unknown variable after upgrading from mySQL 5.7 to 8

After upgrading from mySQL 5.7 to 8.0 on freebsd, I keep getting the follow error, which prevents mysql to start: [ERROR] [MY-000067] [Server] unknown variable 'innodb_large_prefix=true'.  The thing is that setting is not on my my.cnf file. I understand it is deprecated on mySQL 8, but it is not on my configuration. Is there a way to fix it? Best, Francis


public static void main(String[] args) {   Clock c = new Clock();   c.m = c.m + 1;   //where m is a private instance variable in an another class.` }   Why is it incorrect for the main() method using a class Clock to have the second statement below? Please help?


Mail sent from PHP with PHPMailer id going in GMail spam, whatever

I have set up a script in PHP to send emails, using PHPMailer. Using the following: - sending through my own domain SMTP server using TLS; - signing/authenticating the message with DKIM/SPF; - the "From" email address is on the domain from which I am sending, as well as "Reply-to"  Unfortunately, the email is flagged automatically by Gmail as spam. My domain is not blacklisted (as reported by MXtoolbox.com) and has a score on SpamAssasin of 1.49.  The PHP code is as follows:  <?php require 'PHPMailerAutoload.php'; $adresaMail = "contact@hbooking.eu"; $mail = new PHPMailer(); $mail->Sender = $adresaMail; $mail->From = $adresaMail;   $mail->FromName = "Hotel Booking"; $mail->AddReplyTo($adresaMail, "Hotel Booking"); //Reply-To Address $mail->IsSMTP();  $mail->SMTPAuth = true;     // turn on SMTP authentication $mail->Username = $adresaMail;  // SMTP username $mail->Password = "Tele7abc$"; // SMTP password  $mail->SMTPSecure = 'tls'; // use TLS authentication // $mail->SMTPSecure = "ssl"; // turn on SSL use $mail->Host = "localhost"; $mail->Port = 25; // $mail->SMTPDebug  = 1; // Enables SMTP debug information (for testing, remove this line on production mode) // 1 = errors and messages // 2 = messages only  // $mail->ConfirmReadingTo  = $adresaMail; $mail->IsHTML(true); //turn on to send html email  //add image - begin //$mail->AddEmbeddedImage('test.jpg', 'logoimg', 'test.jpg'); //add image - end $mail->Subject = "Hotel booking webpage"; // use this if you want to use image // $mail->Body     =  "Acest email a fost trimis folosind phpmailer - ";  $Body = "<!DOCTYPE html>       <meta charset='utf-8' />     <title></title>

                 HB	                 HBooking.eu

Signup confirmation

Thank you for choosing to be a HBooking.eu member!

Your subscription to our services has been confirmed.
                 You can now log-in and start advertising your hotel nights to all our travel agents and tour operator members across Europe.

Please feel free to contact us for any queries you may have.

Yours truly,
The HBooking.eu team

&copy; HBooking.eu , 2017. This email has been sent automatically; please do not reply to it.

    ";    $mail->Body = $Body;  $mail->AddAddress("bogpop68@gmail.com","Bogdan Popescu");  if($mail->Send()){ $mail->ClearAddresses(); echo "message sent"; } else {echo "did not send";} ?>   Please help. Thank you all in advance.


A nontrivial p-group has nontrivial center

I know this is a very common corollary of the class equation. And I know how to do it by using class equation.   But can you do it bu using group action, maybe find a nice set for G to act on?


I would like to create a norm-like operator with 3 verticals bars instead of two. It has to look like $|||\cdot|||$. I would like to know how to decrease the spacing between the vertical bars such that it has the same spacing as the $\lVert .. \rVert$ command.  There is a command available in the stmaryrd package called \biginterleave, but this command has to much spacing between the vertical bars, especially in display math mode.  Is there some work-around to adjust the spacing between to vertical bars?


I have a problem (BIG PROBLEM) with SPAM.   All the emails my mail server (Debian 8.2 and ispconfig latest stable) send, end up in spam. I'm using Google Apps.  I did a test on spamscorechecker.com and the error message is:   0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid domain   My domain is ambrabaiocchi.it (with valid DKIM and SPF record) and more 3  For more info please check this:  and this: .  How can I solve the problem?  Thanks and sorry for my bad english.


How to convert a recipe calling for active dry yeast into rapid rise yeast?

I have a recipe for rolls where the first stage calls for 2 packages active dry yeast, 1 tbsp sugar, and 1/2 cup warm water to be mixed until the yeast is proofed, and then 1/4 cup cubed butter is added to the proofed yeast.  Then all of that is added to half of the flour (2 cups) and 2 tsp salt and allowed to do the first rise.    If I wanted to use rapid rise yeast instead of active dry, could I skip the proofing step?  Would I need to add the butter at all?  Could I just mix all the dry ingredients, add the warm water and start the dough that way?  What effect would this change have?


Given $p^2+q^2+r^2+1=s+\sqrt{p+q+r-s}$, solve for $s$

The real numbers $p$, $q$, $r$, $s$ satisfy    $$p^2+q^2+r^2+1=s+\sqrt{p+q+r-s}$$    Find the value of $s$.   I don't even know how to start. Thanks!


How to make ttf-mscorefonts-installer package download fonts, after it says it installed?

When I install "Installer for Microsoft TrueType core fonts" (ttf-mscorefonts-installer) from the Software Center on 14.04, it gives a positive response--but after this I get a download error. It seems that the files actually providing the fonts are never retrieved. Is there any way to resolve this?


How do I install NVIDIA drivers in Ubuntu GNOME 14.10?

I have just built my first custom PC with a GeForce GTX 750 Ti Graphics card. I've installed Ubuntu GNOME 14.10 and get a set resolution of 800x600 stretched across a 1080p screen. I've downloaded the official .  When I run the file, it says it must be run without Xorg running. I've have tried pressing Ctrl+Alt+F1 to enter a command line system but instead of displaying a command line login, the screen goes completely blank. I cannot see what I am doing since there is no screen output whatsoever.


How do I close only one Google Chrome window in macOS using mouse?

Ex: I have 3 Chrome windows (each has multiple open tabs). Pressing on the red button in the upper left corner     closes my whole session and I don't want other instances to also die. Only one of them with 4 tabs. Command + W works only for the current tab, not the current window.  How do I achieve this with using mouse? How do I achieve it with the keyboard? (Command + Q closes all Chrome windows so, also, not good).  I am running Google Chrome Version 75.0.3770.100 (Official Build) on macOS Mojave 10.14.5.


What do I need to clean off before I season this cast iron?

Here's my cast iron frying pan. I had seasoned it before but wasn't sure if I'd got it right so I figured I'd start again. I'm not clear on what state it needs to be in before I do that. I sanded a little bit to remove the bumpy black residue but it was an extremely slow process. What is the black on my pan and do I need to remove it all to be silver again before I season?


Is there a difference between "voltage supply" and "power supply"?

A device, circuit, actuator or chemical structure which outputs a fixed voltage level is usually called with one of the following terms.   Voltage Source Voltage Supply Power Supply   Is there any technical difference between these terms or do they imply the same thing?


I would like to get an answer from someone who knows mathematical definitions,  Q: is this claim: "it's possible for something to have probability zero (not approaching, actually zero) and yet be possible." Correct?


How to increase the TeX open file limit?

I noticed that TeX has a open file limit, while using some additional bibliographies with , using hyperref, backrefs and so on (basically only 5 additional newcites were possible in that document before hitting the limit).  I worked around that with migrating from multibib to , which I've discovered then and which seems like a good solution to other bibliography related challenges as well.  Anyways, I found this  and I wondered if the situation changed with current TeX Live distributions. And if yes, how to increase the open file limit in LaTeX now.


I have a certain geometry. See image. I need to create 3 creases/cavities on the surface. I tried 2 methods, see images. One is Knife Projecting mesh edges onto the surface, and then fiddling around with it. The other is using Difference Boolean operation (including cleaning up triangles afterwards). Both methods give terrible results, plenty of artefacts. What is a clean way to achieve the result? Or do I have to unwrap the mesh and create a bump map with these creases?


How do I use this condition inside CASE WHEN?

I want if Status column = 1  Check If there are rows in another table return 'Check' and If no rows return 'In DB'  SELECT ID, UserName, CASE [Status]     WHEN 1 THEN         if ((Select Count(*) From Logs_TB Where Logs_TB.UserName = Users_TB.UserName) > 0)             'Check'         Else             'In DB'     WHEN 2 THEN 'Revision'     WHEN 3 THEN 'Sent' END AS StatusName FROM Users_TB CROSS JOIN Logs_TB     Edit 1:  I have Two Tables  in First Table. I want to get the following result for Column [Status]  if FirstTable.ColumnStatus = 1    if SecondTable.ColumnA = FirstTable.ColumnB Has Rows         'Check'    else         'In DB' else if FirstTable.ColumnStatus = 2    'Revision' else if FirstTable.ColumnStatus = 3    'Sent'     Edit 2    This is an example  I want Select All Rows From Employment Table  and I want to parse column Status to Column As "StatusName"  if Status  = 1 It has two values   First value Check if QualificationID and SpecializationID Has Rows in Table 'Vacancies' return 'Check'  and if no rows in Table 'Vacancies' return 'In DB'  if Status  = 2  'Revision'  if Status  = 3  'Sent'


How can I move customer community from one Dev org to another?

How can I move customer community from one Dev org to another Dev org. I use maven mate and eclipse to move meta data.


how to concatenate string variables into a third?

I need to concatenate two strings in bash, so that:  string1=hello string2=world  mystring=string1+string2   echo mystring should produce     helloworld


Consider this, I want to add two languages on one keyboard with Gboard: English and French for QWERTY (English) keyboard. I open the settings but can't add language to the existing keyboard.  (only applicable if multi-languages are enabled) So to activate it I have to add another keyboard (English)  Now I have French support on the English keyboard and English support on the French keyboard. But I have two keyboards.    What even is the point of this? And is there a way so that I can use only one keyboard (layout) with two languages?


I am wondering how I can install Ubuntu onto my second hard drive in my Toshiba Qosmio?? My main drive is my SSD that runs my normal Windows OS, but I installed a second hard drive in my second hard drive bay and would like to install and run Ubuntu from that second drive?? That way I can choose which drive to boot from whether it's my main drive using Windows or my second drive using Ubuntu??


