I created a website a bit ago that is open-source. Every file has the line:  require('/var/www/civ/other/req.php'); //This loads all code located in /req.php   (The code for /req.php is visible  if that matters)  The eighth line of this connects to the MySQL database:  $con = mysqli_connect('HOST', 'USER', 'PASSWORD', 'DATABASE_NAME');   In the production file, it has the actual host/user/password/database name. Whenever I commit changes, I just manually go to that line and replace the real information with dummy information. However, sometimes I forget and I have to rollback the commit and re-commit, during which time someone could have seen the real password. I've thought about putting it in a text file in a non /www directory with read permissions only given to Apache/PHP and using file_get_contents, however:   Because this is open source, everyone knows the exact path to the file, so someone could trick PHP into echoing the contents Because this file is called on every page, I would double the I/O required to load a page.    How do I store the password so a git commit can't reveal it?

When a PHP application makes a database connection it of course generally needs to pass a login and password. If I'm using a single, minimum-permission login for my application, then the PHP needs to know that login and password somewhere. What is the best way to secure that password? It seems like just writing it in the PHP code isn't a good idea.


$(document).ready(function () {     $('.add-button').on('click', function () {          $('.alert-button').after('<button type="button" class="alert-button">Click me! </button>
');      });       $('.alert-button').on('click', function () {        alert('HI!');      });  });  <button type='button' class="alert-button">Click me! </button>
 <button type="button" class="add-button">Add button!</button>     Hi! My " $('.alert-button').on('click'..." code works on elements created on page load, but not on dinamically created ones.  So i have a page with 2 buttons (please run the snippet above). If you click on "Click me!" alert "Hi!" appears.   But when I duplicate "Click me!" button via pressing "Add button", a click on the duplicated "Click me!" produces no alert "Hi!" (although it also has ".alert-button" class).  I want to see alert "Hi!" when I click on any "Click me!" button.   what am I doin' wrong?:)

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


In classical waves, there is always something that is'waving Thus in water waves the water surface moves up and down, in sound waves the air pressure oscillates and in electromagnetic waves the electric and magnetic fields vary. What is the equivalent quantity in the case of matter waves? Or the is no physical quantity that corresponds to this?

What does a  wave look like? Are de Broglie waves transverse or longitudinal?   Can they be polarized?    What about the de Broglie wave of a ground state neutral spin-zero Helium 4 atom?   What experimental evidence do we have that supports the detailed nature of a de Broglie wave?     I have always assumed that de Broglie waves were mathematically  identical to electromagnetic waves, but I just realized there is no basis for this assumption, and in fact it must be false, unless there is an analogue to both the magnetic and the electric components of the electromagnetic wave.  So what does a de Broglie wave "look like"?


I know that:  for a standard primal $\left\{\begin{matrix} \underset{x}{\operatorname{max}}[c^Tx]\\  Ax \leq b\\  x \geq 0 \end{matrix}\right.$ corresponds the dual $\left\{\begin{matrix} \underset{y}{\operatorname{min}}[b^Ty]\\  A^Ty \geq c\\  y \geq 0 \end{matrix}\right.$;  strong duality states that, if the primal admits optimal solution $x$, dual admits optimal solution $y$ and results $c^Tx=b^Ty$.   How can I use these conclusions to pass from (3) to (6) in the proof described  at page 4? Thanks in advance for any help.

I only know that:  for an LP standard primal $\left\{\begin{matrix} \underset{x}{\operatorname{max}}[c^Tx]\\  Ax \leq b\\  x \geq 0 \end{matrix}\right.$ corresponds the LP dual $\left\{\begin{matrix} \underset{y}{\operatorname{min}}[b^Ty]\\  A^Ty \geq c\\  y \geq 0 \end{matrix}\right.$;  strong LP duality states that, if the primal admits optimal solution $x$, dual admits optimal solution $y$ and results $c^Tx=b^Ty$. And similarly, weak LP duality states $c^Tx \leq b^Ty$.   Unfortunately, as explained  at page 4, to pass from (3) to (6) we need to use respectively conic and Fenchel's duality. I don't know anything about that, with many thanks to my professor, so I can't figure out this proof. Could you help me? Every link is also welcome. Thanks in advance.


I have seen the Unsung Hero gold badge which is awarded on 10 accepted answers with total scores of zero.  My 10 answers have been accepted with score of 0. I have answered a total of 107 questions on which 13 are answers with 0 score. Out of these 13, 3 are answers to my own questions after research, but there are 10 questions which are accepted by other users.   I have still not been awarded the Unsung Hero gold badge. What is the reason?

Formerly List of all badges with full descriptions.  What are badge name's requirements? Why didn't I get badge name ? Which badges can I earn multiple times?    Jump to:                    Note: Some badges are awarded based on score. The term score means the total number of upvotes minus the total number of downvotes.  Any badge with a *** next to it is one of 20 badges that count towards the  displayed on a moderator candidate in an election. The candidate score is a total of 40 points: the first 20 are awarded based on the user's rep divided by 1000 and rounded down; the second 20 represents the total number of unique badges earned of the 20 that count. Note that if the same badge is earned multiple times, it will only count once towards the candidate score.  Any badge with a "(retired)" next to it is no longer awarded, but is retained by users who previously earned them. See  for more info on what it means for a badge to be retired.       Visit the  of the  on any site to see a complete list of badges that you can filter by earned, unearned, or type.


For the past week I've been trying to create a dual boot with Windows 10 and Linux Mint 19 Tara.  The base setup, as intended is supposed to be a simple 1 operating system per SSD:     /dev/sda (250GB SSD) - Windows 10       /dev/sdb (250GB SSD) - Linux Mint 19 Tara   All other data disks are disconnected (for the time being).  I started with installing Windows 10 (onto /dev/sda) making sure I boot of USB using UEFI. Everything went fine and looking at the partitions, I can clearly see an EFI partition.  I then proceeded to boot the Mint USB in the same manner and started install (using ERASE, Encrypt and LVM).  At some point I get prompted with:     The 'grub-efi-amd64-signed' package failed to install into /target/. Without the GRUB boot loader, the installed system will not boot.   This results in a GRUB command-line at boot-time. When I type 'exit' it will then go on to boot Windows.  So, I started researching and found tons of articles and guides all explaining me to do exactly what I've been doing, including disabling 'Secure Boot' and 'Fast Boot' etc in the BIOS.  In my ASUS BIOS there isn't an option to disable 'Secure Boot' directly and I originally simply set the OS Type to 'Other', which works perfectly fine for installing Fedora 28 and Kali. (which I had previously installed on /dev/sdb)  This change was not enough though. So after some more research I found that in order to completely disable 'Secure Boot' I need to delete the key in BIOS. Once I had done that, 'Secure Boot' showed as disabled. Still, Linux Mint installation gave me the exact same error message and failed to install GRUB.  I then started experimenting some more including various approaches to manually setting up partitions. None of it worked and always resulted in the same issue. I eventually found that I seemingly can't install using EFI at all. The only installation that went through properly was, when I booted of the USB without UEFI (while 'Secure Boot' is disabled, obviously).  This clearly isn't what I want though and I've grown extremely frustrated. As a result of failed experimentation, I've had to reinstall Windows several times as well and we all know that's never fun, as it takes the better part of a day to fully update Windows.  I've really started to enjoy Linux Mint on my other (older) system and simply want it on my main system as well, but I'm relatively new to linux and I'm at a loss.  I sincerely hope somebody has some suggestion(s).  Please let me know if you need more information, but keep in mind that I'm fairly new to Linux in general, so be specific with any queries.  Thanks.  Update: I've tried 'Boot Repair' as suggested to some Ubuntu users with similar issues, but I still only get a GRUB command-line at start up.  Update 2: I decided to try another download of Linux Mint from a random mirror and noticed that today the downloaded is is called 'linuxmint-19-cinnamon-64bit**-v2**.iso'. Hopefully EFI install will work now. Will post back with results.  FIXED That did it. After creating a new bootable USB from the now available 'linuxmint-19-cinnamon-64bit-v2.iso', the system installed just fine using EFI. Awesome! :)

The SSD is set to ACHI (whatever it is, it was automatically set). Secure boot is set to Other OS (only other choice).  Linux only. No Windows. Hate Windows. No dual boot. Microsoft hasn't touched my computer in years. Windows can suck it.  I formatted both SSD and HDD drives to GPT. - Corsair 30GB SSD (putting / and swap on here) - Old, ~300GB HDD. No problems with the drive have been found. (putting /home here)   The live Mint USB isn't corrupt. I did the checksum before installing, and have done multiple checks on the USB before booting.  Installing Mint in UEFI mode is resulting in "grub-efi-amd64-signed failed to install into /target/". Any forum I found on this error has not had a solution compatible with my problem. That package doesn't appear to exist. The installer will fail upon this message occurring. I have an internet connection. It's hardwired... (insert Metallica reference here). I can cruise the interwebs during the live boot.  Installing Mint in legacy, not UEFI, is resulting in no OS being found.  Specs: - 18.1 Cinnamon (3.2.6) 64-bit - AMD FX-8350 8 core x4 - 8GB RAM - AMD/ATI Turks XT, Radeon HD 6670/7670    I am not sure what the hell is going on anymore.


Looking to loop through JSON that comes back like this in javascript and access the 'line' and other variables.   { "2":{"league":"MLB","matchnum":"2","site":"1","line":"-120","teamname":"COL"}, "1":{"league":"MLB","matchnum":"1","site":"2","line":"111","teamname":"SF"} }   This appears to be the answer but I think the issue is i'm trying to access a value thats in an object in an object.  for(var i = 0; i < json.length; i++) {     var obj = json[i];      console.log(obj.id); }   Where I am going wrong here? Thanks a lot for your time.

I have a JavaScript object like the following:  var p = {     "p1": "value1",     "p2": "value2",     "p3": "value3" };   Now I want to loop through all p elements (p1, p2, p3...) And get their keys and values. How can I do that?  I can modify the JavaScript object if necessary. My ultimate goal is to loop through some key value pairs and if possible I want to avoid using eval.


