looping in mathematica for using the current value as initial state of next value

Question: i have some initial state $psi[x,t]$. I perform some operation on it and store the value in another state $pi1[x,t]$. Now on the next step i have to use  $psi1[x,t]$ as initial state and perform the functions again and store in  $psi2[x,t]$, Please anybody help me how to use loops for this.
Comment: If it is about *Mathematica*, the software, `NestList` is exactly what you need.
Answer: I think you might be looking for Nest or NestList as noted by Kuba.
<code>NestList[someOperation, psi[x,t], 2]
</code>
gives
<code> {psi[x, t], someOperation[psi[x, t]], someOperation[someOperation[psi[x, t]]]}
</code>
Comment: i am looking for $operation[operation[operation[psi(x,t)]]]$, where $psi(x,t)$ is some initial function then i store the value of $operation[psi(x,t)]$ into $psi1(x,t)$. Later I have to use $psi1(x,t)$ as initial state and perform same operation as $operation[psi1(x,t)]$.  I have to do it n times.
Comment: yes you are right. I am looking for something this. Thank you very much


Drupal version control - professional development

Question: I have been assigned to develop a site in Drupal. I will be working on it alone. Is there a need for version control? An if yes which is optimal for drupal? How should I set the development process? (ex:make a testing site locally, then get it live). Thank you in advance.
Answer: If you've got a complex setup, you may want to look into the Aegir project, which is a Drupal-based tool for managing Drupal site installations.
If your needs aren't big enough to require Aegir, a lot of the tasks which it does can also be automated using Drush, which is a command-line tool for managing a Drupal site.
Even if you feel Aegir is overkill, you should definitely use Drush - it will make your life a lot easier when it comes to deployment between your development and live versions and management thereafter.
As for version control: If you're writing any of your own code, then yes, you should be using version control. If you're simply using Drupal plus third-party modules, then you probably don't need it, since you're not in charge of the code anyway. But you might find it useful nonetheless, because there's always a chance you might find yourself needing to tweak a third party module (or even the core) to get things to work the way you need to, and at that point you will need version control, and it will help if you already have it set up.
You can't very easily do version control on your site content, because it's all in the Drupal database. You can do a certain amount by moving your site structure from database to code using the Features module, at which point it becomes possible to version control it in the same way as other code, but your actual content remains in the database.
To do version control on content, the main option you have is the Diff module, which allows the database to store multiple versions of page content, which can then be administered.
Hope that helps.
Comment: The Aegir Project looks promising as managing sites is a task in itself as well as development. However be aware that the associated modules 'provision' and 'hostmaster' are currently only for Drupal 6.
Answer: Version control is always required. The best i would say is GIT. There are multiple ways of deployment e.g. DOG(Drupal On Git) and a few others.
You can use gitflow also for deployment.
Make use of makefiles and installation profiles if you want your instance to be redistributable.
Make use of features to maintain db changes that you make on your local in sync with the staging or testing server.
Read about the above stuffs mentioned. Comment if you need any more info.
Hope this helps.
Answer: I developed a few Drupal 6 and Drupal 7 sites and in my opinion the first thing you should provide to your site is a robust way to backup and restore it quickly in case of issues (especially after the site has gone live!).
To accomplish these tasks there are a couple of modules:
Backup and Migrate and Backup and Migrate Files (still in dev but functional).
Another interesting feature is the content revisions which will give you the opportunity to roll back to a previous version of a node. It is available every time you create/edit a node.
Working locally have some advantages like speed for example but I work both locally and remotely (hosted somewhere in the wild!) and trust me, it is going to happen all the time that you will need to upgrade a module or make some live changes on a prod site so my choice is again for a smooth and fast backup and restore (database and files/dirs structure) process.
good luck and happy drupaling! :)
Answer: My feeling is that version control is ALWAYS needed. Even if you are working alone, and don't have to coordinate with others, the knowledge that your files are safe, and any changed can quickly and easily be rolled back, is invaluable.
So just for your own peace of mind, use VC. I use SubVersion, which has very nice integration with Windows, NetBeans (my preferred IDE) and almost everything else. There are even do-everything-for-you installers for many platforms.
To deploy, I commit from my development machine, check out to a test server, then check out the tested site to production.


ASP.net debug https on localhost

Question: I have to test a method out on my asp.net application that should work on https. Is there a way where I can run the application on localhost on https so I can debug it?
Answer: YOu could create a self signed SSL certificate and then create a web app with SSL and your self signed certificate on your local machine in IIS (use a URL like http://dummy.test and add that to the hosts file in the c:\windows\system32\drivers\etc folder, have it point to 127.0.0.1), then start VS, attach to the w3wp.exe process and you can debug.
Create a self-signed SSL certificate with IIS 6.0 Resource Kit SelfSSL
Answer: Yep, get yourself a self-signed cert and install it. Generally, though, I'd just disable the need for SSL in the local dev environment.

ASP.net debug https on localhost


Automatic DNS registration only for domain computer

Question: I have a windows domain with a win server 2012 domain controller with dns service installed.
In the DNS server there is the automatic DNS registration, is it possible to limit these registration only for domain machines? Now in my dns I can found anything... printers, mobile devices, and so on.
Answer: <code>To avoid this problem perform the following 3 steps (It is important that you follow all the steps to avoid the issue).

 1. Under Network Connections Properties: On the Unwanted NIC TCP/IP
    Properties -> Advanced -> DNS - > Uncheck "Register this connections
    Address in DNS"

 2. Open the DNS server console:  highlight the server on the left pane
        Action-> Properties and on the "Interfaces" tab select "listen on
        only the following IP addresses". Remove unwanted IP address from
        the list

 3. On the Zone properties, select Name server tab. Along with FQDN of
        the DC, you will see the IP address associated with the DC. Remove
        unwanted IP address if it is listed.

After performing this delete the existing unwanted Host A record of the DC.
</code>
Source : http://support.microsoft.com/en-us/kb/2023004
Comment: I'm a bit confused... I want to remove dns names of devices out of domain, not by ip address or subnet. I may have some domain ip in the same ip range than printers ip. Is it possible?
Comment: Oh my bad, I hope MBu satisfied you. You can still organize your network by filtering mac addresses, making a range for printers, phones etc.
Answer: It looks like you are also running DHCP Server service on a Windows Server. Go to DNS tab in the DHCP scope properties and clear "Dynamically update DNS A and PTR records for DHCP clients that do not request updates" checkbox.
Comment: Assuming you do not have any pre-Windows 2000 machines, your clients either register themselves on their own or are handled by the first flag.
Comment: Ok but clearing this flag, my domain computers will register and update their dns records? Thanks


Can someone steal my WiFi password?

Question: Can someone steal my original SSID password when my pc connects to the other WiFi with the same SSID?
Comment: Your question is [partially answered](http://security.stackexchange.com/q/54231) on Information Security site of Stack Exchange
Comment: "How can I tell if someone is emitting the same ssid?" Turn off your router's wireless transmitter and then immediately begin scanning for transmitting SSIDs
Answer: First, let's be clear that clients don't just send their password across the air in plain text, or in a form that an impostor AP ("Wi-Fi router" in layman's terms) could easily decode. So stealing a key with an impostor AP is not as easy to do as you're fearing.
If you were still using WEP, you should upgrade to WPA2, and you'll be fine, especially if you have a strong password.
If your client PC expected your SSID to use WEP, an impostor AP could ask your PC WEP client to perform "Shared Key Authentication", where the AP sends the client a "challenge" which is a block of random bytes, and then the client encrypts that challenge with his WEP key, and sends that encrypted block back as the challenge response. The impostor AP now has everything it needs to do an "offline" (read: high-speed) brute-force dictionary attack to try to discover your key. The impostor AP could even choose the "challenge" bytes it sends in such a way that make they key easier to recover.
With WPA and WPA2, the AP authenticates itself to the client at the same time as the client authenticates itself to the AP, and neither gives away the password, or even any information that could be used to try to brute-force the password. They just exchange random numbers (known as nonces in this context), and use those random numbers, mixed with the pre-shared key (PSK, a.k.a. network password) they each supposedly know, to derive another key called the PTK. Then they each use that PTK to encrypt (sign) a small message and send it to the other, and they each verify that the other correctly signed the message. That way they both know if the other one knows the same PSK as them, but neither has revealed the PSK to the other.
Comment: relieved! Nice answer
Answer: All of your attack scenarios seem to revolve around your SSID. You could disable SSID broadcast on your network to add a layer of obscurity to help prevent against such an attack.
Disabling SSID broadcast means that your network will be accessible only to those who have the name of the network as well as the password. The most an average individual could see would be an "Other Network" appearing in their available Wi-Fi network list.
Keep in mind that this is effective only against someone with a whim or passing interest in your network. If there is an individual who is set on getting in to your network, they probably will. You need to secure more than your access point to stay safe.
Comment: It's important to notice that finding WiFi networks with SSID broadcast disabled is a trivial task (Eg.: with tools like inSSIDer ). Is it a layer of obscurity? Yes, but a really thin layer that can create more interest in someone who is planning to do bad stuff.

Can someone steal my WiFi password?


Requirements for a Windows domain server

Question: What are the hardware, software and network requirements for a new Domain Server with Windows Server 2003 for 100 users?
Answer: 100 users is nothing even for an entry level server and a switched 100 Mbit/s network.
Best practice dictates:

A second domain controller for reliability
Reliable/redundant hardware (for example, not the glorified desktop tower servers)
100 Mbit/s network card and network infrastructure
Antivirus....  see this site ad-nasuem!

Domain controllers by today's standards have very lightweight hardware and network requirements - yet they are perhaps the most vital part of your network hence go for reliability and redundancy (multiple power supplies, network cards 2nd server, etc...).
Given the broad scope of your question (to put it politely) it is hard to give any specific advice - are they also going to be file servers, DHCP, DNS, etc., etc.  Post more for a better answer.
Answer: You may benefit from perusing the "Planning Domain Controller Capacity" section over at the TechNet library. You will find that, as Jon Rhoades mentioned, 100 users is virtually a non-issue for any server and network device manufactured in the last 5 years. Unless, of course, you have some special uses that should be taken into account. Could you give us more info on what the environment is like? And need for a certificate authority? Lots of files being transferred on the network?
It bears repeating that you should focus less on performance and more on redundancy when specing out a server to be used as a domain controller. It will likely be the linchpin for your network and thus you should protect it like gold. Ideas include:

RAID 1 OS drives, with a hot spare
Failover network card (note: don't dual-home a domain controller)
A seconday DC, as Jon Rhoades mentioned, is a must IMO.
Reliable backup software that is made to take proper backups of a Domain Controller. Don't feel secure until you're successfully restored a few of the backups in a test environment.
Don't install anything extraneous on it. If you must, install it to a directory that is not on the system drive. Have a D: drive that is on a separate physical set of disks and not just a separate partition on the OS disks.
As Jon Rhoades mentioned, get good antivirus for it. However, I'd like to specifically add that not all AV products work on Domain Controllers. Get a product that is specifically advertised to be compatible with a Domain Controller and also manually verify that it is excluding the recommended directories and files. Yes, it's tedious. Not all of our tasks can be as glamorous as grinding out breathtaking regex.
Physically secure it and make sure it stays clean. I've seen servers that had enough lint, dirt and hair stuck in the grills to knit a sweater with. FWIW, carpet in a server room is a bad idea, but I digress. =)
Tripwire scripts to wipe the storage of any machine that scans or otherwise access the DC in a way that is unacceptable.
A trained bear to maul anyone who gets near the DC and doesn't give the secret handshake.

