How do I install the latest Python version in Ubuntu?
How do I install a different Python version using apt-get?
Not every boolean function is constructed from $\wedge$ (and) and $\vee$ (or) NSF IIS status date changed, status still pending Can I store the .git folder outside the files I want tracked? I have an unusual idea to use git as a backup system. So let's say I have a directory ./backup/myfiles and I want to back that up using git. To keep things clean I don't want to have a .git directory in the myfiles folder, so I thought I could create ./backup/git_repos/myfiles. From looking at the git docs, I've tried doing this:  $ cd backup/myfiles $ mkdir ../git_repos/myfiles $ git --git-dir=../git_repos/myfiles init Initialized empty Git repository in backup/git_repos/myfiles/ $ git --git-dir="../git_repos/myfiles/" add foo fatal: pathspec 'foo' did not match any files   You can see the error message I get there. What am I doing wrong? Is Adzerk safe / legitimate? using tar showing, "No Such file or directory" But when I try to run it using  tar zxvf jre-8u151-linux-i586   I get tar (child): jre-8u151-linux-i586: Cannot open: No such file or directory tar (child): Error is not recoverable: exiting now tar: Child returned status 2  What is wrong? The name and place matches prefectly. Dirac Delta function inverse Fourier transform We know that the Fourier transform of the Dirac Delta function is defined as $$\int_{-\infty}^{\infty} \delta(t) e^{-i\omega t} dt = 1,$$  and if I were to reconstruct the function back in time domain, the inverse Fourier transform is defined as  $$\delta(t) = \frac{1}{2\pi}\int_{-\infty}^{\infty} e^{i\omega t} d\omega.$$  How do I compute this integral analytically? "I wish I didn't do" vs. "I wish I hadn't done" This is a silly question but under what conditions is $a^{xy}=(a^x)^y$ true, given all are complex numbers? Speed of light in a gravitational field? I have a 2x2 experimental design. In the experiment, I also collected the participants' professional qualifications (categorical variable- yes /no). I would like to test the effect of controlling this variable on the MSE. I understand that in ANCOVA, the covariate is either an interval or ordinal variable. So should I refer to the test as an ANCOVA if I include professional qualification as an additional variable? Or should it be a blocking variable since &quot;prof. qualification&quot; is categorical. How do I define custom web.config sections with potential child elements and attributes for the properties? The web applications I develop often require co-dependent configuration settings and there are also settings that have to change as we move between each of our environments. All our settings are currently simple key-value pairs but it would be useful to create custom config sections so that it is obvious when two values need to change together or when the settings need to change for an environment. What's the best way to create custom config sections and are there any special considerations to make when retrieving the values? After upgrading to macOS Sierra, I'm getting the notification that "Your disk is almost full. Save space by optimizing storage.":    The options appear to be to store my files in iCloud, automatically delete files, or manually delete files:    My problem/irritation is that I have 80GB free of my 440GB volume.  The question: is there a way to silence this notification in a (semi-)permanent fashion, or to change the threshold it uses for the notification? How do I evaluate several n-th derivatives of a function at one point? Intuitive understanding of the elements in the stress-energy tensor There is an image in the Wikipedia about the :    I have a rough understanding of the stress tensor: you imagine cutting out a tiny cube from the fluid and form a matrix out of the forces on each side of it: it's not hard to see that the forces that push the faces outwards so the x direction of the force on the x side, the y direction of the force on the y side, etc. is the pressure, while other forces directions are the shear stress (these can be non-zero is some jelly-like substance).  Now the first question: Why is the lower half of the spatial part is the momentum flux, while only the upper one is the shear stress on the image? Is the image wrong? Isn't the spatial part describe the classical stress tensor?   The second question is: what's the intuition behind the temporal part?  So if I have a Minkowski spacetime and cut out a cube of it, then it's quite hard to see why "pressure" on the temporal face means density, also why "shear stresses" on the temporal face translate to momentum density, not speaking of the "temporal force components" the spatial faces...  Also stresses are measured in Pascals, mass density is measured in $kg/m^3$ while momentum density is in the units of $Ns/m^3$. These units doesn't seem to be compatible, but still they are in the same matrix, why?  EDIT: It has been pointed out that momentum flux refer to the entire blue part, it indeed have a lighter frame I didn't notice. Then yet another subquestion: what's the difference between the momentum density and momentum flux? I have been trying to show these two inequalities hold for all positive integers n, but I don't know how to proceed at all... I have tried playing around with them but I didn't find anything helpful. I have also tried induction but I couldn't make it work. When you edit a message and repost the contents of  its first revision, the repost is eaten up by chat.  Steps to reproduce:   Join any chat room Post something. Let's say you post abcd Edit that to something else. For example, --- Try to post abcd again. The green (pending) message will show up, but when the response is received, it disappears (the server spits out {"id":null,"time":null} as the response)   This happens more often than you think. Many a time I post something, only to realize that I want to use the magic separator (---) to separate it from a previous block. So I up-arrow, Ctrl-X, and type ---, and then I repost the cut text. Which gets eaten up by the server -- making a small change to the repost fixes things. What does "Suit yourself" mean? I recall Asimov had a character who was The autoc of , clearly based on the word “autokrat” but I don’t recall the exact spelling.  This stumped Google, which would rather correct the spelling to some other word than find a unique word.  In the story, he had gone undercover and the reader did not know either that some other character was in fact the Autoc, until it had been revealed to the main character. Recovering a password for a Word 2007 document What are the primary differences between the rules of D&D 3.5 and Pathfinder? What are some of the rule changes that Pathfinder brings in comparison to D&amp;D 3.5?  I am curious what changes were made so I can explain to my group what it has to offer.