to ls like that.
Best would be to use a shell that can do that sorting in its globs, or rely on GNU extensions if your only need to work on GNU systems:
 cd /mnt/dwh/ftp/dwh &&
   find . ! -name . -prune ! -type d -printf '%T@\t%p\0' |
     tr '\0\n' '\n\0' |
     sort -rn |
     tail -n +21 |
     cut -f 2- |
     tr '\0\n' '\n\0' |
     xargs -r0 rm -f

Here, we're excluding file of type directory, which will affect the numbering but is probably closer to what you want as I don't suppose you want to remove directories. If you want to remove directories, remove the -type d and add the -r option to rm.
Or:
eval "set -- $(COLUMNS=4294967295 ls -Atx --quoting-style=shell-always)"
if [ "$#" -gt 20 ]; then
  shift 20
  printf '%s\0' "$@" | xargs -r0 rm -f --
fi

Or use a generic programming language like perl, python, ruby...


JavaScript onclick event listener not triggering after the first click

Question: I'm working on a web page where I have a button with an onclick event listener to switch between dynamically generated elements. The first click works as expected, but after the first click, the event listener doesn't seem to trigger anymore. Here's the relevant part of my JavaScript:
document.addEventListener('DOMContentLoaded', function () {
    // ... (other initialization code)

    trdmDisplayed = 1;

    nextbtn = document.querySelector('.nextbtn');

    nextbtn.addEventListener('click', function () {
        console.log(`trdm when the button is first clicked: ${trdmDisplayed}`);
        currentlyDisplayed = document.querySelector(`.indexdiv .shading-div:nth-child(${trdmDisplayed})`);
        currentlyDisplayed.style.display = "none";

        trdmDisplayed = (trdmDisplayed % 20) + 1;

        toDisplay = document.querySelector(`.indexdiv .shading-div:nth-child(${trdmDisplayed})`);
        toDisplay.style.display = "block";
    });
});

and here is my html:

    {%for movie in movies %}

              /*
                    other elements...
              */

                    <button class="nextbtn" ></button>

     {%endfor%}

Additional clarification: The dynamically generated elements consist of a fixed set of 20 elements. Upon clicking the button for the first time, the first element successfully transitions from element.style.display = "block"; to "none", and the second element transitions from "none" to "block" as intended and everything is logged onto the console. However, upon clicking the button for the second time, no information is logged to the console, suggesting that the event listener is not being called at all.
I have tried using ChatGPT to find the bug but nothing worked, I've revised my javascript many times but still, nothing worked. I've inspected my html and my css for any potential errors and could not find any.
Answer: Your for loop is creating multiple "next" buttons in your DOM, whereas your
querySelector() only selects the first one created, so the click event listener is tied to the first button only:
nextbtn = document.querySelector('.nextbtn');

That means that when you hide the first "next" button and display the next one, the click event listener won't be added to the new one you're displaying, and so the click won't work.
Instead, have the creation of the next button be outside of your for loop so that you only ever have one and so that you don't hide it when you hide the one of the generated elements:
{%for movie in movies %}

    /*
          other elements...
    */

{%endfor%}

  <button class="nextbtn" ></button>

On a side note, make sure you declare your variables such as trdmDisplayed, nextbtn and currentlyDisplayed with const/let so that they don't become global variables and stay scoped to where they're defined, this will help avoid potentially confusing bugs down the line.
Comment: @HamzahAlkhateeb Glad you sorted it out. Nice, yeah, adding multiple event listeners is best avoided if you can help it, in this case it seems like you should be able to do it with one (by pulling out the button from the loop).
Comment: Thanks for your answer. The issue seems to be, as you suggested, that the query selector is only selecting the first element with the .nextbtn class and ignoring the rest. I had a different solution, which is to use querySelectorAll that returns a NodeList of all the buttons with the class .nextbtn. I then used a forEach loop to iterate over the NodeList and added the event listener inside the loop.
Answer: Assign button in nextbtn outside of DOM contentloaded listener or remove that listener than check if it works.


Is there a gadget that would convert the stereo speaker output into Bluetooth?

Question: I have an old car stereo radio but the car only has a mono speaker. I do not want to do any metal cutting to install new stereo speakers. Thus, is it possible to use the output signal (low impedance) to the speakers and convert it to a Bluetooth signal so I can use a portable Bluetooth speaker?
Answer: A DI-box would do the job, for example most of these would. Look in the specs if it supports speaker output (usually the maximum wattage is specified).
Note that most of them are mono, so look for a stereo version or hook up two of them parallel.
Also look at the voltage (if it is an active one), you need 12V for most cars.
Most DI-box's have balanced output, so you would either have to connect the cold tip to GND or leave it unconnected (the manual of the specific DI-box should tell which is best).
Offcourse you would need a bluetooth interface behind it to connect to your bluetooth speakers.