Here is what I am trying to prove:     Let $a,b,c,d \in ℤ_+$ with gcd$(a,b)=1$. If $a|c$ and $b|c$, prove that $ab|c$. Does the result hold if gcd $(a,b)\neq 1$ ?   I know that gcd $(a,b)=1$ can be written $ax+by=1$ where $x,y$ are integers.  And $a|c$ can be written $c=al$ where $l$ is an integer, b|c can be written $c=bk$ where $k$ is an integer, and $ab|c$ can be written $c=ab(m)$ where $m$ is an integer.   What do I do?

I'm learning about properties of greatest common divisors, specifically when two numbers are relatively prime.  The exercise I'm working through is :     Suppose that $\gcd(a,b) = 1$ and that $a\mid n$ and $b\mid n$. Prove that $ab\mid n$   Proof(so far):   $\gcd(a,b)=1$ implies $am+bk = 1$ for some integers $m$ and $k$.   (Given hint) Multiplying the equation by $n$ yields: $$amn+bkn=n$$  I'm not sure what to do after applying the hint. Am I supposed to show that $ab$ divides both $amn$ and $bkn$?  Thanks in advance.


Please anyone tell me when we have to use "has been, have been , had been" and something  started in past and still continuing is it possible to use has been ?

Non-native speakers often get confused about what the various tenses  and aspects mean in English. With input from some of the folk here I've put together a diagram that I hope will provide some clarity on the matter.  I offer it as the first answer to this question. Consider it a living document. Input is welcome, and good suggestions will be  incorporated into the diagram.    Nota bene: What this is not is a discussion of whether there are  more than two tenses in English. , to which this question is not intended to supply arguments one way or the other.  Here, the aim is to provide an overview of what constructions English-speaking people use for conveying information about actions referring to past, present, and future, and to provide it first and foremost to precisely the people who are likely to use "tense" as a catch-all term in their search, rather than to linguists who know better.  Breaking News There is now an excellent ELU blog article titled  . It is highly recommended reading.


I am using some classic models for ML, such as logistic and linear regression, K-neighbors etc, for a binary classifier. My dataset is complete, i.e. there are no missing values. But there are some meaningless values. Let say in my problem I have an image and I spilt the image to 25 parts. I have 50 features, for each part in the image I have a feature of how many cars are in that part, and the average speed of the cars in that part. In case part has zero cars in it, the second feature for that area will be Null (there is no speed average if there are no cars, and 0 has a meaning so I don't want to say 0) It is not duplicate from missing data questions, since I know there is no real number that I can give for that feature that will be correct, and I have a dependency here, since the first feature is always a real number, by its value I can tell if the second feature has meaning or not (if I could, I would tell the classifier if feature A is 0, ignore feature B, otherwise learn with both of them). What would you suggest?

Consider a statistical problem where you have a response variable that you want to describe conditional on an explanatory variable and a nested variable, where the nested variable only arises as a meaningful variable for particular values of the explanatory variable.  In cases where the explanatory variable does not admit a meaningful nested variable, the latter is usually coded either as NA in the data set, or if it is coded with a value, that value is merely a placeholder that does not have any meaningful interpretation.  This situation tends to arise whenever you have an explanatory variable indicating the existence of a thing, and one or more nested variables describing the characteristics of that thing.  Some examples of this kind of situation in statistical problems are the following:   The explanatory variable is an indicator of whether a survey participant is married, and the nested variable is some characteristic of the spouse (e.g., education, age, etc.); The explanatory variable is an indicator of the presence of an item in a space, and the nested variable is a measure of some characteristic of the item (e.g., size, distance, etc.); The explanatory variable is an indicator of the occurrence of an event and the nested variable is a description of some characteristic of the event (e.g., duration, magnitude, etc.).   In these kinds of situations, we often want to build a regression-type model (in the broad sense that includes GLMs, GLMMs, etc.) describing the relationship between the response variable and the other variables.  It is not obvious how to deal with the nested variable in this type of model.  Question: How do we deal with the nested variable in this type of model?    Note: This question is designed to give a generalised answer to a recurring question on  regarding nested variables in regression (see e.g., , ,  and ).  This question is designed to give a generalised context-independent example of this problem.


I want to extract a sequence out of some text.  The sequence begins with Diagnostic-Code:, the middle part can be any characters even over multiple lines and the end is marked by an empty line (after which the text continues, but this isn't part of the desired sequence).  This does work for the beginning and middle part, but the ending is found too late:    (?s)Diagnostic-Code: (.+)\n\n   The string looks something like this:  ... Status: 5.0.0 Diagnostic-Code: X-Postfix; test.com *this* *should* *be included too*  --EA7634814EFB9.1516804532/mail.example.com Content-Description: Undelivered Message ...   --------- edit ---------  Thank you for the anwer @Gurman!  But java.util.regex does somehow behave differently than regex101.com  Action: failed Status: 5.1.1 Remote-MTA: dns; gmail-smtp-in.l.google.com Diagnostic-Code: smtp; 550-5.1.1 The email account that you tried to reach does     not exist. Please try 550-5.1.1 double-checking the recipient's email     address for typos or 550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1     https://support.google.com/mail/?p=NoSuchUser u11si15276978wru.314 - gsmtp  --E8A363093CEC.1520529178/proxy03.hostname.net Content-Description: Undelivered Message Content-Type: message/rfc822  Return-Path: <no-reply@hostname.net>   The pattern matches the whole multiline diagnostic-code on regex101, but java only matches the first line as group 1:  smtp; 550-5.1.1 The email account that you tried to reach does   The java-code:  diagnosticCodePatter = Pattern.compile("(?i)diagnostic[-| ]Code: ([\\s\\S]*?[\\r\\n]{2})"); matcher = diagnosticCodePatter.matcher(message);     if (matcher.find()) {         diagnosticCode = matcher.group(0);

I have this gigantic ugly string: J0000000: Transaction A0001401 started on 8/22/2008 9:49:29 AM J0000010: Project name: E:\foo.pf J0000011: Job name: MBiek Direct Mail Test J0000020: Document 1 - Completed successfully  I'm trying to extract pieces from it using regex. In this case, I want to grab everything after Project Name up to the part where it says J0000011: (the 11 is going to be a different number every time). Here's the regex I've been playing with: Project name:\s+(.*)\s+J[0-9]{7}:  The problem is that it doesn't stop until it hits the J0000020: at the end. How do I make the regex stop at the first occurrence of J[0-9]{7}?


In Xenial 16.04, I was able to use Network Manager to configure a VPN to autostart per network connection.  In Bionic 18.04, I can't yet find this option.  Is it available via some configuration or additional package?  See also:  and

When I wake the laptop from the sleep I need to get the VPN state as I left it (turned on). Can't find the setting of autoconnect in VPN settings... Need some easy way to ask the system to autoconnect the VPN when the internet is available.  Edit based on comments:  Ubuntu 18.04 has no option to Always connect to VPN when using using this connection.


I have the following question: Prove that a finite $p-$group $G$ with a unique subgroup $H$ of index $p$ is cyclic.  Since the subgroup is characteristic it is normal. I showed that either the center of the group $Z(G)$ is a subgroup of $H$ or $G=Z(G)H$ and the index $Z(G)/(Z(G)\cap H)$ is $p$. But I couldn't continue from this. Any help would be great.

Let $G$ be a finite abelian $p$-group with a unique subgroup $H$ of index $p$. It is a fact that $G$ is cyclic. This can be deduced from the classification theorem for finite abelian groups by writing $G$ as a product of cyclic groups and noting that $G$ does not have a unique subgroup of index $p$ unless there is only one such group. I am wondering if there is a nice proof of this result which does not use the classification theorem. Does anyone know of one?


Just did one tutorial from youtube with colored quick smoke in Cycles and everything goes well and in render view it show me my smoke and i even render it in low quality to look how's it.  After i bake my simulation... Now i can't see what's happened, because i see only BLACK CUBE (smoke domain) and when i start render it just a black cube...  I made this in cycles from the beginning and it's cpu and it used to work fine.  Does someone know what's happening.

So I recently made the switch to cycles rendering and smoke modifiers, but it's been giving me loads of problems already.  This is what the model looks like:   And then when I go to render it, this is the result I get.    Why is this happening?


On Quant SE, a user has been blindly upvoting some of the top users. Specifically, he has been maxing-out his daily vote limit by upvoting every answer from a small pool of users. I  last week, but that didn't seem to stop the "vote stuffing".  I think this is a problem because the fraud detector could cancel the votes, which means that the reputations will swing wildly. Is there a protocol for handling a user like this?

I've had a few concerns over a new form of "spam" - that is, through voting. A while back, I had seen some wild reputation increases to my account, amongst others, that seemingly felt weird - as I've barely participated in asking questions or providing answers. Earlier today, this sentiment was echoed by another user in chat:  and like 250 this month? it seems like someone is spam upvoting  This was another user that saw a 250 rep increase, but has been inactive for quite a while. For a site that hasn't seen more than 5 questions a day, that was really weird. To put things even more out of hand, it seems like each vote has been placed on a question.  I did some investigation of my own, and it seems like I've found a badge hunter. More of a... gold badge hunter. This user is among the top 3 voters of the site. Looking into this user's profile, this user only has under 200 rep, and has posted a single question, which was received differently. One thing caught my eye:  Votes all time              by type 581   up              535    question 1     down            47     answer   Each vote is an up vote (with the exception of one), and there are 535 up votes on questions. There are 535 questions in the entire site. Using reputation stats from user profiles, I came with the conclusion that these votes are...  Done within a short period of time. 5 question votes within a couple of minutes Done in [near] perfect chronological order: The earlier the vote, the earlier the question was asked. As if the user had gone through the list of questions in order, and placed an up vote on each one.   I see this as incredibly problematic. First:  It dangerously inflates reputation. Votes are not done based on their content, but simply for voting. Therefore, reputation loses it value as a way to measure expertise.  It's like serial up voting. Generally, when we hear the term "serial up voting", we think of a voting ring, where one user continuously up votes another. This is negative for the targeted user. Well, here, we've got a voting ring with the site and this user. A user continuously up votes the site, causing negative damage for the site.  We mix good and bad content. Since low quality questions are a victim of the voting spree, many get meddled with the rest of "good quality" questions, despite being closed as off-topic, too broad, or whatever the reason. We can no longer reliably sort questions by quality with the very system that was designed to help us.   ... And the rest of voting fraud issues outlined in .  I've got a couple questions on this:  Is this comparable to serial voting? Should such votes be reversed? How should we determine whether or not to reverse them?  Should we stop this? Let it be? Is this really that big of a problem for sites? (I would argue that it's less of an issue for graduated sites that receive large amounts of content, but what about beta sites that rarely see more than a few questions a day)


References says alignment of a magnetic field of a bar magnet remains same even if we cut it into two or more pieces. According to this cut edges should attract with each other. When I tried it was working in the opposite way. why is it so ?

