laptop not booting to 20.04 usb made with rufus
Why Doesn't a Bootable USB Boot
What is the difference between necessary and sufficient conditions? If $p\implies q$ ("$p$ implies $q$"), then $p$ is a sufficient condition for $q$. If $\lnot p\implies \lnot q$ ("not $p$ implies not $q$"), then $p$ is a necessary condition for $q$.   I don't understand what sufficient and necessary mean in this case. How do you know which one is necessary and which one is sufficient? I use Firefox 35.0 on my Macbook to access Stack Exchange. Recently whenever I access a message or Community site, the "spinning circle" indicating activity starts, and never stops. This doesn't seem to happen on other non-Stack Exchange sites.  Has there been any change to the SE code which may have caused this.    The Web Developer Console shows  The connection to ws://qa.sockets.stackexchange.com/ was interrupted while the page was loading. full.en.js:1 Use of getPreventDefault() is deprecated.  Use defaultPrevented instead. jquery.min.js:3 Deleting another user's directories from my own I am a non-root user, and have made a directory into which other users in my group can write. The directory is setgid, so files and directories within it have the same group.  I can delete files placed into this directory, but if a user creates a subdirectory with files in it, I can't seem to delete those. Is there something special I can do (other than, say, bothering the user in question or the sysadmin about it) to get rid of this subdirectory?  EDIT: Inevitably, of course, someone asks "why?"  The shared folder in question is a mercurial repository. We can't use a shared-account ssh-key-based server for this like mercurial-server, and we can't just host it externally for various reasons. But that part works fine. We use Redmine for project management, but it does not yet read the repo index for file contents - it reads the working directory. So the working directory must be kept up-to-date. crontab has been disabled by the sysadmin, so that's out. So I naïvely put a changeset hook in the shared repo that performed an "hg update". This seemed to work fine initially, until, of course, someone pushed a commit with a new directory. While I had vague thoughts of trying to make a setuid script for the hook, I'll probably just consider safer avenues. I'm confused about the use of symbols $\vdash$ and  $ \models$. Reading the answers to  and  I see that:  the turnstile symbol $ \vdash $ denotes syntactic implication. Then $ S \vdash \psi$ means that $\psi$ can be derived from the formulae in $S$  the double turnstile $ \models $, denotes semantic implication. Then the notation $A \models B$ means simply that B is true in every model in which A is true.  So I understand that, e.g., $(ZFC+ A) \vdash B$ means that $A \Rightarrow B$ is a theorem in ZFC and, in this sense $\vdash$ is a mathematical symbol for a theorem. While $(ZFC+ A) \models B$ means that $ B$ is true in every model of ZFC in which $A$ is true, and, in this sense $\models$ is not a mathematical but a metamathematical symbol.  I understand correctly? And those are the only uses of the two symbols? How to plot stacked bar plot inside table? I have following code in Latex. Which plots only one data series (data2). I would like to plot staked bar plot inside table for both data1 and data2 with different colours.  Any ideas.?  Many thanks.  \documentclass{article} \usepackage{booktabs} \usepackage{multirow} \usepackage{pgfplotstable} \usepackage{filecontents}  % The data \begin{filecontents}{data.txt} accession,data1,data2 C1,150708.4564,481.0388003 C2,49652.53112,275.2190163 C3,37379.1284,58.85806921 C4,34165.85698,26.06571636 C5,30856.19158,35.96802428 C6,15204.22768,26.71594573 \end{filecontents}   \pgfplotstableread[col sep=comma]{data.txt}\data  \newcommand{\errplot}{% \begin{tikzpicture}[trim axis right] \begin{axis}[y=-\baselineskip,   scale only axis,   width=5cm,   enlarge y limits={abs=0.5},   axis y line*=middle,   ytick=\empty,   axis x line*=bottom,   xbar,   bar width=1.5ex,   xmin=0,   visualization depends on=x \as \rawx,   nodes near coords,   every node near coord/.style={   anchor=east,   shift={(axis direction cs:-\rawx,0)}   }  ] %   \addplot [draw=black, fill=red]  table [x=data2,y expr=\coordindex]{\data}; \end{axis} \end{tikzpicture}% }  \begin{document}  % Get number of rows in datafile  \pgfplotstablegetrowsof{\data} \let\numberofrows=\pgfplotsretval  % Print the table \pgfplotstabletypeset[columns={accession,data1,data2},   % Booktabs rules   every head row/.style={before row=\toprule,after row=\midrule},   every last row/.style={after row=[3ex]\bottomrule},   % Set header name   columns/accession/.style={string type,column type=l,column name=accession},   columns/data1/.style={string type,column type=l,column name=data1},    columns/data2/.style={     column name={Data2},     assign cell content/.code={% use \multirow for Z column:    \ifnum\pgfplotstablerow=0    \pgfkeyssetvalue{/pgfplots/table/@cell content}    {\multirow{\numberofrows}{6.5cm}{\errplot}}%    \else    \pgfkeyssetvalue{/pgfplots/table/@cell content}{}%    \fi   }  }, ]{\data} \end{document} At what voltage is a NiMH battery empty? I have a battery pack of NiMH batteries. It is ten cells with 1.2V, 4000mAh each, put together in series. So rated voltage is 12V. After charging, i.e. when the charging device says that it is finished, I measure 14.3V.   