How does a one-sided glass work on atomic level? What does the description of the phenomenon at atomic level look like? I assume that atoms absorb and emit a wave with a changed amplitude. What is responsible for dividing the amplitude level and direction of division?
How does a one-sided glass work? How does a  work? If seen from the outer side, we can see through thinking it is transparent, while if seen from the inside, the glass acts as a mirror. How?
Let $G$ be a group and $H$ a subgroup with $[G:H]=n$. Is it true that $x^n\in H$ for all $x\in G$?   Remarks. The answer is positive whenever $H$ is normal, e.g., for $n=2$. In general, by using the normal core of $H$, one can find an $m\ge 1$ such that $x^m\in H$ for all $x\in G$. When looking at my objects in 3d view I'm seeing a gray cone that seems to be hiding other objects.   Can anyone help me turn this off and explain what it is please.  Screenshots attached. I'm struggling with some concepts in my algebra class. I've chosen these two completely unrelated examples that demonstrate my struggling topics (characteristics and function rings) the two are the following:  $1$) Let $X$ be a set, and let $S$ be a ring. Give a proof that the left distributive law holds for $(S^X, +, *)$.  $2$) Suppose $Y^3 = Y$ for each element $Y$ of a unital ring $R$. Show that $R$ has a finite characteristic d that is a divisor of $6$.  Any example solutions for these proofs would be helpful. Thank you. I'd like to do some URL rewriting (Why? See .) so that instead of users seeing addresses like   labouseur.com/course-compilers.html    they can instead see and use simply   labouseur.com/course-compilers   (Even better, maybe I should restructure that so that it's courses/compilers.)  I'm using a Linux-based shared hosting service for my website, so I do not have administrative control of the server, but I do have control over .htaccess. The references I've read online seemed less than clear to me, so I'm looking for a little clarity and advice here. $$ \lim \limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} $$  According to my textbook the limit equals $2$.  What I have tried:  Using the squeeze theorem:  $$ \lim \limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1}} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 2} $$ $$ 0 \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le 0 $$  I have also tried to use the squeeze theorem with two other equations and obtained different values:  $$ \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2 - 1}{\sqrt{x^2 +y^2 + 1}} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2 + 1}{\sqrt{x^2 +y^2 + 1} - 2} $$ $$ -1 \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le -1 $$ Why can the last block contain a full block of padding in CBC Encryption? I'm trying to understand the SSL Poodle Attack and I'm wondering why the last block of a CBC Record can be full of padding? Wouldn't that mean that the useful data was already a multiple of the key size?  Maybe I'm misunderstanding something else here, as it would seem like you can pad by any number of full blocks of padding. Just don't see why an SSL Library would do that.  Thanks! No Line Break in Author Command? It goes off the page! Thousands of 404 errors in Google Webmaster Tools Because of a former error in our ASP.Net application, created by my predecessor and undiscovered for a long time, thousands of wrong URLs where created dynamically. The normal user did not notice it, but Google followed these links and crawled itself through these incorrect URLs, creating more and more wrong links.  To make it clearer, consider the url     example.com/folder   should create the link     example.com/folder/subfolder   but was creating     example.com/subfolder   instead. Because of bad url rewriting, this was accepted and by default showed the index page for any unknown url, creating more and more links like this.     example.com/subfolder/subfolder/....   The problem is resolved by now, but now I have thousands of 404 errors listed in the Google Webmaster Tools, which got discovered 1 or 2 years ago, and more keep coming up.  Unfortunately the links do not follow a common pattern that I could deny for crawling in the robots.txt.  Is there anything I can do to stop google from trying out those very old links and remove the already listed 404s from Webmaster Tools? Recently a few friends and I came up with an idea for an app. To facilitate the creation of it, we set up LAMP on an Ubuntu Server 12.04. This box is running from my home. We've set up 3 user accounts. I'm still pretty new to Linux, but I have a bit of experience from using Ubuntu on my own box.  Today I was playing around with SSH and looking at the logs (I need to learn how to read that information to know how the server is performing, right?) and I saw the strangest thing.  In /var/log/auth.log and /var/log/auth.log.1 I saw a bunch of failed login attempts for 'root' and a few usernames I'm not familiar with. I looked over them and for as far as I can see no user has been authenticated except for the actual users on the system. A lot of the IP-addresses listed seem to be from Russia.  As of now this server contains nothing but a vanilla Ubuntu Server with LAMP, but even so, with the following command:  sudo grep -i fail /var/log/auth.log | wc -l   I get 3412 as a result. This seems very excessive for a server that has been up since April 8th. It gets worse, because running the above command on auth.log.1 returns 23075 (!!!!) results.  