I just took a rare earth magnet out of an old hard drive. Lacking an appropriate screwdriver, force was used, and the magnet broke into two pieces; one about a quarter of the original size and one about 3/4 the original size.  Let's say this is the magnet:  >>>>>>>>   and the arrows are pointing north, in the original magnet.  It broke into two pieces:  >>>>>}   }>   (where } represents the rough edge of the break).  I'd expect that the two magnets would keep their relative directions, so that the magnets would fit back together at the break, like this:  >>>>>}}>   But instead, the broken edges repel, and the magnet wants to come together so that formerly "north-facing" sides are now connected, like so:  >>>>>}<{   The obvious deduction here is that one of the pieces flipped polarities when the magnet was broken. I don't understand why this would be the case.  So why did one of the pieces flip polarities?  EDIT: To clarify, the actual magnet is a 120-degree arc of a circle. Thus, it's obvious what the original orientation of the pieces were. This isn't simply a case of me getting the pieces flipped over relative to each other.


When we use the sample statistic to find a confidence interval, is there any reason to using the sample statistic after that, when we can instead refer to the confidence interval? For example, let's say I have a sample mean of 50 and have determined a +- 5 interval with 95% confidence. I could say "The population average is 50, plus-or-minus 5, with 95% confidence" I could also say "The population average is between 45 and 55, with 95% confidence" Is the probability of the population parameter occurring uniform across the confidence interval, or, would it be more likely to occur closer to the sample statistic? The reason I ask, is, it seems to me that if the population parameter is more likely to occur closer to the sample statistic then it's useful to say "50, plus-or-minus 5", while if it's uniform then "between 45 and 55" is simpler.

It seems that through various related questions here, there is consensus that the "95%" part of what we call a "95% confidence interval" refers to the fact that if we were to exactly replicate our sampling and CI-computation procedures  many times, 95% of thusly computed CIs would contain the population mean. It also seems to be the consensus that this definition does not permit one to conclude from a single 95%CI that there is a 95% chance that the mean falls somewhere within the CI. However, I don't understand how the former doesn't imply the latter insofar as, having imagined many CIs 95% of which contain the population mean, shouldn't our uncertainty (with regards to whether our actually-computed CI contains the population mean or not) force us to use the base-rate of the imagined cases (95%) as our estimate of the probability that our actual case contains the CI?   I've seen posts argue along the lines of "the actually-computed CI either contains the population mean or it doesn't, so its probability is either 1 or 0", but this seems to imply a strange definition of probability that is dependent on unknown states (i.e. a friend flips fair coin, hides the result, and I am disallowed from saying there is a 50% chance that it's heads).  Surely I'm wrong, but I don't see where my logic has gone awry...


Our party was forced to brawl against a group of orcs in order to gain their respect to speak with their chieftain (long story, we had very good reason for doing this). It then became a battle royale.  Our wizard was at low health and next to our paladin, and had the idea to cast fog cloud to capture himself and the paladin within it so he could leave combat. He cast the spell, and then came down to the debate of whether the paladin would get an opportunity attack even though she was blinded.   The wizard was in threat range, but does an effect that causes an area to become heavily obscured cause the Paladin to lose threat range and the wizard be able to successfully flee to another area of the ring?  Or does the paladin still have threat range and attack the wizard, even with fog cloud covering both of them?  I looked over the rules for 15 minutes after this situation, but nothing came up.  It was ruled in-game that it was fine to make an opportunity attack with disadvantage, but that just doesn't feel right. She might have heard the wizard stepping away, but the fog cloud was already in place. By the D&D rules, would the paladin have been able to make the opportunity attack or not?

When a PC is in melee with a creature, casts the basic invisibility spell, and leaves melee, does an NPC get an attack of opportunity?


Sometimes an answer that is accepted is incomplete or even wrong yet it masks the correct answer. This is an example     Would be nice for community moderators to be able to reorder the answer to make the correct one more visible.

Similar to  but narrower, I'm suggesting we make a particular exception for downvoted accepted answers (those with score less than zero, or some other threshold like -3), so that they stay in the normal sort order and don't jump to the top.  The accepted answer  on bh.se is -5 at time of writing, above an answer with +8 (which is quite a good score on our little site!). It also doesn't help things that the accepted answer is about a mile long so it takes a lot of scrolling to get past it:


Is Charm Monster (or similar magic) obvious to bystanders that the spell is being cast?  I've looked at a number of sources, for example I've looked at the "Sage Advice Compendium" which reads:      Do you always know when you’re under the effect of a spell?      You’re aware that a spell is affecting you if it has a perceptible   effect or if its text says you’re aware of it (see PH, 204, under   “Targets”). Most spells are obvious. For example, fireball burns you,   cure wounds heals you, and command forces you to suddenly do something   you didn’t intend. Certain spells are more subtle, yet you become   aware of the spell at a time specified in the spell’s description.   Charm person and detect thoughts are examples of such spells."   Sage Advice Compendium, Page 11  This describes that the target is not aware if it has no perceptible effect; however in the PHB page 203, it reads:     Verbal (V) Most spells require the chanting of mystic words. The   words themselves aren’t the source of the spell’s power; rather, the   particular combination of sounds, with specific pitch and resonance,   sets the threads of magic in motion. Thus, a character who is gagged   or in an area o f silence, such as one created by the silence spell,   can’t cast a spell with a verbal component.      Somatic (S)      Spellcasting gestures might include a forceful gesticulation or an   intricate set of gestures. If a spell requires a somatic component,   the caster must have free use of at least one hand to perform these   gestures.   PHB 203, emphasis mine  This would say to me that a spell is quite obvious it is being cast by just about anyone (assuming you aren't casting it with subtle spell, as part of the sorcerers class features); however, in the PHB, it says this:      Unless a spell has a perceptible effect, a creature might not know it   was targeted by a spell at all. An effect like crackling lightning is   obvious, but a more subtle effect, such as an attempt to read a   creature's thoughts, typically goes unnoticed, unless the spell says   otherwise.   PHB Page 204  So when we review these sources, it would say that the target is not aware, yet casting the spell is quite obvious if we look at what it says about the vocal and somatic components; furthermore, it says nothing about bystanders and if they would notice these charm spells.  So back to our original question...  Do bystanders or the target's allies recognise you are casting a spell?  I'm asking for a RAW answer please.

Charm Person has verbal and somatic components.  Is there anything in the rules as written that defines how obvious those verbal and somatic components are?  Would it be obvious the caster was casting a spell from 5 feet away?  From across a crowded room?  I'm specifically interested in an answer based on the rules as written, although interpretation and individual opinion are not unwelcome.


I am looking for a good API documentation for Javascript especially related to browsers and DOM. I am not looking for any kind of Javascript tutorial, but simply a documentation for all standard Javascript classes and for classes used in web browsers.  Something similar to Java's Javadoc (  )

I'm a front-end developer and I was looking for opinions about the best all-round online documentation for javascript/css/html/xhtml/dom/browser quirks and support. I've tried Sitepoint, Quirksmode, W3Schools but all of these seem to be lacking in certain aspects and have been using them in combination.


I just accidentally mounted a new drive to a folder that already contained files.  I don't care about them and have them somewhere else, but that folder appears empty now.  I'm curious what happened to the files.  Are they simply deleted by Linux?

On my headless NAS I have sdf1 (a flash-card) mounted as / while /home is mounted from lv00 (an LVM volume backed by a software RAID). To be able to access the machine when the RAID fails, I have a copy of my ssh public key, etc. in /home/foo/.ssh on the file-system from sdf1. To update the files that are hidden by the mounted /home I normally remount lv00 in /mnt/home, do what I have to do, and then move lv00 back in place. Is there a way to achieve this without unmounting /home?


I have a Xiaomi Pocophone F1 with decent specs: Snapdragon 845, 6 GB RAM, and enough storage. I was wondering if there is a tried-and-tested way to install some Linux Distro on it (preferably Ubuntu) for some specific reasons. I've seen some YouTube clips, but their instructions are not fully clear, so I wanted to ask here. Can anybody here give me a walkthrough or point me to a resource I can follow? Any help would be appreciated. Thanks.

I'm discovering the possibilities offered by persistent live USB using Ubuntu 19.10 and I was wondering if it would be possible to boot with Ubuntu on Android (i.e. using your computer capabilities through your smartphone) using those multi-plug USB sticks which have both USB3 and micro-USB2.  In other way: can I get some kind of a boot menu on an Android device in order to boot with a persistent live USB in order to access my Linux computer tools and setup from a wider range of devices?


It is easy to understand that a hole is opposite to an electron in semiconductors. However electrons have spins, up and down, does hole have a spin? Furthermore, if a hole has its spin, how to determine the direction of spin?

