Is the potential energy of molecules related to its temperature?
Do ideal gases at zero Kelvin have potential energy?
Accidental chown under / as root I accidentally run the following command as root chown mike -Rf / backups the point is that I added a space between / and backups my mistake, I stopped the command after 1-2 seconds, how can I recover from this? I have problems with DirectAdmin right now for example when accessing it I recive the error:  Unable to determine Usertype user.conf needs to be repaired http://help.directadmin.com/item.php?id=456   Or I stopped recieving emails, I dont even know what else is messed up right now... 'Possible duplicate' comment not appearing for questions with deleted comments containing the link I posted a comment to a duplicate question on . But I decided to delete it. Afterwards I voted as duplicate and thought a comment would be generated like     possible duplicate of ...   But it didn't. My guess is that the duplicate-comment won't be generated if a comment exists with that link, even if deleted. What happens to the energy when waves perfectly cancel each other? What happens to the energy when waves perfectly cancel each other (destructive interference)? It appears that the energy "disappear" but the law of conservation of energy states that it can't be destructed. My guess is that the kinetic energy is transformed into potential energy. Or maybe it depends on the context of the waves where do the energy goes? Can someone elaborate on that or correct me if I'm wrong? Help ending a proof using binomial theorem: $\sum_{k=0}^n {n \choose k}\cdot\frac{(-1)^k}{k+1} = \frac{1}{n+1}$ This is probably a silly question but I need some help. I opened a file that I've been working on for about a month in the new 2.8 version of Blender. However when I tried to reopen the file in version 2.79, the scene is completely empty. Here is where the problem lies for me, I accidentally saved over the original file save while in version 2.8 . Please help. Thanks! Prove that in a triangle $$r^2+r_1^2+r_2^2+r_3^2=16R^2-(a^2+b^2+c^2)$$ where the symbols have their usual meanings. I am looking for a smaller or elegant proof using trigonometry. A geometric proof would be super cool. I did prove it but it took me ages to do the calculation. Thanks. At the beginning of  we see that Logan (a.k.a. Wolverine) and Colonel William Stryker were working together by the end of the Vietnam War.   For 5 years after the war, he lives in Canada with a girlfriend. But in  we see that Logan was part of some gang at the end of the Vietnam War.   My question is which of these are X-Men movie canon? How to access HTML element without ID? For instance in the snippet below - how do I access the h1 element knowing the ID of parent element (header-inner div)?  &lt;div id='header-inner'&gt;     &lt;div class='titlewrapper'&gt;        &lt;h1 class='title'&gt;        Some text I want to change       &lt;/h1&gt;     &lt;/div&gt;  &lt;/div&gt;   Thanks! Detecting and acting on keyboard direction keys in Java $$ x^2+2(1+a)x+(3a^2+4ab+4b^2+2)=0$$  I tried to make an inequality using the discriminant and I simplified it to get $$a^2+2ab+b^2+\frac{1}{2}≤0$$  But I don't know how to solve this. Let $\mathbb S = \varnothing$.      Then from the definition: $ \bigcap \mathbb S = \left\{{x: \forall X \in \mathbb S: x \in X}\right\}$      Consider any $x \in \mathbb U$.      Then as $\mathbb S = \varnothing$, it follows that: $\forall X \in \mathbb S: x \in X$ from the definition of vacuous truth.      It follows directly that: $\bigcap \mathbb S = \left\{{x: x \in \mathbb U}\right\}$      That is: $\bigcap \mathbb S = \mathbb U$. ()   Proofwiki uses the above "proof" to "prove" that intersection of the empty set is the whole universe.   My question is, is the use of vacuous truth really allowed in axiomatic set theory, like ZFC? I don't see how the use of vacuous truth is justified.   The next problem I can think of is that we cannot really "define" the elements of empty set (to my knowledge, there is no element in empty set) so how can we then prove as the above proof did? This seems to contradict the use of vacuous truth.  