I have completed my master's degree year ago and took a gap of 2-3 years before committing to the Ph.D. Right now my financial condition is worse and I don't want to make any decision in any urgency. My peers are getting enrolled for Ph.D. and I am getting worried by watching them. I am 27 right now and planning to collect enough money and build my resume strong to get into a decent Ph.D. program in Europe or Asia. Is my decision wrong? I need some advice from experienced peoples.   Thank you.
Are there any age limits (formal, informal, or guidelines) that schools use when deciding to accept someone into a PhD program? I'm most curious about the upper age limits. For example, will most schools accept someone in their 40's? How about their 50's?
Why does the integral of the surface area of a sphere equal it's volume?   $$\int{4\pi r^2 \ \mathrm{d}r =\frac{4}{3}\pi r^3}$$  I don't quite understand why the relationship between surface area and volume is this way. Is this true for any other shapes? I've noticed that in comments, when you create `code region` with backticks, the backslash will still work as an escape character within that region (but it should not, IMHO).  To clarify:   In comments, `\\` will be rendered as \, but it should be rendered as \\ In the post body itself, `\\` will be rendered as \\ (i.e., correctly)   This is especially confusing when you enter regular expressions into a comment, since backslash-escaping is very common there, and confusion increases if you are dealing with a regex that is double-escaped for representation in a string.   At some point you lose track how many backslashes you must make so the comment renders correctly, or you don't notice fast enough (or at all) and the comment contains wrong code where the same markup in a question or answer would come out as perfectly correct.   It's just that comments can't be corrected anymore after the grace period, leaving you with the choice of either deleting the comment, thus crippling the conversation, or engaging in a trial-and-error game of writing another comment with even more backslashes to explain the issue.  My question is two-fold:   Will this error be corrected? If yes, existing comments should probably be searched and "fixed" by a routine that tries to do the right thing (this is probably somewhere between hard and impossible) Or, can I rest assured that never ever the behavior of the backslash in comments is going to be changed, so I can start working around this issue by hand, knowing that they won't start displaying incorrectly at some point in the future? Is it possible to split micro USB to USB cable so two cables (data + and data -) go to the PC with USB and two other power cables go to power brick? I have a fresh installation of Ubuntu 14.10 on my laptop. It appears that letters are missing from files and folders, as well as menus and configuration windows. I'm not sure where to start in order to fix this. When editor does not respond to the request for withdrawal I submitted a manuscript to a journal, but due to some issue with that I asked the Editor-in-Chief and Associate Editor to withdraw the manuscript from further consideration. Despite several emails, they are not still responding me nor ended the process.  Now, what should I do? Can I submit the manuscript to another journal? How do you attach a debugger to a Web service? I am using a Web service. Can anybody tell me how to debug through it? PHP & MySQL: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given Self adjoint operators and trace class property This is a variation of the  questioned some time ago.  For a complex Hilbert space $H$ let $T: H \rightarrow H$ be a bounded operator. We call that $T$ is a trace-class operator if the following sum  $$\sum_{i}{\langle |T|e_{i}, e_{i} \rangle} &lt; \infty$$  converges, where $|T| = (T T^{*})^{\frac{1}{2}}$ is the absolute value of the operator.  Assume that  $$\sum_{i}{\langle Te_{i}, e_{i} \rangle}$$  converges for any basis in the space $H$. How to prove that if the aformentioned property holds then the operator is a trace class operator?  The progress on the problem is the following: Given an arbitrary bounded operator $T: H \rightarrow H$, one can use the following decomposition $$T = \big( \frac{T + T^{*}}{2} \big) ^{*} + i \big( \frac{T^{*} - T}{2i} \big) ^{*}$$  The latter line gives the decomposition $$T = A + i B$$ where $A, B$ are normal operators.  For the normal operators we can apply the spectral theorem that proposes that $T$ is unitary equivalent to  $$(UT U^{-1})(f(x)) = g(x) f(x)$$  where  $$U: H \rightarrow L^{2}(X, \mu)$$ $$g \in L^{\infty}(X, \mu)$$  Though this decomposition classify the operator in a broad sence, i see no direct way to conclude the statement. Are the any hints that may extend the previous argument? If not, are there any ways to conclude the statement? What should be done with questions that have been resolved as a comment instead of an answer? I'm trying to go through and provide answers to every unanswered question (search &quot;closed:0 answers:0&quot;), somewhat following the spirit that was blogged about at  .  