When I now discharge, at what voltage should I consider my battery as "empty"? Is this the lowest voltage that I can discharge it to without damaging it? Which voltage is that? How can I use multiple accounts with Telegram? Is there a way to have two copies of  app in Ubuntu each with a different account?  It seems copying the app in another folder does not work. If $X$ is distributed $N(\mu_X, \sigma^2_X)$, $Y$ is distributed $N(\mu_Y, \sigma^2_Y)$ and $Z = X + Y$, I know that $Z$ is distributed $N(\mu_X + \mu_Y, \sigma^2_X + \sigma^2_Y)$ if X and Y are independent.  But what would happen if X and Y were not independent, i.e. $(X, Y) \approx N\big( (\begin{smallmatrix} \mu_X\\\mu_Y \end{smallmatrix}) , (\begin{smallmatrix} \sigma^2_X &amp;&amp; \sigma_{X,Y}\\ \sigma_{X,Y} &amp;&amp; \sigma^2_Y \end{smallmatrix}) \big) $  Would this affect how the sum $Z$ is distributed? Two Bibliographies: one for main text and one for appendix I have a manuscript in which has the following structure:  Main Text Bibliography Appendix   However, there are citations which are only cited in the appendix, and they show up in the main bibliography. I would like to split my Bibliography into two different sections, so that the structure of the paper would look like this:  Main Text Bibliography for Main Text Appendix Bibliography for Appendix   I'm currently using bibtex and a single .bib file, and creating the bibliography with  \bibliographystyle {someBibStyleFile} \bibliography {bibFileName}   I'm interested in a method to split my single bibliography into main bibliography and appendix bibliography with minimal changes to the rest of the document.  I'm aware that biblatex is more powerful than bibtex, but I'm not prepared to make the switch before the deadline of this project. There are many related bibliography-with-multiple-sections type of questions, but I didn't see one that covers this case. Run TTY script every time I open a GUI terminal What are the scope restrictions for setting shopt extglob. and other options? My non-interactive bash shell has extglob off. I would like to turn it on in the statement immediately before a command, but I have noticed that when shopt -s extglob is within an if .. then .. else block, it somehow does not register.   The following extglob-dependant command is not valid: syntax error near unexpected token '('.     Where can extglob be set, and why is there a restriction, at all? Does this apply to other options?  ... GNU bash 4.1.5     This works:    shopt -s extglob if true ;then     touch a.bcd; ls a.@(bcd) fi   This fails:    if true ;then     shopt -s extglob     touch a.bcd; ls a.@(bcd) fi ... line 17: syntax error near unexpected token `(' ... line 17: `touch a.bcd; ls a.@(bcd)' Hiding downvoted questions silences important discussions on Meta I just noticed a particular MSE post today on a topic I care about that was posted almost a week ago, which I entirely missed before. I'm a pretty avid MSE user, and this happens quite rarely to me.     was created by an SE employee, and is essentially the final answer to , which is the 10th most upvoted MSE post with a bit more than 900 upvotes right now. So it's kind of an important post, and on a topic I care about, but I still missed it entirely until it was linked in a comment somewhere else.  The reason I missed it is because it's heavily downvoted. This means that as it has below -8 score, it's hidden from the home page entirely, drastically reducing the visibility of the post. In particular, the negative score removes all visibility a question usually receives from being bumped due to edits, new answers and bounties.   Many of the recent heavily-downvoted Meta posts by SE have been featured manually, which grants them a lot of visibility beyond the particular meta site. This masked the problem pretty efficiently, but it is more of a workaround, and one that isn't applicable to all situations.  Voting means something different on meta sites, and not every downvoted question should be hidden from view. Closed downvoted questions can certainly still be affected by the usual rules on the home page, and that should cover the vast majority of questions that actually have a purpose being on the home page. But open questions should be displayed on the home page on meta sites even if they're heavily downvoted. How can I have `date` output the time from a different timezone? I have a server running with the timezone set to UTC. It seemed like that was generally a good practice (please correct me if I'm wrong).  