My system partially freezes in one type of gnome session and not another

[Edit] Complete restatement of the problem: My system freezes when I plug a memory device into a USB port. I have just upgraded from 18.04 LTS to 20.04 LTS.  All of this hardware has worked without issue for months before the upgrade. Symptoms of the freeze:  Mouse cursor will move, cannot pick anything, no scrolling or right click.  Keyboard doesn't respond.  Alt-F2 will not bring up a terminal, cntrl-alt-T will not bring up a terminal.  sysreq-alt-R-E-I-S-U-B will reboot.  control-alt-F1 will log the user out.  During a freeze, $top stops displaying new information.  The clock freezes at the current time. The freeze can be reliably initiated by: plugging any of several thumbdrives into any USB port plugging a particular microSD memory card into a USB memory card reader The freeze does not initiate when A Logitech Unifying reciever plugged into USB seems to have no problems. Plugging one of several different thumb drives into the USB ports. plugging a different microSD card into a memory card reader. I have two users set up.  One of them is on "Desktop: Gnome" and "Session: Gnome-XORG", and has the freeze problem. The other is on "Desktop: XDG_CURRENT_DESKTOP" and "Session: Ubuntu".  This user does not experience the freeze problem. I'm into stuff I don't really understand here so I don't know what the impact of that means. I have: Uninstalled Nautilus, confirmed the problem happens when Nautilus isn't installed.  Re-installed after sudo apt update and sudo apt upgrade Removed Radeon video card and installed an Nvidia card, problem still occurs Removed the memory sticks, tried installing them one at a time, problem still occurs Done a BIOS memory and hardware test with no problems found. [EDIT] I have Universe, Multiverse, and Restricted repositories enabled. So far all hardware tests and memory tests have checked out OK. Here is some more information that may or may not be relevant: sudo dmidecode -s bios-version A12 ~$ free -h               total        used        free      shared  buff/cache   available  Mem:           31Gi       3.1Gi        11Gi        73Mi        16Gi        27Gi  Swap:         2.0Gi          0B       2.0Gi ~$ ls -al /usr/share/gnome-shell/extensions total 20 drwxr-xr-x 5 root root 4096 Sep 29 12:56 .  drwxr-xr-x 7 root root 4096 Sep 29 12:59 ..  drwxr-xr-x 2 root root 4096 Sep 29 12:56 desktop-icons@csoriano  drwxr-xr-x 3 root root 4096 Sep 29 11:51 ubuntu-appindicators@ubuntu.com  drwxr-xr-x 3 root root 4096 Sep 29 11:51 ubuntu-dock@ubuntu.com  ~$ lspci | grep VGA Thrice 03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] R600 [Radeon HD 2900 PRO/XT]


What tests, certifications and labels do I need on my new electronic gadget?

I have designed a VERY basic lighting gadget -- it's basically a flashlight. It turns on and off with a switch and is powered by a rechargeable Lithium Ion Battery via USB cable. It consists of LED's on a PCB and has a switch to stop charging in order to keep the battery from overheating.   I know I don't need FCC as there is no radio transmission. I know I will need CE for Europe, but am uncertain about what I need for the USA and Canada? I have spoken with UL and gotten a quote, but they won't tell me what exactly I need until I pay and it's extremely expensive.


How can I find out if my installed OS is a 32-bit or a 64-bit?

I am a newbie so maybe my question is not so shiny. I wont to install something (virtualbox) but I have to chose between the 32-bit version and the 64-bit version according to my OS. Problem is that I don't know/don't remember what type of OS it is from that point of view.   So my question is the following: Is there any fast and easy way (for a beginner like me) to find out what kind of OS is using? Thank you!


What is the differance between Linking and Appending an external blend?

What is the differance between Linked and Appended data from external .blend files?


I have a file that is compressed.  I used a program to find out what kind of file it is and it says that it's a gpg file.  How do you uncompress a gpg file?


Why didn't this line of code update the object?

Given that there is a class called Point with a float x and  float y component.  class Point {     public double x;     public double y;     public Point(double x, double y)     {         this.x = x;         this.y = y;     }     public Point()     {         x = y = 0;     }     public override string ToString()     {         return string.Format("({0:F2},{1:F2})", x, y);     } }   Why in the mystery1 function didn't the point p1 get updated to be (11.00, 11.00) since p.x is 11 from the first line?  {     Point p1 = new Point(11, 22);     Point p2 = p1;     int n1 = 33;     int n2 = n1;      mystery1(p1, n1);     Console.WriteLine("n1 = {0}, n2 = {1}", n1, n2);     Console.WriteLine("p1 = {0}, p2 = {1}", p1, p2);      mystery2(p2, n2);     Console.WriteLine("n1 = {0}, n2 = {1}", n1, n2);     Console.WriteLine("p1 = {0}, p2 = {1}", p1, p2); }  static void mystery1(Point p, int n) {     n = (int)p.x;     p = new Point(n, n); }  static void mystery2(Point p, int n) {     p.x = 77;     n = 88; }


I can't swim here. I am not able to swim here. I am unable to swim here.  I think these three sentences seem exactly simlilar. Is there any difference?


Is there any way to save a raw image from my phone's camera?

I have an Android mobile with a 5MP camera. Is there any way to save raw images (similar to Canon CR2, Nikon NEF, etc.) from my Android device?


When "maximise" doesn't mean "maximise" None of the maximise commands provide maximisation to fill the whole screen. When you have Dock not autohidden, then they only go up to the boundary of the dock. When you have Dock hidden they go near the edge of the screen but a few pixels short meaning you can see other apps and the desktop behind them. User error? First I thought it was because I was using third party apps to maximise. I tested in Sizeup, Moom and BetterTouchTools. But it turns out the native maximisation is broken to begin with. Nothing will let a window automatically maximise to the full screen size, there will always be some pixels left over wherever the Dock is even if you have it hidden and at the smallest size setting. Non-solutions At first I thought  was a duplicate and would provide my answer, but alas it doesn't. It is, of course, possible to move the window behind the dock protected pixels then resize it from the opposite side. But this has to be done for every window manually each time. Is there any way to make it so that maximise fully maximises across the entire screen? I really hope there is! Bonus points if anyone can find software that will allow keyboard shortcuts to do a different action moving a window dependant on where it currently is. e.g. in Windows 7 and above you can hit Windows+Left over and over and the window will first maximise half left, then maximise half right on the display to the left of the current display, then to the left of that display and so on. Likewise, Windows+Down will first restore a window, then minimise. Update It's now been most of a year since I posted this question and despite extensive additional searching as well up updating to El Capitan, this OS X bug hasn't been fixed and I haven't been able to find any tool that offers a working solution. Any ideas at all?! Update 2 This has been marked as closed since a similar question has already got an answer - forgive, I can't see the link to this answer and have been unable to find it myself. Update 3 I've now been linked to the "answer" which says that it's not possible without disabling the Dock, Mission Control and the application switcher i.e. making crippling the core multitasking capabilities of the OS (and making it unusuable for me). I can say clearly that cutting off your nose to spite your face is not the sort of solution I was after. The "reason" given is not a) necessary as claimed by any reasoning I can come up with or b) relevant to required a border of clear pixels after maximising, c) true in any way as you can manually move windows behind the border and still have a fully-functioning Dock. I don't understand why this is being marked as answered based on the other question since that's not really an answer even at a stretch - all the "answerer" says is they don't know of any reasonable solution. Since it's possible manually, one would be inclined to believe it's technically possible. And there's no sound reason for "maximised" programs to behave in this way, again this is demontrabl


Primitive Function and Intermediate Value Theorem

This question's my profesors. I know, if function $f$ has a primitive in the range $[a, b]$, then function $f$ satisfies the intermediate value theorem in the interval $[a, b]$. But is the opposite true? Can you help me? "If function $f$ satisfies the intermediate value theorem in the interval $[a, b]$, then function $f$ has a primitive in the range $[a, b].$" Proposition is true? Why is true? Why is false?


Troubleshooting joining a group in Mint in VirtualBox

I am trying to join my user to the vboxsf group to access a VirtualBox shared folder from inside my Linux Mint virtual machine. However I'm encountering a problem that I can't troubleshoot.   I've edited /etc/groups to add my user to the appropriate group.   user394-VirtualBox media # grep user394 /etc/group ... vboxsf:x:108:user394   But I can't access a directory that that group supposedly has permissions to:  user394@user394-VirtualBox /media $ cd sf_Dropbox/ bash: cd: sf_Dropbox/: Permission denied  user394@user394-VirtualBox /media $ ls -lha total 40K drwxr-xr-x   5 root root   4.0K Jul 13 12:51 . drwxr-xr-x  23 root root   4.0K Mar 16 22:04 .. drwxrwx---   1 root vboxsf  28K Jul 13 12:08 sf_Dropbox drwxrwx---   1 root vboxsf    0 Jul 13 12:16 sf_mint-shared-folder   The command groups shows that I'm not a member, yet groups {user} and id seem to indicate that I am:  user394@user394-VirtualBox /media $ groups user394 adm cdrom sudo dip www-data plugdev lpadmin sambashare user394@user394-VirtualBox /media $ id uid=1000(user394) gid=1000(user394) groups=1000(user394),4(adm),24(cdrom),27(sudo),30(dip),33(www-data),46(plugdev),112(lpadmin),118(sambashare) user394@user394-VirtualBox /media $ groups user394 user394 : user394 adm cdrom sudo dip www-data plugdev vboxsf lpadmin sambashare   How can I properly join this group and access these directories?


Prove this inequality having a recursion of square roots?

Let $n \geq 2$. I need to show that $\sqrt{2\sqrt{3\sqrt{4...\sqrt{n}}}} < 3$ for all $n \in \mathbb{N}$. I tried using logarithms and got arithmetico-geometric like series, except for the $\log$ operator. Can't think of a useful inductive argument here.


Simplifying $\binom{n}{0} - \binom{n}{1} + \binom{n}{2} - \binom{n}{3} + \cdots + (-1)^n \binom{n}{n}$

Simplify the expression    $$\binom{n}{0} - \binom{n}{1} + \binom{n}{2} - \binom{n}{3} + \cdots + (-1)^n \binom{n}{n}$$    for positive $n$.   I tried to find a one-to-one correspondence but I'm stuck.  Can anyone help?


Do magic item spells require concentration?

Do magic items that cast a magic effect such as a ring of invisibility require the user to maintain concentration as if they had cast the spell?  Is this also the case if the item casting the spell is an artifact?   If the item is intelligent can it concentrate on the spell?


Can I create an SSH user which can access only certain directory?

I have a Virtual Private Server which I can connect to using SSH with my root account, being able to execute any linux command and access all the disk area, obviously.  I would like to create another user account, which would be able to access this server using SSH too, but only to a certain directory, for example /var/www/example.com/  For example, imagine this user has a HUGE error.log file (500 MB) located in /var/www/example.com/logs/error.log When accessing this file using FTP, this user needs to download 500 MB to view the last lines of the log, but I'd like him to be able to execute something like this:  tail error.log  Therefore I need him to be able to access the server using SSH, but I don't want to grant him access to all server areas.  How can I do this?


How to modify existing, unpushed commit messages?

