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Can one introduce magnetic monopoles without Dirac strings? To introduce magnetic monopoles in Maxwell equations, Dirac uses special strings, that are singularities in space, allowing potentials to be gauge potentials. A consequence of this is the quantization of charge.  Okay, it looks great. But is this the only way to introduce magnetic monopoles? Array index out of bound behavior Is there a way of finding a formula for $\sum\limits_{k=1}^n k^k$? Maybe I'm missing something really obvious, but I've looked around a bit on the Internet and I haven't been able to find anything.  So, what I'm looking for is a formula in closed form to generate the sequence $1,5,32,288,3413,\dots$ Loading D3.js data from a simple JSON string What are the options for a non-EU national who wants to extend his stay in Switzerland (totaling less than 90 days)? Theoretically if I were able to build some sort of device that let me sit 1 foot away from the surface of the Sun (or any star for that matter) without being vaporized, would a star produce any sort of audible sound at that distance?   From my understanding, sound waves need a medium to propagate through (air, water, etc).   Does this mean that all stars are completely silent (in the audible spectrum of frequencies at least) as they fuse  hydrogen into helium?   I know stars emit radio, xray, infrared, ultraviolet electromagnetic waves, but how about audible (20 Hz to 20Khz) frequencies?   For some reason it seems like this process would produce some sort of sound. Infinite series $\sum _{n=2}^{\infty } \frac{1}{n \log (n)}$ Unit testing a method that calls another method I tried this way, I only need to know if this is correct or if there are better ways to solve this:  $2^{1000}$ does not have a factor of $5$ obviously therefore we can assume  $$ 10^{m} &lt; 2^{1000} &lt; 10^{m+1}$$ for some  $m$   Assume $ k = 2^{1000}$, then take log on both sides $\log k = 1000  \log 2 \approx 301.02999 &gt; 301$  Therefore $2^{1000}$ has $302$ digits. I sold an investment in a standard brokerage account at a small loss because I needed the money for a down payment.  I still think it is a good investment, can I buy the same investment in a standard IRA without running into wash sale problems?  I will probably just wait the 30 days any way to avoid any headaches, but I want to know if there is a definitive answer on this.    Being as the cost basis in the traditional IRA doesn't matter, I wouldn't think there would be a problem. Iterated self-composition of arbitrary function Does there exist some notation that represents the iterative composition of a single-input, single-output function with itself? As in, say, $f_5(x)=f(f(f(f(f(x)))))$.  In other words, going by the above (incorrect, I'm pretty sure) notation:  $f(x)=x+1$, $f_n(m)=m+n$  I'm looking for the correct way to express the notion of "$f_n(x)$" for any $f$. I want to make a persistent live Ubuntu USB drive with more than 4GB of storage.   I know there is an option of installing directly on the drive but I don't want to do this as it will restrict the drive from working on different computers.   One option is to make an additional partition with extra space but if I do this how can I get newly installed software to be stored on this partition? Which expressions can be used to close an email? At the end of written communication like emails and letters, it is customary to use a closing . Which formal and informal expressions can be used to end emails? Any software for windows Writing custom (intelligent) microsoft windows firewall extension (C#/C++/C) Writing custom (intelligent) firewall for windows Installing nginx etc. on the same computer and use it as proxy with rules.   "You could not solve all Ddos problems with software" is not answer for this question.I want to reduce Ddos vulnarebility of my server.(It will stop low-level Ddos attacks)  Hosted solutions or cloud services are not related with this question.  