For some reason, this script (run on RHEL v6.9) processes only the first line in the host_file  #!/bin/bash  process() {  ssh $host ls }  while IFS= read -r host do   echo "Running $host"   process   echo "DONE $host" done < host_file #-------End of Script-----------------  $ cat host_file server1 server2

I'm trying to read a text file and do something with each line, using a bash script.  So, I have a list that looks like this:  server1 server2 server3 server4   I thought I could loop over this using a while loop, like so:  while read server; do   ssh $server "uname -a" done < /home/kenny/list_of_servers.txt   The while loop stops after 1 run, thus only running uname -a on server1  However, with a for loop using cat it works fine:  for server in $(cat /home/kenny/list_of_servers.txt) ; do   ssh $server "uname -a" done   Even more baffling to me is that this also works:  while read server; do   echo $server done < /home/kenny/list_of_servers.txt   Why does my first example stop after the first iteration?


Suppose we have a commutative ring $R$ with unity and $a, b \in R$, if $ab$ is a unit, are $a$ and $b$ units as well? My intuition is that they must be, but I'm not sure how to see that.

In a ring If product of finite elements is a unit then can we say each element as unit  For ex., if $q_1 q_2 ... q_m$ is a unit, then can we say each of $q_i$ $\forall i$ is a unit how to prove this?


I need to replace a quick release skewer that came out of the front wheel of the bike. What specific Skewer do I need? How long is the skewer and how thick is the rod of the skewer?  Thank you very much.

I lost my road bike's quick release. Pictured are what I lost. Do I need to find a specific quick release that fits, or does one size fit all/most?


If an opponent, or anything else, makes me sacrifice a creature, and I have a Blood Host or something similar, can I choose to sacrifice the creature with the Blood Host?

Two very closely related questions:  If a card has two different "Sacrifice this creature for X" abilities on it, does sacrificing it give both benefits?  Likewise, if a card requires a creature to be sacrificed, but that creature has a "Sacrifice this creature for X" ability, do you get the sacrifice benefit when you sacrifice it for the other requirement?


I have a vocabulary which has the option Localize. Terms are common for all languages, but their name and description may be localized. set for its multilingual settings.  I have 2 languages on the site. One is English and 2nd is Dutch. I have a term name English term and its translation in dutch is Dutch term.  So is it possible programmatically to get the original term name (English term) from the translated term name (Dutch term) without knowing the tid?  In the question "" the tid is known but here I mentioned that without knowing the tid. So this is a different question.  Any suggestions?

I'm looking for a working method to get the translated term name by tid.  The following code returns the original term name but not the translation.  global $language;  $lang_name = $language->language; // en  $term_id = 788;  $term = i18n_taxonomy_term_get_translation($term_id, $lang_name);     Most examples provided in "" seem not work for Drupal 7.


I'm completely new to Python, I want to download a file by sending a request to the server. When I type it into my browser, I see the CSV file is downloaded, but when I try sending a get request it does not return anything. for example:   import urllib2 response = urllib2.urlopen('https://publicwww.com/websites/%22google.com%22/?export=csv') data = response.read() print 'data: ',  data   It does not show anything, how can I handle that? When I search on the web, all the questions are about how to send a get request. I can send the get request, but I have no idea of how the file can be downloaded as it is not in the response of the request.  I do not have any idea of how to find a solution for that.

I have a small utility that I use to download an MP3 file from a website on a schedule and then builds/updates a podcast XML file which I've added to iTunes.  The text processing that creates/updates the XML file is written in Python. However, I use wget inside a Windows .bat file to download the actual MP3 file. I would prefer to have the entire utility written in Python.  I struggled to find a way to actually download the file in Python, thus why I resorted to using wget.  So, how do I download the file using Python?


how would you get the material that looks like black and white matcap. the last position on the matcaps "menu". the one that look like a comic book.

Is it possible to use Matcap materials as an actual material for a model so that I can render with it? There are certain parts that I want to apply specific Matcaps textures to but I want to actually use them to render and not just for sculpting purposes.  Is this at all do-able?


A function $f$ is called Hölder-continuous on the interval $I$, when there exist a constant $C$ in $\mathbb{R}_{\geq0}$ and an exponent $\alpha>0$ such that $$|f(x)-f(y)|\leq C|x-y|^\alpha$$ for every $x,y$ in $I$.  What is to be proven is that if $f$ is Hölder-continuous with $a>1$, $f$ must be constant.   What I have found out so far:  I need to show that $$a>1 \iff f(x)=f(y)$$ for all $x,y$ in $I$.  After dividing the inequation by $|x-y|^\alpha$ I have  $$\frac{|f(x)-f(y)|}{|x-y|} \frac{1}{|x-y|^{\alpha-1}}\leq C$$  Is there a way to deduct that there is no constant $C$ such that this inequation can be satisfied except when the numerator is $0$?

I want to show that if a function $f:[a,b]\rightarrow \mathbb R$ satisfies a Hölder condition of order $\alpha > 1 $ then it is constant.  The way I think of it is as follows:  $$|f(x) - f(y)| < K|x-y|^\alpha$$  $$\frac{|f(x) - f(y)|} {|x-y]}  < K|x-y|^{\alpha -1}$$  $$\lim_{y\rightarrow x} \frac{|f(x) - f(y)|} {|x-y]} \le \lim_{y\rightarrow x}  K|x-y|^{\alpha -1} =0 $$ As the limit is $0$, we can remove the modulus, so we get:  $$\lim_{y\rightarrow x} \frac{f(x) - f(y)} {x-y} = 0$$ So $f$ is derivable and $f'(x) = 0$ for all $x$ in $[a,b]$. Note that the reason we can add the limit $y\rightarrow x$ is because $[a,b]$ is closed in $\mathbb R$.  However, the question gives as a hint using the mean value theorem. I am not sure why one should do that. You would first have to prove that $f$ is derivable in a similar manner to what I did, and then prove that $f$ is constant. Or is there a simpler way to do it and I am missing it?  Also please inform me of any mistakes I did in the proof (if any)/ Thank you!


I have a sony vaio laptop, bought around june 2012 with Windows 7 pre-installed. My BIOS is a InsydeH20 rev 3.7.  I'm using Ubuntu alone for a long time now, I would like to install a dual-boot with Windows 8.1 alongside Ubuntu 14.04 LTS.  First, I made a backup of all my files and formatted my hard drive. I turned on the UEFI option in my BIOS and I changed the partition table from MBR to GPT. Then, I installed Windows 8, I let it made all the partition it wanted. I upgraded it to Windows 8.1, then I turned off the fast boot option.  I installed Ubuntu on another partition and I created a last partition to share files between Windows and Ubuntu.  When I rebooted, I couldn't see Grub. It loaded right into Windows.. So I used boot-repair from my Ubuntu LiveUSB but that didn't change anything !  Here is the link from boot-repair :   So I would like to have Grub when my computer boots.  Also, I cannot turn off the secure boot option. There is no such thing in my BIOS and I can't see the UEFI setting in Windows. I mean when I'm  there is no UEFI firmware settings.  Hope this is well explained, let me know if you need more informations, Antoine

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


This looks like simple but really weird why this happens. Consider below example  var a = ['1.53','3.00','5.00']; var total = 0; a.forEach(function(t){ total += Number(t) }); console.log(total)//9.530000000000001   This prints 9.530000000000001 instead of 9.53. This could be fixed by total.toFixed(2). But please advise why the 0000000000001 added in the result.

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


I wrote the program below ti implement an algorithm with big arrays but when N is over 820 i have a segmentation fault problem (core dump) because of memory. I use 3 big arrays to implement my code. How can i fix this error?  #define N 400  void upper(float A[N][N], float x[N], float b[N]) {     int i,j;     float sum;     x[N-1] = b[N-1]/A[N-1][N-1];      for(i=N-2; i>=0; i--){         sum = b[i];         for(j=i+1; j<N; j++){             sum = sum - x[j]*A[i][j];         }         x[i] = sum /A[i][i];     } }  void lower(float A[N][N], float x[N], float b[N]) {     int i,j;     float sum;     x[0] = b[0]/A[0][0];     for(i=1; i<N; i++){         sum = b[i];         for(j=0; j<i; j++){             sum = sum - x[j]*A[i][j];         }         x[i] = sum /A[i][i];     } }   void cholesky(float A[N][N],float L[N][N]) {     int i,j,k;     float sum;      for(i=0; i<N; i++){         for(j=i-4; j<i; j++){ //j-4 because i have 0 and i want to do less computations             if(j<0)                 continue;             sum = A[i][j];             for(k=i-4; k<i; k++){                 if(k>=0)                     sum = sum - L[i][k]*L[j][k];             }             L[i][j] = sum /L[j][j];         }         sum = A[i][i];         for(k=i-4; k<i; k++){             if(k>=0)                 sum = sum - L[i][k]*L[i][k];         }         L[i][i] = sqrt(sum);     }    }  void transpose(float L[N][N], float LT[N][N]) {     int i,j;     for(i=0; i<N; i++){         for(j=0; j<N; j++){             LT[i][j] = L[j][i];         }     } }  void table(float A[N][N], float aii, float aone, float athree) {     int i,j;      for(i=0; i<N; i++){         for(j=0; j<N; j++){             if(i==j){                 A[i][j] = aii;             }             else if((i+1 ==j) || (i-1==j)){                 A[i][j] = aone;             }             else if(i+3==j || i-3==j){                 A[i][j] = athree;             }             else{                 A[i][j] = 0;             }         }     } }  void vector(float b[N], float b1, float b2, float all) {     int i;     for(i=0; i<N; i++){         b[i] = all;     }     b[0] = b[N-1] = b1;     b[1] = b[N-2] = b2;     b[2] = b[N-3] = b2; }  int main() {     float A[N][N];     float L[N][N],LT[N][N];     float x[N];     float y[N];     float b[N];     int i,j;      table(A,12,-5,1);     vector(b,4,-1,0);      table(L,0,0,0);     cholesky(A,L);     transpose(L,LT);     lower(L,y,b);     upper(LT,x,y);      for(i=0; i<N; i++){         printf("%f\n",x[i]);     } }

The following code is generating a stack overflow error for me  int main(int argc, char* argv[]) {     int sieve[2000000];     return 0; }   How do I get around this? I am using Turbo C++ but would like to keep my code in C  EDIT:  Thanks for the advice.  The code above was only for example, I actually declare the array in a function and not in sub main.  Also, I needed the array to be initialized to zeros, so when I googled malloc, I discovered that calloc was perfect for my purposes.  Malloc/calloc also has the advantage over allocating on the stack of allowing me to declare the size using a variable.


