Which fingering system is easier on the Roland AE-01, trumpet or recorder?

Question:
The Roland AE-01 (digital wind instrument) has fingering for recorder and trumpet. There is no need to develop blowing technique.

I played the trumpet years ago so I can recall some of it.

In terms of learning at a very basic level, is there more available for either trumpet or recorder?

Will learning fingering for recorder limit my selection of music? For example, to music played by Chris Botti or The Moody Blues. I'm not interested in playing what most might expect from recorder.

As we get older unfortunately it gets more difficult to learn or remember things — that's the basis for the question.
Comment: @ToddWilcox The problem with this instrument is the fingerings are not really recorder or trumpet fingerings. The 'trumpet' fingerings require eight fingers, and the 'recorder' fingerings don't use cross-fingerings or half-holes. The 'recorder' is much closer to  a saxophone.
Comment: To me this is subjective. In some ways trumpet fingering is much easier because you only need to understand seven positions on the trumpet. Both instruments require using "overblowing" to access the full range. Another advantage of the trumpet is valves have only two positions, while recorder hole may be half covered. Some fingering patterns on recorder are unintuitive. Trumpet valves do the same things in all registers. On the other hand, some may find recording fingering makes more sense to them, as PiedPiper's answer suggests. It's a matter of taste.
Comment: It took me a while to understand you're not asking whether an actual trumpet or recorder is easier to play. You're asking about the specific options on the Roland AE-01. I've edited your title to clarify. I still think the question is subjective. If one fingering were universally better than the other in some way, they wouldn't offer multiple fingering options. The options exist because people's brains work differently.
Answer: Most people, possibly even trumpet players, would find the simplified 'recorder' fingerings more logical. Put down all your fingers, take them off one by one and you're already playing a C-major scale. For sharps and flats just add one of the two LH 4th finger keys.
The 'trumpet' fingerings are less logical: the right hand plays the standard trumpet fingerings, but you have to simulate changing harmonics with different combinations of left-hand keys.
Whichever fingering system you choose you'll be able to play any kind of music. You're not restricted to music written for trumpet or recorder.


If I'm angry, which word should I stress in "You just walked in without knocking!"?

Question: In the sentence "You just walked in without knocking!", if I want to emphasize that I'm ANGRY about someone NOT KNOCKING the door, Which word, "just", "without" or "knocking", should I stress
Comment: Unfortunately, this question is a matter of opinion and therefore out of the scope of ELL
Answer: I'd say all 3.
<code>    ^             v   ^       ^
</code>
You just walked in without knocking?
... or even just on just and knocking is good.
(I don't know how to do the intonation arrows. Someone please help me with that.)
In colloquial English, adding a "just" between the subject and the verb often expresses surprise, anger or some similar emotions. Stress is also placed on the "just", sometimes with a pause right after (sometimes also before) the "just".
Additionally, stressing the "without" expresses that you want the listener to do the opposite, that is *to walk in with a knock"
Comment: I don't think "just" should be stressed. To me that puts the emphasis on the recency of the transgression. I'd stress "walked in" the most, and "knocking" slightly less.
Comment: I respectfully disagree. To my ear (native midwestern Am.E speaker), stressing "just" in any combination with other elements gives the sentence an unwanted emphasis that doesn't fit with the OP's requested meaning of expressing anger.
Comment: You can also not stress "*just*", but the word "just" itself puts emphasis and stress on "walked in without knocking" and expresses your feelings towards that action, so it's also often stressed.
Comment: "You **just** had to do that." To my ear, the "just" in this example makes it sound angrier, especially with emphasis on the "just".


Which character has the distinction of being personally identified as the "Mummy" in the most motion pictures?

Question: There are tons of nameless mummies in countless mummy movies, but some mummies are supposed to represent specific individuals. For instance, Imhotep was the main mummy in most of the Brendan Fraser mummy movies. Which character, historic or imagined, has the distinction of being personally identified as a "Mummy" in the most motion pictures?
Comment: Does this mean we have to watch _all_ "mummy" movies to be able to answer this question?
Comment: @Izkata ;) I don't know what kind of voodoo some of you folks conjur up to answer some of these questions. I suspect there's a database outhere somewhere.
Answer: It may be down to:
Imhotep, a real Egyptian chancellor/high priest, popularized as a mummy in Boris Karloff's The Mummy [1932] and the more recent The Mummy [1999] and The Mummy Returns [2001]- both with Brendan Fraser, or:
Kharis, a fictional character, who was featured by Lon Chaney in The Mummy's Tomb [1942], The Mummy's Ghost [1944], and The Mummy's Curse [also 1944]; he was also played by Christopher Lee in The Mummy [1959].
Comment: Boris Karloff wasn't done with CGI.
Comment: +1! I always thought Kharis was much more frightening than Imhotep. It's the difference between CGI trickery and someone you **really** wouldn't want to meet on a dark night!


How do I fade in/out an object in Blender 2.8 Eevee?

Question: I'm kinda new to using Blender Eevee. I used to use Cycles, but that took too long to render. I'm doing a text animation with a video in the background, and I want the text to fade in and fade out. However, I cannot do this because Eevee is different from Cycles. Is there any way I can animate the transparency of an object so I can fade it in and out?
Answer:
Of course it is. The only "catch" is to change Blend Mode under Material > Settings tab to Alpha Blend and turn off Show Backface.
Then regularly you can animate Factor between your shader and Transparent shader (full white colour).
Answer: Looked for a solution to this question
Q: Image bleed when using Import Image as Plane [duplicate]
which is linked here.
My proposal:

I put a math node between image and Mix Shader, set it to multiply. Wit the second value set to 0 the image is not visible. Obviously when I set the second value to one it is fully visible.


Why is there a "show password" functionality in some login forms?

Question: I've noticed that on a lot of login forms in websites and applications that there is a "show password" check box. Why? I myself have seen some hacks that an attacker could hack the input password box. Doesn't enabling the "show password" box constitute as a security risk?
Comment: `I myself have seen some hacks that an attacker could hack the input password box.` Could you expand on this?
Comment: @AbeMiessler, Someone showed me once, how he 'hacked' the password box. But later on he explained that it was just with Firebug(forgot how he `hacked` it). he changed the `type="password"` to `type="text"`. Nothing special
Comment: @AbeMiessler, here is a howto. He's using Chrome, but still the same: http://totallynoob.com/reveal-password-from-input-boxes-with-chrome-tools/
Answer: The 'show password' option is a feature designed for better user experience. This started getting popular with the recent rise in numbers of mobile devices. The small on screen keyboards are notoriously difficult to type with, and when you are unable to see your input it can make it difficult to be sure the password was typed correctly.
I am not sure of any attacks that target readable password fields. In my opinion, if you have malware on your computer that can see your screen, then its quite probable they are capturing your keystrokes as well.
Is it a risk? Yes. This should never be the default behavior, but if a user feels they are comfortable displaying their password (secure in their physical envirioment), then I see no problem with this practice.
This is just my opinion, not a rule.
Comment: Follow up question: Why not post that answer in the dupe-source question? It's clearly referenced in Terry's comment. The question will get bumped up and your answer will get your sweet upvotes.
Comment: I should have checked that before replying, thanks. It looks like Terry's answer is more than complete anyways. Thanks for those sweet upvotes though.


Call settings will pop-up when I open a pdf

Question: So dear clever IT friends here is the thing. I am helping a nice old grandma. She has a Huawei tablet, android in it. The silly device asked when she opened a pdf file "which program would you like to use to open it". She is a nice 80 years old granny and thought she has to go with settings. So she went for it. Now when you try open any pdf file the "call settings will" pop-up instead the pdf file itself.
Any idea how I can find the path to add adobe to pdf files?
Answer: Easier solution:
Hi, the easiest solution is to uninstall and re-install the PDF viewer app from that tablet. Android starts prompting how to open that file as soon as it notices that there are new apps which can handle that file type.
Since you mentioned Adobe Reader, please uninstall it and then install it again from the Play Store. The prompt to select which app to open the PDF with will return. There you can set Adobe as the default to avoid problems in the future.
Appropriate solution:
I am keeping this as a second choice because the Android version is unknown and different OEMs can have a slightly different settings page and slightly different names for each setting item. Still, here we go:

Open Settings app.
Open Apps and Notifications (Or Apps, or something similar which conveys the same meaning).
Tap on All Apps (Can also be See all apps or not exist at all, just choose the option which takes you to the full list of apps)
Scroll down and locate the Settings app. Tap on it.
Scroll and select Advanced > Open by Default.
Finally tap on the Clear all defaults button.

This will remove the default handler for PDF files and Android should once again start offering the choice.


Why does air move from higher to lower pressure?

Question: Somebody answered this question elsewhere and said it's because there is a higher force acting at the high pressure region compared to the low pressure region so a net force pushes it towards the lower pressure region. My problem with this is that pressure is a scalar quantity, not a vector, from what I understand. So how do we know which direction the air moves in the high pressure region? If anybody could also link a diagram showing this that would be helpful as I'm having difficult visualising this. Thanks.
Comment: The air will tend to move in the direction of the steepest pressure gradient.
Comment: ... with a deviation due to the Coriolis force.
Answer: A good way to look a this is thinking of the gas as composed of many small particles.
In this context, air pressure is proportional to the amount of molecular collisions per unit area per unit time of the medium on its walls.
So, if you have a wall separating a higher pressure air from low pressure air, more particles will be colliding on the high P side than on the low P side of the wall. (see picture).

