Evolution operator for time-dependent Hamiltonian

When I studied QM I'm only working with time independent Hamiltonians. In this case the unitary evolution operator has the form $$\hat{U}=e^{-\frac{i}{\hbar}Ht}$$ that follows from this equation  $$ i\hbar\frac{d}{dt}\hat{U}=H\hat{U}. $$ And in this case, Hamiltonian in Heisenberg picture ($H_{H}$) is just the same as the Hamiltonian in Schrödinger picture ($H_{S}$), i.e. it commutes with $\hat{U}$. Now I have a Hamiltonian that depends explicitly on time. Specifically, $$H_{S}=\frac{\hat{p}^2}{2m}+\frac{1}{2}m\omega \hat{q}^2-F_0 \sin(\omega_0t)\hat{q}.$$  And in my problem I need to calculate $H_H$ (Hamiltonian in Heisenberg picture).  I've found that differential equation for $\hat{U}$ (I've mentioned about it above.) has generally solution in the form (with $U(0)=1$) $$U(t)=1+\xi\int\limits_0^t H(t')\,dt'+ \xi^2\int\limits_0^t H(t')\,dt'\int\limits_0^t' H(t'')\,dt''+\xi^3\int\limits_0^t H(t')\,dt'\int\limits_0^t' H(t'')\,dt''\int\limits_0^t'' H(t''')\,dt'''+...$$  So my questions are:   Is there other ways to calculate $\hat{U}$, could give a link or tell me about them? If you know form of the solution for my case, please tell me. If you know any articles or papers articles on this topice, please link them to me, too.


Creating multiple directories using a parameter in a shell script

I'm trying to make a bash script that would make a series of directories  and requesting a parameter of how many directories should be created.  $> ./createDir.sh 5  $> ls  ex_01 ex_02 ex_03 ex_04 ex_05   I tried using mkdir ex_{01..$1} but it does not seem correct. How could I make this work (without using any loop)?


The minimum of two independent geometric random variables

here's a question I got for homework (sorry if my translation is a bit unclear):  Let $X\simG(p_1)$, $Y\sim G(p_2)$, $X$ and $Y$ are independent. Prove that the minimum is also geometric, meaning: $\min(X,Y)\sim G(1-(1-p_1)(1-p_2))$. Instructions: first calculate the probability $P(\min(X,Y) > k)$ and compare it to the parallel probability in (of?) a geometric random variable.  I have no idea where to start, even with the great clue that they've supplied. Any hints?


Intuition behind a conditional probability problem

I was watching the Harvard's statistics course and came across this problem () 9:30.  Pick two cards from a deck of 52 cards what is the probability of getting two aces given:   1/At least one of them is ace  2/ One of them is ace of spades  The math calculation is fine. But I cannot understand the lecturer's explanation to the second problem. How one can tell the answer is $3/51$ without calculating? And how to understand the difference between the two scenarios intuitively?  Here is my attempt. The probability of the second problem is the $p(A \cup B)$ where A is the probability of one card being ace of spades and B is the probability of one card being an ace other than ace of spades.  Because $p(A)=1$ ( it is given by the problem), I can assume it is the sample space. So $p(A\cup B)$ is just $p(B)$, in which there are 51 cards with 3 aces.  But I believe that understanding is false, since the same thing can apply to the first problem. But clearly the answers to the first problem are either equal nor twice the second one.


Is there any sensible reason to use layered .tifs as work files instead of .psd? I recieved a layered .tif file from other agency designer and was baffled as why would someone use it as a format for handing over to someone else. Is this a compatibility issue? Both author and I are working on Adobe CC package, latest versions.  Same goes for embedding files in Illustrator or InDesign. Is there any advantage to convert .psd file to .tif and then link it? In my opinion it impedes workflow - it adds unnecessary steps between editing .psd file and seeing it in other compatibile program.


Is there some elementary proof of invariance of domain?

Invariance of domain at least in statement seems a simple result. I mean, the first time I saw the statement I thought: "the proof can't be that bad", but when I searched for it I saw that it needs even algebraic topology to prove this result.  My doubt is: isn't there any other proof of invariance of domain that don't need to use algebraic topology? Is there some more elementary proof of this result?  Thanks very much in advance!


I have installed and enabled geofield and geofield map, when i am editing the fields for my content types I have no choice for geofield_map?


Xubuntu 14.04 wanting to mount nonessential drive during boot

I have a 4TB NTFS external hard drive that I keep my Movies/TV on it. For some reason, If I boot Xubuntu without the drive plugged-into the computer it will give me an answer along the lines of "Unable to mount /media/tyler/TMC_MASTER_DRIVE the drive is unplugged or unavailable. Please press 'S' to skip mounting or 'M' for manual recovery"   Why am I getting this message? The drive has nothing essential for Linux on it (I can boot Xubuntu just fine after pressing S, it's just kinda annoying)


How do I import my questions from a "browser cookie-based" Stack Overflow account to an OpenID-based account?


Finding the general/closed form of $\sum_{k=1}^n k^a$

I recently noticed the following:  $$\sum_{i=1}^ni=\frac{n(n+1)}{2}$$ $$\sum_{i=1}^{n}i^2 = \dfrac{n(n+1)(2n+1)}{6} = \Bigg(\sum_{i=1}^ni\Bigg) \cdot \frac{2n+1}{3}$$ $$\sum\limits_{i = 1}^n i^3 = \Bigg( \frac{n(n+1)}{2}\Bigg)^2 = \Bigg(\sum_{i=1}^ni\Bigg)^2$$ $$\sum_{i=1}^ni^4=\frac{n(n+1)(2n+1)(3n^2+3n-1)}{30} = \Bigg(\sum_{i=1}^ni^2\Bigg) \cdot \frac{3 n^2 + 3 n - 1}{5}$$  It seems that the sums build on each other in some interesting way, and I'm interested in finding a general form. A cursory investigation found that $$\sum_{k=0}^n k^a = H_n^{(-a)}$$ where $H_n^{(-a)}$ is the $n$th hyperharmonic number of $r$th order. However, I doubt this would help because this (a) is sort of circular given the definition of $H_n$, (b) has no closed form, and (c) doesn't reveal the multiplicative connection among the terms.  Is it possible to derive a closed form for $\sum_{k=0}^n k^a$? Why or why not? And, of course, if one exists, what is it?


Badge progress indicator missing number counts

Something changed recently, and since a picture is worth a thousand words:    Until not very long ago, the "score" and "answers" labels were followed by numbers indicating the values of the progress bars underneath. So "score" might have "90/100" in this example. I'm not seeing that now for any of the badge progress indicators, so it looks like a recently introduced bug.


How to set the Euler angles(XYZ) of an arrow, from its components?

Given a vector(an arrow object) say $\vec A\,= \,P \hat{i} + Q \hat{j} + R \hat{k}$ , how to determine the corresponding Euler angles (XYZ) to be assigned to the vector so that it points in that specific direction. Or is there any another way to make that arrow point in that specific direction given by $\vec A$.


Unable to view the desktop after restart

After setting Java Path and do restart, I was unable to view the desktop, upper right corner controls and left side bar. I able to login with credentials. After that nothing can be done. Just only the purple color window. Unable to do my work. I have shared the image similar to my scenario.


I get up at 6 o'clock in the morning. I get up at 6 in the morning.   Can I use sentense 2?  When can I use only number without o'clock am pm etc?


How do I get a count of all the dead end streets?

I'm working in ArcGis 10.1 - Advanced and I wanted to know how can I identify and get a  count of the number of dead end streets in my road network?


Find all positive integers $a$, $b\neq1$ such that each of the equations:- $$x^2-ax+b=0$$ and $$x^2-bx+a=0$$ has distinct positive integer roots.  I have taken x and y as roots for first equation and p and q for the second equation and got two equations from  the sum of roots and product of roots but I am not able to progress further.Any idea will be appreciated


I am trying to use the etoolbox \ifblank (and its cousin \notblank), but I want to expand any macros in its test statement.  For example:  \documentclass{article} \usepackage{etoolbox}  \begin{document}  \newtoggle{longformt} \newcommand{\longform}{\toggletrue{longformt}} \newcommand{\iflong}[2]{\iftoggle{longformt}{#1}{#2}}  \newcommand{\quoteifnotblank}[1]{%     \notblank{#1}{``#1''}{}% }  % Try commenting this line. \longform  This should be completely blank if the form is short: \quoteifnotblank{\iflong{Some long quoted text}{}}  \end{document}   The problem here is that \notblank sees its argument of \iflong{Some long quoted text}{} as a string, not as code to be expanded, so the quotes always appear.  How do I expand arguments before they are passed to \notblank?


Understanding angular velocity in spherical polar coordinates

I'm a first year physics student and i've just learnt this equation for angular velocity in spherical polar coordinates:   $\omega=\dot{\phi}\mathbf{e_z}+\dot{\theta}\mathbf{e_\phi}$   The diagram i am using is on the RHS of this link:    I don't understand why this eqn is correct. Let's take the case where we imagine a vector going around in purely the xy-plane, a horizontal circle. Therefore $\theta=constant$ so in the above equation, $\dot{\theta}\mathbf{e_\phi}=0$. Now  $\omega$ should be a vector that only has $\mathbf{e_x}$ and/or $\mathbf{e_y}$ component since it is only moving in that xy plane. But, from the equation, we're left with $\omega=\dot{\phi}\mathbf{e_z}$. But $\mathbf{e_z}$ is perpendicular to xy plane, so $\omega$ which is always pointing in a direction on this horizontal circle should have no $\mathbf{e_z}$ component.   I feel like i'm missing something very key. Anyone help me get out?  Much appreciated.


How do i rescale a window in in all 4 directions?

I'd like to minimize/maximize any generic window in all 4 directions. How do I accomplish this? More specifically, I'd like to do this for iterm, but it would be nice if the solution is generic.


References on tensor algebra for machine learning?

So tensors come up a lot in machine learning in various settings. Any math major will have studied linear algebra heavily and it's usually much simpler to use linear operators and the corresponding notation when working with matrices. I assume that similar notation exists for tensors and that using it would bring the same benefits of simpler to memorize formulas and less clutter when doing computations. Are there any good books or other sources that covers this topic?  I'm interested in a theoretical treatment, i.e. the definition, theorem, proof style with the assumption that the reader can handle abstract math.


How to apply polymorphic function on vector of subclasses

Having some trouble with c++ and polymorphism. I realise this is a very simple question but I'm really struggling with the move from java to c++ particularly regarding pointers.  I have a 'Toy' class, and inheriting from that I have 'Doll' and 'Car' classes. In each class I have a function called printToy(); I have a vector which holds Doll, Toy and Car objects. I want to iterate through the vector calling 'printToy()' at each index however when I do this it calls the method from Toy class thus giving me an output of 'Toy Toy Toy' instead of 'Toy Doll Car'. Thanks to anyone who can help me!  Here is the example:   class Toy{     public:     void printToy(){         std::cout<<"Toy"<<std::endl;     } };  class Doll: public Toy{     public:     void printToy(){         std::cout << "Doll" << std::endl;     } };  class Car: public Toy{     public:     void printToy(){         std::cout << "Car" << std::endl;     } };   int main(){     std::vector<Toy> toys;      Toy toy;     Doll doll;     Car car;      toys.push_back(toy);     toys.push_back(doll);     toys.push_back(car);      for(int i = 0; i < toys.size(); i++){         toys[i].printToy();     }      return 0; }


Why are my keyframes not visible in the timeline?