So, I thought I had an uneasy truce with quantum mechanics but I read something today which made spotted combat flare up in my mind again. In solid state semiconductor free electrons certainly have spin, and in order to "annihilate" meeting a hole, it also must certainly also have a spin. All this is perfectly acceptable to me, it is just this idea of a quasiparticle that is in essence a vacuum, an absence, having something as tangible and measurable as spin sits uneasy with me - for some reason. And I know that it is likely me, not the mass of knowledge on QM that is to blame. I suspect I am clinging to a far too "visual" imagination, most things quantum seem to be unsuited for mental visualisation.  My question is basically - how does hole spin interact with the electron spin? Does it work similarly as between any pair of electrons?   I read that in an exciton there are exchange interactions between hole and electron - and they can be both singlet and triplet. I can understand this, if they both have spin - certainly the bound state can be both singlet and triplet. I can also understand exchange interactions between electron and electron - but hole and electron? How? Imagining a sea of electrons with aligned spin, a hole's spin is thus related to the entire sea. The hole is an empty state, and it's state is defined by the state of all electrons in the stea. So this interaction is it an exchange between a single electron and the entire sea? But it is a short range range interaction... This does not compute...  PS: As must be obvious, I am not really a physicist. I am just an intrigued chemist.


list1=[[False]*6]*5 list2=[[False]*6 for _ in range(5)] print(list1==list2) True  It seems that list1 is the same to list2, and list1 is simpler. but why most people use list2?

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


Possibly also known as the question of which comes first, epistemology or metaphysics?  My worldview is conservative Protestant.  Any resources are welcome that delve into this.

In attempting to wrap my mind around the basic vocabulary, concepts, and methods of philosophy, I find myself wondering what the difference is between a philosopher and a theologian.   can have two meanings: 1. Theology is a rational study of the existence of God/gods and the nature of religious ideas. 2. Theology is simply a study of a particular religion (or all religions), really more the practice than the theory, but maybe a mixture.  It seems from an immediate reading that definition 1 would lead to the conclusion that a theologian is a philosopher (perhaps that theology is a branch or subset of philosophy), but definition 2 appears to be rather unphilosophical in nature.    So, how does philosophy answer this question?   Is theology considered a proper subset/branch of philosophy overall? Does it depend entirely on which of the above 2 definitions of theology fits a particular theologian as to whether he is a philosopher or not?   I think this answer is simple and fairly self-evident, but somewhere in my gut I feel like I'm missing something.  Is there a treatment of this question in the literature?    Edit: the answers so far seem to want to redefine theology or other terms - that is fine, but please be clear that you are redfining them, and provide, if possible, sources for why the term should be different than given (support from historical works, other sites, etc.).


Can I install Ubuntu 18.04 LTS with 1 GB RAM. My desktop computer has 2.99 GHz 32-bit CPU and 1GB RAM. What Ubuntu version should I install?

For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?


Maybe I don't know how to phrase my searches properly, but this is what I need to do: Make sure that when a user clicks on my ad, it only comes from one particular site, otherwise returns false, or error.  FILTER_VALIDATE_URL   This only makes sure the URL is valid; I want to make sure it only originates from www.example.com or example.com, etc., but from nowhere else.

What is the most reliable and secure way to determine what page either sent, or called (via AJAX),  the current page.  I don't want to use the $_SERVER['HTTP_REFERER'], because of the (lack of) reliability, and I need the page being called to only come from requests originating on my site. Edit: I am looking to verify that a script that preforms a series of actions is being called from a page on my website.


Well I have installed Ubuntu 18.04 LTS lubuntu tty1. Was working fine for two days, but a problem now. When I try to login, the login page keeps on reappearing  repeatedly without logging me in. Enlighten me on this.

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


I've met the symbol ||- many times in modal logic textbooks, especially in epistemic logic books. But I cannot find any info about how to type or read it. Usually, it means "semantical entailment" or "modelling" in modal logic. But in first-order logic, semantical entailment is symbolised as |=. By contrast, we also use |- to express "syntactical entailment" or "proving". Can anyone help me?

I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?


I've recently been hired as an assistant professor and will be starting this fall.  As I'm beginning to be included on departmental e-mail and in certain decisions, I'm starting to interact (at least via e-mail) with my colleagues.  How should I address them?  As a graduate student and postdoc, I've always addressed faculty as Prof. X unless I was already very familiar with them or unless they've told me to do otherwise.  Is it strange to continue to do this as a professor?  I don't want to be disrespectful, but at the same time it feels a little stuffy to continually refer to everyone as Prof. X until they suggest I do otherwise.

This is one bit of academic etiquette I'm not sure about. When I write to another researcher, a peer (we're both professors). I've never exchanged with before and never met him but I know of him (and he probably knows of me).  Erring on the side of formality, I write to him “Dear professor Mortimer”. I sign with my first name, because that's how I've always signed my emails (there's a formal signature block below, with full name and contact details) and I think it indicates a willingness to be called by my first name (which I prefer, but I don't want to force people one way or the other).  Is that going to be well received? Will people take the hint? Or should I just start using first names from the start? (it does sound weird to write “dear Philipp” to someone you don't know)


I'm looking for a portable tripod with a budget of < $100.  I would appreciate some recommendations in this price range, especially from people who have used a product personally.  These are the requirements:   Maximum load I'll use it with: a Nikon 70-300 mm lens, total weight with camera: 1.5 kg. (This'll put high torque on the tripod head because the lens doesn't have a tripod mount.) Reasonable portability is key.  If I can't carry it using a bicycle or on a hike, I won't carry  it most of the time.  It should fold down to no more than 40-45 cm and weigh less than 1.5 kg.   I'm willing to compromise on maximum height to gain portability.  Also I realise that this price won't get me the smallest and lightest one (note that I tried to keep the requirements reasonable): I'm looking for one of the better alternatives in this price range, and for opinions from people who have actually used one of these.  The other tripod related questions I found on this site did not address this particular situation.

I'm looking to buy a tripod + head (for my Canon 40D), but am not sure if I want to spend more than $100 on it.  So can you suggest options for best tripods for $100 or less? Or, is it important to spend more than that on a tripod?  Extra props for options which might be available in India.


I have researched on my question first, but mostly I found that people want to transfer disk space from HOME to ROOT, while my case is the opposite.  My HOME partition is pretty full right now, while I have 350 Gb on my ROOT> I would like to shift e.g. 200Gb from ROOT to HOME.  NOTE: I do not want to change Windows partition size, I just want to shift between the ubuntu partitions.   I've read that I can use gparted for resizing partition. However, I am not quite sure as to how to do it.  Could you please give detailed steps on these?

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


I have a fixed-column long table, with much text inside, that spans about three pages. I set it using the supertabular package, and for the most part it is working  (I will still have to go back to manually tweak a few things once the document is complete). However, I sometimes wonder if longtable would have been a better choice.   Looking for troubleshooting tips for tables in this site, I noticed that there are a little over three times as many questions tagged for longtable than there are for supertabular. I could speculate that this is either because supertabular has fewer undesirable side-effects or because longtable is the preferred package, therefore more people will have problems with it. I have tried them both, and by putting enough time into them I have gotten the desired results; however, the question still nags me: which one is the right one (or the better one) for which type of long-table?

I have a pretty simple table that needs to span multiple pages. This seems like a job for either the / package or the  package.   The voting on the answers to this  suggest that longtable is the preferred package, yet xtab is much newer and has been revised since that question was asked.  What are the differences between xtab and longtable and when is one preferable to the other?


I am trying to build on the . I have a similar requirement to display a hierarchical tree, but I'm struggling to get the tree layout right. In the example, the link between a node and its child always extends from the center of the parent node. I have managed to change the design in a way that all vertical lines start at a fixed distance from the left edge of the parent node so that all vertical lines are aligned, no matter what the size of the parent node is. However, the child nodes themselves still appear to be positioned in relation to the center of the parent node, making the tree look rather untidy. How can I change this so that the nodes are aligned as well?    \documentclass{article} \usepackage{tikz} \usetikzlibrary{trees} \begin{document} \tikzstyle{every node}=[draw=black,thick,anchor=west] \begin{tikzpicture}[%   grow via three points={one child at (0.5,-0.7) and   two children at (0.5,-0.7) and (0.5,-1.4)},   edge from parent path={([xshift=2ex]\tikzparentnode.south west) |- (\tikzchildnode.west)}]   \node{root}     child { node {shrt}       child { node {looonger}          child { node {veryveryverylong} }       }       child [missing] {}                       child [missing] {}                       child { node {looonger} }       child { node {veryveryverylong}          child { node {shrt} }         child { node {looonger} }         child { node {veryveryverylong} }       }     }     child [missing] {}                   child [missing] {}                   child [missing] {}                   child [missing] {}                   child [missing] {}                   child [missing] {}                   child [missing] {}                   child [missing] {}                   child { node {veryveryverylong}        child { node {shrt} }       child { node {looonger} }     }; \end{tikzpicture} \end{document}

I would like to draw a picture that reflects some file structure. Below code works almost as expected. I need to adjust the connections between nodes so they don't start from the center of the bottom of the parent node but from near the left bottom corner.  How can I do this?  Code:  \documentclass[11pt, oneside]{article} \usepackage{tikz}                           % super package for complex and awesome drawing  \begin{document}  \usetikzlibrary{trees} \tikzstyle{every node}=[draw=black,thick,anchor=west,inner sep=2pt,minimum size=1pt] \tikzstyle{selected}=[draw=cyan,fill=cyan!30] \begin{tikzpicture}[   grow via three points={one child at (0.5,-0.7) and   two children at (0.5,-0.7) and (0.5,-1.4)},      edge from parent path={(\tikzparentnode.south) |- (\tikzchildnode.west)}]   \node {MainFolder-\{version\}}     child { node [label={[xshift=6.0cm, yshift=-0.58cm, color=gray] Documentation for developers}] {References and Documentation/}         child { node [draw=none] {main.html} }         child { node {reference/}             child { node [draw=none] {...}}         }         child [missing] {}     }     child [missing] {}     child [missing] {}     child [missing] {}     child { node {release/}         child { node [draw=none] {libAwesome.a} }         child { node [draw=none] {libAwesome.dylib} }     }; \end{tikzpicture} \tikzstyle{every node}=[] % resets borders of tables \tikzstyle{selected}=[] % resets selected  \end{document}     Ouput:    Ideal:    Any help is appreciated.


I know in order to be irreducible $3-2i$ must not equal zero, it's not a unit and whenever $3-2i=ab$ then either $a$ is a unit or $b$ is a unit.  We can assume $3-2i=(a+bi)(c+di)$ for some $a,b,c,d$ in the integers and both elements are not units.  After this I am not sure where to proceed.

