W: GPG error:  precise Release: The following signatures were invalid: 630239CC130E1A7FD81A27B140976EAF437D05B5 E: The repository 'http://us.archive.ubuntu.com/ubuntu precise Release' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.
There are now errors when updating and I cannot install most software due to a corrupted  /etc/apt/sources.list   file. Is there a copy I can download to replace it?  The file would be for Ubuntu 12.04 (Final Beta) in the United States.
Are the Yongnuo clones of Canon flash equipment and lenses legal to sell/buy? Looking for Scifi Short Story in a Jerry Pournelle edited Anthology I'm looking for the title of the short story, and any of the volumes of anthology it may have appeared in. I know for SURE it's in one of Jerry Pournelle's anthologies, either Star Empires and There will be War, but as I have all the eBook version of THere will be war, I'm almost certain it wasn't there.   Anyway, the book is about a Commodore who went back to the academy to visit. I'm not sure what his name was, but I'm pretty sure he lived at "Mercer Hall". He had 2 roommates, and a butler to take care of all their needs, like putting away their stuff. (He even tried to argue with the hall monitor) The butler once took away their bottle of booze UNTIL they study for mid-term, and only gave it back AFTER they wrote to their mother AFTER the exam.   The book also goes heavily into "Bless you!" or the translated version, "May the great cosmic magnificence be benevolent toward you" or something like that. Basically, it's about as inoffensive as possible, and if you say it enough, and the aliens are reasonable, they will give up and things will resolve peacefully.   My Google-fu is weak and I can't find this particular story, or which volume of anthology was it in.   Little help? The spectral radius of normal operator Is there an easy way to convert a number to a word in PHP? In PHP, is there an easy way to convert a number to a word? For instance, 27 to twenty-seven. How to subtract a day from a date? I have a Python  object. What is the best way to subtract one day? How to remove `t=canonical` from Firefox browser searches made on DuckDuckGo? In Ubuntu 14.04, when I do a search in Firefox using either the address bar or the search bar, the system always adds t=canonical to my searches. So the full string becomes: https://duckduckgo.com/?q=cat+cooking+salmon&amp;t=canonical.  However, if I perform the same search by going directly to the search engine, i.e. typing the search engine name and doing the search from the presented search box, this does not happen. In this case the string is: https://duckduckgo.com/?q=cat+cooking+salmon.    How do I stop Ubuntu/Firefox from adding t=canonical to my search queries? And, why is this behavior there in the first place? How to detect the presence of URL in a string The second part of an exercise asks that I show:     There does not exist a surjective bounded linear map from $\ell^2(\mathbf{N})$ to $\ell^1(\mathbf{N})$.     The first part was to show that these two spaces are separable in their respective $L^p$ norms.    I've really hit a wall on this one.  I know, in fact, that there does exist a surjective bounded linear map from $\ell^1(\mathbf{N})$ to $\ell^2(\mathbf{N})$.  So my intuition says that if there were also one going the other way, then the two spaces would have to be isomorphic, which is false .  But I don't know of any such theorem that I could apply to "the category of Banach spaces".    My only other idea is to argue by contradiction using the open mapping theorem, but nothing is coming to me...  My guess is that separability is also going to be important, given the first part of the exercise.  -Thanks. What does rate of change actually mean? If we have a function, say, $y=x^2$, then $dy/dx=2x$. Now $y=1,4,9,16...$ for $x=1,2,3,4...$ and $dy/dx=2,4,6,8...$ for $x=1,2,3,4...$ Now as $dy/dx$ represents rate of change of y w.r.t x but I can't understand how these particluar values of $dy/dx$ represent change ? I mean for x=3, the rate of change is 6. What does it mean ? Why is.vector on a data-frame doesn't return TRUE? I have the following problem: I correctly obtain a numbered bibliography at the end but along the text the cite_key appear instead of a number. How to fix this problem?   \documentclass[11pt]{book}  \usepackage[]{biblatex} \begin{document} %some text  ... \cite{ABKM2015}... %some text  \begin{thebibliography}{99} \bibitem{ABKM2015} Arroja, F. and Bartolo, N. and Karmakar P. and Matarrese, S. (2015). \newblock The Two Faces of Mimetic Horndeski Gravity             \newblock {\em ArXiV}, 1506.08575 (2015). \end{thebibliography} \end{document}   After compiling I get ... [ABKM2015] ... while I want for example  [1]. Run an exe from C# code bash prompt messed up on arrow up I have made some modification to my prompt with use of colors via tput.  