Is my Apache server under attack
How do I deal with a compromised server?
Is there a way to configure pdflatex to make all but the .tex and .pdf files hidden files? I have asked a  about how to manage all the files generated when my LaTeX files are compiled but the approach in the answer I accepted is still unsatisfactory for the many small documents I generate.    I realize the LaTeX  all the files it generates so I can't prevent their creation.    However is there a way to configure pdflatex to make all but the .tex and .pdf files hidden files (i.e., preceded by .)?   (Edit: The two main systems that I use are tex live on Ubuntu Linux and BasicTeX on OS X) The problem is to prove the following equivalence:  $$2^{\aleph_0}=\aleph_1 \iff \exists\ A,B\in\mathbb{R}^2:\\ \textrm{a)}A\cup B=\mathbb{R}^2 \\\textrm{b)}\ \forall\ \textrm{lines } l\ \textrm{parallel to x-axis, } |A\cap l|\leq\aleph_0 \\\textrm{c)}\ \forall\ \textrm{lines } l\ \textrm{parallel to y-axis, } |B\cap l|\leq\aleph_0$$  I think I know how to prove "$\impliedby$":  Let's assume the RHS and that $2^{\aleph_0}\geq\aleph_2$. Now let's take a sequence $\langle x_{\alpha}:\ \alpha&lt;\omega_1\rangle$. Since $\bigcup_\limits{\alpha&lt;\omega_1}|B\cap x_{\alpha}|\leq \aleph_1\cdot\aleph_0=\aleph_1$ there is such a $y$-coordinate that neither of $(x_{\alpha},y)$ is in $B$. But hence we obtain $\aleph_1$ point which all lie on the same line parallel to $x$-axis. Since $A\cup B=\mathbb{R}^2$ they all must be contained in $A$ $-$ a contradiction as $A$ has at most countably many of those points.  But what about the other implication? Do I contruct these sets by induction? Over all lines or something else? I haven't come up with anything yet, perhaps you could help me. Does $\exp(2ir\pi)$ equal $1$? What's wrong? Since $e^{ix}=\cos x+i\sin x$, thus  $e^{2\pi i}=\cos2\pi+i\sin2\pi=1$     Now I take arbitrary real number $r$ then $e^{i2\pi r}=(e^{i2\pi})^r=1^r=1?$    But this cannot be true since $\cos2\pi r+i\sin2\pi r$  isn't necessarily $1$ for arbitrary $r$. Where did it go wrong? One-byte-off pointer still valid in C? Mathematical journal for an undergraduate I want to make someone a present by subscribing for him to a mathematical journal. (It should appear every month or every two months). The contents should be comprehensible to an undergraduate in mathematics, and be about a broad selection of topics (for example not only analysis).   I expect the content to be something like proposing interesting problems and then giving solutions with some references for further study. Are there some famous journals you could suggest me? I've found strange behavior when closing this  - I definitely see that there are 3 closing votes and 2 of them are at "Off-topic" section:   -but there are no explanations on section itself:   -while, normally, it's expected that it will appear. In custom comments section there are also no closing-votes displayed.   Perhaps it's just my browser (which is FF 26 x64 under Win) - so marking this as a "possible bug". Thank you for your attention. Finding the variable name passed to a function Cannot upgrade unsupported version of Skype for Linux (v5) Types of polynomial functions. Quadratic, cubic, quartic, quintic, ...,? I would very much like to have a complete list of the types of polynomial functions. I know that theres:  Quadratic :                      (AX^2 + BX + C) Cubic     :               (AX^3 + BX^2 + CX + D) Quartic   :        (AX^4 + BX^3 + CX^2 + DX + E) Quintic   : (AX^5 + BX^4 + CX^3 + DX^2 + EX + F)   What are the names of polynomial functions to the further powers? Sexstic? Septic? Octic? I'm not sure, so if someone could enlighten me, then that would be great. Please provide a list that goes at least to the seventh power, but it would be nice if you could go further. Thanks. Difference between correlation and covariance: is covariance only useful if the relation is linear? I'm trying to understand better the difference between  covariance and correlation, besides the fact that the correlation coefficient is a dimensional and has values between $-1$ and $1$.   One unclear point is the following: the correlation coefficient can highlight only a linear relation between two variables, but does  covariance only work for linear relations too? Supposing that the relation is not linear, is the covariance not zero? Is it bigger than in the case in which the relation is linear?   