A question about cancer antigens and their mechanism

Question: Can you name the most common antigen that cancer cells in general can't live without?
Comment: Are you referring to a certain type of cancer?
Comment: Welcome to Biology.SE! We encourage you to do some research on your own and then, informed by what you have learned, ask any questions you still have (ideally with references to reliable sources). ——— Thank you for taking the [tour], but please also go through the help pages starting with [Ask] questions effectively on this site and edit your question accordingly. Thanks!
Comment: @tyersome I actually have searched on internet and read books but all the answers wasn't convenient
Comment: I think that you would benefit from making sure your have a firm grasp on the basics of biology. I say this because you appear to not be using the correct terminology (e.g. You seem to think that antigen is a synonym for protein, which is not correct.) This makes your question unclear and creates the impression that you won't have enough background knowledge to understand the answer to your question assuming it was made clear enough to be answerable. ...
Comment: I recommend you start your review of biology with a relatively accessible and reliable source like [Khan Academy](http://khanacademy.org/science/biology/). Wikipedia is also generally a good starting point and you can then check their references. There are also online platforms called MOOCs that offer free (or very low cost) courses on a wide variety of subjects — two that I am familiar with are [Coursera](http://coursera.org) and [edX](http://edx.org). Finally, textbooks with a good level of detail are also freely available online e.g. from [NCBI](https://www.ncbi.nlm.nih.gov/books/).
Answer: This is a hard question to answer because each type of cancer is a whole different game at the molecular level, however there is something you might be interested in called "hallmarks of cancer" (image 1) which are key features for cancer to thrive. They were originally described by Hanahan and Weinberg (2000) and have been revisited by Fouad and Aanei (2017) in an updated review. The hallmarks of cancer aren't specific genes themselves, but rather broader categories that englobe certain types of genes.
If you want to look at specific genes, we could talk a bit about what more purely data driven approaches have found. There is a very interesting work by Kandoth and collaborators (2013) that presents data from The Cancer Genome Atlas (TCGA), which is a database of different kinds of genomic features from several different cancer types. Among the results of this work (specifically on figure 2 which I include here as Image 2) you can see a table of 127 significantly mutated genes across 12 different cancer types. One gene that is well known in medical literature for being frequently mutated in almost any cancer type (situation which is also observed in the aformentioned table) is TP53 which encodes a protein that is key for genome maintenance in normal cells by participating in DNA damage and repair (which is a cancer hallmark under the "altered stress response" category). In the table you can also spot tissue-specific cancer genes such as APC in colon/rectum cancer and VHL in renal cell carcinoma.
Just to make sure you can understand the table, the gene names are presented in the right (rows) and the names of the cancer types are presented at the top (columns). The description for the cancer types abbreviations can be found here. To the left of the table there is a functional classification of the genes so you can know more or less what a given gene does in a quick manner. The values presented are simple frequencies (divide the number of samples of a particular cancer type that have the mutation over the total number of samples of that same cancer type) expressed as percentages (so they are already multiplied by 100). The final column (Pan-Cancer) shows the same idea, but taking all samples from all cancer types into consideration for the frequency calculation.
So for answering your question regarding if there is a common feature in all types of cancers: strictly speaking at the gene level no, since even the TP53 mutation which is the most common amongst all cancers might not be present in some cancers; however, looking at it by categories of genes (as one or some of the 7 hallmarks) reveals that all cancers apply similar strategies to thrive (they exhibit different mutated genes, but these genes frequently belong to the same biological pathways and participate in similar functions). I hope you find this useful (:

Image 1: 7 hallmarks of cancer (2017 review).