Connection dropouts with RealTek RTL8188CE

I'm an Ubuntu rookie with an unresolved wireless internet connection issue. I've spent a lot of time fiddling around in my never-ending quest to get my connection working properly, but my inexperience is beginning to show and I need a little extra help.   The issue in brief: slow speed (Ookla clocks in at ~5-8Mbps download speed - it should be ~20) and connection dropouts occur every ten minutes.    OS: Ubuntu 14.04 Kernel: 3.13.0-32-generic  I've done some homework and tried a lot of solutions from these forums. I think ultimately the problem is going to be with the driver rtl8192ce. I've tried changing it to rtl8188ce using FreedomBen's , but I can't fathom how to use script for the automatic installation (I have problems with manual installation too, but I don't want to ask two questions in one post, so I'll save them for later). Can anyone help me out? I think I have the .zip downloaded if that's important.  I've included outputs to various Terminal commands below that may also prove helpful.  lshw  description: Wireless interface             product: RTL8188CE 802.11b/g/n WiFi Adapter             vendor: Realtek Semiconductor Co., Ltd.             physical id: 0             bus info: pci@0000:03:00.0             logical name: wlan0             version: 01             serial: bc:ee:7b:e4:e8:22             width: 64 bits             clock: 33MHz             capabilities: bus_master cap_list ethernet physical wireless             configuration: broadcast=yes driver=rtl8192ce driverversion=3.13.0-32-generic firmware=N/A ip=192.168.0.41 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn       lsmod | grep rtl   rtl8192ce              52806  0  rtl_pci                26314  1 rtl8192ce rtlwifi                52835  2 rtl_pci,rtl8192ce rtl8192c_common        47340  1 rtl8192ce mac80211              546051  3 rtl_pci,rtlwifi,rtl8192ce cfg80211              409394  2 mac80211,rtlwifi   iwconfig   wlan0     IEEE 802.11bgn  ESSID:"virginmedia0147357"         Mode:Managed  Frequency:2.462 GHz  Access Point: A0:21:B7:D6:9B:E2          Bit Rate=72.2 Mb/s   Tx-Power=20 dBm          Retry  long limit:7   RTS thr=2347 B   Fragment thr:off       Power Management:off       Link Quality=46/70  Signal level=-64 dBm         Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0       Tx excessive retries:0  Invalid misc:1   Missed beacon:0  lo        no wireless extensions.  eth0      no wireless extensions.   lspci  02:00.0 Ethernet controller: Qualcomm Atheros QCA8171 Gigabit Ethernet (rev 10) 03:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8188CE 802.11b/g/n WiFi Adapter (rev 01)   Sorry if I've missed something obvious, I'm green as grass but, as you can see, willing to suffer a lot of hassle to avoid returning to Windows.


We are installing SAP HANA in a RAID machine. As part of the installation step, it is mentioned that,   To disable the usage of transparent hugepages set the kernel settings   at runtime with echo never > /sys/kernel/mm/transparent_hugepage/enabled    So instead of runtime, if I wanted to make this a permanent change, should I add the above line inside /proc/vmstat file?


mv ~ /dev/null       moves my home directory to a black hole. Can I recover my home directory from /dev/null?


What is relationship of widower to late wife's family (i.e. in-laws)?

I am a widower.  I still have a strong personal relationship with my late wife's family, and I regard them as part of my own family.  They are blood of my blood in the sense that my children are related by blood to both me and them,  but if we had not had children, that link would not exist.    My only direct relation to them was by marriage, and with my wife's death, it would seem that that bond no longer exists; at least not formally.     Is there any enduring relationship by law or tradition for ex relations by marriage, and what would it be called?   Also, what if instead of death, we had been separated by divorce?    And what if I were to remarry,  would that change my relationship to my first in-laws?


I am new to RegEx in python. I have created a RegEx formula which should find some special string from text but it is not working as exprected;  def find_short_url(str_field):     search_string = r"moourl.com|ow.ly|goo.gl|polr.me|su.pr|bit.ly|is.gd|tinyurl.com|buff.ly|bit.do|adf.ly"     search_string = re.search(search_string, str(str_field))     result = search_string.group(0) if search_string else None     return result   It should find all the URL shortner from a text. But the su.pr is detecting as surpr from the text. Is there any way to fix it?  find_short_url("It is a surprise that it is ...")   output  'surpr'   It can affect other shortner too. Still scratching my head.


Why does Sméagol say "gollum" when anxious or crying?

Why does Sméagol say gollum when he's threatened? For example here:     'Leave me alone, gollum! You hurt me. O my poor hands, gollum!... I, we can't find it, gollum, gollum, no, nowhere..."    Then he collapsed again. 'Gollum, Gollum,' he whimpered with his face to the ground.


Calculate: $\lim\limits_{x\to0^-} \frac1{\ln(1-x)}+\frac1x$ without LHR/Expansions

How to calculate $$\lim\limits_{x\to0^-} \left(\frac1{\ln(1-x)}+\frac1x \right)$$ without using L'Hopital, expansions nor integration?   I found the answer:  Using the Mean value theorem on:  $f(x)=e^x-\frac{x^2}2-x-1$  We get:  $0\le\frac{e^x-x-1}{x^2}-\frac1 2\le \frac{e^x-x-1}{x}$  Thus:  $\lim\limits_{x\to0^-} \frac{e^x-x-1}{x^2} = \frac12$  By substituting: $t=\ln(1-x)$ in the original limit we get:  $\lim\limits_{t\to0^+} \frac{1-e^t+t}{t(1-e^t)} = \lim\limits_{t\to0^+} \frac{e^t-t-1}{t^2}.\frac{t}{e^t-1} = \frac12$


How can I repeat the header but not the caption with longtable?

I am trying to set up a longtable where the header is repeated on every new page but the caption only appears once at the top of the page.  The table is defined as follows:  \begin{longtable}{|l|l|l|} \caption{the table caption} \label{tab:11swpkg}\\ \hline \rowcolor{gray} HeaderCol1 & HeaderCol2 & HeaderCol3\endhead     \hline\hline Item11 & Item12 & Item13 \\ \hline Item21 & Item22 & Item23 \\ \hline Item31 & Item32 & Item33 \\ \hline \end{longtable}   This nearly works because the header is indeed repeated after a page break but so is the caption. How can I get rid of the caption after a page break?


I am confused by the orientation of a topological manifold. My understanding is: An orientation of a topological manifold is a choice of generator of the $H^n(M,\mathbb Z)$. So given a manifold, we could have 2 orientation defined on the manifold. For $\mathbb{CP}^2$ on orientation is determined by the complex structure, the other orientation is denoted by $\overline{\mathbb{CP}}^2$. And it is well known that there is no orientation reversing map from $\mathbb{CP}^2$ to itself.  My question is: are they homeomorphic? I guess they are not homeomorphic. But I am confuesed, doesn't the orientations defined on the same manifold, how come after reversing the orientation they become not homeomorphic?


Why does the order of parameters matter for sp_trace_create?

The first batch of the following script calls stored procedure  with parameters in documentation order; the second batch swaps the positions of parameters @tracefile and @options:  DECLARE @new_trace_id INT;  EXECUTE master.dbo.sp_trace_create   @trace_id = @new_trace_id OUTPUT,   @options = 0,   @tracefile = N'C:\temp\TestTrace';  SELECT @new_trace_id AS [@new_trace_id];  EXECUTE master.dbo.sp_trace_setstatus   @trace_id = @new_trace_id,   @status = 2; GO  DECLARE @new_trace_id INT;  EXECUTE master.dbo.sp_trace_create   @trace_id = @new_trace_id OUTPUT,   @tracefile = N'C:\temp\TestTrace',   @options = 0;  EXECUTE master.dbo.sp_trace_setstatus   @trace_id = @new_trace_id,   @status = 2; GO   The first batch creates a new trace, selects its id, and then closes the trace. One result set is returned:  @new_trace_id 2   The second batch fails with an error:     Msg 214, Level 16, State 3, Procedure sp_trace_create, Line 1   Procedure expects parameter '@tracefile' of type 'nvarchar(256)'.   Why does parameter order affect the output of stored procedure sp_trace_create? And why does it fail with such a misleading error message?


Is space expanding equally in every direction?

Does space expand equally in every direction, so that it draws a perfect sphere or is expansion asymmetric, so it creates "bubbles" (when seen from the outside)?


Etymology of "between a rock and hard place"

I don't find any of the origin stories posted for this phrase plausible. Has anyone scoured the many concordances of the English Bible? If the answer is no, I'll embark on the task myself.


Want to visualize rule division of fraction.  For example  1)  2   2     4 _ * _   = _  2   3     6   in this case we "split" each piece of cake in numerator to the 2 "first fraction" and apply the same operation for the denominator.  Could you please clarify rule with devision, why we should turn fractions and multiply it. How can I visualize this rule?  Thanks.


What is the reason behind "non-static method cannot be referenced from a static context"?

The very common beginner mistake is when you try to use a class property "statically" without making an instance of that class. It leaves you with the mentioned error message:     You can either make the non static method static or make an instance of that class to use its properties.   Why? I am not asking for solutions. I would be grateful to know what is the reason behind it. The very core reason!  private java.util.List<String> someMethod(){     /* Some Code */     return someList;             }  public static void main(String[] strArgs){                // The following statement causes the error. You know why..     java.util.List<String> someList = someMethod();          }


Does the ending of Predestination cause a paradox, or does the loop stay closed?

In the final scene of Predestination there's the following dialogue:     John: Your next attack will kill ten thousand more.   John knows this because it is his strongest motivation for hunting down the fizzle bomber.  Later:     Fizzle Bomber: You wanna know what we're gonna do tomorrow?      John: No.      (John shoots the fizzle bomber)   My questions:  Does the ending cause a paradox because John has supposedly stopped the fizzle bomber from executing his big plan, hence erasing the motivation for the events of the movie? If so, what indicates this?  If not, what signs indicate that the big hit takes place earlier in the fizzle bomber's life, before the laundromat encounter?


For past 2-3 years, I could work on my laptop from my room seamlessly but from past 2 days I've been facing some problem with network. It detects my WiFi right but when I try to connect , it pops up the troubleshooting message. I tried restarting my router modem, it didn't work. I can connect to it in my hall. But I can't connect in my room where as my cell phone seems to connect WiFi. I'm currently running in windows 7 professional , please help.


What are the differences in dynamically setting a background-image or creating an img tag?

When querying an API that may or may not have an image, what are the main differences in setting the background-image or actually creating an img tag?

   vs


I've read up a little bit on bonding nics with ifenslave; what I'm having trouble understanding is whether there is special configuration needed in order to split the bonds across two switches. For example, if I have several servers that all have two nics each, and two separate switches, do I just configure the bonds and plug 1 nic from each into switch #1 and the other from each into switch #2? or is there more to it than that?  If the bonds are active-backup, will a nic failure on single machine mean that server may become disconnected since the rest of the machines are using the primary nic and it's using the secondary? Or do you link the switches with one cable as well?