I am a third year student in physics and mathematics and taking a course in which each student need to prepare and give one lecture about some topic related to physics. As I saw String Theory in the topics list I thought it could be a good opportunity to start learn it. I have background in quantum mechanics, statistical physics, analytical mechanics, group theory, and I read the book "quantum field theory for the gifted amateur" until chapter 12.  What topics should I learn before string theory?  I would appreciate any recommendations for books or other material about string theory.

I am in the last year of MSc. and would like to read string theory. I have the Zwiebach Book, but along with it what other advanced book can be followed, which can be a complimentary to Zwiebach. I would like a more mathematically rigorous book or lecture notes along with Zwiebach.   Specifically, mention whether the book discusses string theory   Rigorously? Intuitively?   What's the scope of the book? Does it cover the advanced materials, e.g. Matrix string theory, F-theory, string field theory, etc. Maybe even String Phenomenology?


I have 2 numbers stored as Double, 1.4300 and 1.4350. When I subtract 1.4350 - 1.4300, it gives me the result: 0.0050000000000001155. Why does it add 1155 to the end and how can I solve this so that it returns 0.005 or 0.0050? I'm not sure rounding will work as I'm working with 2 and 4 decimal numbers.


Evaluate the PDF to find K  $1 = \int_0^{\infty} \frac{k}{(1+x)^4}$  using u substitution I got:  $u=1+x$ and $du= dx$  $\int_0^{\infty} \frac{k}{u^4} \to \frac{k}{\frac{-1}{3} u^3}$   Since $u^4 du = \frac{u^{-4+1}}{-4+1}=$ $\frac{u^{-3}}{-3}$  which evaluating gives:  $1=\frac{k}{\frac{-1}{3(1+x)^3}} \vert_0^{\infty} \to \frac{-3k}{(1+x)^3} \vert_0^{\infty} = 0 -3k$   and $k= \frac{-1}{3}$  somehow though they came up with $\frac{-k}{3} \frac{1}{(1+x)^3}$ after integrating $\int_0^{\infty} \frac{k}{(1+x)^3}$   Was my approach correct to use substitution? Where does my work go wrong?

An insurance company's monthly claims are modeled by a continuous, positive random variable $X$ whose probability density function is proportional to $(x+1)^{-4}$ where $0 \lt x \lt \infty$   I need help understanding the reasoning behind the answer:  the PDF is given by:  $1 =\int_0^{\infty} \frac{k}{(1+x)^{-4}}$   Here is my first issue in the first step, where does K come from? We are given the pdf to be $\frac{1}{(x+1)^{4}}$ So to me it would stand that the function we are given is the PDF because it says thats the pdf, and we are then to find the expected value from here which would be equivalent to:  $\int_0^{\infty} x(1+x)^{-4}$ by definition of expected value  My guess would be that the words "proportional to" are key as to why we have a K introduced can someone explain this?  I understand everything except when taking the integral because and solving for 1 because I arrive at $\frac{3k}{(1+x)^4}$ rather than $\frac{-1}{3(1+x)^4}$  Taking the integral of $(1+x)^4$:  $u=1+x$ $du=1dx$ and   $\frac{u^{-4+1}}{-4+1} dx$  which gives $\frac{-3k}{(1+x)^3}$  Which gives me $k=\frac{1}{3}$ when solving $1=\frac{-3k}{(1+x)^4} \Big\vert_0^{\infty}$ rather than $k=3$ as the answer which is the correct answer. Can someone please explain this to me?


Windows 10 x64. Visual Studio 2019 v16.6.1. Rider 2020.1.3.  Microsoft :     You can specify all the values or you can accept the default build   number, revision number, or both by using an asterisk (*). For   example, [assembly:AssemblyVersion("2.3.25.1")] indicates 2 as the   major version, 3 as the minor version, 25 as the build number, and 1   as the revision number. A version number such as   [assembly:AssemblyVersion("1.2.*")] specifies 1 as the major version,   2 as the minor version, and accepts the default build and revision   numbers. A version number such as   [assembly:AssemblyVersion("1.2.15.*")] specifies 1 as the major   version, 2 as the minor version, 15 as the build number, and accepts   the default revision number. The default build number increments   daily. The default revision number is the number of seconds since   midnight local time (without taking into account time zone adjustments   for daylight saving time), divided by 2.   I edited version info in my AssemblyInfo.cs file:  // Version information for an assembly consists of the following four values: // //      Major Version //      Minor Version  //      Build Number //      Revision // // You can specify all the values or you can default the Build and Revision Numbers  // by using the '*' as shown below: // [assembly: AssemblyVersion("1.0.*")] [assembly: AssemblyVersion("1.0.*")] [assembly: AssemblyFileVersion("1.0.*")]   But if I rebuild my project by Rider IDE and check assembly version I see unexpected result:    If I try to do the same in Visual Studio 2019 v16.6.1 then I get compilation error even:    If I set Deterministic to false according  then compilation error doesn't happen but I get the same result:    Why does it happen? How can I fix it?

I was just wondering how I could automatically increment the build (and version?) of my files using Visual Studio (2005).   If I look up the properties of say C:\Windows\notepad.exe, the Version tab gives "File version: 5.1.2600.2180". I would like to get these cool numbers in the version of my dll's too, not version 1.0.0.0, which let's face it is a bit dull.  I tried a few things, but it doesn't seem to be out-of-box functionality, or maybe I'm just looking in the wrong place (as usual).  I work with mainly web projects....  I looked at both:       and I couldn't believe it so much effort to do something is standard practice.  EDIT: It does not work in VS2005 as far I can tell ()


I have this table:

         Id	         Cantidad	         Producto	         Marca	         Precio	         Importe	         Serial

   I add rows to that table with this jquery code:  $( "#name" ).autocomplete({   source: 'http://sosacelulares.com/index.php/product/search',     minLength: 1,     select: function (event, ui) {         var value = ui.item.value;         var data1 = value.split("-");         var data = data1[0].split(" ");         $( "#product" ).show();          var v = data[1];          $.ajax({            async:true,            type: "POST",            dataType: "html",            contentType: "application/x-www-form-urlencoded",            url:"http://sosacelulares.com/index.php/product/get",            data:"id="+v,            success: function(response) {             var returnedData = JSON.parse(response);              $("#product > tbody").append('
' + returnedData[0].id_product + '	<input min="1" type="number" style="width: 100px;" value="" class="form-control quantity" id="quantity" placeholder="Cantidad" required>	' + returnedData[0].name + '	' + returnedData[0].brand + '	<input type="text" style="width: 100px;" value="' + returnedData[0].buy_price + '" class="form-control" placeholder="Precio" required>		<button type="submit" class="btn btn-success">Agregar Serial</button>
');           }          });      },  });   I just look for a name in a text input and then when I find it I just add it to the table. The problem is that the rows that I am adding they have a number input field that it is to add the quantity I test it like this:  $(".quantity").change(function () {   alert(1); });   I do not know why if I change the quantity input that it is ubicated within the new row that i added with jquery it does not work, if I make a change the alert does not appear, what am I doing bad? Thanks!

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


We started working on lists in class and there was this task to separate numbers from a list without creating a new list. So I used sepNum tag along with first inside the list. However it returns nullPointer and I don't understand why. The nullPointer appears at 2nd line in separateNumbers method. Element first exists and is !null.  public void separateNumbers() {     sepNum = first;     while (sepNum.info < 0 || sepNum.info > 9)         sepNum = sepNum.point;      Element previous = sepNum;     Element current = sepNum.point;     while (current != null) {         if (current.info < 0 || current.info > 9){             previous.point = current.point;             current = current.point;         } else {             previous = current.point;             current = current.point;         }     } }   Here's Element class:       class Element {         char info;         Element point;          public Element (char ch) {             this.info=ch;             this.point=null;         }          public String toString() {             return info+(point == null ? " " + point : "");         }     }   I've been trying to figure this out for a few hours now. Can you guys please help?

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


If a said to b "do this or that", would b be disobeying a if it did both? In others words, in English is "or" the same as xor, the exclusive or?

My wife and I are playing a game where you roll dice and move so many spaces in a grid "vertically or horizontally".   In the use of English it is very common to say, this or the other when it comes to making a choice  (exclusive or). Now I know that "or" can also be inclusive, for example "she couldn't read or write", or can be clearly used as an xor "you either come or not" making the statement true for only one of the options but not both.   My issue is where it is not clear whether it is an inclusive/exclusive or, the best example being our game.   I argue that you can move in either direction (inclusive) and the normal use of this conjunction in English should be inclusive unless specified otherwise.   Is this right?


How many integer solutions are there to the inequality $x_1 + x_2 + x_3 \leq 17$, if we require that $x_1 \geq 1$, $x_2 \geq 2$, $x_3 \geq 3$?  The way I did it:  $x_4 = 17-x_1-x_2-x_3-x_4$  $x_1+x_2+x_3+x_4 = 17$  $x_1= x_i + 1$  $x_2= x_{ii}+2$  $x_3= x_{iii}+3$  $x_4= x_{iiii}$  So,  $x_i+1+x_{ii}+2+x_{iii}+3+x_{iiii}= 17$  $x_i+x_{ii}+x_{iii}+x_{iiii}=11$  $3$ bars, $\binom{14}{3} =364$ different ways? Is this the right approach? correct answer?

How many integer solutions are there to the inequality  $$ x_1 + x_2 + x_3 \leqslant 17 $$  if we require that  $$ x_1 \geqslant 1,\; x_2\geqslant2,\; x_3\geqslant 3 $$  My first approach to this problem was to see 3 boxes: $x_1, x_2,x_3 .$ After putting the minimum amount into each box (1 for $ x_1$, 2 for $x_2$ and 3 for $x_3$) we have 11 choices left. Using the star and bars method I got 11 spaces for the variables and 2 for the bars, giving me a final answer of:   $$ \dbinom{13}{2} $$  However, the second way to solve this problem would be to find the total amount of combinations without the restrictions, then to subract for when $ x_1 <1, x_2 <2$ or $x_3 < 3 $.  $$ \dbinom{19}{2} $$ for the first part where 17 is for the places of the integers and 2 are for the separators, but how do we find the restrictions? I am wondering if this has anything to do with a slack variable, our professor hinted at it and I do not know how to apply it to this problem.  Thank you.