I wrote the wrong thing in a commit message.  How can I change the message? The commit has not been pushed yet.


I have a map of   Map<String,Decimal> test = new Map<String,Decimal>();   In this map i am adding values like classname and codepercentagecovered and iterating over the map and creating dynamic table and adding them.        test.put('testclass',0);          test.put('zclass2',30);         test.put('aclass1',0);       If(test!=null && !test.isEmpty()){                 for(String s : test.keySet()){                     strText += '
' + s + '	';                     strText += '' + test.get(s) + '%'+'	';                  }               }   The table looks like this   testclass            0 zclass1              30 aclass1              0   How i can sort the map values so that it starts from 0 and then 30 at last.


How to get the source file name and the line number of a type member?

Considering that the debug data file is available (PDB) and by using either System.Reflection or another similar framework such as Mono.Cecil, how to retrieve programmatically the source file name and the line number where a type or a member of a type is declared.  For example, let's say you have compiled this file into an assembly:  C:\MyProject\Foo.cs  1:    public class Foo 2:    { 3:       public string SayHello() 4:       { 5:           return "Hello"; 6:       } 7:    }   How to do something like:  MethodInfo methodInfo = typeof(Foo).GetMethod("SayHello"); string sourceFileName = methodInfo.GetSourceFile(); // ?? Does not exist! int sourceLineNumber = methodInfo.GetLineNumber(); // ?? Does not exist!   sourceFileName would contain "C:\MyProject\Foo.cs" and sourceLineNumber be equal to 3.  Update: System.Diagnostics.StackFrame is indeed able to get that information, but only in the scope of current executing call stack. It means that the method must be invoked first. I would like to get the same info, but without invoking the type member.


I have downloaded Ubuntu as I would like to make a boot drive on my usb but I can’t get the iso file

Every time I download it it just downloads a winrar package which extracts into the contents of the iso file, I cannot seem to actually download the iso file itself, I am downloading it from Ubuntu’s official website, I want to get the Ubuntu studio flavour I have been searching for hours and have gotten nowhere, people online say that it is the iso file but I even followed their links and it downloaded the same thing, the rufus program doesn’t pick up any iso files anywhere on my device, even after extraction. I can’t see a way around this, please help


Legal to publish books based on SE questions & answers?

One of my SE comrades stumbled across a book on Amazon which seems to basically be a direct ripoff of questions & answers posted to Stack Exchange. Upon further investigation, it appears that the "author" is actually trying to make a career out of this...    Seems pretty shady to me, so I was wondering: is this even legal?    I've seen a , but I don't believe this is a dupe. That thread is asking about royalties for using specific questions/answers, whereas this guy on Amazon seems to be wholesale copying entire branches of Stack Exchange.


glBufferData not working outside main function

I have a problem that I don't know how to solve. I am using C++ with GLEW and GLFW, I initialise GLFW, create the window, make the window the current context, then I initialise GLEW. All of this happens on the main function. The problem appears when the code to create the VAO and the VBO is organised in methods, in classes, I see that the VAO is generated, that the VBO is generated, but when the data is sent to the GPU, using glBufferData, it does not work. If I take this piece of code and move it in the main function, everything works just fine, but outside it, it does not work. This code works perfectly on the main function, but if I move it in other functions, just to make things clear, it stops working. So I think the problem is somehow related with that context. I make the window, the current context, on the main function. Any Idea? // MAIN FUNCTION  unsigned int vaoID; glGenVertexArrays(1, &vaoID); glBindVertexArray(vaoID);  // if I move this code in a method of a class and pass the vao, to bind it again //there it does not work // if I leave it here, like this, it works unsigned int vboID; unsigned int attribPointer = 0; glGenBuffers(1, &vboID); glBindBuffer(GL_ARRAY_BUFFER, vboID); glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); glVertexAttribPointer(attribPointer, 3, GL_FLOAT, GL_FALSE, 0, 0); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindVertexArray(0);  // the drawing part, just the idea, it's in a while, of course. glBindVertexArray(vaoID); glEnableVertexAttribArray(attribPointer); glDrawArrays(GL_TRIANGLES, 0, 6);  glDisableVertexAttribArray(attribPointer); glBindVertexArray(0);  //if I move it here, it's dead void storeDataInAttributeList(int attributeNumber, float data[], int vaoID)     {         glBindVertexArray(vaoID);         unsigned int vboID;         glGenBuffers(1, &vboID);         vbos.push_back(vboID);         glBindBuffer(GL_ARRAY_BUFFER, vboID);         glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW);         glVertexAttribPointer(attributeNumber, 3, GL_FLOAT, GL_FALSE, 0, 0);         glBindBuffer(GL_ARRAY_BUFFER, 0);      }


From one version of Axiom of Choice to another

A version of the axiom of choice is:  Every set $S$ has a choice function $f$, where $f$ is a function from the set of all nonempty subsets of $S$ to $S$, s.t. $f(A)\in  A$ for nonempty $A$.  I'm trying to prove that this is equivalent to:  The product of a family of nonempty sets indexed by a nonempty set is nonempty.  But I'm not sure if I'm correct: Suppose we have a choice function on every set, then for every such product, let $S$ be the set of all nonempty subsets of the union of all indexed sets (which I've assumed to be a set, some shaky ground here) then let $f$ be the choice function on this union, then the product has at least one element which is $(f(A_i),,,,)$ where $i$ are the indices.


Are there any scientifically based predictions or theories of future human evolution?

Reading this  of the stack exchange got me thinking. I believe human evolution is an ongoing process and will not stop. Are there any predictions/theories about the phenotypes and genotypes of humans in the future? and how they may differ in a few thousand years compared to present day?  I remember watching a youtube video and in the video the user predicts that there will be two branches of human species; a short dwarf like species and a much taller species. I'm still skeptical about this claim. Is there any evidence to back it up?  One could argue that modern medicine is preventing natural selection. How will this effect human evolution?


ecrypted home partition .Private folder missing

I have ubuntu installed on a Dell laptop. It was in sleep mode (lid closed) and with low battery charge. When I open it the login screen appear and the laptop turned of (with no power).  After I plug it in and power it on I could not login... looking in forum I found some cases so I block auto mount in fstab, restarted the SO, login from terminal (CTRL +F1) and run   e2fsck -yc /dev/sda2    75/0/0 erros founded and "fixed".  Now, when I mount the sda2 partition (sudo mount /dev/sda2 /home) I see Access-Your-Private-Data.desktop and README.txt like spected but the .Private shortcut that points to /home/.ecryptfs/username/.Private is broken... there is no /home/.ecryptfs folder...   df -h show that only 7Gb of 800Gb is free... so my files is there!  and the lost+found folder is full of files and folders named with #somenumber  the ecryptfs-recover-private says:  find: ‘/run/user/112/gvfs’: Permission denied   and find nothing...  any sugestions?  EDITED:  Thanks guys for the quick return. So... I created another user using only the sda1 partition and the automount still disabled in /etc/fstab  UUID=cf40cc55-18f3-4a20-a5ab-901522d6d383   /   ext4    errors=remount-ro   0       1 #UUID=6ef2647e-1847-4e0e-9a2a-c95ff78a89e4  /home   ext4    defaults        0       2 #/swapfile                      none    swap    sw      0   0   ...now I can login with the new user:  What is weird   I have face this problem before, and recover worked well using ecryptfs-recover-private command like metioned by Seppo Erviälä  , but now I see that the .Private shortcut points to nothing...  I logged in with the new user and mounted the partition (just clcking in taskbar shortcut). Now sda2 is mounted in /media/bocapio/6ef2647e-1847-4e0e-9a2a-c95ff78a89e4   listing content of this folder     ls -lah   drwxr-xr-x    8 root    root  4,0K Abr 27 18:53 . drwxr-x---+   3 root    root  4,0K Abr 28 18:24 .. drwx------  164 root    root   16K Set  3  2014 lost+found dr-x------    2 lucas   lucas 4,0K Abr 25 18:00 lucas   but there is no .Private folder!  sudo find /media -type d -name .Private returns nothig! sudo find /media -type d -name .ecryptfs returns nothing!  I'm afraid that the .Private folder was moved to lost+found folder...   sorry for the first poor explanation...


Clarification about ETFs and Index Funds with regards to sell operations

I'm trying to understand the difference ETFs and index funds in terms of selling them (if you want to get rid off them quickly for any reason).  As far as I understand, if you want to sell an index fund you know 100% sure that you will sell it the same day to request it, when the market closes (so you might need to wait some hours, with all the fluctuation that might involve).  On the other hand, ETFs are traded like stocks, so if you want to sell it you might find that no one wants to buy it. If you need to sell your ETF fast because of an emergency, you might have problems. This is the reason you need to pay attention to the ETF's bid-ask spread, to be aware if you will find easy to sell it if you need (if the ask is high, many people will be willing to buy when you want to sell).  Is the above correct, specially in terms of the problems you might have when you want to sell?


Get path of current script when executed through a symlink

I have a utility consisting of a couple of directories with some bash scripts and supporting files that will be deployed to several machines,  possibly in a different directory on each machine. The scripts need to be able to reference paths relative to themselves, so I need to be able to get the path to the file that's currently being executed. I am aware of the dirname $0 idiom which works perfectly when my script is called directly. Unfortunately there is a desire to be able to create symlinks to these scripts from a totally different directory and still have the relative pathing logic work. An example of the overall directory structure is as follows: /  |-usr/local/lib  |  |-foo  |  |  |-bin  |  |  |  |-script.sh  |  |  |-res  |  |  |  |-resource_file.txt  |-home/mike/bin  |  |-link_to_script (symlink to /usr/local/lib/foo/bin/script.sh)  How can I reliably reference /usr/local/lib/foo/res/resource_file.txt from script.sh whether it is invoked by /usr/local/lib/foo/bin/script.sh or ~mike/bin/link_to_script?


Field that is a subfield of own of its subfields

Let $K$ and $L$ be fields. We have homomorphisms $f: K \to L$ and $g: L \to K$. Are $K$ and $L$ necessarily isomorphic?


