I tried to install gksu by running "sudo apt-get install gksu" command on terminal. But it returns -      Package gksu is not available, but is referred to by another package.   This may mean that the package is missing, has been obsoleted, or   is only available from another source      E: Package 'gksu' has no installation candidate
I downloaded the Upwork desktop App on ubuntu 18.04. When I open it with Gdebi package installer I saw this error:    I tried to install gksu manually via sudo apt install gksu but I got this error  Building dependency tree        Reading state information... Done Package gksu is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'gksu' has no installation candidate   How can I install this software on ubuntu 18.04 (I download it yesturday so it is the most recent version on upwork website) ?
Problems enabling Bitlocker on Surface Pro with Windows 8.1 Using a brand new Surface Pro (first generation) out of the box, installed current updates, then 8.1, and any further recommended updates after 8.1 was installed.   I've installed a two other things that don't seem connected to the issue: the Cisco Anywhere VPN client and Visual Studio 2013.  I'd like to enable Bitlocker, but during the verification step, the following error is displayed, with no options to continue:     This PC deosn't support entering a BitLocker recovery password during startup. Ask your   administrator to configure Windows Recovery Environment so that you can use BitLocker.   The "administrator" in this case is me, and I don't:   ... understand why this has happened ... know how to fix the issue, as if it's really necessary to make this change, what would I do? Prove that $\operatorname{trace}(A) = 0$ if and only if $A^2 = 0$. I have got a new installation of windows recently. Now when I do unpin items from taskbar that were there (IE, Edge, Explorer), they do come back after restart. A pinned chrome does not disappear though e.g.  Anything to fix this issue?  P.S. Just created a new user, and he has the same problem  P.P.S. Sign out is enough to get it back, no full restart needed Is it possible to insert multiple records in Salesforce using cURL at the same time? I would like to find all ellipses which contain 2 given points and has one focus at origin (zero). All in 2D plane.   There are several possible approaches but I'm not sure which is the best - both looks quite difficult to solve algebraically.   using polar equation relative to focus with $(R_1,\phi_1),(R_2,\phi_2)$, being coordinates of points $$ R_1 = \frac{a(1-e^2)}{1-ecos(\phi_1-\theta)} $$ $$ R_2 = \frac{a(1-e^2)}{1-ecos(\phi_2-\theta)} $$ then for given $\theta$ solve for semimajor axis $a$ and eccentricity $e$ using deffinition of elipse as a set of points of the same distance from both foci. Given 2 points of cartesian coordinates $(x_1,y_1),(x_2,y_2)$ and one focus in origin $(0,0)$. For each given distance parameter $L$ solve for coordinates of second focus $(x_f,y_f)$, $$ L = \sqrt{x_1^2 + y_2^2} + \sqrt{(x_1 - x_f)^2 + (y_1 - y_f)^2} $$ $$ L = \sqrt{x_2^2 + y_2^2} + \sqrt{(x_2 - x_f)^2 + (y_2 - y_f)^2} $$ I can also first rotate the coordinate system (or my input points) by given angle (which is my arbitrary parameter) and then use some simplified equation of ellipse which has major axis parallel to x-axis which has just 2 degrees of freedom. But even after this rotation I don't see much simplification of algebraic solution.    Or is there any better way?    The resulting equations are quite difficult to solve. I wonder if there is some trick to simplify it and make it more elegant.  Also, because I would later to implement it into computational code where it would be computed manytimes per second, I would prefer solution inf form which is fast to evaluate numerically ( prefferably without goniometric or any transcedental functions )    Why I'm interested ? - I need it for some optimalization of orbital transfers for spaceship orbiting the Sun. I asked also in physics.stackexchange, and people recomand me that I should rather go to math section. Italian keyboard: entering tilde (~) and backtick (`) characters without changing keyboard layout Here is what the layout of an Italian keyboard looks like:  As you can see, the curly braces, which are absolutely necessary to write code in any of C, C++, JavaScript, Java, Objective-C, and others, appear in purple in this picture. This is because while the other characters can be seen visually as printed characters on most Italian keyboards, these purple characters are actually usually not printed on the keyboard's keys. These characters, found in the upper right corners of the given keys, can usually be generated with the following