Currently, I am a Master's student, and I sent an email to a professor from another department in my university. The email was about a topic which could simply be answered as yes or no. But, I have not received an answer from the Professor yet, and since I use official university email account, I have no doubt that it was not classified as spam.  It will be nearly a week, what should I do next ? Should I go directly and talk with the Professor, assuming that he did not notice my email ? Even if I was not able to arrange an appointment with him via email, should I directly knock his door, will this be considered rude ? I don't think it should be difficult to say a simple no as an answer.

As a grad student, I just find it tremendously frustrating when emails are ignored by faculty (both at my institution and at other places). Is this acceptable? I'd be content with a simple response with one line along the lines of "I have read this email and am busy right now, will respond in X days when I can write a more detailed email." I understand that, as a first year student in my field, I'm not really in a position to request anything of anyone, but it just seems like common decency.  Instead, I never hear back, as if my email has been jettisoned off into oblivion.


Let $G$ be a finite group and $N$ be a normal subgroup $N\lhd G$ such that the factor group $G/N$ is nilpotent. Then there exists a nilpotent subgroup $H$ of $G$ such that $G=HN$.  proof:  I consider an arbitrary nilpotent subgroup $H \leq G$. Then, there exists a number $t$ such that $H^{(t)}=\{e\}$. Since $G/N$ is nilpotent, there exists a number $k$ such that $(G/N)^{(k)}=\{e\}$ implying that $G^k/N = \{e\}$. Also, since $N\lhd G$ and $H\leq G$, $HN$ is a subgroup of $G$. Then, we can write that $|HN|\leq |G|$. If I can show the inequality $|G|<|HN|$, then the proof will be done.   How can I show this equality $|G|<|HN|$?

Let $G$ be a finite group and $N$ be a normal subgroup of $G$ such that $G/N$ is nilpotent.  a) Prove that there exists a nilpotent subgroup $K$ of $G$  such that $G=NK.$  b) Suppose that $N$ is abelian and $Z\left(G\right) =\lbrace e \rbrace.$ Show that if $K$ is nilpotent and $G=NK$ then $K=N_G\left(K\right)$ and $K \cap N =\lbrace e \rbrace.$  Could anyone help me to give a solution for the problem! thank you!


Today John Chan . So now we are forced to see the review view again. I honestly can't recall the last time the review view of the ask a question page yielded anything useful to me. Hence I was very glad I could skip it by simply pressing enter in the tags tab. Can we please have this functionality back, perhaps as a privilege?

This is terrible . I understand that the motivation behind "Review your question" is quality control, but if there is nothing for me to review, why can't the question be submitted in a single click?  Instead the page jumps back, to draw my attention to possibly this:    But it doesn't stand out in the UI, and if you didn't read that the button said "Review your question", it's hard to see why the page just jarringly jumped back instead of posting the question.  Is it really important for me to know that the automated system didn't find any way to improve my question?  Does Stack Exchange have metrics to see how often the question passes the quality check in the first go?  To add a minor point, as a veteran Stack Exchange user, the system doesn't have any reviews most of the time (in fact, the only time it had one is today while posting this question where it reminded me that one of feature-request, bug, .. tags were required).


Please forgive any ignorance I display in the course of this question. Is it possible to plug in a second machine somehow to an unresponsive machine to recover data? I'm very desperate right now and am scouring the internet for any possible options. I'm running Ubuntu off a Live CD.   There was a lack of information provided. Here is updated information:  Running Ubuntu off of a live disk. At first the computer was completely unresponsive. After a few hours, the screen woke up, now there's been a black screen for twelve hours with only the mouse cursor showing. So far I've tried Ctrl+Alt+F1, which didn't work. I have no idea what to use as the second machine; I could use anything Windows or Linux based, loaded on my laptop.  If shutdown isn't an option, is there any other way to access RAM? That's what I'm trying to do by connecting a second machine. I don't even know if this is a viable option, just asking.

Would there by some way to pull the power instead of conventional shut down, and recover the contents of ram without loading the operating system upon the next start-up? I'm trying to recover files open on an unresponsive Ubuntu live cd.  Update:  I read the paper suggested by Alex and I think that's probably my best bet. Like Dan D said, you don't need liquid nitrogen, the paper itself suggests dust cleaner fluid in those cans to lower the temperature. I'll give it a try and post the results here. If anyone has any suggestions, please let me know.  From what I gathered from the paper, I lower the RAM's temperature to around -50 degrees before cutting power, cut power, boot a modified program supplied by the paper's authors from a USB stick, which then dumps the RAM's contents to the USB.


I want to get it to loop at each method/section, but I'm getting errors. When I comment out each do while, they work perfectly, however as a whole I get:     Exception in thread "main" java.lang.StringIndexOutOfBoundsException:   String index out of range: 0 at java.lang.String.charAt(Unknown   Source) at RecursionTester.main(RecursionTester.java:25)   My code:  import java.util.Scanner;  public class RecursionTester {      public static void main(String[] args) {          int power;         int base;         String sentence;         int digit;         int num;         char answer;          Scanner sc = new Scanner(System.in);         do {             System.out.print("What base would you like? ");             base = sc.nextInt();              System.out.print("What power would you like? ");             power = sc.nextInt();              System.out.println(base + " to the " + power + " power is " + raiseToPower(base, power));              System.out.print("\nWould you like raise another number to a power (y or n)? ");             answer = sc.nextLine().charAt(0);         } while (answer == 'Y' || answer == 'y');          do {             System.out.print("Type a sentence and check if it's a palindrome: ");             sentence = sc.nextLine().trim();              if (palindrome(sentence))                 System.out.println(sentence + " is a palindrome");             else                 System.out.println(sentence + " is not a palindrome");              System.out.print("\nWould you like to reverse another text string (y or n)? ");             answer = sc.nextLine().charAt(0);         } while (answer == 'Y' || answer == 'y');         sc.close();     }      //private methods here }

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


I am a not a computer geek, so I probably think this is dumb questions.. I have a vista 32 bit and trying to install Ubuntu, When I run the file with iso player, it said that I need to reboot PC and run as CD. And I do not know how to do this.. The thing is that I don't have a cd to burn that iso file and not sure it will work even if I burn iso file.   Anyone can help me out about it?

I've downloaded the daily Ubuntu 12.04 iso.  I currently have windows 7 x64 operating system installed.  How can I make a bootable usb from the Ubuntu iso?


I'm currently attending Norwegian high school and I'm in a course where we study electricity, automation, electronics, and almost no physics, chemistry etc.   So it will be at least 5-6 years before I can think of taking any education in physics, however, I would like to get the basics going.  So I wondered if anyone has any suggestions regarding books to start reading. I would like some very basic ones, the only physics I've had is junior-high level (newton laws, gravity pull etc.)  Any suggestions?

Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start.  All the questions linked below, as well as others which deal with more specialized books, can be found under the tag  (formerly ).  If you have a question to add, please edit it in. However, make sure of a few things first:   The question should be tagged  It should be of the form "What are good books to learn/study [subject] at [level]?" It shouldn't duplicate a topic and level that's already on the list   Related Meta:


I have always seen a bicycle not standing without any support, it either falls down to the right or to the left, may even to some other direction. But,the same two wheeler when under motion,moves balanced, without falling to either side,even it not falls, when the two wheeler is bent to left or right by the driver, like the one which we could see in the bike races. So, what makes the bicycle at rest to fall? And what makes it not to fall when under motion?    MY VIEW ON THE CONCEPT If the bicycle is at rest, it will be acted upon by downward force ($mg$,where $m$ is mass and $g$ is acceleration due to gravity). If it is affected just by this force, it should have stood without falling, because there is no force which pulls it  to either side to make it fall. I think, it might fall, either due to the direction of wind, or due to the nonuniform distribution of mass, or due to other external forces. If we consider the same bicycle to be under motion, I don't know what makes it not to fall,even affected by nonuniform distribution of force,or direction of wind. I think there might be something related with , ,and forces like  and . (What ever I said, is just my opinion about the concept, I don't claim it to be true. Correct me,if I am wrong anywhere.)

Why does a bike/bicycle fall when its speed is very low or close to zero and is balanced when going with a high speed?


My MacBook Pro was stolen a couple of days ago and Find my Mac had been enabled on it. I have already locked the Mac with a passcode and a message as well as clicked on the play sound feature(on the find my iPhone app), but those actions are pending until the computer comes online. The Mac is on El Capitan and came with Mavericks. The admin user is password protected but I had not enabled FileVault which is the disk encryption feature, so the computer can be wiped by erasing the disk in Recovery. The computer doesn't need to connect to the internet to be erased but it does need an internet connection to reinstall the operating system after the wipe. My question is, if the computer is erased and then goes online, will Find my Mac still work and notify me when it does? Is it still asociated with my Apple ID after the wipe?

Possible Duplicate:          I lost my Macbook Pro recently. I had activated iCloud on the computer, so Find My Mac is operable.   If the thief wipes the hard drive, and installs a fresh operating system, OSX Lion or Leopard, for example, then will I still be able to locate my device? In particular if the thief installs Leopard (which obviously doesn't support Find my Mac) will Find My Mac still work?


Suppose a complex valued function $f$ is of class $C^1$ defined on the disk $|z-z_0|<R,$ and let $C_r$ denote the circle $|z-z_0|=r$ with $0<r<R$. Prove that  $$\lim_{r \to 0}\frac{1}{2\pi i r^2} \oint_{C_r} f(z)\mathrm{d}z={\frac{\partial f}{\partial \bar{z}}(z_0)}.$$ My idea is to estimate $\oint_{C_r} \frac{1}{r^2}f(z)\mathrm{d}z-\oint_{C_r}\frac{\partial f}{\partial \bar{z}}/(z-z_0)dz$ by writting in a parametric form. But I got stuck when I tried to estiamte $f(z)(z-z_0)-r^2\frac{\partial f}{\partial \bar{z}}.$ Can you give me some hints to estimate that quantity? Like can I use talor expansion in polar coordiante?

Well, after spending hours on this problem, I'm still stuck, so I thought I'd turn to you guys. The problem statement is as follows.  Let $f$ be a complex-valued function that is $C^1$ in the disk $|z - z_0| < R$ for some $R>0$, and let $C_r$ be the circle $|z - z_0| = r$. Show that $$\lim_{r\to 0} \frac{1}{r^2}\int_{C_{r}}f(z)dz = 2 \pi i\frac{\partial f}{\partial \bar{z}}(z_0).$$  I tried parametrizing the circle in the usual way and differentiating to see if I get something useful, but no luck. I just can't get the LHS to give me something to do with $\frac{\partial f}{\partial \bar{z}}$, so that I could then put the RHS under the integral and show that the difference between the two can be less than arbitrary $\epsilon > 0$ by the continuity of partial derivatives.  Thanks in advance for your help!


