Relative margins with respect to height
How can I vertically center a "div" element for all browsers using CSS?
Unable to play MP3 or MP4 files in Rhythmbox or Movie Player I am unable to play any MP3 or MP4 files. When I try to open any MP3 or MP4 file, both show an error, a Python 2.7 plug-in is required. Turn a string into a valid filename? I have a string that I want to use as a filename, so I want to remove all characters that wouldn't be allowed in filenames, using Python.  I'd rather be strict than otherwise, so let's say I want to retain only letters, digits, and a small set of other characters like "_-.() ". What's the most elegant solution?  The filename needs to be valid on multiple operating systems (Windows, Linux and Mac OS) - it's an MP3 file in my library with the song title as the filename, and is shared and backed up between 3 machines. Not every open set in $\mathbb{R}^n$, for $n\geq2$, is a disjoint union of countable open balls. I know that every open set in $\mathbb{R}$ can be decomposed as the union of countably many disjoint open intervals and I'm trying to show that this property no longer holds in higher dimensions. For this I'm trying to show that there is no countable, pairwise disjoint open balls whose union is the open square $(0, 1)^2 ⊂ \mathbb{R}^2$. I know that it is because of the corners, but I don't know how to write this in mathematical terms. Thanks for any help. replacement wood threshold insert for metal door I have some late 70's doors and one is missing a threshold insert (the adjustable wood kind), anybody know of where one could by just the "wood strip" that goes in and screws down (there is a metal piece that sticks up into the wood, though you can't see it)?    They have about 4 screws that go down into them? "Series" – a noun of multitude similar to "lot", "majority", "percentage", "proportion"– verb agreement According to Garner's fourth edition  Though serving as a plural when the need arises, series is ordinarily a singular noun. But it is also a noun of multitude, so that phrases such as a series of things take a plural verb. However, the collocation there {has been - is} a series has predominated in print sources. Common nouns of multitude: lot, majority, mass, minority, multitude, percentage, proportion, variety.  However,  reads  When it has the singular sense of &quot;one set,&quot; it takes a singular verb, even when series is followed by of and a plural noun: A series of lectures is scheduled.  Are these dissimilar usages stylic advice? Secondly, the inversion after there also chooses singular elsewhere; why is it so?  When the verb precedes the noun percentage, a singular verb is required. That is, a higher percentage of them are, but there is a higher percentage of them. Punctuation with units I remember reading somewhere that if a unit is abbreviated as one character, there must not be a space between the number and the unit (e.g., 5m, 26K). If the unit is abbreviated as two or more Characters, there must be a space between the number and the unit (e.g., "10 km", "USD 5").   Can you please help me find the source again? Is this recommendation correct? Selectively disable iCloud keychain syncing for WiFi passwords I have iCloud Keychain sync enabled, but I want to stop it syncing WiFi passwords.  I have a portable WiFi hotspot which I use for my laptop and iPad, but I don't want my iPhone to connect to it since it has it's own 3G  Because iCloud is syncing the settings, within about 30 seconds of connecting my laptop to the 3G hotspot, my iPhone will connect itself. If I go into wifi settings on the iPhone and manually disconnect, about 30 seconds later my laptop will disconnect too. It seems with iCloud wifi sync on, I can’t connect my laptop to WiFi without my phone also connecting.  The only way to get around it seems to be disabling Keychain sync in iCloud. I’ve tried Googling, but got no real help on how to disable it without turning off Keychain, which is what I’ve done at the moment.  I also don't want to enable 'Ask before joining networks' on my iPhone, since I'll be manually re-connecting it constantly. After some gorgeous updates I witness this: When i put the code $(f_{\mathcal{X}},f_{\mathcal{X}}^{\partial})$ I get the following:  But I want the subscripts to be aligned. How can I do this? Align  elements side by side How to format a USB flash drive? Unable to cover get set in apex test class I'm trying to simulate a media key press using a custom shortcut.  