I need to find the negations of the following statements:  For every n (is an element of natural numbers) there is a prime number p such that n < p.  There is n (is an element of natural numbers) such that for every prime number p, p < n.  What are the rules of negation for these statements? Thanks!

I was recently playing around with delta-epsilon proofs for limits, which, when true, have the following form:  $$\forall \epsilon > 0, \exists \delta>0 , p \implies q$$  Where $p = (\text{for all $x$, }0 < |x-a| < \delta)$ and $q = (|f(x) - L| < \epsilon)$ (this isn't directly relevant to my question, just showing what these... events? Statements? Propositions? I don't know the word -- what they look like).  I didn't include the actual thing being shown true above about $f(x)$ (I don't know where it'd go), but the more informal statement is "The limit of $f(x)$ as $x$ approaches $a$ is equal to $L$ if for all $\epsilon > 0$ there exists a $\delta>0$ such that for all $x$, $0 < |x-a| < \delta$ implies $|f(x)-L|<\epsilon$."  I wanted to prove a scenario where the limit was knowingly false ahead of time, and it took me some time to notice that this was the new statement to show in order to prove a limit false:  $$\exists \epsilon > 0, \forall \delta>0 , p \not\implies q$$  Now it's something more like, "The limit of $f(x)$ as $x$ approaches $a$ is not equal to $L$ if there exists an $\epsilon > 0$ such that for all $\delta>0$, for all $x$ $0 < |x-a| < \delta$ does not imply $|f(x)-L|<\epsilon$."  My questions:   Is there a formal proof or understanding as to why negation changes for-alls into there-exists and vice-versa? I'm a little unsure why De Morgan's laws don't seem to apply between the "statements" (apologies for my imprecision, I don't know what any of these things are called). For instance could we not think of it as $(\forall \epsilon > 0) \land (\exists \delta>0) \land (p \implies q)$ as in, all of these things must be true -- the epsilon condition must be true AND the delta condition must be true AND $p$ must imply $q$. Then if we negate it, why doesn't it become something like $(\exists \epsilon > 0) \lor (\forall \delta>0) \lor (p \not\implies q)$ as in, the epsilon condition must be true OR the delta condition must be true OR $p$ must not imply $q$. I know intuitively this isn't the case but I don't know why, since the original statement makes sense to me as a chain of ANDs but the negation... still feels like it should be a chain of ANDs whereas De Morgan's laws normally have you invert them to ORs.


I need an app that does the following:   Allow me to paste multiple snapshots from clipboard. Also resize and move them. Draw arrows, write texts...   Just what paint on windows does.  I've tried Gimp but is terrible slow and full of bugs.

I tried out several image editors mentioned on  but some of them (like  and ) were very disappointing. These apps were too simple and low level.  What do you suggest for a (preferably free) image editor on OS X?  P.S: I was using  on Linux and also know that it was released for OS X too, but I want to find new good applications.


When Anakin is introduced to the council to be made a padawan, the council finds fear in him.  Part of their reluctance to take him as a padawan is the fear he seems to possess.  Considering the limited number of jedi and the resources they have, I don't think that placing his mother on a safe planet, not enslaved, would have been very difficult.   In general, they take the children very young so they don't get attached to their family. So it's not like they have many families to take care of. And I'm not saying to pay her mother a monthly income, just to move her to a safe place, and free her. She can survive on her own afterwards.  As they took him older, as an exception, it just makes sense to make another exception and help his mother.  Seeing his mother being tortured in his dreams then seeing her die was the first step on the dark side, which could have been avoided very easily.  So considering that he is the "chosen one" and that he seems pretty unstable, why didn't they take care of his mother?

One thing that's always confused me during Star Wars was the fact that NO ONE freed or even did anything to help Shmi. I mean, this is the mother of the Chosen One. Why didn't the Jedi do anything? I know that they aren't supposed to interact with their original family but they couldn't have at least sent some credits or at least have done something. For that matter, why didn't one of Anakin's AMAZING connections/friends do anything either. One of his mentors was the Chancellor of the Galactic Republic. Padme, the Queen of Naboo saw for herself the pitiful condition of her friend's former life. I don't understand. Why didn't anyone do anything?


I am trying to find the limit of the sequence by using root test and I don't understand why the limit is not zero? (the answer is inf).

Why is     $$\lim_{n \to \infty} \frac{2^n}{n!}=0\text{ ?}$$   Can we generalize it to any exponent $x \in \Bbb R$? This is to say, is     $$\lim_{n \to \infty} \frac{x^n}{n!}=0\text{ ?}$$     This is being repurposed in an effort to cut down on duplicates, see here: Coping with  duplicate questions.  and here: .


While my little brother is occupying my desktop he is also occupying my Skype account. I know about multi login and I am using it, but he keeps sending dirty messages to my friends from the desktop.    Is there any way I can kick him out of Skype?

When using Skype, we can log in to the same account from multiple PCs. Currently I have one PC logged into Skype with my account. The problem is that it was a laptop of my relatives and I cannot access it for now.  How can I sign out of Skype from everywhere logged in to my account?


I have been having problems sending emails from my server to hotmail.com and live.com email addresses. I have read other posts on serverfault but they have not been helpful. Here is the error message. It is very vague     550 SC-001 Mail rejected by Windows Live Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation problems. If you are not an email/network admin please contact your E-mail/Internet Service Provider for help. Email/network admins, please visit  for email delivery information and support   I have visited  and  but nothing has worked. I have a mx record and a valid spf record: v=spf1 a mx ~all which passes google's validation. I have triple checked all spam lists and my IP is not on any list. I am at a loss, any suggestions?

This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating?


I received a question ban yesterday (which I deserved). I thought that Stack Overflow was a tech question and answer site rather than just coding.  I want to un-ban my account but I'm not sure how. I completely rewrote the question (completely different subject now and I good question that I need help with), but how do I get un-banned?

If you are reading this, you may have been affected by one of our post quality bans. If so, it is important that you  to understand what has happened and how to regain the permissions that you lost. While trying to ask a question, one could see:  We are no longer accepting questions from this account. See  to learn more.  Likewise, for answers:  We are no longer accepting answers from this account. See  to learn more.   Why am I getting this message? Are deleted posts taken into account too? Is a question/answer ban the same as a suspension? How do I avoid getting a question ban? How long do I have to wait before I can post again? What can I do to release the ban? How can I reactivate my account? Can I simply create a new account? I'll just ask somewhere else on the SE network, and they'll migrate my question to the correct site! Will a ban on one Stack Exchange site affect my standing on other sites in the network? Does this apply to meta sites too? My account is in good standing. Why am I still blocked?


I'm fairly new to Ubuntu, so I don't know if this is a simple fix or not. I've read some fixes to answers for my problem but I don't really know how to do any of the things they're telling me to do (such as installing proprietary drivers). I'm having the same problem that UbhiSukhpal posted about, but my attempts at fixing the problem have not been successful. Starting Steam from Terminal hasn't worked either. This is the message I get when I try to do start it from the terminal.      chris@chris-VPCEE41FX:~$ steam     Running Steam on ubuntu 15.04 64-bit     STEAM_RUNTIME is enabled automatically     Installing breakpad exception handler for appid(steam)/version(0)     libGL error: unable to load driver: r600_dri.so     libGL error: driver pointer missing     libGL error: failed to load driver: r600     libGL error: unable to load driver: swrast_dri.so     libGL error: failed to load driver: swrast   Any help would be awesome. I apologize if this is going to be tedious. :p

Actually I have installed the new Ubuntu 15.04 64bit, and when I'm trying to install Steam on it, there is a problem. In fact I have downloaded the deb package from steam website, installed it and when I start it nothing happens. I tried to start it from terminal and what I've got  $ steam Running Steam on ubuntu 15.04 64-bit STEAM_RUNTIME is enabled automatically Installing breakpad exception handler for appid(steam)/version(0_client) libGL error: unable to load driver: r600_dri.so libGL error: driver pointer missing libGL error: failed to load driver: r600 libGL error: unable to load driver: swrast_dri.so libGL error: failed to load driver: swrast


I don't know what the answer is but I tried to get some information from the hypothesis and have reached till the result that $f$ is an homeomorphism.  This is because $f$ is bijective and continuous as well as it's inverse is also continuous because $f \circ f=f^{-1}$ and composition of continuous functions is continuous.  What should be my next step? or this is not the way to reach the answer?

Let $f:\mathbb R \to \mathbb R$ be a continuous function such that $f(f(f(x)))=x,\forall x \in \mathbb R$ , then is it true that $f(x)=x , \forall x \in \mathbb R$ ? I can see that $f$ is bijective , hence strictly monotone . But I cannot progress further . Please help. Thanks in advance


how can I make a good 3d model ... This is what i made and this is when i try to open it in Unity, is there a way that i can export it in high quality...

I used node textures in a mesh I exported to .FBX.  I then imported it into Unreal Engine 4 and it didn't import any textures; I clicked the Upload Textures option in Unreal Engine.  Is there something I'm doing wrong or is it Blender?


I have two objects   article_category = ArticleCategory.objects.all() project_category = ProjectCategory.objects.all()   I want to merge these two in one so that I can access them with one object.  something like this.  category = add(article_category,project_category)    what is the way to do this in Django ?

I am trying to build the search for a Django site I am building, and in that search, I am searching in three different models. And to get pagination on the search result list, I would like to use a generic object_list view to display the results. But to do that, I have to merge three querysets into one. How can I do that? I've tried this: result_list = [] page_list = Page.objects.filter(     Q(title__icontains=cleaned_search_term) |     Q(body__icontains=cleaned_search_term)) article_list = Article.objects.filter(     Q(title__icontains=cleaned_search_term) |     Q(body__icontains=cleaned_search_term) |     Q(tags__icontains=cleaned_search_term)) post_list = Post.objects.filter(     Q(title__icontains=cleaned_search_term) |     Q(body__icontains=cleaned_search_term) |     Q(tags__icontains=cleaned_search_term))  for x in page_list:     result_list.append(x) for x in article_list:     result_list.append(x) for x in post_list:     result_list.append(x)  return object_list(     request,     queryset=result_list,     template_object_name='result',     paginate_by=10,     extra_context={         'search_term': search_term},     template_name="search/result_list.html")  But this doesn't work. I get an error when I try to use that list in the generic view. The list is missing the clone attribute. How can I merge the three lists, page_list, article_list and post_list?


I am trying to show that for a nilpotent matrix $A\in M_n(F)$, there exists a natural number $k\leq n$ such that $A^k=0$. Using the Cayley-Hamilton theorem, it is straightforward since a nilpotent matrix has a characteristic polynomial $p_A(\lambda)=\lambda^n$ so apply Cayley-Hamilton to deduce $A^n=0$.  I'm asking for a solution without using the Theorem.  Thank you!