How to find the last two digits of $$(3^{1997})$$ ......  I tried to do $$(3^{1997})$$ (mod 100) . I reached on that $$3^{20}$$ is congruent to 1 (mod 100) .  But the calculation was getting very long after that . If anyone could correct me (or shorten) my method . Actually i have got the answer as 63 by this long process

I was wondering if there is a simpler way to find the last to digits of a power such as $3^{45}$. I reduced it modulo 100 to get the answer, which is 43. But I was curious if there was a simpler, or more eloquent way to get this result.  Here's my method:  Using the fact that $3^4=81\equiv -19 \pmod{100}$ and $19^5=2,476,099\equiv -1 \pmod{100}$  $$ 3^{45}\equiv 3(3^4)^{11}\equiv 3(-19)^{11}\equiv 3(-19)(19^5)^2\equiv 3(-19)(-1)^2 \equiv -57 \equiv 43 \pmod {100} $$  I just felt like this was sort of a messy way to find out that the last two digits are 43.


before in Ubuntu 12.04 when I make simple bash commands, it works but in Ubuntu 13.10 I can only open it with gedit! How I can run it by only one click?

When I double-click on a script in Nautilus in order to run it, the script opens in my text editor with no option to do so.  Using Nautilus, how do I run executable text files and/or scripts?


I have a piece of simple tex code which compiles on all of my computers. But it doesn't show properly on my laptop  \documentclass{standalone} \usepackage{pstricks-add}  \psset{gridcolor=green, subgridcolor=yellow} \begin{document}    \psset{unit=1cm} \centering \begin{pspicture}(-7.5,5.2)(7.5,8.4)   \psgrid   \rput[B](0,8){     \psframebox[linestyle=none,fillstyle=solid, fillcolor=gray!20]{       \Rnode{A0}{$a_0$}       \Rnode{A1}{$\cdots$}       \Rnode{A2}{\color{red} $a_{t-2m-1}$}       \Rnode{A3}{$\cdots$}       \Rnode{A4}{$a_{t-m-1}$}     }   } \end{pspicture} \end{document}   Here I show the problematic result:    It should have a frame box around the content in gray color. Also, it should have shown the grid. I am using Texlive 2014, the most updated version. I compared the log files for the correct result and wrong result, which are exactly the same. No error reported. However, I don't know what is wrong.   Using latex and then dvipdf could get the right file.  I have delete the texlive and reinstalled. Nothing changed. It seems that something related to the operating system is affecting. Please help. Thanks.  I am using Arch linux.

I have problems with XeLaTeX and pst-node: If I want to draw a line between two nodes, but there is nothing drawn in the pspicture. If I only put the nodes with some stuff withoud a line in, the nodes are drawn, but the line is missing.  The way LaTeX -> DVI -> PS -> PDF works, but not direct to pdf with XeLaTeX. Can anyone help me here?  MWE  \documentclass{scrartcl} \usepackage{pstricks} \usepackage{pst-node} \begin{document}  \fbox{     \begin{pspicture}(-1,-1)(2,2)     \rput(1,0){\rnode{A}{Stuff A}}     \rput(0,1){\rnode{B}{Stuff b}}     \ncline{A}{B} \end{pspicture} }  \begin{pspicture}(-1,-1)(2,2)     \rput(1,0){\rnode{A}{Stuff A}}     \rput(0,1){\rnode{B}{Stuff b}} \end{pspicture}  \end{document}   Edit: Added \listfile:     *File List*   scrartcl.cls    2013/12/19 v3.12 KOMA-Script document class (article)   scrkbase.sty    2013/12/19 v3.12 KOMA-Script package (KOMA-Script-dependent bas   ics and keyval usage)    scrbase.sty    2013/12/19 v3.12 KOMA-Script package (KOMA-Script-independent b   asics and keyval usage)     keyval.sty    2014/05/08 v1.15 key=value parser (DPC)   scrlfile.sty    2013/12/19 v3.12 KOMA-Script package (loading files)   tocbasic.sty    2013/12/19 v3.12 KOMA-Script package (handling toc-files)   scrsize11pt.clo    2013/12/19 v3.12 KOMA-Script font size class option (11pt)   typearea.sty    2013/12/19 v3.12 KOMA-Script package (type area)   pstricks.sty    2013/12/12 v0.60 LaTeX wrapper for `PSTricks' (RN,HV)      ifpdf.sty    2011/01/30 v2.3 Provides the ifpdf switch (HO)   pstricks.tex    2014/08/27 v2.57 `PSTricks' (tvz,hv)   pst-xkey.tex    2005/11/25 v1.6 PSTricks specialization of xkeyval (HA)    xkeyval.sty    2014/05/25 v2.7 package option processing (HA)    xkeyval.tex    2014/05/25 v2.7 key=value parser (HA)     pst-fp.tex    2014/08/27 v2.57 `PST-fp' (hv)     xcolor.sty    2007/01/21 v2.11 LaTeX color extensions (UK)      color.cfg    2007/01/18 v1.5 color configuration of teTeX/TeXLive      xetex.def    2014/07/25 v4.03 LaTeX color/graphics driver for XeTeX (RRM/JK)    pst-node.sty    2010/04/22 package wrapper for pst-node.tex   pst-node.tex    2014/08/04 1.35 `pst-node' (tvz,hv)    ***********   I use texlive 2014 with:   This is XeTeX, Version 3.14159265-2.6-0.99991 (TeX Live 2014/W32TeX) (preloaded format=xelatex)  \write18 enabled.


I have not been able to find a working example in QT creator or gallery to use SQLite offline storage API for an Ubuntu touch application.

I'm working on a small game and i'd like to know how can i write/read a user settings file in ubuntu touch?


I was doing a question for Yahoo Answers and suddenly I can't choice. Maybe because I never study English(after elementary and high school), I don't know which is the right sentence?  Of course I know that I should study, and I'll do.  Many thanks.

He will understand that I was not joking.   He will understand I was not joking.  Which of the sentences is correct? Are there any specific rules about the use of "that" in the sentences I reported as example?


I want to write just one Matlab-command in LaTeX. I want this command to be in the same line of my document as other text is:   some text... size(t) ...some text.   I tried \begin{verbatim} size(t) \end{verbatim}.  But this puts the size(t) in an extra line. How can I achieve this?

I have a document where I quiet often refer to source code element, such as class names, I wanted to format these strings differently, but at the beginning I didn't want to fiddle with various options I had, rather I defined my custom command as follows:  \providecommand{\inlinecode}[1]{\texttt{#1}}   Now my question is, what do you think is the best way to define \inlinecode? Note: I often use text with unescaped <, >, e.g., List<T>.   The \texttt looks fine to me, and works with <, >, but sometimes the words overflow the line. Is there any way to tell latex not to overflow the line, but rather "underflow" or insert more spaces between words, which seems to me as (maybe still ugly but) more acceptable than overflow? And is it possible to achieve it by only changing definition of my command, so I won't have to change the whole source?


I recently did a google search which resulted in links to a domain "stackoverflow.com.exactgo.com". If I enter the "Exactgo.com" domain into the browser, reddit.com content is displayed.  I am not sure if this is a phish/fraud or anything similar but I would think that the management of stackexchange might not be too happy about this - provided that the domain does not belong to them.  Here is the google query in question:    one of the results point to:     If you want to see more results, simply google for "what is exactgo.com", most of the results are similarly redirected stackexchange network pages.

We all love & benefit from SO, and want to help keeping it profitable. How can we help? What counts as trademark infringement:  What is an illegal SO clone:  BTW: I want to report . I think it follows the trademark guidelines, but obviously steals the trademark.


I am trying to make a simulation of a program which simulates different threads removing and adding objects in an ArrayList. However, late in the simulation I get concurrentModificationExceptions (when the threads are trying to access and modify the same variable while an iterator is being used to iterate through the data). I have searched it up and seen some topics about this saying that I needed to use locks/synchronization and/or using ListIterators instead of enhanced for-loops, however, none of these options seemed to fix the problem. Here is what I have tried to do so far:  public Object removeSomething1(){     synchronized(this){ //Also tried only putting it around the remove block         for(Object o : myList){             myList.remove(o);             return o;         }     }  }  //This is another variaton which did not yield any improved result  public Object removeSomething2(){     ListIterator<Object> iter = myList.listIterator();         While(iter.hasNext()){             Object s = iter.next();             synchronized(this){                 iter.remove();              }             return s;          }      }  //After some request here is also the simple code which adds to the list  public addSomething(Object o){     myList.add(o); }   I execute 5 threads which calls upon these methods in their run() method in an interval of 500ms (using Thread.sleep()). If I increase the sleep timer in each thread and put a Thread.sleep() between each instanciation of threads, the problem seems to go away, but I want the threads to run at (closely) the same time without them interfering with the iterator at the same time which envokes the ConcurrentModificationException.

We all know you can't do the following because of ConcurrentModificationException:  for (Object i : l) {     if (condition(i)) {         l.remove(i);     } }   But this apparently works sometimes, but not always. Here's some specific code:  public static void main(String[] args) {     Collection<Integer> l = new ArrayList<>();      for (int i = 0; i < 10; ++i) {         l.add(4);         l.add(5);         l.add(6);     }      for (int i : l) {         if (i == 5) {             l.remove(i);         }     }      System.out.println(l); }   This, of course, results in:  Exception in thread "main" java.util.ConcurrentModificationException   Even though multiple threads aren't doing it. Anyway.  What's the best solution to this problem? How can I remove an item from the collection in a loop without throwing this exception?  I'm also using an arbitrary Collection here, not necessarily an ArrayList, so you can't rely on get.


I've been trying to install the extension from  guide, but when I get to to the line to install:  sudo apt-get install nautilus-image-tools   I get:     Unable to locate package nautilus-image-tools   Then I go to the official PPA , but I am not sure how to install a .xz or .gz file!

When I try to install any package through the command line, I get an error.   $ sudo apt-get install <package> Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package <package>   Can anyone help me on this?


Let $X$ a vector space on $\mathbb{R}$ and denote with $\theta$ the zero vector, i must prove that $$0x=\theta$$ for all $x\in X$  Now,  $0x=(0+0)x=0x+0x\Rightarrow$ $0x=\theta$  Correct?