Now guyz, I know we like to cache stuff around here, but when I see a flag count this high;    ... and upon clicking it, I actually see this;        ... I severely doubt caching is solely at play here; I'm aware that the flag count does not exactly match up due to caching and the like (and dupes exist to mention this); but this is a difference of 78 or, 360%.  I've been seeing this since the deploy of the new flagging system last week(ish).

It looks as if the 10k-tools flagged post list is b0rken.  Next to the review link in the toolbar there is a flag counter showing there are 10 flags to be reviewed:    Clicking on that flag counter leads to an empty page:        The moment I visit that page (through clicking on the flags counter, or by going to the review queue first then clicking on Tools, selecting the flags tab if not already selected), the flags counter disappears from the toolbar:    but after a while (half an hour, an hour?) the flag count re-appears in the toolbar.  Either the counter is wrong (presumably taken from a Redis cache somewhere) or the 10k flag review page is falling over every time someone tries to load it.  This at first appeared to happen only on Meta, on Stack Overflow the flags page has plenty to review. However, there are now  on Stack Overflow.


I am making a little game in pygame, for use in reinforcement learning (openAI gym) but I'm encountering an issue with lists/dictionaries. I presume this is to do with empty lists all pointing to the same memory address, but I do not understand why/how or how to avoid it in this scenario.  Ultimately I want to be able to use empty lists or dicts for this, I am trying to group a list of tuples of the form ((int1, int2), int3)) by their second element (int3).  I have tried using copy() when initializing the empty array but with no difference. I did not find/understand anything useful from tutorials or docs pages, so I would greatly appreciate a brief explanation of how to avoid this issue.  def works(t):     lst = [[1],[2],[3]]     lst[1].append([x for x in t if x[1]==1])     return lst  def does_not_work(t):     lst = 3*[list()]     lst[1].append([x for x in t if x[1]==1])     return lst  t = [(('a'), 0), (('b'), 1), (('c'), 1), (('d'),2)] print('Expected Result:') print(works(t)) print('Confusing Result:') print(does_not_work(t))   Expected Result: [[1], [2, [('b', 1), ('c', 1)]], [3]] Confusing Result: [[[('b', 1), ('c', 1)]], [[('b', 1), ('c', 1)]], [[('b', 1), ('c', 1)]]]

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


From my understanding of Fermat's Principle, you decide a start point and an end point for a light ray to travel between, and the light 'chooses' whichever path takes the least time (or technically whichever path the time is 'stationary' at).  So consider the following, you set up the start point, A, and the end point, B in different mediums. Of course the path of minimum time is that which obeys snells law.    However if the light is coming from box which has only has a small hole in it (as shown in the diagram), the light is unable to follow this path of least time. But it is still the path of least time, so why is Fermat's principle no longer obeyed?    Does Fermat's Principle simply not apply for when there are objects that can block/absorb the light? Do we therefore assume that light is able to reach every point in space when using Fermat's Principle? If so, what is the point othe principle?

Here is a question that's been bothering me since I was a sophomore in university, and should have probably asked before graduating:  In analytic (Lagrangian) mechanics, the derivation of the Euler-Lagrange equations from the principle of least action assumes that the start and end coordinates at the initial and final times are known. As a consequence, any variation on the physical path must vanish at its boundaries. This conveniently cancels out the contributions of the boundary terms after integration by parts, and setting the requirement for minimal action, we obtain the E.L. equations.  This is all nice and dandy, but our intention is finding the location of a particle at a time in the future, which we do not know a priori; after we derive any equations of motion for a system, we solve them by applying initial values instead of boundary conditions.   How are these two approaches consistent?


After repeatedly losing data on encrypted drives due to some trivial combination of software and hardware failure, I would like to know if there is a simple tool that keeps local folders synchronized. Like a local "cloud" service that runs on one computer and synchronizes any changes in one folder to the other folder as soon as both folders are available. That way I can keep a copy of the most important files on a different hard-drive.

I want to do one way synchronization.  I am having Folder A on my computer which is constantly updated with content. Another Folder B is used for backup purpose which is on external HDD.  Now what I expect is that whatever extra which is present in folder A should go to folder B. However something which is present in B and NOT in A ""shall NOT be copied to A"".  In a nutshell, the backup folder may copy everything from the source folder, however nothing should be copied form backup folder to the source.


I'm making a blackjack game and have a <button id='standBtn'>Stand</button>. I want to get this button "clicked" automatically if(score(myCards) === 21){/* click Stand button */}

I'd like to make a click event fire on an <input type="file"> tag programmatically.  Just calling click() doesn't seem to do anything or at least it doesn't pop up a file selection dialog.  I've been experimenting with capturing events using listeners and redirecting the event, but I haven't been able to get that to actually perform the event like someone clicked on it.


Normally we fetched the label name by using label.labelname in apex code but i want to fetch the label name by using variable in apex code.Anyone have idea?

In apex you can reference a custom label with system.Label.labelName, but is there a more dynamic way to get a custom label for example system.Label.get(labelName)? I can't find anything like this in the documentation but was hoping it was possible.   I'm trying to have custom labels for fields to support multiple languages. The list of fields I'm showing is built in the controller and displayed inside an apex:repeat tag so I can't hardcode the labels. Is there a way to accomplish this?  Thanks!


I'm currently reading about how the computer works, specifically how the CPU, RAM, hard disk drive work together simultaneously.  According to what I have read, the CPU uses what is called a control unit to get the data from RAM. And then processes the data.  But before the CPU can get data from RAM, the data must be loaded from the Hard Drive to RAM since access to RAM is faster than access to the Hard Drive.  My question is: Can the CPU get data directly from the Hard drive?  How does the Hard disk drive transfer data or load the data to RAM? Just as the CPU to RAM using control unit?  I have read a little about I/O disk. Has I/O disk something to do with this?

I understand that there is such a thing as a disk controller which contains a buffer, but was wondering if the CPU reads directly from this buffer, or whether the data must first go to a specific location in memory, and then allow itself to be read by the CPU?  Does anyone also know what the buffer is called? And how does DMA fit into all this?


Is it possible to create a multi-page PDF using Adobe Illustrator with various elements on a page linked to other pages in same PDF?  The purpose is, we want to output semi-interactive prototypes with Illustrator.  EDIT on receiving a possible duplicate: My question is about creating links that point to different pages in the same file, not an Internet address. (something like #page3)

I am creating a CV in Illustrator and exporting it to a PDF. I just read an article which stated that it is a good idea that we use hyperlinks in the CV so that the employer can just click and not have to copy the address. I like this idea, but I don't know how to add a hyperlink to text in Illustrator. Is it possible?


I manually created a vertex group with needed vertices in blender. How do I get indices of its vertices to then create a vertex group with this vertices via python?

How to select and assign vertices to a vertex group via python? I have a script that generates random hair on sphere, and I want to make it work for a custom head mannequin, so I have to assign vertices to a vertex group for scalp hair, and then apply my script on it, so it adds hair only to the scalp part?


When I ran sudo apt-get update then I found some error. The Error is like below:  W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/main/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/restricted/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/restricted/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs E: Some index files failed to download. They have been ignored, or old ones used instead.   Could anyone please help me why I am getting this kind error message? I've just found the Error message today on my machine

When updating I got this error message:  W:Failed to fetch cdrom://Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)/dists/oneiric/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W:Failed to fetch http://ppa.launchpad.net/synce/ubuntu/dists/your_ubuntu_version/main/source/Sources  404  Not Found   What to do?


I went to a realitives home who has a cealing fan installed  . I noticed the cealing fan has a set up of what I’m trying to accomplish,   with remote and power is controlling a lap in the room .I opened up the switch plate and noticed The wiring is three sets of wiring: All blk capped All white capped All grounding capped And remote cealing fan mounted next to switch The only difference is this cealing fan has the reviver and remote transmitter  option to be able to select different frequencies to communicate with remote and the transmitter  ?? When I remove the cover to the  access thr batteries and on the fan recicer I can see the option to mix the  numbers as well? On The cealing fan I’m trying to connect dose not have these the option to select different frequency on the remote and transmitter? I went home and connected all the wires the same but the fan did not work ?  Dose anyone have any suggestions? I’m thinking to re- purchase a fan that has the option to select the number frequency option  and seen if that has anything  to do with why the fan is not getting power. Thank you anyone Ed Beal if you have any suggestions

The current switch controls an outlet in the corner of the room for a lamp. I pulled it out and noticed three sets of individual wires: two set of wires coming up into the box from the bottom, and one set with a red wire coming down into box.  All the white and grounding wires are capped.  Also all the black wires are capped; one set I’m assuming is the hot since I see it contains a red wire. On the back of the switch, the top two ports have black wires and the bottom right has the one red wire.  There are two black pigtail wires coming off the black capped wires. I tried to connect a separate switch to control a ceiling fan with remote. I ran new wire making the old switch box into a two switch. I ran 14/2 gauge wire to ceiling for fan / light remote combo. Fan didn’t work after multiple re-wiring  combinations. The breaker did pop and half click when it popped. Then I thought to re-wire the ceiling fan wires as if I was going to make it into outlet only and use a tester to indicate an open ground, or a wiring error but the two light on tester are both orange indicating correct wiring. I heard that sometimes the ceiling fan remote transformer goes bad. Should I check batteries and/or unit placement? I’m really confused at this point why the light is not working at least with remote after follow wiring installation instructions that were included with the fan. I think it’s my wiring with the switch. The way I left the wiring is that it has constant power. As if we’re a outlet the current switch does not turn it off.


My Chrome extensions are constantly being deleted.    It happens when my laptop is in use and I reload them every time it happens for fear of my data being corrupted. I estimate they delete themselves twice an hour.   I have found forums discussing this as a Chrome fail, I have not found discussions relating this to a virus.  I have tried:   Cleaning for virus & malware Reinstalling Chrome Uninstalling suspicious programs Junkware removal tools Syncing my settings while leaving out "extensions" Removed the unwanted extension from Google Chrome Run extensions in developer Mode Remove the related registry entries in HKEY Local Machine & HKEY Current User Removed extension's files using  %LOCALAPPDATA%\Google\Chrome\User Data\Default\Extensions & deleted all files & emptied reclycle bin.    I frequently run:   Stinger 32 AdwCleaner Msert CCleaner64 McAffee Security Scan Plus   This started after I removed a series of viruses "Buy The App" and "Cut THee Price."  I thought this might have been related to those, but now all scans have come out clean.     The extensions that delete themselves are Ghostery & AdBlock Plus.  I need help please?

