nonexistent, non-existent or non existent? I see various spellings of the same, which one is correct?  I have considered that the spelling might differ if it is British or American English, but as English isn't my native speak I have no clue.
Is the use of a hyphen between "non" and an adjective strictly necessary? Do I need to put a "-" between "non" and an adjective? As an example in physics we say "a non isolated photon", "non tight photon"... The context is very formal (paper publications and similar). Is there a general rule? Are there some differences between countries?
Is $[0,1]$ a countable disjoint union of closed sets? Connect Tikz nodes via two parallel arrows I am just starting to learn using Tikz and am a little lost within its seemingly infinite amount of options and possibilities.  What I am trying to do is visualize a few Matlab function interaction (which one calls which one, what is the in- and output). Since there are only about six subroutines, I place each one manually as a node. This is an example:  \documentclass{article} \usepackage{tikz} \usetikzlibrary{shapes,positioning}  \begin{document}  \begin{tikzpicture}[auto] \node           [rounded rectangle,draw]        (node1)     {Node 1}; \coordinate [above=of node1]                                (input); \node           [rounded rectangle,draw]    at  (-10:6cm) (node2)       {Node 2}; \draw           [-&gt;,very thick]             ([xshift=0.1cm]  input.south)  --                  node {right}                ([xshift=0.1cm]  node1.north); \draw           [-&gt;,very thick]             ([xshift=-0.1cm] node1.north) --                  node {left}                 ([xshift=-0.1cm] input.south); \draw                                            (node1) -- (node2);  \end{tikzpicture}  \end{document}     Now I would like to apply these double in/out arrows I (probably pretty awkwardly) created using xshift to all node connections, so in this example also for the connection between Node 1 and Node 2. Ideally, the space between these two arrows would be the same, independant of their angle and they would nicely connect to the outer line of the nodes. Any idea how I could achieve this? Similar questions I have found only used rectangle and orthogonal lines. I would like to prove that : If $H$ is a subgroup of $G$ and $K$ is a subgroup of $H$, then  $$|G:K|=|G:H||H:K|$$  I appreciate any clear explanation of this. Thanks ! I am using a Collection (a HashMap used indirectly by the JPA, it so happens), but apparently randomly the code throws a ConcurrentModificationException. What is causing it and how do I fix this problem? By using some synchronization, perhaps?  Here is the full stack-trace:  Exception in thread "pool-1-thread-1" java.util.ConcurrentModificationException         at java.util.HashMap$HashIterator.nextEntry(Unknown Source)         at java.util.HashMap$ValueIterator.next(Unknown Source)         at org.hibernate.collection.AbstractPersistentCollection$IteratorProxy.next(AbstractPersistentCollection.java:555)         at org.hibernate.engine.Cascade.cascadeCollectionElements(Cascade.java:296)         at org.hibernate.engine.Cascade.cascadeCollection(Cascade.java:242)         at org.hibernate.engine.Cascade.cascadeAssociation(Cascade.java:219)         at org.hibernate.engine.Cascade.cascadeProperty(Cascade.java:169)         at org.hibernate.engine.Cascade.cascade(Cascade.java:130) Highlight the difference between two strings in PHP What is the easiest way to highlight the difference between two strings in PHP?  I'm thinking along the lines of the Stack Overflow edit history page, where new text is in green and removed text is in red. If there are any pre-written functions or classes available, that would be ideal. Wrong favicon displayed on Google's mobile SERP For some time now, Google has been displaying a website's favicon next to its title on the mobile SERP according to    But, for one website that I am managing, it is showing a completely different favicon. You can see it if you open the  on a mobile device, I am talking about the orange one:  I am referring to the top result.  As you can see on the , the favicon has been added correctly using the proper meta tag:   &lt;link  rel="icon" type="image/x-icon" href="https://www.hoofgroove.ch/pub/media/favicon/default/favicon.ico" /&gt;   This is according to .  Also, all the browsers are displaying the correct favicon, which is not the orange one but the black&amp;red one.  This meta tag has been used for weeks and also the  has always been the correct one as far as I can tell.  But for some reason, Google is showing the wrong favicon on its mobile SERP.  Any ideas why? checking apt-get update lock file I have a daytime raster of my study area. I have 20+ counters in the study area that count "stuff" with a timestamp. Using  I determined the type of ambient light for each collected data point.   