Please rate and comment. I want to improve; constructive criticism is highly appreciated. Please take style into account as well.  The following proof is solely based on vector space related axioms. Axiom names are italicised. They are defined in Wikipedia (see vector space article).  Vector spaces - Multiplying by zero scalar yields zero vector  \begin{array}{lrll} \text{Let} & \dots & \text{be} & \dots \\ \hline & F && \text{a field.} \\ & V && \text{a vector space over $F$.} \\ & 0 && \text{an identity element of addition of $F$.} \\ & \mathbf{0} && \text{an identity element of addition of $V$.} \\ & \mathbf{v} && \text{an arbitrary vector in $V$.} \\ \end{array}  $$\text{Then, }0\mathbf{v} = \mathbf{0}.$$  Proof. We will denote by $1$ an identity element of scalar multiplication; we will denote by $(-\mathbf{v})$ an additive inverse of $\mathbf{v}$. \begin{align*} 0\mathbf{v} &= 0\mathbf{v} + \mathbf{0}                     && \text{by }\textit{Identity element of vector addition} \\ &= 0\mathbf{v} + (\mathbf{v} + (-\mathbf{v}))   && \text{by }\textit{Inverse elements of vector addition} \\ &= (0\mathbf{v} + \mathbf{v}) + (-\mathbf{v})   && \text{by }\textit{Associativity of vector addition} \\ &= (0\mathbf{v} + 1\mathbf{v}) + (-\mathbf{v})  && \text{by }\textit{Identity element of scalar multiplication} \\ &= ((0 + 1)\mathbf{v}) + (-\mathbf{v})          && \text{by }\textit{Distributivity of scalar multiplication (field addition)} \\ &= ((1 + 0)\mathbf{v}) + (-\mathbf{v})          && \text{by }\textit{Commutativity of field addition} \\ &= (1\mathbf{v}) + (-\mathbf{v})                && \text{by }\textit{Identity element of field addition} \\ &= \mathbf{v} + (-\mathbf{v})                   && \text{by }\textit{Identity element of scalar multiplication} \\ &= \mathbf{0}                                   && \text{by }\textit{Inverse elements of vector addition} \\ \end{align*} QED


Prove $1^{3} + 2^{3} + ... + n^{3}$ = $(1 + 2 + ... + n)^{2}$ for all positive integers n.  I've tried to work with this problem using mathematical induction. However, I really don't understand how to manipulate the right side of the equation. Any help would be greatly appreciated.  Thank you in advance.

How can I prove that     $$1^3+ 2^3 + \cdots + n^3 = \left(\frac{n(n+1)}{2}\right)^2$$    for all $n \in \mathbb{N}$? I am looking for a proof using mathematical induction.  Thanks


I had used my bike for about a year and thought it was about time to replace the chain. The old chain started to skip links, but only sometimes.  I got the right chain from my local bike shop, I sized it up using my old chain, so it should have been the right length.  I put it on, however, now I got problems with shifting my gears (especially to lighter gears). Before the  chain replacement I didn't have problems with shifting between the gears.  It also sometimes skips links.  Does anyone know what might be the problem? Thanks, K

My bike's a 24-gear trail/road hybrid, and I've had it for about three years (although I've been riding it much more lately than in previous years).  For a long while, I've had an issue with chain skip happening seemingly at random, even on level, paved paths, however this issue was always more serious going uphill. I decided to replace my chain yesterday (it's appropriately sized, was pre-lubed, and none of the links locked upon inspection), however on this morning's commute I still got the same amount of skip, likewise more serious going uphill.  I've tried using best practices to avoid this issue, as well:   I avoid pedalling while changing gears I've checked my front and rear derailleur alignment (and adjusted it as best I could, there's still a very, very slight amount of scraping on the front derailleur if the chain has to travel too far laterally e.g. between my largest front sprocket and the smallest sprocket on the cassette on the rear wheel) I've double-checked that the links don't block, multiple times The teeth on the front sprockets as well as on the cassette don't seem to be overly worn down   Two more factors could be relevant to this; this new chain has those "tool-free" break links (you bend the chain to attach or detach one side of the link and break the chain), and I'm a more heavyset guy, so I pedal hard - I think this could be putting more stress on the chain.  I'm not sure what else I can do to reduce chain skip.  Update: I've gone by my LBS and apparently one of the chain gears is in fact worn down (I just didn't know how to tell, apparently).


If a group is of order $m$ and $n$ divides $m$, must the group contain an element of order $n$? Say we have a group of order $120$. Must the group contain an element with order $12$? If not, are there any theorems that tell us what order elements of a group must contain?

Let G be a group of order $n=21$. Now is it possible for converse of Lagrange's theorem to hold? Or if $m \mid n$ will there certainly be a subgroup of order $m$ and if yes are the subgroup unique?


I am traveling from Chennai to Don Mueang International Airport, Bangkok, Thailand, and from there to Mandalay, Myanmar. In Bangkok, the layover time is 8 hours. Do I require transit visa?

My itinerary     Bengaluru(Thai Airways International) --> Bangkok --> 01h15m layover   --> Bangkok(Thai Airways International) --> Taipei(Terminal 1)   ^ The flight numbers being different  While coming back from Taiwan, it would be      Taipei(Terminal 1)(Thai Airways International) --> Bangkok --> 10h45m   stop --> Bangkok (Thai Airways International) --> Bengaluru   ^ The flight numbers being different  So, would I be needing a transit visa for Bangkok?   I just got my stamped passport back from the Taiwan embassy with the visitor VISA stamp.  NOTE: All the above flights are booked at the same time i.e. both my Thai Airways International have the same PNR.  EDIT I got this off from the      National India (IN)             /Transit Thailand (TH)      Thailand (TH)      TWOV (Transit Without Visa): Visa required, except for Holders of   onward tickets for a max.      transit For details, click here time of 12 hours through Bangkok   Suvarnabhumi (BKK). Passengers must have a connecting flight      booked on the same ticket.          This does not apply when traveling on Angkor Air (K6),    Beijing Capital Airlines (JD), Business Air (8B), Cebu    Pacific (5J),   Eaststar Jet (ZE), Golden Myanmar Airlines    (Y5), Hong Kong Airlines   (HX), Indigo (6E), Jeju Air (7C),    Jet Asia Airways (JF), Jetstar   (JQ), Jetstar Pacific (BL),    Jin Air (LJ), JuneYao Airlines (HO),   Lao Central Airlines    (LF), Mandara Airlines (RI), Norwegian Air   (DY), Okay    Airways BK), Orient Thai Airlines (OX), Regent Air (RX),   Shandong Airlines (SC), Shanghai Airlines (FM), Shenzhen    Airlines   (ZH), Siberia Airlines (S7), Sichuan Airlines    (3U), South East   Asian Airlines (DG), Spice Jet (SG), Thai    Smile Airlines (WE),   Tianjin Airlines (GS), Tiger Air (TR),    Trans Aero (UN),   Turkmenistan Airlines (T5), T'way Airlines    (TW), Ural Airlines (U6)   and VietJet Air (VJ).  Visa required, except for Holders of onward   tickets for a max.         transit For details, click here time of 12 hours through Bangkok Don   Mueang (DMK) when traveling on Thai AirAsia (FD) or Thai AirAsia X   (XJ). Passengers must have a connecting flight      booked on the same ticket.


I have google app engine java project that run on google app engine server but when i try to run in local host i get this error INFO] GCLOUD: INFO: Overwriting system property key 'java.util.logging.config.file',  value '/Users/gallavie/Library/Application Support/google-cloud-tools-java/managed-cloud-sdk/LATEST/google-cloud-sdk/platform/google_appengine/google/appengine/tools/java/config/sdk/logging.properties' with value 'WEB-INF/logging.properties' from '/Users/gallavie/workspaces/eclipse/DarimpoServer/target/Darimpo-1.0/WEB-INF/appengine-web.xml' [INFO] GCLOUD: java.lang.NullPointerException [INFO] GCLOUD:  at java.base/java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011) [INFO] GCLOUD:  at java.base/java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:1006) [INFO] GCLOUD:  at java.base/java.util.Properties.put(Properties.java:1334) [INFO] GCLOUD:  at java.base/java.util.Collections$CheckedMap.put(Collections.java:3701) [INFO] GCLOUD:  at com.google.appengine.tools.development.SharedMain.setTimeZone(SharedMain.java:183) [INFO] GCLOUD:  at com.google.appengine.tools.development.SharedMain.postServerActions(SharedMain.java:152) [INFO] GCLOUD:  at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:384) [INFO] GCLOUD:  at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:45) [INFO] GCLOUD:  at com.google.appengine.tools.development.DevAppServerMain.run(DevAppServerMain.java:243) [INFO] GCLOUD:  at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:234) [INFO] ------------------------------------------------------------------------ [INFO] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] Total time:  4.058 s [INFO] Finished at: 2021-06-11T19:50:34+03:00 [INFO] ------------------------------------------------------------------------ [ERROR] Failed to execute goal com.google.cloud.tools:appengine-maven-plugin:2.2.0:run (default-cli) on project Darimpo: Failed to run devappserver: com.google.cloud.tools.appengine.operations.cloudsdk.process.ProcessHandlerException: com.google.cloud.tools.appengine.AppEngineException: Non zero exit: 1 -> [Help 1] [ERROR]  [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch. [ERROR] Re-run Maven using the -X switch to enable full debug logging. [ERROR]  [ERROR] For more information about the errors and possible solutions, please read the following articles: [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException gallavie@Gals-MBP DarimpoServer % mvn clean package [INFO] Scanning for projects...  i get this error when i run the project from eclipse or when i run "mvn appengine:run" command in cmd again the project work fine in real server how i can fix it thank you

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?


I'm trying to understand the difference between zip() and zip(*).  From what I understand, zip() can be used to combine two lists, such that elements with a shared index are together. Such as in these examples:  dict_list = {'First Name': ['Tom', 'Ann', 'Ben'],              'Last Name': ['Haverford', 'Perkins', 'Wyatt'],              'Age': [33, 42, 44],              'Occupation': ['Administrator', 'Nurse', 'Auditor']}  for first_name, last_name, age, occupation in zip(dict_list['First Name'], dict_list['Last Name'], dict_list['Age'], dict_list['Occupation']):              print(first_name, last_name, age, occupation)  #result      Tom Haverford 33 Administrator Ann Perkins 42 Nurse Ben Wyatt 44 Auditor   So why does it seem to me that sometimes, zip(*) behaves this way? For example:  for t in (zip(*dict_list.values())):     print(t) #result      ('Tom', 'Haverford', 33, 'Administrator') ('Ann', 'Perkins', 42, 'Nurse') ('Ben', 'Wyatt', 44, 'Auditor')   Since my dict_list.values() are lists, it seems like zip(*) placed all elements with shared indexes in the same tuple. Which is not that much different from the first code, in which I used zip() in a for loop with dict keys passed into it and with corresponding looping variables  How are zip() and zip(*) behaving in this case?

In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2):


In my text i put my table      \ref{table:3}   AND IN MY TABLE I START BY      \begin{table}[H]\label{table:1} \centering   But imagine my surprise when I see my table being referred as table a in my tex...!!

