Python List Comprehension - add IF condition

I have a list which I am trying to call a function on each of this list's elements (which is also a list) given a certain condition is fulfilled (the element length has to be greater than 1):  videos = [self.__process_video(e) if len(e) > 1 else '' for e in videos]   However, I am getting an error  TypeError: object of type 'generator' has no len()


I would like to create something similar to .  To begin with, I would like to create a rounded and background-colored highlight of a word (or a short series of words).  What package should I use ?  How should I do ?  PS : I am not a Tikz user.


Understanding downside of triple-leveraged ETF

What happens to the price of the triple-leveraged ETF if the S&P 500 loses more than one-third of its value (i.e., the return is below -33 1/3%)?  Does it mean the value is equal to zero?


Inserted image is at the top of the page

I'm trying to insert an image into my paper however it's being inserted at the very top and not where I want it, my .tex file looks something like this:  % Bunch of text here, \begin{figure} \centering \includegraphics[width=12cm]{images/image.jpg} \caption{aaa} \end{figure} % More text after


Does evolving a Pokemon change the moves it has?

Before I decide on what pokemon I want to evolve, I wanted to pick the one with the moves or tricks I wanted to keep. But I'm unsure if evolving the pokemon will change the moves or tricks that is has so it really does not matter.


A man who is kidnapped by lizard/dinosaur people. The females are aggressive and the men docile

I'm trying to find a fantasy/sci-fi book in which the main (human) character is kidnapped by intelligent dinosaurs. The dinosaurs are human sized and their behavior varies strongly based on sex. The females are dominant and generally aggressive, while the males are docile, more artistic and sensitive and used mainly for breeding. Males are kept separate from females.  The lizard/dinosaur type creatures have their own language which uses their tales to communicate. The human main character learns their language to survive, while the female captured with him fails to do so and is killed by the Dinosaurs.  One of the female Dinosaurs decides to keep the main character as a slave, she also rapes him at least once.  When he escapes and rejoins a human village, the main character ends up living with a woman with a harelip.  Later in the story another group of creatures show up who are very sexual and cannot handle their alcohol. The creatures they end up with have beautiful tails they use to hide their genitalia.


How to add a shell script to launcher as shortcut

Possible Duplicate:             I want to add some shell scripts in my launcher as shortcuts..  They are located deep inside and i have to navigate to it every time to execute them...  I tried  link where the 2nd answers seems to solvee it but as said in comments neither can i find any option to add a launcher..  I guess it existed in 11.04 with a "+" button on launcher but i use 12.04.  So how do i get this working?? And i need those commands everytime for sure..!


I have what appears to be a paradox of motion, but it could just be my misunderstanding. It works under the assumptions that motion is fundamentally continuous, that position, velocity, acceleration and all possible $n^{th}$ derivatives of position are continuous functions. If an object is at rest then all $n^{th}$ derivatives of motion are 0, then suddenly as the object moves it changes velocity, in order to change velocity it must accelerate, in order to accelerate it must jolt etc. All possible $n^{th}$ derivatives of motion become non-zero instantaneously. how then can motion be continuous?


How to disable sticky corners in Windows 10?

My question is the same as this one :  But I didn't find the values to change in the registry.  Any idea how to fix this on Windows 10 ?  edit : I tried this :  but it doesn't work. I'm on build 10159.


Why do we need multiple approvers for suggested edits?

I already have the "Edit Questions And Answers" privilege. Yet, if I approve someone else's edit, I'm told that more votes will be required before the edit is accepted.  This seems a bit peculiar to me, since I could just copy the edited version and paste it myself.


Can’t delete filename with odd, long path in Windows 10

I am using Windows 10 and I downloaded a PDF file with a long name but now when I try to delete the file it doesn't respond.  I am not able to rename, move, delete the file. I have also tried to delete file using command prompt and failed.  The file path is shown like this  \\?\C:\Users\chaks\Desktop   Does anyone knows what this file path means???


Java - Background song to my game (How can I add it)

I'm trying to create a game and I'm currently trying to add sounds to it but due to lack of experience I failed to do so so I'm asking for your help. How can I add a background song to my game?


I was reading book "Database System Concepts" (6th edition by Henry F Korth Abraham Silberschatz, S Sudharshan   There is slight confusion between database system and DBMS Are both term same or different?  A database system is a collection of interrelated data and a set of programs that allow users to access and modify these data.  A database-management system (DBMS) is a collection of interrelated data and a set of programs to access those data.  What I understand--- A database system (DBMS) means a set of programs to access and modify data.  A database-management system (DBMS) means a set of programs to only access data.


Is it possible to visit the  as a tourist to Geneva? Are there any guided tours? Which parts can be seen?


How to remove all angle brackets and everything inside using JS?

I have a string of HTML elements,   let test = `<figure><img alt="" src="some_image.jpg"><figcaption>I think DC is better than Marvel <span class="whatever">...`   I need to remove every single <...> so it turns into test = "I think DC is better than Marvel...".  The closest I have gotten is:  var str = "<hello> Test </hello>" str.replace(/<[^>]*/g, ""); //=> "> Test >" str.replace(/<*>*/g, ""); //=> "hello Test /hello"   Not quite, though. How can I achieve this?


After the conclusion of his last fight, is Kisuke Urahara dead?

He doesn't appear in the final chapter of Bleach but that shouldn't necessarily mean he's dead, right?


How exactly does Simon's algorithm solve the Simon's problem?

Problem Statement: We are given a $2-1$ function $f:\{0,1\}^{n}\to\{0,1\}^{n}$ such that: there is a secret string $s\in\{0,1\}^{n}$ such that: $f(x)=f(x\oplus s)$. Challenge: find $s$.     Simon's algorithm says:         Set up a random superposition $$\frac{1}{\sqrt{2}}|r\rangle + \frac{1}{\sqrt{2}}|r\oplus s\rangle$$   Fourier sample to get a random $y$: $$y.s=0\ (\text{mod 2})$$   Repeat steps $n-1$ times to generate $n-1$ linear equations in $s$.         Solve for $s$.   I don't understand steps (1) and (2). Why and how exactly do we set up the random superposition? How does it help? Also, in step (2), what does the dot operator (in $y.s$) stand for? Bit-wise multiplication?


Is there any way to redistribute your skills/perks?

In Fallout 4, is there any way to change your skills/perks after you've gotten out of the vault, with or without cheating?


Quantum Electrodynamics explanation for refraction

I am trying to understand the fundamentals of Quantum Electrodynamics through the simple example of refraction. Let's start with a plane wave coherent state (or a number state) impinging on a boundary along positive $x$ axis with momentum $\hbar k_0$. The initial state is then given by $|\psi\rangle=|\alpha\rangle_{k_x=k_0,k_y=0,k_z=0}|0\rangle|0\rangle|0\rangle\dots$  For the free field case, we have the Hamiltonian given simply by $\hat{H}=\hbar \omega (\hat{a}^{\dagger}\hat{a}+1/2)$ so in the Schrodinger picture the initial state simply gains becomes $|\psi(t)\rangle=|\alpha e^{-i\omega t}\rangle$ due to time evolution under this Hamiltonian.   Now, using interaction picture for convenience, what would the Hamiltonian look like for the case when we have another medium with refractive index, say $n$, which is at an angle to the $x$ axis, as shown below? Using this Hamiltonian how can we see that the light is bent/scattered into a different $\vec{k}$ mode?


Why is a filament lamp an incoherent light source?

I've tried to search for this answer but found no proper explanation.  My previous ideas were...  1) It is not a point source, so the different points on a filament lamp may cancel out the light from other points on a filament lamp  2) It emits light rays at random (even though I've read this, I don't exactly understand what it means. Does it mean a single point on the filament may emit a photon one second and then the next second not emit anything?)  Are these reasons along the right lines? Could someone give a proper explanation as to why a filament lamp is an incoherent light source?


error when running the sudo apt update command

i recently updated to focal fossa and whenever I run the sudo-apt-update I get this error The repository 'http://ppa.launchpad.net/danielrichter2007/grub-customizer/ubuntu focal Release' does not have a Release file.  how to I remove the ppa in question when I try to purge the ppa I get this error The repository 'http://ppa.launchpad.net/danielrichter2007/grub-customizer/ubuntu focal Release' does not have a Release file.\nWarning:  apt-get update failed for some reason


Can a druid in Ape wildshape use weapons?

So, last night i was cooking up a new character and had this in mind. While reading the Wild Shape topic from PHB, i couldn't find anything that rules out the option to turn into an Ape/Giant Ape that can wield a Spear/Club.   Is it possible?


How to create multiple user logins for each ubuntu system

I have 25 systems of ubuntu and I want to create 60 login id and password for students. And any students can use any system to use system using his/her credentials. How can I achieve this?


The number of ways to represent $(n^2+n)/4$ as a sum of $n/2$ distinct integers in $1,\dots,n$

For any positive integer $n$ (using integer division only), let $P(n)$ denote the number of ways in which the integer $(n^2+n)/4$ can be expressed as a sum of exactly $n /2$ distinct elements of the set $\{1,2,3,\dots, n\}$.    What is $P(n)$ in terms of n?  Specifically, how exponential is it? Is this less than $2^{n/2}$?


What is the value of $\sum_{k=1}^{n}k!$?

What is the sum of all the factorials starting from 1 to n? Is there any generalized formula for such summation?


Bash script to receive and repass quoted parameters

I'm trying to get quoted parameters of a bash script to safely be received by a nested script. Any ideas?  test.sh  #!/bin/bash echo $* bash myecho.sh $*   myecho.sh  #!/bin/bash  echo $1  echo $2  echo $3  echo $4   Sample:  bash test.sh aaa bbb '"ccc ddd"'   Result:  aaa bbb "ccc ddd" aaa bbb "ccc ddd"   Wanted result  aaa bbb "ccc ddd" aaa bbb ccc ddd


Understanding the Riemann Surface of the $\sqrt{z}$

I have been trying all the day to understand the Riemann Surface of the $\sqrt z$. I Can not understand . Can anyone help me to understand how this picture is Riemann Surface of $\sqrt z$. The other questioner did not ask this question. He already could visualize my question's answer. So I request you not to try to block this question. This is the only source from where I get help.   Please read that question.    Explanation in simple words will be highly appreciated.


I tried installing Office 2007 in Ubuntu with Wine but it was throwing an error after installing and also when I tried to open a PowerPoint document and save it. Has anybody gotten Office 2007 installed without any issues? Please help me.


I have this graphic. I need to change the color of the graphic to hex color: 1485cc...is there a way to make this graphic match that particular hex color hue...without me having to have to re create the graphic.


How does the Earth's internal heat exist? Is it available from its creation as collision heat? Or is there any other source feeding the heat to the core?


Why pages not blocked by robots.txt are not indexing?

In my google search console's coverage section, the diagram tells that there are 114 excluded pages. It says 40 of them is blocked by robots.txt and 22 of them is excluded by 'noindex' tab, but I didn't exclude or blocked any of them. Even when I test them with google robots.txt tester it says the links are allowed and some of these URLs are those ones that I removed from my site along time ago before I launch the site and allowing bots to crawl. This is my website: e-anatomy.ir


How to overwrite a node setting in Tikz to align Tikz pictures to nodes?

