Anvil, extra lines thingies
Subdivision Surface not making things smooth as they are in the tutorial I am following
Finding an isomorphic subring of matrices I'm struggling a fair amount with this exercise:     Find a subring of $M(2,\mathbb{Q})$ which is isomorphic to a) $\mathbb{Q}$ x $ \mathbb{Q}$ b) $\mathbb{Q}$ c) $\mathbb{Q}[x]$/$x^2$   Now I know a subring must be a subgroup, must contain the elements $0,1$ and must be closed under multiplication. As we are looking for isomorphisms then they must also be ring homomorphisms and must be bijective.  I tried to come up with a random subring and attempt to prove it is an isomorphism. E.g $\left\{\left.\begin{matrix}  a &amp; b \\ c &amp; 0  \end{matrix}\right|a,b,c \in \mathbb{Q}\right\}$ is a subgroup of $M(2,\mathbb{Q})$ and then try and show it's an isomorphism. However I'm stuck here as I don't actually know how to go about finding these specific isomorphisms and I completely lose what I'm doing. Any help would be great. How does SO's new auto-login feature work? SO and SU just told me I've been logged in. I'm guessing because I'm already logged into my Google account... but how does SO know that? Minecraft webpage links in chat? Sort Order on Close Vote Queue The Close-Vote queue is large and growing. I searched for definitive information on how that queue is sorted for reviewers, and the nearest I could find is that it is randomized - but that post was some years old.  Would it be possible to sort on order of votes already received? That is, all questions with 4 votes to close are surfaced first (in random order) to reviewers? Questions with 3 votes would come up before ones with 2, etc. In that manner a given question gets out of 'will it close?' limbo faster.   This feature request would, in my opinion, be supportable if the majority of reviewer votes were going to single-vote questions. I cannot (I think) actually find these numbers. If this is the case, the majority of the work is going to an ever-increasing queue, and proportionally fewer votes are being resolved.  Note there are other distributions that could help get in this direction without being a strict ordering, like weighting the chance a given question is surfaced to a reviewer by the number of votes. However, for discussion purposes I thought I'd keep it simple.  Usual apology if this has actually been addressed. Search is sad-making. Rename a file to parent directory's name in terminal I have to deal with a large number of files nested inside of directories (one file per directory), resembling something like this:  fred/result.txt john/result.txt mary/result.txt ...   I am currently using the following command to process each of those files:  find . -maxdepth 1 -type d \( ! -name . \) -exec bash -c \"cd '{}' &amp;&amp; processResult result.txt\" \;   I am looking for something I can add into the end of this command that will change the filenames to fred.txt, etc. and then later move the file into the parent directory to eliminate the extra layer of directories.  What would be the best way to do this? Which choice of line-breaking parameters gives the minimum number of lines I tried to reproduce the results from the  unfortunately the video link is broken. And I might have overlooked some related settings.  The spot light is barley visible on the ground.    Increasing the Density of the Volume Scatter Node darkens the sky texture but leads to some light cone from the car's headlight. (only 10 samples in preview).    Which settings do I need to change or should I try a different approach?  Integrator settings are default and spotlight settings were copied from the example found in the docs.  Related:    (pre 2.7)  (BI only) Zero module of differentials implies finite extension? Forbid links to open new tabs in Google Chrome What is the range of the validity of Coulomb's law? False proof that $ρe^{iθ} = ρ$ and so complex numbers do not exist? My professor showed the following false proof, which showed that complex numbers do not exist. We were told to find the point where an incorrect step was taken, but I could not find it. Here is the proof: (Complex numbers are of the form $\rho e^{i\theta}$, so the proof begins there) $$\large\rho e^{i\theta} = \rho e^{\frac{2 \pi i \theta}{2\pi}} = \rho (e^{2\pi i})^{\frac{\theta}{2\pi}} = \rho (1)^{\frac{\theta}{2\pi}} = \rho$$ $$Note: e^{i\pi} = -1, e^{2\pi i} = (-1)^2 = 1$$ Since we started with the general form of a complex number and simplified it to a real number (namely, $\rho$), the proof can claim that only real numbers exist and complex numbers