\documentclass{article} \usepackage{algorithm}  \begin{document} \setcounter{section}{54} \section{A section with no label} \begin{algorithm} \label{myalg} \caption{An algorithm with the label `myalg'.} \end{algorithm} Reference to myalg: \ref{myalg}. \end{document}   With this code, the reference givens 55 (the section number); if I move the label after the caption command, I get the correct reference (1).  Why should this be the case? I find it confusing: when thinking about an algorithm as an environment, you expect to be able to label it right after you began it. At the very least I would expect some kind of error or "??" to appear, rather than the previous environment or reference-able entity being used.


I'm trying to change the font size of the references using the shrink of the frame argument. However, if I run this code:  \documentclass{beamer}  \usepackage[american]{babel} \usepackage[utf8]{inputenc} \usepackage{csquotes} \usepackage[style=apa, backend=biber,doi,url]{biblatex} \DeclareLanguageMapping{american}{american-apa}  \begin{filecontents}{literature.bib} @article{foobar,   Author = {An Author},   Journal = {A Journal},   Pages = {1--2},   Title = {Some title},   Volume = {1},   Year = {1900} }  \end{filecontents} \addbibresource{literature.bib}  \begin{document}  \frame{   \textcite{foobar} }  \frame[shrink=50]{   \frametitle{References}   \printbibliography }  \end{document}   I get the following error:  ! Arithmetic overflow. \beamer@shrinkframebox ...\@tempdimc by\@tempcnta                                                    \relax \ifdim \@tempdimc >... l.32 }  ?  ! Emergency stop. \beamer@shrinkframebox ...\@tempdimc by\@tempcnta                                                    \relax \ifdim \@tempdimc >... l.32 }   If I remove the shrink argument it works.  I'm using TexLive 2011 on Debian Squeeze and I updated all my packages ;).

I am using Biber (backend of biblatex) to  make the bibliography. I have two questions about the bibliography.    I want to use a reduced font ONLY for the bibliography (not the citation in the text, that in my text is in numeric style e.g. [1], [2] etc.). In particular, the font of my text is 11 pt and I want to print the bibliography in 10 pt. In the bibliography some text exceeds the text cage, because the ISBN is printed without a break. What is the command I should use for avoid this overfull hbox?


What do you guys think about an accounting Stack Exchange site?  Because the answer is yeah we do. It would be the sexiest thing out there in the Stack Exchange space.

I have an idea or subject that should have a Q&A, and want to propose a new site. How can I do this?  Related:


I am trying to create an Appendix for my experiment figures, and the following is the my code \section{}\label{sec:figures}  \begin{figure*}[h]     \begin{minipage}{0.75\textwidth}           ...     \end{minipage}       \end{figure*}  \begin{figure*}[h]     \begin{minipage}{0.75\textwidth}           ...     \end{minipage}       \end{figure*}  \begin{figure*}[h]     \begin{minipage}{0.75\textwidth}           ...     \end{minipage}       \end{figure*}  \begin{figure*}[h]     \begin{minipage}{0.75\textwidth}           ...     \end{minipage}       \end{figure*}  There is unintentional blank page inserted between the section title and the figures like the following.  How can I make latex not do this unintentional page break? Thanks. Update: I have tried using the float package with \begin{figure}[H]     \begin{minipage}{0.75\textwidth}           ...     \end{minipage}       \end{figure}  The problem with this is that I am using a two-column format and this made the picture overlay on each other.

How to influence the position of float environments like figure and table in LaTeX?   This is a general question and should collect useful answers for all users. I hope we can use this as a reference


I really like the random tests when reviewing, but I find them too easy to spot now, and they don't really cover all possibilities where somebody could create a bad approval.  Feature Proposal  I propose that a new feature that allows users with a very high reputation to create new tests that can then be approved by consensus of high rep users.  This can be either integrated into the review screen, or added as a separate section to the top nav bar that appears after the required reputation is reached.    When submitting an audit you include the following:   Audit Type: Suggested Edits, First Posts, etc... Post Title, Post [For Edits] Changed Title  [For Edits] Changed Post Response for Rejection Response for incorrect Approval   Like a close vote, an audit is approved by multiple high rep users.  Possible New Test Ideas   A test where somebody takes a correct answer and makes it incorrect through a minor change.  There was an answer I was reviewing that was very complicated where the incrementor was moved, and I wasn't sure how that effected the answer. A more subtle change of meaning of a sentence:  There are some very radical audit tests where the text is defaced, but what if somebody rewrites a sentence to change the very meaning?  For example, "How do I assign a function to a variable?" versus "How do variables get assigned by a function?" look very similar, but mean something different.  This might be an especially high risk when somebody is correcting posts by people who speak English as a second language. Bad formatting (I've run across this more than once):  Somebody reformats some code, but actually makes it worse because they didn't see a closing parenthesis or tag.

Some people are complaining about the automatically generated audits. They are based on close reasons and apparently are a little controversial :-)          etc   I propose that for "good reviewers" (definition TBD) an extra UI component be added to let the reviewer suggest this as an audit item. Possibly:   Reject and add as audit button (Close and add as audit, etc) checkbox next to Reject, Close, etc checkbox on the Reject reason, Close reason etc dialog (could get messy, and some actions such as Reopen don't involve a subsequent dialog) dialog after rejecting, closing, Recommend Deletion, etc   Further, after passing or failing an audit, we could ask "good reviewers" "was this a good audit"? Bad audits, whether auto-generated or human suggested, could be removed from use if enough "good reviewers" identified them as such.  Now, what's a good reviewer? I don't want to judge only on behaviour in the review queue. I think flagging well is a good sign. So is editing - maybe an edit-related badge? And yes, some number of reviews would be good. Maybe some ratio of pass to fail on review audits. But not JUST what we do in the queues.  (I first suggested this in my answer to  but I'm bringing it up as a feature request of its own and to apply to all the queues.)


It is well known that $\oplus$ produces a plus sign with a circle around it, similarly $\otimes$ does the and same with the $\times$ symbol, etc.  I was wondering if there a way to make a command which would do the same for $\div$ ?   The command isn't available by default, to my knowledge, and I'm not experienced enough with defining such commands myself.

I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?


At first when I saw the guy not get hurt, I assumed this was a simulated / virtual reality world. Then as the episode goes on it's shown that it's a real, physical place, with artificially intelligent robots. I sort of get the idea that the AI's programming keeps them from harming living things, but if, like in that case, the robots don't know the difference, how can they know not to kill them? They certainly have no qualms about killing each-other?   And then, when the robot shoots the "bad guy" (not sure about character names yet) with the same gun he just "killed" 2 other robots with (the ones who killed the girl's parents), how is it that the guy is immune?   I'm looking for an overall explanation of how the system of not hurting some things (flies, humans, etc) whilst hurting other things (other robots) works, and how their bullets just have no effect of living things, but hurt other robots.

In the first episode of the show Westworld, Ed Harris (a "guest" / human) is being shot at by James Marsden (a "host" / robot). It is as though Ed Harris has a force field around him; the bullets all miss or are blocked.  In the third episode of the series, guest Jimmi Simpson is shot by a host in town. The "bullet" knocks Jimmi Simpson down, and leaves a mark on his chest.  Is this an inconsistency in the scripts, or has the Westworld park changed the way guns work, or do guests get to determine how they'll be affected by being shot by hosts?


I have an interesting question, one that may, or may not be easy :( I've been trying to work out a way to do it integrating options of the 'find' command on linux.  Basically, I have a directory tree, within which could be multiple examples of the files that either need keeping, or deleting. All the files share the same extensions, for sake of argument .XX  (although the idea would be to be as generic as possible so it could be any file). I want to delete all .XX files within the directory tree, EXCEPT where the files lie within a specific folder (will always be the same title, in the example called YYY).  Say I have to following structure (where each sub directory could end up containing many many many files that I don't want to touch or affect alongside those that I do):    folder_root: | |--> Subdir_1/interesting_file_1.XX |--> Subdir_1/interesting_file_2.XX |--> Subdir_1/unrelated_interesting_file_1.AA |--> Subdir_2 |--> Subdir_3/interesting_file_3.XX |--> YYY/interesting_file_4.XX |--> YYY//interesting_file_5.XX   I want to be left with:  folder_root: | |--> Subdir_1/unrelated_interesting_file_1.AA |--> YYY/interesting_file_4.XX |--> YYY/interesting_file_5.XX   The note is, the directory YYY could be anywhere, and there could be many of them, so having a list of directory paths that need excluding to hand to build a large exclusion list isn't possible.  First I did a basic Find as such: find . -iname "*.XX". Then I looked at adding the -printf "%h\n" to output the directories that contain the .XX files. What I'm struggling to do, is take that outputted list, and use it to inform the process of deleting, or as the case may be, not deleting. I suppose I could use grep to remove any YYY folders from the output into a temp file, use a while read loop, then pushd and popd to move in, and then out of the folders, using a simple find . -iname "*.XX" -delete within each sub-directory (then using the -empty switch within find to clean up any empty directories left as a result). This does however, feel very blunt force, with a very large sledgehammer, that could be very system intensive, especially when dealing with potentially hundreds of sub-directories.  I'm interested if there is a 'better' way, that is slicker, generally less intensive overall and reliable (especially if you end up having to run it three or four times for three or four different file types)?  There may not be, but its worth a quick ask :) Why use a sledgehammer when a simple hammer would do!? :)   Final note, I cannot add additional shell commands to the system (and the systems used are a mix of Ubuntu and Centos), so where possible, it would need to use the pre-existing command set (assume no other modules are installed except Tree, which I do know about). I hope the question is clear, and 'generic' enough to be useful to others in different situations if a simple answer is found.

I want to recursively delete all files not accessed in a while in folder a, except all files in the subfolder b.  find a \( -name b -prune \) -o -type f -delete   However, I get an error message:     find: The -delete action automatically turns on -depth, but -prune does   nothing when -depth is in effect.  If you want to carry on anyway,   just explicitly use the -depth option.   Adding -depth causes all files in b to be included, which must not happen.  Anyone know a safe way to make this work?


I know the particular thing I see shouldn't be a big surprise, but if I go to Stack Exchange's home page, I'd like to not be greeted with a major story point for a movie that just came out today.  Other sites such as reddit have strict moderation to keep this stuff off of their front pages.

I've noticed that occasionally "hot questions" from SciFi and the Movies & TV network contain major spoilers about the movie/show discussed.  The Matrix spoilers:      (just now there's something about Cypher betraying Morpheus in the Matrix, which is a big deal for people who haven't seen the movie).   I like browsing through those but fear that one day one of these questions will spoil a show I'm excited about and yet to finish   Breaking Bad spoilers:      (like the finale of Breaking Bad, imagine a question asking why did one character betray another at the end or something).   Can users posting such questions be asked to label those with a tag (such as 'spoilers') and then somehow have the network hide those from the "hot questions" list? Or possibly format them differently?  Similarly, this could apply to the Arcade network too.  P.S. Love how this question spikes in popularity around the time GoT starts running again. I swear it should be fairly simple technically to ban questions that have a tag that says 'spoilers' from appearing in the Hot Network Questions.  P.P.S. Oh, and with every fresh release of Star Wars (The Last Jedi being the most recent one)!  P.P.P.S. Another year, another Game of Thrones, another spike in popularity!


