How can I know if a user plugged an external storage device into a Mac (such as an external hard drive) and moved/copied any data to and from it?
Find out if any files were exported from my MacBook
I have been learning English for 7 years now, and I have read so many grammar books with rules, telling the difference between Present Perfect and Past Simple and I still find it hard to distinguish them.   On paper, it is easy, if it is not a certain (exact) time in the past without any time markers (yesterday, a month ago, etc) it is past simple. Yes, but outside the classroom it is really harder than this . I have heard many people speaking how they want to, mixing the tenses.   So, I will give these sentences which i have heard to be constructed differently, please, if someone can explain the difference to me.     Have you enjoyed the party? / Did you enjoy the party?      I have given the documents today. / I gave the documents today.      I have done this when I have revised it. / I did it when I revised it      What did you do today? / What have you done today ?   Is it possible to use past simple without mentioning a definite time in the past  (without the time markers)?     It has been 3 years since we moved house. / It has been 3 years since we have moved house.      I know him since we met each other/ I know him since we have met each other   Correct me if some of the sentences are grammatically wrong! Schengen Visa Refusal: Justification for the purpose and conditions of the intended stay was not reliable I'm looking for the name of a series of space opera novels I read some time ago, probably between 2003 and 2010.    It may have been published quite a few years before I read it, I don't think it was new at the time. I borrowed the novels from the local library, but I can't find them in its catalogue. I think the covers were fairly dark and plain, though there may have been some artwork on them. There was a totalitarian empire that controlled most planets, possibly ruled by a queen. There was no mention of Earth, the solar system or other real planets, the setting was completely fictional. There were people with psychic/psionic powers, referred to as something like "psi". These people were second-class citizens or slaves. Spaceships were used to travel between worlds. I'm not sure what kind of FTL technology they had, if any. Beyond the edge of the empire was some kind of "dark space", where there was no light. There were some horror themes: When travelling in dark space in one of the novels, a ships crew experienced strange thoughts and hallucinations. I remember finding this quite scary at the time.   Does anyone know which series this could be?  This isn't a duplicate of , since the two questions are about different parts of the same series (the first and second episodes). My network includes machines running Linux and others running Windows. And my machine is running Linux. In the following sentence:     The city is populated by many people.   "many" can be replaced by something like "a great number of" (let us leave the perceived differences between the meanings of these two modifiers out of discussion):     The city is populated by a great number of people.   I understand that this replacement does not change the object "populating the city" from the original "people" to a "number", but rather shows the ability of expressions in the form "[numeral] of" to provide information about the quantity of nouns they modify.  Is this ability due to some special qualities of nouns such as "number", "quantity", "fraction", &amp;c., or is it just one usage of the preposition "of"? describes how to get the changelog for a given package. However, it's the whole changelog.  What I'd like is a way to see what will be changed in whatever I'm about to upgrade. For example, I was imagining something like:  $ sudo apt-get upgrade --show-changelogs Reading package lists... Done Building dependency tree        Reading state information... Done Calculating upgrade... Done The following packages will be upgraded:   foo     -- adds the bar feature for better snazziness     -- removes the deprecated baz feature  1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 8,864 kB of archives. After this operation, 285 kB disk space will be freed. Do you want to continue [Y/n]?    Unfortunately, I don't see anything like that in the man pages for apt-get. Does this or something similar exist?  UPDATE: I've written a  talking about apt-listchanges and Debian changelogs in a little more depth that incorporates some of the feedback in this question. How to find sum of the infinite series $\sum_{n=1}^{\infty} \frac{1}{ n(2n+1)}$ $$\frac{1}{1 \times3} + \frac{1}{2\times5}+\frac{1}{3\times7} + \frac{1}{4\times9}+\cdots $$  How to find sum of this series?  I tried this: its $n$th term will be = $\frac{1}{n}-\frac{2}{2n+1}$; after that  I am not able to solve this. No "Login using Google" option in Android app I registered this ID with my Gmail account, and logged in successfully via web browser. However, while I was trying to log in on the Stack Exchange app in my Android Phone, I don't see any option to log in with Google:    I was told that no user was found with my Gmail account. It is amazing that I can log in via web browser, but cannot do so with the same Gmail account via app. How can I do that?  Just to compare, here is a "normal" login screen of another user:    Where did the Google login go and how can I bring it back?  My app version is 1.0.73, phone is Coolpad 8150D with Android version 4.0.3, kernel 3.0.8. Who was the real "Master Code Breaker"? centos: using epel repository on a server machine Are there any downsides in enabling epel repository on a server machine or is it something every sysadmin does? Calling a function of a module by using its name (a string) What is the best way to go about calling a function given a string with the function's name in a Python program.  For example, let's say that I have a module foo, and I have a string whose content is "bar". What is the best way to call foo.bar()?  I need to get the return value of the function, which is why I don't just use eval. I figured out how to do it by using eval to define a temp function that returns the result of that function call, but I'm hoping that there is a more elegant way to do this. How to make child process die after parent exits? Nested regression model Wheel going badly out of true on final tightening On two occasions (same wheel, loosened everything off and re-did the whole thing after the first time) as I've applied a final half turn to tighten the spokes round the wheel it's gone from being pretty laterally true (within about 0.5 mm) to badly out of true (probably a couple of mm or more out).  