Where can I find a folder containing icons of all my applications, that I can double-click?
How to find out the terminal command of an application?
In PHP (>= 5.0), is passing by reference faster? In PHP, function parameters can be passed by reference by prepending an ampersand to the parameter in the function declaration, like so:  function foo(&amp;$bar) {     // ... }   Now, I am aware that this is not designed to improve performance, but to allow functions to change variables that are normally out of their scope.  Instead, PHP seems to use Copy On Write to avoid copying objects (and maybe also arrays) until they are changed. So, for functions that do not change their parameters, the effect should be the same as if you had passed them by reference.  However, I was wondering if the Copy On Write logic maybe is shortcircuited on pass-by-reference and whether that has any performance impact.  ETA: To be sure, I assume that it's not faster, and I am well aware that this is not what references are for. So I think my own guesses are quite good, I'm just looking for an answer from someone who really knows what's definitely happening under the hood. In five years of PHP development, I've always found it hard to get quality information on PHP internals short from reading the source. Suppose $Y_1, \ldots, Y_n$ is a random sample from a normal distribution with mean $\mu$ and variance $\sigma^2$. Let $S^2$ be the sample variance, which is unbiased for $\sigma^2$.  GOAL: Show that $S = \sqrt{S^2}$ is a biased estimator of $\sigma$.  I realize that $(n-1)S^2/ \sigma ^2$ is chi-square with $(n-1)$ degrees of freedom.  I am given that $$E(S) = E\left[\frac{\sigma}{\sqrt{n-1}} \left[\frac{(n-1)S^2}{\sigma^2}\right]^{1/2}\right] = \frac{\sigma}{\sqrt{n-1}} \int_0^\infty v^{1/2} \frac{1}{\Gamma[(n-1)/2] 2^{(n-1)/2}} v^{(n-1)/2} e^{-v/2} \, dv$$  Can anyone help me understand why they have $v^{1/2}$ and $v^{(n-1)/2}$ (combining them $v^{n/2}$ as I think it should be $v^{1/2}$ and $v^{\frac{(n-1)}{2}-1}$ (combining both terms give $v^{(n-2)/2}$ since the pdf for chi-square distribution is $$ f(v) = \frac{v^{(x/2)-1} e^{-v/2}}{2^{x/2}\Gamma(x/2)},$$ where $x$ is degree of freedom?  Could anyone please tell me which one is the correct answer with explanation?  Thank you Box around single element in list Is there any way in latex to create a simple box around one item in a list?  I tried both \framebox, and \fbox, none of them worked  \begin{enumerate}[label=\Alph*),ref=\Alph*] {\color{red}\item null.}  \item lik vektdifferansen $GT - GK$. \item lik vektsummen $GT + GK$. \item lik vekten av $K$. \end{enumerate}   Works, but   \begin{enumerate}[label=\Alph*),ref=\Alph*]  {\color{red}  \fbox{ \item null.} }   \item lik vektdifferansen $GT - GK$. \item lik vektsummen $GT + GK$. \item lik vekten av $K$. \end{enumerate}   Does not. So yeah, any way to box a single entry in a list? Limit of a function with powers (L'Hopital doesnt work) I have a little problem with limit of this function:  $\lim_{x \to \infty} x^2(2017^{\frac{1}{x}} - 2017^{\frac{1}{x+1}})$  I have tried de L'Hopital rule twice, but it doesn't work. Now I have no idea how to do it. How do I uninstall Ubuntu Wubi? I have a set of values $x$ and $y$ which are theoretically related exponentially:  $y = ax^b$  One way to obtain the coefficients is by applying natural logarithms in both sides and fitting a linear model:  &gt; fit &lt;- lm(log(y)~log(x)) &gt; a &lt;- exp(fit$coefficients[1]) &gt; b &lt;- fit$coefficients[2]   Another way to obtain this is using a nonlinear regression, given a theoretical set of start values:  &gt; fit &lt;- nls(y~a*x^b, start=c(a=50, b=1.3))   My tests show better and more theory-related results if I apply the second algorithm. However, I would like to know the statistical meaning and implications of each method.  Which of them is better? Timestamp in the  is going out of it's boundary.        