Are there any counterexamples which show that $E(XY) = E(X)E(Y)$ cannot imply $X,Y$ is not necessarily independent?
Is there a *simple* example showing that uncorrelated random variables need not be independent?
When we lie down, the "back part of the body" is in contact with the bed. It includes the heels, the calves, the backside, the back, and the back of the neck, and the back of the head etc.  How do we refer to the entire "back part" of the body? No hair theorem for black holes and the baryon number gpgkeys: key C927EBE00F1B0520 not found on keyserver Possible Duplicate:    I am using 10.04 LTS - Lucid Lynx. I shutdown the computer while a software update was running. Then after I restarted my computer and while the update manager was running, I got this error:  Could not download all repository indexes The repository may no longer be available or could not be contacted because of network problems. If available an older version of the failed index will be used. Otherwise the repository will be ignored. Check your network connection and ensure the repository address in the preferences is correct. GPG error: http://toolbelt.herokuapp.com ./ Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C927EBE00F1B0520 Failed to fetch  http://ppa.launchpad.net/rabbitvcs/ppa/ubuntu/dists/**DISTRIBUTION**/main/binary-i386/Packages.gz 404  Not Found   I went through the answers to  and I tried this $ sudo launchpad-getkeys  Please wait... launchpad-getkeys is running an update so it can detect the missing GPG keys Trying to import all the missing keys gpg: requesting key 0F1B0520 from hkp server keyserver.ubuntu.com gpgkeys: key C927EBE00F1B0520 not found on keyserver gpg: no valid OpenPGP data found. gpg: Total number processed: 0 launchpad-getkeys has finished importing all missing GPG keys.  Try running sudo apt-get update - you shouldn't see any key  errors anymore  But when I run sudo apt-get update again, it again shows that the key was not found on the keyserver. How to solve this problem? How do I change folder timestamps recursively to the newest file? Dell R730xd - Best way to configure storage for simultaneous use with ZFS & Hardware RAID I recently purchased a Dell R730xd that came with an H730 RAID card. I would like to bring an existing 6 disk ZFS pool to this server as well as create an additional 6 disk hardware RAID.   Is it possible to configure an H730 RAID card to operate in both HBA and RAID mode simultaneously? And then only manage 6 of the disks in a hardware RAID and allow the OS to manage the remaining 6 disks in a software RAID?  If not, can a Dell R730xd use both an H730 RAID card and an LSI 9207-8i HBA card simultaneously? Would you simply plug one SAS cable from each card into each part of the Backplane? Will I need to purchase any new cables to connect the LSI 9207-8i to the backplane in my R730xd?  Is there a better card to use for ZFS in an R730xd using spinning disks than the LSI 9207-8i? $ echo $(( 255 )) 255 $ echo $(( 33 )) 33 $ echo $(( ~33 )) -34 $ echo $(( ~255 )) -256 $    and my kernel is:  $ uname -a Linux HOSTNAME 3.2.0-40-generic-pae #64-Ubuntu SMP Mon Mar 25 21:44:41 UTC 2013 i686 i686 i386 GNU/Linux     QUESTION: ~ is for negating the number AFAIK. But why does ~33 produce -34 and why does ~255 produce -256? What is the difference between Ubuntu and its derivatives? How do I reset GNOME to the defaults? I was playing around with some settings, and now I need to reset GNOME to it's defaults - how do I do that? How do I unset an element in an array in javascript? How would you know if your (high dimensional) data exhibits enough clustering so that results from kmeans or other clustering algorithm is actually meaningful?  For k-means algorithm in particular, how much of a reduction in within-cluster variance should there be for the actual clustering results to be meaningful (and not spurious)?  Should clustering be apparent when a dimensionally-reduced form of the data is plotted, and are the results from kmeans (or other methods) meaningless if the clustering cannot be visualized? Is an apostrophe with a decade (e.g. 1920’s) generally considered “incorrect”? I typically don’t use an apostrophe with plurals in any situation, but I always assumed that the use of an apostrophe in constructions like acronyms:     Forty BA’s were given out to students this year.   or numbers:     Though the greatest period instability occurred during the 1950’s when. . . .   