Condition for a tensor to be decomposable

Let $V$ be a vector space of dimension 3 with basis $e_1,e_2,e_3$. Let $W$ be a vector space of dimension 2 with basis $f_1,f_2$. Is $e_1\otimes f_1+e_2\otimes f_2$ decomposable? What about $e_1\otimes f_2+e_1\otimes f_3-e_2\otimes f_2-e_2\otimes f_3$? What is the condition for a tensor $$ v=\sum_{i=1}^3 \sum_{j=1}^2 a_{i,j} e_i \otimes f_j $$ to be decomposable, that is, has the form $v\otimes w$ for $v\in V, w\in W$. As a related question, if I'm given any two vector spaces with dimensions $m,n$ and given bases, what is the condition for a tensor in $V\otimes W$ to be decomposable?  I think this has something to do with the linear independence but I'm not very comfortable with the tensor product, so I'm not really sure where to begin.


How to record the output of a bash script from terminal without suppressing the terminal output?

How to record the output of a bash script from terminal without suppressing the terminal output like $ ./bash-script.sh >> terminal.txt ? and I want to record the resulting output to text and keep it in the terminal as well.


i need some help setting up what is basically the same as a piston in a car engine's cylinder. i know i can just use keyframes and NLA strips but im after a more dynamic approach that wont require a bunch of edits to change the speed or phase. ideally i want to connect the rotation to the up and down motion of the control handle im using for the rest of the parts but i am stumped. i have animation nodes installed so solutions using that are also viable. suggestions appreciated as im at my wits end.


Java regex for consecutive exponential terms

I've tested this regex:   String regex = "[e][#](.)+[$]   the regex works well to identify exponential terms, however it breaks when there are two or more consecutive exponential terms.  I test the regex with the usual code:  while(matcher.find()){ String string = matcher.group(); System.out.println("this one: "+string); }   When I type the expression:   e#x$ + 3e#x+1$   string equals to  (e#(x$+3e#x+1$))  By the way, I added the parentheses inside the while loop. They are necessary for what I am trying to accomplish.   I want the result of string to be (e(#x$))+3(e(#x+1$)  I know the problem lies in "(.)+ What I think is happening is that the regex includes the first $, what I need is for it to stop at the first $.   How can I include this logic inside the regex?  thank you


Reset modal with Javascript after submiting data

So basically, I'm making a website with a form inside a modal. After that form submits the data to script.php, whatever script.php sends back is appended to the modal body like so:  // Function to submit data to php $("#formModificarArticulo").on("submit", function(e) {      var postData = $(this).serializeArray();     var formURL = $(this).attr("action");      $.ajax({         url: formURL,         type: "POST",         data: postData,         success: function(data, textStatus, jqXHR) {             $('#divModificarArticulo .modal-header .modal-title').html("Resultado");             $('#divModificarArticulo .modal-body').html(data);             $("#submitFormModificar").remove();             reloadDataTable();         },         error: function(jqXHR, status, error) {             console.log(status + ": " + error);         }     });      e.preventDefault(); });  $("#submitFormModificar").on('click', function() {     console.log("Submit presionado");     $("#formModificarArticulo").submit(); });   So, basically, when the user sends data using the form inside the modal, the modal changes to show something along the lines of "Data sent to server successfully".  After the result from script.php is showed to the user and the user closes it, the modal is supposed to revert back to its original state with the form. This is the function where that magic happens:  // Function to reset modal (function(){      var template = null;      $('#divModificarArticulo').on('show.bs.modal', function (event) {         if (template == null) {             template = $(this).html();         } else {             $(this).html(template);         }          $('#divModificarArticulo').modal({ show: false});     })  })();   The thing is, I can send data pressing the Submit button on the form, the modal brings me the back the results from the server and when I open the modal for a second time the form is back to its original state. For some reason, however, when I press the Submit button for a second time, it doesn't do anything. It's like it's not even pressed.  I'd really appreciate if someone could help me out.


Why does the branch cut of the self-energy begin at $2m$?

Consider a  $\phi(x)$, and let its  be $$ \frac{1}{p^2-m^2-\Pi(p^2)}=\int_0^\infty\mathrm d\mu^2\ \rho(\mu^2)\ \frac{1}{p^2-\mu^2} $$  We usually have $\Pi(m^2)=0$, which implies that there is a one-particle state with mass $m^2$. In terms of the , this reads $$ \rho(\mu^2)=\delta(\mu^2-m^2)+\sigma(\mu^2) $$ where the support of $\sigma(\mu^2)$ is disconnected from $m^2$.  On the other hand, the continuum contribution usually begins at $(2m)^2$, meaning that $\Pi(k^2)$ has a branch cut from $(2m)^2$ to $\infty$. Again, in terms of the spectral function, this is written as $\text{supp}(\sigma)=[(2m)^2,\infty)$.  My question  I would expect that the first bound state to lie close to $(2m)^2$, but slightly below, something around $(2m)^2-\mathcal O(\alpha^n)$, where $\alpha$ is the coupling constant and $n\in\mathbb N$. For example, in a simplified QED model, the bound state of an  has binding energy $\sim 7\mathrm{eV}\sim m\alpha^2$, and so I would expect the branch point to be somewhere around $(2m)^2-m^2\alpha^4$.  I know the value of the self-energy to one loop, and the branch point is indeed exactly at $(2m)^2$. I don't know where to find higher loop corrections, so I cannot conclude whether   1) at higher loops, the branch point moves a bit closer to $m^2$, or 2) it stays at $(2m)^2$.   I would expect that the correct behaviour is 1), but this contradicts the fact that all books I've read always depict the threshold of pair production as an hyperboloid with its bottom sitting exactly at $(2m)^2$. On the other hand, if it turns out that the correct option is 2), I am lead to ask why is perturbation theory unable to correctly predict the position of the branch point (I know this is a subtle issue because bound states are, to some extent, non-perturbative entities; but AFAIK, perturbative calculations do contain a lot of information about bound states).


after upgrading to the newest version I can't start up my pc. I receive the error: The system is running in low-graphics mode  After looking into the forums, I go into the terminal (Ctrl + Alt + F1) I assumed this could be related to graphic drivers.  It seems I need to install libc6-i386, but the dependencies are broken:  $ sudo apt-get install libc6:i386 Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  libc6:i386 : Depends: libgcc1:i386 but it is not going to be installed E: Unable to correct problems, you have held broken packages.   I'm very noob. Not sure what details you would need.  Output of apt-cache policy libgcc1:i386 is  libgcc1:i386: installed version: 1:4.7.3-1ubuntu1 candidate: 1:4.7.3-1ubuntu1 table of versions: *** 1:4.7.3-1ubuntu1 0 500 http://sk.arcive.ubuntu.com/ubuntu/ raring/main i386 Packages 100 /var/lib/dpkg/status


Prove that if $n$ and $m$ are coprime then $2^n-1$ and $2^m-1$ respectively are coprime too

How to prove that if $n$ and $m$ are coprime then  $2^n-1$ and $2^m-1$  are coprime too? I tried with Bezout's identity without results. Thanks


Replace a string with another list of string in multiple files in a loop

I have a list of files in which i have to replace one specific word with another from a list. Input example: File.a.txt text  File.b.txt text  Output expected File.a.txt text.a  File.b.txt text.b    my idea is this: list_of_words="a b" for i in $list_of_words; do sed -i 's/text/text.$i/g' File.$i.txt; done  In the output of each file I end up having for that word just text.$i without inserting the letter in the list as i was expecting i.e. text.a .


Missing ~/.Xauthority file in Ubuntu 17.10

In Ubuntu 17.10, when I log in using Wayland and try to run a GUI app using root access it says   unable to copy the user's xauthorization file   I tried   sudo chown sharif:sharif ~/.Xauthority   but the result was  chown: cannot access '/home/sharif/.Xauthority': No such file or directory   But in Xorg those apps run well.


Optimal subfigure width to span \textwidth

In this example,  \documentclass{article} \usepackage{graphicx} \usepackage{subcaption} \begin{document} \begin{figure}   \centering   \begin{subfigure}[t]{0.33\textwidth}     \centering     \includegraphics[width=\textwidth]{example-image-a}     \caption{a}   \end{subfigure}   \begin{subfigure}[t]{0.33\textwidth}     \centering     \includegraphics[width=\textwidth]{example-image-b}     \caption{b}   \end{subfigure}   \begin{subfigure}[t]{0.33\textwidth}     \centering     \includegraphics[width=\textwidth]{example-image-c}     \caption{c}   \end{subfigure} \end{figure} \end{document}   I chose the subfigure width equally 1/3 with the rationale that the figure span \textwidth exactly. From the result,    one can deduce that there is some overhead.  How do I optimally chose subfigure width so that the figure span textwidth exactly for N = 2, 3, 4, ... subfigures?


jQuery: Checked event on checkbox added later through innerHTML is not working.

There are two checkboxes in my page for which the change event I'm capturing in the below code:   $(':checkbox').change(function(){  alert('hello '+this.checked);  });   But if I add third checkbox to that group and I click this checkbox, the above function is not triggered.   I am adding the third checkbox to the group through the innerhtml code like below:    var text2='
<input type="checkbox" name="vehicle" value="TRUE"/> New function
';  text1=text1+' '+ text2;  parent.innerHTML=text1;   Note: text1 is the existing innerhtml code of existing two checkboxes.


Using differentiation to solve equations

Lets say that I have an equation that can't really be solved via elementary means, for e.g:  $$ e^x = 4x$$  Logically, what is wrong with me using equating derivatives (or integrals for that matter)? For e.g:  $$ \dfrac{d}{dx} (e^x) = \dfrac{d}{dx} (4x) $$  or  $$ \int{e^x}{dx} = \int{4x}{dx}  $$


How to cause "Argument list too long" error?

Context for the question: According to , ARG_MAX is maximum length of command-line arguments to exec() family of functions. Which lead me to believe that's actual number of arguments, however that clearly didn't work:  $ ulimit -s 8192 $ touch {1..18000}.jpg $ rm *.jpg $    Clearly, this works fine, despite being in length over 8192 items. According to , the 8192 is supposedly size in kB. So clearly the previous assumption was wrong.   This is where the actual question comes in: How do I figure out the amount of items that actually will get above 8192 kB limit ? In other words, what sort of computation I have to perform to ensure that *.jpg type of glob will result into Argument list too long error ?  Please note, this isn't a duplicate of . I know about getconf ARG_MAX and ulimit -s values, that's not my question. I need to know how to generate enough arguments in size that will be above the limit. In other words, I need to find a way to get the error, not avoid it.


Null Pointer Exception wen trying to pass parameter and print

im readin from a file in main and in main i store ticks as a variable then i pass it to linkedList.insertNode() then it goes to the Node class and the values are set and when i call the linkedList.printAll(); from main i get a NULLPOINTEREXCEPTION and i dont understand why. Am i not printing ticks value? List Snippet  class List{  private Node ptr;  private int ticks;  private int jobId;  private String name;  public List(){  ptr = null;  }   public void insertNode(int t,int j, String name){     Node node = new Node(t,j,name);    if(ptr == null){      node.next = node;      node.prev = node;     }//end if public void printAll(){    System.out.format("%d",ptr.getTicks());   }   Node Spippet  class Node{   private int ticks;   private int jobId;   private String name;   Node next;   Node prev;    public Node(int t,int j, String name){     this.ticks = t;     this.jobId = j;     this.name = name;     setNext(null);   }   MAIN(snippet)    linkedList.insertNode(ticks,jobId,name);      linkedList.printAll();


How to change the value of the variable within another variable using JavaScript?