$A$ is a $n\times n$ matrix such that $ A^m = 0 $ for some positive integer $m$.   Show that $A^n = 0$.   My attempt: For $n > m$, it's obvious since matrix multiplication is associative.  For $n < m$, $A^n\times A^{m-n} = 0$; not sure what to do next. Also I know that $\det A = 0$.


I installed Ubuntu and then Windows 8. How can I make GRUB work again so that I can choose which system I want to boot?

I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?


The question is  Write a method  isMultiple that determines, for a pair of integers , whether  the second integer  is a multiple of the first. The method  should take two integer  arguments  and return true  if the second is a multiple of the first and false  otherwise. [Hint: Use the remainder operator .] Incorporate this method  into an application that inputs a series of pairs of integers  (one pair at a time) and determines whether  the second value  in each pair is a multiple of the first.har()  Here is my code  import java.util.*; public class Multiples {      public static void main(String [] args){          boolean run = true;          while(run = true){         System.out.print("Enter one number:");         Scanner input = new Scanner(System.in);          int num1 = input.nextInt();         int num2 = input.nextInt();          System.out.println("Do you want to enter another pair(y/n)?");         String a = input.next();            boolean result = isMultiple(num1, num2);          if(result = true){             System.out.println(num1 + " is a multiple of " + num2);         }         else{             System.out.println(num1 + " is not a multiple of " + num2);         }          if(YesOrNo(a)){             break;         }           }       }          public static boolean YesOrNo(String a){              if(a == "y")               return false;             else if(a == "n")               return true;             else                 return true;         }           public static boolean isMultiple (int x , int y)         {              if(x % y == 0 || y % x == 0)                  return true;                 else                  return false;          }       }   I want break the while when enter "n" but it is break no matter what I enter.

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?


In lecture I encountered the following remark:  In $\mathbb{Z}[X^2,X^3]$ the $lcm(X^2,X^3)$  and $gcd(X^2 \cdot X^3, X^3 \cdot X^3)$ do not exist.  I do not understand this at all, for as far as I can see we can "normally" multiply the $X$'s with each other, so intuitively I would say that $X^3 = lcm(X^2,X^3)$ and $X^4 = gcd(X^2 \cdot X^3, X^2 \cdot X^2)$; since $X^2 \cdot X^3 = X^5$. Could you please explain that to me?

Let $R= \mathbb{Q}[x^2 ,x^3 ]$, the set of all polynomials over $\mathbb{Q}$ with no $x$ term. Show that a gcd of $x^5$ and $x^6$ does not exist in $R$.   I am reasoning for the absurd and I am assuming that $gcd (x ^ 5, x ^ 6) = ax ^ 2 + bx ^ 3\in\mathbb{Q}[x^2 ,x^3 ] $, then, for the Bezout identity there exists $p (x) = cx ^ 2 + dx^3$ and  $q(x)= ex ^ 2 + fx ^ 3$ in $\mathbb{Q}[x^2 ,x^3 ]$ such that $x ^ 5p (x) + x ^ 6q (x) = ax ^ 2 + bx ^ 3$, which is absurd since $$9 = deg (x ^ 5p (x) + x ^ 6q (x)) \neq  deg (ax ^ 2 + bx ^ 3) = 3.$$  Is it okay what I did? Thank you very much.


Lately I have been playing a lot as Tracer and noticed my ultimate charges faster than other characters. Do all ultimates charge at the same speed, what exactly effects it?

The information on the :     Ultimate abilities are powerful abilities only available to a hero   once their Ultimate Meter has filled. Progress towards an Ultimate   persists through death. The Ultimate Meter fills by killing/dealing   damage to enemy heroes, though Mercy gradually fills hers through   healing with her Caduceus Staff, and Torbjörn's turret generates   Ultimate progress for him. The amount of Ultimate gained appears to   vary between heroes, and kills seem to grant less Ultimate than   dealing damage.   Nowhere does it explain how quickly the meter is gained, and what % of meter corresponds to damage.  I know that in addition to that, meter is also passively gained for all heroes, albeit very slowly. What is the rate of that passive Ultimate meter? How does damage correspond to ultimate meter %?


I was surprised to discover that locals in switch statements are scoped to the switch statement and not to the case. Why is that? And is it good practice to add curly braces around each case as a workaround.  This won't compile:  switch (n) {     case 1:        var i = 1;        Console.WriteLine(i);        break;     default:        var i = 2;        Console.WriteLine(i);        break; }   This does compile:  switch (n) {     case 1:     {        var i = 1;        Console.WriteLine(i);        break;     }     default:     {        var i = 2;        Console.WriteLine(i);        break;     } }

Why is it that in a C# switch statement, for a variable used in multiple cases, you only declare it in the first case?  For example, the following throws the error "A local variable named 'variable' is already defined in this scope".  switch (Type) {     case Type.A:             string variable = "x";                 break;     case Type.B:             string variable = "y";                 break; }   However, per the logic, the initial declaration should not be hit if the type is Type.B. Do all variables within a switch statement exist in a single scope, and are they created/allocated before any logic is processed?


i am trying to find all instances of a data value in an oracle data base. I have written dynamic sql to look in DBA_TAB_COLUMNS for a specific column name. Then i string together the dynamic slq but there are tables in the DBA_TAB_COLUMNS that do not return anything, the sql just locks up and hangs. it does this even if i run the same query sql as a single query or if i Execute Immediate. So i need to have some sort of time out or error handler in my dynamic sql. As the dynamic sql (simple select statement) just hangs up it does not return any values from some of the tables but does work well for others. so it must time out i suspect. Other than a couple tables that seem to hang the dynamic sql the code works. how do i trap the errors?   set serveroutput on size 300000;  DECLARE     CURSOR guru99_det IS               SELECT      OWNER,                          TABLE_NAME,                          COLUMN_NAME                                                          FROM DBA_TAB_COLUMNS       --*************************************************     --enter the field name you are searching here.                        WHERE COLUMN_NAME LIKE '%STATUS%'        --************************************************             AND OWNER like '%KW%'               ORDER BY DBA_TAB_COLUMNS.OWNER;             s_string guru99_det%ROWTYPE;     sql_str VARCHAR2(32000);     cnt NUMBER;      found_cnt NUMBER;      lp_cnt NUMBER := 0;  BEGIN     OPEN guru99_det;      loop           FETCH guru99_det INTO s_string;          exit when guru99_det%notfound;           sql_str := null;          lp_cnt := lp_cnt + 1;          --BUILD THE SQL STRING           select                           (                                                    'SELECT  ' ||                                                       ' COUNT(*) ' ||                                                     ' FROM  ' ||                                                     s_string.OWNER ||                                                      '.' ||                                                      s_string.TABLE_NAME ||                                                      ' WHERE ' ||                                                     s_string.COLUMN_NAME  ||    --***********************************************  --enter the data value you are searching for here                 '  LIKE ''%CA%''  '                                                       --***********************************************                            ) into sql_str from dual  ;             Dbms_output.put_line( CAST(lp_cnt AS CHAR) || '  sql_str is: '||sql_str);           BEGIN                 EXECUTE IMMEDIATE sql_str  INTO found_cnt ;                  EXCEPTION                     WHEN OTHERS THEN                     DBMS_OUTPUT.PUT_LINE('ERROR');           END;          dbms_output.put_line('found_cnt: > ' || found_cnt ) ;       end loop;      CLOSE guru99_det;  END;

Is it possible to search every field of every table for a particular value in Oracle?  There are hundreds of tables with thousands of rows in some tables so I know this could take a very long time to query. But the only thing I know is that a value for the field I would like to query against is 1/22/2008P09RR8. <  I've tried using this statement below to find an appropriate column based on what I think it should be named but it returned no results.  SELECT * from dba_objects  WHERE object_name like '%DTN%'   There is absolutely no documentation on this database and I have no idea where this field is being pulled from.  Any thoughts?


The harmonic number $H_n$ is defined as $$H_n = \frac11 + \frac12 + \cdots + \frac1n$$ I need to show that $H_n - H_k$ can't be a Natural number, when $n>k$. I understand that the sum is greater than $\ln\big(\frac{n}{k}\big)$ but I don't know how it helps.

Assume that $k,n\in\mathbb{Z}^+$. Prove that the sum \begin{equation*} \dfrac{1}{k+1}+\dfrac{1}{k+2}+\dfrac{1}{k+3}+\ldots +\dfrac{1}{k+n-1}+\dfrac{1}{k+n} \end{equation*} is not an integer.   The case $k=0$ is proved in this question: ""


I'm trying to create a PDF from a file test.tex:  \documentclass{article} \usepackage{fontspec} \setmainfont{Noto Color Emoji} \begin{document} 😺 🌍 \end{document}   Running the command:  lualatex test.tex   produces these log messages:  This is LuaTeX, Version 1.10.0 (TeX Live 2019/Arch Linux) restricted system commands enabled. (./test.tex LaTeX2e <2018-12-01>  luaotfload | main : initialization completed in 0.059 seconds (/usr/share/texmf-dist/tex/latex/base/article.cls Document Class: article 2018/09/03 v1.4i Standard LaTeX document class (/usr/share/texmf-dist/tex/latex/base/size10.clo)) (/usr/share/texmf-dist/tex/latex/fontspec/fontspec.sty (/usr/share/texmf-dist/tex/latex/l3packages/xparse/xparse.sty (/usr/share/texmf-dist/tex/latex/l3kernel/expl3.sty (/usr/share/texmf-dist/tex/latex/l3kernel/expl3-code.tex) (/usr/share/texmf-dist/tex/latex/l3kernel/l3pdfmode.def))) (/usr/share/texmf-dist/tex/latex/fontspec/fontspec-luatex.sty (/usr/share/texmf-dist/tex/latex/base/fontenc.sty (/usr/share/texmf-dist/tex/latex/base/tuenc.def)) (/usr/share/texmf-dist/tex/latex/fontspec/fontspec.cfg))) (./test.aux) [1{/var/ lib/texmf/fonts/map/pdftex/updmap/pdftex.map}] (./test.aux)) 410 words of node memory still in use:   3 hlist, 1 vlist, 1 rule, 2 glue, 3 kern, 1 glyph, 5 attribute, 48 glue_spec , 5 attribute_list, 1 write nodes   avail lists: 2:15,3:4,4:1,5:21,6:1,7:15,9:7 </usr/share/fonts/noto/NotoColorEmoji.ttf   and ends with this error message:  ! error:  (file /usr/share/fonts/noto/NotoColorEmoji.ttf) (ttf): loca table not found !  ==> Fatal error occurred, no output PDF file produced!   I've installed the font using  pacman -S noto-fonts-emoji   and there's indeed a file at  /usr/share/fonts/noto/NotoColorEmoji.ttf   How do I get this to compile?    I'm not tied to LuaLaTeX; if I can create the PDF with another rendering engine, I'll happily do so.

