Pakistani Traveller in Australia, who wants to apply for USA visa
US tourism/business visa from non-resident country
Ubuntu boots from USB but get GRUB rescue after installation I can boot Ubuntu from USB, but when I took the USB stick out of the laptop and booted again, I got an error saying   Error: unknown filesystem. grub rescue&gt;   What can I do to fix this? Is it possible to write a Ping class in C# that will run within Windows 8 Metro environment? Mail App keeps popping up in the background in Mac OS Mojave When I am doing some work on my macbook pro, Mail app's main window keeps popping up in the background, it even pops up when I watch movies by interrupting full screen. This is so frustrating, I can't find out solution to this, googled and went to many discussion forums, no luck, suggestions that I found are very old and outdated. Has anyone faced similar issues or does anyone knows solution to this? I'm using uninstall.php for my plugin to delete all the traces my plugin did to a site on uninstall (delete). I did it in a good way, but even after the deletion there are some fields in the options table:   uninstall_plugins recently_activated _site_transient_update_plugins   in these options there are multiple values from other plugins too.  How can I take care of such traces, how can I remove all those traces too?  I checked WooCommerce and found they leave no traces after there deletion, if the "delete data" checkbox is checked.  How can I do so? Best practices for Feed restructuring in a social app database yum install error I can't run a yum command on my server without getting this:   CRITICAL:yum.cli:Config Error: Error accessing file for config file:///etc/yum.conf   This is what my yum.conf looks like:  # This is the fedorafaq.org yum.conf for Fedora Core 5. # # Note that you also need the rest of the configuration # as described at http://www.fedorafaq.org/#yumconf  [main] cachedir=/var/cache/yum keepcache=0 debuglevel=2 logfile=/var/log/yum.log exactarch=1 obsoletes=1 gpgcheck=1 plugins=1 metadata_expire=1800  # PUT YOUR REPOS HERE OR IN separate files named file.repo # in /etc/yum.repos.d   This is what my yum.repos.d looks like:  fedora.repo fedora-updates.repo fedora-updates-testing.repo   The permissions on those files are 0666 and it won't allow me to make them root:root How does virtualizing differ from emulation, in terms of structure? Someone told me that a virtualizing program like VirtualBox does not work like an emulator does in the sense that it doesn't emulate registers and uses the actual ones for the virtualized data that are on the CPU. Emulators must emulate the registers since they are mostly to execute software that depends on a foreign environment (e.g. a Genesis emulator needs Motorola 68000's registers and memory addresses, so developer must make these resources available as emulated registers).  My main question is, how is virtualization developed? How do we enable an entire OS to run as a process in a virtual machine, but get it to run independently while still making use of the actual CPU? I only know emulation, not virtualization, so if anyone could help that'd be nice!  PS: I am not asking solely what the difference is, but differences in how they run software. How can I pass a class member function as a callback? Quotient rings of Gaussian integers If $a_k\geq0$ is a decreasing sequence converging to $0$, do we have $\lim_{n\to\infty}\frac{\sum_{k=1}^n a_k}n = 0$? How do I debug permissions? How do I debug permissions in Drupal 7?  I use core reporting, error logs, devel module error logs, backtrace and node access permission block but sometimes it is not enough. What else should I check to find out why certain fields, views or blocks are not showing to a user?  I also found there is a  for reporting on permissions called  but it is not available for Drupal 7.  I am using various permission related third-party modules:   - devel node access 7.x-1.x-dev   - fast permissions administration 7.x-2.0  - organic groups access control 7.x-1.x   - profile2 group access 7.x-1.x-dev   - ur-node access 7.x-1.x-dev I have recently installed lubuntu 11.10 on my old laptop (acer aspire 5315 celeron) and observed that fan is not working properly on lubuntu side.I find it strange that it is working perfectly under window vista.   How could I solve this problem? Whats this white stuff on my board? I'm not an engineer, but my monitor stopped working yesterday (it just wouldn't display anything but still gets power) so I figured I'd like to take it apart and see what went wrong.  At the very least I'd get to see what the inside of a monitor looks like :).  Anyway, I took it apart, and also read around about my issue and it seems the capacitors have gone bad, at least some of them.  However, I also noticed some white elastic stuff all over the board.  Some of them are sticking two capacitors together and to the board, but I also see some from where power socket connects to the board.  My question is, what is the white stuff?  Should I replace all capacitors that have white stuff around it, and should I also replace the power socket part?  Or should I just replace the bulging capacitors and leave it at that?  UPDATE: How to send an SMS in iOS 10 Remove suggested apps option in iOS 10 Is there a word with phobia suffix for fear of waking others up? I usually come home after basketball at like 12:30 a.m. and at this time my mom and sister usually sleep (my Dad though is usually up). When I come home, I don't go to sleep right away and will sometimes eat or do something else. When I do so, I do it in stealth, so that I don't wake up anyone. I do out of two things, to be polite as I do not want to wake anybody up and also the fact that if I make a loud noise and wake my mom up, my mom will get mad and lecture me. Does this count as a phobia? In addition, if it does what would the name of it be. Prove that for any prime p, there is a complete set of mod p residues {q1, . . . , qp}, where each qi is prime. I used the theorem {a, a+n, a+ 2n, . . .} contains infinitely many primes if gcd(a, n) = 1 but haven't got much progress. Any comment will be helpful! Suppose $f(x)$ is linear i.e. $f(x + y) = f(x) +f(y) $ and monotone on $[-\infty, +\infty]$, then $f(x) = ax$, a real. Suppose $f(x)$ is linear i.e. $f(x + y) = f(x) +f(y) $ and monotone on $[-\infty, +\infty]$, then $f(x) = ax$, a real.  We know $f(0)=0$, and if one assumes differentiability it is quite easy.      But how does monotone make up for differentiability? Counting surjective functions We have $r$ objects and $n$ boxes. I have to count all the combinations possible if the objects and boxes could be both different. If that happens I can count the number of variations from $n$ to $r$ (number of functions between objects and boxes). I mean, $n^r$.  But if I have to count all the combinations possible if anyone of the boxes is empty ($r\ge n$). Now I have to count the surjective functions.  For example if I have $r$ objects and 1 box. The number of surjective functions is 1. Then, if I have $r$ objects and 2 boxes, the number of surjective functions is $2^r-2$. And finally if I have $r$ objects and 3 boxes, I will count $3^r-2\cdot[3\cdot2^r-3]$. How do I get the formula for $r$ objects and $n$ boxes? Actually snapping to pixel grid Does anyone know if there's a way to have Illustrator CC (2014) constrain control points to the pixel grid? I understand that "Align to pixel grid" makes it so that a shape will try to match the pixel grid, but the actual control points don't line up to said grid... The image I've attached illustrates my problem.