A Tikz picture has four nodes and each node has a new tikz picture, an inheritance problem coming. I have four Tikz pictures where each is inside a node and each node has size of 4cm times 4cm (square) but this size is inherited to other nodes where node size only ~1mm as shown in Bad Demo below with big black circles. So  How can I overwrite Tikz node settings in the inner nodes?  Bad Demo Four tikz pictures jammed together bad    Four tikz pictures with larger node but node style inherited, how to overwrite it?   where my goal is to have each node of size 4cm and each single tikz picture inside each node -- by this I try to make my tikz pictures more accessible and visually pleasing.  MWE \documentclass[english]{article} \usepackage{tikz} \usepackage{pgfplots}  \begin{document} \begin{tikzpicture}  \node[minimum size=4cm](q1)[label=(a) $x_1+x_2$]{ \begin{tikzpicture}[x=2cm, y=2cm] \coordinate [label=$x_1$] (1) at (0,0); \coordinate [label=$x_2$] (2) at (1,0); \node[draw=none,circle,inner sep=1pt,fill=black] (11) at (1){}; \node[circle,inner sep=1pt,fill=black] (22) at (2){}; \end{tikzpicture} };   \node(q2)[right =of q1,label=(b) $x_1+x_1x_2+x_2x_3$]{ \begin{tikzpicture}[x=2cm, y=2cm] \coordinate [label=$x_1$] (1) at (0,0); \coordinate [label=$x_1x_2$] (2) at (1,0); \coordinate [label=$x_2x_3$] (3) at (2,0); \draw (1)--(2)--(3); \node [circle,fill=black,inner sep=1pt] (11) at (1){}; \node [circle,fill=black,inner sep=1pt] (22) at (2){}; \node [circle,fill=black,inner sep=1pt] (33) at (3){}; \end{tikzpicture} };   \node(q3)[below =of q1,label=(c) $x_1x_2x_3+x_1+x_2+x_3$]{ \begin{tikzpicture}[x=2cm, y=2cm] \coordinate [label=left:$x_1$] (1) at (0,0); \coordinate [label=right:$x_2$] (2) at (2,0); \coordinate [label=below:$x_3$] (3) at (1,-2); \coordinate [label=right:$x_1x_2x_3$] (123) at (1,-1); \draw (1)--(123)--(2); \draw (3)--(123); \end{tikzpicture} };   \node(q4)[right =of q3,label=(d) $x_1x_2x_3+x_1x_2+x_2x_3+x_2x_3$]{ \begin{tikzpicture}[x=2cm, y=2cm] \coordinate [label=left:$x_1$] (1) at (0,0); \coordinate [label=right:$x_2$] (2) at (2,0); \coordinate [label=below:$x_3$] (3) at (1,-2); \coordinate [label=right:$x_1x_2x_3$] (123) at (1,-0.8); \draw (1)--(123)--(2)--(1); \draw (3)--(123); \draw (1)--(3); \draw (3)--(2); \end{tikzpicture} }; \end{tikzpicture} \end{document}  where [minimum size=4cm] creates the two big circles, its removal returns the jammed pictures in the beginning. Trials  Trial 1: scope is suggested to avoid the overwriting but LaTeX Error: Environment scope is undefined, why?


How to copy a Linux file into a Windows PC?

How do I copy files in others account in Linux to my Windows PC. I have .  I’ve the access permission to other account (sudo).


What does "Mail Deferred:" mean in Linux Logwatch

I am just analyzing my logwatch logs, and I see the following entries:   SMTP SESSION, MESSAGE, OR RECIPIENT ERRORS  ------------------------------------------   Mail Rejected:        Total:  6   Mail Deferred:        Total:  229   Total SMTP Session, Message, and Recipient Errors handled by Sendmail:  235   ---------------------- sendmail End -------------------------   I only use sendmail for logwatch, so what is causing all these errors, and especially, what are deferred emails.


Work Enegy Conservation & Rolling Bodies

A disc of radius 0.1 m rolls without sliding on a horizontal surface with a velocity of 6 m/s.It then ascends a smooth continuous track. The height up to which it will ascend is Now I'm very confused because my textbook has two formulas regarding this 1/2 mv^2  & 1/2Iw^2 which one should I equate it with mgh?


Prepositions for transportations. In & On

Why "on a plane", "on a bus", but "in a car"?  It's hard to explain. How to explain that to English learners?  This question is not a duplicate. Please, try to understand what I ask.  How to explain that to English learners.  With the examples I gave.


Representing a nonnegative integer as the ordered sum of odd numbers

Numbers of ways of representing a nonnegative integer as the ordered sum of odd numbers. For the first numbers we find that:  $0 \to 0\quad \text{ways}$  $1 \to 1\quad \text{way}$  $2: (1,1) \to 1\quad \text{ways}$  $3: (1,1,1), (3) \to 2\quad \text{ways}$  $4: (1,1,1,1), (3,1), (1,3)\to 3\quad \text{ways}$  $5: (1,1,1,1,1), (3,1,1), (1,3,1), (1,1,3), (5)\to 5\quad \text{ways}$  So, if $A_n$ is the numbers of ways to represent the nonnegative integer n as the ordered sum of $n$ (nonnegative) odd numbers, then $A_n = F_n$ where $F_n$ is the Fibonacci number.  How could this be proved?   I was trying to prove this by induction, but I'm having problems with the induction step. I really don't know what to do there.


Ubuntu 16.04 regular crash, Compiz segfault, error 4 in i965_dri.so, Fresh install

Not that familiar with bug reports but I tried searching  for this error without success. Maybe you can help me identify if this is a duplicate of an existing bug or if a known solution exists. My question build on this previous question  that never received a solution.   My symptoms are similar but not the same, when hovering over or clicking menu button in Ubuntu 16.04, all open windows and menus crash and reappear again after a while. Same effect if I press the home button on my keyboard to open the menu. Also happens when I click Shutdown or Suspend from the top menu. This does not affect all menu items however, I am still able to open Firefox and the File Explorer from the menu. Shortcuts also work (ctrl+alt+T) and tty sessions (ctrl+alt+1-6).   Is this error the same as this perhaps? . Although My windows reappear again and as long as I use shortcuts and avoid alt-tab I can use my laptop.  An extract from syslog tells me this:  Jan  6 15:15:33 mofs kernel: [ 1294.824998] compiz[3930]: segfault at 0 ip 00007f6b31519c16 sp 00007ffc35380cc0 error 4 in i965_dri.so[7f6b30f3c000+82d000] Jan  6 15:15:38 mofs gnome-session[1590]: ** (unity-fallback-mount-helper:1803): WARNING **: Can't call IsLocked() on the Unity.Session object: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: No such interface 'com.canonical.Unity.Session' on object at path /com/canonical/Unity/Session   every new crash creates a new kernel segfault. The gnome warning line occurs sporadically.   I have tried installing Ubuntu fresh again from a USB image but after sudo apt-get update and upgrade it started happening again.  I have also tried reinstalling compiz to no effect.  This bug report  seemed promising although my screen does not turn blue, and I tried reinstalling libgdk-pixbuf-2.0-0 to no effect.   Any help would be appreciated. Let me know if you need more info.   Update: This issue is best reported and updated here  . It also provides workaround solutions until a bug fix is issued


How can I use \multirow and \multicolumn simultaniously?

I want to make below table using latex. But I don't know how to combine \multirow and \multicolumn. How can I make below table using latex?  Thank you very much.


Desktop shortcut for rebooting into different OS

I currently have Windows 10 installed on an SSD. There is another HDD in the machine for storage purposes. I wanted to add another SSD and install another OS (maybe Windows 7). I know I can always choose during the boot process as to which OS to run. However, is it possible to have a shortcut (for any batch file or something) on the desktop of each of the OS to directly reboot into the other OS?


Well I attempted to try this but I failed to solve it: So $$\Phi_{p^{n}}(x)= \frac{x^{p^{n}} - 1}{\Phi_{1}(x) \Phi_{p^{2}}(x) \dots \Phi_{p^{n-1}}(x)}$$  Now I'm just stuck here. I saw a result somewhere on the net that said $\Phi_{p^n}(x) = \Phi_p(x^{p^{n-1}})$. I would just use that, but I don't see why that result is true or know how to show that's true.  How do I approach this?


"Results found containing ___" too close to header

Search for ,        ,                        and you will see that "results found containing __" is just a little too close to the header. It's not like there isn't  to have it be a little lower, closer to "Search":          The UI has been updated since I took the above screenshots, and the text you search for is  (which fixes another design issue but not the one in this question):


I want to update only beamer as I have beamer.cls 2012/10/15 development version 3.24. I fear when updating TeXlive to have problems when compiling other tex files. What can I do to just update beamer? Thank you.


Editing Folder permissions for var/www/html

I need to edit my php.ini file so I can upload large sql files into MySQL, but I don't know how to do it.  If I go to var/www/html and try and drag-and-drop phpinfo.php there it won't let me (not enough permissions).   Can someone please tell me how to edit the permissions of the folder so I can add files to it? (terminal method is preferred, but UI is fine too).


How to test apex classes with Pagereference?

I'm struggling to test a class with pagereference. Following is the class...  public with sharing class redirectOrderPartner{  public String currentRecordId {get;set;} public orders__c orderId {get;set;}  public redirectOrderPartner(ApexPages.StandardController controller) {      }     Public Pagereference go(){      currentRecordId  = ApexPages.CurrentPage().getparameters().get('orderid');      system.debug('---currentRecordId  ---'+currentRecordId  );     orderId = [select id from orders__c where name =: currentRecordId limit 1];      system.debug('---orderid---'+orderId);      PageReference pageRef = new PageReference('/apex/OrderTrackingClass?id='+orderId.id);     pageRef.setRedirect(true);     return pageRef;    }   }   Following is what I tried....    @isTest  public class redirectOrderPartner_TEST  {             static testMethod void Test(){            Account acc = new Account(Name='ABC Corp.');           insert acc;            orders__c tempOrder = new orders__c(name = '0001234567', account__c = acc.id );           insert tempOrder;            Test.startTest();            PageReference pageRef = Page.redirectOrderPartner;           Test.setCurrentPage(pageRef);            ApexPages.Standardcontroller sc = new ApexPages.Standardcontroller(tempOrder);           ApexPages.currentPage().getParameters().put('Id',tempOrder.name);           PW_redirectOrderPartner ec = new redirectOrderPartner(sc);           ec.go();                                   Test.stopTest();       }   } I get the following error message on testing..     System.QueryException: List has no rows for assignment to SObject   What am I missing? Thanks


I am trying to construct a simple timeline in LaTeX with dates below points on the line and words above the line referring to a range.   I have included an image of what I am looking for that I constructed in Powerpoint. When adding this as an image into latex, the scaling makes the image unclear. Figured it will also be more professional to include actual latex timeline.


Where to report if you find a site exactly like Stack Overflow

I found a site which is working exactly like Stack Overflow. Should I report that to Stack Exchange? If so, how?


What does the @ symbol sign do in Latex?

