When a field extension $E\subset F$ has degree $n$, can I find the degree of the extension $E(x)\subset F(x)?$

This is not a problem I've found stated anywhere, so I'm not sure how much generality I should assume. I will try to ask my question in such a way that answers on different levels of generality could be possible. I'm also not sure that this question isn't trivial.  Let $E\subset F$ be a fields (both can be finite if needed), and let $n$ be the degree of the field extension ($n$ can be finite if needed). Can we find the degree of the extension $E(x)\subset F(x)$ of rational function fields?   Say $E=\mathbb F_2$ and $F=\mathbb F_4$. Then $(F:E)=2.$ I can take $\{1,\xi\}$ to be an $E$-basis of $F$. Now let $f\in F(x),$ $$f(x)=\frac{a_kx^k+\cdots +a_0 } {b_lx^l+\cdots+b_0 }$$ for $a_0,\ldots a_k,b_0,\ldots,b_l\in F$  I can write $a_0,\ldots a_k,b_0,\ldots,b_l$ in the basis: $$\begin{eqnarray}&a_i&=p_i\xi+q_i\\&b_j&=r_j\xi+s_j\end{eqnarray}$$  But all I get is $$f(x)=\frac{p_k\xi x^k+\cdots+p_0+q_kx^k+\cdots+q_0} { r_k\xi x^k+\cdots+r_0+s_kx^k+\cdots+s_0},$$  and I have no idea what to do with this. On the other hand, my intuition is that the degree of the extension of rational function fields should only depend on the degree of the extension $E\subset F,$ even regardless of any finiteness conditions.


Declaring variables inside a struct in c

I wanted to make an object oriented preprocessor to my programming language which converts my language into C (like early C++). And I want to simulate the classes with structures. And the question is: how can I declare a variable inside a struct like this:   typedef struct { //equivalent of class    int a = 5;    int (*sub)(int) = &int_sub; //function of a class, uses an external declared function } class_name;   I tried the code above but the compiler wrote this:  error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token         void (*sub)(int) = &int_sub;   I have two questions:   Can I declare a variable inside a struct? If yes, how?


Grub not loading after Windows 8 Install

My system was configured to dual boot Ubuntu 12.04.1 LTS and Windows 7. Today I got my hands on the MSDN release of Windows 8 and I installed it over my Windows 7. Now the computer just boots to Windows 8 directly without loading the GRUB screen.  So I followed the steps as suggested in: . Running this command:      ls -l /dev/disk/by-label/   gives the following output:      total 0     lrwxrwxrwx 1 root root 10 Sep 11 07:51 Entertainment -> ../../sda2     lrwxrwxrwx 1 root root 10 Sep 11 02:45 PENDRIVE -> ../../sdb1   Also fdisk -l command gives this as the output:      Disk /dev/sda: 320.1 GB, 320072933376 bytes     255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors     Units = sectors of 1 * 512 = 512 bytes     Sector size (logical/physical): 512 bytes / 512 bytes     I/O size (minimum/optimal): 512 bytes / 512 bytes     Disk identifier: 0x1246aa23         Device Boot      Start         End      Blocks   Id  System     /dev/sda1   *        2048   319582199   159790076    7  HPFS/NTFS/exFAT     /dev/sda2       319582208   602906623   141662208    7  HPFS/NTFS/exFAT     /dev/sda3       602908672   625135615    11113472   83  Linux      Disk /dev/sdb: 1939 MB, 1939865600 bytes     64 heads, 63 sectors/track, 939 cylinders, total 3788800 sectors     Units = sectors of 1 * 512 = 512 bytes     Sector size (logical/physical): 512 bytes / 512 bytes     I/O size (minimum/optimal): 512 bytes / 512 bytes     Disk identifier: 0xc3072e18         Device Boot      Start         End      Blocks   Id  System     /dev/sdb1   *        2248     3788799     1893276    c  W95 FAT32 (LBA)   So I assume that I have to run this: sudo grub-install /dev/sda3 to get GRUB up and running. But I am getting this error:      /usr/sbin/grub-probe: error: cannot find a device for /boot/grub (is /dev mounted?).   Can anyone please guide me in the right direction? The current Ubuntu installation is far too customized to my needs to lose it to a boot manager issue! Any help is much appreciated!


How did 'sanction' come to have two opposite meanings?

Sanction is an unusual ambiguous word to me. In some cases it means to approve some action, while in other cases it means to prohibit or punish some action; and there being near opposite meanings, context is especially essential for correct interpretation.  What is interesting to me is: historically, how did sanction come to capture two opposite meanings like this? The etymology seems to trace back to the single Latin word sanctio, meaning a decree. But did sanctio have strong opposing meanings or connotations like our modern word sanction? Or how and when did the divergence occur over time?


Why is $\sqrt{2\sqrt{2\sqrt{2\cdots}}} = 2$?

Why is $\sqrt{2\sqrt{2\sqrt{2\sqrt{2\sqrt{2\sqrt{2\cdots}}}}}}$ equal to 2? Does this work for other numbers?


How to find range $a_{75}$ of the term of the series $a_n=a_{n-1}+ {1 \over {a_{n-1}}} $

If $a_1=1$ and for n>1$$a_n=a_{n-1}+ {1 \over {a_{n-1}}} $$ $a_{75}$ lies between (a) (12,15) (b) (11,12) (c) (15,18)  Now , in this question, I rewrote, $a_n-a_{n-1} = {1 \over {a_{n-1}}}$, to make a telescopic type and summed the terms to get $$a_n-a_{1}= {1 \over {a_{n-1}}}+ {1 \over {a_{n-2}}}...{1 \over {a_{1}}}$$ And as ${1 \over {a_{r}}} <1$ for all r , I got $a_{75} <76$ , but it's of no help as , the upper bound is much higher. I got no further ideas , on how to solve it, please help.


Remove SKYPE HELPER popup easy way Mac OS X

I found this and tested it on MacBook. No need to open the terminal. Just do it before the Skype update to be installed.  Go to Skype prefs and check for Update. If it is available, the popup window for Skype Helper will show up. IGNORE IT FOR NOW. Go to ˇAbout Skypeˇ and when it opens THEN go to the popup and authenticate it. The green or blue button will be visible on Skype window for update. – Click on it. Done. If it asks you again for authentication, it is normal.


Where to set environment variables for all users

Apologies in advance if this question is very simplistic! I have Ubuntu 12.04. I manually installed Maven by downloading the binary tarball file and extracting it to the /opt/ folder. I then set the relevant export variables with the following commands:  export M2_HOME=/opt/apache-maven-3.0.5 export PATH=$PATH:$M2_HOME/bin   For good measure, I added these into the /home/andrew/.bashrc file (with andrew being the main user profile). However, I later realised that obviously this only set the path variables for that particular user. When I change to a secondary user, they don't detect the maven installation as they don't have the export variables.  How do I set global variables to govern something like this?


Comment owner should be notified if comment is flagged as obsolete (not otherwise)

Frequently, I suggest a post author to make a particular change.  The author makes the change, then notified me in a comment to inform me.  I delete my comment (which is now obsolete) and flag the other comment for being obsolete as well.  Then a moderator needs to come along, verify the comment is indeed obsolete, and delete it.   The moderator workload would be reduced significantly if the comment author was notified as well.  The comment author will probably have the conversation in fresh memory.


burn ubuntu to usb flash drive for install to computer

Do i have to use a disc to load ubuntu on to my pc. Can't i partition it and install a copy?  Or copy/burn to a usb drive.  Sorry new to this.


How to start and stop the Apple's Swift based productive server (program written by me) on Ubuntu linux?

I am currently developing a chat program where the Server as Ubuntu + Swift and client as JavaScript + WebSocket. Finally I reached the 0.1 version and I need to deploy it for public use.  I am renting a Virtual Cloud Server with Ubuntu 16.04 LST and I installed Swift 3 and my developed chat server as collection of .swift files. I can compile and run my chat server using swift commands. But as soon as I close my SSH connection the server stops. Yea, I can understand why.    How can I start my chat server permanently on my Virtual Cloud Server? Do I really need to make it as a service e.g. service squid start then how?   Where to start? I searched a lot in internet but could not find any example or advice. Any help? Thank you in advance.


Installing a .deb package on Arch - Is it possible?

The problem is simple - I have a .deb package and I want to install it on my Arch Linux. Is this possible? If yes, how?


Elementary central binomial coefficient estimates

How to prove that $\quad\displaystyle\frac{4^{n}}{\sqrt{4n}}<\binom{2n}{n}<\frac{4^{n}}{\sqrt{3n+1}}\quad$ for all $n$ > 1 ?     Does anyone know any better elementary estimates?   Attempt.  We have $$\frac1{2^n}\binom{2n}{n}=\prod_{k=0}^{n-1}\frac{2n-k}{2(n-k)}=\prod_{k=0}^{n-1}\left(1+\frac{k}{2(n-k)}\right).$$ Then we have $$\left(1+\frac{k}{2(n-k)}\right)>\sqrt{1+\frac{k}{n-k}}=\frac{\sqrt{n}}{\sqrt{n-k}}.$$ So maybe, for the lower bound, we have $$\frac{n^{\frac{n}{2}}}{\sqrt{n!}}=\prod_{k=0}^{n-1}\frac{\sqrt{n}}{\sqrt{n-k}}>\frac{2^n}{\sqrt{4n}}.$$ By Stirling, $n!\approx \sqrt{2\pi n}\left(\frac{n}{e}\right)^n$, so the lhs becomes $$\frac{e^{\frac{n}{2}}}{(2\pi n)^{\frac14}},$$ but this isn't $>\frac{2^n}{\sqrt{4n}}$.


Need I leave and reenter the Schengen area after my work visa expires to become a tourist?

I am an American citizen living in Poland for 6 months.  I arrived in Poland on March 1, 2016 without a work visa (i.e, on a business trip).The count toward my Schengen days began.   I received my National Long-Stay Work Visa to legally work in Poland on April 7, 2016 at the consulate in Chicago and then returned to Poland on April 10th.  The work visa expires on July 7th. I intend to travel Europe until my scheduled departure on July 31.  My question is as follows: Because I entered the Schengen area on February 1, and received my entry tourist stamp - do I need to exit and reenter the Schengen area on July 7th in order to reestablish myself as a tourist in the Schengen area?    Or, am I allowed to remain in the Schengen area from July 7th until July 31st without exiting and reentering - since I already have my Schengen entry stamp from February 1?  Please note: The Schengen Borders Code states:     Periods of stay authorised under a residence permit or a long-stay   visa shall not be taken into account in the calculation of the   duration of stay on the territory of the Member States.


Where is Stack Overflow on Area 51?  Usually, when you head to search and type something like EL&U (I wanted to check the stats), it pops up.  But when I search Stack Overflow, nothing comes up.  Why is this?


Java : How to block other program from accessing file if one program is using it?

I have 2-3 programs which can modify file but I want to block others if one program is using it. I cant use synchronization in this. Is there any other provision ?


Google Forms quiz submit ONLY when ALL correct

I would like to use Google Forms to create a simple 5 question multiple choice quiz.  When the user has selected their answers and clicked Submit I would like to display immediate feedback on the same page. They should not be able to proceed until all of the answers are correct.  So let's say they answer 1 - 4 correct but 5 is incorrect, I'd like to display message along the lines of;     Are you sure? Try again.   Once they select the correct answer for number 5, they can then proceed to submit the form and the results are recorded as normal.  Basically, I don't want to record the results until all of the questions have been answered correctly.  Is this possible?


