Permissions, owner, group inheritance?
What permissions should my website files/folders have on a Linux webserver?
Are mixed geometry types allowed in shapefiles? Does the shapefile support mixed geometry types (ie. point and polygon all in the same file)? Creating intuition about Laplace & Fourier transforms The topological space $X=\omega_1\cup \{\omega_1\}$ is not first countable but $\omega_1$ is. Here $\omega_1$ denotes the set of all countable ordinals and $\{\omega_1\}$ is the first uncountable ordinal. Cardinality of $\omega_1$ is $\aleph_1.$And also $\omega_1$ is called the limit ordinal meaning it is the limit point of the set $\omega_1.$  Here I want to prove two things. $1)$ $\omega_1$ is first countable. and $2)$ $\{\omega_1\}$ is the limit point of $\omega_1$. But since no sequence converges to $\{\omega_1\}$, using this I could say that our space $X$ is not first countable.  $1)$ The proof of this I got from  with just one question: it says we need to prove that such an $S(y)$ exists,and I'm thinking $S(y)=\cap\{u\in \omega_1:u\gt y\}.$ This is correct$?$ But here is a chance that the countable base around $y$ may be finite and not countably infinite.  $2)$ If possible let us assume that $\omega_1$ is not a limit point of the set $\omega_1.$ $U$ be a nbd of $\omega_1$ that does not intersect $\omega_1.$ Then what are the elements of $U$ like? The ones coming before $\omega_1$  cannot be uncountable because $\omega_1$  is the first. Then they must be countable. This is absurd so no such $U$ exists. Thus $\{\omega_1\}$ is a limit point.  Are my proofs correct? Thank you. It would seem that far-away stars are at such a distance that I should be able to take a step to the side and not have the star's photons hit my eye. How do stars release so many photons to fill in such great angular distances? Did Voldemort refer to Snape as one of the missing Death Eaters at his rebirth? In Goblet of Fire, Voldemort says of the missing six Death Eaters:     “And here we have six missing Death Eaters… three dead in my service. One,   too cowardly to return… he will pay. One, who I believe has left me forever… he   will be killed, of course… and one, who remains my most faithful servant, and   who has already reentered my service."   The answer to  speculates about who the three dead Death Eaters were.  We know who the last one is. I’m guessing one of the remaining two is Karkaroff. Is the other Snape? If so, which one? Could I have a hint for testing the convergence of the following series please?  $$\sum_{n=2}^\infty\frac{1}{(\ln n)^{\ln n}}$$  Edit  The integral test does not work because $\int_1^n\frac{1}{(\ln x)^{\ln x}}dx$ has not an elementary primitive.  Thank You. This code in JS gives me a popup saying "i think null is a number", which I find slightly disturbing. What am I missing?    if (isNaN(null)) {   alert("null is not a number"); } else {   alert("i think null is a number"); }     I'm using Firefox 3. Is that a browser bug?  Other tests:    console.log(null == NaN);   // false console.log(isNaN("text")); // true console.log(NaN == "text"); // false     So, the problem seems not to be an exact comparison with NaN?  Edit: Now the question has been answered, I have cleaned up my post to have a better version for the archive. However, this renders some comments and even some answers a little incomprehensible. Don't blame their authors. Among the things I changed was:   Removed a note saying that I had screwed up the headline in the first place by reverting its meaning Earlier answers showed that I didn't state clearly enough why I thought the behaviour was weird, so I added the examples that check a string and do a manual comparison. Finding the error in this proof that 1=2 I have a "proof" that has an error in it and my goal is to figure out what this error is. The proof:  If $x = y$, then  $$ \begin{eqnarray} x^2 &amp;=&amp; xy \nonumber \\ x^2 - y^2 &amp;=&amp; xy - y^2 \nonumber \\ (x + y)(x - y) &amp;=&amp; y(x-y) \nonumber \\ x + y &amp;=&amp; y \nonumber \\ 2y &amp;=&amp; y \nonumber \\ 2 &amp;=&amp; 1 \end{eqnarray} $$    My best guess is that the error starts with the line $2y = y$. If we accept that $x + y = y$ is true, then   $$ \begin{eqnarray} x + y &amp;=&amp; y \\ x &amp;=&amp; y - y \\ x &amp;=&amp; y = 0 \end{eqnarray} $$  Did I find the error? If not, am I close? passthrough graphics card to virtualbox So I'm trying to get my laptops NVIDIA fx 880m to pass to a virtual box running window seven on a linux mint 17 install.  So far everything seems to be (maybe) heading in the right direction:  the device passed through happily, when I booted the virtual box it installed a bunch of new drivers, but when I try to install the NVIDIA driver on the guest it can't find the card. I looked under the device manager and there's no listing for the nvidia card under the pci bus, my guess would be that I need to disable it in the host so that it can be passed through to the guest (the virtual box manual said they can't be shared) but I'm not sure how to do so. Can anybody help with this? This question does not seem to me to be a duplicate of , because here the given solution was that it was not possible with a windows host, however in this case the host is linux How to access new colour schemes in version 10? How can we play split screen in the XBOX 360 version of Minecraft? My little brother and I want to play Minecraft together on the Xbox 360, and we heard there was a split screen option. We've looked inside the options menu but weren't able to find it. Does the game really have a split screen option, and if so, how do we enable it? Make a failed SSH forward a fatal error I have a script which connects to a remote host to replicate some files via SSH.  I must connect to an rsync daemon listening on port 873.  To accomplish this I have a ssh configuration like this.  