What should I do if my Windows computer seems to be infected with a virus or malware?  What are the symptoms of an infection? What should I do after noticing an infection? What can I do to get rid of it? how to prevent from infection by malware?   This question comes up frequently, and the suggested solutions are usually the same. This community wiki is an attempt to serve as the definitive, most comprehensive answer possible. Feel free to add your contributions via edits.


, but could a much stronger and faster animal? This viral video shows a moose running across a body of water:   Some say the video is fake. Others think the water must be shallow. We probably won't resolve these issues here. My question is: could this actually happen (in deep water)? I imagine that in theory, a sufficiently strong animal could kick the water really hard and if it moved across the surface really fast, it could stay above the water. But could a real animal with a moose's strength and weight do it?

I was thinking about Flash, the superhero, or the little boy in the Incredibles.   There is  that doesn't answer a lot. Especially, I don't think surface tension would help a lot for a human to run over water, I think one would have to build on the inertial effect of the water.  There is one empirical approach based on figuring out the speed at which bare-footed water skiing is done, but I wasn't able to find a decent number. Still the difference may be that a hypothetical runner would have to propulse herself over the water, which may or may not make the thing more difficult.  Hence, I raise the question here.


I have stumbled upon a "feature" of Python, like so:  x = 256 x is 256   # returns True  x = 257 x is 257   # returns False   Integers in range [-5, 256] (inclusive) return True, while others return False.  I understand that the 'is' operator tests for the same reference, while the '==' operator tests for the same value. However, I don't understand the dark magics involved here, and Googling "Python is" doesn't help. Anyone have a nudge in the right direction?  My intuition is that the numbers that return True have permanent locations in memory - behind the scenes, Python is replacing both 'x' and '256' with a reference to that location. Less frequently used numbers do not, and are thus stored in whatever memory is available. But I wasn't a CS major, so I'm behind the curve on the "lower level" aspects of programming. (Working on it, however...)

Why does the following behave unexpectedly in Python?  >>> a = 256 >>> b = 256 >>> a is b True           # This is an expected result >>> a = 257 >>> b = 257 >>> a is b False          # What happened here? Why is this False? >>> 257 is 257 True           # Yet the literal numbers compare properly   I am using Python 2.5.2. Trying some different versions of Python, it appears that Python 2.3.3 shows the above behaviour between 99 and 100.  Based on the above, I can hypothesize that Python is internally implemented such that "small" integers are stored in a different way than larger integers and the is operator can tell the difference. Why the leaky abstraction? What is a better way of comparing two arbitrary objects to see whether they are the same when I don't know in advance whether they are numbers or not?


Let $l^2 = \{x = (x_n)| x_n \in \mathbb{R}, \sum_{n=1}^{\infty} x_n^2 < \infty\}$  be the Hilbert space of square summable sequences and let $e_k$ denote the $k^{th}$ co-ordinate vector (with $1$ in $k^{th}$ place, $0$ elsewhere). Which of the following subspaces is NOT dense in $l^2$?   span$\{e_1-e_2, e_2-e_3, \ldots\}$ span$\{2e_1-e_2, 2e_2-e_3, \ldots\}$ span$\{e_1-2e_2, e_2-2e_3, \ldots\}$  span$\{e_2, e_3, \ldots\}$                                                        I have knowledge in Analysis , metric spaces , Topology. Still I find this problem   unacquainted. Can anyone please tell me which portion to read to be able to answer this question?

Let $l^2 = \{x = (x_n)| x_n \in \mathbb{R}, \sum_{n=1}^{\infty} x_n^2 < \infty\}$  be the Hilbert space of square summable sequences and let $e_k$ denote the $k^{th}$ co-ordinate vector (with $1$ in $k^{th}$ place, $0$ elsewhere). Which of the following subspaces is NOT dense in $l^2$?   span$\{e_1-e_2, e_2-e_3, \ldots\}$ span$\{2e_1-e_2, 2e_2-e_3, \ldots\}$ span$\{e_1-2e_2, e_2-2e_3, \ldots\}$  span$\{e_2, e_3, \ldots\}$   By definition, we have to prove that for any $x \in l^2$ and for any $\epsilon > 0$, there exists $y$ in the respective sets such that $\|x-y\| < \epsilon$. How to proceed further?


I'm looking to recreate this effect in Photoshop by giving a shadow only to the corners of the rectangle (in this case a sticky note):

Where can I find PSD file or tutorial to create the effect of frame with shadow (see red arrow in image)


Click:   Profile -> View network profile -> accounts or activity  Any community you've selected to "hide" from actually is not hidden here; it's completely public. I logged out and tested it on my own profile and nothing is actually hidden.  So, what's the point...? I'd really like to not have my profile tied to certain communities where things are more personal but I really don't want to have to make a separate account and lose my previous points/badges.

My communities are visible to the Moderators and Stack Exchange employees, Its fine. But it says, "Other people may also be able to associate your presence on those communities with your public list in certain cases." If other people also can see my hiding communities then what is the uses of Hide communities here in Stack Exchange? Every general users are able to see my communities here.


This question hasn't popped up in any of my games, whether as DM or player, but I thought of it while coming up with character concepts and wondered how it should be ruled. If a caster does not have hands, can they perform the somatic components of their spells? For example, if a player has the idea to have a caster born without arms who uses somatic components using their "ghost limbs" should they be able to since the restriction that they're not wielding weapons or a shield isn't being infringed? Alternatively, if the above is true, does that mean players couldn't disable an enemy caster they captured by Skywalker-ing their hands so they don't have a free hand to cast the spell with? The Player's handbook describes somatic components as:  Spellcasting gestures might include a forceful gesticulation or an intricate set of gestures. If a spell requires a somatic component, the caster must have free use of at least one hand to perform these gestures.  But I don't know how I'd interpret this. I guess the main question is do somatic component rules emphasize having a (free) hand or do they emphasize not wielding an item/weapon? Are there any official rules for these edge cases or is there a way to interpret the rules on somatic components that answers these questions?

My DM and I have been having friendly arguments, and we recently came to what would happen if my character lost all their limbs.  As a gnome beastmaster I said I would always sit on my mount and use mage hand (from magic initiate) when I need to eat or lift things. HOWEVER he argues I wouldn't be able to perform the somatic component.  So, I ask: is there a way to cast spells without arms? My argument is that since I am learning the cantrip after losing my arms I would have learned it in a way that works with my stumps, but he points out the PHB is pretty clear you need a free hand.


I've seen the other questions, but almost all of them deal with manipulating quantum states so that the other person reads a message in the data.  However, you cannot force a quantum state on something without breaking entanglement. So here is my idea.  I know that it can't work, but I don't know why.  If someone could point out the flaw, I would appreciate it.  I do not claim to be an expert. So there is the .  If I pass a single photon through a double slit, it will create an interference pattern.  This is the evidence that it is in a quantum state because a single particle should not be interfering with itself. In reading article above, this also works my photon happens to be entangled with another photon. Now in the quantum eraser section of the linked article above, it goes on to mention that if you apply a filter to one of the photons (i.e. measure it), than the interference pattern of both collapses.  Thus, by measuring the quantum state of one, both collapse. So, here is how I propose FTL communication. Method Lets say I create streams of quantum entangled photons.  I will split up the pairs of quantum entangled photons and send one half to $A$ and the other half to $B$ in order.  Thus, the first photon that $A$ receives will be entangled with the first photon that $B$ receives. At $B$'s end, each photon will be run through the double slit to detect whether an interference pattern exists.  If there was an interference pattern, then this is encoded as a binary $0$.  If there isn't an interference pattern, then this is a $1$.  It doesn't matter which slit the photon is known to travel through - the simple absence of the interference pattern is enough. At $A$'s end, to communicate, I will encode my message in binary and then encode each bit in photon stream.  If the next bit is a $1$, I will measure the next photon, thus collapsing its quantum state and eliminating the interference pattern.  If the next bit is a $0$, I will not measure the next photon. Example $A$ needs to send 1101.  $A$ would measure the first, second, and forth photons.  At $B$'s end, when these photons are run through the double slit, you would see that the first, second, and forth have no interference pattern, so you would know they are $1$s.  The third retains an interference pattern, so it would be a $0$. Two-Way Communication This allows $A$ to communicate to $B$ instantly.  For $B$ to communicate back, you could create another set of streams where $A$ runs the photons through the double slit and $B$ measures to collapse the quantum state on some photons.  Alternatively, odd numbered photons can be used for the reverse communication, so long as both $A$ and $B$ agree. Summary So, what is wrong with this method?  It does not try to force a photon to go through a slit, but rather uses the act of observing or measuring to collapse the quantum state.

It is often stated, particularly in popular physics articles and videos, that if one measures a particle A that is entangled with some other particle B, then this measurement will immediately affect the state of the entangled partner.  For example, if Alice and Bob share an entangled pair of electrons and Alice measures her spin in the $x$ direction, then Bob's spin will also end up spinning in that direction, and similarly if she measures in the $z$ direction. Moreover, the effect will be instantaneous, regardless of the spatial distance between the two particles, which seems at odds with special relativity.  Can I use a scheme like this to communicate faster than light?


Use the precise definition of a limit to show that $$\lim_{x\to 0} e^x=1.$$ By definition, I understand I need to show that: for every $\epsilon>0$, there exists a $\delta>0$ such that $0<|x-0|<\delta \implies |e^x-1|<\epsilon$ for all $x$. I am able to show this, by finding such $\delta$, if I assume $(e^x-1)>0$ but otherwise not. Any idea on how to proceed with the general case with the absolute value is appreciated.

We have been asked to prove the above statement through the two sub-proofs:   Firstly we must prove that $e^x$ is increasing and then prove that $\log(x)$ is also an increasing function.   After we are asked to prove that using the delta-epsilion definition of a limit that $\lim_{x \to 0} e^x = 1$.   I have done all of this but still don't see where the instructor is going with this.


My Firefox is using a lot of memory. I noticed that as soon I open the firefox browser (with default tab), it opens 5 processes in the taskbar. After that it starts one process for each tab. Is this normal behavior of Firefox or is it some problem with my browser?

According to  on MDN, Firefox 57 finally runs things in different processes.  So is Firefox 57 multithreaded?  In particular, how many cores does it use at most? Say I open 20 tabs at once on a quad-core machine, will Firefox 57 launch as many threads, or at least as many as needed to max out my CPU?  (Chromium for instance spawns a number of sub-processes and very easily uses all the resources available. Firefox up to 56 in GNU/Linux is rarely seen going over 135 % of one core however many tabs I open.)