You get the idea. =)
Comment: Don't forget that you'll need to do periodic Bear maintenance to ensure the training isn't forgotten.  I combine this task with our annual auditors' inspection of the DC.
Answer: Like any database, the DC will benefit from being able to load the entire ntds.dit file into memory (rather than having to access the copy on disk all the time) so size the RAM appropriately.
That said, for 100 users, I don't think you're going to need that much (unless you have 1000s/millions on non-user objects taking up all the space).
A server with a recent dual-core CPU and 1-2GB RAM should do you fine.  As your requirements grow, modify the hardware appropriately.
And, of course, get two and take backups... :)
Answer: You can get by with a dual core, dual NIC server with about 1024 MB of RAM.  Windows 2003 has DC available OOTB; just add the Active Directory services role.


Getting Current User in .NET Core Console

Question: In a .NET Core console application (note: not ASP.NET Core!), how can I get the current user? To be clear, I'm looking for what used to be available as Thread.CurrentPrincipal, which no longer exists.
PlatformServices does not contain this information, and neither does Environment.
Answer: Got it. A possible option is to use WindowsIdentity:
WindowsIdentity.GetCurrent().Name

It is necessary to add the System.Security.Principal.Windows package.
Of course, this is for Windows only.
Another option is to use Claims:
ClaimsPrincipal.Current

For that, the package to add is System.Security.Claims. In Windows, by default, the identity will be empty.
Comment: What I hear between the lines: ClaimsPrincipal is the future ;)
Comment: `ClaimsPrincipal.Current` will *not* work in a controller, it will be null. You need to access the `HttpContext.User` property, which will indeed be a `ClaimsPrincipal` instance.
Comment: Good news.  Environment has been re-added to .NET Core.  https://apisof.net/catalog/System.Environment.UserName
Comment: in a console application `ClaimsPrincipal.Current` is null
Comment: Good to know. A static API for ClaimsPrinciple does not make so much sense anyway IMHO.
Answer: System.Security.Principal.Windows is not available unless you import the DLL manually. The following worked for me:
Environment.UserName;

According to the .NET Core System.Environment Source Code, this solution "should suffice in 99% of cases."
Note: Be sure you are targeting DotNetCore 2.0 or later as 1.0 and 1.1 do not have this definition.
Edit Jan 22 2019: The link to the old source of the method has gone stale. PR 34654 moved System.Environment to live in CoreLib. For those curious to read the source code, you may still do so, though the comment suggesting it "should suffice in 99% of cases" has been removed.
Comment: Make sure you're targeting `DotNetCore 2.0` or later. `DotNetCore 1.0` and `DotNetCore 1.1` do not appear to have `.UserName`.
Comment: I don't seem to have a `.UserName` in `Environment`
Comment: Cool works for me. @Foxtrek_64 anyway to set the user? As I am deploying it on Linux server and want to set user to service account
Answer: If you want to reuse IIdentity abstraction to pass through your middle layer do this:
var identity = new GenericIdentity(Environment.UserDomainName + "\\" + Environment.UserName, "Anonymous");

P.S. in core 2 console app:
ClaimsPrincipal.Current and Thread.CurrentPrincipal are always null (unless you have setup them) and this code will not work either:
IPrincipal principal = new GenericPrincipal(identity, null);
AppDomain.CurrentDomain.SetThreadPrincipal(principal);

after this ClaimsPrincipal.Current and Thread.CurrentPrincipal are still null.
WindowsIdentity.GetCurrent() works, but there should be more strong reasons to reference System.Security.Principal.Window then get the "user name".
Comment: Future readers.  For the GenericIdentity idea....watch out for the auto-magic-voodoo'ed IsAuthenticated gets set to True !  Thanks RP for the idea.  Here is the code to see the voodoo.   https://github.com/microsoft/referencesource/blob/master/mscorlib/system/security/principal/genericidentity.cs  (find "public override bool IsAuthenticated")


Counting triples with a fixed sum using Kronecker delta and complex integration

Question: Let $(n_1,n_2,n_3)$ a triple of non-negative integers summing up to $27$, i.e. $n_1+n_2+n_3=27$. I want to count how many triples there are satisfying this constraint, using the contour integral representation of the Kronecker delta. In principle, I should be able to count the number of triples in two different ways:
$$
I_1=\sum_{n_1=0}^{27}\sum_{n_2=0}^{27}\sum_{n_3=0}^{27}\delta_{n_1+n_2+n_3,27}
$$
$$
I_2=\sum_{n_1=0}^{\infty}\sum_{n_2=0}^{\infty}\sum_{n_3=0}^{\infty}\delta_{n_1+n_2+n_3,27}
$$
(I believe I should be allowed to extend the range of the summations to $\infty$, landing on $I_2$, as clearly numbers $n_i>27$ cannot contribute to the counting). However, if I carry out the calculation in the two cases using the integral representation of the Kronecker delta function, the second 'version' ($I_2$) seems problematic (also for Mathematica).
Using
$$
\delta_{a,b}=\frac{1}{2\pi\mathrm{i}}\oint_{|z|=1}dz\ z^{a-b-1}\ ,
$$
I obtain
$$
I_1 =\frac{1}{2\pi\mathrm{i}}\oint_{|z|=1}\frac{dz}{z^{28}}\left(\sum_{n=0}^{27} z^n\right)^3=
\frac{1}{2\pi\mathrm{i}}\oint_{|z|=1}\frac{dz}{z^{28}}\left(\frac{-1+z^{28}}{-1+z}\right)^3 =\mathrm{Res}\left(\frac{1}{z^{28}}\left(\frac{-1+z^{28}}{-1+z}\right)^3;\{z,0\}\right) =406\ ,
$$
using Cauchy's residue theorem (there is a pole of order $28$ in zero and a removable singularity at $z=1$ on the contour). The answer is correct. However, if I attempt to compute $I_2$
$$
I_2 =\frac{1}{2\pi\mathrm{i}}\oint_{|z|=1}\frac{dz}{z^{28}}\left(\sum_{n=0}^{\infty} z^n\right)^3=
\frac{1}{2\pi\mathrm{i}}\oint_{|z|=1}\frac{dz}{z^{28}}\left(\frac{1}{1-z}\right)^3
$$
I run into potential troubles, as the earlier removable singularity has now become  a 3rd-order pole right on the contour. This presumably forces me to reinterpret it as a Cauchy principal value integral (which I am not super-familiar with). Mathematica has also some problems in evaluating the integral in $I_2$ (setting $z=\exp(\mathrm{i\theta})$), while the integral in $I_1$ is perfectly fine. Now, assuming that the $n_i$s can be safely extended to $\infty$ (I do not see why they shouldn't), I would be grateful if you could help me with the evaluation of the PV integral $I_2$ and confirm that it also yields 406. And if it doesn't, where do things go wrong? Many thanks in advance.
Answer: Imagine permitting $M$ terms in each sum in $I_1$.  Then the integrand is
$$\frac1{z^{28}}\left (\frac{1-z^M}{1-z} \right )^3 = \frac1{z^{28}}\left (1-3 z^M + 3 z^{2 M}-z^{3 M} \right ) \sum_{n=0}^{\infty} \binom{n+2}{n} z^n$$
For example, if $M=7$, then we have contributions at $n=27$, $n=20$, $n=13$, and $n=6$, so that the total number of triples becomes
$$\binom{29}{27} - 3 \binom{22}{20} + 3 \binom{15}{13} - \binom{8}{6}  = \frac12 (29 \cdot 28 - 3 \cdot 22 \cdot 21 + 3 \cdot 15 \cdot 14-8 \cdot 7) = 33$$
When $M \gt 27$, it no longer matters what $M$ is; the answer will remain $406$ as $M$ increases.  Thus, this is how we view the Cauchy principal value: we take the limit as $M \to \infty$.
It should be noted that the actual integral represented by $I_2$ doesn't even exist as a Cauchy PV, as we have a triple pole on the contour.  The only way I see around this problem is to consider $M$ very large but finite.
Comment: @PierpaoloVivo: To be honest, I am a bit puzzled too.  But keeping $M$ finite and large is the only way I can reconcile how this all works.  I guess the problem is that, near $z=1$, $z^M$ may not be as small as we would like.  I'll bet that's the origin of the misunderstanding.
Comment: many thanks for your answer. However, I am still a bit 'puzzled' by the fact that I started from a seemingly legitimate expression $I_2$ (in terms of sums extending to infinity), and end up with an integral expression for $I_2$ that apparently does not make sense (even as a PV). Is this then a case where the limit ($M\to\infty$) and the contour integral cannot be exchanged? I would then love to learn which hypotheses of what theorem are violated in this case...


Effectiveness of flaming spears as a psychological weapon in a hunter-gatherer society

Question: In my world, there is a tribe that covers themselves in ash and attacks in the dark, with torch spears. While this is clearly a really good way to be seen and picked off by archers, in a time of superstition and belief in spirits would this be a good tactic to frighten their enemies?
Comment: When the Romans landed in Ynys Môn, they were greeted by scary natives with torches. http://resourcesforhistory.com/celtic_druids.htm It scared them a little bit. Assuming that tribes are more easily scared than highly developed Romans (I doubt there is any scientific research on that topic), the answer seems to be yes. I think you can add several things to make them even more scary (shouting, dancing, whatever)
Comment: Hi Jim. I see you have accepted an answer already. While it is entirely up to you whether, which and when to accept an answer, it is generally recommended to wait at least 24 hours before doing so. For more on this, please see the post [Please wait at least 24 hours before Accepting an answer](https://worldbuilding.meta.stackexchange.com/q/5023/29) on [meta].
Comment: That depends. It is shown that even Homo Habilis controlled fire, so if a tribe knows how to use fire... then they won't be frightened. But if they don't know how to use fire, the answer is quite obvious.
Comment: Well, of course the other tribe knows about fire. But could the flaming weapons still create an otherworldly appearance?
Comment: See also, [flaming sword](https://worldbuilding.stackexchange.com/questions/31968/advantages-of-a-flame-sword)
Answer: I think the benefits don't weigh up against the downsides.
An additional downside to take into consideration is that the spears will negatively affect the vision of the warriors. Having a bright source of light in front of them instead of behind them, will blind them and wash away the darker visuals in front of them.
So they will see less, while they become better visible to their opponents. You can easily try this out at night on a walk or such.
Answer: It depends on a few factors:

Is the tribe known for wielding flaming spears into battle? Are they known for beating their enemies? The enemy's perception would be such if the tribe has a long history of warfare and a tradition of carrying burning spears into battle. So this would be arousing fear on account of reputation.
Is the tribe completely obscure and uses this method unlike any other tribe or clan etc. This would arouse fear on account of obscurity. People fear the unknown.
Does the tribe use powder/resin/oil mixtures to color the flames and make them look really otherworldly? This causes fear on account of superstition alone, especially if no one else knows these techniques.