For the ring $\Bbb{Z}[\sqrt{d}]=\{a+b\sqrt{d}\mid a,b \in \Bbb{Z}\}$ where $d$ is not divisible by the square of a prime, prove that the norm $N(a+b\sqrt{d})= |a^2-db^2|$ satisfies the assertions: $N(x)=0$ if and only if $x=0$; $N(xy)=N(x)N(y)$ for all $x$ and $y$; $x$ is a unit if and only if $N(x)=1$; and if $N(x)$ is prime, then $x$ is irreducible in $\Bbb{Z}[\sqrt{d}]$.


I have a database dedicated server with one quad-core cpu and 48GB Memory.  Total database size is about 6GB and my ultimate goal is to get the maximum performance out of this system.  At First, to get maximum performance I set innodb_buffer_pool_size to '35GB' with innodb_buffer_pool_instance to 5, thinking that each instance will take up 7GB so total 35GB will be optimum.  But after several days, Innodb_buffer_pool_pages_free says I had 26GB free space in the buffer pool.  So I increased the instances number to 10 and waited some weeks, but the Innodb_buffer_pool_pages_free says about the same thing.  Was my calculation(expecting that 7GB * 5 instances would take up 35GB of buffer pool) wrong? Then how can I use all the free buffer pool size? Should I increase the buffer pool instances even more? Or run 2 mysqld processes to get replication or something?  If anyone get any clue, please give some hint to get the point right about my issue.

Server Characteristics  Total system RAM: 8GB (running MySQL + other stuff than MySQL on it i.e. not dedicated to MySQL) Number of CPU Cores: 6 I have data in the db amounting to about 2GB I have InnoDB Buffer Pool Size set to 4GB  Which is better:  Innodb Buffer Pool Instances set to 1? Innodb Buffer Pool Instances set to 2 (2GB in each)? Innodb Buffer Pool Instances set to 4 (1GB in each)? Innodb Buffer Pool Instances set to 8 (the default setting)  I'm thus not sure as to how to reason when it comes to Buffer Pool Instances and also the whole "use instances or suffer OS Swap when having such large InnoDB Buffer Pool Size".


If I want to capture a pipe character | in the capture group of a regular expression then it needs to be backslash escaped so it isn't interpreted as an alternator.  (and\|or) matches the string "and|or" (and|or) matches the strings "and" and "or"   What other characters need to be escaped inside a capture group in order to be interpreted literally? Is there a comprehensive list of these characters?

I am tired of always trying to guess, if I should escape special characters like '()[]{}|' etc. when using many implementations of regexps.  It is different with, for example, Python, sed, grep, awk, Perl, rename, Apache, find and so on. Is there any rule set which tells when I should, and when I should not, escape special characters? Does it depend on the regexp type, like PCRE, POSIX or extended regexps?


I am reading A First Course in Differential Equations with Modeling Applications (10th Edition) and here is a definition:     Any function $\phi$, defined on an interval $I$ and possessing at least $n$ derivatives that are continuous on $I$, which when substituted into an $n$th-order ordinary differential equation reduces the equation to the identity, is said to be a solution of the equation on the interval.   I am wondering why the condition "on an interval $I$" is important (this has been emphasized in other places of the book). For example, why it is not okay to say that $$y=x^{-1}, x\neq 0$$ is a solution to the differential equation $y'=-x^{-2}$?

I understand a domain is the set of input elements a function is defined for (and can have breaks in it e.g. union of 2 sets) and a interval is a continuous range of real numbers. Why do we speak of the solution to a differential equation over an interval instead of an domain? If the solution to an ODE is just a function, and we normally speak of functions as having a domain, then why wouldn't we use domain?


I have done a lot of work to resolve the issue, and have even searched for the solution, but no result.  Suddenly I struck with this problem, probably due to some unknown short key combination. Brush in Adobe Photoshop, has become rough edged. Especially when its Hardness is 0, it looks like made up of particles only.

Sorry, I don't know how to describe this strange behavior. I have no idea what happened on my brush... Please help me. Thanks a lot!!


As part of my research I need to find the detailed list of books written using TeX, LaTeX.... I am from Computer Science background, and found some books written making use of TeX, LaTeX... Could you please give a list of books written using this. I know the list is large. It would be ok to include major titles only.

If you were asked to show examples of beautifully typeset documents in TeX & friends, what would you suggest? Preferably documents available online (I'm aware I could go to a bookstore and find many such documents called 'books'). Extra bonus for documents whose LaTeX source is available.  This is not an idle question. Seeing great examples of any craft is both educational and inspiring, let alone explaining why we prefer TeX to Word or other text editors.  For instance, I like how Philipp Lehman's  looks. I don't know enough LaTeX to realize how much customization was done, but the ToC looks polished.  Your nominations, please ...


My client found that Waze app is showing License agreement to user with two buttons Decline and Accept. I am trying to tell him that best way is to have just one button and let users leave app if they don't agree with terms and conditions. But he wants to do this this way. I know that there are several ways how to quit app but I think no one will be approved by Apple in review process. So how Waze do it? When I click on Decline button app goes dark and then quits. How can this be approve in review process? Screenshot from Waze:

I am programming an iPhone app, and I need to force it to exit due to certain user actions.  After cleaning up memory the app allocated, what's the appropriate method to call to terminate the application?


My PC was booting very fast because I have SSD however after I enabled and disabled bitlocker now my PC boot time is 1 minute and 10 sec !! I tried to use windows performance recorder to see what is wrong but once started the recorder I could not login into windows because of blue screen !! so i disabled the recorder.  Any advise how I find the problem that made my boot time slow ?  Here is the event pic   Here are the data    EventData     BootTsVersion 2    BootStartTime 2019-02-01T20:23:29.029447200Z    BootEndTime 2019-02-01T20:25:18.984717500Z    SystemBootInstance 453    UserBootInstance 451    BootTime 82979    MainPathBootTime 13279    BootKernelInitTime 39    BootDriverInitTime 441    BootDevicesInitTime 4344    BootPrefetchInitTime 0    BootPrefetchBytes 0    BootAutoChkTime 0    BootSmssInitTime 3448    BootCriticalServicesInitTime 121    BootUserProfileProcessingTime 463    BootMachineProfileProcessingTime 53    BootExplorerInitTime 3552    BootNumStartupApps 4    BootPostBootTime 69700    BootIsRebootAfterInstall false    BootRootCauseStepImprovementBits 0    BootRootCauseGradualImprovementBits 0    BootRootCauseStepDegradationBits 0    BootRootCauseGradualDegradationBits 0    BootIsDegradation false    BootIsStepDegradation false    BootIsGradualDegradation false    BootImprovementDelta 0    BootDegradationDelta 0    BootIsRootCauseIdentified false    OSLoaderDuration 904    BootPNPInitStartTimeMS 39    BootPNPInitDuration 5099    OtherKernelInitDuration 111    SystemPNPInitStartTimeMS 5193    SystemPNPInitDuration 397    SessionInitStartTimeMS 5608    Session0InitDuration 1441    Session1InitDuration 407    SessionInitOtherDuration 1599    WinLogonStartTimeMS 9056    OtherLogonInitActivityDuration 153    UserLogonWaitDuration 9638    I already tried windows performance kit and because of the recorder I could not even login into windows because of blue screen. In addition I posted the time of each process and it appear BootPostBootTime is the problem but I dont know what it is and how to solve it.  Update Here is a picture from process monitor display the most taken time at startup but I dont know how to fix this as I afraid to stop a process that will take down windows so please advise  As for Bitlocker all drives are unencrypted and the service is not running

When I start my PC, it boots into Windows (Windows 7 32-bit) quite happily, I login and the main Windows screen appears. At that point, however, the system is extremely unresponsive for up to 5 minutes - if I click on Firefox to start it, nothing appears to happen for a long time, etc, etc. The mouse and Windows UI is responsive, but programs take forever to start, webpages seem to hang (or at least load extremely slowly) and so on.  I imagine that the issue is with one or more programs that run on startup, but I don't know quite how to identify which one it might be. The event log shows nothing of any obvious interest. I can't see any high CPU activity in task manager or Process Explorer, and I can't hear any high disk activity.  I'd rather understand what's happening and then work out how to address it, than have to go for a blind "switch things off and see what helps" approach, but maybe that's being optimistic :-)  I suspect disk bottlenecks or network, but I don't know how I could set something up to diagnose this (and in particular, given that I can't get programs to start in a timely manner, I'd prefer something that automatically starts and logs data for later analysis than something like Process Explorer, which always leaves me worrying that by the time it started the problem had gone away :-)  I guess my ideal would be 2 things:   Something that gave me an overall "what are the current key bottlenecks in this system" summary (ideally, which could be set to run in the background and collect data for later analysis). Some means of starting a program (say, Firefox) and have it record what was going on in terms of waits and delays in the system.   Unfortunately, I've never really found anything like either of these.  I'm not a professional systems admin - my background is database admin - so if there are "obvious" tools to look at or try, then I'd be grateful to know of them (particularly if the information they give is easy for an amateur to analyze) :-)


Is there any budget lens for Nikon d5600 which is best for both portrait and landscape? I'm looking for one lens which does both portrait and landscape.

I have just bought a new DSLR (a Nikon D3000). I want to take photos of flying birds, mountains, and close-up portraits. Is there a single lens well-suited for these types of photography, so that I don't need to carry multiple lens while traveling?


A set $L$ consists of $2008$ integers, none of which have a prime divisor   larger than $24$. Prove that $L$ has four elements, the product of which   is equal to the fourth power of an integer.

Given a set $M$ of $1985$ distinct positive integers, none of which has a prime   divisor greater than $26$, prove that $M$ contains at least one subset of four distinct elements, whose product is the fourth power of an integer.   I couldn't even start.


Why Maxwell Distribution of Velocities curve is Bell Shaped?   Apart from mathematics,   Is there any intuitive reason behind it?  Is there any quantum mechanical reason behind it? Is there any explanation with which we can imagine the necessity of distribution to be Bell Shaped?