We have certain URLs of the city and their alias-names. For example:  Primary URL: /used/cars-in-mumbai/ Alias URL: /used/cars-in-bombay/  We can't remove "Alias URL" as it's hard-coded at multiple places.  We have two choices when a request comes from "Alias URL":  1) Redirect alias URL to primary URL.  2) Do not redirect but set the canonical as primary-URL.  Which is an ideal approach?

This is a general, community wiki question regarding duplicate content.  If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on .     What does Google consider to be duplicate content? Will the way I am presenting my content result in a duplicate content penalty? How can I avoid having my site's content treated as duplicate content?


So I know that subgroups of $(\mathbb{R},+)$ are either isomorphic to $x \mathbb{Z}$ for $x\in \mathbb{R}$, or dense in $\mathbb{R}$.  I don't see how (if?) this descends to the quotient, though. Denote $G = \mathbb{R}/\mathbb{Z}$. If $H \leq G$, then by the third iso theorem there is a group $\mathbb{Z} \leq \tilde{H} \leq \mathbb{R}$ such that $H \cong \tilde{H}/\mathbb{Z}$. How to proceed? I'm very lost.    (Also, from this it supposedly follows that for $x\in\mathbb{R}$ the image of  $$ \phi_x:\mathbb{Z} \to G, \quad n \mapsto nx + \mathbb{Z} $$ is dense in $G$ if $x$ is irrational. I also don't see this: For any $x$, the image of $\phi_x$ is $x\mathbb{Z} + \mathbb{Z}$, is this not cyclic? The above result would then imply that the image is not dense. Somewhere is an error in my thought process.)

Let $T=\{z:|z|=1 \mathbin{\text{and}} z \in \mathbb C\}$ be the unit circle in the complex plane, considered as a topological group under complex multiplication and the usual topology. Show that every subgroup of $T$ is either dense in $T$ or finite.  How to prove the denseness?


In Harry Potter multiverse, there is a law called International Statute of Secrecy, referenced in Harry Potter and the Deathly Hallows since 1689 and the Harry Potter wiki says,     The law was laid down by the International Confederation of Wizards to safeguard the wizarding community from Muggles and hide its presence from the world at large.   [1}:    The wiki mentions and sources that there was widespread persecution of wizarding children by Muggles, increasing witch hunts. Eventually after deliberations, the international wizarding community agreed to hide the entire wizarding world, including hiding magical beasts, beings and spirits from the wizarding world.   It seems to me, that wizards are afraid of Muggles. Also, this is referenced in the recent movie, Fantastic Beasts and Where to Find them, where MACUSA, the International Confedrations of Warlocks and President Picquery is so concerned of getting exposed. What would happen if the wizarding kind is exposed? And the real question is why do they need to be afraid of Muggles. Muggles are based on the book and movie examples of Vernon Dursley, Jacob Kowalski or even Senator Shaw, are naturally dumb, have a different physiology and simply cannot win any Muggle-Wizard scenario. Also I know actual history was different, but couldn't wizards and witches escape the witch hunts? I mean they can Apparate, use brooms, kill/torture/read and tamper minds of Muggles, who in my opinion are just like the 'weaker mind' in Star Wars and can be influenced. And another point is they could also manipulate so many magical creatures against Muggles: Dragons, Thunderbird, Basilisk, Spiders, Merpeople, Inferi, Dementors(Muggles have no cure), Giants, Werewolves, Vampires(maybe) and Muggles simply can't win in any scenario.  Even the Muggle Prime Minister says in Half Blood Prince,     Prime Minister: But for heaven's sake, you're wizards! You can do magic! Surely you can sort out... well... anything!   Cornelius Fudge: The trouble is, the other side can do magic too, Prime Minister.   -Harry Potter and the Half Blood Prince, The Other Minister   It seems clear that Muggles are scared of wizards and witches, not the other way round. Wizards should have no reason to expose themselves for they could anytime take control as Grindelwald or Voldemort tried.  Additionally, it seems odd that wizards and witches rely on this secrecy as if they are subservient to Muggles.

In the Harry Potter universe, there is a huge effort to hide the Wizarding world from the Muggle world. From the Platform 9 3/4 at King's Cross Station, to Diagon Alley, to the Knight Bus, everything was made so that the Muggles couldn't detect them.  Why was this really necessary?    In Potterverse, magic was a real thing with thousands of years of proven history. So, it could provide a wealth of knowledge for Muggles.  One answer could be that magic might scare Muggles.  But, I don't think it would after thousands of years. It would be no different than any other new and revolutionary technology. After a reasonable duration, Muggles could become used to it.


I'm trying to understand the construction of these two sentences and would appreciate any help/thoughts:        The house sold for more than expected.   The house fetched more than expected.      To me both sentences seem to convey the same meaning,that is, the value that was obtained after selling the house was greater than expected.   What I'm really trying to determine is why the verb to be isn't necessary to form the passive here, in either sentence and whether it has something to do with sold and fetched being used in an intransitive form.

I wonder what the reason is to say These cakes sell well instead of These cakes are being sold well.   I understand that it’s shorter but it doesn’t work with any verb, does it? For example, The house is being built can’t be substituted by The house is building.  So, what justifies and makes it acceptable to compose such a sentence which we can see in the example with the verb sell? Does it have something to do with the verb used or something else? If so, are there many verbs which can be used that way?


I am very new to jQuery Validation will someone please correct me in where I am going wrong with the rule I am trying to add.  <script>      $("#form").validate({          focusInvalid: false,     rules: {         ownership: {             required: true         },         vin: {             required: true,             validateVin: true         },         // Same for other fields     },     messages: {         ownership: "This field is required.",         vin: "Invalid VIN",         // Repeat for other fields     } });  // create your custom rule jQuery.validator.addMethod(validateVin(this.value, Number($("#vehicleyear").val()))) {     function validateVin(vin, date) {         var re;         if (date >= 1981) {             re = new RegExp("^[A-HJ-NPR-Z\\d]{8}[\\dX][A-HJ-NPR-Z\\d]{2}\\d{6}$");         } else if (date < 1981) {             re = new RegExp("^[A-Z\\d]{2,17}$");         } else {         }         return vin.match(re);     }, 'Please enter valid VIN.'}); </script>   This is supposed to check two fields, first it checks to see what year is picked vehicleyear then depending on the year it checks an input vin to see if the regEx matches. If it does not match correctly then it should say invalid vin.   When I run mine it does not even use the regEx but I cannot figure out why. Any help with this would be greatly appreciated!

How do you create a simple, custom rule using the jQuery Validate plugin (using ) that doesn't use a regex?  For example, what function would create a rule that validates only if at least one of a group of checkboxes is checked?


In the script below, something strange happens when the second loop starts. The list area_1 changes value even though it is not involved in that loop at all. Same happens with area_2 after the third loop. server_1 = 'x1' server_2 = 'x2' server_3 = 'x3' table = [     {'Terminal': 'site_1', 'City': 'London', 'Station': server_1},     {'Terminal': 'site_2', 'City': 'London', 'Station': server_1},     {'Terminal': 'site_3', 'City': 'London', 'Station': server_2},     {'Terminal': 'site_4', 'City': 'New York', 'Station': server_3},     {'Terminal': 'site_5', 'City': 'New York', 'Station': server_1},     {'Terminal': 'site_6', 'City': 'New York','Station': server_2},     {'Terminal': 'site_7', 'City': 'Tokyo', 'Station': server_3},     {'Terminal': 'site_8', 'City': 'Tokyo', 'Station': server_3},     {'Terminal': 'site_9', 'City': 'Tokyo', 'Station': server_2}     ] city_index = [      {'City':'London', 'Lat': 51.48,'Long': -0.14 },     {'City':'New York', 'Lat': 40.69,'Long': -74.26 },     {'City':'Tokyo', 'Lat': 35.51,'Long': 138.64 } ] area_1 = [] for i in city_index:     area_1.append(i)     area_1[-1].update({'Station': server_1, 'Count of terminals': sum(q['City'] == i['City'] and q['Station'] == server_1 for q in table)}) area_2 = [] for i in city_index:     area_2.append(i)     area_2[-1].update({'Station': server_2, 'Count of terminals': sum(q['City'] == i['City'] and q['Station'] == server_2 for q in table)}) area_3 = [] for i in city_index:     area_3.append(i)     area_3[-1].update({'Station': server_3, 'Count of terminals': sum(q['City'] == i['City'] and q['Station'] == server_3 for q in table)})  all = area_1 + area_2 + area_3  for i in all:     print(i)  Output: (Notice the station key) {'City': 'London', 'Lat': 51.48, 'Long': -0.14, 'Station': 'x3', 'Count of terminals': 0} {'City': 'New York', 'Lat': 40.69, 'Long': -74.26, 'Station': 'x3', 'Count of terminals': 1} {'City': 'Tokyo', 'Lat': 35.51, 'Long': 138.64, 'Station': 'x3', 'Count of terminals': 2} {'City': 'London', 'Lat': 51.48, 'Long': -0.14, 'Station': 'x3', 'Count of terminals': 0} {'City': 'New York', 'Lat': 40.69, 'Long': -74.26, 'Station': 'x3', 'Count of terminals': 1} {'City': 'Tokyo', 'Lat': 35.51, 'Long': 138.64, 'Station': 'x3', 'Count of terminals': 2} {'City': 'London', 'Lat': 51.48, 'Long': -0.14, 'Station': 'x3', 'Count of terminals': 0} {'City': 'New York', 'Lat': 40.69, 'Long': -74.26, 'Station': 'x3', 'Count of terminals': 1} {'City': 'Tokyo', 'Lat': 35.51, 'Long': 138.64, 'Station': 'x3', 'Count of terminals': 2}  All 3 lists become identical at the end = area_3. Can someone please explain why this is happening? Why are area_1 and area_2 being overwritten?

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?


I'm pretty sure we didn't do anything over at Space Exploration, but we just got all our questions and answers taken away:    This makes it look like we have the most unengaged audience in the history of mankind. Could it be fixed?

MSO, Stack Apps, Robotics, Expression Engine Answers, Sustainable Living and Network Engineering all have 0 questions, 0 answers and 0 users on .


When I am doing regresion, I get a p-value 1.86e-1, what does this mean? Also there are p-values like <2e-16, what is the actual number? Thank you for answering.

