I'm not entirely sure how normal this is, but since I was a child, I've been able to produce myself voluntarily a "chill" sensation that seems to start on my head and traverse the rest of my body, being least intense in the feet. Looking around the internet and forums, looks like other people but not everybody also describe this ability. However, unlike other people's reports, I don't see "goose bumps" on my skin, at least there aren't any visibly; it's just the sensation.  Does anybody know if there are any relevant studies or knowledge out there about "voluntary goose bumps"? Is there even a proper name for that?
I can get goosebumps at will, regardless of the environment. Its mostly visible on my arms, and I can feel it on my head. It requires some level of concentration to achieve this.  My questions are : what biological mechanisms are involved in doing this ? Is it common ? Is it useful ?
I am using QGIS and I created a vector grid on a crop field in order to cut it into plots. I want to save each grid cell into individual polygon shapefiles automatically.  Here is an example of a vector grid I would like to split into 117 shapefiles:    Eventually, I did it manually with the selection tool and "Save as" but it is really time-consuming when there are more than 100 plots to save.    Is there any way to do it faster and more automatically?  Each plot as an attribute named "Plot" that can discriminate against them (basically being id + 1). It's the attribute used here to label them. Is everything greater than None? Calculating conditional entropy given two random variables I have been reading a bit about conditional entropy, joint entropy, etc but I found this: $H(X|Y,Z)$ which seems to imply the entropy associated to $X$ given $Y$ and $Z$ (although I'm not sure how to describe it). Is it the amount of uncertainty of $X$  given that I know $Y$ and $Z$? Anyway, I'd like to know how to calculate it. I thought this expression means the following:  $$H(X|Y,Z) = -\sum p(x,y,z)log_{2}p(x|y,z)$$  and assuming that $p(x|y,z)$ means $\displaystyle \frac{p(x,y,z)}{p(y)p(z)}$, then  \begin{align} p(x|y,z)&amp;=\displaystyle \frac{p(x,y,z)}{p(x,y)p(z)}\frac{p(x,y)}{p(y)}\\&amp;=\displaystyle \frac{p(x,y,z)}{p(x,y)p(z)}p(x|y) \\&amp;=\displaystyle \frac{p(x,y,z)}{p(x,y)p(x,z)}\frac{p(x,z)}{p(z)}p(x|y)\\&amp;=\displaystyle \frac{p(x,y,z)}{p(x,y)p(x,z)}p(x|z)p(x|y) \end{align} but that doesn't really help.  Basically I wanted to get a nice identity such as $H(X|Y)=H(X,Y)-H(Y)$ for the case of two random variables.  Any help?  Thanks I have searched the web a lot and could not find an answer that fits my situation. Here are two links that are quite contradictory:       My situation:  I've visited Portugal in December 2012 for 29 days on a Schengen visa valid from December 1st, 2012 to February 1st, 2013 for research purposes (I am a Ph.D. student). I want to visit Sweden from February 10th, 2013 to May 10th, 2013 (89 days). I have applied for a Schengen visa again (for research). How will the 90/180 rule work in my situation? Show that $a \star b=a \cdot b+a+b$ is binary operation for the group $\Bbb{ Q} \setminus \{-1\}$ The group $\left(\Bbb{ Q}\setminus\{-1\},\star\right)$ has as its underlying set the rational numbers different from $-1$ and the operation $\star$ is defined as $a \star b=a \cdot b+a+b$ where multiplication/addition are the usual operations with rational numbers.Show that this is a binary operation.  What I did (Please help verify):  identity element has to be 0 since $a\star 0 = a+0+a(0)$ so for $a\star b=0$ we have  $ab+a+b=0$ $$ab+a=-b \\ a(b+1)=-b \\ a=\frac{-b}{b+1}$$ so $b$ cant be $-1$ since that solution is not in $\Bbb{Q}$. Similar question might have been answered here. Is this operation true for all groups? I think so.  Thanks for the tips and help. I would like to see everything on my computer screen in grayscale (like say the kindle screen). How do I do this? How can one differentiate between "who" and "whom"? Many times, I've been asked the difference between "who" and "whom". I myself know the difference, but it is hard to explain to others. What is the easiest way to explain it to those with a basic understanding of English? A mnemonic (if possible) would help. Schengen Business visa without a business invitation letter $f:\mathbb R \to \mathbb R$ be a continuous such that $f(f(f(x)))=x,\forall x \in \mathbb R$ , is $f(x)=x , \forall x \in \mathbb R$? Let $f:\mathbb R \to \mathbb R$ be a continuous function such that $f(f(f(x)))=x,\forall x \in \mathbb R$ , then is it true that $f(x)=x , \forall x \in \mathbb R$ ? I can see that $f$ is bijective , hence strictly monotone . But I cannot progress further . Please help. Thanks in advance When to switch to a CDN? Export Windows 7 search results to a text file How to import a module given its name as string? I'm writing a Python application that takes as a command as an argument, for example:  $ python myapp.py command1   I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:  myapp/     __init__.py     commands/         __init__.py         command1.py         command2.py     foo.py     bar.py   So I want the application to find the available command modules at runtime and execute the appropriate one.  