I'm practicing on camera movements based on a tutorial by polyjord and I noticed that my keyframes are missing in the timeline at some point:  Q: How do I get my keyframes back?


Project is targeting .Net framework 4.6 which is not installed

...but it is.  Co-worker has installed VS 2015 (I am using 2013). He created a project targeting .net 4.6.  I grabbed the project from TFS and tried to open it, but got the following error message "The C# project MyProject is targeting ,net framework, Version=v4.6, which is not installed on this machine." .  I downloaded .net 4.6 and the targeting pack, then restarted my box.  Tried to open the project again and got the exact same message.  Am I going to have to install VS2015 or is there a better fix?  EDIT: I have the 'Targeting' pack and the below link is for a 'Multi-Targeting' pack.  I have yet to find a working link to a multi-targeting pack. Is there a difference?


sentence = "Hello" print sentence print sentence[:]   Both outputs the same thing, i.e. Hello  So, when and why to use/not use [:] ?  Thanks! :)


Is there a way to use an inline PNG image in an Outlook e-mail?

In my work as a developer I sometimes find myself sending details emails with screenshots to illustrate some point or problem. The content of these screenshots is often text. So knowing that PNG is much better at handle compression of images with text, I save my screenshots as PNG and insert them into my email. However whenever I check my sent mail, the images are clearly being sent as a JPG because they look horribly compressed.  I'm using Outlook 2003 as my email program. Is there some setting I can change to make Outlook send inline images as PNGs?


Which of these two statements is correct?  Did you know 1 in 4 kids have an undetected vision problem? Did you know 1 in 4 kids has an undetected vision problem?


Display opportunities associated with an OpportunityLineItem

I'm trying to display opportunities associated with an OpportunityLineItem on a Visualforce page on the OpportunityLineItem object   I have a problem in the select I do not know how to retrieve the OpportunityLineItem name in this request I have hard code the OpportunityLineItem name  public List<OpportunityLineItem> getOpp() {     return [SELECT TotalPrice, Opportunity.Name, Opportunity.StageName,                     Opportunity.Account.Name, Opportunity.id, Product2.Name              FROM OpportunityLineItem               WHERE Product2.Name='GenWatt Diesel 10kW'     ]; }


I am trying to make separate signal planes in eagle using the polygon tool. The problem is that when I draw the first polygon, regardless of whether I draw it small or large once I name it to GND and hit the "Ratsnest" tool, it will just occupy the whole space of the PCB leaving no space for other planes. How can I fix that?  Also I need one of the planes to be exposed copper, by drawing a polygon on either the bstop or tstop layers, I am getting what I need. The problem is that I don't know how to connect it to another part (say a transistor)?


Does infalling matter ever cross the event horizon?

Assume you are immortal, then say if you fell towards a blackhole,  to an observer far away you will appear to slow down as you approach event horizon and gradually come to stand still.  However for you, your time flow will appear normal and never stopped.  Now as we know that there cannot be two different times in the fabric of spacetime , its same time flowing slower near heavier objects than away from them.  In other words you'll have some very real time flow difference like your 1 second = years for far away observer.  Now as you fall towards blackhole you should see the rest of the universe speeding up like a fast forwarded video tape (ignore lack of actual vision due to light bending and other things). By this logic when you hit the event horizon the universe's time would be going infinitely faster and hence the blackhole would have evaporated by that time and universe would end before you cross the event horizon.  So how can you ever fall inside one?


Would it be possible to lighten the color of the new top bar?

The new top bar layout is fine, but the black color is very visually jarring/intrusive.  Is using a lighter color an available option?


How to randomly assign color to objects in an array

I have this stack of 1610 bricks. The stack was built by starting from one brick, and then applying 3 consecutive arrays on it (3 dimensions). I want each brick to be randomly assigned any of 4 fixed colors, but the node I came up with (picture) only seems to assign a single color to the entire stack. What did I do wrong, or what is an alternative way? PS: I want to keep the Arrays (if afterward I want to adjust the distance between the bricks, or the dimensions of the bricks)


In PostgreSQL, what is the difference between a "Stored Procedure" and other types of functions?

I understand the distinction between:   Scalar functions Set-Returning-Functions (SRF)s Internal functions Window functions Aggregate functions of all sorts User-Implemented functions (which in PostgreSQL can be implement in any language) Etc.   In SQL Server "Stored Procedures" are permitted through EXEC. What does that provide over any other function executed with SELECT that returns NULL?  When PostgreSQL gets Stored Procedures what will they bring me, and what is the formal distinction if any between a function and a stored procedure in the spec?  I read


Photons are bosons so, in principle, they are perfectly happy to exist together in the same state.  But is there a limit on how many can exists in a finte volume? Does QED or vacuum breakdown eventually kick in?


Showing that any linear operator can be written as a sum of Hermitian matrices

Let $(V, \mathbb{C})$ be a complex - valued vector space. Let $A$ be any linear operator acting on this vector space. Suppose that $B = \{|v\rangle_{k}\}_{k=1}^{n}$ is a basis set for $(V, \mathbb{C})$. Then, the linear operator $A$ may be written as $A = \sum_{k=1}^{n}A_{kj}|v_{k}\rangle \langle v_{j}|$ - in terms of it's outer product.  I would appreciate hints in the direction of assisting me in writing $A = B + iC$ where $B,C$ are Hermitian and $i$ is an imaginary number.


Quantum mechanical gravitational bound states

The quantum mechanics of Coloumb-force bound states of atomic nuclei and electrons lead to the extremely rich theory of molecules. In particular, I think the richness of the theory is related to the large mass ratio between the nucleon and the electron. This mass ratio leads to the Born-Oppenheimer approximation which gives rise to a complicated effective potential for the nuclei which posses many local minima: the molecules.  I wonder whether there are analogical phenomena in which the bound states are gravitational. It seems that if we take a collection of electrically neutral molecules and neutrinos, it should be possible to form a large number of bound states, in particular because of the large (not so long ago deemed infinite) mass ratio between molecules and neutrions. Of course neutrinos are highly relativistic and I can't tell how it affects things.  Now, even if we leave neutrinos alone, the typical size of such a bound state is  $$\frac{\hbar^2}{G  m^3}$$  where $m$ is proton mass. Google calculator reveals this to be 3.8 million light years. Holy moly! However, this is still much smaller than the observable universe. Can there be places in the universe sufficiently empty to contain such bound states? What would be the effect of general relativistic phenomena (expansion of space)? EDIT: I guess no place is sufficiently empty at least because background radiation is everywhere. Maybe these creatures will become relevant in a very distant future when the background radiation cools off considerably?  Summing up:     What is known about the quantum mechanics of gravitational bound states of electrically neutral molecules and neutrinos?   I'm tagging the question as "quantum gravity" since it involves gravity and quantum mechanics. Of course it is not quantum gravity in the usual sense of studying Planck-scale phenomena. I think the tag is still appropriate  EDIT: Gravitional bound states of molecules will often be unstable with respect to collapse to a van der Waals bound state (thx Vladimir for bring up the issue of vad der Waals interaction in the comments). However the lifetime of these states is very long.


Java: toString vs. string concatentation?

Is there a reason to prefer either string concatenation or invoking toString when converting objects to string representations?  Does string concatenation cause the object's toString method to be invoked?  String s; Properties p = System.getProperties(); s = p.toString(); s = "" + p;


Drop down site selector in Data Explorer lists IT Security, not Information Security

In the site selector on Data Explorer, Security Stack Exchange is still listed as IT Security, not Information Security.


If $f$ and $g$ are analytic in a domain $D$ such that $\overline{f}g$ is also analytic, what is $f$ and $g$?

I tried to solve it with Cauchy Riemann equations, let $f = u+iv,g=a+ib$ then we have $u_x = v_y,u_y=-v_x,a_x=b_y,a_y=-b_x$.  Consequently, since $f^{'}g$ is analytic also, we have Cauchy Riemann equation for this as well, $$(au+bv)_x=(bu-av)_y~~~~~~(au+bv)_y= -(bu-av)_x$$  After simplifying, we have $$au_x = bu_y ~~~~~~~bu_x = -au_y$$  Then i am kind of stuck here. The answer to this question is $f$ is a constant in $D$ or $g = 0$ in $D$.  Any help will be appreciated.


What have I done wrong? Flamed for asking a question?

Just look at what happened here, very simple question:


How do I extract text output of "system" function of c++, as it returns int value?

Hello thanks for looking into this, I need to extract text output of system function in std c++, I want the below program to return the text output that it prints in terminal, #include <bits/stdc++.h> using namespace std;  int main(int argc, char const *argv[]) {     system("git remote -v");     return 0; }   this gives on terminal origin  https://github.com/pawan-nirpal-031/Graphics-Lab.git (fetch) origin  https://github.com/pawan-nirpal-031/Graphics-Lab.git (push) orign   https://github.com/pawan-nirpal-031/Graphics-Lab.git (fetch) orign   https://github.com/pawan-nirpal-031/Graphics-Lab.git (push)  I want it to return this text output as a c++ string datatype.


Photo Streams from two or more iCloud accounts into same iPhoto library?

I'd like to connect iPhoto on my MBP to my photo stream and my wife's photo stream. We each have our own Apple ID and iCloud account. Can iPhoto connect to multiple iCloud photo streams?  Thanks.


Why does BitLocker want a recovery key instead of a password?

I have a .vhd image of a BitLocker encrypted drive.   When I mount and double click the drive, BitLocker wants me to enter a 48-digit recovery key and doesn't ask for a password.  Why is that so and how can I enter a password instead?    Note: I don't have either the key or the password of this drive. I'm trying to brute force the password using forensic software.


how to change this dynamic rows to columns

I have following columns (it is dynamic, more rows in table with same ID).Type can be duplicate.  +--------------+---------+------------ | ID           | TYPE    | VALUE     | +--------------+---------+------------ |            1 | A     | one         | |            1 | B     | gas         | |            1 | C     | age         | |            1 | D     | two         | |            1 | E     | gas         | |            1 | F     | age         | |            2 | G     | env         | |            2 | H     | mas         | |            2 | I     | sat         | +--------------+---------+-----------+   I am trying to get following output  ID | A  | B | C | D | E | F | G| H | I 1    one  gas age two gas age null null null 2    null null null null null env mas sat   How it is possible in Mysql


What do solid/striped lines on a wire indicate?

What do solid or dashed lines on a wire indicate?  Is there a difference between the solid and dashed indicators?