The document class my Uni provides has a bunch of lines that appear to define macros with "@" in the name, like this:  \newcommand{\uni@title}{} \renewcommand{\title}[1]{\renewcommand{\uni@title}{#1}}  \newcommand{\uni@year}{} \renewcommand{\year}[1]{\renewcommand{\uni@year}{#1}}   But when I tried defining macros with a @ in the name it didn't work:  %this works \newcommand{\helloworld}[1]{Hello #1 !} \hello{everyone}  %this gives tons of error messages and %prints weird stuff to the document: \newcommand{\hello@world}[1]{Hello #1 !} \hello@world{everyone}   What are they @ signs doing in my document class file then?    Anyway, the reason I am asking all of this is that the \year macro is . I am thinking about renaming all the commands to something more namespaced and less ambiguous. Is camelCase the only way to go? I tried uni@year and uni_year and I'm getting the impression that macro names can only be alphanumeric...


Inbox chops messages in the middle of an HTML character reference

The messages in the inbox get chopped if they too long, and the chop can occur in the middle of an HTML character reference as can be seen in this screenshot:    The character being chopped is [ and it appears inside a code snippet, in case it makes a difference.


Update Ubuntu 16.04.3 LTS to Ubuntu 16.04.5 LTS

I would like to know if it is possible to update from Ubuntu 16.04.3 LTS to Ubuntu 16.04.5 LTS.


My question states: Given sets A and B, show that A \ (A ∩ B) = (A ∪ B) \ B.  This is where I got to before I got stuck: $$x \; \in \; A \; \setminus \; (A∩B)$$ $$x \; \in \; A \quad and \quad \notin \; (A∩B)$$ $$x \; \in \; A \quad and \quad (x \notin A \; or \; x \notin \; B)$$ $$ x \; \in \; A \quad and \quad x \; \notin \; B$$


Quoting in ssh $host $FOO and ssh $host "sudo su user -c $FOO" type constructs

I often end up issuing complex commands over ssh; these commands involve piping to awk or perl one-lines, and as a result contain single quotes and $'s.  I have neither been able to figure out a hard and fast rule to do the quoting properly, nor found a good reference for it.  For instance, consider the following:  # what I'd run locally: CMD='pgrep -fl java | grep -i datanode | awk '{print $1}' # this works with ssh $host "$CMD": CMD='pgrep -fl java | grep -i datanode | awk '"'"'{print $1}'"'"   (Note the extra quotes in the awk statement.)  But how do I get this to work with, e.g. ssh $host "sudo su user -c '$CMD'"?  Is there a general recipe for managing quotes in such scenarios?..


Summation of answers and comments: Use "an" before a word that begins with a vowel sound, otherwise, use "a". Still not clear on which to use before acronyms that can be read as letter-by-letter or as the words they represent. Side note: In the future, I'll only use acronyms where there is no need for "a" or "an" before them.  If an "a" or an "an" is needed, I'll write the words of the acronym. I'd use: "Nightmare of an operator of N.Y.C.'s subway/Subway..." Simpler sentence: Instead of "An NYU student" or "A New York University student", "A student of NYU" or "A student of New York University".  Original Question: I'm pretty sure I use the correct "a"/"an". Something like: if the next word (expanded from acronym, if exists) starts with "a"/"e"/"i"/"o"/"u"(/"y"?) => use "an", otherwise => use "a". A (bad?) example from : "An N.Y.C. Subway Operator's..." What are the "official" rules?


How do I restore an accidentally deleted initrd image?

I accidentally deleted the initrd image on my system.  How do I restore it?


I am seeing different results from the find command between being run manually on the command line vs run in a script.   If I run the following on the command line:   find . -name '*.txt' ! -name '*20120427.txt'    I get all the .txt files in a directory except for the ones with the date that I want to avoid.  But when I have this same line in a script with a variable to identify the date:  FDATE=`date +%Y%m%d` find . -name '*.txt' ! -name '*${FDATE}.txt'    The script finds all the .txt files including the ones with the date I want to avoid.   The only difference between the 2 is that I am passing the FDATE variable in the script. Is there something obvious I am missing? I do not understand why the results are coming out different.


gnuplot shell variable substitution and arrays

I need to use shell variables in my gnuplot commands, for which I'm using the here document style. I also need to use loops inside the gnuplot code. Both these things are working.  Now -- I want to use a gnuplot for loop's index to access a shell array variable. This is where I've been stuck all day.  I have something like this:  for ((i=0; i<=10; i++)) do var[$i] = i*10 done  gnuplot<<EOF do for [j=1:10]{ #need to access ${var[j]} somehow val=sprintf("${var[%d]", j) ##doesn't work } EOF   Individual access like ${var[1]} works. I suspect this may need using backquotes and/or expr, but am not sure.


Physicists have estimated the universe to be flat and infinite, but I can't seem to understand what this actually means. First of all, what do they mean when they say that the universe is infinite,  do they mean that space is unbounded? Or do they mean that the space is currently bounded and is expanding forever (so the bounds are getting further apart) ? And if space is unbounded, how does it expand, how can infinity get larger?  Finally a flat universe could also be bounded if for example it has a toric shape which has zero curvature, could this be a possible shape of the universe?    What also confuses me is that, since the beginning of time, the universe had a very small size, but how did it become infinitely large in a finite amount of time?


I have had my 70d for about 2 months. I had the wifi function set up and it was working fine. This past weekend it asked for me to re-enter my password. I have no idea why I used as my password. How do I go about retrieving of resetting it?  Thanks!


How can I fix sfdx error: "The \"path\" argument must be of type string. Received type undefined"

I'm getting an error similar to  and I've checked to see if I could resolve it in the same way, but it appears to be a different issue.  Whenever I try to push, deploy or convert to metadata, I'm getting the error      TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined   This error also shows up in the Problems tab in VS Code, but clicking on it gives me another error (Unable to open "": File is a directory.)    This issue was reported on the  by others over the last 8-9 months, but there's no clear resolution. I've added more detail (json error output) there.  The only "path" argument I can find is in the sfdx-project.json, and it's clearly a string:  {   "packageDirectories": [{ "path": "force-app", "default": true }],   "namespace": "",   "sfdcLoginUrl": "https://login.salesforce.com",   "sourceApiVersion": "46.0" }   I'm completely stuck with no clear way to debug this. Would appreciate any ideas...


I had two OS on my PC Windows 7 and Ubuntu in separated partitions. After trying to change windows 7 to windows 8, it works good but Ubuntu has disappeared and the weird thing is that, its partition appeared on my hard drive but I can't switch between them. How can I get Ubuntu back?


Single quote or Double quote in Node.js?

I am learning Nodejs from scratch and I would like to make it a habit of using either single quote or double quote in Node.js. I read few answers elsewhere in Stackoverflow which said that it's purely dependent on the coding style used by the team.   So, which one should I use? Or rather, which one does the expert programmers use? in Apis and elsewhere.


What is the max weight a standard bycycle would take?

I would like to get back into cycling again, however over the last couple of years I have piled a few needless pounds on. I currently weight 178kg (392 lbs), would a standard bike frame withstand my weight? I'm hoping to loose substantial weight hopefully by cycling each day as I've never been much of a runner. But do I need to loose this weight before I start cycling. I had been looking at the Carrera Vengeance Mens Mountain Bike 2015 - 22".


2000s (or earlier) fantasy novel where the main character wears spider silk clothes because of her sensitive skin

I'm searching for a fantasy novel I read years ago - in the early 2000s, though it might have been published earlier. The main thing I remember is the main character (female I think) had to wear spider silk clothing because she had super-sensitive skin. More, even normal spider silk wasn't smooth enough because she could be the legs of the spiders that use to skitter across the silk. This might of been a magical sense or it must have just been really sensitive skin. It had to be special smoothed.  I think but am not sure it was a sequel to an earlier fantasy series, but I didn't read that series.


I stumbled upon this particular expansion that was included in  post.    $$ \displaystyle \arcsin^{2}(x) = \frac{1}{2} \sum_{n=1}^{\infty} \frac{1}{n^{2} \binom{2n}{n}} (2x)^{2n}$$    This caught my eye because I remember trying to derive a Taylor series for $\arcsin^{2}(x)$ a while ago without much success.  Can anyone prove this or point me to a material that would show a proof of this identity?  EDIT :  Feel free to use any mathematical apparatus at hand. I'm not interested in a proof fit for a certain level, nor am I looking for utmost elegance (though that would be lovely).


Can't download install an iso file for Windows in a USB stick with WoeUSB

Whenever I try it says:   Installation failed! Exit code: 256 Log: WoeUSB v@@WOEUSB_VERSION@@   ==============================   Error: Target device is currently busy, unmount all mounted partitions in target device then try again /usr/bin/woeusb: line 512: 31020 Terminated               while true; do       sleep 0.05; echo 'pulse'; done Target device is busy, please make sure you unmount all filesystems on target device before detaching it.   How can I fix it?


I have made a duplicity backup with Ubuntu 14.04 in another laptop of my home directory.  I copied all duplicity back files to my current laptop to "/home/user/Ubuntu-backup"  How do i browse the content of that backup see if it is worth restoring? I want to restore how do i restore from those files.


Playing Sound with Ubuntu QML Toolkit preview

I've installed the Ubuntu QML Toolkit Preview as per the instructions on  (with a minor fiddle to get it working on 12.04).  I'm trying to write an app that plays a sound file.  Aparrently you can do this using QtMultiMediakit in QtQuick 1, but not in QtQuick 2 as used by the toolkit.  Is it possible to write an app using the toolkit that plays sound?


Why does my Mac's list of "Open with" applications start listing the apps twice and sometimes three times?

When I right-click on a file on my Mac OS desktop and then in the contextual menu, I move to the "Open with...", the list of potential applications to "open with" has applications listed multiple times, sometimes three or four times, right next to each other!   Why does this happen? How do I fix it? how do I stop it from re-occurring?   See this snapshot of the contextual menu showing the doubling up:     Now I have Mountain Lion on a 13" MacBook Pro, but this problem existed before I upgraded to Mountain Lion.


Will unplugging a USB key without safely removing it cause problems?

I often pull out the USB stick without having to first eject USB, but so far I have not had any problems.   Would this lead to problems in the future?


I'm trying to prove by MI. I have already distributed n+1, but now I'm stuck on how I can show 9 divides the RHS since $42n$ and $3n^3$ does not divide evenly.   $$(n+1)^3+(n+2)^3+(n+3)^3=3n^3+18n^2+42n+36$$


Increasing the contents of a list by a certain number within a range function

Hello how can I make a list of numbers that will increase by an x amount until the range is complete. Like I want set = [i for i in range(2,11)] I want the contents of list to be increase by 0.1, so its contents are going to go like [2, 2.1, 2.2, 2.3...... etc.]. Also how can I only print the contents of set1 of elements from the code below. instead of the outputs being (2, 1, 1) (2, 1, 2) (2, 2, 1) (2, 2, 2) (3, 1, 1) (3, 1, 2) (3, 2, 1) (3, 2, 2) it would be(2) (2) (2) (2) (3) (3) (3) (3). Thanks for the help :) import itertools set1 = [i for i in range(2,4)] set2 = [i for i in range(1,2)] set3 = [i for i in range(1,2)]               list_set = [set1, set2, set3] for element in itertools.product(*list_set):   print(element)


Fonts: Arial Narrow (or equivalent)in LaTeX

I may be opening an old wound here...my University's preferred font is Arial Narrow.  I have very little experience with working with fonts; I usually stick with CMR, which at least provides a perfect match across the entire document; mathematics and all.  However, back to Arial Narrow.  My first attempt was to put  \fontfamily{phv}\fontseries{mc}\selectfont   (following the instructions at ) straight after \begin{document}; this typeset the body of the text beautifully, but kept sections headings in cmr bold.  I tried to download all the nonfreefonts with getnonfreefonts but for some reason they all ended up in the wrong directory.    I tried using \usepackage{helvet} which certainly works across the entire document, but gives me an ordinary, not narrow, font.  I'll try using \usepackage{uarial} once I move that new font tree out of /usr/local/share/texmf and into /usr/share/texlive/texmf-dist/.  But if there's any better, or more straightforward way...?


