When I download anything using Google Chrome or Mozilla Firefox and I use the "Show in folder" option (or "Open Containing Folder" in case of Firefox) it does not work correctly, instead, it open the directory with my text editor Atom...  What I can do to make it work properly?  PS: My OS is Elementary.
Since I installed EasyTag on my Arch Linux several other programs use EasyTag instead of Nautilus as filebrowser.  For example, Firefox starts EasyTag if I click on "open containing folder".  Where can I set Nautilus as my "standard file browser"?
How to make a water vortex I'm very new to Blender and I'm trying to make a water vortex like this.(may be not the easyest first project for a newbie)     I watched several tutorial on liquids particle etc but I'm not sure what is the best aproach. What I tried  until now:   I made a particle system with a vortex force field. It looks good, but I'm not able to add the right material.      I played around with the fluid physics, the water looks good but if I add a vortex force field it does nothing.   I would be very grateful if somebody could point me in the right direction because I'm definitely stocked. Restricting T to string and int? How to use manual partitioning during installation? Supremum and infimum of sets I've recently started to study supremum and infimum, and I'm having trouble determining the supremum and infimum of the following sets:  $ A = \left\{ {mn\over 1+ m+n} \mid m, n \in \mathbb N \right\} $ $ B = \left\{ {mn\over 4m^2+m+n^2} \mid m, n \in \mathbb N \right\} $ $ C = \left\{ {m\over \vert m\vert +n} \mid m \in \mathbb Z, n \in \mathbb N \right\} $ $ D = \left\{ {n\over 3} - \left[{n\over 3}\right] \mid m, n \in \mathbb N \right\} $   In $D$, the $[\; ]$ denotes the integral part of ${n\over 3}$.   $E = \{x \mid x \text{ is decimal fraction between } 0 \text{ and } 1 \text{ that has the digits } 0 \text{ and } 1\}$.  In my progress so far I was able to verify that sup $\{x \in A\} = +∞$  Setting $m = (n-1)$ to get  $$ \frac{mn}{1+m+n}= \frac{n(n-1)}{1 + n + n-1} = \frac{n(n-1)}{2n} = \frac{n-1}{2} $$  That way $\frac{n-1}{2}\in A$ for every $n\geq 2$. Thus, the supremum of $A$ is bigger than $\frac{n-1}{2}$ for every integer $n$.  I don't know how to go past this. x_x  Any help would be greatly appreciated! Where to place my local website starting with the 2.4.7 version of apache2? I recently installed Ubuntu 14.04, then I installed lamp-server and placed my webpages in /var/www directory, but when I opened localhost in the browser there was nothing. I think that happened because Zend updated Apache.  Whatever the reason may be, I want to know where to keep my php files so that I can access them from my browser. I am a newbie to Drupal, and I really don't understand the difference between sub-theme and base theme. Why can't I directly edit the base theme?  I am working on a website which is live and has bartik as default theme. I don't know where to start. What's the best way of handling permissions for Apache 2's user www-data in /var/www? Has anyone got a nice solution for handling files in /var/www? We're running Name Based Virtual Hosts and the Apache 2 user is www-data.  We've got two regular users &amp; root. So when messing with files in /var/www, rather than having to...  chown -R www-data:www-data   ...all the time, what's a good way of handling this?  Supplementary question: How hardcore do you then go on permissions?  This one has always been a problem in collaborative development environments. What is the exact use of the symbols $\partial$, $\delta$ and $\mathrm{d}$ in derivatives in physics? How are they different and when are they used? It would be nice to get that settled once and for all.  $$\frac{\partial y}{\partial x}, \frac{\delta y}{\delta x}, \frac{\mathrm{d} y}{\mathrm{d} x}$$   For what I know, $\mathrm{d}$ is used as a small infinitisemal change (and I guess the straight-up letter $\mathrm{d}$ is usual notation instead of italic $d$, simply to tell the difference from a variable). Of course we also have the big delta $\Delta$ to describe a finite (non-negligible) difference. And I have some vague idea that $\partial$ is used for partial derivatives in case of e.g. three-dimensional variables. Same goes for $\delta$, which I would have sworn was the same as $\partial$ until reading this answer on Math.SE:    Then to make the confusion total I noticed an equation like $\delta Q=\mathrm{d}U+\delta W$ and read in a physics text book that:     The fact that the amount of heat [added between two states] is dependent on the path is indicated by the symbol $\delta$...   So it seems $\delta$ means something more? The text book continues and says that:     a function [like the change in internal energy] is called a state function and its change is indicated by the symbol $\mathrm{d}$...   Here I am unsure of exactly why a $\mathrm d$ refers to a state function.   So to sum it up: down to the bone of it, what is $\delta$, $\partial$ and $\mathrm{d}$ exactly, when we are talking derivatives in physics.  Addition  Especially when reading a mathematical process on a physical equation like this procedure:  $$\delta Q=\mathrm{d}U+p\mathrm{d}V \Rightarrow\\ Q=\Delta U+\int_1^2 p \mathrm{d}V$$  It appears that $\delta$ and $\mathrm{d}$ are the same thing. An integral operation handles it the same way apparently? How do I upgrade from 14.04 LTS to 16.04.1 LTS? The Newtonian description of gravity can be formulated in terms of a potential function $\phi$ whose partial derivatives give the acceleration:  $$\frac{d^2\vec{x}}{dt^2}=\vec{g}=-\vec{\nabla}\phi(x)=\left(\frac{\partial\phi}{\partial x}\hat{x}+\frac{\partial\phi}{\partial y}\hat{y}+\frac{\partial\phi}{\partial z}\hat{z}\right)$$  However, in general relativity, we describe gravity by means of the metric. This description is radically different from the Newtonian one, and I don't see how we can recover the latter from the former. Could someone explain how we can obtain the Newtonian potential from general relativity, starting from the metric $g_{\mu\nu}$? Permanently turn off new Google Maps and go back to old one I found new Google Maps slow, useless (routes with only two points) and wrong. Is there any way, I can turn it off completely and go back to favored old Google Maps? Or is this &mdash; as with everything in Google &mdash; one way trip?  