Why on assigning value to a specific index in 2d array of python, changes all the index with the value?  def binomial_coff(n, k):     inter = [[-1]*(n+1)]*(n+1)     for i in range(n+1):         inter[i][0] = 1         inter[i][i] = 1     print(inter)     for i in range(2, n+1):         for j in range(1, i):             inter[i][j] = inter[i-1][j-1] + inter[i-1][j]             print(i, j, inter[i][j], inter[i-1][j-1], inter[i-1][j])     print(inter)     return inter[n][k]   I had tried the block in jupyter notebook and repl.it

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?


If $A$ and $B$ are sets, and $A$ is an element of $B$ does this mean that every element of $A$ is in $B$, or some element of $A$ is in $B$, still makes $A$ element of $B$?

I have to prove a few different statements.   The first is if $A \subset B$ and $B \subset C$ then prove $A \subset C$. This one is fairly straight forward, but I'm stuck on how the next one differs.   Prove that if $A \in B$ and $B \in C$ then $A \in C$.   I don't really understand how to put this in logical symbols. I've only seen $a \in A$ written out but never "a set $A$ is an element of a set $B$".  Here's what I have for a proof at this point, assuming I understand what "a set $A$ is an element of a set $B$" means: suppose $A \in B$ and $B \in C$.  Then $A \in C$.


Let we have the following sequence $$x_n=\left(\frac{n^n}{n!}\right)^{\frac{1}{n}}$$ Determine if  the following sequence is convergent  and find its limit

I'm trying to find  $$\lim_{n\to\infty}\frac{n}{\sqrt[n]{n!}} .$$   I tried couple of methods: Stolz, Squeeze, D'Alambert  Thanks!  Edit: I can't use Stirling.


I have a set of commands that i am executing through java. I stored them in .bat file and then executing through java. When i run bat file through command prompt it executes but when i execute it through java, only 1-2 commands execute and program exits. Please suggest me the solution for this.   Please suggest me the jar file too if any other command referenced  Code:  public static String cmdExec(String cmd) throws IOException {          Process p = Runtime.getRuntime().exec(cmd); }

In my Java application, I want to run a batch file that calls "scons -Q implicit-deps-changed build\file_load_type export\file_load_type"  It seems that I can't even get my batch file to execute. I'm out of ideas.   This is what I have in Java:  Runtime.    getRuntime().    exec("build.bat", null, new File("."));   Previously, I had a Python Sconscript file that I wanted to run but since that didn't work I decided I would call the script via a batch file but that method has not been successful as of yet.


Apologies if this question has already been answered somewhere already.   Is there somewhere I can view a list of tags which have been burninated/blacklisted from certain sites?  UPDATE:  I'm building a script which tags documents with relevant Stackoverflow tags. I was seeking a way of excluding at least some meta/unhelpful/ambiguous tags from my corpus of tags, to get rid of some noise in my data. Shadow Wizard's suggestion basically provides what I need.

Would it be possible to make the list of blacklisted tags public?  The list would help establish precedence when determining if a tag should be put forward for burnination. This will simplify the task of proposing and evaluating a .  For example, when I  come across a tag I believe shouldn't be used, I  in a hope of finding burninated tags that are similar. If I find something similar, I submit a burnination request; otherwise I simply clean up the tags and move on. Having a definitive list will substantially speed up this process.


Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


How can I get the right answer to the 3rd squirrel question ("how many candies" etc.), as I am gaining 21 of them each second and I am not very good at mental calculus? ;)

I encountered The Squirrel at "A tree."              |   |                                                                         |   |                     "   Hello, I'm The                        |             |                        Squirrel. I can                        |             |                      provide you candies,                     |             |                      and lots of things.                                    |                      I know how much you                                    |        _.-'''-,      love candies. But I                                    |      .'        `\     feel alone in this                                    |     /           /          forest.       "                         |        |    /      .--^_^                                                   |        |    |     /  C ,,\                                                           |    |    |   \  _.)                           ___                            |     \   |   /  \                   ____.----'.-'                            |      '-, \./ \)\)               .-' --  __.-'                   |            \        `-/   );/           ___/  - _.-'                        |             \_________''--'-'________.-' --    /                            |              -   --        -  -     -     __.-'                                              -    --    -     --   --  /                                                 _________________________.-'                                 He asks you some questions. What are the correct answers, and what is the reward for getting them correct?


Me getting a hangover is nothing like her getting a hangover.   -     I'd rather contemplate you singing than him singing.   Is this grammatically correct?

I assume that the following sentences are grammatically correct:   He resents your being more popular than he is. Most of the members paid their dues without my asking them. They objected to the youngest girl's being given the command position. What do you think about his buying such an expensive car? We were all sorry about Jane's losing her parents like that.   I'm still getting used to this possessive gerund structure. It sounded so weird to me at first. Is the structure used in both formal and informal contexts? Are there any alternative structures that result in the same meaning and are more frequently used? (Examples taken from )


Consider the following 3D potential: $$V(r)=\begin{cases}-V_0 \ \ \ \ \ \ & r \leq a\\ 0 &r > a\end{cases}$$ we want to find the eigenfunctions for $\ell=0$, in particular we are interested in the bounded states. Of course we get: $$\left[\frac{p_r}{2m}+V(r)\right]R(r)=ER(r)$$ and so with: $$u(r):=rR(r)$$ $$-\frac{\hbar ^2}{2m}u(r)+V(r)u(r)=Eu(r)$$ so for bounded states we get: $$u(x)=\begin{cases}A\sin{\alpha r}+B\cos{\alpha r} \ \ \ \ \ \ & r \leq a\\Ce^{-\beta r} & r > a\end{cases}$$ I kind of breeze trough this introductory part, I hope it's all clear. Now I have a problem: I would like to impose continuity and continuity of the derivative in $a$, to get more information about the shape and the energy of the solution, in particular I would like to find the number of bounded state in function of the value of $V_0$; but the calculation that derives from this procedure seems pretty hard. But: looking for the resolution for this exercise I found out that $u(r)$ must be $0$ in $r=0$, and this of course implies that in the first region the function becomes a $\sin$. $$u(x)=\begin{cases}A'\sin{\alpha r} \ \ \ \ \ \ & r \leq a\\Ce^{-\beta r} & r > a\end{cases}$$ and this, other than being the correct system of equations, greatly simplify the calculations. However: I don't understand why $u(r)$ must be zero in $r=0$. So my question is: Why must $u(r)$ be zero in $r=0$?

I was playing around with a 3-D potential $V$ such that $V_{(r)} = 0$ for $r<a$, and $V_{(r)} = V_0>0$ otherwise. By using the Schrödinger Equation, I showed that: $$\frac{-\hbar}{2m}\frac{1}{r^2}\frac{d}{dr}\bigl(  r^2\frac{d}{dr}\bigr)\psi = E\psi$$  I then used the substitution $\psi_{(r)}=f_{(r)}/r$ and $k=\sqrt{2mE}/\hbar$ to get: $$\frac{1}{r}\frac{d^2f_{(r)}}{dr^2}=-\frac{k^2}{r}f_{(r)} \tag{I}$$  which describes the wavefunction $\psi_{(r)}=f_{(r)}/r$ inside the sphere. Hence, the differential equation has the domain $0\leq r<a$, and I cannot multiply both sides by $r$. This is unfortunate, because there is a similar equation for the outside of the sphere: $$\frac{1}{r}\frac{d^2f_{(r)}}{dr^2}=\frac{k'^2}{r}f_{(r)}$$ As this is outside the sphere, I can multiply both sides by $r$ to get a familiar differential equation that can be solved easily: $$\frac{d^2f_{(r)}}{dr^2}=k'^2f_{(r)}$$  If I do the same thing to $(I)$, I obtain the equation for simple harmonic motion, but substituting the solution back into $(I)$ as a sanity check gives a division by zero when evalutating for $r=0$. After that, I tried a number of substitutions to make $(I)$ have a more recognisable form - to no avail. Then I had the idea of multiplying my trial solution by some other function of $r$ so that upon substitution into $(I)$, the evaluation of $r=0$ doesn't give an infinity... but I don't know quite how to do that...  Long story short..... my question is: what trick do I need to get a meaningful solution to $(I)$?


I am new to vi editor.I am using to edit one of my file. But when i opened it through vi i can't edit it properly. when pressing arrowkeys it inserts alphabets(toparrow-A,bottomarrow-B,leftarrow-D,rightarrow-C).I dont know what is happening?  How to solve this problem?

Recently I installed ubuntu in my laptop for using c programming. but when I open the terminal and typed vi test.c, It open it but it will not work properly. when i pressed backspace it will not work and when i press arrow key it will print some alphabets. What will i do to work properly. please anybody help for this related problem. thank you


$f(x)$ is defined on$(0,\infty)$, and $\frac{f(x)}{x}$ is monotone decreasing, how to prove  $\forall a>0,b>0$ $f(a+b)\leq f(a) +f(b)$. Thanks pretty much in advance

If $\frac{f(x)}{x}$ is decreasing in $(0,\infty)$, prove that $f(a+b) \leq f(a) + f(b)$ for $a,b >0$


The post editor image uploader supports drag-and-drop and it also supports pasting an image directly into the window.  The chat uploader does support drag-and-drop (as long as you drop directly into the filename text box) but does not support pasting an image into the window.  Can chat get the same  that the sites have?

We've already got it for questions and answers. Let's get it for chat too! Most of my images come from screen captures so this would be really great!


In the Harry Potter world, we see many forms of continuation beyond death -- ghosts, portraits, and even newspaper clippings appear to retain some part of the personality of the original person. However, they all appear to be mere echoes of the original.  Despite this, ghosts and portraits continue to learn and act as the original, and thus may be considered indistringuishable from the outside.  Enter the Resurrection Stone. This Hallow supposedly brings back the souls of the dead, allowing discussion (and tearful moments for our hero, who then... purposefully loses it in a forest).  However realistic these spirits are, they don't appear to have any special features that differentiate them from the other magical constructs, so how does one know that they are the actual, unique soul of the original person? Granted the nature of the Hallows -- being either unique artifacts of unique power, or merely super well enchanted items with standard powers, it would be fitting for the "spirits" to merely be duplicates, as in the case of paintings and ghosts.  Is there any proof (via word of god, most likely) that the Resurrection Stone actually brings back the actual spirit of the person called?

Dumbledore himself said that no spell can reawaken the dead. Isn't that the main objective of the resurrection stone? If one can't reawaken the dead then what is the use of the stone? Surely then one of the Hallows is flawed?