I want to use Noto Color Emoji with lualatex (package fonts-noto-color-emoji on my box). However, this fails as follows. How to use Noto Color Emoji with lualatex?  \documentclass{article} \usepackage{fontspec} \setmainfont{Noto Color Emoji} \begin{document} 😺 👅  \end{document}   Error:  $ lualatex emoji.tex  This is LuaTeX, Version 1.07.0 (TeX Live 2019/dev/Debian)   restricted system commands enabled. (./emoji.tex LaTeX2e <2018-12-01>  luaotfload | main : initialization completed in 2.224 seconds (/usr/share/texlive/texmf-dist/tex/latex/base/article.cls Document Class: article 2018/09/03 v1.4i Standard LaTeX document class (/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo)) (/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.sty (/usr/share/texlive/texmf-dist/tex/latex/l3packages/xparse/xparse.sty (/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3.sty (/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3-code.tex) (/usr/share/texlive/texmf-dist/tex/latex/l3kernel/l3pdfmode.def))) (/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec-luatex.sty (/usr/share/texlive/texmf-dist/tex/latex/base/fontenc.sty (/usr/share/texlive/texmf-dist/tex/latex/base/tuenc.def)) (/usr/share/texlive/texmf-dist/tex/latex/fontspec/fontspec.cfg))) (./emoji.aux) [1{/var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map}] (./emoji.aux))  409 words of node memory still in use:    3 hlist, 1 vlist, 1 rule, 2 glue, 3 kern, 1 glyph, 5 attribute, 48 glue_spec , 5 attribute_list, 1 write nodes    avail lists: 2:15,3:4,4:1,5:21,6:1,7:13,8:1,9:6 </usr/share/fonts/truetype/noto/NotoColorEmoji.ttf ! error:  (file /usr/share/fonts/truetype/noto/NotoColorEmoji.ttf) (ttf): sfnt  table not found !  ==> Fatal error occurred, no output PDF file produced!


I'm creating an invite only website, so my question is if I need to create a sitemap xml and upload to Google and others search engines with all pages? With only the main page (that'll be open for everyone)?   And what others SEO tips I could use in a scenario like this?   I'm new to SEO, sorry for the newbie questions.  Thanks!

We have a website dedicated to our ActiveX and .NET components that has been working for more than 12 years. The site consists of 2 parts: the static part (product descriptions and articles) and the dynamic part (forum dedicated to our tools).  Google indexes the static part without any problems - all the pages are found due to a good textual hyperlink menu system. These pages also have good positions in SERPs.  However, many SEO pro's insist that we need to have a sitemap.xml file to enhance the positions of our website in the "eyes" of Google or other search engines like Bing. My 2 questions related to this are the followings:  1) Do we really need sitemap.xml for our website?  2) If so, how to code the dynamic forum pages in it?


In Star Trek: TNG, how can Data wish to be human if he is emotionless? How could he wish for something (anything) since that would involve desire, which is an emotion?

Starting with Encounter at Farpoint, at the very start of the series, when Riker first meets Data in the holodeck, Data, when asked if he considers himself superior to humans, says, "I am superior, Sir, in many ways, but I would give it all up to be human."  He has a desire, a want, and a longing to be human.  Isn't this an emotion in itself?  There's no reason or need for him to have such a desire.  If it's programmed into him, he would be able to find it somewhere in his memory and perhaps (if it's not read-only) re-write it.  Where could this desire come from if it's not from envy or longing or some other type of emotion?  Is it possible he had this and some other simple emotions all along?


While using a brand new MacBook Pro, with Touch Bar, somehow the Dock got locked.  I didn't do anything that I know of.  Nothing moves at all, in or out.  I'm trying to remove and add items, apps, and nothing takes.

I'm using OS X Yosemite (10.10.2) and recently I have been unable to drag or move any items on the dock. Right clicking them gives no option for "remove from dock", and the icons cannot be rearranged. New icons cannot be added, old icons cannot be deleted.  I have tried restarting, and resetting dock preferences to default, and killall Dock, as suggested by earlier askers. None of it works.  I heard about problems with PushBullet - but I do not have PushBullet. Just in case, I deleted a lot of random applications. Still nothing works.  I've tried various commands from lots of answerers on other questions. I've consulted the Mac Help pages. Nothing.  Does anyone know how I can resolve this? After resetting my Dock in an attempt to fix it, it is now filled with the default icons too. This is really limiting my productivity.


Is there a way to automatically generate a Keynote presentation from a source file written in text format, Markdown format, or org-mode?   I know that Pandoc and other tools can generate HTML-based slideshows from Markdown. But Keynote allows you to put all your speaker notes to yourself in "Presenter View," which allows you to have a detailed view of your slideshow + notes on your laptop, and project a clean presentation that is not cluttered up with all your speaker notes.   (Whereas with HTML presentations, since there's only one window, you either have to put your speaker notes in the presentation slide itself, or put your speaker notes elsewhere.)   So can I generate a Keynote presentation, or at least a barebones one with slide headlines, from another source?  Example  # A headline  ![some image](http://google.com/image.jpg)  Some text here.  # A headline  ![some image](http://google.com/image.jpg)  - bullet point - bullet point  # A headline  ![some image](http://google.com/image.jpg)  Some text.   > Speaker notes.

I need to import a text file (consisting of subtitles) into a Keynote presentation. I need to turn each subtitle into a single slide, interspersed with blank (black) slides. I'd like to create an Automator action in order to do this.  I think the way to do this is to filter paragraphs ending in two line breaks, but I don't know how to do it.


I'm a beginner in Python and I'm studying from the book Learning Python 5th edition by Mark Lutz.  In studying scoping and object reference, I've run across one thing that I quite did not understand. I understand that when you assign an object to other object, they're merely sharing a reference to the same address unless you perform top-level copying. However, I noticed that when you 'nest' the object, two objects no longer share the same address.   For example,  >>> L = [4, 5, 6] >>> X = L * 4                   # Like [4, 5, 6] + [4, 5, 6] + ... >>> Y = [L] * 4                 # [L] + [L] + ... = [L, L,...]  >>> X [4, 5, 6, 4, 5, 6, 4, 5, 6, 4, 5, 6] >>> Y [[4, 5, 6], [4, 5, 6], [4, 5, 6], [4, 5, 6]]   >>> L[1] = 0                    # Impacts Y but not X >>> X [4, 5, 6, 4, 5, 6, 4, 5, 6, 4, 5, 6] >>> Y [[4, 0, 6], [4, 0, 6], [4, 0, 6], [4, 0, 6]]   This is the part I don't understand. Why does changing L object impact Y but not X?

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?


I have a vector image in SVG format.(without georeferences)  I am trying to display it using OpenLayers to display properties of different polygons in it.  I tried converting it to GeoJSON but the resulting render appears to be stretched (ratios are not preserved).  Is there a transformation or a map projection that I am missing  or recreating a GeoJSON from scratch the only relevant choice?

I have a vector image in SVG format. (without georeferences)    I am trying to display it using OpenLayers to display properties of different polygons in it.  I tried converting it to GeoJSON but the resulting render appears to be stretched (ratios are not preserved).  Is there a transformation or a map projection that I am missing or recreating a GeoJSON from scratch the only relevant choice?


Early 20th century texts on calculus of variations use a very strongly slanted Delta. A sample is below. It is much more slanted than the  \mathit{\Delta} discussed in , and more slanted than in    The specific difference is that I want the upper vertex farther to the right than the bottom right one.  How can I match this in LaTeX?

I would like to insert the below mathematical symbol, it looks like a big Delta but different. Is there command to obtain a similar shape?


Same error as a lot of users here, but I'm running Catalina, so I'm not sure if that changes things and I would rather make sure I'm going about it the right way so I don't make things worse.   I tried to delete a partition, and disk utility crashed halfway through. I restarted and got the folder with the ? on it.   I would greatly appreciate if someone could guide me to fixing this without losing all of my data. Thanks.  E: I realise I should probably add a little more info. I have an Early 2013 15” MBP with the 500GB SSD.

Yesterday, I have tried to delete an Ubuntu partition. Since, my Mac (13", MBPro mid-2014) doesn't boot. Now, I boot on Mac OS copy with an USB. i follow different subject of this forum (like this : ), and my volume partition change from FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF to 48465300-0000-11AA-AA11-00306543ECAC. But I still can't boot to it...    Thank you very much !


In the late 1980s, I read a novel series that spanned several generations of a human colony on a Earth-like extraterrestrial planet.  It was probably available through Scholastic Books (in Canada) since that's where a lot of these novels came from at the time at my elementary school. Almost certainly it was a kid's book (preteen/young adult).  The protagonists were children and many of their interactions were with robot guardians. I think they had no parents and been raised by humanoid robots since birth, and as it was written from their perspective, they had no memory of their travel (e.g. cryogenics or a colony ship). The planet had Earth-like flora and fauna (if there was any talk of terraforming, it happened before the first novel began).  One detail I remember is that the robots made prefab houses for everyone from some kind of plastic resin. These were initially intended as temporary housing with the expectation that the humans would soon build proper permanent houses, but in later books in the series (at least a generation after founding) it was clear this goal had not been realized, and surviving humans were either still living in these huts or in very primitive dwellings (e.g. wooden huts).  One of the themes in the later books (set after the first generation) was the descent of the human colony into ignorance and selfishness accompanied by a rejection of the still-functioning robots and the legacy of Earth.   Would be very curious to know if anyone can identify this novel series and how far my memory has strayed from the truth.

I read a series of books written in English (possibly a trilogy) in the early 1980s and was hoping to find them again for my children. The details I remember are:   It was set on a planet and spanned many, many years over the course of the books There was a sort of 'housekeeper/protector' robot that featured in all of them but was slightly the worse for wear by the end One of the books had a young dark-skinned boy who made the hike up to the house where the robot was, and someone made reference to the fact that his dark skin protected him from the incredibly fierce sun found in the higher regions of the planet.


The usual flow of electronic communication is added to at Christmas by many written notes and greetings hand-written in haste, among which are mistakes. “Xmas Peas and Love” comes to mind. We term such slips typos when in printed or electronic form, a shortened form of  typographical error   Other than the long phrase slip of the pen, do we have a similar short term for a hand-written error?