At higher temperatures (for an ideal gas), the Maxwell-Boltzmann distribution is spread more widely and has a lower maximum. At lower temperatures, the spread is much more narrow and the peak is much higher. Why is this so? I was thinking that this is to maintain constant area under the curves, but the integration of the curve gives total energy—and total energy should not be constant since temperature is increasing.  So why does the distribution curve change thus? I’m looking for an explanation that’s intuitive or that involves math not surpassing first-year university level calculus. I would appreciate it if it could be explained without the Maxwell-Boltzmann distribution equation, since at this level I’m really treating this qualitatively.


I have made a simple model with the window with archimesh addon. With the window material i have set to travel the light inside.     But no light travel inside through the window    What is missing the blend file attach below

Here's a sample scene:  A room with a window, a point light to project light into the room, an HDR environment outside the room and a nice Image by Rembrandt that should be somewhat reflected on the glass:    Using a standard glass shader on the window, the direct light from the lamp does not shine into the room, regardless of how bright that light is. So I can't recreate the impression of hard day light, with clearly defined areas of light and shadow.    Adding a transparent shader to the glass shader I get a very pleasing result. The light from the lamp illuminates into the room creating defined shadows, transparency seems unaffected, to see the HDR in the background, the refection seem correct to me (I also like how I get double reflections from the thick glass).    Even though I am quite happy with this solution, I've gotten a few comments on making a setup with light path nodes controlling the mix of transparent and glass. The biggest issue is that the reflections on the glass are brighter than what they should be.  So the question is: By using this approach am I messing up any of the qualities of glass? And if so, what would make a proper glass shader that is realistic, in terms of letting direct light through, while keeping reflections, refraction and transparency?  A file to play with:    The HDR image used was created by


So i have a bulk of images having white border and text embedded at bottom.I tried to use irfanviewer xnviewer to bulk crop it however it didnt work...the problem is the images have same specific resolution is 1024 * 768 however border around it doesnt always start froma specified pixel at top left corner. So batch croppers dont work. Is there a method to detect and remove the white borders while preseving the 1024 *768 size?

I need to scan a large volume of book covers and even though the scanner (HP) most of the time scans/auto-sizes, many are left with white/grey space on the sides.  What is the best way I can automate the "crop" on these images?  Is there some software/tools that automate this?


DECLARE @Count BIGINT   SELECT @Count = Count(ID)  FROM Users;   SELECT TOP 50       CustUser.[ID],     CustUser.[FirstName] + ' ' + CustUser.[LastName] FirstName,     CustUser.[NickName],     CustUser.[UserName],     R.[Name] Roles      FROM     (SELECT                 ROW_NUMBER() OVER(ORDER BY US.ID Desc) AS Row,          US.[ID], US.[FirstName], US.[LastName], US.[NickName],          US.[UserName], US.[Password]      FROM           [Users] US) CustUser LEFT JOIN      Category CL ON CustUser.[LoginModeCode] = CL.CategoryCode LEFT JOIN      Category CS ON CustUser.[StatusCode] = CS.CategoryCode  LEFT JOIN     UserRoles UR ON UR.UserID = CustUser.ID LEFT JOIN     Roles R ON R.ID = UR.RoleID WHERE      CustUser.ID = 3 AND      [Row] > (1 - 1) * 50   ORDER BY     FirstName   This query returns the below output  ID   FirstName       NickName          UserName             Roles                 ---------------------------------------------------------------------------- 3     ram              jk                 ram               Developer           3     ram              jk                 ram               TeamLeader     Roles only different in above rows. I am combining two rows.      But I want this output   ID   FirstName   NickName    UserName    Roles                                              --------------------------------------------------------------  3    ram            jk         ram       Developer, TeamLeader

How do I get:  id       Name       Value 1          A          4 1          B          8 2          C          9   to  id          Column 1          A:4, B:8 2          C:9


In my class of Time Series, the professor mentioned about the sequence of real numbers $(a_n)_{n \in \mathbb Z}$ and the sum $$\sum_{-\infty}^{+\infty} a_n$$  I've searched on the Internet but could not find a definition for the sum from $-\infty$ to $+\infty$. Is there a standard definition for this kind of sum?

This is a really basic question, but I'm unsure about the definition for convergence of  $$\sum_{i=-\infty}^\infty a_i$$ The definition  $$\sum_{i=-\infty}^\infty a_i=\lim_{n\to \infty} \sum_{i=-n}^n a_i$$ seems too loose to me, but the strongest definition I can think of: $$\sum_{i=-\infty}^\infty a_i=\lim_{\|A\|\to \infty}\sup_{A\subset\mathbb{Z}}\sum_{i\in A}a_i$$ seems too strong. There are also others like $$\sum_{i=-\infty}^\infty a_i=\lim_{n\to\infty}\sum_{i=-n}^{0}a_i+\lim_{n\to\infty}\sum_{i=1}^na_i$$ but this seems a bit arbitrary.  More specifically: if I'm asked to show that a certain series of functions $$\sum_{i=-\infty}^\infty f_i$$ converges, then which sequence of partial sums should I consider?    edit: yet another possibility is to consider these types of series only if they converge absolutely, in which case these considerations are irrelevant.    edit2: The problem with the splitting definition is that it does not seem to work when considering different modes of convergence. For example, if I want to show that $\sum_{i=-\infty}^\infty f_i$ converges uniformly, I would need for a given $\epsilon$ need to find a $\delta(\epsilon)$ s.t. for $N>n$ the $N$th partial sum close enough to the limit function for all $x$ in my domain. However, here we have no well defined $N$th partial sum, since we have split our sum in the definition of the limit. So how do we define uniform convergence in this case?


I tryed to download the Tale of Two Kingdoms mod for Minecraft. I opened up the bin and there was no minecraft.jar! How do I download minecraft.jar so I can download Tale of Two Kingdoms?

The other day I was trying to download something for Minecraft and it involved my bin folder. So I was looking for it and couldn't find it. I then thought that I might have accidentally deleted it, but didn't find it in the trash. I have no idea how to get the bin folder back with all the Minecraft binary files in them.


How can I make this kind of light?  Try to imagine plastic bottle of milk with light bulb inside of it, exact same thing (Like on picture)

I need to know how to make the buttons in my blender project look the same as in this photo. Mine all look pale, even with the emission material. Is there anyway I can get my buttons like this?


From what little I know about general relativity, energy (and equivalently mass) distorts and curves spacetime due to the Einstien Field Equations. I also know "wormholes" are theoretically solutions to the field equations, that connect two points in spacetime.  However, how do these two definitions work with eachother? Energy distorts space into a fourth dimension, I understand that, but using that description, how could a wormhole "connect" those two points? The way I've seen it describes it folding over a piece of paper and poking a pencil through it - but that seems like a cop out. What's the equivalent of "folding" in physics, and does a theoretical wormhole actually fold the space?   How can two distortions in a uniform 3D space possibly connect to eachother?

Lately I encountered a few times references to wormholes as a way to reach distant places in the universe in a short time. I have to admit I don't have a proper knowledge of the mathematics behind wormholes (although I won't mind a complete GR explanation in the answer, if necessary). All I know is that wormholes are usually compared to something analogous to a tunnel through the planet Earth to reach distant places in less time. The problem is, if I want to reach the other side of the planet I have to travel 20.000 km on its surface and "only" 12.000 km through its center. While the latter is surely shorter, it's still more than 50% of the initial value and this is the best-case scenario. For shorter distances, the difference becomes more and more negligible.  Now, I know enough of GR to understand that this explanation could be a simplification so extreme that any comparison makes little to no sense, but I'm curious to understand if the same problems arise for wormholes too. I don't really care if wormholes exist, are traversable by spaceships and both the crew and the vessel can survive the travel undamaged, I know they are still a theoretical construct and probably there is more than one formulation for it. What I'm really interested in is:   How much shorter will the travel be? I'm interested in Earth proper time, because if the reduction is only in the spaceship proper time, the we can achieve the same result "simply" by traveling closer to the speed of light. Does the amount of reduction in time depend on the distance between the endpoints? If so, it seems unpractical to travel to near stars through wormholes, if the spacetime geometry of our galaxy doesn't help somehow (local curvature should be higher than global curvature).


Given that $A$ and $B$ are abelian groups, prove that the direct product of them $$A\times B$$ is an abelian group. Given that $A\times B$ is an abelian group, prove that $A$ and $B$ are both abelian.   I used the basic property of Descartes product: $$(a,b)\cdot(c,d)=(a\cdot c,b\cdot d)$$ to prove each argument.   $(a,b)(c,d)=(ac,bd)=(ca,db)=(c,d)(a,b)$; $(a,b)(c,d)=(c,d)(a,b)\implies (ac,bd)=(ca,db)\implies ac=ca, bd=db$.   I am not sure whether this property of Descartes product can be applied to groups. This question appears to be the 30th question out of 36 questions in an exercise, so I guess it's not that easy.  This is my first post, so please forgive me for any wrongdoing!:)

This is an assignment question: I just need know whether I am on the right track.....  Let $G_1,…,G_n$ be groups. Prove that the direct product $G_1×⋯×G_n$ is abelian if, and only if, each of $G_1,…,G_n$ is abelian.  I know that this question have already been discussed before, I've got two thing that I need clarification on.... Is it wise for me to start this prove by assuming that $G_1,....,G_n$ (which is for each group) are Abelian, and work toward showing that the direct product of the group is abelian secondly, is there any second part of the prove that I haven't considered..  thank you...  I'll really appreciate any help


I purchased a Toshiba C850 Laptop and I'm trying to install the 64 Bit version of Ubuntu 12.10 alongside Windows 8, allowing me to dual boot.  I burnt a Ubuntu 12.10 DVD, disabled Secure Boot on the Laptop and then loaded the DVD. When I selected Install Ubuntu I see that the installer hasn't recognised Windows 8 on the drive and only gives me options to erase the entire disk or to do "something else".    I've seen that it recognises other partitions but it doesn't correctly find Windows 8.    In this situation, how can I safely install Ubuntu 12.10 alongside Windows 8

Whenever I startup from the LinuxLive USB, and try to install Ubuntu 12.04, it only gives me two options instead of the usual 3 or 4. My options are "Replace Windows 7 with Ubuntu" and "Something Else". Whenever I go into "Something else", it looks extremely confusing. How do I install it side-by-side while using the "Something else" section? These are my partitions.   /dev/sda /dev/sda1 ntfs (104Mb, System Required Partition) /dev/sda2 ntfs (1000097Mb, Windows 7 Partition)   Or should I try reinstalling my installer on a CD rather than USB and maybe then it will have the "Install alongside" function?


