I just gave in to the App Store's constant nagging about upgrading to Yosemite. Aside from an unhappy Chrome, there is this kextd process that's constantly running close to 95% CPU. This results in the fan also running constantly and my battery being drained.  Things I tried but didn't work:   removed all the .plist files upgraded to 10.10.1 when it came out this morning called Apple support who had me delete a cache file (/System/Library/Caches/com.apple.kext.caches/Startup/kernelcache/loadedkextmt.plist)   The process doesn't start straight at boot, but maybe 10 minutes later during use.  How can I get this kextd process to quiet down?
I have a 13" MBP late 2009, 2.53 GHz, 4 GB RAM, and on OS X 10.8.3. As soon as I boot up the fans start going at the highest rpm and like I mentioned the kernel_task is always at around 90% when no apps are being run. I read somewhere that I should try safe boot and see the effect but there is none. Any ideas as to what is causing it?  Thanks
Show all the file up to the match grep --before-context 5 shows 5 lines before the match.  I want to show everything before the match. Doing grep --before-context 99999999 would work but it is not very... professional.  How to show all the file up to the match? When should I use GET or POST method? What's the difference between them? Existence of minimal prime ideal contained in given prime ideal and containing a given subset Let $R$ be a unital commutative ring, $P$ $\subseteq$ $R$ a prime ideal, $X\subseteq P$ a subset. Show there exists a minimal (inclusion minimal) prime ideal contained in $P$ which contains $X$.   My approach: Let $\langle X\rangle$ be the ideal generated by $X$. $P^c$ is a multiplicative set, as $P$ is prime. $\langle X\rangle\subseteq P\subseteq R$ and $P^c\cap\langle X\rangle=\emptyset $ so by Zorn's lemma there exist prime ideal $I_1$ satisfying $\langle X\rangle\subseteq I_1\subseteq P$. As $I_1$ is prime, it's complement is a multiplicative subset which does not intersect $\langle X\rangle$, hence I can find prime ideal $I_2$ satisfying $\langle X\rangle\subseteq I_2 \subseteq I_1$ and so on... I've got an infinite descending chain of prime ideals and I can't be sure that the process will stop.  Hints will be appreciated, thank you.   Edit: Can I conclude that every prime ideal contains a minimal prime ideal? If you get stuck in research, at what point in time should you ask for help? It's always worthwhile to take some time to try to figure it out by yourself. But eventually there's a point where you're unsure how much more time it would take to figure it out by yourself (which could take far longer than you originally think), and when asking for help could be more helpful.  So for analytical or computational research, what are some guidelines for when you should ask for help (from either your adviser, other grad students, or other researchers) when you get stuck? Poll in background for StackExchange™ MultiCollider SuperDropdown™ inbox events and update the titlebar accordingly à la Facebook "No root file system defined" error while installing ubuntu I am new to linux/ ubuntu and just downloaded the v11 of ubuntu to learn linux. I faced this "No root file system is defined" error while trying to install it. This is how I was proceeding -    Downloaded ubuntu v11 from the ubuntu.com website, wrote the iso into a bootable cd, and then got into the linux installation process on restarting; everything fine till here. In one of the screen during installation, there are three choices - install alongside windows, something else etc.. Since I have windows 7 in the C drive, I selected the first option - "Install alongside another OS".      Let me interrupt here to give my existing system details - HardDisk   size: 640GB.  Number of existing partitions - 5 C drive - label   windows - 160GB - has windows 7 installed D drive - label linux -   160GB - does not have any data E drive - label backup - 100GB - has   some data F drive - label entertainment - 100GB  - has some data G   drive - label work - 90GB  - has some data All of the above are in   NTFS format.    In the screen that follows, an image is shown with 2 parts and each part is shown to have size equal to 80GB. There is a horizontal slider in the middle of these two images, with which I can resize the partitions. The right side partition is labeled Linux. There is also an option to do 'advanced partitions'. On clicking advanced partitions on the above screen, a new screen is shown in which the partitions existing in my computer are shown - but the labels are different. I see that there are two partitions with size = 160GB each (as expected), and so I assumed that the first 160GB would be my existing C drive and the second on would be the partition which I had labeled as linux (drive D). So I selected the linux partition and clicked on proceed/ install now, and then this error was shown - "No root file system defined".. and I cannot proceed after this.   