I have installed eclipse in Ubuntu 18.04 via Snap. And in the snap folder, I can see eclipse, where I want to add few lines in eclipse.ini file, but I'm getting "E45: 'readonly' option is set (add ! to override) " msg , even I'm not able to change file permission.  -rw-rw-r-- 1 root root 586 Apr  5 20:25 /snap/eclipse/12/eclipse.ini

I have installed a package using snap and I need to modify one of the files but when I try to change its ownership or permissions, I always get the following message:  sudo chmod +x ./my_file.js chmod: changing permissions of '/snap/my_app/my_file.js': Read-only file system   How can I modify files that are installed via snap?


I am about to start learning about light, having some knowledge of electromagnetic waves. I know an accelerated charge produces changing electric field which produces a changing magnetic field and vice versa thus EM waves propagate in space. Now I have doubt when we start speaking of light as a wave we draw the common sine wave to represent the same.But what does that waving thing actually represent in physical sense? What is actually oscillating that we represent in light wave?![edit:Have a look at image.In the image you can see light waves represented as something like sine curve.I wanted to ask if light is an electromagnetic wave it should have two field oscillating-one electric and other magnetic, but as shown in image which is commonly found in books explaining interference etc. why we have only a single curve and what is that]?()

Why do we say that electromagnetic wave is oscillating? Or does light propagate really in a wavy form like this image?    What is making the photons oscillate and how is it oscillating is it oscillating back and forth (and if oscillating back and forth how does it move if its moving back and forth at the same point?)?  Why do we say that the EM field is constantly changing when in the above picture its constant? (we know that a compass is not able to follow an electromagnetic radiation because the EM field is constantly changing)


I would like to ask a simple question but I'm unable to understand the logic behind it.     From an urn containing $M$ balls $n$ balls are drawn with replacement. What is the probability that at least one ball is drawn more than once?   Thank you in advance.

In sampling without replacement the probability of any fixed element in the population to be included in a random sample of size $r$ is $\frac{r}{n}$. In sampling with replacement the corresponding probability is $\left[1- \left(\frac{1}{1-n}\right)^r\right]$.  Please help me show how this is proved.


I have come across an exercise that I cannot solve and honestly, to me, it doesn’t even seem true.  It goes like this:   Let $G$ be a non empty set and $*$ an associative operation on $G$ such that:   $\exists e\in G:\forall x\in G: x*e = x$ (right identity) $\forall x\in G: \exists y\in G: x*y = e$ (right inverse)   Prove that $(G,*)$ is a group. (Hint: start by proving that $g*g = g \implies g = e$).  I tried to solve this in the following way:  $g*g = g \implies (g*g)*r = g*r \implies g*(g*r) = e \implies g*e = e \implies g = e$ where $r$ is a right inverse of g.  We can actually see that the statements $g*g = g$ and $g = e$ are equivalent.  After this I tried to prove that the statements implied the existence of a left identity and its equality with $e$, but I had no success so far.  Hope you can help and thank you in advance.

Let $(G, *)$ be a semi-group. Suppose   $ \exists e \in G$ such that $\forall a \in G,\  ae = a$;  $\forall a \in G, \exists a^{-1} \in G$ such that $aa^{-1} = e$.    How can we prove that $(G,*)$ is a group?


Is it possible to make bash run clear && ls -A --color whenever I hit enter on an empty line?  I don't know it that's relevant, but I'm using set -o vi for vi mode.

In bash, from inside PROMPT_COMMAND, is there a way to tell if the user just hit 'return' and didn't enter a command?


I was looking at Canon lenses and I saw that there were a lot of different 35mm f/1.4 lenses that varied greatly in price and I'd like to know why there is such a huge range of prices for a single lens. I know that L lenses are higher quality lenses but that only explains a small part of this question. Here are the lenses I saw listed on B&H photo:  $399 - Samyang 35mm f/1.4 AS UMC  $459 - Rokinon 35mm f/1.4 AS UMC (AE Chip)  $479 - Samyang 35mm f/1.4 AS UMC (AE Chip)  $599 - Tamron SP 35mm f/1.8 Di VC USD  $899 - Sigma 35mm f/1.4 DG  $999 - Canon 35mm f/1.4L USM  $1799 - Canon EF 35mm f/1.4L II USM  $1850 - Zeiss 35mm f/1.4 Distagon T  What factors make each of these lenses cost the prices they are? In addition, I'm a little bit extra curious about what makes the 1.4L II cost twice as much as the first version?