$f(z)=xy+iy$  $f(z)=u(x,y)+iv(x,y)$  $u=xy$, $v=y$  $\frac{\partial u}{\partial x}=y$, $\frac{\partial v}{\partial x}=0$  $\frac{\partial u}{\partial y}=x$, $\frac{\partial v}{\partial y}=1$  We see that $\frac{\partial u}{\partial x} \ne \frac{\partial v}{\partial y}$, except for $y=1$  Also, $\frac{\partial u}{\partial y} \ne -\frac{\partial v}{\partial x}$, except for $x=0$  The Cauchy-Riemann equations are not satisfied anywhere in the z-plane except at the point $x=0$, $y=1$, i.e. $z=i$  $f^{'}(z)=\lim_{\delta z-> 0}\frac{f(z+\delta z)-f(z)}{\delta z}$


How could one write a script or programme that waits for a keypress and outputs its X-name (Return, BackSpace, etc.) including modifiers, in a format accepted by xdotool (eg. Control + Alt + b)?


why is execute() PDO function return false?

public function updateTodo($iSequence, $aTodo) {     //@TODO      $sTodo = $aTodo['todo'];     $stmt = $this->oConnection->prepare("UPDATE t_todolist          SET todo = $sTodo          WHERE sequence = $iSequence");      $stmt->execute(); }   Im doing a todo list for some reason i cant update my database because my $stmt is executing false.


Can't complete sign in process to App Store

When I try to sign in with my Apple ID via the App Store, it seems it is not connecting. I tried to put a different password and it notified me that it was wrong, but with the correct one it only seems to work, but then i'm not getting in.  More specifically, when I put in my correct password, it doesn’t error out (like if I put in an incorrect password), instead the login window just disappears.  In iTunes and Books I can sign in and sign out whenever I like, so I really can't see where the problem is.  Any suggestions?


I have finally managed to boil down a problem I have been struggling with for a few weeks.  I use SSH with "authorized keys" to run commands remotely.  All is fine except when I do it in a while loop.  The loop terminates after completing any iteration with an ssh command.  For a long time I thought this was some kind of ksh weirdness, but I now discovered bash does in fact behave identically.  A small sample program to reproduce the problem.  This is distilled from a larger implementation which takes snapshots and replicates them amongst the nodes in a cluster.  #!/bin/bash  set -x  IDTAG=".*zone" MARKER="mark-$(date +%Y.%m.%d.%H.%M.%S)" REMOTE_HOST=sol10-target ZFSPARENT=rpool  ssh $REMOTE_HOST zfs list -t filesystem -rHo name,mounted $ZFSPARENT | grep "/$IDTAG    " > /tmp/actionlist  #for RMT_FILESYSTEM in $(cat /tmp/actionlist) cat /tmp/actionlist | while read RMT_FILESYSTEM ISMOUNTED do    echo ${RMT_FILESYSTEM}@${MARKER}    [ "$ISMOUNTED" = "yes" ] && ssh $REMOTE_HOST zfs snapshot -r ${RMT_FILESYSTEM}@${MARKER}    echo Remote Command Return Code: $? done   (Note there is a TAB character in the grep search expression as per the definition of the behaviour of the zfs list "-H" option.)  My sample have some ZFS filesystems for the root where all the "zones" have their root file system on a dataset named similar to  POOL/zones/app1zone POOL/zones/group2/app2zone    etc.  The above loop should create a snapshot for each of the selected datasets, but in stead it operates only on the first one and then exits.  That the program finds the right number of datasets can be easily confirm by checking the "/tmp/actionlist" file after the script exists.  If the ssh command is replaced by, for example, an echo command, then the loop iterates through all the input lines.  Or my favourite - prepend "echo" to the offending command.  If I use a for loop in stead then it also works, but due to the potential size of the list of datasets this could cause problems with the maximum expanded command line length.  I am now 99.999% sure that only those loops with ssh commands in them give me problems!  Note that the iteration in which the ssh command runs, completes! It is as if the data pipped in to the while loop is suddenly lost...  If the first few input lines don't perform an ssh command, then the loop goes on until it actually runs the SSH command.  On my laptop where I am testing this I have two Solaris 10 VMs with only about two or three sample datasets, but the same is happening on the large SPARC systems where this is meant to go live, and there are many datasets.


Minimal polynomial of matrix with rank 1

Let $A$ be an $n \times n$ matrix over $\mathbb{K}$ such as $\text{rank}(A)=1.$ Show that it's minimal polynomial is $m_A(x) = λ(λ-a) , a \in \mathbb{K}.$  I tried to prove it using induction. My work so far:  Let $n =2$ and $A = \begin{bmatrix}a&b\\c&d \end{bmatrix}$:   If $c=0_{\mathbb{K}}:$  Since $\text{rank}(A)=1$, $d=0_{\mathbb{K}}$. So, $A=\begin{bmatrix}a&b\\0&0 \end{bmatrix} \implies \det(A-λI) = λ(λ-α) = m_A(λ)$ If $c\ne 0_{\mathbb{K}}$  $A = \begin{bmatrix}a&b\\c&d \end{bmatrix} \to \begin{bmatrix}a&b\\0&-ad/c +b \end{bmatrix} \implies b = ad/c \implies A = \begin{bmatrix}a&ad/c\\c&d \end{bmatrix} \implies \det(A-λI) = λ(λ-(α+d)) , (a+d) \in \mathbb{K}$   On that point, I tried letting $n=3$ and writing the matrix in the form of $A = \begin{bmatrix}A_1&0\\0&A_2 \end{bmatrix}$,after Gauss elimination, where $A_1$ is a $2 \times 2 $ matix and $A_2$ is a $1 \times 1$ matrix and working my way from $n=k$ to $ n =k+1$, but it seems like I'll be doing way too much work. I there a better/shorter way of doing it?


Getting the value with mod in the equation

I have the equation de ( mod x ) = 1 I currently have the values for e and x. Is there a way that I can get the value for d? I tried doing (x + e) + 1 but when I insert it into the equation, I get an answer that isn't 1.


In C#, why doesn't a subclass field's default value override the superclass field's default value?

I'm sure this is a duplicate but I can't find an answer. I'm new to C# and having trouble understanding why this is happening: I have one class that inherits from another. I want the subclass to override a public field on the superclass, in this case the public field a. But it doesn't seem to work: class Foo {    public string a = "x";     public string A()    {       return a;    } }  class Bar : Foo {    public string a = "y"; }  ...  new Foo().A() // Returns "x" new Bar().A() // Returns "x" also...why?  I would expect the last line to return "y" but instead it returns "x", ignoring the fact that I've overridden the value of the a field. Why isn't it working? And what is the standard way of getting the behavior I want? I'm entering this code into the csharp REPL, if that matters.


*Why* Does the SQL Server Debugger Require Sysadmin Privileges

I recently posted a question looking to . I am finding that there really isn't a feasible solution to this.   My question here is, WHY does the sql server debugger require sysadmin privileges? I want to understand the reasons behind designing it this way.   In a dev environment, developers should be able to do dev activities such as using the built-in debugger tools without granting sysadmin, instead of being told to basically build his own debugging mechanism using print statements, etc.   SQL server has privileges for so many specific roles/tasks, etc, it's odd not to see a separate one for this e.g. which could be granted only in a dev environment, etc.  I don't think this question is a duplicate of the others, since this question is not about how to use the debugger if you aren't a sysadmin, but rather, it is so I can understand why it is designed this way.


Data from ajax is not passing to PHP file

I have this html page with ajax function called upload(name) to send a data to a PHP file (upload-ad-image-inc.php) for a image upload process.  I have already tried passing data using ajax to the relevant PHP file (upload-ad-image-inc.php).   And I got the passed data using a POST and assign it to a variable and so far so good. Data is passed but it is kind of missing after that.   This is my Ajax function:         function upload(name) {             $(document).ready(function () {                 $.ajax({                     url: 'includes/upload-ad-image-inc.php',                     type: 'POST',                     dataType: "json",                     success: function (data) {                         alert(data);                     },                     data: {                         file: name                     }                 }).done(function (data) {                     alert(JSON.stringify(data));                 });              });         }   this is my upload-ad-image-inc.php   $ind = filter_input(INPUT_POST, 'file');   echo $ind; //it shows file name successfully   $adId = $_SESSION['adid'];  $userId = $_SESSION['userid'];   //after this the value of $ind is missing, cannot apply to any of above.   //They show empty outputs   $file = $_FILES[$ind];  $fileName = $_FILES[$ind]['name'];  $fileTempName = $_FILES[$ind]['tmp_name'];  $fileSize = $_FILES[$ind]['size'];  $fileError = $_FILES[$ind]['error'];  $fileType = $_FILES[$ind]['type'];   echo $fileName; //this is where my problem. It doesn't show file name      In this part I get the file name attributes value   $ind = filter_input(INPUT_POST, 'file');   echo $ind; //it shows file name successfully      but in below i don't get anything but empty values     $file = $_FILES[$ind];  $fileName = $_FILES[$ind]['name'];  $fileTempName = $_FILES[$ind]['tmp_name'];  $fileSize = $_FILES[$ind]['size'];  $fileError = $_FILES[$ind]['error'];  $fileType = $_FILES[$ind]['type'];   echo $fileName; //this is where my problem. It doesn't show file name   This is my `HTML'
                              <input style="display: none;" type="file" accept="image/*" onchange="readURL(this, 'blah1', 'file1');" id="file1" name="file1" class=" btn btn-primary">                 <button style="display: none;" type="submit" name="submitUpload" class="custom-file-control btn btn-primary"> Save</button>                                             <input style="display: none;" type="file" accept="image/*" onchange="readURL(this, 'blah2', 'file2');" id="file2" name="file2" class=" btn btn-primary">                 <button style="display: none;" type="submit" name="submitUpload" class="custom-file-control btn btn-primary"> Save</button>                                             <input style="display: none;" type="file" accept="image/*" onchange="readURL(this, 'blah3', 'file3');" id="file3" name="file3" class=" btn btn-primary">                 <button style="display: none;" type="submit" name="submitUpload" class="custom-file-control btn btn-primary"> Save</button>                                             <input style="display: none;" type="file" accept="image/*" onchange="readURL(this, 'blah4', 'file4');" id="file4" name="file4" class=" btn btn-primary">                 <button style="display: none;" type="submit" name="submitUpload" class="custom-file-control btn btn-primary"> Save</button>


How to prove that a nilpotent operator has a basis representation that is strictly upper triangular?