I'm trying to prove (using induction) that:  $$\sum_{k=1}^n \frac{1}{n+k} = \sum_{k=1}^{2n} \frac{1}{k}(-1)^{k-1}.$$  I have found problems when I tried to establish an induction hypothesis and solving this because I've learned to do things like:  $$ \sum_{k=1}^{n+1} \frac{1}{k}= \sum_{k=1}^{n}  \frac{1}{k} + \frac{1}{n+1}.$$  But, in this case, $n$ appears in both parts of summation and I have no idea  how make a relation with    $$\sum_{k=1}^n \frac{1}{n+k}  $$ and $$\sum_{k=1}^{n+1} \frac{1}{n+1+k}.  $$   Because I've seen tha, the case with "$n+1$" should be like:   $$\sum_{k=1}^{n+1} \frac{1}{n+1+k} = \sum_{k=1}^{2n+2} \frac{1}{k}(-1)^{k-1}$$  and I cant find a connection between  $$\sum_{k=1}^{n+1} \frac{1}{n+1+k} $$ and $$\sum_{k=1}^{n} \frac{1}{n+k}.$$  Could anyone help me with this?

The title pretty much summarizes my question. I am trying to prove the following:  $$\displaystyle \forall N \in \mathbb{N}: \sum^{2N}_{n=1} \frac{(-1)^{n-1}}{n} = \sum^{N}_{n=1} \frac{1}{N+n}.$$  I tried proving this using induction. Starting with the base case $N = 1$:  $$\displaystyle \sum^{2}_{n=1} \frac{(-1)^{n-1}}{n} = \frac{1}{1} + \frac{-1}{2} = \frac{1}{2} = \frac{1}{1+1} = \sum^{1}_{n=1} \frac{1}{N+n}.$$  My problem is the inductive step for $N+1$, starting with  $$\displaystyle \sum^{2(N+1)}_{n=1} \frac{(-1)^{n-1}}{n} = \sum^{N+1}_{n=1} \frac{1}{(N+1)+n}.$$  And now my problem:  \begin{align} \sum^{2(N+1)}_{n=1} \frac{(-1)^{n-1}}{n} &\Leftrightarrow \sum^{2N}_{n=1} \frac{(-1)^{n-1}}{n} + \sum^{2}_{n=1} \frac{(-1)^{n-1}}{n} \\[1em] &\underset{\Leftrightarrow}{\text{ind. hyp.}} \sum^{N}_{n=1} \frac{1}{N + n} + \sum^{2}_{n=1} \frac{(-1)^{n-1}}{n} \end{align}  Is this the correct start, and if so, how do I continue?


Maybe an illegal question. Sorry.  Having read that a photon has both wave and a light characteristics it is natural for a novice like myself to wonder "what is the amplitude? "  Naturally I have looked on wiki and other sources and there are a number of answers some of which appear not so much to contradict one another of varying opinions of which is the most meaningful in physics.   I seem to get a higher number of physics sources saying the amplitude depends on how many photons you have and if you have one the question has no meaning.  Of course I have not idea if this is accurate or how one would even test this.   Maybe there are some physics teachers in the audience that can give me a layman's intuition with a little math tossed in.

Referring to this question   I'm curious about what is a amplitude of a light wave. Especially for light from a thermic source.


I have a  with shapelength and shapearea, and would like to convert to WGS84 to use with ggmap.    Eventually, I would like to get plot google map of individual regions of the shapefile, and overlay it with other date  What can I use in R program to do this, i.e. convert to WGS84?

I have a number of shapefiles in different CRSs (mostly WGS84 lat/lon) that I'd like to transform into a common projection (likely Albers Equal Area Conic, but I may ask for help on choosing in another question once my problem gets better-defined).  I spent a few months doing spatial stats stuff in R, but it was 5 years ago.  For the life of me, I cannot remember how to transform an sp object (e.g. SpatialPolygonsDataFrame) from one projection to another.  Example code:  P4S.latlon <- CRS("+proj=longlat +datum=WGS84") hrr.shp <- readShapePoly("HRR_Bdry"), verbose=TRUE, proj4string=P4S.latlon)  # Shapefile available at  #   http://www.dartmouthatlas.org/downloads/geography/hrr_bdry.zip  #   but you must rename all the filenames to have the same  #   capitalization for it to work in R   Now I have a SpatialPolygonsDataFrame with appropriate projection information, but I'd like to transform it to the desired projection.  I recall there being a somewhat unintuitively-named function for this, but I can't remember what it is.  Note that I do not want just to change the CRS but to change the coordinates to match ("reproject", "transform", etc.).  Edit  Excluding AK/HI which are annoyingly placed in Mexico for this shapefile:  library(taRifx.geo) hrr.shp <-    subset(hrr.shp, !(grepl( "AK-" , hrr.shp@data$HRRCITY ) |                                      grepl( "HI-" , hrr.shp@data$HRRCITY )) ) proj4string(hrr.shp) <- P4S.latlon


I have a kind of problem. I am trying to hard-link all my dotfiles [files that customize certain apps] in one folder for ease of use, called ~/dotfiles/ , but multiple programs that I have, have entire directories for that. Some are in .config, some just have a directory at the home folder, so I tried to check whether I could hard-link a directory.  After looking into it, I saw all the problems, warning, etc. about hard-linking directories, and why it's a giant nono. So I'm fully discouraged from hard-linking directories, however, I still need to do it somehow.  I found a way around this, which is by creating directories within ~/dotfiles/ and hardlinking the contents of the directories INTO those created ones, but that immediately hit a brick wall called boredom and repetition. A bunch of programs had multiple dirs, some with nested directories, and I didn't feel like spending a lot of time creating directories just so that I'm able to hard-link config files.  All I'm wondering is this. Is there a way to simulate a hard-link?   For example, I have a directory called ~/Testconfig/, and I want to hard-link it into ~/dotfiles/. Theoretically, a hardlink would place a directory in ~/dotfiles/ with all of it's contents, including its files and its nested directories.  Is there a way to achieve that without actually creating a hardlink?  My idea is that a bash script could be made that automates all of this, but I know next to nothing about bash, so that would be difficult.

The example below is simplified to show the core of the problem, not the problem itself(my file tree is more complicated than that).  Let's say that I have two files I want to back up; one in ~/somedir/otherdir, the other in ~/otherdir/somedir/. I want to backup files from both directories in one git repository. How can I do this? Soft links only carry information about where file is stored, not the actual file, whereas hard links are somewhat foreign to me. Is this a case where hard links should be used?  Clarification: I want to use git because of four reasons: I want to store dotfiles/scripts/configurations that are text files and keep track of changes over time, I know git, I have a private git repository I could use to store them, and I want to be able to share these files across multiple PCs.


Let $( | )$ be the standard inner product  on $\mathbb{R^2}$ , and let $T$ be the linear operator $T(x_1,x_2)=(-x_2,x_1)$. Now $T$ is 'rotation through $90°$' and has the property that $(\alpha |T\alpha)=0$ for all $\alpha$ in $\mathbb{R^2}$ . Find all inner products $[   |   ]$  on $\mathbb{R^2}$ such that $[\alpha | T\alpha]=0$ for each $\alpha$.  My Attempt since $\alpha\in \mathbb{R^2}$. So let us assume $\alpha=(x,y)$ then $(\alpha |T\alpha)=((x,y) | T(x,y))=-xy+xy=0$ where $x,y\in \mathbb{R}$. So I think we have as many inner product on $\mathbb{R^2}$ as positive real numbers in $\mathbb{R}$. Is it correct? Any help or hint will be appreciated.

Suppose that we are dealing with the real field $\mathbb{R}$ and we define $T:\mathbb R^2\to\mathbb R^2$ by $$T(u,v):=(-v,u).$$ It is trivial to see that $\langle(u,v),T(u,v)\rangle = 0$ for all $u, v \in \mathbb{R}$, where $\langle \, \cdot \, , \, \cdot \, \rangle$ is the standard inner product.  A question in Hoffmann-Kunze asks us to define all possible inner products $[ \, \cdot \, , \, \cdot \, ]$ such that $[\alpha, T(\alpha)]=0$ for all $\alpha\in\mathbb R^2$ and $T$ is as above. How does one find all such inner products?


I upgraded to Ubuntu 18.04.  I have Dbvis (DbVisualizer - database editortu) installed, but now it will not work.  I get the following when I run dbvis from the command-line:  java.awt.AWTError: Assistive Technology not found: org.GNOME.Accessibility.AtkWrapper at java.awt.Toolkit.loadAssistiveTechnologies(Toolkit.java:807) at java.awt.Toolkit.getDefaultToolkit(Toolkit.java:886) at java.awt.Toolkit.getEventQueue(Toolkit.java:1736) at java.awt.EventQueue.invokeLater(EventQueue.java:1294) at javax.swing.SwingUtilities.invokeLater(SwingUtilities.java:1295) at com.onseven.dbvis.DbVisualizerGUI.main(Z:594) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at com.exe4j.runtime.LauncherEngine.launch(LauncherEngine.java:85) at com.install4j.runtime.launcher.UnixLauncher.main(UnixLauncher.java:62)  :~$ java -version openjdk version "10.0.2" 2018-07-17 OpenJDK Runtime Environment (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.1) OpenJDK 64-Bit Server VM (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.1, mixed mode)  :~$ javac -version javac 10.0.2   Any thoughts on how to resolve this? Thanks for any help.

$ java -jar aprof-plot.jar Exception in thread "main" java.awt.AWTError: Assistive Technology not found: org.GNOME.Accessibility.AtkWrapper     at java.awt.Toolkit.loadAssistiveTechnologies(Toolkit.java:807)     at java.awt.Toolkit.getDefaultToolkit(Toolkit.java:886)     at java.awt.Toolkit.getEventQueue(Toolkit.java:1734)     at java.awt.EventQueue.invokeLater(EventQueue.java:1264)     at aprofplot.Main.newWindow(Main.java:33)     at aprofplot.Main.main(Main.java:359)   Possible explanations I saw here was to install Java-access-bridge. But I am unable to install libaccess-java-bridge.


I've read than in 2014, Google will reward HTTPS sites in ranking. In the other hand, I have also read that HTTPS is slower than HTTP.  So, in my site, I just have a few HTTPS pages, so my question is: Should I put all my site in HTTPS, or just the few pages I need?

I would like to set up a new business site. I plan to direct www.example.com to example.com and only use that domain. My plan is also to only use HTTPS and not HTTP.   Does this affect the SEO for the site? E.g. do Google put lower or higher rank for sites that is only available via HTTPS?


John is feeling well.   John is feeling good.      "well" is an adverb and "good" is an adjective.  Is #2 grammatically correct at all or is it ok to construct Subject + Linking Verb + Adjective    where adjective is describing the subject?  If #2 is grammatical, what is the difference between the two sentences?

Most of the time, I use good and well interchangeably. However, on many occasions I would find well or good a misfit. Please suggest the proper usage.