Image 2: frequency of mutation by gene and cancer type.
References:

Fouad, Y. A., & Aanei, C. (2017). Revisiting the hallmarks of cancer. American journal of cancer research, 7(5), 1016–1036. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5446472/
Kandoth, C., McLellan, M. D., Vandin, F., Ye, K., Niu, B., Lu, C., … Ding, L. (2013). Mutational landscape and significance across 12 major cancer types. Nature, 502(7471), 333–339. doi:10.1038/nature12634
National Cancer Institute. TCGA Study Abbreviations. Retrieved from https://gdc.cancer.gov/resources-tcga-users/tcga-code-tables/tcga-study-abbreviations
Comment: This looks like a good answer and you've done a nice job of providing supporting references. However, please include the complete reference information since links can break. One easy way to get that information is to search for the paper on [Google Scholar](https://scholar.google.com/) and click on the " symbol to get reference information. This is a [good example](https://biology.stackexchange.com/questions/59695/how-do-trees-communicate-in-the-wood-wide-web?rq=1) of how to format references. ...
Comment: In addition, since answers here "must be comprehensible without reference to external sources" it would be helpful to insert the figure and table you refer to into your answer Thanks!
Comment: oh ok I wasn't sure if pasting the literal image of the resource was ok. I'll modify the answer soon enough
Comment: That looks much better! +1
Comment: Thank you so much, you're answer really helped me


What is the possibility of a depressurization emergency during a commercial flight where all or some of the oxygen masks fail?

Question: Can we calculate this? Or is it almost impossible?
Comment: For the case "all masks", a pressure sensor triggers the masks release when the cabin equivalent-altitude is more than 14,000 ft. If it fails, the crew is informed and [can override it](http://aviation.stackexchange.com/questions/21904/do-cockpit-panels-have-an-indication-that-oxygen-masks-in-cabin-have-been-deploy)
Comment: http://stats.stackexchange.com/
Answer: The oxygen system for passengers in an airliner is generally powered by a chemical oxygen generator.
The generator contains chemicals, which when they come into contact with each other, commence a reaction that produces oxygen for a few minutes.
The act of pulling down the mask triggers the contact between the chemicals.
A generator typically serves two or three seats, and each generator is independent of the others on the aircraft. They are not part of a single system with common points of failure.
The panel behind which the masks is opened by a pressure switch, and can also be opened manually.
However the crew will use bottles of oxygen, and the flight crew will use a more complex system that also includes smoke hoods.
Conceivably (anything is possible) a manufacturing fault or sabotage could render every single one of the generator/mask sets inoperative, but it would be an extraordinarily unlikely thing to happen.
People often imagine a system of pipes carrying oxygen to all the masks, but in fact such a system is rarely used. One notable example is the earlier (-100 to -400) variants of the Boeing 747, in which the oxygen is indeed piped. And, apparently, may have not always worked as expected:

The flight crew donned their oxygen masks and manually deployed the passenger oxygen masks.
[...] The PIC was also advised that there appeared to be no oxygen flowing through any of the passenger cabin oxygen masks, however this did not seem to have had any ill effect on the passengers. After the PIC cycled the passenger oxygen switch, a momentary surge of oxygen through the passenger masks was observed.

(from an Australian Transport Safety Bureau report into a November 2001 incident)
Comment: The 747-100 through -400 models used oxygen canisters and piping for the passenger oxygen system rather than chemical oxygen generators. I don't know about the 747-8
Comment: @TomMcW thanks I have updated the answer.


Themekey with mobile detect not working properly

Question: I am using themekey module with mobile detect module for switching mobile and desktop version of themes. Some time it works and some time not. On Apple devices it load the mobile version. I'm currently using a Shared Hosting provider and I'm using boost module in order to generated my caching.
Comment: Are you using some kinda of caching  ? There was a problem with the mobile detect module + caching. Which was solve last weekend.
Comment: Try to remove the boost module and see if works ?
Comment: I am shared hosting with out the cache or boost module the server will be overloded. Is there any other solution for this.
Answer: The mobile detect module had some issue with caching. The Drupal 7 Core caching have been supported since few weeks ago by a sub-module call "Mobile Detect Caching."
However, the developer mention that he boost probably would not work.... Here is what the developer said:

It will only work with Apache(?). I doubt it will work with Varnish,
  Boost, or similar. I suspect it will work with {cache_page} in
  alternate caches, but I didn't test this.

In the comments you mention that you are using a Shared Hosting and you depend on the boost module and what you should do ?
Well, I would recommend you to follow the issue Drupal Cache + Mobile Detect Conflict where the still discussing this module caching issue. In addition to follow you should ask for boost support or an alternative. They might try to implement this module with the boost module.
In the mean time, I would recommend to used a free CDN called CloudFlare and let them generated the caching instead of the boost Module. However, you probably would not get the same results as the Boost module.


When is kapton tape useful as a bed adhesive?

