what I want to manipulate is the first element of v, the second print is supposed to be   [[3], [], [], [], []].   Code:  v = [[]] * 4  print(v) v[0].append(3);  #what i want to manipulate is the first element of v  print(v)   output:   [[], [], [], [], []] [[3], [3], [3], [3], [3]]

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


$$\sum_{k=1}^\infty \mathrm{(1-\frac{1}{k})}^{\mathrm{k}^{2}}$$ I tried using the limit comparison test with $$\sum_{k=1}^\infty \mathrm{(1-\frac{1}{k})}^{\mathrm{k}^{}}$$ but this leads to a limit of 0, which doesn't help. I think this may involve some use of  $\mathrm{e}^x$, but I don't know where else to start. Any suggestions?

Found the alternative form: $\sum _{k=1}^\infty ((1-\frac{1}{k})^{k})^k$. Tried various criteria, no luck so far.


All I remember is a guy who is dying from some kind of radiation, and is trying to find and punish the murderer of his race. He is the last of his kind, and has extreme fighting training, and is one of the best from his race. His race was made up of warriors, and could fight and beat nearly any foe. I think the protagonist was called Keith, or Kyle. He has a ship, and some battle equipment, and, if I remember correctly, a pet of some sort. The enemy was an organization called Darkwing or something similar. I can't remember much more, but I liked the books (it was a series) and really want to find it again!

I remember that the main character is trying to find the group that destroyed his home planet while he was on a mission. His planet was very difficult to live on and the people became expert in martial arts and were the best soldiers in the galaxy. They were mercenaries and often helped against tyrants. There was a very memorable section in at least one book about an initiation task that the main character had to do in that he had to survive in their wilderness for days. He was at some point surrounded in a old building by thousands of poisonous worm/snake creatures that he managed to survive until rescued by the leaders.


I am developing a web application using struts2 and jsp. I want to implement logout functionality in it. Although, I am able to remove the session but the browser's back button sends me back to the previously visited pages. I added the following code in each of the jsp file for preventing the caching. But this is not working. Kindly help.. So that after logout one cannot access the pages.     Code :-   <% response.setHeader("Cache-Control","no-cache"); // HTTP 1.1  response.setHeader("Pragma","no-cache"); //HTTP 1.0  response.setDateHeader ("Expires", 0);  %>  I have added this code in head tag of each and every jsp page.

Our investigations have shown us that not all browsers respect the HTTP cache directives in a uniform manner.  For security reasons we do not want certain pages in our application to be cached, ever, by the web browser. This must work for at least the following browsers:   Internet Explorer 6+ Firefox 1.5+ Safari 3+ Opera 9+ Chrome   Our requirement came from a security test. After logging out from our website you could press the back button and view cached pages.


Suppose $\gcd(a,b,c)=1$ (though the pairwise $\gcd$s may or may not be $1$). I have a pretty complicated proof that there is an integer $m$ such that $\gcd(c, am-b)=1$; it's probably not worth presenting here. Does anyone see a simple proof? Edit: Here is the proof I have. Let $d_m = \gcd(c, am-b)$ and assume that $d_m>1$ for all $m$, so that each $d_m$ is a nontrivial divisor of $c$. Let $p_1, \dotsc, p_k$ be all the primes dividing any $d_m$ (the set is finite since each $p_i\mid c$), and assume $p_i\mid am_i-b$. Use the CRT to find $m$ such that $m \equiv m_i+1\mod{p_i}$ for each $i$. By assumption, some $p_i\mid am-b$, but also $p_i\mid am_i-b$, so that $p_i\mid a(m-m_i)$. But $p_i\nmid m-m_i$ by construction, so that $p_i\mid a$, and then $p_i\mid b$. But also we know $p_i\mid c$, contradicting $\gcd(a,b,c)=1$.

I can't crack this one.      Prove: If $\gcd(a,b,c)=1$ then there exists $z$ such that $\gcd(az+b,c) = 1$ (the only constraint is that  $a,b,c,z \in \mathbb{Z}$ and $c\neq 0)$


The 'last seen' date on the profile page seems to have lost its color. This makes me sad. Let me illustrate:    I really like the color because it tells me stuff without me actually having to read. Please bring back color to mSE.

I am used to see timestamp everywhere by it's color. The recent timestamps are a little bit reddish everywhere. E.g. in Meta Stack Overflow:  Last edit:        Last seen:        But in Meta Stack Exchange they have same color everywhere even for recent time:  Last edit:        Last seen:         Please make it something like this:


I have a project organized as such: proj ├── main.py ├── netbatch │   ├── __pycache__ │   ├── monster.py │   └── test_monster.py └── workers     ├── __pycache__     ├── ldb     │   ├── __pycache__     │   └── handle.py     └── strawberry.py  strawberry.py contains import ldb.handle ... if __name__ == '__main__':  and main.py contains import workers.strawberry import workers.ldb.handle  When I run strawberry.py the import works as expected, but when I run main.py, I see the error:   File "/tmp/proj/workers/strawberry.py", line 3, in <module>     import ldb.handle ModuleNotFoundError: No module named 'ldb'  I'm using version 3.6.3

What is __init__.py for in a Python source directory?


If hypothetically a electron does manage to move in a specified orbit (we always find it anywhere on a particular locus), would it break Heisenberg uncertainty principle?

The quantum-mechanical model of atoms was derived from Heisenberg's uncertainty principle, which states that the position and momentum of a particle cannot both be determined to an arbitrary degree of accuracy. In order to understand the distribution of electrons in an atom, the momentum of an electron in the uncertainty principle is converted into its energy. The principle becomes "we cannot determine both the position of an electron and its energy to an arbitrary degree of accuracy". The idea that electrons exist in orbitals comes from the solving of the Schrödinger equation, which yields the principle quantum number, the angular momentum quantum number, the magnetic quantum number, and the spin quantum number. For each atom, a combination of the first three Schrödinger parameters specifies a unique electron orbital. It is noticeable that the Schrödinger equation simplifies the uncertainty principle to the extent that we are only uncertain about the position of an electron, but not its energy anymore. Each electron orbital represents a probability distribution map of electrons that fall under it. Theoretically, we can find an electron that falls under a given orbital at any position within the probability distribution map that it specifies. But the problem is, each orbital has a fixed energy value. No matter where in the orbital we find the electron, its energy does not vary. In other words, when we look at an atom and want to determine the position and energy of one of its electrons, we assign it to an orbital. The contradiction is that as soon as the electron is assigned an orbital, we fix its energy, and the only indeterminate variable is its position. So, does electron orbital theory contradict the uncertainty principle, where there are two indeterminate variables? A very concise version of my question: the Heisenberg uncertainty principle implies that we cannot simultaneously determine the position and energy of an electron. But if we divide the outer space of an atom into electron orbitals, like the electron orbital theory does, and assign each electron to an orbital, we wind up being able to determine the energy of each electron!


I looked at it yesterday and didn't share it.  But today tried to look at it again and it didn't show up?  And when I go to the URL it brings me to six photos of myself.

I didn't get a Facebook look back movie. I've been on Facebook since it was “thefacebook” in 2005 and I've shared my little heart out.   Anybody know if the automated video is linked to security settings or other things that might be locking me out?   I get the lame collage of 6 pictures that were all posted in the last week. No, thanks. I'd rather have a movie.


I'm begginer at this that's probably why I'm having this error while I'm trying to do something very simple.  I just want to get the current user ID and use it in other classes. But I'm getting NullPointerException Error for the ExecuteQuery() line.  Let me share the code:  public class LoginPage extends javax.swing.JFrame {  private Connection conn=null; private ResultSet rs=null; private PreparedStatement pst=null; private PreparedStatement sta=null;  ConnectionDB connect=new ConnectionDB();   public LoginPage() {     initComponents(); }  public void getCurrentUser(){     try{             PreparedStatement c;             conn=connect.getConnection();             PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users where Mail=?");             stmt.setString(1, lMail.getText());             ResultSet rss=sta.executeQuery();             if(rss.next()){                 int CurrentUserID=rss.getInt("ID");             }         }         catch(SQLException ex){             System.out.println("SQL Exception Error!1");         } }  private void loginButtonActionPerformed(java.awt.event.ActionEvent evt) {                                                  String sql="SELECT * from users where Mail=? and Password=?";     try{         conn=connect.getConnection();         pst=conn.prepareStatement(sql);         pst.setString(1,lMail.getText());         pst.setString(2,lPass.getText());         rs=pst.executeQuery();      if(rs.next()){         getCurrentUser();                 JOptionPane.showMessageDialog(null, "Welcome!");         new ListPage().setVisible(true);         dispose();     }     else     {         JOptionPane.showMessageDialog(null, "Wrong mail-password combination!");         lPass.setText("");     }     }     catch(SQLException ex){         System.out.println("SQL Exception Error!");     } }                                "ResultSet rss=sta.executeQuery();" is the NullPointerException part.  I gave hours to solve this but I couldn't so I need your help.  Thank you

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


OK, I downloaded ubuntu-16.04-desktop-amd64.iso  Why it has amd64 in the name confuses me.  And I don't know what to do with the file.  I really don't care to bother with a CD of any kind.  What I was expecting was a file I would click and then it would download more data.  When done a window would pop up about executing a program that would install.  Then I expected the usual screens as shown in the Installation Guide.   I was hoping to put any expanded files or install on a thumb drive and skip a CD altogether.  So, what do I do with this image file?

I would like to see a full how-to guide on how to install Ubuntu.


If I get banned from a single community (as opposed to all of SE) will that communities hot questions stop appearing in my feed?  I like Hot Questions but due to  I've clicked into a few of them and I keep getting these sites in Hot Questions. I like Hot Questions as it shows me questions from new-to-me sites that I do find interesting which are outside of my usual interests.   There are some feature requests, workarounds, and user scripts to tune Hot Questions but I'd rather just not see these sites at all.

I was going to make a filter for the "" by excluding some sites from it.  I noticed  which talks about "negative filtering" but does not explain how one can do it or if it is possible.  There does not seem to be a way to do this, though.  On the filter page, my only options are:  So how can I do "All sites except [list]"? It would also be nice if this could include similar functionality with the meta checkbox.  Something like "All main & meta sites except..."


When running the function: function updateCells() {   var ss = SpreadsheetApp.getActiveSpreadsheet();   var spreadsheetSummary = ss.getSheetByName('Summary');   const range = spreadsheetSummary.getDataRange()   const values = range.getDisplayValues()   const transposeCheck = values[0].map((_, iCol) => values.map(row => row[iCol]).some(cell => cell))   var countBoolean = transposeCheck.filter(Boolean).length + 1   var spreadsheetCommunityGroups = ss.getSheetByName('Community Groups');   var cellValueCommunityGroups = spreadsheetCommunityGroups.getRange('A12').getValue();   var summaryCommunityGroups = OFFSET('A2', 0, countBoolean);    sreadsheetSummary.getRange(summaryCommunityGroups).setValue(cellValueCommunityGroups); }  I receive the error ReferenceError: OFFSET is not defined. What I want is to place the value of A12 from the Community Groups sheet into the cell "1 column to the right of the last cell in row 2" of the Summary sheet. I count the number of occupied columns and 1 and save this as countBoolean, and this is what I am using to offset the columns.