AFAIK, the suggested edits timestamp was near to it's type (i.e. asked, proposed) like this:        Checked on Chrome (27.0.1453.110 m), Firefox (21.0) on Windows XP  The issue is in other Stack Exchange sites as well. E.g. Have a look at  on Physics.SE. Also in   Can we fix this? I have two related problems that are causing me big trouble:  Let $\;a_1,...,a_n\in\Bbb R\;,\;\;a_i\neq 0\;\;\forall\;i\;$ , and let $\;b_1,...,b_n\in\Bbb R\;,\;\;b_i\neq b_j\;\;\forall\,i\neq j\;$ .  (1) Prove that the equation  $$a_1x^{b_1}+\ldots+a_nx^{b_n}=0$$  has at most $\;n-1\;$ different zeros in $\;(0,\infty)\;$ (Hint: Use induction)  (2) Prove that the equation  $$a_1e^{b_1x}+\ldots+a_ne^{b_nx}=0$$  has at most $\;n-1\;$ different zeros in $\;\Bbb R\;$ .  Now, the following is what I've done so far: for a differentiable function $\;f\;$ ,  I can prove that if $\;f'(x)=0\;$ has $\;n-1\;$ different zeros, then $\;f(x)\;$ has at most $\;n\;$ different zeros, using the mean value theorem, say.  But I can't see how to use induction in this case: if I differentiate in the first problem, I get $$0=f'(x)=a_1b_1x^{b_1-1}+\ldots +a_nb_nx^{b_n-1}=\frac1x\sum_{i=1}^na_ib_ix^{b_i}$$  ...and now?! How does induction kick in here? I though perhap something like: if we suppose WLOG $\;b_1&lt;b_2&lt;...&lt;b_n\;$ , then perhaps inducting on $\;\lfloor b_n\rfloor\;$, but it gets messy and blurry if $\;b_n&lt;0\;$...  Any help, hints are very much appreciated. Proving surjectivity of $\cos(z)$ and $\sin(z)$ and find all $z : \cos(z) \in \mathbb R$ and all $z: \sin(z) \in \mathbb R$ I was trying to find a font which has obsolete jamo and the right combining behaviour. Yesterday I found out about , which seems to have both of these. However, when I use it in XeTeX, I get some seemingly-arbitrary hanja (or blank spaces) instead of the expected characters.  (I’m guessing the composing behaviour will fix itself when the right characters are selected. And yes, I know that Code2000 is working perfectly in this example, but unfortunately it is the ugliest font in the world. :p)  MWE:  \documentclass{article} \usepackage{fontspec}  % 1. precomposed: U+BB47 % 2. separate jamo: U+1106, U+116E, U+11BA % 3. obsolete [separate jamo]: U+113B, U+119F, U+11EB \newcommand\test[1]{#1 &amp; {\fontspec{#1}{뭇; 뭇; ᄻᆟᇫ}} \\}  \begin{document}  \begin{tabular}{rl} \test{Arial Unicode MS} \test{Batang} \test{Code2000} \test{Gulim} \test{GungSeo} \test{HeadLineA} \test{Nanum Brush Script} \test{Nanum Myeongjo} \test{Nanum Pen Script} \test{Noto Sans Korean} \test{PCMyungjo} \test{PilGi} \test{Adobe Gothic Std} \test{Adobe Myungjo Std} \test{Apple SD Gothic Neo} \test{AppleGothic} \test{AppleMyungjo} \end{tabular}  \end{document} Is there a limit to a total number of months a holder of UK multiple entry visitor visa can spend in UK per calendar year? A relative of mine has received a multiple-entry UK visa for 2 years. Is there a particular limit on how many months in total per year she can stay in UK? The way I understand the current rule is that such visitors can enter UK as many times as they want as long as they do not stay for longer than 6 months per single visit. However, does this mean that if she stayed with us for 5 months and went back home for 1-2 months, she could come and stay for another 5 months? I heard that it is advisable to spend only 180 day per calendar year in UK and not more, but I could not find that rule in any official UK Home Office documents. Thanks in advance for any info about this. Incorrectly answered 'No' to "Any previous visa refusals..." on a UK Standard Visitor visa application. How can I fix my mistake? I'm from Lebanon and I've been working in Saudi Arabia for nine years. In 2012, I put the money that I collected from my job as a teacher in my father's Lebanese account since I didn't have one in Lebanon. During the interview, my interviewer told me that my application will be rejected because I don't have proof that this money is mine and clearance officer will think someone else gave me the money. I didn't know that I had to bring with me from Saudi Arabia an employment letter and bank statements to prove that this money is mine and I earned it by working in Saudi Arabia. Anyways, my visa did get refused as my interviewer had told me it would be.    