I found  text on this matter, but it seems useless. I have the feeling, that it discuss something completely different. It says about lite indicator in bottom-right corner. I don't have something like that. And provided links, that should switch new Google Maps engine between WebGL and canvas-based, simply doesn't work. All of them opens new window with annoying advertisment about new maps.  I even tried pasing part of URL, they're talking about (force=canvas) into any URL that my new Google Maps uses. Of course without any luck.  So... is there any way, I can get rid of new Google Maps, once and permanently?  UPDATE: In these days (April, 2015) Google , that soon new Google Maps will be the only one available. To my extremely negative surprise, this question will become invalid soon! :( Why exactly can't a single resistor be used for many parallel LEDs? Why can't you use a single resistor for a number of LEDs in parallel instead of one each? What autofocus zone selection mode should I use for action/event shooting? I have a Canon 7D, and typically shoot everything I do in its single-point autofocus zone select mode, because I usually want fine control over exactly what the camera is focusing on and I often find that its two automatic focus zone select modes don't focus on what I want in focus.  For most of the photography I do, this is fine -- I have enough time that I can compose the shot the way I want, use the joystick on the back to select the right focus point, and take the shot at my leisure.  However, recently I've been doing more event/action photography, and I've been running into issues with this mode of operation.  Too often, I will see a person start to do something interesting, but my autofocus point is not in the right place -- so by the time I get the camera up, adjust the settings, and move the autofocus point, the opportunity to take the shot has passed.  My question is, what autofocus zone selection mode and workflow should I use for this type of photography?  I could use the 5-zone partial-auto mode (which gives me a choice of top, middle, bottom, left, or right, and then the camera chooses the points within my selected region), but I find that the time needed to switch in between that mode and the single-point mode is similarly prohibitive, and I have to hope that the camera chooses the right thing to focus on. Resolve build errors due to circular dependency amongst classes I often find myself in a situation where I am facing multiple compilation/linker errors in a C++ project due to some bad design decisions (made by someone else :) ) which lead to circular dependencies between C++ classes in different header files (can happen also in the same file). But fortunately(?) this doesn't happen often enough for me to remember the solution to this problem for the next time it happens again.  So for the purposes of easy recall in the future I am going to post a representative problem and a solution along with it. Better solutions are of-course welcome.     A.h  class B; class A {     int _val;     B *_b; public:      A(int val)         :_val(val)     {     }      void SetB(B *b)     {         _b = b;         _b-&gt;Print(); // COMPILER ERROR: C2027: use of undefined type 'B'     }      void Print()     {         cout&lt;&lt;"Type:A val="&lt;&lt;_val&lt;&lt;endl;     } };       B.h  #include "A.h" class B {     double _val;     A* _a; public:      B(double val)         :_val(val)     {     }      void SetA(A *a)     {         _a = a;         _a-&gt;Print();     }      void Print()     {         cout&lt;&lt;"Type:B val="&lt;&lt;_val&lt;&lt;endl;     } };       main.cpp  #include "B.h" #include &lt;iostream&gt;  int main(int argc, char* argv[]) {     A a(10);     B b(3.14);     a.Print();     a.SetB(&amp;b);     b.Print();     b.SetA(&amp;a);     return 0; } Change this behavior to allow for spelling corrections and the like: "Edits must be at least 6 characters" Can a sql server table have two identity columns? I need to have one column as the primary key and another to auto increment an order number field. Is this possible?  EDIT: I think I'll just use a composite number as the order number. Thanks anyways. I use Chrome across 4 different workstations and I have my extensions synced across all of them.  The problem I have is that one of the extensions () works great if you've got an actual mouse, but on a trackpad on Ubuntu, it just gets in the way.  If I disable it on the Ubuntu machine, it gets disabled on all Chrome installations due to its .  Q: Can I selectively disable an extension on just a single machine? If $f:D\to D’$ is analytic and $u: D'\to R$ is harmonic then the composition of $u$ and $f$ is harmonic in $D$ If $f:D\to D’$ is analytic and $u: D'\to R$ is harmonic then the composition of $u$ and $f$ is harmonic in $D$.  How can I show that the above statement is true/false? Can anyone help me? How do you effectively study physics? How does one read a physics book instead or just staring at it for hours?   (Apologies in advance if the question is ill-posed or too subjective in its current form to meet the requirements of the FAQ; I'd certainly appreciate any suggestions for its modification if need be.) How do I change a switched outlet to a half-hot outlet? I am trying to change a switched outlet to a half-hot outlet. If you can see the picture, the outlet currently only has a white, black, and ground wire coming to it.   The switch is on the other side of the wall and it would be eextremely difficult and ugly to run another wire to it. (no crawl or attic space). So my question is, can I change the current outlet/wiring within the outlet to make it a half-hot? My understanding is that removing the brass connector will just make half of it dead.