I want to know, in JavaScript, if is possible to change value of the variable within another variable.  var a; a= 0; b= a; b= 1;  alert(a);   Why output of var a is 0 ? How can I have like output 1 ?  if b == a why when i change value of b doesn't change even value of var a ?


Why are flags on posts that are several years old not reviewed as quickly as recent ones?

When I flag posts from several years ago, the flag seems to be never reviewed, unlike recent posts which can reviewed within minutes. I have >10 case like things with flagging things written more than 2 years ago. Why don't such flags get reviewed as fast as recent posts? They always last for months. Note: I've read , but it doesn't address the difference for old posts vs recent posts.  Moreover, if  about flag expiry get implemented, flagging old posts would mean such flags can not get reviewed. Update Ok, there is no common share about the correlation of a several years old post with less than 1000 view tend to not get it's flags reviewed. I will create a query on data.SE for this.


Specify which interpreter to use at command line

Ok, so I can write a shell script with bash, sh, or zsh in mind etc. And I can put a hashbang at the top of the file like so:  #!/usr/bin/env bash   which will tell the kernel which interpreter to use to execute the file.  However, I just realized, I don't know how to tell the machine which interpreter to use at the command line.  e.g., if I write:  $ foo bar baz   at the command line, how do I know what interpreter is being used to interpret that command? How can I tell the computer to use a particular interpreter?  Hopefully the question is clear.


"You've earned (badge)" panel layouts are broken

When I visit  I see this:     The "Congratulations! You've earned (badge)" section has dropped down completely beneath the tabs under it. The "You've earned a new privilege!" section has a gap at the bottom:     Shog9 says in comments how to reproduce this:     Gotta have earned a badge, not dismissed the notification, and be looking at your own profile.


Does the speed of light vary depending on what it travels through?

The title is pretty much self explanatory. Does the speed of light vary depending on what it is traveling through? The speed of light through vacuum is 299792458 meters per second but does it change if it would say travel through air or water? If so why and if not why?


We can define trace if $A =\sum_{i} \langle e_i, Ae_i\rangle$ where $e_i$'s are standard column vectors, and $\langle x, y\rangle =x^t y$ for suitable column vectors $x, y$. With this set up, I want to prove trace of AB and BA are same, so it's enough to prove that $$\sum_{i} \langle e_i, ABe_i\rangle =\sum_{i} \langle e_i, BAe_i\rangle$$ but how to conclude that?


Pasted text is reduced in size when copied from ask question description/body

Steps to Reproduce ##   Tap ask a question type some text in body/description field copy/cut  Paste in different location Notice text size is smaller   Expectation  Given I have copied text, when I paste the text in the same or a different location, then the text size will be the same as when I copied it.   App Version: 1.6.6.2 Device: iPhone 7 OS Version: Version 13.1.3 (Build 17A878)


SO's access to linkedIn when importing to Careers 2.0

When importing linkedIn to my Careers profile I get asked whether I accept the access to my profile requested by SO.  These include:   Your profile overviewName, photo, headline, and current positions Your full profileFull profile including experience, education, skills, and recommendations Your connectionsYour 1st and 2nd degree connections Invitations and messagesSend messages and invitations to connect as you   I don't think SO needs to know my connections, but I can live with it (#3). What I can't live with is #4; linkedIn, and my connections, are professional. I don't think unsolicited messages to 'connect' or anything via that account is acceptable.  Is there any way to opt out of just that last one?  Confused about what mandatory meta tag to put this under. Should I be requesting this feature be made?


Is the answer to the question "How many moments in time exist between any two particular moments?", infinitely many?

This question is related to Xeno's paradox, and to the discrete/continuous time debate, but it comes from a slightly different angle.  If the answer is infinitely many, why would this not be a contradiction of the law of conservation of information, in that each of the infinite moments could be said to contain different coordinate information regarding the position of any moving object which would mean the universe contains uncomputable infinite information?  Also, doesn't the truth of relativistic curved spacetime making clocks tick differently in different parts of space mean that the divisibility of time passing changes where effected by gravity, i.e. it isn't infinite everywhere?


Is using same key pair for both encryption and signing secure in RSA

In GPG, we can use same key pair for encryption and signing. Can't/Shouldn't we do this in RSA. I am using  RSAES-OAEP and RSASSA-PSS, not raw RSA btw.


How to copy an object by value, not by reference

I want to make a copy of an object, then after some logic, re-assign the original object the value of the copy.  example:  User userCopy = //make a copy  foreach(...) {   user.Age = 1;   user.ID = -1;    UserDao.Update(user)     user = userCopy;   }   I don't want a copy by reference, it has to be a copy by value.  The above is just a sample, not how I really want to use it but I need to learn how to copy by value.


Should I use "is" or "are" when the subject is a list of percentages before a collective noun?

I am stuck in choosing the correct verb (is or are) for the following sentence, since generation is uncountable (singular agreement) and it is preceded by multiple percentages (plural agreement).  Which one should I use?     70, 40, 10, 60, and 10% of the old generation is/are selected randomly for the crossover, mutation, swap, reversion, and insertion operators, respectively.


Short story about the death of a giant tree

I'm looking for a short story about a very old, giant tree that contains an extremely valuable substance at its heart. Don't recall if in a magazine or an anthology; perhaps 10 pages? In English. I guess 40-50 years ago. The tree's planet is visited by a spaceship with three people: two not-nice male scavengers who intend to harvest the substance and a weaker man bullied by the other two. They find the tree, fallen over (I think maybe a giant storm toppled it?), and the two rip out its heart for the substance. Somehow the weaker person is left unconscious at the dying tree. The tree sends tendrils into him, observes that his makeup is inferior, and does various things to his body to strengthen him greatly. He then goes back to the ship and the two thug-types try to bully him further, but he's no longer the weak person he was, and demonstrates this--I think maybe (really weak recollection) by pressing his thumb into a metal bulkhead and deforming it. I don't recall much else. It’s stuck with me for decades. Would love to find it again. Thank you!


My new kernel has CONFIG_DEVTMPFS enabled, and thus my /dev is mounted as devtmpfs. My old kernel was not using CONFIG_DEVTMPFS, and /dev used to be mounted as plain tmpfs.  Now I have noticed, the size of /dev/ is ridiculously large: 8GB, which is half of my RAM:  df | grep devtmpfs devtmpfs         devtmpfs  7.8G     0  7.8G   0% /dev   In the past, when my /dev was mounted as tmpfs, the size used to be 10MB  df | grep tmpfs tmpfs                 tmpfs        10M     0   10M   0% /dev   Seems to me, 10MB is more than enough for /dev. Why does /dev/ allocate 50% of my RAM by default? Where can I change this ?


Discontinuous functions with closed graphs

I tried looking up a question regarding graphs of continuous functions on this site, but all the ones I found consider functions from $\mathbb{R}$ into $\mathbb{R}$. I have been pondering the following question: given a general topological spaces $X, Y$, and a function $f: X\to Y$, when does $Graph(f)$ closed in $X\times Y$ imply that $f$ is continuous. By the closed graph theorem, this is true whenever $X$ and $Y$ are both Banach spaces.   Also, it is fairly easy to prove that whenever $Y$ is a Hausdorff space and $f$ is continuous, then $Graph(f)$ is closed, but I do not think that the converse is true, so I am trying to find an example where $X$ is some topological space, $Y$ a Hausdorff space, $f: X\to Y$ a function with a closed graph in $X\times Y$, but who fails to be continuous. As of yet I have not been able to find such a counterexample, partially because I have no clue where to look for such a counterexample. I would really appreciate getting some directions to go in.


Block search engine from indexing Currency Words as content keywords

I have one website with currency converter on it and Google WMT is considering the currency words as Content keywords. Is there anyway to block search engine from indexing this Currency Words like "Dollar, pound and all that". I am new in this and any help will be appreciated.


Is there a prime which is the form of $10^n + 1$ except $2, 11, 101$?  I confirm there isn't such prime for $n < 64$.


Does SSL really matter for most websites?

I've been pretty paranoid about learning to "do security right" for this site I'm building (first non-trivial site I've made), and I've noticed something that bothers me: SSL.  I've read plenty of security threads here, on StackOverflow, and elsewhere that goes on at length about regenerating session ids after n uses, and how your passwords need to be salted, hashed, and never stored in plain text. I've read plenty about how to detect when a session has been hijacked, by tracking IP addresses, user agents, and by using tracking cookies.  What I don't understand is what any of this matters when the website logs you in via a normal HTTP POST and sends your password over the wire in plain text?   I understand that all the other methods I listed are needed to reduce your overall exposure, and maybe there are some sites that just don't need that much security anyway, but I guess what I'm asking is:   When is it ok to not bother with SSL?   Sites like Gmail, your bank, and LinkedIn, I can see having a reason to use SSL, but what makes it ok that sites like Facebook and reddit don't bother (hell, PlentyOfFish even stores your password in plain text and even emails it to you weekly as a reminder!?!)?  How concerned should I be with making sure SSL is setup (especially since I'd be starting with a shared host, and I'm being pretty cheap to start)? My site won't hold any particularly personal information, if that helps. If the site becomes a success, I'd seriously look at paying the extra for the added security.


Will unplugging/replugging the power cable on a powered off computer damage the hardware components?

I just removed the cable connected to my computer and switched off the power supply switch. Then I opened the computer case in the side just to gently blow some air to get the dust out. But after just about less than 5 minutes after blowing some air, I closed the CPU and plugged back the power cable and turned on the switch.  But what I noticed was that my keyboard had "Num Lock" "Caps Lock" and "Scroll Lock" lights all lit up even if I did not press the power button in the computer yet. It disappeared as soon as I turned on my computer. When I got to the desktop I got an error: "Default Radeon WattMan settings has been restored due to unexpected system failure" but nothing seems to be wrong. I am just wondering why it never appears except for the time I unplug the power cable and turn off the power switch just now. Is there damage to the computer if you keep removing the power chord? Does it get a power surge or get shocked?


How to copy file to another user (have password, no root)?

I am user_a and I have a password for user_b, so I can use su user_b to do things as user_b.  I want to copy a file from user_a to user_b.  I don't want other users besides user_a and user_b to see the file, and I don't have root on the machine.  So the usual trick of moving the file to /tmp is not acceptable.


Can an object tethered to a spaceship be pulled out of event horizon?