Question: I've long since been aware that some people swear by Kapton tape as a bed adhesive, with MatterHackers claiming that Kapton tape is the recommended bed adhesive for ABS.
What makes Kapton tape so useful for printing with ABS? Is it also useful for printing with other materials?
Comment: Personal experience with ABS from Ultimaker in a UM3E: use UHU glue stick, works like a charm. Kapton tape sticks way too much, is a pain to remove from the bed when it's used, and you always risk breaking your print when you try to pry it off the Kapton tape.
Comment: I've had limited success with Kapton tape; I believe this is a holdover from when beds did not typically get hot enough for ABS. If your bed gets to ~80C, Aquanet (or another ultra-hold, non-lubricated hairspray) is better than Kapton tape. For the best results, use the Anycubic Ultrabase heated to 90C.
Comment: So I see... In that case, was Kapton tape the only option, becoming the defacto tool despite its weaknesses? What I'm hearing now is that its disadvantages outweigh its advantages.
Answer: I tested Kapton tape for PLA, ABS, PETG and XT. I know it works for other materials as well. What you need to keep in mind is that many materials only stick to Kapton tape well if you use a heated bed.
The advantage of Kapton tape in comparison to other materials is its heat endurance and mechanical stability. It protects the glass underneath, while you remove the print from the surface. Some filaments stick so well to glass that you may break chunks out of it.
The major disadvantage of Kapton tape is the time to apply the tape to the print surface and its very smooth surface pattern which seems odd in comparison to the rest of the print.


What's the best way to secure wordpress site?

Question: What steps have you taken? Would love to get some useful insight.
Answer: WordPress makes a very nice getting started guide over at the WordPress Codex
I'll highlight a few I use on all of my sites:

File permissions
For Directories
find /path/to/your/wordpress/install/ -type d -exec chmod 755 {} \;
For Files
find /path/to/your/wordpress/install/ -type f -exec chmod 644 {} \;
Move wp-config.php up 1 directory than the default, chmod 400 wp-config.php

<files wp-config.php>
order allow,deny
deny from all
</files>

Securing wp-includes
#Block the include-only files.
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^wp-admin/includes/ - [F,L]
RewriteRule !^wp-includes/ - [S=3]
RewriteRule ^wp-includes/[^/]+\.php$ - [F,L]
RewriteRule ^wp-includes/js/tinymce/langs/.+\.php - [F,L]
RewriteRule ^wp-includes/theme-compat/ - [F,L]
</IfModule>

disable file editing in builtin editor define('DISALLOW_FILE_EDIT', true); add that to your wp-config.php
install plugin like Wordfence to help out with security
turn automatic updates on
check and double check file permissions
if running centos enable selinux and set correct permissions on files and directories
read the Codex for a full list of recommended settings


Can voltage be measured manually?

