Estimating population standard deviation from subsample means
Estimate the population variance from a set of means
iOS: Compare two dates How do I start Nautilus as root? Is there any way to ensure that a specific USB key always gets the same drive letter? Relativity and Galaxy Rotation Speed How to calculate temperature in Wire? Let's say I have 1m of 2,5mm² copper wire, insulated with H07V-K. The wire carries 40A and environment temperature is 25°C. The wire is suspended in free air. How hot will the wire get? And how can I calculate it for other values?  The use case is a 12V-230V AC converter I want to hook up to my car and determine the minimum wire thickness required. Because it's only used from time to time and not buried in a wall I suspect I can use thinner wires. This is a temporary thing and doesn't need to be up to code. Proving the convergence of $\sum\limits_{n=1}^{\infty}\frac{1}{1+z^n}$ for $|z| > 1$ Programmatically, how does "rooting" a device enable access? Uninstalling/reinstalling QGIS plugin where uninstall is disabled? Plugin Raster->TerrainAnalysis->slope which had initially worked, started showing what another questioner referred to as a "crazy histogram":   Before finding his question and the answer, I endeavored to uninstall and reinstall the plugin.  I found/still find (QGIS 2.0.1, now upgraded to QGIS 2.4, on Ubuntu 14.04), the plugin "uninstall" button grayed out/disabled.  It's working, but I am worried about having a plugin I installed that does not offer an option to be uninstalled.  Failing anything else I would be tempted to use the path information to rename the .so library and see if it disappeared. Regular Expressions: Is there an AND operator? I am trying to remove all files and subdirectories in a directory. I used rm -r to remove all files, but I want to remove all files and subdirectories, excluding the top directory itself.  For example, I have a top directory like images. It contains the files header.png, footer.png and a subdirectory.  Now I want to delete header.png, footer.png and the subdirectory, but not images.  How can I do this in linux? Is there a minimum damage rule? In D&amp;D3e, if you successfully hit a target you always did at least 1 point of damage (before applying Damage Resistance), even if you had a Strength penalty.  I can't find any mention of that rule in the 5e PHB.  Does the rule no longer apply, or did I just overlook it? How to get the valid URL of a Link field from within a Twig template? I have a Link field named field_my_link (machine name).  Within a Twig template I can get the link's URL value with this:  {{ node.field_my_link.uri }}   If inside the Link's URL there is an external URL, e.g. http://example.com it works good.  But, if inside the Link's URL there is stored an internal URL, e.g. "/node/11", I get a value like this:  "internal:/node/11"   with the "internal:" prefix.  How can I get the valid URL?  For example, if the link's URL is "http://example.com" I want "http://example.com" (this already works), if the link's URL is "/node/11" I want the relative URL "/node/11", if the link's URL is "&lt;front&gt;" I want the URL "/", etc.    EDIT  I can get the value I want within a PHP preprocess function, using this:  $url = $variables['node']-&gt;get('field_my_link')-&gt;first()-&gt;getUrl();   How can I access the same value within the Twig template?  I know I can do this within the preprocess function:  $variables['my_url'] = $url;   Then access the url within Twig using {{ my_url }}, but I would avoid to write a preprocess function each time I have a link field. How to say that you have plans to go to the movies tonight (but you are not sure yet, maybe you will have a pizza)? I mean there are options:     I am going to the cinema tonight.   Way too much certainty in this. For me it means that you have already bought tickets, the least.     I am going to go to the cinema tonight.   Sounds a bit awkward.     I will go to the cinema tonight.   Sounds too formal to me. Which of these sentences is correct, and why?   "What if the Moon was a Disco ball?" or  "What if the Moon were a Disco ball?" Proving that: $\lim\limits_{n\to\infty} \left(\frac{a^{\frac{1}{n}}+b^{\frac{1}{n}}}{2}\right)^n =\sqrt{ab}$ Let $a$ and $b$ be positive reals. Show that $$\lim\limits_{n\to\infty} \left(\frac{a^{\frac{1}{n}}+b^{\frac{1}{n}}}{2}\right)^n =\sqrt{ab}$$ Here's an example of a short conversation between me and a native speaker via text messages:  A: I'm so exited for this app B: Yeah, me too A: We start tomorrow B: OK   Shouldn't it be "We are starting tomorrow"?! How to do something to each file in a directory with a batch script How do you iterate over each file in a directory with a .bat or .cmd file?  For simplicity please provide an answer that just echoes the filename or file path. Can I use set instead of List to resolve the duplicate id issue If you take a look into this issue     I have provide an answer of using set&lt;Sobject&gt; instead using list&lt;Sobject&gt;  i.e.  if( !contacts.values().isEmpty() ){   set&lt;Contact&gt; setContacts = new set&lt;Contact&gt;();   for( Contact objCon : contacts.values() ){     if(!setContacts.contains(objCon)){         setContacts.add( objCon );     }   }  update new list&lt;Contact&gt;(setContacts); }   even if(!setContacts.contains(objCon)) is not needed  if( !contacts.values().isEmpty() ){   set&lt;Contact&gt; setContacts = new set&lt;Contact&gt;();   for( Contact objCon : contacts.values() ){         setContacts.add( objCon );   }  update new list&lt;Contact&gt;(setContacts); }   So is there any condition/use case where this answer might fail? I am trying to create a schema page in LaTeX. It shall look like this.   How can I create schema code which look like this image? There should be also a click to go function. When the user clicks on the user_schema link he should be redirected to that page.  What classes I can use for this? Any suggestions would be appreciated.    \documentclass{article} \usepackage[utf8]{inputenc}  \begin{document} \maketitle  \section{User schema} \mySchema{Users} {     _id: ObjectId - Id do registro     name: String - Nome do usuário     date: Date - Data de Cadastro     ren_date: Date - Data de renovação do Cadastro     email: String - Lorem ipsum dolorsitamet, consecteturadipisicingelit, sed do eiusmodtemporincididunt ut labore et dolore magna aliqua. Ut enim ad minimveniam, exercitationullamcolaborisnisi ut aliquipexeacommodoconsequat. Duisautereprehenderit in voluptatevelit esse cillumdolore eu fugiatnullapariatur. Occaecatcupidatat non proident, sunt in culpa quiofficiadeseruntmollit.     access_log: Array [          {              date: String - Data da ocorrência.             user: ObjectId - Usuário que executou.             action: String - Ação Executada.         }         {              date: String - Data da ocorrência.             user: ObjectId - Usuário que executou.             action: String - Ação Executada.         }     ]     \link{group}{group_id}: ObjectId - Id do grupo. } \end{document}   Here is the image how should it appear: What does the human body use oxygen for besides the final electron acceptor in the electron transport chain? My biology teachers never explained why animals need to breathe oxygen, just that we organisms die if we don't get oxygen for too long. Maybe one of them happened to mention that its used to make ATP. Now in my AP Biology class we finally learned the specifics of how oxygen is used in the  due to its high electronegativity. But I assume this probably isn't the only reason we need oxygen.   What other purposes does the oxygen we take in through respiration serve? Does oxygen deprivation result in death just due to the halting of ATP production, or is there some other reason as well? What percentage of the oxygen we take in through respiration is expelled later through the breath as carbon dioxide?