"Typos" are acknowledged as "technical" errors, ones that obviously aren't caused by the writer's poor spelling. Although less frequent than in typing, they can also occur in handwritten texts, as a result of absent-mindedness or just an accidental stroke of the pen.   Since the text wasn't actually typed, it sounds funny to call them "typos". Is there a more fitting word, one that reflects the "accidental" nature of the error?


Calculating the sum of $\sum\frac{n^2-2}{n!}$  I want to calculate the sum of $\sum_{n=0}^{+\infty}\frac{n^2-2}{n!}$.   This is what I have done so far:  $$ \sum_{n=0}^{+\infty}\frac{n^2-2}{n!}=\sum_{n=0}^{+\infty}\frac{n^2}{n!}-2\sum_{n=0}^{+\infty}\frac{1}{n!}=\sum_{n=0}^{+\infty}\frac{n}{(n-1)!}-2e$$  And here I don't know how to deal with the $\frac{n}{(n-1)!} $. Any tips?  EDIT: One of the answers recommends to write down the sum as follows:  $$\sum_{n=0}^{+\infty}\frac{n^2-2}{n!}=\sum_{n=0}^{+\infty}\frac{n(n-1)}{n!} + \sum_{n=0}^{+\infty}\frac{n}{n!}-2\sum_{n=0}^{+\infty}\frac{1}{n!}$$  Which equals to:  $$\sum_{n=0}^{+\infty}\frac{n(n-1)}{n!} + \sum_{n=0}^{+\infty}\frac{n}{n!}-2\sum_{n=0}^{+\infty}\frac{1}{n!}=\sum_{n=0}^{+\infty}\frac{(n-1)}{(n-1)!}+\sum_{n=0}^{+\infty}\frac{1}{(n-1)!} -2e$$  But here I have negative factorials. What should I do next? Or can I just say that $\sum_{n=0}^{+\infty}\frac{1}{(n-1)!}=e$?

For some series, it is easy to say whether it is convergent or not by the "convergence test", e.g., ratio test. However, it is nontrivial to calculate the value of the sum when the series converges. The question is motivated from the simple exercise to determining whether the series $\sum\limits_{k=1}^{\infty}\frac{k^2}{k!}$ is convergent. One may immediately get that it is convergent by the ratio test. So here is my question:     What's the value of $$\sum_{k=1}^{\infty}\frac{k^2}{k!}?$$


How to delete an array in an object in Javascript? For example I want to delete:  RandomObject.array = [];   So that when I use RandomObject in ways such as copying it into another object, the array is not included.

Say I create an object as follows: let myObject = {   "ircEvent": "PRIVMSG",   "method": "newURI",   "regex": "^http://.*" };  How should I remove the property regex to end up with new myObject as follows? let myObject = {   "ircEvent": "PRIVMSG",   "method": "newURI" };


“Any physical theory is always provisional, in the sense that it is   only a hypothesis: you can never prove it.”      Excerpt from Stephen Hawking, A Brief History of Time, iBooks.   So does that mean that Theory = Hypothesis?

What's the difference between ,  and ? I think I'm confused now because I exactly learned the misconception one as explained below in high school.  According to this university's website it says that what I learned from school is a misconception. Is this explanation generally accepted among the scientists.     MISCONCEPTION: If evidence supports a hypothesis, it is upgraded to a   theory. If the theory then garners even more support, it may be   upgraded to a law.      CORRECTION: This misconception may be reinforced by introductory   science courses that treat hypotheses as "things we're not sure about   yet" and that only explore established and accepted theories. In fact,   hypotheses, theories, and laws are rather like apples, oranges, and   kumquats: one cannot grow into another, no matter how much fertilizer   and water are offered. Hypotheses, theories, and laws are all   scientific explanations that differ in breadth — not in level of   support. Hypotheses are explanations that are limited in scope,   applying to fairly narrow range of phenomena. The term law is   sometimes used to refer to an idea about how observable phenomena are   related — but the term is also used in other ways within science.   Theories are deep explanations that apply to a broad range of   phenomena and that may integrate many hypotheses and laws. To learn   more about this, visit our page on the different levels of explanation   in science.


How to find all Ring homomorphisms from  $\mathbb Z_m$ to $\mathbb Z_n$ (with the usual ring structure ) ?

I face the problem of finding how many non-trivial ring or group homomorphisms there are from $\mathbb{Z}_m$ to $\mathbb{Z}_n$, where $m<n$. Is there any general formula?   At the moment, I want to know how many ring homomorphisms there are when $m=12,n=28$.  Please help.


I am trying to prove the expression: $\exists x P(x) \implies Q(y) \Longleftrightarrow \forall x [P(x) \implies P(y)]$ I was hoping I could get some intimation on what to do next. For your time I am beforehand very appreciative. I'll start proving first  $[\exists x P(x) \implies Q(y)] \implies \forall x [P(x) \implies P(y)]$ $$\exists x P(x) \rightarrow Q(y)$$ [Existential Instantiation] $$P(a) \to Q(y)$$ [Idempotency] $$P(a) \wedge P(a) \to Q(y)$$ [Extraction] $$P(a) \to (P(a) \to Q(y))$$ [Material Implication] $$P(a) \to ( \neg P(a) ∨ Q(y)) $$ [DeMorgan] $$P(a) \to \neg (P(a) \wedge \neg Q(y)) $$ [Simplification] $$P(a) \to \neg (P(a))$$ This is as far as I've gotten. I seem to be really stuck. If anyone could provide me with suggestion on how to proceed from here I will greatly appreciate it. Thank you kindly.

Let $M,N$ be sets, $Q_M$ a set that depends on $M$ and $P(\cdot,\cdot)$ a property with two parameters (is it ok, to call these "parameters" or would "variables" have been better ?). Consider the following three statements:    i) $(\forall x\in M)(\forall y\in Q_M)[P(x,y)\Rightarrow x \in N]$   ii) $(\forall x\in M)[((\exists y\in Q_M)[P(x,y)])\Rightarrow x \in N]$    iii) $N=\{ x\in M \mid (\exists y\in Q_M)[P(x,y)]\}$  I would very much like to know the following:   I have been told that i) and ii) are equivalent, since they are an instance of a general scheme $$ (\forall x)(\Psi \Rightarrow \Phi) \Leftrightarrow  ((\exists z)\Psi) \Rightarrow \Phi),  $$ which holds if $z$ is not mentioned in $\Phi$, as Carl Mummert I think explained a long time ago  - I can't find the entry right now. What are the "values" the $x,z,\Psi$ and $\Phi$ have to take, such that this scheme shows the equivalence of i) and ii) ?      What kind of setting do you need in which you can prove this general scheme ? Is it only predicate logic ? Or do you need ZFC to formalize this logic so you can you use set-theory to prove it ?        How to you prove it (or a corrected version of it, if the above is flawed; it seems to me that quantifiers are missing) ? Is ii) equivalent to iii) ? How do you rigorously prove that ? Which ZFC axioms are needed for that proof ?


When I do select query on single table then I get output rows ordered by primary key which is perfect, following query:  select * from recondata where importid=131;    but when I'm joining this table to another table output of row is random, ReconStatus contains only statusId (Primary key) and Status and in ReconData, dataID is primary key and there are no other key. I'm using following query:  select dataid,coalesce(clientPortfolioname,portfolioName) as portfolioName,                             Status, Message, PositionId, PositionIdType,    PositionName, ClientMarketValue,                             ClientCurrency, ClientMarketValueBase, MarketValueBase, MarketValueLocal,                             MVDiff, SourceInstrumentType, Weight, WeightByClient, ImportType,AssetType,                             AssetName,ExtraInfo                             from                              ReconData rd inner join ReconStatus rs on rd.StatusId = rs.statusid                             where                             ImportId=131;   Output is also not based on primary key of second table. Can someone explain on what basis MS SQL is ordering output rows ?

How does SQL Server figure out the order of the records in the result set of query execution?  I am trying to make heads or tails of it but find myself scratching my head. When I change the fields I am selecting the order also changes. When I execute the below SQL with a SELECT * I get the same records but in a much different order.   SELECT TOP (900)     AD.ATTACHMENTID,     AD.NAME,     AD.ISINLINE,     AD.INSERTEDDATETIME,     ATMT.ATTACHMENTBLOB,     U.UFID   FROM ATTACHMENTDETAIL AD WITH (NOLOCK)   INNER JOIN MESSAGEATTACHMENT MA ON MA.ATTACHMENTID = AD.ATTACHMENTID   INNER JOIN ATTACHMENT ATMT ON ATMT.ATTACHMENTID = AD.ATTACHMENTID   INNER JOIN MESSAGE MSG ON MSG.ID = MA.MESSAGEID   INNER JOIN MESSAGEDETAIL MD ON MD.MESSAGEID = MA.MESSAGEID   INNER JOIN [USER] U ON U.ID = MD.USERID   LEFT OUTER JOIN XmlExtractionMapping XM ON MA.MESSAGEID = XM.MessageId     WHERE AD.FILEBOXTOKEN IS NULL      AND (XM.XMLEXTRACTIONDATE IS NOT NULL OR           (MSG.MESSAGESOURCEID = 1 AND MD.FolderId <> -4))     AND AD.ISINLINE = 'FALSE'


And also, I don't really understand the difference between a valid document and a well formed one. Help?

I wasn't aware of a difference, but a coworker says there is, although he can't back it up. What's the difference if any?


I am struggling with the intuition behind terms in the Bayes' Theorem. In the simple example of a deck of cards we have:  $$ P(King | Red) = \frac{P(Red | King)P(King)}{P(Red)} $$  The terms in this equation are intuitive to me. P(Red | King) is the proabability a card is red given that it is a king. P(King) and P(Red) is just the probability of a card being a king or red (1/13 or 1/2 respectively).  I am trying to apply this intuition to a more complex example, consider some data that we assume is distributed binomially with probability parameter theta, we observe 10 trials (N=10). This gives: $$ y \sim Binomial(N,\theta) $$ Which implies that: $$ p(y | \theta) = \binom{N}{y} \theta^y (1 - \theta)^{N-y} $$ And again we get Bayes' Formula:  $$ P(\theta | y) = \frac{P(y | \theta)P(\theta)}{P(y)} $$  The P(y | theta) term can be thought of as a surface (see pic below).    However what is the intuition behind the remaining two terms $P(\theta)$ and $P(y)$ ?  What is the probability that $\theta = 0.4$? The space is no longer discrete like the simple example and so this doesn't really have meaning. This leads me to believe that these terms now relate to integrals over the surface in the diagram above. Is my understand correct?