If the wall is removed, the particles won't collide with the wall and will just fly through it. Since the number of collisions per unit time is higher on higher P side than on the low P side, it is natural that there will be a net flow of particles towards the low P side, until the pressure equilibrates on the entire volume.
Answer: The Navier-Stokes equations of fluid flow can be written as $$\rho\left [ \frac{\partial v}{dt}+(v\cdot \nabla) v \right ] = -\nabla P + \rho g + \mu \nabla^2 v.$$
The left side is basically the "$ma$" in Newton's equation $F=ma$, and the right side is the total force. The first term is the pressure term that interests us, the other two gravity and viscosity.
$\nabla P$ is the gradient of the pressure, turning the scalar pressure field into a vector field. It can be viewed as pointing in the direction of the greatest rate of increase of the function. This is a hint of what is going on: what matters is not pressure, but pressure differences. Regions with constant pressure do not cause wind, but if there is an imbalance of pressure then air will move to reduce it, and hence flow along the (negative) gradient until the pressure difference is removed.
Answer: Thermodynamics to the rescue.
Forget the sun, the earth's motions, the effects of altitude, etc. Think of two reservoirs of a monomolecular gas, equal in volume (keeping it simple!) but A is of higher pressure than B.
Connect the two with a valved tube, and open the valve. The pressure equalizes simply because there are initially more molecules in A to make their way into B than vice versa. Statistical mechanics in its crudest form. More precisely, B, which permits longer mean-path lengths, has become available to the higher pressure gas in A, and the pressure equalizes through a macroscopic transfer of gas, based on the statistical understanding of the motions of trillions of trillions of identical particles. This happens more or less rapidly depending on the cross-section of the throat of the valve.
Notice that I have nowhere described the process of diffusion.
One might say of this that initially there was lower entropy, thus work could be extracted, and was-- the work of equalizing pressure. Or one could invoke the equipartition theorem, which states that Entropy will have her way: energy gets parcelled out equally to all degrees of freedom. The Navier-Stokes equation, abstruse and elegant as it is, is the exfoliation of some entirely commonsense notions. The gas laws follow rather more directly.
Thermodynamics, or statistical mechanics, is often- or perhaps always-- the basis of a branch of physics. The Dutch physicist Verlinde derived Newtonian mechanics from thermodynamics! And I am sure that more work like his will be done.
And I notice that an even simpler answer has been entered while I was dithering with grammar! My complements.
Comment: Pieter, think of a tank of gas being vented in outer space. The gas released finds itself in a region where the mean-path-length (between collisions- that's the term I wanted) is arbitrarily large. It goes, and doesn't come back. We think macroscopically that the vacuum is pulling it out of its tank, or the pressure is pushing it out, but the real story is microscopic, atom-scaled--  statistical mechanics.
Comment: But initially, while there is a pressure difference, there is no random walk. You describe diffusion, with for example one gas on one side and a different gas on the other side. It takes a very long time to mix.
Answer:
My problem with this is that pressure is a scalar quantity, not a
  vector, from what I understand. So how do we know which direction the
  air moves in the high pressure region?

$\let\rho=\varrho$
I think you are asking for a more fundamental answer, at a classical
macroscopic level. This I'll try now.
You're perfectly right, pressure is a scalar. Even though, from a more
sophisticated viewpoint, it could be called an "isotropic tensor". Quite
intimidating, but conveying a more basic meaning of the concept.
What is meant is simple. Let's view on an example. Suppose you have a
tank filled of water. Take a solid cube, tie it to a wire and drop it
into the water, leaving it suspended at half height. Assume two faces
of the cube stay horizontal, the other four vertical.
Because of pressure water pushes on all six faces. It's a property of
fluids (liquids and gases) discovered by Pascal that the force on any
face is always perpendicular to that face and its intensity is $F =
P A$ ($P$ pressure, $A$ face's area). This remains true if also you
rotate your cube in any direction.
I've just stated the famous Pascal's principle. You may well take it
as an experimental truth.
Note that I've written $P$ for pressure, tacitly assuming its value is
the same everywhere. If it's so, net force of water on cube is
obviously zero, since forces on opposite faces cancel each other. But
I expect you to protest: "Hey, I heard of buoyancy, of Archimedes'
principle. Where did it get lost?"
You're absolutely right, and I pretended of forgetting all that to the
benefit of my presentation. Of course it isn't true that pressure is
the same everywhere. It isn't if water is resting in a gravitational
field, as we are accustomed to see. Maybe you know of another
fundamental law of hydrostatics: Stevin's Law:
$$P = P_0 + \rho g h$$
where $P$ is pressure in a point at depth $h$ under water's free
surface, $P_0$ is the atmospheric pressure just above water, $\rho$
water's density, $g$ the intensity of gravitational field (assumed
uniform).
Then it's no longer true that forces on opposite faces cancel. It
remains true for vertical faces, but not for the two horizontal faces.
If $P$ is pressure on upper face, the one $P'$ on lower face is
higher:
$$P' = P + \rho g a$$
if $a$ is the side of cube. Resultant of both forces is upward
directed and amounts to
$$F_{\mathrm{net}} = \rho g a^3 = \rho g V = M g$$
where $M$ is the mass of a volume $V$ of water (the cube's volume).
We have retrieved, for this special case, Archimedes' principle.

Now we are able to tackle you main question. It deals not with a static
uniform situation such as the one considered so far, but with a
nonuniform atmosphere, where pressure differences cause air to move.
To ask why there are pressure differences is another story I'm not
going to face.
So let's substitute atmosphere for our water tank and in place of a
solid cube consider a small air volume, only ideally separated from
the rest by a closed surface in form of a cube. If for some reason it
happens that pressure on opposite sides (e.g. a couple of vertical
sides) is not the same then on that air cube a net horizontal
force will act, from the higher side towards the lower one.
We're only left to apply 2nd Newton's Law to conclude that the air
cube will be accelerated from high pressure towards low pressure. You
were already warned in other answers that things in the atmosphere may
not be so simply treated - there will be other forces, first of all
friction, then the "mysterious" Coriolis' force. Actually it's very
rare that air moves straightly from high to low pressure: more
frequently it goes on spiraling around high or low pressure regions
(viz anticyclonic or cyclonic regions) with a diverging (for
anticyclon) or a converging (for cyclon) component.
Answer: Here is an easy way to think of this.
The atmosphere is an ocean consisting of air and its depth and density determine the pressure we measure all the way down at the bottom of that ocean, where we live.
Since cold air is denser than warm air, a region of the atmosphere consisting of cold air will be slightly heavier than the (warmer) air surrounding it and hence will tend to sink towards the bottom of the ocean and spread out underneath the warmer air around it.
In addition to this, the air ocean has currents in it like the water ocean does, and those currents sometimes collide and pile the air ocean up to a slightly greater depth in that region. the pressure we experience down at the bottom underneath one of those pileups will be greater than normal, and the pileup strives to sink down under its weight and spread out against the bottom.


HTML entities to Hex equivalent

Question: I have legacy xml files with html entities such as — etc. How can I convert this entities to hex equivalent such as —. Is there any easy way to do this using a batch command or something else? I am not high level programmer so any detail help will be appreciated.
Answer: Just a simple find and replace may be all you need. Most, if not all text/code editors have a find/replace function.
Chances are that there are only a few characters strings that make up the majority of what you need to replace and fortunately, they're all pretty unique so it's unlikely that you'll have any accidental replacements.

HTML entities to Hex equivalent


Tools to convert from 16-bit RGB to 24-bit RGB and vice versa

Question: Are there any image editing or research tools, hopefully OSS, which will allow me to:

map colors (images) from 16-bit RGB (565) to 24-bit RGB (888) space or vice versa
save files in PNG, GIF, or JPEG
give user the ability to control how colors are mapped from 16-bit space to 24-bit space.

I found one issue that discusses something similar but I'm hoping I'll be able to run these tests without writing any code.
 convert 24bit RGB to ARGB16
Here's a little background for this request.
I'm working on a project evaluating an LCD display panel.  The native bit depth of the panel is 24-bits (RGB 888) and it is currently available on an evaluation kit that uses an LCD controller that supports 24-bit output only.
The LCD controller on the product for which this panel is being evaluated only supports 16-bit output (RGB 565).  In the final design the remaining bits for each color channel on the panel will be connected in some way.
The evaluation kit does not take RGB inputs (as mentioned above it only takes PNG, JPEG, or GIF). I'm looking for a way to create 16-bit and 24-bit RGB files which will then be converted to a PNG.   By manipulating the values of the R, G and B channels in the source files (16-bit and 24-bit) I want to compare the difference between driving a 24-bit display with 24-bits of color and 16-bits of color (extended to 24-bits).
I'd also be interested in learning about others experiences with this sort of evaluation and the sanity of my proposed test methodology.
Thanks.
Answer: I had posted this question on the graphic design stack exchange and received a few comments and answers that were helpful.
https://graphicdesign.stackexchange.com/q/12648/8539


Looking for old anime cartoon about magic fire cards

Question: I believe it aired on Nicktoons or Cartoon Network back in 2012. I did my digging and the two strongest candidates are Dinosaur King and Duel Masters. The scene I remember clearest is the main character getting into a fight with what looked like the antagonist group, and he created a fire card out of nothing. Even the antagonist says "oh, a fire card" or something. They use a device that looks like the one in Dinosaur King. Any thoughts?
Answer: Is that Tai Chi Chasers? It has the main character using a fire card.

Tai Chi Chasers is set in a fantasy world that is influenced by East Asian mythology. Within this fantasy world, two ethnic groups, the protagonist Tigeroids (Korean: 호족) and the antagonist Dragonoids (Korean: 용족) are engaged in a long-running armed conflict over Tai Chi cards, a set of 500 magical artefacts that both groups seek for their own purposes.
The plot revolves around the main character Rai, a child who discovers that he is descended from the Tigeroids after his community is attacked. He therefore possesses various magical abilities that all Tigeroids possess. Rai becomes a combatant in the Tigeroid armed forces, and enhances his magical abilities. He also becomes a member of an elite group of combatants, known as the Tai Chi Chasers.
Tai Chi Chasers utilizes Korean hanja to represent the various magical abilities and artefacts present throughout the series. In the English language version, distributed by 4Kids Entertainment, the hanja characters are referred to both by their Korean pronunciations and their English language translations.

The enemy does not say "Oh, a fire card", but he does note that it is a "Tai Chi card" and that it is impressive that Rai can produce and use it would an "Activator".
It was broadcast on the South Korea Cartoon Network channel, although it looks like it was distributed by the CW in the United States.
Comment: Hi, welcome to SF&F.  Can you give us any information about this?  What matches the question and what doesn't?  Was it on one of the networks mentioned in the question?
Comment: The card has "火" which is the letter in Chinese/Japanese that means "fire".
Comment: @Laurel: Well, apparently the Korean hanja character, but most of those characters kept their Japanese/Chinese ideogram.


clarification for the solution of $(z^3=|z|^2 +4)$!?