If the answer is 'yes' to the above questions, the same answer goes for your question.
Covering themselves in ash and attacking at night also gives a ghostly appearance, I would presume, so the scare factor rises again. If the samurai were able to use a fairly banal thing like a stylized facial armor (Mempo) to scare their enemies, a famous/obscure ash-covered warrior tribe wielding strange-colored flames in the night would definitely spark fear in any enemy.
Answer: Pretty poorly.
I'm going to assume that by hunter gatherer society they don't do much metalworking. This means that their spear is going to be made of mostly wood, bone, sinew, and rock. A flaming spear made of such materials is going to be structurally weakened and unbalanced by the attachment of a wick.
Sure it would look scary at first, but attacking like this loses the element of surprise. There aren't any lighters or matches available so a small fire would need to be built to light the torches. This could be done out of sight of the enemy meaning that they would be detected as they approach, or a fire could be built immediately before the attack which would attract curious people wondering  "Why does our enemy stop to build a fire before attacking us?".


Edit a manuscript after submit and approve it

Question: I submitted my manuscript to a Springer journal and after viewing the submission, I approved it. But now I need to edit one of my references, but the Edit button is not available after approving the submission. How can I edit it? Should I submit a new manuscript?
Comment: Look for an "upload a revised copy" button. This is generally discouraged, but can be done within a few days after initial submission, without much of an issue. If several days have passed, then seek editor's approval.
Answer: I think that submitting a new manuscript will just confuse them. The version you submitted will be checked and reviewed. You will get back a report and, hopefully, a request to update and resubmit changes. Make your changes then.
If that isn't enough to satisfy you, then contact the editor of the journal and ask for advice on how to proceed. But what you have discovered is pretty common.
The journal needs, for now, a stable version that can be sent to reviewers. You are just at the beginning of the process and will have time to fix things.
Comment: Probably not worth a worry at this point. It might even be missed by reviewers. But journals for all practical purposes never publish the first version sent to them. You are lucky if you only need to revise once or twice.
Comment: Submitting a new manuscript won't confuse them - modern editorial management systems have tools precisely to detect duplicate submission. It's an administrative hassle, though, and I agree that the easiest way is just to wait until revisions or copyediting (if the manuscript is immediately accepted) to make a non-essential change like this one.
Comment: Hmmm. Deer Buffy??? No, Dog Buffy. Ha.
Comment: Therefore, a mistake in referencing is common and does not cause the editor to reject it. right?
Comment: Thanks dear @Buffy, you helped me to control my stress.
Comment: Just be sure to inform the editor when at the time of proof editing you'll made whatever little change
Answer: Just wait for the revision cycle to complete and incorporate the change at that time.  You are talking about a very small nitpicky change.  No reason to disrupt the cycle now.
Note, if they accept the paper without revision, write in at that time to request the change and with an edited version (or a brief email explaining that you will make the change in camera review, if they have that).


Windows Kernel Name\Version?

Question: Mac OS X has the Darwin 10.6.0 Kernel, and Ubuntu has the Linux 2.6 Kernel, so in Windows what is it called?
Answer: The kernel file itself is ntoskrnl.exe.  It is located in C:\Windows\System32.
If you view the properties of the file, you can look on the Details tab to see the true version number running.  You can see other versions of the kernel on your system under C:\Windows\winsxs\amd64_microsoft-windows-os-kernel* and C:\Windows\winsxs\x86_microsoft-windows-os-kernel*.  My current kernel, for example, on Win 7 x64 is 6.1.7601.17592.  6.1 indicates Windows 7.  7601 indicates SP1 (RTM lists 7600).  The final number is the current revision.  If your system has multiple processors or multiple cores in the processor, the details panel will also show that the original file name is ntkrnlmp.exe.  The "mp" here means "multiple processors".  At one point Windows used different kernels for a system if it had one or more than one processor.  I don't know if this is still the case and the internal filename is still kept this way for historic reasons, or if the single processor core version still exists.  I don't have a single core system to test on, currently.
In the WinSXS directory, my system currently has quite a few revisions of the kernel (most from the RTM version of Windows 7):
6.1.7600.16385, 6.1.7600.16539, 6.1.7600.16617, 6.1.7600.16695, 6.1.7600.16792, 6.1.7600.20655, 6.1.7600.20738, 6.1.7600.20826, 6.1.7600.20941, 6.1.7601.17514,  6.1.7601.17592, 6.1.7601.21701.
You notice that my system is not using the highest version of the kernel on the system (6.1.7601.17592 vs 6.1.7601.21701).  However, it is using the version which was the last one to be digitally signed so even though the final version number is lower, the file is newer.  I'm not sure how MS determines what that final version number is going to be.
Comment: @umar please, keep CAPS LOCK off...
Comment: SO CAN IT BE CALLED "NT Kernel"
Comment: Sure, but that would refer to any kernel from Windows NT 3.5 through Windows 8 including the server editions.  All of those are [NT kernel-based](http://en.wikipedia.org/wiki/File:Windows_Family_Tree.svg).  Most often people will refer to the product name when referring to the kernel, or the [internal Windows version](http://en.wikipedia.org/wiki/Comparison_of_Windows_versions#NT_Kernel-based_2) like @Journeyman Geek did.
Answer: Well, it tends to be Microsoft Windows Version [6.1.7601] for windows 7 - the main change should be the numbers which are MajorVersion.MinorVersion.Build. Vista was 6.0.xxxx, and XP was 5.1.2600 for SP3.
You can find this with the 'ver' command
Comment: `ver` from the command prompt.  `winver` from the Run dialog.
Answer: Windows:

Windows 7 - Click Start or the Windows logo -> right click Computer -> then click Properties. Look in System.
Windows Vista and Windows Server 2008 - Click Start or the Windows logo depending on what you have -> then click Control Panel -> System and Maintenance -> System.
You could also try Clicking Start or the Windows logo -> then if you have a "Start Search" field type winver -> then Double-click winver.exe from the results. If you had a run box instead of search just click Run -> type winver -> click OK.
Windows XP and Windows Server 2003 - Click Start -> Run -> Type winver then click OK. You could also try typing msinfo32 or sysdm.cpl if you like. Lastly you might try typing dxdiag. Windows might prompt you to verify drivers click No.

Windows Kernel Name\Version?


How to store European Currency in MySQL?

Question: On a new project I work on I have data in CSV format to import into a mysql table. One of the columns is a price field which stores currency in the european format ie. 345,83.
The isssue I have is storing this decimal seperator. In most European currencies the decimal seperator is "," but when I try to insert a decimal number into a field (ex. 345,83), I get the following error: "Data truncated for column 'column_name' at row 'row #'". If I use '.' instead of ',' it works fine. Could you please help me with, how to store this format in mysql?
Comment: Just to clarify - this is not exactly a mysql problem, but a question about parsing European numbers? If you've had this column as a double you'd know what to do.
Answer: you can store it as a regular decimal field in the database, and format the number european style when you display it
edit: just added an example of how it might be achieved
$european_numbers = array('123.345,78', '123 456,78', ',78');

foreach($european_numbers as $number) {

    echo "$number was converted to ".convert_european_to_decimal($number)."\n";
    // save in database now
}

function convert_european_to_decimal($number) {
    // i am sure there are better was of doing this, but this is nice and simple example
    $number = str_replace('.', '', $number); // remove fullstop
    $number = str_replace(' ', '', $number); // remove spaces
    $number = str_replace(',', '.', $number); // change comma to fullstop

    return $number;
}

Comment: As I understood the OP that's exactly what he tries to do but fails due to the fact that MySQL uses the dot as the decimal separator. You cannot store values with a comma in a DECIMAL column.
Answer: Use number_format or money_format, it's pretty much what you preffer.
Comment: please be aware that money_format() is undefined on windows systems
Answer: It's worse than you think. The number 1234.56 may be written in Europe as:

1234,56
1 234,56 (space as a group separator)
1.234,56 (dot as a group separator)

In .net the number parser can works according to a given culture, so if you know the format it does the hard work for you. I'm sure you can find a PHP equivalent, it'd save you a lot of trouble.
Answer: You could import the currency field into a VARCHAR column and then copy this column into a DECIMAL column while replacing the , by a . in all rows using MySQL string-manipulation-functions.
UPDATE <
>
    SET <<decimal-currency-col>> = REPLACE(<<varchar-currency-col>>, ',', '.');

Comment: @S. Gehrig: Correct, but a bit overkill considering the OP is using PHP.
Comment: That depends: if the OP has to some calculations (some accumulations for example) on the MySQL side, he has to store the values in an appropriate data type.
Answer:
Some data types do not have a direct
  correlation between SQL Server or
  Access and MySQL. One example would be
  the CURRENCY data type: MySQL does not
  (yet) have a CURRENCY data type, but
  creating a column with the definition
  DECIMAL(19,4) serves the same purpose.
  While MSSQL defaults to Unicode
  character types such as nCHAR and
  nVARCHAR, MySQL does not so tightly
  bind character sets to field types,
  instead allowing for one set of
  character types which can be bound to
  any number of character sets,
  including Unicode.

from http://dev.mysql.com/tech-resources/articles/migrating-from-microsoft.html
Answer: You could also consider multiplying it by 100 and storing it as INT.
Before inserting the price to the DB:
$price = (int)$price*100;

After receiving price from the DB:
$price = number_format($price, 2, ',', ' ');

Answer: Try replacing the "," with "."?

$price = str_replace(",", ".", $price);

Comment: @Thilo. Yes I think it should be a dot in this case as it appears to be the decimal separator.

In the UK we use a comma as the thousands separator and a dot for the decimal e.g. 1,250.25

However the French and other European countries use them the otherway round e.g. 1.250,00.