I have a problem with the interpretation of a test result in which the p-value is 8.6e-28. How should it be interpreted? What is the e for?  Specifically, I used White's Test for the homoscedasticity assumption of a linear regression:  White's general test statistic :  150.0535  Chi-sq( 9)  P-value =  8.6e-28


Hi I am now trying to write bubble sort implementation. Then I find that if I reinitialize the array then sort this array again, the time to sort is much smaller than the first time. Here is my code:       import java.util.Random;  public class test {  public static void main(String[] args) {     // TODO Auto-generated method stub      long start;     long end;     int [] array = new int [1000];       initializeArray(array);     start = System.currentTimeMillis();     bubble_srt(array);     end = System.currentTimeMillis();     System.out.println("To sort the array using bubble sort, we need " + (end - start) + " ms");      initializeArray(array);     start = System.currentTimeMillis();     bubble_srt(array);     end = System.currentTimeMillis();      System.out.println("To sort the array using bubble sort, we need " + (end - start) + " ms"); }     public static void bubble_srt(int array[]) {     int n = array.length;     int k;     for (int m = n; m >= 0; m--) {  //starts from the rightmost position in arrayy         for (int i = 0; i < n - 1; i++) { //starts from the leftmost position in array             k = i + 1;              if (array[i] > array[k]) {                 swapNumbers(i, k, array); //choose a bigger one to the i+1 position             }         }     } }  private static void swapNumbers(int i, int j, int[] array) {      int temp;     temp = array[i];     array[i] = array[j];     array[j] = temp; }  public static void initializeArray(int array[]){      Random ran = new Random();      for(int i = 0; i < array.length; i++){          array[i] = -ran.nextInt(10001) + 5000; // create a random number rangre from -5000 - 5000      }   }  }   The time to sort the first array is 13ms,  while to sort the second array is 5ms. But in fact we should get the similar result... But my result detour and every time the time to sort the second array is much smaller than the first array. I am quite confused about it...

How do you write (and run) a correct micro-benchmark in Java?  I'm looking for some code samples and comments illustrating various things to think about.  Example: Should the benchmark measure time/iteration or iterations/time, and why?  Related:


What function should I use to find $\frac{1}{\sqrt{a}}$ without using division?

Suggest algorithm for the numerical calculation $ \frac{1}{\sqrt{a}} \ a > 0 $ without division, use Newton's method.  My idea is:  $$ \frac{1}{\sqrt{a}} = (\sqrt{a})^{-1} = a^{-\frac{1}{2}}$$ $$ x = a^{-\frac{1}{2}} \Rightarrow f(x)=x^2 - a^{-1}$$ And next step is calulate $ f'(x)=2x $, but after substitution I got: $$ x_{n+1} = \frac{x_n^2+a^{-1}}{2x_n}$$ And know I still have divion, I guess. Maybe you've better idea on this task?


In my coding, I always do  grep -rnIi "abcabc" . --color  But, how to make an alias that can let me type only one word with my search string? Is that possible?

For bash script, I can use "$@" to access arguments. What's the equivalent when I use an alias?


Suppose $|G|=pm$,where $p\nmid m$. Then if $H\mathrel{\unlhd}G$ and $|H|=p$, than $H$ has to be characteristic. We call a subgroup characteristic when $\varphi(T)\subset T$, $\forall \varphi \in Aut(G)$.  My proof: Suppose $g\in \varphi(H)$ and $g \notin H$. Since $\varphi$ is bijective $|\varphi(H)|=|H|=p$. So $\langle g\rangle|p$ i.e. $\langle g\rangle =p$. Since $H$ is a normal group and $\langle g\rangle$ is another subgroup, $\langle g\rangle H$ is also subgroup of $G$. So $p^2||G|=pm$ which contradicts to the fact that $p\nmid m$.  Is the idea right? Which parts would you advice to fix?

I'm stuck on this exercise from Herstein's topics in algebra:  Suppose that $G$ is a group and $|G| = pm$, where $p \nmid ~ m$ and $p$ is a prime. If $H$ is a normal subgroup of order $p$ in $G$, prove that $H$ is characteristic.  How to prove that? What we know:   $H$ and $\varphi(H)$ have prime order $p$, so they must be cyclic and abelian They are both normal subgroups of $G$   how to show that, in fact, we have $H = \varphi(H)$ for every automorphism $\varphi$ ?


How to calculate $5^{2003}$ mod $13$   using fermats little theorem  5^13-1  1 mod 13  (5^12)^166+11 mod 13  a+b modn=(a modn + b modn) modn  (1+11mod13)mod13  12 mod 13 = 12  why answer is 8 ?   how do we calculate this  thanks

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


Q: Prove that $\frac{1}{5}n^5+\frac{1}{3}n^3+\frac{7}{15}n$ is an integer for every integer n. In fact, I already have a method, but it seems too long. So I would first (1)is there any problem with my logic? (2) Is there any better/faster method to do these kinds of questions?  My solution: $$\frac{1}{5}n^5+\frac{1}{3}n^3+\frac{7}{15}n$$ $$=\frac{1}{15}(3n^5+5n^3+7n)$$ Then my next time is to use M.I to prove that $(3n^5+5n^3+7n)$ is divisible by $15$ for positive integers. And for negative integer, I switch it into -$(3n^5+5n^3+7n)$ and it also satisfies the divisibility of $15$.  But the above seems too clumsy. This course is "Intro to number theory". Is there any beter method to do it?

Using congruences, show that the following is always an integer for every integer value of $n$: $$\frac{1}{5}n^5 + \frac{1}{3}n^3 + \frac{7}{15}n.$$


I tried to pass parameters to bash in shebang of executable script:  #! /usr/bin/env bash -ex  false   But I get an error:     /usr/bin/env: ‘bash -ex’: No such file or directory   Should I avoid to use /usr/bin/env in favor of /bin/bash to avoid error, or there is a way to stick with /usr/bin/env?  I am on Ubuntu 16.04.3.

I am wondering whether there is a general way of passing multiple options to an executable via the shebang line (#!).   I use NixOS, and the first part of the shebang in any script I write is usually /usr/bin/env. The problem I encounter then is that everything that comes after is interpreted as a single file or directory by the system.  Suppose, for example, that I want to write a script to be executed by bash in posix mode. The naive way of writing the shebang would be:  #!/usr/bin/env bash --posix   but trying to execute the resulting script produces the following error:  /usr/bin/env: ‘bash --posix’: No such file or directory   I am aware of , but I was wondering whether there was a more general and cleaner solution.    EDIT: I know that for  scripts, there is a way to achieve what I want, documented in  of the manual:   #!/usr/bin/env sh  exec guile -l fact -e '(@ (fac) main)' -s "$0" "$@"  !#   The trick, here, is that the second line (starting with exec) is interpreted as code by sh but, being in the #! ... !# block, as a comment, and thus ignored, by the Guile interpreter.  Would it not be possible to generalize this method to any interpreter?     Second EDIT: After playing around a little bit, it seems that, for interpreters that can read their input from stdin, the following method would work:  #!/usr/bin/env sh sed '1,2d' "$0" | bash --verbose --posix /dev/stdin; exit;   It's probably not optimal, though, as the sh process lives until the interpreter has finished its job. Any feedback or suggestion would be appreciated.


I need to get the value from column RR from the same raw the button is clicked   the problem here is that the code only works when i use evaluate in console in google developer tools  Table :

                Date	                RR	                Origin	                Destination	                CNEE	                Status	                Details

   data values for each row :     var rootRef = firebase.database().ref().child("Requests");        rootRef.on("child_added", snap =>{       var DateValue = snap.child("Date").val();     var RRValue = snap.child("RR").val();     var OrgValue = snap.child("Origin").val();     var DestValue = snap.child("Destination").val();     var CustAccValue = snap.child("Customer Account").val();     var StatusValue = snap.child("Status").val();      if (StatusValue != "Done")     {         $("#table_body").append("
<td " + DateValue +        "	" + RRValue +        "	" + OrgValue +        "	" + DestValue + "	" + CustAccValue + "	" + StatusValue + "	<Button onclick=\"expandTriggered()\" class=\"lisnClick\">" + "details" + "</Button>
");     }    here where the code does not work only when using evaluate      $(".lisnClick").click(function() {     var refer = $(this).closest("tr")                            .find(".valueRRField")                             .text();                                 alert(refer);       // Output   });

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.


Situation:  Question A have close vote "duplicate of B" Question B has closed as duplicate of A.   (I seen 1 more before it)  It's at least strange. What will happen if it will closed?

I was browsing SO today when I stumbled across these two questions:    So, both questions are closed.*  The problem?  Each questions is closed as a duplicate of the other; within one minute of each other (they were both closed "8 minutes ago" when I first checked).  Can we add a feature to detect this and prevent a circular Close as Duplicate like this?  Better yet, prevent newer questions than the current one from showing up in the Close as Duplicate list.  *As of 2010/06/17 18:32 UTC the first question is now reopened and the second deleted.


Is it possible to rasterize a text layer in Photoshop CC where each letter gets its own layer?

I have a word in a text layer in photoshop. I want each character to be on a separate layer, how can I do that?


Is there a workaround for the iOS inability to easily delete ALL (or large blocks of) email from my iPhone and iPad ?

How do you mass-delete emails in iOS Mail? I don't know if this is documented anywhere, but just to bring it to current attention…


I have the following query:  EXEC ('SELECT  ID,           Date,           Type,                                   FROM DB2T.BBT') AT DB2   How do I store this into a table so that I can add results from another query to do it? I'm very new to sql and have done a lot of searching but it seems everything I find is specific to that scenario. Is there a simple way to do this?

How do I do a SELECT * INTO [temp table] FROM [stored procedure]? Not FROM [Table] and without defining [temp table]?  Select all data from BusinessLine into tmpBusLine works fine.  select * into tmpBusLine from BusinessLine   I am trying the same, but using a stored procedure that returns data, is not quite the same.  select * into tmpBusLine from exec getBusinessLineHistory '16 Mar 2009'   Output message:     Msg 156, Level 15, State 1, Line 2   Incorrect syntax near the keyword   'exec'.   I have read several examples of creating a temporary table with the same structure as the output stored procedure, which works fine, but it would be nice to not supply any columns.