Question: $(z-2)(z^2+z+2)=0$
so the solutions are
$$z=2;$$$$z^2+z+2=0;$$
$$z=-(1+-\sqrt{-7})/2$$
I removed the absolute value for imposing a solution in the field of real, but only because I saw it on wolfram alpha, now I ask you! I can always impose a solution in the real numbers to remove the absolute value? and if yes I have to discard all imaginary values?
Comment: You can't. Surely $2$ is a solution. But this does not imply you can "divide by $z-2$": it's not a polynomial function.
Answer: Let us proceed in the conventional way:
Let $z=r(\cos\theta+i \sin\theta)$ where $r$ is real
$\implies |z|=r$ and $z^3=\{r(\cos\theta+i \sin\theta)\}^3=r^3\cos3\theta+ir^3\sin3\theta$ (using de Moivre's formula)
$\implies r^3\cos3\theta+ir^3\sin3\theta=r^2+4$
Clearly $r\ne0$
Equating the imaginary terms $r^3\sin3\theta=0\implies \sin3\theta=0\implies 3\theta=n\pi$ where $n$ is any integer
$\theta=\frac{n\pi}3$ where $n=0,1,2$ (A more general set of values of $n$ has been discussed here)
If $n=0,2,\cos3\theta=1$ and $r^3-r^2-4=0\implies r=2$ (as you have found)
$\implies z=2(\cos0+i \sin0)=2$ and $z=2(\cos\frac{2\pi}3+i\sin\frac{2\pi}3)=-1+\sqrt3i$
If $n=1,\cos3\theta=-1\implies  z=-2(\cos\frac\pi3+i \sin\frac\pi3)=-1-\sqrt3i$
Answer: To solve $z^3=|z|^2+4$, one may first look for $r=|z|$. Obviously, $r^3=r^2+4$ hence $(r-2)(r^2+r+2)=0$ Since $r^2+r+2\ne0$ for every real number $r$, one knows that $r=2$. Now, if $z=2\mathrm e^{\mathrm i t}$, the equation to solve becomes $8\mathrm e^{3\mathrm i t}=2^2+4=8$, that is, $\mathrm e^{3\mathrm i t}=1$.
Finally, the equation $z^3=|z|^2+4$ has exactly three solutions $z$, corresponding to the third roots of unity, namely,
$$
-1+\mathrm i\sqrt3,\qquad-1-\mathrm i\sqrt3,\qquad2.
$$
Answer: As can be seen easily that $z^3$ is real. Now as it is real hence, $z^3=\bar{z^3}$ $\implies$ $z=\bar{z}$.
The equation is $$ z^3=|z|^2+4$$ $\implies$ $$ z^3=z\bar{z}+4 $$ $\implies$ $$z^3=z^2+4$$ $\implies$ $$(z-2)(z^2+z+2) $$ And then as you proceeded.


QFX10002-36Q Full BGP Question

Question: I want to use a QFX10002-36Q with 4x Full table and 2x IXP and total received routes from all of them will be around 3.6-4 Milion routes, QFX10002-36Q datasheet said that this switch can hold 10M RIB IPv4 routes and 4Milion IPv6 routes and a totally 2M IPv4/IPv6 routes in FIB. referring to the juniper documents it can hold my full tables in RIB then it will install best path on the FIB (best paths from all neighbours are around 900K) and I do not have IPv6.
so there will be no problem if I want to use this switch in this scenario, do I understand this correctly?
Comment: Did any answer help you? if so, you should accept the answer so that the question does not keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
Answer: According to the juniper system overview the switch has 16Gb of RAM.
As of today the Internet IPv4 full table is around 850 000 routes.
So, yes the switch can handle 4 times the full table without issues.
Note that even if you don't plan to use IPv6 today, it's better to take it into account to be able to add it later (and the sooner the better).
Comment: although you really should plan to use IPv6 today... not necessarily use it, but certainly plan for it

QFX10002-36Q Full BGP Question


Source for the prohibition against Nivul Peh (foul mouth)

Question: What is the source for the prohibition against Nivul Peh (using foul language)?  Is it Biblical?  Rabbinic?  "Asmachta" (based on a principle derived from the Torah but ultimately not considered a Biblical mandate, ie., not a Mitzvah)?  And based on the answer to the above, how severe is the prohibition (when can it be overridden, what, if anything, is the penalty, etc.)?
Comment: related/answer http://judaism.stackexchange.com/a/14260/759
Comment: @DoubleAA, dunno. I was just pointing it out in case anyone saw it differently or questioned why I was tagging both [tag:lomdus] and [tag:halachah-theory]
Comment: Note that this is the first time I've used Lomdus (that I remember), and that I'm trying to use it in accordance with [DoubleAA's scheme](http://meta.judaism.stackexchange.com/a/678/5).
Comment: Is my 'scheme' policy?
Comment: 2 add. sources: gemara pesachim about לשון נקייה, & Rambam's explanation of לשון הקודש
Comment: Where did you hear the term?
Comment: Your question currently renders Nivul Peh as "using foul language" however as there are no "vulgar terms" in LHK or Aramaic as well afaik, it seems to me "speaking lewdness" or "talking of obscene things" might be more descriptive. That is, it's more a matter of topic and less diction. The example given in Shabbat 33a is a person talks obscenely about why a bride enters a chuppah; he can do this nivul peh without vulgar words.
Answer: Yerushalmi Terumoth (ch. 1):
ולא יראה בך ערות דבר (דברים כג): ערות דיבור זה - ניבול - פה
Also, see Mesilat Yesharim (ch. 11) about the severity of this sin, where he brings this and other sources.
Comment: So is it an asmachta or what? this does not answer the question.
Answer: Isaiah 9:16-

Therefore the Lord will take no pleasure in the young men, nor will he pity the fatherless and widows, for everyone is ungodly and wicked, every mouth speaks vileness. And for all this, his anger is not turned away, his hand is still upraised.

As @GershonGold pointed out, the Talmud (Shabbos 33a) derives from here that nivul peh is a very bad thing. It would seem strange that a Prophet would be decrying a certain behavior, especially in such terms, if it only went against a decree of the rabbinic courts, and not something defined as wrong by God himself. If we can't find an allusion to the wrongfulness of nivul peh in the Torah (i.e. the Pentateuch) then we should look harder. From textual context alone I don't think it makes sense to equate this with lighting Chanuka candles or muktza.
One suggestion: The Rambam understands the concept of refining ones character to be included in והלכת בדרכיו - the obligation to walk in the ways of God. I'd assume this could fall under that.
Comment: Kedoshim TiHyu?
Comment: @SethJ Note that Rashi's pshat on that is to keep far away from arayos; naval birshus hatorah is Ramban
Comment: Much of morality in general is not addressed by the Torah, and there is no reason to assume that it is d'orayta. Dividing the options for the source of a prophets exhortation into d'orayta and d'rabanan is therefore, IMHO, totally misleading.
Comment: @SethJ Perhaps.
Comment: This does not fully answer the question with regard to law, but it may not be so cut and dry.
Answer: I cannot find mention of nibbul peh in Rambam's Mishneh Torah, or in other lists of the mitsvot, such as Yereim, Semag, Semak, Ramban's addenda to Sefer Hamitsvot, etc.  I therefore assume that according to Rambam, et al. it is not a Biblical prohibition and that the associated derashot are asmakhtot. I similarly find no mention if it in the major codes such as the Arba'ah Turim and the Shulhan Arukh. Their combined silence seems to imply that it is not a formal rabbinic prohibition either. That does not mean, however, that performing it is permissible, or even that doing so does not violate a rabbinic, or even biblical commandment. It just means that it is not its own legal category (in spite of its distinct name).
For example, cannibalism and public nudity can both be extremely problematic, even-though it is likely that neither is the subject of a discrete prohibition.
Comment: It appears that the commentless downvoter could think of nothing coherent to say. Probably just an emotional vulgar expression. Given the irony of such a response to this question he chose to vent his frustration into a commentless downvote.
Comment: @sethj it appears that i answered `What is the source for the prohibition against Nivul Peh (using foul language)? Is it Biblical? Rabbinic? "Asmachta" (based on a principle derived from the Torah but ultimately not considered a Biblical mandate, ie., not a Mitzvah)? ` Rendering `how severe is the prohibition` unanswerable since a non-technical prohibition has no measurable severity. Incidentally, mine is the only answer that brings evidence to whether the prohibition is biblical rabbinic or neither. Is something bothering you about the answer?
Comment: @SethJ^^^^^^^^^^^
Answer: שבת לג ע"א says that due to the sin of Nivul Peh many Tzaros and bad Gezeiros happen and young people pass away. So I guess it is Rabbinic in nature.
Comment: Maybe it falls into some biblical category...
Answer: I would like to elaborate the Passuk in Isaiah above (9,16),
עַל־כֵּ֨ן עַל־בַּחוּרָ֜יו לֹא־יִשְׂמַ֣ח׀ אֲדֹנָ֗י וְאֶת־יְתֹמָ֤יו וְאֶת־אַלְמְנוֹתָיו֙ לֹ֣א יְרַחֵ֔ם כִּ֤י כֻלּוֹ֙ חָנֵ֣ף וּמֵרַ֔ע וְכׇל־פֶּ֖ה דֹּבֵ֣ר נְבָלָ֑ה בְּכׇל־זֹאת֙ לֹא־שָׁ֣ב אַפּ֔וֹ וְע֖וֹד יָד֥וֹ נְטוּיָֽה.
Therefore the Lord will take no pleasure in the young men, nor will he pity the fatherless and widows, for everyone is ungodly and wicked, every mouth speaks vileness. (translation taken from above)
Speech in question is called נבלה, which is the שורש of an animal that died without slaughter.
The reason that an animal is called that, the animal died not in its proper way and therefore becomes wasted because of how it ended. As you won't find a dead Rasha being called נבלה because Humans don't end at death.
In regards to this Passuk, when one uses words which make the listener only hear the word and not what the speaker is trying to say, his point is "dead on arrival" and becomes a "נבלה" word.
This would be the parameter if defining if it is in fact a דבר נבלה, that is if the word is the only thing heard, destroying the true point the speaker is trying to make and deadening his speech in effect.
Disagreeing with the idea that it's defined by society. It's defined based on it's actual effect. Some are worse than others though.


Why is the Milky Way today about the same diameter as the visible universe was when recombination happened 378000 years after the Big Bang?