Rails Paperclip precompile error

Question: I modified my Paperclip-using model like this:
class UsersPicture < ActiveRecord::Base
attr_accessible :user_id, :users_picture_id, :photo
belongs_to :user
has_attached_file :photo,
   :url => "users_pictures/:attachment/:id/:basename.:extension",
   :path => ":rails_root/users_pictures/:attachment/:id/:basename.:extension"

before_create :rename_file_name

def rename_file_name
  extension = File.extname(photo_file_name).downcase
  filename = File.basename(photo_file_name).downcase
  timestamp = Time.now.to_i
  name = Digest::MD5.hexdigest("#{filename}")
  self.photo.instance_write(:file_name, "#{name}_#{timestamp}#{extension}")
end
end

Before I inserted the before_create method, everything was fine.
But now my log says:
ActionView::Template::Error (users_pictures/photos/88/8b7474622cf5bbc140ed7defe1ae76a8_1351088476.jpeg isn't precompiled):
8:

9:   Users picture file:
10:  <% if @users_picture.photo.exists? then %>
11:             <%= image_tag @users_picture.photo.url %>
12:         <% end %>
13:

14:
app/views/users_pictures/show.html.erb:11:in `_app_views_users_pictures_show_html_erb__597237708__324410398'
app/controllers/users_pictures_controller.rb:18:in `show'

I was searching for solutions but there was always remembered to use "image_tag". But I am currently using it ?
The index works just fine of course, but the show method does not :/
What can I change ?
Edit: When I remove the image_tag, I get:
users_pictures/photos/88/8b7474622cf5bbc140ed7defe1ae76a8_1351088476.jpeg
And this is also the correct path.
Answer: Try prefixing the image path with /
<%= image_tag "/" + @users_picture.photo.url %>

From https://stackoverflow.com/a/11318133/418819

Rails Paperclip precompile error


EntityFramework adding new object to nested object collection

Question: This question is a continuation of:
EntityFramework adding new object to a collection
Now I understand that when using DbSet EF won't load the entire collection into memory
But what if I have something like the following code:
public class User
{
    public int UserID { get; set; }
    public string UserName { get; set; }
    public ICollection<Role> Roles { get; set; }
}

public class Role
{
    public int RoleID { get; set; }
    public string RoleName { get; set; }
    public User User { get; set; }
}

public class MyContext : DbContext
{
    public DbSet<User> Users { get; set; }
    public DbSet<Role> Roles { get; set; }
}

public class SomeClass
{
    public void AssignRoleToUser(int userID, Role role)
    {
        var ctx = new MyContext();
        var user = ctx.Users.First(x => x.UserID.Equals(userID));

        user.Roles.Add(role);

        ctx.SaveChanges();
    }
}

In this case, I'm not using the DbSet object to add a new object to the Role collection, instead, I'm adding a new role to a specific user using an ICollection collection
So what happens in this case?
Does EntityFramewrk have to load into memory all the user's roles in order to perform the insert?
Comment: in this provide code, above you are not adding new role as your ctx.Users is just use to retrieve data.
Answer: In provide code above you are not adding new role as your ctx.Users is just used to retrieve data. Somewhat similar issue is addressed in this SE post - Linq To Entities - how to filter on child entities.
I would advice to look at this short and useful article - Entity Framework 4.0 FAQ – Getting Started Guide.
Answer: No. EF does not need to know what 'Roles' the User has.
You need to learn what happens in regards to change tracking:

Once the query is run the change tracker receives an object entry for 'user'. The state of this user is 'Unchanged'
You add a new role to the user's Roles collection. This simply adds a change tracker entry for this new role and marks it as 'Added'
On SaveChanges() EF will look at your change tracker and see that the user object has not changed so nothing needs to be done there. There is also an entry for the new role which states that it needs to be added. So an SQL query will be written to insert this role.

Simple as that. You can always debug and add a watch for the state of the change tracker. The entries can be found by calling DbContext.ChangeTracker.Entries().
EF will blindly send off the 'add' to the DB.


DNS Zone config with Centos Web Panel doesnt work

Question: I have been trying for hours now to setup my domain with the CentOS Web Panel and own nameservers.
I did change the nameserver at the domain registrar and entered the IP values for these nameservers, so:
ns1.domain.com resolves to IP1
ns2.domain.com resolves to IP2

That works, I did check that with ping ns1.domain.com
But if I try to ping domain.com, it doesn't work.
My domain.com.db zone file:
(I replace the IPs with ip1, ip2, ip3, ip4)
; Generated by CWP
; Zone file for domain.com
$TTL 14400
domain.com.      86400        IN      SOA     ns1.domain. info.domain.com. (
                2019052314      ; serial, todays date+todays
                86400           ; refresh, seconds
                7200            ; retry, seconds
                3600000         ; expire, seconds
                86400 )         ; minimum, seconds

ns1.domain.com. 14400 IN A IP1
ns2.domain.com. 14400 IN A IP2
domain.com. 86400 IN NS ns1.salarom.com.
domain.com. 86400 IN NS ns2.salarom.com.

domain.com. IN A IP1

localhost.domain.com. IN A 127.0.0.1

domain.com. IN MX 15 domain.com.

mail IN CNAME domain.com.
www IN CNAME domain.com.
ftp IN CNAME domain.com.
; Add additional settings below this line
_dmarc 14400 IN TXT "v=DMARC1; p=reject; rua=mailto:email@example.com"
domain.com. 14400 IN TXT "v=spf1 +a +mx +ip4:IP1 ip4:IP2 ip4:IP3 ip4:IP4 ~all"
mta2 14400 IN A IP2
mta3 14400 IN A IP3
mta4 14400 IN A IP4
@ 14400 IN NS ns1.domain.com.
@ 14400 IN NS ns2.domain.com.
mail.domain.com 14400 IN A IP1

Hope you can help me!
Best regards,
Answer: Solved!
Oh my god after like 6 hours of google & try and error i got it.
The zone (why ever) wasnt added to the named.conf by cwp ...
can be closed!


Keeping Kosher and Leather

Question: I would like to ask a question regarding something I am quite confused by. Why is it okay to wear leather from an animal slaughtered not in a kosher fashion yet you cannot eat that animal's meat? To simplify this question and keep it in context, let's keep this as our primary example. I think a cow would be the perfect jumpoff point for this question. If I understand correctly, the primary reason Jewish people cannot eat just any beef/meat from a cow is that it must be slaughtered in a humane way, according to certain laws, in order to spare the animal undue pain and suffering. Assuming this is the primary reason for this specific example, why is wearing the skin of this animal (cow) which may or may not have been slaughtered in a kosher way okay?
Comment: "Assuming this is the primary reason" - you know what they say about when you assume... the fact is that only (human) FOOD must be slaughtered ritually. This doesn't apply to killing non-kosher animals or kisher ones killed for non-food purposes. Clearly, the requirement for "humaneness" is not the defining purpose of the commandment, else it would be forbidden to kill ANY animal without ritual slaughter, regardless of intended use.
Answer: The short answer "Because G0d said so"
The longer explanation, fills up volumes of books explaining "why" Hashem said so. You can start with Maimonides "Moreh L'nivuchim' (Guide for the Perplexed), as well as all the books that comment on it. While one of the reasons for the laws may include the humane treatment, the laws of ritual slaughter are not just for humane reasons, or for health reasons, or for any other possible reason, but for raising the meat that we eat to the level of a sacrifice (again among others). The requirement to treat an animal humanely is a separate restriction and applies no matter if the animal is to be eaten or not. Thus the requirement not to cause "tza'ar baalei chaim" (pain to living creatures) would require one to kill an animal humanely, whether by kosher slaughter or some other means.
Note also that there are many means of slaughtering humanely (although shechitah seems to be the most humane) none of which will allow a Jew to eat the meat. Additionally, if a person treats an animal inhumanely, but does not cause it to develop signs of treifus (such as lung lesions), then the meat would still be kosher after shechitah. On the other hand, if he treats it completely humanely and just misses cutting both the windpipe and the esophagus (to the 51% mark) by just a fraction (such as 49.99999% rather than 50.0000001%) the animal is not kosher.
Given that the Torah does not forbid the use of an animal that has not been slaughtered by shechitah (it is mutar b'hana'ah) we see that if someone has violated the laws of "humane treatment", then he is the one who has done wrong. The sin does not attach to the object. Note that the Torah has to explicitly forbid the use of meat cooked in milk (for a non food purpose) (asur be-hana'ah) as well as forbidding the actual cooking itself.
Answer: Basically, the Bible says only eat it if it was killed properly. If it died any other way, you can feed it to your pet (i.e. you can derive benefit from it), just don't eat it. The same would apply to a cow that died of old age! There are only three categories of dead animals -- "kosher slaughtered"; "kosher slaughtered but it was going to die soon anyhow of disease or injury"; and "died some other way."
Presumably, eating something signifies a deeper connection.
Comment: How about Shor Haniskal, Chulin Baazara etc. which are Asur BaHanaah?
Answer: Something which is surprisingly not mentioned by most of the commentators here is that the basic reason why do most of the complicated laws of kosher killing of animals exist is to get sure that the animal was really killed because of the human action, not died because of a unrelated disease. This follows from a general prohibition of eating meat of animals which died because of natural causes (see Shemoth 22:30, Dvarim 14:21).
The test example is the following. Assume you find a corpse of a cow in a forest. Will you be allowed to eat its meat? Surely you won't.  Will you be allowed to use its leather for you clothes? Why, on Earth, not?!
The explanation that shchita minimises animal's suffering is probably very modern (and, honestly speaking, a bit controversial). If you are looking for a kind of  "social" or "cultural" explanation for the status-quo halacha, I think this is indeed more related to the ancient fear of eating animals which died because of unknown and perhaps dangerous for human diseases.

Keeping Kosher and Leather


HAProxy Active Passive VIP Issue

Question: I have a very basic question, we all know that when we configure
HAProxy in the Active-Passive manner then there is a VIP. Outside
service will access the VIP and the traffic will be routed to
appropriate inner services.  Now, my question is if the LAN
connectivity between the Active-Passive HAProxy goes down will the VIP
still be able to perform the same task? Or the behavior will be different?
Answer: It all depends on what software you use for VIP management. But the most likely scenario is that both instances will try to allocate the VIP and that might cause a major outage. This is known as a split-brain situation, read up on it in the internet.

HAProxy Active Passive VIP Issue


In Back to the Future, why was the speed 88 miles per hour?

