How do I know if my iPad has a virus
Is it possible for an iPad to get a virus?
What recourse do I have if I believe a moderator has abused their privileges? One or more of the following things happened to me on a Stack Exchange site:   My post(s) were wrongly deleted or locked by a moderator A moderator posted a wrong comment on one of my posts I was suspended, but did not do anything wrong I asked a meta question, but the question was closed and/or deleted A moderator discredited me in public ...   I think a moderator has abused their power, but I feel powerless against them.  What recourse do I have now? What can I do when I feel that a moderator has abused their power, and has been repeatedly unfair in their dealings with me? RegEx for Javascript to allow only alphanumeric I need to find a reg ex that only allows alphanumeric. So far, everyone I try only works if the string is alphanumeric, meaning contains both a letter and a number. I just want one what would allow either and not require both. I've been stuck on this problem for about an hour.     In an ideal transformer, the same flux passes through all turns of the primary and of the secondary . Show that in this case $M^2=L_1L_2$, where $M$ is the mutual inductance of the coils, and $L_1$, $L_2$ are their individual self-inductances.   My first instinct was the following: If we isolate the response of each coil to the other one, we get the equations $N_1\Phi_1=MI_2$ and $N_2\Phi_2=MI_1$, where $\Phi$ is magnetic flux going through a single turn of the coil and $I$ is current. Likewise, if we isolate the response of each coil to itself, we get the equations $N_1\Phi_1=L_1I_1$ and $N_2\Phi_2=L_2I_2$. I would now naturally want to say "Now just multiply $N_1\Phi_1$ and $N_2\Phi_2$ both ways, and get the desired result!" i.e.,  $$(N_1\Phi_1)(N_2\Phi_2)=(MI_2)(MI_1)=(L_1I_1)(L_2I_2)\implies M^2=L_1L_2$$  But that's incorrect, because the response of the coils to themselves and to the other coil are different quantities (i.e. not necessarily equal).  Realizing this, I write down the more general equations.  $$N_1\Phi_1=MI_2+L_1I_1$$ $$N_2\Phi_2=MI_1+L_2I_2$$  Now even with the hypothesis that $\Phi_1=\Phi_2=\Phi$, I still can't see how the identity $M^2=L_1L_2$ follows. Could you help clear up my confusion?  *Taken from D. Griffiths Introduction to Electrodynamics (4th ed.), Problem 7.58. Why doesn't xpath work when processing an XHTML document with lxml (in python)? ffmpeg working from command line in Terminal but not in an Automator shell script! I have a lot of filesystems:   / on a PCI-E SSD swap on a SATA SSD /media/ned is a RAID5 array /tmp lives on RAM Parts of /home/oli are symlinked and bind-mounted in from ned I also have /media/jeff/ which is RAID1 that I store backups and bind-mount ~/.wine in off.   It's actually a lot more complicated than that. There are all sorts of extra symlinks that I need to untangle in the long run but for now I just need a nice way of taking a path and finding out where it physically lives. When I get an idea for something I'd like to make in Blender, I hit up Google for specifics, then blender SE when I get stuck.   I'm very overwhelmed by the immensity of Blender and I'm a little afraid that this self-directed approach is going to lead me to develop bad habits. Is there a "best practice" way of learning to use Blender? Do characters provoke opportunity attack when they leave another character's reach who is not facing them? "You can make an opportunity attack when a hostile creature that YOU CAN SEE moves out of your reach."   In 5E do you have to specify which way your character is facing at all times?  If an enemy who is behind him leaves melee range but his back is to him does that enemy provoke an opportunity attack?    Are enemies within five feet and 360 degrees of a character considered to be within reach?  For example... Kruska and Atone are attacking Dip.  Dip is facing or only attacking Kruska.    Then Atone moves out of Dip's reach (melee range 5 feet) to engage a silly looking wizard.    Does Atone's move provoke an opportunity attack from Dip even though he's not facing him?  Is he assumed to be able to see him? Pass Method as Parameter using C# Here is my attempt to prove the Well-Ordering Principle, i.e. that any non-empty subset of $\Bbb N$, the set of natural numbers, has a minimum element.  Proof. Suppose there exists a non-empty subset $S$ of $\Bbb N$ such that $S$ has NO minimum element. Define $A = \left\{n\in \Bbb N : (\forall s\in S)(n \leq s)\right\}$. It is obvious that $1\in A$. Suppose $n\in A$, then for each $s \in S$, there exists $q \in N$ such that $n + q = s$. Since $q \ge 1$, $n+1 \leq s$, for all $s\in S$. By Principle of mathematical induction, $A = \Bbb N$. Take any $s_0 ∈ S$, then $(\forall s\in S)(s_0 \leq s)$. (This contradicts that $S$ has no minimum element).  How do I prove the statement without invoking Mathematical Induction? Also, I read that the proof of Principle of Mathematical Induction makes use of Well-Ordering. Can it be proven independently of Well-Ordering too? How can I give other drives and partitions short, meaningful names in nautilus? In nautilus and Unity the external drive has a nice short descriptive name "mcat", but all partitions on the 4 internal drives are displayed as a size (834 GB filesystem) or a huge 32-character string form of a GUID:  I'm guessing the external drive is nice, short, sweet and readable because that drive may have no partitions (well, just one I guess) and that name may be the drive label, whereas partitions usually don't have names. That may explain my problem, but doesn't solve it.  