I found some sentences like "Most people work by day and sleep by night." Is it appropriate to use these sort of wordings like "sleep by night"?  If so, what's difference between "sleep by night" and "sleep at night"?

say by has the meaning of      6. indicating the period in which something happens: ‘this animal always hunts by night’   Then do we need to say, ‘Why does the sky glitter by night?’ And can’t we say, ‘Why does the sky glitter at night?’?   If we can use both, what’s the difference between the two?


In the Android App, one cannot distinguish between normal posts abs community wiki ones. Firstly example, below is a screen shot of a question from the mobile view, and the same from the app:    Screenshot from app:    Why is there an anomaly like this? This should be edited as fast as possible.

I'm requesting that Community Wiki questions and answers display differently than non-wiki ones or otherwise indicate that they are wikis.  Example CW post in browser:    How the same post looks in the app:    One can clearly see it is impossible to distinguish between CW and regular posts in the Android app.


On any 18.10 application when I have an open window which is very wide and I then open a new window of same application the new window will auto maximize its size.   How can I disable this auto-maximize on new window creation? If it's possible, I wish to disable any type of auto-maximize window behavior  I tried following suggested solution from 18.04 which fails to work on 18.10 :      Open Terminal and run  gsettings set org.gnome.mutter edge-tiling false       You may also have to run  gsettings set org.gnome.shell.overrides edge-tiling false

Each time I open any application, it zooms to fill-up the entire desktop and so I am always forced to use "Unmaximize" using Alt+Space menu.


I was trying to solve the problem asked in . The answer that had been accepted didn't work for me, but I eventually an answer that worked for me. I would like to add my answer to the original question to help other people like me who come across this question. However, I can't find the answer question button. Is there something I'm missing?

Questions can be closed or marked as duplicates.  What does it mean for a question to be "closed"? What does it mean for a question to be marked as a "duplicate"? Who can close a question? What are the reasons for closing a question ? Is closure the end of the road for a question? When are closed questions eligible for deletion?   Related        For more information, see "" in the .


I'm importing stuff from a Drupal site that has a couple of alias URLs:  /node/123 /my-alias-node-title   My new site is a very simple CMS handmade in PHP by me as a practice.  In the new system, the URL for each page has this format:  /contenido.php?id=30   I've managed to rewrite all traffic to a PHP file (reenvio.php) using a rewrite rule:  My .htaccess file is like this:  Options +FollowSymLinks RewriteEngine On RewriteCond %{SCRIPT_FILENAME} !-d RewriteCond %{SCRIPT_FILENAME} !-f RewriteRule ^.*$ ./reenvio.php   My PHP file consults the database and do the redirects. So, when users type /node/123 they get redirected to /contenido.php?id=30  Is that a problem from an SEO perspective? My pages will still link to URLs like /my-alias-node-title but my users will end up seeing /contenido.php?id=30   Is there any way to address this issue in a different, better way? Because after all, the user still sees the ugly URL, so I assume Google sees it as well.

Simple question  What is better:  http://www.example.com/product/123/subpage/456.html   or  http://www.example.com/product?123/subpage/456   As far as I know they would rank the same SEO wise, but my SEO knowledge might be a little off. Also the last one seems to be easier and cleaner to implement on my end.  Please explain to me which is better and for what reasons.


I'll cut right to the chase: I am trying to parse a string with strtold to get a long double, but it is giving me the wrong value. Specifically, I am parsing the number 97777777777777777777777777777777777777.0, but strtold parses it as 97777777777777777779155292002375958528.000000.  I check errno, HUGE_VALL, and end_ptr, but errno does not report an error, my number is no where near HUGE_VALL, and end_ptr is empty. I've been trying to debug this for a while, but I'm at my wits end.  I don't think this is a bug in strtold because the same problem happens if I take out some 7's from the number.  This code works for small numbers, like 97.  I would greatly appreciate it if someone could help me here.  The code:  #include <stdio.h>          // printf #include <stdlib.h>         // strtold #include <errno.h>          // errno #include <string.h>         // strerror #include <math.h>           // HUGE_VALL  int main(int argc, char** argv) {     char* theNum = "97777777777777777777777777777777777777.0";     printf("HUGE_VALL = %Lf\n", HUGE_VALL);    // just to make sure I'm not insane     char* endbuf;     errno = 0;     long double n = strtold(theNum, &endbuf);     if (n == HUGE_VALL && errno != 0)     { printf("strtold err: %s\n", strerror(errno)); }     else     { printf("strtold status: %s\n", strerror(errno)); }     printf("the number: %Lf\n", n);     printf("endbuf: %s\n", endbuf);     return 0; }   Output:  HUGE_VALL = inf strtold status: Success the number: 9777777777777777777835998445568.000000 endbuf:    Some details:  64-bit Red Hat Linux: (uname -i says x86_64)  Running Red Hat Enterprise Linux Server release 7.1 (Maipo)  gcc (GCC) 4.8.3 20140911 (Red Hat 4.8.3-9)  I'm compiling using c99: c99 primefactors_test.c ../../src/primefactors.c -o primefactors_test -I../../include/ -O3 -lm  I also tried a simpler compile statement where I take out all of the unneeded dependencies: c99 primefactors_test.c -o primefactors_test -lm

In follow up to , it appears that some numbers cannot be represented by floating point at all, and instead are approximated.  How are floating point numbers stored?  Is there a common standard for the different sizes?  What kind of gotchas do I need to watch out for if I use floating point?  Are they cross-language compatible (ie, what conversions do I need to deal with to send a floating point number from a python program to a C program over TCP/IP)?


A = [['2','4'],['1','2']] B = [] for i in A:   for x in A[i]:     B.append(x) print(B)      TypeError: list indices must be integers or slices, not list   I expected to use two loops to iterate all the elements in A. A[i] is the first list element in A. And the second for loop should iterate the A[i] and append all the elements into B. However, the error says must be integers or slices, not list. I don't know why i can not iterate elements in A[i]. I am very appreciate if anyone can help.

What's the difference between the list methods append() and extend()?


Considering the potential energy of interacting particles, how does covalent bonding lower the energy of the system?

why in a covalent bond are "the bonded electrons are in a lower energy state than if the individual atoms held them at the same proximity"?  Also is it correct that " I think when you start pushing two molecules together orbitals between the two start overlapping - forming covalent bonds?"  Essentially why are covalent bonds made? A QM description would be nice but I don't really know QM so a somewhat reduced-to-classical explanation of the QM explanation would also be nice!


For a binary string of length $n$ that has at most $k$ $1$'s, it makes complete sense that the total number of possibilities is  $\sum_{j=0}^{k} \binom{n}{j}$. But I am struggling to wrap my head around  $\sum_{j=0}^{k} \binom{n-1-j}{k-j}2^j$ being an equivalent way of counting. I can see where the $2^j$ comes from but I can't quite see the $n-1-j$ part. Can someone could give me some guidance on what that method of counting is actually saying?

Give a combinatorial proof for this identity for non-negative integer $k$ and $n$ such that $0 \leq k < n$   $$\sum_{j=0}^{k} \binom{n}{j} = \sum_{j=0}^k \binom{n-1-j}{k-j}2^j$$   My attempt: I tried to reduce this identity. Since $k,n$ are nonnegative integer and $k<n$ then I can change the upper limit into  $$\sum_{j=0}^{n-1} \binom{n}{j} =2^n-1 \quad \text{and} \quad \sum_{j=0}^{n-1} \binom{n-1-j}{n-1-j}2^j = \sum_{j=0}^{n-1} 2^j ~.$$  So, I just need to show $$\sum_{j=0}^{n-1} 2^j =2^n-1 $$ using combinatorial proof. Am I right? I really need helps


Is it possible to get the value of $i^i$? I want to know what the result of it is.

According to WolframAlpha,  but I don't know how I can prove it.


When I try to move my files into /opt with the command mv, bash says that I don't have permission.

To be short, I want to copy a folder to a location /usr/share/screenlets/.... in Ubuntu 10.04 system. I tried by logging in as root from terminal giving su.   I even changed my user account type to ADMINISTRATOR; Yet, no use. PASTE option in the context menu's list in the folder /usr/share/... is INACTIVE.  How can I copy those files?


I have a list of 11 numbers, and I want to test the product of all combinations against some rule (2^11 possibilities).  I came across , but it seems to return a list of all combinations, which I think would take up to much memory.  My C++ thinking would be to go through each binary number 0x001 to 0x7FF and multiply each number where its corresponding bit is 1.  Example with 4 numbers: My list is [2, 3, 5, 7]  The first binary number would be 0001 giving - 2 = 2  Later we would get to 1110 and the product would be 3 * 5 * 7 = 105  Is there a better way of doing this in python? A bit manipulation doesn't seem like the right way to go.

I have a list with 15 numbers in, and I need to write some code that produces all 32,768 combinations of those numbers.   I've found  (by Googling) that apparently does what I'm looking for, but I found the code fairly opaque and am wary of using it. Plus I have a feeling there must be a more elegant solution.  The only thing that occurs to me would be to just loop through the decimal integers 1–32768 and convert those to binary, and use the binary representation as a filter to pick out the appropriate numbers.   Does anyone know of a better way? Using map(), maybe?


I have problem when I implemented this command  sudo apt-get install tcl8.5-dev tk8.5-dev   And I get this:   fawaz@fawaz-Lenovo-B590:~$ sudo apt-get install tcl8.5-dev tk8.5-dev Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  tcl8.5-dev : Depends: tcl8.5 (= 8.5.11-1ubuntu1) but it is not going to be installed  tk8.5-dev : Depends: libx11-dev but it is not going to be installed              Depends: libxss-dev but it is not going to be installed              Depends: libxext-dev but it is not going to be installed              Depends: libxft-dev but it is not going to be installed              Depends: tk8.5 (= 8.5.11-1) but it is not going to be installed E: Unable to correct problems, you have held broken packages. fawaz@fawaz-Lenovo-B590:~$    PLZ help me

After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


I am working on the project which is totally based on search. To trigger the search I have 8 fields and one of them is mandatory. I came up with one option to narrow down the search and also to reduce the number of fields to show up in advance.  Before   After   I think the user will always come to the system with some motivation. Since this is a search based system, keeping multiple fields might increase the decision time for the user or may mislead his motivation.   I am not sure which one has more advantages over the other.  Do you think search by field will work better and help the user to start the search as quickly as possible.

I have been asked to come up with a search mechanism for a database. The database stores details about electors.   Is a multiple search field interface better than a single search field interface? The single search can search across all the fields the multi box can.  Drawbacks of single: it can't differentiate between strings that could be a name or part of an address eg 'Woods' vs 'Woods avenue' but the user is not likely going to be searching for something so vague; they are likely to have a unique ID or combination of details eg 'Woods SW6 2LT'  here are the alternatives (state of the system: the user has run some search and the then cleared all the search fields for some reason)      What are the pros and cons of each approach? Are multiple boxes better than one?