So far, I've been able to achieve the simulation I need using the command:  xdotool key XF86AudioPlay   It works perfectly, it pauses or starts the music player every time it is run.  The problem comes when trying to run it as a shortcut.  First I tried to run an alias with a custom shortcut, but it did not work.  As explained on :     The commands run by keyboard bindings are not parsed via a shell. Your best bet is to create a directory bin in your homedir.   Next I created the suggested script and named it simplay:  #!/bin/sh xdotool key XF86AudioPlay   It is located inside a bin folder which is part of the PATH, this works fine and can be run from any location.  When trying to create the Custom Shortcut, I was unable to get it to execute, the configuration is the following:  Name: test Command: simplay  Shortcut: Ctrl+Alt+R   After searching a bit more I found another way to execute the shortcut:  gnome-terminal -e simplay   I tried it on a terminal and noticed that when executing it it would rapidly open a new terminal window, execute the child process, pausing the music and immediately close the window.  I changed the command on the shortcut and when hitting it I noticed the same behavior opening a terminal and immediately being closed but this time the child process did not pause the music, which makes me think that the script has been called on all my previous attempts but it is somehow not being able to execute.  How can I solve this problem according to your knowledge? Suppose we rotate the graph of $y = f(x)$ about the $x$-axis from $a$ to $b$.  Then (using the disk method) the volume is $$\int_a^b \pi f(x)^2 dx$$ since we approximate a little piece as a cylinder.  However, if we want to find the surface area, then we approximate it as part of a cone and the formula is $$\int_a^b 2\pi f(x)\sqrt{1+f'(x)^2} dx.$$  But if approximated it by a circle with thickness $dx$ we would get $$\int_a^b 2\pi f(x) dx.$$  So my question is how come for volume we can make the cruder approximation of a disk but for surface area we can't. Show some indication that account is banned from asking new questions At what level of complexity should I consider UL listing my widget? Countability of disjoint intervals According this problem/solution set from an MIT class (http://ocw.mit.edu/courses/mathematics/18-100c-analysis-i-spring-2006/exams/exam1_sol.pdf), the assertion:  "Every collection of disjoint intervals in R is countable."  is True, because "every interval contains a rational number", and the rationals are countable.  It seems to me this should be False, with possible counterexample:  { [x,x] | x is an element of R}  ie the set of all singelton intervals on R. Why isn't this a valid counterexample? Prove that $\frac{a_1^2}{a_1+a_2}+\frac{a_2^2}{a_2+a_3}+ \cdots \frac{a_n^2}{a_n+a_1} \geq \frac12$ Let $a_1, a_2, a_3, \dots , a_n$ be positive real numbers whose sum is $1$. Prove that $$\frac{a_1^2}{a_1+a_2}+\frac{a_2^2}{a_2+a_3}+ \ldots +\frac{a_n^2}{a_n+a_1} \geq \frac12\,.$$  I thought maybe the Cauchy and QM inequalities would be helpful. But I can't see how to apply it. Another thought (might be unhelpful) is that the sum of the denominators on the left hand side is $2$ (the denominator on the right hand side). I would really appreciate any hints. Suppose $m_1, m_2, m_3,\ldots, m_k &gt; 1$ and not necessarily pairwise relatively prime. Also $a_1, a_2,\ldots, a_k\in\Bbb Z$. What can we say about the solutions of the following congruence equations: $\begin{align*} x&amp;=a_1\mod m_1\\ x&amp;=a_2\mod m_2\\  &amp;\phantom{1}\vdots\\ x&amp;=a_k\mod m_k \end{align*}$ Six simple tips to get Stack Overflow reputation fast From "6 Simple Tips to Get Stackoverflow Reputation Fast" at codexon.com:   Be the First to Answer. Even at the cost of quality. Use Downvotes and Comments Strategically Use obnoxious in-your-face formatting and lists. Be Aware of the 200 rep/day Limit Edit, But Don’t Edit Too Much Associate your other accounts   Courtesy of . Agree? Disagree? Walnuts? Cantaloupe?