I am having trouble with my Geforce GT 840M on my brand new Ubuntu instillation, it does not seem to be listed as my graphics card.    However the card is listed under lspci    I have tried installing drivers for it from the Nvidia website but after going through the instillation process ( cntrl+alt+1 then,  sudo service lightdm stop , then sudo sh NVIDIA-Linux-x86_64-340.32.run ) My instillation no longer works. When logging into a user the top bar as well as the dock do not appear.   I also seem to be unable to get drivers for it from the software &amp; updates menu as it tells me that there are no updates available.
I just ordered the Nvidia GTX card. I have a dilemma, though. Should I keep using the driver which is available in "additional drivers" in Ubuntu, or should I install the driver from the Nvidia site?  So which driver is the best for me?
Which wire is negative on this PC fan? I just got this PC fan and it has a 3 pin connector, I know the wire with the white stripe is positive but how can I find out which of the other two wires are negative?  If you can't see the photo, here is a link to it: Can helium disappear from Earth? Helium is lighter than air, so it should fly off from Earth. Is it possible that in the future we will run out helium? Consistency of an order statistic in exponential distribution I have two questions.   1) If $X_1,X_2,X_3,...,X_n$ constitute a random sample of size $n$ from an exponential distribution, show that $\bar X$ is a consistent estimator of the parameter $\lambda$.    This is my attempt: Mean of exponential distribution is $\lambda^{-1}$. Thus by central Limit theorem $E(\bar X)=\lambda^{-1}$. Using mean square consistency, if  $\lim_{n\to \infty} E[(\bar X -\lambda )^2]=0$ then $\bar X $ is consistent for $\lambda$. Since $$ E[(\bar X -\lambda )^2]= E[(\bar X)^2]+E(\lambda)^2-2\lambda E(\bar X) , $$  I get $$ \lim_{n\to \infty} E[(\bar X -\lambda )^2] =    \lim_{n\to \infty} {2 \over \lambda ^2 }+\lambda^2-2 . $$ Clearly this is not equal to $0$. How can I show this is consistent? I tried using Chebechev inequality as well. But even using that I couldn't.    2) Is $X_{(n)}$ a consistent estimator for $\lambda$? If $P[|X_{(n)}-\lambda|&lt;\epsilon]$ approaches $1$ as $n$ goes to infinity for all $\epsilon &gt; 0$ then $X_n$ is a consistent estimator for $\lambda$.    The probability density function of $X_{(n)}$ is $f_n(x) = n \lambda e^{-\lambda x}(1-e^{-\lambda x})^{n-1}$,  for $X&gt;0$.  Thus \begin{align*} P[|X_{(n)}-\lambda|&lt;\epsilon]  &amp;= P[\lambda -\epsilon&lt;X_{n}&lt;\lambda+\epsilon] \\  &amp;=P[0&lt;X_{n}&lt;\lambda+\epsilon] \\  &amp;=\int_0^{\lambda+\epsilon} n \lambda e^{-\lambda x}(1-e^{-\lambda x})^{n-1}\\  &amp;= (1-e^{- \lambda X_{(n)} }), \end{align*} where $X{(n)}$ takes values in $[0 , \lambda+ \epsilon]$.  Thus, can I say $\lim_{n\to \infty}[1-e^{-\lambda(\lambda+\epsilon)}]^n=1$? Why aren't search engines indexing my content? Genetically modified humans study insectoid alien miners with super-intelligent hive-mind This is a short story that appeared in a collection. Two genetically-modified humans (corporate anthropologists, basically) travel to a planetoid inhabited by an insect race that is mining the planet in order to study the race. While there, they are practically ignored, as the individual members of the race lack consciousness. The humans determine a type of pheromone is used to control the worker caste, and co-opt several members to create a living area. They make plans to put the mining towards human ends, but before that can happen they are discovered. The presence of the artificial pheromones wakes up a hive-mind, super-intelligent bug, who then bargains with the surviving member of the team (the man) after killing and taking over the female member of the team.  The collection was read at some point between 2000-2005. In C/C++, are global variables as bad as my professor thinks they are? I was browsing flight price at Singapore Airlines website, and a one-way flight from SIN to SFO cost this much:    That's quite expensive. I tried browsing around and found that a return flight from SFO to SIN and back to SFO cost much cheaper:    It's really weird because the second ticket includes the exact same flight that cost 1900+, but it's almost half the price. The reason for this counter-intuitive situation is explained in the answers this question   If I am located in Singapore and my intention is to fly one-way to SFO, is it safe to book the flight in the second picture and only board SFO-SIN leg? Will they deny me because I miss the SIN-SFO flight? What’s the rule to decide whether you add -er or whether you add -or when creating an agent noun from a verb?    Sometimes it’s -er:      read > reader hate > hater hit > hitter   But other times it’s -or:    meditate > meditator collect > collector Why isn't an upgrade to 20.04 from 18.04 available yet? I want to use do-release-upgrade to upgrade from 18.04 to 20.04, but I can't do that do-release-upgrade Checking for a new Ubuntu release There is no development version of an LTS available.  