Java Concurrent Modification Exception (enumerator)

I have a problem with this source code. The outer for loop doesn't iterate:     java.util.ConcurrentModificationException       at java.util.Hashtable$Enumerator.next(Hashtable.java:1387)         The Foo function only reads from myVar and returns a Hashtable .  As a matter of not rewriting myVar function, I've created an auxiliary variable called iteratingHashTable.  while (condition) {      Hashtable<String, Boolean> iteratingHashTable = new Hashtable<String, Boolean>();      iteratingHashTable = myVar;      for (Map.Entry entry : iteratingHashTable.entrySet()) {          if (value.equals(entry.getValue())) {             String analyzingURL = entry.getKey().toString();             myVar.replace(analyzingURL, true);              Hashtable<String, Boolean> listedLinks = Foo(myVar, entry.getKey().toString());              if (listedLinks != null) {                  for (Map.Entry entry1 : listedLinks.entrySet()) {                      if (!entry1.getKey().toString().isEmpty()) {                         myVar.put(entry1.getKey().toString(), entry1.getValue().equals(true));                     }                 }             }         } else {             condition = false;         }     } }


How to merge multiple rows into single row if the id is same?

id   name    2    ravi kumar     2    mohit kumar    ...   and I want to result   id name    2 ravi kumar / mohit kumar     ...   Thanks


This is my script  #!/bin/bash exec < filelist.txt     while read updatedfile oldfile; do     #   echo updatedfile = "$updatedfile" #use for troubleshooting     #   echo oldfile = "$oldfile" #use for troubleshooting                if [[ ! $updatedfile =~ [^[:space:]] ]] ; then  #empty  line exception                 continue # empty line exception                fi                if [[ ! $oldfile =~ [^[:space:]] ]] ; then  #empty line exception                 continue # empty line exception                fi              echo Comparing $updatedfile with $oldfile             if diff "$updatedfile" "$oldfile" >/dev/null ; then                 echo The files compared are the same. No changes were made.             else                 echo The files compared are different.                 cp -f -v $oldfile /infanass/dev/admin/backup/`uname -n`_${oldfile##*/}_$(date +%F-%T)                 cp -f -v $updatedfile $oldfile              fi               done #go through rest of servers from list while read server <&3; do   #read server names into the while loop     serverName=$(uname -n)  if [[ ! $server =~ [^[:space:]] ]] ; then  #empty line exception     continue  fi     echo server on list = "$server"  echo server signed on = "$serverName"  if [ $serverName == $server ] ; then #makes sure a server doesnt try to ssh to itself     continue  fi     echo "Connecting to - $server"     ssh "$server"  #SSH login     exec < filelist.txt     while read updatedfile oldfile; do     #   echo updatedfile = $updatedfile #use for troubleshooting     #   echo oldfile = $oldfile   #use for troubleshooting                if [[ ! $updatedfile =~ [^[:space:]] ]] ; then  #empty line exception                 continue # empty line exception                fi                if [[ ! $oldfile =~ [^[:space:]] ]] ; then  #empty line exception                 continue # empty line exception                fi              echo Comparing $updatedfile with $oldfile             if diff "$updatedfile" "$oldfile" >/dev/null ; then                 echo The files compared are the same. No changes were made.             else                 echo The files compared are different.                 cp -f -v $oldfile /infanass/dev/admin/backup/`uname -n`_${oldfile##*/}_$(date +%F-%T)                 cp -f -v $updatedfile $oldfile              fi               done done 3</infanass/dev/admin/servers.txt   I get the error when I try to ssh to my list of servers.  Pseudo-terminal will not be allocated because stdin is not a terminal.   Then my script doesn't correctly ssh and compare the files from the newly logged in server.. Does anybody know why this is?


Postgres declare table as a parameter for a function?

I would like to create a function that operates on a table, for example  create or replace function test(t table)      returns void language plpgsql as $func$ begin        select * from t limit 10; end; $func$   Then, I can call the function with any tablename, e.g.  select test(myTable);   How would I do something like this?


Can locative "there" be omitted when the location is explicit?

Is      In the park is a tree.   grammatical as      In the park there is a tree.   ? Moreover, how about inaccusative verbs like:     In the park sits a dog.   ?  Thanks for any help.


How to show explicitly that $\{(x, y)| x^3 = y^2\}$ is not a smooth manifold?

Lately I've been watching a course in differential topology and the instructor gave the set $\{(x, y)| x^3 = y^2\}$ as a subset of $\mathbb{R}^2$ which is not a smooth manifold with no explanation, and I'm wondering how to explicitly show that this set is not a one-dimensional smooth manifold?


Most of something is plural or singular?

I am writing a literature review. My question is which sentence is correct?   Most of the existing work focus on... Most of the existing work focuses on ... Most of the existing studies focus on ...   Thanks


In the video  from 03:00 to 05:00  I hope that both the clocks would read the same equal amount ,say,1 revolution, in measuring the time elapsed for the flash to return to the laser fired.   And the both Sarah and Adam may feel the time elapsed to be different in their own perspectives which might have arised from "the speed of light is same for all observers.   I think i am right upto this extent.  Now, Is time dilation an illusive phenomenon in which one may feel "a one single tick of a clock" which can be "one minute" for another one WHILE for both of them, the clock is universal and runs at same pace ???   Why do Sarah and Adam feel the time elapsed to be different ?? in what way ?


Is it okay for a PhD student to go on holidays in breaks?

I am a first year STEM PhD student in a US university, but I come from a different country. I took a couple of weeks off in this winter break to travel within the US, as it was too expensive to visit my home country.  Now, I have two options -  1. To visit my home country in the next winter (2016-17) for around a month.  2. To visit my home country in the coming summer (2016) for a short period (say 2 weeks) and get back to work AND to go back again in the next winter for around a month.  Now, the problem with 1 is that there is still a year to go (well, almost a year), and so there is a possibility of being homesick. So, there is 2. However, I am concerned if it will be seen as I am slacking off / going on holidays too many times etc. Now, I obviously understand that I should discuss this with my advisor and s/he should take the decision, but I am concerned if this is even a reasonable discussion topic (as opposed to the idea being so preposterous that there is no point even asking, and I should just stick to 2)  Note that even if I go on a short holiday in the summer, I plan to spend most of the summer doing research at my university.  So, tl;dr: Is going on holidays in 3 consecutive breaks considered reasonable? Or is it too preposterous?


The equivalence of homogenous systems of linear equations in two unknowns that have the same solutions

I am self-studying Linear Algebra by Hoffman & Kunze.   Exercise 6 in Section 1.2: "Prove that if two homogenous systems of linear equations in two unknowns have the same solutions, then they are equivalent."   I am trying to solve this problem by induction (see the first bullet point below).  I am hoping to solve this problem using only the information provided in the book thus far. In this text, two systems are equivalent if each equation in one system can be written as a linear combination of equations in the other system. So far the text has defined the following phrases: solution of a linear system of equations, equivalent systems, and homogenous system of equations. It has not yet covered linear dependence.  Some notes on previously asked questions:    seems to be asking the same thing, and while the OP was able to solve it with the hints given in the comments, they did not post the solution. I am trying to solve this problem by induction on the number of equations in one of the systems of equations, as suggested in the comments of that post. My trouble arises when attempting to invoke the inductive hypothesis (IH). Starting with $N+1$ equations, I cannot simply add two equations together to obtain an equivalent system of $N$ equations in order to invoke the IH. The new system of $N$ equations may have solutions that the system with $N+1$ did not.  asks the same question, but the answer uses material and intuition not yet covered by the text at this point.  I have found this question answered on , but with a different approach.


How to get current number values from different input box by jquery click funcion

I have two input boxes in same page.  <input type="number" class="q"  /> <input type="number" class="q"  />   if i click on 1st input box it alerts the current value.But if i click on the 2nd input box it againt alerts the 1st input box value. How would i get the current value of that 2nd input box?  Here is the jQuery function:  $(".q").on("click", function() { var orderQty = $('.q').val(); alert(orderQty) });   Problem Solved:  Working jQuery Code:  $(".q").on("click", function() { var orderQty = $(this).val(); alert(orderQty) });


How to check whether a directory is empty or not in Shell Scripting?

I have a directory. It is empty. If i perform ls -lrt , it shows total 0  How do I specify an If condition to perform something, only if the directory is empty. I mean to ask how to capture that 0 value.


I'm trying hard to write a regex that should catch any http address. (background: I'd like to use it in a tkinter window, a simple editor, to transform an http address into a clickable link) Due to how complicated they can be, which is the better regex?  alessandro


OP removing question after answer selected

I've just answered .  After accepting the answer, the OP then changed his question to another problem - which I know I shouldn't have answered (I should have requested as new question) but I updated my answer anyway.  The OP has now edited his question to remove the essence of either the original or new problem, and instead has a statement saying that the problem has been fixed.  What is the correct thing to do here?  Roll the question back so it's in its original state? Roll it back to the "new problem" state? Leave it and let him continue to get downvoted and/or closed by people who didn't see the original question?


How is possible to create a pressure greater than Earth core's pressure in laboratory?

Recently is been reported than metallic hydrogen has been observed in the laboratory at a pressure of around 4,890,000 atm. This as far as I know is even greater than Earth's core theorized pressure. How did they make to create such pressure in laboratory?


Illustrator: applying gradient to multiple objects not working

I created a logo by converting my text to outlines. Grouped them together using the pathfinder - unite feature.  I'd like to apply a single gradient to the group, but for some reason I can't. Nothing happens when I drag over the gradient tool over the group. What could be the problem?


How do I associate an uploaded file to an Organic Group?


How to make Ubuntu disk from other machine bootable?

I have two computers, this one runs Windows 10.  I removed the Ubuntu disk from another computer and plugged in this one. The BIOS can detect the ubuntu drive, but didn't list it as bootable.  I want to be able to boot into ubuntu and windows. I think I have to add an entry to the Windows 10 EFI partition, in that partition there's a /EFI/bootx64.efi, and I'm wondering where's the equivalent for that in my ubuntu disk, and I don't know where I should put it. Should it be named /EFI/Ubuntu/bootx64.efi or what?  (I'm using DiskInternals Linux Reader to access my Linux partition at the moment.)


How to slice every nth element in index using python?

this might look like a simple question but I could not figure out the solution.  Assuming I have this list  my_list = [1,2,3,4,5,6,7,8,9,11,22,33,44,55,66,77,88,99]   I am attempting to slice item in this list and increment it by index. In short, I want to get the result like this  [1, 2, 3] [2, 3, 4] [3, 4, 5] [4, 5, 6] [5, 6, 7] [6, 7, 8] [7, 8, 9] [8, 9, 11] [9, 11, 22] [11, 22, 33] [22, 33, 44] [33, 44, 55] [44, 55, 66] [55, 66, 77] [66, 77, 88] [77, 88, 99]   But what I got is like this  [1, 2, 3] [2, 3, 4] [3, 4, 5] [4, 5, 6] [5, 6, 7] [6, 7, 8] [7, 8, 9] [8, 9, 11] [9, 11, 22] [11, 22, 33] [22, 33, 44] [33, 44, 55] [44, 55, 66] [55, 66, 77] [66, 77, 88] [77, 88, 99] [88, 99] [99]   I want to slice my_list to several smaller set each with length of 3. But the result I got also included the list that have length below than 3.  This is the python script I use  my_list = [1,2,3,4,5,6,7,8,9,11,22,33,44,55,66,77,88,99]  m = 0  def incr():     global m     for n in range(len(my_list)):         if n < len(my_list):             n = m + 3             new_list = my_list[m:n]             print new_list             m+=1         else:             pass  incr()   I figured that I could add if len(new_list) < 3 but I do not quite sure how should I modify the script for that.  Thank you for your help.


Is it possible to run everything without sudo?

Ignoring security reasons, is it possible to do? And how to do it?


How to adjust the selection 'hotspot' distance?

Blender's default behavior makes it easy to select a mesh element without the need to hover the mouse cursor exactly over it. Sometimes it's really helpful, sometimes not. I wish I could either adjust that "hotspot" distance between my mouse cursor and the mesh element I want to select or disable it altogether. Thank you.


I'm having trouble understanding what exactly an empty set is. Does $\varnothing$ mean $\{\}$ ? and what is the difference between $\varnothing$ and $\{\varnothing\}$ ? If someone could shed some light on this, and provide a couple of more examples to help me learn what this weird concept is, I'd greatly appreciate it.  Thanks!


