Locked out of 15.04 after the latest update An automatic update ran yesterday (7/7/2015) and now I am locked out of X windows.  The login screen has gone extra large, so the login box takes up a large part of the screen.  When I try and log in it accepts the password, then dumps me back to the login screen.  I can switch to the terminal with ctrl-alt-F1 and log in OK so there is no issue with my password, but then I am stuck in text mode.    How do I fix this?  Update:  I think I found the cause in syslog:  Xlib: extension "GLX" missing on display: gnome-session-is-accelerated: No hardware 3D support gnome-session-check-accelerated: Helper exited with code 256 gnome-session[...]: CRITICAL: We failed, but the fail whale is dead. Sorry... lightdm[...]: ** lightdm CRITICAL **: session_get_login1_session_id: assertion 'session!=NULL' failed   So it appears that it is failing because it is not getting 3D acceleration, despite having an Nvidia GTX 960 card.   But I still have no idea how to fix it.
Ubuntu gets stuck in a login loop My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M
I have this, in D1:  =sum(D3:D)   I want D1 to always be the sum of the rest of column D (D2 is a header)  I sometimes move a row, from eg 8 to 3, and that causes D1 to change to sum(d4:d).    I want D1 to stay as my sum of the column. Prove $\operatorname{rank}(AB) = \operatorname{rank}(B)$ I am given the info that A is an invertible  m by m matrix and B is a m by n matrix. By solving for the null space $ABx=0$, I get $A^{-1}ABx=A^{-1}0$, therefore $Bx=0$. I concluded that the null spaces of A and AB must be equivalent, and therefore the nullity(AB) = nullity(B) = some number p. Therefore rank(AB) = n-p = rank(B)   (because both AB and B are m by n matrices).   Is this proof valid, specifically the null space step? How can I implement a comprehensive apa-style citation and bibliography I am really new to LaTeX and I need a comprehensive solution for my Thesis  I have this problem since two days and I couldn't find any solution in any other post.  I work with BibDesk on Mac  And I used Packages apacite and natbib  @article{Ha89, Author = {Peter M. Haas}, Date-Added = {2017-02-06 21:15:57 +0000}, Date-Modified = {2017-02-06 21:45:06 +0000}, Journal = {International Organization}, Lastchecked = {03/02/2010 12:54}, Number = {3}, Pages = {377-403}, Publisher = {Peter Haas}, Read = {0}, Title = {Do regimes matter? Epistemic communities and Mediterranean pollution control}, Urldate = { http://www.jstor.org/stable/2706652}, Volume = {43}, Year = {1989}}   this is a stripped version of my document:  \documentclass[11pt, oneside]{article}  \usepackage{lipsum} \usepackage[margin=1in, left=1.5in, includefoot]{geometry}   \usepackage{ragged2e} % REFERENCE PREAMBLE %\usepackage{url} \usepackage{apacite} \usepackage{natbib} %\usepackage{biblatex-apa}                                                   % Bullet preamble \renewcommand{\labelitemi}{$\bullet$} \renewcommand{\labelitemii}{$\diamond$} \renewcommand{\labelitemiii}{$\circ$} % graphics preamble \usepackage{graphicx}   %Allows you to import images \usepackage{float}      %Allows for control of float positions %HEADER AND FOOTER STUFF \usepackage{fancyhdr}  \pagestyle{fancy} \usepackage{graphicx}        \usepackage{amssymb} %Zeilenabstand 1,5 wenn aktiviert  \usepackage{setspace}\makeatletter\newcommand{\MSonehalfspacing}{\setstretch{1.44}\ifcase \@ptsize \relax\setstretch {1.448}\or\setstretch {1.399}\or\setstretch {1.433}\fi}\newcommand{\MSdoublespacing}{\setstretch {1.92}\ifcase \@ptsize \relax\setstretch {1.936}\or\setstretch {1.866}\or\setstretch{1.902}\fi}\makeatother\MSonehalfspacing %Zeilenabstand Code fertig \usepackage[hidelinks]{hyperref}   %allows for clickable reference %                       BEGIN OF DOCUMENT \citeA{source} %                       REFERENCES  \renewcommand{\sectionmark}[1]{\markright{\thesection\ #1}} \fancyhf{} \rhead{\fancyplain{}{Identifying the Regime}} \lhead{\fancyplain{}{List of References}} \cfoot{\fancyplain{}{\thepage}}  \setlength\bibitemsep{1.9\itemsep} \bibliography{/User/Desktop/Thesis/references/mybib.bib}                   \bibliographystyle{apa} \addcontentsline{toc}{section {\numberline{}References}                                                       \end{document}   I would like to have the bibliography entry include a retrieved from    I tried to deactivate hyperref – as suggested in another post – but it didn't work. I also tried to activate and deactivate natbib and apacite as well.   I would really appreciate any help... Help me understand Bayesian prior and posterior distributions In a group of students, there are 2 out of 18 that are left-handed. Find the posterior distribution of left-handed students in the population assuming uninformative prior. Summarize the results. According to the literature 5-20% of people are left-handed. Take this information into account in your prior and calculate new posterior.    