Question: Has the Milky Way undergone an expansion of space time independent of the universe as a whole or did the gas that created the Milky Way heat up and expand? Whatever the answer, why the current diameter ?
Comment: Why is my car about the same length as an elephant?
Comment: They aren't the same size. The part of the Universe that is observable _today_ was ~86 million lightyears in diameter at recombination. The observable Universe _at that time_ was much smaller, but still ~1.7 million lightyears, more than a factor of 10 larger than the Milky Way.
Answer: The visible Milky Way is about 100,000 light years in diameter (Goodwin et al. 1998) - so no coincidence there. Of course, this is a bit of a "how long is a piece of string problem" - the "edge" of the Milky Way is not sharp and some stars can be found, certainly as far as 300,00 light years from the centre (Kafle et al. 2014).
If you include the dark matter halo, then it is possibly ten times bigger again, so I can't see any numerical coincidence.
Also note that the Milky Way is just one galaxy. Other galaxies can be bigger or smaller, even in the local group of galaxies. Thus, any quoted similarity between the size of the Milky Way and the light travel time at the epoch of recombination must just be a coincidence.
Gravitationally bound objects like the Milky Way do not expand with the universe.
Answer: The Baryonic portion of the Milky way (i.e not including dark matter) is 100,000 light years in diameter. The epoch of recombination, and the present galactic evolution's "finetuneness" is rather a coincidence. Big bang expanded rapidly due to dark energy i.e cosmological constant and inertia whereas the Milky way galaxy evolved slowly through mergers, formation of nebulae, primordial interstellar medium accumulating to form galaxies, so it is a mere coincidence. The present diameter is due to the amount of baryonic mass distribution (it has no galactic nucleus) it has swallowed, and that depends the rotational velocity which in turn concludes the diameter, other than things like the inertial speed of the gas when it started to accrete to form a proto galaxy.
Milky way has always been a condensed region ever since it started accretion, the cosmological constant was weaker at that time, so the Hubble velocity did not play a role in the galactic evolution. Nor did gas heat up, and  cause it to expand, as it solely relies on mergers, and especially the tidally interactions by the local group which was more closer at that time, had affected the arm rotational speed a little bit, and it would not heat up, rather it would cool down. However in few galaxies the quasars may actually play a role to expand but this is not the case for the Milky Way.
Thanks, hope it helps you!


Why is Int supposed to be a Psion's key stat when they don't use it?

Question: I've been reading the rulebooks and handbooks for a while and one thing doesn't stop to bother me - INT is always mentioned as Psion's most important attribute, yet unless you want a Shaper psion, you need to invest into something else (like DEX for Nomad and CHA for Telepath). It seems a little bit contraditory to me since those sources tell me that INT is the reason a Psion can cast at all and has all those bonus PP because of that, yet somehow high CON of Savant gives him all the PP and manifestations.
I've got that if the attribute is 9 or lower you can't manifest any power with that attribute (even with Expanded Psionics), but the rest seems illogical to me. Can anyone explain this, please?
Comment: What you're describing is the **horribly broken** 3.0 Psionics ruleset, not the 3.5 version, almost all of which can be found for free online (such as [here](http://www.d20srd.org/) under Psionic Rules), since *Expanded Psionics Handbook* is largely Open Game Content.
Answer: There are two different varieties of D&D 3 Psionics.
The 3.0 Psionics Handbook gave Psions a different key ability score based on their specialisation. Nomads used Dex and Telepaths used Charisma for instance.
In the 3.5 update to Psionics, this was changed so that all Psions used Int as their manifesting statistic.
Comment: Oh, so this Psionic Handbook is for 3.0 edition... No wonder it sounds contraditory. Thanks for a quick answer and for the mystery solved 8)


Color Management. What is the difference between display device, view transform and sequencer?

Question: All these settings are found in the color management section. I hear that filmic is the best to use, and it has filmic default for the view transform. But under sequencer sRGB is default. Under display device the default is set on sRGB with no filmic option. could someone please explain what the different terms display device, view transform and sequencer mean?
Comment: Related: (possible duplicate? ) [what is the difference between color models sRGB-rec709-XYZ etc and which cases I need to prefer one?](https://blender.stackexchange.com/questions/129720/what-is-the-difference-between-color-models-srgb-rec709-xyz-ets-and-which-c/129987#129987)
Answer:
I hear that filmic is the best to use

Don't just trust what you hear, or rely on other people's opinions. You can make your own informed decision if you understand how filmic blender works, and then you will be able to harness that information for your particular artistic needs.
Filmic works for rendered scenes that use a large dynamic range, but it might make other images look completely wrong.
Start by reading Render with a wider dynamic range in cycles to produce photorealistic looking images before you continue.

Are you back from reading the link?
The main concept to understand is how the filmic blender color transform uses a completely different scale to convert the rendered information than the "default" (sRGB) transform. In other words the filmic blender transforms are designed to convert scene referred data to display referred using a much larger range of values. More on that later.
Now on to your real question:

could someone please explain what the different terms display device, view transform and sequencer mean?

Display Device
The value here depends on what kind of monitor is attached to your computer. This settings controls how color values are presented on your screen.

sRGB or default. Most monitor display images using sRGB. Use this unless you know that your monitor is of a different kind.
DCI-3P Those with apple monitors and imacs from late 2015 or later, or with monitors or professional projectors that use the DCI-3p color space would need to choose this option
Rec-709 If you are using ah HDTV as a computer display, most likely you need to choose Rec-709
"None" should be used when you want to export an image without any color device transforms. Useful for those who want to export images using a linear scale (or a "gamma" curve with value 1), like bump maps or normal maps.

Why does it matter? An image that is meant to be displayed in one type of monitor will look wrong or different if displayed in a monitor that is expecting other kind of information.
View Transform
The controls in this section determines the conversion from scene referred data to display referred data is done.
What does that mean?
Rendering and compositing is best done when the scene values use an unlimited linear scale (scene referred), which corresponds to the way things work in nature, and makes computations more physically accurate. However, these values do not directly correspond to human perception or the way display devices work. In other words, a scene might contain more information than the one that can be displayed or stored in most image file formats. So a conversion has to take place to make the generated scenes viewable in a way that our eyes understand correctly, but they also need to be stored in a format that can only accomodate a very small amount of information. The view transforms will scale and bend the original linear values so that then they can be stored and displayed correctly in specific devices. Once the images have gone through this transformation, their values will be in what is called display referred data.
Some of the view transform choices
Default Does no extra conversion besides the conversion for the display device.
Filmic For more photorealistic results and better handling of high dynamic range. The contrast can be adjusted by changing the Look option for the Filmic view transform.
Raw Raw bypasses any color space conversion.
Log Intended for exporting images as log encoded.
False Color Shows a heat map of image intensities, to visualize the dynamic range. Dark areas will show as dark blue, mid tones will be green, red areas will be shown as red, and values outside of the displayable range will be shown as white.
Looks
Looks are additional transformations that are applied after the view transform to have different artistic effects. In the case of filmic it gives you a more nuanced control on the overall contrast of the scene.

Sequencer
The color space that the Sequencer operates in. By default, the Sequencer operates in sRGB space, but it can also be set to work in Linear space like the Compositing nodes, or another color space. Different color spaces will give different results for color correction, crossfades, and other operations.
Keep in mind that the sequencer works for the most part with rendered images and video files that are already in a specific color space (most likely sRGB), so unless you know that your sources come in a different color space you should leave it at the default.
So why not use filmic for the sequencer? Unless your images are saved as Scene Reffered using a linear scale (like OpenEXR files), it makes no sense to process them using color transforms that expect a much large dynamic range. If you use filmic blender to display an image that is meant to be seen using the sRGB it will look dark and the colors will all be wrong, whites will show as very light gray.
Comment: Thank you for such a in depth reply. I have a Mac and it has dci-p3, however when I put the display device to this, the option to use filmic for view transform disappears. Do you know why this may be?
Comment: @Pat Try the original filmic -blender from github https://github.com/sobotka/filmic-blender.  Read the text on the page carefully. It details how to deal with dci-p3.
Comment: read also https://blender.stackexchange.com/questions/117995/colors-are-off-outside-of-blender/118002#118002. Maybe @troy_s can shed some light?
Comment: https://github.com/sobotka/filmic-blender has the Apple DIsplay P3 transform, and in theory it works. Selecting it as a Display Device should give all of the same view transforms listed under sRGB. I'd note that Display P3 is different from DCI-P3, in that the white point is D65. Also note that Blender is broken, and that the canonized sRGB OETF won't display correctly. Who knows if something else is broken as well. Not many folks care any more.
Comment: is there any way to preview the changes of the color management?  I end up having to render to see the final effects of those changes which is cumbersome.


Bounded function of compact normal operator on Hilbert space is normal

Question: Let $H$ be a Hilbert space and consider a compact normal linear operator $A:H \to H$. Moreover, let $f$ be a bounded function on the spectrum $\sigma(A)$ of $A$ and consider the operator $f(A)$ in the sense of functional calculus.
I want to show that $f(A)$ is also a normal operator. I know that a bounded linear operator $B:H \to H$ is normal if and only if
$$ ||Bx||=||B^\star x|| \quad \forall x \in H,$$
which might be useful in this context.
Answer: For a compact normal operator $A\ne 0$, there are eigenvalues $\lambda_n$ and orthogonal projections $P_n$ onto the corresponding eigenspaces $P_n\mathcal{H}$ with eigenvalue $\lambda_n$ such that
$$
                  A = \sum_{n} \lambda_n P_n, \;\; I=\sum_{n}P_n\\
                P_n P_m = 0,\;\; n\ne m, \\
                  P_n^2 = P_n = P_n^*.
$$
Suppose $f$ is a bounded function on the spectrum of $A$.
Then $f(A)=\sum_{n}f(\lambda_n)P_n$ is normal because $f(A)^*=\sum_n \overline{f(\lambda_n)}P_n$ commutes with $f(A)$. In fact,
$$
       f(A)^*f(A)=\sum_{n}|f(\lambda_n)|^2P_n=\sum_{n}|\overline{f(\lambda_n)}|^2P_n=f(A)f(A)^*.
$$
Alternatively,
\begin{align}
      \|f(A)x\|^2 &= \|\sum_n \lambda_n P_n x\|^2 \\
   & =\sum_n |\lambda_n|^2\|P_nx\|^2 \\
   & =\sum_n |\overline{\lambda_n}|^2\|P_nx\|^2  = \|f(A)^*x\|^2
\end{align}
Answer: For any $f \in B(\sigma(A))$  we have $f(A) \in C^*(A)$.
Since $f \mapsto f(A)$ is a $*$-homomorphism, we also have $f(A)^* = \overline{f}(A) \in C^*(A)$.
Therefore $$f(A)f(A)^* = f(A)^*f(A)$$
since $ C^*(A)$ is a commutative $C^*$-algebra.
Answer: The functional calculus is a $*$-homomorphism, and since the algebra $B(\sigma(A))$ of bounded functions on $\sigma(A)$ is commutative, we have
$$f(A)f^*(A)=(ff^*)(A)=(f^*f)(A)=f^*(A)f(A).$$


Posting School Yearbook photos on private Group FB page made up of former students

Question: I am co-Administrator of a private FaceBook group of former students who attended my high school. I frequently take photos with my camera of photos printed in our high school yearbooks & post them in the group. Members enjoy seeing the old 50+ year old photos of students & teachers.
 One lady announced on the private FB page that I was breaking the law by posting photos of people without their permission. That I had no right to do so. I told her the yearbooks were sold to the public, so there was no expectation of privacy, plus I was taking the photos with my camera from the printed pages. (Many of the students are already deceased.)  What is the law?
Answer: The main issue is that you may have violated copyright law by posting the pictures. The photographer would normally hold the copyright in the photos, so even if the yearbooks were sold and made publicly available, you can't copy the photos (including taking pictures of the pictures). It is possible that as part of the yearbook arrangement, copyright was instead assigned to the individual student (unlikely) or some school-related organization such as "Class of 1969". Permission of the subject is not required; permission of the copyright holder would be.
Comment: I checked all 5 yearbooks and whoever the photographer was (he was hired by the school to take the photos) - long dead by now I'm sure - is not mentioned and no copyright material anywhere in book. These were very amateurish photos, & whoever was hired must have had very limited skills. Certainly, he had no copyrights to anything.
Comment: Back in the 50's & 60's, no one thought about legal matters.