I'm working on an add in that generates new structures for an addressing system. The tool is working well, but as it runs, at some point it changes tabs in the Table of Contents to the "List By Source" tab. I'm guessing it does this either when I add temporary tables or shapefiles.   The fact that it changes tabs is not a problem, but I would like for the tool to leave the user in the TOC tab "List By Drawing Order" when it is finished.   Is there any way for a python code to change tabs in the TOC ?

I would like to be able to script some things that are not exposed via arcgisscripting or ArcPy.   How do I access  from Python?


I'm rendering long animations and it's important to me to save time. In the preview, a frame is rendered in 30 seconds, but if I render the animation, the render time of one frame increases to 2 minutes. Why does this happen and how can I get the final render with time of the preview render?

When I'm using rendered viewport it initially takes a while before rendering starts, but once it does, I can freely move around and rendering a new view happens almost instantaneously. When on the other hand I'm rendering a movie, for each frame Blender takes a significant amount of time before rendering even starts, usually doing the following:  Synchronizing object, Updating images, Updating meshes, Updating Scene BVH, Packing BVH,  Why does it do this? And is it possible to disable this to increase movie rendering speed?


I began to answer this proof and got stuck in middle of it. Given: $f(z)$ is analytic in the domain D, $|f(z)|$ is analytic in the domain D. Proof: $f(z)$ is constant in D. $f(z) = u + iv$ , where $u$ and $v$ are real-valued function in the domain D. By hypothesis, $f(z)$ is analytic and Cauchy-Riemann Equations holds. $$\frac{\partial u}{\partial x} = \frac{\partial v}{\partial y} , \frac{\partial u}{\partial y} = - \frac{\partial v}{\partial x}$$ then $|f(z)|$ , where $u$ and $v$ are real-valued function in the domain D and the Cauchy-Riemann Equations holds. $|f(z)| = \sqrt{u^2(x,y)+v^2(x,y)} \rightarrow |f(z)|^2 = u^2(x,y) + v^2(x,y)$. Then $\frac{\partial u}{\partial x} (u^2) = 2uu_x$ , $\frac{\partial v}{\partial y} (v^2) = 2vv_y$ , $\frac{\partial u}{\partial y} (u^2) = 2uu_y$ , $-\frac{\partial v}{\partial x} (u^2) = -2uu_x$. This is where I am confused where to go to show its constant or not.

Show that if $f$ is analytic in a domain $D$ and $|f(z)|$ is constant in $D$, then the function $f(z)$  is constant in $D$.     Here is what I try so far.  So we are given that $|f(z)|$ is constant in $D$, so that means $|f(z)|^2 = u^2 + v^2$ is also constant.  If either $u = 0$, or $v = 0$, then $f(z)$ is constant.  $$\frac{\partial|f(z)|^2}{\partial x} = 2u \frac{\partial u}{\partial x} + 2v \frac{\partial v}{\partial x} = 0$$  $$\frac{\partial|f(z)|^2}{\partial y} = 2u \frac{\partial u}{\partial y} + 2v \frac{\partial v}{\partial y} = -2u \frac{\partial v}{\partial y} + 2v \frac{\partial u}{\partial x} = 0 $$  So what do I do to finish this proof? Would I have to use the Cauchy Riemann equation?


I have an object myobject, which might return None. If it returns None, it won't return an attribute id:  a = myobject.id   So when myobject is None, the stament above results in a AttributeError:  AttributeError: 'NoneType' object has no attribute 'id'   If myobject is None, then I want a to be equal to None. How do I avoid this exception in one line statement, such as:  a = default(myobject.id, None)

If I had a dictionary dict and I wanted to check for dict['key'] I could either do so in a try block (bleh!) or use the get() method, with False as a default value.  I'd like to do the same thing for object.attribute. That is, I already have object to return False if it hasn't been set, but then that gives me errors like     AttributeError: 'bool' object has no attribute 'attribute'


I am using phpmysql for my website. And I store Unicode in utf8_general_ci.  When I tried to display the Unicode column using php some ????????? is displayed instead of Unicode data.  Note: I just tried to retrieve the data from database using mysqli.   Thanks

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I tried compiling a ~1 year old document today and noticed that I got an error when using a uppercase greek letter in a chemical reaction.   Here's an MWE (with an example from the mhchem manual):   \documentclass{article} \usepackage{mhchem} \begin{document} $\ce{x Na(NH4)HPO4 ->[\Delta] (NaPO3)_x + x NH3 ^ + x H2O}$ \end{document}   It should produce:   But instead gives an error:   ! Undefined control sequence. <argument> ...r_lower_case:f {Delta}}\prop_get:cV                                                    {l__chemgreek_uppercase_ma... l.4 ...PO4 ->[\Delta] (NaPO3)_x + x NH3 ^ + x H2O}   I've made sure my packages are up to date:   Package: mhchem 2015/11/29 v4.03 for typesetting chemical formulae   I'm guessing this package is important:   Package: chemgreek 2016/01/07 v1.0d interfaceforuprightgreeklettersforuseinchemistry (CN)   It doesn't make any different if I load mhchem in compatibility mode ([version=3]).  Last time I compiled my file correctly, I had version 3.21 of mhchem and chemgreek seem to not have been used by mhchem (not loaded in log file).  Package: mhchem 2015/03/13 v3.21 for typesetting chemical formulae   Can the error be reproduced on other machines?  Is it a known bug? Is there a quick-fix?    Here's the file list as requested by @JosephWright:   *File List*  article.cls    2014/09/29 v1.4h Standard LaTeX document class   size10.clo    2014/09/29 v1.4h Standard LaTeX file (size option)   mhchem.sty    2015/11/29 v4.03 for typesetting chemical formulae    expl3.sty    2016/01/03 v6358 L3 programming layer (loader)  expl3-code.tex    2016/01/03 v6358 L3 programming layer  l3pdfmode.def    2015/11/11 v6250 L3 Experimental driver: PDF mode l3keys2e.sty    2015/12/20 v6326 LaTeX2e option processing using LaTeX3 keys  l3regex.sty    2015/12/20 v6326 L3 Experimental regular expressions l3tl-build.sty    2015/12/20 v6326 L3 Experimental token list construction l3tl-analysis.sty    2015/11/09 v6244 L3 Experimental token lists analysis   l3flag.sty    2015/12/20 v6326 L3 Experimental flags l3str-convert.sty    2015/09/26 v6106 L3 Experimental string encoding conversio ns     calc.sty    2014/10/28 v4.3 Infix arithmetic (KKT,FJ)  amsmath.sty    2016/03/03 v2.15a AMS math features  amstext.sty    2000/06/29 v2.01 AMS text   amsgen.sty    1999/11/30 v2.0 generic functions   amsbsy.sty    1999/11/29 v1.2d Bold Symbols   amsopn.sty    1999/12/14 v2.01 operator names chemgreek.sty    2016/01/07 v1.0d interfaceforuprightgreeklettersforuseinchemis try (CN)   xparse.sty    2015/12/20 v6326 L3 Experimental document command parser graphics.sty    2016/01/03 v1.0q Standard LaTeX Graphics (DPC,SPQR)     trig.sty    2016/01/03 v1.10 sin cos tan (DPC) graphics.cfg    2010/04/23 v1.9 graphics configuration of TeX Live   pdftex.def    2011/05/27 v0.06d Graphics/color for pdfTeX infwarerr.sty    2010/04/08 v1.3 Providing info/warning/error messages (HO)  ltxcmds.sty    2011/11/09 v1.22 LaTeX kernel commands for general use (HO)   ifthen.sty    2014/09/29 v1.1c Standard LaTeX ifthen package (DPC) supp-pdf.mkii pdftexcmds.sty    2011/11/29 v0.20 Utility functions of pdfTeX for LuaTeX (HO) ifluatex.sty    2010/03/01 v1.3 Provides the ifluatex switch (HO)    ifpdf.sty    2011/01/30 v2.3 Provides the ifpdf switch (HO) epstopdf-base.sty    2010/02/09 v2.5 Base part for package epstopdf   grfext.sty    2010/08/19 v1.1 Manage graphics extensions (HO) kvdefinekeys.sty    2011/04/07 v1.3 Define keys (HO) kvoptions.sty    2011/06/30 v3.11 Key value format for package options (HO)   keyval.sty    2014/10/28 v1.15 key=value parser (DPC) kvsetkeys.sty    2012/04/25 v1.16 Key value parser (HO) etexcmds.sty    2011/02/16 v1.5 Avoid name clashes with e-TeX commands (HO)  ***********

I updated MikTex 2.9 Monday, and now can't compile while loading 'mhchem'. I'm using pdflatex [Version 3.14159265-2.6-1.40.16 (MiKTeX 2.9 64-bit)] to compile the following:  \documentclass{article} \usepackage[version=4]{mhchem} \begin{document} Hello, world! \end{document}   throws the following error:  ! LaTeX error: "kernel/command-not-defined"  ! Control sequence \prop_get:Nn undefined.  ! See the LaTeX3 documentation for further information.  ! For immediate help type H <return>.  l.180 ..._variant:Nn \prop_get:Nn           { cV }  | This is a coding error.  | LaTeX has been asked to use a control sequence '\prop_get:Nn': this has not been defined yet.


I'm flying from New Zealand to Europe and can't decide what flights to book. Flights via the US take the same time as flights via Asia. Which ones would be best for jet lag? Does departure/arrival time matter for jet lag too?

I was having a discussion with a friend about this. Usually, I understand that when traveling east, jet lag is worse than when traveling west.   However, when the time difference is (about) 12 hours, I posed that there would be no difference, as the directionality of the time shift makes no difference to the time of day at your destination (3 PM +/- 12 hrs is 3 AM, the only difference is the date).   My friend countered that it's not the time difference at the destination per sé that makes the difference, but the length of daylight during the flight. When traveling east, you'd fly into the sun, which would cause your perceived days to be compressed. When traveling west, your day would be extended. In their view, this made the difference.  I'd like scientifically sound proof of either one of these hypotheses, but personal experience is also much appreciated.


How do u know when the "ou" in route is pronounced as "oo" or "ow"? Or does it just depend on the person who says it

I have always used both "root" as in route 66 and "rooter" as in the networking device. The latter has gotten me funny looks often, however I could not bring myself to accept the inconsistency. Today I heard "rowt"  used for a path of movement by a radio presenter. Which is correct?