Custom date format with jQuery validation plugin

How can I specify a custom date formate to be validated with the  for jQuery?


finding locus of z using information about $z^2$

I came across this interesting question,it is as follows: a complex number $z$ satisfies the equation $|z^2-9| + |z^2| = 41$ and we are required to find the locus of $z$ and maximum value of |z| my approach: one of the easiest but very lengthy method is $z= x +iy$ putting this into the equation, squaring both sides and equating real and imaginary parts = 0, I finally obtained $|z+3| + |z-3| = 10$ and it is easy to see that $\max (|z|) = 5$. however we wanted to know if there is an easier and more convenient method to solve this question .kindly help us out.


Prove $2^n - 1$ is NOT a prime number, when n is NOT a prime number also

I started with $n = 2k$ , $2^{2k} - 1 = (2^k - 1)(2^k + 1)$, where i go from there...


Do I need a transit Visa, if my layover at LHR airport is of 20 hours extending on to the next day

I am an Indian Citizen traveling to Montreal, Canada via LHR airport on a study permit. My layover at LHR(London-Heathrow) is 20 hours which goes to the next day. Consequently, I'll have to recollect my entire checked in baggage and get it rechecked for the next flight which binds me to go through the immigration again.   I wish to ask if I would need a transit visa or any other such document?


Random Sample vs. As Large a Sample as Possible?

I'm struggling to differentiate scenarios where you would use random sampling vs. getting as large a sample as possible. For instance, one thing I am trying to test is the notion that being in a "home" arena boosts player performance.  I have collected individual football game data for every game over the past 10 years. I have over 34000 observations of players performance during this time span. Would it have been more prudent for me to take a random sample of say, 1000 players over the past 10 years?  I just don't understand why, in the above scenario, I'd take a random sample of 1000 when I can just take all of the players performances from the past 10 years.


Take $A_{1}=\{ z: 1<|z|<R_1 \}$ and $A_{2}=\{ z: 1<|z|<R_2 \}$, wirh $R_1, R_2 > 1$. Then $A_1$ and $A_2$ are biholomorphic  if and only if $R_1= R_2$. My work: If $R_1= R_2$ then $A_1$ is biholomorphic to $A_2$ is clear. But for the converse, I asserted that if $f$ is a biholomorhism between $A_1$ and $A_2$ then $f$ maps the inner circle of radius $1$ of $A_1$ to the inner circle to the inner circle of $A_2$, I used open mapping theorem to prove this. But I cannot see anything after this.


Hamiltonian and non-Hamiltonian connected graph using the same degree sequence

I'm trying to find out if it is possible to construct a connected Hamiltonian and a connected non-Hamiltonian graph using the same degree sequence. For disconnected graphs it would be easier, I could choose a degree sequence of $(2,2,2,2,2,2)$ and have $C_6$, which has a Hamiltonian path, and two disjoint 3-cycles, which are non-Hamiltonian.  How to do it with two connected graphs?


Is it possible to launch a program in a specific language?

I'm a developer, and my primary language is French, so I use Mac OS X in French. However, I need on a regular basis to open an application in English to do support.  Right now I'm going to the International System Preferences and I put English above in the languages list, then I open the app I need to run in English. When I'm done, I switch it back to French.  This is an annoying process. Is there something else I can use, like a command-line program, to launch an application in a specific language?


Are there any chat rules on Stack Overflow?

I am just wondering about whether there are any rules about chat topics on Stack Overflow?   When I first entered the PHP chat room, people were talking about music.   Does Stack Exchange monitor this?


Irrationality of $\sum_{p\in\mathbb{P}} \frac{1}{2^{p}}$

Let $\mathbb{P}$ be the set of prime numbers, and consider $m=\displaystyle\sum_{p\in\mathbb{P}} \frac{1}{2^{p}}$. Is $m$ irrational?  In the following  , the author recalls several sufficient criteria for irrationality. When applying some of this criteria to $m$ I arrive that the condition of some of the criteria are not satisfied by means of Bertrand´s Postulate.  I found a similar result by Sándor:  Let $\lbrace a_m\rbrace$, $m\geq 1$ be a sequence of positive integers such that $$\text{lim sup}\frac{a_{m+1}}{a_1a_2\cdots a_m}=\infty \;\;\;\;\text{and}\;\;\;\;\;\;\text{lim inf}\frac{a_{m+1}}{a_m}>1$$ Then the series $\displaystyle\sum_{m} \frac{1}{a_m}$ is an irrational number.  I have yet to prove that if $f$ is a continuous function then $\text{lim sup} \;f(a_m)=f(\text{lim sup}\, a_m)$. Assuming this;  $$\text{lim inf}\; P_{m+1}-P_{m}>1$$ where $P_m$ is the $m$-th prime.  But I have trouble with $$\text{lim sup}\; P_{m+1}-\sum_{j=1}^{m}P_{j}$$ my guess is that $$\text{lim sup}\; P_{m+1}-\sum_{j=1}^{m}P_{j}\neq\infty$$ so $$\text{lim sup}\frac{2^{P_{m+1}}}{2^{P_1}\cdots 2^{P_m}}\neq\infty$$   and this theorem will result useless to tell if $m$ is irrational.   How can I prove (or disprove) that $m$ is irrational (are there any other simpler criteria)? How can I use Dirichlet criterion  or Hurwitz criterion? What is its ?    Any help is highly appreciated.      Edit: That $m$ is irrational is clear by the criteria provided in the comments, namely that if $x$ is rational then the binary representation of $x$ is periodic. The number $m$ in binary expansion has $1$ in the $P$-th position and zero elsewhere. As there are arbitrarily large gaps between primes; then the binary representation fails to be periodic.  So the question that remains unsolved is:   What is its irrationality measure?


Where is a good place to start reading about logic?

I would like to learn logic as an introductory subject. I am an undergraduate student and would appreciate any suggestions for books/articles where I can start from, also any books/articles about logical fallacies (indications regarding the level of difficulty would be helpful.)


Edit:  Recently I've been rendering a fairly geometry dense indoor scene, with one window. I was finding that even at 524 render samples, the scene was grainy, and also really REALLY slow!   I had a portal over the window and my world resolution was at 2048 (supposed to decrease grain) I was rendering with 3 diffuse, 4 glossy, 8 Transmission, 0 volume and a total of 8 max bounces and 4 min.  The render time was around 7 minutes per frame (grainy) and increasing rendertime wouldn't have been an issue, provided this wasn't an animation. However, I remember a while back, on a "speed up cycles" vid, that AO bounces was mentioned?


I am requesting a new server from our Server team. Which is better for SQL Server performance: 2 CPUs with 8 cores per CPU or 1 CPU with 16 cores?


Ubuntu 18.04 boots forever, how can I check systemctl?

I started my Ubuntu 18.04 this morning and it is booting for over 20 minutes now. I already figured out, that by pressing escape, I can get into a mode where I am able to see what is going on. It says: "failed to mount media/m-proc" see systemctl status "media-m\\x2dproc.mount" for details.   But I don't know how to do that. How can I access a terminal or something if it is still booting? Sorry, for this very basic question!


OS X El Captain - Terminal shortcut is not working

I defined a shortcut for opening a Terminal, but it isn't working.  Any ideas?


unable to dual boot ubuntu 16.04 with windows 7

I have downloaded ubuntu 16.04 from  and tried to install it alongside Windows 7.  The following are the steps i have followed:   My C: drive is partitioned with 100GB and I have unallocated 40GB of space to install ubuntu in the C: drive. While installing I don't see the Install ubuntu alongside Windows 7 option, so i have chosen "something else" option. The 40GB unallocated space is shown as unused space, it didn't let me  use this 40GB space, so I chose other partitions space and set 4GB for swap and the rest to root In the end I selected Windows load manager and continued the installation The installation successful message was displayed and upon restaring the system neither was Windows 7 on my drive nor Ubuntu.   I have tried to search some solution for this but couldn't find any.  How can I dual-boot my system correctly?


What is a "Post" defined as? Does it include all of the following, or just a subset:   Questions Answers Comments Community Wiki Questions Community Wiki Answers Chat message other things?   I'm asking in the context of Badge definitions like "Edited 100 posts that were inactive for 6 months".


Lagrangian mechanics vs Hamiltonian mechanics

First of all, what are the differences between these two:  and ?   And secondly, do I need to learn both in order to study  and ?


How to validate phone numbers using regex

I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:   1-234-567-8901 1-234-567-8901 x1234 1-234-567-8901 ext1234 1 (234) 567-8901 1.234.567.8901 1/234/567/8901 12345678901   I'll answer with my current attempt, but I'm hoping somebody has something better and/or more elegant.


How to \citeauthor without switching to \bibliographystyle{plainnat}?

I know there are a few questions regarding this, but I couldn't find the solution specifically for such problem: how do I \citeauthor{}, but keep the citing style that I want (I use \bibliographystyle{ieeetr}).  My .tex file looks something like this:  \usepackage{natbib} \usepackage[utf8]{inputenc} \usepackage[english]{babel}  \citeauthor{smith}  \begin{document}     \bibliographystyle{ieeetr}     \bibliography{References} \end{document}   And .bib file:  @Article{smth, author ="Smith, Anton", title  ="The title", year  ="2019", journal = "Some journal", volume  ="1"}   I get the (author ?) instead of Anton.  So how would I keep my citing style but use \citeauthor?


I successfully mounted a Windows share folder by editing /etc/fstab. Now I'm trying to rsync Ubuntu folders to the mounted Windows share folder in Ubuntu system.   I'm using the command rsync -av --delete /sourceFolder/ /Mounted cifs format windows share folder/. Everything works fine without the option for the permissions.  The copied file permissions follow the uid, gid, dir_mode options in /etc/fstab file, not the rsync -a option.   Is there a workaround to preserve the file permissions when backing up? Or is my approach wrong fundamentally?


I've got a '70s road bike with shift cables which work quite well and so I see no immediate reason to replace them, but the cable ends were not crimped with end caps and so they've frayed out to ridiculous levels. However, I can't just cut off the frayed end and re-crimp it because then my cables would be too short; Is there any way for me to "save" these cables and avoid having to re-cable the bike? Is there no way to "de-fray" the ends even if it doesn't leave them in "pre-frayed" condition?


I was watching , and came across a sentence in which they form the plural of "no" with an apostrophe:     There are a thousand no's for every yes   But shouldn't it be nos?  Or is this just for the sake of readability? Like,     We need to dot the i's and cross the t's   Edit: Apparently this has been discussed .


Why do we refer to morning, afternoon and evening as 'in the morning', 'in the afternoon', 'in the evening' but not 'in the night' instead we say 'at night.'


How do I get the Broadcom STA wireless driver to load in Ubuntu 12.04? This is on an Inspiron 1721

When I try to activate it a jockey.log is created.  This is the internal wireless that worked in Ubuntu 11.10.  Doesn't now that I upgraded to Ubuntu 12.04.  I'm using a USB wi-fi for now.


How can I see the output of the Visual C++ preprocessor?

I want to see the output of the Visual C++ Preprocessor on my code -- i.e., the equivalent of gcc -E. For the life of me, I cannot find the relevant compiler switch. How do I accomplish this?


How can I install Ubuntu encrypted with LUKS with dual-boot?

The Ubuntu installation disk has an option to install Ubuntu encrypted using LUKS. However, there is no option to perform an encrypted installation along-side existing partitions for a dual-boot scenario.  How can I install Ubuntu encrypted alongside another partition from the live disk?


Positive integer solutions to $3x^4-3x^2+1=y^2$

I need to solve $$3x^4-3x^2+1=y^2$$ over the positive integers.  I've tried setting $x^2=t$ and considering the discriminant. I've tried rewriting into $3(2x^2-1)^2+1=(2y)^2$. I've tried substituting $x=3a\pm 1$. The problem would be easy by bounding if the leading coefficient is a perfect square.