I would like to use the exportRange Function and set the target to off center by one column.  How can I accomplish this?  function exportRange()      {    var import = SpreadsheetApp.openById('1KTvAvC6UCePjyEiOmyTlCokdiHMwYbKBJRAKDxaAIPQ');    var ss = import.getSheetByName('Business Division Master Contact List');     var SRange = ss.getRange(3,1,ss.getLastRow(), 16);         //Get full range of data    var A1Range = SRange.getA1Notation();    //get A1 notation id the range    var SData = SRange.getValues();          //get the data values in range     var tss = SpreadsheetApp.openById('1bfew3H4gluutxuo1tDRr8rwNCZHSuw16oHYthT_f8CM');    var ts = tss.getSheetByName('Business Contact List'); // ts = target sheet    ts.getRange(A1Range).setValues(SData);   //set the target to the source values   }


If we keep a computer charging, does it affect the battery so much that battery-life is greatly shortened? I am trying to find out why someone else's computer battery always gets bad after a couple of months using it. Is it just education on being aware to remove the plug when batteries are full, or is there any trick to use? Details The particular computer is HP, and the battery is Li+. But information about other battery types on this same respect is welcome.

There are many superstitions on what you must never do lest your battery become worthless - and by worthless I mean hold about 16 - 24 seconds of charge. This has happened to every laptop I have ever owned, and I just got a new one, so please help me sort out fact from fiction. Here are some of the things I've heard:   Do not keep your laptop fully charged. You must run it completely down every so often. Do not use your laptop plugged in to the wall. Only plug it in when it needs charge. If you will not be using your laptop for a long period of time, don't leave it at full charge. Do not leave your laptop running 24/7.   The first two I know to be complete fiction: this was true of old batteries such as you might have had in an iPod in 2003, but modern batteries function better when kept at or near full charge. Devices even have circuitry to prevent you from completely depleting your battery, as this is dangerous.  The third point sounds probable, and I'd be interested to know if it was true. However, it doesn't really apply to me because I'm not really the type to leave my laptop alone for a day, much less a "long period of time"  The fourth seems most likely of the above, but only because of causality: I have always done this, and my batteries have always crapped out on me. I've generally treated a laptop like a desktop with a battery backup, and that I can move from one room to another if necessary. The fact that my batteries tend to last less than 30 seconds has further entrenched this behavior. Should I be trying to break this habit?  Are there any other things that ruin laptop batteries? I love that I can actually use my new laptop unplugged :) I'd like to keep it that way.  Update: Additional question: If the computer will be used for an extended period of time plugged in, does it make sense to remove the battery first?  Update 2: I know people with laptops older than mine, who actively use their laptops as much as I do, and their batteries still hold about an hours' charge while mine holds less than 30 seconds, hence my belief that something I'm doing kills them.


I'm asking if there is a 3x3 area and if a player hits a specific part of that area can he be teleported to a similar 3x3 area I set up?

I am trying to teleport a player to certain coordinates once they enter an area.  The idea is that they walk into a really small building, but once they turn a corner, they get teleported into a larger building.   Please refer to the adventure map named '5 Cubed', if you need help understanding what I am asking.


I am trying to make an implementation of a Binary Tree for a Words each of a which have a pattern (ex hello - pattern is ABCCD)  I keep getting a null pointer exception on the line it states         while(pos.getPattern() != null || a){   I dont understand why- there are checks in place. Also when I print pos.getPattern()  - I get a string not a null value  I could really use some help  public void AddWord(String word) {     TreeNode pos = root;     boolean a = true;     String pat = PatternMaker.MakePattern(word);     while(pos.getPattern() != null || a){          if (pos.getPattern().equals(pat)) {             WordList list = pos.getList();             list.insertWord(word);             pos.setList(list);             a = true;         } else if (pat.compareTo(pos.getPattern()) > 0) {             pos = pos.getRight();         } else {             pos= pos.getLeft();          }     }     if(pos ==null){         pos = new TreeNode(word, pat);     } }


And if so, can it be kept alive somehow?  (This is not a duplicate question since I did not know that logging out will kill a process. Maybe others also don't and so ask the wrong question.   I would suggest that the answers include a link to the other .)

Let's say I launch a bunch of processes from a ssh session. Is it possible to terminate the ssh session while keeping those processes running on the remote machine?


I'm trying to display the selected checkbox row's values in vf page using wrapper class concept. But instead of the selected records, it is displaying all records values. here is my code.  Controller:  public class WrapperCls {  public List<myWrapper> wrapList {get;set;} public List<Account> accList {get;set;}  public WrapperCls () { wrapList = new List<myWrapper>(); for(Account a : [SELECT Name,Phone FROM Account])   wrapList.add(new myWrapper(a)); }  public void SelectedBox() { accList = new List<Account>(); for(myWrapper myWrap : wrapList) {      if(myWrap.isSelected = true) {     accList.add(myWrap.acc);  } } }  //Wrapper Class formation public class myWrapper { public Account acc{get;set;} public Boolean isSelected{get;set;}  public  myWrapper(Account a) { acc = a; isSelected = false; }    } }   VF Page:  <apex:page controller="WrapperCls"> <apex:form > <apex:pageBlock >   <apex:pageBlockButtons >     <apex:commandButton value="ShowDetails" action="{!SelectedBox}" rerender="tableId"/>   </apex:pageBlockButtons>   <apex:pageBlockSection columns="2">     <apex:pageblockTable value="{!wrapList}" var="w">       <apex:column >         <apex:facet name="Header">           <apex:inputcheckbox />         </apex:facet>         <apex:inputCheckbox value="{!w.isSelected}"/>        </apex:column>         <apex:column value="{!w.acc.Name}"/>     </apex:pageblockTable>     <apex:pageBlockTable value="{!accList}" var="a" id="tableId">       <apex:column value="{!a.Name}"/>       <apex:column value="{!a.Phone}"/>     </apex:pageBlockTable>   </apex:pageBlockSection> </apex:pageBlock> </apex:form> </apex:page>

Is it true that I cannot have OR or AND operators in if statements in APEX?  I have an object that has a picklist Code__c, and I need to execute some code if the code is set to either A or B.  How would I write something like:  if(pc.Code__c = 'A' || pc.Code__c = 'A') { }   Tia.


I believe this was written to order by someone like Asimov, but I can't find it.  An administrator works and works and gets promoted, finally, to teacher -- the crown of a school career.

I am trying to find a short story I remember reading probably in the sixties, about a reverse career path where the ultimate goal and privilege is to be a classroom teacher.


What am I doing wrong here?  counter = 0  def increment():   counter += 1  increment()   The above code throws an UnboundLocalError.

The following code works as expected in both Python 2.5 and 3.0:  a, b, c = (1, 2, 3)  print(a, b, c)  def test():     print(a)     print(b)     print(c)    # (A)     #c+=1       # (B) test()   However, when I uncomment line (B), I get an UnboundLocalError: 'c' not assigned at line (A). The values of a and b are printed correctly. This has me completely baffled for two reasons:   Why is there a runtime error thrown at line (A) because of a later statement on line (B)? Why are variables a and b printed as expected, while c raises an error?   The only explanation I can come up with is that a local variable c is created by the assignment c+=1, which takes precedent over the "global" variable c even before the local variable is created. Of course, it doesn't make sense for a variable to "steal" scope before it exists.  Could someone please explain this behavior?


I'm trying to understand how the this keyword works in this context.  function Person(name) {     this.name = name;     this.sayName = function() {         alert('My name is ' + this.name);     }; }   var p = new Person('Smith'); p.sayName();  // 'My name is Smith'  var q = p;  q.sayName();  // 'My name is Smith'  q = p.sayName;  q();  // 'My name is'   ???   Why is the last example not picking up 'Smith'?    Is it because q is simply pointing to a function (i.e. the object the method belongs to is not recognized in this context)? Since q is in the global space, this is global within the function (i.e. the caller of sayName() is the global space or window)?

In JavaScript, the "this" operator can refer to different things under different scenarios.   Typically in a method within a JavaScript "object", it refers to the current object.  But when used as a callback, it becomes a reference to the calling object.  I have found that this causes problems in code, because if you use a method within a JavaScript "object" as a callback function you can't tell whether "this" refers to the current "object" or whether "this" refers to the calling object.  Can someone clarify usage and best practices regarding how to get around this problem?     function TestObject() {             TestObject.prototype.firstMethod = function(){                       this.callback();                       YAHOO.util.Connect.asyncRequest(method, uri, callBack);              }              TestObject.prototype.callBack = function(o){               // do something with "this"               //when method is called directly, "this" resolves to the current object               //when invoked by the asyncRequest callback, "this" is not the current object               //what design patterns can make this consistent?               this.secondMethod();             }             TestObject.prototype.secondMethod = function() {              alert('test');             }         }


I've been trying to do it, but it's not working, my object has 2 elements, and it returns 1 element only :/  Here's the code I have  var jumbo = document.getElementsByClassName("jumbotron"); var button = document.getElementById("changebg");  var tiles = {   tile1 : {     header : "header1",     desc : "desc1"   },   tile2 : {     header : "header2",     desc : "desc2"   } };  function getObjectLength(obj){   var count = 0;   for ( var i in obj) {     if (obj.hasOwnProperty(i)) {       count++;     };   };   return count; };  function changeBackground(){   document.getElementsByClassName("jumbotron")[0].innerHTML = getObjectLength(document.getElementsByClassName("jumbotron")); };

I have a JavaScript object. Is there a built-in or accepted best practice way to get the length of this object? const myObject = new Object(); myObject["firstname"] = "Gareth"; myObject["lastname"] = "Simpson"; myObject["age"] = 21;


I remember reading a series of 3 short sci-fi stories or novels in the late 90s. The books themselves were older, probably from the 80s.   The three booklets all had the same protagonist: a psychic gambler, as far as I remember.   In one book he fixed a planet that had to deal with psychic-linked fauna. The settlers there had set up automated defense systems, which angered the fauna, forcing them to attack.  In another, he crash-landed in an early renaissance world. He brown-nosed up to one of the houses that ruled there, using his knowledge about electricity. He built a Morse Machine, that used a modified Morse code. I believe or was HTH encoded like our SOS as ...---... .  My memory fails me on the contents of the last book.  Which series is that and who wrote it?

