How to write a chemical formula?
Typesetting Chemical Formulas
System settings won't open on Ubuntu 20.04 LTS after adding System76/pop PPA I'm trying to open System Settings but it won't open in any way. Using GUI, Settings are trying to load for a moment and then they are gone. Using Terminal (gnome-control-center), I get: (gnome-control-center:8823): GLib-ERROR **: 14:44:15.433: ../../../glib/gmem.c:138: failed to allocate 13477064712 bytes Trap Trace/breakpoint (core dumped)  I tried: sudo apt-get remove gnome-control-center sudo apt autoremove sudo apt-get install gnome-control-center  With multiple reboots, but I had no result. UPDATE!: Same errors persist BUT, when I type: sudo gnome-control-center  (instead of just &quot;gnome-control-center&quot;) suddenly System Settings appear! Is it a user permissions issue? Any suggestions? UPDATE#2: After some system updates, sudo gnome-control-center now spawns &quot;Segmentation fault&quot;. The "correct" way to write a set without a specific element is as follows: $S \setminus \{s\}$  But in some contexts this is cumbersome to write/type or read, and it detracts from the flow of the writing. Is it acceptable to just use $S \setminus s$?  Edit: By "cumbersome" i mean they look bad when you're trying to inline formulas in LaTeX. Programmatically close aspx page from code behind What is the best way to close an ASPX page from the code-behind?    I have a button event handler that I want to close the page after the user has clicked an ASP.NET button on the page.  I have tried to programmatically add a JavaScript method that contains a window.close() command to the OnClientClick event to close the page but it does not work.  The button is also a asp:AsyncPostBoskTrigger for an AJAX Update Panel.  The application uses .NET Framework 3.5. Man travelling alone across a planet, thinks about a fearsome creature that he hears behind him About fifteen years ago I read a short story about a man on a planet (possibly Mars or the Moon), travelling alone between bases. It's written in the first person and as he's walking across the planet, he's thinking to himself about this fearsome creature that preys on people. It sneaks up on them, makes some noise and then attacks them. Just as he turns the final corner of the canyon he was walking through and sees the door to the other base, he hears the creature behind him making its noise and the story ends.  It was in a short story collection but I don't remember the name of the story or the book it was in. Any help would be much appreciated. How should I phrase an important question that I need to ask a professor? bi-directional sync with rsync Bottom frame of listing appears on top of the next page Why do we need virtual functions in C++? Difference between modelAttribute and commandName attributes in form tag in spring? Is voting to balance in the spirit of the site? The other day I saw an answer which was ok. Not great but not bad. So no reason to upvote or downvote. However the answer already had a single downvote. I felt this was unfair so upvoted the answer to keep it at what I felt was a fair score. It wasn't until afterward that it occurred to me that I should have perhaps solely voted on the content of the answer.  Is this a reasonable reason for an upvote or should I have left the answer alone? Advice/literature on combining items with different response scales into composite scales? Let's say I have some self-report items measured on a 5-point Likert scale (Strongly Disagree to Strongly Agree) and other items measured on a 4-point Likert scale (Never, Rarely, Sometimes, Often). Can anyone point me to literature (or practical advice) on combining these items into a composite scale? Let's assume for the sake of argument that we have some empirical evidence that items should be combined.  Some ideas:  1. Sum raw scores  Pro: Easy  Con: Max responses on the 5-point scale (originally 4's) drive up the total scale score more than max responses on the 4-point scale (originally 3's).  