Anyhow, one of the servers I connect to, in order to scp files, is running on EDT and stores files that I need to copy in the format /path/to/filename/data20120913  I looked at trying to rsync files using something like find's -mtime -1 flag for files modified in the last day, but I didn't have any luck.  I don't mind just using scp to copy the current day's file, but as of right now there is a 4-hour window where running date +%Y%m%d will give a different day on each server and that bugs me a little.  Looking through man date I see that I can have the time output as UTC, but I don't see a way to have it output as another timezone like EDT  I suppose I could also use something like the GNU date extension date -d 20100909 +%s to get the date in seconds from the epoch, apply a manual 4 * 60 * 60 second calculation, and see about rendering that as a date - but then when daylight time kicks in it will still be an hour off.  Is there a simpler way to output the date in a YYYYMMDD format for EDT on a server that is set to UTC ? What word describes random unfitting accusations I really dont know how to describe this. Im having a discussion with someone, I was sharing information that I found on a topic. Randomly im called out as being rude when nowhere was there evidence of rudeness exchanged. This person seems to have a history of claiming people have a problem or are being rude out of the random blue.   Is there a word to describe these random accusations that dont connect to anything? A fellow player is uncooperative with the group and gets GM favoritism. How do I handle this? I actually have two situations but they are interconnected. Our group is currently playing a Dresden game. The GM and one of the players are married. Along with that, he is a new member to the group. I can understand her (the GM) wanting to make him feel welcome but it has gone into the the realm of blatant favoritism. A few examples:   Every idea he has is deemed fantastic, wonderful, awesome and is always successful. Most of the time he doesn't have to roll to see if he succeeds; he just does. After a series of major setbacks to the other player's characters, I joked that her husband was the only one left to mess with. Her answer to that was that she would absolutely not be messing with him in the game. He and his character were safe from that. In the last session, he and another player had to make the same roll using the same skill for the same information. He needed a fair to succeed. The other player needed a great. Not the first time that has happened.    The second part of this has to do with him as well. As I said, he is new to the group. When we were discussing a game to play, it was made clear that it would be cooperative. We would all be working together to a common end. However, he will not- I mean ever- share any information with the rest of the group. No matter how vital or needed that information is to advance the story, he just smiles and says he's got nothing. To try and get around this problem, a group aspect was created. That way if a situation or information that everybody needed to know came up, a fate chip could be played and anyone who wanted to be a part of it could be present. He is totally abusing it. Now, instead of just not telling us anything, he adds give me a fate chip and maybe I'll tell you something. It's like he is trying to beat us at the game and that is not the way it was set up.    So, the question to these two situations is what do I do? How do I handle this in a rational and sensitive way? To complicate things further, the GM is my best friend. He is her husband. I don't want to put her in the middle but I am about ready to quit the game. I am tired of it being his game and everyone else being bit players. Should I talk to her or should I talk to him? If anyone has had experience with this, any advice would be appreciated. Keep values selected after form submission Why is my find not recursive? I am running the following command, but it is not performed recursively:  find . -name *.java   I know there are java files further down in the current directory but it is performing the find on the current directory only. I am using OS X, 10.9. How can I hide my code in visualforce page? We, as high school students have been taught that-because Bohr's model of an atom assigns specific orbits for electrons-that it is better than Rutherford's model. But what Rutherford failed to explain was why electrons don't emit EM waves &amp; fall into the nucleus. I don't see how the introduction of 'atomic orbitals' overcame this defect. Can't it still radiate EM waves? Why does the zoom sometimes stop at a point?