Location of Tcl 8.6 library and Location of Tk 8.6 library: not found

Command was   sudo auto-apt run ./configure   Error message:  DISTRIB_DESCRIPTION="Ubuntu 16.04.1 LTS"     Location of "tcl.h": /usr/include/tcl8.6     Location of "tk.h": /usr/include/tcl8.6     Location of Tcl 8.6 library: not found     Location of Tk 8.6 library: not found     Location of X11 library: /usr/lib/x86_64-linux-gnu     Checking if your system already has zlib installed: yes.  Not all settings could be determined! See above for details.  The default Makefile was written. You will need to edit it before you can compile Scid.   I also can't find the libraries. How do I overcome this?


I am trying to convert a old desktop into ubuntu (or Debian) machine. I have already looked up the  but still have following questions. In order to provide details, here is all the info I have collected on the current hardware on this machine:   Dell Dimension 3100/E310 with BIOS version A03 CPU : Processor 80547 Pentium 4 Prescott DT 2.8GHz 800 MHz bus, Hyperthreading capable Intel EM64T (Processor ID 0F49) RAM : 1.25GB 533MHz DDR2.  I have found reports of others successfully running 4GB, and according to 915G specs at  this can take upto 8GB RAM. But,  I am not sure if 915G refers to what i find in BIOS as Intel 82915G/GV/910GL Express chipset. Would like confirmation from someone knowledgable about intel chipsets. The above link also shows couple of things that I do not understand. It says Supported FSBs::   533/800MHz,  but also says Memory Types::     DDR 333/400, DDR2 400/533.  Since I am planning to upgrade RAM, can i buy DDR2 800MHz ?  I see DDR3 is selling for even lower prices now a days, but I am not sure if i can use a DDR3 on this. The above intel link also says under memory specs, Physical Address Extensions::    32-bit and I was wondering if this means that I CAN NOT run ubuntu/debian 64 bit versions. I need the 64 bit version of one of these OS installed because I plan to run mongoDB server on this machine, and mongoDB supports only 64 bit versions of these two OS. My understanding of PAE makes me guess that "32-bit" means that it supports more than 4GB memory space and 64 bit architectures. Hard Drive:  Currently Hitachi 7200rpm SATA 80GB. Under Windows 7 control panel I see that SATA Controller is Intel 82801FB Ultra ATA 2652(and Ultra ATA 266F).  Come thanksgiving, I want to get a SSD, but since I do not see AHCI listed anywhere in BIOS, i wonder if this hardware will support SSD.  Wireless: I currently have 2 wireless N adapters, but not sure if either of them will work under Ubuntu or Debian. First is a Zonet ZEW1642D model PCI card that has RaLink chip RT3062F.  Second is a Linksys N300 USB adapter that has been certified for Windows 7, but i do not see linux listed on the box.  Do i need to buy a wireless card for this machine and if so, where can i find compatible cards for this hardware ? Ubuntu version:  I have already looked up the  but it says only older versions of Ubuntu were tested on this hardware. Will i be ok with installation of latest Ubuntu/Debian ? Goal is to run this machine as a learning machine at home and run simple apps. MongoDB server would be installed but only for learning purposes. Which flavour of linux is recommended - Ubuntu or Debian ? I am mentioning Debian because i read a webpage that said Debian is more suited for server machines. But this is not a industry server, but home machine. Video upgrade : Will i get better performance on this, if i upgrade to a PCI video card ? No gaming on this machine, but potentially internet streaming maybe done for Netflix or Hulu movies. Currently my plan is to upgrade to 8GB RAM and SSD as the basics. In today's market prices, this is going to cost me about $150. I am guessing that if Wireless card is needed that would cost another $25 for Ubuntu. So, if i add $50 for a video card, that would bring upgrade costs to about $225. But a newer laptop with SSD+4GB ram is about $350, here in bay area (Toshiba Satellite Radius 11 L15W-B1120, Pentium N3540, 11.6" Convertible Laptop With 4GB, Memory, 128GB SSD, Windows 8.1). I only have to add a wireless card and reformat it for Ubuntu. The only sacrifice here would be the lower 4GB RAM on the laptop. As i finish writing the question, i am starting to wonder if this machine is worth upgrading, but would like to find answers to my questions anyways. This would become the 5th PC i have at home, and wife would object if she saw me getting yet another new laptop :-)   Thanks a bunch for reading my long post.


Oracle: How can I implement a "natural" order-by in a SQL query?

e.g,  foo1 foo2 foo10 foo100   rather than  foo1 foo10 foo100 foo2   Update: not interested in coding the sort myself (although that's interesting in its own right), but having the database to do the sort for me.


What is wrong with the following sentence:      The Central Limit Theorem  implies that, as the sample size grows, the error distribution approaches normality.   Am I correct by saying that it should in stead state the MEAN of the sample error approaches zero as sample size grows?


In QGIS (2.10.1 on a Mac), I am trying to make some multiline labels on a map I have with a bunch of trees in them. In the attribute table I have columns with the Latin scientific name, the English name (when one exists), the year the tree was planted etc.  I am labelling the trees in my map with an expression like this:  genus_species + '\n' + case     when  "english_species" is not null then  "english_species" + '\n' end + to_string( "planted_year")   This works well for the rows where english_species is not null, however whenever I have a row with no English name, the entire expression just seems to break and nothing is printed, not even the scientific name or the year (which always exists).  I have tried adding a  when  "english_species" is null then ''   But that doesn't work either. The expression just breaks for rows with no value in the field english_species.


Why is my Canon 300D not switching on despite changing both batteries and the CF card?

My Canon 300D is 12 years old and has worked perfectly until now. It will not switch on. Nothing lights up. There is no change to anything when the power button is switched on. Changing both batteries and CF card twice makes no difference.  Does anyone have any idea what might be the problem?


Drag and drop onto Python script in Windows Explorer

I would like to drag and drop my data file onto a Python script and have it process the file and generate output. The Python script accepts the name of the data file as a command-line parameter, but Windows Explorer doesn't allow the script to be a drop target.  Is there some kind of configuration that needs to be done somewhere for this work?


$ \sigma _{H}\sigma _{Q}\geqslant \frac{h}{4\pi }\frac{d\left \langle Q \right \rangle}{dt}$  $\Delta E = \sigma _{H}$  $\Delta t = \frac{\sigma _{Q}}{d\left \langle Q \right \rangle / dt}$  $\Delta E \Delta t \geq \frac{h}{4\pi }$  Q is any observable  I know that $\Delta E$ represents the standard deviation of energy distribution, but what does $\Delta t$ represent precisely?  I read an answer saying "It is the average time of the expectation value to change by one standard deviation, but I don't understand this sentence, I need some clarification.


module nvidia is not found error - bumblebee

today I've installed bumblebee with nvidia-current, but when I check if bumblebee is  ok (bumblebee-config),I can read this     [ERROR] Module "nvidia" is not found.   What can I do?  Thanks you in advance


Please show suggested edits to tag wikis and the corresponding excerpt together

When there are many suggested edits in the queue, a random selection of them is shown.  This is more annoying than useful, but there's a case when it's especially annoying: if someone edits both a tag wiki and the corresponding excerpt, the two are not shown together to reviewers. This leads to extra reviewing effort.  Please ensure that suggested edits to a tag wiki and the corresponding excerpt are always shown together. (Keep allowing different decisions, of course.)  I guess this feature request won't be implemented until the new  UI comes out, but please do make sure it's done there.


Is there a squarefree number between any two squares?

I'm trying to prove that $\sqrt{x} \leq 2^{\pi(x)}$ for all $x \geq 0 \in \mathbb R$, where $\pi$ is the prime-counting function. To do this, I note that $2^{\pi(x)}$ may be viewed as the number of different products we may produce from the $\pi(x)$ different primes that are at most $x$; since in each such product the power of each prime is at most one, each product is squarefree. Since by convention 1 is squarefree, then $2^{\pi(x)}$ is precisely the number of squarefree numbers at most $x$.  Furthermore, $\lceil \sqrt{x}\rceil = \left|\{n^2 : n^2 \leq x\}\right|$ (with equality if and only if $x$ is a square), so that proving that $\sqrt{x} \leq 2^{\pi(x)}$ is equivalent to showing that there is an injection $$f : \{n^2 \in \mathbb Z : n^2 \leq x\} \to \{n : n \leq x \text{ and $n$ is squarefree}\}.$$ Supposing that for any integer $n \geq 1$ there is some squarefree number $k$ such that $n^2 < k < (n + 1)^2$, then producing such an injective function is trivial. But I do not see a way to prove this last claim: that between any two squares there is a squarefree number. How does one prove this statement?


Unknown apps/processes with number only are shown in the battery screen

There is a mysterious app, 99070 that is consuming power on my Nexus 5X. Any idea how I determine what it is?  There is no option to stop or uninstall it. My phone is a Nexus 5X running stock Android 6.0.


How to play a sound effect in java program when needed

Basically I am remaking snake for a high school computer science project. I am trying to add a sound effect every time the the snake and the ball hit. I just need to put in the sound at this point. Which classes should I use for sound that are up to date in java and where I can play the sound whenever I need it.


Given a package name, how can I find out what will change if I install the package?

Given a set of apt commands and packages to apply (e.g. install foo bar baz, autoremove quux blerg bang), is there a way to calculate the diff of the system state that will be produced if I run the commands?  By "system state" I don't merely mean whether a given package will install/remove other packages, but what kinds of actual changes get produced -- files being deleted or moved, scripts getting run, et cetera.


Can Minecraft be played by two players locally on the same account?

I just bought Minecraft. Now, my brother wants to play with me but my Mom doesn't want to buy another. We use the same Wifi network. Can we do this?


I can pick a number in the interval from all real numbers from 0 to 1. Say this number is 0.42. Now the probability for drawing this number most be zero since we have infinity many numbers in the interval 0 to 1. Is this true and is it not a paradox ?


How do i prove that a subset of a finite subset is finite?

Let $n\in\omega$ and $F\subset n$.  How do i prove that $F$ is finite?  I know that this can be proven by constructing a function in a following way: take $f(0)$ as the least element of $F$ and then take $f(1)$ as the least element of $F\setminus \{f(0)\}$ and continue this process. Since $F\subset n$, $F$ has a maximal element. Thus this process must be done in a finite step.  However, i don't know how to prove this precisely. How do i write down "this process must be done in a finite step" in first-order logic and so on. Please help :)


I wonder if anybody have experience with migrating to the latest Gen8 HP microserver from existing architectures.    In my case the server what I would migrate would have 2X  Intel® Xeon® Processor E5450 (12M Cache, 3.00 GHz, 1333 MHz FSB) and 24 GB ram and I would replace this with 1X Intel® Xeon® Processor E3-1220L v2 (3M Cache, 2.30 GHz) and 16GB ram.  Looking at the CPU comparison, this would result in a much slower server:   I would be running 8-10 lightly loaded Vmware vms on top of it. Only used by 1-5 users irregularly. Would I notice significant degradation in performance?  Thanks


What is duplicate content and how can I avoid being penalized for it on my site?