Is there some way to give reasonable names to these partitions in nautilus and Unity? Is there a way to save selection by faces I'm trying to find a way to save selection faces, tried Vertex Group, the issue with Vertex Group is that it adds the faces that are marked by 4 vertices that are added to the Vertex Group, there are some cases were this doesn't apply, the image explains what I mean. So is there a way to save my selected faces, so I don't have to go through the whole process of reselecting them each time I need to do so? If you check the image, I didn't assign the hatched faces to the Vertex Group, still when I select the Vertex Group, they get selected, I understand that they got selected because the four boundary vertices are assigned to the Vertex Group, I need to save only face selection, not vertex selection. I'm trying to wire up 6 RGB LEDs in parallel, all controlled from a single source (well, three sources, one for each colour). The LEDs came supplied with resistors to limit the current of 270 Ohm for a 5v supply.  The problem is, 6 LEDs x 3 colours = 18 resistors, which is a lot, and means I need a much bigger board and a lot more soldering.  So, can I instead wire the LEDs in parallel with each other, with a single resistor protecting all six? (3 resistors in total, one for each colour). How do I calculate the value of that resistor?  More details:  The LEDs are being driven from a  to supply a bit of current, which is in turn controlled by a Netduino providing a PWM signal on the three channels.  . If I've correctly understood the data sheet they want 20mA of current, and forward voltages of 2, 3, 3 volts (for R,G and B respectively?). The supplied resistors were all 270 Ohm, so the channels may not be balanced quite right.  For extra credit: I'm only using 3 of the transistors in my driver chip, which has 8 in total. could I wire the PWM from the netduino to a second trio of transistors, and split the LEDs into two groups of three? Is it worth the effort?  PS I don't have any diagramming tools to hand, but I can provide a diagram (drawn in paint) if it would help clarify my question. (see also ) Is there a way to scale up the bevel object on one end of a curve, a little bit over each point?  I notice the vertex "weight" slider will tweak how much influence each vertex has on the others, is there something like this that can scale the bevel object up a little bit?  Preferably with the option to constrain X,Y,Z independently What permissions should my website files/folders have on a Linux webserver? This is a  about File Permissions on a Linux web server.   I have a Linux web server running Apache2 that hosts several websites. Each website has its own folder in /var/www/.  /var/www/contoso.com/ /var/www/contoso.net/ /var/www/fabrikam.com/   The base directory /var/www/ is owned by root:root. Apache is running as www-data:www-data. The Fabrikam website is maintained by two developers, Alice and Bob. Both Contoso websites are maintained by one developer, Eve. All websites allow users to upload images. If a website is compromised, the impact should be as limited as possible.  I want to know the best way to set up permissions so that Apache can serve the content, the website is secure from attacks, and the developers can still make changes. One of the websites is structured like this:  /var/www/fabrikam.com     /cache     /modules     /styles     /uploads     /index.php   How should the permissions be set on these directories and files? I read somewhere that you should never use 777 permissions on a website, but I don't understand what problems that could cause. During busy periods, the website automatically caches some pages and stores the results in the cache folder. All of the content submitted by website visitors is saved to the uploads folder. After offering a bounty to , I realize that I cannot comment on the question because I no longer have the required reputation. Is it possible to change this behavior, so that the bounty owner can comment only on the post with the bounty irrespective of their reputation? While bounty owners are told that they'll lose privileges at the time they place a bounty, it makes sense to allow them to interact with potential answerers/commentators to help solve the problem, or at least provide additional information. Ubuntu missing from HP boot menu I have a HP laptop with Windows 8.1 and Ubuntu 14.04 dual booted. I used to use F9 key to enter boot menu and chose Ubuntu and then GRUB would appear where I would chose Ubuntu again. This was working fine all this while. Either a hardware change or a Windows update has caused the Ubuntu option to go missing from the boot menu itself.  How do I fix this and boot into Ubuntu again? Add a duplicate:0|1 search operator Is there any way you could revive Guest Sessions in a future LTS distro?  Guest sessions are good security - they give me just enough power to do what I need to do on a daily basis without risking my system. In short, Guest sessions save me from myself.  I had upgraded from 16.04 to 18.04, gotten a problem I couldn't fix and was all to happy to wipe and rebuild my hard drive and return to 16.04.  I can't be the only one who feels this way. I have put a bounty on , however I don't see it appear in the  (also not when I'm not logged in).  Why is this. Aren't all bounty questions supposed to be visible there?