Undergraduate quantum book treating density operators, mixed states, and entanglement
Quantum information references
There are many cards that can put multiple permanents onto the battlefield simultaneously, such as , , or .  How do these interact with the following types of abilities?  As [this permanent] enters the battlefield... You may have [this permanent] enter the battlefield as... [This permanent] enters the battlefield with... When [a permanent with certain characteristics] enters the battlefield...   Justification There have been many questions already about particular instances of this situation.  This question is intended to be a canonical question and answer to all questions such as:      Note to moderators: three of these five questions have already been marked as duplicates pointing to this one.  Can we do the same for the remaining two? Regression Proof that the point of averages (x,y) lies on the estimated regression line How do you show that the point of averages (x,y) lies on the estimated regression line? UV mapping not filling faces I have tried to map this simple object, but the uv mapping does not correspond to what i see in the textured object. It cuts the image a bit on top and a bit on the bottom of the faces. It does not fill the faces with the texture, even though i have mapped them correctly. Does anyone know what could be happening? Thanks in advance. I get Chrome notifications from several websites and they work when I don't even have any tabs open for those sites.  But sometimes I get these Chrome notifications when I am not at my desk or looking at my laptop.  As some of these notifications are useful to me, I would like to be able to access any that I have missed.  Is there a way to view the notification history? Let $G$ be a finite group and $N$ a normal subgroup of $G$ of index $4$. Prove that $G$ has a subgroup of index $2$ (hence normal) and if $G/H$ is not cyclic then $G$ is equal to the union of three proper subgroups.   I understand that $G/H$ is isomorphic to $\mathbb{Z}_4$ or $\mathbb{Z}_2\times \mathbb{Z}_2$. Let $K^*$ be a subgroup of $G/H$ of order $2$. Then $K^*\cong K/H$ for some $K$ such that $H$ is normal in $K$ and hence $[G:K]=[G/H:K/H]=4/2=2$.  If $G/H$ is not cyclic then $G/H\cong \mathbb{Z}_2\times \mathbb{Z}_2$. I don't know how to prove $G$ is the union of three subgroups. Could it be true that as $G/H$ is the union of three proper subgroups $K_1^*,K_2^*,K_3^*$ then the corresponding groups $K_1,K_2,K_3$ have union equal to $G$? Would anyone give me a hint to prove this?  Thank you. I have a bash script that makes a cURL request and writes the output to a file called resp.txt.  I need to create an exclusive lock so that I can write to that file and not worry about multiple users running the script and editing the text file at the same time. Here is the code that I expect to lock the file, perform the request, and write to the text file: ( flock -e 200 curl 'someurl' -H 'someHeader' &gt; resp.txt ) 200&gt;/home/user/ITS/resp.txt  Is this the correct way to go about this?  My actual script is a bit longer than this, but it seems to break when I add the flock syntax to the bash script. If someone could explain how these file descriptors work and let me know if I am locking the file correctly that would be awesome! External Hard Drive no longer working I am on a MacBook Pro 13 running latest Sierra. I have an external Seagate solid state hard drive that was working and out of the blue stopped working. The only thing on it was my Adobe Lightroom images/videos. Not the LR DB files. I'm sure you have all heard this woe before, so I won't dwell on that. And yes, I back up to the cloud. AWS S3 specifically. Though I am traveling South East Asia for the last year, and staying in cheap hostels. So good internet is hard to come by sometimes. I can't back it up after every export. While most of it is backed up, there is some that is not.  Moving on. The symptoms seems to change every time I plug it in. The first sign was it ejected on it's own. I plugged it in again, and it wouldn't mount. Disk Utility recognized it, so did the command line diskutil list but it wouldn't mount. I rebooted and it worked for a second. Then I could only get to it from the command line. Then trying to frantically back up to my local what was not backed up to the cloud, it all failed. Basically just a cp -R [directory] [local-directory] command.  After some more frantic unplugging and re-plugging plus some command line manual mounts, I finally got it to where the Disk Utility would be able to run first aid on it. It failed. I don't recall the error. So I put it in a freezer. After a few hours I tried again. It is not any better. It still will not mount. Now Disk Utility sees it, but with no partition. I can't even give me information about how much space is used on it.  I have also tried it from a Windows machine. It did not mount. I have tried other cables. No success. As well as tried my other USB port. I also have another working external hard drive exactly like the one giving me issues. It works on all cables and USB ports.  I do have Docker running with a Ubuntu container, I'm trying to think of a way to see if I can try to get to the USB from there. I also have a USB that I have thought about running a live Ubuntu on there to see if I can mount and retrieve the data or fix the HDD that way. But if it will not mount, I doubt these will work.  Can anyone else think of any other tricks I can try myself to see if I can repair this or at least retrieve the data without paying for a service or software? If not, those suggestions are also welcome.  