Host blah     LocalForward 10873 127.0.0.1:873     Hostname 10.2.4.1   Unfortunately because of the timing of this script, there is a small chance that on occasion when it attempts to establish the SSH session another similar script will have the port open to a different host.  If I connect while another ssh session is open I get the obvious message Address already in use.  me@local:~$ ssh blah bind: Address already in use channel_setup_fwd_listener: cannot listen to port: 10873 Could not request local forwarding. Linux remote 2.6.26-2-amd64 #1 SMP Tue Jan 25 05:59:43 UTC 2011 x86_64 motd... remote:~$    What I want to have happen is to have the SSH client immediately exit with a exit code so I can put some logic into my script to report a failure instead of trying to run any commands against the port forwarded to the incorrect host. Reprojecting LiDAR data with libLAS, error: "latitude or longitude exceeded limits"? I have a lidar file (file.las) with the following spatial reference:  Spatial Reference:            PROJCS["NAD83 / UTM zone 11N",     GEOGCS["NAD83",         DATUM["North_American_Datum_1983",             SPHEROID["GRS 1980",6378137,298.2572221010002,                 AUTHORITY["EPSG","7019"]],             AUTHORITY["EPSG","6269"]],         PRIMEM["Greenwich",0],         UNIT["degree",0.0174532925199433],         AUTHORITY["EPSG","4269"]],     PROJECTION["Transverse_Mercator"],     PARAMETER["latitude_of_origin",0],     PARAMETER["central_meridian",-117],     PARAMETER["scale_factor",0.9996],     PARAMETER["false_easting",500000],     PARAMETER["false_northing",0],     UNIT["metre",1,         AUTHORITY["EPSG","9001"]],     AUTHORITY["EPSG","26911"]]   Then I reproject it to WGS84 with las2las:  las2las --a_srs EPSG:26911 --t_srs EPSG:4326 -i file1.las -o output.las   And I get:   Spatial Reference:                GEOGCS["WGS 84",         DATUM["WGS_1984",             SPHEROID["WGS 84",6378137,298.257223563,                 AUTHORITY["EPSG","7030"]],             AUTHORITY["EPSG","6326"]],         PRIMEM["Greenwich",0],         UNIT["degree",0.0174532925199433],         AUTHORITY["EPSG","4326"]]   But when I try to revert the transformation: from WGS84 to NAD83/UTM 11N, I get an error:  las2las --a_srs EPSG:4326 --t_srs EPSG:26911 -i output.las -o wgs2utm.las ERROR 1: latitude or longitude exceeded limits error: Could not project point for ReprojectionTransform::latitude or longitude exceeded limits0.   Why I got this error, if I am just reversing the transformation (originally from NAD83 to WGS84, and then from WGS84 to NAD83)?. In C# how do I get the list of local computer names like what one gets viewing the Network in windows explorer How to know if a time series is stationary or non-stationary? How to *quickly* get a list of files that have bad sectors/blocks/clusters/whatever? My wife's Windows 7 (64-bit) box has suddenly developed a SMART "disk is bad" status.  I'm attempting to copy everything off (no admonishments about lacking a backup regimen, please, I know already  :(  ) by creating a System Image across the network to a different machine, but it gets to a certain point and starts taking forever.  Doing a chkdsk reveals that certain files cause this by having many bad blocks (like dozens of thousands in a row, if the event log is any indication) and causing the system to do its standard try-to-recover-and-relocate-upon-access thing.  But this is taking so long, I'm afraid the disk will fail completely before I can get the damned thing copied.  However, several of the files so far have been ones that she has copies of elsewhere, so I am able to just delete them prior to retrying the backup to speed things up considerably.  So:  is there some tool or procedure that will try reading each file, and upon hitting a bad block, just tell me about it and skip to the next file?  So I can see which ones I can just dump and which I need to let it try to recover? Installing QGIS with ECW support on Mac? I bought a imac recently and I tried to install qgis: without success! It is not possible to read the raster files.  I installed GDAL ECW plugin, but it is necessary to copy and paste another file from  ERDAS ECW/JPEG2000 following this instruction.  "VERY IMPORTANT POST-INSTALL  You MUST download and install the ECW SDK yourself. I don't have the means to enforce export restrictions. I'm sorry, but installation is a manual process for now:  Go to . Select "ERDAS ECW/JPEG2000 SDK" from the Product popup. Click on the MacOSX line, then the Download Now link.  Open the downloaded disk image and run the installer. It will install into the top of your boot drive, /Intergraph. Dig into this folder to Desktop_Read-Only/redistributable/libstdc++.  Copy the libNCSEcw.dylib file to:  /Library/Application Support/GDAL/1.11/Libraries  and copy the whole Desktop_Read-Only/etc folder here to:  /Library/Application Support/GDAL/1.11  so it looks like (there may be other files in Libraries and PlugIns for other installed plugins):  Library Application Support GDAL 1.11 etc Libraries libNCSEcw.dylib PlugIns gdal_ECW_JP2ECW.dylib  You can trash the installed Intergraph folder when done to save a few hundred MB of space.  I failed the procedure! Could you help me? How to check if a service is running on Android? How do I check if a background service is running?  I want an Android activity that toggles the state of the service -- it lets me turn it on if it is off and off if it is on. How is pressure an intensive coordinate? Switching from one area of graduate study to another? Is it possible to switch from one area of graduate study to another in US universities? For example, suppose someone has enrolled in a computer science phd program. Can he switch over to math(or physics) phd program in the same school later?(or say from applied mathematics to pure mathematics?)  What are the steps for doing for doing that?