Why does my grid not want to center vertically?
How can I vertically center a "div" element for all browsers using CSS?
How do I join a Windows Active Directory? We have a "mix-mode" Lab. and we want to migrate to Ubuntu, from Windows.  In this process, how do we add Ubuntu workstations to a Windows Domain / Active Directory ('AD') setup? I am doing an animation. The images I have attached show 2 different render layer view node results.    Image one shows a cube on layer 1, and 2 icosphere on layer 2. I have layer 2 set to fast blur. I have to use transparent film and therefore I use the Alpha over nodes in composition.  Image two shows a cube and 1 icosphere. Image 1 should not be showing 2 icospheres, as the left most one is behind the cube.    Image 2 is from the same render result, and is correcting showing only 1 icosphere. However, that icosphere should be blurred as it is on layer 2. It seems for whatever reason I can not have both the correct composition effect and also have every object's visibility render correctly. I can only either have everything work fine, with no composition, or composition with every emission object showing through every other object in the scene.   I am aware that masks would solve this problem, but because of the complicated setup of object materials and particles, masking produces these very strange and suddenly appearing artifacts. Material Indexing also produces odd artifacts and does not consistently effect the appropriate materials.   This is also a new problem, I did not have this issue in the last blender version. So, material indexing is out, masking is out, object indexing is out.       I want to use the compositor to blur certain layers, but every emission object in the scene shows through. It shows through as though it was on x-ray, regardless if it is behind another or inside another object. The first image is an example of this, the left icosphere is behind the cube, and should not be visible. That is the problem. Why is it visible when it shouldn't be? java.rmi.NoSuchObjectException: no such object in table I am writing a very simple RMI server, and I am seeing intermittent java.rmi.NoSuchObjectExceptions in the unit tests.   I have a string of remote method calls on the same object, and while the first few go through, the later ones will sometimes fail. I am not doing anything to unregister the server object in between.  These error do not appear always, and if I put in breakpoints they tend to not appear. Are those Heisenbugs, whose race conditions dissolve when looking at them through the slowed down execution of the debugger? There is no multi-threading going on in my test or server code (though maybe inside of the RMI stack?).  I am running this on Mac OS X 10.5 (Java 1.5) through Eclipse's JUnit plugin, and the RMI server and client are both in the same JVM.  What can cause these exceptions? I could have modifications ready for a specific question that was downvoted. I felt like the best thing to do was to delete the post first.  Is it possible to flag for moderator attention after you deleted the post ? Ability to update profile from the Stack Exchange Android App Polygamma function series: $\sum_{k=1}^{\infty }\left(\Psi^{(1)}(k)\right)^2$ Applying the , I found: $$S=\displaystyle\sum_{k=1}^{\infty }\left(\Psi^{(1)}(k)\right)^2\lt\dfrac{2}{3}\pi^2$$ where $\Psi^{(1)}(k)$ is the polygamma function. Is it known any sharper bound for the sum $S$? Thanks. Cardinality of equivalence relations in $\mathbb{N}$ I came across this long proof on this site:    But I would like to know whether my direction can work.  Say we want to find the cardinality of all equivalence relations in $\mathbb{N}$. Since it is a subset of all relations in $\mathbb{N}$, I conclude it has a cardinality smaller or equal to $\aleph$. Now, define an injective function from $P(\mathbb{N})$ to the set of equivalence relations by matching each subset of $\mathbb{N}$ with the identity relation (which is an equivalence relation in $\mathbb{N}$.  Therefore the cardinality of all equivalence relations in $\mathbb{N}$ is greater or equal to $\aleph$ and using CSB we get the desired result.  Seems legit? Can't pair apple wireless keyboard Keyboard: Apple Wireless Keyboard (model number MC184LL/B)  System: Macbook Pro Early 2011 running OS X 10.8  The keyboard gets detected and when I try to pair it, the system asks to enter some numbers through the keyboard.   However when I press the key (on the wireless keyboard) nothing happens, the only key that seems to work (i.e. to move to the next key in the code) is 0. I can also press enter to confirm but it always fails (since the only code I can enter is 0000...0).   I've also tried pairing from the bluetooth preference and changing the passcode option. However this won't work either.   Any ideas? The keyboard was paired with another MacBook Pro (I don't have access to it anymore). Is there any method to 'reset' the keyboard to factory settings? I am confused with the grammar here. Which is grammatically correct?       At which time will you call me?     At what time will you call me?    And why? My webcam just came on "out of the blue" I just had a case of a user who re-posted his question because his first question was closed as a duplicate. And, logically, I closed his re-post as a duplicate of his original, asking him to edit his original and explain why it's not a duplicate, so we can reopen it.  