I listened to this on audiobook and it was great.  The premise was a human ends up travelling to an alien planet. The aliens have a perimeter to their 'base' that is under constant attack from the planet's animals. It is revealed towards the end that there is some sort of signal being transmitted that is making all the animals and plant life attack a certain point on the planet (where the aliens are).   Other major plot points I remember: The human traveller falls in love with an alien. The aliens have a sort of virtual training environment that simulates life outside the perimeter, where plants attack you etc. There is a secondary alien group that the human ends up with, and although they are rivals to other group, they have a trade set up.   Any help much appreciated! Thanks.


Let $R$ be a commutative ring with identity. Let $I,J$ be ideals of $R$, such that $I\subseteq J$. Then the canonical map  $\Phi: R/I\rightarrow R/J$ defined as $\Phi(I+x)=J+x$ is a surjective ring homomorphism.   Now take $R=\mathbb{Z}$ and $I=m\mathbb{Z}$ and $J=n\mathbb{Z}$ where $n\mid m$. It is clear that the image of ${(\mathbb{Z}/m\mathbb{Z})}^{\times}$ under $\Phi$ is contained in ${(\mathbb{Z}/n\mathbb{Z})}^{\times}$. If we denote $\phi$ as the restriction of $\Phi$ to ${(\mathbb{Z}/m\mathbb{Z})}^{\times}$ then we have  $$\phi:{(\mathbb{Z}/m\mathbb{Z})}^{\times}\rightarrow {(\mathbb{Z}/n\mathbb{Z})}^{\times}$$  I checked a few cases and it seems $\phi$ is surjective. Is it true in general ?

If $m|n$. Why the map $f\colon \mathbb{Z}_n^\times \to \mathbb{Z}_m^\times$ given by $a \mod{n}\mapsto a \mod m$ is a surjective homomorphism of groups?  Attempt: I proved it is well a well defined homomorphism because the canonical projection $\overline{f}\colon \mathbb{Z}_n \to \mathbb{Z}_m$ is a surjective ring homomorphism, it extends $f$ and maps units to units.  But I can't prove surjectiveness. Given $a\in\mathbb{Z}$ such that $(a,m)=1$ I'm looking for a $k\in\mathbb{Z}$ such that $(a+k\cdot m,n)=1$. I don't know why one of the $n/m$ candidates for such $k$ makes the number $a+k\cdot m$ an unit modulo $n$.


Is there a possible word that describes a want for a tragic event to occur. Like a death of someone close. I have only gotten a few close words but they don't really satisfy what I'm trying to describe. (Catharsis, depressed, melancholy, masochist)

Is there any word or phrase or idiom that describes a person who takes the pleasure from the misfortunes of others?


I tried to install Ubuntu 14.04 LTS as a dual boot on my Alienware 15 R3 by following .  However, when I boot Ubuntu from live USB (which means "Try Ubuntu without Installing"), Ubuntu gets low graphics mode and can't go further.  I think this might be related to graphic card (GTX1070). Ubuntu 14.04 Live ISO cannot deal with GTX 1070, but I'm not sure how to fix it.  When I tried Ubuntu 16.04 instead, it successfully worked but I need 14.04 LTS.  Do you have any idea?  My Alienware 15 R3 is:   CPU: Intel R Core i7-7820HK GPU: GTX1070 8GB Memory: 16GB DDR4 2400MHz (2x8GB) Hard disk: 256GB SSD+ 1TB HDD   Thanks in advance

Note: This is an attempt to create a canonical question that covers all instances of "low-graphics mode" error that occurs to a user, including but not limited to installation of wrong drivers, incorrect or invalid lightdm greeters, low disk space, incorrect installation of graphics card like ATI and Nvidia, incorrect configuration of xorg.conf file while setting up multiple monitors among others. If you are experiencing the "low-graphics mode" error when trying to login but none of the following answers work for you, please do ask a new question and then update the answers of this canonical question as and when your new question gets answered.   When I try to boot into my computer, I am getting this error:  The system is running in low-graphics mode Your screen, graphics cards, and input device settings could not be detected correctly. You will need to configure these yourself.   How do I fix the failsafe X mode and login into my computer?  Answer index:


I'm trying to convert a python script to C# and i'm trying to make sure it's in 1 line of code.  How would I go about converting this line?  if op.scale in (2, 4, 8):   yeah op.scale is a integer datatype so it's checking if it matches any of those values in the array.  I know in C# you can use Range but this isn't a range question  if (Enumerable.Range(2,8).Contains(op.scale))   A attempt I just tried.. looks promising but I got to get it to compile.  if(Array.Exists(new Integer() {2,4,8}, element => element == op.scale))

What would be the best way to look in a string[] to see if it contains a element. This was my first shot at it. But perhaps there is something that I am overlooking. The array size will be no larger than 200 elements.  bool isStringInArray(string[] strArray, string key) {     for (int i = 0; i <= strArray.Length - 1; i++)         if (strArray[i] == key)             return true;     return false; }


I have a catalyst server running on a VM.  [info] Hello powered by Catalyst 5.90103                                                                                HTTP::Server::PSGI: Accepting connections at http://0:3009/   And connecting within the VM  vagrant@precise32:/var/log/apache2$ curl 'http://localhost:3009' DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" etc ...   The port seems to be listening  vagrant@precise32:/var/log/apache2$ netstat -an | grep "LISTEN " tcp        0      0 0.0.0.0:36300           0.0.0.0:*               LISTEN      tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN      tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      tcp        0      0 0.0.0.0:3009            0.0.0.0:*               LISTEN        Connecting remotely I can see port 80 but not 3009  curl 'http://localhost:80' curl: (52) Empty reply from server curl 'http://localhost:3009' curl: (7) Failed to connect to localhost port 3009: Connection refused   I've seen similar threads but nothing has helped. This is iptables  vagrant@precise32:/var/log/apache2$ sudo iptables -L Chain INPUT (policy ACCEPT) target     prot opt source               destination          ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:http ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED  Chain FORWARD (policy ACCEPT) target     prot opt source               destination           Chain OUTPUT (policy ACCEPT) target     prot opt source               destination   And the firewall is turned off  vagrant@precise32:/var/log/apache2$ sudo ufw status   Status: inactive   I'm very new at VM, I'm not sure if this is a hosts problem, an apache problem or a cataylst problem.  I did try running a python server and couldn't connect to that either.  All advice is much appreciated.  Thanks  EDIT - I've looked at similar posts, the general solutions there are not listening ports or firewall.  I don't think either applies here.

This is a  about Connection Refused    We see a lot of questions to the effect      When I try to connect to a system I get a message      Connection refused      Why is this ?


i want to get rid of filling a query form on daily basis and want to automate it. But it is having captcha and i want to turn off captcha so that i can automate form using selenium webdriver using python.

How can I automate "Enter CAPTCHA" using Selenium WebDriver?


I am studying mathematics and I am very interested in computer science but I want to know in what areas of mathematics must I focus on.

I'm a computer science major and like many of us we have to take two additional sciences. These two additional science courses are in addition to three semesters of calculus,two semesters of physics, and one semester each of linear algebra and discrete math.  I could take the easy way out and take an algebra based astronomy course, but I want the most bang for my buck as it relates to my major.What other types of math classes should I take? I do enjoy math a lot and have always done well.


Please I want to know the difference between the two words( dialect and accent)

The definition that I have had in my head for most of my life is:  dialect: a variation of the original language (usually regional), sometimes even using different vocabulary and grammar accent:  a discernible influence of another language (usually because the speaker is not talking in his native tongue)  Yet, I keep hearing about Southern, Scottish or New York accents...shouldn't these be more accurately called "dialects"? I could see that the answer might not be as clear cut in the US as in the UK because there are probably far more "native" American speakers whose ancestors' native language was not English... Disclaimer: I'm German myself and I'm more or less assuming that "accent" and "dialect" directly correspond to their German "lookalikes": "Akzent" and "Dialekt". Maybe the semantics of those two words are simply different in English? If so, feel free to close this question.


I often build large projects. An example is a site that is built with Jekyll. The build takes about 20 seconds, and changes thousands of HTML files. The same happens when I build the documentation of some projects.  Tracker store picks this up, and then starts indexing them, causing huge CPU spikes.    I don't need tracker to index these build-artifacts. The build artifacts go into one, or at most a very few, known directories, but these might have subdirectories. I do want tracker to keep indexing most of my system, I like the features it offers on Ubuntu.   Is it possible to selectively disable tracker indexing or monitoring a certain directory and its subdirectories? On e.g. Android a .nomedia file avoids Android from indexing it: does something like this exist for Tracker, or is there another kind of config for this?

I am running Ubuntu GNOME 15.10 with GNOME 3.18, and I would like to know if I can do any of the following and if so how:   Make it so that a folder is not indexed but leave its contents indexable (so that if I search for that folder's name in my system nothing will come up, but if I search for its contents, that will come up) Make it so that a folder is not indexable and nor is any of its contents (and if it contains sub-folders within it then it should recursively not allow any contents in them to be indexed nor the contents of any sub-sub-folders in the sub-folders etc, nor any of those sub-folders themselves) Make it so that individual files in a folder are not indexable, though not having any impact on other contents nor the parent-folder   So, are any of these variants possible? I believe the indexing program is called Tracker which indexes files and folders and their contents and allows for one to search for them on the system.


I want an air-freshener because I can't stand bad smells.  Here, isn't 'I can't stand bad smells' a coordinate clause? It is complete in itself, right? It's only after adding 'because' that the sentence becomes subordinate. But 'because' is a conjunction. So, if we want to check if a clause is coordinate or subordinate, shouldn't we exclude the conjunction ('because') here? Edit: Thanks to the people who have answered this question! Below, I am writing what I have inferred/concluded from all the answers. I request everyone, to inform if what I understood is correct or not.  subordinate clauses are necessary in the sentence to convey its full meaning, and that coordinate clauses are of greater value/importance than subordinate ones.  Coordinate and subordinate clauses can exist without the help of each other, and will make complete sense, but in order to convey the whole meaning of the original sentence, it is important to use them both.  Let's say in this sentence, both are making complete sense on its own, but coordinate clauses are more important. "I want a freshener" is more important than telling its reason. "I can't stand bad smells", which is the subordinate clause in this sentence, can stand alone, but it is of lesser importance in the original sentence.

