I have an old desktop PC with following configuration...  AMD Athelon 1.4 GHz 256 MB RAM 40 GB IDE HDD 8-MB shared VRAM USB 1.0 External Sony CD/DVD RW connecting through USB  Which is the best version of Ubuntu live OS that can be used for this PC. The PC currently has a bit unstable version of Windows XP. And I have a Lenovo A10 Ideapad with Android 4.2 Jellybean which does not connect to the USB DVD writer.
For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?
Currently, for all my commands that require root access, I have to type them out on a command line.  I would like for the GUI to prompt me to key in my password, when sudo is required, instead of having to type out the commands from command line.  Is there any way to enable this? Previously one version of Ubuntu desktop had this feature out of the box.  This version of Ubuntu (that I am now running) I upgraded from a server installation.  I will add, my user account is already added to sudo group. Thus I can run commands such as sudo gedit or sudo apt-get but I'm not able to install software in the Ubuntu Software Center. Flattening a shallow list in Python Is there a simple way to flatten a list of iterables with a list comprehension, or failing that, what would you all consider to be the best way to flatten a shallow list like this, balancing performance and readability?  I tried to flatten such a list with a nested list comprehension, like this:  [image for image in menuitem for menuitem in list_of_menuitems]   But I get in trouble of the NameError variety there, because the name 'menuitem' is not defined.  After googling and looking around on Stack Overflow, I got the desired results with a reduce statement:  reduce(list.__add__, map(lambda x: list(x), list_of_menuitems))   But this method is fairly unreadable because I need that list(x) call there because x is a Django QuerySet object.  Conclusion:   Thanks to everyone who contributed to this question.  Here is a summary of what I learned.  I'm also making this a community wiki in case others want to add to or correct these observations.  My original reduce statement is redundant and is better written this way:  &gt;&gt;&gt; reduce(list.__add__, (list(mi) for mi in list_of_menuitems))   This is the correct syntax for a nested list comprehension (Brilliant summary !):  &gt;&gt;&gt; [image for mi in list_of_menuitems for image in mi]   But neither of these methods are as efficient as using itertools.chain:  &gt;&gt;&gt; from itertools import chain &gt;&gt;&gt; list(chain(*list_of_menuitems))   And as @cdleary notes, it's probably better style to avoid * operator magic by using chain.from_iterable like so:  &gt;&gt;&gt; chain = itertools.chain.from_iterable([[1,2],[3],[5,89],[],[6]]) &gt;&gt;&gt; print(list(chain)) &gt;&gt;&gt; [1, 2, 3, 5, 89, 6] Non-EU spouse of UK citizen Schengen visa requirements I'm a British citizen and my wife is in the UK on a spouse visa. She holds a BRP card. We're planning to visit Germany and some other Schengen countries, and I've got a question around visa requirements/supporting documents.  I've read in few places (i.e ) that the visa requirements are more relaxed if the applicant is a spouse of a UK citizen, and is travelling with the UK citizen.  How relaxed are the requirements? Does my wife need to submit supporting documents for accommodation, finances, flight booking, etc.? Or is it simply submitting the application form alongside the passports and BRP? (i.e standard documentation for Schengen visa application section from ) Is there a general theorem stating why the restricted Lorentz group's exponential map is surjective? The exponential map for the restricted Lorentz group is surjective. An outline of why is shown on the wiki page .  Is there a more general theorem that states that for some class of Lie groups or Riemannian manifolds (which includes the restricted Lorentz group), the exponential map is surjective?  There is a theorem stating that compact, connected Lie groups have surjective exponential maps. But as the restricted Lorentz group is not compact, this isn't applicable. What is the difference between the | and || or operators? I have always used || (two pipes) in OR expressions, both in C# and PHP. Occasionally I see a single pipe used: |. What is the difference between those two usages? Are there any caveats when using one over the other or are they interchangeable? Electrostatic charge leakage What are the ways electrostatic charged objects leak charge in humid conditions?  Can airborne particles pick up charge by contact, then be repelled hence removing charge? If so would it be a significant factor? Short version: In what circumstances is dd safe to use for copying data, safe meaning that there is no risk of corruption due to a partial read or write?  Long version — preamble: dd is often used to copy data, especially from or to a device (). It's sometimes attributed mystical properties of being able to access devices at a lower level than other tools (when in fact it's the device file that's doing the magic) — yet dd if=/dev/sda is the same thing as cat /dev/sda. dd is sometimes thought to be faster, but . Nonetheless, .  Problem: dd if=foo of=bar is not, in fact, the same as cat &lt;foo &gt;bar. On most unices¹, dd makes a single call to . (I find  fuzzy on what constitutes “reading an input block” in dd.) If read() returns a partial result (which, according to POSIX and other reference documents, it's allowed to unless the implementation documentation says otherwise), a partial block is copied. Exactly the same issue exists for write().  