With the code below (a tiny snippet from a book) the example quotation for the word Agerasia starts on the same line with the word itself.  I don't think the result makes a clear enough distinction between the main text and the quote. I thought of starting on a new line but \ gives an error "there is no line to end". MWE Main file \documentclass{memoir} % \let\providelength\relax \title{Interesting words} \author{Peter Flom} % \usepackage{hyperref} \usepackage[marginpar]{todo}  \usepackage{url} \usepackage{varioref} % \let\providelength\relax  %% A convenience command, for typesetting the %% word and pronunciation  %\newcommand{\entry}[2]{\medskip\noindent{\Large\textbf{#1} (#2)\par}} \newcommand{\entry}[2]{\medskip\noindent{\Large\textbf{#1} \normalsize{#2} \par}}    %\newcommand{\sclabel}[1]{\normalfont\scshape #1} \newcommand{\sclabel}[1]{\leavevmode{\normalfont\scshape #1}} %% Less spacing around lists \firmlists  \begin{document}      % \include{Intro}      \include{Peopletest} urces}          \end{document}  and here is peopletest \chapter{Words describing people}\label{C:People}     \entry{Agerasia}{Age erase ee ya} \label{Agerasia} %On Medium %From OED Brought back    \begin{flexlabelled}{sclabel}{0pt}{0.5em}{0.5em}{*}{\leftmargin}       \item[Definition]       \textit{n.} Youthful appearance in an old person, but not through artificial means (such as plastic surgery).       \item[Etymology]       From Greek combining \textit{a-} (not) \textit{geras} (age) and \textit{ia} via Latin \textit{agerasia},       \item[Anti-thesaurus] \leavevmode         \begin{description}            \item[Appearance] -- which has nothing to do with youthfulness            \item{Neanimophism} -- (See neanimorphism \vpageref{Neanimorphism}).            \item[Visual aspect] -- see above         \end{description}       \item[Usage]       See the example, below.       \item[Examples]       \begin{quote}          Although many people go to extreme lengths to appear young, some are blessed with agerasia.       \end{quote}       \item[Frequency]       Ngram viewer found no uses until 1953; now it's very rare indeed, about 1 in 6.5 billion words and the OED notes that it is ``chiefly in dictionaries''.   \end{flexlabelled} \vspace{0.5in}

I have the following LaTeX code:  \documentclass{article} \begin{document} \begin{description}  \item[foo] bar  \item[baz]  bang  \end{description}  \end{document}   and it produces the following PDF:    I want the definition of the item (in this case the "bar" and the "bang") to be on a separate line from the item (eg the "foo" and the "baz").  However this is part of a system that autogenerates documention, so I can't change the source code. I can put style things in the header of each documention, so I need some sort of LaTeX command that will make all definition list (in LaTeX speak, a "descripition list") go onto a new line.


So today one of my answers was edited and the edit itself was quite tricky - it was looking legit though actually was invalidating my answer, so I've declined it.  Then I've got this message:   My question is following - what this testing is about (how massive it is, what exactly are you trying to achieve, who is in the test group etc.)?

I recently received this rather amusing message while reviewing a user's first post:  Congratulations! This was only a test, designed to make sure you were paying attention. This post has already been removed, but thanks for taking time to leave feedback for the author.   What is the purpose of this test? How does the audit work? What happens if I fail? Why was the system expecting me to negatively review a good post, or positively review a bad post? A review is obviously an audit. Should I report it? Do review audits count toward the Reviewer badge? Do robo-reviewers dream of electric sheep?


I have a domain www.test.com which points to a website which was created using WIX. Hence, the nameserver in my www.test.com (GoDaddy is the registrar, so I can edit my nameserver at ) domain points to   ns7.wixdns.net ns8.wixdns.net   Now I want to have admin.test.com to point to my S3 bucket http://admin.test.com.s3-website-ap-southeast-1.amazonaws.com/Login  I have set my S3 bucket Properties > Static Website Hosting > Redirect Requests to admin.test.com and add alias record in Route 53 as suggested by    Now I'm pretty sure I need to point my domain's nameserver to this Route 53, but I'm confused what and/or where I should do it. If I change the nameserver in  to something else, pretty sure my wix hosted website will be inaccessible.

I am trying to host some static content in an Amazon S3 bucket and to have that content available through my own domain.  The bucket in question is called "e.tl-dr.org" and I have "index.html" set as the index document. I can visit  and I see the contents of index.html (just "test"). This works fine.  I also have added the CNAME entry for "e.tl-dr.org" pointing to "s3.amazonaws.com" from within my registrar's site. (I am not using the AWS Route 53 DNS services, which is what most tutorials about this seemed to be geared at.) So now "" correctly shows the file, but just the bare domain only gives me S3's standard 403 message.  Is there anything else I need to set up to get this working?


I have cut out this selected piece with a knife and i want it to be a part of its own in the right colon (scene section). Right now its still part of the cube around of it. What is the option for this?

I've just made a set of armor by using a male body mesh model I downloaded and selecting certain faces from the model and duplicating them to create viable armor pieces.   Since the pieces are just duplicated from the same mesh male model, then it's still part of the same object.   How do I separate the armor piece from the model to make the pieces separate?


I am wondering if there is anyway to search for a certain word or phrase in all tables/rows in SQL.   I have tried,   SELECT *  FROM all_tab_cols WHERE column_name LIKE '%WORD%' ;    However, this doesn't bring back what I want.   My desired output would be this query bringing back 'WORD' that is in all tables and all columns and all rows. I know its a very general search which may bring back a lot of data but I need to search for a certain word and have no idea which table/column this word is in.

Is it possible to search every field of every table for a particular value in Oracle?  There are hundreds of tables with thousands of rows in some tables so I know this could take a very long time to query. But the only thing I know is that a value for the field I would like to query against is 1/22/2008P09RR8. <  I've tried using this statement below to find an appropriate column based on what I think it should be named but it returned no results.  SELECT * from dba_objects  WHERE object_name like '%DTN%'   There is absolutely no documentation on this database and I have no idea where this field is being pulled from.  Any thoughts?


Let $M$ and $N$ be $R$-modules ($R$ a commutative ring with identity). Let $m \in M$ and $n \in N$. Is there any necessary and sufficient condition to have $m\otimes n = 0$ (as an equation in $M\otimes_RN)$.

Let $A$ be a commutative ring and let $F$, $E$ be $A$-modules. Then $E$ is the direct limit of its finitely generated submodules. Serge Lang, in his Algebra, p. 604, remarks that a technique to test whether an element of $F \otimes E$ is zero, is to examine its image in $F \otimes N$, as $N$ varies over the finitely generated submodules of $E$. Could somebody please explain why this is a valid technique? What is the image of an element of $F \otimes E$ in $F \otimes N$?


I've never encountered the OGR geometry type MULTILINESTRING25D before (or any of the *25D types). What are these? How do they differ from other types? I couldn't find any useful documentation from the rest of the internet.

[EDIT: In my original post, I had received an error that was based on a typo, so I scrapped that part of the question, but left the questions that still apply.]  In the  it says:  -nlt type: Define the geometry type for the created layer. One of NONE, GEOMETRY, POINT, LINESTRING, POLYGON, GEOMETRYCOLLECTION, MULTIPOINT, MULTIPOLYGON or MULTILINESTRING. Add "25D" to the name to get 2.5D versions.   Does this part: Add "25D" to the name to get 2.5D versions apply to both loading things into postgres as well as exporting data from postgres to .shp files?  Additionally, I am assuming 25D to meant that one can have a z value that corresponds to each pair of xy coordinates (as is the case with PolygonZ shapefile types), but that these coordinates may not overlap. Is this correct? What is the intended distinction in this case between 2.5D and 3D?  Thanks


I'm trying to use TPL inside a while loop and I need to pass to the task some values that then changes into the loop. For instance, here it is shown an example with an index that is incremented (necessarily after the line in which the task creation is requested):  int index = 0; Task[] tasks; while(/*condition*/) {     tasks[index] = Task.Factory.StartNew(() => DoJob(index));     index++; }   But of course it does not work, since the index value can be incremented before the task start. A possible solution could be to pass also a WaitHandle on which waiting before incrementing the index and that has to be signalled into the DoJob method, but it doesn't seem to me a really good solution. Any other idea?

I met an interesting issue about C#. I have code like below.  List<Func<int>> actions = new List<Func<int>>();  int variable = 0; while (variable < 5) {     actions.Add(() => variable * 2);     ++ variable; }  foreach (var act in actions) {     Console.WriteLine(act.Invoke()); }   I expect it to output 0, 2, 4, 6, 8. However, it actually outputs five 10s.  It seems that it is due to all actions referring to one captured variable. As a result, when they get invoked, they all have same output.  Is there a way to work round this limit to have each action instance have its own captured variable?


I'm a Software Engineering and Mathematics student. And I'll probably get my engineering degree much sooner than my Maths degree (I'm not sure I'll get it, but I'll try, as Eng. takes a lot of time off my day).  So, my question is pretty simple: Can an engineer get a Maths doctorate?  For further details, my engineering course has pretty basic maths stuff: Calculus, a bit of logic, introductory number theory, graph theory, some numerical analysis, etc.  However, I'm enrolled in a pure maths course which covers pretty 'advanced' stuff, will it matter that I passed these subjects even if I don't get my math degree?  E: Please consider reopening this question, I've added details that may be relevant to this particular scenario.

Can I be admitted to graduate school in a different field from my degree?  Specific cases include:   If I've taken plenty of advanced courses in field X in the process of completing a degree in another field, can I apply to graduate school in X? What if I haven't taken many courses in X, but I have acquired a good grasp of X through self-study or working in a related field? What if I've never studied X, but I have done very well in an unrelated field?  Could I be admitted to graduate school in X on the basis of general intellectual promise, and then make up the missing background after enrollment?   Note that this question is an attempt to provide a comprehensive answer, to avoid the need for a profusion of field-specific questions on this topic (see the associated ). Please feel free to edit the question or answer to improve them.


I understand that the inter-galactic space is expanding but galaxies themselves are not. What is happening to the space within a galaxy? Is it fixed by the gravity of the galaxy or is it expanding and moving out around it?  Using the coins on a balloon analogy, is the balloon surface under the coins (galaxies) stuck to the coin and constrained or is it free to expand out, slipping underneath the coins leaving them in the same place (and the same size)?

I have looked at other questions on this site (e.g. "why does space expansion affect matter") but can't find the answer I am looking for.  So here is my question: One often hears talk of space expanding when we talk about the speed of galaxies relative to ours. Why, if space is expanding, does matter not also expand? If a circle is drawn on balloon (2d plane), and the balloon expands, then the circle also expands. If matter is an object with 3 spatial dimensions, then when those 3 dimensions expand, so should the object.  If that was the case, we wouldn't see the universe as expanding at all, because we would be expanding (spatially) with it.  I have a few potential answers for this, which raise their own problems:   Fundamental particles are 'point sized' objects. They cannot expand because they do not have spatial dimension to begin with. The problem with this is that while the particles would not expand, the space between them would, leading to a point where the 3 non-gravity forces would no longer hold matter together due to distance Fundamental particles are curled up in additional dimensions a la string theory. These dimensions are not expanding. Same problems as 1, with the added problem of being a bit unsatisfying. The answer seems to be (from Marek in the previous question) that the gravitational force is so much weaker than the other forces that large (macro) objects move apart, but small (micro) objects stay together. However, this simple explanation seems to imply that expansion of space is a 'force' that can be overcome by a greater one. That doesn't sound right to me.