I wish to prove the following:  if $T:X\to X$ is a nilpotent (and the     linear space $X$ is finite-dimensional), then there exists a basis     of $X$ such that the matrix representation of $T$ is upper     triangular with zero diagonal elements.  I was trying to prove $\{x_1,...,x_{k+1},v, Tv, ..., T^{n-k-2}v\}$ is a basis for $X$ where $x_i$ are basis for $N(T)$ and $v,..., T^{n-k-2}v$ are basis for $R(T)$ where $T^{n-k}=0$ and $n-k$ is minimal. However the matrix representation w.r.t this basis is diagonal. Is there an easy way to prove this ?  I know that for all $T:X\rightarrow X$, there exists a basis that the matrix representation is  upper triangular. How is this useful?


How to decrease .pdf size without losing quality

Background  I want to decrease size of the .pdf filled with images. In Preview in can be dome through Export and set Quartz Filter-> Reduce File Size before saving.    Problem  The file indeed decreased from ~30MB to 0.37MB.   But the result has such poor quality that images are barely readable.  Question  I saw an examples of using Image Magic to achieve that - but can it be done by Preview without any external software?


2 versions on the same software with different features

I installed Darktable in the past through Ubuntu Software Center and it worked perfectly. However, in the Darktable preferences tab, OpenCL was not enabled.   I really want to have OpenCl enabled as it boosts Darktable's performance. Thus I made sure I had the correct NVIDIA driver that allows OpenCL configuration enabled and tried running darkatbe-cltest, which failed and showed this error message:  darktable-cltest not known  You can install it with sudo apt install darktable   I was a bit confused, because I already had Darktable installed as described above.   But I did proceed with sudo apt install darktable, which installed a new version of Darktable on my computer.   I also used sudo add-apt-repository ppa:pmjdebruijn/darktable-release, in order to update to the newer version. Oddly, this new version now supports OpenCL!  Now I have 2 different versions of Darktable on my computer, both version 2.6.2. However, one supports OpenCL, while the other does not. Also the layout of the two versions is slightly different (different font size and padding).  When I run Synaptic, I can only see one version of Darktable, the one installed from the terminal.   And when I try to find packages installed through Ubuntu Software Center, like Discord, I can't find them in Synaptic.   Because I thought Ubuntu Software Center was a GUI of the terminal, it is a bit strange not to find every package installed in Ubuntu Software Center.  (NB: I have to mention that I did run sudo apt-get update  && sudo apt upgrade a few times and also  updated through Synaptic some of the packages I saw there.)


Could 'cogito ergo sum' possibly be false?

I've heard it postulated by some people that "we can't truly know anything".  While that does seem to apply to the vast majority of things, I can't see how 'cogito ergo sum' can possibly be false.   No matter what I am, no matter in what way I'm being tricked, no matter how I may be deluded, I must exist in order to - in some way - be considering this right now (or be being tricked right now).  Is 'cogito ergo sum' necessarily correct, or have I missed something?


What to do with a likely collaborator who is not answering mails?

A few months ago, I contacted a person who conducted research in a topic that could easily be combined with my own work.  For this reason, I sent him an e-mail exposing my research and why it could be interesting to collaborate, taking into account his results. He answered me and showing interest in the work (that is what I read between lines). Furthermore, he recommended me some literature.  When I read about half of the documentation, I sent him a mail with the insights I got and several of my publications, justifying my points. He answered me again, discussing some points and glad to have my work pending to read.  I finished his readings and I sent back my impressions. He continued the discussion and excused himself because of not having read my papers.  After two months, I have no reply from him. What should be my next step towards the collaboration?


Shortest path from points in one layer to points in another layer via roads in QGIS

I'm looking for a way to calculate the shortest path from addresses to subway stations via a network of roads.  I have the , however, the addresses and subway stations are point layers that do not overlap with vertices in the roads layer.  In QGIS, is there a way to calculate the shortest distance from the address/subway station points to the roads, create vertices at those locations, then calculate the shortest distance via the roads network?   black squares - addresses white circles - subway stops gray lines - roads


A very minor bug appeared when I used the flag review tool today for the first time ever.    Steps to reproduce:   Open flag review, select question Vote to close the question Attempt to flag the question   I believe it should state a number (instead of "undefined") for how many more votes are needed, and it should show the action (putting the flag you assigned a moment before) as completed.


MacTeX 2015: TeX Live Utility stuck on "Validating Server..."

After having upgraded to MacTeX 2015, whenever I run TeX Live Utility, it stays stuck with the "Validating Server..." message.    Clicking the "Home" button causes it to crash.  However, tlmgr update --all from the terminal works fine, so I don't think it's about some mirrors not carrying TeX Live 2015 yet.  Has anyone else encountered this problem with TeX Live Utility, or is it specific to my installation?  Is there a known fix for the problem?  This is TeX Live Utility version 1.21.


Avoiding labeling features if overlapped by another layer in QGIS?

With QGIS 2.12.2, how can I set up layer labeling to avoid placing labels where features from another layer already exist?  For example, if I have a stream/river polyline layer that contains lake "centerlines", and I place a "lake" polygon layer above it in the drawing order, I don't want the river layer to place a label inside the lake.  Instead, I would rather have the river labeled outside of the lake (as needed).  That way, I can place labels from the lakes layer and I don't run into label collisions.  Here is an example, where (I have intentionally put the lines on top for visual purposes) what I am hoping to achieve is no river center-line labels shown inside the lake polygon:


Can subtle spell be used through a warlock's familiar, and does it stop the stealth from being broken if it is currently sneaking

With the new Tasha's Cauldron of Everything feat Metamagic Adept, warlocks get access to Subtle Spell. Can Subtle Spell be used in conjunction with a chain warlock's familiar to cast, say, death ward at range without someone knowing?


How to understand "nonlinear" as in "nonlinear dimensionality reduction"?

I am trying to understand the differences between the linear dimensionality reduction methods (e.g., PCA) and the nonlinear ones (e.g., Isomap).  I cannot quite understand what the (non)linearity implies in this context. I read from  that     By comparison, if PCA (a linear dimensionality reduction algorithm) is   used to reduce this same dataset into two dimensions, the resulting   values are not so well organized. This demonstrates that the   high-dimensional vectors (each representing a letter 'A') that sample   this manifold vary in a non-linear manner.   What does     the high-dimensional vectors (each representing a letter 'A') that   sample this manifold vary in a non-linear manner.   mean? Or more broadly, how do I understand the (non)linearity in this context?


This is a soft question. I'm searching for examples of mathmatical statements (preferably in number theory, but other topics are also fine), that seem to be true, but are actually not. Statements where observing some examples would let you think it is always true, but then there is a well hidden counter-example.  If Riemann's $\zeta$ function had a zero beside the critical line, this would be such an example I'm looking for. Or if Fermat's Last Theorem would be false.  Do you know any such surprising counter-exmaples?


Is "must have four cats" the same as "must have got four cats"?

On Cambridge Online Dictionary, the phrase "have got" is considered a formal alternative to simply "have", for example:  He has four cats.   He has got four cats.  I want to ask: Does adding an additional modal verb (e.g. must) change the meaning, or is the meaning of "must have got" & "must have" still the same? In other words, do these sentences mean the same thing?:  He must have four cats.   He must have got four cats.  How about with modals apart from must?


Separate wallpaper for login screen and desktop? (16.04 LTS)

I've tried searching for an answer to this with no luck.  I had a go at the method detailed  but as soon as I log out the new wallpaper is there for a brief second before it changes back to my desktop wallpaper.  I feel silly asking a question like this as it must be simple but I can't figure it out. Any help would be appreciated!


Distinct roots of $ax^2-bx+c=0$ in $(0,1)$, where $a,b,c\in \mathbb{Z}^+$

Question Statement:- Let $a,b,c$ be positive integers and consider all the quadratic equations of the form $ax^2-bx+c=0$ which have two distinct real roots in $(0,1)$. Find the least positive integers $a$ and $b$ for which such a quadratic equation exist.   Attempt at a solution:- Let $f(x)=ax^2-bx+c$. Now as the roots of $f(x)=0$ lie in $(0,1)$ hence $f(0)\cdot f(1)\gt0$. $$D\gt0\implies b^2-4ac\gt0$$ $$f(0)=c \\ f(1)=a-b+c$$ As, $a,b,c\in\mathbb{Z}^+$, so $$f(0)\ge1 \implies c\ge1\tag{1}$$ $$f(1)\ge1\implies a-b+c\ge1\tag{2}$$ $$f(0)\cdot f(1)\ge1\implies c(a-b+c)\ge1\implies c^2+(a-b)c-1\ge0\tag{3}$$ Now, for the quadratic inequality in $c$ that we obtained in $(3)$, for it to hold we get $$D\le0\implies (a-b)^2+4\le0$$ The above inequality doesn't hold $\forall a,b \in \mathbb{Z}^+$. After arriving at this conclusion I am kind of stuck on what to conclude from the above result or rather am I going in the right direction. A little push in the right direction in the form of a hint or rather what should be the line of thought for attempting the question. Please don't write the solution, just the line of thought to arrive at the solution would be enough.


Casting a multivariate linear model as a multiple regression

Is recasting a multivariate linear regression model as a multiple linear regression entirely equivalent?  I'm not referring to simply running $t$ separate regressions.   I have read this in a few places (Bayesian Data Analysis -- Gelman et al., and Multivariate Old School -- Marden) that a multivariate linear model can easily be reparameterized as multiple regression.  However, neither source elaborates on this at all.  They essentially just mention it, then continue using the multivariate model.  Mathematically, I'll write the multivariate version first,  $$ \underset{n \times t}{\mathbf{Y}} = \underset{n \times k}{\mathbf{X}} \hspace{2mm}\underset{k \times t}{\mathbf{B}} + \underset{n \times t}{\mathbf{R}}, $$ where the bold variables are matrices with their sizes below them.  As usual, $\mathbf{Y}$ is data, $\mathbf{X}$ is the design matrix, $\mathbf{R}$ are normally distributed residuals, and $\mathbf{B}$ is what we are interested in making inferences with.   To reparameterize this as the familiar multiple linear regression, one simply rewrites the variables as:  $$ \underset{nt \times 1}{\mathbf{y}} = \underset{nt \times nk}{\mathbf{D}}  \hspace{2mm} \underset{nk \times 1}{\boldsymbol{\beta}} + \underset{nt \times 1}{\mathbf{r}}, $$  where the reparameterizations used are $\mathbf{y} = row(\mathbf{Y}) $, $\boldsymbol\beta = row(\mathbf{B})$, and $\mathbf{D} = \mathbf{X} \otimes \mathbf{I}_{n}$.  $row()$ means that the rows of the matrix are arranged end to end into a long vector, and $\otimes$ is the kronecker, or outer, product.  So, if this is so easy, why bother writing books on multivariate models, test statistics for them etc.?  It is most effective to just transform the variables first and use common univariate techniques.  I'm sure there is a good reason, I just am having a hard time thinking of one, at least in the case of a linear model.  Are there situations with the multivariate linear model and normally distributed random errors where this reparameterization does not apply, or limits the possibilities of the analysis you can undertake?    Sources I have seen this: Marden - Multivariate Statistics: Old School.  See sections 5.3 - 5.5.  The book is available free from:   Gelman et al. - Bayesian Data Analysis.  I have the second edition, and in this version there is a small paragraph in Ch. 19 'Multivariate Regression Models' titled: "The equivalent univariate regression model"  Basically, can you do everything with the equivalent linear univariate regression model that you could with the multivariate model?  If so, why develop methods for multivariate linear models at all?  What about with Bayesian approaches?


How do I locate an app on the iPhone spring board / home screen?