I have a basic tex file and a bibliography which is exported from Mendeley  However, when I want to cite in the author-year style, I get the error:   Package natbib Error: Bibliography not compatible with author-year citations. (natbib) Press <return> to continue in numerical citation style.  Any clue what's wrong?  Minimum working example:  \documentclass[letterpaper, 10pt]{article}  \usepackage[authoryear]{natbib} \usepackage{lipsum}  \begin{document}  \lipsum[1-4] \nocite{*}  \bibliographystyle{apalike} \bibliography{articles}  \end{document}    A snippet of my .bib library:  @article{shortcode, author = {Lastname, Firstname}, file = {:/path/to/file.pdf:pdf}, journal = {Journal name}, number = {xx}, pages = {x--xx}, title = {Title}, volume = {xx}, year = {xxxx}     }


Recent graduate with new job: Choose Roth 401(k), or traditional 401(k)?

I just graduated, and I'm starting a new job soon. My employer has pretty good policy for matching 401(k) contributions, so I want to invest as much as possible, especially during this first year.  My question is: should I invest in a traditional 401(k), a Roth 401(k), or some combination of the two? On the one hand, tax rates may be much higher when I retire, and I might be in a higher tax bracket, so a Roth 401(k) would be good. On the other hand, I might be in a lower tax bracket when I retire, so a traditional 401(k) might be better. It's hard to know where I will stand in 30 years.  Is this the same trade-off as with a traditional / Roth IRA, or is there any other tax difference I should know about?


How many elements does the ring $ℤ[X]/(X^2-3,2X-4)$ have? Describe the structure of this ring.

I'm making exercises to prepare for my ring theory exam:     How many elements does the ring $ℤ[X]/(X^2-3,2X-4)$ have? Describe the   structure of the this ring.   I find it always difficult if the ideal is generated by two elements.   I thought about someting like this. $X=2$ and $X^2=3$. Therefore $4=3$ therefore $1=0$. As $2=1$ then $X=0$. And then everyting seems to become $0$.   I'm not sure if I'm allowed to see it this way, but this is the first thing that comes to my mind.


How do I find the controls after adding in an object?

Where else can I find this after adding in an object?


Ubuntu Software Center buy button doesn't work

I just bought the new Humble Bundle, and I want to play the games on Ubuntu, but whenever I click on "Download with Ubuntu" the software center comes up on the page of the game, but whenever I click on the buy button it comes up with this message: Unable to load page     Problem occurred while loading the URL    Cannot resolve proxy hostname   ()   And so I can't buy the games. Could someone please help me? Thank you for reading, ~Joel


I will start studying "measure theory" in a self-taught way. I would like to know if you could recommend some books? I was thinking of starting to study with: "Kesavan, S. (2019). Measure and integration. (First Edition). Singapore " My study methodology is a theoretical book + a book with many problems to solve. Thanks so much!


Expected value of two successive heads or tails (stuck on computation)

Problem: This is problem 33 of section 2.6 (conditioning) in Bertsekas, Tsitsiklis intro to probability text.  We are given that a coin has probability of heads equal to p and tails equal to q and it is tossed successively and independently until a head comes twice in a row or a tail comes twice in a row. What isthe expected value of the number of tosses?  Solution:  Let $X$ be a random value that tracks the number of tosses. In addition, let $H_k, T_k$ be the event that a head or tail comes up on the kth flip respectively. The solution I am looking at involves using total expectation theorem.  I outline the following steps in the solution.  We can partition the sample space into $H_1$ and $T_1$, allowing us to invoke the total expectation theorem. Hence,  $E[X] = pE[X|H_1] + qE[X|T_1]$  Again by total expectation theorem, we can utilize another partition to obtain  $E[X|H_1] = pE[X|H_1,H_2] + qE[X|H_1,T_2] = 2p + q(1 + E[X|T_1])$  $E[X|T_1] = qE[X|T_1,T_2] + pE[X|T_1,H_2] = 2q + p(1+E[X|H_1])$  Stuck: The solution follows up by saying that we can combine the above two relations and use the fact that p+q = 1 to obtain  $E[X|T_1] = \frac{2+p^2}{1-pq} , E[X|H_1] = \frac{2+q^2}{1-pq}$  I have been staring at this for a while now, but I cannot seem to see the steps of the computation. I'd be very grateful if someone could fill in the details regarding the computation. Thank you.


It is possible to define coordinates using trigonometric ratios with the construction of a geometric figure, as in the attached example but it does not work for me.  \documentclass{book} \usepackage{tikz}  \begin{document}  \begin{tikzpicture}     \draw (0,0) -- (1,3);     \draw (0,0) -- ({cos(30)},{tan(45)}); \end{tikzpicture}  \end{document}


When posting an xkcd link in chat, it doesn't get oneboxed when using the https version of the URI:  vs  The first one gets oneboxed, but the latter just displays the link.


Let R be a ring. Prove that if $x^2=x$ for each $x \in R$, then R is a commutative ring.   Ok, so I'm just looking for some confirmation that I'm doing this correctly.  If we suppose $x,y \in R$ Let's consider $(x+y)^2$,  Then $(x+y)^2 = x^2+xy+yx+y^2$ but $x^2=x$ and $y^2=y$   We can also see that for all $x \in R, x=-x$  So, $(x+y)^2= x+xy+yx+y$  Also, by our given  $(x+y)^2=(x+y)$ so   $x+y =x+xy+yx+y$, Solving this algebraicly gives us $-yx=xy$ but since $(-yx)^2=(yx)$,   We have, $yx=xy$, Therefore R is commutative. Does that about wrap it up?


Different font sizes in mobile site and responsive website on mobile

This is how post looks in responsive design on mobile  And that's how in mobile site  The font on responsive design looks as small as what subscript and superscript fonts used to look like. Can we have little bigger fonts? I'm using Firefox on Android 10.


Precise meaning of and comparison between influential point, high leverage point, and outlier?

Influential observations are those observations that have a relatively large effect on the regression model's predictions.        Leverage points are those observations, if any, made at extreme or outlying values of the independent variables such that the lack of neighboring observations means that the fitted regression model will pass close to that particular observation.   Why is the following comparison      Although an influential point will typically have high leverage, a high leverage point is not necessarily an influential point.


Can you save an image with a white background as a transparent image out of Photoshop?

I'm having issues with artwork I would like to use for my website. Unfortunately, the artwork I have came included with a white background behind it. I realize I can manually remove the white background using tools like the Magic Wand in Photoshop, but I've found that the edges of the artwork lose their sharpness. Is there anyway in Photoshop to just save an image out where the white background is picked up as the part of the artwork that is suppose to be transparent?


Abuse of "This edit is too minor ..." hinders link and spelling correction

Why do reviewer block improvements of tag wikis, which just fix spelling and broken links? Is it more important to have larger edits than better content? And why is there no flag option to report such cases?   Example:    If the reason is that some reviewers are bored accepting smaller fixes, what could be done to ensure that improvements are not stopped by the moods of these community members?


Subscription bug: receiving emails for questions with tags that do not match my filter

As of yesterday, I've started receiving emails for a subscription that do not match my filter.  My filter:  (shows items with tags  or  across all StackExchange sites)  Time of first email: 14 March 2017 at 10:22 UTC  Subject of first email: New questions in Smalltalk Filter filter for Mar 14 - Stack Exchange  Items in first email:        These are in no way related to my filter (tags include  and ). I've also checked that none of the tags have a synonym that would explain the issue.  There do not seem to be existing recent questions relating to my topic (the closed one I saw was about  from a while ago). I thought the first email was a one-off mistake, until I received another email with three more items that don't match that filter today so I thought I'd better report it.  The filter has been working for months if not years - please fix subscription emails, and let me know if any further information or forwarding the emails to someone would be helpful in debugging.


I want to write a code which gives me all the possible combinations of n elements in a k length k>n.The issue with this code is that i run out of memory quite fast.I was wondering if someone knew how to fix this with generators.I don't want to get all the possible combinations of a list elements. I want to get all the combinations of the elements in a certain length. Thanks.  def allstrings(alphabet, length):     """Find the list of all strings of 'alphabet' of length 'length'"""      if length == 0: return []      c = [[a] for a in alphabet[:]]     if length == 1: return c      c = [[x,y] for x in alphabet for y in alphabet]     if length == 2: return c      for l in range(2, length):         c = [[x]+y for x in alphabet for y in c]      return c  if __name__ == "__main__":     for p in allstrings(['a','b','c'],4):         print (p)


I want to compare the current date with the day before and the day next date. Here is how I get current date and upload to firestore: java.util.Date utilDate = new java.util.Date(); java.sql.Date sqlDate = new java.sql.Date(utilDate.getTime());  Map<String, Object> map = new HashMap<>(); map.put("time", sqlDate);  db.collection("users").document(user.getUid()).update(map);   Firestore screenshot:  To get date from firestore db.collection("users")                 .document(user.getUid())                 .get()                 .addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {             @Override             public void onComplete(@NonNull Task<DocumentSnapshot> task) {                 if (task.isSuccessful()) {                     DocumentSnapshot document = task.getResult();                     assert document != null;                     if (document.exists()) {                         Date userDate = document.getDate("time");                                       }                 }             }         });  Format of date Sun Apr 26 17:59:05 GMT+05:00 2020 I want to get the next date and the previous date. Something like below:  Previous date: Sat Apr 25 17:59:05 GMT+05:00 2020 Today date: Sun Apr 26 17:59:05 GMT+05:00 2020 Next date: Mon Apr 27 17:59:05 GMT+05:00 2020  Any suggest me how to get previous and next date from firestore using current date(uploaded to firebase).


I want to prove the statement that completion of a ring w.r.t. maximal ideal is local. Let $\mathfrak{m}$ be a maximal ideal of a ring $A$, and $\hat{A}$ be an $\mathfrak{m}$-adic completion of $A$. I know that my statement can be verified if an element $$X:=1+\Sigma_{i\geq1} x_i $$in $\hat{A}$is unit in $\hat{A}$ ($x_i \in \mathfrak{m}^i$). Using the geometric series, we should verify that $$1/X = 1/\{{1-(1-X)}\} = \Sigma(1-X)^i$$ is an element in $\hat{A}$. But I don't know why this element is in $\hat{A}$, because even though a general element in $\hat{A}$ can be represented by infinite series with each term lies in $\mathfrak{m}^i$, but $$1/X = \Sigma(1-X)^i = 1-(x_1+x_2+\cdots)+(x_1+x_2+\cdots)^2-\cdots $$ contains infinite operation "in $\mathfrak{m}^i$", which is absurd. Can anyone tell me why we can say that $1/X$ is in $\hat{A}$?


I want to make some notification to user every day at the same time:     any_hour:50    And I wrote to crontab -e:     50 * * * * DISPLAY=:0 /usr/bin/notify-send -i /home/nazar/Pictures/icons/download_manager.png "Break" "Make a break for 10 min"   When I run it from console:     notify-send -i /home/nazar/Pictures/icons/download_manager.png "Break" "Make a break for 10 min"   I have desired result:    But when I working at PC I don't have this output at desired time.  Any suggestion?  UPDATE:  I updated cron job to:     50 * * * * DISPLAY=:0 /usr/bin/notify-send -i /home/nazar/Pictures/icons/download_manager.png "Work Break" "Make a break for 10 min, please!" 2>&1 | tee -a cron.out   After executing it file was created but it is empty.   I tried to update my cron job as follows:  00 13 * * *  /home/nazar/Documents/scripts/lunch_break_job.sh 50 *  * * *  /home/nazar/Documents/scripts/pc_break.sh  # just cron test */1  *  * * *  /home/nazar/Documents/scripts/cron_job_test.sh   and cron_job_test.sh looks:  #!/bin/bash  export DISPLAY=0.0 export XAUTHORITY=/home/matrix/.Xauthority  if [ -r "$HOME/.dbus/Xdbus" ]; then   . "$HOME/.dbus/Xdbus" fi  /usr/bin/notify-send "hello"   when I run this script from terminal:     ./cron_job_test.sh    I get notification correctly. But crontab doesn't run this script every minute.  Why does this happen? And how to resolve execution of this cron job?


