This laptop has 3 years of use. After Windows 7 boots it starts having this freezing "waves" that last for a few seconds to a few minutes. I can use it again for a few seconds or minutes and then it happens again.  During the freezes the mouse still moves, but no clicks or keys are effective. Almost anything I try to do seem to trigger the freeze, like trying to connect wifi, trying to enter the Task Manager, trying to install Google Chrome.  In safe mode with network the problem is still present. I noticed it happening even in the BIOS utility (transitions from menus freezing for 2sec). I already restored de OS to the factory state with a full restore (formatting HDD) and it still happens. Thus, I don't think it's SW related.  I know the fan can still spin because I can hear it and there is hot air flowing through the vent. After the boot it's always making noise. After the first freeze it goes silent and no noticeable air flowing.  It never really freezes in a hard way and never turn off or restart. The HD Led never goes off, it's always on or blinking fast, like there is a lot of HD operations going on.  SMART stats:
A machine is described as being "really slow" or "freezing". How can I troubleshoot/resolve this issue? What should be the first steps to take?
The Node Editor won't work for the object selected I'm still learning, but I'm trying to follow a tutorial to apply texture to a model. I only want to apply the texture to one object in the scene, so I selected it, unwrapped it, and painted over it. Now I selected it in the Edit Mode (I can't select it in the Object mode because all is locked together) and went into Node Editor, but the nodes are greyed out.  Why? Are intermediate rings of finitely generated ring extensions also finitely generated? Left and right subscript / superscript I am trying to put two subscripts at the left and right of a character. For example, something like:  _{t} p_{x}  where p is in the middle. How do you do this? Someone flagged my question as already answered, but it's not I asked a question regarding a very specific feature of a program and whether or not it works with a larger program.  Within hours someone had marked it with "This question may already have an answer here of a similar question, but not related to my question.  The question I asked IS NOT ADDRESSED in the referred-to question. It's frustrating to spend half an hour putting together an intelligent and specific question, and then have someone mark it as a duplicate (or possible duplicate), which apparently causes people to skip over my question. I haven't received any more responses since the question was flagged.   Two questions:  (1) How do I get this flagging removed and (2) what's the best way to prevent these "helpful" flaggings in the future? In &quot;Introduction to Mathematical logic&quot; by Elliot Mendelson , page $59$ . I couldn't understand the basic preliminary notations for the rigorous definition of Satisfiability. For example , at a line they said, &quot;Moreover, instead of talking about the $n$-tuples of objects that satisfy a wf that has $n$ free variables, it is much more convenient from a technical standpoint to deal uniformly with denumerable sequences. What we have in mind is that a denumerable sequence $s = (s_1, s_2 , s_3 , ... )$ is to be thought of as satisfying a wf $\beta$ that has ${x_j}_1 , {x_j}_2 ,  ... , {x_j}_n$ as free variables (where $j_1 &lt; j_2 &lt; ... &lt; j_n$ ) if the $n$-tuple $\langle {s_j}_1 , {s_j}_2 ,  ... , {s_j}_n \rangle$ satisfies $\mathscr B$ in the usual sense.