It seems that  is used, and it still points to 18.04. Do you know when (or how?) can I upgrade to 20.04? Dimension of a subset Hartshorne's Algebraic Geometry defines an $\mathcal O_X$-module $\mathscr F$ to be quasi-coherent if there is an open affine cover $(U_i=\operatorname{Spec} A_i)_{i\in\mathcal I}$ of $X$ such that each $\mathscr F\rvert_{U_i}$ is isomorphic to the sheaf of modules $\widetilde{M_i}$ associated to some $A_i$-module $M_i$. It is later proved that this is equivalent to the statement that for any open affine $U=\operatorname{Spec} A\subseteq X$, there exists an $A$-module $M$ with $\mathscr F\rvert_U\cong\widetilde M$.  On the other hand, Grothendieck's Éléments de Géométrie Algébrique defines $\mathscr F$ to be quasi-coherent if every point $x\in X$ admits an open neighborhood $U\subseteq X$ such that $\mathscr F\rvert_U$ is isomorphic to the cokernel of a morphism of free $\mathcal O_U$-modules.  Now I wonder how those definitions are equal. I tried proving it by myself, but both directions seem quite nontrivial to me... Any hints? Down vote changed to up vote caused reputation meter to pass daily maximum Is there any way in unix to find out who accessed certain file in last 1 week? It may be user or some script ftp it to some other place. Can I get a list of user name who accessed certain file? How can I find out who is accessing particular file?? How to treat differentials and infinitesimals? In my Calculus class, my math teacher said that differentials such as $dx$ are not numbers, and should not be treated as such.  In my physics class, it seems like we treat differentials exactly like numbers, and my physics teacher even said that they are in essence very small numbers.   Can someone give me an explanation which satisfies both classes, or do I just have to accept that the differentials are treated differently in different courses?  P.S. I took Calculus 2 so please try to keep the answers around that level.  P.S.S. Feel free to edit the tags if you think it is appropriate. On this link (Sentinel1  for a SLC product), the resolution is written as a range from the highest corresponding to low incidence angle, to the lowest resolution corresponding to high incidence angle.  My question is how is the resolution related in general to the incidence angle? And if they are really related, why is the resolution affected by the change in the incidence angle? has been edited by .   , see revisions 3 to 4.   Now what he did is totally inexplicable to me, as a matter of fact he destroyed the answer. The new version is neither syntactically valid nor does it make any sense.  Still, the edit got "peer-reviewed" and nodded off.  Is there any way to deal with these kinds of things, other than sighing heavily and rolling back the edit?  Rhetorical side question: Could this be a side-effect of people grinding for reviewer badges? I've seen several examples of code like this:  if not someobj:     #do something   But I'm wondering why not doing:  if someobj == None:     #do something   Is there any difference? Does one have an advantage over the other? Do there exist general conditions under which we can conclude that continuity on a topological space is detected by $\mathbb{R}$? Whenever $X$ is a topological space, let us say that continuity on $X$ is detected by $\mathbb{R}$ iff for all functions $f : X \rightarrow Y$ where $Y$ is another topological space, we have that if every continuous function $c : \mathbb{R} \rightarrow X$ satisfies "$f \circ c$ is continuous", then $f$ is itself continuous.   Clearly, continuity on $\mathbb{R}$ is detected by $\mathbb{R}$ It is shown  that continuity on $\mathbb{R}^2$ is detected by $\mathbb{R}$. Clearly, it is not the case that continuity on $\mathbb{Q}$ is detected by $\mathbb{R}$, since every continuous mapping $\mathbb{R} \rightarrow \mathbb{Q}$ is constant.      Question. Do there exist general conditions underwhich we can conclude that continuity on a topological space is detected by $\mathbb{R}$? Projecting a point onto a convex set decreases its distance from each point of that set For a convex set $K$, $x\in \mathbb{R}^d$ and $y=\Pi_K(x) $ (the projection of $x$ onto $K$), we want to show that for any $z\in K$ it holds that: $\|x-z\| \ge \|y-z\|$.  $$ $$  I'm not sure if the following proof is valid:  $$ y=\Pi_K(x) = \arg \min_{y\in K} ||y-x||  \Rightarrow \forall z\in K \langle y-x,y-z\rangle =0 $$ $$ ||y-x||^2_2+||y-z||^2_2=||x-z||^2_2  \quad (Pythagoras)$$  $$ \Rightarrow ||y-z||^2_2 \le ||x-z||^2_2 $$ $$ \Rightarrow||y-z|| \le ||x-z|| $$ Finding the limit of $(1-\cos(x))/x$ as $x\to 0$ with squeeze theorem How do I find:  $$ \lim_{x\to0}\frac{1-\cos(x)}{x} $$  Using the squeeze theorem.  Particularly, how would I arrive at its bounding functions?   If possible, please try not to use derivatives.