He went to bed, for he was tired. (For = coordinating conjunction) He went to bed, because he was tired. (Because = subordinating conjunction) Is this correct? If so, I'm confused. In all the examples and explanations I've found online it says 'for' is a preposition unless used in that particular way above, in which case it becomes a coordinating conjunction (FANBOYS). But to me it seems like 'for' has the exact same function and meaning as 'because' in the above example. Both could be replaced with 'due to the fact that...' Why is 'because' subordinating but 'for' coordinating?  FANBOYS: for, and, nor, but, or, yet, so


I've been reading that it is possible to keep Cid alive after Celes wakes up from you coma on Solitary Island in Final Fantasy VI, from what I've read if I end up saving Cid, instead of Celes finding out about the raft from Cid's note he shows it to her himself  Considering that there are only 2 good fish that will raise Cid's health, his health drops by 1 every second your not in a menu, you can let it drop bellow 30 and have to raise it above 255 to save him it seems like a hell lot of work and I've always thought that after Cid's death and Celes's attempted suicide due to her now being left alone in the world made for a better motivation for her to search for Locke after seeing that bird.  So i'm wondering, apart from the slight change in how he finds the raft to leave the island, is there any worth while changes what would validate spending so much time trying to save Cid cause i remember spending 10 minutes getting fish repeatedly to get nowhere so I just then waited

At the start of the World of Ruin phase of the game, Celes can feed fish to Cid.  Based on the quality of the fish, Cid will either either live or die.  How does the rest of the game change based on whether Cid lives or dies?


I'm a Ugandan going to Ecuador, transiting in Amsterdam. Do I need a visa?

I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows:  Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland


Is this correct? or can the same thing be written in a better/more correct way?:  "The country has 2 million inhabitants, of which 300000 reside in the capital." Thanks

How does one correctly apply “in which”, “of which”, “at which”, “to which”, etc.?   I'm confused with which one to apply when constructing sentences around these.


I have a debt from 4 years back that is on my credit report. Because I have been out of the country for 4 years, I did not know about the debt until now. My question is, does paying the debt reset the 7 year clock on my credit report, or will it just continue for 7 years from the original date?  I have no problem paying the debt (whether it is valid is a whole other story), but I do not want to fight with this for another 7 years.  Update: This is in California, the debt will be out of SOL by the end of January. But they have just called me (did not say i was here though).

Let me explain a little more. I was the victim of a car accident and medical bills went through the roof. I had about $16k racked up, then my settlement finally kicked in 3 years later and paid it all off (except for that pesky $8). What happened was when we queried the debt from the hospital I went to, they somehow missed that $8 (out of the $16k) and sent it to collections. This all happened about 4 years ago. I didn't receive any letters in the mail for some reason as well. I did a credit check a few months ago to get a car loan, and my banker found the collection. I need to get rid of it, because a job I want to apply for also looks at my credit.    Should I pay it off? I would not like it to be on my credit history... Can I dispute it since they failed to bill me for it in the first place?


How can I apply one part of the weight paint on the other side of the mesh with symmetrized bones?

How can I mirror my weight painting to the opposed side of my character? I know that there is Mirror function, but it doesn't assign the weight to bones on the opposed side. Can I do it manually?


I have following questions about anonymity on SE sites:   In which cases (or how) can a user become anonymous on an SE site? Are there any levels of anonymity on SE sites? Can a registered user be anonymous as well? Can I have a normal profile on one SE site & an anonymous profile on another SE site using a single SE account (or email)?   How I define anonymity: as , see the grayed-out profile of the owner of this post.

Say I want to join and discuss sensitive topics on e.g  and still stay completely anonymous. Wouldn't this be impossible if anyone could see my other accounts on other SE sites. Where I might tell more about my self, where I work and so on?  Is it possible to hide your other accounts on your Stack Exchange account page? Should it be possible or even the default option?  I understand the idea of having your accounts on SO and Meta connected. But what is the main reason of having every one of your SE accounts connected?


How can I determine all files and folders that given user can write to? The user is nobody. Some script in bash or python, perhaps? I'm using Ubuntu 11.04

I am root. I would like to know whether a non-root user has write access to some files - thousands of them. How to do it efficiently while avoiding process creation?


I was wondering if adding http:// into my links was a bad thing for SEO optimization.  I know that is unnecessary but I have several links that are displayed in multiple subdomains.  I try to explain it better:   The main site is in http://www.example.com and in every page there are some links to other pages I have, for example, http://search.example.com and http://account.example.com that has the same header with links that point to http://www.example.com   So, my question is, if the spyder goes to http://www.example.com and finds several links that point to http://www.example.com/page1 instead of /page1, ecc. would this hurt indexing?

Our site's navigation links are currently in relative form:     The SEO company I mentioned in my  recommends we change them to absolute links:     This is to "ensure search engines get the correct and working URL for the pages". Is this really something that should be taken into account or is this another case of extra work with no added benefit?


http://cdn.sstatic.net/askubuntu/all.css  http://[2400:cb00:2048:1::be5d:f53a]/askubuntu/all.css   is not reachable via IPv6.  When trying to access any site, cdn.sstatic.net is not reachable via IPv6 http and therefore does not load.   If IPv6 is disabled, all sites work just fine.   ICMP/Ping works just fine, but http traffic times out.   Tracing route to 2400:cb00:2048:1::be5d:f53a over a maximum of 30 hops  1 1 ms 1 ms 1 ms vlan10.dhk10.core-backbone.com [2a01:4a0:1337::1] 2 1 ms <1 ms <1 ms xae0-4023.nbg20.core-backbone.com [2a01:4a0:0:4023::2] 3 3 ms 4 ms 4 ms xae0-2002.fra20.core-backbone.com [2a01:4a0:0:2002::4] 4 3 ms 3 ms 3 ms ae51-3356.edge7.Frankfurt1.Level3.net [2001:1900:5:2:2::75] 5 3 ms 3 ms 3 ms vl-60.edge4.Frankfurt1.Level3.net [2001:1900:104:5::9] 6 3 ms 3 ms 11 ms Telia-level3-10G.Frankfurt.Level3.net [2001:1900:5:3::24e] 7 88 ms 88 ms 88 ms prs-b8-v6.telia.net [2001:2000:3018:2a::1] 8 98 ms 97 ms 97 ms cloudflare-ic-154355-prs-b8.c.telia.net  [2001:2000:3080:567::2] 9 89 ms 89 ms 89 ms 2400:cb00:2048:1::be5d:f53a  Trace complete.

For about 2 weeks, multiple people (around 10 that I know of) in our company are having trouble accessing Stack Overflow; independently of the browser, and on Linux as well as Windows. The symptom is that assets loaded from cdn.sstatic.net keep waiting forever or until they time out.   On my machine the status is that at some point those requests time out and a version of the page without any images or CSS appears.  For some Windows users reboots help, for others it doesn't.   Meta Stack Overflow (now Meta Stack Exchange) always loaded for me.  A workaround for my machine was to disable IPv6 temporarily on Linux with the command echo 1 | sudo tee /proc/sys/net/ipv6/conf/all/disable_ipv6.  Note that no other site (that I visit) has been affected like this.  Update 2013-08-12: our network guy did some checking and insists the problem lies with Cloudflare. We seem to have issues when trying to connect to them with IPv6. We can't go around and disable our IPv6 Support since we need it for our internal infrastructure. We employ the following workaround (sadly only works with Firefox):   Go to about:config find the configuration key called network.dns.ipv4OnlyDomains Set it to the following list of domains (or add them if you already have something in this key): cdn.sstatic.net,www.cloudflare.net,cdn-careers.sstatic.net


I am trying to fit a UML diagram in a page, but it overflowing to the right. I've tried hfill, flushright, flushleft but none of this work. Here is the code:  \documentclass[twoside,openright,titlepage,numbers=noenddot,headinclude,  footinclude=true,cleardoublepage=empty,abstractoff,BCOR=5mm,paper=a4,fontsize=11pt,ngerman,american]{scrreprt} \usepackage{classicthesis} \usepackage{tikz-uml} \usetikzlibrary{positioning}  \begin{document} See next page\clearpage \begin{figure}[ht]   \begin{tikzpicture}     \umlclass{Accuracy}{}{}     \umlclass[right=5mm of Accuracy]{DepParsing}{}{}     \umlnest{DepParsing}{Accuracy}     \umlclass[right=5mm of DepParsing]{LabeledSentence}{}{}     \umlassoc{DepParsing}{LabeledSentence}     \umlclass[right=5mm of LabeledSentence]{Tokens}{}{}     \umlclass[above right=3cm and 2mm of LabeledSentence.north]{TrainSentence}{}{}     \umlclass[above=5mm of LabeledSentence,left=5mm of TrainSentence]{TestSentence}{       + words:Vector[Str]\\       + tags:Vector[Str]\\       + tree:Vector[Str]     }{       + size:Int     }     \umlVHVinherit{LabeledSentence}{TestSentence}     \umlVHVinherit{LabeledSentence}{TrainSentence}     \umlclass[x=0,y=0,left=5mm of TestSentence]{Node}{       +lex:Str\\       +pos:Int\\       +posTag:Str\\       +dep:Int\\       +left:Vector[Node]\\       +right:Vector[Node]     }{}     \umlassoc[mult=1..*,pos=0.5,recursive=-190|190|3cm]{Node}{Node}     \umlassoc[mult2=1,mult1=*]{Node}{TestSentence}     \umlassoc{LabeledSentence}{Tokens}     \umlclass[below=5mm of DepParsing]{SVMAdapter}{}{}     \umlassoc{SVMAdapter}{DepParsing}     \umlclass[left=5mm of SVMAdapter]{SVMProblem}{}{}     \umlnest{SVMAdapter}{SVMProblem}   \end{tikzpicture} \end{figure} \end{document}   Here is the output:    What can I do?  NOTE: I am using ClassicThesis  Best regards

I have a document containing a table which is slightly too wide for the page. But instead of growing to the right side only, I would like to have it centered on the page.  I have tried to use the center environment but this doesn't seem to help.


I am a user of Fedora 30. I installed Fedora on a USB memory stick and use it with Windows 10 on the same computer. How do I set the options in fstab to make it read-write to an NTFS-formatted Windows 10(hdd 01) or secondary disk(hdd 02)?

I have Windows and Arch Linux in dual with UEFI. I want to mount my another NTFS partition in Arch. I mounted the partition with mount /dev/sda5  /mnt/Apps command. Then added the output of genfstab -U /mnt/Apps in /etc/fstab file. The output is as follows:  UUID=01D158CC7C2A61A0 /mnt/Apps ntfs rw,nosuid,nodev,user_id=0,group_id=0,allow_other 0 0   But when I unmount and remount that partition all files and folders shows with root uid and gid and 0777 permission. I also tried with changing uid and gid to 1000 but same result. So, my question, what is the correct way to add NTFS partitions in fstab so that I can read & write all file and folder both with normal user (1000:1000) and root (0:0)?


While some gold badges are cumulable without huge effort, like  (10,000 views) or  (score of 100), it seems that the time spent in reviewing cannot be rewarded anymore past 1,000 review tasks, as the  badge can only be awarded once (per queue).  I propose that reviewing way above the current Steward threshold should still award something. This could maybe or maybe not help to pop the , but at least it would be nice to recognize the work of super active reviewers.  Possible rewards ideas (open to discussion):   a silver Steward every 1,000 review tasks above 1,000. Maybe a different name? a gold Steward every 1,000 * 2^n review tasks for n in 0 … ∞.