If $a < x_{n} < b$ and $\lim_{n \rightarrow \infty}x_{n}=x$ then prove that $a \leq x \leq b$. I am taking two case where the sequence is monotonic and non-monotonic. If the sequence is increasing then it would converge to its supremum and if its decreasing then it will converge to its infimum, hence the limit being greater than $a$ and less than $b$. But I am not sure how to go on about the non-monotonic case.

I'm stuck with the proof of the following:  Suppose that $(s_n)$ converges to $s$, $(t_n)$ converges to $t$, and $s_n \leq t_n \: \forall \: n$. Prove that $s \leq t$.   I've tried starting with $s_n \leq t_n \: \forall : n$ and the definitions of each limit (i.e. $|s_n - s| \leq \epsilon \: \forall \: n > N_1$), but I'm not really getting very far. Any help is appreciated!


I have followed some guides and it seems to be a very simple task. still, I cannot make it work.  I can minimize app to tray:   private void Form1_Resize(object sender, EventArgs e)         {             if (FormWindowState.Minimized == this.WindowState)             {                 ntfIcon.Visible = true;                 ntfIcon.Icon = SystemIcons.Application;                 ntfIcon.BalloonTipText = "Antispin";                  ntfIcon.ShowBalloonTip(500);                 this.Hide();             }             else if (FormWindowState.Normal == this.WindowState)             {                 ntfIcon.Visible = false;                 this.Show();             }         }   But I cannot make it restore from tray      private void ntfIcon_DoubleClick(object sender, EventArgs e)         {            this.WindowState = FormWindowState.Normal;          }   Simply, the window will not show up, even adding this.Show() after the windowstate  Any help please? Compiling winform under win10

Is there an easy method to restore a minimized form to its previous state, either Normal or Maximized?  I'm expecting the same functionality as clicking the taskbar (or right-clicking and choosing restore).  So far, I have this, but if the form was previously maximized, it still comes back as a normal window.  if (docView.WindowState == FormWindowState.Minimized)     docView.WindowState = FormWindowState.Normal;   Do I have to handle the state change in the form to remember the previous state?


Could one give me a bijection between $[0,1]$ and $[0,1)$ ?  I am trying to find a function $f:[0,2]\to[0,2]$ such that $\forall0\le x\le2,f^{-1}(x)$ is a tuple (2 elements), and such a bijection would give me an answer easily.

A) Specify a bijection from [0,1] to (0,1]. This shows that  |[0,1]|   =  |(0,1]|    B) The Cantor-Bernstein-Schroeder (CBS) theorem says that if there's an injection from A to B and an injection from B to A, then there's a bijection from A to B (ie, |A| = |B|). Use this to come to again show that   |[0;1]| = |(0;1]|


Let X be an infinite dimensional  normed $\mathbb K$-linear space .Prove that $\partial B(0,1)=\{x\in X: ||x||= 1\}$ is not weakly closed in $X$.   We know that a convex subset of $X$ is weakly closed iff it is closed w.r.t. the normed topology. But here $\partial B(0,1)$ is not convex in X.   (definition of weak topology): Let $X$ be a normed $\mathbb K$ -linear space . The weak topology of $X$ is the smallest topology $J_{\omega}$(which is a subset of the normed topology of X) such that $f:(X,J_{\omega})\to\mathbb K$ is continuous for all $f \in X^*.$  Please someone give some hints.  Thank you.

I want to prove that in an infinite dimensional normed space $X$, the weak closure of the unit sphere $S=\{ x\in X : \| x \| = 1 \}$ is the unit ball $B=\{ x\in X : \| x \| \leq 1 \}$.  $\\$  Here is my attempt with what I know:  I know that the weak closure of $S$ is a subset of $B$ because $B$ is norm closed and convex, so it is weakly closed, and $B$ contains $S$.  But I need to show that $B$ is a subset of the weak closure of $S$.  $\\$  for small $\epsilon > 0$, and some $x^*_1,...,x^*_n \in X^*$, I let $U=\{ x : \langle x, x^*_i \rangle < \epsilon , i = 1,...,n \} $  then $U$ is a weak neighbourhood of $0$  What I think I need to show now is that $U$ intersects $S$, but I don't know how.


I found many tutorials on how to use VoiceInteractor I applied VoiceInteractor.PickOptionRequest.Option[] options = {option1, option2};             VoiceInteractor.Prompt prompt = new VoiceInteractor.Prompt("say cheese or you can say something else");             VoiceInteractor voiceInteractor = getVoiceInteractor();             boolean b = voiceInteractor.submitRequest(new PickOptionRequest(prompt, new PickOptionRequest.Option[]{option1, option2}, savedInstanceState) {                 @Override                 public void onPickOptionResult(boolean finished, Option[] selections, Bundle result) {                     if (finished && selections.length == 1) {                         Intent intent = new Intent(FullscreenActivity.this, ScrollingActivity.class);                         startActivity(intent);  has given me enough delay, when I keep getting the exception  E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.ai.asni_assistant, PID: 17454     java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.app.VoiceInteractor.submitRequest(android.app.VoiceInteractor$Request)' on a null object reference         at com.ai.asni_assistant.FullscreenActivity$2.onClick(FullscreenActivity.java:87)         at android.view.View.performClick(View.java:6597)         at android.view.View.performClickInternal(View.java:6574)         at android.view.View.access$3100(View.java:778)         at android.view.View$PerformClick.run(View.java:25885)         at android.os.Handler.handleCallback(Handler.java:873)         at android.os.Handler.dispatchMessage(Handler.java:99)         at android.os.Looper.loop(Looper.java:193)         at android.app.ActivityThread.main(ActivityThread.java:6669)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) I/Process: Sending signal. PID: 17454 SIG: 9 Disconnected from the target VM, address: 'localhost:50320', transport: 'socket'  I am ready to share information on what i'm working on if someone has another solution to that exception or it's something within another part of the code that is the part of the code for the permissions if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_CALENDAR) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.INTERNET) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {         builder.show();         requestPermissions(new String[]{Manifest.permission.RECORD_AUDIO, Manifest.permission.INTERNET, Manifest.permission.READ_CALENDAR}, 3);         return;     }  It did pop up once for audio recording permissions but it didn't do it for the internet and I know why and for the calendar but that was ambigious. it is 3 hours until now since I got the crash with null pointer exception.

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


This is a newbie follow-up question on the solution for how to use the same email address for multiple users presented here:     My question: where do I add this code (file name and location in file)?    I know this is probably extremely obvious to someone with even a little experience with Wordpress development.  Any direction / help would be most appreciated.   Thanks, Mike

Many posts here or somewhere else contain code, but they do not say where to put it.  Example:  I have found this post:  I'm a newbie with PHP. Where exactly should I place the code from the answer?


Last Sunday or Monday  I posted a question that boiled down to:; How to install 18.04?  say, starting by 15 April.  My desktop is having trouble with 17.04 and 17.10.  Screwy!  Okay, I'll try again.  I messed up 7.04 And 7.10 on my largest desktop. (I'm writing this on my laptop.)  What I want to do is install 18.04 Om my desktop and go from  there.  I've been using Ubuntu since 5.04 LTS And have stuck with it.  A disability limits me to the use of only my left hand. A friend who lives 2000 miles away configured a RAID when he was here last Fall.  He is a new father and cant fly back until 2019. He said that Installing Ubuntu 18.04 Would be "very difficult".  Considering my hassles With 17.04 And 17.10, I thought installing 18.04 LTS and staying there Would be my best bet.  This is one of the few times I've had this much troubles with Ubuntu;  previously I have  waited at least until the middle of April.  To Anybody: Do I have to create a DVD  with 18.04?  What is a "Start Up Disk"?  Thanks to Richard G for his suggestions.  Gary Kline  PS:  The above was my post within the past week++; it is for anybody in the Ubuntu community.  What's the best way of upgrading to 18.04?  I have only        2 DVDs left!

I would like to see a full how-to guide on how to install Ubuntu.


For finding the solutions for $z^3−5=−12i$, I calculated $\theta$ as $-67.3^\circ$. I can then write $z=r^{(1/3)}e^{i\theta/3}$ where I can substitute $e^{(i\theta/3)}$ as $\operatorname{cis}(2\pi k/3+θ/3)$ where I took $k$ as $0,\,1,\,2$. Is this right?

I cant get any good reference in my books regarding cube of complex numbers. Please help me find cube roots of the Complex number i+1??


The textbook says that to express "There is a $P$ that is $Q$", one can write the following preposition: $$ \exists x [P(x) \land Q(x)\ ] $$ However, I am unsure why I can't write like this: $$ \exists x [P(x) \rightarrow Q(x)] $$ For the case of universial quantifier, I have the opposite question. The textbook says "All  $P$ is $Q$" can be written as below: $$ \forall x [P(x) \rightarrow Q(x)] $$ and I am unsure why I can't write like this: $$ \forall x [P(x) \land Q(x)] $$ I do understand that $P \land Q$ and $P \rightarrow Q$ are different in that $P \rightarrow Q$ also accepts vacuously true. But I am curious why $\forall$ can  accept vacously true while $\exists$ cannot.

I'm not quite sure that I really understand WHY I need to use implication for universal quantification, and conjunction for existential quantification.  Let $F$ be the domain of fruits and  $$A(x) : \text{is an apple}$$  $$D(x) : \text{is delicious}$$  Let's say: $$\forall{x} \in F, A(x) \implies D(x)$$ Is correct and means all apples are delicous.   Whereas, $$\forall{x} \in F, A(x) \land D(x)$$ is incorrect because this would be saying that all fruits are apples and delicious which is wrong.  But when it comes to the existential quantifier: $$\exists{x} \in F, A(x) \land D(x)$$ Is correct and means there is some apple that is delicious.  Also, $$\exists{x} \in F, A(x) \implies D(x)$$ Is incorrect, but I cannot tell why. To me it says there is some fruit that if it is an apple, it is delicious.  I cannot tell the difference in this case, and why the second case is incorrect?


This object looks fine in this mode. It has a shiny material on 2 selected faces.   However, it turns black in this mode. It looks like wire, with hundreds of edges.

I have created two bezier circles, then converted them to meshes. When I press tab to enter edit mode, the objects appear completely black.   You can see the exact tutorial I am    Why do they appear black, and not have any subdivisions? Is this a problem with blender, or is there a setting I need to change?   Edit Mode   Edit Mode + Wireframe view


I have moved my eggs to a mini-fridge and, despite attempting to get a good-quality one, it seems as though the temperature even on max cold doesn't get below 40°F throughout the refrigerator. I really hate food poisoning and, especially now, would very much like to avoid going to the hospital or damaging my health. Are US eggs (high quality, from Alexander farms) left in a fridge above safe temperature for over a week still safe to eat? Does the float test work to detect salmonella? Is there something I can use them for that's high enough temperature to eliminate the risk?  Thanks in advance!