How do I tell a script to wait for a process to start accepting requests on a port?

I need a command that will wait for a process to start accepting requests on a specific port.    Is there something in linux that does that?  while (checkAlive -host localhost -port 13000 == false)   do some waiting  ...


Adjoint representation, standard basis - $\mathfrak{sl}(2)$ and Killing form

Let $L$ be the Lie algebra $\mathfrak{sl}_{2}$ (char ${F}$ $\neq$ 2).   Take as standard basis for $L$ the three matrices:     $x=\begin{pmatrix} 0&1\\0&0\end{pmatrix}, y= \begin{pmatrix} 0&0\\1&0\end{pmatrix}$ and $h=\begin{pmatrix} 1&0\\0&-1\end{pmatrix}$.   When using the adjoint representation, the three matrices become:  $ad_{x}=\begin{pmatrix} 0&-2&0\\0&0&1\\0&0&0\end{pmatrix}, ad_{y}=\begin{pmatrix} 0&0&0\\-1&0&0\\0&2&0\end{pmatrix}$ and $ad_{h}=\begin{pmatrix} 2&0&0\\0&0&0\\0&0&-2\end{pmatrix}$.   Therefore $\kappa$  (the Killing form) has matrix  $\begin{pmatrix} 0&0&4\\0&8&0\\4&0&0\end{pmatrix}$.  Can someone explain how the adjoint and further, the Killing form, are calculated here?  I see now how to calculate the adjoint and the Killing form.   $ad_{x}(x)$ = $[xx -xx] = 0$  $ad_{x}(h) = [xh - hx]$ = $\begin{pmatrix} 0&1\\0&0\end{pmatrix} \times \begin{pmatrix} 1&0\\0&-1\end{pmatrix}$ - $\begin{pmatrix} 1&0\\0&-1\end{pmatrix}\times\begin{pmatrix} 0&1\\0&0\end{pmatrix}$ = $\begin{pmatrix} 0&-2\\0&0\end{pmatrix} = -2x$  $ad_{x}(y) = [xy - yx]$ = $\begin{pmatrix} 0&1\\0&0\end{pmatrix} \times \begin{pmatrix} 0&0\\1&0\end{pmatrix}$ - $\begin{pmatrix} 0&0\\-1&0\end{pmatrix}\times\begin{pmatrix} 0&1\\0&0\end{pmatrix}$ = $\begin{pmatrix} 1&0\\0&-1\end{pmatrix} = h$  Then, these become the three columns of $ad_{x}$. Do the same for $y$ and $h$.   For the Killing form,   $\kappa(x,x) = tr(ad_{x}ad_{x})$ $\kappa(x,h) = tr(ad_{x}ad_{h})$ $\kappa(x,y) = tr(ad_{x}ad_{y})$  $tr(ad_{x}ad_{x}) =tr(\begin{pmatrix} 0&-2&0\\0&0&1\\0&0&0\end{pmatrix}\begin{pmatrix} 0&-2&0\\0&0&1\\0&0&0\end{pmatrix})= tr(\begin{pmatrix} 0&&\\&0&\\&&0\end{pmatrix}) = 0$.  $tr(ad_{x}ad_{h}) =tr(\begin{pmatrix} 0&-2&0\\0&0&1\\0&0&0\end{pmatrix}\begin{pmatrix} 2&0&0\\0&0&0\\0&0&-2\end{pmatrix})= tr(\begin{pmatrix} 0&&\\&0&\\&&0\end{pmatrix}) = 0$.  $tr(ad_{x}ad_{y}) =tr(\begin{pmatrix} 0&-2&0\\0&0&1\\0&0&0\end{pmatrix}\begin{pmatrix} 0&0&0\\-1&0&0\\0&2&0\end{pmatrix})= tr(\begin{pmatrix} 2&&\\&2&\\&&0\end{pmatrix}) = 4$.  Thus, these three entries are the entries for the first row.  Repeat for $h$ and $y$.


Break a Foreach when counter reaches 5 | PHP

I'm trying to stop the foreach when $counter reaches 5 , but i can't , i've tried to change the "break;" place , my try/catch inside the if,  but with no success, i keep getting 103 games(image) and I only want 5 .........     $leagues= $api->getLeagueEntries("RANKED_SOLO_5x5", "Gold", 'I');           $counter = 0;           foreach ($leagues as $t=> $op) {          if (++$counter < 5) {                      }                 try {                     $account_id = $api->getSummoner($op->summonerId);                     $date = time();                     $ab = $api->getMatchlistByAccount($account_id->accountId,  "420", null, null, $date, NULL, null, null, null);                               echo "<pre>" ; var_dump($ab);   echo "<pre>" ;                       break;                 } catch (Exception $e) { }             }


Does anyone know how to do a clean install of Ubuntu on this chromebook? By this I mean that I want to totally remove ChromeOS and only use Ubuntu, I don't want to use Crubuntu. Just a link to a guide would be fine, thanks! :)


Ubuntu Software apps cannot access non-system disks

I'm using Ubuntu 18.04.2 x64 installed on an internal SSD. The PC also has internal and external HDDs.  The problem is that any application that has been installed from Ubuntu Software doesn't have access to those HDDs.   E.g., I cannot save any file from Opera to them, and Inkscape cannot open/save the files from/to those HDDs.   I've tried changing the apps' permissions in Ubuntu Software itself but they are never saved.  How can I overcome such issues?


soul dropping some accented letters from the end of words

I'm using soul to letterspace headings in a Hungarian document and compiling it with lualatex.  For some reason soul drops some of the accented letters at the end of a word, but not all. In the example below, only ő and ű are affected:  \documentclass{minimal} \usepackage{fontspec} \setmainfont[Ligatures = TeX]{TeX Gyre Pagella} \usepackage{soul} \begin{document} \noindent \so{áll llá ÁLL LLÁ}\\ \so{íll llí ÍLL LLÍ}\\ \so{űll llű ŰLL LLŰ}\\ \so{őll llő ŐLL LLŐ}\\ \so{üll llü ÜLL LLÜ}\\ \so{öll llö ÖLL LLÖ}\\ \so{úll llú ÚLL LLÚ}\\ \so{óll lló ÓLL LLÓ}\\ \so{éll llé ÉLL LLÉ} \end{document}


A person contracts a biological pathogen that is collectively intelligent, forming a symbiosis

Trying to identify a story where:   A person (man/woman?) somehow contracts a pathogen that leans to communicate with him. The pathogen is something like an amoeba. the person is hunted by others trying to take or contain the pathogen. the pathogen is intelligent and can communicate with the person. they become an enhanced symbiotic organism, and use the skills to avoid capture.


How can I typeset the equality symbol ::= used in the definition of syntactic categories of BNF grammars?  I would like to use it both in typewriter font (using \texttt) and in math mode.  Both \texttt{::=} and $::=$ (or $:\coloneqq$) are ugly.


Java - Implementing a Linked List from scratch

In Java, I have to create a linked list from scratch (not allowed to use the LinkedList import).  I have been provided with this code as support:  public class Link<E> {     private E e; // the element contained in this linked list     private Link<E> next; // the next element of the linked list      public Link(E e, Link<E> n) {         this.e = e;         this.next = n;     }      public Link(E e) {         this.next = null;         this.e = e;     }      /**      * Method to set the element      */     public void setElement(E e) {         this.e = e;     }      /**      * Method to set the next linked list element      */     public void setNext(Link<E> e) {         this.next = e;     }      /**      * Method to get the element.      */     public E getElement() {         return this.e;     }      /**      * Method to get the next linked list element      */     public Link<E> getNext() {         return this.next;     } }   With this code provided, I have to create a LinkedList with the following methods:   Add objects at a specific index; addAt(data, index) Retrieve objects using the index; getAt(index i)   I have come up with the following code:  import java.util.*;  public class LinkedList<E> {      private Link<E> head, tail;     protected long size;      public LinkedList() {         super();         this.head = null;         this.tail = null;         this.size = 0;     }      public void addAt(Object data, int index) {          Link<E> temp = new Link(data);          Link<E> current = head;          if (data == null) {             throw new NoSuchElementException();         }          if (current != null) {             // crawl to the requested index or the last element in the list, whichever comes             // first             for (int i = 0; i < index && current.getNext() != null; i++) {                 current = current.getNext();             }         }          // set the new node's next-node reference to this node's next-node reference         temp.setNext(current.getNext());          // now set this node's next-node reference to the new node         current.setNext(temp);      }      public Object get(int index)     // returns the element at the specified position in this list.     {         // index must be 1 or higher         if (index < 0)             return null;         Link<E> current = null;         if (head != null) {             current = head.getNext();             for (int i = 0; i < index; i++) {                 if (current.getNext() == null)                     return null;                  current = current.getNext();             }             return current.getElement();         }         return current;      }  }   However, I get a NullPointerException which I can't wrap my head around at:   temp.setNext(current.getNext());    Besides the NPE, I have another question: would there be a cleaner way to implement a LinkedList from scratch?


I added a line  xrandr --output HDMI1 --rotate right  in /etc/rc.local to rotate one of my monitors at startup, but it doesn't work (


Got/Gotten- Which one should I use and is there a trick?


Let $C$ be an axiomatisable class of structures for some given first-order signature, i.e. there is a set $T$ of sentences whose models are exactly the members of $C$.  Apparently it follows from the compactness theorem that: If $C$ contains arbitrarily large finite structures then it must contain an infinite structure.   Can someone explain this result? The compactness theorem tells me that $T$ has a model if each finite subset of $T$ has a model but I don't see how this relates to the size of structures in $C$.


I have forgotten my authentication password.Ubuntu 14.4

I have followed instructions found on line ie GRUB, recovery mode, etc but I get stuck at the point of typing in a new password as that screen is read only.  I have then followed more instructions to set to read/write ie - mount -rw -o remount/...... this did not work.  Help please.  I would need step by step instructions as I don't understand most of the terminology.  Thanks  Thanks for the responses.  The problem is that when I get to reset 'read only' to 'read write' with the command given it just does not work. I don't get an error it just reverts to the line as before I entered the read/write command.  Thank you Muru but it won't accept the remount command.


How can I install the terminal emulator from elementary OS Freya on ubuntu 15.04 Vivid?

I like the elementary OS terminal emulator quite a lot and I'd love to have it on my main machine, which is running Ubuntu 15.04 Vivid.  Is it possible without compromising Ubuntu's stability?


How to search for a folder or file in parent folders

I tried to search for a folder in its parent folders instead of its child sub-folders (usually any search bash command will do). I need to know whether any reverse alternative for any search commands actually exists.


How to automatically hyphenate within \texttt?

This question was phrased as a bug report for LaTeX and I thought it would be helpful to be presented here (including an answer).  The person had a lot of "common words" in typewriter font sprinkled around his text and he was surprised that this text would not automatically hyphenate and he had to manually insert \- to mark hypenation points.


I want to make a PhD thesis but my qualifications are bad .. do I have any chance

This is my question:  I want to do a thesis but my qualifications are bad so I do not know if I will be able to find a thesis advisor.  What can I do? Are there universities who do not care about qualifications if you have some ideas?  I can propose some ideas for thesis (in .pdf) but do not know if they will be enough.


Is $\mathbb E(\mathbb E(X\mid \mathcal F) \mid \mathcal G) = \mathbb E(X \mid \mathcal F\cap \mathcal G)$?