Cauchy inequality says $$|\sigma_{xy}|&lt;\sigma_{x} \sigma_{y}$$  Which seems to say that the covariance is maximum when there is a perfect linear relation.    So I do not get what does happen if the relation is not linear, and, if covariance is not a suitable parameter in that cas I don't get the reason for that, since simply looking at the definition:  $$\sigma_{xy}=\frac{\sum(x-\bar{x})(y-\bar{y})}{N}$$  it looks like that this should be non zero for any kind of relation (like parabolic).  So can this be a difference between the use of covariance and correlation coefficient? (The first is useful for any kind of relation, the second one only for linear ones). Why did the Nazgûl not attack a second time at Weathertop? Should an adverb go before or after a verb? For example:     The word rarely turns up outside of those contexts.      The word turns up rarely outside of those contexts.   Which one is correct and why? I am wanting to find the correlation between two variables: a categorical vegetation variable (with categories 1-4)  and a continuous variable of erosion (with values anywhere between 0.2 and 9). I think I would be required to use a non parametric test to find the correlation, but bit of a newby to stats so could anyone suggest the best test to use? I also wanted to know how sample size can affect these tests, ie with a sample size of 100 or 1000? The most obvious answer everyone over the Internet is giving to this question is "Because anime is produced much faster compared to manga, they need to put in fillers in order to slow down the anime series". However, that shouldn't be the only reason.  For example, consider One Piece. The show is going on for more than 500 episodes, and less than 10% are fillers. Comparing that to Naruto, the show has almost the same number of episodes (original and Shippuuden combined), but almost 50% of its episodes are fillers. Needless to say, the manga of Naruto is so far ahead that the anime won't be able to catch up even if they produce 100+ episodes without any fillers. Configuring auto-completion with TeXstudio TeXstudio does a pretty good job with autocompletion. For example, when I type \eqref{, it already comes with suggestions, see the example below.    However, suppose that I don't want to use \eqref but a customized command using newcommand (I do this so that I can quickly switch to different styles, e.g., some for journals/conferences "Eq. (1)" is needed, whereas sometimes "(1)" suffices). In this case, TeXstudio does not do the auto-completion, see the example below.    Is it possible to configure TeXstudio such that it does the auto-completion for custom commands that require a reference?  Note that one option is to redefine \eqref using \renewcommand, but I'm looking for another way so that I can use if for many more commands, not just for \eqref.   Here is my MWE:  \documentclass{article} \usepackage{amsmath}  \newcommand{\alternative}[1]{Eq.~(\ref{#1})}  \begin{document}     \begin{equation}         \label{eq:emc2}         E = mc^2     \end{equation}     I can refer to the equation using \eqref{eq:emc2} and using \alternative{eq:emc2}. \end{document} How to install with Wubi when it says "Could not retrieve the required disk image files"? I tried to install Ubuntu 12.10 with the Wubi installer while running Windows, because my PC does not accept my BootCD as a bootable medium.  But Wubi showed me this error:  Ubuntu-Installationsprogramm (X) Ein Fehler ist aufgetreten: Could not retrieve the required disk image files Weiter Informationen finden Sie in der Protokolldatei: c:\users\username\appdata\local\temp\wubi-12.10-rev273.log   What can I do, because I want to get rid of my Windows 7 and use the way better Ubuntu 12.10?  Thanks for your huge answer, now my next problem after trying to install wubi with the .iso is, that the same error shows up again and i am not shure which part of the errorreport you need.  Can you tell me? Because i'm not that good at linux. SEO repeated keywords in domain and url Get files in a directory sorted by last modified? How can I retrieve mp3 metadata in Python? Show that product of primes, $\prod_{k=1}^{\pi(n)} p_k < 4^n$ This an interesting problem my friend has been working on for a while now (I just saw it an hour ago, but could not come up with anything substantial besides some PMI attempts).  Here's the full problem:  Let $x_{1}, x_{2}, x_{3}, \cdots x_{y}$ be all the primes that are less than a given $n&gt;1,n \in \mathbb{N}$.   Prove that $$x_{1}x_{2}x_{3}\cdots x_{y} &lt; 4^n$$  Any ideas very much appreciated!