Are uncountable nouns considered irregular plurals like man men?

Question: Is "rice", for example, considered an irregular plural?
Answer: For the more common usage (as an uncountable, or mass noun), "rice" isn't a plural, so the issue of whether it's regular or not simply doesn't arise. But when we speak of, say, different rices of the world, it's just a regular plural.
On the other hand, it's not impossible for a word which is a mass noun to have an irregular plural. In some contexts fish is a mass noun (Japan consumes much of the world's fish). And in some other contexts, it's a countable noun that's irregular in that the plural is the same as the singular (I caught three fish). But it can also be a regular plural (The parable of the loaves and the fishes).
Comment: @Karthik, the discussion is about a linguist's notion of countability: your question seems to assume that it is the mathematician's concept of countability, which is quite different and not relevant here.
Comment: +1 for good examples. What is the notion of countability doing here? EG. we say a real number, or the real numbers, even though they are uncountable, and same for an integer or the integers, which we call countably infinite.
Comment: @karthik: The notion of "countability" is here because OP asked whether *uncountable nouns* could be considered "irregular plurals". To which I'm saying *"No, because in its 'pure' form a mass/uncountable noun doesn't have the singular/plural attribute anyway"*. But in fact many if not most such nouns do have 'countable' variants -  which, like most other nouns, have regular plurals. *Fish* is an oddity in that respect, but you could call *man* a mass noun in some contexts (**Man is just a small component of the thin 'bio-film' covering this planet**) - unquestionably with an irregular plural.
Comment: +1: It is worth mentioning that certain mass nouns (rice, toast, cattle, corn, etc.) are count nouns that require a *counter* to refer to individual elements in the mass: one doesn't say "three toasts" unless one is talking about a salute involving alcoholic beverages; one says "three slices of toast" instead.
Comment: @ColinFine  yes, I got it after FumbleFinger's response. I took the uncountability to math. :)
Answer: No, it is not the case that rice has a singular form rice and an identical plural form. One way to tell is by considering subject-verb agreement. If there were a plural rice, then we would expect to see examples where the verb is plural, such as *rice are white. Not only do we not see such examples, but we find them to be ungrammatical. This same test can be applied to other nouns to discover if they simply have a plural form that shares its shape with the singular form (e.g., sheep are stupid) or not (e.g., *water are wet).
(the * indicates an ungrammatical string)


What is the purpose of extrausers?

Question: Can someone explain the purpose, and benefits, of having an additional and separate extrausers user database in certain Linux systems (such as in Debian or in Ubuntu Core)? Why is not the standard /etc/{group,passwd,shadow} enough?
Comment: Please tell, where these extrausers are?
Comment: Normally located at **/var/lib/extrausers/{group,passwd,shadow}**.
Comment: I don't have it.
Answer: Debian's libnss-extrausers package makes it very easy to combine users and groups from two sources:
I use my private home PC and laptop regularly to remotely mount file systems from the sec=krb5 NFS file server of my university department. In order to see and use in commands like ls -l, groups, chgrp, cd ~user/, etc.  the user and group identifiers associated with files, these need to be listed in the local getent/nsswitch database. I have my private family-member users in /etc/passwd. I don't want to use LDAP on a private home PC or laptop, as this would cause inconvenient delays when the LDAP server is not reachable (when the VPN to the university department is down). So I simply use a script that regularly copies all users and groups in the department's LDAP server in /var/lib/extrausers/{group,password} on my private machines.
The /var/lib/extrausers/ mechanism makes this extremely convenient: my script can simply overwrite all files in there, without having to modify /etc/{group,passwd} and having to keep track where which entry in there came from. I could even maintain these extra users and groups there via an automatically updated deb package.
I'm currently looking for a similar solution for macOS, and I wish it too had /var/lib/extrausers. Any suggestions?
Answer: Well it can be usefull when you want to mix "manualy" maintened passwd files an automated deployment of "immutables" local users with tools like chef/puppet/ansible for exemple (there are other way yes).
Comment: There is a better explanation in Debian bug #791661.

What is the purpose of extrausers?


What do we say "A big Flower Pot" in English

Question: I have a Big Pot in which there is a Big Plant. But I don't know what do we say it in english in my native language, we say it, "Gamla"
Also, there is no Flower it! :P
It looks like this: https://www.dropbox.com/s/r4z35d4kn2f6b57/Nature-Pot-and-Plant-Photograph-520x693.jpg
Comment: It's a plant, so 'plant pot'. Telling us what your native language is would also be helpful.
Comment: It's entirely proper to call it just *a big pot*. If you're talking about planting something in it, nobody will think you're talking about a cooking pot.
Answer: I would call it a planter:

3) A container, usually decorative, for potted or unpotted house plants
Answer: You may call it as a plant pot or even flowerpot.
Wikipedia shows a picture of 'flowerpot' which is empty and not necessarily to have flowers in it.

As for the dictionary,

flowerpot (n) - (Horticulture) a pot in which plants are grown.

Plants may or may not have flowers there.
Important- Not to confuse it with pot plant which means...

pot plant (n) - A plant suitable for growing in a flowerpot (especially indoors).
Comment: Sorry Maulik, my point is that a "pot plant" almost exclusively refers to a marijuana plant. I don't know any native language speaker who would refer to any plant in a pot or any plant capable of being potted (i.e., houseplants or indoor plants) as a pot plant.
Comment: Many older British gardeners would still use "pot plant" with no reference to drugs, but the "correct" British English term is now "potted plants". (See Google for examples of use). Also, large plant pots for outdoor use are sometimes just called "containers", in BrEng, especially if they are made in a different shape or material from small flowerpots.
Comment: Actually a pot plant is something else entirely ;-)
Comment: @Jim I defined it but put this additionally as it contains the same words in reverse order. For non-native speakers, I'm pretty sure it'll be helpful :P
Comment: I'm pretty sure that if people start going around talking about "pot plants" according to your definition **They will be misunderstood**
Comment: @Jim oops, that's not **my** definition! If you don't like WW there, here's another one - http://www.merriam-webster.com/dictionary/pot%20plant


Ways of detecting underground bodies of water

Question: I saw one way to achieve this using the magnetotelluric way, but I need some solid fundamental way to understand it. Any book recommendations would be appreciated.
Comment: Are you just interested in the magnetotelluric method or others methods as well. You  ask one question in the title but a specific question in the body of the text. Could you please clarify.
Comment: This question is a bit vague. Search for resources under 'hydrogeology' or 'aquifer exploration' and then come back with a more pointed question. Or, as Fred says, if you're interested in magnetotellurics, ask about that (after reading about it!).
Comment: The water is in rock formations, aquafers. The technology is seismic exploration.
Answer: You may want to explore this question from Space Exploration SE. Strictly speaking, the question refers to ice detection, but the methods described there can also be used to identify liquid water.

Seismic measurements. These may be used to identify different phases of ice as well as liquid water, because different phases of the same chemical makeup will lead to different propagation of the seismic waves. Ref. 1 describes how the technique may be applied to outer-planet moons to reveal the water/ice structure.

Inclusions. The same answer also describes the direct finding of high-pressure ice (Ice VII) in diamonds on Earth 2. The high-pressure ice does not reveal bodies of water as such, but it gives evidence of molecular $\ce{H2O}$ originating from the deep mantle.

References

S.C Stähler, M. P. Planning, S. D. Vance, R. D. Lorentz, N. van Driel, T. Nissen-Meyer, S. Kedar (2018). "Seismic propagation in icy ocean worlds". Journal of Geophysical Research: Planets, 123. https:// doi.org/10.1002/2017JE005338.

O. Tscauner, S. Huang, E. V. B. Prakapenka, C. Ma, G. R. Rossman, A. H. Shen, D. Zhang, M. Newville, A. Lanzirotti, K. Tait (2018). "Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth's deep mantle".
Science 359 (6380), 1136-1139. https://www.science.org/doi/10.1126/science.aao3030.
Answer: I want to add to the initial answer from Oscar:
But first, as a matter for geophysical terminology clarification, let's separate two very important concepts: detection (i.e. "I see the top or the bottom or something in between the top and bottom, whatever that is...") and resolution (i.e. "I see the top and bottom, whatever that is...").
For the specific question, here's my take on it: there are many, many well-documented ways of doing this. Direct (well-logs, cores, etc.) and remote (seismic and potential fields). For seismic methods, that's usually reflection or refraction. And, for potential fields, that usually is electrical resistivity surveying (and then some kind of 2/3-D inversion) or GPR.
As for sources, there's a lot of useful stuff here.


What is alternative parenthesizations?

Question: I'm a person using english as the second language and reading CLRS book at a slow pace due to my poor english. I have a problem with understanding the meaning of the word 'alternative'. In page 303 on CLRS, says:

we should convince ourselves that exhaustively checking all possible parenthesizations does not yield an efficient algorithm.Denote the number of alternative parenthesizations of a sequence of n
  matrices by P(n). Since we can split a sequence of n matrices between
  the kth and (k+1)st matrices for any k = 1,2,...,n-1 and then
  parenthesize the two resulting subsequences independently, we obtain
  the recurrence ...(omitted)

What is the word 'alternative parenthesizations'? is this word equivalent to the 'all possible parenthesizations' in the above block quote? searching dictionary for the word 'alternative' is not helpful to me.
Thank you in advance.
Answer: Depending on the context, "all alternative parenthesizations" means either "all possible parenthesizations" or "all possible parenthesizations apart from the one we were just talking about."
The sense of the word "alternative" being used here is "one of two or more available possibilities."