However, I'm finding this much more difficult than it needs to be, as many of the questions have already been answered without the use of an &quot;answer&quot; - but instead, in the form of a comment by either the OP or another poster. I wouldn't mind reading through and skipping these, as long as there was some appropriate action I could take to at least assist with preventing these questions from being seen again from the same query - either by myself or another SO member.  Is there such an appropriate action?  Should we vote to close?  If so, using what reason? Even if I vote to close, what are the chances that 4 other users will also view the question and also vote to close?  (i.e., will my individual vote even do any good?  Is there any report to show recent close votes, so that others may also review and contribute supporting close votes?) Should we post some sort of an answer - even just something to the effect of &quot;this was already answered by the OP's own comment to his answer (above)&quot;? Would something like this be appropriate to flag for moderator attention, and let the moderators deal with it?  (Or would this be considered too trivial?) Should we rename the question title to something standard that can be used in a search exclusion?  (Maybe &quot;SOLVED:&quot;?)  Basically, how can I help to denote questions as &quot;This question is no longer in active search of an answer - though better answers may still be appreciated.&quot;? I've already reviewed , which was closed as a duplicate of  - but this requires effort on part of a user who may very likely no longer be active. Otherwise, is there something I should be doing to improve my search to filter out these types of questions? I've run across this many times, so I don't consider it to be a rare issue.  However, the last question like this I just ran across, prompting this question, was .  In this case, the question was self-answered by the OP in the form of a comment, this question is the OP's only question, the OP has no other visible activity on SO, and the OP hasn't been seen on SO since he registered and posted the question 5 months ago. Another one I just ran across is .  However, here the &quot;answer&quot; comment was posted by a reputable and recently active SO member.  Should I leave a comment directed at him, asking him to re-post his comment as an answer, or should I post my own answer echoing his comment?  (Or something else?) Yet another is .  Interestingly, the OP actually self-edited the question to include the &quot;SOLVED:&quot; prefix on to the question, instead of posting his resolving comment as an answer (and ideally accepting it) as he was asked to do by another comment.  This brings up another good idea - is there a &quot;standard&quot; we should use to rename the titles on these &quot;resolved but unanswered&quot; posts that could be used as a search exclusion?  (Also added to the above list.) change whole font of beamer to arial bold italic? how to change the font of the content to bold italic ?  thank you   here my cool superbe example:  \documentclass[14pt,t]{beamer} \usepackage{url} \usepackage{hyperref} \usepackage{graphicx} \usepackage{grffile} \begin{frame}\maketitle\end{frame} \begin{frame} \frametitle{test0} \begin{itemize} \item test \item test \begin{itemize} \item test \end{itemize} \end{itemize} \end{frame} \end{document}   A possible solution would be to use:  \usepackage{helvet} \renewcommand{\familydefault}{\sfdefault} \renewcommand{\rmdefault}{phv} \renewcommand{\sfdefault}{phv} %\renewcommand{\mddefault}{b}   % this content bold with b \renewcommand{\bfdefault}{phv} % Helvetica has no bx series \renewcommand{\updefault}{sl}   But it does do helvel arial bold for the whole document, and maybe there are ways to have the items/text of the slides in bold italic, and to keep normal phv for the top of the slide (frame title)? Two similar limit problems I have two limit problems which are quite similar, so I've put them both into this post.   $((4^{10}+2^{n})^{\frac{1}{n}})$ $((3n^{2}+n)^{\frac{1}{n}})$   Attempt:  For 1, I'm not sure if this is permissible. I know that $\lim_{n \to \infty}(x^{n}+y^{n})^{\frac{1}{n}} = \max\{x,y\}$. Obviously $4^{10}$ is a constant so it's not quite in the same form, but I believe it is still okay to use this result, and so the limit is $2$.  For 2, I've got $((3n^{2}+n)^{\frac{1}{n}}) = (n(3n+1)^{\frac{1}{n}})$, but then I'm not too sure how to proceed.   I also thought of taking the log and proceeding that way, however in the notes I'm learning from they haven't covered l'hopital yet, so I'm trying to not use it.  Thanks. What does it mean to "align" partitions? I am familiar with what partitions are, but I saw , and realised I didn't know what "aligned partitions" are.  So what does it mean to "align" partitions? What are the benefits, and the downsides? I know this is a total noob question but then again, when it comes to PostgreSQL I am a total noob...    I have installed the OpenGeo suite on my computer, running Windows 7, 64-bit.  I have downloaded the tutorial data and have been working through it.  I would like to access the database that I have made with ArcGIS so I can start learning about how that works.  However, when I try to connect to the database using the "Add Database Connection..." I can't seem to figure out what to put in for 'Instance' - everything I've tried (localhost, localhost,54321, my IP address with and without the port, my computer name) doesn't seem to work.  