Updating Qlabel Document rectangle called for label that is not a text label. Why?
Qt signaling across threads, one is GUI thread?
What is the "correct" way of embedding text into math mode? Lets say I have something like:   \[ Let x = number of cats \]   (This is a contrived example, but pretend we are actually inside a long align environment block...) "Let" and "number of cats" need to be written like normal text, while x= needs to be math type text.  I've seen this:  \[ \mbox{Let } x = \mbox{ number of cats} \]   and this:  \[ \textrm{Let } x = \textrm{ number of cats} \]   They seem to produce equivalent output, but I'm not sure which is the "correct" one. Also, they are not ideal in that the extra space needs to be placed inside the text mode block, otherwise it is ignored as math mode and butts the text right up against the math.  Ideally there would be some command which allowed embedding text into an equation, which correctly inserted leading and trailing space around the block as required without adding space inside the text block.  How does one do that "correctly"? Why doesn't backpropagation work when you initialize the weights the same value? Why doesn't backpropagation work when you initialize all the weight the same value (say 0.5), but works fine when given random numbers?   Shouldn't the algorithm calculate the error and work from there, despite the fact that the weights are initially the same? Use of Indefinite Articles(a,an) Consider the following sentences:  I am staying in a hotel nearby. I am staying in an hotel nearby.  I know that both are correct. But I would like to know why? I do not see any proper reason for the second one as the 'h' is not silent as in French. So, what could be the reason? According to the , /opt is for "the installation of add-on application software packages".  /usr/local is "for use by the system administrator when installing software locally".  These use cases seem pretty similar.  Software not included with distributions usually is configured by default to install in either /usr/local or /opt with no particular rhyme or reason as to which they chose.  Is there some difference I'm missing, or do both do the same thing, but exist for historical reasons? Deriving curvature formula How do you derive the formula for unsigned curvature of a curve $\gamma (t) = (x(t), y(t)$ which is not necessarily parameterised by arc-length.   The formula given is $$|\kappa (t)| = \left|\frac{x'' y' - y'' x'}{((x')^2 + (y')^2)^{3/2}}\right|$$  All the definitions of curvature in my notes give it in terms for an arc-length parameterisation $T'(s) = \kappa(s) N(s)$. This is apparently meant to be 'easily derivable', am I missing something? How to get GNOME Shell "Applications overview" to show the full name of applications Can I watch the progress of a `sync` operation? I've copied a large file to a USB disk mounted on a Linux system with async. This returns to a command prompt relatively quickly, but when I type sync, of course, it all has to go to disk, and that takes a long time.  I understand that it's going to be slow, but is there somewhere where I can watch a counter go down to zero? Watching buffers in top doesn't help. Distribution of Product of Random Variables with one being the normal distribution. How many permanent SPECIAL points are available in Fallout 4? External hard disk detection issue what exactly happened:  I have a Seagate 1 TB external hard disk.It was working fine till now.The problem started when I plugged it in my android phone and then back in my pc then simply it does not showup anywhere and :  It does not appear in file explorer   It does not appear in disk management   It is not listed in Diskpart command   It only appears in Device Manager under disk drives   It does not appear in BIOS  only makes sound when plugged and unplugged.  disk spins and light is also showing.   . What I already tried:   updated usb drivers.  used new cable also.  plugged in another pc  usb mass storage is also enabled in BIOS  no issue in any usb port  Anything else i can do? Let $\mathbb{F}$ be a finite field.  Let $a_1,\dots,a_n \in \mathbb{F}$ be given.  I want to know whether there exists $x_1,\dots,x_n \in \mathbb{F}$ such that  $$a_1 x_1^2 + a_2 x_2^2 + \dots + a_n x_n^2 = 1.$$  My question: Can we characterize when this equation has a solution, i.e., by some criterion on $a_1,\dots,a_n$?  