Issue with DIV overlay within CSS style, image over image

I have CSS style within HTML. A responsive image grid is produced from SQL images. I am trying to create a bookmark overlay to add as favourite.   I've tried a number of tutorials.  Also, have copied the image DIV and changed the Z position to place above the image, but cannot see the overlay image at all.   style sheet:  #gridview {   text-align:center;  } div.image {   margin: 10px;   display: inline-block;   position: relative;   z-index: 1; } div.image img {   width: 100%;   height: auto;   position: relative;   border: 1px solid #ccc;   z-index: 1; } div.image img:hover {   box-shadow: 0 5px 5px 0 rgba(0,0,0,0.32), 0 0 0 0px rgba(0,0,0,0.16);   z-index: 1;   position: relative; } div.bookmark {   margin: 10px;   display: inline-block;   position: absolute;   z-index: 3; } div.bookmark img {   width: 100%;   background-image:       url("https://images.justwatch.com/static/compile_jw/assets/ribbon-filled.png");   height: auto;   position: absolute;   z-index: 3; } div.bookmark img:hover {   box-shadow: 0 5px 5px 0 rgba(0,0,0,0.32), 0 0 0 0px rgba(0,0,0,0.16);   z-index: 3;   position: absolute; } #grid {   margin-bottom:30px; } @media screen and (min-width: 1224px) {   div.image {     width: 154px;   } } media screen and (min-width: 1044px) and (max-width: 1224px) {   div.image {     width: 154px;   } } @media screen and (min-width: 845px) and (max-width: 1044px) {   div.image {     width: 154px;   } }   PHP / HTML page:  var tbl_body = ""; for (var i = 0; i < data.length; i++)  {   var tbl_row = "";   var t = i;   tbl_row += ("

 ");   tbl_row += ("
");   tbl_body += tbl_row  } return tbl_body;   The outcome should be the poster image, with overlay of the bookmark image in the top corner of each poster.


Empty intersection in chain rule for probability

I am looking at the expansion of the  for probability. $$ P\left(\bigcap_{k=1}^nA_k\right)=\prod_{k=1}^nP\left(A_k\middle|\bigcap_{j=1}^{k-1}A_j \right) $$ if n=2, then the terms will be: $$ P\left(A_1,A_2\right)=P\left(A_1\middle|\bigcap_{j=1}^{0}A_j\right)P\left(A_2\middle|\bigcap_{j=1}^{1}A_j\right)=P\left(A_1\right)P\left(A_2\middle|A_1\right) $$ What is the definition of the intersection where top limit is smaller than bottom limit? $$ \bigcap_{j=1}^{0}A_j=\hspace{1mm}? $$ An empty sum = 0 while an empty product = 1. Is this an empty intersection?  Thanks for the help!


Highlight text in code listing while also keeping syntax highlighting

I’m using the listings package for code listings. Now I try to highlight some part of the code using \hl from the soul package.  Here’s an example of a resulting query where the injected part of a SQL injection should be highlighted:  \begin{lstlisting}[escapechar=@,language=SQL] SELECT name, password FROM users WHERE name='@\hl{' UNION SELECT "10", 1 \#}@'; \end{lstlisting}   But inside the highlighted part the SQL syntax highlighting is not applied.  So I tried to use \lstlinline for the code part inside \hl as well but it didn’t work:  \begin{lstlisting}[escapechar=@,language=SQL] SELECT name, password FROM users WHERE name='@\hl{\lstinline[language=SQL]$' UNION SELECT "10", 1 #$}@'; \end{lstlisting}   Although this \lstinline part works outside the lstlisting block, it doesn’t work inside it. The error I get for that particular line is:     Extra }, or forgotten \endgroup.   Maybe I’m just missing just some special syntax to get this working. Or is it not possible at all to get proper syntax highlighting for the \hl-highlighted part as well?


One click shutdown Ubuntu and load into alternative bootup

I have a dual boot system with Ubuntu 11.04 and Windows 7.  My GRUB bootloader defaults to Ubuntu. I mainly use Ubuntu, but I occasionally need to bootup Windows to do a few things.  If I need to do something in Windows I can "shutdown" Ubuntu and select Windows 7 in the bootloader. However, it would be more efficient if I could do this in one click from Ubuntu.   Is it possible to press a key in Ubuntu which means "Shut down, and then boot into Windows"? (or for that matter Shut down and boot into any non-default bootup)


Prove:$|x-1|+|x-2|+|x-3|+\cdots+|x-n|\geq n-1$   example1: $|x-1|+|x-2|\geq 1$  my solution：(substitution)  $x-1=t,x-2=t-1,|t|+|t-1|\geq 1,|t-1|\geq 1-|t|,$  square,  $t^2-2t+1\geq 1-2|t|+t^2,\text{Since} -t\leq -|t|,$  so proved.  question1 : Is my proof right? Alternatives?  one reference answer:   $1-|x-1|\leq |1-(x-1)|=|1-x+1|=|x-2|$  question2 : prove:  $|x-1|+|x-2|+|x-3|\geq 2$  So I guess:( I think there is a name about this, what's that? wiki item?)  $|x-1|+|x-2|+|x-3|+\cdots+|x-n|\geq n-1$  How to prove this? This is  question3. I doubt whether the two methods I used above may suit for this general case.  Of course, welcome any interesting answers and good comments.


What would someone who is prejudiced against a country be called?

The reason why I asked was because I saw a movie and that question came up in my mind.  Racist doesn't seem to be the right word, as country doesn't necessarily imply race.  An example of how it might be used would be:     This movie was about a group of ______ who victimised immigrants from   the neighbouring country.


Why is this non-linear transformation not a Lorentz transformations? It does preserve $x^2 + y^2 + z^2 - c^2t^2 = x'^2 + y'^2 + z'^2 - c^2t'^2 $

The Lorentz transformation is a mapping of the $x', y', z',$ and $t'$ coordinates relative to $x, y, z, t$ that preserves the speed of light:  (1) $x^2 + y^2 + z^2 - c^2t^2 = x'^2 + y'^2 + z'^2 - c^2t'^2 = 0$  If $K'$ is moving with speed $v$ in the $x$ direction relative to $K$ (so that $K$ is moving with speed $-v$ in the $x$ direction relative to $K'$), and we use the Galilean transformation, we get an erroneous  (2) $x'^2 + y'^2 + z'^2 - c^2t'^2 = -2vxt + v^2t^2$  which is NOT equal to zero, and hence does not describe a sphere of radius $ct$ emanating from the origin of $K'$, but something else (I'm pretty sure it's a sphere that's been shifted negatively in the $x$ direction by a small amount, relative to $K'$). The Lorentz transformation says we modify both the $x' = x - vt$ and the $t' = t$ relationships in order to ensure that we end up getting 0.  However, as a naive mathematician, I look at equation (2) and think, "Ok, so we've got to modify the rule for $x'$, or $t'$, or both, to get rid of that nasty $-2xvt + v^2t^2$ term in the $x'$ rule. Why not just set $t'$ up so that instead of coming out to $-c^2t^2$, it actually comes out to $-c^2t^2 + 2vxt - v^2t^2$, so that the extra terms cancel out?" I naively went ahead with this idea and I got the following coordinate transformation:  $$ x' = x - vt\\ y' = y\\ z' = z\\ t' = \frac{1}{c} \sqrt{(v^2 + c^2)t^2 - 2vxt} $$  If you plug this into (1), you get 0 like you're supposed to.  Now, I haven't been able to find an explanation as to why this transformation is unsatisfactory. Of course, it's no longer linear - but is there some basic reason why the transformation must be linear? Obviously this transformation satisfies Einstein's postulate about the constancy of the speed of light for all inertial observers.  Presumably, then, it must violate the first postulate, regarding the equivalence of all physical phenomena for inertial observers - otherwise we'd need more information in order to derive the Lorentz transformation, which I think is supposed to be derivable from the two postulates alone.  So, in the end, I have one question I'm trying to answer:   Does this transformation violate equivalence for inertial observers? Why? (ideally, someone could give me an example of a force that suddenly appears in my coordinate system that didn't already exist in the other coordinate system)


grep the man page of a command for hyphenated options

Suppose I want to know the usage of -i switch in grep command without scrolling. I need the specification just for that command or at least see the screen show that first. So how? As you can say that in general not just for grep -i.


What is the longest additional time ever added in Europe's top five leagues?

What is the longest additional time ever used in Europe's top five leagues? Please mention the details of the match.


Viruses at this period of time do not fit the current definition of life.   Much of the reasoning behind this is that we currently believe that all life must be made up of cells.  Also, many biologist/scientists say that viruses are not living because all they are is just chemicals carrying out their predefined chemistry.   Has anyone every considered the fact that cells, the supposed building blocks of life, themselves simply only carry out predefined chemical actions? All actions cells carry out are chemically driven, not consciously or spiritually driven. Cells do not make choices, they follow chemical directions present in their DNA and RNA. Viruses act very similarly, following the action transcribed in their DNA or RNA.   How can we really even draw a defined line of what life is?


Is there any way of automating the startup of applications on virtual desktops on Windows 10?

Every time I start my computer I need to go to each different virtual desktop that I have and start the applications that I usually use on that virtual desktop, this is specially cumbersome for me because I use two monitors and I need to start two applications per virtual desktop for each monitor and then drag them to the correct monitor.   Is there any way I can automate this task?


A mathematically illogical argument in the derivation of Hamilton's equation in Goldstein

In the book of Goldstein, at page 337, while deriving the Hamilton's equations (canonical equations), he argues that  The canonical momentum was defined in Eq. (2.44) as $p_i = \partial L / \partial \dot q_i$; substituting this into the Lagrange equation (8.1), we obtain $$ \dot p_i= \frac{\partial L}{\partial q_i} \tag{8.14}$$ so Eq. (8.13) can be written as $$ dL = \dot p_i dq_i + p_id \dot q_i + \frac{\partial L}{\partial t}dt \tag{8.13′}$$ The Hamiltonian $H(q,p,t)$ is generated by the Legendre transformation $$ H(q,p,t) = \dot q_i p_i - L(q, \dot q, t), \tag{8.15}$$ which has the differential $$ dH = \dot q_i d p_i - \dot p_i d q_i - \frac {\partial L}{\partial t}, \tag{8.16} $$ where the term $p_i d \dot q_i$ is removed by the Legendre transformation. Since $dH$ can also be written as $$ dH = \frac{\partial H}{\partial q_i}d q_i + \frac{\partial H}{\partial p_i}d p_i + \frac{\partial H}{\partial t}d t, \tag{8.17} $$  However, if $H$ is defined to be a function of $q,p,t$, then how can we define $H(q,p,t) = \dot q *p - L(q,\dot q,t)$, i.e $\dot q$ is not an argument of $H$ whereas it is in its definition. Moreover, when he is taking the differential of $H$, he argues that $pd\dot q$ is removed, but he does not say why. I mean mathematically speaking this whole argument is plan wrong, as far as I can see, so assuming that it is not the case, what am I missing in here ?


How can I modify the power button behaviour?

I want the PC to shut down without any dialogue, but let time for the applications to close properly.  One solution is, to change powerbtn.sh to: shutdown -h now but that does not wait for all applications to close.


Quadratic form under $\mathbb{C}$ finite-dimension vector space always have a nonzero vector that yields zero?

Let $ V $ be a vector space of finite dimension on $\mathbb{C} $ and $ \dim(V) \gt 1 $. Show that for every quadratic form $ q : V \to \mathbb{C} $ there exists $ 0 \neq v \in V $ such that $ q(v) = 0 $.  It certainly has something to do with the fact that we are in $\mathbb{C} $ and not $ \mathbb{R} $, but I'm since $ q $ can be represented by any non-singular complex matrix, I don't know how this is even possible.  (edit: V is of finite dimension)


How to get current UTC time in seconds in Python?