Observations: In practice, I've found that dd can cope with block devices and regular files, but that may just be that I haven't exercised it much. When it comes to pipes, it's not difficult to put dd at fault; for example try :  yes | dd of=out bs=1024k count=10   and check the size of the out file (it's likely to be well under 10MB).  Question: In what circumstances is dd safe to use for copying data? In other words, what conditions on the block sizes, on the implementation, on the file types, etc, can ensure that dd will copy all the data?  ( has a fullblock flag to tell it to call read() or write() in a loop so as to transfer a full block. So dd iflag=fullblock is always safe. My question is about the case when these flags (which don't exist on other implementations) are not used.)  ¹  I've checked on OpenBSD, GNU coreutils and BusyBox. Retrieving Current Location and Zip using Geolocation Button relative polar coordinates for TikZ elements in axis environment I would like to annotate a patch plot with lines whose start and end points are given in absolute polar and relative polar coordinates, respectively.  The patch plot, based on cartesian data, comes out as a circular shape centred around the origin (0,0) and shall be simulated here by a plain circle.  Lines should start at the circumference of the shape and point away from the shape under a given angle and have a well defined length. Therefore, the use of relative polar coordinates for the line's end point.  What seems to be straightforward with TikZ (left) fails inside the axis environment of pgfplots (right): neither the inclination angle nor the length of the line are correct if relative polar coordinates are used.    What is wrong with the rel. polar coordinates here?  The code:  \documentclass{standalone}  \usepackage{pgfplots} \pgfplotsset{compat=1.13}  \begin{document}  \begin{tikzpicture}   \draw(0,0) circle[radius=0.01];   \draw[blue] (0,0) circle[radius=1];   \draw[thick] (45:1) -- ++(45:0.5); \end{tikzpicture}  \begin{tikzpicture}   \begin{axis}[tiny,enlargelimits,   axis equal,   xmin=-2,xmax=2,   ymin=-1,ymax=1,   xtick={-2,-1,0,1,2},   ytick={-2,-1,0,1,2},   grid=major,   ]   \draw[blue] (0,0) circle[radius=1];   \draw[blue, dashdotted] (0,0) -- (45:2);   \draw[thick] (45:1) -- ++(45:0.5); %  \draw[thick] (45:1) -- (45:1.5); %absolute coordinates do work   \end{axis} \end{tikzpicture}  \end{document} Since it's Friday and others are playing games, here's another one to take us into the weekend.  Everyone knows about those Russian nesting dolls (called matryoshka dolls, I believe). A small doll nests inside a larger, which itself is inside a larger doll, and so on.   This game does the same with words. You start with a three-letter word, add a letter to make another word, and so on. Longest word wins. The catch? Each additional letter has to form a legitimate word.  Here's one to start you off:     bur   burr   burro   burrow   burrows     Good luck. Uploading video to youtube in right format I have a Sony CX115 and I have a little footage I'd like to put on youtube. I've downloaded Arista from the Ubuntu Software Center and then I've downloaded its Youtube HD plugin. I've converted my video and uploaded it to youtube... The result is a flashy video with a lot of grey in it:    What could I do to publish it in high quality so it'll be viewable? How can I create a new extensible symbol? Given an arbitrary thin vertical symbol, can I create a new math delimiter from it (and if so, how)?   Edit: Ideally, I would like to be able to create an extensible symbol, either built out an existing normal symbol, or even made from scratch.  Edit 2: I am pretty sure that what I am after is an explanation of how to create a .tfm file for an extensible symbol (which Werner's answer describes the general structure of, but not how to make one).    For example, let's say I wanted to use the \dagger () or \wr () symbol as a delimiter, and write expressions like    \[\left\ldagger \sum_{n=1}^\infty a_n \right\rdagger\]   where the symbol scaled appropriately. Would there be any distinction between declaring a symmetric delimiter (like \vert), as opposed to one that has inherently different "left" and "right" versions like [ and ]?  Now, even being unaware of the inner workings of TeX, I imagine that there has to be lots of information in the fonts for how a delimiter is to be scaled in different situations, and if I try to make my own delimiter, this information won't be present. Would I need to get deep into FontForge or equivalent to achieve my custom delimiters, or is there an easier way? How can I restart a Windows 7 computer without screen or mouse? I've recently had problems with my work computer not recognizing either of its attached screens.  I've also had problems with my home computer "locking" the mouse to one app, and no longer acknowledging clicks on, say, the start menu.  In both cases the computer is still running, and I can close apps and so forth with the keyboard.  Restarting usually addresses the problem.  What's the simplest way to restart a Windows 7 computer by the keyboard alone?  Something consistent across all versions would be super.  