How do I know if a given food or ingredient I have is still good, or if I should discard it?  How can I best preserve a food or ingredient?     This broad question is intended as a "general reference" question to quickly answer many how long will food keep for? questions. Please feel free to edit this question to expand and clarify as needed.


I want to install Kali linux on my laptop which was preinstalled with windows 8,windows 8.1,Ubuntu 13,04.  Windows 8 installed on  dev/sda1Windows 8.1 installed on dev/sda6Ubuntu 13.04 installed on dev/sda8I want to install kali linux  on dev/sda3 partition.Is that possible to install and boot all four os's?

I would love to triple-boot Windows XP Pro, Ubuntu 12.10, and Backtrack 5 R3, but is this safe for my harddrive/other OSs on the computer?


I have 2046 mb of DDR3 ram , an Intel core 2 duo E7500 processor  and Asus P5G41C-M LX mother boad can in this system Ubuntu 14.04 LTS can be installed error free and run  smoothly.

I'm thinking about installing Ubuntu Desktop, but I don't know what flavor is the best for my system. What are the minimum and recommended hardware requirements? What kind of CPU? How much memory? Should I have Hardware Acceleration? What flavor should I use?  This is an attempt of a canonical answer. My answers have the "official  requirements", the recommended are a mix of official sources and opinion based (along with the answer it's told the source). You can comment or edit if you feel that the information is obsolete or incomplete. It is a good rule of thumb that any system capable of running Windows Vista, 7, 8, x86 (Intel) OS X will almost always be a lot faster with any Ubuntu flavor even if they are lower-spec than described below.


I heard that a black hole is not black because it's escape velocity is greater than or equals to the speed of light. But instead it is black because the light that gets emitted from a black hole gets red shifted due to the curvature of space-time near that black hole.     Is it true or not?   If it is true then tell me how does light even escape from a black hole to be red-shifted in the first place?

In  (ignoring Hawking radiation), why is a  black? Why nothing, not even light, can escape from inside a black hole? To make the question simpler, say, why is a  black hole black?


I'm new in the GIS world.   I have a bunch of points (around 40,000), which are split in categories (1 to 9) and have a field which specifies their membership to a polygon (~50) (e.g, 30, which would mean that the point is located in polygon 30).  Some zones do not contain points of all categories.  I wish to know the frequency of each category per zone, in such a way that in the end I would have a table with the first column for the categories, and the zones listed in the first row.  Did somebody have the same challenge? How did you solve it?

Is there a way of calculating the number of unique text strings in a field in ArcGIS 10.1? I have a number of repeated strings in this field, but would like to calculate the number of unique strings in a field based on groupings from another field.  E.g  - Current table:  Field 1    Field 2    Apple      Green      Apple      Red        Apple      Red Citrus     Yellow Citrus     Green Citrus     Orange Citrus     Orange   Result:  Field 1    Field 2 Apple      2 Citrus     3


just found my stackoverflow  in this site. with a lot of others. without answers. all the questions are attributed to one Rajesh Kumar .Also find an identical site named . thought you should know.

NB The following is a community-generated list of websites that republish Stack Exchange content without attributing it properly. It is no longer being maintained, because the procedure for reporting such sites has changed; see the duplicate for more information. There are a number of license-violating clones of Stack Exchange sites popping up that use Stack Exchange's  data without following our Creative Commons attribution terms. Those terms are , and are also included as a .txt file in every data dump we produce.  Google now has  in search results. Also, you can :  The option to block a site appears when you click a search result and then navigate back to the search results page. Click the "Block" link next to that result to block all pages within the site's entire domain.   This post was created as an attempt to organize information originally posted . You may also be looking for .


How did the Asgardians survive? I've been trying to noodle this through for a while now after seeing Avengers: Endgame. At the End of Thor: Ragnarok, the Asgardians are all on Thor's ship looking for new lands.   At the beginning of Infinity War, Thanos attacks the ship and comes aboard. There's been a slaughter and only a few Asgardians are left. Those are either killed directly by Thanos (Helmdal, Loki) or, well, basically Thor, who is picked up by the Guardians of the Galaxy.  In Endgame we find out that there are some Asgardians still alive,      including Valkyrie, the Rock guy, and presumably enough to populate a town.   Where did they all come from? How'd they survive? Did I miss an explanation?   Edit: To be clear, in addition to whatever other Asgardians there might be in the universe (which might have been 50% decimated with the snap), I'm asking about the Asgardians on the ship at the end of Thor Ragnarok.

In the opening scenes of Infinity War, Thanos and the Black Order     have killed basically everyone aboard the Asgardian ship, which amounts to everyone who escaped the destruction of Asgard itself at the end of Thor: Ragnarok.  After this, Thanos destroys the whole ship using the Power Stone.  The end result is that Thor is picked up as the only survivor, by the Guardians of the Galaxy.   Of course, we learned during Thor: Ragnarok that not all Asgardians are necessarily on Asgard (Valkyrie was living on Sakaar, after all).  Do we have any indication that there are any other such Asgardians anywhere else in the MCU at the current time, or is Thor now officially (or at least "as far as we know") the last of the Asgardian race?  I'd prefer an official confirmation if one exists anywhere.


I am trying to create a fishnet of x by x miles for all USA, same as this basically:   However, I want to do this with python.  My current code works but it doesn't take distance in miles, but rather in degrees, and therefore it doesn't take into consideration how for different lat, lon points the conversion of distance to degrees changes ().  This is my current code:  from pygeoif import geometry import shapefile import numpy as np  sq_len_deg = 1 lats = np.arange(26, 50.1, sq_len_deg) lons = np.arange(-125, -69.9, sq_len_deg) a=[] geometries=[] for lat in lats:     for lon in lons:         a.append([(lon,lat),(lon,lat-sq_len_deg),(lon-sq_len_deg,lat-sq_len_deg),(lon-sq_len_deg,lat)])         geometries.append('POLYGON ((%s %s, %s %s, %s %s, %s %s))'%(lon,lat,lon,lat-sq_len_deg,lon-sq_len_deg,lat-sq_len_deg,lon-sq_len_deg,lat)) w = shapefile.Writer(shapefile.POLYGON) w.field('test','N') for i,poly in enumerate(geometries):     w.poly([geometry.from_wkt(poly).exterior.coords])     print(i)     w.record(i) w.save('officialpysh')   I can see this going into two directions, some function already exist and I can use this, or a suggestion on how to modify this code.

I'm working with a geodataframe of points and I need to create a grid of rectangular polygons.   I know how to have bounds of the geodataframe with gdf.geometry.bounds. Now using this information and with 2 variables length and width  (L, W) of rectangular polygon, how can I create a grid ?


Overnight, my MBP would not power on with the power button. The Battery was full and the LED on the charger was green. SMC Reset did not bring any results.  So I opend up the Mac, disconnected and connected the battery from the logic board and connected the charger to MPB. MPB turned on automatically, but the power button still doesn't work.  I had problems with Caps-Lock and a few keys, but after cleaning the keyboard connector they disappeared.  Power Button still does not work. Any suggestions?

This is an attempt to write a canonical QA for this issue, as per the Meta post:   I expect it to be periodically edited with the goal of becoming a comprehensive information resource.  I have a MacBook Pro that has a key(Shift, Return,   Command, P, etc.) that doesn’t respond when pressed or is stuck in the down position.    It's possible that my favorite beverage was spilled (or some other liquid damage).  It's also possible that I have no idea what happened.  It was working yesterday and suddenly today it's no longer working.  Is there any way to bypass or remap the key?  Can I  have the system ignore it completely?  (This question can also apply to external USB keyboards or the Bluetooth keyboards)


I am currently planning on writing a bigger shell script. The script itself consists of many smaller scripts. I want to organize it modular. For example:  . ├── mainScript.sh └── modules     ├── moduleScript_1.sh     ├── moduleScript_2.sh     └── moduleScript_3.sh  1 directory, 4 files   The mainScript will import the modules and defines some shared variables. The single modules are designed to be also useable on their own, so that I can run a module from console if I only need it's certain function.  I know that I can "source" the files just like:  #! /bin/bash  sharedVariable="share"  source ./module/moduleScript_1.sh source ./module/moduleScript_2.sh source ./module/moduleScript_3.sh   ...but I am worried about scopes and interfering variables or functions.  Is this file structure actually a good practice, or is there a better, more advanced, way to handle bigger scripts with multiple modules?  Thanks in advance!

Does anyone know of any resources that talk about best practices or design patterns for shell scripts (sh, bash etc.)?


I'm trying to install WPS office in kubuntu . i've got this error :   cannot satisfy dependencies.  I try to install libpng12-0 but the error is still occurred. anyone help me to fix this issue

I could install with an error message "unknown media /ALL". It could not run WPS Office.


Consider this problem :  Let $S^{1}  =\{(x,y)\in \mathbb{R} \times \mathbb{R} \mid x^2 +y^2 =1\}$. Let $f: S^1 \to \mathbb{R}$ be a continuous function. Prove that there exits $x\in S^1$ such that $f(x)=f(-x)$.  I am not able to construct such a function and I am not getting any ideas on which result I should use for construction. Can you please help me with that?

Question is to prove :  $f : S^1 \to \mathbb R$ is continuous then $f(x)=f(-x)$ for some $x\in S^1$  I guess it would be helpful to use intermediate value theorem  Assuming $f(x)\neq f(-x)$ then given any $p\in (f(-x),f(x))$ (assuming $f(-x)<f(x)$) there exists $y\in (-x, x)$ such that $f(y)=p$  I am not very sure of how to use this..   It would be helpful if someone can give some hint which would help me to solve this..  Thank you.


With a list like so:  int[] numbers = {1,2,2,3,3,4,4,5};   I can remove the duplicates using the Distinct() function so the list will read: 1,2,3,4,5  however, I want the inverse. I want it to remove all of the numbers that are duplicated leaving me with the unique ones.  So the list will read: 1,5.  How would this be done?

I have been working with a string[] array in C# that gets returned from a function call. I could possibly cast to a Generic collection, but I was wondering if there was a better way to do it, possibly by using a temp array.  What is the best way to remove duplicates from a C# array?


The markdown used on Stack Exchange and the one used on GitHub are fairly similar, but have some subtle differences. For example, on GitHub, you can add ``` before and after a set of lines to format them as code, but that doesn't work on Stack Exchange.  As someone who writes markdown on both sites, I find these subtle differences inhibit the development of muscle memory (e.g. I often type ``` on Stack Exchange, only to realize (again) that it doesn't work and erase and correct it).  Is there any plan /  path forward to converge these two flavours of Markdown?  Note: I gave ``` as an example, but I'm asking about general convergence between the two flavours, rather than one particular extension.