This process has worked like that for years now, but suddenly I realized that with the new message, question repetition is even encouraged:     This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.   Clearly, a new user who finds their questions closed will now be happy to just post their question again and again, until it's not a duplicate anymore, instead of just fixing their original post.  We need to be more explicit about this, and show this message to the OP of the question:     If those answers do not fully address your question, please edit your question and explain why it is not a duplicate.   The original message should still be visible to other users and visitors, as they can't fix that question, of course. UV mapping a straight image around a ring shaped flat mesh Is it possible to mapping a image around a ring shaped mesh? I would imagine there should be a way to curve/distort the image around the mesh. If not, how can I straighten out the mesh easily instead to fit the image? The collection of all subsets of $\mathbb{Z}$ is uncountable, due to   But how can I prove that the collection of all finite subsets of $\mathbb{Z}$ is countable? Suppose that   $$f(x)=1+\sum_{n=1}^\infty a_n \frac{x^n}{n!}\ \ \forall \ x\in \mathbb{R}$$   where $\sup_{x&gt;0}\left|e^xf(x)\right| &lt; \infty$ and $\sup_{n\in\mathbb{N}} |a_n|&lt; \infty$.      Prove that $a_n = (-1)^n$ , $\forall n\in \mathbb{N}$   It seems amazing to me. What we need to prove is $f(x)=e^{-x}$. It seems insufficient to prove this strong conclusion, but actually it is true and all the "counterexamples" I found were wrong.  My attempt  Put $g(x)=e^x f(x)$. $$\left|g^{(n)}(0)\right|=\left|\sum_{k=0}^n \binom{n}{k} f^{(k)}(0)\right|\le 2^n\sup_{n\in\mathbb{N}} |a_n|  $$ Put $h(x)=g(\frac{x}{2})$. Thus  $$h^{(n)}(0)=\frac{1}{2^n}g(0) \le \sup_{n\in\mathbb{N}} |a_n|$$ which implies that $$h(x)=1+\sum_{n=1}^\infty b_n \frac{x^n}{n!}\ \ \forall \ x\in \mathbb{R}$$ where $$|b_n|\le \sup_{n\in\mathbb{N}} |a_n| \ \ \forall \ n\in\mathbb{N}  \,\,\,\,\,\&amp; \,\,\,\,\,  \sup_{x&gt;0}\left|h(x)\right| &lt; \infty $$   And hence if $b_k&lt;0$, then there exists $l&gt;k$ such that $b_l&gt;0$. I want to yield a contradiction by supposing this, but I failed.  Any hints or other new ideas? Thanks in advance!   (I heard that this problem can be solved by complex analysis. This is the reason why I attach the complex-analysis tag.) Change location of macOS Notification Center alerts? Is it possible to change where macOS Notification Center alerts appear on the screen?  They currently appear at the top right of the screen with the menu bar:    Alerts appearing in the top right tend to cover up work I'm doing more often than not. They cover up browser tabs, toolbar icons, and window titles.  I would prefer, say, the bottom right corner of the screen.  If moving the alerts is not possible, is it possible to change the screen on which they appear? First of all, am I being crazy in thinking that if $\lambda$ is an eigenvalue of $AB$, where $A$ and $B$ are both $N \times N$ matrices (not necessarily invertible), then $\lambda$ is also an eigenvalue of $BA$?  If it's not true, then under what conditions is it true or not true?  If it is true, can anyone point me to a citation?  I couldn't find it in a quick perusal of Horn &amp; Johnson.  I have seen a couple proofs that the characteristic polynomial of $AB$ is equal to the characteristic polynomial of $BA$, but none with any citations.  A trivial proof would be OK, but a citation is better. Inequality with exponents $x^x+y^y \ge x^y +y^x$ Let $x,y$ be positive numbers. Prove that $x^x+y^y \ge x^y +y^x$.   This question appeared in Summer 1991 Russian Olympiad team test. Apparently, I tried to come up with different approach such as Jensen, Karamata's inequality and nothing works so far. I just need a discussion here. Hints are not necessary. Mapping Russia - Int'l dateline splitting polygon If derivative of function is less than or equal to 4, prove the existence of point $c$ so $f(c)=c^2$. I am struggling to construct a simple proof of the following.  Suppose $f(x)$ is differentiable for any real value $x$ and that $f'(x) \le 4$ for all real values of x. Prove there is at most one real value $c&gt;2$ such that $f(c) =c^2$.  I am completely lost on where to start on this proof and any help would be greatly appreciated! Let $M=\big( \begin{smallmatrix} A & B \\ C & D \end{smallmatrix} \big)$. Prove $\det(M)=\det(A)\cdot \det(D-C·A^{-1}·B)$. Let  (shown in matrix blocks) $M=\big( \begin{smallmatrix} A &amp; B \\ C &amp; D \end{smallmatrix} \big)$ a square matrix such that $A$ is invertible and $D$ is a square matrix. I have to prove that  $$\det(M)=\det(A)\cdot \det(D-C·A^{-1}·B)$$  I also have an indication to use it: Consider previously these cases: \begin{align*} A_1 &amp;= \begin{pmatrix} A &amp; 0 \\ 0 &amp; I \end{pmatrix},\\ A_2 &amp;= \begin{pmatrix} I &amp; 0 \\ 0 &amp; D \end{pmatrix},\\ A_3 &amp;= A_1·A_2,\\ A_4 &amp;= \begin{pmatrix} I &amp; A^{-1}·B \\ 0 &amp; I \end{pmatrix},\text{ and}\\ A_5 &amp;= A_3\cdot A_4. \end{align*}   The problem is difficult in general for me and I don't even know how to use the indication.