&quot; I didn't quite understand why they used ${s_j}_1$ and ${x_j}_1$ instead of $s_1$ and $x_1$ . Maybe there is a critical detail I am missing out? Also , Another passage for the rigorous definition: &quot;Let $M$ be an interpretation of a language $\mathscr L$ and let $D$ be the domain of $M$. Let $\sum$ be the set of all denumerable sequences of elements of $D$. For a wf $\mathscr B$ of $\mathscr L$ , we shall define what it means for a sequences $s= (s_1, s_2, ... )$ in $\mathscr L$ to satisfy $\mathscr B$ in $M$. As a preliminary step, for a given s in $\sum$ we shall define a functions $s^*$ that assigns to each term $t$ of $\mathscr L$ an element $s^{*}(t)$ in $D$.&quot; They did say that for each $s = (s_1, s_2, ... )$ , there is a defined function $s^*$ , but even after further reading the text afterwards , I still did not understand how exactly $s^*$ is defined from $s$ . Can someone tell me where the gap in my understanding here is? I recently changed my username to Undo. I was amazed when I pressed Submit and saw that it actually went through - surely someone somewhere was using this same username.  Out of curiosity, I then search the SO user list for Undo - and found  with Undo as thier name. They have 50 rep. I have around 1,500.   Is there some kind of pecking order, I.e. a high-rep user can 'steal' a low-rep user's name? Or is this a bug?  Or can two users have the same username without causing the SO servers to go down in a burning ring of fire? Academic papers using Stack Exchange data How can I make LightDM the default display manager? I have LightDM installed and can start it with sudo start lightdm. But at boot, GDM is still the default. How can change this so LightDM is loaded automatically at boot instead of GDM? If I know $\| f_n - f \|_{L^p(\mathbb{R})} \to 0$ as $n \to \infty$, do I know that $\lim_{n \to \infty}f_n(x) = f(x)$ for almost every $x$? Positrons versus holes as positive charge carriers : [The Dirac sea is a theoretical model of the vacuum as an infinite sea of particles with negative energy. It was first postulated by the British physicist Paul Dirac in 1930 to explain the anomalous negative-energy quantum states predicted by the Dirac equation for relativistic electrons. The positron, the antimatter counterpart of the electron, was originally conceived of as a hole in the Dirac sea, well before its experimental discovery in 1932.]  and:  [Dirac's idea is completely correct in the context of solid state physics, where the valence band in a solid can be regarded as a "sea" of electrons. Holes in this sea indeed occur, and are extremely important for understanding the effects of semiconductors, though they are never referred to as "positrons". Unlike in particle physics, there is an underlying positive charge — the charge of the ionic lattice — that cancels out the electric charge of the sea.]  It always confused me to think of holes as positive charge carriers in semi-conductors as not being real: real electrons move from one lattice-position to another lattice-position, which effectively looks like a positive hole in the lattice that is moving in the other direction, but in reality a real electron moves, the hole is kind of an "illusion".  On the other hand the positrons are always introduced as real hard-core particles.   The quotes from the Wikipedia article make me unsure: how should I look upon these phenomena?   Edit: holes in a Dirac sea give rise to real pos. entities in one case and to unreal pos. entities in another - how can we distinguish, is it a matter of formalism? Statistical inference when the sample "is" the population Best way to clone an installation (copying to identical hardware) Kind-of like  but slightly different (I think), in that I have 6 identical Acer Aspire Revo R3610 machines. One is (almost) configured to my requirements - when I'm done preparing it I'd like to make the other 5 machines absolutely the same. I'm very new to Ubuntu, what's the most straightforward (easiest) way of doing this?  