This is a general, community wiki question regarding duplicate content.  If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on .     What does Google consider to be duplicate content? Will the way I am presenting my content result in a duplicate content penalty? How can I avoid having my site's content treated as duplicate content?


I have two date ranges, (start1,end1):::>>date1  && (start2,end2):::>>date2  . I want to check if the two dates isOverLaped. My flow chart I assume "<>=" operators is valid for comparing.  boolean isOverLaped(Date start1,Date end1,Date start2,Date end2) {     if (start1>=end2 && end2>=start2 && start2>=end2) {         return false;     } else {         return true;     } }  Any Suggestion will be appreciated.


I am travelling From San Francisco to New Delhi via Amsterdam (Schiphol AMS). I have Indian passport and a valid US visa on it. Do I need any kind of visa in Schiphol airport. There is 3 hours of break before I catch my flight from AMS to New Delhi.  And also please tell me if I need any visa while coming back from New Delhi to San Francisco. Thanks in advance.


I've noticed a lot of people having similar issues with finding a driver for NETGEAR A6100 AC600 WiFi Adapter.  I've been struggling with a lot of the threads and drivers posted on github. Many of the ones listed are referencing a rtl8812au driver while I believe my particular one is a rtl8811au.  I ran the wireless info script that is floating around and these are my results      I did get this driver to make and install but it doesn't seem to do anything.  I still don't have any wireless connections popping up.  Any help on this matter would be much appreciated..


To comma or not to comma, that is the question

In the  there are lots of numbers on display, including 1000, 2500 or 10000. The display is erratic though:    Same number, two displays. Both appear valid to me: 1000 or 1,000 but please, make it consistent. My eyes hurt! :) I just found , but there it's discussing the whole network while I'm asking just for that specific page. For a start.


Find the remainder when $10^{20^{30}}$ is divided by $23$   I guess this question is fairly simple, but I just want to make sure I'm on the right track. My answer is shown below. If it is incorrect, please don't downvote it; I'll delete it soon after.  Edit: here's my work  Notice that $10^{2}\equiv 8\mod 23$, $8^2\equiv -5 \mod 23$, and $(-5)^2\equiv 2\mod 23$. Thus, $10^{16}\equiv 2\mod 23$ and $10^4\equiv -5\mod 23$ and so $10^{20}\equiv -10\mod 23\Rightarrow 10^{20^{30}}\equiv (-10)^{20^{29}}\equiv ...\equiv (-10)^{20}\equiv-10\mod 23\equiv 13\mod 23$.   mb I could use Fermat's Little Theorem. I guess I could make this more formal too.


kpfont integrals have a lot of empty space both on the left and on the right ever with smashoperator:    How do I kern the function "into" the integral and reduce the white space of the left document-wide?  \documentclass{article}  \usepackage[intlimits]{kpfonts} \usepackage{amsmath,mathtools}  \begin{document} \begin{equation} I = \int_{t_{k}}^{t_{k+1}} f(t) dt \end{equation}  \begin{equation} SMOP = \smashoperator{\int_{t_{k}}^{t_{k+1}}} f(t) dt \end{equation} \end{document}


What kind of components are black blobs on a PCB?

In low-cost mass-produced items I often run into black blobs of what looks like resin applied directly on top of something on the PCB. What are these things exactly? I suspect this is some kind of custom IC that is layed out directly on the PCB to save on the plastic  housing/connector pins. Is this correct? If so, what is this technique called?    This is a photograph of the inside of a cheap digital multimeter. The black blob is the only non-basic piece of circuitry present, along with an op-amp (top) and a single bipolar junction transistor.


Files on my USB gets corrupted and content set to the letter ÿ

I have been having a problem on a USB. Whenever I save any type of file, it will get corrupted, and when opening any of these files with notepad, everything is set to the letter "ÿ". Does anyone have any ideas how to fix this? I am using Windows 10 operating system, whenever I try to write to it, Windows does now show the writing process, but yet still copies a file to it, then it dissapears form the drives list and i have to unplug it and plug it back in. It says:  "There is a problem with this drive. Scan the drive now and fix it."  Whenever it is plugged in, and is very hard to wipe as it takes multiple attempts, is there any way I can fix this? This happens with all file types I have tested. Oddly, the names of all the files remain the same, its just the content that get set to the letter "ÿ". To answer some of the questions: This is an old USB and, has not been tested on another computer, although I have not had any problems with the USB ports on my computer, and still do not now, and I am aware you can only open .txt files with notepad, but for the purposes of testing and the fact I cannot open the other files (due to them being corrupt),  I have opened them with notepad, all files, .txt and not all get set to the letter "ÿ".


Suppose $a_0$ and $B$ are positive numbers , define a sequence $a_{n+1} = \frac{1}{2}(a_n +B/a_n)$. Show that $a_{n+1} \geq\sqrt B$.


Prove that for all $x$, $\sum_{j=0}^{n}ℓ_j(x)=1$  $ℓ_j(x)$ are obtained by means of Lagrange interpolation and are defined as $ℓ_j(x)=\prod_{i=0, i\neq j}^{n}\frac{x-x_i}{x_j-x_i}$ where  $x_i, i=0,1,...,n$ are the nodes given to interpolate, with which I have to prove that $\sum_{j=0}^{n}\prod_{i=0, i\neq j}^{n}\frac{x-x_i}{x_j-x_i}=1$ but I do not know how to do this, could someone help me please? Thank you very much.


Maximum Likelihood Estimator and MVUE for theta-squared

Let $Y_1,\ldots,Y_n$ denote a random sample of size $n\ge4$ from Bernoulli ($\theta$) distribution where $$0 < \theta < 1$$ is the success probability.  How would I derive the maximum likelihood estimator (MLE) of $\theta^2?$  Also, with $\hat{\theta}=Y_1Y_2$ being unbiased for $\theta^2$, and $U=\sum(Y_i)$ is a minimal sufficient statistic for $\theta$, how would I "Rao-Blackwellize" $\hat{\theta}$ and explicitly derive the conditional expectation, $E[\hat{\theta}|U]$, to come up with the minimum variance unbiased estimator (MVUE) for $\theta^2?$  These questions are confusing me because it is asking for $\theta^2$ instead of just $\theta$. If someone could please show/tell me what to do/steps to figuring this out that would be amazing!


Ubuntu filesystem is running out of space?

So I am new to Ubuntu and everything seemed to be working fine till a few days ago.  Now I constantly get a dialog box saying the filesystem is running out of space.   Here is the system monitor screenshot. Ubuntu is on /dev/sda5  I am aware there are other similar questions but the answers seem very technical. Can someone help with this considering I am very new to Ubuntu.  Should I just do a fresh install after backing up the drive?  TIA    cat /procs/mount output:


Recording Mobile Device for Usability Testing Sessions

Hi everyone i have a question regarding recording mobile device usability testing sessions.   do you suggest any external device i can attache to the camera to record the test? if you familiar with mobile usability testing recording , what is your methodology or process ? what kind of device are you using to run the test? can you share some useful articles or links on the internet?   Regards,


Is there a canonical explanation for how Ant-Man's weight works when he shrinks down that's consistent with the various events depicted in the film?    I think the explanation given in the film is roughly "the suit compresses the space in-between atoms, so your size decreases, your density increases, and your total mass stays the same", however it seems to be portrayed in contradictory ways.  For instance:   He can float in water, and even be sent shooting through the air by a relatively gentle flow of water filling a bathtub.  This wouldn't happen if he retained his original mass, as he'd essentially be the densest thing on the planet and should sink like a stone even in a vat of molten lead. Upon landing after being ejected from the bathtub, the ceramic tile underneath him shatters.  That takes a significant amount of force, and similar effects are used at other points in the movie where he falls onto (or straight through) various things. He's able to get sucked into a vacuum-cleaner.  One that didn't even appear to be a high-end, extra powerful vacuum-cleaner, let alone one capable of sucking up a 200 pound piece of dust.   He can run along the barrel of a gun as someone shoots it, apparently without causing them to drop the weapon or even have trouble continuing to aim it.     Does a more consistent explanation exist in other media, that would fit with the above examples?  Or is this simply a case of the power being made to do whatever happened to be most convenient at the time?


Can Nexus card be used at US airports if arriving from country other than Canada?

If you have a Nexus membership (and NOT Global Entry), have you used your card at the Global Entry kiosk at an US airport to get the Global Entry benefits?  Nexus can clearly be used at participating Canadian Preclearance airports to enter the US and you get the Global Entry Benefits.   A lot of people say that Nexus is superior to Global Entry program and they point out the following facts. 1. Nexus is cheaper ($50 as opposed to Global Entry which costs $100) 2. Nexus gets you into the fast lane when entering Canada from USA by air/water/land. Global Entry does not give you that benefit. 3. Nexus gets you into fast lane when entering Mexico from USA (because of the reciprocal benefits between Nexus and Sentri program). Global Entry does not give you that benefit. 4. "using Global Entry kioks when entering the United States.."  Reference:   I am having trouble understanding the item number 4 above. Does Nexus give you the "Global Entry" benefit, only if you are using the Nexus kiosks at one of the ten preclearance airports (Reference: )?   Whatever I read suggests that Nexus card CANNOT be used with the Global Entry kiosks at the US airports, if arriving at US from any country other than Canada (say, Brazil or Japan) or from any Canadian airport other than the Pre-clearance airports.


Must CSRs be generated on the server that will host the SSL certificate?

Is it necessary to generate the CSR (Certificate Signing Request) on the same machine that will host my web application and SSL certificate?  This  says so, but I'm not sure if that's true, because it would mean I'd have to buy a separate SSL certificate for each server in my cluster.     What is a CSR? A CSR or Certificate Signing request is a block of   encrypted text that is generated on the server that the certificate   will be used on.


C# Dictionary issue for reference type as Key

I have class that implements interface as below  class Person : IHuman { }   I have created dictionary as below  Dictionary <IHuman, collection<int>> dic = new Dictionary <IHuman, collection<int>>();   Now I add one key value pair as belwow  dic.Add (person, myCollection);   Again when I use containsKey for "same person object and with same HashCode" as below  if (dic.ContainsKey(person)) {     dic[person] = mynewcollection; } else {     dic.Add (person, mynewcollection); }   Here ContainsKey() returns false and creates one more key value pair with same person object.  I wondered how it possible... Please help me to sort out this issue.


I am a research undergraduate student who is in full time research internship in university. I realized that research needs A LOT of patience to obtain validated results A LOT of exploration. A LOT of roads and initial ideas that lead to no results or can't be implemented. I don't feel the dopamine rush that i feel when working on short term projects. So how do you stay motivated ? what's your secret ?


$\ker T\subset \ker S\Rightarrow S=rT$ when $S$ and $T$ are linear functionals

I would like only a hint to the following exercise:  Let $V$ be a vector space over the field $K$, and $T$, $S$ linear functionals on V such that $Tv=0\Rightarrow Sv=0$. Prove that there exists $r\in K$ such that $S=rT$.  I know how to prove this when $V$ is finite dimensional. I show that if there is no such constant $r$ then $n-2=\operatorname{dim}\textrm{ }(\ker\textrm{ }T\textrm{ }\cap \ker\textrm{ }S)=\operatorname{dim}\ker T=n-1$, a contradiction. But this approach doesn't seem to help at all for the stated problem.