key combinations: (RIGHT SHIFT or LEFT SHIFT) + (RIGHT CTRL or LEFT CTRL) + (Alt or AltGR) + ([ or ]) (Actually as the MSKLC application shows, SHIFT + AltGr + [ and SHIFT + AltGr + ] are enough to generate the curly braces.) Characters such as the at (@) sign (called 'chiocciola' in Italian) and the hash (#) key (called 'cancelletto' in Italian) found in the lower right hand corner of the keyboard can be generated easily as follows (AltGr + @) or (AltGr + #). Such characters are also fundamental to programming as they can, for instance, be found in CSS, namely with media queries and with selectors referring to the id html attribute. Upon further inspection, we can see that all of the US ASCII keyboard / programmer's keyboard are covered by the keys of the Italian keyboard, except for the following, which are the tilde, which is especially useful on the Linux command line and is used to refer to a user's home directory on such system, as well as the back-tick (`), also known as the back-quote, which is also very useful on the Linux shell when we want to turn the output of a command into a command-line input. So, here comes the question: With all those empty upper-right hand corners of keys, why isn't there a better way of generating these characters, perhaps through a CTRL-ALT-SHIFT modifier key combination? All I've been able to find regarding generation of these characters are the following ALT-codes:  ALT code 96  corresponds to ` ALT code 123 corresponds to { ALT code 125 corresponds to } ALT code 126 corresponds to ~  and to generate a character via an ALT code, you make sure that the NumLock key on your keypad is toggled on, hold down the ALT key, enter the keycode, and release the ALT key. ALT code are documented at:  If someone knows of a better way of inserting these characters from an Italian keyboard without switching the keyboard layout in the Control Panel, then please let me know. Thanks. Do the druid's uses of the Wild Shape feature recharge while still in Wild Shape?  Say a 10th-level Circle of the Moon Druid spends two uses of Wild Shape to transform into an Air Elemental, whose form she can stay in for the next 5 hours. After 2 hours, she takes a short rest, but does not drop the Wild Shape. She has another couple of hours to keep the Air Elemental form.  My main concern: Does she get her two uses of Wild Shape back with that short rest? Or, does she have to drop the Air Elemental form first before taking the short rest to recharge Wild Shape? Writing XML to a file without overwriting previous data Cauchy-Product of non-absolutely convergent series While grading some basic coursework on analysis, I read an argument, that a Cauchy product of two series that converge but not absolutely can never converge i.e. if $\sum a_n$, $\sum b_n$ converge but not absolutely, the series $\sum c_n$ with $$c_n= \sum_{k=0}^n a_{n-k}b_k$$ diverges.  Although we didn't have any theorem in the course stating something like this, it made me wonder if it was true. Send mail without MFMailComposeViewController How force Chrome to use google.com search engine without https Rendered image doesn't show what Rendered Viewport shows... (pictures below) Quantum Entanglement - What's the big deal? Bearing in mind I am a layman - with no background in physics - please could someone explain what the "big deal" is with quantum entanglement?  I used to think I understood it - that 2 particles, say a light-year apart spatially, could affect each other physically, instantly.  Here I would understand the "big deal".  On further reading I've come to understand (maybe incorrectly) that the spatially separated particles may not affect each other, but in knowing one's properties you can infer the other's.  If that it the case, I don't see what the big deal is... 2 things have some properties set in correlation to each other at the point of entanglement, they are separated, measured, and found to have these properties...?  What am I missing? Is it that the particles properties are in an "un-set" state, and only when measured do they get set?  (i.e. the wave-function collapses).  If this is true - why do we think this instead of the more intuitive thought that the properties were set at an earlier time? Suppose we have two twins travelling away from each other, each twin moving at some speed $v$:    Twin $A$ observes twin $B$’s time to be dilated so his clock runs faster than twin $B$’s clock. But twin $B$ observes twin $A$’s time to be dilated so his clock runs faster than twin $A$’s clock. Each twin thinks their clock is running faster. How can this be? Isn’t this a paradox? How do I resume a release upgrade? Yesterday I started the upgrade from 12.10 to 13.04, but I interrupted it because it was taking too long. Now if I restart it, it doesn't proceed.  