As we announced in our post on  to the Review Queues, the Steward badge can now be earned more than once per queue. The purpose of this post is not to debate the merits of this decision ( already exists), but to explain the nuts and bolts of how it will be backfilled. This is how it will appear on your profile if you have earned it multiple times:  Once we push the visual design changes live across the network, this is how badge attainment will look on /review/close/stats:  For those of you who have already completed enough reviews to earn multiple Steward badges, we will be retroactively awarding them to you, starting today. The backfill script will run about twice an hour, and your achievements trophy will light up as each one is awarded. For those of you who have done thousands and thousands of reviews, things may be a bit noisy, so we thank you in advance for your patience. It may take up to two days for all of your badges to show up.


I have an espresso machine that I tore down, reassembled with fewer components then modified it to fit a specific setup -- kind of DIY project.   The machine has an autofill circuit. After I removed the controller and SSR, the machine does not have an autofill circuit, which is fine when I turn on the pump to refill manually. The only problem is checking the water level to find out when I need to refill the boiler. I fitted a sight glass for that purpose, but I still need another aid to notify me whether the water level is OK or not, mainly in case someone else is using it.   I want to add  a small buzzer/LED which is activated only when the water level drops below a certain point, OR just a LED which lights up so long as the water level is fine.   There is a water level probe. The boiler is grounded so if there is water touching it there will be a circuit/current through the probe, and if water is below the tip then there is no circuit (this is my understanding, so please correct me if it is not correct.)  There are buzzer/LED gadgets that can be bought cheap, but I want to know how it would work with the water level probe? I tried connecting the probe to a LED then  to one of electric current poles; I thought it should light up when there is water touching the probe, but it does not seem to work, or maybe it is just the wrong way to do it. :)   Any help is appreciated.

I wanted to create a circuit that Lit's up an LED when water level rises to a certain level.   I have created the following schematics following the  However since the LED lit up even though there was no water i needed to add the R1 resistor.          – Schematic created using   Now i want to do the opposite. I want the LED to not light up when both probes are connected with water and lit up only when water level drops.   For that i have created a following circuit swapping the BC546B (NPN) with BC556B (PNP) transistor.          However this lights the LED when the probes are not connected with water but even shorting them doesn't turn off the PNP transistor (that is LED is still glowing). Removing the R1 and path to ground from base of the PNP makes it glow dimly (it glows more when i hold the water probe) and connecting them then does turn off the PNP.  Why is that ? I thought i can turn off the PNP by applying a small amount of voltage to its base?   How can i fix my circuit so that it works ?   Ps. i have also tried with a darlington PNP transistor TIP 125 and it doesn't work


When constructing tag wikis, it seems that the tag wiki of the same tag in different websites must be built every time.  It seems that there is something can be improved. It repeats much and is not .  For example:  The information of  in  softwareengineering.stackexchange.com could be the information of  on stackoverflow.com.  I guess most tag wikis of different websites of stackexchange.com could be the same.  Because the knowledge is there, and it reflects the truth.  On the other hand, different websites of stackexchange.com has their own feature. So the community wiki may be has a content offset accordingly.  The tag wiki is unified and has its own feature on different websites of stackexchange.com.  I don't know how to achieve it.    I don't think this question is a duplicate of .  The question is based on the fact. I found that many tags information on other websites programming-related is to copy small part of the tag info on Stack Overflow.  Another example:  on codereview.stackexchange.com is not much like the answer below at least now, compare to  on Stack Overflow.  The naming duplicate question seems that it looks good, and "I" think it is reasonable.  Talk is cheap; what I discussed exists on programming-related websites, not cooking.

Was unable to find rationale for separate tags accros SE sites.   Tag function According general definition in information systems, a  (such as an Internet bookmark, digital image, database record, or computer file). This kind of metadata helps describe an item and allows it to be found again by browsing or searching. Tags are generally chosen informally and personally by the item's creator or by its viewer, depending on the system, although they may also be chosen from a controlled vocabulary.  On SE - the same:  is a () word or phrase that describes the topic of the question help you identify  or relevant to you.  tag origin and quality  Where from tags are originated and what are tag quality parametres?  problems and contradictions examples related with SE tags  Humanity is facing information overload.  are created for collecting and sharing personal knowledge on questions or problem solving. But tag's descriptions are not matter of personal knowledge - it's just matter of , i.e. vocabulary/dictionary, or taxonomy/ontology or, speaking in general, human lexic conceptual apparatus / framework. So why time has to be spent on fact's duplicating and sharing?  At the same time We are living at the linked data times. IMHO it's the biggest blunder having same tags with different descriptions in different SE sites unlinked. Tags (and so - descriptions) should be unified.  So I'm calling to unify all tags across SE sites as feature request. Maybe automatic linking to Wikipedia and/or some other decent dictionary would be reasonable.  solution examples  This is not a duplicate of


I am an international student on F1 visa. Can I day trade US stocks?  As a day trader I will be placing multiple buy sell orders within a day. Is there any limit to number of orders that I can place per day?  Is there a maximum limit on dollar value of trades? Is it legal for me to trade given I'd pay my taxes due on my trading profits?  I will be trading solely for myself. Will it be considered work and hence illegal?  I know long-term investing is allowed for F1 visa holders given they are in good academic standing and their visa status is maintained. Is day trading allowed too?

I am foreign graduate student in USA. I recently completed my undergrad (from USA) and have a bit of money saved up. I know that F1 students cannot work off campus and other business activities such stock trading etc are prohibited as well. I wanted to know if opening an account in an investment management firm like Charles Schwabb or Betterment is allowed. I would not be working but I will still be earning a small interest on my deposits. If that is not allowed, are there any good and legal ways for foreign students to earn a little interest on savings?


Prove that  $$\frac{z}{(1-z)^2} = \sum_{n=1}^{\infty} nz^n.$$  Do I need to do this by induction or by any other way?  Please help.

How can I evaluate $$\sum_{n=1}^\infty\frac{2n}{3^{n+1}}$$? I know the answer thanks to , but I'm more concerned with how I can derive that answer. It cites tests to prove that it is convergent, but my class has never learned these before. So I feel that there must be a simpler method.  In general, how can I evaluate $$\sum_{n=0}^\infty (n+1)x^n?$$


I'm a beginner programmer and I want to know how can you upload your pygame on websites like coolmathgames or any game websites, do you upload your code after you get a deal with them? do you save it into a file and then upload it through some button? Like how does the whole thing work. Thanks!

I have a Pygame game, and I was wondering if there was any way to embed it into a webpage to make it easily playable, or if there is a games website that accepts Pygame games.  EDIT: I am now using Unity and am not after the answer anymore, but please answer if you want as it could help others.


In classical theory (e.g., classical mechanics and electromagnetic theory), we introduce the complex values for the mathematical convenience, e.g., A=(a+a*)/2. There, the use of complex values (or vectors) is not necessary as we can in principle describe everything with real values (or vectors).  However, in quantum mechanics and quantum optics, why do we need to use the complex vector to express a quantum state? Would it possible to describe a quantum state with a real vector although it will not have a mathematically elegant forms?  Some book says it is just a postulate. Does this mean that we should not try to prove or demonstrate why the complex vector is a necessary since it is just correct as the complex vector based description fits experiment results very well?   Would there be any kind of reasonable explanation for why we describe a quantum state as a complex vector in Hilbert space?

1.  Why is the wave function complex? I've collected some layman explanations but they are incomplete and unsatisfactory. However in the book by Merzbacher in the initial few pages he provides an explanation that I need some help with: that the de Broglie wavelength and the wavelength of an elastic wave do not show similar properties under a Galilean transformation. He basically says that both are equivalent under a gauge transform and also, separately by Lorentz transforms. This, accompanied with the observation that $\psi$ is not observable, so there is no "reason for it being real". Can someone give me an intuitive prelude by what is a gauge transform and why does it give the same result as a Lorentz tranformation in a non-relativistic setting? And eventually how in this "grand scheme" the complex nature of the wave function becomes evident.. in a way that a dummy like me can understand.  2.   A wavefunction can be thought of as a scalar field (has a scalar value in every point ($r,t$) given by $\psi:\mathbb{R^3}\times \mathbb{R}\rightarrow \mathbb{C}$ and also as a ray in Hilbert space (a vector). How are these two perspectives the same (this is possibly something elementary that I am missing out, or getting confused by definitions and terminology, if that is the case I am desperate for help ;)   3.   One way I have thought about the above question is that the wave function can be equivalently written in $\psi:\mathbb{R^3}\times \mathbb{R}\rightarrow \mathbb{R}^2 $ i.e, Since a wave function is complex, the Schroedinger equation could in principle be written equivalently as coupled differential equations in two real functions which staisfy the Cauchy-Riemann conditions. ie, if $$\psi(x,t) = u(x,t) + i v(x,t)$$ and $u_x=v_t$ ; $u_t = -v_x$ and we get $$\hbar \partial_t u  = -\frac{\hbar^2}{2m} \partial_x^2v + V v$$ $$\hbar \partial_t v  = \frac{\hbar^2}{2m} \partial_x^2u - V u$$ (..in 1-D) If this is correct what are the interpretations of the $u,v$.. and why isn't it useful. (I am assuming that physical problems always have an analytic $\psi(r,t)$).


For my project, we want to deploy a demo server and publish my ASP.NET MVC 5 app to it. I'm familiar with developing applications in this environment, but I have no experience in deploying it to an actual server. Our sys admin does not have extensive experience with ASP.NET applications or IIS, but is reasonably well-versed in Windows Server.  Now, I can't really find what system requirements there are for the server - only for some older versions of ASP.NET MVC (e.g. version 2 or 3).  I am not asking in terms of capacity - I need to know the actual software version requirements:   What Windows Server version is the minimum? Which IIS version Any other software we'll need?

This is a  about capacity planning for web sites. Related:      What are some recommended tools and methods of capacity planning for web sites and web-applications? Please feel free to describe different tools and techniques for different web-servers, frameworks, etc., as well as best-practices that apply to web servers in general.


E.g. cold call in marketing, cold open in movies. Also "unsolicited" and "unexpected" seem to be synonyms  but is there a better one?

Did it exist before The Telephone - has it always been associated with 'sales'?  Here is .