Closing some of the ports and protocols via Microsot Windows Firewall is not related with this question.  Any idea?  EDIT After Questions  Low level: sample scenerio: 500 zombie clients and each of them sending 100 Custom Get/Post requests per second)   Web Application is on IIS. I want to stop attacks before they reach to IIS.  EDIT After Helpful Comment  How can the DDOS attack achieve its aim?   Exhausting bandwidth ( Not related with my question) Exhausting network hardware of server (NIC) ( Not related with my question) Exhausting server resources (RAM,CPU)  (Yep, I mean this)   If you stop attacks late, then you lost more resources! (Is this false?)   You can stop attacks on Web Application Level (in Asp.net MVc Code or in Handler) You can stop attacks on IIS (Dynamic Ip Restrictions)  You can stop attacks on lower levels (Firewall ..)   EXTRA INFO ABOUT THE LAST ATTACK (7 Hours ago)  When I connected server during the attack IIS Cpu Utilization was %92-%99. And when I try to connect homepage I got this error:  A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: SSL Provider, error: 0 - The wait operation timed out.) Why we can't implement AES 512 key size? Out of curiosity why we can't implement AES 512 key size?    Please explain somehow i can understand! I'm not an expert. I'm using TeXLive 2014. Here's a MWE:  \documentclass{article} \usepackage{tkz-fct}         % Must appear before {thmtools}  \usepackage{thmtools} \declaretheorem{theorem}  \begin{document}   \begin{tikzpicture}     \tkzInit  % No need to even plot anything!   \end{tikzpicture}    \begin{theorem}[A Silly Theorem]     Let $a = 1$. Then $a &gt; 0$.   \end{theorem} \end{document}   The error message is:  ! Extra \endcsname. \kv@processor@default ...fincsname\@xa \endcsname                                                   \csname iftrue\endcsname \... l.12   \begin{theorem}[A Silly Theorem]   If the optional theorem name is removed, all is well. Adding \protect{} doesn't help.  Any idea how to remove this conflict?  Thanks! Why must $a$ and $b$ both be coprime when proving that the square root of two is irrational? Suppose we wish to prove that the square root of two is irrational. We begin by assuming that it is rational.  Namely, where both $a$ and $b$ are integers $$\frac{a}{b} = \sqrt 2  % MathType!MTEF!2!1!+- % faaagCart1ev2aaaKnaaaaWenf2ys9wBH5garuavP1wzZbqedmvETj % 2BSbqefm0B1jxALjharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0x % bbL8FesqqrFfpeea0xe9Lq-Jc9vqaqpepm0xbba9pwe9Q8fs0-yqaq % pepae9pg0FirpepeKkFr0xfr-xfr-xb9Gqpi0dc9adbaqaaeGaciGa % aiaabeqaamaabaabaaGcbaWaaSaaaeaacaWGHbaabaGaamOyaaaacq % GH9aqpdaGcaaqaaiaaikdaaSqabaaaaa!31D3! $$  Why is it so important that both $a$ and $b$ be coprime and the fraction be irreducible?  That is, if $a$ and $b$ are not coprime and the fraction is indeed reducible, then$$\frac{a}{b} \ne \sqrt 2  % MathType!MTEF!2!1!+- % faaagCart1ev2aaaKnaaaaWenf2ys9wBH5garuavP1wzZbqedmvETj % 2BSbqefm0B1jxALjharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0x % bbL8FesqqrFfpeea0xe9Lq-Jc9vqaqpepm0xbba9pwe9Q8fs0-yqaq % pepae9pg0FirpepeKkFr0xfr-xfr-xb9Gqpi0dc9adbaqaaeGaciGa % aiaabeqaamaabaabaaGcbaWaaSaaaeaacaWGHbaabaGaamOyaaaacq % GHGjsUdaGcaaqaaiaaikdaaSqabaaaaa!3294! $$ Canonical has recently announced , which is Ubuntu with a specific interface for mobile devices.  Where can I get phones with this version of Ubuntu pre-installed? If no devices are available yet, where can I pre-order one? Maximum Likelihood Estimate with different parameters Cascading Dropdown I am new to SharePoint 2013. What I need to figure out is based on the following situation. I have several school districts with multiple schools within the school district. I would like to create a cascading dropdown that 1st lists the districts and then will automatically populate a list of schools within a particular district when the district is selected. Can someone tell me if this is possible and if so what steps do I take to achieve it?    Thank you!