What is alternative parenthesizations?


using foreach statement on a serializable dictionary

Question: I have a serializable dictionary that I created for a WCF REST web service
[Serializable]
public class jsonDictionary<TKey, TValue> : ISerializable
{
    private Dictionary<TKey, TValue> _Dictionary;
    public jsonDictionary()
    {
        _Dictionary = new Dictionary<TKey, TValue>();
    }
    public jsonDictionary(SerializationInfo info, StreamingContext context)
    {
        _Dictionary = new Dictionary<TKey, TValue>();
    }
    public TValue this[TKey key]
    {
        get { return _Dictionary[key]; }
        set { _Dictionary[key] = value; }
    }
    public void Add(TKey key, TValue value)
    {
        _Dictionary.Add(key, value);
    }
    public void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        foreach (TKey key in _Dictionary.Keys)
            info.AddValue(key.ToString(), _Dictionary[key]);
    }
}

I need to search through this dictionary to determine if 1 of several possible keys are present.  I figured I would do this using a foreach statement kinda like so
foreach(var pair in dictionary)
{
    switch(pair.key)
    {
        case "something":

        Break;
        case "somethingelse":
        Break;
     }
}

However I keep getting the error:
    foreach statement cannot operate on variables of type 'ZTERest.jsonDictionary<string,string>' because 'ZTERest.jsonDictionary<string,string>' does not contain a public definition for 'GetEnumerator'

I know I have to do something with the IEnumerable or IEnumerator interface but I'm not sure how.
Answer: Your class needs to implement IEnumerable to perform foreach on the Key of the dictionary, hence your class would look as below
public class jsonDictionary<TKey, TValue> : ISerializable, IEnumerable<TKey>

Then you need to implement the following methods from the IEnumerable interface as shown:
public IEnumerator<TKey> GetEnumerator()
{
    // Since we want to iterate on the Key we specifiying the enumerator on keys
    return _Dictionary.Keys.GetEnumerator();
}

IEnumerator IEnumerable.GetEnumerator()
{
    return GetEnumerator();
}

Then when you perform a foreach the keys from dictionary are fetched hence you can have your foreach as shown:
foreach(var key in dictionary)
{
    switch(key)
    {
         case "Something":
             // do something
             break;
         case "SomethingElse":
             //do something
             break;
    }
}

Comment: This is great, thanks, and does answer my question.  I chose the other answer because it does it a little more efficiently.
Comment: Your welcome. thats is fine but just that you wanted to use the foreach on your custom dic object did post that. :)
Answer: A dictionary provides a key/value lookup for a reason, it's not something that you usually iterate through. The generic Dictionary<> object that your class is wrapping already has a method called ContainsKey() that will do exactly what you're looking for, without the overhead of going through every single key/value pair to see if it's there. There's no need to expose an iterator, just add this to your class.
public bool ContainsKey(TKey key)
{
    return _Dictionary.ContainsKey(key);
}

And call it like this.
if (dictionary.ContainsKey("Something"))
{
    //do something
}

Answer: In case you actually need to iterate through the dictionary (instead of just checking if a certain key exists) the Dictionary.Keys property returns an enumerable collection which you could use iterate through the dictionary:
foreach(var key in dictionary.Keys)
{
    if(dictionary[key] == "something")
    {
        // Do something
    }
}


Are there two non-isomorphic number fields with the same degree, class number and discriminant?

Question: If so, do people expect certain invariants (regulator, # of complex embeddings, etc) to fully 'discriminate' between number fields?
Answer: John Jones has computed tables of number fields of low degree with prescribed ramification.  Though the tables just list the defining polynomials and the set of ramified primes, and not any other invariants, it's not hard to search them to find, e.g., that the three quartic fields obtained by adjoining a root of $x^4 - 6$, $x^4 - 24$, and $x^4 - 12x^2 - 16x + 12$ respectively all have degree $4$, class number $1$, and discriminant $-2^{11} \cdot 3^3$.  On the other hand these three fields are non-isomorphic (e.g. the regulators distinguish them, the splitting fields distinguish them...).
Answer: An example (this is exercise 21 in Chapter 2.2 of Borevich and Shafarevich) is given by the three cubic fields obtained by adjoining a root of $x^3-18x-6$, $x^3-36x-78$ and $x^3-54x-150$. The resulting fields are non-isomorphic cubics with class number one and discriminant $22356$.
Comment: This is the smallest discriminant shared by three nonisomorphic totally real cubic fields.
Answer: This isn't quite your question, but there are nonisomorphic number fields with the same zeta function. They are built in this way: Take a Galois extension $K/Q$, with Galois group $G$. Find subgroups $H_1$ and $H_2$ so that $G/H_1$ and $G/H_2$ are nonisomorphic as sets with $G$-action but $C^{G/H_1}$ and $C^{G/H_2}$ are isomorphic as vector spaces with a $G$-action. Then look at the fixed fields of $H_1$ and $H_2$.
Because there is a lot of freedom in this construction, I would guess that you can manipulate it to avoid detection by any of the easy invariants you mention.
Comment: If you choose them so that the isomorphism k^{G/H_1} = k^{G/H_2} works over any field (there are examples in my undergrad thesis), the class numbers have to be the same.
Answer: Here's a degree three example with minimal discriminant: the two cubic fields given by $x^3-21x-35$ and $x^3-21x+28$ both have discriminant $3969=63^2$, both are Galois, both have class number 3. The regulator of the first is about 4.20169 and that of the second is about 12.59419. This is the smallest (positive) discriminant of a degree 3 field to have two non-isomorphic fields of that discriminant.
Comment: Indeed. Hopefully desert islands will have free wifi some time soon.
Comment: There are examples with smaller absolute discriminant: the "pure" cubic fields obtained by adjoining cube roots of 6 and 12. Both have discriminant -972 and class number 1, but they're not isomorphic.  Pure cubics give lots of examples like this -- I was able to find 5 fields with common discriminant and class number.
Comment: It's easier (well, if you were on the proverbial desert island without a computer) to check they are not isomorphic by looking at prime splitting: 2 is inert in the first and splits in the second.
Comment: @Ari: yeah, sorry, I meant of *positive* discriminant.
Answer: I recently heard a fascinating talk by Drew Sutherland on work he's done on this sort of question. Rather than trying to summarize his talk, here is a link to the slides for his talk. He also indicated that he'll be posting an article soon on the ArXiv, but it's not quite ready yet.


Butal error on apt-get

Question: pi@raspberrypi:~ $ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
Setting up linux-image-4.9.0-6-rpi (4.9.82-1+deb9u3+rpi1) ...
No diversion 'diversion of /boot/vmlinuz-4.9.0-6-rpi by rpikernelhack', none removed.
No diversion 'diversion of /boot/config-4.9.0-6-rpi by rpikernelhack', none removed.
No diversion 'diversion of /boot/System.map-4.9.0-6-rpi by rpikernelhack', none removed.
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-4.9.0-6-rpi

gzip: stdout: No space left on device
E: mkinitramfs failure cpio 141 gzip 1
update-initramfs: failed for /boot/initrd.img-4.9.0-6-rpi with 1.
run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1
dpkg: error processing package linux-image-4.9.0-6-rpi (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of linux-image-rpi-rpfv:
 linux-image-rpi-rpfv depends on linux-image-4.9.0-6-rpi; however:
  Package linux-image-4.9.0-6-rpi is not configured yet.

dpkg: error processing package linux-image-rpi-rpfv (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 linux-image-4.9.0-6-rpi
 linux-image-rpi-rpfv
E: Sub-process /usr/bin/dpkg returned an error code (1)
pi@raspberrypi:~ $ sudo apt-get upgrade

Comment: What is "butal"? Does your RPi fail to boot?
Answer: According to the output posted above:
gzip: stdout: No space left on device
Can you clear some space on the device, to allow the files to be unpacked?

Butal error on apt-get


Is it possible to deduce the conservation of angular momentum from the conservation of energy?

Question: Is it possible to deduce the law of conservation of angular momentum from the law of conservation of energy? If possible, by what sense the conservation of angular momentum has the status of law, if it can be deduced from other law (and therefore, strictly speaking, would be a theorem)?
Comment: Note that conservation of *momentum* (not *angular* momentum) *can* be deduced from conservation of energy plus Galilean or Lorentz invariance.
Answer: No.  Angular momentum and energy are two different quantities.  In fact, angular momentum can be conserved when energy is not.  See, for instance, the famous case of the figure skater pulling their arms in and spinning more quickly.
Let's say our figure skater reduces their moment of inertia to some fraction $n$ of their original moment of inertia.  Then:
$$\begin{align}
I_{0}\omega_{0} &= I_{f}\omega_{f}\\
I_{0}\omega_{0} &= nI_{0}\omega_{f}\\
\omega_{f} &= \frac{1}{n}\omega_{0}
\end{align}$$
However, we have:
$$KE_{i} = \frac{1}{2}I_{0}\omega_{0}^{2}$$
And
$$\begin{align}
KE_{f} &= \frac{1}{2}I_{f}\omega_{f}^{2}\\
&= \frac{1}{2}nI_{0}\left(\frac{1}{n}\omega_{0}\right)^{2}\\
&= \frac{1}{2n}I_{0}\omega_{0}^{2}\\
&= \frac{1}{n}KE_{i}
\end{align}$$
So, the final kinetic energy of our figure skater is greater than their initial kinetic energy!  Angular momentum is conserved, but energy is not.
(of course, we know that overall energy is conserved, so you may ask where this extra energy came from--the answer is that it requires net work in order to pull your hands in while you're spinning.  So no violation of the rules of physics here.)
Answer: The conservation of angular momentum and energy in a mechanical system are distinct, independent conservation laws. The deep reason for this is that, because of Noether's theorem, conservation laws are in correspondence with the symmetries of the system. Thus if a system is time-translation invariant - if experiments behave the same no matter what the starting time is - then energy is conserved. Analogously, if a system is rotation invariant - if the outcome of experiments is independent of the system's orientation - then angular momentum is conserved.
Because of that, angular momentum conservation can no more be derived from energy conservation than it is possible to derive rotation invariance from time-translation invariance.