do not. My suspicion is that the error occurs in step $4$ to $5$ , but I am not sure if that really is the case. Vertical alignment in tabularx X column type I'd like to create a new column type which works exactly like a X column from tabularx but that also has the text vertically centered. I tried with the newcolumntype command but I can't figure out where to put the second column type? Example:  \newcolumntype{n}{&gt;{\centering\arraybackslash}X}   Where should I put the mto specify that the cells content should be vertically centered? Find the inverse of a Trig Matrix I don't have a clue of what's going on. We haven't learn this in class so I need all the help possible. The more detailed of an explanation, the better. Thanks in advance. The only info I have is that this matrix is Orthogonal. Which means I know the answer, just don't know how to get it.  \begin{bmatrix}        \cos\theta &amp; -\sin\theta \\        \sin\theta &amp; \cos\theta       \end{bmatrix} To find out how something is called is the one thing I don't know how to use Google for.  If I have a vector $v$ and a symmetric matrix $H$, then the operation $v^T H v$ gives me some sort of projection of the matrix $H$ on the vector $v$. For example if $H$ is the Hessian, the operation gives me the second derivative in the direction of $v$.  What is the name of this operation? Why does Worf want O'Brien to go to Minsk? I've just watched the last 20 minutes of an episode of Deep Space 9, and towards the end Worf is very insistent that O'Brien and his wife move to Minsk. Is there any in or out of universe reason for this? Markdown source:  `http://google.com`  - `http://google.com`     - `http://google.com`   Rendered result:  http://google.com   http://google.com   http://google.com    Note that the third code span is a link. Adding a newline before the list item makes the link disappear. Show if a user is online, idle, or offline on their account page? I want to display the status of the user on the account page. I added the following code in the theme I am using. It works, but users are never displayed offline. Why? What is wrong in the code? user.html.twig &lt;div class=&quot;bs-field-status&quot;&gt;   {% if status == 'Online' %}     &lt;i class=&quot;user-online fa fa-circle fa-lg&quot;&gt;&lt;/i&gt; Online   {% elseif status == 'Absent' %}     &lt;i class=&quot;user-absent fa fa-circle fa-lg&quot;&gt;&lt;/i&gt; Absent   {% else %}     &lt;i class=&quot;user-offline fa fa-circle fa-lg&quot;&gt;&lt;/i&gt; Offline   {% endif %} &lt;/div&gt;  bootstrap_subtheme_front_office.theme &lt;?php /**  * @file  * Bootstrap sub-theme.  *  * Place your custom PHP code in this file.  */  use Drupal\Core\Database\Database;  /**  * Implements hook_entity_presave().  */ function bootstrap_subtheme_front_office_preprocess_user(&amp;$variables) {   // get user object   $user = $variables['elements']['#user'];   //- The user has logged in at least once   if ($user-&gt;getLastLoginTime()) {     if (account_is_logged_in_less_then_thirty_minutes($user-&gt;id())) {       $status = 'Online';     }     else {       $status = 'Absent';     }   }   else {     $status = 'Offline';   }   $variables['status'] = $status; }  /**  * @param $uid  *  * @return bool  */ function account_is_logged_in_less_then_thirty_minutes($uid) {   $connection = Database::getConnection();   $query = $connection-&gt;select('sessions', 'sessions')     -&gt;fields('sessions', ['sid', 'uid', 'timestamp'])     -&gt;condition('sessions.uid', $uid, '=')     //- chef if the user was online in 30 minutes (60 * 30)     -&gt;condition('sessions.timestamp', \Drupal::time()         -&gt;getRequestTime() - (60 * 30), '&gt;')     -&gt;execute();   //- Get result.   $results = $query-&gt;fetchAll(\PDO::FETCH_OBJ);   return (count($results) &gt; 0) ? TRUE : FALSE; } Pytest is in PATH but not found Evaluate the following limit of finite sum Using Fingerprint reader in 16.04 I have a Dell laptop with fingerprint reader inbuilt. I just ran lsusb on terminal and got the following result:   Bus 002 Device 003: ID 138a:0011 Validity Sensors, Inc. VFS5011 Fingerprint Reader Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 003 Device 002: ID 046d:c077 Logitech, Inc. M105 Optical Mouse Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 004: ID 05ca:1820 Ricoh Co., Ltd Integrated Webcam Bus 001 Device 003: ID 0a5c:21bc Broadcom Corp. BCM2070 Bluetooth 2.1 + EDR Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub   Is it possible to use fingerprint scanning instead of traditional login with 16.04 and Unity ? Thanks.