A proper wanna-be generalization of the "tower property" of conditional expectations would be:  $$\mathbb E(\mathbb E(X\mid \mathcal F) \mid \mathcal G) = \mathbb E(X \mid \mathcal F\cap \mathcal G)$$  regardless of, whether the $\sigma$-algebras $\mathcal F$ and $\mathcal G$ can be compared with $\subseteq$.  My guess is this is false. What is a counterexample? (or proof?)


What is a StackOverflowError, what causes it, and how should I deal with them?


If $A^2=0$, then show that $I−A$ is invertible.  I am getting nowhere that leads me to the hint: $I+A$.


How to get rid of the page break after the sections?

I am very new to LaTeX and really only know how to use templates. I am making a LaTeX with the document class article that uses \include{} to put in the various sections in and it will start a new page after each section. I want to get rid of that. How do I do that?  This is my code  \documentclass[oneside]{article} % %% Based on a TeXnicCenter-Template by Gyorgy SZEIDL. \usepackage{amssymb} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{graphicx} \usepackage{mathrsfs} \usepackage{wrapfig} \usepackage{lipsum} \usepackage[margin=0.9in]{geometry} \usepackage[affil-it]{authblk}     \begin{document} \title{Awesome Title} \author{student} \affil{University} \author{studen} \affil{university} \author{PI} \affil{University} \maketitle \begin{abstract} words \end{abstract}  \include{intro} \include{model} \nopagebreak \include{vaccReg} \include{results} \include{conclusion} \appendix \include{AppendixModel} \include{methods}  \bibliography{MeaslesBibliography} \bibliographystyle{apalike}  \end{document}   I hope this is enough information


The Interpretation of $|\psi|^2$ and the No-Clone Theorem

The standard interpretation of $|\psi|^2$ is taken as the probability density of the wave-function collapsing in the given infinitesimal small region. The way this probability is interpreted (at least in the text-book by Griffiths) is that if I prepare a large number of identical states and then perform a measurement on each of them then the probability associated with $|\psi|^2$ actually represents the statistical results of the measurements made (individually) on all these wave-functions of the entire ensemble. This seems like a good enough argument to accept $|\psi|^2$ as the probability density of the wave-function collapsing in a given infinitesimal small region even if I have only one wave-function.  But the  suggests that it is fundamentally impossible to make two states that are completely identical and thus, to my understanding, it makes absolutely no sense to talk about those identical wave-functions that were used to project $|\psi|^2$ as the probability density.  Put in other words, if I can't replicate a wave-function at all then how do I confirm in my laboratory that the probabilities obtained by $|\psi|^2$ actually represents the likely-hood of the collapse happening in a given region?   Edit Is it the catch that the No-Clone Theorem suggests only that a given state can't be evolved to a state identical to another state and it allows the two states being identical if they are so from eternity?


How does Feature Scaling help Gradient Descent?

I am following deep learning.ai's videos on Coursera. I have a couple of questions about feature scaling using the formula:  $$ (x - \mu)/ \sigma $$  Edit: There are similar questions which deal with the same topic, but none of them answer these questions in particular. I have highlighted the question in bold to emphasise.  1.) What is the use of subtracting the mean? My understanding is that dividing by the SD scales the features and subtracting the mean centres the data around zero. But why is centring the data around zero useful?  2.) I understand that the values of mean and SD should be consistent across training and test sets. Are $ \mu $ and $ \sigma $ calculated on the entire dataset(train and test together)? Or are the values calculated on the train set and then applied to the test set?  Thanks in advance.


Young Adult Fantasy about children living with an elderly woman and learning magic related to their skills

I'm trying to track down a book I borrowed form a library in the UK around 2000/2001. Here are the details I remember:  The story is set in a fantasy world; no connections to our world The main characters are four children who have no connection initially but are brought together over the course of the story The children are all taken in by an elderly woman who starts to develop their magical skills Each of the children has a different type of magic: one is nature, another is related to fabric or clothes A significant plot point is the girl with nature based magic takes in and rears a baby bird. A lot of time is spent discussing how much work it will be to care for this animal The title may have something to do with weaving or thread but I might be confusing this with another story


Consequences of losing Hong kong landing slip

I have lost my Hong Kong landing slip. What will happen when I exit Hong Kong? Can I get a visa for mainland China without the landing slip? Can the Hong Kong landing slip be replaced?


I bought a one-pound tube of pork sausage. After opening it, and putting it in a zip-lock bag (weeks before the sell-by date), the remainder turned gray on the outside the next day. I understand that turning gray is normal and does not necessarily mean that meat has gone bad. I am not confident in my ability to identify meat that has gone bad by smell.  When should I throw it away? Should I just cook it all at once, and keep the cooked product if I don't want to eat it all? (I trust cooked food in the fridge for a longer time than it is likely to take me to eat all of it, so this is a viable possibility, but inconvenient.) Should I be splitting it into smaller portions and freezing it?


Difference between logical implication and AND and when to use what

I am confused between logical implication and local and. When to use what. Logically i can make sense on which to use but intuitively i am not able to. For ex., Not All that glitters is gold Diagrametric representation: Glitters set is disjoint with gold set It can be expressed as $\neg \forall x \{ glitters(x) \implies gold(x)\} \equiv \exists x \{ glitters(x) \land  \neg gold(x)\}$ But if i think 2 disjoint sets. I think i can write it as $\forall x \{ glitters(x) \land \neg gold(x) \}$ or $\exists x \{ glitters(x) \land \neg gold(x) \}$  or $\forall x \{ \neg glitters(x) \land  gold(x) \}$ or $\exists x \{ \neg glitters(x) \land  gold(x) \}$ . But if i use logical implication formulae , these seem to be wrong. But the above representations look like 2 disjoint sets right? I am not able to grasp the differences between the above.


Covering an 8x8 board with L and O Tetromino

I solved a puzzle about proving that if a rectangular board can be covered by L-Tetrominoes then the number of squares must be a multiple of 8. I based the solution on a colored board (like a chessboard) and 2 types of L-Tetrominoes Either:  _____ |BLACK|     |WHITE|_______   |BLACK| WHITE| --------------  or  _____ |WHITE|     |BLACK|_______   |WHITE|BLACK | --------------    The follow up puzzle is: Prove that an 8x8 board can not be covered with 1 O-Tetromino and 15 L-Tetrominoes. The O-Tetromino is:  ____ ____ |    |    |     |----+----|     |____|____|      I thought of the following proof: If I use 1 O-Tetromino then there remains a board of 8x8-4 = 60 squares. 60 is not a multiple of 8 and we have already shown that for a board to be covered with L-Tetrominoes must be a multiple of 8. Therefore the 8x8 board can not be covered with 1 O-Tetromino and 15 L-Tetrominoes Is this proof valid? It seems to informal also in relation to the approach I followed to prove that the L-Tetrominoes cover a board of x8 If it is not, then how can I prove it?


How do I set up the sources.list to select kernel packages from a local repository?

I am creating a local repository which will contain all the debians (debs) for Ubuntu. It will also contain kernel debians for 2 different branches like say 1.1 and 2.1  I have created a single empty debian package, say test-package which contains information for all other dependent debians from same repo. Currently it has information on kernel 1.1.  Structure of local repo is as follows:  The folder dists/xenial/release/test-package contains folders k, l, m, v which contain debs.  The folders binary-amd64 and binary-i386 are also created which contains Packages file for corresponding architectures.  Steps performed on the client machine:   Adding URL in sources.list Running command apt-get install test-package   My issue is:  How can I inform sources.list to pick specific kernel installation and its corresponding debians (debs) available from local repo. i.e. it should install either 1.1 or 2.1 kernel.  TIA


How to generate the following symbol(s) in book class?

Is it possible to generate symbol(s) like to following in book-class     The image has been produced by the following code,  \documentclass{article} \usepackage{kpfonts}  \begin{document}  $\varprod_{i=1}^n A_i$  $$\varprod_{i=1}^n A_i$$  \end{document}   but I don't want to use kpfonts.


Login as other user setting for other profile except System Adminsitrator

If a user is setup as System Administrator profile, the user can login as other user. However, is there any option that I can enable this function for other profile except System Administrator because I don't want to give them other System Administrator permission access?  In the past as I remember in summer 12, there's an option called "managing user permission" which allow me to disable or enable the profile to login as other user. But I don't see this anymore.


I have a minecraft image as a reference image in my blend file, but it automatically blurs it.  I know how to fix this with materials, but not with ref images.  How do I fix this?


How can I save a command output to a file in real-time?  For example, if my command is python log.py where log.py contains:  import time print('testing') time.sleep(100) # sleeping for 100 seconds   and if I save the output with python log.py | tee command.log or python log.py > command.log, the command.log file typically won't contain the output of python log.py, namely testing, until it finishes executing. Instead, I don't want to have to wait ~100 seconds to be able to view testing in command.log.


Ubuntu desktop suddenly points to home folder

As of now, my desktop has begun showing the contents of my home folder (~) instead of the contents of ~/desktop. I must have changed something, but I have no idea what, or what I was doing exactly when it happened.  How do I re-point gnome to the right folder?  I'm running Ubuntu 11.04.


I accidentally made a /kill @p command repeat. Can I fix it?

On my server, I accidentally used a command block to make /kill @p repeat over and over.   I don't know the coordinate of the command block, and I don't have McEdit. I am using PuTTY to connect to the server.   Is there any way I can disable the command blocks, and if so, how?


How do attack rolls and criticals affect a 2d6 vs 1d12 damage roll?

For example, given the probability distribution between two similar weapons:     D&D 5E Weapons - Basic Rules pg.48:      Damage Discrete Distribution - :      Its evident that Greatsword is more reliable and has a higher mean damage roll.  But how does this change if we factor in an attack roll with some chance to hit? Do critical hits make the Greataxe preferential?


The question is about the following library, which is expected to try to become part of boost.    Trying to compile with this makefile:   CC = g++ CFLAGS = -c -O2 -Wall -std=c++1y -DHAVE_CSTDDEF  -I    ./stacktrace/include -lunwind -DBOOST_STACKTRACE_USE_LIBUNWIND LDFLAGS = -L ./stacktrace/include -lunwind -DBOOST_STACKTRACE_USE_LIBUNWIND SOURCES = $(shell find ./src -name '*.cpp') OBJECTS = $(SOURCES:.cpp=.o) EXECUTABLE = main  all: $(SOURCES) $(EXECUTABLE)  $(EXECUTABLE) : $(OBJECTS)  $(CC) $(LDFLAGS) $(OBJECTS) -o $@ -pthread -lipopt   .cpp.o:  $(CC) $(CFLAGS) $< -o $@ -pthread -lipopt    Here is the output:  g++ -c -O2 -Wall -std=c++1y -DHAVE_CSTDDEF  -I ./stacktrace/include -lunwind -DBOOST_STACKTRACE_USE_LIBUNWIND src/common.cpp -o src/common.o -pthread -lipopt  g++ -c -O2 -Wall -std=c++1y -DHAVE_CSTDDEF  -I ./stacktrace/include -lunwind -DBOOST_STACKTRACE_USE_LIBUNWIND src/impl/deterministic_algo.cpp -o src/impl/deterministic_algo.o -pthread -lipopt  g++ -c -O2 -Wall -std=c++1y -DHAVE_CSTDDEF  -I ./stacktrace/include -lunwind -DBOOST_STACKTRACE_USE_LIBUNWIND src/impl/magic_algo.cpp -o src/impl/magic_algo.o -pthread -lipopt   g++ -c -O2 -Wall -std=c++1y -DHAVE_CSTDDEF  -I ./stacktrace/include -lunwind -DBOOST_STACKTRACE_USE_LIBUNWIND src/main.cpp -o src/main.o -pthread -lipopt  g++ -L ./stacktrace/include -lunwind -DBOOST_STACKTRACE_USE_LIBUNWIND ./src/common.o ./src/impl/deterministic_algo.o ./src/impl/magic_algo.o ./src/estimator.o ./src/evaluator.o ./src/input/input_data.o ./src/input/input_links.o ./src/input/input_reader.o ./src/input/market_reader.o ./src/ialgorithm.o ./src/main.o -o main -pthread -lipopt   ./src/impl/magic_algo.o: In function     `boost::stacktrace::stacktrace::stacktrace()': magic_algo.cpp:    (.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0x4f): undefined reference to `_Ux86_64_getcontext' magic_algo.cpp:    (.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0x91): undefined reference to `_ULx86_64_init_local' magic_algo.cpp:(.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0xad): undefined reference to `_ULx86_64_step' magic_algo.cpp:(.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0xc6): undefined reference to `_ULx86_64_init_local' magic_algo.cpp:(.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0x209): undefined reference to `_ULx86_64_step' magic_algo.cpp:(.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0x247): undefined reference to `_ULx86_64_get_proc_name' magic_algo.cpp:(.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0x2a2): undefined reference to `_ULx86_64_get_proc_info' magic_algo.cpp:    (.text._ZN5boost10stacktrace10stacktraceC2Ev[_ZN5boost10stacktrace10stacktraceC5Ev]+0x5c9): undefined reference to `_ULx86_64_get_proc_name' collect2: error: ld returned 1 exit status makefiles/opt-makefile:11: recipe for target 'main' failed