I have a computer that is kinda stumping me. It has something that has hijacked the browser with ads by dealpeak.  I have checked browser extensions, hosts files, proxy servers, scanned with malwarebytes, MSE and spybot all to no result. Malwarebytes was set to scan for rootkits as well.  Also manually scanned over task manager to see if anything was out of the ordinary and did not see anything but did not do more than check the folder anything I did not recognize was running out of. I may have to go back and check all those that were in safe folders(ie c:\program file\lenovo).  Lenovo running windows 7. Can't give more specs because it is not right in front of me.


I'm looking for some Firefox (4 or 5) extension to save a group of tabs (better if can be done directly in Panorama view). What I mean by "Save tabs" is not to restore them when Firefox starts.   I always have the browser opened and a LOT of tabs (work and personal life related) eating my RAM. So when I'm not working, I would want a way to save those tabs but keep them closed while I still use Firefox. So when I have to start working again, I will restore that saved tabs back again.  I know I could use something like Read It Later, but I really need a way to say "hey, save this group of tabs and close them". RIL makes me do it per tab, which is annoying since I'm used to have A LOT.


I am getting the sign up screen whenever I open the Pokemon GO app. What's wrong?

Whenever I open Pokemon GO, I get the screen I would get if I had just downloaded the game. It's asking me to sign up with a google account or if I have Pokemon trainers club. There is nothing I can press other than those buttons. What's wrong and how can I fix.


How do you get the first file in each subdirectory matching a list of file extensions?  My goal is to run a program on just any one of the files in a series of subdirectories.  For example, below there are 3 subdirectories.   I want to run the program on subdir1/file.dat, subdir2/file.d01 and subdir3/file1.dat given that I want to find files that have extension .dat or .d01.    subdir1 - file.dat, file.d01     subdir2 - file.d01, file.d02, file.d03     subdir3 - file1.dat, file2.dat   The following worked great for awhile, until I started to encounter directories like the last two.  subdir3 is problematic, since all files end up getting processed.   find . -name "*.dat" -exec mixb {} \;


Proving that $f_2+f_4+\cdots+f_{2n}=f_{2n+1}-1$ for Fibonacci numbers by induction

Given: $f_1 = f_2 = 1$ and for $n \in\mathbb{N}$, $f_{n+2} =f_{n+1} + f_n$. Prove that $f_2 + f_4 + \dots   + f_{2n} = f_{2n+1}- 1$.  Would you start with setting $f_2 + f_4 + \dots   + f_{2n}= a_n$? Then for the base case let $a_1=1$ LHS$=1$ and RHS$=2-1=1$ so base case holds. Then the inductive hypothesis: Assume $f_2 + f_4 + \dots   + f_{2n} = f_{2n+1}- 1$ $\textbf{NTS}$: $f_2 + f_4 + \dots   + f_{2n} +f_{2n+2} = f_{2n+3}- 1$ Inductive step: By inductive hypothesis $f_2 + f_4 + \dots   + f_{2n}=f_{2n+1}- 1$ So $f_{2n+1}- 1+f_{2n+1}$=$f_{2n+2}- 1$. As was to be shown. Is this correct or did I need to show more algebra in my inductive step ?


Using glmnet we run the following regression   cvfit = cv.glmnet(x,y, alpha = 0, intercept = FALSE)   where $y$ is the response variable and $x$ is the input matrix. The input matrix is a partitioned matrix of the form $x=[H,D]$ where    $H$ is an $n\times p_{1}$ matrix of tests results and   $D$ is an $n\times p_{2}$ matrix of patient-specific dummies. That is, we allow each patient to have a different $y$-intercept.    We specify intercept = FALSE because we are interested in the point estimates of the dummies. The columns of $H$ are highly correlated reflecting the fact that the tests often capture similar characteristics. As a consequence, the point estimates come with large standard errors and this is the reason why we regularize. We have $n=1000$, $p_{1}=50$, $p_{2}=70$.   Our question: Should we regularize the dummy variables?   As I see it (I am happy to be corrected), there are arguments for and against regularizing the dummies.    We should not regularize the dummies because the parameter instability is "caused" by $H$ and not $D$ (in fact, $D^{T}D$ is the identity matrix) and we should concentrate on regularizing $H$. By regularizing both $H$ and $D$, we may not regularize $H$  enough.  We should regularize the dummies as well because the presence of $D$ may already help to alleviate the problems caused by the multicollinearity of $H$. By regularizing both $H$ and $D$, we may not need to regularize as much as if we only regularized $H$.    The table below shows that, contrary to my expectation, lambda is larger if we regularize the dummies as well.     ------------------------------------------------ Regression lambda   log(lambda)        mse ------------------------------------------------      1       0.161     -1.829         0.910      2       0.034     -3.396         0.869 ------------------------------------------------   Where the codes for the two regressions are   Regression 1: cvfit = cv.glmnet(x,y, alpha = 0, intercept = FALSE) Regression 2: cvfit = cv.glmnet(x,y, alpha = 0, intercept = FALSE, penalty.factor = p.fac)


I've already read and re-read the  here and  about cUrl to Apex. Those both dealt with only one parameter in the body of the request. This cUrl seems a bit trickier -- I can't seem to hack it.  I'm trying to make a call to Twilio's Notify API (allows you to send bulk messages in a single api call.) It works from cUrl, but I can't figure out how to parse it in Apex.  Here's the cUrl:     curl -X POST https://notify.twilio.com/v1/Services/[messageServiceId]/Notifications \ --data-urlencode "Body=Test Message from Pat." \ --data-urlencode 'ToBinding={"address": "+18005551212", "binding_type": "sms"}' \ --data-urlencode 'ToBinding={"address": "+18005551233", "binding_type": "sms"}' \ -u [my AccountId]:[my AuthToken]   And here's what I've been trying in Apex:  Http http = new Http(); HttpRequest request = new HttpRequest(); String AccountSid = [my AccountSid]; String AuthToken = [my AuthToken]; request.setMethod('POST'); Blob headerValue = Blob.valueOf(accountSID+':'+authToken); String authorizationHeader = 'BASIC '+ EncodingUtil.base64Encode(headerValue); request.setHeader('Authorization', authorizationHeader); String body = 'Test message from Pat'; List<String> phoneNumbers = new List<String>(); String baseUrl = 'https://notify.twilio.com/v1/Services/'; String ServiceSid = [messageServiceId]; String NotificationsSuffix = '/Notifications'; request.setEndpoint(baseUrl + ServiceSid + NotificationsSuffix); String payload = ''; payload += 'Body=' + body; payload += '&ToBinding=[{"address":"+18005551212","binding_type":"sms"},{"address":"+18005551233","binding_type":"sms"}]'); request.setBody(payload); HttpResponse response= http.send(request); System.debug(response);   Note that "body" is one of the required parameters for the Twilio API -- it refers to the body of the message to be sent. Therefore, I've used the variable called payload for the body of the http request.  I'm not clear if I should be using urlEncode on the body elements, or how to concatenate them. Should I be using the question mark and/or ampersand?


Is it good to ignore (@) errors that happen due to external factors?

I have a LDAP server request in my code. I open an connection with ldap_connect and check that returned descriptor is valid, but then I make a search request with ldap_search using the open descriptor. But sometimes due to the network failure or something else, ldap_search fails with warning Search: Can't contact LDAP server.  On my production server I treat all warnings as fatal errors, so the whole page render fails.  Should I just prepend ldap_search with @ and just check the value returned (I do check it now as well) or there's a better way to handle this?


Stop pages being accessible via index.php/XXXX

I have a Drupal 8 (served via Apache) site with clean URLs enabled, however, I'm having an issue where every page is accessible over two URLs, for example example.com/index.php/example and example.com/example.  I would like to redirect the URLs containing index.php to the other URL. I'm also open to suggestions to completely disable pages being served over the first type of URL.


Can I use past tense in "now that" clause? Is the following sentence correct?  Now that Tony was no longer present, there was a distinct change in her attitude.


I have always wondered why diamonds shine. Can anyone tell me why?


Show that the metric $d_1$ on $C([0,1])$ does not give rise to a complete metric space.  $$ d_1(f,g) = \int_0^1 |f(s)−g(s)| \, ds $$


What is the association of the 4 house animals to the Hogwarts houses and who picked them?

In Harry Potter each Hogwarts house has its own animal that represents it; is it ever explained how these animals came to represent a specific house? I never read a canon explanation to who chose the animals, is that known?


How do I delete or change a cover photo? Every guide I find is at least two years old and NONE OF IT is relevant to the new business listings in Google+.    Not the user photo/icon—that's a piece of cake to update. I'm trying to change the big cover photo that looks like it came from 1996. I did not set this page up originally, but the admin account was handed to me, so I have full access. I deleted every photo in the admin account at . These images also do not exist anywhere in the "manage" section of the business listing. There's no edit or remove button hovering over the image while logged in as the admin. They do appear in the album "Scrapbook photos" when viewing the Google+ page above, but this album does not appear to be editable.


What is the fastest way to cool hot soup?

I am making vegetable soup for about eight people and would like to cool it in little time. Refrigeration seems to be a good choice, but I would like to know if there are better methods/techniques out there.


everyone! I'm pretty new to LaTex and I'm trying to get a grasp of it to use it on my thesis. I'm trying to setup a nice workflow so I won't get stuck every couple minutes before I start actually writing the whole thing down. I'm using TexMaker 5.0.2 and BiblaTex on MacOs High Sierra. The workflow that I found to work (with the help of a more experienced friend) is: Select for references.bib file > Run the "1. Biber" command > Select the main.tex file > Run the quick build (which is now default only: LatexToPdf + View PDF) I will say this may be dumb to do, but I am a newbie after all :)  Could anyone help me set up a custom Quick Build to do this in just one click?  P.S. I tried the option LatexToPdf + Bib(la)Tex + LatexToPdf (x2) + View PDF but it doesn't seem to work for me.. And I don't fully understand what's he's trying to do...  Thanks all :)


How do Invulnerabilities Interact with Multiple Damage Types?

If an attack does, say, 10 Radiant and Fire Damage and the target has 5 Fire invulnerability? Do they take no damage, or half damage?  I see that  covers resistances, however, I wasn't sure if the same applied to invulnerability, which wasn't covered in the linked question.


Find $\tau \in A_6$ such that $\tau \sigma \tau^{-1}=\sigma^{-1}$

Let $$\sigma = \begin{pmatrix} 1&2&3&4&5&6\\ 4&5&2&1&6&3\end{pmatrix}\in S_6.$$ Then $\sigma = (1\text{ }4)(2\text{ }5\text{ }6\text{ }3)$ and thus $\sigma^{-1}=(4\text{ }1)(3\text{ }6\text{ }5\text{ }2)$. Then ${\rm sgn}(\sigma)={\rm sgn}(\sigma^{-1})=1\Rightarrow \sigma,\sigma^{-1}\in A_6$. I now have to find $\tau \in A_6$ such that $\tau \sigma \tau^{-1}=\sigma^{-1}$.   I know that $$\tau=\begin{pmatrix}1&2&3&4&5&6\\ 4&3&2&1&6&5\end{pmatrix}$$ solves it since $$\tau \sigma \tau^{-1}=(\tau(1)\tau(4))(\tau(2)\tau(5)\tau(6)\tau(3))=(4\text{ }1)(3\text{ }6\text{ }5\text{ }2)=\sigma^{-1},$$but $\tau \not \in A_6$ and this is where I'm stuck.  Am I going in the right direction?  Any help is appreciated. Thank you for your time.