It seems obvious that people are trying to break into the server. Not that it contains anything of value, but once we start making progress on the app we wouldn't want our intellectual property stolen.  Should I be worried? And what can I do about it?  EDIT:  I found some very useful information  and this allowed me to run a script that splits and sorts all the invalid passwords and invalid users that tried to log in. May come in handy to someone who ended up here through Google! Show bounded and convex function on $\mathbb R$ is constant Changing CSV layer attribute value from text to number in QGIS? I read in a CSV file for linking to a .shp file.   All the variables that are just numbers came in as text.   How do I change the text variables to numeric in QGIS? Is changing your passport a good strategy for removing a negative immigration history in Schengen? When certain nationalities of people want to travel in the Schengen zone, they are required to apply for a Schengen visa. This is a straight-forward process for most, but when an applicant has had problems with removals or refusals they may be reluctant to apply because they want to avoid the complexities of serial visa refusals. This reluctance may lead some into wondering how their history can be expunged, and this line of thought inevitably leads to the idea of getting their passport replaced with a new one.  This sounds like a great formula for people who have had prior refusals or removals.  In essence they can become 'reincarnated' as a first-time traveller and hence avoid the unpleasantness of revealing their prior interactions with the Schengen authorities.  The relevant parts of the application form are shown here...    Nothing asks about a prior removal or refusal, and the applicant is left with simple denials for 3 questions in order to present themselves as a first-time traveller.  Assuming the person is happy to set aside the moral issues associated with denying their history, are there any holes to this strategy?  This question is scoped to Schengen visa applications so that it will not be unmanageably broad, but answers from other regimes (particularly the affluent Commonwealth and the USA) are acceptable as long as the main points are relatively consistent with Schengen. Ackermann Function primitive recursive Is it possible to level grind in Normal Mode? So in Awakening, we can use Reeking Boxes... but what of Three Houses? I'm not far off from the beginning of the game- I have just recently finished the mock battle, actually, but I noticed this calendar mechanic in the game (and in extension, the activity points stuffs). Apparently, the days just... jump.  With this info, I assume there's only a limited number of days before reaching the so-called War Phase... so this brings me back to the question: are there maps or battles that I can replay again and again so that I can level grind the characters, or are there only a limited amount of maps/battles that I can participate in? How can I programmatically force-stop scrolling in a UIScrollView? MWE:  \documentclass{article}  \usepackage{listings}  \begin{document}  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII hardware/software  \end{document}   This results in this output:    If \usepackage{listings} is commented out, the hyphenation rules return to normal:    And just to note, in the actual environment I'm working in, it will also hyphenate between hard•ware, while with listings enabled, it hyphenates hardware/•software, as in the first image:    Two questions:   Why is this happening? Is there a way to disable this? I don't really want this behaviour just because I'm typing code occasionally in a document. Is there a grammatical term for moving a word to the front or back of a sentence? There is a function in Arabic grammar where you may bring forward in sentence order a word - as well as deferring it.  For example: if the sentence order is Subject - Verb - Object, you can bring the object forward to be before the subject,  yielding Object - Verb - Subject or Object - Subject - Verb.  Similarly, if you have Noun Phrase - Verb Phrase, you can move the verb phrase forward so you get Verb Phrase - Noun Phrase.  This is used to add emphasis to the item brought forward. The same applies to moving the item to the end of the sentence.  Is there a grammatical term in English that represents this function or functions? Losing permissions by adding capability? I observed the following phenomenon that I can not explain. After adding the CAP_SYS_ADMIN capability, unshare is no longer able to write to /proc/self/setgroups.   In fact, writing to this file requires the capability, but that is achieved by changing the user namespace. So why does adding the capability to the parent process prevents writing to this file?  me@myhost:~$ unshare -r root@myhost:~# exit logout  me@myhost:~$ sudo setcap cap_sys_admin=ep /usr/bin/unshare me@myhost:~$ unshare -r unshare: cannot open /proc/self/setgroups: Permission denied  me@myhost:~$ sudo setcap cap_sys_admin= /usr/bin/unshare me@myhost:~$ unshare -r root@myhost:~#   By the way: I am running Ubuntu 16.04.4 LTS with kernel version 4.4 and the version of util-linux (including unshare) is 2.27.1. How quickly is antibiotic resistance lost? Objects Not Showing in Other Workspace Viewports, Only Default