I know the beta distribution should be used here. First, with $\alpha$ and $\beta$ values as 1? The equation I found in the material for posterior is   $$\pi(r \vert Y ) \propto r^{(Y +−1)} \times (1 − r)^{(N−Y +−1)} \\ $$  $Y=2$, $N=18$  Why is that $r$ in the equation? ($r$ denoting the proportion of left-handed people). It is unknown, so how can it be in this equation? To me it seems ridiculous to calculate $r$ given $Y$ and use that $r$ in the equation giving $r$. Well, with the sample $r=2/18$ the result was $0,0019$. The $f$ should I deduce from that?  The equation giving an expected value of $R$ given known $Y$ and $N$ worked better and gave me $0,15$ which sounds about right. The equation being $E(r | X, N, α, β) = (α + X)/(α + β + N)$ with value $1$ assigned to $α$ and $β$. What values should I give $α$ and $β$ to take into account prior information?  Some tips would be much appreciated. A general lecture on prior and posterior distributions wouldn't hurt either (I have vague understanding what they are but only vague) Also bear in mind I'm not very advanced statistician (actually I'm a political scientist by my main trade) so advanced mathematics will probably fly over my head. I frequently prefer to look for questions on superuser .    I have never been able to determine how these search results are ordered.  Typically, search results are returned in order of relevance and the search help says they are "weighted heavily towards question title matches", but in this case, you would think that the search would order them based on whatever tab is currently selected (newest, hot, active)?  I ordinarily never stray outside of 'newest', but it's clear the results are not sorted by age. The other day I was trying to download something for Minecraft and it involved my bin folder. So I was looking for it and couldn't find it. I then thought that I might have accidentally deleted it, but didn't find it in the trash. I have no idea how to get the bin folder back with all the Minecraft binary files in them. I am trying to prove a result, for which I have got one part, but I am not able to get the converse part.  Theorem. Let $R$ be a commutative ring with $1$. Then $f(X)=a_{0}+a_{1}X+a_{2}X^{2} + \cdots + a_{n}X^{n}$ is a unit in $R[X]$ if and only if $a_{0}$ is a unit in $R$ and $a_{1},a_{2},\dots,a_{n}$ are all nilpotent in $R$.  Proof. Suppose $f(X)=a_{0}+a_{1}X+\cdots +a_{n}X^{n}$ is such that $a_{0}$ is a unit in $R$ and $a_{1},a_{2}, \dots,a_{r}$ are all nilpotent in $R$. Since $R$ is commutative, we get that $a_{1}X,a_{2}X^{2},\cdots,a_{n}X^{n}$ are all nilpotent and hence also their sum is nilpotent. Let $z = \sum a_{i}X^{i}$ then $a_{0}^{-1}z$ is nilpotent and so $1+a_{0}^{-1}z$ is a unit. Thus $f(X)=a_{0}+z=a_{0} \cdot (1+a_{0}^{-1}z)$ is a unit since product of two units in $R[X]$ is a unit.   I have not been able to get the converse part and would like to see the proof for the converse part. How can we replace $\sup$ with $\max$ in definition of subordinate norm for finite-dimensional vector space? I'd like to extract the text from an HTML file using Python.  I want essentially the same output I would get if I copied the text from a browser and pasted it into notepad.    I'd like something more robust than using regular expressions that may fail on poorly formed HTML.  I've seen many people recommend Beautiful Soup, but I've had a few problems using it.  For one, it picked up unwanted text, such as JavaScript source.  Also, it did not interpret HTML entities.  For example, I would expect &amp;#39; in HTML source to be converted to an apostrophe in text, just as if I'd pasted the browser content into notepad.  Update html2text looks promising. It handles HTML entities correctly and ignores JavaScript.  However, it does not exactly produce plain text; it produces markdown that would then have to be turned into plain text. It comes with no examples or documentation, but the code looks clean.    Related questions: How to increase Scrollback lines in Ubuntu(14.04.2) server edition? I can see only limited lines on terminal by using shift+ pageup. in Ubuntu desktop version, there is option to make scroll-back lines unlimited. how to do it in Ubuntu server version. please suggest. To find minimum distance between two curves Order of general- and special linear groups over finite fields. Strip whitespace from jsp output Can I use lens brand X on interchangeable lens camera brand Y? I've got some lenses of brand X, but I've just got a new camera of brand Y. How can I tell if it's possible to use my lenses on my camera? I accept that I may lose a lot of automatic functionality like autofocus, aperture control and metering when using an adapter to connect the two. I have an issue with my Minecraft launcher - I downloaded modpack for minecraft then the launcher started an update for the modpack version which it's 1.6.2, however then I started to get the issue      [15:40:59 ERROR]: Gave up trying to download      for job 'Version &amp; Libraries'      [15:40:59 ERROR]: Job 'Version &amp; Libraries' finished with 26   failure(s)! (took 0:01:06.362)   At the same time I had just downloaded Avira antivirus and ran it, but unfortunately  removing it and trying again didn't help. I've tried to restore the system to the point before downloading the antvirus and the mod pack a 2 days ago, I've tried turning off the firewall and I have tried removing the whole .minecraft folder all with no luck at all. I can't figure it out, all the servers are working and I have good internet connection but some of the files download fine and other don't.  