Ubuntu 14.04 boot error on Windows 8.1 - SYSLINUX 4.07 EDD
Not booting from USB or CD (SYSLINUX Message)
How to drive multiple LEDs from a Li-ion battery (with varying voltage)? I want to supply constant voltage to my LED's but the supply varies from 3.7V to 4.2V (Li-ion battery). I cannot use 3.3V voltage regulator as it will need at least 4.3V voltage at the input but my battery can supply only 4.2V max. so is there any other way I can supply regulated 3.3V to my LED.   RGB LED = 3.3V, 60mA Battery = 3.7V - 4.2V, 3000mA Number of LEDs = 24 The LED's are connected in parallel Last months I have lots of referrer spammers in my GA statistics. Their count is ~10x higher than count of legit visitors (my site is not very popular yet). I've turned on an option to hide known spammers in GA settings, but it didn't help at all. It seems these spammers are using scripts to spam directly to GA (i.e. they are not logged in my IIS).  Is there anything I can do to stop these spammers?    UPD 10 months later, and they started spamming using fake target page names... and Google is still doing nothing about it. I've only found a recursive algorithm of the extended Euclidean algorithm. I'd like to know how to use it by hand. Any idea? Primary ideals of $\mathbb{Z}$ Let $R=\mathbb{Z}$ I must prove that      In $\mathbb{Z}$ the primary ideals s are precisely the ideals $(p^k)$ where $p$ is a prime number and $n\ge 1$.   $$$$ The definition of primary ideal.     Definition. An ideal $I$ of the ring $R$ is called primary if for all $a,b\in R$ $$(ab\in I\quad\text{and}\quad a\notin I)\Rightarrow b^n\in I, \text{for some positive integer $n$}.$$   Therefore I must prove that      $$(n)\;\text{is primary in}\;\mathbb{Z}\iff n=p^k, k\ge1,p\ge2,\;\text{where}\;p\;\text{is a prime}.$$   Proof ($\Leftarrow$) We suppose that $n=p^k$ for same prime $p$ and $k\ge 1$. Let $a,b\in\mathbb{Z}$ such that $ab\in(p^k)$ and $a\notin (p^k)$. Then $p^k\nmid a$, but $p^k \mid ab$ I no longer know how to proceed.  $(\Rightarrow)$ Let $(n)$ a primary ideal and we suppose for absurd that $n$ is not a power of a prime, then? how could I proceed?  Now, let $ab\in (p^k)$ with $a\notin(p^k)$, then $p^k\mid ab.$ Can I conclude that $p^k\mid b$?   How can I set up the other implication? Thanks Boot drops to a (initramfs) prompts/busybox If the electric field is the gradient of the potential, then can we say that whenever potential is zero, the electric field is zero? For example, in a dipole, at the center of the two charges making up the dipole, the potential is zero but the electric field is non-zero. But if $E = -\operatorname{grad}V$, then why is $E$ not zero?  Another example: In the case of two positive charges, the electric field is zero at the mid-point of line joining them, but potential is non-zero. What am I misunderstanding here? Database does not update automatically with MySQL and Python I'm having some trouble updating a row in a MySQL database. Here is the code I'm trying to run:  import MySQLdb  conn=MySQLdb.connect(host="localhost", user="root", passwd="pass", db="dbname") cursor=conn.cursor()  cursor.execute("UPDATE compinfo SET Co_num=4 WHERE ID=100") cursor.execute("SELECT Co_num FROM compinfo WHERE ID=100") results = cursor.fetchall()  for row in results:     print row[0]  print "Number of rows updated: %d" % cursor.rowcount  cursor.close() conn.close()   The output I get when I run this program is:     4Number of rows updated: 1   It seems like it's working but if I query the database from the MySQL command line interface (CLI) I find that it was not updated at all. However, if from the CLI I enter UPDATE compinfo SET Co_num=4 WHERE ID=100; the database is updated as expected.  What is my problem? I'm running Python 2.5.2 with MySQL 5.1.30 on a Windows box. Problem in skew-symmetric matrix Let $A$ be a real skew-symmetric matrix. Prove that $I+A$ is non-singular, where $I$ is the identity matrix. If we have a complex scalar $\phi$ we know that the gauge-invariant interaction with $A$ is given by $A^\mu J_\mu$, where $J$ is the Noether current of the $U(1)$ symmetry of the Lagrangian $$ J_\mu\sim \phi^\dagger\partial_\mu\phi-\phi\partial_\mu \phi^\dagger \tag{1} $$  If we have a real scalar instead, $J=0$ and the field doesn't couple to $A$: real particles aren't charged.  My question is: what if we took $$ J_\mu\sim \phi\partial_\mu\phi \tag{2} $$ to couple $\phi$ to $A$? The interaction is Lorentz invariant and renormalisable, but it is not gauge-invariant, which is probably a bad thing. At what point would this theory break down?  This is probably very naïve, but I think that the Feynman rules for this theory are straightforward. So I guess the theory makes sense at least perturbatively. The theory is probably flawed at a more fundamental level, but I cant't seem to find where (some kind of gauge anomaly perhaps?) Removing nodes from an XmlDocument What is the minimum time to consider with a connecting flight in the USA? Given the extensive time taken for immigration formalities in the US, what is the shortest time to consider between connecting flights in the US, when coming from abroad?  