The simplest explanation would be that I've managed to mess up by missing spokes/over under-tightening some of them, but I'm fairly sure that's not the case.  What else could cause this?  This is a rear wheel with a fair amount of dish. I'm worried that I might be over-tightening. On both occasions I decided to do a final half turn as the non drive side seemed a little loose, but I was concerned the drive side might be over tight. Could this cause a sudden change in trueness?  I've got the wheel back to a reasonable state, but I'm no longer sure I have even tension in the spokes. Isomorphism of a product $C_n \times C_m$ of cyclic groups with the cyclic group $C_{mn}$ TeX Live 2016: minted doesn't work with LuaLaTeX (bug fixed in June 2016) I've installed TeX Live 2016 as it was released today (thanks to the developers for that).  Now I have the following MWE:  \documentclass{article} \usepackage{minted} \begin{document}  \begin{minted}{ruby} class Foo   def init     pi = Math::PI     @var = "Pi is approx. #{pi}"   end end \end{minted}  \end{document}   When running pdflatex --shell-escape test.tex it runs through the file and produces the PDF as expected. Doing the same with lualatex --shell-escape test.tex fails with  This is LuaTeX, Version 0.95.0 (TeX Live 2016)   system commands enabled. (./test.tex LaTeX2e &lt;2016/03/31&gt; Babel &lt;3.9r&gt; and hyphenation patterns for 1 language(s) loaded. (/opt/texlive/2016/texmf-dist/tex/latex/base/article.cls Document Class: article 2014/09/29 v1.4h Standard LaTeX document class (/opt/texlive/2016/texmf-dist/tex/latex/base/size10.clo)) (/opt/texlive/2016/texmf-dist/tex/latex/minted/minted.sty (/opt/texlive/2016/texmf-dist/tex/latex/graphics/keyval.sty) (/opt/texlive/2016/texmf-dist/tex/latex/oberdiek/kvoptions.sty (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/ltxcmds.sty) (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/kvsetkeys.sty (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/infwarerr.sty) (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/etexcmds.sty (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/ifluatex.sty)))) (/opt/texlive/2016/texmf-dist/tex/latex/fancyvrb/fancyvrb.sty Style option: `fancyvrb' v2.7a, with DG/SPQR fixes, and firstline=lastline fix  &lt;2008/02/07&gt; (tvz)) (/opt/texlive/2016/texmf-dist/tex/latex/float/float.sty) (/opt/texlive/2016/texmf-dist/tex/latex/base/ifthen.sty) (/opt/texlive/2016/texmf-dist/tex/latex/tools/calc.sty) (/opt/texlive/2016/texmf-dist/tex/latex/ifplatform/ifplatform.sty (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/pdftexcmds.sty (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/ifpdf.sty) (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/luatex-loader.sty (/opt/texlive/2016/texmf-dist/scripts/oberdiek/oberdiek.luatex.lua))) (/opt/texlive/2016/texmf-dist/tex/generic/oberdiek/catchfile.sty) uname -s &gt; "test.w18"  ! Package catchfile Error: File `test.w18' not found.  See the catchfile package documentation for explanation. Type  H &lt;return&gt;  for immediate help.  ...                                                l.93     \CatchFileDef\@tempa{\ip@file}{}  ?    As mentioned, it's a freshly installed TeX Live 2016; I've also checked the installed Pygmentize version, which is 2.1.3 (installed via pip). Testing with TeX Live 2015, the above code, however, works without problems with both pdflatex and lualatex.  Does anybody have a hint for me on how to fix this, or is it a bug in lualatex or minted (or whatever other package) that should be reported?  Update: With minted version 2.2 (2016-06-08), the package loads the shellesc package automatically, as mentioned by @David Carlisle and @egreg in the comments; therefore, the problem should not occur any more, if you have this version installed. Question  If $|G|=p^3$ and $G$ is not abelian show that $G'=Z(G)$  Attempt   Since $|G|=p^3$ then $G$ is solvable and let $$1\leq G^{(n-1)}\leq...\leq G^{(n)}=G,(1)$$  be its derived series.We know that $G^{(n-1)}$ is an abelian subgroup of $G$ so $|G^{(n-1)}|=p$ or $p^2$ (since $G$ is not abelian).Hence we have that $\bigg|\dfrac{G}{G^{(n-1)}}\bigg|=p$ or $p^2$ so $\dfrac{G}{G^{(n-1)}}$ is abelian $\Rightarrow G'\leq G^{(n-1)}$ so $(1)$ is $1\leq G' \leq G,(2)$.   Furthermore, $Z(G)\not=1$ (since $G$ is a $p-$group) and $\dfrac{G}{Z(G)}$ is abelian $\Rightarrow G'\leq Z(G)$  Is this correct so far? How could I continue? Why is there so much fear surrounding LiPo batteries? I've been trying to design a charging system for a small robot powered by a 2S 20C  (LiPo) battery. Were I to trust everything I read online, I would believe that the LiPo will kill me in my sleep and steal my life savings. The common advice I read, if you are brave enough to use LiPo batteries, is "never leave unattended", "never charge on top of a flammable or conductive surface", and "never charge at a rate faster than 1&nbsp;".  I understand why this is prudent, but what is the actual risk with LiPo batteries?  Nearly every cell phone, both Android and iPhone alike, contains a LiPo battery, which most people, including myself, charge while unattended&mdash;often-times while left on a flammable or conductive surface. Yet you never hear about someone bursting into flames because their cell phone exploded. Yes, I know there are freak accidents, but how dangerous are modern LiPo batteries? Why do so many online commenters treat stand-alone LiPo batteries like bombs waiting to go off, but don't even think twice about the LiPo sitting in their pocket? How to merge all scene geometry into a single mesh? During my attempt to upgrade my Xubuntu 14.04 installation with  sudo apt-get dist-upgrade   I made the mistake of interrupting the process by closing my laptop, which caused it to suspend to disk. After re-opening, the monitor remained black, so I was forced to reboot the system. I have since discovered many failures of drivers (wlan0 missing, USB memory stick cannot be mounted, USB mouse not recognised, and maybe more undiscovered problems with hardware).   My beginner's attempts to manually repair the single problems could have made it even worse. During the installation of the current distribution I chose to encrypt my whole hard disk.