An object cannot escape the event horizon by catapulting it outside the black hole. However, what if instead of relying on escape velocity, the object was tethered to a ship orbiting well outside the event horizon? The object needs not to be pulled out at speeds higher than $c$, but rather can be pulled slowly.  Assume the gravity gradient between the ship's orbit and the tether's other end is manageable, the mass of the object is small enough to be pulled without too much burden on the ship's engines, and the tether is strong enough. (Or it's just a loose end). Would such an object be pulled-out of the event horizon?


How to write DVD from bootable pen drive

I have a bootable USB pen drive which has bootable Ubuntu. Now I want to write to a DVD from the pen drive. How can I do this? Please explain it, so that I can save the software for future.


Where can I ask about Software Licenses/Licensing?

Is it appropriate to ask questions about software licenses/licensing on ? Or is the appropriate place  ? Or is there no appropriate site currently and we should suggest such a site on ?


Let $(x_n)$ be a bounded sequence of real numbers such that $x_n \ge0$ for each $n \in \mathbb N$. Show that $\liminf(\sqrt{x_n})=\sqrt{\liminf x_n}$.   I assume we need to consider the subsequence of ($\sqrt{x_n}$), but I'm really confused with the  notion on "boundedness". Can I assume the question implies an upper bound on $(x_n)$?  Even then wouldn't the equation be implied? Given how roots generally affect limits.


What substances I can use to clean the touch sensitive screens like iPhone, iPad?

I heard that you are not supposed to use substances containing alcohol because it will destroy the anti-grease coating layer that's above the glass.  The problems is that just water and microfiber cloth is not always enough and I want to know what is safe to use.  Update: Please do not recommend a specific product, or at least do not recommend it wihout specifing the content. This is important because most products are not usually available outside the US.


If $r+\frac{1}{r}$ is an odd integer then $r$ is irrational

Suppose that there is a real number $r$ such that $r+\frac{1}{r}$ is an odd integer.Then $r$ is irrational.   Let $r\in \Bbb Q$ then $r=\dfrac{p}{q}\implies \dfrac{p}{q}+\dfrac{q}{p}=$odd  $\implies \dfrac{p^2+q^2}{pq}$ is odd integer.  Since  $r+\frac{1}{r}$ is an odd integer$\implies pq\mid p^2+q^2$  How to derive a contradiction from here?


Solo traveller from UK to John F. Kennedy International Airport, NY

I'm a single traveller going to JFK for my 70th Birthday. I'm very anxious. I have baggage to collect. I have no idea what to do after landing.    What happens and where do I go first, will I be told?


How to share a drive between Ubuntu and Windows 10

My laptop has a 1TB HDD. I'd like to install Ubuntu on it. Is it possible to do this, except make it so that Windows and Ubuntu share the entire drive, without formatting it? Also, if this is possible, I'd like to have all of Ubuntu's system files tucked away in a single directory on the drive, and have custom locations for some of the /home directories.


I believe all SO users have the same notification area, where the see the hot questions across all the stack exchange sites. The three tabs, hot questions, all sites, inbox indicate the respective question that is hot or commented on. I have seen this feature as broadly classified. Basically If I am active in StackOverflow C# tag, it doesn't make a sense for me to see a hot question from tex.stackexchange.com. I am wondering if this can be customized.  Basically I would like to be updated in this bar about a hot question from a subject area that I am mostly active in, or say I can subscribe to hot questions from a particular tag of Stack Overflow, rather than from the whole bunch of tags available. Is that possible. May be we have have a fourth tab, that shows hot questions for the tags you have subscribed to.  Can that be done or is there any other option where I can get notified about hot questions from a particular tag area.


Can markdown mini replace an en dash with a normal hyphen in URLs?

Further to Tim Stone's response to my  regarding what turned out to be an en dash in an URL: Would it be reasonable for markdown mini to replace en dashes with normal hyphens? Or is that Wikipedia article's URL just a fluke?


Unity launcher made with Alacarte iconless

trying to create a launcher with a .png image file and main menu keeps on removing it. is .png not supported or do I need to edit the image first?


Postgres : Relation does not exist error

I used pg_restore to load my postgres db with a dump file. I connected to my db with my user :  sudo -u arajguru psql dump  select current_user;  current_user  --------------  arajguru   Now I was able to see all the newly created tables:  dump=> \dt                List of relations  Schema |       Name        | Type  |  Owner    --------+-------------------+-------+----------  public | Approvals         | table | arajguru  public | Approvers         | table | arajguru  public | Conditions        | table | arajguru  public | Entities          | table | arajguru  public | EntityDefinitions | table | arajguru  public | Projects          | table | arajguru  public | Rules             | table | arajguru  public | run_history       | table | arajguru (8 rows)   But when I try to fire a select * query, it gave me this error:  dump=> select * from Approvals; ERROR:  relation "approvals" does not exist LINE 1: select * from Approvals;   What can be the reason for this error? Please help.


Given $f$ is continuous and $f(x)=f(e^{t}x)$ for all $x\in\mathbb{R}$ and $t\ge0$, show that $f$ is constant function

This question was asked in :     Let $f: \mathbb{R} \to \mathbb{R}$ be a continuous function such that   for all $x\in\mathbb{R}$ and $t\ge 0$, $$f(x)=f(e^{t}x)$$ Show that   $f$ is a constant function.     My attempt:  Suppose that $f$ is not a constant function. Then $f(0)\ne f(x_0)$ for some $x_0 \in \mathbb{R}$. We eliminate the possibilities that $x_0>0$ and $x_0<0$, thus proving that our assumption was wrong.  Case 1: ($x_0>0$). Let $k$ be any real number between $f(0)$ and $f(x_0)$ (not inclusive). Then by the intermediate value theorem,  there exists $y_0 \in (0, x_0)$ such that $f(y_0)=k$. But $f(y_0)=f\left( e^{\ln \left( \frac{x_0}{y_0}\right)  } y_0\right) = f(x_0)$ which contradicts our assumption that $f(y_0)$ was between  $f(0)$ and $f(x_0)$.  Case 2: ($x_0<0$). Let $k$ be any real number between $f(0)$ and $f(x_0)$ (not inclusive). Then by the intermediate value theorem,  there exists $y_0 \in (x_0, 0)$ such that $f(y_0)=k$. But $f(x_0)=f\left( e^{\ln \left( \frac{y_0}{x_0}\right)  } x_0\right) = f(y_0)$, a contradiction again.    Is this proof correct? I was probably looking for a direct proof if there's any. Alternative proofs are welcome.


How can bonds reach 0 and negative interest rates? why would someone buy them?

I know what coupon rate and yield to maturity is but I do not understand very well the interest rate of 0.07% in 1 year Treasury bonds, for example. And how can bonds reach 0 and negative interest rates? why would someone buy it?


How to find orthogonal vector to an arbitrary 3 dimentional vector

Given a vector $\begin{bmatrix}a\\b\\c\end{bmatrix}$ what is a simple solution to find any vector perpendicular to it?


Imaging an iso in a certain partion of usb-drive to make it bootable and Windows-compatible storage

I have a usb-drive which I want to use both as storage (for windows too) and as a (Linux) Bootable. So I have to image the ISO of the linux distribution that I have into a specific partition of my usb drive. Suppose the drive is sdc and I have made two partitions: sdc1 for storage(NTFS) in the beginning and sdc2 (FAT32) following that (I use GParted).  I know that for the simple case of just making the drive bootable we use dd as :      dd if=name.iso of=/dev/sdc bs=512k   That would of course image the iso in the drive, not the specific partition,making it impossible to use the usb as storage. I thought of using /dev/sdc2 as the destination instead of /dev/sdc but after googling I concluded that's not how it's supposed to work. So why can't I just use /dev/sdc2 ? I tried both:  Writing to /dev/sdc changes any partitions I have made and it creates 2 partitions  in the beginning and leaves the rest unallocated, as it's supposed to.Writing to /dev/sdc2  doesn't "mess" with the partitions I have and it just writes in the second partition.  So what do I have to do? Do I have to partition the drive in another way (I've read this ) ?   Having done the partition correctly, how must I use dd to write in a specific partition?


Closed form of product of complex numbers

I'm stuck in a proof where I want to get a closed form of something. This is the last thing I need to complete my proof:  Apparently for small $n\geq2$, the product $\prod\limits_{k=1}^{n-1} (1-\exp(\frac{2ki\pi}{n}))=n$.  How can i show it for all $n\geq2$?  It does not seem too hard to show, so any hints are welcome. Thanks in advance


Why couldn't Harry always see Thestrals? (since the age of one)

In both the books and films, it's made clear that Harry saw his mother dying when he was a baby. He clearly remembers this, due to the flashbacks that are induced every time he gets near a Dementor.  However, he only sees the Thestrals (creatures that require you to have seen death for them to appear visible to you) after Cedric Diggory dies.  Why is this?


Display citation key in bibliography in beamer presentation

I have a beamer presentation where I cite books and papers using alphanumeric keys (as provided by the style = alphabetic flag). The whole thing looks as follows:    In the bibliography on the last page however I do not have the alphanumeric keys:    I wonder whether I could also have the alphanumeric keys be displayed in the bibliography instead of just the reference and the icon.  My biblatex configuration currently looks as follows:  \usepackage[ backend=biber, style=alphabetic, sorting=ynt, maxbibnames=99 ]{biblatex}   I have tried a lot of things and failed but I assume there is probably an easy way to fix this.


Finding the n-th arrangement of items with repetitions

I'm new to Stackexchange and maybe I do not have the correct mathematical terms for the question I'm about to ask.  I'm given a multiset of given size $N$ which consists of zeros and ones.  Example:   Multiset size $5$ with number of ones: $2$, number of zeros: $3$  How many distinct arrangements (sequences) of all these items are possible?  First arrangement is: $0,0,0,1,1$  Listing all arrangements in ascending order:  1:  $0,0,0,1,1$  2:  $0,0,1,0,1$  3:  $0,0,1,1,0$  4:  $0,1,0,0,1$  5:  $0,1,0,1,0$  6:  $0,1,1,0,0$  7:  $1,0,0,0,1$  8:  $1,0,0,1,0$  9:  $1,0,1,0,0$  10: $1,1,0,0,0$  Because in a real task the set size could be much larger than this example, is it possible without iterating through all arrangements:   To find the $n^{\text{th}}$ arrangment in the  list (example $7^{\text{th}}$ permutation = $1,0,0,0,1$) ? To calculate the index if I'm given the arrangement (example $0,1,0,1,0 = 5$) ?   I'm looking for an algorithm suitable for implementation in some programming language.


Run Windows inside a virtual machine on Linux for gaming

Since making the full time move to using Linux (Fedora) from Windows, I've found the migration fairly easy and haven't had much disruption in how I do my work.  However, there are some games I like to play such as Football Manager and some older games which rely on 3D rendering (either software or hardware). At the moment I have a VirtualBox VM running Windows XP and 95% of the games I've installed on this have failed to run due to problems with the graphics card (the virtual graphics card).  What I would like to do is get the VM to use the laptop's actual physical graphics card directly, or something similar. I know there is a performance issue, but most of the games I play are over 5 years old and I'm not bothered about graphic quality etc. I just want it to work.  I don't have to use VirtualBox, I just used it because I'm used to it. If VMWare or another virtual technology is a better option than VirtualBox then I will use it.