And of course, there is issue of using the whole universe as a set, and I don't think this is allowed.... (Maybe proof above is using a different axiomatic set theory, as I am using ZF-minded thoughts...) I've got a couple of URL autocomplete suggestions where Chrome suggests the wrong URL consistently.   How can I delete the incorrect entry from the address bar's suggestion list? The page I want shows up too but it's never the first result. What is the name of an anime from 80s-90s movie/series in which there is a scene, maybe the end, where a girl (who has an​ armor) exchanges age with a dying man in a beach, so the man transforms into a baby and the girl grows to a woman? Should an image carousel on a mobile site automatically rotate? The optical density of a medium is quantified by its refractive index $n$. Does it have any correlation with the mass/number density of the medium? In other words is an optically denser medium must have a greater mass density compared to an optically rarer medium? Is there any adjustment required when computing the correlation coefficient between:   continuous and discrete variable  two discrete variables ?    Thanks ! Access nested dictionary items via a list of keys? Maximum and minimum value of Determinant of $3 \times 3$ Matrix with entries $\pm 1$ Find Maximum value of Determinant of $3 \times 3$ Matrix  with  entries $\pm 1$  My try:  I considered a matrix as :  $$A=\begin{bmatrix} 1 &amp;-1  &amp;-1 \\  -1 &amp;1  &amp;-1 \\   -1&amp;-1  &amp;1  \end{bmatrix}$$  we have $$Det(A)=-4$$ and maximum is $4$, but how can we show that these are max and min values?   I also tried as follows:  By definition Determinant of a matrix is dot product of elements of any row with corresponding Cofactors  hence  $$Det(A)=a_{11}C_{11}+a_{12}C_{12}+a_{13}C_{13}$$  By cauchy Scwartz Inequality we have  $$a_{11}C_{11}+a_{12}C_{12}+a_{13}C_{13} \le \left(\sqrt{a_{11}^2+a_{12}^2+a_{13}^2}\right)\left(\sqrt{C_{11}^2+C_{12}^2+C_{13}^2}\right)$$  any way to proceed here? I have an app to deploy in production that uses 'honor system' security. That is, all users connect to the DB using a SQL user/passwd credential and the app manages permissions itself. The latter part doesn't bother me as much as the fact that the connection object contains embedded credentials and can be copied around freely. I'm try to find some way to limit connections to a more limited set of clients. I can create firewall rules to limit by IP, of course. Is there any way to 'prequalify' SQL logins either by Machine account or domain membership? Option clash for package xcolor I'm writing a report, and have a rather large table in my appendix. I'd like to emphasize some specific values by coloring some single cells. I'm trying to do it with xcolor. But receiving the error:  ! LaTeX Error: Option clash for package xcolor. See the LaTeX manual or LaTeX Companion for explanation. Type H &lt;return&gt; for immediate help. ... l.17 The package xcolor has already been loaded with options: [] There has now been an attempt to load it with options [table]   My preamble looks as follows  \documentclass[a4paper,oneside,article]{memoir} \usepackage[latin1]{inputenc} \usepackage[T1]{fontenc} \usepackage[danish]{babel} \usepackage{lmodern} \usepackage{graphicx}     \graphicspath{{Figures/}} \usepackage{fullpage} \usepackage{modroman} \usepackage{float} \usepackage{caption} \usepackage[numbers]{natbib} \usepackage{url} \usepackage{pgfplots} \usepackage{mathtools} \usepackage[table]{xcolor}   And take out of my table  \begin{table}  \centering   \begin{tabular}{|c|c|c|}        \hline    \cellcolor{green!25}D &amp; x &amp; D/$L_0$ \\        \hline    65 &amp; 2600 &amp; 0,417\\        \hline    60 &amp; 2400 &amp; 0,385\\   \end{tabular}  \caption{Bestemmelse af bølgehøjde}  \label{tab:Q1} \end{table}   Read some other questions asking more or less the same. And the answer to them seems to be a "collision" between packages. I have no idea how to find the problem. So my question is:   Where is the "collision"? How on earth would I have found it without help ?