Question: I am a novice in the subject of electricity so please bear with me if my questions seem naive. What I basically wanted to know is that what is voltage in its essence and whether it can be measured manually (given a simple example, of course) rather than with a voltmeter. Like so far in my study of electricity, I think of voltage as something that is dictated by the electric field and columbs force, whose value depends on the shortest distance (since electric force is conservative) between points A and B (across which we are measuring the voltage). Please correct me if I am wrong!
      Like, lets say there is a bunch of positive charge at one side, and bunch of negative charge at other size. There is, of course, electric fields radiating to and from these charges and there is also force of attraction between these charges. So with these situation, I think that is particualr value of voltage is something that is specifically dependent on distance between these charges and the force you have to exert against the columbs force that already exists?
      So with this in mind, lets say that we have a simple example of couple of electrons and positive charges at a particular distance (whether it is in static electricity or dynamic electricity in a ciruit), can we calculate what the voltage may be between them by hand (by mathematical calculation, not physically) instead of using a voltmeter? I know this is long. But i feel that my understanding is either faulty or incomplete, so I needed second opinions. Thank you.
Comment: If you know Ohm's law and the power formulas, you can calculate anything you want, but it still takes a meter.
Answer: Yes, with some amount of practice, one can tell 120V from 220-240V by using just hand's fingers. However, I would not recommend this method to anyone.
Comment: I meant by mathematical calculation by "hand" or "manually" not literally.
Answer: Yes, it happens to be the case that if you knew exactly where all of the charges were in a system, and how strong those charges are, then you can calculate the voltage on an arbitrary point.
To do this, you simply divide the charge by how far away it is, and add all these numbers up, keeping in mind that you should cancel out charges of opposite signs.
If you are not measuring the charge by how strong its force is (for example as Gaussian units do), you will have to use a conversion factor to get the units of electric potential that are more natural for you (for example the SI unit of volts), however, this is just a fixed number that once you work it out once must be true for every other situation that you come into contact with.
For example, in the cgs system, where we measure charge in "statcoulombs" also called "esu", the force between two charged particles (in dynes, $\text{1 dyne} = 10^{-5}\text{ N}$) is equal to the charges of the two particles (in esu) divided by the number of centimeters between them. If I am sitting near two charges, one of which is $\text{2 esu}$ located $\text{5 cm}$ away, the other is $\text{-3 esu}$ and is located $\text{3 cm}$ away, the electric potential is $\frac25 - \frac33 = -0.6\text{ dyne}\cdot\text{cm}/\text{esu}$ (equivalently, you could say $-0.6 \text{ esu}/\text{cm}$ or call these "statvolts", $-0.6\text{ statV}$.)
This means that if I brought in a test charge of $\text{1 esu}$ from infinity, where the electric potential is 0, I would get $\text{0.6 dyne}\cdot\text{cm}$ of energy. You can look up that in terms of charge, $\text{1 esu}$ is about $3.33564\times10^{-10}\text{ C}$ in SI units and $\text{1 erg}=1\text{ dyne}\cdot\text{cm} = 10^{-7}\text{ J}$ exactly, so the conversion factor turns out to be that one "statvolt" is almost exactly $\text{300 V}$, so this is actually $\text{-180 V}$ in the more-familiar SI units. Note that only potential energy differences really exist, and therefore only voltage differences exist, and this voltage is being implicitly compared with the $\text 0V$ off at an infinite distance away from these charges!
Therefore, we know some example configurations where this calculation doesn't work, usually involving infinite lines or planes of charge with some charge density: you divide the charge into little charges spread out, and you work out that the voltage is always something like "infinity." This is because this way of working out the voltage above assumes that we're taking the voltage to be 0 at infinity, but these configurations require giving or taking infinite amounts of energy to move a particle out to infinity! In such cases we find it much more helpful to have the voltage be infinite out at infinity, and finite for all nonzero finite distances from the infinite wire/sheet. So we have to be a bit more crafty; we have to say "I know that voltage is not absolutely defined but only defined up to a constant, I am going to choose some place in real space to have 0 voltage, and then if I am at a distance $r$ from a charge $q$ that is a distance $L$ from that place, we will say that its actual electric potential upon me is $\frac qr - \frac qL,$ so that no matter what, if I am at this special place my voltage is 0." Then we can work out a voltage function for those cases as well, and it won't be infinite everywhere.
Answer: Yes, you can calculate the voltage by hand. Voltage is something that measures the pressure between two points, where the pressure force is the electric force. It's just like air pressure, in that voltage pressure can cause things to move. But if you don't complete the circuit, just like when you don't let air out of a balloon, the voltage just stays and no current flows.
But enough analogies. I don't know where you are in your education, but voltage comes from multiplying the average electric field by the distance between two points.

For example, I want to know the voltage between a point with an electric field magnitude of 10 N/C (newtons per coulomb), and another point with a field magnitude of 10 N/C as well. The points are 1mm away from each other. Before you can say what voltage is where, you choose reference ground, 0V. The first point, say, is 0V. Then we travel 1mm to the next point. The average electric field over this distance is obviously 10 N/C, and the distance is 1e-03 meters (1x10^-3 = 0.001 = 1mm). So you get the voltage between those points: 0.01V.
Now, that way of thinking will not get you far in practice. Be very careful about when this idea does and does not apply.

In reality, voltage is continuous, and has direction, so instead of multiplying averages, we take a vector integral of the electric field vector. It's the same thing, but we use a dot product instead of a scalar product, and it gives you an equation usually. Vector integrals like this are simple if you know vectors and calculus beforehand, but if you aren't familiar with those topics, you'll have a lot of ground to cover and it wouldn't be worth getting too far into, without properly educating yourself on the mathematics of both beforehand.
For more on the proper definition of voltage, look to the Wikipedia page on it. The integral definition comes up fairly quickly.