In Win XP, I believe it was Ctrl-Alt-Delete; pause; Alt-R for Restart; Enter to select.  But on 7 Ctrl-Alt-Delete no longer brings up the same menu.  I'd use Ctrl-Alt-Esc for the Task Manager, but it no longer has a Restart menu (at least on Win 7 Home). Installing Autodesk Maya on Ubuntu is possible, but can be a bit challenging.  Assuming that one already has the required specs and a solid graphics card driver installed, how can it be done? When you have a link from lets say twitter that is t.co/foo that links back to your website how does that effect SEO and how do the major search engines handle Shortened URLs? Over the weekend Sprint and T-Mobile announced again that they would try to merge.  Assuming the powers that be in the US don't have any issue with this deal and it moves forward as proposed, what does it mean for me as a shareholder?  I have 2,000 Sprint shares, and as part of the deal it looks like one Sprint share will be worth ~10% of a T-Mobile share as of the price on Friday.  So does that mean that, if this goes through in early 2019, my 2,000 Sprint shares would turn into 200 T-Mobile shares? What if the price of Sprint stock goes up from here? What if it craters? Is this price/ratio set in stone?  If my stock does get converted, does that happen automatically? Will Fidelity all of a sudden show that I own TMUS stock instead of S? In a very small static universe with only a particle, does it make sense to talk about time? I am sorry if this question is silly; it′s just one of those things I wished I asked before leaving university.  If there were a static universe only as big as the size of two particles, say electrons, and there were one electron in it going back and forth from point A to point B: would time also go back and forth in the future (point B) and in the past (point A), or would it be considered to  go forward as it does for us? would it be possible to know how long that electron stayed at point A or point B, would it even make sense to ask? I guess what I am asking is: does time move forward only because there are so many particles moving in this enormous space that it is almost impossible they would all be back in the same position they held at least once before relative to each other? does time exist only as a consequence of a lot of particles and their position relative to each other, and the space for them, just like heat? I have had no problems exporting .fbx files for Unity except recently some of my .fbx started to rotate the mesh. The asset is correctly oriented, but the mesh is rotated 90 degrees. Is there an explanation and fix for why this happens sometimes, and works properly otherwise? Storing the original document class page layout with geometry Is it possible, using the geometry package, to store (and restore) the original layout specified by the document class (in my case, the class is report)?    Here is some context.  I have been editing a long document in the default page layout for the report document class.  Now I found out that I need a title page.  There is a particular title page layout, and in fact, it works perfectly if I just load the geometry package with its default and change just two settings.  But then I want the rest of the document back in the original page layout!  I can't do something like \restoregeometry, since I think geometry just overrides the class options... i.e. there doesn't seem to be anything to restore.  Similarly, it seems I can't use \savegeometry or \loadgeometry.  So how can I get back to my original layout for the rest of the document without painstakingly hard-coding in all of the specific page layout variables?    Here is a minimum working example:   \documentclass[a4paper,10pt]{report}  \RequirePackage[a4paper,dvips]{geometry} % g1 \geometry{top=2.5cm,bottom=2.3cm}        % g2  \begin{document}  \input{the_title_page}  \SomeGeometryCommandsHere  % g3  \input{the_rest}  \end{document}   If I run the above code with the lines labeled "g" commented out, then the title page does not have the correct page layout, but the rest of the document is formatted perfectly.    If I leave lines g1 and g2 uncommented, then the title page has exactly the correct layout, but no matter what I put for g3 (e.g. \loadgeometry, \restoregeometry, etc.) I can't recover the original layout that I had when g1 and g2 were commented.  Of course, I could completely specify the original layout exhaustively in line g3, and this should in principle work.  However, I spent almost one hour on this last night and when I still couldn't get it formated correctly I decided I really needed a smarter solution. I've tried to find any solution or proof for $$\langle x| x' \rangle=\delta(x-x'),$$ but I only came to this post:   So I got the information, that the vector $|x\rangle$ form a dirac-normalized basis for the Hilbert Space.   I know that the dirac-delta distribution is defined like this: $$\delta(x-x') = \begin{cases} 0 &amp;\mbox{if } x\neq x' \\ \infty &amp; \mbox{if } x=x' \end{cases},$$ this means that my x' is a point on my x axis where I have my infinite high peak. And also $$\int_{-\infty}^{\infty}dx\cdot \delta(x-x')=1.$$  But how actually correlate this with the scalar product of vectors x, x' in the Hilbert Space that form a so-called 'diracl-normailzed" basis of it?  Can you give me some tips on this please? Or maybe you actually know a link, where this is explained.