Question: Why not use 89, maybe 100 miles per hour? Is 88 the fastest a DeLorean can go? In other metrics, I have:

Unit
Equivalent
Abbreviation

Miles per hour
88.00
[mph][mi/h]

Miles per second
0.0244
[mps][mi/s]

Yards per second
42.944
[yps][yd/s]

Feet per second
128.832
[fps][ft/s]

Kilometers per hour
141.3648
[km/h][kmh][kph][kmph]

Kilometers per second
0.0393
[km/s]

Meters per second
39.3
[m/s]

Knot
76.3931
[kn] nautical mile per hour

Mach Speed
0.1155
[Ma] (speed of sound)

Light Speed
1.3110e-7
[c]

There does not appear to be anything special about this number. So why was it 88 MPH?
Comment: I'm guessing because the led display would seem more dramatic if all the lights were lit up and since 88 is the number that would do this, it was what was chosen.
Comment: Must be for the yards per second metric - I see 42 in there.
Comment: @OghmaOsiris - I think you can even take this explanation in-universe. Imagine that the speed is arbitrary - you fix it by changing variables in the machine...Doc has to come up with an arbitrary large speed, and since he's using an LED display for the spedometer, he decides it would look cool. We know that Doc has a flair for the dramatic anyhow.
Comment: @JanusBahsJacquet 70 MPH is more common on highways in America because there was originally a national speed limit of 65 MPH on all highways.  It's been repealed since 1995, but some states (including mine) still have a 65 mph speed limit.  Other states have higher or lower limits, but most aren't any higher than 80, so 88 would be considerably fast (and faster than legal in 1985, when a 55 MPH limit was the national law https://en.wikipedia.org/wiki/National_Maximum_Speed_Law )
Comment: The point is that it's 236,544 furlongs per fortnight.
Comment: 5280 ft in a mile. 5280/60=88
Comment: The train had to push the DeLorean 88 mph but the speedometer was calibrated for standard tire circumference. On the train tracks, the tires were removed so only the rims were on the tracks, thus the speedometer would move faster given the same velocity, requiring less velocity for time travel when pushed via train. In other words, its not consistent.
Comment: @ChrisB.Behrens: precisely. Because it's *cool*.
Comment: There's also the fact that you wouldn't normally (unless you're on the Autobahn) travel at 88 Miles Per Hour.  So setting it that high seems like a safe bet to avoid accidentally activating the time machine.
Comment: @Zibbobz Is that really true in the US? 88 mph or 140 kph is a perfectly common speed to travel on most motorways/highways in most of Europe, which is something I always found rather odd about this.
Comment: Borrowed from numerology - "The energy represented by the numerology number 88 is, foremost, an analytical approach to efficient business for accomplishing substantial goals."
Comment: @JanusBahsJacquet Indeed, 140 km/h is about the speed you end up with after hitting the breaks because a Golf dared to enter the left lane on a German Autobahn ...
Answer: As you can see here the original set of DeLoreans were fitted with speedometers that went up to 85 MpH:

Further evidence on Wikipedia supports this.
The fact it needs to reach 88 MpH may be an indication that the DeLorean is souped up, or that time travel is impossible. Or even just it needs to be turned up to 11 to get time travel.
Comment: so many cars of the 1980s had speedometers that only went to 85, that the case for "up to 11" is strong.
Comment: That's because in 1979, the NHTSA made a regulation limiting speedometers to 85 MPH (as well as special emphasis on 55, which was the national speed limit at the time).
Comment: @JustJeff :  :) I can't resist... about the "up to 11": http://xkcd.org/670/
Comment: Luckily, I could smell the TVtropes link from a mile away so I managed to avoid clicking on it. The day is saved! :)
Comment: @Pureferret The 140 mph speedometer was for cars intended to be sold in the UK and Europe; at the time US regulations required that speedometers top out at 85 mph. DMC now has a [replacement 140 mph speedometer](http://store.delorean.com/p-7088-speedometer-140mph.aspx) and [metric cluster](http://store.delorean.com/p-7098-inst-cluster-assy-metric.aspx) for sale.
Comment: This would be a good in-universe explanation for why Doc's Delorean had an extra [digital speedometer](http://backtothefuture.wikia.com/wiki/Digital_speedometer) mounted on top of the dashboard (out-of-universe, they probably just put it there so the audience could easily see the speed in point-of-view shots looking out the windshield)
Comment: To add to my comment above, p. 67 of *We Don't Need Roads: The Making of the Back to the Future Trilogy* notes that a 1979 law set by the National Highway Traffic Safety Administration required that all speedometers have a maximum speed of 85 mph to encourage safer driving, and that although it was repealed 2 years later, production of DMC-12s ended before the repeal so they all had that limit. So, special effect supervisor Kevin Pike "not only replaced the manufacturer's speedometer with one that went beyond the regulated amount, but added a digital display for additional good measure."
Comment: I actually had  some doubts. This picture implies that not all Deloreans have the same  dash or speedometer: http://www.deloreanowners.org/gallery/IMG_2331.jpg
Comment: And as many people have expressed in comedy, just getting a DeLorean to 85 was a challenge...
Answer: I think that the answer is in four parts:

It had to be fast enough to be dramatic without being extreme.
OghmaOsiris may be right - 88 would completely fill an old style LED display.
Eighty-eight has a certain alliterative/poetic rhythm to it.
The number 8 is the symbol for infinity rotated 90 degrees.
Comment: +1 for "has a certain alliterative/poetic rhythm to it." Eighty-eight miles per hour has a certain ring to it.
Comment: FWIW, 88mph is one of the most common speeding tickets (historically) in the US because there's a "lamp test" switch on many 7-segment radar units that lights up the entire panel of LEDs, including all of the seven segments of each digit, so that the officer can point out to the victim that the radar really showed them going 88mph.  This is probably not as true now as it was in the 1980s.
Answer: Some nice speculations here, but according to producer and co-writer Bob Gale, they only picked it because it was a memorable number. On the Back to the Future blu-ray (probably the DVD too), if you go to the "Extras" menu and turn on "Q&A commentary with director Robert Zemeckis and producer Bob Gale", then play the movie with the audio from the Q&A, if you skip ahead to 26:38 in the movie you'll hear Bob Gale say:

The fact that everybody says, "Why 88 miles an hour? What's so special
  about that?" It's easy to remember. That's all. There's no special
  significance to that.

And there's also an interview here where he adds that aside from being memorable, another reason was that it was fast enough that the characters wouldn't accidentally go that fast when just driving the DeLorean around (and not trying to escape Libyan terrorists):

Two reasons. First of all we wanted it to be a speed that somebody
  wouldn't accidentally drive at. The other thing is, is it's easy to
  remember. Everybody remembers 88 miles an hour. Maybe you'd remember
  89 miles an hour. I don't know, 88 just had the right ring to it.
Comment: A word of god answer. Can't beat that.
Comment: @Marakai - Keep in mind the question was posted in April 2012 and an answer was accepted one day later, while I didn't come across the question and post my answer until over 2 years later in 2014...my answer has been gaining in points since then, but Rodrigo, who asked the question, doesn't seem to have been active on this site for a while, so he may not have seen my answer. This is sort of a drawback of the "only the original question asker can choose what answer is accepted" system, but see [this question](http://meta.scifi.stackexchange.com/q/7719/22250) for some ideas about workarounds.
Comment: I'm still so new to actively participating on SE that stuff like this takes me aback. I mean, democracy is all fine and dandy, but what the hell? Here's another case of a resourced, researched, documented answer not the accepted answer. I know people don't want Wikipedia style edit wars (much appreciated, that!), but seriously, is there remedy here beyond flagging stuff?
Comment: We should keep this answer at 88 upvotes.
Comment: @Hypnosifl thanks for that. I like the approach with a new question and flagging the old one. This is also quite topical as I had started a question on History Meta: there it was a bit more "serious": answers where at least parts were sourced from far-right propaganda websites were being accepted. In those cases flagging is another option, but it requires some time and patience.
Comment: Not only is 88 intrinsically easy to remember (due to the double digits), it already had an association in the minds of many car lovers: the [Oldsmobile 88](https://en.wikipedia.org/wiki/Oldsmobile_88), which was commemorated in an R&B song, [Rocket 88](https://en.wikipedia.org/wiki/Rocket_88), which many consider to be the first rock 'n' roll record.
Comment: 88 is the number often used in neo-nazi symbolism. Letter H is letter number 8 in the alphabet. Therefore 88 would represent HH which represents the old Nazi salute "Heil Hitler!"
Comment: @miško I think we can be pretty sure that wasn't the intent since screenwriter Bob Gale [comes from a Jewish family](https://en.wikipedia.org/wiki/Bob_Gale#Early_life)
Answer: An in-universe explanation with a bit of math makes it all clear:
A Delorean DMC-12 is 4216 mm long. When travelling at 88 mph, the car then travels its own length in 4216mm/88mph = 107.2 ms. So this is how long the time-travelling wormhole-thingy that opens in front of the car has to be open, or alternatively the minimum time the flux capacitor is actually in effect. Could this time interval be significant?
Note how the Delorean arrives in the same location on earth after travelling in time, but can arrive at different times of day. Assuming it is gravity-bound it must still somehow be able to translate along the circumference of the earth, to correct for Earth's rotation.
We know that the time-travel takes place in California, which is at 37 degrees north latitude. If you travel due east from 37 degrees north and circle the earth, the distance travelled is "circumference of earth" * cos(37) = 32 005 km. Now notice that light travels this distance in 32 005 km/"speed of light" = 107 milliseconds!
It is then clear that Doc Brown uses the speed of the car to modulate the duration of travel, but in space, not in time. With reference to Minkowski space-time, the car leaves its normal time-like curve for a spacelike but performs a translation in space when passing through its lightcone, where it attains exactly the speed of light.
107 milliseconds affords travel to any point in time while returning to the same point on earth. A round-trip might be necessary depending on whether you travel forward or backward in time. If the car had been at the equator, the car would have to travel at only 70.38 mph. This would actually be a disadvantage as Doc Brown would have to provide more energy to keep the wormhole open for longer.
Not that the energy requirements are that large actually. The Delorean is stated to require 1.21 Gigawatts for time travel. Watt is Joule per second and 1.21 GJ/s * 107 ms = 130 megajoules. This is about the energy released by combusting one gallon of gasoline. A gallon per trip makes for good mileage on a time machine.
Edit1: As Stephen Collings points out in a comment below, this need to expend energy very quickly also explains why the Flux Capacitor, according to the professor, is so central to the time machine's design. It's not the energy requirements themselves that's the hard issue, but the ability to release it all in an instant, and within the confines of a car no less.
Edit2: People ask: Why is it that we account for the rotation of the earth but not the movement of the earth around the sun? Why doesn't the car appear in outer space?  Simply put, the law of conservation of energy keep the time-travelling car earth-bound. If you lift an object, it gains potential energy. This energy has to come from somewhere. If you move a car from earth's surface to outer space, it gains A LOT of potential energy.
How much? The potential difference between the earth's surface and faraway space is given as GMm/r where G is the gravitational constant, M is the mass of the earth, r its diameter and m is the mass of the car. The nominal weight of a Delorean DMC-12 is 1230 kg, which equates to an outer-space potential of about 77 Gigajoules. More or less the energy expended by a car in a whole year. There is nowhere for this energy to come from.
The law of conservation of energy therefore stops the car from translating to outer space. Put another way, the car follows the most energetically favourable path along the 4D spacetime gravity well. Similar to how water flows along bends in a pipe, without spending energy on turning around corners.
Comment: @Dave: Sometimes I'm thinking guys like us in the scifi forums have put more thought into the movies than the scriptwriters did.
Comment: +1 for what is either the most obscure intentional explanation of a number ever, or the most amazingly awesome coincidence ever.
Comment: 0_0              (that is all I wanted to say)
Comment: Assuming the writers actually did this math to come to the magical number and didn't just say "uh, sure, 88 mph, whatever" hella-props to them!
Comment: This answer is awesome, except that Earth not only rotates but also moves through space (at about 107,000km/h). But still, awesome explanation.
Comment: This is not an in-universe explanation (even though it is cleverly disguised by making *in-universe* the second word in the answer).   It is fan-fiction.   Without some evidence the writers had anything like this in mind, it is just hand-waving and deserves no place on this site.   Sorry to be a dissenting curmudgeon.
Comment: 130 megajoules isn't much energy, but dissipating all of it in a tenth of a second still pretty hard. Capacitors might have that kind of power output, but then the volume needs go up for the energy storage. You'd need ultracaps outmassing the delorean. That flux capacitor really does make time travel possible!
Comment: I barely understand a word, however it sounds pretty solid to me.
Comment: @Damon - But even if the Earth didn't move through space the answer would make no sense in terms of compensating for the rotation of the Earth. If you make different-sized jumps through time, the Earth should rotate by different amounts--but this answer says the car *always* must travel at such a speed so that, during the time the car travels one car length, something traveling at the speed of light would travel exactly *once* around a line of latitude (i.e. along the path the a point on the ground would travel during 1 day, if the Earth itself didn't move--even if the jump is *not* 1 day!)
Comment: This answer really makes no sense to me. To quickly summarize, you're saying that during the same time period the car travels one car length, light must travel around the Earth and back to its starting location, along  the surface of the Earth rather than in a straight line as light normally travels, and along a line of fixed latitude rather than along any other possible path along the surface (like a line of fixed longitude). And you seem to be saying that light must *always* make exactly one trip around the Earth in this way, regardless of the size of the jump in time. But why?
Comment: the earth is spinning. (1000 miles/hour tangent)  It is orbiting the sun.  (67000 miles per hour) The sun is orbiting the center of the galaxy. (492 mph)  The galaxy itself is moving.  Space is expanding. I think that a wormhole would try and rip the car apart.  The trick is to make it have small diameter or small duration.  The projectors have to allow it to move independent of the car.  The speed of the car has to be an interaction of those.  the guidance system is more of an accomplishment than the flux capacitor.
Comment: I wish I could upvote this about a dozen more times.
Comment: This makes no sense from a physical perspective. While it's true that the car is gravitationally bound to the Earth so staying on the Earth during time travel requires no extra energy (as compared to materialising in empty space), _the same is true of the car's location on Earth. For the purposes of the time ranges in the movies, California is stationary; the angular momentum of the car due to its position on the Earth would keep it in California, just as surely as its potential energy due to gravity would keep it on the ground.
Answer: Not covered in the other answers, I believe viewer safety has to be factored in.
A driver of average competency begins to seriously increase the risk of crash when 20kph over the speed limit, as shown in this figure:

If they made it lower, it probably wouldn't have been cool enough to take effect. But if they made it higher, they'd run the risk of people actually trying to do it.
And honestly, they can't buy the sequel if they're dead.
Answer: According to the Daily Telegraph:

"...the production designers thought it looked cool on the digital speedometer and would be easy for the public to remember."
Comment: Where did the Telegraph get this info from?


Is it common for MMA fighters to fight with fractures?

Question: I read this article recently and was surprised to hear that an MMA fighter was medically cleared to fight even though they had a fractured toe. I understand Khabib is a beast but isn't there usually a medical checkup before each bout, how exactly did this slip the radar? Is it common for fighters in MMA to be cleared with injuries as significant as fractures or was this just a rare occasion?
Answer: I don't know what the UFC's exact protocols are, but to reliably find all possible fractures, you'd have to do whole-body X-rays, and I'm pretty sure they don't do that. Then you'd also have to do whole-body MRIs to find torn ligaments, etc. ...
It is important to distinguish the examinations needed to get a license from the checkup on fight day. The former may include MRI scans, ECGs and EEGs, blood tests and other procedures that would detect long-term health issues, but these tests only have to be done every couple of years, so they would not reveal any recent injuries.
From what I've seen in amateur organizations, the medical checkup on fight day consisted of visual inspection, pulse/ blood pressure, pupil dilation, and a couple of questions - "are you feeling well? Any recent concussions? Are you taking any medications?" As far as I know, in the UFC, fighters are obligated to disclose any relevant injuries (fractures, torn ligaments etc.), but I have never heard of any punishment for failure to disclose.
How often does this happen? No one knows, but UFC-level fighters are incredibly tough and pain-resistant people who fully expect to go into a fight more or less banged-up from their training camps, and the negative consequences of disclosing an injury and having an important fight cancelled may (in their opinion) outweigh the risks of keeping their mouth shut and hoping for the best.
Comment: Very helpful answer, thank you. I am wondering if you could comment on how medical suspensions play into this? Since looking at this (below) website it looks like suspensions are issued for lacerations and when xrays are requested to confirm post fight injuries. I would be curious to know how an xray request is decided, is a medical checkup done beforehand for example? If the xray comes back with fractures I would then guess another would be needed later to confirm things have healed? There's very little info on this anywhere. https://www.mmamania.com/ufc-medical-suspensions-and-injuries


Problems in installation of magento on wamp

Question: Hello guys can  anyone help me with the issue im having with installation of magento.
my problem is that i have downloaded the magento on wamp and during my installation i got the error and the msg it si giving is FATAL ERROR : Maximum execution time of 60 sec exceeded in
c:\wamp\www\magento\lib\varien\db\adapter\pdo\mysql.php on line 276. plz provide me with the solution any one coz im stuck on this for long enough thanks in advance
Answer: Modify your php.ini with this setting:
max_execution_time = 1800

I also modify the memory limit allocated to php when using Magento
memory_limit = 512M

Alternatively you can edit index.php, if you don't have php.ini access.
ini_set('max_execution_time ', 1800);

Comment: thanks for the answer but still the same problem is there can you tell me is there any other alternative thaks
Comment: it cannot give the SAME error if you modify maximum execution time. if the script reaches the 1800 sec = 30min.. something is wrong with your server configuration.
Answer: The exact resolution is as below
This is not an apache or php timed-out message. It really means that the mysql engine timed out. So we will give the mysql some more time to wait until it reports that the operation failed. To make this happen, lets go ahead and change the line with value
mysql.connect_timeout = 60
to
mysql.connect_timeout = -1
in the php.ini file and it will do the trick. The value -1 means unlimited seconds to wait before the mysql connection times out.
Answer: HI,
I had the same problem. None of the solutions provided above helped me.
What I did was change both the max_execution_time and max_input_time to 1800. This worked for me. I was able to then get Magento installed.
Answer: Change the value of max_input_time in php.ini to a safest value; time is expressed in seconds. Do give a try of 1800
max_input_time = 1800
You would get it worked
Answer: If its giving you the same error then it means that you have not changed the settings in php.ini file.
In windows if you install wamp you will have, php.ini in php folder and apache folder.
Make sure that you have modified in both files and restart your server. (I know its strange)
Try 1
Browse wamp's root folder and click on phpmyinfo link under tools section.  This will give you the information of your php installation and settings.
look for "Loaded Configuration File", there you will have the location of your exact php.ini file that is used in your wamp installation.
Try to update the Max_execution_time in that file.  Hope this will solve your problem.
Usually, you will not get problems like this.
Try 2
May be your antivirus is stopping the request to execute for more than 60 seconds, just trying stopping your anti-virus for a moment and check another time.
I hope this will solve your problems.
Answer: I got the same problem, as suggested I did the following changes.

(wampserver-path)\bin\apache(Apache Version)\bin\php.ini - Set the
value max_execution_time = 1800
(wampserver-path)\bin\php(PHPVersion)\php.ini - Set the value
    max_execution_time = 1800

But it didn't work. Then I made the next change

In the host/(path-to-magento)/index.php, just after the opening <?php
tag, added the following. set_time_limit(1800);

<?php
set_time_limit(1800);
//** Other bunches of code
?>

Then tried to install a fresh copy. It worked! Hope this helps...


Anyone want to meet in chat and play some online blitz?

Question: Are there any players around who would like to meet in chat and play some online blitz?
At some point we can potentially arrange a tournament with site users.
It will help new users see our site live, and it will be an interesting opportunity for users to play and improve.
Hope to see you in the chat room!
Answer: I think that we've got to arrange something on lichess.


International Kapow! The Semi-Finalists

Question: Simple Rules:
Each circle represents a category - which is as of yet unknown.
Each of the tiles below belongs to at least one of the categories.  Two have been placed for you - where do the others go and why?  Hopefully, this one is slightly harder than the last one - but I have been a poor judge so far!
Answer: In order to satisfy the title in full, the labels should be arranged like this:

Because the two ovals in this Venn diagram represent:

 Left - Words which appear at the end of names of world countries:
 GERMANY, SWEDEN, CANADA (or GRENADA), SPAIN, HUNGARY, and DENMARK.

Right - Words which appear as the last 4 letters of first names of Take That members:
 JASON Orange, HOWARD Donald, GARY Barlow, and MARK Owen.

 GARY and MARK, therefore, both appear in the crossover section between the two ovals.

The logic behind this arrangement is fully suggested by the title, since:

 'International' reflects the use of countries of the world, and 'Kapow!' is a Batman-esque equivalent of 'Take that!' Furthermore, 'semi' suggests words that are only partially complete, and 'finalists' implies the use of the final parts of words.
Comment: Sorry unsure how to spoiler on mobile.  You have one half right - the title can be used for more help.
Comment: @AlteringIntegral Aha, pretty sure I've got it now then! :)

International Kapow! The Semi-Finalists


Is there an Arch based live persistant distribution?