I read a book on pop sci book on quantum mechanics and the author said that electrons do not fall into the nucleus due to quantum mechanics- which principles suggest this (I think it was Heisenberg's Uncertainty and Pauli's Exclusion Principle) and why?  Also, I've heard that if Bohr's planetary model were correct, then electrons would lose energy/momentum and fall in- is this true and again, which physics principles say this?

I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course.   In particular,    I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus. Even if the electron actually orbits the nucleus, wouldn't that orbit eventually decay?  I can't reconcile the rapidly moving electrons required by the planetary model with the way atoms are described as forming bonds. If electrons are zooming around in orbits, how do they suddenly "stop" to form bonds.     I understand that certain aspects of quantum mechanics  to address these problems, and that there are  of atoms. My question here is whether the planetary model itself addresses these concerns in some way (that I'm missing) and whether I'm right to be uncomfortable with it.


So I had this question as extra credit on my exam and no one was able to solve it.  I tried to do integration by parts but that just keep on expanding with no solution in sight.  I have also tried to take the derivative of the integral but that didn't seem to help either.  How would I integrate $\int_{0}^{\infty}e^{{-u}^{2}}\cos(ux)du$?

Prove that :  $$ \frac{\sqrt{\pi}}{2} e^{-\frac{a^2}{4} } =\int_0^{\infty} e^{-x^2} \cos( a x) \ \mathrm{d}x$$    the only thing I can think of is differentiating the RHS and trying to get :  $$ -2 f'(a) =a f(a) $$ But I couldn't do it.  Can anyone show me how to do this ?


I was under the impression that tar does not compress files. Imagine my surprise when I tar up a million small files (du -h ~ 4.2G) and the resulting tar was a quarter of the size (ls -lh mytar.tar ~ 1.3G)!  Clearly these tiny files were taking up space beyond their reported size, and an  suggests that each non-empty file takes up at least 1KB regardless of it's size. But where does this 1KB come from, does it differ across filesystems (this is ext4), and does a 1.01 KB file take up 2KB?   In short, how do I measure the true file size, especially many files in a directory? I tried du --apparent-size -h and I'm only getting 437M so I quite confused at the three vastly different numbers.

When I sum up the sizes of my files, I get one figure. If I run du, I get another figure. If I run du on all the files on my partition, it doesn't match what df claims is used. Why are there so many different figures for the total size of my files? Can't computers add?  Speaking of adding: when I add the “Used” and “Available” columns of df, I don't get the total figure. And that total figure is smaller than the size of my partition. And if I add up my partition sizes I don't get my disk size! What gives?


I am trying to write a paper in LaTeX.  I am able to indent most of the paragraphs by using \\ at the end of the previous paragraph and adding a blank line in between the paragraphs like so.    This is the last sentence of the previous paragraph.  \\  This is the first sentence of the next paragraph.   However, I am unable to indent the first paragraph of my paper or any of the first paragraphs in any of my sections.  Any advice is welcome.

I am just curious that the following format looks good to you or not? The preamble I used is just   \documentclass[12pt,a4paper]{article}  \usepackage{amsmath} \usepackage{amsthm} \usepackage{amssymb}   I don't feel it's so good because the first paragraph has no indent but the second does. If the first paragraph is much longer, than it's fine. But if not, it looks strange. Should I leave it, or you have suggestions for this?


I'm sending some polish names via $_GET, and when I'm trying to var dump it, I'm getting sth like:  A?a   which should be:  Ała   In url it looks like:  A%B3  I've set ehaders to utf-8, ant still it doesnt work. How can I solve this?  EDIT: it looks like problem starts from getting this text from database. It looks like it should in table, but when rying to SELECT it and echo - the problem starts

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


How would I prove the following:      Show that an odd prime $p$ can be written on the form $p=x^2+2y^2$ for some $x,y\in\mathbb Z$ iff $p\equiv_8 1, 3$. Hint: use the quadratic reciprocity and the fact that $\mathbb Z[\sqrt{-2}]$ is a Euclidean domain.

For a prime $p \equiv 1$ or $3$  (mod $8$), show that the equation $x^{2} + 2y^{2} = p$ has a solution.   I'd like to see an elementary proof.


I am learning DOM manipulation with JS. Using JS I am creating several divs from an array and want to call a JS function on each of them.  I wrote 2 versions:  version 1 for simplicity to check if it would work at all. Ant it does work. But version 2 (that I need) doesn't work.  What is wrong with version 2? Can someone help me please?  Version 1:  document.addEventListener('DOMContentLoaded', function() { const arr = ['AAA', 'BBB', 'CCC']; arr.forEach(add_elms);  function add_elms(arr) {     // Create div     const item = document.createElement('div');     item.innerHTML = arr;     // Add button      const go = document.createElement('button');     go.setAttribute('onclick', 'this.parentElement.style.color = "red"');     go.innerHTML = 'Go';     item.append(go);     document.querySelector('#target').append(item); };  });   Version 2:  document.addEventListener('DOMContentLoaded', function() { const arr = ['AAA', 'BBB', 'CCC']; arr.forEach(add_elms);  function add_elms(arr) {     // Create div     const item = document.createElement('div');     item.innerHTML = arr;     // Add button      const go = document.createElement('button');     go.className = 'gobutton';     go.innerHTML = 'Go';     item.append(go);     document.querySelector('#target').append(item); };  document.querySelector('.gobutton').forEach(function(button) {     button.onclick = function() {         this.parentElement.style.color = "red";     }; });   Any ideas what's wrong with my Version 2? Thanks!

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


In this code:  protected static void HandleExceptions(Exception E) {     switch (E)     {         case MongoWriteException _ :         {   what does the discarded variable ('_' here) is supposed to be?

I've been looking at F# recently, and while I'm not likely to leap the fence any time soon, it definitely highlights some areas where C# (or library support) could make life easier.  In particular, I'm thinking about the pattern matching capability of F#, which allows a very rich syntax - much more expressive than the current switch/conditional C# equivalents. I won't try to give a direct example (my F# isn't up to it), but in short it allows:   match by type (with full-coverage checking for discriminated unions) [note this also infers the type for the bound variable, giving member access etc] match by predicate combinations of the above (and possibly some other scenarios I'm not aware of)   While it would be lovely for C# to eventually borrow [ahem] some of this richness, in the interim I've been looking at what can be done at runtime - for example, it is fairly easy to knock together some objects to allow:  var getRentPrice = new Switch<Vehicle, int>()         .Case<Motorcycle>(bike => 100 + bike.Cylinders * 10) // "bike" here is typed as Motorcycle         .Case<Bicycle>(30) // returns a constant         .Case<Car>(car => car.EngineType == EngineType.Diesel, car => 220 + car.Doors * 20)         .Case<Car>(car => car.EngineType == EngineType.Gasoline, car => 200 + car.Doors * 20)         .ElseThrow(); // or could use a Default(...) terminator   where getRentPrice is a Func<Vehicle,int>.  [note - maybe Switch/Case here is the wrong terms... but it shows the idea]  To me, this is a lot clearer than the equivalent using repeated if/else, or a composite ternary conditional (which gets very messy for non-trivial expressions - brackets galore). It also avoids a lot of casting, and allows for simple extension (either directly or via extension methods) to more-specific matches, for example an InRange(...) match comparable to the VB Select...Case "x To y" usage.  I'm just trying to gauge if people think there is much benefit from constructs like the above (in the absence of language support)?  Note additionally that I've been playing with 3 variants of the above:   a Func<TSource,TValue> version for evaluation - comparable to composite ternary conditional statements an Action<TSource> version - comparable to if/else if/else if/else if/else an Expression<Func<TSource,TValue>> version - as the first, but usable by arbitrary LINQ providers   Additionally, using the Expression-based version enables Expression-tree re-writing, essentially inlining all the branches into a single composite conditional Expression, rather than using repeated invocation. I haven't checked recently, but in some early Entity Framework builds I seem to recall this being necessary, as it didn't like InvocationExpression very much. It also allows more efficient usage with LINQ-to-Objects, since it avoids repeated delegate invocations - tests show a match like the above (using the Expression form) performing at the same speed [marginally quicker, in fact] compared to the equivalent C# composite conditional statement. For completeness, the Func<...> based-version took 4 times as long as the C# conditional statement, but is still very quick and is unlikely to be a major bottleneck in most use-cases.  I welcome any thoughts / input / critique / etc on the above (or on the possibilities of richer C# language support... here's hoping ;-p).


How can I fill the area between two concentric circles (or even slightly eccentric) using only tikz (preferably without pgfplots)? I have found many sort-of similar questions, but nothing that quite addresses this.  \documentclass[tikz,border=1pt]{standalone}  \begin{document} \begin{tikzpicture}     \draw (0, 0) circle (1);     \draw (0, 0) circle (1.2); \end{tikzpicture} \end{document}   I want to fill the area between these two with the color gray. I would prefer not to fill the inner circle with white color, but leave that transparent, or unfilled.