Before I go, I'd like to clear up one more thing. The electric field exists at all points in the entire universe - it is a concept, not a physical entity. (At least, not classically, and the new quantum electrodynamics might beg to differ, but that comes later. ) When we talk about the electric field of this and that, we mean their contribution to the electric field. But the electric field itself exists at all points, because it is a sum-total thing for all points.
As well, the electric field is not separate from the electric force. The electric field is the electric force. The E field is one way of representing a force in space, at a distance from whatever is causing it. For example, the electric field at some point will show what direction and how strong the force an electron would feel at that point. When people talk about the electric field moving through space, they really mean the electric force is moving through space. The field just changes as that force moves through it.
Ask yourself, then: What is the electric force?
And for that matter: What is the magnetic force?
The electric force exists wherever a charged object feels a force. So, in electrostatics we have charge A and charge B. Coulomb's law is the only way to determine the electric force, and from that electric force we can say that the electric field around the charges has changed. Once charges move, though, something new happens.
The magnetic force is the force that a charged particle feels, when it moves. Forget permanent magnets, we're talking pure magnetic force. Since all motion is relative, and charged bodies most fundamentally are particles like electrons, we say that the magnetic force is the result of charged things moving past each other. Which, you might notice, is not too different from the electric force, which is the force between charged particles if they were stationary.
Eventually, you see, thanks to topics like relativity, that the electric force and the magnetic force are the same phenomenon, with different points of view. You also find that an electric force causes two charged particles to move towards or away from each other, and then that movement causes a magnetic force, and every time they change position the electric force between them changes, and so on in a chain reaction. This is called near-field electromagnetic forces. See technologies like NFC (near-field communication). Eventually, in a totally amazing move, the electromagnetic forces can unbound themselves from their source, travelling not through molecules and charges, but rather moving as a force of its own. That's electromagnetic radiation, and it exists in the far-field.
These are the major points that, for whatever reason, nobody talks about in electromagnetics. From now on, if you see the phrase "electric field", conceptually think "electric force." Know that it is not the same as the electric force mathematically, because a field and a force are not the same. But they are so closely linked, that conceptually they are exactly the same. Even if the electric field is 0 at most places, it exists at all points.
Good luck with E&M!
Sam Gallagher
Comment: While it might make sense to use the word 'pressure' in the context of a flowing fluid analogy, it is a mistake to use it other than in that context. Voltage (electric potential) is neither force not pressure. It is energy per unit charge as measured against an agreed reference.
Comment: More specifically, voltage measures change in _potential_ energy per unit charge. And in fact, one synonym for voltage is electric pressure, and not against reason. The reason air flows out of a compressed tank is the same reason current flows in a circuit. The failures of the analogy are not lost on me, but pedagogically it is a much more sound method of describing voltage than using maths, which leave much to be desired. Frankly, I assume this knowledge is used in tandem with typical high school E&M education.

Can voltage be measured manually?


Disconnected wireless router security

Question: I've changed ISP and am using their router.  I wish to donate my old NETGEAR router still with its original Network Key (password).  Would someone obtaining this router somehow get access to my computer files and data even though I am no longer using that network or ISP? Thanks.
Comment: why not just factory reset the router before getting rid of it?
Comment: No they will not.
Answer: No.
If your computer is not connected to the router, other people having access to it won't be able to access your computer through it.
You could pose a convoluted (and highly unlikely!) scenario where a three-letter-agency recorded all your wireless traffic, then buy your router to attempt decrypt the messages that were sent in plaintext (ie. using only the Wi-Fi encryption) through that router in the past once they learnt the password you were using. This would require that they had recorded the initial 4-way handshake for that session, which requires being highly targeted. This would not allow decryption of anything you hadn't sent that session, or that were separatedly protected (eg. inside a HTTPS connection).
Comment: If all traffic was captured including the 4-way handshake, session keys are defeated.
Comment: @multithr3at3d I should have checked the details of WPA-PSK before posting. Answer updated.
Answer: No, the only thing that they might get access to would be any saved configurations on the devices,
But aside from that your new router and all devices behind it are not connected in any way.

Disconnected wireless router security


Possible move ConnectedDevicesPlatform to another drive?

Question: The ConnectedDevicesPlatform @C:\Users\username\AppData\Local\ConnectedDevicesPlatform is continuously writing data to my SSD to D drive, is it possible to disable this service or move to another drive?
Answer: According to your description " ConnectedDevicesPlatform is continuously writing data ", we can check if the data is associated with Bluetooth, or Printers & Scanners as well as music players, storage devices, mobile phones, cameras, and many other types of connected devices.
According to the following two articles, this service is used for Connected Devices Platform scenarios and corresponding files are all c:\windows\system32\cdp*.dll:
cdp.dll
cdprt.dll
cdpsvc.dll
cdpusersvc.exe
I think we can not disable this service and can not move the ConnectedDevicesPlatform folder to another drive.
For details we can refer to the following articles
What is the CDPUserSvc service?
Connected Devices Platform Service - What does it do?


deep learning : how to retrain an already trained model on different data?