Arghh I just know people are going to hate me for asking this...  I was just playing around with inheritance and I noticed you can instantiate a subclass object in one of two ways when you write code. So then I wondered if there is any functional difference between these two methods. So in the code below, does this produce the exact same result...a MountainBike object, or is there some difference I should know about? Bicycle is the superclass for this example. If I do Bicycle bike or MountainBike bike I am effectively making a MountainBike due to new MountainBike()? So basically the difference is just semantics at this point?   Bicycle bike = new MountainBike();  MountainBike bike = new MountainBike();


Prefix and postfix operators inheritance

Consider the following code:  // Only prefix operators struct prefix {     prefix& operator--() { return *this; }     prefix& operator++() { return *this; } };  // Try to represent prefix & postfix operators via inheritance struct any : prefix {     any operator--(int) { return any(); }     any operator++(int) { return any(); } };  int main() {      any a;      a--;     a++;     --a; // no match for ‘operator--’ (operand type is ‘any’)     ++a; // no match for ‘operator++’ (operand type is ‘any’)      return 0; }   I tried to create a hierarchy of classes. The base class, only to realize the prefix increment/decrement operators. And to add a postfix versions in derived class.   However, compiler can not find the prefix operation for the derived class object.   Why is this happening, why prefix operators are not inherited?


Today I voted up the wrong answer. I noticed that there's no way to undo your votes. When you have voted an answer you are forced to vote it, even if you don't want to. I immediately noticed the error and I could just change my vote to up or down, not delete my vote. It makes no sense at all, imho. Since you are able to change your vote within 5 minutes, you should also be able to remove your vote entirely. I can't believe no one noticed that before...


I am very confused on what path and contour integrals actually represent. I tried looking for an answer on Google but the only examples were related to Quantum Mechanics. For instance, real Riemann integrals can be thought as "the area under the curve". What about path/contour integrals? Also, is there a difference between path and contour integrals, or are they the same thing? I've been thinking of contour integrals as path integrals where the path is a "closed loop", but I'm not sure if that's the case. It's all so confusing, and not being able to visualise these concepts makes it feel like I'm just memorising formulas and theorems without any reason. I have been thinking about path integrals as integrating over a curve in three dimensions. For example, in an $xyz$ coordinate system (with $y$ pointing “up”), we have a path on the $x$-"$z$" plane and integrate over that path. That is, instead of integrating over and along "$y=0$", we integrate over a certain path. But I don't know if this is a correct way to think of path integrals. This issue has been frustrating me a lot because I'm now studying theorems that involve path/contour integrals and I just can't understand what they really do or mean. By path integral I mean $$\int_{\gamma\vert_{[a,b]}}f(z)\hspace{0.2em}dz = \int_{a}^{b}f(\gamma(t))\cdot\gamma'(t)\hspace{0.2em}dt$$ where $f:U\subseteq\mathbb{C}\rightarrow\mathbb{C}$ is a function that satisfies all conditions for complex integration and $\gamma:[a,b]\rightarrow U\subseteq\mathbb{C}$ is at least a piece-wise regular path. Any help would be appreciated.


Idea for running the quadratic sieve in a sub-quadratic space like the general field sieve

Quadratic sieve is an improvement for the , it is searching for b-smooth values on the polynomial $ax^2-bx+c$ (See the ) where $ax^2-bx+c$ is of the size of $N^\frac{1}{2}$. I got an idea of how to reduce this size to $N^\frac{1}{3}$. By doing this I hope to dramatically improve QS running time. Let $N$ be the number we wish to factor.  Let $F(x)=x^2−N^2=(x+N)(x−N)$ Let $H(x) = F(f^2db−N+f^2dx)$ where $b,d,f$ are positive integeres  $$H(x)=(f^2db−N+f^2dx+N)(f^2db−N+f^2dx−N)=f^2d(b+x)(f^2db+f^2dx−2N)$$  Let $f^2db−2N=−c^2$ Let $Q(x)=H(dx^2)$  $$Q(x)=f^2d(b+dx^2)(f^2db+(fdx)^2−2N)=f^2d(b+dx^2)((fdx)^2−c^2)=f^2d(b+dx^2)(fdx−c)(fdx+c)$$ If we manage to set up the system such that $b,fd \approx N^\frac{1}{3}$(it implies that $d=1$), then we will be working on 3 polynomial of the size of $N^\frac{1}{3}$. We can use the same sieving and congruence of square technics as we used in QS, with one additional requirement that all of the three polynomials need to smooth in order for some $Q(x)$ to be smooth. This idea raises two questions:  How to pick $b,c,d,f$? How much harder is it to sieve on three polynomials compare to one?  While I still need help with 2, I found an answer for 1.  Pick a prime $p$ in quadratic residue mod $2N$ with a size about $N^\frac{1}{6}$, Find what is the smallest $c$ in $f`(c)=f^2db=N-c^2$ that is going to be divisible by this prime. It can be efficiently computed using Tonelli's 1891 note. Then you got a $c$ of the size of $N^\frac{1}{3}$ and $f$ of the size of $N^\frac{1}{6}$ and $db$ of the size of $N^\frac{3}{6}$, with some luck and repeating this process multiple times, it's possible to extract a square out of $db$ such that $f$ becomes $N^\frac{1}{3}$  I tested this idea with a random 300 bits numbers,  is far from being optimized, but after running for an hour I was able to generate $f$ of $73$ bits. This already allows making a sub-quadratic setup with b 116 bits, $f$ 73 bits, and $d$ 40 bits.  - N 1656661855224614241967626091052145902421605836026342398847614444684800200797305356470390167  - c 570181232531678014712574953020  - f 6934515693275786467781  - db 68901963423007279523881523815951134611979711694  Please tell me what do you think about this idea and help me solving 2.


Why a bar magnet broken from between repel on joining again even if the poles are opposite, i.e. North and South.


What does the rounded star icon do exactly on ? I cant find anything in the FAQ or on meta about it.  Thanks.


I have a cable texture and a simple curve. I want to map the texture on the curve so that it looks like a cable.   Note : I dont want to convert the curve to mesh and the map with uv. Reason is i dont want to make more verts and the file size heavy. Any suggestion. Thanks


Copy Windows 7 recovery partition to a bootable external drive

I would like to copy my netbook recovery parition to a bootable external HDD because two of my partitions were damaged including the partition which contained the Master Boot Record. I wasn't able to repair the mbr but I needed the machine so I installed a Win 8 on it but now I want to reinstall the factory win 7 which is on the offline recovery partition but I don't know how can I copy it to a bootable drive.


Good day i have another question. I'm making a good progress in rigging. thanks too the this community but i encountered a problem  When i move the character the collar doesn't follow. The character is downloaded here  And sorry for asking too many question. i learn from doing things than watching all the stuff. if i watch a whole series of tutorial i got distracted and lost interest. And this is the blender file  This question is different


Is there a website where I can post my CV where potential academic employers can find me? To be more precise, I'm looking for postdoctoral position in the areas that uses differential geometry but could also use statistics, for example, computational neuroscience, computer vision, manifold learning etc.  P.S. this is my main question. But if you could answer the same question for industries for using the above topics and could access my CV online, that'd be well appreciated, because in case I don't get a postdoc, I'm keeping myself open to industry too.  Thanks in advance!


What is the difference between $\gg$ and $\gt$?

What is the difference between $\gg$ and $\gt$ ?  Thank you $\infty$ times.


What is the best way to evaluate $8^{126}$ mod $9$?   So there is a path for $8^{126}$ :  $8^2 = **8$,  $8^3 = **4$,  $8^4 = **6$,  $8^5 = **8$,  $8^6 = **4$,  $8^7 = **6$,   so 126 should end with $**8$. $8$ mod $9$ is $8$.  I am not sure it's the way way to approach it, thanks!


I want to insert lstlisting inside a tcolorbox which must has a title and title can be hidden whenever I need, also it's top right and bottom left corner will be rounded something like this:     I know how to use tcolorbox and lstlisting but I don't know how to use them together. Could anyone please help me? Any alternate solution without tcolorbox will be also appreciated.  My code snippet :  \documentclass[10pt,a4paper,oneside]{book} \usepackage[utf8]{inputenc} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{graphicx} \usepackage[left=2.00cm, right=2.00cm, top=2.00cm, bottom=2.00cm, showframe]{geometry} \author{Ravi} \title{How to wite code in \LaTeX}  %%%%%%%%%%%%%%% CODE STYLE %%%%%%%%%%%%%%%  \usepackage{blindtext} \usepackage{xcolor}  \definecolor{pblue}{rgb}{0.13,0.13,1} \definecolor{pgreen}{rgb}{0,0.5,0}  \renewcommand{\rmdefault}{phv} \usepackage[T1]{fontenc} \usepackage[ttdefault=true]{AnonymousPro}  \usepackage{listings} \usepackage[T1]{fontenc} \usepackage{inconsolata} \lstset {     language=Java,%     basicstyle=\fontfamily{AnonymousPro}\selectfont,%     keywordstyle=\bfseries\color{pblue},     stringstyle=\bfseries\itshape\color{green!40!black},%     commentstyle=\bfseries\itshape\color{black!60},%     showspaces=false,     showtabs=false,     breaklines=true,%     showstringspaces=false,     %breakatwhitespace=true,     %numbers=left,%     %numbersep=8pt,%     %numberstyle=\tiny,%     rulecolor=\color{white!60!black},%     breaklines=true,%     frame=single,%single     %keepspaces=true,%     xleftmargin=1.5mm,%\parindent     xrightmargin=1.5mm,%     framerule=1.2pt,%     backgroundcolor=\color{gray!8},%     %morecomment=[s][\bfseries\color{orange!40!red}]{@}{Override},     tabsize=1, } \lstset{emph={%           downto, for, String, TextView, Toast, Button, EditText, ImageView, Typeface, Intent, WebView, WebSettings, SwipeRefreshLayout, RelativeLayout, Animation, AlertDialog, SharedPreferences, Editor, ToggleButton, CardView, LinearLayout, gradient, shape, %     },emphstyle={\bfseries\color{pblue}}% }  \begin{document}     %\maketitle     \chapter{Hello \LaTeX}      \begin{lstlisting}         String s = "Hello World";          Animation from_top = AnimationUtils.loadAnimation(this, R.anim.from_top);         imageView.setAnimation(from_top);          // change activity with fade animation          new Handler().postDelayed(new Runnable() {         @Override         public void run() {         Intent intent = new Intent(MainActivity.this, Main2Activity.class);         startActivity(intent);         overridePendingTransition(R.anim.fade_in,R.anim.fade_out);         finish();         }         }, SPLASH_TIMEOUT);     \end{lstlisting}  \end{document}