I try to find a reasonable solution for this equation but i couldent  I try to study lots of material but i couldent solve it. I am a high school student and try to learn. Integral  cos(log x)dx


A simple finite group $G$ with $n$ p-Sylows is isomorphic to a subgroup of $\mathbb A_n$

I am trying to solve this problem:  Let $G$ be a finite and simple group, and let $p$ be a prime number such that $p$ divides $|G|$. If $n_p(G)=n$ for $n>1$ (n_p denotes the number of p-Sylows) then $G$ is isomorphic to a subgroup of $\mathbb A_n$.  What I thought of was the following:  I consider the action of $G$ on $X$={H subgroup of G, H p-Sylow} by conjugation. Then there is a morphism $$\psi:G \to S(X)$$ $$g \to gSg^{-1} \space \forall S \in X,$$  where $S(X)$ is the set of all bijective functions $f:X \to X$. First of all, I would like to affirm $S(X) \cong \mathbb S_n$, but I don't know if this is true. Second, note that  $Ker(\psi) \neq G$ because if not $n_p=1$ and $Ker(\psi)$ can't be a proper subgroup because if that was the case $Ker(\psi) \lhd G$, then we have $Ker(\psi)=\{e\}$.  By the first isomorphism theorem, $G \cong G/Ker(\psi) \cong Im(\psi)$. Now, if I could show that $Im(\psi)$ is isomorphic to a subgroup of $\mathbb A_n$, then I would be done.  I would appreciate any hints or suggestions.


Wake-on-LAN quit working with latest kernel (Bionic)

WOL was working great on Bionic until yesterday's kernel update. How to diagnose/recover it?  Edit: if set to boot from 4.15.0-23 kernel it works. If set to boot from 4.15.0-24 it does not.  Edit2: WoL can be enabled with   sudo ethtool -s [card] wol g   but it isn't persistent. Searching for how to set it every boot.  Edit3: Per a comment by Kai-Heng Feng on this  this was an advertent change! (and therefore not a bug)  This is because the fix of LP: #1752772 has one commit [1] that disables WoL by default. Set WoL explicitly should solve your issue.  [1] https://github.com/torvalds/linux/commit/7edf6d314cd061e1d0a1b7bc0b511d64322c3f72


I was recently involved in a discussion on headphones, and realized I came short on a word for 'Audio' that could be used in the same way the word 'optically' is used for 'Optics'.   For example, I could say, "Lens A is optically superior to Lens B".   Is there such an equivalent word for 'audio'?


warning: passing argument x of 'xyz' from incompatible pointer type

If a variable is declared as:  char ** argv;    And a function's definition is something like:  extern int my_system(const char *argv[]);   Now if we are passing the argument in the function as:  (my_system(argv))   then it throws the warning passing argument 1 of 'my_system' from incompatible pointer type.  What can be the possible solution to this?


Why can't I define the upper range of my code with a variable? - Numerical Integration Method

I'm relatively new to Python, so my code is very simple. I have a project to write code which approximates integrals using the rectangle rule, followed by the trapezium rule:      a = float(input('Lower limit ---> '))  while True:     b = float(input('Upper limit ---> '))      if b > a:         break     elif a == b:         print('Integral = 0.')     else:         print('Invalid input.')  N = float(input('Number of integral divisions ---> '))  h = float((b - a) / N)  print('For the integral in the range {} to {} with {} divisions, the step size is {}.'.format(a,b,N,h))   def f(x):     return(np.exp(-x) * sin(x))  summation = (f(a) + f(b))  for points in range(a, N - 1):     summation = summation + f(a + (points * h))  I = h * summation  print(I)   Near the end, I try to use a for loop from the initial limit to minus 1 the number of step sizes. I've defined this as a float but it I keep getting the error      TypeError: 'float' object cannot be interpreted as an integer.   Any ideas how to fix this?


Did any vulcans ever appear in TNG other than Spock and Sarek?

The question is pretty straightforward:   The only Vulcans I ever saw on TNG were Spock and Sarek. Did any other Vulcans make any appearances? I know there was an effort to avoid Vulcan stories, but surely Picard and co. must have run into some other Vulcan besides Spock and his dad.


Ubuntu 14.04, Intel Chromebook, no sound

I am a total newbie to Ubuntu, and I'm not sure what to do here. I have a Toshiba Chromebook. I had a friend install the latest version of Ubuntu on it for me. For a while, the audio in Ubuntu was working fine, but now I can't hear any audio whatsoever.  How can I fix this?


What should I look for when buying a used bicycle?

I'm moving to a city where I can ride a bicycle to the grocery store, coffee shop etc. I want to purchase a decent used bicycle. I'm leaning towards a bike that's in between a "10-speed" or road-bike and a mountain bike. What should I look for when choosing a particular bike?  I've never purchased a used bicycle. Other than classifieds (e.g., Craigslist), what types of places can I look? What other issues should I consider, such as size, visual appearance, leaking tires, etc.? How can I make sure it's not stolen?


find the number of ordered triples $(x,y,z)$ satisfying $$x\mid yz-1$$ $$y\mid xz-1$$ $$z\mid xy-1$$ and $0<x,y,z<2014$  note: $x,y,z$ are integers  I found $(2,3,5)$ as one set of solution (actually $6$), and I tried change $$x\mid yz-1\Longrightarrow xk_1=yz-1$$but it didn't work.  Any idea/hint of how can I make progress?  Thank you in advance.  Note:I DO NOT want a computer testing all combinations.


SQL How to Select * into temp table output from stored procedure with paramaters

I've looked through many questions before asking the following: I don't have permissions to edit this Stored Procedure, only to run it and define the parameters. I need to aggregate the data from the output. For that, I am trying to store the output of the Stored Proc into a Temp table first. This is what I am trying to do, but obviously SQL doesn't recognize this:  SELECT * INTO #temp1 FROM     (         EXEC [dbo].[LockedStoredProc]          @START = '12/01/2016'         ,@END = '12/01/2018'         ,@PLAN_TYPE = 'all'         GO     )  Is there any way to get this to work the way I am trying to? I am using Microsoft SQL Server Management Studio.  Thanks!


The `ntpdate` command was removed from Mojave. What to use now?

In the latest macOS version (Mojave 10.14 Beta) the ntpdate tool has been removed. What I want to do is to simply restart the computer clock using an NTP server:  sudo ntpdate -u pool.ntp.org   Has Apple published the reasoning behind the removal, and have they replaced it with something else?


Repeated visits to the US on a multiple-entry tourist visa. Will I have any problems?

I've been re entering US three times this year. First was last February 13 where I entered using a J1 visa but I had to comeback home after 4 days because of some misunderstanding with the sponsor. And then last March 10 I returned to US using a multi entry tourist (B) visa and left on March 31st. Then the third one was last May 22 and then I came back home recently which was 10th of August. And now I am planning to return next month using a multi entry tourist (B) visa again on the same city and state to visit someone.   Will there be any problem when I return to US with an immigration officer?


How can I check the available version of a package in the repositories?

How can I check the version of the available package in the Ubuntu repositories without installing it?


Is there any different between $\mathbb{C}[x]$ and $\mathbb{C}[[x]]$

I know that $\mathbb{C}[x]$ stands for polynomial in $x$ with coefficients from $\mathbb{C}$, so that is  $$a_0+a_1x+a_2x^2+ \dots a_nx^n \in \mathbb{C}[x]$$  Than what is $\mathbb{C}[[x]]$?


Installing Ubuntu on a VM | Can anyone help with this warning?

I am fairly new to Ubuntu but I must say first of all... I LOVE IT! I am going through all of the installation and setup for it, but when I get to the installation type screen that is where my worry started. The screen looks as follows: This computer currently has no detected operating systems. What would you like to do?⚪Erase disk and install Ubuntu Warning: This will delete all your programs, documents, photos, music and any other files in all operating systems Will this delete everything in my host machine? Thanks in advance. PS: My apologies for the awful formatting, this is my first time posting here as im sure you can tell.


MacBook Pro can't run hardware test with pressing "D" key on reboot

I have a 13" Late 2012 MacBook Pro which works fine. I am trying to run Hardware test following the instructions in the Apple Support document, , but it is not working.  If I hold the D key while booting, it does not do anything. However, If I hold Option + D and then chose Wi-Fi connection in recovery mode, it shows the following error:  Error: 0x8000000000000003. Cannot Load 'EFI/Drivers/TestSupport.efi'  Status: 0x00000003   There is installed macOS Mojave 10.14.4 over USB today.  Update: The question:       doesn't describe my situation, because in the mentioned case, Option + D works, and no error message is thrown.


Way too much spaced between a table and a paragraph

I'm new to LaTex so I don't how to correct this problem. The right part of the image shows the pdf and the left one shows the code. As you can see, there is nothing more than words but the space in the pdf is way too much. Any idea on how to correct this?    Any advice would be much appreciated.


Should I stir my sourdough starter before measuring?

I'm new to using sourdough starter and some directions aren't very clear. I'm not sure if it needs to be stirred down before I measure for cooking and for feeding it. I've been stirring down the starter before measuring both when feeding and when cooking with it. Is that the right way? Also, I've only been keeping 1/2 cup of starter to feed, adding 1/2 cup water and 1 cup flour. If I keep more, do I need to increase the amount of flour and water I add?


Coordinate UV option is missing under Mapping

I'm trying to texture a simple plane, but whenever I go to mapping I don't find the UV option that should be there. Here are my steps:   Make new object (ShiftA) then add mesh > plane Add texture and then open the texture I want to use  Go to mapping and then click the coordinate option and there is no UV option.


The system is running in low-graphics mode error in “Virtualbox”

Hi guys this error just popped up in my VirtualBox. After the error screen shows up, I press command+F1(I use a Macbook) and a command line comes to the screen that wants me to login. After logging in, i tried   sudo apt-get autoremove  sudo apt-get autoclear   then press command+F8 but same error still remains.


difference between cp rm and mv in file transfers

I could write mv as  mv() {    cp $1 $2    rm $1 }   Therefore, in file transfers cp rm and mv could be equal, but there are dissimilarities.  How are the two options different?


Find a unit tangent vector to a curve that is an intersection of two surfaces.