We want to prove that $a+b\sqrt2+c\sqrt3 +d\sqrt6 =0$ where $a,b,c,d \in \mathbb Q$ such that $a=b=c=d=0$.  Can we prove that    there exists no linear combination of $1, \sqrt3, \sqrt6$ that gives $\sqrt2$ there exists no linear combination of $1, \sqrt2, \sqrt6$ that gives $\sqrt3$ there exists no linear combination of $1, \sqrt3, \sqrt2$ that gives $\sqrt6$ there exists no linear combination of $\sqrt2, \sqrt3, \sqrt6$ that gives $1$   Which would mean they are all linearly independent?  So for the first one, I would do suppose there does exist $a,b,c \in \mathbb Q$ such that $\sqrt2=a+b\sqrt3 + c\sqrt6 $ but we can minus $a$ from both sides and then square both sides, then we would get after rearranging: $$\sqrt2 = \frac{2+a^2 -3b^2 - 6c^2}{2a+6bc}$$ which can't be true so there is no linear combination.  And then do similar for the rest of the 3 parts I named?  This question is very linked to  but I decided to make a new thread because asking this is very lengthy as you can see.

How do I prove that $1$,$\sqrt{2},\sqrt{3}$ and $\sqrt{6}$ are linearly independent over $\mathbb{Q}$? $\mathbb{Q}$ is the rational field.  I want to know the detail about the proof. Thanks in advance.  Actually I know any two of them and three of them are linearly independent.


Is there a rule for the placement of the subject to the second sentence? I mean  , but subject also ...  or  , but also subject ...

I think I generally agree with the statement  When using not only . . . but also in a sentence, parallelism should be the goal. It means that the words following both parts of this correlative conjunction (i.e., not only and but also) should belong to the same parts of speech.   However, the Cambridge dictionary has an example that is not 100% parallel in my eyes, as "but also" is split:  Not only did she forget my birthday, but she also didn’t even apologise for forgetting it.   What I would expect, with maximum parallelism, is  Not only did she forget my birthday, but also she didn’t even apologise for forgetting it.  Is my expectation wrong? Is my formulation acceptable?


I am creating a image carousel where the other images hover behind the focused one. As you can see in my fiddle the click event works when you click the first image to the left, but not for the next image that appears there. Any inclination as to what I'm doing wrong?  I am new to jquery and I'm sure there is an easier way to do this but I'm trying to figure it out and I am getting stumped every time. Here is my fiddle...

   .position-1 {     position: absolute;     left: 30%;     transform: scale(1.1);     box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19); } .position-2 {     opacity: .4;     position: absolute;     z-index: -2;     left: 10%; } .position-3 {     opacity: .4;     right: 10%;     position: absolute;     z-index: -2; } .position-4 {     opacity: 0;     z-index: -10;     left: 30%;     position: absolute; }  $("#content-2.position-2").click(function() {   $("#content-2.position-2").addClass(" position-1");     $("#content-2.position-2").removeClass("position-2 ");     $("#content-3.position-3").addClass(" position-4");     $("#content-3.position-3").removeClass("position-3 ");     $("#content-4.position-4").addClass(" position-2");     $("#content-4.position-4").removeClass("position-4 ");     $("#content-1.position-1").addClass(" position-3");     $("#content-1.position-1").removeClass("position-1 ") }); $("#content-4.position-2").click(function() {   $("#content-4.position-2").addClass(" position-1");     $("#content-4.position-2").removeClass("position-2 ");     $("#content-2.position-1").addClass(" position-3");     $("#content-2.position-1").removeClass("position-1 ");     $("#content-1.position-3").addClass(" position-4");     $("#content-1.position-3").removeClass("position-3 ");     $("#content-3.position-4").addClass(" position-2");     $("#content-3.position-4").removeClass("position-4 ") });

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I'm working on a 2D array. The problem is really simple but I can't figure it out. When I try to access the value from index array[i-1][j] it is throwing a Null Pointer exception. While it seems completely legitimate to me to access a index like array[2-1][2] . Why it is not working? Is there any logic behind why I can't access array from one back index OR am I doing it wrong please explain.  Code to declare and initialize array:  this.Result = new Integer[len][6];   Code where Null pointer exception occurring:  for(int i=0;i<Result.length;i++) {     if(i==0){         Result[i][4]=0;     }     else if(Result[i][1]!=null) {         Result[i][4]=(Result[i-1][2]+Result[i-1][3])+Result[i][2];     } }   Thanks in advance and please ignore grammar mistakes.

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


If I install LAMP in my Ubuntu 16.04 Desktop and make it as my web development environment, would it break my Ubuntu 16.04 desktop?

I just installed Ubuntu on my computer as a beginner and found out there is no LAMP server available in the software center. I'm somehow stuck on how am going to install LAMP server on my Ubuntu since there is no particular website for doing that.  Please , where are the sources where I can install LAMP server into my computer and the processes I will follow to make it work.  Thanks.


Could anyone give me example of the following?  A group $G$, a subgroup $H$, $a$ is a fixed element in $G$, such that $aH$ is a proper subset of $Ha$ and $aH \neq Ha$.

Let $G$ be a group, $H\subseteq G$ a subgroup and $a\in G$ an element of the group. Is it possible that $aHa^{-1} \subset H$, but $aHa^{-1} \neq H$?   If $H$ has finite index or finite order, this is not possible.


I played a little with the compiz settings and the Unity top panel and dash disappeared.  They aren't loaded anymore. I tried  but I had no success.  Temporary I installed kubuntu-desktop (KDE) that runs fine, but I want Unity back.  How can I do this?    Solution  I posted my solution .

When I login, nothing happens.   I am presented with my desktop wallpaper.    No Dash, no Launcher, nothing.


I want to use unicode character 2259 "estimates" in my document, but cannot find it in the symbols-a4 list or via .  It looks exactly like this: ≙  The closest I get is \triangleq: ≜, but it has a different meaning.

Recently in some LaTeX documentation I noticed that there is a special LaTeX command for the symbol meaning "corresponds to", which is similar to an equal sign with a hat on top. \hat{=} or \widehat{=} both do not give satisfying results (my personal view). Unfortunately, I cannot remember which documentation it was! Does anyone know the command or the documentation where to find it?   The symbol I am looking for:    PS: I have already tried  but it didn't produce anything useful! Also, browsing  wasn't successful.


How do I get such a notation for vectors in LaTeX?

Apologies for the cryptic title, but I was not sure how best to phrase the question in one sentence. I am essentially trying the create a vector symbol with \rightharpoonup as the top instead of the arrow.  The output to the following code will feature an overset harpoon over x, next to a simple \bar{x}. Observe that on the left, the top symbol is significantly higher and bigger than on the right one.  \documentclass{article}  \usepackage{amsmath,amsfonts,amsthm,amssymb}  \newcommand{\vect}[1]{\overset{\rightharpoonup}{#1}}  \begin{document} $$ \vect{x} \quad \bar{x} $$ \end{document}   I would like to create something that looks in every way like the right hand symbol, except using something that looks like \rightharpoonup at the top.  If this command sequence already exists in LaTeX, please use that as an answer, because I have searched for and failed to find it so far.


This question is from Nielson and Chuang's Quantum Computation and Quantum Information:    Here $|\alpha\rangle$ is given by: $$\frac{1}{\sqrt{N-M}}\sum_{x} "|x\rangle $$ where $\sum_{x}" |x\rangle$ is the sum of states which are not the solution.  and $|\beta\rangle $ is given by: $$ \frac{1}{\sqrt{M}}\sum_{x} ' |x\rangle $$ where it represents all $M$ solutions.  $\theta$ is defined by: $$\cos\Big(\frac{\theta}{2}\Big) = \sqrt{\frac {N-M}{N}}$$  I understand everything mentioned above as well as the further geometric visualization. However, I am having trouble trying to come up with a justified way to solve this exercise. The only thing that I understand is that $G$ must be a unitary Matrix made up of trigonometric functions. How can I approach this problem?

I have seen that it is possible to represent the Grover iterator as a rotation matrix $G$. My question is, how can you do that exactly? So we say that $|\psi\rangle$ is a superposition of the states of searched and not searched elements, that can be represented like this: $$|\psi\rangle=\sqrt{\frac{N-1}{N}}|\alpha\rangle+\sqrt{\frac{1}{N}}|\beta\rangle$$ Now you can rewrite that so you get this expression: $$|\psi\rangle=\cos(\theta/2)|\alpha\rangle+\cos(\theta/2)|\beta\rangle$$ I have seen that an application of the Grover iteration can be represented as a rotation matrix, e.g. in this form: $$G=\begin{pmatrix}\cos(\theta)&-\sin(\theta)\\\sin(\theta)&\cos(\theta)\end{pmatrix}$$ But how do you get to the shape, what are the necessary steps and calculations?  I hope that the question is expressed as understandably and clearly.


Like this :  I hava a float number 25.56,I could translate it to the four hexadecimal number E1 7A CC 41 in js.And the translate way is called as union in C.  But I don't know how to change the E1 7A CC 41 to the float in js

How do you convert decimal values to their hexadecimal equivalent in JavaScript?


I am pretty new to jQuery so I have a problem with this. I am trying to check if input is empty by jQuery. I have this script:    $('#submit').click(function(){   if($.trim($('#username').val()) == ''){     alert('Input can not be left blank');   } }); <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input name="username" id="username" type="text" placeholder="Enter your Username"/> <button class="btn btn-info btn-block login" name="submit" id="submit" type="submit">Create an Account</button>     Thanks for reply.

I saw , but I didn't see a JavaScript specific example. Is there a simple string.Empty available in JavaScript, or is it just a case of checking for ""?


Why is Down syndrome more common than say trisomy 18? Is chromosome 21 easier to replicate? Or is it because those babies are more viable?

Certain  such as trisomy-21 (Downs syndrome), trisomy-18 (Edward syndrome), Turner syndrome (XO) etc are more common than others.  I had a vague thought that it is related to chromosome size: the chromosomes which are towards the extremes of size will be affected in an improper segregation event.   Chromosomes 13, 18, 21 and Y are among the smaller chromosomes in humans, and are commonly associated with aneuploidy (but 22 which is also small is not affected). The larger ones are unaffected (X is an anomaly).   I thought that longer ones should be more affected because more  bridges have to be broken, but it seems that is not the case.   Is there any association of chromosome size and frequency of aneuploidy?    EDIT   If the difference is because of differential lethalities then does the length correlation still hold true? Smaller the chromosomes, lesser the genes and hence lesser would be the effect of extra copy on the cellular biochemical networks.