Please let me know two things here:   During the screen in point number 3 above, the image with slider was shown. Which partition (drive c: or d: or anyother) is being referred to here? Which one am I actually resizing - is it the existing c: drive which has windows 7 installed already, that is getting shrunk and then ubuntu getting installed in the remaining space? What does ""No root file system defined" error mean? How do I select the proper partition and continue with the installation?    P.S.:  I had already partitioned my drives as mentioned above, and the D drive with 160GB was specifically left free for installing ubuntu. I would like to Select D drive during setup and install ubuntu here, while still keeping the already installed windows7 in C drive.  Thanks! How would I identify what's causing my Mac to permanently hang on shutdown? Whenever I try to shutdown or reboot my Mac (Macbook Pro 15" Retina late 2013, OS X 10.11.3) it closes all programs like normal and then it goes into that black screen with the progress bar. When it gets to about halfway it permanently hangs and won't ever finish rebooting. I looked at the log viewer and couldn't find anything in particular. Is there a way to monitor a shutdown more closely and find out what's causing it to get stuck? A question about the higher-order Weyl variation for the geodesic distance I have a question in deriving Eqs. (3.6.15b) and (3.6.15c) in Polchinski's string theory vol I p. 105.   Given      $$\Delta (\sigma,\sigma') = \frac{ \alpha'}{2} \ln d^2 (\sigma, \sigma') \tag{3.6.6}$$   where $d(\sigma,\sigma')$ is the geodesic distance between points $\sigma$ and $\sigma'$.   It is said for the Weyl variation $\delta_W$,     $$\partial_a \delta_W \Delta(\sigma,\sigma')|_{\sigma'=\sigma}= \frac{ 1}{2} \alpha' \partial_a \delta \omega(\sigma) \tag{3.6.15a} $$   $$ \partial_a \partial_b' \delta_W \Delta(\sigma,\sigma')|_{\sigma'=\sigma}= \frac{ 1+ \gamma}{2} \alpha' \nabla_a \partial_b \delta \omega(\sigma) \tag{3.6.15b} $$   $$ \nabla_a \partial_b \delta_W \Delta(\sigma,\sigma')|_{\sigma'=\sigma}= - \frac{  \gamma}{2} \alpha' \nabla_a \partial_b \delta \omega(\sigma) \tag{3.6.15c} $$   Here $\gamma=-\frac{2}{3}$.   I know the reason for the factor of $1/2$ in the RHS of Eq. (3.6.15a) and I can derive it. But, putting $\nabla$ on LHS and RHS of Eq. (3.6.15a) will not lead to (3.6.15c). I guess it is because there is some higher-order terms in the geodesic distance where the treatment of (3.6.9)-(3.6.11) omitted. But I don't know how to get it. I tried $ds^2= g_{ab} dx^a dx^b= (\eta_{ab} + h_{ab})dx^a dx^b $ to separate the deviation of Minkowski metric, but I cannot get the factor $\gamma$   My question is, how to derive Eqs. (3.6.15b) and (3.6.15c) (especially there is a prime, $'$, namely $\partial'_b$ in the LHS of (3.6.15b) but not in the RHS) Seeking SF Short Story from late 1970s/early 1980s about dystopian future with an old man playing a piano I read this in the late 1970s or early 1980s, possibly as part of a juvenile fiction anthology/collection. From what I remember in this story a post-apocalyptic society requires each member to go out before their 18th birthday and kill an "oldster" adult (i.e. I think over 30 similar to the time in Logan's Run) to make room for themselves.  Otherwise they will be killed.   The kids actually cut off the hand of the victim which has a tattoo on it with the birthdate/age. In this case, the world has gotten to the point the person who kills the oldest person gets a "prize" of one more year of life beyond 30. Note, this is NOT Logan's run nor the novel upon which it is based.   The hero in this case finds an old man, the oldest he had ever seen (something like 45-50 I think) making wonderful sounds with a strange device. It was a piano.   He then confronts the old man  SPOILER ALERT     ... but cannot bear to kill him. The old man takes pity on the boy and offers him his hand to take back so he can live. The boy asks if the old man will still be able to play the piano with just one hand. The old man smiles and says "Yes, but not as well. " Then, the boy decides to stay with the old man and risk becoming an outlaw so he can learn to play the piano. Shocking? - MacBook stubby earthed charger UK I have no idea why. But apple have not earthed the stubbly plug for the macbook pro transformer. So on the short lead the only way the charger is earthed is when I touch it or the macs unibody which gives you a sort of vibrating feeling on your palms.  When I went to the genius bar to complain about it they said that it was completely 'normal'. Where their definition of normal is that every MacBook does it. I have had 4 MacBooks and all have done it.    The genius did say that he though he has seen a few earthed 3pin plugs. So my question is where can I pick one up? or how could we force apple to earth the stubby plugs and recall them? In python, if I say  print 'h'   I get the letter h and a newline.  If I say   print 'h',   I get the letter h and no newline.  If I say  print 'h', print 'm',   I get the letter h, a space, and the letter m.  How can I prevent Python from printing the space?  The print statements are different iterations of the same loop so I can't just use the + operator. comment.sty and UTF8 encoding I noted that if I use comment.sty and a there is a block of text containing UTF8 characters inside a comment environment, the compilation aborts!  