It looks like now when I try to do an arrow up lookup after few moves up, the prompt is being cut into half, what I mean by this is:  From this:  PROD mysuer@server1.domain.com:~$ vim .bashrc   To this:  PROD mysuer@servegit rebase origin/add_pool   ctrl + c brings everything back to normal.  I have found some posts indicating that this may be due to the issue with missing escapes for [ however I don't see an issue here:  My code:  #red for prod, green for lab  COLOUR_RESET=$(tput sgr0) COLOUR_GREEN=$(tput setaf 2) COLOUR_BLUE=$(tput setaf 6) COLOUR_YELLOW=$(tput setaf 3) COLOUR_RED=$(tput setaf 1) BOLD=$(tput bold)  if [[ $HOSTNAME =~ .*\.domain.com$ ]]; then   COLOUR=$COLOUR_RED   PROMPT_TEXT="PROD" fi  if [[ $HOSTNAME =~ .*\.lab$ ]]; then   COLOUR=$COLOUR_BLUE   PROMPT_TEXT="LAB" fi   MYPROMPT="$COLOUR$BOLD$PROMPT_TEXT$COLOUR_RESET \[\u@$COLOUR$BOLD$(hostname -f)$COLOUR_RESET:\w\]\$ "  PS1=$MYPROMPT   UPDATE: @KamilMaciorowski has pointed out a similar question although it was not relating to a tput colors. "There are currently N bounties, worth X reputation" dynamic ad and the new sidebar width You've probably seen this sidebar ad on one or more -enabled Stack Exchange sites over the years:    The image is dynamically generated from a non-officially SE app that uses the Stack Exchange API to fetch the bounties from a given site.  As far as I understand, the rendered image automatically scales to the allotted ad space - when the sidebar ads were 220x250, it would render in the sidebar as a 220x250 image while still looking quite oversized in the  meta (as it does right here).  With the new 2016 campaign starting, can we test whether this awesome dynamic ad works with the new sidebar width? diophantine equation: $x^2 +y^2 = z^n$ Prove that $x^2+y^2=z^n$ has a solution $(x, y, z)$ in $\mathbb{N}$ for all $n\in\mathbb{N}$  I tried to prove this by induction, but couldn't. ( This was probably because the solution for some $n$ isn't necessarily related to the solution for $n+1$)  I can't seem to see any other way other than induction for proving the statement. Any help/hints on solving this problem, or any alternative approach will be highly appreciated :) A little background:  I do not know what the specifics are, but I've noticed that a quick edit after a post will often times not result in an edit being posted. It's as if there was no edit. Edit: According to Bart this amount of time is five minutes.  The problem:  A user made a really bad post (said that ~ in C# wrt integers was used for deconstruction). I down-voted said post. Post quickly disappeared (I guess poster realized they screwed up and took back the post). Later, I come back and see my down vote but the answer is now correct (that ~ is the bitwise complement operator). I try to get rid of my down vote because it is no longer appropriate. However, it has been about half an hour and there is no edit posted (presumably the poster made an edit within the non-posting edit window) so I can't take my vote back.  Suggested solution:  If post gets edited (even within the non-post edit window) mark all the votes as changeable. I would guess that this would either involve an update on a table of votes or adding a column for last edit time which is not bypassed by the grace period. I realize that this may be an entirely non-trivial change, but unless the non-posting of edits is somehow changed to make sure the edit was trivial it seems this is necessary. I mistakenly deleted around 2,000,000 records from a remote SQL Server 2008 table.  The server is not granting me access to the backup files on the server side.   Is there any way to get back these records? How can I add reflection to a C++ application? I'd like to be able to introspect a C++ class for its name, contents (i.e. members and their types) etc. I'm talking native C++ here, not managed C++, which has reflection. I realise C++ supplies some limited information using RTTI. Which additional libraries (or other techniques) could supply this information? why does fdisk add one additional sector when creating partitions? I'm playing around with fdisk and I tried to create a partition on an empty USB drive. Here's how that went: Command (m for help): n Partition number (1-128, default 1): 1 First sector (34-61187102, default 2048): 2048 Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-61187102, default 61187102): +30000000           Created a new partition 1 of type 'Linux filesystem' and of size 14,3 GiB.  so just one partition with 30 million sectors. However, when I check how many sectors it contains I get:  I'm checking with a different program and I see again that additional sector:  Sorry for the pettiness :) I'm learning. Let $X$ be a non-negative random variable and $F_{X}$ the corresponding CDF. Show,   $$E(X) = \int_0^\infty (1-F_X (t)) \, dt$$   when $X$ has : a) a discrete distribution, b) a continuous distribution.   I assumed that for the case of a continuous distribution, since $F_X (t) = \mathbb{P}(X\leq t)$, then $1-F_X (t) = 1- \mathbb{P}(X\leq t) = \mathbb{P}(X&gt;  t)$. Although how useful integrating that is, I really have no idea.