I noticed a video titled something like "What is an NFT?" and immediately thought the title is wrong and it should be "what is a NFT?" But after trying to pronounce it with "a" I understand (I think) why people say and write "an NFT". Also did some searching and found both "an NFT" and "a NFT" are used for videos and articles. Is the easy pronunciation what makes people use "an NFT" or there is some rule for why "an" is used?

The indefinite article "an" is used when the following word starts with a vowel sound. For example one write "an adjective" but "a noun".   However, when an abbreviation is used, should this be based on the expanded meaning, or on the letters of the abbreviation.  Specifically, one writes "a noun phrase". However, here on ell.se, the abbreviation "NP" for 'noun phrase" is commonly used. If this were pronounced by sounding out its letters, as "En-Pee" it would call for "an". If it were read as "noun phrase"  it would call for "a". Should one write "a NP" or "an NP" here on ELL?  I incline to "a NP" and i used that in  just a few minutes ago, but I am not at all sure.


There are 5 points on a plane, from which no 3 points are collinear. Proove, that from this points you always can choose 3, which are vertices of obtuse triangle. I already figured out, that they must form a Pentagon, but I cannot come up with ang idea.

I have no idea how to prove it, any advice?


Say I have an great answer that I have already revised 9 times and now I have a substantial edit to make so that the answer will be even better, is there any way I can make those edits without my answer becoming a community wiki?  If the answer is no, then it's not likely that I'll edit it.  Feature Request: Maybe we could allow popular answers (which users tend to put more work into) more revisions before they become CWs.

I would like to update  to add some new information. (I realized that when "walking the clustered index" of a table that has a multi-column clustered index, in most cases a great simplification can be achieved by using WITH TIES in the update statement to enable working only with the first column of the clustered index. I'd also like to change a couple of other minor things.)  However, if I make this update, I'll hit 10 updates, and the answer will get converted to community wiki. I hate asking moderators to remove community wiki status--it seems like a waste of their time. At the same time, it bugs me that my answer is not as good as it could be! And yes, it bugs me to lose the reputation if it goes community wiki.  Note that I am doing my best to make more substantial edits and fewer trivial ones, so I don't run into this limit as often. But it does happen sometimes. You can look at the answer history to see if you think that my 8 edits were excessive or not.  Should I:   Avoid making the edit, Make the edit in pursuit of having the best answer and just take my lumps so I don't inconvenience moderators, Or make the edit and flag for a moderator as it's not that big a deal for them?


If I'm playing a level 5 character with Spellcasting and multiclass to gain level 1 Warlock gaining Pact Magic, can I use my primary spell slots to cast my Warlock spells?  For example, is casting Hex using one of my 3rd level slots allowed?

The Pact Magic paragraph on page 164 of the Player's Handbook multiclassing section reads:      you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know.   If I were to multiclass as a Warlock 5 / Rogue 3 Arcane Trickster and cast a Warlock spell using my Arcane Trickster's 1st level spell slot, would it be cast as a 3rd level spell?  From the Warlock Spell Slots section on page 107 of the Player's Handbook:      The table also shows what the level of these slots is: all of your spell slots are the same level.   The  appears to only address the issue of spell slot recovery, not casting.


Im using SQL Server 2005.  I have a table1 with  3 columns. And table2 with 4 columns.  I want to insert the records from table1 into table2.  But I dont want to insert into column1 from table2.  I want to start inserting from column2 on.  What can i do? Thanks...

I am trying to INSERT INTO a table using the input from another table. Although this is entirely feasible for many database engines, I always seem to struggle to remember the correct syntax for the SQL engine of the day (, , , , and ).  Is there a silver-bullet syntax coming from an SQL standard (for example, ) that would allow me to insert the values without worrying about the underlying database?


I have upgraded to 20.04. Arduino IDE loaded with: snap install arduino  as suggested (version 1.8.13). The port selection item cannot be selected. As suggested in other posts, I have done: sudo usermod -a -G dialout $USER  Actually, this added dialout in groups. I rebooted, dialout is still in groups, but still the port cannot be selected and, of course, I cannot upload anything on Arduino.

As we know Arduino has non-official Snap which can access serial ports only if  (but not indicated in snap find output):  $ snap find arduino Name                  Version  Developer  Notes  Summary arduino-mhall119      1.8.5   mhall119   -      Arduino IDE   Arduino packages from repositories :     Package arduino  trusty (14.04LTS) (electronics): AVR development board IDE and built-in libraries [universe] 1:1.0.5+dfsg2-2: all xenial (16.04LTS) (electronics): AVR development board IDE and built-in libraries [universe] 2:1.0.5+dfsg2-4: all artful (electronics): AVR development board IDE and built-in libraries [universe] 2:1.0.5+dfsg2-4.1: all bionic (electronics): AVR development board IDE and built-in libraries [universe] 2:1.0.5+dfsg2-4.1: all    According to  site the latest version of Arduino IDE is 1.8.9.  One can download IDE from official site, extract and install it with install.sh. Then when newer version will be released repeat this action. But it looks difficult and not user-friendly.  How can I get latest Arduino IDE installed in user-friendly way?


I am trying to find the last 2 digits of $\ 49^{19}$ but I am having some trouble. So far I know that   x = $\ 49^{19}$ mod 100 x = $\ 49^{19}$ mod 25 x = $\ 49^{19}$ mod 4  I can then apply the CRT and set u = 4 $\ *$ ( $\ 4^{-1}$) mod 25 and v = 25 $\ *$ $\ 25^{-1}$ mod 4. However I am having trouble finding x.

I am trying to get an idea of how the  can be used to finish up , in which the problem  $$7^{30}\equiv x\pmod{ 100}$$  is attempted by splitting the modulus into relatively prime factors $25$ and $4,$ arriving at  $$\begin{align} 7^{30}&\equiv1\pmod4\\ 7^{30}&\equiv-1\pmod{25} \end{align}$$   I understand that the CRT may be called upon because $m=\prod m_i,$ and we have the same $7^{30}$ value on the LHS, but I don't know how to carry it out.  The question was touched upon in  as the second entry:     How do I efficiently compute  $a^b \pmod c$ when $b$ is less than $c.$ For instance $5^{69}\,\bmod 101.$   However, I don't see this particular point clearly worked out, perhaps because it is a multi-pronged question.    Following , this seems to be the verbatim application of the CRT without any added concepts or shortcuts:  From @gimusi's answer (upvoted):  $$\begin{cases} x \equiv 7^{30} \pmod4\\ x\equiv 7^{30} \pmod{25} \end{cases}$$  rearranged into  \begin{cases} x \equiv 1 \pmod4\\ x\equiv -1 \pmod{25} \end{cases}  Given the general form of the equations above as $x\equiv a_i \pmod {m_i},$ the  $x\equiv a_1 b_1 \frac{M}{m_1}+a_2 b_2 \frac{M}{m_2}\pmod M$ with $M=\prod m_i,$ and with   $$b_i =\left(\frac{M}{m_i}\right)^{-1}\pmod {m_i}.$$  The inverse of $\frac{M}{m_i}$ is such that $\frac{M}{m_i}\left(\frac{M}{m_i}\right)^{-1}\pmod {m_i}\equiv 1.$   Calculating the components:  $$\begin{align} a_1&=1\\ a_2&=-1\\ M&=4\times 25 =100\\ \frac{M}{m_1} &= \frac{100}{4}=25\\ \frac{M}{m_2} &= \frac{100}{25}=4\\ b_1 &= \left(\frac{M}{m_1}\right)^{-1} \pmod 4 = (25)^{-1}\pmod 4 =1\\ b_2 &= \left(\frac{M}{m_2}\right)^{-1} \pmod {25}= (4)^{-1} \pmod{25}=19 \end{align}$$  Hence,  $$x=1\cdot 25 \cdot 1 + (-1)\cdot 4 \cdot 19 = -51 \pmod{100}\equiv 49.$$


I asked a question. It was put on hold. I rephrased the question but later decided to repost the edited question. It was flagged as a duplicate. Now,  I would like to delete one of them.   How can I do that?

What circumstances can cause a question or answer to be deleted, and what does that actually mean?    How can a post be deleted? When can't I delete my own post? Can I still see my post even after it's deleted? Can I see a list of my deleted posts? How can I undelete one of my posts? What does deletion mean for a post? How do votes to delete work? What are the criteria for deletion? What else should I know about deleted posts? If I flag my question with a request to delete it, what will happen?       For more information, see the articles about  and  in the .


Let $n\in\omega$ and $F\subset n$.  How do i prove that $F$ is finite?  I know that this can be proven by constructing a function in a following way: take $f(0)$ as the least element of $F$ and then take $f(1)$ as the least element of $F\setminus \{f(0)\}$ and continue this process. Since $F\subset n$, $F$ has a maximal element. Thus this process must be done in a finite step.  However, i don't know how to prove this precisely. How do i write down "this process must be done in a finite step" in first-order logic and so on. Please help :)

We define $A$ to be a finite set if there is a bijection between $A$ and a set of the form $\{0,\ldots,n-1\}$ for some $n\in\mathbb N$.  How can we prove that a subset of a finite set is finite? It is of course sufficient to show that for a subset of $\{0,\ldots,n-1\}$. But how do I do that?


The most statistics I ever took was a few lessons on it back in high school. What always bothered me is how arbitrary the definitions seemed. For instance, I remember having trouble with the definition of standard deviation.     The standard deviation of a set of values $X$ is the square root of the average of the squared of the differences between each value in $X$ and the average of $X$.   At school, standard deviation was never given any more precise definition than "a number that gives you a rough idea how 'diffuse' the dataset is". While I can see in a very approximate way that this is basically correct, it's a long way from how definitions of concepts in math are usually explained. Usually there's a precise notion that we're trying to capture, and a clear explanation as to how our definition captures that notion.  But here, when I asked for further information, I was told things like "you square the differences to make them positive", when what I was hoping for was something like:   A specific real-world concept that the definition captures. A class of problems in which the definition arises naturally. A specific mathematical property that we would like to have, which leads necessarily to this particular definition.   Is there any rigorous basis for the definitions in statistics, or do we genuinely just make up formulae that kinda sorta get us something like what we're trying to calculate? Have I just never seen statistics as it really is, or is it actually very different to every other field of mathematics? If the former, can you recommend a book that explains statistics in the way I'd like?