So I have this equation   $4y_{k+1} = 2y_k$.  If i divide both sides by 4, I get   $$y_{k+1}=\frac12y_k$$   However, the equation can be re-written as   so that  $$y_{1}=\frac12y_0$$  and  $$y_{2}=\frac12 y_1=\frac1{2^2}y_0$$  and   $$y_{3}=\frac12 y_2=\frac1{2^3}y_0$$ $$\cdots$$  This is a difference equation, where the initial condition first is y=0 and then y=2.   Can somebody please explain how , from $$y_{k+1}=\frac12y_k$$ i can get to the following equations?

So I have the difference equation $4y_{k+1} = 2y_k$.  I need to solve this equation, first with the initial condition $y_0 = 0$ and then with the initial condition $y_0 = 2$.  The professor wrote on the answer sheet that applying iteratively the recurrence relation it is easy to check that:  $y_k= (1/2)^k y_0 $.  Since I missed the lecture where he explained this, can somebody explain how to come about with this question?  I imagine that once I get the equation, then the initial condition $y_0 = 0$ gives us the particular solution $y_k = 0$. Thus the other initial condition $y_0 = 2$ is verified by the solution $y_k = 2(1/2)^k$.  Any help on how to get to the equation $y_k= (1/2)^k y_0$ will be appreciated.


Is there a way to see what updates/upgrades you have without actually installing them in Ubuntu. I need to write a script to see if there are any updates available for out gitlab server, if there is, it will email me the list of pending updates but NOT install them. I've looked online, but can't seem to find any such command.  Thanks.

I want my cron-run reporting script to notify me in case there are updates for my packages. Is the a way to make apt-get give me the list of available updates but don't do anything more?


How to prove $\left|\frac{w-z}{1-\bar{w}z}\right|$ < 1 if |z|<1 and |w|<1?    Please give me a hint.

Prove if $|z| < 1$ and  $ |w| < 1$, then $|1-zw^*| \neq 0$ and $| {{z-w} \over {1-zw^*}}| < 1$Given that $|1-zw^*|^2 - |z-w|^2 = (1-|z|^2)(1-|w|^2)$I think the first part can be proven by saying $|1-zw^*| = 0$ if and only if $zw^*$ = 1.  And given the conditions that cannot be true. However I don't know if this part is right.


Sometimes I get the url of a video embedded in a webpage and download it, just to find the file has no extension name. I can play the video with a player, so it must be legal. How do I determine the extension name of the video file in such circumstance?

What is the best tool to obtain the media/codec details of any video/audio file?  I use Windows, but feel free to suggest for your favorite OS too.


If $ f $ is Lebesgue integrable then $|f|$ is Lebesgue integrable but does the converse of the result is also true?

How can we prove the statement?  $f$ is Lebesgue integrable if and only if $|f|$ is Lebesgue integrable.  First, suppose $f$ is Lebesgue integrable, by definition, $f$ is measurable and nonnegative, so $f=|f|$ and $\displaystyle \int_E f \, d \mu=\int_E|f| \, d\mu$ implies that $|f|$ is Lebesgue integrable.   Second, suppose $|f|$ is Lebesgue integrable, if $f$ is nonnegative, then $f=|f|$, so $f$ is Lebesgue integrable; if $f$ is negative, then how can I prove?


I've already logged in before and when it asked if I wanted to link my park I said no. Now, when I log out and log back in, I log in automatically and it doesn't ask me if I want to link my park. Is there any way to get it to ask me again so I can link my park?

Imagine my surprise when I find out that Dragonvale is on Android now, in addition to iOS. So, to see what all the craze is about, I decide to get into it. I don't really have a Facebook, so I just bypassed all that. However, this locks me out of all the social stuff, including free Gems. This is, obviously, Not Ideal, so I made a Facebook account basically just for Dragonvale. Seems simple enough.  Too bad that, apparently, my Local Park isn't my Facebook Park! Is there a way to force my Local Park to be my Facebook Park? Or am I screwed unless I want to start over, which I'd really rather not do?


Implementing logistic regression and getting different results depending on whether I minimize squared error or maximize log likelihood.  When are the two equivalent?

Title says it all. I understand that the Least-Squares and Maximum-Likelihood will give the same result for regression coefficients if the model's errors are normally distributed. But, what happens if the errors are not normally distributed? Why are the two methods no longer equivalent?


Two people agree to meet at a coffee shop. They each independently pick a random moment in time between 8 a.m. and 9 a.m. and show up exactly at their selected time. But they are very impatient, and only stay for 10 minutes after when they arrive. What is the probability that they meet? Express your answer as a common fraction.

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


how're you doing? I am somewhat new to ubuntu and finding problem changing the root user name. My terminal displays priyank@Alex right now. I changed the second name to Alex using hostname and hosts. What I want is to make it Alex@Alex. Can anyone temme how can I do it?

I made a mistake in the username at the time of installation. So I changed the name of the user after logging in by creating a guest account with SUDO rights. But when I checked the list of users using ls /home command I am not seeing the new name for the user instead Old name is appearing. But I use the new name to login.   Is it like I need to change the name inside Home directory separately? Also , if there is any other changes needs to be done .. ?


How would you show that $37 \times 2^{220} - 14 \times 5^{87} \times 7^{87}$ is divisible by $17$?   I tried finding the actual answer of the equation to show that it is divisible by $17$, but I think I need a more efficient and stronger proof. What could this proof be?

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


I have a text file like so:   <!--START OF FILE --> random text <meta> more random text </meta> x x x x x x x  more random text that I dont need  x x x x x x x  I need everything from this point onwards ...   I need to remove everything between <!--START OF FILE --> and the second x x x x x x x like so:  I need everything from this point onwards ...   I tried using sed '/<!--START OF FILE -->/,/x x x x x x x/d' test.txt but this removes the block between the first occurence of x x x x x x x which is not what I want.

I have a text in a text file, where I want everything that is between strings like \{{[} and {]}\} to be deleted - including these strings themselves.  These two string can lie on different lines as well as on the same line. In either case,  on the line on which the beginning \{{[} lies, I don't want the text before, i.e. left, of it to be deleted - and the same holds for the text after {]}\}.  Here is an example: Given a text file with the content   Bla Bla bla bla \{{[} more bla bla even more bla bla bla bla.   A lot of stuff might be here.  Bla bla {]}\} finally done.  Nonetheless, the \{{[} show {]}\} goes on.   the script should return another text file with the content  Bla Bla bla bla  finally done.  Nonetheless, the  goes on.   Unfortunately this simple-looking task turned out to be too difficult for me to do with sed. I'm happy with any solution in any language, as long as I don't have to install anything on my standard linux machine (C and some java is already installed).


discovering TCP socket, I made a very simple test based on my understanding of the subject and some tuto found on the net  Server :  void Server(void) {   int localSocket;   int distantSocket;    sockaddr_in serverInfo;   sockaddr_in clientInfo;    int sizeOfSocketInfo = sizeof(struct sockaddr_in);    /* Open Socket */   std::cout << "open socket" << std::endl;    localSocket = socket(AF_INET, SOCK_STREAM, 0);   if (localSocket == -1)   {     std::cout << "open failed, error - " << (int)errno << std::endl;     exit(errno);   }    /* Configure server */   serverInfo.sin_addr.s_addr = INADDR_ANY;   serverInfo.sin_family = AF_INET;   serverInfo.sin_port = htons(61001);    /* Bind Socket */   std::cout << "bind socket" << std::endl;    if (bind (localSocket, (sockaddr *) &serverInfo, sizeof(serverInfo)) == -1)   {     std::cout << "bind failed, error - " << (int)errno << std::endl;     exit(errno);   }    /* Wait for client */   std::cout << "Wait for client ..." << std::endl;    listen(localSocket, 1);   distantSocket = accept(localSocket, (sockaddr *)&clientInfo, (socklen_t*)&sizeOfSocketInfo);    std::cout << "client connected  - " << inet_ntoa(clientInfo.sin_addr) << std::endl;    /* Close Socket */   close (localSocket);   close (distantSocket);    std::cout << "socket closed" << std::endl; }   and client :   void Client(void) {   int localSocket;   sockaddr_in clientInfo;    /* Open Socket */   std::cout << "open socket" << std::endl;    localSocket = socket(AF_INET, SOCK_STREAM, 0);   if (localSocket == -1)   {     std::cout << "open failed, error - " << (int)errno << std::endl;     exit(errno);   }    clientInfo.sin_family = AF_INET;   clientInfo.sin_port = htons(61001);   clientInfo.sin_addr.s_addr = inet_addr("127.0.0.1");    /* Open Socket */   std::cout << "connect to server" << std::endl;   if (connect(localSocket, (sockaddr*)&clientInfo, sizeof(clientInfo)) < (int)0)   {     std::cout << "connect failed, error - " << (int)errno << std::endl;     exit(errno);   }    std::cout << "connected !" << std::endl;    close(localSocket); }   When I launch the server in one terminal and the client in another one, it seems to be ok :  server side :   > ./tcpTest -s open socket bind socket Wait for client ... client connected  - 127.0.0.1 socket closed >    and client side :   > ./tcpTest -c open socket connect to server connected ! >   But, if, just after this first try, I launch the server again ...  > ./tcpTest -s open socket bind socket bind failed, error - 98 >   And I have to wait a "certain time", I don't know exactly how long, one minute maybe, to have the server working again.  I can't figure out what's happening, looking to open socket with sockstat does not show anything strange (I only see mozilla socket).  I found this guy having the same problem but in Ruby    If this is really the same problem, how can I apply the same solution in C++ ? Or do you have any idea ?  Thank you

I have used SO_REUSEADDR to have my server which got terminated to restart with out complaining that the socket is already is in use. I was wondering if there are other uses of SO_REUSEADDR? Have anyone used the socket option for other than the said purpose?


I'm using REST api towards Salesforce for inserting various kinds of data from our other systems. And for data that is regarded as configuration (in this case a list of freight forwarders) we have created a custom metadata object Carrier__mdt). So now I have created a script to populate this object. And it's not working:     message: 'entity type cannot be inserted: Carrier',     errorCode: 'CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY',  I have tried giving every kind of access right to the object and it's field, but no go.I'm doing a POST request on the object URL https://XXXX/v51.0/sobjects/Carrier__mdt I've seen other people ask this question before, and been given every kind of answer from "that is not possible" to "it works now". Can it be done?

I am trying to update a custom metadata type record through the standard Salesforce connectors in Talend. But I receive an error that says "unable to update entity type".  Are we able to update these records through API? If yes, how do I achieve it?  Thanks in advance.


Would anybody indicate me what is the grammatical structure applied in this sentence?     This is too vague a term   I have seen this structure sometimes and, although they sounded strange in the beginning, I'm starting to naturally use it on my essays.

You're too clever a man to imagine this.   The above sentence was , a man of excellent rhetorical skills.   Since he said it, I doubt it's wrong, grammatically. But, I wonder if there is an explanation for this. Because adjectives always come after the article not before it. e.g. You're a clever man.   How could this be, grammatically?