Cant install via Ubuntu Software- "apt transaction returned result exit-failed"

I'm using 17.04 ( Clean Install ), and as far as I remember, every try to install any sofware- it fails with that error code.  I tried sudo apt-get update && apt-get upgrade and problem persists.  any idea why?   edit: Using software Updater gave this result :   edit : output of update  guy@LG-LAPTOP:~$ sudo apt-get update && apt-get upgrade [sudo] password for guy:  Ign:1 http://il.archive.ubuntu.com/ubuntu zesty InRelease Ign:2 http://il.archive.ubuntu.com/ubuntu zesty-updates InRelease               Ign:3 http://il.archive.ubuntu.com/ubuntu zesty-backports InRelease             Err:4 http://il.archive.ubuntu.com/ubuntu zesty Release                           503  Service Unavailable Get:5 http://security.ubuntu.com/ubuntu zesty-security InRelease [89.2 kB]      Err:6 http://il.archive.ubuntu.com/ubuntu zesty-updates Release                   503  Service Unavailable Get:7 http://archive.canonical.com/ubuntu zesty InRelease [10.2 kB]             Err:8 http://il.archive.ubuntu.com/ubuntu zesty-backports Release                 503  Service Unavailable Get:9 http://archive.canonical.com/ubuntu zesty/partner Sources [1,416 B]       Get:10 http://archive.canonical.com/ubuntu zesty/partner amd64 Packages [1,616 B] Get:11 http://archive.canonical.com/ubuntu zesty/partner i386 Packages [1,612 B] Get:12 http://archive.canonical.com/ubuntu zesty/partner Translation-en [708 B] Get:13 http://security.ubuntu.com/ubuntu zesty-security/main amd64 DEP-11 Metadata [11.7 kB] Get:14 http://security.ubuntu.com/ubuntu zesty-security/main DEP-11 64x64 Icons [9,219 B] Get:15 http://security.ubuntu.com/ubuntu zesty-security/universe amd64 DEP-11 Metadata [14.4 kB] Get:16 http://security.ubuntu.com/ubuntu zesty-security/universe DEP-11 64x64 Icons [31.0 kB] Reading package lists... Done                                          E: The repository 'http://il.archive.ubuntu.com/ubuntu zesty Release' does no longer have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://il.archive.ubuntu.com/ubuntu zesty-updates Release' does no longer have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://il.archive.ubuntu.com/ubuntu zesty-backports Release' does no longer have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. guy@LG-LAPTOP:~$    output of apt get  guy@LG-LAPTOP:~$ sudo apt-get install putty Reading package lists... Done Building dependency tree        Reading state information... Done The following additional packages will be installed:   putty-tools Suggested packages:   putty-doc The following NEW packages will be installed:   putty putty-tools 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 661 kB of archives. After this operation, 2,713 kB of additional disk space will be used. Do you want to continue? [Y/n]  Err:1 http://il.archive.ubuntu.com/ubuntu zesty/universe amd64 putty-tools amd64 0.67-3   503  Service Unavailable Err:2 http://il.archive.ubuntu.com/ubuntu zesty/universe amd64 putty amd64 0.67-3   503  Service Unavailable E: Failed to fetch http://il.archive.ubuntu.com/ubuntu/pool/universe/p/putty/putty-tools_0.67-3_amd64.deb  503  Service Unavailable E: Failed to fetch http://il.archive.ubuntu.com/ubuntu/pool/universe/p/putty/putty_0.67-3_amd64.deb  503  Service Unavailable E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing? guy@LG-LAPTOP:~$


How can free up space for new partition in Ubuntu?

I have installed Ubuntu 20.04 LTS in my whole hardisk which is 1 TB. Now I want to free up space and to create partition to install Windows 10. I tried Gparted. But partition can't be done there. I can not decrease the size.  So, how I can do it?


Cat 5/6 in same conduit as power: is NM-B required, or is THHN acceptable?

Preface: I'd like to avoid the question of whether one should run data and power together; my question is focused on Code compliance.  I'm trying to ensure I interpret Code correctly when running Cat 5/6 cabling and power together in the same conduit.  For starters, I understand that nothing in Code prohibits one from doing this; I'm trying to ensure I understand how to do it properly.  I'm wiring a basement office for power and data, and I'll be running the electrical in EMT.  My plan was to pull THHN for the power rather than pull NM-B, but then 800.133(2) Exception 1 made me scratch my head.  Is my understanding of the Article that if I want to run both data (Cat6) and power in the same conduit, that the power needs to be sheathed (i.e. NM-B).  Is it unacceptable to pull individual THHN conductors and the Cat6 together in the same conduit?     800.133 2) Other Applications. Communications wires and cables shall be separated at least 50 mm (2 in.) from conductors of any electric   light, power, Class 1, non–power-limited fire alarm, or medium-power   network-powered broadband communications circuits.      Exception No. 1: Where either (1) all of the conductors of the   electric light, power, Class 1, non–power-limited fire alarm, and   medium-power network-powered broadband communications circuits are in   a raceway or in metal-sheathed, metal-clad, nonmetallic-sheathed, Type   AC, or Type UF cables, or (2) all of the conductors of communications   circuits are encased in raceway.


How to disable the skype ads (advertisement)?

The Skype client shows a disturbing colored ad at the bottom of the client. The ad is unnecessary and only takes away important space for the contact list.  How can I remove that permanentely?    Even after clicking the close sign on the ad, the ad appears again each time I open/click Skype again...


How long will spaghetti last in the refrigerator when stored in a sealed container?

How long will spaghetti with sauce containing diced tomatoes last in the refrigerator when stored in a sealed container?


Uniform continuity on bounded subset of $\mathbb{R}$ implies boundedness of the function

The Problem : Let $f:B \subset \mathbb{R} \to \mathbb{R}$ be uniformly continuous on a bounded set $B$. To show that $f(B)$ is bounded.  I have done the simplified case when $B$ is an interval (using Weierstrass' theorem and local boundedness induced by continuity). But what if $B$ is not an interval? Can we always write B as finite union of intervals? Any help will be greatly appreciated. Thank you.


In the most basic sense, what is abstract algebra about?  Wolfram Mathworld has the following definition: "Abstract algebra is the set of advanced topics of algebra that deal with abstract algebraic structures rather than the usual number systems. The most important of these structures are groups, rings, and fields."  I find this, however, to say the least, not very informative. What do they mean by abstract algebraic structures? Along these lines, what are groups, rings, and fields then?  I've been told by a friend that groups, essentially, are sets of objects, although, this still leaves me wondering what he means by objects (explicitly).  I don't need anything rigorous. Just some intuitive definitions to give me some direction.  Thanks!


Map-Navigation Project, How is road data generally stored/represented?

Navigation systems like the Garmin and TomTom have always fascinated me.  I've wanted to implement small map/navigation applications to try out various pathing algorithms and expand on my knowledge of them.  This is a two part question:  1.) How is Map data stored?  - When you have a network of roads, how is this data generally stored?  What parts of the data are retained inorder to reproduce a map later?  Is each road stored as a series of points where it changes direction? What kind of file formats is this data stored in? Are there publically available libraries for easily parsing these files? Does anyone have specifics on how map/road data is stored/represented it would be very helpful.  2.) Navigation/Pathing - When doing basic pathing on this map data (a la Garmin) is my assumption correct that it is converted to a directed graph?  Is each road intersection a vertex with the edge weights the distance between vertexes?  This is what I was thinking about doing so I could try some basic well known pathing algorithms and see what I get.  I've seen  publically available map data on the US but I'm not sure how it is represented and if it is detailed enough for me to be able to build my directed graph out of it.  If anyone has any information I would appreciate it. The more detailed knowledge you have the better.


I've started writing an answer for this question:  and when I submitted it, I noticed it had been closed 30 minutes ago. Usually, when this happens, I see an orange warning on top of the page and I'm not able to submit my answer. Can someone explain why I could submit it this time?


Zip the folder and its content in python(2.2.1)

I have a folder and some files inside the folder. I need to zip the folder along with its content. For example: the folder name is "Help" adn it has around 20 files inside it. Now i need to make it as "Help.zip" which consist of 20 files. And need to delete the "Help" folder. Once Zipped only the zip folder should be available. Can some one help me by passing an example or a link. As i m very new to python.  Note: I have a very old version of Python. Its 2.2.1 :(


Can I see my own answer's deletion reason?

Can I see or be informed of deletion request reason(s)?  On sites where I have deletion request privileges, for someone else's post, I can click on the "delete (n)" link and see what's been suggested (and then cancel if I was only looking).  I have one deletion request for an answer on a site where I don't have deletion request privileges. In this specific case I don't care much about the answer -- it also has a current score of -1 (and no comments) -- but I noticed I can't find out what the reason for the deletion request is.  For questions, close reasons are reported to the OP so they may attempt to fix the problem. I believe that same opportunity should be offered to answerers.


How can i evaluate $\int _0^1\frac{\ln ^2\left(x\right)\ln \left(1-x\right)\ln \left(1+x\right)}{x}\:dx$

I want to evaluate $$\int _0^1\frac{\ln ^2\left(x\right)\ln \left(1-x\right)\ln \left(1+x\right)}{x}\:dx$$ I tried integration by parts and shape it in a way that i could expand either $\ln$ terms. $$-\int _0^1\frac{\ln ^3\left(x\right)\ln \left(1-x\right)}{1+x}dx+\int _0^1\frac{\ln ^3\left(x\right)\ln \left(1+x\right)}{1-x}\:dx$$ After this i tried expand the terms but i still couldnt go through, any different approaches are welcome.


Where can I find the total number of flags (helpful/not helpful)?

From the post , I can see comment/answer that we can only see the flags in our own profile and not others. Also it is available in our profile section. The reason why i am asking is because, going through the badges section, I can see 3 moderation badges:         Where can I see the list of flags that I cast and how useful they were? Please note that I am not talking about upvotes/downvotes. Update : As per @Servy's comments i can see a detailed list through the flag-summary link. But it still doesnt show actually a simple count like :  Total Flags : 100 Helpful Flags : 50 Non-Helpful : 50  Hope i am more clear..


I am trying to create a pattern in QGIS that could look like a wall with several bricks but I'm not quite sure I understood the custom dash pattern tool.  When I try to do something like this, the pattern never gets perfect, see the image below. Is there anyone who could advise me something?


Being an English language learner for about 30 years, I still make mistakes. In a written language, when I have misspelled and noticed it in a timely manner, I simply navigate to a wrong word and edit it.  However, in a spoken conversation, when I use a wrong word, I must stop and correct myself by saying a correct one. I've seen many ways to do that, but I'm still not sure which one to use:  He's going to school...   ...er... she's going; ...sorry, I mean, she's going; ...oops, she's going; ...I'm sorry, let me restate it from the beginning, she's going;   What is the grammatical and polite way to correct myself in a spoken conversation? Let's stick to a formal/business context if it matters.  Also, what part of a sentence should I repeat to make it clear?


How to create a new keyboard shortcut using the Windows key?

Windows has built-in key shortcuts for locking your machine (WinKey+L) and for starting Explorer (WinKey+E). I'd like to create a similar new shortcut, WinKey+X, to start one of my favourite  replacements for Explorer.  I've tried the usual method, creating a shortcut and then setting the Shortcut key to WinKey+X, but it shows up as CTRL+ALT+X and doesn't work when I press the WinKey. It does work if I press CTRL+ALT+X.  How can I make the Windows key version of the shortcut work?