Let's take the numbers 0-10.  Their mean is 5, and the individual deviations from 5 are -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 And so the average (magnitude of) deviation from the mean is $30/11 \approx 2.72$.  However, this is not the standard deviation.  The standard deviation is $\sqrt{10} \approx 3.16$.  The first mean-deviation is a simpler and by far more intuitive definition of the "standard-deviation", so I'm sure it's the first definition statisticians worked with.  However, for some reason they decided to adopt the second definition instead.  What is the reasoning behind that decision?


I want to animate a plane xyz coordinates, its scale on xyz and its rotation on the z axis based on a text file data where each line its a frame.  Example text file:  2265.48 563.242 0 166.402 166.402 100 7.3225 2266.61 562.668 0 166.529 166.529 100 7.32268 2267.35 562.864 0 166.622 166.622 100 7.32859 ...   Where the data is organized like this:  [x coordinate] [y coordinate] [z coordinate] [x scale] [y scale] [z scale] [z rotation]   I dont have experience in python so i would like a helping hand if possible.

I would like to do 3D animations.  M spheres appear moving around and rotating along N frames (all spheres will appear in every frame).   For each sphere at every frame, these values are saved in a text file, which I'd like Blender to read:   position   angle rotation   Is it possible to read this file from blender, (so that Blender will create N frames and move and rotate at each frame the M spheres with the data read)?  I can write the file with the positions and angles in the most easily format to perform this. Eg. csv file:  time step | sphere number | x | y | z | mx | my | mz   (where m is refered to the rotation components)


Situtation   I want to install ubuntu alongside windows 7. I have 3 partitions on my internal hard-disk (C,D,E) and one external hard disk drive. I have removed external hard disk drive (from USB port) as i do not want to mess-up with my data on the this drive. I formated (as NTFS) my drive D in windows 7 to install ubuntu on this drive. Created a bootable USB with ubuntu 14.04.1   Problem   Installation is showing Windows 7 detected but no option to install alongside windows.       Updated          output of     sudo parted -l

I'd like to see the full How-To on how to use manual partitioning during Ubuntu installation. The existing guides (at least those I found here) cover only automatic part and leave untouched the manual part (or extremely short and contain no pictures).  I'd like to cover such situations:     If your disk contains other systems:


If an opponent gains control of my turn using  could they spend all my mana on  if I don't have any creatures in my graveyard?

Say I have a  on the field and a . The equip cost for piston sledge is "sacrifice an artifact". If I control no creatures, can I sacrifice the Mycosynth Wellspring to the Piston Sledge to benefit from its ability, or does the equip ability require a valid target in order to pay its cost?


I am familiar with group theory and topology. Now I am studying the concept of  topological group. As per , it is defined as follows: Let $G$ be a group together with a topology $\textit{T}$ defined on it. Then the topological space $(G,T)$ is said to be a topological group, if the following two functions  $G \times G \to G$, $(x,y) \mapsto xy$, $G \to G$, $x \mapsto x^{−1}$  are continuous. I can understand that the first condition gives a relationship between the binary operation defined on $G$ and the topology $T$. But I couldn't get why the second condition is necessary ? What will happen if we exclude the second condition ?

According to , a topological group $G$ is a group and a topological space such that  $$ (x,y) \mapsto xy$$ and $$ x \mapsto x^{-1}$$  are continuous. The second requirement follows from the first one, no? (by taking $y=0, x=-x$ in the first requirement)  So we can drop it in the definition, right?


I will soon receive a buiness visa after one month duration is 3 months. I might sound funny, but will I get into a trouble if im not a buiness man?? I dont even have work, but I mean I have saved my money. But like buiness visa require me to fill in some working information , so I randomly fill in some working information that i have worked before. Will this be a problem??  Have any one also traveled in Russia over 30 days as buiness visa holder? If so please I really hope I can hear from you , I have no one to ask in Taiwan.  Is there some regions that business visa holder can't enter? Because I know there are a lot of region that tourist visa holder can not enter, but I mean I'm a business holder.

I want to ask about registration within seven days in each new city in Russia. I know there are a lot of people asking this question before but I really need more data about this. I would love to provide a bit more information about myself than ask for questions.  I’m from Taiwan. I really hope someone who has traveled in Russia more than two weeks could answer my question with your experiences.  So basically next year I am planning to live in Russia 90 days with business visa, and I don’t have friends over there. I basically want to live nearby Couchsurfing, or directly ask people if I could stay with them, because I don’t have that much of money to living hotel or live in hostel  every day.  I was living in Vladivostok Russia for 30 days but when I left customs nothing happened -- customs never checked my registration. On top of that I googled, and a lot of people seemed to have the same situation as me: no one checked their ”within 7 days registration”; on the other hand, there are a bunch of people who are claiming that I must register or otherwise I will have big trouble.  Here are my questions:   Since I’m planning to live in different cities by hitchhiking, how can I register ”registration within 7 days stuff?” Has anyone been stopped by police and had their registration checked?  Has anyone been traveling on a buiness visa like me as well? How is the process of registration? Is it complicated and time consuming? No one talk about the valid time for the registration; for example, if I was planning to stay in whatever which city for 10 days, but then I stayed for 20 days, do I need to register again? Even though I stay in the same city?   Or is it so that with registration in a city, it doesn’t matter how many days you stay? It's just a proof that I’m actually visiting there?


Epson L210 printer and scanner was working in Ubuntu 14.04 but upgrading to 16.04 only printer is working. I have the scanner driver deb amd 64 package but I don't know how to install.

How do I install a .deb file via the command line?


Since to days ago I'm receiving DDOS atacks in my server. I've installed mod_evasive in apache and it works right! It writes the log and send the email with de IPs.  But there's a problem: Apache doesn't add the DROP rule in iptables (or at least it doesn't appear)  I'm using apache in Plesk, the configuration file is like:  DOSHashTableSize 3097 DOSPageCount 1  DOSSiteCount 50 DOSPageInterval 1 DOSSiteInterval 1 DOSBlockingPeriod 600 DOSSystemCommand "sudo /sbin/iptables -A INPUT -s %s -j DROP" DOSEmailNotify "xxx@xxx.com" DOSLogDir "/var/log/evasive/"   Here is my 'sudoers' file:   apache ALL=(ALL) NOPASSWD: /sbin/iptables -A INPUT -s [0-9.]* -j DROP   But that doesn't help.  Thanks in advance.

This is a  about DoS and DDoS mitigation.   I found a massive traffic spike on a website that I host today; I am getting thousands of connections a second and I see I'm using all 100Mbps of my available bandwidth.  Nobody can access my site because all the requests time out, and I can't even log into the server because SSH times out too!  This has happened a couple times before, and each time it's lasted a couple hours and gone away on its own.  Occasionally, my website has another distinct but related problem: my server's load average (which is usually around .25) rockets up to 20 or more and nobody can access my site just the same as the other case.  It also goes away after a few hours.  Restarting my server doesn't help; what can I do to make my site accessible again, and what is happening?  Relatedly, I found once that for a day or two, every time I started my service, it got a connection from a particular IP address and then crashed.  As soon as I started it up again, this happened again and it crashed again.  How is that similar, and what can I do about it?


I'm building my own website for a project. I have an event page where I show all upcoming events. Every time you add an event, the page will get bigger. ATM, the footer is in the middle of the page because there are not enough events.  The problem is, I want the footer to be on the bottom of the screen, unless the page is bigger than the screen. If the page is bigger than the screen, the footer should be on the bottom of the page.  I tried to use height: 100% or height: 100vh but they put the height on "fit to screen", so if there are for example 20 events (bigger than the screen), the footer will be stuck on the bottom of the screen and the events will go through the footer.  The page now looks like this:     and the table is build up like this:

       Date/Time	       Event

                      #_EVENTDATES                 #_EVENTTIMES         	                      #_EVENTLINK             {has_location}
#_LOCATIONNAME, #_LOCATIONTOWN #_LOCATIONSTATE{/has_location}

I have a simple 2-column layout with a footer that clears both the right and left div in my markup.  My problem is that I can't get the footer to stay at the bottom of the page in all browsers.  It works if the content pushes the footer down, but that's not always the case.


The first screenshot is using the default keyboard. You can see the input fixed to the top of the keyboard.  I'm using Gboard in the second screenshot. No matter how far I scroll, I can't see my input.

The Japanese keyboard on iOS dynamically changes it's height to show suggestions and hides the input box of new mobile chat.        Additionally, third-party keyboards make the input box completely hidden. The chat seems to treat third-party keyboards as having no height.        iOS 9.2.1 / Mobile Safari  There is no problem in old (stable) design but it doesn't fix the input box to bottom!


I know that I can use Sylow's theorem because $7$ is prime, and so is $2011$. So, $14077$ has the form $p^{a}m$ where $p \nmid m$ for some $a$ and $p$ is prime. Moreover, we know from previous results that there are exactly two subgroups of the group of order $14077$, one subgroup for each divisor of $14077$.  Both of those subgroups then, call them $Q_{7}$ and $Q_{2011}$ would be cyclic because each has prime order. So...is this good enough to prove that the group of order? I feel like I am missing a step, and I have seen other problems use external direct products.  Do I need to do that here to show $Q_{14077}=Q_{7}$ X $Q_{2011}$?

I don't know about the Sylow Theorems.  But I have been wondering about a proof of the fact that a group or order $pq$ where $p$ and $q$ are distinct primes must be cyclic. I can't quite work out the details, but here is the general idea. I would like help with filling in details. I assume that it is already known that $G$ has subgroup(s) of order $p$ and subgroup(s) of order $q$.  If $G$ is a group of order $pq$ ($p\neq q$), then I know that $G$ has a subgroup $H$ of order $p$ and a subgroup $K$ of order $q$. Then $H\simeq \mathbb{Z}_p$ and $K\simeq \mathbb{Z}_q$.   But then $H\oplus K \simeq \mathbb{Z}_{pq}$, so I would think that $H\oplus K \simeq G$. I guess one could do an internal direct product instead of an external direct product, but I don't know that $H$ and $K$ are normal subgroups.  I am asking for help completing this argument.  Edit: I see from the comments below that I might need to assume that the smaller prime does not divide the larger prime minus $1$. Or maybe it is enough to assume that the primes are greater than or equal to $3$ (Still distinct).