For example, a  is about US$110, while another  is about 14 times as expensive, at about $1450.  Is the 1.8 or 1.2 the main reason for the price difference?  The same goes for some variable lens, such as , and , which costs several times more.


What do you call a word used as a verb like:  To hoover instead of to vacuum. A kleenex instead of a facial tissue or paper handkerchief. etc.  Brand verbification? Is there a single word to describe it?  tia, Plumafina

Some people use a term for a popular special case in place of a generic term.  (Often this popular special case is a particular product in that category.)  I think that this is a common phenomenon.  Is there any word/phrase for it?  For example, “Coke” officially refers to a  (I think), but some people seem to call any carbonated soft drinks “Coke.”  In Japanese, famikon is the Japanese name for , a video game console which was extremely popular in 1980s and early 1990s, but some Japanese people call any video game console famikon even if it is not really a famikon.  (As an aside, calling a video game console famikon when it is not really a famikon is even a stereotype of a “mother unfamiliar with technology” in Japan.)  I am looking for a term which refers to this kind of usage of words.


I have an ordinal dependent/response variable with 9 levels. I have 26 independent/predictor variables that include nominal, ordinal, interval, and ratio data types. Should I use stepwise ordinal logistic regression?

I am trying to do an ordinal logistic regression (ordinal outcome variables with more than 2 categories) with nominal (more than 2 categories for some) predictor variables, as well as nominal (more than 2 categories for some) covariates/moderators.  First of all, I would like to test for effect interaction to see which of my covariates/moderators are indeed moderators so that I can treat them as such.  Second of all, I would like to know what's the best way to come up with the optimal model? Do I need to do dummy variables for the covariates? Can I do a stepwise for ordinal regression?


I am writing a small server with express, mongo and mongoose. My code:      const express = require('express');     const MongoClient = require('mongodb').MongoClient     const mongoose = require('mongoose');      const COLOURS = ["e6194b", "3cb44b", "ffe119", "0082c8", "f58231", "911eb4", "46f0f0", "d2f53c", "fabebe", "e6beff"];      var url = 'mongodb://localhost:27017/test';     mongoose.connect(url);      var app = express();      var db = mongoose.connection;     db.on('error', console.error.bind(console, 'connection error:'));     db.once('open', function() {         console.log('Database connected and open');     });      var deviceSchema = mongoose.Schema({         mac: String,         ip: String,         colourIndex: Number     });     var Device = mongoose.model('Device', deviceSchema);      app.get('/register', function (req, res) {         console.log("Registration: ");         console.log("    MAC: " + req.query.mac);         console.log("    IP : " + req.query.ip);         Device.find({ mac: /req.query.mac/ }, function(err, deviceList) {             if (err || deviceList.length == 0) {                 console.log("  Cannot find " + req.query.mac + ": " + err);                 Device.count({ mac: /req.query.mac/ }, function( err, count){                     var index = count;                     console.log("There are " + count + " matching");                     var device = new Device({ mac: req.query.mac, ip: req.query.ip, colourIndex: index }); //                  device.save(function (err, device) { //                      if (err) { //                          res.status(500).send("Internal error"); //                          return console.error(err); //                      } //                      res.status(202).send(COLOURS[index]); //                  });                     res.status(202).send(COLOURS[0]);                 });             } else {                 console.log(deviceList);                 res.status(202).send("Success");                       console.log("  Colour index: %s", deviceList[0].colourIndex);             }         });     });   When I try to use mac: /req.query.mac/ to find the device, it fails EVERY time. If I leave it blank, it does return the devices (I added duplicates to check with the commented out code).  I have tried looking at the  and

I would like to create a String.replaceAll() method in JavaScript and I'm thinking that using a regex would be most terse way to do it.  However, I can't figure out how to pass a variable in to a regex.  I can do this already which will replace all the instances of "B" with "A".  "ABABAB".replace(/B/g, "A");   But I want to do something like this:  String.prototype.replaceAll = function(replaceThis, withThis) {     this.replace(/replaceThis/g, withThis); };   But obviously this will only replace the text "replaceThis"...so how do I pass this variable in to my regex string?