I would want to get current UTC time formatted to HH:MM:SS. What is the easiest way to do it?


Every answer I've found to get a video's duration with ffmpeg contains grep, which cmd doesn't natively have.  I know there's a "Grep for windows" thing, but I'd rather use a function that comes with the command line.  So when I do ffmpeg -i input I get  Input #0, flv, from 'vid_test001.flv':   Metadata:     creationdate    : Fri Sep 19 15:58:17   Duration: 00:00:12.44, start: 0.000000, bitrate: 806 kb/s     Stream #0:0: Video: flv1, yuv420p, 320x240, 1k tbr, 1k tbn, 1k tbc     Stream #0:1: Audio: nellymoser, 22050 Hz, mono, flt   I'd like to to get the Duration from this, which is "00:00:12.44" in this case


As my built-in NIC was not supported by Ubuntu out-of-the-box I was forced to use a USB NIC for temporary installation-time Internet connection.  And the USB NIC has taken the eth0 name making the built-in NIC to become eth1.  Sure, this doesn't really matter but just for the system "prettiness" I would like eth1 to become eth0 letting any newly attached NIC to become eth1.  Is this possible?


Stock dividend payments; how is payment made?

Dividend payments; where do they get paid into?


bash -c in subshell gives EOF parsing error

Why does the following script work as expected (prints hello)  #!/bin/bash  foo=$(bash -c 'echo hello') echo $foo   while this script:  #!/bin/bash  cmd="bash -c 'echo hello'" foo=$($cmd) echo $foo   gives the following error:  hello': -c: line 0: unexpected EOF while looking for matching `'' hello': -c: line 1: syntax error: unexpected end of file


I dont know my user password and have tried many suggestions to add user ,change password etc without avail,ls home produces no such file or something ,although I can open Home on the desktop.Can I reinstall over the existing installation without losing data links etc and change the user password then Brian


I have come across this passage on BBC news website.   "Video and pictures taken by resident Malcolm Carter and sent to the BBC showed the fire that burned on the terrace area earlier on Friday morning had been put out and significantly less smoke was coming from the building."  I do not understand why no articles or an S at the end were used for the word "video". Isn't video a countable noun? Shouldn't it be:  "A video and pictures taken by ..."  or   "Videos and pictures taken by ..."  Is there a grammar rule that I do not understand?


We can a make a directory named $"dollars"&<>\dogs if we surround it with single quotes like the following   mkdir '$"dollars"&<>\dogs'   However, what if I want to include a single quote in the directory name?  If I want my directory name to be $"dollars"&<>/dogs'  Then How can I use the single quoting method  do this ?  I tried to do   mkdir '$"dollars"&<>/dogs'' But this didn't work for and also   mkdir ''$"dollars"&<>/dogs'' didn't work either.  I even tried to put a backslash before it, but there was no use !


Field Show that F is a field under + and $\cdot$ and F = $\{a + b\sqrt{3}\} | a, b \in \mathbb Q\}$

Show that F = $\{a + b\sqrt{3}\} | a, b \in \mathbb Q\}$ is a field under the operations + and $\cdot$, where + is given by $(a + b\sqrt{3}) +(c + d\sqrt{3}) = (a + c) + (b+d)\sqrt{3}$ and $\cdot$ is given by $(a + b\sqrt{3}) \cdot(c + d\sqrt{3}) = (ac + 3bd)+ (ad + bc)\sqrt{3}$  Do I just have to show it satisfies all the $A1 - A4, S1 - S4$ axioms?    For example:  $A1 = u + (v + w) = $  $$=(a + b\sqrt{3} + ((c + d\sqrt{3}) + (e + f\sqrt{3})) = (a + b\sqrt{3}) + ((c + e) + (d + f)\sqrt3{}))$$  $$= (a + c + e) + (b + d + f)\sqrt{3}$$  Also:  $$(u + v) + w = ((a + b\sqrt{3}) + (c + d\sqrt{3}) ) + (e + f\sqrt{3})$$  $$= (a + c + e) + (b + d + f)\sqrt{3}$$  Satisfies one of the eight of the axioms. Is this what I am suppose to do?    If so, I don't get how to check the scalars for example  S1: $r(u + v) = ru + rv$  $$= r((a + b\sqrt{3}) + (c + d\sqrt{3}))$$  $$= r((a+c) + (b+d)\sqrt{3})$$  Unsure what to do after this


Let A and B be sets. Show that A is a subset of B if and only if for any set C, one has A union C is a subset of B union C.

Can you verify my proof if it is right?  Let $A$ and $B$ be sets.  (a) Show that $A$ is a subset of $B$ if and only if for any set $C$, one has $A$ union $C$ is a subset of $B$ union $C$. (b) Show that $A$ is a subset of $B$ if and only if for any set $C$, one has $A$ intersect $C$ is a subset of $B$ intersect $C$.  Edited Solution :  (a)  (=>) Given A is a subset of B, this implies A U B = B. Given a set C, A U B U C = B U C. Since A is a subset of B, this implies A U C is a subset of B U C.      Solution 1 :(<=) Given A U C is a subset of B U C , For A U C , x is a member of A U C . For B U C, x is a member of B U C. Suppose x is a member of A but not a member of B, meaning A is not a subset of B. Therefore , A U C is not a subset of B U C. Hence, A must be a subset of B.      Solution 2 :(<=) Given A U C is a subset of B U C, For A U C, x is a member of A U C and for B U C, x is a member of B U C. Suppose C is a disjoint set. Since A U C is a subset of B U C, it follows that A is a subset of B.  (b) (=>) Since A is a subset of B , it follows that A U B = B. [A intersect C] is a subset of A and  [B intersect C ] is a subset of B by definition of intersection. Let x be member of A and member of C. Since [ A intersect C ] is a subset of A, x must be in A. Let x be a member of B and member of C. Since [ B intersect C ] is a subset of B, x must be in B. Therefore, A intersect C is a subset of B intersect C.  (<=) Since A intersect C is a subset of B intersect C, suppose we let Set C be a subset of B and a subset of A as well. C is a subset of A implies A intersect C is equals to C. C is a subset of B implies B intersect C is equals to C as well. Since A intersect C is equals to B intersect C, A is a subset of B.


content made by .append() doesn't work in function of jQuery

HTML
     <button type="button" class="close" data-close="messageBox" aria-label="Close">              </button>          Error:     Enter a valid email address
   jQuery  message_box({     id: "messageBox",     content: "Please enter a value to required field(s)",     hint: "Error:",     icon: "glyphicon-exclamation-sign",     class: "alert-danger" });   JS  function message_box(options){     var options_defaults = {         id: false,         content: "Message content",         hint: "Message hint",         icon: false,         class: false     }     var options = $.extend(options_defaults, options);     if(options.id != false) {         if(options.icon != false) options.icon = ' ' + options.icon;         if(options.class != false) options.class = ' ' + options.class;         $message_box = $('#'+options.id).empty();         $message_box.append($('<button></button>', {type: 'button', class: "close", 'data-close': options.id, 'aria-label': "Close"}).append($('', {class: "glyphicon glyphicon-remove", 'aria-hidden': true})))             .append($('', {class: "glyphicon" + options.icon, 'aria-hidden': true}))             .append($('', {class: "sr-only"}).html(options.hint))             .append($('').html(" "+options.content))             .attr("role", "alert").removeClass().addClass("alert" + options.class);     } } $(document).ready(function() {     $('.close').click(function() {         $id = $(this).attr('data-close');         $(this).closest('#'+$id).hide();     }); });   the 'message_box' function removes the contents inside the div and creating a new content just like in the HTML.  when I test, the div with the id=messageBox closes/hide when I click the button. but when the jQuery runs and removes the content inside the messageBox then create a new one with the same structure. and now when I click the button, it doesn't hide the div anymore. when I inspect the original HTML and the Appended content, I don't see any difference in them.  APPENDED VER.
     <button type="button" class="close" data-close="messageBox" aria-label="Close">              </button>          Error:      Please enter a value to required field(s)
   Thanks for anyone that can help me!


UK VISA Refusal! Submitted All Necessary Documents! (Graduation Ceremony In London)

Now i need to re-apply! what are the steps that i can take to make my application and all documents strong and not get rejeceted.   As per i have my graduation ceremony and i definitaly want to attend it.


Non abelian groups of order $p^3$ upto isomorphism

This question is different from all the similar questions on this site. In this Question I ask for the proof or reference for proof of the following problem


Why is my C++ function that deletes a pointer safely throwing an error?

everyone. Recently, I have been learning how to develop a function to delete a pointer safely. However, something weird happened when I made my safe_delete() code shown below. #include <iostream> using namespace std;  template <class T> void safe_delete(T* ptr) {   delete ptr;   ptr = NULL; }  int main() {   int var = 10;   int* ptr = &var;   safe_delete<int>(ptr); }  Running the code in repl.lt (I am afraid that it might cause a memory leak), here is what I get: munmap_chunk(): invalid pointer exited, aborted  What does the above error mean? I currently guessed that munmap_chunk() is some function used in the implementation of delete. The above source code is taken from stack overflow's answers. Something is weird. I just added templates to the function, which I believe is correct. Can anyone tell me why is this error happening?


Why is the last line of my code not printing? Also, what's the simplest way for me to round numbers to 2 decimals?

When running my program, the last line displaying yearly gas expense is not showing... what have I done wrong? Also would like some help rounding figures to 2 decimal points...  I tried implementing a few strategies but none of them worked. Any help is appreciated!  public class GasExpenses { public static void main(String[] args) {  //Use scanner in order to retrieve user input. Scanner keyboard= new Scanner(System.in);  //Declare variables. int milesPerWeek; double milesPerGallon,costOfGas;   System.out.println("GAS EXPENSES");  //Get user input. System.out.println("How many miles do you drive a week?"); milesPerWeek = keyboard.nextInt();  //Get user input. System.out.println("How many miles per gallon does your auto get?"); milesPerGallon=keyboard.nextDouble();  //Get user input. System.out.println("What is the current cost of gas?"); costOfGas=keyboard.nextDouble();  //Calculate miles per year. int milesPerYear=(milesPerWeek*52); //Display calculated yearly mileage. System.out.println("At " + milesPerWeek + "miles per week, you travel "+ milesPerYear + " miles per year.");  //Calculate and display calculated weekly & yearly gallons of gas used. double gallonsPerWeek=(milesPerWeek/milesPerGallon);  System.out.println("Gallons per week:" + gallonsPerWeek); double gallonsPerYear=(gallonsPerWeek*52); System.out.println("Gallons per year:" + gallonsPerYear);  //Calculate and display calculated weekly & yearly gas expense. System.out.println("With gas at $" +costOfGas + " per gallon, you will spend: "); double weeklyGasExpense=(costOfGas*milesPerWeek); System.out.println("Gas expense per week: $" +weeklyGasExpense); double yearlyGasExpense=(costOfGas*milesPerYear); System.out.println("Gas expense per year: $" +yearlyGasExpense);  //Calculate and display calculated weekly & yearly gas expense based on increased gas price. double costIncrease= (costOfGas+1); System.out.println("If gas goes up by one dollar per gallon to $" + costIncrease +(" per gallon, you will spend:")); double weeklyIncreasedGas=(costIncrease*milesPerWeek); double yearlyIncreasedGas=(costIncrease*milesPerYear); System.out.println("Gas expense per week : $" +weeklyIncreasedGas); System.out.print("Gas expense per year : $" +yearlyIncreasedGas); }}


How to split string by forward slash in SQL Server?