The intersection of the two surfaces given by the Cartesian equations $2x^2+3y^2-z^2=25$ and $x^2+y^2=z^2$ contains a curve $C$ passing through the point $P=(\sqrt{7},3,4)$. These equations may be solved for $x$ and $y$ in terms of $z$ to give a parametric representation of $C$ with $z$ as a parameter.  (a) Find a unit tangent vector $T$ to $C$ at the point $P$ without using an explicit knowledge of the parametric representation.  (b) Check the result in part (a) by determining a parametric representation of $C$ with $z$ as a parameter.  For (b), I solved the two equations for the surfaces given to get $y^2=25-z^2$ and $x^2=2z^2-25$. Since we're looking for the curve that contains $P$, $x$, $y$ should be positive so we get $y=\sqrt{25-z^2}$ and $x=\sqrt{2z^2-25}$. So from this I get the parametric representation $(\sqrt{2z^2-25}, \sqrt{25-z^2},z)$ for the curve $C$.   Is this the correct way of finding the parametrization? Moreover, I do not know how to find the unit targent vector $T$ to $C$ at $P$, without getting a parametrization. How can I find this? The answer to $T$ is $\frac{1}{\sqrt{751}}(24,-4\sqrt{7},3\sqrt{7})$.   I would greatly appreciate any solutions, hints or suggestions.


The isometry group of $\mathbb{R}^n$, $\def\Isom{\operatorname{Isom}}$ \begin{eqnarray*} \Isom_n(\mathbb{R})=\{f\colon \mathbb{R}^n \to \mathbb{R}^n: f ~  \text{is an isometry}\}. \end{eqnarray*}  How to prove that \begin{eqnarray*}\Isom_n(\mathbb{R}) \cong \left\{\begin{bmatrix} A & \mathbf{t}  \\ \mathbf{0} &  1\end{bmatrix}: A\in O(n), \mathbf{t}\in \mathbb{R}^n \right\}? \end{eqnarray*}  Here $O(n)$ is the $n\times n$ orthogonal group.


Choosing my name as an author when publishing a scientific paper, can I use my "unofficial" first name?

I have one official first name which appears on my ID card. I have another first name which friends call me by. Is it possible to use my unofficial first name and official family name to publish scientific papers? How can I prove to someone that I am one of the authors?


Why every second even number have same number of even and odd Divisors.

Question: I was looking for natural numbers with same number of odd and even Divisors.Then I observed that, every second number in the list $2,4,6,8,10,12,14,...$ is such a number. Following list shows that, $2,6,10,14,...$ are even natural numbers that have same number of odd and even Divisors. $2 \qquad 1 \qquad 1\quad\ast$ $4 \qquad 1 \qquad 2$ $6 \qquad 2 \qquad 2\quad\ast$ $8 \qquad 1 \qquad 3$ $10 \qquad 2 \qquad 2\quad\ast$ $12 \qquad 2 \qquad 4$ $14 \qquad 2 \qquad 2\quad\ast$ $16 \qquad 1 \qquad 4$ $18 \qquad 3 \qquad 3\quad\ast$ ......... How we can prove this in general? Is there is something special about this? Note: I just copied the above list from  answer given here,


Let $f$ be holomorphic on an open disk containing the unit circle, except in a pole $w$ on the unit circle.  Assume that f has a power series expansion $\displaystyle \sum_{k=0}^{\infty} a_n z^n$ in the open unit disc.  Show that  $\dfrac{a_n}{a_{n+1}} \to w$.  How can I do this?


Why can't I recast aged close votes and flags that were cast a long time before the change allowing recasting?

In March 2015,  was made to the close voting system, to allow users to recast close votes and close flags 14 days after they age away.  However, according to , apparently votes that were cast before the change was made cannot be recast. The user in question was trying to recast a vote in 2016, but was prevented because they cast a now-aged vote back in 2011.  Why is this the case? Is this intentional, or is it a bug?


Does taking the power goes from left to right or from right to left? What is 2^2^3?

Does taking the power goes from left to right or from right to left? For example, what is 2^2^3?   According to a textbook I was reading, all operations are executed from left to right, which would make me think that 2^2^3 =$(2^2)^3=4^3$. However, my calculator says it is equal to $2^{(2^3)}=2^8=256$.


We have angle=arctan(dy/dx), but what happens when dx=0?

Here is a formula: $\text{angle}=\arctan(dy/dx)$.  I can find an angle with my calculator for any value except $dx=0$.  My question is: is there no angle or, is there something that says when $dx=0$ the angle is found differently?


How to clean an E: drive (new Recovery drive since Windows 10 1803) on HP laptop

I started getting warnings about running out of space on my E: drive.  I've read many articles, threads and posts online about how to clean the drive but none of them resolved my issue.  My machine specs:  OS: Win 10 Pro  Version: 1803  OS build: 17134.1  I disabled hiding of protected/system files to see what's on the E: drive but I don't see any clutter. I ran the disk clean up several time as an admin to no avail. Any tips and suggestions how to clean up the E: drive would be much appreciated! Thanks.


Categorical Principal Component Analysis - using Count, Continuous, Ordinal variables together

I have some variables and I want to reduce their number for further analysis. I initially thought of combining them using factor analysis. But since the variables are of all kinds (rating, count, ordinal, continuous dollar amount) I am thinking about using CATPCA for it. However, I have some questions about the technique -   Is CATPCA the right approach or Latent Class Factor Analysis would be the better one? By using the different kinds of variables together - how will the object scores be interpreted? For example - The rating question is on a 10 point scale but the dollar amount ranges from 0 to 1000s, so what will the object score obtained after CATPCA represent? And is it comparable to the Factor Score obtained from traditional PCA? For ordinal variables - Do all of them need to be in the same form, e.g. 1 meaning lowest and 10 meaning highest? Or can they be used in whatever form they are? Is it good to categorize the count and continuous variables based on their distribution and then treat then as ordinal/categorical variables?   I would highly appreciate any help you can provide!


Resize root partition from home partition space (swap in the middle)

I want to resize my root partition using Gparted but before doing it I want to make sure I'm doing it correctly.  Here is a screenshot of my GParted:    So, my question is:  Assuming I launch Ubuntu from a LiveCD and I get to run GParted how should I give space from the home folder to the root folder knowing that the SWAP is in the middle?  What is the correct process to minimize the risk of screwing up?


Import package.* or Import package.class_name

Are there any performance advantages or disadvantages to using either?   I notice in eclipse whenever I need to import something due to a class missing, it imports only that specific class.  Understandably because that is the only class I am using at the time.  For instance, I could have package.models.  This models folder contains 8 classes that define the structure of data tables.  This may be a small example but are there any performance advantages/disadvantages between using package.models.* compared to package.models.specific_model_name?  I asked this because when I first started in my programming career I used to get slaughtered for using "select *" in my queries.  I was curious if the same holds true for the importing of classes, which I have never really heard anyone mention before throughout my career.  Edit:  Thank you for all who responded.  I unfortunately do not have enough reputation to give anyone any upvotes.  I also would more lean towards this one being a duplicate, .


Can I assign multiple HREFLANG Attributes to the same Domain?

I am working on a website, which is looking to targeting multiple Regions and Languages, using the following Domains:   www.example.com (American English targeting US Traffic); en-gb.example.com (British English, targeting UK Traffic); en-au.example.com (Australian English, targeting Australian Traffic)   To help indicate these Regional and Language variations, I have assigned the following hreflang Attributes, within the <head> tags:  <link rel="alternate" hreflang="en-us" href="https://www.example.com" /> <link rel="alternate" hreflang="en-gb" href="https://en-gb.example.com" /> <link rel="alternate" hreflang="en-au" href="https://en-au.example.com" />   x-default  As well as targeting American English speakers, in the US, I would also like the https://www.example.com Domain to be the 'catch-all' website that targets all traffic that does not fit the other Domains' criteria.  With this in mind, would it be okay to add the hreflang="x-default" Attribute so that the https://www.example.com Domain ends up with an additional hreflang Attribute pointing to it?


Excel - Need to get a figure from one worksheet to another (it's complicated)

I have an Excel workbook with 2 worksheets.  One worksheet is for the input of stock transactions, the other has an overview of the portfolio.  So on the portfolio worksheet I would like to have a column with the total number of each stock.  Now to get this I would need a formula to check the name of the stock on the portfolio worksheet, say this is in B column, and then find the last input of this stock on the transactions worksheet (C column), and finally get the total number of stocks I have calculated on that row, say on J column.  Example:  Portfolio Worksheet    B    |      C       |         F             | Stock  | Last Price   | Cumulative Units      | IBM    |     ###      | (formula needed here) |   Transactions Worksheet    A   |   C    |         J        | Date  | Stock  | Cumulative Units |  ###  |  IBM   |   10000          |  ###  |  IBM   |     20000        |  ###  |  IBM   |       30000      |   I need a formula in cell F of the portfolio worksheet to check the value of B column (name of stock), and then search in the Transactions worksheet my last input of that stock and output the cumulative Unit figures on that row, e.g., 30,000.  I'm trying to make an Excel version of an online Google sheet portfolio tracker and the formula on the Google sheet is      =iferror(INDEX(arrayformula(filter(Transactions!J:J,Transactions!C:C<>"",row(Transactions!C:C)=max(if(Transactions!C:C=B2,row(Transactions!C:C),0)))),1),0)


What is the maximum capacity for a Time Capsule's hard drive?

I am thinking of buying a Time Capsule with a small hard drive and upgrading the drive to something larger. There is  on the web as to how to do it, but I am having a hard time finding any details as to what the upper limits of drive size are. It's especially confusing since there are  of Time Capsule, and each one may have a different upper limit. So, what is the upper limit of each? And, if you only know the answer to one specific one, that would be great, too.


I have the following class:  class MyClass{     string field1, field2; }   And I have List<MyClass> thats contains the following:  list.Add(new MyClass("1","1")); list.Add(new MyClass("1","2")); list.Add(new MyClass("1","3")); list.Add(new MyClass("2","2")); list.Add(new MyClass("3","2"));   I want to find the most frequent value of field1, this case I have three times the value "1", one time the value "2" and one time the value "3", How can I get the maximum count value of field1 (this case is "1")?


Help icon in the stackexchange.com is not working

The help icon in the Stack Exchange site's top bar is not working.     I navigate to my  and clicked on that icon, it is not responding. In other sites it is listing the drop down list.


My understanding of electrical resistance is, it arises due to the collision of the electrons with atoms in the path or in other words phonons. From the time of my undergrad years, I have been searching for a reason so as to explain why is there an electrical impedance of vacuum. I don't understand what provides this electrical impedance! There is no matter in vacuum to cause any collision. Also, the impedance is constant and does not have any dimensional part in it. That is confusing too. Is the explanation connected to the finite energy of vacuum or something else related to quantum field theory?


A subset of a polynomial ring and its ideal.

Let $P=K[x_1,\dots,x_n]$ be a polynomial ring over a field $K$ and $I = (f)$ be a principal ideal in $P$ generated by $f \in P - \{0 \}$. Moreover let $L \subset \{x_1, \dots, x_n \}$ and $\hat{P} = K\{x_i : x_i \notin L \}$. Show $I \cap \hat{P} = (0) \iff f \notin \hat{P}$. (Exercise 4, Section 3.4 from Kreuzer and Robbiano, Computational Commutative Algebra, vol. 1.)   So I know that in one direction, if $f \not\in \hat{P}$, then $f$ contains a variable in $L$, but then $\hat{P}$ cannot contain any variable that is not in $L$. So the intersection must be $0$. (this need some justification...?) I am not sure about the other way. If someone could show me both, that would be good.


Noob(ish) to Linux here, and trying to pick up new/useful tricks; I was wondering if there's some way to send the output of a command straight to the clipboard? Something similar to (pseudo-code): dircolors --print-database > clipboard