The full log is here:  [15:40:59 WARN]: Couldn't download https ://libraries.minecraft.net/net/sf/jopt-simple/jopt-simple/4.5/jopt-simple-4.5.jar for job 'Version &amp; Libraries' java.net.SocketTimeoutException: connect timed out         at java.net.TwoStacksPlainSocketImpl.socketConnect(Native Method) ~[?:1.7.0_45]         at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source) ~[?:1.7.0_45]         at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source) ~[?:1.7.0_45]         at java.net.AbstractPlainSocketImpl.connect(Unknown Source) ~[?:1.7.0_45]         at java.net.PlainSocketImpl.connect(Unknown Source) ~[?:1.7.0_45]         at java.net.SocksSocketImpl.connect(Unknown Source) ~[?:1.7.0_45]         at java.net.Socket.connect(Unknown Source) ~[?:1.7.0_45]         at sun.security.ssl.SSLSocketImpl.connect(Unknown Source) ~[?:1.7.0_45]         at sun.net.NetworkClient.doConnect(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.http.HttpClient.openServer(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.http.HttpClient.openServer(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.protocol.https.HttpsClient.&lt;init&gt;(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.protocol.https.HttpsClient.New(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source) ~[?:1.7.0_45]         at java.net.HttpURLConnection.getResponseCode(Unknown Source) ~[?:1.7.0_45]         at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(Unknown Source) ~[?:1.7.0_45]         at net.minecraft.launcher.updater.download.ChecksummedDownloadable.download(ChecksummedDownloadable.java:49) ~[launcher.jar:?]         at net.minecraft.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:108) [launcher.jar:?]         at net.minecraft.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:12) [launcher.jar:?]         at net.minecraft.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:89) [launcher.jar:?]         at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.7.0_45]         at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.7.0_45]         at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.7.0_45]         at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.7.0_45]         at java.lang.Thread.run(Unknown Source) [?:1.7.0_45] [15:40:59 ERROR]: Gave up trying to download https ://libraries.minecraft.net/net/sf/jopt-simple/jopt-simple/4.5/jopt-simple-4.5.jar for job 'Version &amp; Libraries' [15:40:59 ERROR]: Job 'Version &amp; Libraries' finished with 26 failure(s)! (took 0:01:06.362) Install Spyder3 without Anaconda on ubuntu 16.04 novel with psi slavery Name the novel, 197x.  Setting is a world of human(oid)s most of whom have the psi ability to enslave weaker others.  (Maybe the word slave and its derivatives are not used.)  Masters and slaves form a tree rather than a dichotomy; everyone delegates as much as they can. The protagonist is an outworlder on a mission, maybe simply doing a survey.  He wears the green robe of a native subculture who lack the power (or maybe they renounce it?) and are immune to it – by law or custom, I think, rather than by nature. His host or primary contact is Jael Forty of Lant, the number being how many slaves he can control; it can fluctuate. Is it possible to use the fact that $\sum_{n=1}^\infty \frac{1}{n^4} = \frac{\pi^4}{90}$ to compute $\sum_{n=1}^\infty \frac{(-1)^n}{n^4}$? How do I put a stencil-like texture across a sectioned object? Let $p(x)$ be a polynomial of degree $n$ satisfying $p(x)\geq 0$ for all $x$. That is, for all $x$, $p(x) = a_n x^n + a_{n-1} x^{n-1} + \cdots + a_1 x + a_0 \geq 0$, $a_n\neq 0$.  Show that $p(x)+p&#39;(x)+p&#39;&#39;(x)+\cdots+p^{(n)}(x)\geq 0$ for all $x$ where $p^{(i)}(x)$ is the $i^\text{th}$  derivative.  My interest: I know that, we can rewrite the LDE as follows  $$ p(x)+p&#39;(x)+p&#39;&#39;(x)+\cdots+p^{(n)}(x) = Lp(x) $$  where $L := I + D + D^2  + \cdots + D^{(n)}$. Can we say anything about a linear operator of this kind so that it does not change the sign of the input it takes? I can try to solve the question by writing for all the derivatives and factoring them using $p(x)$, but I think there should be a clever way of showing this by the properties of $L$. Can I figure out a solution by just looking at $L$ and the sign of $p(x)$ as in the question? Where should I look for that?