As an iOS developer I have many (>150) apps installed on my iPhone. Sometimes I cannot figure out on which home screen an app is located.  I know how to start the app by using the search. And if the app uses a lot of storage I can go to "Settings -> General -> iPhone Storage" and delete it.  But is there any way to find the installed app in the spring board without looking at every home page and in every folder?


I'm dealing with something like $\sum_{j=2}^{n-1}j^2$. I know I can do this $\sum_{j=1}^{n-1}j^2 - \sum_{j=1}^{1}j^2$.  Would that be equal to $\frac{j(j+1)(2j+1)}{6} - j^2$ or I'm missing some properties with $n-1$?  If so, which ones?


Why is any number N of base B, whose digits sum to a multiple of a prime factor P of B-1, also divisible by P?  (Also, how do you ask that question more succinctly?)  For examples:   B=7, P=2, N=22 B=7, P=3, N=12 B=10, P=3, N=18   By way of background, this came from thinking about how any number whose digits sum to a multiple of 3 is also divisible by 3. I can get as far as generalising it to the above question, and I can vaguely see "why" but haven't been able to prove it.  The vaguely why is that each number in B is constructed of multiples of digits in 0..B-1, whether you are summing digits or digits^(0..B-1). (maybe?)  Also thought it might be something to do with how carrying works when you're adding numbers.


Proving that there exists $a\in R$ such that $a \equiv a_k \pmod{I_k}$

Let $I_1,...,I_m$ be ideals of a ring $R$ such that $I_j+\cap_{k\neq j}I_k=R$ for every $j\in\{1,...,m\}$. Then if $a_1,...,a_m\in R$ there exists $a\in R$ such that $a \equiv a_k \pmod{I_k}$ for every $k\in\{1,...,m\}$.   Fix $k\in\{1,...,m\}$. To show $a \equiv a_k \pmod{I_k}$ (for some $a$) is equivalenltly to show that $a_k\in I_k+a$. Since $a_k\in R=I_k+\cap_{t\neq j}I_t$, then $a_k=b_k+c_k$ for some $b_k\in I_k$ and $c_k\in\cap_{t\neq j}I_t$. However, clearly this $c_k$ is not the same for all of the $a_k's$.  Would anyone give me a hint? Thank you.


Why can't electrons fall into the nucleus?

I read a book on pop sci book on quantum mechanics and the author said that electrons do not fall into the nucleus due to quantum mechanics- which principles suggest this (I think it was Heisenberg's Uncertainty and Pauli's Exclusion Principle) and why?  Also, I've heard that if Bohr's planetary model were correct, then electrons would lose energy/momentum and fall in- is this true and again, which physics principles say this?


How to specify Nurbs path vertices in python?

I'm trying to write a script which creates a Nurbs path curve, bevels it, and then stores the location of each vertex/point in that curve. I've been writing it based on the code displayed in the info panel, but it doesn't show what the vertices are supposed to be called - so I can't refer to them in the script.  Update: After following Ratt's links, I modified  for Nurbs Path and am now stuck again, though it's still progress. Below is one version I tried out, but the error message says that Curve has no attribute path_points. Of course it doesn't, because I made that up because I don't know what the Nurbs Path equivalent for bezier_points is.  import bpy import random  def pathPointLoc(cu, typ, points):      for (n) in enumerate(points):         nurb = cu.path_points[n]         print(nurb.location)      return  cu = bpy.data.curves.new("MyCurve", "CURVE") ob = bpy.data.objects.new("MyCurveObject", cu) scn = bpy.context.scene scn.objects.link(ob) scn.objects.active = ob  cu.bevel_object = bpy.data.objects["BezierCircle"] cu.taper_object = bpy.data.objects["BezierCircle"]  pathPointLoc(cu, "NURBS", [(0,0,0,1), (0,0,1,random.randint(1,4)), (0,1,1,1), (1,4,1,1)] )


Finding an explicit map associated with the quotient ring of Gaussian integers

Let $a+bi\in\mathbb{Z}[i]$ with $\gcd(a,b)=1$.  I know that $\mathbb{Z}[i]/\langle a+bi\rangle\cong\mathbb{Z}_{a^{2}+b^{2}}$ by a ring homomorphism $\phi:\mathbb{Z}[i]\to\mathbb{Z}_{a^{2}+b^{2}}$, which maps $x+yi$ to $x-(ab^{-1})y\pmod{a^{2}+b^{2}}$ with $\ker\phi=\langle a+bi\rangle$.  My question is:  Is there a ring homomorphism as above $\phi$ if $\gcd(a,b)=d>1$?  I found the relation $\mathbb{Z}[i]/\langle a+bi\rangle\cong\mathbb{Z}_{d}\times\mathbb{Z}_{(a^{2}+b^{2})/d}$ if $\gcd(a,b)=d>1$.  But, i couldn't find the ring homomorphism between $\mathbb{Z}[i]$ and $\mathbb{Z}_{d}\times\mathbb{Z}_{(a^{2}+b^{2})/d}$ with kernel $\langle a+bi\rangle$  Give some advice! Thank you!


We are selling our house, and I have not noticed any problems myself with our water pressure, but the home inspector's report said--- Water pressure rising and dropping as pump is running and shutting down. This is improper. Water pressure should maintain even pressure after the pressure tank. Recommend plumber to evaluate.   I always thought it was normal for some change...that a pressure switch is set between two readings to come on and off and the pressure in the house would fluctuate between these two pressures.  What am I misunderstanding?


What's a word that describes a useful metaphorical precept? "Money is time" might be an example of a _______. For some reason I am associating these (wrong) words with this one: allegory, syllogy, anecdote—so maybe it is similar to these. "Analogy" might be the closest synonym I have thought of so far, similarly "analogue" almost works. Bruce Lee's "be water" isn't an instruction to literally become water, but a metaphor to encourage flexibility and adaptability. If I said "I am water" I would be using a _________. Somehow I associate this word with sages and wise masters in the mountain. Like _______s could be used for expressing comprehensions about the Dao. "There is no spoon" kind of resonance.


Beamer - align with LHS and RHS replacement

I'm writing an presentation of the project where I took a "standard" equation and modified it slightly. I would like to therefore show this by replacing the standard equation with its modified version.  I've seen a few solutions here, but they all deal with RHS replacements and don't work with the LHS.  I would like (this is merely as an example)  A &= B   to be replaced by   A + C &= B^D  while maintaining the alignment around the equations. I've tried using  \alt<2->{A + C}{A} &= \alt<2->{B^D}{B}  but while \alt solves RHS replacement (especially if used with \phantom to deal with possible vertical erros), with a variable LHS the result still wobbles. How can this be solved?


Conditional branch with \ifinner and Spacing in higher derivative (2 independent questions)

I made some macros shown below, which outputs ordinary/partial derivative. I was checking whether they work as I expected, and found that \dif{y}{x} expands to \tfrac{\difd y}{\difd x} in align environment. I want to use \tfrac only in sentences, not in any display math modes. How should I change the definition in order to expands \dif{y}{x} to \dfrac{\difd y}{\difd x} in align environment, gather environment and so on?  I have another question. I think higher derivatives written with my command (especially partial ones) make a little much space before f. In terms of mathematical typography, which is proper: \frac{〈operator〉^{#1}#2}{〈operator〉#3^{#1}} or \frac{〈operator〉^{#1}\!#2}{〈operator〉#3^{#1}}?    EDIT (June 13, 2015 at 23:28 JST): The first question has been settled.  EDIT (June 15, 2015 at 14:21 JST): As David Carlisle points out, my question was a duplicate of  and commath package should not be used. Then, I have another question. In the linked page, there is a macro named \spx, the definition of which is in the below. Since we can see {^{#1}} in the definition, it seems to be an improved ^. What is the difference between this \spx and \^ and which should I use, "\(p)dif@nth and \@(p)dif" or "\spx without \@ifnextchar"?  My macros  % ----- differential operator ----- \def\difd@rm{\mathop{\mathrm{d}\!}\mathstrut} \def\difd@it{\mathop{d\!}\mathstrut} \def\makedifdrm{\let\difd=\difd@rm} \def\makedifdit{\let\difd=\difd@it} \makedifdit % default setting % % ----- ordinary derivative ----- \def\dif{\@ifnextchar[\dif@nth\@dif} \def\dif@nth[#1]#2#3{     \ifinner     \tfrac{\difd^{#1}#2}{\difd#3^{#1}}     \else     \dfrac{\difd^{#1}#2}{\difd#3^{#1}}     \fi } \def\@dif#1#2{     \ifinner     \tfrac{\difd#1}{\difd#2}     \else     \dfrac{\difd#1}{\difd#2}     \fi } % % ----- partial derivative ----- \def\pdif{\@ifnextchar[\pdif@nth\@pdif} \def\pdif@nth[#1]#2#3{     \ifinner     \tfrac{\partial^{#1}#2}{\partial#3^{#1}}     \else     \dfrac{\partial^{#1}#2}{\partial#3^{#1}}     \fi } \def\@pdif#1#2{     \ifinner     \tfrac{\partial#1}{\partial#2}     \else     \dfrac{\partial#1}{\partial#2}     \fi }   Definition of \spx and its usage  \newcommand{\spx}[1]{%     \if\relax\detokenize{#1}\relax         \expandafter\@gobble     \else         \expandafter\@firstofone     \fi     {^{#1}}% } \newcommand\pd[3][]{\frac{\partial\spx{#1}#2}{\partial#3\spx{#1}}}


why am I getting this error meassage when trying to sign up on Area 51 with OpenID account?

I am trying to make an account by clicking the OpenID button on Area 51 site. I get this instead:  why?


I was wondering if someone could help me clarify something regarding the effect of swapping two rows on the sign of the determinant. I know that if $A$ is an $n\times n$ matrix and $B$ is an $n\times n$ matrix obtained from $A$ by swapping two rows, then $$\det(B)=-\det(A)$$ but I don't know how to prove this. I have been looking for proofs at internet, and read in both in textbooks and lectures notes that are available that this result is very hard to prove and most approaches rely on induction and so was wondering if there is something wrong with using that $\det(AB)=\det(A)\det(B)$ and then writing $B=EA$ where $E$ is an elementary matrix swapping two rows and using this result to get $\det(B)=\det(E)\det(A)=-\det(A)$ (since showing that $\det(E)=-1$ in this case is not that hard).


What is the difference between String.Empty and "" (empty string)?

In .NET, what is the difference between String.Empty and "", and are they interchangable, or is there some underlying reference or Localization issues around equality that String.Empty will ensure are not a problem?


What operation does $\|$ denote in ANSI X9.63 KDF?

Can someone tell me in laymens terms what this is?  $$K_i = \mathrm{Hash}(Z \| \mathit{Counter} \| [\mathit{SharedInfo}])$$  What do the double pipes represent?


Is there any automated way to tightly fit an irregular set (say tree-shaped) of nodes in TikZ?  The standard approach (using fit = (v1) (v2) ... (vk)) uses predefined shapes (eg. circle or rectangle) that might include vertices outside the desired set v1,v2,...,vk.


Ubuntu 20.04 change background to solid colour

There was an option to change background to solid color. However, I notice that that option is no longer there. The only options available are to use existing image or to add picture. Was this setting moved to somewhere else?  Here are some of the option available in the previous version Ubuntu Studio 18.04 64-bit  Look at the solid colour settings there


What does the upgrade button in the advanced warfare building do?