Until now I have always entered the US at my destination. This is not always the cheapest option. I was told that 3 hours is the advised time to go through immigration and boarding of a connecting flight. Online booking sites still offer connecting flights, with a transfer times sometimes even less then 1 hour. iPhone call log / history Generating random results by weight in PHP? I know how to generate a random number in PHP but lets say I want a random number between 1-10 but I want more 3,4,5's then 8,9,10's. How is this possible? I would post what I have tried but honestly, I don't even know where to start. In X-Men Origins: Wolverine,      Wolverine is shot through the head with what appears to be a vibranium bullet by William Stryker. He remarks that the brain will grow back but the memories won't.   So the projectile penetrated the adamantium skull and damaged the brain. Adamantium is an inorganic substance. It will survive anything that would otherwise destroy the rest of Wolverine's body. But if anything (such as vibranium) manages to damage the adamantium, it is not covered by Wolverine's healing abilities.  Does this mean that Wolverine has an Achilles' heel on his forehead? If so, how did he take a bullet to the exact same spot in X-Men: United (at Ice Man's home)? Like most Python developers, I typically keep a console window open with the Python interpreter running to test commands, dir() stuff, help() stuff, etc.  Like any console, after a while the visible backlog of past commands and prints gets to be cluttered, and sometimes confusing when re-running the same command several times.  I'm wondering if, and how, to clear the Python interpreter console.  I've heard about doing a system call and either calling cls on Windows or clear on Linux, but I was hoping there was something I could command the interpreter itself to do.  Note: I'm running on Windows, so Ctrl+L doesn't work. Infinitely many primes for quadratic residues I was reading a textbook. I found that it was mentioned the speed of sound increases with increase in temperature. But sound is a mechanical wave, and it travels faster when molecules are closer.   But an increase in temperature will draw molecules away from each other, and then accordingly the speed of sound should be slower. How is it possible that the speed of sound increases if temperature increases? What is the relation of speed of sound and temperature? The subscript size for formulas in beamer presentation First of all sorry because this question may be duplicated. I don't know why the question was uploaded with another user's name and I can't edit it (may be you can delete the previous question with the same title). The question is the following:  I am creating a beamer presentation where I have a lot of formulas. Between the packages used I have \usepackage{amsmath} and the theme for the presentation is \usetheme{Warsaw}.  As it can be seen in the attached picture, the size of the sub(super)script is bigger than the normal writting.     Anyone knows a set of basic packages in order to get the classical formulas, without these size changes?  The code is the following  \documentclass[]{beamer}  \setbeamercovered{transparent}   %--------------------------% % To add enumeration index %--------------------------% \addtobeamertemplate{navigation symbols}{}{%     \usebeamerfont{footline}%     \usebeamercolor[fg]{footline}%     \hspace{1em}%     \insertframenumber / \inserttotalframenumber  } \setbeamercolor{footline}{fg=black} \setbeamerfont{footline}{series=\bfseries}   %---------------------------------------------------------------------------------%  \usepackage{amsmath,amssymb}    % Theme for the presentation \usetheme{Warsaw} % Change the colour \usecolortheme{spruce}  \setbeamertemplate{footline}{}  % Delete the footline with the names    \begin{document}    \begin{frame} \frametitle{\textbf{Algorithm}: step \texttt{s}}   \scriptsize  \textbf{STEP \texttt{s}}  \vspace{0.25cm}  Let $B^{(s-1)}$ be the variable  for the $\mathit{(s-1)}$-th step, let's take the sets $I_+^{(s-1)}$ and $I_-^{(s-1)}$ of length $r_+^{(s-1)}$ and $r_-^{(s-1)}$ respectively,and define:\\  \vspace{0.25cm}  \begin{center}  $B^{(s+)}= \sqrt{\tfrac{(r_+^{(s-1)} + 1)*r_-^{(s-1)}}{r_+^{(s-1)} + r_-^{(s-1)} + 1}} $  \end{center}   \end{frame}  \end{document} What is the correct possessive for nouns ending in "‑s"? LIGO flawed by the identical expansion of laser wavelength and arms in presence of a gravitational wave? , Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming to directly detect gravitational waves. The device measures the phase shift laser beams.  If I understand this well, the measurement assumes that a suitable gravitational wave reduces and prolongs one of the tubes and the extension will take effect in the phase-shifting laser beams.  But I think if there's a gravitational wave that passes through it, it will affect everything, even the laser beam. This means that when the wave lengthens or shortens the tube, it also lengthens or shortens the wavelength of the laser beam.  In my opinion, therefore, this device does not work. Or am I wrong?