What is the difference between the words "over" and "above" as far as its usage in prepositions is concerned? I have heard that it is used to differentiate between the things which are static and which are moving. I sincerely do not know whether it is correct or not.

I read in some good grammar book that "Above" and "over" can both mean "higher than": The example from the book  Can you see the helicopter above/over the palace?   Then below it was written that We prefer "above" when one thing is not directly over another The example from the book  We've got a little house above the lake  The question is is the helicopter in the first example directly over the palace or no if both "above" and "over" can be used?


I have a program that will perform a lengthy calculation which may take several days to be completed.  Is there a way to save the program's running state; so I will be able to turn off the computer and run the program from a saved state. Or if the program crashed for any reason I can restart it from a saved state (and not from the outset)?

I developed an algorithm for a fairly hard problem in mathematics which is likely to need several months to finish. As I have limited resources only, I started this on my Ubuntu 12.04 (x86) laptop. Now I want to install some updates and actually restart the laptop (the "please reboot" message is just annoying).  Is there a way to save an entire process including its allocated memory for continuation beyond a reboot?  Here is some information about the process you might need. Please feel free to ask for further information if needed.   I called the process in a terminal with the command "./binary > ./somefile &" or "time ./binary > ./somefile &", I cannot really remember. It's printing some debug information to std::cerr (not very often). It's currently using roughly 600.0 kiB and even though this will increase, it's unlikely to increase rapidly. the process runs with normal priority the kernel is 3.2.0-26-generic-pae, the cpu is an AMD, the operating system is Ubuntu 12.04 x86. it runs since 9 days and 14 hours (so too long to cancel it ;-) )


Show that the sequence $1+\frac{1}{2!}+\frac{1}{3!}+\cdots+\frac{1}{n!}$ is Cauchy. I'm not sure where to start with this problem, I know that if I can show that the sequence is convergent I can manipulate the inequality definition of the limit to have $|X_m-X_n|<\epsilon$ but I don't get how to prove the limit exists.

Let $(x_n)_{n\in\mathbb{N}}$ be a real sequence given by $$x_n=1+\frac{1}{2!}+\cdots+\frac{1}{n!}$$ I would like to prove that, for each $\varepsilon>0$, there exists $n_0\in\mathbb{N}$ such that if $n>m>n_0$ then $$|x_n-x_m|=\frac{1}{(m+1)!}+\cdots+\frac{1}{n!}<\varepsilon$$ In other words, I want to prove that $(x_n)$ is a Cauchy sequence. I know this sequence is a Cauchy sequence because it's convergent, but I want to prove it by definition of Cauchy sequence.  Thanks.


I have CANON EOS-600D DSLR. few days before I was on my terrace to capture some sunset scenes. When I was returning It was almost dark but I saw a bat flown to  nearby tree and hung itself there. I started taking its pictures with flash on but was not able to adjust the 55-250mm lens properly. Later by seeing the previous images I did some trial and error and successfully clicked the pictures. But is there any faster way to do the same? I am a beginner and trying to learn of my own.