was more or less ok. I would personally use BAs and 1950s here, but I've never thought the apostrophe in this case was necessarily “incorrect”. What say ye? Dragon souls not activating new words So if I understand correctly you can learn new words and the souls will activate these words. I just killed a dragon and when it died it looked like I absorbed the soul but it didn't unlock any of the words I have.   I noticed some dragons actually have a name so do certain dragons unlock certain words? I don't see the gear button next to the Sign in button at the login screen. I have Nvidia drivers installed (for Nvidia 730 GT card). Ubuntu boots into Xorg as seen from the terminal with echo $XDG_SESSION_TYPE which outputs x11.  How do I switch to Wayland? Raspberry Pi + IRFZ44N to control a 5050 RGB LED strip: current seems to be limited Frequency of the sound when blowing in a bottle In my Master thesis, I used this:  \begin{itemize}[label=\ding{167}] \item Access Windows XM from Ubuntu Server \item List the directories contents of Windows XP \end{itemize}   The output is:  My question: must I avoid the use of  such beautiful things when writing my thesis or is it a normal thing to do ? Using the itemize environment inside a caption The following code does not compile. However, if I remove the itemize environment it does. I googled for this problem, and found suggestions that using the caption package would solve the problem, though I did not find any clear description of why the problem occurred in the first place. See for example    I'm using Debian squeeze with TeX Live 2009-11. The included version of caption has   \ProvidesPackage{caption}[2009/10/09 v3.1k Customizing captions (AR)]   I also tried downloading and using the caption package from     but this doesn't change anything. I put the sty files in my current directory. I assume that overrides the system files. This one corresponds to  \ProvidesPackage{caption}[2010/01/09 v3.1m Customizing captions (AR)]   Error message and example file follow.  *******************************************     ERROR: Argument of \@caption has an extra }.  --- TeX said --- &lt;inserted text&gt;                  \par  l.13     }  --- HELP --- From the .log file...  I've run across a `}' that doesn't seem to match anything. For example, `\def\a#1{...}' and `\a}' would produce this error. If you simply proceed now, the `\par' that I've just inserted will cause me to report a runaway argument that might be the root of the problem. But if your `}' was spurious, just type `2' and it will go away. ******************************************************  \documentclass{article} \usepackage{caption} \begin{document}  \begin{figure}     \captionsetup{singlelinecheck=off}     \caption     {       foo       \begin{itemize}       \item bar       \end{itemize}     } \end{figure} \end{document} IDW Publishing are bringing out a , Assimilation2, set in ST:TNG (presumably the TNG in the timeline prior to the events of the 2009 movie) featuring the 11th Doctor.  Is the canon of these two universes at all compatible?  Both feature a lot of time travel, so we've seen the development of humanity through many centuries in the future.  Are there direct contradictions that make it impossible for these two universes to merge, without some sort of trick like having the Doctor come from an alternate universe?  Or, given the vast spread of time, is it possible that the events of the Star Trek stories have taken place between Doctor Who stories? I am running Ubuntu GNOME 15.10 with GNOME 3.18, and I would like to know if I can do any of the following and if so how:   Make it so that a folder is not indexed but leave its contents indexable (so that if I search for that folder's name in my system nothing will come up, but if I search for its contents, that will come up) Make it so that a folder is not indexable and nor is any of its contents (and if it contains sub-folders within it then it should recursively not allow any contents in them to be indexed nor the contents of any sub-sub-folders in the sub-folders etc, nor any of those sub-folders themselves) Make it so that individual files in a folder are not indexable, though not having any impact on other contents nor the parent-folder   So, are any of these variants possible? I believe the indexing program is called Tracker which indexes files and folders and their contents and allows for one to search for them on the system. I would like to change the caption in the List of Tables in a way it is different from the caption in the corresponding table. How can I do that? Does there exist a command to do that?