Is there the dark mode (inverted colors) in the 'Preview' Application for PDF reading?

I am using the “Preview” application for reading a PDF file on a MacBook Pro. Is there any way in I can read it in dark mode?   You can do it in Adobe Acrobat Reader by changing background and text color, but can “Preview” do that too?


I've been trying to install wine on my ubuntu 18.04 (64 bit) for an hour but couldn't succeed.  I do as all of the tutorials and instructions do it:  sudo dpkg --add-architecture i386 wget -nc https://dl.winehq.org/wine-builds/Release.key sudo apt-key add Release.key sudo apt-add-repository 'deb http://dl.winehq.org/wine-builds/ubuntu/ xenial main' sudo apt-get update sudo apt-get install --install-recommends winehq-devel   But I always get the following results:  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  winehq-devel : Depends: wine-devel (= 3.10.0~xenial) E: Unable to correct problems, you have held broken packages.   This is the instruction in  and also there is a  video doing the exact same procedure as above and succeeding, what is wrong? How can I install wine properly?


Use the system Compose database in Gtk applications

I'm using a X server which doesn't implement the  XKB extension (it is VNC, but I don't think it matters, my vncviewer is running on Windows XP, I don't think it matters either).  I've set up a Compose aka Multi_key key.  By setting the XLOCALEDIR and LC_??? environment variables, I'm able to point to a Compose file to which I've added some key combinations.    They are working in some programs (xev, emacs, kate, konqueror) and not others (firefox, OpenOffice, gnome-text-editor).  The applications who aren't working have their own set of compose combinations. They aren't taking the locale into account to choose the Compose data base. Modifying the system provided one on another machine where I've root access hasn't any effect on them.  The fact that it is working with xev makes me think that the basic settings are correct and it is the non working applications which aren't take them into account.  Does someone know how I may persuade them to do so without having root access?


Two Timelines, (Almost) Same Event, but Several Years Apart?

In Fringe's season 1, the episode  (1x13) shows how  travels on VertusAir flight 718. We witness how he develops some strange symptoms, withdraws into a lavatory and transforms into a porcupine-like monster.  At the end of season 3, Peter "switches" the timeline (changing the past and making the present continue in a different timeline henceforth) from blue- to orange-verse. Various statements throughout the 4th season indicate time (the date) was not reset; Olivia and Walter have been working on Fringe cases for some three years etc. - hence it is safe to say that season 4 plays 3 years after season 1.  Then, in the episode  (4x16), the events from 1x13 happen again, up to the point of Bowman's transformation, which this time doesn't happen (not aboard the plane, anyway). As far as I can tell, great care was taken to exactly recreate the events from the season 1 episode, including hiring the same actors to play the flight attendants once again ( and ), so obviously this is supposed to be the same event with slight changes.  Peter, as well as Olivia - who is in the process of regaining her memories from the blue-verse -, remember the events from 1x13 and note the difference that Bowman's transformation happened later this time, implying that in the orange-verse, everything related to flight 718 played out the same way, except for the small difference that the transformation happened a bit later.  BUT ... all of this happened 3 years later!! Is there any explanation for this?  How unlikely is it that in the orange-verse timeline, Marshall Bowman is on the very same flight with the very same flight attendants 3 years after the same would have happened in the blue-verse? Mind you, this is not a "small change" in the course of events while mostly everything else stays the same.  So, why did Peter and Olivia realize the transformation happened a tad later in the orange-verse timeline, but were not baffled by the fact that essentially the same events as in the blue-verse happened, but three years later?  EDIT: Not only the flight and the flight attendants were the same in both episodes. The passenger next to Bowman was the same, an elderly lady played by  both times, as well. Moreover, the transcripts of  and  reveal that the dialogue between Bowman, the passenger next to him, and the cabin crew is the same down to the lines of text until the moment of transformation.  Interestingly, the announcement by the captain in the beginning seems to be different - starting the inflight movie + selling headsets vs. circling before beginning the final descent + selling snacks. On the other hand, this could be presumed to be a slight retcon, as in 4x16, it was crucial for the plot that the plane would be close to landing, and starting the inflight movie would not make much sense right before landing.


What do the components of the taxable income in the Schedule D Tax Worksheet mean?

calculates the tax on the taxable income by   first decomposing the taxable income in line 1 into  lines 19, 20, 28, 31, 37 and 40,  then taxing on them at different tax rates of regular tax rate, 0, 0.15, 0.20, 0.25, and 0.28. The resulted taxes are in lines 42, 21, 29, 32, 38 and 41. finally summing their taxes into line 43   I wonder what the amounts in lines 19, 20, 28, 31, 37 and 40 mean?  Without understanding what they represent, it is hard to understand the rationale underlying the worksheet. My purpose is to    understand which part of the taxable income is taxed at which tax rate, and  sort the different parts of the taxable income according to their tax rates, and find out which parts have relative high tax rates, and which have low tax rates.   Thanks.  p.s.   Do you agree that the worksheet was written like a computer program with little readability, e.g. no suggestive names for most lines?  What are some ways for us to understand the worksheet?


How to randomly sample values given the extremly small and large log-probabilities?

Assume a long list of log-values. The list consists of very small negative numbers, very large negative numbers, as well as very large positive numbers. To avoid numerical overflow/underflow, I need to stay in log space. Now the question is, how can I randomly select an element of this list, with a probability proportional to its value? A naive way would be to switch back from the log space, but that will result in nan. Another naive way is to stay in the log space and just sort and then normalize all the values but this is still can cause numerical underflow.  An example array:  [-4.92636e+08, 1.92636e+06, -1.85264e+03, 2.2636e-04]


Most effective way to get rid of existing spam mails in thunderbird? API?

I have my own mail server (hosting package) on which spam assassin is installed, which basically does no help at all. I get a LOT of spam mails, between 50 and 100 daily. All from a different sender/domain/server, many have a similar subject but it changes a lot aswell. Some try to sell stuff, some try to install stuff, but none of them are any legitimate business at all.  The e-mail account(s) those go to are business accounts on my own domain, simply changing my mail everywhere is not an option. I use thunderbird as my mail client.  I've been out of office for a bit and I now have thousands of unread mails, simply deleting all won't work because around 5% are important.  I have a text file containing thousands of subjects from scam mails that I frequently get. Is there anyway I can use this to automatically delete all mails with the same subject on specific mail accounts?  I know there is the message filters feature in thunderbird, but I don't feel like manually adding thousands of subjects to it at all.  I have enabled thunderbird's junk detection, but it has no training data yet so it doesn't help with existing mails.  I tried the search filter "Junk level percentage greater than 0" and it showed me around 400 mails (I'm guessing this comes from spam assassin on the server?), there's still thousands left that are classified as non-spam by the server and thunderbird though.  Do I have any reliable (I do not want anything that might not be spam to be considered as spam and deleted) option of detecting what is spam that is already existing?  What I'm thinking is an advanced search filter that matches any mail in an account which subject matches any subject within a text file (one subject per line) or similar approach, so I'm guessing my real question would be:  Is there a way to programatically/API access thunderbird and search/delete mails?


About a weaker form of normal subgroup definition

The usual definition of a normal subgroup $H$ of group $G$ is that $x^{-1}Hx=H$ hold for all $x \in G.$ A weaker form of this is to assert only the containment $$x^{-1}Hx \subseteq H \tag{1}$$ should hold, for each $x \in G.$ If it does, then for any specific $x,$ equality in $(1)$ be deduced by applying it both as is, and with $x^{-1}$ replaced by $x$. Thus the "weaker" form is equivalent to the usual one, provided one assumes it holds for all $x \in G.$  My question concerns cases of a group $G$, a subgroup $H,$ and a choice of just one $x\in G.$ According to Hall's group theory text, in the case of infinite $H$ the containment $(1)$ need not imply equality.  So I'm looking for such examples: A group $G$ with a subgroup $H$ and some specific $x \in G$ for which the containment $(1)$ holds without equality. That is, we have $x^{-1}Hx \subset H,$ where the containment is proper.


How does Zion population square with how it's built?

The Architect says that The One must choose 23 people (16 female, 7 male) to create new Zion.     After which, you will be required to select from the Matrix 23 individuals - 16 female, 7 male - to rebuild Zion.    But this doesn't seem to make any sense considering the following two statements (listed in un-cited form on )   Zion, according to the Architect, has been completely destroyed five times by the time of the sixth One, Neo, meets the Architect. As a result, the actual year on Earth is estimated to be closer to 2699, not 2199.  This means that Zion grows to its final pre-destruction size in only 100 years. Yet, the current Zion has - at least according to Wikia - a population of over 250,000 humans.   How can one square those 3 facts?  It seems completely impossible to both generate a population of quarter million, AND all that advanced Zion infrastructure, in just the space of under 5-6 generations (100 years) if you start with 23 people. (Even allowing for non-natural population growth - i.e., culling out people from the Matrix, the way Neo was extracted. That seems a very labor intensive and non-scalable process - one ship can not extract more than a couple of people a day given its size and medical facilities).   Is there some canon explanation for this discrepancy? Are one of the two facts that Wikia lists incorrect/noncanonical? Did Architect lie to Neo? Do the machines somehow help build up Zion and populate it further?


Is it bad SEO practice to link to hundreds of internal pages on one page?

I have a site with 200 pages.  On each page, I would like to set up links to the rest 199 pages. I did this because I want my users to link to other pages easily.  But is this a very bad practice for SEO? Will Google hate this?


How can i create a instance of the following Class and access its methods. Example:  public class A {     public static class B {         public static class C {             public static class D {                 public static class E {                     public void methodA() {}                     public void methodB(){}                 }             }         }     } }


Android app fails to load deleted questions even if I have the rep to view them

Trying to view a deleted question in Android app fails, the app shows "Loading the question failed", and doesn't say why.


how to fix broken packages on ubuntu 14.04

I have uninstalled lamp but I want to install it again. But when I run this command  sudo apt-get install lamp-server^   But when I run this command through this error message  Unable to correct problems, you have held broken packages. how to fix that?


Why can't we read voltage between just one pin of a loaded capacitor and any ground?

I know that we can only read voltage across a capacitor if it's two pins are connected to the voltmeter or can't talk about any potential difference between totally different systems if they do not have a common ground. But as I think about it more, I started getting confused and can not understand the physical reason why this is the case. Let me introduce a case;         – Schematic created using  First I charge my capacitor via battery. Numbers are trivial. Then;         Then I measured the voltage to be sure that its charged. After that;         Than I connected the negative probe to any universal ground(earth, a big copper plate etc.) and from common knowledge I know that I could not measure any voltages but I could not understand the physical reason of why. If voltmeter is measuring the current across its probes than why the charge carriers do not flow from the capacitor plates to ground? If voltmeter measures the electric field like an electroscope than why a plate with charge carriers and a ground do not create an electric field? Thanks for reading and sorry for trivial question.