I have to teach the Bayes formula to some undergraduates, in the form:  $$ P(A|B) = \frac{P(A \cap B)}{P(B)} = \frac{P(B|A)P(A)}{P(B)} $$  I was wondering if anyone had any really thoughtful or alternative ways of teaching it instead of the standard approach.


I googled this question many times but could not find a good reason why the knowledge of command line is important.Some say GUI cannot be used always but there are no examples supporting their statement.

Is the command line a popular choice thing, or do I have something wrong here?  In modern Linux there's dozens of fresh, robust, 3-D rendered GUIs, graphical-based APIs, and desktop interfaces that could easily implement the commands entered in to the command interpretor text-based UI on the GUI through a more robust featured program that encompasses GUI elements better.  What I am trying to say is, why is the command-line still so popularly used in 2013?  I mean I can agree that before both the memory in computers was so minimal that a fancy GUI would be starving the main memory, but nowadays memory DOES come cheap, GUIs are 3-D, we have mobile power machines getting better every day so to speak, so why are we still punching commands in to interpretor parsing terminal UI emulations?  Why isn't there a more robust and graphical way to implement the commands, only through a more modern GUI?  For example, how about "ls" or "list" as a button that will generate a table view of data, or "umount" implemented in a button that generates a table view of current mount points?  Overall, why doesn't a more modern implementation of the command interpretor come in to play, featuring the exact same control and capabilities just in a more convenient decor?  PS: I should add this here as well ... I'm not saying every command should be implemented with a GUI-based program with fancy widgets and such. I'm just saying that I figured we'd have a makeover of the command-line, or maybe that some ideas can be better expressed, optimized, managed, or cycled through easier with visual aspects than just "words". No means to start an argument, but to find out why nothing has diverted this way over so many years and advancements of graphics in operating systems/software.


import java.util.*;  class token { public static void main(String args[]){     Scanner input = new Scanner(System.in);     Random number = new Random();      System.out.println("Do you want to play again(y/n)? ");     String in = input.nextLine();         do{     int num1,num2,sum;     num1 = 1+number.nextInt(6);     num2 = 1+number.nextInt(6);      sum = num1 + num2;       System.out.print("Dice 1: "+num1);     System.out.print("\nDice 2: "+num2);     System.out.print("\nSum: "+sum);      if(sum%2==1){         System.out.println("\nYou have lost 1 token.");     }else if(sum>10){         System.out.println("\nYou have won 2 tokens.");     }else if(sum>11){         System.out.println("\nYou have won 2 tokens.");     }else if(sum>12){         System.out.println("\nYou have won 2 tokens.");     }else{         System.out.println("\nYou have won 1 token.");     }      System.out.println("Do you want to play again(y/n)? ");     String in1 = input.nextLine();       }while(in == "y");  } }   So I tried to use a do while loop but unfortunately, it does not loop at all. Sample output: Do you want to play again(y/n)?  y Dice 1: 3 Dice 2: 4 Sum: 7 You have lost 1 token. Do you want to play again(y/n)?  y  I want my program to continuously loop unless the user enters n.

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?


Some examples: "never" might be written as "neva" "I don't know" is sometimes written as "iono" or "I dunno" on various internet media. My question is: is there a word for this particular technique of spelling a term in the way it is (sometimes) pronounced?

For example,      Night -> Nite   Through -> Thru   The -> Da   Though -> Tho     Nite even appears in some dictionaries as having the same meaning as night.  What is it called when words are deliberately written incorrectly but the pronunciation and meaning are kept unchanged?


Let $G$ be a group of order $21$ contains an element $a$ of order $7$ . Prove  that $A$=($a$) ,the subgroup generated  by $a$ , is normal in $G$ .   I'm more concerned with how I can derive the prove of this question

Question is to :  Find the number of Normal subgroups of a nonabelian group $G$ of order $21$ other than $\{e\}$ and $G$.  What I have done so far is :  As $|G|=21=3\cdot7$  we have :  No. of sylow $3$ subgroups $1+3k$ dividing $7$ leaving out possibilities $1$ or $7$  No. of sylow $7$ subgroups $1+7k$ dividing $3$ leaving out only possibilities $1$.  So, we have a unique sylow $7$ subgroup and so it is normal.  I remember somehow that any normal group should come from a normal sylow subgroup or something like that.  S0, I prefer to conclude there is only one Normal subgroup for a non abelian group of order $21$.  Please let me know if this is true and please help me to fill that gap :      I remember somehow that any normal group should come from a normal sylow subgroup or something like that.   Thank you.


Earlier today, Stack Exchange went down for a period of time due to a routing issue. At the time, I was browsing on my iPhone via the native app, and suddenly my connections were timing out, as indicated by the black stripe above the table view. As I thought it was an error on my end, I immediately sprang to check my connection to other sites. As I came to realize though, the network was just down for maintenance on the routing issue and would be back up momentarily. Then I realized: at this point, there is not much distinguishing a local network error from an error/maintenance period on the site.  Is there any way we can have a more obvious way of detecting the site is down for maintenance and not simply down from the mobile app? It's not imperative, just something that would be nice to have.

Yesterday  (or at least part of it) was (briefly) in read-only mode, during that time on the website there was a banner indicating that the site was in read only mode. However withing the iOS app there was no such indication, worse if you tried to take some action (I only tried voting, but I'm assuming other actions would have been the same) it would fail without saying why.


When we observe a galaxy farther than 13 billion light years away, we see that galaxy as it was 13 billion years ago. But back then, that galaxy was much closer to us ,if indeed we live in an expanding and accelerating universe. The question is, why we see it so far when in fact it was very close to us and the time for the light to reach us was much shorter?

I was reading this article this morning:    Scientists have discovered a gamma-ray burst whose light has taken 13.14 billion years to reach Earth. This much is cool and interesting. However, the assumption is then stated that this is "the most distant single object yet spied by a telescope".  But hold on a minute. It is also known that galaxies are moving away from each other at incredible speeds, most faster than the speed of light, because the space/time between them is expanding (or something like that... I'm no scientist!)  So these so-called amazingly distant objects, well for starters, they don't exist any more... They are things that happened billions of years ago. But not only that, they are probably objects that were only a few million light years away from us when they actually took place. So surely then, the objects themselves aren't the most distant ones, but the light from them has been distorted such that the light has taken that long to reach us?  Furthermore, if the galaxies are spreading out faster than the speed of light, who is to say this explosion actually happened 13.1 billion years ago? Isn't it possible that the light was created say 5 billion years ago, but has taken much longer to reach us because of the expanding space between the galaxies?  I'm sure this stuff has already been considered by scientists, but I find it weird the way news articles always assume that just because light travels at a specific speed, that it's always going to take the same amount of time to reach us.  Or am I getting it wrong? I'd love to know!  EDIT: For people discussing the whole faster-than-light-speed thing, I came across :     As you look at galaxies further and further away, they appear to be moving faster and faster away from us. And it is possible that they could eventually appear to be moving away from us faster than light. At that point, light leaving the distant galaxy would never reach us.   When that happens, the distant galaxy would just fade away as the last of the photons reached Earth, and then we would never know it was ever there.   And :      That mysterious dark energy force, which is accelerating the expansion of the Universe is making the most distant galaxies move faster and faster away from us. Eventually, they will cross an event horizon and appear to be moving away from us faster than the speed of light. At this point, any light emitted by the galaxy will cease to reach us. Any galaxy that crosses this horizon will fade away from view, until its last photon reaches us. All galaxies will disappear from view forever.


In the hyperbolic plane, let a circle of radius r be given. If we want to circumscribe a regular polygon with n sides around this circle (i.e., if we want the sides of the polygon to be tangents of the circle), how large must n be?

Does there exist a relationship in terms of $r$ and $n$ to represent how large $n$ must be if $r$ of the circle is given in the hyperbolic plane? (The edges of the regular $n$-gon are tangent to the circle.)  This is a follow-up question to


Let $(a_n)_{n\in \mathbb{N^*}}$ a strictly positive sequence such that $\displaystyle : \lim_{n\to +\infty} \sum _{k=1}^n a_k=+\infty$. Show that for all sequence $(b_n)_{n\in \mathbb{N^*}}$ of real numbers such as $\displaystyle \lim_{n \to +\infty} b_n = l \in \mathbb{\bar{R}}$, we have $:$ $$\lim_{n\to +\infty} \frac{a_1b_1+a_2b_2+a_3b_3+...+a_nb_n}{a_1+a_2+a_3+...+a_n}=l$$  I tried to use some inequalities such as the Cauchy inequality which gave me $\sum a_kb_k\le \sqrt{\sum a_k^2\ \cdot \ \sum b_k^2 }$ I also tried the definition of the limit with Cesaro lemma yet it doesnt work  Any idea ? thanks

Let $\{x_n\}_{n\in\mathbb{N}}$ be a sequence with $\lim\limits_{n\to\infty}x_n = a$, $\{t_n\}_{n\in\mathbb{N}}$ be a sequence with $\lim\limits_{n\to\infty}t_1+t_2+\ldots+t_n = +\infty$.  Prove that  $$\lim_{n\to\infty}\frac{t_1x_1+t_2x_2+\ldots+t_nx_n}{t_1+t_2+\ldots+t_n} = a$$  My idea is use that  $$(t_1+\ldots+t_n)\min\{x_n: n\in\mathbb{N}\}\leq t_1x_1+\ldots+t_nx_n \leq (t_1+\ldots+t_n)\max\{x_n: n\in\mathbb{N}\}$$  But I'm not sure if $\lim\limits_{n\to\infty}\min\{x_n: n\in\mathbb{N}\} = \lim\limits_{n\to\infty}\max\{x_n: n\in\mathbb{N}\} = \lim\limits_{n\to\infty}x_n$.


How can I check if an url is made with an ip address instead of a domain name?  For example:   http://www.yeouuuuu.com/bla https://www.bbc.co.uk/something http://yeou:password@my.service.com/ //return true; http://172.10.10.100/test //return false; because there is an IP.   ip4 regex:  ipv4 = RegExp('((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|   [0-9])\\.){3}(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])');

Does anyone have a regular expression handy that will match any legal DNS hostname or IP address?  It's easy to write one that works 95% of the time, but I'm hoping to get something that's well tested to exactly match the latest RFC specs for DNS hostnames.