I am trying to install Kubuntu 15.04 from a liveUSB on a hard drive without a prior OS. The machine has a GeForce GTX 980 GPU. The primary problem is that when I boot from the USB and begin the installation process, I eventually see the message Input Not Supported floating across a blank screen. I open a terminal, use the default login parameters, and edit the GRUB config file using the following command:  sudo nano /etc/default/grub   I find the following line and remove the hash (#):  #GRUB_GFXMODE=640x480   I save the grub config file and try to run the following command:  sudo update-grub   I am met with the following error:  /usr/sbin/grub-probe: error: failed to get canonical path of '/cow'   I have read the articles here about this error, such as , but I do not understand the nature of mounting here. My hard drive is sda and the usb where ubuntu installer is located is sdb. The lsblk command also shows -sdb1 as a location with a type of part /cdrom.   I have included an image below which elucidates my configuration. Could someone please clarify how I have to mount grub given my configuration? My goal is to get Ubuntu to install and run with this 640x480 resolution so that I can update the drivers and all that once I have finally booted to the desktop. I have used the nomodeset option in the past, but it does not further the installation process. If anyone has any advice on how best to proceed from here to get to that goal, I would be exceptionally grateful.

I am trying to install Ubuntu 12.10 for quite some time, and passing hurdles one by one. Now I am in a situation as follows.  I have got a PC and 10 GB HDD which will be totally dedicated to Ubuntu so no option of Wubi and dual boot.  I was trying to install from DVD, but it is getting stuck at "Out of frequency" error. So I had to adapt for USB boot option. But my PC is USB non bootable, so workaround is "Plop Boot Manager". So I am doing the installation procedure as follows:   starting  from a CD drive which is having plop installed. opting for for USB boot in plop options. booting begins from USB. monitor eventually gives "out of frequency" error press Shift+Alt+F1 to get the terminal. open the grub with sudo nano /etc/default/grub. do necessary changes. sudo update-grub.   Now here I am getting error as follows:   /usr/sbin/grub-probe:error:failed to get canonical path of /cow.     My system is   P4 3.06 GHz, 1 GB ram , 10 GB HDD without an OS, monitor CRT lg StudioWorks (7 years old). Mobo Mercury P4 266a NDMx (865 equivalent). The whole system is perfectly in working condition under XP, but it is USB non bootable, and all other devices working perfectly.  What should I do next?


public void addNodes(int[] keys){         //TODO             add(keys, root);     }      private void add(int[] keys, Node auxRoot){         if(auxRoot == null){             System.out.println("Root " + keys[0]);             auxRoot = new Node(keys[0]);             int[] newKeys = new int[keys.length-1];             for(int i =  0; i < keys.length-1; i++){                 newKeys[i] = keys[i+1];             }             add(newKeys, auxRoot);         } else if(auxRoot != null && keys[0] < auxRoot.key){             System.out.println("Left " + keys[0]);             if(auxRoot.left == null){                 auxRoot.left = new Node(keys[0]);                 if (keys.length > 1) {                     int[] newKeys = new int[keys.length - 1];                     for (int i = 0; i < keys.length - 1; i++) {                         newKeys[i] = keys[i + 1];                     }                     add(newKeys, auxRoot);                 }             } else if(auxRoot.left != null){                 add(keys, auxRoot.left);             }          } else if(auxRoot != null && keys[0] > auxRoot.key){             System.out.println("Right " + keys[0]);             if(auxRoot.right == null){                 auxRoot.right = new Node(keys[0]);                 if (keys.length > 1) {                     int[] newKeys = new int[keys.length - 1];                     for (int i = 0; i < keys.length - 1; i++) {                         newKeys[i] = keys[i + 1];                     }                     add(newKeys, auxRoot);                 }             } else if(auxRoot.right != null){                 System.out.println("keep going");                 add(keys, auxRoot.right);             }         }     }   I made this add auxiliary method for the addNode, for some reason, when I print out the key of the root it still null. Why is this the case? I am passing the root to the add auxiliary method. I understand is pass-by-value. How do I change this method to make root have a value.

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


What's the best way to extract numbers (with dot in between sometimes)from string in one line?  var str = "ghjkhjgbkhj123.45khgbkhjgk67   8kjhgkj hg13.99sads";   I need an array of [123.45, 67, 8, 13.99];  str.match(/\d+/g)  returns slightly different results - it doesn't count ".".

What is the regular expression for a decimal with a precision of 2?  Valid examples:  123.12 2 56754 92929292929292.12 0.21 3.1   Invalid examples:  12.1232 2.23332 e666.76   The decimal point may be optional, and integers may also be included.


Nurses, therapists, and others in similar caring roles often use "we" when talking to patients.     How are we doing today?   I'm looking for the grammatical/technical name of this mode of speaking, and especially a reference on it that I can link to.  I believe I have heard it called either "clinical we" or "therapeutic we," but I can't find resources when Googling for those terms.

What is the term for the condescending usage of "we" that essentially means "you"?  For example, when talking to a child, you might say "we need to be on our best behavior."  A slight variant could be the instructive tone commonly found in mathematical proofs, e.g. "we see from (xxx) that (yyy), which tells us that (zzz)..."  I thought for quite some time that this was the meaning of "the ", but it turns out that is a different thing.  What is the condescending usage actually called?


I've been racking my brain trying to figure out why my if statements won't print, can someone offer some help?  import java.util.Scanner;  public class Sound{      public static void main(String[] args){              Scanner x = new Scanner(System.in);              System.out.println("Enter the type of medium: ");             String medium = x.nextLine();             System.out.println("Enter the distance traveled: ");             double distance = x.nextDouble();            if(medium == "air"){             double time = distance/1100;             System.out.println("This is how long it takes: " + time);          }          else if(medium == "water"){             double time = distance/4900;             System.out.println("This is how long it takes: " + time);          }          else if(medium == "steel"){             double time = distance/16400;             System.out.println("This is how long it takes: " + time);          }       } }

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


List<Account> Scope = [SELECT id FROM ACCOUNT]; // This is the query being used  global void execute(Database.BatchableContext BC, List<Account> scope)      {            List<Account> accounts = [SELECT id, (SELECT outreach_status__c,Initial_Contact__c, Champion__c, Finance_DM__c, Operations_DM__c, Executive_Sponsor__c ,LastActivityDate FROM Contacts) FROM Account WHERE Id in :scope]; }   Or is it  List<Account> Scope = [SELECT id FROM ACCOUNT]; // This is the query being used      global void execute(Database.BatchableContext BC, List<Account> scope)      {            List<Account> accounts = [SELECT id, (SELECT outreach_status__c,Initial_Contact__c, Champion__c, Finance_DM__c, Operations_DM__c, Executive_Sponsor__c ,LastActivityDate FROM Contacts) FROM Account WHERE Id = :scope]; }   Basically I am not sure if I should use "ID IN :Scope" or "ID = :Scope". I am asking this because I am finding that not all records are being processed.

I have some dynamic SOQL code in which I'd like to identify whether a method argument is a collection or a single value:  SObject[] query(SObjectType sobType, String field, Object data) {     // Want to know if data is a collection e.g. set or list     // that requires an "in" or a single value that requires     // an "=" in the query. (May also need to use separate bind variables.) }   I note that the sort of check shown immediately below seems to require an exact match for the type of the collection (Id in this case to return true) which is not what I want:  Object o = new Set<Id>(); System.debug(o instanceof Set<Id>);   Is there a simple way to make this determination?  (Yes there are various other ways to code this; checking first to see if there is a direct solution.)  PS  Looks like great caution is needed when using .


In some simple mathematics, here I am trying to get the percentage of targets which have been done from the total number.  The ones which have been done are positive.  In my understanding, the following mathematics should give me a percentage of 50, but running it, Python insists on giving me zero.  Why would that be?  Total =  2 Positives = 1 Percentage = (Positives/Total)*100 print ('Percentage is: ' + str(Stat) + '%\n' )  >>>Percentage is: 0%

For example, the standard division symbol '/' rounds to zero:  >>> 4 / 100 0   However, I want it to return 0.04. What do I use?


Is it possible to obtain small labels with proof.sty?  \documentclass[a4paper,12pt,twoside,openright]{book} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[german,english,italian]{babel} \usepackage{easylist} \usepackage{amssymb,amsmath,amsthm,varwidth,bussproofs,syllogism, mathrsfs, proof} \begin{document}      $$\infer[\wedge I]           {(A \wedge B)}           {A & B}      \qquad      \infer[\to E]           {B}           {(A \to B) & A}      $$ \end{document}   I tried to use \small, but it doesn't work.

MWE:  \documentclass{article} \begin{document} $\wedge{\small\wedge}{\tiny\wedge}$ \end{document}   All the \wedges have the same size...


This was the last part of an exam question. I have spent a long time looking for such an example but have failed (sequences when one of the three conditions is dropped are easily found but I couldn't find one when all three are required). Could you also give the way you thought of the example in your answer please?   Thanks!

I have a question that says "Show that there is a bounded sequence $x_n$ which is not convergent but has the property that $x_n - x_{n+1} \to 0$ as $n \to 0$.  What does this mean? Do I need to come up with an example or does the problem actually want me to prove such proposition?  By the way, I see that this sequence looks like Cauchy because of $x_n - x_{n+1} \to 0$ as $n \to 0$, but it is obviously not.


I currently have a "friend" that has an account on my dedicated server which is running Ubuntu. Not getting into specifics, but he said he will use ~2gb max and he's using ~10gb. On to the question. Is there a way to limit his account to a maximum of say.. 3gb? Killing the process(es) would be fine too.  I've done some googling but still not found a solution :/

So I have 4 GB RAM + 4GB swap. I want to create a user with limited ram and swap: 3 GB RAM and 1 GB swap. Is such thing possible? Is it possible to start applications with limited RAM and swap avaliable to them without creating a separate user (and not installing any special apps - having just a default Debian/CentOS server configuration, and not using sudo)?  Update:  So I opened terminall and typed into it  command: ulimit -v 1000000 which shall be like 976,6Mb limitation. Next I called ulimit -a and saw that limitation is "on". Then I started some bash script that compiles and starts my app in nohup, a    nohup ./cloud-updater-linux.sh  >& /dev/null &... but after some time  I saw:    (which would be ok if no limitations were applied - it downloaded some large lib, and started to compile it.)  But I thought I applied limitations to the shell and all processes launched with/from it with ulimit -v 1000000? What did I get wrong? How to make a terminal and all sub processes it launches be limited on ram usage?


I need a book on elementary topology which is good to read and easy to understand the concepts. Please give me a reference which book should I use..

I am a graduate student of math right now but I was not able to get a topology subject in my undergrad... I just would like to know if you guys know the best one..


Let $F(n)$ be $n$-th Fibonacci-number. Then the following holds: $$F(n)^2+F(n+1)^2=F(2n+1).$$ I have proved, but I want a brief proof. Do you know anything about it?