How to configure blender so that it uses only 50% of total CPU when rendering?

I need to render a very computer-intensive scene using cycles and for some reasons, I decided to use my home computer (i5 3.30 Ghz, 10 GB RAM, 2TB Hard Drive) to render it. However, the problem is that many people needs to use this computer. So, being generous and feeling responsible, I want to know whether there is a way to configure blender so that it uses only half of the total CPU. (Currently, it is using 100% all the time).   Thanks!


Find the smallest numbers in the second column corresponding to index values in first column

I have some very large tables and I need to extract specific rows. I am illustrating the task using a simple example. Say, I have weighed a number of apples, bananas and oranges. I need to extract the weight of the smallest apple, banana and orange  Original table:  Apple 3 Banana 8 Orange 2 Apple 7 Banana 9 Orange 13 Apple 9 Banana 1 Orange 11   Desired output:  Apple 3 Banana 1 Orange 2


How to disable pulseaudio automatic device switch?

My speakers are plugged via optical output. Each time my screen wake up from sleep, pusleaudio automatically switch to HDMI audio where nothing is plugged.  How can I prevent that ?


How to determine surprise when only part of a side is stealthy?

Here’s the basic rule for Surprise (Player’s Basic Rules, p. 69):  If neither side tries to be stealthy, they automatically notice each other. Otherwise, the DM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (Perception) score of each creature on the opposing side. Any character or monster that doesn’t notice a threat is surprised at the start of the counter.  I’m not sure how to interpret that last sentence. For example, suppose that the players try to sneak up on on some monsters, so they roll Dexterity (Stealth) checks. The thief and the champion both roll 14, but the evoker only rolls 9. The DM compares this to the monsters’ passive Perception: a cyclops with 8, a dire wolf with 13, and a giant owl with 15. The cyclops doesn’t notice any threat, so it’s surprised. The owl notices all the threats, so it’s not surprised. But what about the dire wolf? It notices the evoker but not the rogue or the champion. Which is correct:  The dire wolf noticed a threat (the evoker) so it’s not surprised. It didn’t notice a threat (the rogue and champion) so it’s surprised.  If the former is true, could the rogue and champion take advantage of the group check rule to help the less-stealthy evoker hide from the dire wolf? Group Checks (Player’s Basic Rules, p. 59):  To make a group ability check, everyone in the group makes the ability check. If at least half the group succeeds, the whole group succeeds. Otherwise, the group fails. Group checks don’t come up very often, and they’re most useful when all the characters succeed or fail as a group.   covers a couple of related situations, where a rogue sneaks up separately from the rest of the players, or where all of the monsters use a single group Dexterity (Stealth) roll, but not this case where all of the players try to sneak with different rolls.


Accidental Format of Windows Hard Disk by Linux

I had Windows on my hard drive and with tons of data on that. Windows got corrupted and all tried failed to repair it and in absence of windows media I tried installing Linux but by accident it got formatted and Linux got ready. I thought it will create a different partition where it it will keep the windows partition unchanged. Post format I don't see my personal data.  Let me know how I can restore and recover my data.


Can I interchange while and when in the following sentences? 1- He waited while/when I combed my hair. 2- He was waiting while/when I was combing my hair.


The Great Gatsby by F. Scott Fitzgerald     1) Whenever you feel like criticizing any one," he told me, "just remember that all the people in this world haven't had the advantages that you've had."     Why "told me" and not, "said to me"? I was taught "say" to attach to quote, and "tell" in another situation.       2) He didn't say any more but we've always been unusually communicative in a reserved way, and I understood that he meant a great deal more than that.     Why "say" and not "tell"?


How do I predict ball movement, after collision, in game of pool?

I'm trying to draw lines that predict the movement after collision between two balls, in a game of pool. How do I do that?  I heard it can be done via raycasts, but how do I draw a line?


GLM Binomial, with factor predictor, why model without the intercept

In an exercise that asks to estimate the odds ratio the GLM is fitted without the intercept (see code below). It's the first time I see such a configuration and at first sight it seems right but I am unable to find an intuitive justification of why, I just generally feel that this way everything is explained by the levels of the predictor, but if I must explain why this is good and whether it is correct I can not. Can someone explain - wether fitting without intercept is correct, in this case and in general with response and regressor both factors - why - whether fitting with the intercept would be right or wrong - if right what would be the differences, in this and similar cases (factors, continuous variables it's clear)  library(MASS)    str(shuttle)  'data.frame': 256 obs. of  7 variables:   \$ wind     : Factor w/ 2 levels "head","tail":   \$ use      : Factor w/ 2 levels "auto","noauto": # other vars omitted  fit <- glm(use ~ wind-1, family = "binomial", data = shuttle)    coeff <- exp(coef(fit)) oddsRatio <- coeff[1]/coeff[2] print(oddsRatio)  windhead [1] 1.032323


Getting around the FAT32 4GB file size limit

I recently purchased a 32GB USB 3 stick that was formatted FAT32.  I plugged it into my computer and attempted to copy a film onto it, the file was over 4GB however and it would not let me copy the file across because of the .  After some googling I found that I could format my USB stick to have an  format which would mean I could put files onto the stick greater than 4GB in size and the drive would work on both my Mac and my PC.  The problem with this solution is that my PS3 cannot detect the USB stick when it is formatted with exFAT.  I would like to know if there is a way I can have my USB stick formatted so it can have files greater than 4 GB and work on my PC, Mac and PS3.


How is expansion of the Universe consistent with the speed of light?

I have a question that I believe is related to @PetTaxi's question here: , but I didn't want to hi-jack it.    My issue is this.  I'm assuming the most distant objects in the observable universe are 46 B light years away.  A photo from one of these galaxies has been traveling 13.7B years.  I assume the galaxy that emitted the photon was 13.7B light years away at the time the photon was emitted.  So, the problem for me is, the galaxy is now 46B light years away which implies in my mind that the galaxy moved 32.3 B light years (the difference in where it was versus where it is now) in only 13.7B years.  But of course, that can't be true because it would mean faster than light travel.   So, how does a galaxy get that far away in such a short time?  There is likely something fundamental here I don't understand about how the universe is expanding....


How many fix point free permutations of 5 elements are there?

I am trying to find out how many fix point free permutations of 5 elements there are. A permutation is fix point free, if $\pi (i) \neq i$. I am trying to solve this problem using the inclusion exclusion principle but I really have no idea how to approach this problem. I hope somebody can help.


Insert multiple rows into table sql, oracle

I have used the following code to insert into my table but when executed, it says 0 rows effected. insert ALL  INTO CUSTOMER (CustomerID, FirstName, Surname, Address, ContactNumber, Email)  VALUES ('11011', 'Jeffery', 'Smith', '18 Water Rd', '0877277521', 'jef@isat.com') INTO CUSTOMER (CustomerID, FirstName, Surname, Address, ContactNumber, Email)  VALUES ('11012', 'Alex', 'Hendricks', '22 Water Rd', '0863257857', 'ah@mcom.co.za') INTO CUSTOMER (CustomerID, FirstName, Surname, Address, ContactNumber, Email)  VALUES ('11013', 'Johnson', 'Clark', '101 Summer Lane', '0834567891', 'jclark@mcom.co.za') INTO CUSTOMER (CustomerID, FirstName, Surname, Address, ContactNumber, Email)  VALUES ('11014', 'Henry', 'Jones', '55 Mountain Way', '0612547895', 'hj@isat.co.za') INTO CUSTOMER (CustomerID, FirstName, Surname, Address, ContactNumber, Email)  VALUES ('11015', 'Andre', 'Williams', '5 Main Rd', '0827238521', 'aw@mcal.co.za') select * from CUSTOMER;


DVD R/RW Drive Would only read CDs not DVDs

My laptop has a Matshita uj8b1as DVD/r/RW drive, and recently it started refusing to read data from DVDs, I thought there was something wrong with the setting of the software so I reinstalled Windows 7. But even with Windows 7 freshly installed, it still wouldn't read from a DVD.   I wanted to know if this is a hardware failure, so i tried loading a boot CD when the computer booted up. The drive read the boot CD without problems. but the Drive wouldn't read the DVD I put in there.   I also looked into •HKEY_LOCAL_MACHINE •SYSTEM •CurrentControlSet •Control •Class •{4D36E965-E325-11CE-BFC1-08002BE10318} and did not find upper and lower filters  When a DVD is loaded, I double clicked on DVD/CD RW drive in My Computer, the DVD R/RW ejects and says "Insert a disc, Please insert a Disk to Drive F:" I tried everything I knew how to do (reinstalling Windows 7, Uninstalling the driver and reinstalling it in Windows Device Manager) but I still couldn't fix the problem. I want to be able to use the drive again. I really appreciate your help!


How can i upgrade to Ubuntu 14.04 final from 14.04 Beta correctly?

I tried to upgrade to 14.04 Final release from 14.04 Beta. I executed following commands:  sudo apt-get update sudo apt-get dist-upgrade   My system updated packages after dist-upgrade. However after do-release-upgrade it gives the following output:  vijay@vijay-Inspiron-5520:~$ sudo do-release-upgrade Checking for a new Ubuntu release No new release found   How to upgrade from beta correctly?


Is it safe to travel in Japan considering the nuclear situation?

Are there any areas that should be avoided and are there any steps I should take to protect myself from radiation?


Limit of $\sum\limits_{k=0}^n \frac{{n\choose k}}{n^k(k+3)}$ when $n\to\infty$

What is $$ \lim_{n \to  \infty} \sum_{k=0}^n \frac{{n\choose k}}{n^k(k+3)}\ ?$$ I know the way by integration and that the answer is $e-2$ but I am more interested in use of sandwich theorem which provides a maxima or a closed form to it. Expansions may also be useful.


Who opened the store room door in The Shining?

The movie "The Shining" is a psychological horror, in genre. So there should not be any supernatural activity going on in the film.   In one scene towards the climax, Jack was locked in the store room by his wife and the door of the store room was locked from outside. While he was talking with Grady, after their conversation, the door was unlocked and let Jack flee from the store room. The question is who opened the door? There were only three people at the hotel including Jack, his wife and son. Since there is no ghostly activity shown in the movie (except for some hallucinations), what is the most probable description of it?


How is circular motion possible on a banked road when there is no Friction?

It is given here that the maximum safe speed of a vehicle on a banked road having coefficient of friction $0$, is $V =\sqrt{R g \tan \theta}$, where $\theta$ is the angle of banking. I can't understand how circular motion is possible without friction.