Question: I have a model (a convolutional neural network) that has already been trained on set of training data for human pose estimation. It works very well for simple cases, but I want to make it more robust to human truncation and occlusion. For this I prepared a different set of data that covers such "difficult" situations. I intend on taking the current weights and biases as initial values for the model and train it using gradient descent and back-propagation on this new set of data. As I lack experience in deep learning, before I go on and apply this, is this "correct" from a scientific point of view? should I change something before (such as the loss function...)?
Answer: If you learn separably on two different data sets you can expect second data set training will blur results from first training. You can avoid this by stop second training early however estimate in what point is very difficult task and still you won't have guarantee that second training do not obliterated first training results. So finally you can expect that after two training your model will have higher quality response to data similar to second data set, and lower quality to first data set (comparing to model learnt only on first data set).
I strongly recommend you to merge two data sets if its possible (you can use already learnt network to learn on merged set), or prepare additional flow in higher layers of your network.


How does WinSxS resolve DLL names to DLL locations?

Question: If I link a module against mydll.dll, which is deployed using WinSxS, the PE header in my module will simply reference "mydll.dll". How does Windows determine at runtime, firstly that this dependency should be loaded via WinSxS, and secondly what assembly it's in?
Comment: Why? It has a lot of relevance to programming (as the recent /. story, where 90% of the readers don't understand what SxS is or how it works, has shown).
Comment: Hi mmyers - as the article states, it may be useful for sysadmins but it is primarily aimed at programmers. WinSxS is one of those mechanisms that everybody needs to understand, but nobody does :-)
Comment: At a best guess, it has one version of the DLL set as default unless a Manifest file tells it otherwise.
Comment: I think this belongs on Super User, not SO.
Comment: I withdraw the comment (but won't delete it, since that would just confuse later readers).
Answer: It does so via the "activation context". In my opinion, WinSxS does not make any sense until you learn about the activation context and how it is managed.
I've put a rather long blog post explaining the details at http://omnicognate.wordpress.com/2009/10/05/winsxs/.
To summarise the article, the activation context is a structure that WinSxS uses at runtime to resolve unversioned object names (eg. DLL names) to the full information about how to locate them. The purpose of "manifests" in WinSxS is to construct activation contexts. Without understanding how and when these activation contexts are constructed and how they are managed (they are held on a thread-local stack), it is not possible to reason through the steps involved in loading a DLL via WinSxS and it is therefore impossible to diagnose the majority of problems that can arise.
Comment: This article was posted in Q/A format due to suggestions on meta: http://meta.stackexchange.com/questions/24608/what-is-the-etiquette-for-posting-an-article.
Comment: Note: I suggest putting at least a little bit of the article into the answer, to establish its relevance.


jde Gregorian date comparison

Question: Gregorian date comparison in crystal report. For example, if {@WO due date}< 7/18/2013 then XXX else XXX
When I check if there is an error, the system shows me that the "7/18/2013" is not a date, but I don't know what is the right format for the gregorian date for comparison. Would someone help me on this?
Thanks!
Answer: if {@WO due date}< datea(7/18/2013)

jde Gregorian date comparison


What is the difference between ground speed and airspeed?