To be clear: This answer explains the fundamental reason why the two conservation laws are independent, and why it would be useless to even try. This argument can be strengthened using this converse to Noether's theorem: conservation of energy and of angular momentum are equivalent to time-translation and rotation invariance. These symmetries are independent, and contribute independent dimensions to the Lie symmetry group of the system's evolution, so they cannot be derived from each other.
As Jerry Schirmer said, it is trivial to construct a counterexample, which is what his answer contains.
Further, this independence argument does also extend to linear momentum. (For a simple counterexample, try a particle in a box - conserved energy but not momentum - or a free particle in a time-dependent but spatially homogeneous electrostatic potential - conserved momentum but not energy.) Of course, neither of these systems obeys boost invariance.
The underlying theme is this. If I have two different conserved quantities, $A$ and $B$, then I can sometimes find a third conserved quantity by taking their Poisson bracket (or their commutator in QM), so long as that is not zero. For example, conservation of $p_x$ and $L_z$ implies conservation of $p_y$. The key to this is that the associated symmetries are also related: translation invariance along $x$ and rotation invariance about the $z$ axis, together, imply translation invariance along the $y$ axis. Similarly, space translation invariance and boost invariance imply time translation invariance.
Comment: @EliMC: the two symmetries are independent of each other.  It is trivial to construct a model that is not rotationally invariant but is time-translation invariant, or vice versa.
Comment: This is not quite right, because if I take your argument and replace "angular momentum" with "momentum" everywhere, the conclusion is false, and yet you haven't invoked any properties of angular momentum that differ from those of momentum. The difference is that time translation invariance plus boost-invariance (Galilean or Lorentz) implies spatial translation invariance but not rotational invariance.
Comment: The Noether's theorem says there is a conserved quantity, but does not prevent such is consequence of other conservation law.
Comment: @BenCrowell See response in edit.
Comment: OK, that works better.
Answer: Some conservation laws are related to conservation of angular momentum.
There is a famous example (from Feynman if I recall correctly), where you assume an infinite flat space and conservation of angular momentum about any point, and then you get conservation of linear momentum for free.
Intuitively, to get say the $x$ component of linear momentum is conserved in a region you consider a coordinate system centered at the region, and consider the angular momentum about a point way off in the $y$ (or $z$, or any direction orthogonal to $x$) such a super great distance away and then effectively conservation of angular momentum about that distance point requires conservation of the $x$ component of linear momentum.
There is also a conservation law for angular momentum:
$0 = (x^{\alpha} T^{\mu \nu} - x^{\mu} T^{\alpha \nu})_{,\nu}$,
from flat space Special Relativity and the symmetries of the stress-energy tensor.  In fairness, this might be considered cheating (as a derivation) since most derivations of the symmetry of the stress-energy tensor assume that little bits of matter don't spin arbitrary fast as you look at smaller and smaller bits of them.
Comment: If you assume an infinite flat space and rotational invariance about every point, then you also get translational invariance, because the composition of two rotations by pi about parallel axes gives a translation. Similarly, whatever dependencies happen between the conservation laws will be mirrored in the symmetries.


How to activate a lever with another lever?

Question: I am trying to build a Wimpy in minecraft, and it uses a rail system to deliver food. I have two sides of the restaurant, but one rail switching between the two sides. A redstone torch doesnt work, so I need to activate the lever with another lever from the kitchen
Answer: Have you tried using an inverter?  Levers are emitters, not receivers.  An inverter will work both as an emitter and receiver
Answer: Levers can not interact with other levers. To get a similar effect you could use memory cells and buttons. Wiki entry on logic gates.
Components that would be of interest:

XOR (Only returns true if one input is true but not both)

Memory Cells (Allows the system to remember button presses)

Monostable circuit (Allows altering of redstone signal duration)

To get the track to switch try powering the block below the intersection with a torch or repeater.


An attacker has my IP address;So what?

Question: There seems to be a general bad vibe for someone having your IP address, but what are the real dangers? After all, I give my IP every time I connect to a website, regardless of the legitimacy of said site.
Assuming a malicious party has obtained my IP and wish to do Bad Things, what can they do?
Comment: Knowing an IP address is useless. We all already know all addresses. What is needed is some knowledge of what hardware/software/firmware resides at a given address.
Answer: What every company on the planet with assigned static IPs does.
At a minimum, firewall with default drop on unneeded inbound ports, patch all exposed services for vulnerabilities, don't have unneeded services listening, enable some sort of intrusion detection.
And you're not going to do anything much on inbound DDOS. Usually you have to do something to invite this kind of attention.
If they seriously want to mess with you, they will do targeted attacks by other means than directly working with an IP address. Once they're successful on that end, their malware phones home and knowing the IP address ceases to become an issue.
And it answers the question kind of in reverse. They will scan your IP to find out what kind of services are responding, attempt to use any replies to fingerprint both the responding OS and any service versions to see if there are vulnerabilities that can be exploited. And then there's the old Distributed Denial of Service attach where they just slam the door shut so you can't get out.
Comment: I'm sorry, the title was misleading. I wasn't trying to ask "What should I do?" but instead "What can an attacker do?". I have edited the title appropriately.
Answer: I suppose you have a router with an active firewall. Your computer or smartphone connects to that router and gets a local IP address. That IP address is not public, and as long as you have no ports open on the firewall, no port forwarding to your computer, it should be relatively safe. The router does have a public address, and that can be used in several ways.
You can connect directly to the internet, and this is the case with smartphones which connect via 2G, 3G or 4G. Do these computers have firewalls, open ports? In general I guess they don't have open ports, unless you start something like an FTP-server. And they don't have a firewall if I'm correct. As long as there are no open ports this is not a problem. I suppose these IP addresses are dynamic, so after a while you get a new one, but I'm not sure if that is really the case. (As @Josef says in his comment, providers have a firewall that protects the phone which connects directly via 2/3/4G, and this seems logical.)
So your IP address... It's just a number, not secret in any way. It's one in a list of numbers starting with 0.0.0.0 and ending with 255.255.255.255. You are nothing but a number just as any of us is. What can be a problem is that if someone knows you, knows your (static home) IP address, and wants to target you personally.
The average hacker tries to install a rootkit on your computer. The hacker that targets you personally can use anything. Your IP address won't be that important.
Start a webserver at Amazon or Linode, open up the SSH port, monitor that port, and you'll see that on no time hundreds of attempts are done to login, just based on IP address. Day in day out, it never stops. Nothing personal, just business as usual in the modern world.
You focus on an attack. I guess the real issue is about privacy, because you can be tracked across websites. Hackers in general don't benefit from this because they don't control all those sites and cannot monitor their logs. Facebook and Google do. The NSA probably does. Someone who hosts a website where you post personal info can use it. Especially those "like" buttons that you see everywhere, on news sites, blogs etc - they are the a true privacy issue as those buttons are downloaded from Facebook or Google, and then they get your IP and know that you visited that one page.
There are many browser addons that promise to protect you, but only use the original ones like Privacy Badger, Adblock Plus or Ghostery. Addons that have a similar sounding name cannot be trusted and should not be used.
One example I just saw: A hacked DDoS-on-demand site offers a look into mind of "booter" users
Comment: Almost all mobile providers have at least stateful inspection enabled, so you don't have any ports open to the Internet! Apart from security, a reason is that this enhances battery lifetime a lot! On the (IPv4) Internet, there is so much "noise" (random portscans etc.) that you get a package at least every few seconds at every IP! Your mobile device would have to wake up (uses power), send a confirmation (uses power) handle that package (99% of the time drop it), go back to sleep. I can disable the firewall and get a public IP at my provider. If I do, my tablet lasts only about half as long!
Answer: They could ISPDox you (Call your ISP up and claim to be with support, claim their lookup system is down and ask for your information). After that they will have your Name and Address, and they could SWAT you or ruin your credit score / dox you by publishing your SSN and other information online.
Comment: ISP Doxing seems to be a US/Comcast specific problem?! http://hacksociety.net/Thread-Tutorial-How-To-ISP-Dox - Apparently this is common with Comcast? My ISP would never do something like this, or would they? Why does it matter that their lookup system is down? My ISP can see that my connection is working. Why would they give this info?
Comment: How can an attacker get your SSN from the ISP support line??
Comment: @SPRBRN I have no idea why, but ive seen it happen loads of times with all different ISPs, although I have heard it is easiest with Comcast.
Comment: Imagine the conversation: "I know my IP address but I forgot my own name, can you help me?"
Answer: When the attacker has the IP address he can search the network that you are in and can attack on the same network. Such attacks can be DoS attack.
Comment: This is only correct for ipv4; default ipv6 allocation is /64, it will take very long time to scan - even more so in non-lab environment.
Comment: @OlegMazurov Wouldn't DDoS or DoS against IPv6 still be an issue since the packets are only dropped due to non-existent/unrechable host *after* the ISP?
Comment: @hexafraction could be; although I'm yet to see a DoS on v6. The way things are configured at my ISP I can get another prefix every 10 minutes (and since ipv6 pool is so large I don't think this will ever be restricted); the packets aimed at the previous prefix will then be dropped at ISP.
Answer: Your question is just too broad.
In general, your device in the perimeter, that has that IP address assigned to one of their interfaces, may publish on that interface some services that would be accessible to the attacker.
Some services may require authentication (hopefully) and others may not. In every case, all the packets arriving to that IP will be processed by the OS kernel and dispatched properly if necessary. If the dispatching engine for those packets have a vulnerability just by listening to packets your system may be compromised. This is a rare case but it is possible. You may be hacked although you have not got any open ports. Difficult by possible.
If additionaly, you have open ports listening like 80 for a web server, 22 for ssh and others, the attacker may look for vulnerabilities in that services and exploit them to access your system.
Just hiding your IP is not a solution because an attacker may find it but you have to harden your system assuming that the attacker will get your IP eventually. In the other hand, not exposing your public IP is always a good thing if possible.
Comment: `not exposing your public IP is always a good thing if possible.` But why? Assuming that I have no services running, I see no reason to attempt to keep your IP hidden.
Comment: @shelvacu That you have no open ports does not mean that your TCP/IP stack does not listen to incoming packets. For example, if someone finds a vulnerability in the kernel code that manages incoming ICMP packets by exposing your IP but not having open ports you still can be hacked. I repeat, it is difficult, but it is possible to be hacked without any open ports because the kernel is listening to incoming packets. in the case the packet does not arrive to the kernel it still is read by the network card driver that may be also vulnerable.
Answer: It could cost you money
Suppose the attacker sends large amounts of data too you, that gets dropped by your router/firewall.  You might exceed a data-plan.
Also, there have been reports of DDoS attacks against gaming tournaments and such.  This could possible cost you money.
Suppose you ran a business from home, and during a critical update/release/event you were attacked.