What I'd like to do:   Add a grey/semi transparent overlay to reflect the ambient light (Dusk, Sunrise, day, sunset, and dark). The end goal: produce a time-based visualization of the data collection that highlights the time of the day. Or be able to produce a snapshot at a certain time with the proper shaded overlay. Think of this as this the image: First, when I never had installed sl:  diogosaraiva@Ubuntu:~$ sl O programa 'sl' não está instalado actualmente. Pode instalá-lo escrevendo: sudo apt-get install sl   traslaction: "The program 'sl' is not currently installed. You can install it by typing:"  But when I'm tired of it and I remove it by typing sudo apt-get remove sl per example...  I get this when I type sl:  -bash: /usr/games/sl: Ficheiro ou directoria inexistente   translate: "-bash: /usr/games/sl: No such file or directory" instead of:    diogosaraiva@Ubuntu:~$ sl O programa 'sl' não está instalado actualmente. Pode instalá-lo escrevendo: sudo apt-get install sl   This appears with others packages too...  How I get rid of this: -bash: /usr/games/sl: Ficheiro ou directoria inexistente ?  I want see the original:  diogosaraiva@Ubuntu:~$ sl O programa 'sl' não está instalado actualmente. Pode instalá-lo escrevendo: sudo apt-get install sl   Output of type sl  sl está hasheado (/usr/games/sl) show that the interval of the form $[0,a)$ or $(a, 1]$ is open set in metric subspace $[0,1]$ but not open in $\mathbb R^1$ On the metric subspace $S = [0,1]$ of the Euclidean space $\mathbb R^1 $, every interval of the form $A = [0,a)$ or $(a, 1]$ where $0&lt;a&lt;1$ is open set in S. These sets are not open in $\mathbb R^1$   Here's what I attempted to show that $A$ is open in $S$. I have no idea how it is not open in $\mathbb R^1$.  Let $M = \mathbb R^1$, $x \in A  = [0,a)$ . If $x = 0$, $ r \leq \min \{a, 1-a\}, \\\  B_S(0; r) = B_M(0,r)\cap[0,1] = (-r, r) \cap[0,1] = [0,r) \subseteq A $  If $x \neq 0, r \leq \min \{x,|a-x|, 1-x\},  \\B_S(x; r) = B_M(x,r)\cap[0,1] = (x-r, x+r) \cap[0,1] \subset (0,x) \text{ or } (x, 1) \subset A$ I have  experience where empty spaces cause unwanted effects. It is not easy to trace the cause of these unwanted effects. In order to eliminate any doubt, I often overuse % as follows.   \usepackage% [% left=3cm, right=3cm% ]% {geometry}   or  \newcommand{\mycommand}% {% This is my command.% }   I got an extreme example that will break what Leo Liu said     In fact, only spaces which would be   output have to be removed by comment.   The following code does not produce output, but we cannot remove the % and leave a blank line between two elements of a list below.  \newpsstyle{gridstyle} { gridwidth=0.4pt, % griddots=0 }   Shortly speaking, where are the necessary places to be appended with % to remove unwanted spaces? Countable or uncountable; family of disjoint triangles? If we say that $\mathcal{S}$ is a family of disjoint triangles on a plane, is $\mathcal{S}$ a countable or an uncountable set?  I believe that it is an uncountable set since $\mathbb{R}$ is uncountable and our triangles' corner coordinates are $\in \mathbb{R}$, but I cannot prove this formally, any tip would help. Prove that $\binom{m+n}{m}=\sum\limits_{i=0}^m \binom{m}{i}\binom{n}{i}$ I need to proof this following equality :  $$\binom{m+n}{m}=\sum_{i=0}^m \left(\binom{m}{i}\binom{n}{i}\right)$$  This is what I did combinatoric proof:  Left : subset with $m$ members from $m+n$  Right : $\binom{m}{i} \rightarrow$ The number of subsets in set $m$ could also be written as $2^m$ AND $\binom{n}{i} \rightarrow$ the number of subsets with $m$ members from set $n$  In case $ n \leq m \implies \binom{n}{i}=2^n$  So this is what I came up with I still can't see why those expression are equal.  Any ideas? Thanks. How to connect to device via SSH over direct ethernet connection I have a device that I need to connect to over SSH. The device is connected to my workstation via a direct ethernet connection. I'm attempting to assign the connected device an IP address somehow that I can SSH to, however all of the guides I'm finding have the user configure the IP from whatever device they're working with (namely Raspberry Pi's and so on). This is not something I can do with this device as I've no physical interface to work with.  I've been recommended to setup a DHCP server on my workstation so it would take care of this for me, however I've no idea how to configure it and none of the guides I have followed have been helpful. With that approach, I seem to have been able to bind an IP to the interface the device is connected on, however SSHing to that IP just brings me back to my own machine.  So my main question is: How do I assign an IP address to a device directly connected to my computer via ethernet cable without having any kind of access to the device (no interface, keyboard, monitor, etc). If the answer is to set up a DHCP server on my machine, how do I properly configure this and get an IP I can SSH to?  