Question: What is difference between ground speed and airspeed? Is ground speed used only for takeoff or is it used for flight too?
Comment: Not a duplicate... the referenced question is asking about a video game, and got an answer with more formulas than a college level Aero course.  This question is asking for a straightforward answer to the concepts of airspeed and groundspeed, and aviation.se doesn't have that -- at least not in the referenced "duplicate" question. Voting to reopen.
Comment: You are headed east at an indicated 100mph, the air mass you are in is headed west at 10mph, your indicated air speed will be 100mph, the ground speed will be 90mph since you have a 10mph head wind. If the air mass were heading east (tail wind) at 10mph, your indicated airspeed would still be 100mph, but your ground speed would increase to 110mph. Make sense?
Comment: GPS speed is the same as Ground speed.  The "Flight Simulator" video game question and answers are also applicable to real life so the question has been answered correctly. I vote to remain closed.
Comment: Snarky answer: it's literally the magnitude of the component of the wind speed in the direction of travel.
Answer: The ground speed is the speed the aircraft is making over ground below.
The indicated airspeed (IAS) is the speed shown on the airspeed indicator. This will be different than the ground speed for various reasons, such as wind and the attitude of the aircraft. For example, if the aircraft is diving then the IAS will be greater than the ground speed. In fact, if the aircraft were diving straight down, then the ground speed could be 0 while the IAS was hundreds of knots per hour.
The indicated airspeed is the usual measure used in flight.
The ground speed can be calculated to estimate the time of arrival of the aircraft at some destination.
Comment: The question as posed I did not regard as requiring a detailed technical answer and such an answer I think would be more confusing than helpful for him. Getting into calibrated air speed, true airspeed, equivalent airspeed and so on is just overkill here and there are already other answers that cover such things. As for the example, I think it is useful to give a very simple and easy to understand example why IAS can differ from ground speed.
Comment: If you want to keep it really simple you could say that ground speed is the speed of the aircraft in relation to the ground, and that airspeed is the speed of the aircraft in relation to the air around it.   The mass of air that the aircraft flies through is usually a moving body in relation to the earth(wind), and that accounts for the difference between ground speed and airspeed .
Comment: In my opinion this answer is poorly written. The answer should include information how Indicated airspeed relates to True airspeed and how True airspeed relates to Ground speed. The implication that difference between ground speed and indicated airspeed can be partially due to the aircraft diving is misleading and totally unnecessary.


"Status" meaning in this sentence

Question: Permanent resident card is the official proof of your status in Canada.
Does the word refer to condition and circumstances?
Answer: status sense 1.
Used here its a legal term referring to the reason you can reside in Canada. Everyone has such an official status in their home country or if they go to a foreign country.
Answer: Status, in this case, refers to your immigration status, or the legal definition of your right to live in Canada.
In the entry for status in the Oxford Dictionaries Online, it is meaning 1.2, "The official classification given to a person, country, or organization, determining their rights or responsibilities."
In your example, your permanent resident card is your official proof that you are a legal permanent resident of Canada, and have all the rights and responsibilities that permanent residents are guaranteed under Canadian law.
Since your question suggests that you are reading up on permanent residency in Canada, here are some potentially helpful links:
Government of Canada page on permanent residency
Wikipedia page on Canadian permanent residency
Answer: I suppose you could say it's circumstances. Someone's legal status in a country is referring to if they are there legally, illegally, a permanent citizen, there on work visa, have a student visa, etc.

"Status" meaning in this sentence


What is hypervisor? examples for type1 and type2

Question: What is hypervisor, and what are the differences between type1 and type2?
Examples for type1 and type2 ? Most questions out there are about the difference between type1 and type2, and the definitions are a bit loosely.
Answer: Debates between type 1 and type 2 happen because hypervisors don't neatly fit in those categories.
ESXi is a small dedicated kernel that removed general operating system components. It has its own drivers and so has a hardware comparability list. You can't run any program on it, the console is for troubleshooting and not the preferred way of accessing it.
Hyper-V has a root partition that runs Windows and has direct access to devices.   Root creates child partitions, so it is not strictly accurate to say the hypervisor creates Hyper-V guests. And you can run any Windows role on that root partition. It get put in the type-1 category because you are basically booting a "bare metal VM". A general purpose OS running guests sounds a little like type-2, however.
I don't find an academic definition of type 1 and 2 nearly as interesting as block diagrams and other descriptions of actual hypervisor components.


What is the meaning of these motor characteristic keywords?

Question: could anybody please explain the following terms?

Speed, rated load (RPM)
Rated load (N)
Rated voltage (V)
Max Static Force (N)
Max Current (A)
Max Load (N)
Answer:
Speed, rated load: This figure is the speed the motor is rated to run at when loaded with its rated load. (see below)
Rated load: This is the load the motor is rated to operate under. Essentially, this is the torque at which the motor is designed to operate. It should work fine with lower loads (how low depends on the motor), but exceeding this is not recommended. (are you sure that this metric is in newtons? It should be newton-meters.)
Rated voltage: This is the terminal voltage the motor is designed to run at. Basically, this is the voltage you should apply to the motor if you want to use it at full speed under its rated load.
Max static force: This is the torque the motor can provide when stalled, i.e., when not spinning. This is also known as stall torque or start-up torque.
Max current: Exceeding this current through the motor's windings will cause damage to the motor. Do not attempt to run the motor under this condition, though brief overloads are sometimes okay.
Max load: The maximum torque the motor can provide. Do not exceed this, or, again, you will cause damage to the motor.