2. Rescale and sum  Put all of the items on a 0-1 scale and sum. So the 4-point items (0,1,2,3) would be multiplied by (4/3)/4 and the 5-point items (0,1,2,3,4) would be multiplied by 1/4, resulting in possible values of (0,.33,.66,1) and (0,.25,.50,.75,1), respectively. This way max responses on the 5-point scale (originally 4's) would not drive up the total scale score more than max responses on the 4-point scale (originally 3's).   Pro: Items would have equal weighting. (could be a con, depending on your perspective).  Con: Ignores differences in variability between items on different metrics?   3. Standardize and sum  A related approach would be to standardize all of the items (z score) and then sum.  Pro: Addresses differences in variability between items on different metrics  Con: Total scale score becomes less interpretable and sample-specific. The latter makes it hard to benchmark as a measure to be used in other settings/other samples.  4. PCA or other data reduction   4a. EFA to get factor loadings. Multiply scaled items by factor loadings.  4b. PCA to get score of first principal component.  Pro: Items weighted by influence.  Con: Same as #2. EFA-derived scores could vary a lot depending on rotation/extraction choices. Some would not advise on ordinal data.    Overall: I like #2 because it seems easier to compare results across different samples. Thoughts? Alternative ideas or concerns about the ideas presented? Let $|A|=\alpha, |B|=\beta, |C|= \gamma$ be cardinals and $\beta \leq \gamma$. Prove $\alpha ^{\beta}\le \alpha ^{\gamma}$.  So from the given we know that there's an injection $f:B\to C$ and some functions $h:B\to A, g: C\to A$. We want to prove there's an injection $l_1:A\to C$. It appears that $f$ doesn't help here.  Trying to take representatives from $A$ and show they're in $C$ and there's an injection doesn't work so maybe the function should be $l_2: h \to g$ but I don't know how to work with it. Remove dots & Page numbers from TOC I am using example given here by @stephan .  Works great however I want to get rid of dots and page numbers.  I added this to the preamble   \let\Contentsline\contentsline  \renewcommand\contentsline[3]{\Contentsline{#1}{#2}{}}   that removed the page numbers, but do not know how to remove the dots. I would appreciate your help. Its hard to get result without understanding the basics. Leverage browser caching for Facebook, Google+, or other 3rd party resource files I tested my website with Google PageSpeed Insights.  I did cache optimization in my .htaccess, but it didn't affect resource files that are from Facebook and Google+  Leverage browser caching      http://connect.facebook.net/fr_FR/all.js (20 minutes)      https://apis.google.com/js/plusone.js (30 minutes)      https://oauth.googleusercontent.com/…e:rpc:shindig.random:shindig.sha1.js?c=2 (60 minutes)   What can I do to solve this? Examples of a non-commutative division ring Why would you put Identity Increment other than 1 in SQL? Proving question on sets I am unable to understand this question. I have to say whether its true of false and then prove it but I can't proceed with the question unless I understand it.     Let $S$ be the set of stars in our galaxy. There is exactly the same   number of subsets of stars in our galaxy as there are functions   $f:S\rightarrow\{\alpha,\beta\}$ In my situation, it's for a local build/staging server running ubuntu server. Things I'd like to know are:  Why I should/shouldn't use LVM?  What problems might it cause in terms of either regular server operation or things I might want to do later? (ex. partitioning)  Why I should/shouldn't use encrypted LVM instead of LVM?  What problems might encrypted LVM cause in terms of either regular server operation or things I might want to do later? (ex. partitioning) Suppose $f$ is a differentiable function over $\mathbb{R}$ satisfying $f(0) = 0$. Show that if $f'$ is strictly increasing, then $\frac{f(x)}{x}$ is increasing over $(0,\infty)$.   Attempt:  Since $f'$ is increasing we know that $f'' &gt; 0$ for all $x$. Now let $g(x) = \frac{f(x)}{x}$ and thus $f(x) = xg(x)$. Then we wish to show that $g'(x) &gt; 0$ on $(0,\infty)$ and so since $f'(x) = xg'(x)+g(x)$ and $f''(x) = xg''(x)+2g'(x) &gt; 0$, we have $g''(x) &gt; \frac{-2g'(x)}{x}$. I am not sure how to use this though to prove the statement. How do you do load testing and capacity planning for web sites?