I am using the TikZ package to show a set of complex numbers where those I want are in the outer part of a circle with a radius 2, and where the circle with radius 1 is not in the set:   I want to let the inner circle be white, with the axes showing completely, but I am not able to find out how. I am using two circles with semi-transparent fillings. Is there any way to make only the outer part filled? Relevant code below.  (This is where I got most of the code: )  \begin{tikzpicture}     \begin{scope}[thick,font=\scriptsize][set layers]     \draw [->] (-4,0) -- (4,0) node [above left]  {$\Re\{z\}$};     \draw [->] (0,-4) -- (0,4) node [below right] {$\Im\{z\}$};     \iffalse% Single     \draw (1,-3pt) -- (1,3pt)   node [above] {$1$};     \draw (-1,-3pt) -- (-1,3pt) node [above] {$-1$};     \draw (-3pt,1) -- (3pt,1)   node [right] {$i$};     \draw (-3pt,-1) -- (3pt,-1) node [right] {$-i$};     \else% Multiple     \foreach \n in {-3,...,-1,1,2,...,3}{%         \draw (\n,-3pt) -- (\n,3pt)   node [above] {$\n$};         \draw (-3pt,\n) -- (3pt,\n)   node [right] {$\n i$};     }     \fi     \end{scope}     \draw[solid] (0,-1) circle (1);     \draw[solid] (0,-1) circle (2);     \path [draw=none,fill=gray, fill opacity = 0.1] (0,-1) circle (2);     \path [draw=none,fill=white, fill opacity = 0.7] (0,-1) circle (1);     \node [below right,black] at (1.2,1.2) {$A=\{z\in\mathbb{C}:1\leq|z-(-i)|\leq2\}$}; \end{tikzpicture}


First time I get Ubuntu to load up without having to change secure boot, UEFI but it doesn't detect my preinstalled Windows 8 on the hard drive. The option to install alongside Windows isn't available but cleaning the whole disk is always highlighted.

Whenever I startup from the LinuxLive USB, and try to install Ubuntu 12.04, it only gives me two options instead of the usual 3 or 4. My options are "Replace Windows 7 with Ubuntu" and "Something Else". Whenever I go into "Something else", it looks extremely confusing. How do I install it side-by-side while using the "Something else" section? These are my partitions.   /dev/sda /dev/sda1 ntfs (104Mb, System Required Partition) /dev/sda2 ntfs (1000097Mb, Windows 7 Partition)   Or should I try reinstalling my installer on a CD rather than USB and maybe then it will have the "Install alongside" function?


Let's say I have a charged particle in front of me. If I start spinning in place, the charged particle will appear accelerated to me from my reference frame. If the laws of physics pertaining to this scenario are valid in all reference frames, if I spin with with an appropriate angular velocity to bring the emitted waves into the visible light spectrum, will I see light? If there are many such particles, will the entire room light up for me and remain dark for a stationary observer next to me?

Take 2 observers and a charged particle,  Observer S is stationary to the particle and sees the electric field and no magnetic field as he is stationary to the particle.  Observer A decides to accelerate and decelerate over and over back and forth in front of the particle.  From A's frame of reference, it can be said, by the equivalence principal, that the particle is accelerating and decelerating in A's frame of reference and therefor should emit a EM wave.  So A sees a Em wave come off the particle.  But wait, S does not see any such thing, other than A moving back and forth...  What am I missing?? Thanks! Eric


Question mentioned like this find out the electric field inside and outside a spherical shell of radius r which carries a uniform surface charge density sigma.  In the above question it is not mentioned that the shell is conductive or non conductive than how one can attempt  this question and what assumption required for it.

It is quite easy to derive the gravitational field intensity at a point within a hollow sphere. However, the result is quite surprising. The field intensity at any point within a hollow sphere is zero.   What exactly is the reason behind this? Except for, of course, the mathematics behind it. Is there any logic why the field intensity should be zero within a sphere? For example, it is logical to say that the field intensity would be zero at the center, as all the intensities cancel out. However, this cannot be the case for any point within the sphere.


I know that induced electric field lines form closed loops but we always see that in textbooks, induced electric field lines are drawn circular loops. So my question is that are induced electric field lines always circular in nature or can they be of any shape, and I also want to know why everyone draws these lines as circular?

Whenever we have a changing magnetic flux through a conductor an induced electric field is generated. It is often said that these induced electric field lines are circular in shape.But why is this so?Why are these field lines not elliptical for example? How can this shape be mathematically derived?  Also does this have anything to do with equipotential surfaces?Do such non-conservative electric fields even produce a potential field?If not why?


Problem says:     Let G   be an abelian group. Prove that Aut(G)   is abelian if   and only if G   is cyclic.   And I solved $(\Leftarrow)$ direction as follow:  Suppose that $G$   is cyclic.   Then $Aut(G)=\{\varphi_{1},\cdots,\varphi_{n}\}$   where $\varphi_{i}(g)=g^{i-1}$  . Thus, for $\varphi_{i},\varphi_{j}\in Aut(G)$  , $\varphi_{i}\varphi_{j}(g) = \varphi_{i}(g^{j-1})  = (g^{j-1})^{i-1}  = (g^{i-1})^{j-1}  = \varphi_{j}(g^{i-1})  = \varphi_{j}\varphi_{i}(g)$  Therefore, $\varphi_{i}\varphi_{j}=\varphi_{j}\varphi_{i}$   for $1\leq i,j\leq n$  . Hence, $Aut(G)$   is abelian.   But I worried about the case where $G$ is infinite and the other direction.

Is there an example in which $G$ is a finite abelian group and $\textrm{Aut}(G)$ is abelian but $G$ not cyclic?


I'm trying to create a product slider after a $.load() method but it doesn't work.  I'm loading an external page in a #main div   $(".product").on("click", function (e){      $("#main").load("products.html");  });   /* products.html*/

                                            <button>P1</button>

                                            <button>P2</button>

   /* previous and next buttons */  $(".prev").on("click", function(){             console.log("going to prev");             var currentPage = $(".page.active");             var prevPage = currentPage.prev();             currentPage.fadeOut(300).removeClass(".active");             prevPage.fadeIn(300).addClass(".active");              if(prevPage.lenght ==0){                 $(".page").last().fadeIn(300).addClass(".active");             }         });  $(".next").on("click", function(){             console.log("going to next");             var currentPage = $(".page.active");             var nextPage = currentPage.next();             currentPage.fadeOut(300).removeClass(".active");             nextPage.fadeIn(300).addClass(".active");              if(nextPage.lenght ==0){                 $(".page").first().fadeIn(300).addClass(".active");             }         });   when I click on next or previous non action is launched. Could you please help?


I have no idea how to prove this:  Let be $B$ a prime ideal of a commutative ring $A$. Show that $A_B$, the ring of fractions respect $B$ as multiplicative set is a local ring.  Any suggestions?

I would like to know, why $ \mathfrak{p} A_{\mathfrak{p}} $ is the maximal ideal of the local ring $ A_{\mathfrak{p}} $, where $ \mathfrak{p} $ is a prime ideal of $ A $ and $ A_{\mathfrak{p}} $ is the localization of the ring $ A $ with respect to the multiplicative set $ S = A -\mathfrak{p} $ ? Thanks a lot.  N.B. : I have to tell you that I'm not very good at Algebra, so please, be more kind and generous in your explanation, and give me a lot of details about this subject please. Thank you.


The  spell allows one to teleport an object:     This spell instantly transports you and up to eight willing creatures of your choice that you can see within range, or a single object that you can see within range, to a destination you select. If you target an object, it must be able to fit entirely inside a 10-foot cube, and it can't be held or carried by an unwilling creature.   Suppose I want to send a chest full of items to someone far away. If I cast teleport on the chest to send it to them, do the contents go with it, or do they stay behind and spill out onto the floor where the chest used to be?  Does the answer change if, instead of a mundane container, I use a ?

There doesn't seem to be a weight limit on teleport anymore but, for the purposes of looting a dungeon, what is an object?  I can see how you can fill a chest and then teleport the chest and its contents. It is container and so all its contents are also teleported.  How about a 10' long table stacked with gear? Is the table also a container in the same way or would teleporting a table not teleport the tablecloth?


As of now I am clear with the concept of serialization as well as the use of serialVersionUid. I have a doubt and would appreciate you all in helping me understand this scenario. Tried a lots but not getting appropriate help from Google.  1)Sender serializes an Object with a serialVersionUid  2)Receiver deserializes the same Object.  Where does the serialVersionUid come from?I suppose JVM will extract it from the serialized class. So is the receiver expected to have the same class loaded in memory, before deserializing? If then why there would be an Exception because of serialVersionUid mismatch, since the receiver will extract the serialVersionUid from the serialized class. And if this is the case, then why would we require serialVersionUid at all?

Eclipse issues warnings when a serialVersionUID is missing.       The serializable class Foo does not declare a static final   serialVersionUID field of type long   What is serialVersionUID and why is it important?  Please show an example where missing serialVersionUID will cause a problem.


I just asked   After thinking about this for a while, I'm wondering why the C# Compiler emitted IL like that.  Why couldn't it say some IL like: "Call T's default constructor"?

When you have code like the following:   static T GenericConstruct<T>() where T : new() {     return new T(); }   The C# compiler insists on emitting a call to Activator.CreateInstance, which is considerably slower than a native constructor.   I have the following workaround:  public static class ParameterlessConstructor<T>     where T : new() {     public static T Create()     {         return _func();     }      private static Func<T> CreateFunc()     {         return Expression.Lambda<Func<T>>( Expression.New( typeof( T ) ) ).Compile();     }      private static Func<T> _func = CreateFunc(); }  // Example: // Foo foo = ParameterlessConstructor<Foo>.Create();   But it doesn't make sense to me why this workaround should be necessary.


After plain installation of Ubuntu 16.04 LTS gnome-software doesn't work. It has opened once with GUI, but installation of Unity Tweak Tool didn't finish.  When starting again, GUI doesn't come up. When opening from terminal, a warning appears, but the application GUI doesn't open.  $ gnome-software (gnome-software:7052): Gs-WARNING: failed to open plugin /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: cannot open shared object file: No such file or directory   Does anybody have same experience, and eventually, a solution?    According to the recommendation:  $ dpkg-query -S /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so gnome-software: /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so   Proposed reinstall of gnome-software did not help.    As workaround, use Synaptic Package manager and command line.

Ubuntu Software instantly crashes as I try to open it. Tried to access from terminal and gives the following error:  (ubuntu-software:5523): Gs-WARNING **: failed to open plugin /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: cannot open shared object file: No such file or directory