How to make my Ubuntu lock up?
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How to solve $\frac 1{1.2.3}+\frac 1{2.3.4}+\frac 1{3.4.5}+...$ As my question says,   $$\frac 1{1.2.3}+\frac 1{2.3.4}+\frac 1{3.4.5}+...$$  As far as $\frac 1{1.2}+\frac 1{2.3}+\frac 1{3.4}+...$ is concerned, we can write it as $\frac 1{n-1} - \frac 1{n}$ What can we do here? What does it mean to say "a divides b" I am not a number theorist and I am learning about relations.  I encountered a relation that says      $a \leq b$ if $a$ divides $b$   Can someone clarify what it means to a number to divide another number?  Does it mean what I think? $a$ divides $b$ if $a | b \in \mathbb{Z}$?     So given a set $S = \{a, a^2, a^3, \ldots\}$, with relation $a | b \leftrightarrow a \leq b$, does the relation hold   going from left to right or right to left? i.e. $a|a^2, a^2|a^3, \ldots$ Listing multiple compound words How do I list multiple things that are compound words?  In my own language I'm used to writing these lists like this:  "I kicked foot-, basket-, and volleyball"  The sentence is supposed to mean that I kicked all types of balls (football, basketball and volleyball). However, it does not seem correct to me. Should I write them as whole words, with or without hyphen, or how? Find the first occurrence/starting index of the sub-array in C# Creating a responsive menu system for a site with a lot of content I am currently creating a website which has a lot of content - text. For this I need a serious menu structure with 5-10 menu items per menu and at least 15 menu-blocks per main menu item.   Further it has to be accessible via mobile.   Till now I have used panels and added menus inside the panels. But mobile isn't to happy about that and the list-names in the menus overlap the content.   How would you go about solving this issue? I trust you experts here! :-) Heap versus Stack allocation implications (.NET) From an 1 about Heap and Stack, it raised me a question: Why it is important to know where the variables are allocated?  At  someone pointed that the stack is faster. Is this the only implication? Could someone give a code example where a simple allocation location change could solve a problem (eg. performance)?  Note that this question is .NET specific  1 the question is removed from SO. Novel about a man who has his car stolen and is cryogenically frozen with his cat? So this is a bit of a memory game of my behalf, but I'm trying to remember the name of a (presumably) Sci-Fi novel with only a recollection of the following:   A man owns a (yellow?) car parked outside his house along with a cat The car goes missing or is stolen The man decides to be cryogenically frozen for 75 (fairly sure, could be 50?) years along with his cat (I might be muddling up novels but I'm sure there was a cat...?) He takes a walk along the street X years in the future when he wakes up and the currency he has in his pocket is now worthless   I don't think I got that far into the book and all the above happened relatively early.  I read it about 10 years ago and at a guess, it's an 80's novel - all of the above details might be inaccurate, but I'm certain about the cryogenic freezing and the currency aspects.  I'd be surprised if this one gets anywhere! GIS Point or discrete longitude and latitude columns? I see that the Point type is made to store geometric coordinates, however I don't see what problem it is trying to solve, or what advantages it offers over simply using two numerical columns. It's 16 bytes, so is it just an abstraction for two 8 byte floats? Or is it a string containing some kind of geohash that optimizes the performance of certain queries?  Let's say I want to get all the points for a specific viewport on a Leaflet map... with numerical columns representing latitude and longitude, I'd just filter for all the rows that have a latitude number between the N/S bounds and a longitude number between the E/W bounds, easy. I looked into using Point here, but the syntax is cumbersome and it seems to me like unnecessary overhead for development and for database performance... is it? App Store asks for old Apple ID when installing updates I got a MacBook that a colleague of mine had used previously. It runs OS X 10.10.2. I created a new administrator account for myself and turned off the "admin" flag on the old account.  I also entered my iCloud / Apple ID account, so that it syncs my calendars and contacts correctly, and even in the App Store, I am signed in with my correct account.  But when I try to install pending software updates (that is, OS X system updates!), the window that pops up has the the e-mail address of my colleague filled in and greyed out—and I can't change it.     