My project structure is organized as follows:  My requirement is such that I need to create multiple 'apps' that utilize some common code contained within common\util.py and service\writer.py (for the sake of this example, those files contain print statements). The contents of app01\main.py is: from ...common.util import print_text print_text("Hello World!")  When I execute app01/main.py (python.exe C:/ProjectX/code/apps/app01/main.py), I receive the following exception: File "C:/ProjectX/code/apps/app01/main.py", line 1, in <module> from ...common.util import print_text ValueError: attempted relative import beyond top-level package  I tried moving files/directories around but cannot resolve this issue. Would appreciate it if someone can let me know as to how to fix this problem.

Imagine that you want to develop a non-trivial end-user desktop (not web) application in Python. What is the best way to structure the project's folder hierarchy?  Desirable features are ease of maintenance, IDE-friendliness, suitability for source control branching/merging, and easy generation of install packages.  In particular:   Where do you put the source? Where do you put application startup scripts? Where do you put the IDE project cruft? Where do you put the unit/acceptance tests? Where do you put non-Python data such as config files? Where do you put non-Python sources such as C++ for pyd/so binary extension modules?


trigger ServiceEnquiryOwnershipTrigger on Service_Enquiry__c (before insert) {         System.debug('~~~ Begin');          Set<String> accset = new Set<String>();          for(Service_Enquiry__c s : Trigger.new)         {             accset.add(s.Account__c);         }           Map<Id,Account> accMap = new Map<Id,Account>([SELECT ID,OwnerId FROM Account WHERE ID IN :accSet]);          for(Service_Enquiry__c s : Trigger.New)         {             System.debug('~~~ Inside Loop');            try           {                       if(s.Account__c != null)                       {                            System.debug('~~~ Account Match Found');                            s.OwnerId = accMap.get(s.Account__c).OwnerId;                            System.debug('~~~ Owner Id = '+s.OwnerId);                        }                       else                       {                           System.debug('~~ Account Not Found'); //BELOW LINE THROWS EXCEPTION                           s.OwnerId = SEMapping__c.getValues(s.Lead_Office__c).Manager__c;                           System.debug('~~~ Owner Id = '+s.OwnerId);                        }           }           catch(Exception e)           {              System.debug('~~~ Inside Exception');               s.OwnerId = SEMapping__c.getValues('Default').Manager__c;               System.debug('~~~ Owner Id = '+s.OwnerId);               s.System_Comments__c = 'Exception occured while assigning ownership';           }         }          System.debug('~~~ End');     }   As commented in the code snippet I get an exception at the line  s.OwnerId = SEMapping__c.getValues(s.Lead_Office__c).Manager__c;   In that custom settings I have knowingly put an inactive user to trigger an exception. In the catch block i intended to get a default user (who will always be active) and keep that as owner whenever there is an exception. The exception is indeed getting thrown but for some reason it is not being caught by the "catch" block.  Let us assume inactive user as XXX and the default active user as YYY  The following occurs (obtained from the debug log)  ~~~ Begin ~~~ Inside Loop ~~ Account Not Found ~~~ Owner Id = XXX ~~~ End   What I expected (when there is an exception)  ~~~ Begin ~~~ Inside Loop ~~ Account Not Found ~~~ Owner Id = XXX ~~~ Inside Exception ~~~ Owner Id = YYY ~~~ End   I get the following exception   13:20:02.0 (280750383)|FATAL_ERROR|System.DmlException: Insert failed. First exception on row 0; first error: INACTIVE_OWNER_OR_USER, operation performed with inactive user [XXX] as owner of 01Ip0000000Ck3E: []   Can someone tell me what I am missing ?

I have a problem with my trigger. In Sandbox, everything works fine. When I deploy it to production, I receive multiple exceptions - which is really strange, because I got angry and put the whole code in "try" block. When I put everything in "try" block, it shouldn't be possible not to catch an exception! This is how my code looks: trigger UpdateLeadField on Lead (before insert, before update) {      //debugging in progress     try{         if(Trigger.New[0].SomeField__c==NULL)         {             for(Lead obj: trigger.new)                 obj.SomeField__c = obj.OwnerId;             return;         }              if (Trigger.New[0].OwnerId != Trigger.Old[0].OwnerId)          {             for(Lead obj: trigger.new)             {                 if(Trigger.New[0].SomeField__c==NULL || [SELECT Name FROM UserRole Where Id = :[SELECT Id, UserRoleId FROM User WHERE Id = :obj.OwnerId][0].UserRoleId].Name == 'Some role')                 obj.SomeField__c = obj.OwnerId;             }         }     }     catch (Exception e)     {         System.debug(e);     } }  The main problem seems to be with Web-to-Lead - When deployed, it stops working. The exception:  Apex script unhandled trigger exception by user/organization: 005C00000XXXXXX/00XXXXX0000LXXQ UpdateLeadField: data changed by trigger for field Some field: id value of incorrect type: 00GC00000XXXXXqMAC  "Some field" is a lookup field.


I am trying to use a feature from the  called StringUtils. However this requires you download the libary and add it so I can use the code import org.apache.commons.lang3.StringUtils;. My problem is I am unsure of where to add it to so that I may compile my program in command prompt. I am also unaware of what file I should to add into the required folder.  Any help would be greatly appreciated.

Is there a way to include all the jar files within a directory in the classpath?  I'm trying java -classpath lib/*.jar:. my.package.Program and it is not able to find class files that are certainly in those jars.  Do I need to add each jar file to the classpath separately?


I'm trying to figure out a way to locate multi-line strings embedded in a binary file. The code I've got will identify non-multi-line versions of the pattern, but not the multi-line versions.  I've tried this with with re.findall():  import re a = open('file', 'rb') b = a.read() c = re.findall(b'[<]{2}.*?[>]{2}', b, re.MULTILINE)   And with re.search():  import re a = open('file', 'rb') b = a.read() c = re.search(b'[<]{2}.*?[>]{2}', b, re.MULTILINE) c.group()   In each case, the code will return non-multi-line substrings, but not those where a \n character appears in the string.  Any ideas?

For example, this regex  (.*)<FooBar>   will match:  abcde<FooBar>   But how do I get it to match across multiple lines?  abcde fghij<FooBar>


I am trying to make glutonous rice wine, purchased the "Angel rice yeast (amalyze)" from asian market, the "white cookie/powder" broke rice down into sugar. I have measured, it is 40%, very sweet to taste. But it just does not ferment. The sweetness always there, does not reduce. The liquid pools out is very sweet. .does that means it has being converted from starch to sugar already ? I tried to pitch the champage yeast into it, it only last 2 days, before bubbles stopped. Why? Is it too sweet (40%Brix) for champage yeast? Thanks

I am trying to make glutonous rice wine, purchased the so call "yeast" from asian market, the "white cookie/powder" broke rice down into sugar. I have measured, it is 40%, very sweet to taste. But it just does not ferment. The sweetness always there, does not reduce. I tried to pitch the champage yeast into it, it only last 2 days, before bubbles stopped. Why? Is it too sweet (40%) for champage yeast? Thanks


I am experiencing the hyperref split-link issue described in  .  I tried to update the hyperref package as recommended as well as the oberdiek package which also seems to have some hyperref-related files.  My hyperref.sty is now at v6.83m, hobsub-hyperref.sty at v1.13.  The  compiles without problems, but my document still generates the same error.  My documentclass is elsarticle (version 1.2.0).  The following suffices to produce the problem:  \documentclass[5p]{elsarticle}  \usepackage{kantlipsum} \usepackage{hyperref}  \begin{document}  \begin{frontmatter} \end{frontmatter}   \kant*[1-4] \kant[5] \href{http://tex.stackexchange.com}{This is a very very   very very very very very very very very very very very very very   very very very very very very very very long link.} \end{document}   Both the 5p option and frontmatter seem to be required, though the latter may be empty.

I started using showkeys in one of my documents and see this error  \pdfendlink ended up in different nesting level than \pdfstartlink   A bit of google suggests that this "happens when hyperref is used under pdftex and a citation splits across a page boundary". (See: ).  But this package is only useful at drafting stage where the text is changing frequently i.e. the chance of the error is high. Is there a general way to smoothly use showkeys with hyperref? Thanks.


I get an Error for setOnMouseClicked when I click on empty row on the table. This only happens when I click on an empty row at first after running the code. my method is this: table.setOnMouseClicked(e -> {                 try {                     User selected = table.getSelectionModel().getSelectedItem();                     String query = "SELECT * FROM persons WHERE PersonID=?";                     pst = conn.prepareStatement(query);                     pst.setString(1, selected.getPersonID());                     rs = pst.executeQuery();                      while (rs.next()) {                         txtFirstName.setText(rs.getString("Firstname"));                         txtLastName.setText(rs.getString("Lastname"));                         ((TextField) txtDob.getEditor()).setText(selected.getDob());                         }                      pst.close();                     rs.close();                 } catch (SQLException ex) {                     ex.printStackTrace();                 }             });  this is what I get in my console. This only happens when I click on How can I solve this ? Exception in thread "JavaFX Application Thread" java.lang.NullPointerException     at application.Main.lambda$8(Main.java:266)     at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)     at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)     at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)     at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)     at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)     at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)     at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)     at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)     at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)     at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)     at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)     at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)     at javafx.event.Event.fireEvent(Event.java:198)     at javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3470)     at javafx.scene.Scene$ClickGenerator.access$8100(Scene.java:3398)     at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)     at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)     at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)     at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)     at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381)     at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)     at java.security.AccessController.doPrivileged(Native Method)     at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417)     at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)     at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)     at com.sun.glass.ui.View.handleMouseEvent(View.java:555)     at com.sun.glass.ui.View.notifyMouse(View.java:937)     at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)     at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)     at java.lang.Thread.run(Thread.java:748)

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?


Hi Guys, Can somebody explain to me why, when assigning a material to specific vertices, it doesn't seem to line up. Am I doing something wrong or is it supposed to be like this? Thanks!

I have tried to map this simple object, but the uv mapping does not correspond to what i see in the textured object. It cuts the image a bit on top and a bit on the bottom of the faces. It does not fill the faces with the texture, even though i have mapped them correctly. Does anyone know what could be happening? Thanks in advance.