Calculating a weighted mean and weighted SD from multiple mean/SD/different sample sizes?

QUESTION EDITED: I have 10 different patients, who have undergone heart procedures and we have collected some measurements of cardiac electrical activity from the same region of all ten hearts. Due to a number of reasons, the data collected from each region comprises a different number of points/measurements. This has been analysed by proprietary software and we have been given only three values for each patient. The mean (electrical conduction velocity in cm/sec), the SD and the number of points that were used by the software to calculate this mean/SD (n) for each patient.  Mean SD n  I have NOT been provided with the individual values associated with each point for each patient, only the those three numbers. The number of points for each patient varies quite a bit - some are 47, some are 17 so as an example, the first two patients have the following: Patient 1  Mean = 2.5cm/s SD = 0.8 n = 47  Patient 2  Mean = 3.5cm/s SD = 1.5 n = 17  and so on for all 10 patients Is there a way I can find (a) MEAN of the MEANS and (b)appropriate SD for the mean of the means WITHOUT needing the individual values of each point? I think I understand how to find a weighted mean: Multiple each mean by n of that patient/cumulative n of all 10 patients and then add them all together (as in this example ) That should (I think) provide me with an overall mean of the conduction velocity of this region of the heart from these 10 patients. But how do I then calculate the SD of this mean of means for when we want to present this data in a medical journal? I would imagine it wouldn't work exactly the same way as a weighted mean?


Basically, I have this function that finds the last non-blank cell in a range while skipping columns I don't want it to search. The value is returned, but I want it to return the cell address (for something else I am trying to make work). Here is my formula:     =IF(ISERROR(INDEX({M5,N5,O5,P5,R5,S5,T5,U5,W5,X5,Y5,Z5,AA5,AC5,AD5,AE5,AF5,AH5,AI5,AJ5,AK5,AM5,AN5,AO5,AP5,AQ5,AS5,AT5,AU5,AV5,AX5,AY5,AZ5,BA5,BB5,BD5,BE5,BF5,BG5,BI5,BJ5,BK5,BL5,BN5,BO5,BP5,BQ5,BR5,BT5,BU5,BV5,BW5,BX5},MAX(({M5,N5,O5,P5,R5,S5,T5,U5,W5,X5,Y5,Z5,AA5,AC5,AD5,AE5,AF5,AH5,AI5,AJ5,AK5,AM5,AN5,AO5,AP5,AQ5,AS5,AT5,AU5,AV5,AX5,AY5,AZ5,BA5,BB5,BD5,BE5,BF5,BG5,BI5,BJ5,BK5,BL5,BN5,BO5,BP5,BQ5,BR5,BT5,BU5,BV5,BW5,BX5}<>"")*COLUMN(A5:BA5)))),"Error", (INDEX({M5,N5,O5,P5,R5,S5,T5,U5,W5,X5,Y5,Z5,AA5,AC5,AD5,AE5,AF5,AH5,AI5,AJ5,AK5,AM5,AN5,AO5,AP5,AQ5,AS5,AT5,AU5,AV5,AX5,AY5,AZ5,BA5,BB5,BD5,BE5,BF5,BG5,BI5,BJ5,BK5,BL5,BN5,BO5,BP5,BQ5,BR5,BT5,BU5,BV5,BW5,BX5},MAX(({M5,N5,O5,P5,R5,S5,T5,U5,W5,X5,Y5,Z5,AA5,AC5,AD5,AE5,AF5,AH5,AI5,AJ5,AK5,AM5,AN5,AO5,AP5,AQ5,AS5,AT5,AU5,AV5,AX5,AY5,AZ5,BA5,BB5,BD5,BE5,BF5,BG5,BI5,BJ5,BK5,BL5,BN5,BO5,BP5,BQ5,BR5,BT5,BU5,BV5,BW5,BX5}<>"")*COLUMN(A5:BA5)))))


Get value of ASP.NET Webform TextBox using JS/JQuery

I have an asp control for a textbox and a script that's trying to get the value from the textbox but it wont fire the alert:  <asp:TextBox ID="txtEmailList" runat="server" TextMode="MultiLine"></asp:TextBox>  <script>     $(document).ready(function () {         $("#btnCopyAll").click(function () {             alert(document.getElementById('#txtEmailList').value);         });     }); </script>   I tried:  alert(document.getElementById('<%txtEmailList.ClientID%>'));   As per  answer, but it did not work.  How do I accomplish this?


I can't install dropbox client: Cannont open libatomic.so.1

After using the installation tool from the main dropbox page on Ubuntu 18.04 - LTS (Bionic Beaver), I tried to start it using the dropbox launcher for the app and never started.  Then, I tried to install it for Ubuntu using what is explained in the Ubuntu main page: .   The issue: When I launched the daemon through the terminal using ~/.dropbox-dist/dropboxd I got the following exception:  File "dropbox/sync_engine/nucleus/thin_client/client.pyc", line 28, in <module> File "dropbox/foundation/metrics/amp/remote_sink.pyc", line 10, in   <module> ImportError: libatomic.so.1: cannot open shared object file: No such file or directory !! dropbox: fatal python exception: ['Traceback (most recent call last):\n', '  File "dropbox/client/main.pyc", line 7919, in main\n', '  File "dropbox/client/main.pyc", line 7843, in main_startup\n', '  File "dropbox/client/main.pyc", line 942, in __init__\n',  '  File "dropbox/sync_engine_boundary/factory.pyc", line 147, in make_default_file_system\n',  '  File "dropbox/sync_engine_boundary/factory.pyc", line 99, in __init__\n',  '  File "dropbox/sync_engine_boundary/factory.pyc", line 118, in _initialize_classes\n',  '  File "dropbox/sync_engine/nucleus/classic_client/sync_engine.pyc", line 276, in <module>\n',  '  File "dropbox/sync_engine/nucleus/classic_client/thin_adapter/in_proc.pyc", line 98, in <module>\n',  '  File "dropbox/sync_engine/nucleus/classic_client/wrapped_thin_client.pyc", line 26, in <module>\n',  '  File "dropbox/sync_engine/nucleus/thin_client/client.pyc", line 28, in <module>\n',  '  File "dropbox/foundation/metrics/amp/remote_sink.pyc", line 10, in <module>\n',  'ImportError: libatomic.so.1: cannot open shared object file: No such file or directory\n'] (error 3) Aborted (core dumped)   How can I solve this?


Is it possible to programatically detect if you have reached a governor limit?  For example, you can make 200 future calls per license per 24 hours. IF you hit that limit SFDC just starts to blow up on you. Is there some way to determine if you are under/over on the limit so you can react accordingly?  I'd prefer not performing an action if I'm over the limit rather than catching the exception and continuing to try in subsequent calls as it's a bit inefficient.


I saw a question yesterday asking about civilian starships and shields, and that reminded me of another question I had. Is every starship supposed to have blasters, or some kind of weapon on them? Or do only certain ships have weapons?


How to add border to a text only and align center

I am new to Html & CSS. I want a heading which contains text like "Women safty". I want to warp the heading text with border. But when I apply border to text the border covers all the area in the width both left and right.I just want to add border around text only and the text needs to be in center.


Why does the bounty award button appear on deleted answers?

Clearly this is an edge case and I probably shouldn't have even tried awarding the bounty to a deleted answer, but why is the bounty award button even available?  It's not a bug since someone added in the notification seen in the final image.  But that sure seems like a roundabout way to let the user know that they can't award a bounty to a deleted answer.  The second step is particularly strange since the system really ought to know that the warning is pointless: no bounty can be awarded.  My suggestion is to rip-off the  and let bounties be awarded without the warning.  Then remove the single click button from deleted answers.


apt broken install/update/remove causes input/output error for linux-image package

I can't install/update/remove anything because of this error, nor does google return anything specifically for linux-image-4.10.0-42-generic (It does for other things, but I am not sure what to touch as I am not an advanced user)  dpkg: unrecoverable fatal error, aborting:  reading files list for package 'linux-image-4.10.0-42-generic': Input/output error   I just tried to apt-get remove apt (then I was going to follow answer ) but the result is the same error.  How do I fix this?  I am trying to avoid reinstalling the system and everything on it  I'm using Ubuntu MATE 16.04  Further tests advised by N0rbert  ls -al /var/lib/dpkg/info/linux-image-4.10.0-42-generic.list -rw-r--r-- 1 root root 82416 Dec 18  2017 /var/lib/dpkg/info/linux-image-4.10.0-42-generic.list   head -n5 /var/lib/dpkg/info/linux-image-4.10.0-42-generic.list /. /lib /lib/firmware /lib/firmware/4.10.0-42-generic /lib/firmware/4.10.0-42-generic/tigon


I have added a plane in top view. I have then extruded the plane according to a floorplan in topview.  I don't know what happened, but when I switched my view, I could see that some parts of it are for some reason high up in the air.  I would like to ask how I can bring everything back down onto the grid / floor.  And if somebody could tell me how this might have happened, I would also be glad.


I send email in PHP, and it's go to spam.  Here is the code:  $headers = 'From: noreply@nitrobit.net' . "\r\n" .            'MIME-Version: 1.0' . "\r\n" .            'Content-type: text/html; charset=utf-8' . "\r\n" .            'X-Mailer: PHP/' . phpversion(); mail($to, $subject, $message, $headers);   Here is the Headers:  Delivered-To: superdown.me@gmail.com Received: by 10.114.185.6 with SMTP id ey6csp45195ldc;         Sun, 15 Sep 2013 04:01:53 -0700 (PDT) X-Received: by 10.180.126.3 with SMTP id mu3mr9155535wib.27.1379242912725;         Sun, 15 Sep 2013 04:01:52 -0700 (PDT) Return-Path: <nitrobit@nitrobit.net> Received: from ns3365488.ovh.net ([2001:41d0:a:2c2e::1])         by mx.google.com with ESMTPS id n7si9138570wja.151.1969.12.31.16.00.00         (version=TLSv1 cipher=RC4-SHA bits=128/128);         Sun, 15 Sep 2013 04:01:52 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning nitrobit@nitrobit.net does not designate 2001:41d0:a:2c2e::1 as permitted sender) client-ip=2001:41d0:a:2c2e::1; Authentication-Results: mx.google.com;        spf=softfail (google.com: domain of transitioning nitrobit@nitrobit.net does not designate 2001:41d0:a:2c2e::1 as permitted sender) smtp.mail=nitrobit@nitrobit.net Received: from apache by ns3365488.ovh.net with local (Exim 4.76)     (envelope-from <nitrobit@nitrobit.net>)     id 1VLA5V-0002Ck-Po     for superdown.me@gmail.com; Sun, 15 Sep 2013 13:01:57 +0200 To: superdown.me@gmail.com Subject: NitroBit - סיסמה עבור קנייתך X-PHP-Originating-Script: 0:ipn.php From: NitroBit noreply@nitrobit.net Reply-To: superdown.me@gmail.com X-Mailer: PHP/5.3.27MIME-Version: 1.0 Content-type: text/html; charset=utf-8 Message-Id: <E1VLA5V-0002Ck-Po@ns3365488.ovh.net> Date: Sun, 15 Sep 2013 13:01:57 +0200   What did I do wrong?  Thanks, and sorry for my English


Why must we "avoid discussions in comments"?

I've just started getting these messages:     Please avoid extended discussions in comments. Would you like to automatically move this discussion to chat?   Why should one avoid doing this? I think it adds to the site...  (Tagged  in more ways than one!)


I constantly get killed by a command block in minecraft 1.11, how can I fix this?

I keep getting killed by a command block in minecraft 1.11, and I can't type anything, how to fix this? I Could not find a solution for minecraft "1.11" before, but i solved it by using NBTExplorer.