Question: I'm currently installing Archlinux on my new computer but Windows seems to be installed using UEFI and I'm quite in a rush right now and I don't have time to install Archlinux using EFISTUB or something like that (it seems very painfull to perform).
So here is my question : Is there a live persistant distribution based on Archlinux (and quite easy to install) ?
Except FaunOS because I can't find it anywhere on the internet (it seems that the project has been discontinued). In the best case I would like to have a Gnome3 desktop. Can someone help me ? =)
Answer: Archbang and Manjaro both are distroes based on Arch-Linux with an easy to use install script, both have ability to be used as a Live system using a CD/DVD drive or any USB drive;
In USB mode there are some way to install ArchBang as a persistent system.
Here is a tutorial on how to make a live persistent distribution.
Take look at chakra, it has a very nice installer.
Comment: Never had the time to try this, but anyway I just figured that I didn't mark your answer as validated. Thank you :)
Answer: Since you're running Arch on your desktop computer already, the archiso scripts could be what you're looking for:

Archiso is a small set of bash scripts that is capable of building fully functional Arch Linux based live CD and USB images. It is a very generic tool, so it could potentially be used to generate anything from rescue systems, install disks, to special interest live CD/DVD/USB systems, and who knows what else. Simply put, if it involves Arch on a shiny coaster, it can do it. The heart and soul of Archiso is mkarchiso.
Answer: I'm glad hassan_noori answered this question first as I didn't know yet Arch Bang guys have built up a script to add persistence on a live-usb install.
As for Manjaro, stable 0.8.11 has no possible persistence, I've been told Manjaro-dev (aka 0.9) has it though I cannot recollect my source. Might come in handy along with the distro powerful and easy to use tool to build a custom ISO called ManjaroISO. I used it last month and achieved all my goals :)
Arch linux can be installed on any USB2/3 device (look the wiki for "Installing Arch Linux on a USB key" with over 2GB free space in a way that allows using your USB install on multiple machines. This is what the distro recommends.
Be aware the rudd-o guide has great ideas indeed, but part of it is outdated especialy beware the GRUB install. I tried it and the boot failed, so continue reading for updated commands.
Using this simple command from Arch (without the grub-mkconfig part) worked well for me to quickly install GRUB2 on external USB sticks. Or go with syslinux as nicely explained by Dirk-Jan here also for an external USB device (works with Syslinux 6).
Good luck and happy New Year :)
Comment: Well thanks for that detailed answer, it helps a lot. I don't feel the need for such a distribution now (mainly because I only work on my Arch laptop now) but that may come in handy at some point :)
Answer: Look here: http://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/
Universal USB installer is a Live Linux USB Creator WITH PERISTENCE.
It says:
"Universal-USB-Installer-126.96.36.199.exe – September 7, 2012 – Changes
Update to support Liberte 2012.3, Knoppix 7.04, Lucid Puppy 528.005, parted magic 2012.08.09, and Archlinux 2012.08.04. Added WifiSlax."
It says further down the list that Archbang can be installed.
Comment: I'm running Arch on my desktop computer so the .exe isn't a solution :D


Can the white noise in multivariate GARCH have different distributions?

Question: I have two datasets of log returns, one is clearly normal while the other is t-distributed. I want to fit these with a mutlivariate GARCH model. A multivariate GARCH model is defined as
$$\mathbf{r}_t=\mathbf{H}_t\boldsymbol{\epsilon}_t$$
Where $\mathbf{H}_t$ is the conditional covariance matrix and $\boldsymbol{\epsilon}_t$ is white noise. In the litterature most authors state that $\boldsymbol{\epsilon}_t$ is IID(0,1). I have not understood the identicality requirement. Is it possible to have different distributions for the elements in the vector $\boldsymbol{\epsilon}_t$? If no, why not and what would be a workaround in this case?
Answer: To answer your question briefly, yes, it possible to have different distributions for the elements in the vector $\mathbf{\epsilon}_t$. Now an elaboration:
Your model formulation is incomplete.

The mean vector $\mathbf{\mu}_t$ of $\mathbf{r}_t$ may be nonzero and time-varying, turning $\mathbf{r}_t=\mathbf{H}_t\mathbf{\epsilon}_t$ into $\mathbf{r}_t=\mathbf{\mu}_t+\mathbf{H}_t\mathbf{\epsilon}_t$ and adding an equation for $\mathbf{\mu}_t$.
The variance dynamics should be characteristic of GARCH. There should be an equation for $\mathbf{H}_t$ containing an autoregressive component (lag of $\mathbf{H}_t$) and a "moving-average" component (lag of $\mathbf{\epsilon}_t$), or something roughly equivalent to that. Otherwise, multivariate GARCH is not a relevant name for the model.
The distribution of $\mathbf{\epsilon}_t$ must be i.i.d. with zero mean and identity variance matrix. The i.i.d. requirement is stricter than white noise that you refer to in the title of your question.

Referring to point 3., there is no requirement for the components of $\mathbf{\epsilon}_t$ to have identical univariate distributions. E.g. copula-GARCH models build on the multivariate distribution of $\mathbf{\epsilon}_t$ being specified using arbitrary marginal distributions and an arbitrary copula (but still obeying the requirements in point 3.).
Comment: I see, so I.I.D. means that the vector $\boldsymbol{\epsilon}_t$ has the same distribution over time but the elements of the vector itself do not necessarily have to have the same distribution. That clears it all up.
Comment: Thanks! Just to clarify, in point 3 you reiterate that the distribution must be i.i.d. do you mean independent? Otherwise, I do not understand how this adds up with the rest of the answer since using multiple distributions would make it not i.i.d. by definition.
Comment: @IsaacE, the multivariate distribution as a whole must be i.i.d. Regarding "identical", it means $\mathbb{\epsilon}_t$ and $\mathbb{\epsilon}_s$ must have the same distribution for any pair $(t,s)$. That does not mean the univariate distributions of the different components $\mathbb{\epsilon}_{t,i}$, $\mathbb{\epsilon}_{t,j}$ must be the same. One could be N(0,1), the other could be standardized Student-$t$ etc.
Comment: As usual with downvotes, I would appreciate a constructive comment to follow along. That would help me improve my answer and leave it in the best shape for the readers.


What do humanitarian sciences refer to?

Question: When to use humanitarian sciences and human sciences in contrast? According to my uni materials, humanitarian sciences should have something to do with scientific function style of texts.
Answer: The OED has no entry for humanitarian sciences, but it does have one for human science, meaning, those academic subjects in which people or their actions form the object of study, as contrasted with the natural sciences or physical sciences; the humanities, (in later use esp.) the social sciences.

1833   E. B. Pusey Remarks Prospective & Past Benefits Cathedral
  Instit. in C. Thirlwall Let. to Revd. Thomas Turton on Admission of
  Dissenters to Acad. Degrees 14   Whatever schooling of the affections,
  or expansion of the whole mind and spirit, may be required for the
  right cultivation of the human sciences, must be much more necessary,
  when the things hereafter to be handled are the things of God. 1846
  Times 8 June 4/3   If Adam Smith is a prophet, if political economy is
  the first of human sciences, and its doctrines above all
  contradiction, then Sir James is undoubtedly a very enlightened man.
  1893   Geogr. Jrnl. 2 355   And the divorce between human
  sciences—history, economy, politics, morals—and natural sciences has
  been accomplished entirely by ourselves, especially during our
  century. 1943   Lasswell & McDougal in Yale Law Jrnl. 52 214   The
  great contribution of modern specialists on the human sciences is less
  in the realm of general theory than in the perfecting of method by
  which ancient speculations can be confirmed, modified or rejected.
  2001   C. Freeland But is it Art? vi. 174   Art theorists draw on
  philosophy, and also on the human sciences, such as anthropology,
  sociology, and psychology, especially perceptual psychology.

If, as the OED suggests, human sciences is synonymous with the humanities, it is worth quoting those senses 2a and 2b of humanities.

2a. In singular and plural. Literary learning or scholarship; secular
  letters as opposed to theology; esp. the study of ancient Latin and
  Greek language, literature, and intellectual culture (as grammar,
  rhetoric, history, and philosophy); classical scholarship. In later
  singular use, chiefly in Scottish universities: the study of Latin
  language and literature.
2b. In plural (usually with the). The branch of learning concerned
  with human culture; the academic subjects collectively comprising this
  branch of learning, as history, literature, ancient and modern
  languages, law, philosophy, art, and music. Hence also in singular:
  any one of these subjects. The humanities are typically distinguished
  from the social sciences in having a significant historical element,
  in the use of interpretation of texts and artefacts rather than
  experimental and quantitative methods, and in having an idiographic
  rather than nomothetic character. Cf. human science n. at human adj.
  and n. Special uses 2.

Referring to the last few words of 2b, it seems to be suggesting that human sciences should be distinguished from social sciences, the latter making more use of "experimental and quantitative methods".
Answer: A humanitarian science is one concerned with the promotion of human welfare.
Since the 1930s, the word "humanitarian" has also been used to describe a crisis that causes widespread human suffering (i.e. "a humanitarian crisis"). A person concerned with humanitarian sciences is a philanthropist.
Human sciences are those that are concerned with the nature of people and the way in which they interact with one another and with themselves; i.e. psychology, sociology, etcetera.
Comment: I see. Even though this may sound fairly abstract, humanitarian thoughts and actions described in a text could have something to do with science. Or maybe someone just swapped humanitarian for human.
Comment: But of course; Environmental Sciences are arguably humanitarian in nature because the study of the environment contributes to the education of people who have the potential to contribute to the betterment of conditions for humans.
Comment: Environmental sciences, fair enough.

What do humanitarian sciences refer to?


Origins of quote: "Do not meddle in the affairs of dragons for you are crunchy and taste good with ketchup."

Question: I've grown up loving the quote "Do not meddle in the affairs of dragons for you are crunchy and taste good with ketchup." and I've been searching around to find out where it came from (with only a small amount of luck).
I discovered that it came from Suzanne McMinn, however, I have no references beyond that. Did she get it from someone else? Which book did it appear in?
Comment: A new user tried to edit the question with this reply: "This quote is from the Enchanted Forest Chronicles by Patricia C. Wrede. It's either in *Dealing with Dragons* (book 1 of the series) or *Talking to Dragons* (book 3 of the series). -JennA".  I've rejected the edit, but I thought the information might be useful as a comment.
Comment: @PatDobson Goodreads is unreliable as well - it was wrong on [this one](https://literature.stackexchange.com/questions/2516/where-do-i-find-edmund-wilsons-quote-no-two-persons-ever-read-the-same-book).
Comment: According to GoodReads it's a quote by Suzanne McMinn : https://www.goodreads.com/quotes/83627-do-not-meddle-in-the-affairs-of-dragons-for-you - No idea which book it's from though
Comment: My elementary school principal had a really nice printout of (a slightly different version of) this quote on her door.
Answer: This looks like a spoof of the quote from The Lord of the Rings, by J.R.R. Tolkien:

Do not meddle in the affairs of wizards, for they are subtle and quick to anger.

It comes from The Fellowship of the Ring:

'But it is said: Do not meddle in the affairs of wizards, for they are subtle and quick to anger. The choice is yours: to go or wait.'
  'And it is also said,' answered Frodo: 'Go not to the Elves for counsel for they will answer both no and yes.'
  'Is it indeed?' laughed Gildor. 'Elves seldom give unguarded advice, for advice is a dangerous gift, even from the wise to the wise, and all courses may run ill.'
The Fellowship of the Ring, chapter 3

As for where the dragon part is from, I found a book called Dragonswan, by Sherrilyn Kenyon.
The first line is:

Be kind to dragons, for thou art crunchy when roasted and taste good with ketchup. (Google Books).