I am looking at the solution of this problem:  $$\cos \left(\alpha \right)+\cos \left(\beta \right)+\cos \left(\gamma \right)=4\sin \left(\frac{\alpha }{2}\right)\sin \left(\frac{\beta }{2}\right)\sin \left(\frac{\gamma }{2}\right)$$ and it says this in the solution as the first step: $$\cos \left(\alpha \right)+\cos \left(\beta \right)+\cos \:\left(\gamma \:\right)=2\cos \left(\frac{\alpha +\beta }{2}\right)\cos \left(\frac{\alpha -\beta }{2}\right)-2\cos \left(\frac{\alpha \:+\beta \:}{2}\right)^2+1$$  I understand that the $\cos \alpha +\cos \beta=2\cos \left({\frac {\alpha +\beta }{2}}\right)\cos \left({\frac {\alpha -\beta }{2}}\right)$ is used, however how is the $cos \:\left(\gamma \:\right)$ transformed? I assume I should use the $\alpha +\beta +\gamma =\pi $ to replace $\gamma$ but can't seem to figure it out? Any help is very much appreciated. x

I humbly ask for help in the following problem.  If  \begin{equation} A+B+C=180 \end{equation} Then prove \begin{equation} \cos A+\cos B+\cos C=1+4\sin(A/2)\sin(B/2)\sin(C/2) \end{equation} How would I begin the problem I mean I think $\cos C $ can be $\cos(180-A+B)$. But I am unsure what to do next.


my attempt: SELECT * into table_joe FROM table_names WHERE username LIKE '%Joe%' But this fails saying the new table (table_joe) is an undeclared variable. Thank you!

I am trying to INSERT INTO a table using the input from another table. Although this is entirely feasible for many database engines, I always seem to struggle to remember the correct syntax for the SQL engine of the day (, , , , and ).  Is there a silver-bullet syntax coming from an SQL standard (for example, ) that would allow me to insert the values without worrying about the underlying database?


Planning to re-create new service accounts for our Sql-Servers, I wondered if - from a security perspective - it maybe better to have one domain account per Service and per Server or to create one domain-account per service only and re-use those on the different servers?   DOMAIN\Service-SSRS DOMAIN\Service-SSAS DOMAIN\Service-SSIS  vs.  DOMAIN\Service-SQL01-SSRS DOMAIN\Service-SQL01-SSAS DOMAIN\Service-SQL01-SSIS DOMAIN\Service-SQL02-SSRS DOMAIN\Service-SQL02-SSAS DOMAIN\Service-SQL02-SSIS etc.   We are doing this because we want to have a uniform and consistent configuration on all servers, something that is not yet in place today. I feel like having single accounts for every server might allow more flexibility and so is counterproductive...  Are there specific pros / cons? Is there a lot of usage of having separated service accounts for every server?

Is there any negative performance impact for using the same service account and agent account to run SQL Server and SQL Agent respectively for all SQL server instances running at a small company of say 35 servers? The biggest database is 0.5 GB. any suggestions are welcome. Thank you.


I really hope this is a duplicate.  Here is a screenshot:  When a post has lots of tags on the mobile responsive layout ('full site' in the footer), they don't wrap round and you end up with horizontal scroll bars. Expected The tags wrap nicely onto the next row. Actual They don't.

This appears to be a css bug which (I think) has recently been introduced. It's most visible when viewing questions on Stack Exchange sites using mobile devices (the full site with responsiveness, not the mobile site) but can easily be reproduced by resizing a browser window on a question where the combined width of the tags is large. A couple of example questions show this behaviour:  On Meta Stack Overflow:   On Meta Stack Exchange:     Using the Meta Stack Overflow question to demonstrate (as the total width of the tags is larger):  At 1100px, the tags just about fit into their containing div.     At 800px, the tags appear on top of related questions:     At 450px, the tags are now wider than the view (the last tag is completely off the screen), causing scroll bars to appear:      This doesn't happen to lists of questions - the tags flow onto multiple lines:     Reproduced on: { Firefox 81, Chrome 84, Edge 84 } on Windows 10, and Chrome 85 on Android 11.


I'm an American citizen working and living in Germany on an EU Blue Card. My family (wife and 2 children) is here with me. We were all issued standard German Aufenthaltstiteln (residence permit cards) by the Ausländerbehörde in our district. My card has an "Art des Titels" (permit type) of Blaue Karte EU (EU Blue Card). My wife's card and children's cards have an "Art des Titels" of Aufenthaltserlaubnis (residence permit).  I know that as an EU Blue Card holder I can travel freely in the Schengen Area. Can my family also travel freely in the Schengen Area, and if so, can they travel by themselves or do I have to be with them? I asked the Ausländerbehörde agent during our appointment and she answered yes to both questions. But now that we have the cards, I'm confused, because I thought the right to travel freely in the Schengen Area beyond the visa-free 90/180 rule was granted by the Blue Card program, while a "regular" residence permit in an EU country does not grant this right. (At least that was my understanding, any part of which may be totally wrong!)  My Aufenthaltstitel says:     Art des Titels      BLAUE KARTE EU      Anmerkungen      19A I.V.M 2 ABS.1 NR2A BESCHV PASS(-ERSATZ)-NR. XXXXXXXXX PASS GÜLTIG BIS XX-XX-XXXX SIEHE ZUSATZBLATT   My wife's Aufenthaltstitel says:     Art des Titels      AUFENTHALTSERLAUBNIS      Anmerkungen      32 ABS. 1 NR. 5 PASS(-ERSATZ)-NR. XXXXXXXXX PASS GÜLTIG BIS XX-XX-XXXX ERWERBSTÄTIGKEIT GESTATTET   My children's cards are the same as my wife's.

I have requested for a French long term (Type D) student visa from a consulate in India. It's a national Type D visa and not a Schengen visa. My question is that can we still go to other Schengen countries on this visa? If not then can we get a Schengen visa from a consulate in France?


How do you go about comparing two servers in order to figure out how many of one, you could replace with a newer one?  In particular, I have the following  Old server: ProLiant BL460c G6 (1.86 GHz, Intel Xeon E5502) New server: ProLiant BL460c Gen9 (1.80 GHz, Intel Xeon E5-2630L v3)  I can go onto CPU benchmarking website and compare the CPUs   (for a direct comparison)   (for benchnmark)  However, I am not sure how to be able to say that my G6s can be replaced by x G9s? How do I factor in core count and memory? Anyone know a smart way of doing this, or any other metrics to use?

This is a  about  Related:      I have a question regarding capacity planning. Can the Server Fault community please help with the following:   What kind of server do I need to handle some number of users? How many users can a server with some specifications handle? Will some server configuration be fast enough for my use case? I'm building a social networking site: what kind of hardware do I need? How much bandwidth do I need for some project? How much bandwidth will some number of users use in some application?


This is what Terminal answer to my every sudo apt-get update:  Err:16 http://ppa.launchpad.net/flimm/ooo-thumbnailer/ubuntu bionic Release     404  Not Found [IP: 91.189.95.83 80] Err:17 http://ppa.launchpad.net/gwibber-daily/ppa/ubuntu bionic Release   404  Not Found [IP: 91.189.95.83 80] Err:18 http://ppa.launchpad.net/pcf/miro-releases/ubuntu bionic Release   404  Not Found [IP: 91.189.95.83 80] Err:19 http://ppa.launchpad.net/ubuntuone/nightlies/ubuntu bionic Release   404  Not Found [IP: 91.189.95.83 80] Reading package lists... Done E: The repository 'http://ppa.launchpad.net/flimm/ooo-thumbnailer/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ppa.launchpad.net/gwibber-daily/ppa/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ppa.launchpad.net/pcf/miro-releases/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ppa.launchpad.net/ubuntuone/nightlies/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default.   Any ideas?

When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?


I am relatively new to setting up my own programming environment from scratch. I followed  tutorial and set up a virtual machine as well as a virtual environment. When I started working on a project and installing packages (presumably on my virtual environment once I activated it), it did not take long until I was completely lost.  I don't understand how to track:   The differences between pip and pip3 (What does it mean if a package in installed for Python2 vs for Python3?) How to see if a package is actually installed locally vs globally? How to see if a package is installed for a specific user vs globally?  What is the difference between virtual environment package installation vs only for a user vs globally? Etc...   Could someone either answers some of the questions above or point me to a good place to learn the basics and to learn how to properly set up package management well, so that I can build and update packages with confidence going forward.   I am running a Ubuntu 18.04.2 LTS  P.S. Maybe this questioned is asked already somewhere, but I could not find the answers.

I am a bit confused about the cases in which the above commands must be used when downloading python packages. I was trying to download a package named pyudev in accordance with an answer with this . I executed this command :  sudo pip install python-pyudev   but received the following message :  Downloading/unpacking python-pyudev    Could not find any downloads that satisfy the requirement python-pyudev Cleaning up... No distributions at all found for python-pyudev Storing complete log in /home/vineet/.pip/pip.log   However the following worked fine :  sudo apt-get install python-pyudev   When is apt-get supposed to be used to install packages and when is python-pip used?


I have table people containing people, their city and their money balance: id    city_id    money 1     1          25 2     1          13 3     2          97 4     2          102 5     2          37  Now, I would like to select richest person from each city. How can I do that using Oracle SQL? Desired result is: id    city_id    money 1     1          25 4     2          102  Something like that would be useful: SELECT * as tmp FROM people GROUP BY city_id HAVING money = MAX(money)

Table:   UserId, Value, Date.   I want to get the UserId, Value for the max(Date) for each UserId. That is, the Value for each UserId that has the latest date. Is there a way to do this simply in SQL? (Preferably Oracle)  Update: Apologies for any ambiguity: I need to get ALL the UserIds. But for each UserId, only that row where that user has the latest date.


I have a simple table (set up for testing purposes) with just an id bigint(20) auto_increment column and 2 rows.  Now, if I try select * from abc where id = '1', it works fine obviously, but any of these will also return the same row:   select * from abc where id = '1d' select * from abc where id = '0001blah'   What's the deal? Does it have something to do with quotes? I always thought = meant it would return only the exactly matching rows...

I don't have this kind of ID in my table, still MySQL is giving me a result.  This same result is giving when i place in my php code.


How can I auto-sync my files from Google Drive and make them in a Google-Drive folder whenever a new file added/removed it would update the changes rather than downloading the whole Google Drive from scratch whenever I try to access it.  I have used the native Google Drive app on my Windows and MacOS devices and they worked perfectly.

I'd like to install a  client for Xubuntu (12.04).  I'm getting non-English Google results, and I didn't find  in the Xubuntu repositories.   Does anyone know of a client that works well for Ubuntu or it's supported derivates (or installation instructions for grive?)


I have heard that a positron is like an electron moving backward through time. Can someone elucidate this statement for me. I would like to hear a deeper explanation of what we believe anti-matter to be, why it annihilates with matter and how this relates to relativity.

Some sources describe antimatter as just like normal matter, but "going backwards in time". What does that really mean? Is that a good analogy in general, and can it be made mathematically precise? Physically, how could something move backwards in time?


I found that login in to Stack Exchange from another device put my privacy under risk. I can press Log Out button but I don't have to enter my password any more. This is insane!  The problem is that I forgot my registration email and accidentally created another account. Now I cannot sign out from this account to sign in to another. This UX makes so much pain to user.