Prove that if $f$ is the Fibonacci sequence then $f_{n+1}^2+f_n^2=f_{2n+1}$ holds for all n. Instead of trying doing this by induction, I need to do it by trying to just replacing the explicit formula for $f_n$. I am stuck at this step:  $f_{n+1}^2+f_n^2=\frac{1}{5}[\phi^{2n}(1+\phi^2)+(1-\phi)^{2n}(1+(1-\phi)^2)]$  Believe me that this is equivalent to $\frac{1}{\sqrt{5}}[\phi^{2n+1}-(1-\phi)^{2n+1}]$  Maybe it's just a simple algebra problem, but I don't know how to get that expression. Thanks


I followed the 'Debian-based Linux distributions' guide on the VirtualBox website.  After sudo apt install virtualbox-5.2 I got the error:  vboxdrv.sh: failed: modprobe vboxdrv failed. Please use 'dmesg' to find out why.  There were problems setting up VirtualBox.  To re-start the set-up process, run   /sbin/vboxconfig as root.   dmesg: Loading of unsigned modules is restricted; see man kernel_lockdown.7.  How can I fix this?  I read something about secureboot but I don't want to disable it.  Do I have to sign the VirtualBox module (how? add custom sign key?) or is there another way?  I'm running Kubuntu 18.04 Kernel 4.15.0-23-generic.  EDIT  After following this guide   and executing sudo modprobe vboxdrv I got the error modprobe: ERROR: could not insert 'vboxdrv': Required key not available. With modinfo vboxdrv I see:  filename:       /lib/modules/4.15.0-23-generic/misc/vboxdrv.ko version:        5.2.12 r122591 (0x00290001) license:        GPL description:    Oracle VM VirtualBox Support Driver author:         Oracle Corporation srcversion:     63368184ED096B3022FD087 depends:         retpoline:      Y name:           vboxdrv vermagic:       4.15.0-23-generic SMP mod_unload  signat:         PKCS#7 signer:          sig_key:         sig_hashalgo:   md4   So it looks like it's not signed right? Whats wrong with this? I tried to sign it manually with /usr/src/linux-headers-4.15.0-23-generic/scripts/sign-file sha256 ./MOK.priv ./MOK.der /lib/modules/4.15.0-23-generic/misc/vboxdrv.ko with the same result.

I upgrade from Ubuntu 15.10 to 16.04 and since then VirtualBox 5.0.18 isn't starting my VMs anymore. It complains that 'vboxdrv' isn't loaded. So I try to load it and get the following error:  $ sudo modprobe vboxdrv modprobe: ERROR: could not insert 'vboxdrv': Required key not available   I believe it is related to secure boot which I use and which I want to continue using. Actually with Ubuntu 15.10 secure boot and VirtualBox were working just fine.  Also I tried $ sudo apt-get --reinstall install virtualbox-dkms which built the kernel module successfully but didn't solve this issue.  Any idea how to get vboxdrv loaded while keeping secure boot enabled?  Update 2: Also I tried executing sudo mokutil --disable-validation. When executing this command, during the next boot I get prompted to disable secure boot, add a key or hash from disk. Since I don't want to disable secure boot, it seems that this doesn't solve my issue either. Also I want to keep UEFI activated for a parallel Windows installation.  Note: If you don't mind disabling secure boot, see  instead.


If I try to build a new file on Tex Studio I get the following error message  "Error: Could not start the command: pdflatex.exe -synctex=1 -interaction=nonstopmode "texstudio_lN2796".tex"   and nothing basically moves.   Has it ever happened to anybody?   Thanks Manuel

I just downloaded and installed Texmaker. I've never used any (La)TeX before.  When I click the Run button with an arrow next to "Quick build" I get an error saying "Could not start the command". Why? What do I need to do?


It's true that keeping lithium batteries fully charged degrades them quicker than at half charge (). I bring my laptop with me in the day, but run it on the charger in the evenings.  Besides removing the battery (not possible on many new laptops), is there a way to run the laptop off the AC adapter without the battery charging?

When your laptop's battery is 100% charged, should you leave it plugged in so any battery power doesn't get used, or will that cause overcharging, overheating, etc.? Should the laptop be unplugged when the battery level is 100%?  I'm asking because my laptop's screen tends to get dim when unplugged, so I don't like to run it on battery.


Every time I run audacious from terminal, I have to type this: audacious my_song.mp3 >& /dev/null &  Is there an alias for this, so that if I only type audacious my_song.mp3 it will become audacious my_song.mp3 >& /dev/null &.  P/S: & is to make audacious run in background and >& /dev/null is to ignore some infomation from stdout and stderr.    My short answer:  $ cd # to go to home directory $ # make directory where you save your aliases $ mkdir alias.d && cd alias.d $ cat << EOF > audacious.sh #!/bin/bash audacious "$@" > /dev/null 2>&1 & EOF $ chmod u+x audacious.sh $ cd # to go to home directory $ echo "alias audacious='~/alias.d/audacious.sh'" >> .bash_aliases $ source .bash_aliases # make sure your .bashrc source .bash_aliases

I want to know if I can pass an argument with an alias command.  for example:  alias d="dmesg|grep -iw usb|tail -5"    Now d will print the last 5 lines. If I want to use d to print a different number of lines, I have to make change in the alias command declaration of d again.  Is there any way I can modify the declaration of an alias so that I don't have to retype the declaration to change the number of lines. Like incorporating passing the number of lines as an argument while declaring alias for d? Or is there some other method to solve this?


I want to show that a function $f$ entire s.t.  f(z+1)=f(z)=f(z+i)  for all $z$, must be constant.  I think what I need to do is show that the function is bounded in some region of the complex plane, and then by periodicity it must be true that the function is bounded everywhere, and hence by Liouville must be constant. Can someone help me do this? Thanks!

Let $f: \Bbb C \to \Bbb C$ be an entire (analytic on the whole plane) function such that exists $\omega_1,\omega_2 \in \mathbb{S}^1$, linearly independent over $\Bbb R$ such that: $$f(z+\omega_1)=f(z)=f(z+\omega_2), \quad \forall\,z\in \Bbb C.$$Prove that $f$ is constant.   The intuition seems clear to me, we have the three vertices of a triangle given by $0$, $\omega_1$ and $\omega_2$. All points in the plane are one of the vertices of that triangle under a suitable parallel translation. The constant value will be $f(0)$, fine. Throwing values for $z$ there, I have found that $$f(n\omega_1) = f(\omega_1) = f(0)=f(\omega_2) = f(n\omega_2), \quad \forall\, n \in \Bbb Z.$$  I don't know how to improve the above for, say, rationals (at least). Some another ideas would be:   Checking that $f' \equiv 0$. I don't have a clue of how to do that. Write $w = a\omega_1+b\omega_2$, with $a,b \in \Bbb R$, do stuff and conclude that $f(w) = f(0)$. This approach doesn't seem good, because I only have a weak result with integers above. Finding that $f$ coincides with $f(0)$ on a set with an accumulation point. This seems also bad: the set on with $f$ coincides with $f(0)$ by which I found above is discrete.    Nothing works and this is getting annoying... And I don't see how analyticity comes in there. I'll be very thankful if someone can give me an idea.  (On a side note.. I know that this title is not informative at all. Feel free to edit if you come up with something better.)


I have an ASUS X551M that I am trying to boot from the CD ROM. When I go to the boot menu the screen says:  Boot Option #1   Windows Boot Manager  Add New Boot Option Delete Boot Option  There is no option to boot from anywhere else! Please help!

I just bought a new PC and the default installed OS is Windows 8. I want to install Windows 7 but when I go into the boot options screen I only have one option:  Windows Boot Manager   I can't find my DVD drive. It is plugged in and visible under SATA options. How is it that I don't see it in the boot options menu?  The weirdest thing is that the drive is working perfectly inside Windows. So Windows 8 can detect it but the BIOS can't? I'm stuck with Windows 8... Any ideas?


I have the following protoboard (see picture below)    Each hole has a distance of 0.5mm   I want to link components between them. I found a few ways to do that:  1) Use tiny wires to connect the components  2) Solder the part of the board I'm using. However, issue is the dots between them are tiny (very actually) and my iron is kind of unfit for precision work.  Any insights would be great.  Cheers  Update:   Please find the size between holes of my protoboard and the the size of the tip of my iron (size in mm and cm)

I have a PCB which has the perfect size for a project of mine, so I would like to use it if possible. However, the copper plating on the back side of PCB only surrounds the individual holes (that is, no holes are interconnected). See picture right here:    I find this strange. How can this be useful? I would definitely need some copper tracks with interconnected holes in there because some components need to be connected to each other. Am I supposed to make my own tracks somehow?  I saw some stuff online about people who would insert multiple wires in the same hole to make interconnections, but this seems undesirable. I'd rather avoid that if there is some way to make tracks.


What is the metric of comparison for DPI and the resolution of an image? I'm rendering a PDF to multiple JPEGs with Automator, and I'm wondering what DPI would be best to use?

I've been seeing the word 'DPI' pop up quite a lot when I export my work out in Photoshop and Illustrator. While I know that DPI stands for 'dots per inch', and that if you have too low of a DPI on an image, heavy pixellation occurs if you try to zoom in, what would be the optimal DPI for what situations?  For example (Situations):   Exporting a print A4 design Website layout Logo (Website only - Roughly smaller than the current SE Graphic Design one.) Logo (Scaling up and down - From business cards to large banners.)


I've asked this around and I'm RACKING MY BRAIN trying to figure it out.   Which one is the correct verb form in the following sentence?     The craziest thing I've ever done is go / to go / going scubadiving in Belize   Some people say that both the to + verb and the ing forms are correct, because you need a noun there and the bare form is a verb; other people say only the to + verb is the correct one here, because the ing form only applies when you reverse the sentence (going scubadiving is yadda yadda) and not when you place the subject in the end.  I know many people would use the bare infinitive to be quicker while speaking, but that just sounds wrong to my ears as it's a verb!  Can you please tell me, once and for all, which is the correct verb form?

As a native speaker of English, the gerund version of this sentence sounds better:  infinitive:     When used together in chains,   extension methods are an unprecedented   tool to produce extremely concise   code.   gerund:     When used together in chains,   extension methods are an unprecedented   tool for producing extremely concise   code.   But how can I explain to someone learning English how to decide in situations like these whether to use the infinitive or the gerund?


I just wonder what the code for the symbol _| is. (The symbol besides v in the picture below.)     Thanks a lot.

See the above excerpt from John Lee's Introduction to Smooth Manifolds. In differential topology and linear algebra, there's an operator called the interior product or contraction operator, denoted $\iota_X(\omega)$ or alternatively with some other "half box" like operator $X_|\omega$. Does anyone know how to markup that operator in LaTeX?   Google has turned up nothing except for this thread:   That thread did receive an accepted answer, which was \invneg from the MnSymbol package, but the suggestion given there does not seem correct to me. Or at least, it does not match what I'm familiar with. That answer results in an inverted negation symbol, whereas the contraction operator should have a stroke down at the floor of the line, and a long stroke going up almost the full height of the line. It can be found in many texts, but why can I not find the correct LaTeX markup?