There is no default split function in SQL Server 2012 that I'm using.  I want to split the string (ex: /Folder1/Folder2/) by /.   if string is /Folder1/ then output should be Folder1, if string is /Folder1/Folder2/ then output should be Folder2, if string is /Folder1/Folder2/Folder3/ then output should be Folder3.


Is it gramatically incorrect to begin a sentence with 'But'?

I am wondering because I was told that it is, but from what I've seen it's pretty widely used.  Thanks!


It's a bad practice to use unicode in math?

Recently, I discovered the unicode-math package that permits to insert unicode characters inside math environment. This permits, even in its basic configuration, to use all the greek letters and most of the math operators directly in the source file reducing the amount of code like \alpha, \gg, \leq, etc. inside your equation making even complex equation readable directly in the code. This is obviously an huge advantage IMHO but is it without any risk and without drawbacks?  The risk that comes to my mind is to confuse one character for another very similar. While there isn't this possibility using macro, it could happen typing it directly.  The drawback that comes to my mind is that the symbol is fixed, in the sense that its appearance is glued to its semantic meaning. This is a things that usually one should tries to avoid, if possible. i.e. amsmath package gives us six different dots (\dots,\dotsc,\dotso,\dotsb,\dotsi,\dotsm) that have the same appearance but different semantic meaning and one can change the appearance of the symbol of one semantic meaning without affecting the others.  Probably I wrote something wrong or there are more things to say on the subject but my question still remains: is it a bad practice to use unicode-math? If not, what is the best way to use it? There are risks? If yes, what they are? There are drawbacks? If yes, what they are?   I know that that discussion should be posted on meta but this is a discussion about a package, so I think that it's better to post it here. If this isn't the place where asking such a things, please move the question or write in the comments where should I post it.  Edit: As pointed out in by Ulrike Fischer in , I completely miss the whole picture about unicode-math. But my question still remain even if it should be reformulated into this one: What are the pros an cons of using unicode inside math instead of LaTeX macros?  As pointed out in the comments, this could be read as on opinion based question, it is not. I'm not asking which solution is the best in your opinion. I'm asking what are pros and cons of using unicode inside math instad of the classical macros that LaTeX offers.


Linking stackexchange account with answers that have cited papers without access while applying for research opportunities

I am a sophomore currently and was active pre-university on one of the daughter sites. While answering questions, I would reach upon specific research papers, paywalled. I broke through them using means that are not so legal. My answers reflect the primary reasons and interests as to why I want to research in that specific field are on that account. Is it advisable to refer to my StackExchange account in my cover letter? I have cited all articles properly; however, screenshots have been posted in many answers.


Proving the inequality $2^n ≤2^{n+1}−2^{n−1}−1$

I've tried multiplying each side by $2^n$, factoring out a 2, but I find myself going in a circle. What's the best way to solve this?  $2^n ≤2^{n+1}−2^{n−1}−1$.   For all integers n


Grouping or Clustering Points that are within 45 miles of each other using ArcGIS Desktop?

I have a project in ArcGIS (ArcMap 10.2) where I want to identify naturally occurring dense spots of points and then form groups in that dense area, where points are within 45 miles of each other. This would mean that not so dense areas will be left out and not become part of any group?   I don't have access to Point Density tool. I run Python code for Grouping Analysis but I get errors due to Python or GIS version mismatch.


3 particles A,B and C are situated at the vertices of an equilateral triangle ABC of side d at t=0 .

My question is related to the , with a slight modification.  Question: Three particles, $A$, $B$ and $C$, are situated at the vertices of an equilateral triangle $ABC$ of side length $d$.  Starting at $t=0$, each particle moves with a constant speed $v$.  $A$ always has its velocity along $AB$, $B$ along $BC$ and $C$ along $CA$. At what time will the particles meet?  Modification: What would be the equation of the curve followed by the bodies? (If it can be found; provide minimal amount of variables to find it if currently available ones don't suffice.)  Additional challenge: Could this entire problem (with the added modification) be generalized for an $n$-sided polygon following a particular path in each case?  My understanding of this: So in the link above, you can see that it is described as a logarithmic spiral but how do we prove this? Moreover it references a pursuit curve, how do we know this?


Some of my coworkers are having troubles on their Macs - DNS resolution does not work under Mac OS X. They're running Snow Leopard 10.6.8. They can use DNS in a Windows 7 virtual machine (VMware Fusion 3.1.3) running under OS X. The computers are 15" MacBook Pros, early 2011 model.  Things they've tried that have not worked:   turning airport on/off rebooting using wired connection instead wifi deleting connection credentials and adding it again turning off Mac firewall using fixed static IP manually setting DNS servers restarting mDNSResponder the fixes from    EDIT response Martín's answer:  • Can you ping the DNS you want to use?  $ ping apple.com ping: cannot resolve apple.com: Unknown host   • What is/are the IP address(es) of the DNS(s) you want to use?  This is a company DNS server that is given with DHCP, it works well for other people. I've also tried Google's 8.8.4.4 and 205.171.3.65 (which I found from GRC's DNS Benchmark to be the fastest).  • Have you tried using 8.8.8.8 (google) or any of the OpenDNS    208.67.222.222 or 208.67.220.220?  It doesn't work, see Google Chrome output:     The server at www.apple.com can't be found, because the DNS lookup failed. DNS is the network service that translates a website's name to its Internet address. This error is most often caused by having no connection to the Internet or a misconfigured network. It can also be caused by an unresponsive DNS server or a firewall preventing Google Chrome from accessing the network.   • Can you ping those hosts?  $ ping 8.8.8.8 PING 8.8.8.8 (8.8.8.8): 56 data bytes 64 bytes from 8.8.8.8: icmp_seq=0 ttl=58 time=3.925 ms   • creating a blank user  A guest user account was created, the DNS issue was still there when using the guest account.  • nslookup and dig both work fine  $ nslookup www.apple.com 8.8.8.8 Server:  8.8.8.8 Address: 8.8.8.8#53  Non-authoritative answer: www.apple.com canonical name = www.isg-apple.com.akadns.net. www.isg-apple.com.akadns.net canonical name = www.apple.com.edgekey.net. www.apple.com.edgekey.net canonical name = e3191.c.akamaiedge.net. Name: e3191.c.akamaiedge.net Address: 184.24.141.15      $ dig @8.8.8.8 www.apple.com ; <<>> DiG 9.6.0-APPLE-P2 <<>> @8.8.8.8 www.apple.com ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11298 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0  ;; QUESTION SECTION: ;www.apple.com.   IN A ;; ANSWER SECTION: www.apple.com.  1041 IN CNAME www.isg-apple.com.akadns.net. www.isg-apple.com.akadns.net. 38 IN CNAME www.apple.com.edgekey.net. www.apple.com.edgekey.net. 8794 IN CNAME e3191.c.akamaiedge.net. e3191.c.akamaiedge.net. 17 IN A 184.24.141.15 ;; Query time: 4 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Tue Oct 4 09:25:28 2011 ;; MSG SIZE  rcvd: 158   • also flushing the DNS cache was done but it didn't help  sudo dscacheutil -flushcache sudo killall -HUP mDNSResponder   EDIT 2:   $ cat /etc/resolv.conf # # Mac OS X Notice # # This file is not used by the host name and address resolution # or the DNS query routing mechanisms used by most processes on # this Mac OS X system. # # This file is automatically generated. # domain {redacted}.com nameserver 8.8.8.8 nameserver 208.67.222.222


After beating the final boss, can I return to the original castle?

I've defeated the final boss in a very cheesy way (Babarian Tank with a lot of Damage Return).  Now I have a hard time even getting some money in the castle of New Game Plus - is there some way to return to the old "easy" castle ?


Windows 7 network icon says "Disconnected" when connected

Since I built my PC, the network icon in Windows has always displayed as if there were no internet connection, despite there being an active connection to the internet.  I've tried uninstalling the Ethernet device driver and installing the latest version, but that did not help. I've disabled all unused network adapters. I've also tried clearing the tray icon cache using the method detailed here: . Unfortunately the issue still persists. I'm not sure what to try next.   I was reading this article:  and am thinking the issue might be linked to NCSI in Windows, but am not sure how to troubleshoot if this is the case.


Faithful representation implies group is cyclic

Suppose there is a faithful representation $\rho:G\to SL_2(\mathbb{R})$. Prove that $G$ is cyclic.   I know there has to be something special about its representation being special (no pun intended) because e.g. the Klein 4 group has a non-special representation. Also it has to be important that it's in two dimensions, because $SO(3)$ contains non-cyclic groups.  Apart from that, I haven't really made any progress. Any hints?


Find the coefficient of $x^9$ in the expansion of $(1+x)(1+x^2)(1+x^3)...(1+x^{100})$

The coefficient of $x^9$ in the expansion of $(1+x)(1+x^2)(1+x^3)...(1+x^{100})$.  I tried the following concept, how to sum 9 using 1-9 only without repetition.  1:9, 2:1+8,3:7+2, 4: 6+3, 5: 5+4,  6:1+2+6 ,7:1+3+5, 8:2+3+4  The answer is 8.  How will it be solved using Binomial theorem.


Lost OS(windows 10) and partitions(which had all my files) while installing ubuntu 14.10(which now, I upgraded to 15.04 since testdisk did not work in 14.10). I would like to know if there is any chance to recover my lost files from the partitions which I had before. Now all the partitions are combined to one 991 GB partition hard disk with just ubuntu 15.04 in it. I am new user of Ubuntu. Please help me. Thank you. Tried Testdisk did not work.


I'm struggling with finding this sum:  $$\sum\limits_{i=0}^{\infty}\frac{i}{4^i}$$  Any pointers would be greatly appreciated.  I have not found any information of use elsewhere, but maybe I am using the wrong search terms.


Ubuntu 17.10 / Gnome 3: Hide users from login screen

I have a few users in my system which I only use for specific applications, but I never want to log in as these users from the login screen. I would like to keep the users, but remove them from the list. Alternatively, setting myself as the default login user would also work. How do I achieve this?  I've tried creating a file for the user in /var/lib/AccountsService/users/EWF (EWF is the user I want to hide) with the following contents:  [User]   Language=    XSession=gnome   SystemAccount=true   But the file just gets deleted after I restart, and the user still appears in the login list.  I've also tried adding the following section in /etc/gdm3/custom.conf  [Greeter] Exclude=user1,user2,nobody   but that didn't help either.