Currently, Stack Exchange’s Markdown parser only allows four-space indents to represent code blocks:      // some code     // another line of code    and other Markdown implementations allow for an alternative syntax, that doesn’t require indenting each code line:  ``` // some code // another line of code ```   This is much more convenient to type out. It would be super useful if Stack Exchange could support this syntax.    By extension, this syntax also allow you to specify the source language right after the opening ```:  ```js // some code // another line of code ```   …which would then enable syntax highlighting for that specific language. Although it’s interesting metadata, I don’t think this feature is needed on Stack Overflow, as the syntax highlighting library works pretty well for various languages.  So, even if you would allow this syntax but ignore the ```language, this would greatly improve my productivity on Stack Exchange.  What do you think?  The moderators are currently collecting feedback regarding this feature, so please post a comment with your thoughts. Good idea? Bad idea? Don’t really care? What do you think are the benefits/drawbacks? Experiences? Let them know! Thanks!


I have been browsing youtube and wikipedia but couldn't find anything related to algorithm's runtime, can someone explain to me what does it mean if an algorithm has a run time of O(log*(n))?

I'd prefer as little formal definition as possible and simple mathematics.


I don't really understand the meaning of the term: "Industry sources" in this text. please aware me. "Details of the agreement have yet to be made public, but industry sources have said Noble and Delek will be allowed to keep control of Leviathan, the world's largest offshore gas discovery of the past decade. "

"To care all about the appearance of a matter or a law, without paying attention to its meaning/spirit and essence"  Actually, I look for a suitable word for to express such meaning, and place it in this text:    The Pharisee Jews were so/very/too ................ . That is to say, they were paying attention to the appearance of religious orders, but they didn't care about the spirit of those orders at all. Jesus told them: "You argue about the uncleanness of a dish with one another, but you do not argue about what is earned through usury or a forbidden and unclean way, that you eat in the same dish?! You're okay with usury, but you judge on trivial matters, such as the egg that a chicken laid on Saturday (Jewish holiday)?!"  The words I have found so far are:   Formalistic    and   Superficial observer   Also im not sure about to choose among these:  1. Appearance of religious orders  or  2. Outward of religious orders    Please leave me any kind of improvements and changes you think works within the whole text.


Hi is there any possibility that you located between 2 sound sources and u hear nothing? as we know 2 wave in opposite direction will destroy each other...

What happens to the energy when waves perfectly cancel each other (destructive interference)? It appears that the energy "disappear" but the law of conservation of energy states that it can't be destructed. My guess is that the kinetic energy is transformed into potential energy. Or maybe it depends on the context of the waves where do the energy goes? Can someone elaborate on that or correct me if I'm wrong?


I received the following rejection letter from the journal editor. It does not look like “rejection and resubmission” to me. Should I revise and resubmit? Is there any chance of acceptance?     ... I very much regret to inform you that your manuscript has been rejected. Below are the comments and recommendations for this manuscript.        If you wish, please consider the suggestions made by the reviewers and/or Editor's Office and, possibly, consider submitting a new version to the journal.  If it meets the journal requirements, we will then send it out for independent peer review.  It has been our experience that those who follow the reviewers' comments and re-submit their paper generally are successful in publishing in ABC.  However, the decision to rewrite the paper rests with you...

I sent a paper to a top tier journal in science a few weeks ago. I received the feedback from the editor saying he declined to publish/ accept my paper at the moment but if I corrected/ responded to the comments provided by reviewer, he/ she would consider to publish my paper.   I went to paper tracking website only to discover that my paper is classified as "reject and resubmit". Does that mean if I responded/ did everything suggested by reviewer, there'll be high possibility my paper will be outright rejected?   The comments from reviewer was not that harsh, but I wonder whether I'll be wasting my time if I went back to the lab and did what he said. I only have 2 months to respond.   Also, what is the difference between "reject and resubmit" and "major revision required"? This is my first submission and I'm confused.  Hope anyone can enlighten me.


I want to discuss my technical and coding related problems with users on stackoverflow. How can I chat with individual user to discuss my problem?

Sometimes I find questions or answers by users and I would like to ask the user a specific question that doesn't (yet) fit as a full SO question.  Adding a comment with @username doesn't necessarily seem appropriate, as it isn't a comment on the question or answer per se.  So, can I somehow open a chat or contact that user without putting in a comment?


I just did a clean install of windows 7 professional 64-bit on my skylake build and I was able to install windows 7 fine, I even installed the usb drivers, chipset drivers and the rest of the drivers needed. I installed it from a dvd (it had service pack 1 on it) and had a brand new product key (never used on another pc), even when I go to system properties it says that "windows is activated," but when I plugged my ethernet in and connected to the internet, windows update isn't finding any updates. I open windows update and it has been searching for updates the last 30 minutes now and found nothing, Does anyone knoe what go be wrong because I know the dvd would not have the most recent updates? Yes, my internet works fine I am able to go on google chrome and surf the web.

I installed Windows 7 fresh and installed SP1. Now, when I try to check manually for Windows Updates it just hangs on the Checking for updates screen.    I tried running the tools in , but this did not fix the issue either:  No matter what I do it just hangs on the "Checking for updates..." screen and goes no further.


I need some help on how to make a camera separately for a phone model step by step. Like for example: a Samsung galaxy s8 camera.  And also just one more question: How do you put a phone screen image on the phone model? I just started blender.

I want to do in my 3D model a bulging camera block. Of course, I know this can be done using the "extrude" tool. But I can't use subdivide modifier, consequently I can't do that. And I want to do a "notches" (It's Google Translate, not me) for power button (like power button in Moto Inc. Smartphones)      So, I hope you understand me, because I'm not good in english. Please, don't throw tomatoes at me :) And remember, I don't want to steal someone's design of smartphone, I'm just learning to do something like this.   This is my .blend file:


I'm not a mathematician nor do I otherwise use it seriously, but every once in a while I just play around with a formula that I generate (usually to look complex or designed to get really big [like a factorial function]), but this time, I think I found something interesting. I generated the following formula: $$f(x)=\sum_{n=1}^{x}(\prod_{m=1}^{n}(\frac{1}{m}))$$ I plugged into Desmos (originally, I was testing if they had fixed their summation and product functions on their graphing calculator) and I realized that the limit was some constant. I decided to explore this myself and, to speed up the process, I plugged in $10$ for $x$ and I got something close to the constant: $$\sum_{n=1}^{10}(\prod_{m=1}^{n}(\frac{1}{m}))\approx1.7182\ldots$$ If we plug in 100, instead, we get a similar value: $$\sum_{n=1}^{100}(\prod_{m=1}^{n}(\frac{1}{m}))\approx1.7182\ldots$$ Seeing this, I was curious about mathematical constants. I know that $\varphi=\frac{1+\sqrt{5}}{2}\approx1.6\ldots$ and $\sqrt{3}\approx1.732\ldots$, so this constant must be represented as the following: $$\varphi\leq c \leq\sqrt{3}$$ Is there a constant here, or did I just discover something (probably useless) here? If there is a constant here, what is it used for? If not, then are there potential uses?

I guess the proof of the identity $$ \sum_{n = 0}^{\infty} \frac{1}{n!} \equiv \lim_{x \to \infty} \left(1 + \frac{1}{x}\right)^x $$ explains the connection between such different calculations. How is it done?


I'm trying to solve the pde: $$u_t = (u_x)^{-1} \quad u(t,x) \geq 0 \text{ for positive real }x,t, \text{ and } u(0,0)=0$$  by separation of variables with $u(t,x) = f(t)g(x)$.  By rewriting with the substitution i get to $f f' g g' =1$. Trying to solve for $f(t)$ I keep $x$ constant so $g g'=c$ and then $ff' = \frac{1}{c}$.   From here though I can't see how to proceed, should I guess a function $f$ to satisfy this and if so how do I go about it?

How do I solve the partial differential equaiton  $u_{t} = (u_{x})^{-1}$  subject to the conditions $u(t,x) \geq 0$ and $u(0,0) = $0. Use the separation Ansatz $u(t,x) = f(t)g(x)$.  The inverse in confusing me


I tried looking up the difference between has and have and it generally has to do with plurals, but that doesn't seem to be changing in this case. Why do you use have in one case and has in another?

Does and has both are used with singular pronouns (He has the bottle , He does play cricket , etc) whereas Do and have are used with plural pronouns ( They have the bottle , Do they like cricket? , etc)  But still we use Does with have ( She does have a car ). Why? Shouldn't it be     She does has a car.


As light is affected by gravity ( gravitational lending and black holes), it would seem that gravity causes acceleration.   Acceleration has two parts: direction and magnitude. It is clearly evident that gravity affects the former of the two. It would seem that it does not affect the later component because light is currently at the universal 'speed limit' (not counting taychons).   What is going on here? Is the magnitude component affected by gravity?

Gravity causes anything with energy to accelerate toward the source. Black holes, for example, have such strong gravity that they pull in light and don't let any escape. But can acceleration still apply to light? The speed of light is constant, of course, but why are photons affected by gravity yet aren't accelerated by it?  Edit: My main question is why photons aren't affected in the same way as most other particles. I'm perfectly aware that it cannot surpass lightspeed, but I want to know what makes it unaffected by acceleration while other particles are affected.


I think my solution has been incorrectly mistaken with the solution of another question. It has also been edited so it looks like the solution is the one pointed by the duplicate, but this obviously did not solve my problem, just avoided the exception raised (the surface of the problem). Since my efforts to reopen the question have been useless, I have opened a new one .    I am getting a ConcurrentModificationException and I am not able to solve this problem. So I remove a series of elements from a list and I get an error.  This is the error:  04-Nov-2016 15:49:50.488 SEVERE [http-nio-8080-exec-199] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [Faces Servlet] in context with path [/...] threw exception [java.util.ConcurrentModificationException] with root cause  java.util.ConcurrentModificationException     at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:886)     at java.util.ArrayList$Itr.next(ArrayList.java:836)     at com.ex.PersonController.removeGroup(...)     at ....   The Java code:  public void removeGroup(int age) {     if (person != null) {         List<Person> friends = person.getFriends();         List<Person> removeFriends = new ArrayList<>();         if (friends != null) {             for (Person p : friends) {                 if (p.getAge() == age) {                     removeFriends.add(p);                 }              }             friends.removeAll(removeFriends);         }     }     EDIT: Note that  apparently is not solving my problem. It avoids raising an error, though, but the results displayed by JSF are not correct. Is it possible that JSF is trying to refresh while my list is not fully updated?    EDIT2: I don't think this is a duplicate. The error I got with some of my tests is gone with  or  (note that even with the .add() approach I got the same error for some reason). But JSF is still not printing what I expect. I write again the code that BalusC removed from my question with a bit more of information:  The xhtml Java code:  <c:forEach items="#{personController.groupedPersons}" var="personG">     <h:commandButton action="#{personController.removeGroup(personG.key)}" type="submit" value="Remove" >         <f:ajax render="@form" />     </h:commandButton>     #{personG.key} - #{personG.value.size()} </c:forEach>   So the first time I execute the page, personController.groupedPersons returns the right list of persons (a HashMap<Integer, List<Person>>) and prints it just fine. At this point I have 2 groups: a group of 3 Person of the same age and another Person with a different age. When I click on remove the group of the 3 persons with the same age, I trace the code and with the Iterator it removes all the necessary persons without raising a ConcurrentModificationException. The returned list of person.getFriends(); is size = 1, which is correct. Then the ajax code renders the form. personController.groupedPersons is called again and returns 1 person as expected. I have verified and this is the return person I actually expect. But then the JSF does print the wrong #{personG.key} (the one I removed) and null #{personG.value.size()}.  I know it might be difficult to follow, but can you think of any explanations for this?    EDIT 3: This is even funnier... If I delete the group that has 1 person, it is removed and then the JSF prints correctly the group with 3 persons. If I delete the group with 3 persons, they are removed and JSF prints (as I said in EDIT2) the key of the group I just removed and size() is null. Is it possible that I am on a concurrency problem here between JSF refreshing the page at the same time as I am modifying the list?  (this was originally my worry, that the ConcurrentModificationException came from a concurrency problem between the XHTML and my managed bean, and not only within the code of the Managed Bean). That could explain why I got a ConcurrentModificationException even when I added in the list instead of removing from it.