I couldn't find any, I tried to write $\cos(z)$ as $\cos(x)\cos(iy)-\sin(x)\sin(iy)$ which then gave me  $\cos(x)\cosh(y) - i\sin(x)\sinh(y) = -2$   $\sin(x)=0$ so that imaginary part become $0$  now we have to find $\cosh(y) = -2$ which is not true for no $y$.  is it right or i made a mistake in my substitutions?


"To start" or "to begin" while referring to work or studies times?

What's the correct or acceptable option to refer to the time or work times from the following options?     1)  "In which hour do you begin / start to work tomorrow"?    (it's not his first day at work, I'm just asking him about the time that he's going to START or to BEGIN tomorrow there.)     2) "In which time are you going to begin / start the university (or   studies) tomorrow.   (As well as example NO.1, it's not his first day at the university, I'm just asking him about the time that he's going to START or to BEGIN tomorrow there.)


Can I travel more than once on my Multi entry Schengen Visa?

I was given a Schengen Visa by the Greek embassy in Cape Town, valid for one year, duration of stay 90 days. I went to Greece last Sept for 10 days.  It says valid for all Schengen States.  Can I use it again to go to France this year in July? Or do I have to apply for a new Schengen for France?  My visa expires on 14 Sept 2014.


If $\{x_{2m}\}$ and $\{x_{2m-1}\}$ converge to the same limit, does $\{x_m\}$ converge?

Given a sequence $x_1<x_2<x_3<x_4<\ldots,$ I found both subsequences $\{x_{2m}\}$ and $\{x_{2m-1}\}$ converge to $\lambda^*$. In this case, can I say $\{x_m\}$ also converge to $\lambda^*$? (i.e. a sequence $\{x_m\}$ is divided into two subsequences $\{x_{2m}\}$ and $\{x_{2m-1}\}$)  If so, if the rate of convergence is superlinear for both subsequences $\{x_{2m}\}$ and $\{x_{2m-1}\}$, can I also say that $\{ x_m\}$ converge superlinearly?   What is more curious to me is the case where two subsequnces converge at different rates of convergence. For example, if $\{x_{2m}\}$ converges linearly to $\lambda^*$ and $\{x_{2m-1}\}$ converges superlinearly to $\lambda^*$, what is the rate of convergence of $\{x_m\}$?


Light bending by gravity? Photons are massless!

We know that when light passes through a black hole it bends. But I couldn't understand why? As light is composed of photons and we know that photons are massless, we also know that gravity and mass relation, .      How can photons experience gravity? What is making them to bend their path?   What I thought (may be pure nonsense) is due to the nature of spacetime itself, which decides the trajectory around the black hole. Not exactly the mass affected by gravity. This is how I explained it to myself or convinced myself. But I have no background to defend it.  Forgive me, I have no background in GR (General Relativity). If this can be answered more on physical ground without invoking more maths(little or most necessary maths is good).(How to explain this to Ist year undergrad, if he/she ever ask me?)


Improve file-info visibility in Finder's preview pane

I find the file information in the preview pane in column view is far more useful than the thumbnail.  I wish I did not have to continually resize the Finder window or scroll the preview pane to see the info I'm looking for.  As you can see below, the useful info is hidden in default  size  of Finder's new window under the preview options like rotate etc.        Is there a way to do any of these to achieve the said goal (listed in order of decreasing likelihood!):   reduce the size of the preview "thumbnail" covered by black here,  reduce the amount of whitespace(grey here) around the preview "thumbnail" (only significant for landscape thumbnails), remove the preview "thumbnail" altogether,  reorder the content of the preview column(bring file info up and send thumbnail down)?    includes the options:   resizing the Finder in every new window (which is labor intensive). Using View menu> Show Preview Options to turn off Quick Actions (which must be done for each file-type, and only reveals a small amount of file info).


Why Are 3pt and 0.0pt plus 3.0pt Different?

I was tuning abovedisplayskip and found that \abovedisplayskip=3pt and \abovedisplayskip=0.0pt plus 3.0pt return different results—the former gives a slightly wider space. For example, the following returns pages 1 and 2 equally spaced only if 0.0pt plus 3.0pt. \documentclass{article}  \usepackage{amsmath}  \begin{document} %\abovedisplayskip=3pt \abovedisplayskip=0.0pt plus 3.0pt hello. hello. hello. \begin{equation} y=x. \end{equation} \clearpage  hello. hello. hello. \begin{align} y=x. \end{align}  \end{document}  Why are 3pt and 0.0pt plus 3.0pt different?


Quick introduction to manifold theory for Riemannian Geometry at level of Lee/Petersen?

I'm taking a course on Riemannian geometry using Lee and Petersen, and I'm falling a bit behind mostly because it has been a long time since I thought about differential geometry.   I took a course on differential geometry using do Carmo about two years ago, and remember a little bit, but it did not cover much manifold theory (and did not talk about tangent spaces, derivations, connections, differentials, etc).   Is there a good text that has a reasonably concise introduction to the essentials of manifold theory that I'd need to survive and get something out of the Riemannian geometry course? I've got a fairly strong analysis/ point-set topology and algebra background; it's mostly the geometry aspect that I'm lacking. I've been relying on Bishop/Goldberg's Tensor Analysis on Manifolds to get by, but am wondering if there are other (consise) texts/sets of notes I should be looking at.


component.find({ instancesOf : "c:componentName"}) not working

I have 2 components. VariationComponent and PGP_Tab_bar_item. I create PGP_Tab_bar_item in the markup of VariationComponent . Want to perform some action on PGP_Tab_bar_item if event is fired from PGP_Tab_bar_item component.  I am using component.find({instancesOf:}) but it is giving an empty Array[].  VariationComponent :  <aura:attribute name="projects" type="Project__c[]" />  <ul class="slds-tabs--default__nav" role="tablist"> <aura:iteration items="{!v.projects}" var="project" indexVar="index">     <c:PGP_Tab_bar_item project="{!project}" isProgramme="false" variationId="{!v.variationId}" active="false"/> </aura:iteration> </ul>  <ui:button label="Save" press="{!c.handlePGPTab}" class="slds-button slds-button--brand" aura:id="handle" />   Controller:  handlePGPTabEvent : function(component, event, helper){     var tabs = component.find({ instancesOf : "c:PGP_Tab_bar_item" }) ;     console.log(tabs); // output Array[] in console }


Why do some includes need the .h and others not?

Why is map imported as #include <map>, but stdio imported as #include <stdio.h>?


Is there any way of getting to the first 15 reputation (at which point you can actually do something) on Stack Overflow other than by asking questions?  My problem is this: if I see a good answer that works, I can't vote for it (not enough reputation).  I have been programming for many years and often see a question I could contribute, but I can't (not enough reputation).  I so far have never needed to ask a question (I know how to use a search facility, and so can find an already existing answer).    Therefore asking questions can't possibly be the only mechanism to get enough reputation to get started, can it?  Because if it is then as more and more questions get asked on Stack Overflow, the need to ask new ones will diminish, so if this is the only mechanism of gaining those first few reputation, soon all new joiners will never be able to contribute, or will need to re-ask already answered questions (not good for anyone).  Advice on how to get those first few reputation gratefully received.


I'm studying topology since a few months ago and I have never caught a good intuition of the topological spaces, but now I think that I did.  My intuition is the next; as many people point out the open sets capture a notion of nearness, (but I did never understand the exact way of this nearness intuition),the points in the open sets are near, and two points in distinct open sets are far, and then the axioms try to capture the behaviours of the opens.  To find a good intuition I have worked with two examples of spaces which I named A and B; A=[{a,b,c,d,e,f},({a,b,c,d,e,f},{},{a,b,c,e,f},{e,f},{a,b},{a,b,d,e,f},{a,b,e,f})], B=[{a,b,c,d,e,f},({a,b,c,d,e,f},{},{a,b,c,e,f},{a,b,d,e,f},{a,b,e,f})] and I obtained the next pictures (and here is my first question: are these  the correct spatial representaition of the spaces? A is in the right, B is the left, the black circles represent points):                                                                                And then the union axiom allows to establish different degrees of nearness, specifically the opens that aren't union of other opens  have near points, and the unions have points nearer than other points that aren't. Concretely in the space A; {e,f} and {a,b} are nearer than c and d, then the unions allow to speak of a "global " nearness.  The intersection axiom also talk about  different degrees of nearness, in the way that if we have near points and we have other near points that have common points, then than points are near, and in fact they are nearer, and so the intersection  talk of a "local" nearness.  And finally the axiom of the necessary membership of the space itself and the empty set, guarantees the fact that "there are nothing outside the space" or the totality of the space and in that sense all the points are near in the space.  Is this a good intuition? if not, please give me a good one.


I am new to Ubuntu and I want to install VirtualBox in Ubuntu through terminal. Can you guys please provide me the command to install it?


What is the meaning of ? I'm little confused about the word as there are some terms like moment of momentum, moment of mass, moment of force, etc. I want to know what exactly is meant by the word "moment".


Integral domain that is not Cohen-Macaulay

There exist finitely generated algebras over a field that are integral but not Cohen-Macaulay (bottom of ). What is an example?


At Theros Beyond Death prerelease, I was playing with  for the first time. It happened to me to forget about the card at the end of my turn and only remember at the beginning of the turn of my opponent, and saying so. He told me I had missed the trigger, and I didn't argue much as that was my fault. However I know this is not an optional trigger, I must exile the top card of my library at my end step. The only part that is optional is being allowed to play the exiled card.  I didn't think about calling a judge at that time, but since that was a mandatory action and there wasn't lots of actions from both of us after the missed trigger, were we supposed to rewind and fix the game state? I only thought about the fact that by not exiling the card, I could not play it and was losing on card advantage so not fixing the game was "fair" to my opponent. However, I forgot that one card would could have been permanently exiled and the effect have changed much more the outcome of the game.  How am I supposed to handle a mandatory effect without calling a judge? Were we supposed to rewind the game state to fix it if both had agreed?


Distribution of hat sigma in simple linear regression model

How can I prove that the distribution of estimated σ^2 (the distribution of the estimated variance of errors εi, in case of homoschedasticity) is equal to a chi-squared with n-2 df * σ^2/(n-2) ?


What are the different subjects in number theory to do research?

What are the different unusual subjects in number theory? I am adviced sometimes to think before going into research in number theory as these subjects like number theory, algebraic geometry are highly old and most the works are done so that a people need a lot of prerequisites to go into that subject and the problems are tough. That's why I am bit nervous. Is it really true? I have come to know about different areas in number theory like ergodic number theory, probabilistic number theory, modular forms and I have studied elementary, algebraic as well as analytic number theory a bit and I love studying number theory. If the subject would be very terse in research then it would be very difficult to work with it. So I am worried. Please give me some advice.


How to plot the mean and variance of a conditional Gaussian Distribution?

I found the attached image on the website, .  How can I generate this nice image in latex? How can I generate it with specific values? based on an internal calculation?