Is there a clean characterization, in terms of $a_1,\dots,a_n$ and the properties of $\mathbb{F}$?    Here's what I can see immediately.  First, if $n=1$, there is an easy answer (the equation has a solution iff $a_1$ is a square in $\mathbb{F}$).  Second, if any $a_i$ is a square in $\mathbb{F}$, the equation has a solution (set all other $x_j$'s to $0$), so we can assume that all the $a_i$'s are non-squares and that $n \ge 2$.  Third, if $-1$ is a square in $\mathbb{F}$, then the equation has a solution: we can take $x_2 =  \sqrt{-a_1/a_2} \cdot x_1$.  But what about the case where $-1$ is a non-square in $\mathbb{F}$?  Is it always guaranteed to have a solution in this case? Request of a domain with no virtualhost in apache ends to default virtualhost If I ask Apache for domain.com that has no Virtual Host setup in Apache configuration, Apache will show the default Virtual Host. How can I prevent this from happening or simply drop the connection? Send authors an inbox message if their question is closed I think it would really help if you get notified that a question of yours was closed.  Especially for the multi-site power user, usually (at least for me) a question is asked and then left alone for while. I rely on the network-wide inbox to tell me when someone has commented or answered, but if I don't receive any messages then I tend to assume that the question wasn't answered or even noticed. It's only when I check the question a day or two later to see what I can add do I find out it was closed.  This would be especially helpful for duplicates, where the answers you need are already there. A message to the effect of, "Closed as duplicate of question" is just like notifying me that a new answer has been added!  Unfortunately, question closures can remain unnoticed by their askers until months have passed. By then, the questions may either be too old to migrate to the correct site, or may , depending on the specific closing reason. We should notify users of these question closures so that they can improve them and learn from their mistakes.  Could closed questions get added to the inbox? I would like to insert the below mathematical symbol, it looks like a big Delta but different. Is there command to obtain a similar shape? What is the value of lim$_{n\to \infty} a_n$ if $\lim_{n \to \infty}\left|a_n+ 3\left(\frac{n-2}{n}\right)^n \right|^{\frac{1}{n}}=\frac{3}{5}$? Let $\{a_n\}$ be a sequence of real numbers such that $$\lim_{n \to \infty}\left|a_n+ 3\left(\frac{n-2}{n}\right)^n \right|^{\frac{1}{n}}=\frac{3}{5}.$$  What is the value of $\lim_{n\to \infty} a_n$? Ever since I upgraded to 13.10, the software updater does not show all the available updates. Some will appear and can be installed just fine, but once it claims that all software is up to date, using sudo apt-get upgrade shows that there are still more packages waiting to be updated. I can update them via the command line, but that only solves things temporarily. I'm not sure why some show up and others don't. How can I make Update Manager update all packages?  Update-manager shows this:    But apt-get shows this:   Thanks! What does \s! do? 1st example:  \starttypescript [\s!serif] [paratype]   \definefontsynonym [ParatypeSerif-Regular] [\s!name:PTSerif-Regular] [\s!features=\s!default]   \definefontsynonym [ParatypeSerif-Italic] [\s!name:PTSerif-Italic] [\s!features=\s!default]   \definefontsynonym [ParatypeSerif-Bold] [\s!name:PTSerif-Bold] [\s!features=\s!default]   \definefontsynonym [ParatypeSerif-BoldItalic] [\s!name:PTSerif-BoldItalic] [\s!features=\s!default] \stoptypescript   2nd example:  \definefont[SerifS][\s!file:GenBkBasR at \smallfontsize]   Is \s! only related to fonts? Should I use it in my typescript files? Search which man sections contain a given entry Connect Talend to Salesforce using OAuth JWT Flow I followed the steps exactly mentioned here  for connecting Talend to salesforce.  I have done the configuration in Talend and added the test(sandbox) URL in the advanced setting. I am facing an error while trying to establish the Oauth connection (JWT) between Talend ETL tool and salesforce: {'error':'invalid_grant','error_description':'invalid assertion'} Here is the screenshot of the configuration and error message:   Please help to resolve this issue. folder content doesn't get refreshed automatically in ubuntu 14.04