SMTP mail error 452 4.3.1 Insufficient system storage

I have a server which uses Postfix as the mail system. The issue I am having is I am not able to send or recieve email. If I send an email I get an instant reply from the server which says:  Subject:    test Sent:   16/05/2011 19:08  The following recipient(s) could not be reached:  'myemail@mydomain.com' on 16/05/2011 19:08 452 4.3.1 Insufficient system storage   I have check the following:  Disk space, there are gigabytes of free space on all partitions. Mailbox quotas, there are no quota,s set on any mailbox.  I cleared all the mail logs and rebooted the server but I still cannot send email. does anyone have any pointers for me to look at next.  I have looked at the main.cf file and here are the results:  virtual_mailbox_domains = $virtual_mailbox_maps, hash:/var/spool/postfix/plesk/virtual_domains virtual_alias_maps = $virtual_maps, hash:/var/spool/postfix/plesk/virtual virtual_mailbox_maps = hash:/var/spool/postfix/plesk/vmailbox transport_maps = hash:/var/spool/postfix/plesk/transport smtpd_tls_cert_file = /etc/postfix/postfix_default.pem smtpd_tls_key_file = $smtpd_tls_cert_file smtpd_tls_security_level = may smtpd_use_tls = yes smtp_tls_security_level = may smtp_use_tls = no smtpd_sender_restrictions = check_sender_access hash:/var/spool/postfix/plesk/blacklists, permit_sasl_authenticated, check_client_access pcre:/var/spool/postfix/plesk/non_auth.re smtp_send_xforward_command = yes smtpd_authorized_xforward_hosts = 127.0.0.0/8 smtpd_sasl_auth_enable = yes smtpd_recipient_restrictions = permit_mynetworks, check_client_access pcre:/var/spool/postfix/plesk/no_relay.re, permit_sasl_authenticated, reject_unauth_destination virtual_mailbox_base = /var/qmail/mailnames virtual_uid_maps = static:110 virtual_gid_maps = static:31 virtual_transport = plesk_virtual plesk_virtual_destination_recipient_limit = 1 smtpd_client_restrictions =  myhostname = mydomain.com message_size_limit = 2048000000


What does “the lowest common denominator” mean in the context other than math?

In the  (May 31) article under the title, “Stephen Hawking angers Trump supporters with baffling array of long words,” Andy Borowitz wrote;     “Speaking to a television interviewer in London, the theoretical   physicist, Hawking called Trump “a demagogue who seems to appeal to   the lowest common denominator. --- “For a so-called genius, this was an   epic fail,” Trump’s campaign manager, Corey Lewandowski, said. “If   Professor Hawking wants to do some damage, maybe he should try talking   in English next time.”        Later in the day, Hawking attempted to clarify his remark about the presumptive Republican Presidential nominee, telling a reporter, “Trump bad man. Real bad man.”   From the context of Professor Hawking’s remark, I take “the lowest common denominator” as referring to the  “social segment of low educated, unsophisticated people,” but I’m not sure.   I thought  "common denominator" is a simple mathematic term. What does it mean in the context of the above quote?  Mr. Trump’s campaign manager says Professor Hawking should try to talk in English. Is this a farfetched way of using “common denominator” from math to politics?   Did Professor Hawking misuse "the common denominator"? Or does Mr. Trump's campaign manager not understand the meaning of "common denominator", which some call an "everyday-use" English phrase?  P.S.  I found the following definition of 'common denominator' in Oxford Advanced Learners English Dictionary;   2) an idea, attitude or experience that is shared by all the members of group - see also Lowest common denominator.  Readers English Japanese Dictionary at hand, published by Kenkyu-sha, a foreign language, especially English language dictionary specialist publisher in Japan, and rated as the most reliable English Japanese dictionary totally dropped the reference to this paticular meaning.  It was a learning. I told to myself that I should have made more homework on English-to-English dictonaries beforehand.


Compiz Config animations does not work (ubuntu mate)

i downloaded compizconfig settings manager and even though i'm enabling some animations they do not work, for example i enabled the wobbly windows animation and it does not work.  I'm running ubuntu mate 18.04 on a virtual machine on my lenovo yoga 710 latop. thanks for the help.


Can two LED circuits with a shared ground use a single resistor?

I wonder if anyone can help me, a complete beginner, with a very basic question? I currently have a red LED connected to a GPIO pin on a Raspberry Pi, and a green LED attached to a different GPIO pin. Both pins output 3.3v, and I have a 330 resistor on the anode of each LED. Ground is shared, as in the diagram below:    I want to fit this onto as as small a PCB as possible. From my (very) basic understanding, I think I can get away with a single 330 resistor on the between the two LEDs and ground, as in this diagram:    Am I correct in this? Many thanks.   Edit: It seems that I have asked a question that has been raised multiple times. As a complete novice, I wasn't aware that this is regarded as the LEDs being in parallel (I thought that two power sources differentiated this from the other parallel LED questions I saw posted). Anyway, I thank those who took the time to help, and I will attempt to digest the responses.


How do I get the Wings of Valor Pre-order bonus?

I pre-ordered the physical game but it won't arrive until April 1, 2014...  The CSR said a code is bundled with the game.  I don't know if this is true or they're just misinformed.  Elsewhere I read that any copy of Reaper of Souls activated before March 31, 2014 will receive the wings.  So if I go to the store and buy it, activate it, is it all just the same?


Is the projectivization of a variety well-defined?

Given an affine variety $X$ embedded in affine space $\mathbb{A}^n$, there is a simple-minded construction which associates a projective variety $\mathbb{P}(X) \subseteq \mathbb{P}^n$, as follows. If $I \subseteq k[x_1,\dots, x_n]$ is the ideal defining $X$, then $\mathbb{P}(X)$ is defined by the homogeneous ideal $\mathbb{P}(I)\subseteq k[x_0,\dots,x_n]$, where if $f = \sum a_{i_1,\dots,i_k} x_1^{i_1}\cdots x_k^{i_k} \in I$, then $\tilde{f} = \sum_{i_1,\dots,i_k} x_0^{D - i_1 - \dots - i_k} x_1^{i_1}\cdots x_k^{i_k} \in \mathbb{P}(I)$ for $D$ large enough to make all exponents positive.  This is a well-defined operation turning an affine variety (or more generally, affine algebraic set) in $\mathbb{A}^n$ into one in $\mathbb{P}^n$. But it would appear to depend on the embedding of $X$ into $\mathbb{A}^n$. Is this the case? That is, if I have two isomorphic subvarieties $X,X' \subseteq \mathbb{A}^n, X \cong X'$, are the resulting projectivizations $\mathbb{P}(X), \mathbb{P}(X')$ necessarily isomorphic? I suspect not, but I don't have a counterexample.  A little googling turns up something called the  which may be relevant, but it apparently requires a graded ring as input, and the function algebra of $X$ will not typically be graded as far as I can see.


git log shows something like this:  commit hash3 New feature  commit hash2 bugfix  commit hash1 Initial commit   I want to squeeze first two commits, into one "Initial commit", to clean history. If i do:  git rebase -i hash1   It doesn't show first commit, so that I could squeeze bugfix commit into it. If i mark bugfix commit with "s", it says there is no previous commit to squeeze to. So how do i make git rebase -i, so that it shows whole history, including the first commit, so i could squeeze it?  I know I can just remove repository, make new one and have one single commit, but i do want to have commits "initial commit" and "new feature" in history.   Thank you!


SQL joining huge tables by excluding just one column in select statement

I have three huge tables each with many many columns (say 500 each). Each of these tables joins together to form that data that I need by the 'USER_ID' field.   What is the easiest way to select this without duplicating the "USER_ID" field 3x?  I don't want to have to type out 'select table1.col1.....table3.col500'   my current query:  select table1.*, table2.*, table3.* FROM table1 JOIN table2 on table1.user_id  = table2.user_id JOIN table3 on table1.user_id =  table3.user_id   I'd like to do some sort of 'except table2.user_id, table3.user_id' in the select portion of the statement so I don't see this column there 3x...


Given Bernoulli probability, how to draw a Bernoulli from a uniform distribution

I have a set of probability corresponding to Bernoulli experiment. How to draw Bernoulli random number given these specific probability from a uniform(0,1) distribution. I know we can draw from binom, but using uniform distribution can vectorize the operation and make it so much faster.


How to change the default font size of XTerm?

XTerm font is very small. How can I set it larger?


Could a slider be considered duplicate content when used on all pages of my site?

I have content in my HTML slider and I am showing it on all web pages. Do crawlers consider this content duplicate?


Allow new users to comment for X times in a day

While reviewing "First Posts" on Stack Overflow, I often come across new users posting comments as answers. It seems (at least to me) they are not doing this because they are unaware of how Stack Overflow works but because they can't comment on any question they are forced to put it as answer.  I have found duplicate questions for my request like:   ,  and    but the best explanation I have found is an  to .     I think the main reason this isn't supported is there's no way to   downvote comments, which would make them attractive to spammers. If   somebody comments on the top answer in a question the only way to get   rid of it is for six people to flag it. Comment flags don't show up on   10k tools, so it needs to be six people that happen to stumble across   the spam comment, or a moderator that checks the list manually. People   can comment every 15 seconds, so that can get out of hand pretty   quickly. Comments also aren't listed on the user's profile page, so   it's hard to see at a glance if a user has been spamming   So I am suggesting allowing new users (with less than 50 reputation points) to comment only 5 times every day or only 25 times times until they reach 50 reputation points or any other variation of it.


I saw in   that $y^2 = 1+x^4$ is (the affine equation of) an elliptic curve. Why is it the case? Typically, SAGE tells me it is isomorphic to $y^2 = x^3 - 4x$, which is an elliptic curve with Weierstrass equation, but I don't know how to prove this.  Thank you!


I am building a platform that will have a similar structure to Twitter and I am tirelessly looking for something that could replace the terms for connections between users.   On Twitter the terms "Follower" and "Following" are used to describe such relationships, however, those terms were established in the Twitter ecosystem and I feel like it might not immediately be clear to users what those terms refer to. Do you have any suggestions/synonyms for terms that convey the meaning of the aforementioned words ?   In Twitter's ecosystem the term "Following" describes a unidirectional relationship between user A and user B, where A is interested in events of user B, but not necessarily the other way around.   The term "Follower" describes the inverse relationship, where user B is interested in events by user A, and not necessarily vice versa.   Bonus question: Can you name a term that depicts a bi-directional relationship between user A and B, where both A and B are interested in each other's events ? (Bi-directional connection).   I tried to come up with terms that seem quite... obvious ... but they might not be semantically correct.   Followers: Connecters/Connected [users]  Following: Connectees (not an official english word)/Connected to  Bi-directional relationship: Connections  While very abstract, do you think these terms would convey the intended meaning ? I ask this because English is my second language and I cannot afford to gamble on those essential terms.


Why is this happenning with switch (Java)?

Its pretty much clear that switch statements can take string value in Java and something like this :  String s="diljit" switch(s){  ..  ....}   will always compile.. s is a object of type String.... but on the other hand switch statement cannot take  objects of other classes? Why is this happening and How will i validate this question with a suitable answer..  Can switch statement take objects or not?


I'm using classicthesis.sty and my footnote numbers are not showing.   I do use this command at the beginning of each chapter:   \let\thefootnote\relax\footnotetext{ }   Do you think this is related? How do I show footnote numbers with \footnote{}? Thanks!  According to another post I read here, this should work, but it does not.   \documentclass[parskip=half,10pt,twoside]{scrbook}  \usepackage[     dottedtoc,     floatperchapter,     parts ]{classicthesis} \usepackage{}  \begin{document}   \chapter{Test} \vspace{30ex}  \let\thefootnote\relax\footnotetext{something unnumbered}   \newpage  There should be a footnote number here\footnote{test} \end{document}   Thanks for any suggestions!