Last May, I was granted a US visitor visa Multi Entry for 5 years. I wanted to visit the US in August for 10 days but my mom entered the hospital so I had to postpone it. Now I'm applying for a teacher training program in the UK. I received an invitation letter from Brighton University and so I applied for a UK Standard Visitor visa. After I paid and printed the application, I realized that I answered the question Any previous visa rejections ... with "NO" and I don't know how should I fix this.  Please note that I still didn't give my biometrics, I still didn't use my US visa which I received on May 2016, I paid for my application so I can't amend it online. I'm supposed to give my biometrics and submit my documents this Monday.  If I don't say anything will they check it and refuse me?    Will my US visa be an advantage and they will disregard the previous rejection or should I correct it when I submit my documents this Monday? How does one account for the momentum of an absorbed photon? warning message at command line `sudo` Everytime I try to sudo something at the terminal, I get a warning message:  alexandre@XPS-15Z $ sudo mount file.iso /mnt/ -o loop [sudo] password for alexandre:  no talloc stackframe at ../source3/param/loadparm.c:4864, leaking memory   It's just annoying to get that all the time. How do I solve that? I'm on Ubuntu 14.04 (upgraded from 13.10) Why didn't the mirror universe's tech progress past the main timeline's? In Star Trek TOS, we see the Defiant disappear to unknown parts  ('The Tholian Web'), and Star Trek: Enterprise revealed that the Defiant went back in time to the mirror universe ('In a Mirror Darkly', parts 1 &amp; 2).   Because of this, one might wonder why (in-universe) the mirror universe didn't obtain (and maintain) technological superiority over the main timeline. (Granted, the out of universe answer is that TOS depicted the two universes as having essentially the same level of tech)  So does any work (whether STO, or a pocket books work) address why the mirror universe didn't simply leap frog the main universe's technology?   (Or to put it another way, why did the mirror universe's technology appear to stagnate for a century after obtaining access to the Defiant's advanced technology?) I have just updated to Minecraft 1.7.4 and now all of a sudden there are barely any mobs spawning.  I checked to make sure that I was in normal difficult and I saw 1 creeper but that is all.  Also I tried different difficulties. Another thing - mobs seem to to spawn normally in the nether and all other mobs except aggressive mobs spawn like they should.  Please if you know how to fix this, please help! Can I boot memtest86+ if I'm using UEFI? Downloaded the Ubuntu 16.04.2 .iso install disk and flashed it onto a USB stick.  Booting on the USB stick, there is no memtest86+ option (along with "Try Ubuntu").  Is there a way to add it to the install options?  (it's for a UEFI boot PC running normally Windows, its owner does not want to install Ubuntu. "memtest86+" is completely free (unlike "memtest86"), but is quite old, and does not offer a UEFI boot - this is why having it within the Ubuntu options makes things easier) A while back I read about the super Kamiokande detector detected a large neutrino flux and then several hours later a supernova was seen. Anyone know of this with sources? I don't recall the source at the moment. Using GParted to remove windows partition How can Cooper communicate with his daughter before the time he went to space? In the movie Interstellar it's shown that after Cooper fell into the Black Hole, he communicates with his daughter Murph through some codes as Ghost. My doubt is how can he communicate to his daughter before he goes into space? I didn’t get the logic of that part. Can anyone please make it clear?