You could get hacked
I don't want to spread FUD.  However, my firewall picks up automated attacks on a daily basis.  If the public-facing devices on your network are insecure, your network could be compromised.
If you know an IP, you can identify the ISP.  The company, the employees, and the equipment can be a security risk.  I've found several articles, but none I feel comfortable linking.  When was the last time you got a letter stating your modem's firmware was patched?

You could be implicated
I knew a nearby "small-town" ISP that banned certain protocols--even if it was unsolicited.  Instead of blocking or throttling it, they would cancel your agreement.  Needless to say, they weren't popular.
On the other hand, suppose a criminal organization accidentally faxed or mailed you a copy of their criminal plans.  Law enforcement might implicate you.  A similar situation could arise concerning technology.  Although the seriousness of each case should light.  Regardless, it would cause a major headache!

An attacker has my IP address;So what?


Data transfer between servers extremely slow

Question: I have an application running on a Live environment with a  Web Server which is running Windows Server 2008 R2 with a QuadCore Xeon processor with 8GB of ram and a Database Server with the same configuration but with an additional disk with 2TB of space. The database server runs SQL Server 2008 R2. The two machines are connected through a crossover connection.
The application processes large loads of data from .csv files located in the webserver and stores them to the database. The data transfer and the number of items being processed per minute is very low compared to our benchmark times, which were set on a staging environment with a Web Server and Database Server running only 4 gb of ram. The staging environment processed a single .csv file at the rate of 6000 items per minute. The same file processed in the live environment ran at the rate of 2500 per minute. The staging environment, however is not running through cross cables but is using a standard switch. Suggestions as to why there is a drop in performance are welcome.
Comment: does the live enviro have AV running where the staging didn't?  Also by default w2k8r2 runs in power saving mode which slows things down quite a bit.
Comment: Actually both live and staging environments had had AV removed and both environments are running  w2k8r2.
Answer: Check that you are not getting packet errors. Ensure that the auto configuration for the nics is working properly or hard code the values for speed, duplex, etc. This used to be a common problem, but has improved over the last decade with better nics and switches.
Comment: We set the network configuration from automatic to 100mbps Full Duplex. This time we tried to emulate it using the same network configuration as the staging, still no change. However, we tried transferring a standard file of around 20mb over the connection, it seemed to transfer just fine


How can I (preferably metaphorically) explain DNSSEC without technical jargon?

Question: How can I explain a non-technical person the purpose of Domain Name System Security Extensions (DNSSEC) and the risks of not using DNSSEC? It would be nice to use a metaphor, so that it's also easy to remember for a non-technical person.
Answer: Regular DNS responses are like business cards - while you can generally trust them when someone hands theirs to you, they're actually just ink and card stock, and anyone who is even a little motivated can get their own made by a print shop.  And there's no way to enforce their validity; I can go to (for example) VistaPrint and they'll ship my "He-Man, Master of the Universe" cards right to me.
DNSSEC DNS responses are like drivers licenses.  They've got a picture.  They've got a mag strip with a copy of the information.  They've got holographs that are difficult to forge.  They've got layers printed in special ink that only show up under ultraviolet light.  In short, a number of technical measures have been taken to make them hard to forge.
When authentic data is important, DNSSEC/licenses are preferred.  Just as the Post Office requires a license and not a business card for identification, so your business might require DNSSEC data for use in connecting to your bank.
Answer: At the request of @schroeder (I'll also give it a shot myself).
A customer goes weekly to a local store because a friend told him that company A  (who runs the store) is trustworthy. The customer does not actually know company A, he just knows the local store because the store is in his area.
One day, company A got bankrupt and a not so trustworthy company B buys the local store, continuing it's original business exactly the same as before. The customer doesn't notice a difference and keeps buying at the local store that is now owned by a not so trustworthy company B, without knowing the difference.
When the local store was protected with DNSSEC, the local store would actually notify the customer that company A changed to company B and reject the customer from entering the store.
Comment: For the benefit of the techies out here who may not be DNSSEC experts, can you clarify what the Store and the Company represent? I assume the Store is the website and the Company is the webserver?
Comment: I think the store is the recursive DNS server whereas the company behind it is the authoritative DNS server. But I have been wrong before. Good analogy either way.
Comment: @GeorgeBailey yes, metaphorically "the store" is the registered domain and the "company" is the web server indeed.
Comment: dnssec wouldn't really protect against this scenario.  If you were to sell your DNS name to someone else (i.e. you sell the store) the new owner would also get a DNSSEC signed DNS entry.  The analogy would be more like someone hijacking your entries in the yellow pages or billboards with your business name, but using a different address across town.  DNS Sec is more like an ID for a business, like gowenfawr alludes to that you present to the yellow pages publishers when creating an advertisement.
Answer: Security (in exchange of data, and DNS is data) boils down generally to three properties:

authenticity: making sure the data is received from the real party it should come from and not from a third party trying to mimic the real part
confidentiality: making sure no third party of the conversation can understand what is discussed
integrity: making sure no third party can alter the conversation (even without understanding it), which is most often translated to making sure to detect any tampering immediately IF any third party is indeed altering the conversation.

There 3 properties are related, but separated. Sometimes you need one, sometimes all 3.
Contrary to popular belief, authenticity is often more "important" than confidentiality or said differently confidentiality without authenticity is often of dubious merits: even if you got data in such a way that noone saw it, if you don't really know where it came from for real, what is the difference if you get it in the clear as it could have come from anyone?
DNS exchanges happen between two parties but data flows through many intermediate systems. Hence, when arrived, by default, you have no guarantee about authenticity, nor confidentiliaty, nor integrity.
DNSSEC was designed to solve only the authenticity problems. It adds to all DNS data a "signature", exactly like in real world, that authentifies the content. You get the data you requested and you get (if everything is setup correctly) the guarantee that the data did in fact come from the true owner of the data (and you get also in part the guarantee it has not been altered in transit). You specifically DO NOT get any guarantee about confidentiality, that is even with DNSSEC, "anyone" sees what names you have requested. For that, DNS over TLS and DNS over HTTPS have been designed, they offer no guarantee on authenticity but offer guarantees on confidentiality and integrity.
Comics
If you need metaphors and things more graphical the below can help.
You can find starting page 3 at https://meetings.icann.org/en/marrakech55/schedule/sun-dnssec-everybody/presentation-dnssec-everybody-06mar16-en.pdf a presentation of DNSSEC using cave men and blue smoke signals.
It is given in many forums, but is clearly very high level, with its blue smoke. It may help to start discussing things in more details if needed.
You can find a more recent one, graphical at:
https://howdnssec.works/ about "Why do we need DNSSEC?" and it is open to future more works.
Comment: Regardless if they are comics, images or whatever, answers saying "your answer is in this link" are not accepted. You need to have content *here*. Thanks for adding content.


How to create a custom route in Google Maps, then navigate it on a mobile?

Question: When you get directions in Google Maps on the desktop, a route is generated which can then be changed by dragging new waypoints into the route.  I would like to save this custom route and send it to my phone to navigate via Google Maps navigation on the phone.  How can I do this?
Answer: Although you can't do exactly what I wanted, I've discovered a way to do something pretty similar.
First, get the directions and the generated route.  Next, drag the waypoints into the route.  Next, instead of sending to the phone immediately, go through the route, right click on each waypoint in turn, and click "Add a destination".  The waypoint will be added to the end of the destinations list; DO NOT reorder this list yet or the other waypoints will be lost.
Once you've added each waypoint as a destination in order, drag the final destination (in the destinations list on the left) to the end.  This will have created a route going from your original point A to B, but with the desired waypoints as destinations.  When you now "Send directions to your phone", these destinations will be included in the route that Google Maps navigation follows.
Unfortunately, I still haven't found a way to save this list of destinations.  That would be ideal.  If anyone knows a way, please comment and I'll update this answer to show it.
Comment: This works great, but has a quirk that it gives you the travel time to the first destination instead of of the whole trip.  Google fails again as usual.


If Uniswap's domain goes down, how can we remove our tokens from a Liquidity pool manually without a front end interface?

Question: Let's assume Uniswap's domain and front end interface is taken down. How can I as a user manually remove my tokens from a liquidity pool? What do I need and todo?
Answer: You can call the Uniswap's contracts directly. Specifically, you should call the Router02 contract, which handles all the details.
Depending on your use case, you need to decide which function to call, since there are many variants. You can find the documentation at https://uniswap.org/docs/v2/smart-contracts/router02/
You will need some way to create a transaction from the right wallet which calls the Router contract's functionality. I think there is no fast&easy solution here - I would personally write some javascript script for it, utilizing ethers.js.
Comment: Just as a tip if you try doing this - test it with a small amount before trying to move everything.


Deleting notes in ipod

Question: All my notes are synced to my gmail account and can be accessed. Now if I delete all my notes on my ipod, would it also delete all my notes in my gmail because it syncs.
I do not want the notes in gmail to be deleted.Thanks for the help.
Answer: If you delete the notes from the app, then yes, they'll be deleted from Gmail. However, if you just want to take the notes off the iPod, you can just switch off "Notes" for your Gmail account under Settings > Mail, Contacts, Calendars.
Comment: Sounds good. Could you confirm my inference that if I have deleted all my notes on my ipod after having switched off 'Notes', and then on a latter day would want to sync with gmail the notes i had stored latter, then it would wipe off the existing notes in Gmail as it has been deleted in the app.

Deleting notes in ipod


Manipulating large graphs using JGraph

Question: I have an acyclic graph that has about 100,000 nodes.
I want to be able to edit the graph and basically visualize it by zooming in and out of portions.
My Question: Is JgraphT a suitable candidate for this type of an application?
Answer: JGraphT isn't a visualization library, it's about graph structure and algorithms. It uses JGraph 5 for visualization, not the latest version JGraphX(aka 6). JGraph 5 performs more poorly than 6, and I doubt it can hit 100k nodes.
If it's just visualization you're after, try a simple test case with JGraphX. I doubt it'll work out of the box, but with a bit a tuning, it's certainly possible.

Manipulating large graphs using JGraph