These quotes appear to have been merged.

Okay, nobody knows where this first came from, but here's something from July 27, 1999, in the Salon magazine:

All this, and he has a wickedly weird and original sense of humor. "Do not meddle in the affairs of wizards," Marceau once said, "for you are crunchy and taste good with ketchup."

It's also apparently in the 24th of February, 1999 issue of the Plainview Daily Herald, according to this website, but their archives appear to be down (and the Wayback Machine is turning up blank).

The Quote Investigator Twitter account responded to a request for help with an even earlier use of the quote, from Usenet (July 10 1989):

Do Not meddle in the affairs of Wizards, for you are crunchy and go
  well with catsup

I don't know if Brian Beattie was the first to write this line (it appears as part of his signature on that post), but the quote was there, in some form, in 1989.
I tried sending an email to the email address included in the post, but...

On this Yahoo Answers thread someone mentioned that it was from the Dragon magazine. There are archives available here, for now. I looked through the first 150 magazines, after which it isn't older than the quote above, with a Ctrl + F search for do not m, and didn't find anything - if anyone else want to see if they can find anything, they are welcome to - like, the Ctrl + F search doesn't work on images.
Comment: Relevant: http://web.mit.edu/tritan/Library/text/misc/quotes
Comment: I would have tried searching for "crunchy" and "ketchup" as they seem to be the important words in the quote.
Comment: @user14111 - I didn't want to use 'ketchup' because of alternate spellings (catsup) and I didn't want to have to do double the work.


Is there latexmk functionality for LuaTeX?

Question: I am a big fan of latexmk and lately I have been looking a bit towards LuaTeX. However I am yet to find a way to get the functionality of latexmk (mainly recompilation on changes and automatic rerun an appropriate number of times to resolve cross references and such) for LuaTex. Is there something similar and if not how do you LuaTeX people survive without it? :)
Answer: You can use Lua(La)TeX with latexmk by setting the -pdflatex parameter:

-pdflatex=<program> - set program used for pdflatex.
                       (replace '<program>' by the program name)

So latexmk should call lualatex instead of pdflatex if you invoke it like this:

latexmk -pdflatex=lualatex -pdf <texfile>

or with newer versions of latexmk there is direct Lua(La)TeX/XeLaTeX support:

-lualatex
    Use lualatex.  That is, use lualatex to process the source file(s) to pdf (in place of pdflatex).
    This option is exactly equivalent to specifying the following sequence of options:
  -pdflatex="lualatex %O %S" -pdf -dvi- -ps-
Comment: How can one pass `--shell-escape`?
Answer: Instead of adding the -lualatex flag to each application of latexmk, you could
place the following

$pdflatex = 'lualatex -file-line-error %O %S';
$pdf_mode = 1;

in an '.latexmkrc' file. This file should reside in your home folder, if you use
lualatex in all your jobs, or in the folder(s) where your lualatex jobs are.
More generally, you will find a host of examples and boilerlate code for .latexmkrc in the respective CTAN repository
Answer: Since version 4.51 of latexmk, you can use the following .latexmkrc:
$pdf_mode = 4;
$postscript_mode = $dvi_mode = 0;

Comment: For the second line `$postscript_mode = $dvi_mode = 0;`, I think both default to false/0 anyway.
Comment: For more info [latexmk man page](https://mirror.aarnet.edu.au/pub/CTAN/support/latexmk/latexmk.txt): "$pdf_mode [0] ... If equal to 4, generate a pdf version of the document using lualatex".
Answer: The following syntax is valid, as of latexmk 4.80. To have latexmk use LuaLaTeX to build a PDF file (the usual choice), just do
latexmk -pdflua foo.tex

Alternatively you could use the seemingly equivalent -lualatex option instead of -pdflua. To add the -shell-escape option, since this was asked about in a comment, just do
latexmk -pdflua -shell-escape foo.tex

This is directly from the documentation one obtains from texdoc latexmk, namely the latexmk manual. One can get a shorter help summary from latexmk -h or latexmk --help. There is also some additional documentation in the latexmk source file, which is a Perl script, specifically about how latexmk detects build dependencies.
Additional comment. The current manual says the following

-lualatex

Use lualatex. That is, use lualatex to process the source file(s) to pdf. The generation of dvi and postscript files is turned off. This option is equivalent to using the following set of options

-pdflua -dvi- -ps-

This appears to be incorrect or out of date. Perhaps it was correct once. But just using -pdflua does not generate any DVI or PostScript files. It would be surprising if it did. So I presume the -lualatex and the -pdflua options are the same. At any rate, I cannot see any differences between them.
Comment: Technically, if everything is as it appears, `-lualatex` does do the same thing as `-pdflua -dvi- -ps-` (and both these options are equivalent to `-pdflua`). It is inaccurate to say the manual is "incorrect"; maybe it would be more accurate to say the manual is "misleading" because it adds the extra `-dvi- -ps-` when there is no need to do so.
Answer: I currently run MacTeX under macOS Ventura, and I use lualatex as my default engine for everything nowadays. This is my current .latexmkrc file, which I keep in my home directory.
# Custom .latexmkrc file.

# Always create PDFs and set default engine to LuaLaTeX.
$pdf_mode = 4;
# Set the lualatex variable.
$lualatex = 'lualatex --file-line-error %O %S';

# The next two preview variables are mutually exclusive!
# Preview after each build.
# Equivalent to -pv on command line.
# $preview_mode = 1;
# Preview continuously.
# Equivalent to -pvc on command line.
# $preview_continuous_mode = 1;

# Comment out to use Preview.app.
# Give -pv on the command line.
$pdf_previewer = 'open -a Skim.app %S';

# Special latexmk makeindex line for .dtx files.
$makeindex = "makeindex -s gind.ist %O -o %D %S";

# Files to be cleaned.
$clean_ext = "deriv equ glo gls gsprogs hd listing lol" .
" _minted-%R/* _minted-%R nav snm synctex.gz tcbtemp vpprogs";

The very last line is treated as having a comment by the code formatting here, but it is not a comment in the .latexmkrc file.


depth of field to work not working

Question: I have blender 2.78 and I am trying to get the depth of field to work, but I just can't make it. I think I have all that as needed the camera and the target  an object, the compositing is on, I even have the cameras limits set to the target object, I tried to render it in blender internal, in cycles and in the 3D window, but nothing seems to work. I'm wondering is it possible to get the dof to work without using nodes and if it's possible what should i do.
I now try to add more information that i think is needed. I have set the measurement system to metric in the scene , and the object that is the target has the value of 1.0 as size. the camera I used is canon aps-c. I  have tried different focus-stop values that seemed not to help. I'm not sure what the lens is that I'm using, or where to find the lens used ? I wonder that if i have difficulties with this because I can´t somehow set the right distances between the camera and the object and do nut fully understand the relation between the metric grid, object size, and the distances and adjustment´s needed to make the depth of field seen. I have read many depth of field tutorials, but I seem to miss awarness of something very essential to get it work. I have NOT been using nodes when trying to do this .
Answer: Depth of field (as defined by circles of confusion) depends on three factors:

The length of the lens used (in mm). Longer lenses will have less depth of field
The distance to the subject. The closer the camera is to the object the more critical focus will be, and the depth of field will be shallower.
The f stop on the lens. Higher f-stops will give you larger depth of field (more things will be in focus) Smaller f-stops will reduce the depth of field.

You are using a wide angle lens (35mm) and a very high  number for f stop (31.8), and your object are quite large and far away.  with those settings is very unlikely that you will see the effects of selective focus (which I presume is what you are looking for). Lower the F-stop to something like 1.4 or even less than 1 to see the effects. Also in cycles you can preview the depth of field in preview render mode.
Comment: I didi not had  the dof checked in the shader´s menu . :) mayby i can get somewhere now , thanks .
Answer: Check dimensions of your mesh in metric length. You can't get blurry effect if your camera aiming object that too far.
To make it work without scaling down your all object, lowering the aperture rasio of your camera.
example, i create mug and in metric length, it has 3m heights. then i set aperture to f-stop with 0.8 number rasio in DoF section.
Comment: Can you please edit this, and make the answer clearer.
Comment: This does not provide an answer to the question. Once you have sufficient [reputation](http://blender.stackexchange.com/help/whats-reputation) you will be able to [comment on any post](http://blender.stackexchange.com/help/privileges/comment); instead, [provide answers that don't require clarification from the asker](http://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead). - [From Review](/review/low-quality-posts/36151)
Answer: If you make your aperture smaller by reducing the F stop, you can get less depth of field (more blur).
To read more about depth of field, read this question: https://photo.stackexchange.com/questions/2/how-can-i-maximize-the-blurry-background-sharp-subject-bokeh-effect

depth of field to work not working


How do I remove labelled emails from my inbox?

Question: I have emails in my inbox that have been labelled under different label names. I now want to remove these emails from the inbox so that they only appear under their individual labels. So far, I can only remove the emails from the inbox by opening each email and removing the 'inbox' label, which is a time-consuming task. Is there a simpler method to remove multiple labelled emails already in the inbox from the inbox?
Answer: Select one or more emails by clicking on the box to the left of each message.
Once the first one is selected, the "archive" button will appear at the top. Clicking Archive removes the inbox label from each of the messages/conversations that you selected. No other labels are removed when you click Archive.


How to do AddonPreferences using extensions_framework?

Question: I have seen scripts taking user preference values using classes built over AddonPreferences. Is it possible to do the same using extensions_framework by Doug Hammond. Why I am asking this is I need to get a path to an executable from the user, like a path to a renderer. The script which I made does all its class registration / unregister happens through EF. So is it possible to get the path from pref?
Comment: I think I should provide some starting point for you to experiment with this link contains the code but it is not woking... https://github.com/afilash/BlenderExperiments/tree/master/BlenderExperiments/src/customeRender
Answer: No (as of 2.68), the Python extensions_framework directory has no references to AddonPreferences.
You could contact Doug Hammond about this or check on adding support yourself.


Cluster manager for Linux/Java processes, log gathering

Question: I have some Java servers (though Java in fact doesn't matter here, it can be any executable) which I want to run on multiple machines. Is there some cluster management software, which would allow me to say, for example "start 3 instances of service A, and 5 instaces of service B". In case one node dies, start the services on another server.
It would also be nice to have some kind of an admin console, where I could see which servers work, which services work were etc. (Of course with a nice dashboard with lots of green ;) ). Or at least a REST interface to get that info easily.
Going a step further, such a cluster manager could take care of gathering logs from the services, and alerting an adinistrators if there are errors in any of them. Or maybe that's a separate service?
Does such a thing exist? (preferrably in an open-source version of course)
Answer: I feel like supervisord might be useful in your case ?