For reference, I am using Ubuntu 16.04 with OpenSSH installed. The device is also running some flavor of Linux and has SSH software installed, but again there's no way to interact with it except through SSH. I also do not have access to my router, so plugging the device in there and letting the router do the work is not an option. "For security reasons, framing is not allowed; click OK to remove the frames." on Imgur upload Ok first, there's that lugubrious use of the semicolon; not necessary.  Second, I didn't open a frame!  You did!  Alls I tried to do is upload a 5MB animated .gif file via Imgur.    Looking further into this, Imgur actually posts an error when you upload an animated .gif larger than 2MB.    Go figure! When I upload an image to Stack Overflow, I cannot see my JPEG file in my post. It's all blank. I've tried it with different files, but gotten the same result. I have a batch file which I use to create an .apk file on my Windows machine. Now I need to be able to create the .apk file in Ubuntu but I don't know how translate my .bat file to a script to be able to run it on Ubuntu.  Below is the batch file which works fine on Windows.  Will you please give me some hints on how I can run it on Ubuntu?  @echo off set PAUSE_ERRORS=0 :user_configuration  :: Path to Flex SDK  set FLEX_SDK=C:\sdk\flex_sdk_4.5.1.21328  :: Path to Android SDK set ANDROID_SDK=C:\sdk\android  :validation if not exist "%FLEX_SDK%\bin" goto flexsdk if not exist "%ANDROID_SDK%\platform-tools" goto androidsdk goto succeed  :validation if not exist "%FLEX_SDK%\bin" goto flexsdk if not exist "%ANDROID_SDK%\platform-tools" goto androidsdk goto succeed  :flexsdk echo. echo ERROR: incorrect path to Flex SDK echo. if %PAUSE_ERRORS%==1 pause exit  :androidsdk echo. echo ERROR: incorrect path to Android SDK in 'bat\SetupSDK.bat' echo.  if %PAUSE_ERRORS%==1 pause exit  :succeed set PATH=%PATH%;%FLEX_SDK%\bin set PATH=%PATH%;%ANDROID_SDK%\platform-tools  :: Android packaging set AND_CERT_NAME="PeymanApp" set AND_CERT_PASS=fd set AND_CERT_FILE=cert\SampleApp.p12 set AND_ICONS=icons/android  set AND_SIGNING_OPTIONS=-storetype pkcs12 -keystore "%AND_CERT_FILE%" -storepass     %AND_CERT_PASS%  :: Application descriptor set APP_XML=application.xml  :: Files to package set APP_DIR=bin set FILE_OR_DIR=-C %APP_DIR% .  :: Your application ID (must match &lt;id&gt; of Application descriptor) set APP_ID=air.com.doitflash.SampleApp  :: Output packages set DIST_PATH=dist set DIST_NAME=PeymanApp  :validation %SystemRoot%\System32\find /C "&lt;id&gt;%APP_ID%&lt;/id&gt;" "%APP_XML%" &gt; NUL if errorlevel 1 goto badid goto end_validation  :badid echo. echo ERROR: Application ID (APP_ID) does NOT match Application descriptor '%APP_XML%'     (id)  echo.  :end_validation  set TARGET= set PLATFORM=android  ::call bat\Packager.bat if "%PLATFORM%"=="android" goto android-config  :android-config set CERT_FILE=%AND_CERT_FILE% set SIGNING_OPTIONS=%AND_SIGNING_OPTIONS% set ICONS=%AND_ICONS% set DIST_EXT=apk set TYPE=apk goto start  :start if not exist "%CERT_FILE%" goto certificate :: Output file set FILE_OR_DIR=%FILE_OR_DIR% -C "%ICONS%" . if not exist "%DIST_PATH%" md "%DIST_PATH%" set OUTPUT=%DIST_PATH%\%DIST_NAME%%TARGET%.%DIST_EXT% :: Package  echo true echo. call adt -package -target %TYPE%%TARGET% %OPTIONS% %SIGNING_OPTIONS% "%OUTPUT%"     "%APP_XML%" %FILE_OR_DIR% -extdir lib/ echo. if errorlevel 1 goto failed goto end  :certificate echo Certificate not found: %CERT_FILE% echo.  if %PAUSE_ERRORS%==1 pause exit  :failed echo APK setup creation FAILED.  if %PAUSE_ERRORS%==1 pause exit  :end How do I disable a bottom panel with the list of open windows on GNOME 3? How do I disable "Workspace dock" (a bottom panel with the list of open windows and a workspace indicator-cum-switcher), the one that is over "Plank" in the screenshot below?    I'm using Ubuntu 17.10. The best stack-up possible with a four-layer PCB? I'm designing a 4 layer PCB and I know that the standard stack-up is  Signals GND VCC Singals  (GND and VCC can be switched depending on the layer with more signals) The problem is, I don't really want to connect all ground pins through vias, there are just too many of them ! maybe because I'm not used to 4 layer PCBs, anyway, I've read a  by Henry W. Ott about a different stack-up  GND Signals Signals GND  (Where the power is being routed with wide traces on the signal planes) According to him, this is the best stack-up possible with a four-layer PCB, for the following reasons: 1.Signal layers are adjacent to ground planes. 2.Signal layers are tightly coupled (close) to their adjacent planes. 3.The ground planes can act as shields for the inner signal layers. (I think this requires stitching ??) 4.Multiple ground planes lower the ground (reference plane) impedance of the board and reduce the common-mode radiation. (don't really understand this one) One problem is cross-talk, but I really don't have any signals in the third layer, so I don't think that corss-talk will be an issue with this stack-up,am I correct in my assumption ? Note: The highest frequency is 48MHz, there's a wifi module on the board too. Reading JSON from a file?