Minimal Example  \documentclass{article} \usepackage[T1]{fontenc} \RequirePackage[utf8]{inputenc}%this file is stored as UTF8 file! \RequirePackage{comment} \specialcomment{privateSolution}     {\begingroup\itshape\noindent\textbf{Solution}\\}     {\endgroup} %\excludecomment{privateSolution}%Use it to remove solutions!  \begin{document} \title{Comment.sty and UTF8 test file} \maketitle \section{UTF8 character test} In which alphabet characters àìùòè are common? \begin{privateSolution}     The Italian alphabet contains àìùòè. \end{privateSolution}  \begin{comment}     The Italian one! It contains àìùòè. \end{comment} \end{document}   Has anyone the same problem? Any workaround?  Thanks in advance. Q: How many arrangements of a,a,a,b,b,b,c,c,c are there such that  $\hspace{5mm}$ (i). no three consecutive letters are the same?  $\hspace{5mm}$ (ii). no two consecutive letters are the same?  A:(i). 1314. ${\hspace{5mm}}$ (ii). 174.  I thought of using the General Principle of Inclusion and Exclusion along with letting $p_i$ denote a property that.. , and doing so, I will evaluate $E(0)$, which gives us the number of arrangements without any of the properties.   How do I go about doing that? I am trying to use the method stated above in solving this question, but I am unable to generalize the properties $p_i$. Does a family of a distribution have a different definition for statistics than in other disciplines?  In general, a  is a set of curves, each of which is given by a function or parametrization in which one or more of the parameters is varied. Such families are used, for example, to .  For statistics, a family according to  is the result of varying the shape parameter. How then can we understand that the gamma distribution has a shape and scale parameter and only the generalized gamma distribution has, in addition, a location parameter? Does that make the family the result of varying the location parameter? According to @whuber the meaning of a family is implicitly A "parameterization" of a family is a continuous map from a subset of ℝ$^n$, with its usual topology, into the space of distributions, whose image is that family.  What, in simple language, is a family for statistical distributions?  A question about relations among of the statistical properties of distributions from the same family has already generated considerable controversy for a  so it seems worthwhile to explore the meaning.  That this is not necessarily a simple question is born out by its use in the phrase , which has nothing to do with a family of curves, but is related to changing the form of the PDF of a distribution by reparameterization not only of parameters, but also substitution of functions of independent random variables. Plotting graphs using bash Pretty self descriptive, without being able to view the source of the noise how can we tell the difference between a sound in front of us and a sound behind us if pitch, volume and distance are all the same.   Also assume that it is not biased to one side more than the other, e.g its not to your left or right but directly in front or behind.   I'm interested in knowing if it is a part of the ear that makes this distinction, or a function of the brain. Limiting OpenVPN bandwidth I'd like to give users a certain amount of traffic. Let's say user A gets 1 GB and user B get 5 GB.  I have a great script which does log all this info, however this script is called when the user disconnects (client-disconnect).  Now, my problem is the following: what if user A uses up 1 GB of data and simply never disconnects? He would be able to use thousands of GB's. Is there any way run a specific script periodically within OpenVPN (so no crontab, since OpenVPN passes environment variables). How to find all subgroups of a direct product? I am wondering how do we find all subgroups of a direct product? Is there a method to find it?  For example, how can we find all the subgroups of $\mathbb{Z}_2\times\mathbb{Z}_2$?  There is the answer: $\{(0, 0), (1, 0)\}, \{(0, 0), (0, 1)\}, \{(0, 0), (1, 1)\}$, and the improper and trivial subgroup. But I do not know the method how to find it.   All I can think about is the following: since the order of $\mathbb{Z}_2\times\mathbb{Z}_2$ is $4$, the order of a subgroup of it can be $1,2$ or $4$.   If order is $1$, then it is trivial, and if order is $4$, it is proper. Then, the order of a subgroup is $2$. We know all the elements of   $\mathbb{Z}_2\times\mathbb{Z}_2$, so we try all the pairs.   Is that the method?   But what if we are given a bigger order product, such as $\mathbb{Z}_2\times\mathbb{Z}_8\times\mathbb{Z}_3\times\mathbb{Z}_9$? It looks very long to try all possibilities.   Can anyone help?  Thanks Incompatible pointer type initializing 'CustomCellView *' with an expression of type UItableViewCell Determine all $f : \mathbb R \rightarrow \mathbb R$ such that $f(f(x) + y) = f(x^2 - y) + 4yf(x)$. Determine all $f : \mathbb R \rightarrow \mathbb R$ such that $$f\big(f(x) + y\big) = f(x^2 - y) + 4yf(x)$$ for all $x,y\in\mathbb{R}$.   $f(x) = 0$ is obvious , but how can we find all other functions?  Thanks in advance!