My question is not about the random perks that soldiers get when they are promoted while you have an AWC built (like ).  My question is about the button appearing at the top of the AWC to change the soldier abilities. What does the feature at the top do?


Why can't I delete my answer in the Stack Exchange App?

I recently answered the wrong question, and tried to delete the answer. However, in the "Stack Exchange" App, there is no button for deleting a answer as on the website, also not at the button labeled "More". Why is this?  Here the screenshot from the web version with the "Delete" Button.    Here the mobile version.    And here the "More" Submenu.


Loop over files with specified extensions

I have a situation where I'd like, in bash, to loop over all of the .h and .c files in a directory.  I.e., for file in *.{h,c}; do     ... done  However, if I have a directory that has, for example, no .h files, *.h is one of the "files" iterated over by the for loop.  I've read  and I believe I understand why it is not expanding. So, how should such a loop be carried out?


How to unload an assembly from the primary AppDomain?

I would like to know how to unload an assembly that is loaded into the main AppDomain.  I have the following code:  var assembly = Assembly.LoadFrom( FilePathHere );   I need/want to be able to unload this assembly when I am done.  Thanks for your help.


Apologies if this is a repeat question but,   what formatting commands do i need to use if I want a single digit number to be displayed with a zero in front?  i.e. the number '2' would be displayed as '02'.   [But, I do not want any value above 10 to have extra zeros in front]  cheers


Strengthening Bertrand's postulate using the prime number theorem

In its page on  Wikipedia says      It follows from the prime number theorem that for any real    $\varepsilon >0$ there is an $n_0 > 0$   such that for all $n > n_0$    there is a prime $p $  such that $n < p < ( 1 + ε )n$  .   I need to quote this result for  $\varepsilon = 1/2$. I'd like a reference more formal than Wikipedia.


Calculating area and projection using QGIS

I am facing problem calculating area and projection in general, using QGIS 3.18.3. preface: I am using EPSG: 32643 projected CRS. I aim to compute area and the result is fine correct in this image.  Calculating Area on Bing Map using Measuring tool When I load another layer as shown in image (EPSG: 32643) then the coordinates changes to (lat,long) and the area also is incorrect. I am sure that this layer is in correct EPSG. Not sure why the coordinates displayed does not give Cartesian coordinates.  The coordinates are not in (X,Y) format Attached is the associated information for the layer.  How to resolve this issue and get the coordinates in correct format?


I'm using HTACCESS to force all my pages to redirect to the HTTPS version. However the home page is still able to go to the HTTP version.   I tried 2 examples from this post:   And they work, but not for my home page as I mentioned. HTTPS is redirecting everywhere except the home page.   RewriteCond %{HTTPS} !on RewriteCond %{HTTP_HOST} ^www\.yourdomainhere\.com* RewriteRule ^(.*)$ https://www.yourdomainhere.com/ [L,R=301]   And  RewriteCond %{HTTPS} off RewriteCond %{HTTP:X-Forwarded-Proto} !https RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]   Edit: When I go to the HTTP version of the home page, any time I click a link it redirects to the HTTPS home page instead of the respective link. After that once on the HTTPS home page all links work correctly.


How do we "restore" notepad after crash?

I was running NotePad and Chrome when my computer suddenly shuts down.  After reboot, chrome was able to "restore" itself such that I didn't lose any data.  However, how do we "restore" notepad.exe?


Enable print Background colors and images option in Javascript

Am using window.print() to print the page in jquery. But when am printing the background colors and images are not applying in the print window popup until i check the option is Background color and images for browser print settings.  Is there any way to do handle this from jQuery (by implementing the code) by default?.


What color suns has Superman encountered, and what effects did they have on him?

We all know that under a red sun - like Krypton's - , and a yellow sun - like ours - .    What about other colors?  Which colors has he encountered, and what did each of these stars do to him?


I have a remote Windows 2012R2 server that runs a lot of important stuff. I, stupidly, accidentally, did an ipconfig /release on that server from the other side of the continent. Now that server no longer has an IP address and I have no way of accessing it. There is nobody nearby with physical access.  I have full access to literally everything on that network, but I can not figure out any way to have it refresh its IP address or reboot. I have admin access to:   the DNS server the DHCP server the AD DC server the router guest Hyper-V machines that are still running on that server other random workstations on the domain the MAC address of the server in question   The only thing I don't have is a remote power switch to reset the damned server. I'm travelling for a month and I desperately need this server up, but I seem to have screwed myself so hard with this that there is no recovery. Does anyone have any ideas of any way to force this thing to renew its IP address or reboot?  This question has been marked as a duplicate, but it really is not. The other question is about steps to prevent situations like the one I am in to happen. But my question is, once I have lost contact with my remote machine, is there anything that can be done, given the considerable amount of information I have about the LAN of the remote machine? Is there for instance a generalization of a magic packet technology which can restart a machine, or something similar?   In other words: given that I am already stuck, is waiting my only option?  UPDATE: turns out that the ipconfig /release only released the IPv4 address, but it still had an IPv6 address. Once I found that from looking through the router logs, I was able to reboot it using that and the shutdown -r -m \\IPv6Address command.    EDITOR'S NOTE (Scott): Note that this solution (and the others suggested in the comments below) is irrelevant and not applicable to the question of which this one is allegedly a duplicate.


How do I get the NOT, NAND, NOR and XNOR logic gates to work?

The Contraptions Workshop DLC introduced a range of "Advanced switches". Playing around with these, I found the AND, OR, and XOR gates to work exactly as expected, but not the NOT, NAND, NOR and XNOR gates. Here's a fairly long explanation of what I've tried to get them to work:     This was my first attempt at using a NAND gate (which should be transmitting power unless both inputs are turned on):    Reading up, I discovered that the N- gates "only transmit power if their inputs are connected directly to the output of other logic gates."  My next attempt, which I expected to work based on the information above, was to have an AND gate feeding into the NOT gate as such:    But, despite the NOT gate's input coming directly from the AND gate, the NOT gate did not turn on.   The problem seemed to be that:   if the previous gate transferred power as its conditions were met, the NOT gate would invert the power and stay off.  if the previous gate's conditions were not met, no power would pass onto the NOT gate for it to be able to turn on the light.   As a final attempt, I ran the AND's output into a NAND gate instead, which I can have one input powered whilst still having it (hopefully) turn on:    So, from what I understand:   The NAND gate should be receiving power from the generator, in order for it to be able to turn on if its conditions are met. The AND gate is not transmitting power, so the NAND gate should have its conditions met. The light is still not turning on.     My question is, how do I get these N- gates to function? What is the logic behind when they transmit power? Perhaps I'm making an obvious mistake here like wiring them wrong, or have a misunderstanding of how these gates are intended to work.


What are the differences between Pandemic and Pandemic 2013?

I have seen that there is a new edition of Pandemic for 2013.  What are the differences between Pandemic and the "New Challenge" version?  Can I convert my original edition to use any of the new rules?  Is the original Pandemic compatible with the 2013 expansion packs?


Redirecting Standard Output And Standard Error to One File

I have come to understand that we have two methods of redirecting both stdout and stderr to the same file. The first method is: ls -l /bin > ls-output.txt 2>&1 As the author of  states: Using this method, we perform 2 redirections, first we redirect stdout to ls-output.txt and then we redirect stderr(file descriptor 2) to stdout(using file descriptor 1).  The order of redirections is important.  ls -l /bin 2>&1 >ls-output.txt would redirect stderr to screen.  My question is: Like in many programming languages, was the command designed with some associativity and precedence rules in mind and how do we read the command while writing it on screen? and what is the sequence of the backend execution of the command?  Here's what i think about the execution sequence: First, the command ls -l /bin sends its output to stdout and error to stderr(any one of those). Then, the stderr is redirected to stdout.(if there is any error, eg: if ls -l /binn is used) Now, the stdout stream contains one of the two(either output or error) which it then redirects to the file ls-output.txt


Why can't I drive this Tapcon into concrete?

I'm trying to drive a 2 1/2" long 3/16" diameter Tapcon into a 50 year-old concrete slab/subfloor to attach a new toilet flange. The instructions on the case of Tapcons said to drill a hole in the concrete with a 5/32" bit. Did that with a Bosch Bulldog SDS; that part was easy. Next the instructions say to drive the screw in with a #2 Phillips head bit. So I put a new #2 bit in my Bosch 1191VSR drill and switch it into hammer drill mode. But I can only get the screw about 1/2" in and then it just stops turning, and the bit comes out of the screw head and begins to strip the screw. I feel like there's some technique I'm missing, or else my bits are defective. But I tried two different ones, and the same thing happened each time. Or maybe it's my drill? From stationary, I can not get the screw turning. I need to back it out a bit and start again. It feels like the torque is too low at slow speeds. What am I doing wrong?


Who is at the highest level of command at Ubuntu?

Just like my question asks - who is at the head of Ubuntu and how do I contact them?


How do i solve this limit: $\lim_{x\to 0}{x-\sin(\sin(...(\sin x)))\over x^{3}}$

I have the next limit : $$\large \lim_{x\to 0}{x-\sin(\sin(\overbrace {\cdot \ \cdot \ \cdot }^n(\sin(x))\overbrace {\cdot \ \cdot \ \cdot }^n))\over x^{3}}$$ $\sin(\sin(...(\sin(x))...))$-is n times. I have no idea. Someone can help me? Thank you!


How to determine which version of Ubuntu desktop is installed

What command is used to determine which version of Ubuntu desktop is installed?


The Tuesday Birthday Problem - why does the probability change when the father specifies the birthday of a son?

I've most recently read about the  via twitter and I, as probably most other people, was sure that the probability has to be 1/2. After having read through a lot of solutions which were not identical at all, I've come to the conclusion that $P = \frac{13}{27}$ sounds the most reasonable. The corresponding argument was as follows: Say the older child is the boy born on Tuesday. Then, if the younger child is female, there are seven possibilities and analogous if the younger child is male. In case the younger child is the boy born on Tuesday, for an older daughter, again there are seven possibilities, but for an older son, there are only six, because the case that the older son was born on Tuesday has already been counted. Thus, $$P = \frac{6+7}{6+7+7+7} = \frac{13}{27}. $$ My first question is: Is this the correct solution? I've found other websites giving different solutions, however I could never agree with any of those. In case this is the correct solution: Why does the probability change when the father specifies the birthday of a son? (does it actually change? A lot of answers/posts stated that the statement does matter) What I mean is: It is clear that (in case he has a son) his son is born on some day of the week. I could replace Tuesday with any day of the week and the probability would be the same. Say the father would have stated:  I have two children. (At least) One of them is a son.  Then, without loss of generality, we could say that this son is born on a Tuesday and again we would have $P = \frac{13}{27}$. But looking at an equivalent (?) problem, we get a completely different probability: Let's toss two coins consecutively and say heads is equivalent to "son" and tails to "daughter". Then, if we know that we tossed at least one heads, if it was the first tossed coin, the probability for another heads is 1/2. If the second coin was heads, then we can only take the case in account where the first coin was tails. So the probability for two heads is $P = \frac{1}{3}$. So my second (actually third) question is: Where did I go wrong? Lastly I want to ask (as my knowledge in probability/statistics is limited to what I have been taught in high school) whether the argument which gives $P=\frac{13}{27}$ for the original Tuesday Birthday Problem already takes the possibility of twins in consideration. Can it be regarded as a special case of two boys both born on Tuesday (I ask because in every argument leading to this probability there was a distinction between older child = boy vs. younger child = boy)? Thank you very much in advance for any answer.