Python defines an __import__ function, which takes a string for a module name:     __import__(name, globals=None, locals=None, fromlist=(), level=0)      The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.       Source:    So currently I have something like:  command = sys.argv[1] try:     command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"]) except ImportError:     # Display error message  command_module.run()   This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.  Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added. Why is it important to apply transformation to an objects data? For $a,b,c,d \in \mathbb{R}$, is $\sqrt{a^2+b^2} + \sqrt{c^2+d^2} \geq \sqrt{(a+c)^2 + (b+d)^2}$? I have tried to show this using the fact that $\sqrt{x+y}\leq\sqrt{x}+\sqrt{y}\; $  for non-negative $x,y$ but haven't been able to arrive at a proof. Animations about a young man pulled into a fantasy setting with dragons? I'm looking for an animation (more likely a film not a series) that I watched as a kid, watched early 90's I'm sure it contained a book loving male main character (wears glasses might have even had an amulet) who gets pulled into a fantasy via a magic book  Setting with dragons and an evil wizard, I remember it being on TV as I never had it on VHS.  Same sort of animation technique as visionaries or thundercats.  Thanks. Windows 8 disk usage is 100% Ubuntu 12.04 comes with Gimp 2.6, so I installed Gimp 2.8 using the instructions below:   sudo apt-get purge gimp*   sudo add-apt-repository ppa:otto-kesselgulasch/gimp   sudo apt-get update   sudo apt-get install gimp    When try to open help, I get the message below. How do I install and configure the help for 2.8 on Ubuntu? How do I detect running processes using a library package? This command is doing the rounds for detecting currently running processes using glibc:  lsof | grep libc | awk '{print $2}' | sort | uniq   I find it intensely annoying, since /libc/ matches not only libc, but on my system:  /lib/x86_64-linux-gnu/libcap.so.2.24 /lib/x86_64-linux-gnu/libcgmanager.so.0.0.0 /lib/x86_64-linux-gnu/libcom_err.so.2.1 /lib/x86_64-linux-gnu/libcrypt-2.19.so /lib/x86_64-linux-gnu/libcrypto.so.1.0.0 /usr/lib/libcamel-1.2.so.45.0.0 /usr/lib/unity-settings-daemon-1.0/libcolor.so /usr/lib/unity-settings-daemon-1.0/libcursor.so /usr/lib/x86_64-linux-gnu/colord-plugins/libcd_plugin_camera.so /usr/lib/x86_64-linux-gnu/colord-plugins/libcd_plugin_scanner.so /usr/lib/x86_64-linux-gnu/gtk-3.0/modules/libcanberra-gtk3-module.so /usr/lib/x86_64-linux-gnu/libcairo-gobject.so.2.11301.0 /usr/lib/x86_64-linux-gnu/libcairo.so.2.11301.0 /usr/lib/x86_64-linux-gnu/libcanberra-0.30/libcanberra-pulse.so /usr/lib/x86_64-linux-gnu/libcanberra-gtk3.so.0.1.9 /usr/lib/x86_64-linux-gnu/libcanberra.so.0.2.5 /usr/lib/x86_64-linux-gnu/libcap-ng.so.0.0.0 /usr/lib/x86_64-linux-gnu/libck-connector.so.0.0.0 /usr/lib/x86_64-linux-gnu/libcolordprivate.so.1.0.23 /usr/lib/x86_64-linux-gnu/libcolord.so.1.0.23 /usr/lib/x86_64-linux-gnu/libcroco-0.6.so.3.0.1 /usr/lib/x86_64-linux-gnu/libcupsmime.so.1 /usr/lib/x86_64-linux-gnu/libcups.so.2 /usr/lib/x86_64-linux-gnu/samba/libcliauth.so.0 /usr/lib/x86_64-linux-gnu/samba/libcli_cldap.so.0 /usr/lib/x86_64-linux-gnu/samba/libcli-ldap-common.so.0 /usr/lib/x86_64-linux-gnu/samba/libcli-nbt.so.0 /usr/lib/x86_64-linux-gnu/samba/libcli_smb_common.so.0 /usr/lib/x86_64-linux-gnu/samba/libcli_spoolss.so.0 /usr/lib/x86_64-linux-gnu/samba/liblibcli_lsa3.so.0 /usr/lib/x86_64-linux-gnu/samba/liblibcli_netlogon3.so.0   I understand that libc is used by pretty much everything, but I'd like to refine this command. Consider its applications for other libraries. How can I do this?  The flaw in this approach, in my opinion, is that the package providing libc may include a whole host of other shared library files (all of which may or may not be covered under the umbrella term that is the library name, like glibc, or libboost-python). Using a word boundary or - to mark the end of libc doesn't really fix this. This may not be a flaw, perhaps, as Braiam points out, since many or all of these .so files may link to a core file in which the flaw resides, as is the case for libc6 on Debian.   If a specific OS/distro is needed, assume Debian Linux.  Also annoying is that this command could be condensed to lsof | awk '/libc/{print $2}' | sort -u. How do I emit light from inside a object? Identifying records in MC to delete I'm trying to delete a large number of records from SFMC to avoid being charged extra. I've run several different SQLs to help identify the records I don't need, but when I run the Contact Count report, it still shows approx 100K billable contacts and approx 60K distinct email addresses.  Here are the SQLs I've tried:   No Opens in past 5 days Leads/Contacts not in SFDC  SubscriberKey as Email Address Leads/Contacts where SubscriberKey is Empty Unspecified records (DE populated by MC Support)    These efforts reduced the count a good amount, but not as much as I was expecting.   Has anyone else gone through this process before and if so, what queries can you share that might help my case?