Note that I'm signed in with a different (correct) account in the App Store. When I go to Featured and click Account on the right, it has my correct e-mail address filled in:    How do I make the App Store "forget" the old Apple ID?  I  where it just says "it's not possible", and that apps are glued to the original account the Mac was set up with, but that doesn't make a lot of sense, especially in a company where laptops may be handed over from one person to another. Add bst file with LaTeX / MiKTeX I'm trying to use elsarticle-num-ident.bst, an exact copy of  C:\Program Files (x86)\MiKTeX 2.9\bibtex\bst\elsarticle\elsarticle-num.bst    but every time I run LyX, I get the bibtex error  I couldn't open style file elsarticle-num-ident.bst   This is despite reconfiguring LyX and restarting, and despite running MixTex's Settings/Options' "Refresh FNDB" as Administrator.  It also doesn't work if I put the .bst file in the same folder as the .lyx file.  How should I help lyx/bibtex/Mixtex find the .bst file?  Once I get the identical copy to work, I plan to edit it to not print URLs, as suggested .  Related questions: I read this book about 20-30 years ago. It's about a group of teenagers who wake up in a huge room where each is on a separate platform. As the book progresses, they go unconscious and the platforms change, move or become connected. The children are punished or rewarded through a variety of methods including food and pain. The goal is to get them to either hurt each other, or see if they band together, I can't quite remember. Please tell me if this sounds familiar. When I slam my hand onto my keyboard, only a maximum of 6 keys will be registered, I've tested this for the past few minutes and was unable to get more than 6. Is this the same on all keyboards? If not, what would be the distinguishing factor, If yes: why 6 specifically?  For clarification: I do not have a usecase for this, I am simply curious "Closed" (square) root symbol I found a cool trick in the  which allows the square root sign to be altered such that it &quot;closes&quot; over its contents. Here's an example:  (&quot;closed&quot; root on the left, normal one on the right) The way they do this is as follows: % New definition of square root: % it renames \sqrt as \oldsqrt \let\oldsqrt\sqrt % it defines the new \sqrt in terms of the old one \def\sqrt{\mathpalette\DHLhksqrt} \def\DHLhksqrt#1#2{% \setbox0=\hbox{$#1\oldsqrt{#2\,}$}\dimen0=\ht0 \advance\dimen0-0.2\ht0 \setbox2=\hbox{\vrule height\ht0 depth -\dimen0}% {\box0\lower0.4pt\box2}} The cool thing is that (as far as I've tested it) this works regardless of the math font and with pdftex as well as xetex. However what is not possible is mulitple roots, such as \sqrt[3]{a}. Those produce incorrect output when this &quot;trick&quot; is being used. So my question is, is somebody able to tweak this code so that it works for multiple roots as well? How to get city name from latitude and longitude coordinates in Google Maps? Possible Duplicate:          I have seen  in SQL. I wonder how would you approach the opposite problem: splitting coma delimited string into rows of data:  Lets say I have tables:  userTypedTags(userID,commaSeparatedTags) 'one entry per user tags(tagID,name)   And want to insert data into table  userTag(userID,tagID) 'multiple entries per user   Inspired by  question  EDIT  Thanks for the answers, actually more then one deserves to be accepted but I can only pick one, and the  with recursions seems pretty clean to me. It works on SQL Server 2005 and above.   For earlier version of SQL Server the solution  can be used.  For working with text data type  will be helpful. Thanks again. Remove last character from line I want to remove last character from a line:  [root@ozzesh ~]#df -h | awk  '{ print $5 }' Use% 22% 1% 1% 59% 51% 63% 5%  Expected result:  Use 22 1 1 59 51 63 5 I have a Google Apps for your domain account for my domain which we will call DomainA  I have since replaced that domain with DomainB which is set up in the Google Apps account as an alias.   Since I want to let DomainA expire at some point in the future, I would like to change my primary domain to DomainB in my Google Apps account with DomainA as an alias.   How can I do this? Any good application for data usage monitor? I was wondering if there are any good applications to monitor how much data I use on my laptop in a month. My net connection has a restriction of how much data I can use after which the speed goes down considerably. I saw ntop, but I just wanted to ask if there are any other good options or suggestions regarding this. Regards. ART has better performance and better battery life on paper at least.  Should I consider switching to it on my moto g? What are the results I can expect? What precautions should I take? Is it easy to turn back to dalvik? What is the purpose of the EBP frame pointer register?