The machines are going to live on different networks if that might otherwise be a problem (eg with Windows you can clone disks but you then have to make registry changes afterwards if they're going to run on the same network etc). The hardware in all 6 machines is, I stress, the same!  How can I efficiently clone one source image on to these identical machines?  Please restrict one software/solution per answer I've been through the Windows 10 upgrade, and am experiencing a recurring "INTERNAL_POWER_ERROR", which is stopping me from logging in.  I'd like to be able to try to boot to safe mode, but it appears that pressing F8 during boot is no longer enough, so how can I boot in safe mode (or any of the other recovery options) on a Windows 10 PC that doesn't let me log on? I want to prove that $\lim_{(x,y)\to (0,0)} \frac{\sin(x+y)}{x+y} = 1$  Is it sufficient to say that if $u = x+y$ then as $(x,y) \rightarrow (0,0)$ then $u \rightarrow 0$ and then evaluate $\lim_{u\to 0} \frac{\sin u}{u}$ which is 1 by L'Hôpital's rule?  I feel that this is somehow "cheating" and I would really like to prove it in a more rigorous way, i.e., by using an $\epsilon$ - $\delta$ argument.  I have tried for a long time to use the one variable version and prove that if $0 \lt \sqrt{x^2 + y^2} \lt \delta$ then somehow $0 \lt |x+y| \lt \delta$ and it would follow from the one variable case that $| \frac{\sin(x+y)}{x+y} - 1| \lt \epsilon$. However, because $|x+y| = 0$ when $y = -x$ I am not getting anywhere with this.  Any input on this would be helpful :) Unloading classes in java? I have a custom class loader so that a desktop application can dynamically start loading classes from an AppServer I need to talk to. We did this since the amount of jars that are required to do this are ridiculous (if we wanted to ship them). We also have version problems if we don't load the classes dynamically at run time from the AppServer library.  Now, I just hit a problem where I need to talk to two different AppServers and found that depending on whose classes I load first I might break badly... Is there any way to force the unloading of the class without actually killing the JVM?  Hope this makes sense addplot3[surf] creates lines instead of a surface I have been trying to create a surface plot but I am unable to get it to work. Any help would be greatly appreciated. I've tried using surf which only produces lines instead of a surface (Fig. 1). Note: Although I was originally able to produce output, thesurf plot no longer compiles: "Package tikz Error". I've tried compiling with both pdflatex and lualatex with -shell-escape flag.    Figure 1  I also tried to use the patch style plot. This produces gibberish (Fig. 2)    Figure 2  MWE:  \documentclass{article} \usepackage{pgfplots} \usepgfplotslibrary{external} \usepgfplotslibrary{patchplots} \tikzexternalize  \begin{document} \begin{figure}[t]   \centering    \tikzsetnextfilename{surface_plot}   \begin{tikzpicture}     \begin{axis} [       height=12cm,       width=15cm,       grid=major,       grid style={dotted},       colormap/jet,       mesh/ordering=x varies     ]       %\addplot3[patch,patch type=biquadratic,shader=faceted interp,patch refines=3] coordinates {       \addplot3[surf] coordinates {  (-6,-6,446.788)  (-5,-6,423.361)  (-4,-6,413.264)  (-3,-6,402.349)  (-2,-6,388.948)  (-1,-6,391.747)  (0,-6,386.874)  (1,-6,423.778)  (2,-6, 439.19)  (3,-6,449.074)  (4,-6,462.155)  (5,-6,484.399)  (6,-6,505.412) (-6,-5, 423.48)  (-5,-5,392.382)  (-4,-5,406.696)  (-3,-5,392.592)  (-2,-5,371.158)  (-1,-5,384.142)  (0,-5,394.666)  (1,-5,408.105)  (2,-5, 422.51)  (3,-5,420.173)  (4,-5,445.816)  (5,-5,464.731)  (6,-5,485.349) (-6,-4,402.646)  (-5,-4,371.879)  (-4,-4,376.239)  (-3,-4,396.874)  (-2,-4,382.761)  (-1,-4,386.665)  (0,-4,397.148)  (1,-4,410.875)  (2,-4,425.998)  (3,-4,385.143)  (4,-4,420.458)  (5,-4,438.432)  (6,-4,    458) (-6,-3,423.219)  (-5,-3,370.582)  (-4,-3,464.786)  (-3,-3,443.921)  (-2,-3,425.196)  (-1,-3,427.138)  (0,-3,438.002)  (1,-3, 453.97)  (2,-3,473.021)  (3,-3,418.583)  (4,-3,435.887)  (5,-3,414.993)  (6,-3,475.148) (-6,-2,401.995)  (-5,-2,385.612)  (-4,-2,438.956)  (-3,-2,418.583)  (-2,-2,400.093)  (-1,-2,400.773)  (0,-2, 410.58)  (1,-2,426.024)  (2,-2, 444.92)  (3,-2,397.131)  (4,-2,413.739)  (5,-2,431.741)  (6,-2,451.267) (-6,-1,382.978)  (-5,-1,335.274)  (-4,-1,416.598)  (-3,-1,396.718)  (-2,-1,378.348)  (-1,-1,377.455)  (0,-1,32.0089)  (1,-1,400.683)  (2,-1,419.918)  (3,-1,377.371)  (4,-1,393.286)  (5,-1,374.648)  (6,-1,429.077) (-6, 0,365.902)  (-5, 0,350.965)  (-4, 0,397.527)  (-3, 0, 378.36)  (-2, 0,360.454)  (-1, 0,358.447)  (0, 0,    363)  (1, 0,381.147)  (2, 0,401.177)  (3, 0,362.155)  (4, 0,378.174)  (5, 0,395.513)  (6, 0, 414.34) (-6, 1,372.511)  (-5, 1,326.945)  (-4, 1,407.215)  (-3, 1,388.646)  (-2, 1,371.945)  (-1, 1,371.003)  (0, 1,380.027)  (1, 1,396.414)  (2, 1,416.602)  (3, 1,374.897)  (4, 1,391.276)  (5, 1, 373.32)  (6, 1,428.284) (-6, 2,391.149)  (-5, 2,376.191)  (-4, 2,406.941)  (-3, 2,369.633)  (-2, 2,393.583)  (-1, 2,394.184)  (0, 2,404.263)  (1, 2,420.588)  (2, 2,  440.5)  (3, 2,416.631)  (4, 2,374.948)  (5, 2,391.855)  (6, 2,418.511) (-6, 3,375.967)  (-5, 3,361.698)  (-4, 3,357.421)  (-3, 3,368.273)  (-2, 3,377.106)  (-1, 3,378.664)  (0, 3,369.175)  (1, 3, 382.42)  (2, 3,397.821)  (3, 3,377.942)  (4, 3,384.944)  (5, 3,387.862)  (6, 3,424.429) (-6, 4,396.478)  (-5, 4,381.554)  (-4, 4,376.162)  (-3, 4,388.843)  (-2, 4,375.881)  (-1, 4,378.384)  (0, 4, 355.14)  (1, 4,403.654)  (2, 4,419.779)  (3, 4,398.599)  (4, 4,407.113)  (5, 4,426.715)  (6, 4,448.245) (-6, 5,409.364)  (-5, 5,380.492)  (-4, 5,387.843)  (-3, 5,360.034)  (-2, 5, 362.23)  (-1, 5,364.909)  (0, 5,358.321)  (1, 5,363.226)  (2, 5,379.325)  (3, 5,397.152)  (4, 5,410.086)  (5, 5,433.909)  (6, 5,460.548) (-6, 6, 423.99)  (-5, 6,408.967)  (-4, 6,400.475)  (-3, 6,372.922)  (-2, 6,371.116)  (-1, 6, 373.92)  (0, 6,384.778)  (1, 6,  398.8)  (2, 6, 415.62)  (3, 6,420.127)  (4, 6,436.064)  (5, 6,461.957)  (6, 6,491.123)        };     \end{axis}   \end{tikzpicture}      \end{figure} \end{document}   Thank you so much. I'd like to setup a WCF service to send emails. The System.Net.MailMessage doesn't seem to be serializable, and cannot be passed in a [DataContract]  The error I receive is      Type 'System.Net.Mail.MailAddress'   cannot be serialized. Consider marking   it with the DataContractAttribute   Any suggestions? I'm looking for a short story from about 50 years ago about a robot who escapes after being slated to be melted down and discovers while in hiding that it has evolved to have some supernatural powers. Does any particle ever reach any singularity inside the black hole? I've been working with ArcGis for a while now and was wondering if there was a way to change positions of parameters inside the toolbox for the user. The only time I have seen this done in arc toolbox is with the Raster clip tool with the Rectangle parameter where the 4 parameters are aligned in a circle in the toolbox.     I don't know if what I want is possible since I haven't seen anyone else do it.