How to list Trans-Siberian as a hotel on a Russian visa application

I'm filling out my visa application and my understanding is that I should ensure the list of hotels on my application, so that it matches what's on my tourist invitation. I got Moscow and Irkutsk filled out fine, and TRANSSIB showed up on the list of cities, so I entered that, but the invitation also includes the train as a "hotel". Anyone know how I should enter it, since both address and phone number are mandatory fields that aren't going to exist (the invitation doesn't give anything to enter for those fields either)? I'm specifically referring to the Do you plan to stay anywhere (hotel, individual) during your stay in Russia? section, which then asks for the name, address, and phone number of each.


Why do I get question which i'm not interested to answer?

These are my favorite tags:    But I still get question like these     Can somebody tell me how I should configure my account so that I get questions related to my "favorite tags"? or is it some kind of bug that I found out :) ?


Limit of the nth root of integral of $f$ is $\sup f(x)$

Let $f:[0,1]\to\Bbb{R}$ be continuous. How do I show that $\lim_{n\to\infty}\left(\int^1_0{f(x)^n}\right)^{1/n}=\sup_{0\leq x\leq 1}f(x)$?  I tried writing $\left(\int^1_0{f(x)^n}\right)^{1/n}=\left(f(x)^{n+1}/(n+1)\right)^{1/n}$. But I don't know what to do next.


Trying to prove $p,p \to (r \to q) \vdash (\neg q \to \neg r)$ by using natural deduction.

Inference rules allowed are: $\lor$, $\wedge$, $\rightarrow$, $\neg$ introductions and eliminations.  In question, it says I am allowed to make use of a lemma or equivalence as long as I provide a proof of it by natural deduction too. (I will come to that soon enough, hopefully.)  First of all, that "$,$" between $p$ and $p \rightarrow (r \rightarrow q)$ made me a bit confused, but I ended up assuming that comma just splits two premises we are given. I tried to not dig too much and proceeded to make proof, however I got stuck after using implication elimination on $p \rightarrow (r \rightarrow q)$ and obtaining $(r \rightarrow q)$. From there on, I have a sense that I will just use 4-5 more steps and reach $(\neg q \to \neg r)$ but I just couldn't figure it out.  Then I realized that I can make use of equation $p \rightarrow q \equiv \neg p \lor q $ .  As stated in question, I tried to prove this equation by natural deduction (I know at this point I am just making things harder than it is supposed to be, but what the heck..)  This is the proof I tried to make in fitch style:    If you realize I am using double negation here and I am not even sure if that is even allowed to use.  From here, I just needed to show that $(r \rightarrow q) \equiv (\neg q \rightarrow r)$ knowing $(\neg r \lor q) \equiv (\neg \neg q \lor \neg r)$ and that is $(\neg r \lor q) \equiv (q \lor \neg r)$   But if you realize, that means I will have to prove double negation law "$\neg \neg q \equiv q$" as well as commutative law "$(\neg r \lor q) \equiv (q \lor \neg r)$". Like these extra two small proofs are not enough, I also have to use them with proper notation/syntax in latex aside with fitch style proof tables.  This makes me realize that it is definitely a bad idea to make this proof by natural deduction using these "transformation" equivalences if I may call them that.   So, I think I need to give up on that idea and stick to direct proof with implications.  However, as stated above, I am stuck after implication elimination. Could you guys help me figure it out how to move forward from there?  P.S: Reason I state all those unnecessary steps is that, I think it is just more appropriate to not just "ask for a direct answer" but provide my thought process. Another challenge of doing this proof for me is that having to use fitch style proofs in latex. I just can't figure out where to place that "p" before comma in the question. Anyway, enough confusion!


I tried to improve  thinking the poster had messed up his code tags, in fact he hasn't as far as I can see, they just don't work?  Editing the post suddenly fixes the problem without changing any text (though you can't save with 0 edits).


Lunch Meeting Probability for two person to meet in given 1 hour slot and none would wait more then 15 minute.

Two friends who have unpredictable lunch hours agree to meet for lunch at their favorite restaurant whenever possible. Neither wishes to eat alone and each dislikes waiting for the other, so they agree that each will arrive at a random time between noon and 1 pm, and each will wait for the other for 15 minutes or until 1:00. What is the probability that the friends will meet for lunch on a given day?


List out the ways in which we can deploy the files to the SharePoint

What are the possible ways in which we can deploys files to:-   The SharePoint hive (folders in hive) The SharePoint content db (libraries, etc)   By files I mean css, js, masterpage, site page, html page, images, doc files, ppt, and other files. Ofcourse there will be ways to deploy them to hive and ways to deploy them to the content db which will depend upon the requirements. I am just making an attempt to collect the possible ways for reference and planning.  Incase you feel its broad topic it would be nice of you to list out the ways. Explanations are not expected.  Here is a sample answer:-  1. The SharePoint hive (folders in hive)  -mapped layout folders (project -> add item)  -mapped images folder (project -> add item)  -mapped folder (project -> add item)  2. The SharePoint content db (libraries, etc)  -Use modules (project -> add item -> select module, then update the elements.xml)


Can you recommend a CSS Framework (or UI Framework) for enterprise web apps?

Is there a CSS Framework that tries to provide for business applications, specifically?  I've looked at the Mocha UI which is based on MooTools. Honestly, though, I'd like to avoid dealing with Javascript and Moo (or jQuery / jQuery UI). I tend to believe that most of what you need for a simple web app can be handled in CSS without the Javascript mods to it.  Many of the polished CSS is aimed at blogging or web publishing needs that are different from the UI needs of a business app. It seems like this must be a problem that someone has solved, but I can't seem to find a solution.  My hope would be that proposed solutions would be language agnostic (work with PHP, ASP, CF, etc.). However, if there is a framework rooted in a language that handles the UI in a very "finished" sense, then I'd be interested in looking at that, even if it meant adopting a framework that forced the use of a particular server-side language.  My goal is not to go MVC, just have some nice looking CSS that would fit an application.  BOUNTY: I decided to start a bounty on this question because I think there must be some useful "starting points" (stated minimally) of CSS which are geared toward web apps, with my preference being that they're hopefully:   platform independent or accomodating various dev platforms, and free or nearly free (as in, not $1000 for a collection of controls)   "Inspirational" Example: (play on words intentional, sorry) I did find a church website development company that published a  which is very enticing, but it seems like it's usable only to those who develop church sites using their software as a service (?). Regardless, the CSS and complementary graphics are not out there for public consumption.


Visa requirements for transit through Panama

I am an Indian national with a valid visa for Costa Rica. Do I need a visa to transit through Panama?


I've already installed hplip, it printed a test page, but it won't print from any program. It shows the printer in the list of printers, and it's checked as the default printer. I've restarted a couple times.   When I plugged the USB cable for the printer into the computer after installing hplip, it said printer detected. Then after a couple seconds it said the printer was ready for use.   When I send something to the printer, a pop-up shows that a document was sent to the printer - but there's a triangle with an exclamation point in it next to the message. A few seconds another pop-up indicates that the printer has completed printing the job but it didn't print anything.


I have got a serious doubt.  I have read, "yellow light from a low pressure sodium vapour is monochromatic"  How can it be monochromatic when yellow light is a combination of red and green primary colours?


Flagging a series of no longer necessary comments

I have several times seen situations where there is a conversation in comments that is no longer necessary (e.g. "can you clarify x", "clarification", "you should ask x as a separate question", "okay, I've asked it separately and edited this question").  In this situation, is it appropriate to flag each of the comments as no longer necessary or should I only flag one and leave whoever is handling the flag to remove any others?  From looking around it seems that in some cases it might be appropriate to flag the question or answer and request that the comments be removed but is that still the case if there are valid comments among to out of date ones?


On force being directly proportional to the rate of change of momentum

Newton's second law says that $F_{Net}=\frac{dp}{dt}$. I do realise that when the net force on a body is zero it keeps its current velocity, so one can infer that the force is somehow related to acceleration. But how do we move from this $F_{Net}=f\left(\frac{dv}{dt}\right)$ to simply the rate of change of momentum? Why would Newton think of momentum (i.e why include the mass constant)? Why not momentum cubed for instance?  EDIT: check


How can I install Microsoft Word & Excel in Ubuntu 14.04?

I need to install Microsoft Word & Excel in Ubuntu 14.04. Please assist step by step as I am new to Ubuntu.  Thanks!


Difference between light tail and heavy tail distribution

I read numerous websites including wikipedia on heavy and light tail distributions. However, I am not quite understanding the distinction between the two. In some sources, it notes that light tail distribution has uniform distribution while heavy tail has a larger distribution. Hence, I am led to believe that heavy tail distributions are just distributions with greater variance than light tailed distributions. Are there more nuances to this understanding? Can someone elaborate on this concept?


What was Hydra's plan for dealing with The Hulk?

In Captain America: The Winter Soldier;      It is revealed that Agent Sitwell is a double agent for Hydra, who is then interrogated on rooftop by Captain America, Black Widow and The Falcon.   This character then proceeds to explain what Hydra's overall plan is;      Which is to target and murder individuals which may pose a threat to Hydra's new world order, either now or in the future. In the interogation scene, Bruce "The Hulk" Banner is specifically mentioned by name as one of Hydra's targets, as is Dr Stephen Strange. We also see later than Tony Stark is listed as one of the targets when the INSIGHT helicarriers are booting up.   However, we know very well that The Hulk is more than a little difficult to stop when he gets angry, and we also know from The Avengers/Avengers Assemble that;      Bullets are not enough to kill The Hulk, which is revealed when Bruce Banner talks about how he attempted to take his own life, only for the "other guy" to spit the bullet out.   Is there any point in Captain America: The Winter Soldier or any related film-canon material (tie-in comics, TV shows, other films etc) that we find out why Hydra thought that the INSIGHT helicarriers would be able to take on The Hulk, or if they had another plan for dealing with him?


I cooked quinoa like rice and ate half of it. I am planning to have the other half for breakfast. Is it safe to leave it in room temperature overnight (I don't have a refrigerator)?


How to Add Background Images in 2.8 and later

2.81a here. I am trying to add a "background image" similar to how , so that I see a screen that looks something like this:    However I can't figure out how/where to access this screen in 2.81a as the UI is wildly different. Any ideas?  I am new to Blender so if you can provide a click-by-click list of instructions it would be enormously appreciated!


Why doesn't this code terminate my program? Java

I am trying to implement the System.exit(0); in java to terminate my program when the word "exit" is typed into the console. I wrote the following method:      public static void exit(){      Scanner input = new Scanner(System.in);     Str1 = input.next(String);      if (str1 = "exit"){          System.exit(0);     }      else if (str1 = "clear"){          System.out.println("0.0");     }        }   and it doesn't seem to be working.  Does anyone have any suggestions?  Thanks P.S the "clear" is just supposed to return 0.0 when "clear" is entered into the console, if you could not already tell.


I am not good at English. And I used to say that I want to become a software developer. But Some people are using that I want to be a [something]. Which one is correct? And at what situations we should use which one? I read in many websites. Answers I have found so far are  Be is abbreviation of become. Both are same. Be is representing continuous thing. Become represents future.  I can't understand it because of people usage. Could anyone please further explain the difference between these two?