I have $\alpha= 2^{1/3}+\sqrt{2}$ and $E(\alpha)=\mathbb{Q}$, I want to prove that $E=\mathbb{Q}(2^{1/3}, \sqrt{2})$. I tried to compute the irreducible polynomial of $\alpha$, but I didn't get anywhere. Any hint?

I have to find the minimal polynomial of $\sqrt 2 + \sqrt[3] 2$ over $\mathbb Q$. The suggested way of doing it is to prove that $\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2]$ first.  I can prove that. It's enough to prove that $\sqrt 2,\sqrt[3] 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2]$ and that $\sqrt 2 + \sqrt[3] 2\in \mathbb Q[\sqrt 2,\sqrt[3] 2]$. The latter is obvious and $\sqrt[3] 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2]$ will follow from $\sqrt 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2].$ It remains to prove $\sqrt 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2].$  For $\alpha=\sqrt 2 + \sqrt[3] 2,$ we have   $$ \begin{eqnarray} &\alpha^0&=1,\\ &\alpha^1&=\sqrt 2 + \sqrt[3] 2,\\ &\alpha^2&=2+\sqrt[3]4+\sqrt 2\sqrt[3]2\\ &\alpha^3&=2+2\sqrt 2+6\sqrt[3]2+3\sqrt 2\sqrt[3]4\\ &\alpha^4&=4+4\sqrt 2+12\sqrt[3]4+8\sqrt 2\sqrt[3]2\\ &\alpha^5&=32+4\sqrt 2+20\sqrt[3]2+4\sqrt 2\sqrt[3]2 \end{eqnarray} $$  If I can express $\sqrt 2$ as a linear combination of $\{\alpha^0,\alpha^1,\cdots,\alpha^5\}$, I'm done. I don't know how to find out whether $$\{1,\sqrt 2,\sqrt[3]2,\sqrt[3]4,\sqrt 2\sqrt[3]2,\sqrt 2\sqrt[3]4\}$$ are linearly independent over $\mathbb Q$ but I think I don't have to care. I can use Gaussian elimination anyway. I write the matrix  $$\left[ \begin{array}{rrrrrr|r} 1 & 0 & 2 & 2 & 1 & 8 & 0\\ 0 & 1 & 0 & 2 & 1 & 1 & 1\\ 0 & 1 & 0 & 6 & 0 & 5 & 0\\ 0 & 0 & 1 & 0 & 3 & 0 & 0\\ 0 & 0 & 1 & 0 & 2 & 1 & 0\\ 0 & 0 & 0 & 3 & 0 & 5 & 0 \end{array}\right]$$  and by performing row operations I obtain a row echelon form, which proves that I'll obtain the reduced row echelon form if I want, which will give me the desired coefficients $a_0,\cdots,a_5$ such that   $$\sqrt 2=\sum_{i=0}^5a_i\alpha^i.$$  I don't have to find the coefficients -- I'm just satisfied with their existence.  If this is correct, I have proven that   $$\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2].$$  But I don't know how to proceed further. Of course, I can find the minimal polynomials of $\sqrt 2$ and $\sqrt[3] 2$ over $\mathbb Q$ but I don't know how to find the minimal polynomial of $\sqrt 2$ over $\mathbb Q[\sqrt[3]2]$ or the minimal polynomial of $\sqrt [3]2$ over $\mathbb Q[\sqrt 2].$  What I did is this. I wrote the equation  $$x=\sqrt 2+\sqrt [3]2$$  and by squaring and cubing obtained  $$W(x):=x^6-6x^4-4x^3+12x^2-24x-4=0.$$  I belive this is the required polynomial but I would need to prove that it's irreducible over $\mathbb Q.$ Eisenstein's criterion doesn't work, which means I'm lost.  Could you please help me with this? I would like to know three things.  1) Is my proof of $\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2]$ correct?  2) How can I use this fact? I believe it's supposed to make the solution easier to find.  3) How can I tell whether $W(x)$ is reducible over $\mathbb Q$ or not?  EDIT: 1) has been answered by André Nicolas in a comment. All of this answers 3) but I would like to ask whether we could know that the polynomial is irreducible without knowing that $\sqrt 2+\sqrt[3]2$ is its zero. Also, it would be to know whether  4) there is a theorem that would give me $\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2]$ without the need of performing the Gaussian elimination?  For these numbers it was possible to do, but a bit higher dimension and it would turn out impossible without a computer.


I am writing a plug-in for a software using C#. My plug-in generates a directory, containing a couple of text files, that I need to transfer to a computational cluster. At the moment I am transferring the files manually with the PowerShell (or the Ubuntu plug-in for Windows) using "scp -r -P location/on/windows location/on/cluster", but I would like to do this step automatically by including it in my plug-in.  I have looked around online for guidance and I have found some helpful documentation, but I am still quite lost.   So far I've managed to open the shell, but how to add a sequence of commands I still don't understand.    if(x)   }       OpenPowerShell(@"C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe");   }     static void OpenPowerShell(string path)   {     Process.Start(path);   }   Could someone please help me out with this or point to some helpful documentation?  Thanks, David

I need to execute a PowerShell script from within C#. The script needs commandline arguments.  This is what I have done so far:  RunspaceConfiguration runspaceConfiguration = RunspaceConfiguration.Create();  Runspace runspace = RunspaceFactory.CreateRunspace(runspaceConfiguration); runspace.Open();  RunspaceInvoke scriptInvoker = new RunspaceInvoke(runspace);  Pipeline pipeline = runspace.CreatePipeline(); pipeline.Commands.Add(scriptFile);  // Execute PowerShell script results = pipeline.Invoke();   scriptFile contains something like "C:\Program Files\MyProgram\Whatever.ps1".   The script uses a commandline argument such as "-key Value" whereas Value can be something like a path that also might contain spaces.  I don't get this to work. Does anyone know how to pass commandline arguments to a PowerShell script from within C# and make sure that spaces are no problem?


How can I use existing pySpark sql functions to find non-consuming regular expression patterns in a string column?  The following is reproducible, but does not give the desired results.  import pyspark from pyspark.sql import (     SparkSession,     functions as F)  spark = (SparkSession.builder          .master('yarn')          .appName("regex")          .getOrCreate()          )  sc = spark.sparkContext sc.version # u'2.2.0'  testdf = spark.createDataFrame([     (1, "Julie", "CEO"),     (2, "Janice", "CFO"),     (3, "Jake", "CTO")],     ["ID", "Name", "Title"])   ptrn = '(?=Ja)(?=ke)'   testdf.withColumn('contns_ptrn', testdf.Name.rlike(ptrn) ).show()   +---+------+-----+-----------+ | ID|  Name|Title|contns_ptrn| +---+------+-----+-----------+ |  1| Julie|  CEO|      false| |  2|Janice|  CFO|      false| |  3|  Jake|  CTO|      false| +---+------+-----+-----------+   testdf.withColumn('contns_ptrn', F.regexp_extract(F.col('Name'), ptrn, 1)).show()   +---+------+-----+-----------+ | ID|  Name|Title|contns_ptrn| +---+------+-----+-----------+ |  1| Julie|  CEO|           | |  2|Janice|  CFO|           | |  3|  Jake|  CTO|           | +---+------+-----+-----------+   testdf.withColumn('contns_ptrn', F.regexp_replace(F.col('Name'), ptrn, '')).show()   +---+------+-----+-----------+ | ID|  Name|Title|contns_ptrn| +---+------+-----+-----------+ |  1| Julie|  CEO|      Julie| |  2|Janice|  CFO|     Janice| |  3|  Jake|  CTO|       Jake| +---+------+-----+-----------+   The desired results would be:  +---+------+-----+-----------+ | ID|  Name|Title|contns_ptrn| +---+------+-----+-----------+ |  1| Julie|  CEO|      false| |  2|Janice|  CFO|      false| |  3|  Jake|  CTO|       true| +---+------+-----+-----------+   As the third row in the Name column contains 'Ja' and 'ke'.  If regexp_extract or regexp_replace are able to extract or replace non-consuming regular expression patterns, then I could also use them together with length to get a Boolean column.

Obviously, you can use the | (pipe?) to represent OR, but is there a way to represent AND as well?  Specifically, I'd like to match paragraphs of text that contain ALL of a certain phrase, but in no particular order.


I am stuck on the following problem :  Let $\,f \colon \Bbb R^2 \to \Bbb R $ be continuous map such that $\,f(x)=0\,$ for only finitely many values of $x$. Then which of the following options is correct?  either $f(x)\le 0 \forall x \,\text{or}\, f(x) \ge 0 \forall x$  the map $f$ is one-to-one  the map $\,f$ is onto  none of the above    My Attempt: Since $\,f(x)=0\,$ for only finitely many values of $x$, $\exists x_1=(a_1,b_1),x_2=(a_2,b_2) \in \Bbb R^2$ such that $f(x_1)=0=f(x_2)$ whereas $x_1 \neq x_2$. So, $f\,$ is not one-to-one. Also,it is a many-to-one mapping and so can not be onto. I am confused about options 1 and 4. Can someone point me in the right direction with some explanation? Thanks and regards to all.

Let  $f : \mathbb{R}^2\rightarrow \mathbb{R}$ be a continuous map such that $f(x)=0$ only for finitely many values of $x$. Which of the following is true?   Either $f(x)\leq 0$ for all $x$ or $f(x)\geq 0$ for all $x$. the map $f$ is onto. the map $f$ is one one. None of the above.   What I have done so far is :   I would take polynomial in two variables.. This need not be like $f(x)\geq 0$ for all $x$ or $f(x)\geq 0$ for all $x$.So,first option is eliminated. The map is not one one assuming that $f$ has more than one zero. So, third option is wrong.   I could not think of an example in which it is not onto..  Only examples i am getting in my mind are polynomials and they are onto..  So, I am having trouble with surjectiveness of the function.  Please help me to clear this.  Thank you..


I came across the Ubuntu Software Center application while I was looking through Ubuntu Software in Ubuntu 16.04. It had the same icon and a lot of the same apps as the Software app. Can anyone explain this to me?

GNOME Software (the default software center in Ubuntu 16.04, also called Ubuntu Software) is annoying! It keeps checking for updates and throws pop-ups in my face the whole day and thus mooches my net and also makes it very disturbing to use my machine. Is there any 100% safe means to remove it and install the classic Ubuntu Software Center (the default software center till Ubuntu 15.10)? Also, will the packages in the classic one be up to date?


Prove that $1^n-3^n-6^n+8^n$ is divisible by $10$ for all $n\in\mathbb{N}$  It is divisible by $2$ and $5$ if we rearrange it will it be enough   $(1^n -3^n)$ and $(6^n -8^n)$ is divisible by $2$.  And $(1^n-6^n)$ and $(8^n-3^n)$ is divisible by $5$.  Hence $\gcd(2,5)$ is $1$ and it is divisible by $2\cdot5=10$.  Is it correct?