We all know you can't do the following because of ConcurrentModificationException:  for (Object i : l) {     if (condition(i)) {         l.remove(i);     } }   But this apparently works sometimes, but not always. Here's some specific code:  public static void main(String[] args) {     Collection<Integer> l = new ArrayList<>();      for (int i = 0; i < 10; ++i) {         l.add(4);         l.add(5);         l.add(6);     }      for (int i : l) {         if (i == 5) {             l.remove(i);         }     }      System.out.println(l); }   This, of course, results in:  Exception in thread "main" java.util.ConcurrentModificationException   Even though multiple threads aren't doing it. Anyway.  What's the best solution to this problem? How can I remove an item from the collection in a loop without throwing this exception?  I'm also using an arbitrary Collection here, not necessarily an ArrayList, so you can't rely on get.


Let $V$ be a vector space over $\Bbb C$, $p$ is a polynomial over $\Bbb C$ and $a\in \Bbb C$ .     Prove that $a$ is an eigen value of $p(T)$ where $T$ is   a linear operator on $V$ $\iff$  $a=p(\lambda$ ) for some eigen value $\lambda$ of $T$.   Atempt:$a$ is an eigen value of $p(T)$ where $p(z)=(z-\lambda_1)(z-\lambda_2)\ldots (z-\lambda_n)$ say.  $\implies p(T)v=av\implies (z-\lambda_1)(z-\lambda_2)\ldots (z-\lambda_n)(v)=av$  But how to show that $a=p(\lambda)$.  Please help.

Suppose $T:V\to V$, $p\in \mathcal{P}(\mathbb{C})$ (polynomials with complex coefficients), and $a\in \mathbb{C}$. Prove that $a$ is an eigenvalue of $p(T)$ if and only if $a=p(\lambda)$ for some eigenvalue $\lambda$ of $T$.  I can prove: if $a=p(\lambda)$ then $a$ is a eigenvalue of $p(T)$ because: $$Tv=\lambda v$$ $$T^kv=\lambda^k v$$ $$p(T)v=p(\lambda)v=av$$  But, how can I justify the other direction?  Thanks for your help.


I want to add the following to the file /etc/securetty using sed:  pts/0 pts/1 pts/2 pts/3 pts/4 pts/5 pts/6 pts/7 pts/8 pts/9   I wrote the following command for this purpose:  sed -i '$a pts/0\\npts/1\\npts/2\\npts/3\\npts/4\\npts/5\\npts/6\\npts/7\\npts/8\\npts/9' /etc/securetty   which gives me the output:  pts/0\npts/1\npts/2\npts/3\npts/4\npts/5\npts/6\npts/7\npts/8\npts/9   I'm clearly missing out on something here. What could be wrong in my sed command?

I am writing a bash script to look for a file if it doesn't exist then create it and append this to it:  Host localhost     ForwardAgent yes   So "line then new line 'tab' then text" I think its a sensitive format.  I know you can do this:  cat temp.txt >> data.txt   But it seems weird since its two lines. Is there a way to append that in this format:  echo "hello" >> greetings.txt


Even after reading this excellent answer at , I still do not know how to get over the partition problem.  Because there is no "edit" button.  Rakesh Godhala said:     In sb4, there is 480 GB disk space, you can create required space from   that partition   This is what I do:   Click the sb4. Click "change" button. (there is no "edit" button for me to hit) Select as shown:  Click "OK", and then I get the following:    You can see the sb4 type is changed to ext4. and I dare not click "continue", because I fear it will erase my Windows 8. Also, it did not ask me to set space size, I think this is the wrong step.  And I get stuck. So what should I do?

I'd like to see the full How-To on how to use manual partitioning during Ubuntu installation. The existing guides (at least those I found here) cover only automatic part and leave untouched the manual part (or extremely short and contain no pictures).  I'd like to cover such situations:     If your disk contains other systems:


Most of us who are studying mathematics are familiar with the famous $e^{ix}=cos(x)+isin(x)$. Why is it that we have $e^{ix}=cos(x)+isin(x)$ and not $e^{ix}=sin(x)+icos(x)$? I haven't studied Complex Analysis to know the answer to this question. It pops up in Linear Algebra, Differential Equations, Multivariable Equations and many other fields. But I feel like textbooks and teachers just expect us students to take it as given without explaining it to a certain extent. I also couldn't find any good article that explains this.

Could you provide a proof of Euler's formula: $e^{i\varphi}=\cos(\varphi) +i\sin(\varphi)$?


In the end of The Revenge Of The Sith, Darth Vader and Palpatine are watching the construction of the first Death Star. This scene probably takes place less than a year after the previous scenes (according to the answers to  question), but it would still be 18-20 years before it is fully operational in A New Hope. However, the second Death Star only takes about 5 years to build (assuming that they weren't expecting Death Star I to be destroyed)(the time between episodes IV and VI).  The first one was much smaller (2-3 times), but still took 5 times as much time to finish. Why?  Ok, the first one was a first, and had glitches, but surely it wouldn't take 5 times longer to build the first version then to improve the design massively, and increase the size!  Note: As I consider Disney to have seriously messed up canon, I would prefer Legends answers if the films (I-VI) do not supply one.

The first Death Star was in construction at the end of Episode III (presumably 19 BBY). The ending shot is this picture, with only small portions of the superstructure completed:    19 years later, the Death Star has only been recently completed (the novel Death Star places the completion about 1 BBY). So we assume it took about 18 years to build, and that's with tons of Wookiees working on it. Fast-forward to Return of the Jedi in 4 ABY, and the second Death Star is significantly built, and is "fully operational":    They had learned from their mistake on the first Death Star, and had covered up the thermal ports. Presumably they did not just make a patchwork fix, but re-engineered that portion. Anyway, it seems unlikely the progress made on the second Death Star occurred in only 4 years. Both Death Stars cost huge amounts of money and resources, and having two in construction would have been much more difficult to hide. So were both in construction at the same time?


what's the PHP equivalent of Ruby's "||=" assignment idiom?  The scenario is I want to instantiate an object or array "on demand," and not necessarily when a class is initialized.  I've tried to find this in the PHP docs, but I'm having difficulty finding things I need in there (miss the Ruby).  Thank you!

In Ruby you can easily set a default value for a variable   x ||= "default"   The above statement will set the value of x to "default" if x is nil or false  Is there a similar shortcut in PHP or do I have to use the longer form:  $x = (isset($x))? $x : "default";   Are there any easier ways to handle this in PHP?


I would like to make sure my (very superficial) understanding of electron shells, subshells, and orbitals is correct. I did look them all up on the Internet, but none of the sources said exactly what I think is going on, so I might be wrong. So, as far as I understand, shell, subshells, and orbitals are not, strictly speaking, actual, physical locations around an atom's nucleus. Shells and subshells are more like abstractions: shell $1$ is the set of all electrons of an atom with principal quantum number $1$, and subshell $s$ is the set of all electrons of an atom with quantum azimuthal number $0$. Orbital $1s$ is not a place either, it's a probability function that tells you how likely you are to find an electron with $n = 1$ and $\ell=0$ in a given point in space. Still, the plot for $1s$ will basically describe a physical location around the nucleus, if you consider all points in space where the probability isn't $0$ as points of that location. (Or nearly zero, as I seem to recall it's never exactly zero.) However, I also read that for $k > l$, electrons with  $n=k$ are more energetic and hence farther away from the nucleus than electrons with $n=l$. So, I guess that there are only certain regions of space around the nucleus where an electron with $n=k$ can be, and that they're generally larger than the regions described by orbitals. So, ultimately, I guess that both shells and orbitals can be seen as locations, although they aren't strictly speaking. I don't know about subshells, because I'm not sure if electrons can only have specific values $\ell$ at a specific distance from the nucleus. Am I making any sense?

I am learning the basics of quantum mechanics and am familiar with the Schrödinger equation and its solution, but I was confused about what the familiar atomic orbital shapes represent? Do they represent nothing physical and are just plots of the wavefunction in 3D polar co-ordinates? Or do they represent the region where probability of finding an electron is $90\%$? Or something else? Levine 7th ed. states that  An atomic orbital is just the wavefunction of the electron  Wikipedia instead states that  In atomic theory and quantum mechanics, an atomic orbital is a mathematical function describing the location and wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. The term atomic orbital may also refer to the physical region or space where the electron can be calculated to be present, as predicted by the particular mathematical form of the orbital


Update:  A solution has not been provided.  I have given examples of why.  Maybe I am doing something wrong, but I am not an Ubuntu expert, that is why I am here for help.  It is no help when repositories keep moving and the experts expect all users to be experts.  Are there any experts here that are truly willing to actually help?  The instructions   seem to be outdated and do not indicate if 1.0.27 needs to be removed first.  The only reason I want to downgrade is to get my scanner working under 18.04LTS.  My understanding is that 1.0.27 is hosed up for genesys_gl847 scanners (including my Lide 100)  and the only viable solution is to down grade sane backend back to version 1.0.25  There does not seem to be any urgency to fix the bug as it has been there since the release of Ubuntu 17.04 with none of the known patches being applied.  I have seen many comments on this forum fixing the issue on 17 and 18 releases, most of them involve downgrading the package.  Unfortunately, the step by step solutions are all out dated as the repositories have moved and the threads have closed.  I came here hoping to get assistance to fix the issue which is possible and apparently a little over my head.  Yes, going to 16 is a work around, but not a solution.  And why the Ubuntu 18.04LTS developers decided to go with an experimental package (libsane1_1.0.27-1~experimental3ubuntu2_amd64) vice a known stable package is beyond  my comprehension.  I came to this forum in search for assistance with a solution which does exist, just a little beyond my capability with Ubuntu.  @user535733 Your suggestion did not work, but maybe I did it wrong.  There are several packages, the process failed on the first one I tried.  See below:    $ sudo dpkg -i libsane_1.0.25+git20150528-1ubuntu1_amd64.deb Selecting previously unselected package libsane:amd64. dpkg: regarding libsane_1.0.25+git20150528-1ubuntu1_amd64.deb containing libsane:amd64:  libsane1:i386 conflicts with libsane (<< 1.0.27-1~)   libsane:amd64 (version 1.0.25+git20150528-1ubuntu1) is to be installed.  dpkg: error processing archive libsane_1.0.25+git20150528-1ubuntu1_amd64.deb (--install):  conflicting packages - not installing libsane:amd64 Errors were encountered while processing:  libsane_1.0.25+git20150528-1ubuntu1_amd64.deb $

I want to downgrade some packages. I search and find  and this  and this .  But i just want to do it with dpkg.  Could i just run dpkg -i package-name? If yes then what will be done with the highest already insatlled version?!