Upgrade Debian Jessie (8) to Buster (10) possible or need to go sequential in versions upgrades?

Just started working with a Debian Jessie (8) in a production environnent. While presently deployed it is not seeing any heavy use yet. I was looking at the OS , and I was thinking about how convenient it would be to just upgrade it before is start seeing some more steady use in our environment and possibly making things more complicated with a later upgrade.  I was looking for a procedure to upgrade from Debian v.8 to v.10 but most documented  are sequential in order (e.g. 8 -> 9, or 9 -> 10).  My question: should I upgrade sequentially, or there is some proper documented way to skip a main version while upgrading?


Opening other Python 3 files using tkinter

I am currently working on making a program using tkinter that when pressing a button it opens the Python program, however I am having some problems with it. I have tried using os.system('filename.py'). That opens the file, but then crashes the GUI, making the user have to restart the GUI. I have also tried importing it as a module but that just does the same as when using os.system.   Can anyone possibly help me open a Python file in a completely new window/terminal?


excel - activate addin through a Group Policy object

I have an addin that I'm installing on the roaming profile of users.  Yet I have to activate it manually for every users.    I thought about activating it automatically with GPO.  I read  but it seems to be big for what it is.  Is there a way to activate it automatically with a GPO, in a simpler way?   Thanks


I have to run some code only when a particular element in the DOM (img tag) exists, if not then I want to run some other code. Below is what I have till now.  Original Code:   ed.on('blur', function (e) {         var iFrame = $('iframe');          $("img[src*='blob']", iFrame.contents()).each(function (i) {             var originalUrl = $(this).prop('src');             var that = $(this);             // SOME CODE             );         });   Below is what I want      ed.on('blur', function (e) {     var iFrame = $('iframe'); ******If ( img[src*='blob' exists in the iFrame )********     $("img[src*='blob']", iFrame.contents()).each(function (i) {         var originalUrl = $(this).prop('src');         var that = $(this);         // SOME CODE        );     }        else     {        // Do something else     } });   So basically if I cannot find  $("img[src*='blob']" in the iframe I want to run some other code. Please guide me.


I recently bought a WD Green HDD (WD30EZRX) and it came without any screws. What size screws do I need for it? The screw size is not listed in the product specification on the manufacturer's website as far as I can find and I couldn't find anything via google either. The standard computer screws are too thick for the holes.


Expand the username auto-completion to everyone who can be notified

@username auto-completion for comments was , and is already active on MSO.  However, it only seems to auto-complete the usernames of people who have commented on the post. According to , the list of users who can be explicitly notified also includes:   Anyone who edited the post Anyone who started a bounty on the question The ♦ moderator or  who cast a binding close vote on the question   Why not auto-complete those, as well?


I'm not the most experienced person when it comes to commands. I worked out how to do stuff like when holding x you have y effect. I wanted to think of something that gave other people an effect when hit. Here is what I came up with but I got stuck when it said it couldn't execute the command.  /scoreboard objective add nokill dummy  /scoreboard objective add poi dummy  /scoreboard players set [player] nokill 1  /scoreboard players add @a poi 1 {SelectedItem:{id:minecraft:diamond_sword,display:{Name:{Poison sword}}}}  /execute @a[score_poi_min=1] ~ ~ ~ /effect @p[score_nokill_max=1,r=5] {HurtTime:1} minecraft:poison 10 1


how to calculate  network  address of an IP with subnet mask 202.145.90.7/20? How many hosts can be there?


Mikrotik RouterOS - How to prevent all devices in a VLAN from initiating any connections outside of the VLAN?

I'm using a RouterOS device as a router on a stick. I'd like to isolate a certain VLAN from the outside world so that the VLAN cannot instantiate any connections to other VLANs or to the Internet (WAN). I've set up the following firewall rule: /ip firewall filter add chain=forward \     action=reject reject-with=icmp-admin-prohibited \     connection-state=!established,related,untracked \     in-interface=vlan120  It works for ping: ping www.google.com PING www.google.com (172.217.20.4) 56(84) bytes of data. From _gateway (192.168.120.1) icmp_seq=1 Packet filtered  It works for tcp: telnet www.google.com 80 Trying 172.217.20.4... Trying 2a00:1450:400d:805::2004... telnet: Unable to connect to remote host: Cannot assign requested address  But it does not work for udp: nc -z -v -u time1.google.com 123 Connection to time1.google.com 123 port [udp/ntp] succeeded!  Any help appreciated!


If two sets have a natural (asymptotic) density, does their union?

Let $\Omega=\mathbb{N}$. For each $E\subset\Omega$ let $N_n(E)$ be the cardinality of the set $E\cap \{1,2,\ldots,n\}$. Define $C=\left\{E: \lim_{n\rightarrow \infty} \frac{N_n(E)}{n} \text{ exists}\right\}$. Show that $C$ isn't a field.  I already know that it isn't closed to finite union of non-disjoint set but I can't see why. I saw a post that somebody said "the set of natural numbers whose first digit is 1 doesn't have this limit". I'm in trouble to see why this limit wouldn't exists in finite unions. Thanks in advance.


Evaporation of large charged black holes

Black holes evaporate (Hawking Radiation) acting as black bodies with the temperature inversely proportional to the mass.  No physical process, be it evaporation or any other "trick", can make a black hole "super-extremal", namely it can't make the square of the angular momentum or the charge too large compared to the mass. As the mass drops due to evaporation the charge and angular momentum must also drop.  Angular momentum can be shed with photons, because photons have spin and can be emitted in a non-radial direction.  Charge is trickier. There are three methods to shed charge:   Accrete oppositely charged particles. This can be stopped, hypothetically at least, by isolating the hole. Emit charged particles. There are no massless charged particles, so a temperature << 511keV strongly suppresses this positron and electron generation, so making the hole large enough should stop this. Break down the vacuum with the electric field (requires ~10^18 V/m). Again, making the hole large enough should suppress this because the electric field in the vicinity of a near-extremal charged hole scales as 1/M.   If all three of these are suppressed, we have a new candidate for the longest lived objects possible! So will a large enough black hole evaporate itself toward extremity after which there will be essentially zero Hawking radiation?


Suppose $x > 0$. Prove that $\frac{\sqrt{x}}{x+1} \leq \frac{1}{2}$.

Suppose $x > 0$. Prove that $$\frac{\sqrt{x}}{x+1} \leq \frac{1}{2}$$  Hey everyone, here is a simple math prove question, but I had a hard to start this proving, please give me some ideas to deal with this. Thanks


Apache 2.4 and PHP7.4 on Ubuntu 16.04 - Unable to execute php files

I have been through multiple threads on Ask Ubuntu and other sites with no success.  Apache 2.4.43 is installed and working.  PHP 7.4 is installed and php -v and running php -r "phpinfo();" indicates php is running correctly as well, but opening either an .html file or .php file in Chrome either shows a blank page or the source code, not the intended output, indicating Apache is not executing php scripts. I have reinstalled multiple times, including a complete purge and reinstall of both apache2 and PHP with identical results, tried adding <FilesMatch> lines to apache2.conf, and many other items found in similar posts to apache2.conf, all to no avail.  I have on previous Ubuntu systems run Apache and PHP fine, but this time no luck.


How does Wolverine's healing factor work?

I am interested to know how exactly Wolverine's body regenerates/heals from wounds.  From what I understand about the 'human' body's healing is that it uses a complex system of metabolism and other processes; but Wolverine's healing is powered by his healing factor or Hyper-regeneration.  How does his healing factor work? i.e. where does his body get the energy to power such regeneration?  The Hulk gets his "powers" (strength, mass etc) from an unlimited source via the cosmos (not exactly sure how this works, but I do get the concept); Is Wolverine's healing factor the same or a similar concept?  *Canon only answers please


I have seen a wide variety of different estimates for the maximum current rating for copper wire.  For example, for 24-gauge copper wire,  claims that a copper wire will fuse after 10 s if carrying a current of over 29 A.  On the other hand,  claims a maximum current of only 3.5 A for chassis wiring and 0.577 A for power transmission.  What is causing the disconnect between these wildly divergent estimates of the maximum current?  Moreover, which of these estimates is most useful for estimating the maximum current that is safe for use in an electromagnet (both with and without insulation)?  Thank you.


How can I use french fonts like à , ç etc. in HTML or PHP?

I am using   <meta charset="utf-8">   still doesn't work. The fonts are broken. Any workaround without using html equivalent like "&Agrave;"?  Some guys are showing me the example of this  but it's not what I am looking for. I am not messing around database input or output. I just need to show plain text in html or php files but those french fonts are not showing properly. I can use their html equivalent but it is very tedious to edit all fonts one by one. I just wanted a simple workaround  Please check this image for better understanding. I wrote été but it is showing like the image below in Firefox browser. I am using it on wamp.


How can I find out if a specific program is installed?

I want to find out if a  program - Chromium for example - is installed on Ubuntu or not. Manually or as a package.  How do I know if a program is installed via command line?


I would like to see the activity on of the SQL server. So I can run a query when the server load is low. I know there is an activity monitor in SQL server but my company doesn't want me to give the rights to use this tool. Apparently you can kill other people queries and this is too dangerous.  Is there a way to check the status of the server with code? (Or view the activity without needing those rights so I can manually run them?)


Suddenly Gmail and Hotmail block our emails

Starting from yesterday, all emails sent from our server are being rejected by Gmail and Hotmail.  Everything was working properly until now.  Here are the error messages received:  Gmail  Failed Recipient: email@gmail.com Reason: Remote host said: 550 5.7.1 [server IP 1] Our system has detected an unusual rate of 5.7.1 unsolicited mail originating from your IP address. To protect our 5.7.1 users from spam, mail sent from your IP address has been blocked. 5.7.1 Please visit http://www.google.com/mail/help/bulk_mail.html to review 5.7.1 our Bulk Email Senders Guidelines. el7si1434447wib.69 - gsmtp   Hotmail  Failed Recipient:address@hotmail.com Reason: Remote host said: 421 RP-001 (BAY0-MC3-F30) Unfortunately, some messages from [server IP] weren't sent. Please try again. We have limits for how many messages can be sent per hour and per day. You can also refer to http://mail.live.com/mail/troubleshooting.aspx#errors.   I do know the point of those messages - they both blocked our server because it might be sending out spam.  However, I don't understand what exactly could have caused this.     Was someone spamming Gmail/Hotmail addresses from our server?   Did some of the recipients report our emails as spam? Any other possibilities?   I'm honestly not sure where to look at first.  Thanks!


How to create test data for a class that checks for historical data?

I have a class that processes some data returned by a query. The query is based on the createddate column of the object. In this case, the query specifically retrieves data created 3 days before today.  So as an example, the query would have the  Select Id, Name, Amount__c FROM MyCustomObject__C WHERE CreatedDate = TODAY - 3 as the condition to fetch records.  In my test class any records I insert in the MyCustomeOBject__c would always have the CreatedDate = TODAY  So how can I make test data that was created 3 days ago?


How can I boot with an older kernel version?

The latest kernel is causing problems with my sound, which worked fine with an older version. As I have only Ubuntu installed, Grub is not getting displayed while booting. How can I manually choose my kernel version while booting?