Is there any possibility to clean the mess it left when I interrupted it and make a clean restart of this update? Prevent abstract environment to reset pagenumbering URL line breaks with biblatex How do I allow long URLs to have line breaks at any point. This is in the bibliography not the main text. I am trying to save space so don't want extra spaces to be added to make it only break at slashes, for example, as it does by default.  I am using biblatex+biber. $f$ differentiable except in $1$ point Boot problem after hanging and manual power off ( Stopping User Manager for UID 121... ) My Ubuntu stalled while running Android's VirtualBox version, so I powered off the system. But after reset it stopped during this line:     Stopping User Manager for UID 121... _ So i googled it and have read  question and tried these steps:  Boot into Recovery Mode, drop to a root shell, and follow the steps below:   Run mount -o rw,remount / to mount the drive in Read-Write mode.Run sudo apt-get purge nvidia-* to purge the NVIDIA driver.You may also need to purge xserver-xorg and reinstall it, which will  require you to enable networking in Recovery.Reboot. You may have to add the nouveau.modeset=0 flag in GRUB to boot properly (Check my Q&amp;A for specifics).   You should be past the screen flicker and be at your desktop.  But in doing this step:  Now reinstall the NVIDIA drivers the proper way:sudo apt-get install  nvidia-367 (or 340, 352, 364, 370, whichever works).Reboot again.  I found i have not internet, and my WiFi is not in ifconfig list!!! By running :     Iw wlp2s0 scan   I get :  N180211 not found I also search for it and not understand why WiFi gone off. Now i thinking to use live USB of ubuntu to download NVIDIA and xserver-xorg and the install the by dpkg command during tty2. Update : in Ubuntu live i have this settings :  ubuntu@ubuntu:~$ sudo lshw -c video   *-display                         description: VGA compatible controller        product: HD Graphics 620        vendor: Intel Corporation        physical id: 2        bus info: pci@0000:00:02.0        version: 02        width: 64 bits        clock: 33MHz        capabilities: pciexpress msi pm vga_controller bus_master cap_list rom        configuration: driver=i915 latency=0        resources: irq:129 memory:a2000000-a2ffffff memory:b0000000-bfffffff ioport:6000(size=64) memory:c0000-dffff   *-display        description: 3D controller        product: GM108M [GeForce 920MX]        vendor: NVIDIA Corporation        physical id: 0        bus info: pci@0000:03:00.0        version: a2        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress bus_master cap_list        configuration: driver=nouveau latency=0        resources: irq:128 memory:a3000000-a3ffffff memory:90000000-9fffffff memory:a0000000-a1ffffff ioport:3000(size=128)  and ubuntu@ubuntu:~$ sudo lshw -c display   *-display                         description: VGA compatible controller        product: HD Graphics 620        vendor: Intel Corporation        physical id: 2        bus info: pci@0000:00:02.0        version: 02        width: 64 bits        clock: 33MHz        capabilities: pciexpress msi pm vga_controller bus_master cap_list rom        configuration: driver=i915 latency=0        resources: irq:129 memory:a2000000-a2ffffff memory:b0000000-bfffffff ioport:6000(size=64) memory:c0000-dffff   *-display        description: 3D controller        product: GM108M [GeForce 920MX]        vendor: NVIDIA Corporation        physical id: 0        bus info: pci@0000:03:00.0        version: a2        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress bus_master cap_list        configuration: driver=nouveau latency=0        resources: irq:128 memory:a3000000-a3ffffff memory:90000000-9fffffff memory:a0000000-a1ffffff ioport:3000(size=128)  and : ubuntu@ubuntu:~$  cat /etc/os-release NAME=&quot;Ubuntu&quot; VERSION=&quot;18.04.3 LTS (Bionic Beaver)&quot; ID=ubuntu ID_LIKE=debian PRETTY_NAME=&quot;Ubuntu 18.04.3 LTS&quot; VERSION_ID=&quot;18.04&quot; HOME_URL=&quot;https://www.ubuntu.com/&quot; SUPPORT_URL=&quot;https://help.ubuntu.com/&quot; BUG_REPORT_URL=&quot;https://bugs.launchpad.net/ubuntu/&quot; PRIVACY_POLICY_URL=&quot;https://www.ubuntu.com/legal/terms-and-policies/privacy-policy&quot; VERSION_CODENAME=bionic UBUNTU_CODENAME=bionic  please consider the above three output has token form Ubuntu live flash system. What do you suggest and what do you think about reason of this failure? Also do you think it must be reported by me in ubuntu site, or it will be done automatically? Thanks. Do virtual particles actually physically exist?