What characteristics do living organisms (like humans or plants) have that viruses don't?
Why isn't a virus "alive"?
"I think him to be about 50" or "I think he is about 50"? Why is     $$\lim_{n \to \infty} \frac{2^n}{n!}=0\text{ ?}$$   Can we generalize it to any exponent $x \in \Bbb R$? This is to say, is     $$\lim_{n \to \infty} \frac{x^n}{n!}=0\text{ ?}$$     This is being repurposed in an effort to cut down on duplicates, see here: Coping with  duplicate questions.  and here: . Convergence in Probability Prove : $p$(n│even number of ODD parts)=$p$(n│distinct parts ,number of ODD parts is even ) $AB-BA=I$ having no solutions The following question is from Artin's Algebra.      If $A$ and $B$ are two square matrices with real entries, show that $AB-BA=I$ has no solutions.    I have no idea on how to tackle this question. I tried block multiplication, but it didn't appear to work. PHP eval issue with PHP + HTML code Highlight text in code listing while also keeping syntax highlighting I’m using the listings package for code listings. Now I try to highlight some part of the code using \hl from the soul package.  Here’s an example of a resulting query where the injected part of a SQL injection should be highlighted:  \begin{lstlisting}[escapechar=@,language=SQL] SELECT name, password FROM users WHERE name='@\hl{' UNION SELECT "10", 1 \#}@'; \end{lstlisting}   But inside the highlighted part the SQL syntax highlighting is not applied.  So I tried to use \lstlinline for the code part inside \hl as well but it didn’t work:  \begin{lstlisting}[escapechar=@,language=SQL] SELECT name, password FROM users WHERE name='@\hl{\lstinline[language=SQL]$' UNION SELECT "10", 1 #$}@'; \end{lstlisting}   Although this \lstinline part works outside the lstlisting block, it doesn’t work inside it. The error I get for that particular line is:     Extra }, or forgotten \endgroup.   Maybe I’m just missing just some special syntax to get this working. Or is it not possible at all to get proper syntax highlighting for the \hl-highlighted part as well? Word for two collections that do not have any elements in common I'm looking for a word for when you have a collection A and a collection B and they have no overlap.  In mathematical terms: the relation between two sets where the intersection is empty. Like in this Venn diagram:    The word that keeps popping up in my mind is disparate sets, but I don't feel that completely covers the meaning when I look at the definition, because that doesn't seem to preclude overlapping sets that are different:     disparate   1. distinct in kind; essentially different; dissimilar:   disparate ideas. Boy and girl paradox is driving me crazy How can I repair a buried 120v cable splice to make it meet code? I have an electrical question. I have a cable feeding an outdoor yard light. It was cut, I spliced it, soldered it and wrapped it with tape. Is there a way to splice and bury it safely to code? If not, I'll need to dig a 30 foot trench to replace the whole length.  Was about 8 inches below ground, surfaced over the years and probably hit with the weed trimmer.   It is outdoor cable inside copper tubing. Years ago when I bought the wire I knew outdoor was gray. The box said outdoor but it is white like indoor wire.   It was spliced about 20 years ago but am fixing up house and like to hide the ugly splice. I need to rename a bunch of files in order to fix their sort order, therefore I need to be able to do a sort of "find and replace" so I can replace chunks of the filenames at a time.  What tools should I use? I prefer GUI but a command line tool recommendation would also be fine. VAR/VECM/ARDL optimal lag selection Question 1: Is it necessary to consider AIC and the BIC criteria when selecting the lag for a VAR, VECM or ARDL model OR can I use something else?  Example: Can I pick 12 lags because the model simply produce great results when I do or do I have to use the AIC/SIC criteria?  Question 2: A simple google search tells me that its possible to select lag 4 when quarterly data, 12 when monthly etc. Is that a valid approach ? Beamer in LyX: no sperator option avaiable I have been using beamer in LyX for a while now. Love it. But I just got a new computer, istalled LyX again and when I create a new beamer file (or open an old one) the "separator" option that is used to end a frame is not avaiable.  I do not know if there is something wrong with my installation or if I should install some package, or something else.  Has anybody ever run into this problem as well?  Thank you for the help.  Edited: Thank you for the answers, I basically need to update lyx on the other computers now. Does Java Connection.close rollback? Does Java Connection.close rollback into a finally block?.  I know .Net SqlConnection.close does it.  With this I could make try/finally blocks without catch...  Example:  try {     conn.setAutoCommit(false);     ResultSet rs = executeQuery(conn, ...);     ....     executeNonQuery(conn, ...);     ....      conn.commit(); } finally {    conn.close(); } Crash adding comment Why do archery arrows tilt downwards in their descent? Today I was walking using my iPhone 6S running iOS 9.3 as a pedometer and it shutdown.   When I got home and plugged it in, it said 30% capacity.   That seems strange. I would expect it for 2% or 5% to preserve RAM, but 30%? Maybe there is a setting I don't know about.   My question is: Why does my iPhone power off when the battery is down to 30%?   Edit: this is not a duplicate of the low battery crash as I witnessed the low power shutdown and it was not a crash. Quantum mechanical books for mathematicians I'm a mathematician. I have good knowledge of superior analysis, distribution theory, Hilbert spaces, Sobolev spaces, and applications to PDE theory. I also have good knowledge of differential geometry. I would like to study the Semiclassic Analysis, but perhaps I must first study the foundations of quantum mechanics. So I would like to know what book you recommend me to begin studying quantum mechanics. I'm primarily interested in a mathematical point of view. I have seen some books of this type, but I would like to have some other opinion.  Thanks for every reply In the book Principles of Physics by Resnick Halliday: The decrease in Potential energy of a parallel plate capacitor due to a dielectric is because the slab would start to oscillate and the energy would transfer back and forth between the kinetic energy of the moving slab and potential energy stored in the electric field. First of, can somebody provide me the math of the SHM and could somebody explain why it would become the potential of the capacitor i.e. the electric field and not the potential of the slab? As the slab is doing SHM, shouldn't the slab(and not the capacitor) have potential energy at one point of time and kinetic at another like a spring? If the SHM is because of the electric field due to the conducting plates in capacitors, won't they always be in one direction (Plus, it's magnitude is not even a function of distance!)? Could someone be kind enough to provide the math and the reason for Potential and Kinetic Energy transfer question? TikZ arrow emanating from node at an angle for a distance How do I draw a line of length l and at an angle of a from a circular node N in TikZ?