Update   I made the mistake in original post that it was a Solid State Drive. This is my mistake, it is actually a spinning disk hard drive. I bought them long ago and have been traveling with them for so long I just forgot. Question is updated to reflect this. Now diskutil list does not show it at all. The Disk Utility app also does not see it. Based on suggestion from @Allen I seeked out the USB to SATA cable. I did not quite find it, as my options are extremely limited where I am at. Though a local expat on a facebook group was able to help me with a empty 2.5 casing that I was able to extract the drive from original casing and put it in his blank case. It now mounts. Though it has the "click of death" sound to it. And data is not really reachable. While I can ls the directories and Adobe Lightroom does not have the exclamation mark when it can not reach the actual external files. Right clicking on the images and clicking on "Show in Finder" or any other variation of trying to get to the files through Finder or terminal, I have no success. It usually hangs and I get the spinning wheel. Since Adobe Lightroom imports these images into directories named by date, I am going to send the drive off to a data recovery service and ask to recover just unbacked up directories i.e. dates. Next time I will make harder efforts to backup and probably get an actual SSD.   I think this can be closed, due to my low reputation points I can not close this myself. What are the differences between a HashMap and a Hashtable in Java? What are the differences between a  and a  in Java?  Which is more efficient for non-threaded applications? $$\lim\limits_{n\to\infty} \int_{0}^{1} f(x^n)dx = f(0)$$  when f is continuous on $[0,1]$  I know it can be proved using bounded convergence theorem but,  I wanna know proof using only basic properties of riemann integral and fundamental theorem of calculus and MVT for integrals ...   Thank you. On a whim the other day, I changed my meta name from Lord Torgamus to Popular Demand.  I just noticed that the old name has "stuck" to the author tag of ; everywhere else on meta, my new name displays as expected.  Is this a feature?  Is it a bug?  Mostly I'm just curious, as I can't think of a strong reason in favor of keeping this behavior or a strong reason for changing it.  A question somewhat like this has been raised before as , but the previous poster implied that the issue had something to do with migration, which my situation shows is not the case. When logging in C#, how can I learn the name of the method that called the current method? I know all about System.Reflection.MethodBase.GetCurrentMethod(), but I want to go one step beneath this in the stack trace. I've considered parsing the stack trace, but I am hoping to find a cleaner more explicit way, something like Assembly.GetCallingAssembly() but for methods. Centering with \includegraphics not with \begin{figure}? I mess up with things when I try to use the figure-thing: the picture is not appearing with the correct alignment (apparently because I forget the float package). Now I want to use only the graphicx package with \includegraphics. How can I center the \includegraphics without figure?  Not working or doing centering to the document afterwards.  \includegraphics[width=0.5 \textwidth]{./Pictures/r.png}{\centering} \includegraphics[width=0.5 \textwidth]{./Pictures/r.png}\centering As well as many of the other features talked about during macOS Mojave's release like dark mode and the addition of new apps like Home, another key feature of macOS Mojave seems to be it's heightened focus on both privacy and security.   As quoted under the "Camera and Microphone Now Require Your Permission" section of  article:      Apple also announced that other categories of data, such as your Messages history and Mail database, will be protected in a similar manner to macOS Mojave's new camera and microphone permissions.   I understand that after the update, when an app requests to use your camera or microphone, you will receive an alert like the one below:    However, I am more intrigued by the following:     ...other categories of data, such as your Messages history and Mail database, will be protected in a similar manner...   I have been unable to find much information about this online and I do not currently have the pre-release version of macOS Mojave installed and am therefore unable to test this new feature but I am curious to know what exactly this feature will mean.   Has Apple publicly documented how this will work? How do I edit the boot order in the GRUB menu to have Windows first? I have a dual boot on my computer of Windows 7 and Xubuntu 12.10. The Linux boot is 1st and the Windows 2nd. I would like to reverse the boot order in the GRUB menu. I need to know the steps to go about editing GRUB. I do most of my work on Windows and need it to be 1st so I can boot up and not watch it. Get list of all tables in Oracle? I'm officially breaking up with Salesforce Date parsing. This has got to be the most frustrating thing.  I have the following date in a JSON string (full JSON below):     2017-06-03T10:34:24.000Z   But when I try to deserialize the data:  Opportunity[] results = (List&lt;Opportunity&gt;)JSON.deserialize(res, List&lt;Opportunity&gt;.class);   I get the following error:     System.JSONException: Cannot deserialize instance of date from VALUE_STRING value 2016-12-05T16:19:44.000Z   I have looked at so many date parse issues before and from what I've gathered  it must be in ISO 8601 - though ISO 8601 can take various shapes:   All of the following seem to recommend exactly what I've done          How should I format this date string?  Thank you!  Full JSON string:  [{   "name":"OpportunityABC",   "CloseDate":"2017-06-03T10:34:24.000Z",   "StageName":"Pre-Engagement",   "Amount":"4810308.0", }] To EAV or not to EAV? Please help me to prove this trigonometric equation.  $\cos \left( 36^\circ \right)-\cos \left( 72^\circ \right) = \frac{1}{2}$  Thank you. Creating Logo with Fancy Font I am trying to creating a logo that resembles this one shown below, but I do not know the best way of going about it. I know of a fonts package that may be useful, but not sure how to overlay the letters on top of each as so. Would anyone know a neat way of accomplishing this?  Picture of Logo: Reason for the current trend to use «she» as the gender-neutral pronoun?