Around 1990 I saw a cartoon movie on Super-channel (Europe). Think it was an anime. It was about a prince and a princess who were fond of each other but their countries were at war. The prince was from an industrial country and they had tanks and guns. The princess was from an agricultural country and they used bows and arrows and hot-air balloons. It had a sad and/or melancholic ending. Can't remember anything else. I would like to see that movie again. Does anybody knows the title?

I would like to find out the title of a Japanese anime feature film (not a series) that I saw on Romanian TV in the early 90s.   It was about a feud between the peoples of two planets (one very technologically advanced, the other not). The two planets go to war against each other, and a young man from one of the planets falls in love with a princess from the other planet.  I recall a scene where the army of the second planet take off in hot air balloons when they go to war.  The only other thing I recall is that there is a dam next to the village where the young man lives, and for some reason he opens the dam gates and floods his own village.   I do not recall there being robots in the movie, however I remember very vaguely that the technology level was probably at the level of late 19th century Europe on one planet and pre-industrial on the other one.  What it's not:   Nobunaga the Fool Aldnoah Zero Queen Millennia Uchuu Senkan Yamato (movie)


For real sequences $\{a_n\}$ and$\{b_n\}$. Prove that $\limsup_{n\to \infty} a_n+b_n\le \limsup_{n\to \infty} a_n+\limsup_{n\to \infty} b_n$  If $\limsup a_n=a$ and $\limsup b_n=b$, where $a,b\in\Bbb R$. By Rudin theorem 3.8 of $\limsup a_n=a$, $$\forall \varepsilon>0, \exists N\in\Bbb N\ni \forall n>N, a_n<a+\varepsilon$$ So, $\forall n>N,a_n+b_n<a+b_n+\varepsilon$ and take $\limsup$ both side we get, $$\limsup_{n\to \infty}(a_n+b_n)<a+\varepsilon+\limsup_{n\to \infty}b_n=a+b+\varepsilon$$, which is true $\forall \varepsilon>0$, let $\varepsilon\to0$, we have $$\limsup_{n\to \infty}(a_n+b_n)\le a+b$$ Is my attempt correct? I have read some answers, but all of them choose some subsequence and the symbol of subsequence is not easy to read, hence I try to use another definition to prove this statement.

I am stuck with the following problem.     Prove that $$\limsup_{n \to \infty} (a_n+b_n) \le \limsup_{n \to \infty} a_n + \limsup_{n \to \infty} b_n$$   I was thinking of using the triangle inequality saying $$|a_n + b_n| \le |a_n| + |b_n|$$ but the problem is not about absolute values of the sequence.  Intuitively it's clear that this is true because $a_n$ and $b_n$ can "reduce each others magnitude" if they have opposite signs, but I cannot express that algebraically...  Can someone help me out ?


I've recently downloaded Ubuntu from the Windows Store (I'm running windows 10) and I wanted to start familiarize with it, I saw that it's possible not only to have the bash command line, but also a graphical interface. However, in the tutorial I saw () it seems that the method to start up the GUI is outdated/not working properly, could someone help me setting the GUI up so I can start Ubuntu inside Windows and use it? Thank you.

I searched around, and currently there are two methods suggested; installing an enhancement for Windows Subsystem for Linux and installing an XServer.  I want to know which method is the most hassle-free (easy to install AND to use), and which one is less memory-heavy.  I just want Synaptic and CMake. Why couldn't that be a builtin feature?


Soundness property, to my knowledge is the property that:   $\Gamma \vdash \varphi \implies \Gamma \vDash \varphi$   If $\varphi$ is provable (a syntactic consequence) from $\Gamma$ then $\varphi$ is also a semantic consequence of $\varphi$, which I believe is saying $\varphi$ is "true".  But what if, for example, $\varphi \in \Gamma$ and $\varphi = \bot$? It appears conceivable that some of the assumptions in $\Gamma$ are false, and then we might be able to prove things from it, but semantically they would be false.  It's possible I just have the definition of soundness wrong but how is this accounted for? We would normally say that the Hilbert system is both complete and sound but is this still the case even if we begin with a $\Gamma$ that contains some false premises? Or is it "sound only in certain cases"? How does this work?

Soundness: $a \vdash b \implies a \vDash b$, i.e. if we can prove something, it will also be true. We don't want a system where we start out with something true and dedice something false. However it is conceivable that even if our system is sound, maybe it's quite incomplete/limited regarding what we can express, which is why we also would like...  Completeness: $a \vDash b \implies a \vdash b$, i.e. if we can show something is true, it's also provable. We want to be able to prove all true statements. However it is conceivable that even though we can prove all true statements, maybe it also proves false ones as well, which is why we'd also like the soundness property from before.  Do I have the right idea?   If so, how would I begin to prove soundness? If we are already given $a \vdash b$ I'm not sure what all we must iterate over in e.g. propositional logic to show that we always get true statements. Especially since it seems possible I could pick a false $b$ that contradicts.


I'm looking for a group isomorphism between the group of integer polynomials (with addition) and the group of positive rationals (with multiplication).   I was thinking a map between generators of $\mathbb{Q}^*$, $1/p$, where $p$ is prime to irreducible polynomial in $\mathbb{Z}[x]$, but I am not exactly sure how it works. Any idea would be appreciated.

In one of my assignment, I was told that $(\mathbb Z[x], +)$ and $(\mathbb Q_{>0}, .)$ are isomorphic, with $$\phi (\sum_{k=0}^n a_k x^k) = \prod_{k=0}^n p_k^{a_k}$$ is a one-to-one surjective group homomorphism, where $p_1 = 2$; $p_2 = 3$; $p_3 =5$, and so on.  I know that this proof is based on the decomposition of numbers into a product of primes. But I don't think that it is correct. For instance, for $\frac12 \in \mathbb Q$, I cannot find a corresponding polynomial $f \in \mathbb Z[x]$ such that $\phi(f) = \frac12$.  If this proof is wrong, then are $(\mathbb Z[x], +)$ and $(\mathbb Q_{>0}, \cdot)$ really isomorphic?


I am hoping someone can help me out here.  For some reason my system has stopped letting me sudo.  I can log into the machine just fine.  When I attempt to install a package or sudo -i, I get asked for my password then get told that my account is not part of the sudoers file.  There is only one user account on the machine.  I have attempted to use the recovery method off this site found here:   When I try to change the password using Jorge's method I get an error: passwd: Authentication token manipulation error  passwd: password unchanged  So I attempted the "drastic" measures:  mount -o remount,rw / nano -B /etc/shadow  and deleted my encrypted password.  Saved the file and restarted the machine.  No password require, I hit return at the prompt. But I still cannot go to sudo.  I tried sudo -i with the blank password and get: Sorry try again...   So I used passwd to change my password.  It accepted the change.  I then tried sudo -i and again I got user not a member of the sudoers group!  I tried logging out and back in, it accepted my password to log in but not sudo -i or anything using sudo.  Please help me get my user back into the sudoers group.  Thanks (not feeling all that great but hopeful..)

I clean-installed Ubuntu 11.10 today, and then installed VirtualBox.  This required me to add myself to the vboxusers group, and since 11.10 seems to no longer have a graphical app to add users to a group, I ran the following command:  sudo usermod -G vboxusers stephane   This is a problem.  I now see what I should have run instead is:  sudo usermod -aG vboxusers stephane   The end result is I'm no longer in the groups I should be in.  Including whatever group is required to run "sudo".  When I run any command as sudo now, I get the following:  $ sudo ls [sudo] password for stephane:  stephane is not in the sudoers file.  This incident will be reported.   Is there a way to fix this, or do I need to re-install from scratch again?


So my friends have a server, and I was trying to join the server, but every time I try, I would be able to connect and see the terrain load around me, but after a while, the server would just kick me off and show the error message: Internal Exception: java.io.IOException: Connection reset by peer. So I'm just wondering if anyone knows a way to fix this problem

On both my computers, the entire internet connection goes down when the Minecraft Server crashes. A reboot is needed to get the internet back.  Error is something like Internal exception: java.net.SocketException: Connection reset by peer  Why is this and how can I stop it?  EDIT: PCs are both XP SP3 and have RealTek integrated network cards  EDIT #2: I am accepting @Oak's answer since it a good summary for this problem, however in my case I deleted %appdata%\.minecraft\bin\minecraft.jar and let the game recreate it and it seems to have fixed the issue. At least for 2 people on a local network.... we'll find out later if it comes back when we get a few more friends on the server using our public IP.  EDIT #3: Problem came back again with more people on the server however the app linked below by Oak to buffer network packets fixed it


I have seen solutions of splitting a file with respect to pattern matching and line matching but what I want is the following.  The scenario is, let's say I have a file file1  -   A.B|100|20 A.B|101|20 A.X|101|30 A.X|1000|20 B.Y|1|1   Now I want to split this file into 3 different files just based on the first column where the 1st file would be all the lines containing A.B in the first column, the 2nd file should have all the lines with A.X and so on.  If the first column changes in  any way, there should be a new file created for those lines. Is there any way of doing it with bash  or awk?  Since there is no way of actually knowing before hand what the first column value is, I wasn't able to use any feature like split or cut. Thanks for the help in advance!

We will generate a csv file with below values  yp1234,577,1,3 yp5678,577,3,5 yp9012,132,8,9   I need to extract data and create files based on second column. If it's 577 then the whole line has to be extracted and placed in a separate file. I mean I need a file having lines with second column as 577 alone and another file with second column as 132 alone  I tried using IF but didn't work