Under the Login's page where it shows the social networks you can login with,  How does one delete those ?


Are quotients of a PID by non-prime ideals ever a PID?

I've proved that any quotient of a PID by a prime ideal is again a PID as an exercise, and got into thinking about quotients by non-prime ideals. Are they ever a PID? More concretely, say $R$ is a PID and $I$ is an ideal of $R$ which is not prime. Is $R/I$ ever a PID? Testing with $R=\mathbb{Z}$ and $I=4\mathbb{Z}$ this isn't the case, since $\mathbb{Z}/4\mathbb{Z}$ isn't even an integral domain (and by definition cannot be a proper PID). In rough terms the proof of the earlier statement follows: Let $R$ be a PID and let $P$ be a prime ideal. If $P$ is the zero ideal, then $R/P$ is isomorphic to $R$ and thus a PID. If $P$ is a nonzero prime ideal of $R$ it must be maximal. Thus $R/P$ is a field, which is trivially a PID. I have a hard time imagining this proof is "reversible", since there should be more cases of $R/P$ being a PID but no field. Instead I got about as far as this: Suppose $I$ is an non-prime ideal of the PID $R$. Thus there must exists some $(ab)\in I$ such that $a\notin I$ and $b\notin I$. Since $R$ contains no zero divisors, we must have that $a$ and $b$ are nonzero. Thus $R/I$ contains elements $a+I$ and $b+I$. However $$(a+I)(b+I)=(ab)+I=I$$ since $(ab)\in I$. Thus $R/I$ contains zero divisors, and can't be a PID. Is this correct? How could one think otherwise? Thanks in advance!


Question regarding to canonical factorization of $n!$?

The problem is: write 101! in canonical form. I solved it by try to find the highest power of each factor prime factor less than 101. When running factor() function using TI-89, I realized that the power of each prime factor decrease.  So I guess I have two questions:   How can write this idea using Math notation? I'm think of $\prod$ and $\sum$ notation, but I don't know how to express this idea. As a programmer, I want to write a program to handle this situation. I could check every prime factor, however, I'm curious about the decrease of these prime factor. Is there any pattern behind the scene? If there is, it would increase my algorithm a bit.      Update Based on Aryabhata's answer, my attempt is: $$\prod_{i=1}^{\infty}p_i^{\sum_{k=1}^{\infty} \left\lfloor\frac{n}{p^k}\right\rfloor}$$  Does it make sense?    Thanks.


Function $f: \mathbb{R} \to \mathbb{R}$ that takes each value in $\mathbb{R}$ three times

Does there exist a function $f: \mathbb{R} \to \mathbb{R}$ that takes each value in $\mathbb{R}$ three times? If not, how could I prove that such a function does not exist?


How Can I Only Allow Uniform Resizing in a WPF Window?

I don't want my window to be resized either "only horizontally" or "only vertically." Is there a property I can set on my window that can enforce this, or is there a nifty code-behind trick I can use?


Determine hyperlink to display based on client's browser

Is it possible to display a different hyperlink based on whether user is viewing the page from which the link is on in IE, Edge, or Chrome? Use case:  We are using a vendor-based app that works well in Chrome and Edge but not so well in IE.  We'd like to detect which browser the user is hitting the link from and, IF using IE, use a link that has the "microsoft-edge..." prefix on the URL. ELSE, use a link without that prefix. I'm guessing there is some sort of javascript that could do this but not sure and not a super-techy user.


Why superconductivity at room temperature is SO important that the physics world is running behind it like AI in computer science field?


Find all integral solutions  $x^3-9=y^2$  I tried many times but still no idea how to solve it. I will be grateful for any help.


What is the name of this big plant with a purple trunk and green to purple berries?

I have photographed the following plant in our garden in Pittsburgh, PA.  Do you know the name of the plant?


How to pull out XML object within JSON, then attach it to the JSON it's a part of?

{             "Name": "John",             "Email": "John123@gmail.com",             "XMLObj": "<Root><Organization xml:space=\"preserve\"><Language><string>EN</string></Language><Description><string /></Description><TypeCode><string>Type 123</string></TypeCode></Organization></Root>"  }  I know how to deserialize the JSON into an object. I can even get the XML data into its own field that way, however what I'd like to do is convert the XMLObj into elements upon deserializing that tie to Name and Email fields. I can ignore <Root><Organization xml:space=\"preserve\"> and the ending </Organization> and </Root> tags. And a field is just "</string>" when it is empty. I need a function parse the XML Object, convert to JSON, and keep it with the corresponding data to that record. So, result would look like this: {    "Name":"John",    "Email":"John123@gmail.com",    "Language":"EN",    "Description":"",    "TypeCode":"123" }  How do I accomplish this?


I looked it up. It means "while" and is used mostly in Britain. Could anyone explain to me how to use it?


What Nvidia driver is needed for a server?

I'm trying to run a server on Ubuntu 20.04 and need nvidia-docker for that I need a nvidia driver however the nvidia-driver-[version]-server and nvidia-driver-[version] packages both seem to install a desktop env X11. Did I miss something in the install or do I need to install in some other way like via the .run package. I found this  but there is not a real answer to the question. Edit: This Question is answered here:


I'm currently trying to reference my dissertation. I have created a file called reference.bib and have used the tools in bibtex to create a list of sources that I have used.  I have tried to integrate these references into my work (written in texmaker) but the reference is coming up like this (??) and when I put this command,   \bibliographystyle{plain}  \bibliography{reference}  \end{document}  nothing is showing up? Can anyone explain what I'm doing wrong - this is the first time I've used tex? Thank you


How can I activate a guard dog on cod ghosts?

How do I activate a guard dog on cod ghosts?


After a working break of a couple of weeks, I start do work on my last project. But I can not edit my postgis-layers anymore! Its possible that I did several system-upgrades, and maybe there was also a postgis-update, and I updated to QGIS 2.12 but I can not exactly tell, what could be the reason.  I have the right ownership of the table and all Privileges (arwdDxt*)  As you can see in the editing-bar - I can not make any changes to the layer


Restore a SQL Server 2012 backup file in SQL Server 2016/2014

I have SQL Server 2012 backup files and want to restore these to SQL Server 2016/2014. Will it work?  I need to find this out before I uninstall SQL Server 2012.


After I posted this question, I found a similar post that seemed to answer it: . I'll leave this in place for now, as I am not sure how to mark my own question as a duplicate  In attempting to debug a SOQL query error, I encountered a strange behavior with Database.query and bind variables. Specifically, when I run this code:  String userQuery = 'SELECT Id FROM User'; if (true) {     List<String> firstNames = new List<String>{'James','Joe'};     userQuery += ' WHERE FirstName IN :firstNames'; } Database.query(userQuery);   the Database.query statement executes with no errors, despite the fact that the variable firstNames does not exist in its context. However, when I add an else clause:  String userQuery = 'SELECT Id FROM User'; if (true) {     List<String> firstNames = new List<String>{'James','Joe'};     userQuery += ' WHERE FirstName IN :firstNames'; } else {     List<String> firstNames; } Database.query(userQuery);   I receive a null object reference exception. It seems like Salesforce is checking to see if the variable is only declared once beforehand and, if so, uses its value in the context it was declared. This seems strange to me, so I was wondering if anybody here has any insight into what is going on under the hood.


Remove mounted drive icon from Ubuntu dock in Ubuntu 19.10 Eoan Ermine

When you mount a drive or have Google account integration with "Files" application on in Ubuntu 19.10, an icon appears in the dock.   How do I change this behavior? I don't want any of these icons to show up on the dock.


Let $X \subset \mathbb{R^m}$. Show that if any continuous function of real value and defined in $X$ reaches a value maximum, then $X$ is compact.  I have seen several proofs of this exercise, but using more complex topics such as the Tietze Extension theorem and other answers I have seen prove the contrapositive. Can I make a simpler demonstration using only real analysis elements? And if that is possible, what would a demonstration be like for this exercise?


Which version of Ubuntu can I use on an old laptop?

I have a old laptop with the following specifications:  AMD Brazos Dual core 1Ghz 4GB ram  Will my laptop be able to run Ubuntu? If yes then which version will I need to install?


I was watching the movie 21 yesterday, and in the first 15 minutes or so the main character is in a classroom, being asked a "trick" question (in the sense that the teacher believes that he'll get the wrong answer) which revolves around theoretical probability.  The question goes a little something like this (I'm paraphrasing, but the numbers are all exact):  You're on a game show, and you're given three doors. Behind one of the doors is a brand new car, behind the other two are donkeys. With each door you have a $1/3$ chance of winning. Which door would you pick?  The character picks A, as the odds are all equally in his favor.  The teacher then opens door C, revealing a donkey to be behind there, and asks him if he would like to change his choice. At this point he also explains that most people change their choices out of fear; paranoia; emotion and such.  The character does change his answer to B, but because (according to the movie), the odds are now in favor of door B with a $1/3$ chance of winning if door A is picked and $2/3$ if door B is picked.  What I don't understand is how removing the final door increases the odds of winning if door B is picked only. Surely the split should be 50/50 now, as removal of the final door tells you nothing about the first two?  I assume that I'm wrong; as I'd really like to think that they wouldn't make a movie that's so mathematically incorrect, but I just can't seem to understand why this is the case.  So, if anyone could tell me whether I'm right; or if not explain why, I would be extremely grateful.


How to take a white product on a white background?

I can't get a decent white background on my product shots  Here are few samples       After editing in Photoshop


I've 3D tracked a scene and the positional tracking is amazing my model is staying exactly where it should be, but then my camera rotates, and for whatever reason instead of the model rotating it just slides sideways. I've set the y-axis, scale, floor, origin and wall and I have at least 20 trackers. What am I doing wrong?


As is well known pretty much all integration rules come from differentiation rule, so the substitution rule comes from the chain rule, and the integration by parts comes from the product rule, indeed $$(uv)'=uv'+vu'\implies\int uv'dx=uv-\int vu'dx.$$ But I never saw a rule that used the Over Rule $$(u/v)'=\frac{u'v-v'u}{v^2}=\frac{u'v}{v^2}-\frac{v'u}{v^2}=\frac{u'}{v}-\frac{uv'}{v^2}\implies \int \frac{u'}{v}dx=\frac uv+\int\frac{uv'}{v^2}dx$$ Is this like a new rule or does it already exist?


Repost it with a minimal working example for the amsmath must be loaded earlier than mathspec problem

See the following mwe:  \documentclass{article} \usepackage{amsmath} \usepackage{mathspec} \usepackage{unicode-math}  \begin{document} \begin{equation*}   1 + 2 = 3  \end{equation*} \end{document}   Run the above code with xelatex will meet the following error:  ! Package mathspec Error: `amsmath' must be loaded earlier than `mathspec'.  See the mathspec package documentation for explanation. Type  H <return>  for immediate help.  ...                                                l.54 \RequirePackage{amsmath}  ?    $ xelatex --version XeTeX 3.14159265-2.6-0.999991 (TeX Live 2019)  Regards