The cookies for subdomain, 'openid.stackexchange.com' are not, as claimed, actually removed from the browser upon logging out of stackexchange.com, but they should be.  Applies to: * stackexchange.com, date: January 8, 2012  Desired result:   Upon logging out of Stack Exchange, Stack Exchange OpenID local credentials stored 'in your browser' (or stored anywhere on the user's computer) should actually be deleted, as promised. For example, Stack Exchange OpenID browser cookies actually should be deleted. Logging in again should require explicitly entering one's credentials again. This might be email address and password. It is misleading to claim that (all relevant) 'local credentials in your browser' are deleted, since anyone else sitting down at the same computer can merely click the login links and immediately be accepted as the same, previous user! (See procedure to duplicate, below.)   Procedure to duplicate the problem in FireFox:  Versions (Menu-Help-Troubleshooting Information-Application Basics-User Agent): * Mozilla/5.0 (Windows NT 5.1; rv:9.0.1) Gecko/20100101 Firefox/9.0.1   Start FireFox. In Firefox's cookies manager (Menu-Tools-Options-Privacy), click the button, 'Exceptions', enter stackexchange.com and stackoverflow.com, and each time, click the button, 'Allow for Session'. Click the button, 'Close'. Click the button, 'Show Cookies'. Type, 'Stack', select stackexchange.com and stackoverflow.com if they are there, and each time, click the button, 'Remove Cookies'. Close Firefox. Start Firefox. Close webmail notifier windows. Log out of Gmail. Wait ten seconds. Click the back button on the browser to make sure one is not still logged in to Gmail. Open a tab for,  . In , if you have it, allow the domains, 'stackexchange.com' and, 'sstatic.net' and refresh. Click the link at the top, 'login'. On the resulting page, click the box, 'Log in with Stack Exchange.' Enter one's Gmail email address and Stack Exchange password, which results in a successful Stack Exchange login. Click the link at the top, 'logout'. The resulting web page has an orange button labeled, 'logout', above which is presented the text, 'Clicking Log Out will clear all local credentials in your browser.' Click the orange button labeled, 'logout'.   One might think that one has completely logged out safely from Stack Exchange, with no possibility of simply clicking back in. But, not true!   Now the page has the link at the top, 'login'. However, the Firefox Cookie Manager still shows cookies under domains, 'stackexchange.com' and 'openid.stackexchange.com'. Click the link at the top, 'login'. On the resulting page, again click the box, 'Log in with Stack Exchange.' See the login unexpectedly succeed, without entering any email address or Stack Exchange password!


I want to set the background of my initial login screen to black. The problem is, everytime I turn on my laptop and login, it sets it to this blurry image of a beach.     So I tried setting my ubuntu.css file to use only black and its still using the beach background.    How do I change the initial login screen background to black?  UBUNTU 18 LTS

So i installed Ubuntu 18.10 fresh install and i did have the normal new login screen of ubuntu gdm3. Ive been downloading gnome themes and i noticed after i did everything(idk if its from installing new themes) when locking the computer i still get the normal lock screen  And when i slide it up i get the stamdart login screen:   Lock screen  Login screen    But now it gets weird when i click on "Log in as another user" i get a new different type of log in screen, which comes when booting into ubuntu after the logo loading screen too(on this login screen the tap-to-click also doesnt work!):   2nd login screen    EDIT: Im sorry i forgot to add a question  - What is this(is this normal?) and how to set it back to default?  Added theme:  Named "flat remix"   I would be happy for your help Thanks Best Regards!


I know that besides the effects of Newton's theory of Gravitation on the satellite's motion, one has to take account of the retardation of the satellite's clocks when compared to earth-fixed clocks. Is this just an effect of Special Relativity? Or are there other effects that must be taken into account, which would not be predicted by Special Relativity alone, but which only occur in General Relativity?

I am reading A Brief History of Time by Stephen Hawking, and in it he mentions that without compensating for relativity, GPS devices would be out by miles. Why is this? (I am not sure which relativity he means as I am several chapters ahead now and the question just came to me.)


This question is not a duplicate of  I believe. I have not been able to find a clear answer about virtual destructors with multiple inheritance. The question I am asking is how come the intermediate classes in multiple-inheritence don't need a virtual destructor.   I am trying to understand who should have a virtual destructor and why.   class Person{ public     virtual ~Person(){         cout << "person destruction" << endl;     } };  class Student: virtual public Person{ public:     ~Student(){         cout << "destroying student" << endl;     }   }; //Faculty being a Faculty member class Faculty: virtual public Person{ public:     ~Faculty(){         cout << "destroying faculty" << endl;     } };  class TA: public Student, public Faculty { public:     ~TA(){         cout << "destroying TA" << endl;     } };   I understand that you cannot do polymorphic deletes. When I do something like:  //A - case when Person doesn't have a virtual destructor Person *p = new Student(); delete p;   It crashes WHEN my base class doesn't have a virtual destructor. Makes sense. BUT when I do:  //B Faculty *f = new TA(); delete f;    How come this does not crash? Why is this not analogous to the previous case? Faculty does not have a virtual destructor.   Thanks in advance!

I have a solid understanding of most OOP theory but the one thing that confuses me a lot is virtual destructors. I thought that the destructor always gets called no matter what and for every object in the chain. When are you meant to make them virtual and why?


Why would students return to Hogwarts knowing that Snape was headmaster and that they would likely be mistreated there?

From what I’ve read on here, people remained at Hogwarts after Dumbledore’s death, mainly in Dumbledore’s Army. But why wouldn’t the parents just have their children come home?  Also, I know the Ministry was largely controlled by Death Eaters, but how did Snape remain Headmaster, especially with someone like McGonagall still present?


So I have a main website, example.com. I created a subdomain for a client. Let's say it is called client.example.com. This client is a coffee shop website. I already registered it and it is indexed on Google Search Console. What I want, is that when clients search for the coffee shop (in this case if they search for "client"), the subdomain will appear. When I search for the name of the coffee shop, the subdomain is not appearing. It is however, appearing when I search for "client example". When I search for the subdomain, and then the name of my main page, it does appear. This is the proof that the subdomain is actually being indexed. How can I make the subdomain (in this case the coffee shop) rank and appear in Google, without having to mention the name of the domain (main website)?

What are the best ways to improve a site's position in the Google search results?


I was trying to install Kali linux in a dual boot fashion when I accidentally ended up install a terminal only version of Debian as a second partition. So I decided to retry, which meant I needed to delete the Debian partition. When I tried to in Disk Utility, it gave me errors, so I booted into internet recovery mode and removed the partitions there. I then proceeded in clicking the Apple Logo and selecting the choose boot partition thing. It showed nothing. At first I panicked, thinking I had somehow deleted all of my data. I tried creating a second partition, so I could install Mac OS there and then fix my mac from there. I clicked on the create partition, waited 3ish hours while I went out, came back and it said preparing to partition. So I rebooted and saw that the partition type was: FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFF. So I installed Mac OS X onto a painfully slow flash drive (15-20MB/s) and then looked up my problem. I found other solution people had created only they were specific to the exact case. I do not know what the partition type is supposed to be so here is my info: /dev/disk1 is the USB flash drive that is running MAC OS X so I can use my laptop.  sh-3.2# diskutil list /dev/disk0    #:                       TYPE NAME                    SIZE       IDENTIFIER    0:      GUID_partition_scheme                        *500.3 GB   disk0    1:                        EFI NO NAME                 209.7 MB   disk0s1    2: FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF               450.1 GB   disk0s2 /dev/disk1    #:                       TYPE NAME                    SIZE       IDENTIFIER    0:      GUID_partition_scheme                        *31.4 GB    disk1    1:                        EFI EFI                     209.7 MB   disk1s1    2:                  Apple_HFS Fixer OS                30.5 GB    disk1s2    3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3   And here is some more:  sh-3.2# gpt -r show /dev/disk0     start       size  index  contents         0          1         PMBR         1          1         Pri GPT header         2         32         Pri GPT table        34          6                 40     409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B    409640  879039128      2  GPT part - FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF 879448768   97656259          977105027         32         Sec GPT table 977105059          1         Sec GPT header   How can I mount this partition again? Which command should I use?

How can I get back my data from the FFFF… partition which is ~350 GB by fixing the partition table?     977105059           1                     Sec GPT header Riccados—MacBook—Pro:~ Riccado$ sudo gpt —r show /dev/disk0s2        start        size        index        contents            0   683645536 Riccados—MacBook—Pro:~ Riccado$ sudo gpt —r show /day/disk0        start        size        index        contents            0           1                     PMBR            1           1                     Pri GPT header            2          32                     Pri GPT table           34           6           40      409600             1       GPT part — C12A7328—F81F-11D2-6A46-00A0C93EC938       409640   683645536             2       GPT part — FFFFFFFF—FFFF—FFFF—FFFF—FFFFFFFFFFFF    684055176     1269536             3       GPT part — 48465300-0000-11AA—AA11-00306543ECAC    685324712    49224610             4       GPT part — OFC63DAF-8483-4772-8E79-3D69D8477DE4    734549322         694    734550016     8073216             5       GPT part — 0657FD6D—A4AB-43C4-84E5-0933C84B4F4F    742623232   233212248             6       GPT part — 53746F72-6167-11AA—AA11-00306543ECAC    975835480     1269544             7       GPT part — 426F6F74-0000-11AA—AA11-00306543ECAC    977105024           3    977105027          32                     Sec GPT table    977105059           1                     Sec GPT header  Riccados—MacBook—Pro:~ Riccado$ diskutil unmountDisk /dev/disk1 Unmount of disk1 failed: at least one volume could not be unmounted  Riccados—MacBook—Pro:~ Riccado$   The disk is 500 GB in total. 350 GB is assigned for macOS, 120 GB for Windows and 30 GB for Ubuntu.  This morning when I woke up, I tried to boot my Mac but it didn't boot successfully as it is just showing the prohibitory sign. So I tried to fresh install macOS, pressing command ⌘-R when starting the Mac to enter Recovery Mode. But only the Windows partition (120 GB) is showing to reinstall macOS on instead of the original 350 GB partition. I reinstalled macOS on the 120 GB partition. Now I don't know how to retrieve my files back from the old 350 GB partition. They all are in same disk. Linux is not booting now too.


What is the oldest science fiction story? It doesn't need to be set in the future, it could also be set in the past or a combination of the two. Plese include the author, thanks!

I have been reading a lot of Jules Verne's work written in the 1800's.  Very clearly science fiction. Mary Shelley's Frankenstein (1818) has some serious science in it also.    What is the earliest work that is recognized as being science fiction?