I installed and created the nyc test database according to all the instructions in the OpenGeo tutorial pages but am at a total loss here.  I know this must be an easy thing to deal with, I just can't get my head around it.  Can someone with more experience throw me a bone on this one?    Frustratingly enough, QGIS connects to the database with almost no effort and everything works fine - but my organization is heavily ESRI focused and switching to QGIS is a long shot...  EDIT Thanks everyone for pitching in on this.  I really appreciate the advice, it's what makes this site great.  I have installed    OpenGeo Suite 3.0.1 with no extensions ArcGIS Desktop 10.1, no license for server   I just went to the Opengeo website and downloaded the Windows installer and installed the default configuration. I have tried every permutation for the instance name that I can think of - using colons and commas, my machine name, localhost, postgresql, server, my IP address, random curse words, anything I can think of.  I have been using port 54321 instead of 5432 because that is what the OpenGeo workshop told me to set up my 'nyc' practice database to use.    It seems that localhost should work, here is a shot of the server properties from pgAdmin: Forcing a SimpleXML Object to a string, regardless of context Does DTIME(O(n)) = REGULAR? Which preposition should follow "guide" here, "on," "to," or "for"? The following link includes a guide ___________ how to use it.  How should I fill in the blank, on, for, or about? LaTeX Error: Option clash for package xcolor I have an option clash between package xcolor and another package, but I don't know which. Here is my MWE  \documentclass[10pt]{beamer} \setbeamertemplate{navigation symbols}{} \usepackage{caption} \usepackage{subcaption} \usepackage{url} \usepackage{color} \usepackage[usenames]{xcolor}  \author{The author} \title{Package conflicts} \date{October 3rd, 2012}  \begin{document}  This is supposed to be \textcolor{olivegreen}{olivegreen} \end{document}   And the error message is :  This is pdfTeX, Version 3.1415926-1.40.10 (TeX Live 2009/Debian) entering extended mode (./error_xcolor.tex LaTeX2e &lt;2009/09/24&gt; &lt;blablabla&gt; ! LaTeX Error: Option clash for package xcolor.   I hope this is enough log for you guys. At this time of the day, I'm hoping for America to save my french ass ... again : ) How do I set up shared folders in a Windows Virtualbox guest? I have installed VirtualBox OSE on Ubuntu 11.04 and Windows XP pro as the virtual machine. Now I want to have a shared folder which can be accessed on both, my host Ubuntu machine, and my WinXP guest virtual machine.  How can I do that? Exploring $ \sum_{n=0}^\infty \frac{n^p}{n!} = B_pe$, particularly $p = 2$. I was exploring the fact that $$ \sum_{n=0}^\infty \frac{n^p}{n!} = B_pe,$$ where $B_n$ is the $n$th Bell number.   I found this result by exploring the series on wolframalpha and looking up the sequence of numbers generated. I have no experience with Bell numbers other than knowing that they represent the number of ways of partitioning a set.   What I tried  Looking at the base case we can verify $$\sum_{n=0}^\infty \frac{n}{n!} = \sum_{n=1}^\infty \frac{1}{(n-1)!} = e. $$  But then I realize that $n^2$ is going to be difficult.  Specifically what I want  I am doing this for fun, so I just want to glean some sort of lesson out of this. Resources that let me learn for myself are just as good!   An accepted answer will have any one of the following:   A proof that $\sum_{n = 0}^{\infty} \frac{n^2}{n!} = 2e$ (this interests me a lot) A description of why this series is related to Bell numbers and the number of partitions of a set A link to some resource that introduces Bell numbers and/or their connection to this series. I've got a NI Traktor Audio 2 sound card I'd like to get working with Mixxx, but I don't seem to have any success so far. The card seems to be supported in Ubuntu out of the box, and it seems to work well with ALSA, but I cannot select it in Mixxx and I'm not sure whether is something I can do to make it see it (e.g. through).  So for testing purposes, on the command line I can execute aplay to check each channel:  aplay -D plughw:2,0,0 test.wav   and  aplay -D plughw:2,0,1 test.wav   That works well: I can hear the test sound on each channel (A and B)  The relevant output for this card using aplay -D is:  hw:CARD=TraktorAudio2,DEV=0      Traktor Audio 2, Traktor Audio 2      Direct hardware device without any conversions plughw:CARD=TraktorAudio2,DEV=0      Traktor Audio 2, Traktor Audio 2      Hardware device with all software conversions   From those 2 items on the output, plughw is the one that works, whereas hw doesn't.  The problem is that Mixxx only lets me select the hw card, which does not seem to work. I'd like to be able to select the plughw card, which is the one that's working.  I've tried suspending Pulse Audio as suggested by , but that did not seem to work. I also played around with an .asoundrc file similar to the one  (which was for an older model of this sound card), but also without success.  Any ideas on how to make Mixxx show the right card (and channel, while we are at it)?  Thanks!