I've been trying to take some long exposure shots at night with my Canon 450D. The problem I'm having is that I can't seem to get a shot in focus. The low light conditions prevent AF from working at all, nor is there enough light for me to get the focus correct by hand. I've tried through the viewfinder and the LCD, but they're both so dark I can't tell if I'm in focus or not.  Perhaps this is a lens issue? I have the 18-55mm ƒ/3.5 kit lens and the 50mm ƒ/1.8 EF lens; neither of them have focus markings, so I'm not sure if I'm hitting ∞ or if my lenses are even capable.  Thank you very much for the suggestions. I’m not able to shine a light, as I’m hoping to get landscapes and night sky shots, and I don’t have anything powerful enough to reflect back. I tried focusing with the 50mm ƒ/1.8 wide open, but I couldn't see anything. I don't think lens speed is going to make a difference.  It sounds like trial and error is my best shot here, which is unfortunate.  Side note: It sucks that the 450D has no way to display the focal length. This info is recorded in the image metadata, so it would seem like it should be available.  I have two more options that I came up with:   Set up during the evening, when there is enough light to focus, then take the shot at night. Potentially impractical due to time, but I see no reason it wouldn’t work. Use another camera. I tried again with my PowerShot S90, and got significantly better results. I was able to manually set the focus to infinity, and the wider angle / smaller sensor meant that I didn't have to worry as much about depth of field causing blur. While the S90 only allows for 15s exposures, CHDK removes that limitation.


I am trying to make a bash script that automates the installation of several packages that I use on any ubuntu machine.  I frequently create virtual machines either through Amazon AWS or Digital Ocean and would like to just run one script to install all the packages I use.  Some of the packages I would like to install are Emacs and Node.js  The normal way I install these would be to run apt-get install Emacs, and while doing this I am always prompted with a warning about how much space this app will take up and if I am sure I want to continue.  Is there a way to automate this process, from a script, and always say "yes" to these prompts?

Of course when you type:  sudo apt-get install whatever   It asks you:   Do you want to continue [Y/n]?    Is there any way I can just install it without it asking me if I want to continue? I don't really care about space, I have more then enough.


I'm doing a school project and my question is, how does gravity affect light  although it's massless?

I understand that a black hole bends the fabric of space time to a point that no object can escape.   I understand that light travels in a straight line along spacetime unless distorted by gravity. If spacetime is being curved by gravity then light should follow that bend in spacetime.  In Newton's Law of Universal Gravitation, the mass of both objects must be entered, but photon has no mass, why should a massless photon  be affected by gravity in by Newton's equations?  What am I missing?


Help I'm stuck. My login page was looping I checked online came here and most solutions didn't work for instance I didn't have the .Xauthority file listed when I ran the command ls -lah, so I stumbled on a solution which people said worked , chown -R $HOME:$HOME sudo so now if I type commands like ls -ld /usr /usr/bin I get drwxr-xr-x 10 Mickey Mickey and drwxr-xr-x 2 Mickey mickey, and my computer is in low graphics mode I can only access it through tty3. Please I don't want to loose my files.

I have run following command accidentally   sudo chown [username] -hR /   Now sudo su getting error:  sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set   How to Solve This?


So, one of the spellcasters in my group wants to cast invisibility on the thief to have him scout out a dungeon. The Players Handbook doesn't specifically say the caster must be in sight range of the target and there is a little bit of debate between group members on whether the caster needs to maintain sight range to maintain concentration on the spell, or whether it just works no matter what (checks willing) for an hour.

Here are two scenarios:    A powerful enemy caster is concentrating on some high-level offensive spell (Incendiary Cloud, Earthquake, etc.)--one PC casts Banishment and the caster fails the save. Can the enemy caster maintain the spell from the demi-plane? A PC casts Expeditious Retreat and Blink on themselves: when transported to the Ethereal Plane, can they maintain the effect?   Currently, I'm leaning towards 'no' in the first case and 'yes' in the second, based on this last line from Blink:     You can only affect and be affected by other creatures on the Ethereal Plane.    In other words, as long as you're in the same plane as the effect you want to maintain, then yes.


Need to evaluate the integral   $$ \int_{- \infty}^{\infty} \frac{x^4}{x^8 + 1}dx $$  I'm having trouble finding the poles.  I was trying to do this before and got that the poles in the upper plane occurred at $e^\frac{i\pi}{8}$,  $e^\frac{3i\pi}{8}$, $e^\frac{5i\pi}{8}$, $e^\frac{7i\pi}{8}$. I don't know if this is right.   I know once I find the poles I have to use the equation  $$ Res(f; z) = \frac{P(z)}{Q'(z)}$$ where $f = \frac{z^4}{z^8+1}$, $ P = z^4$ and $Q' = 8z^7$ and $z$ is a pole of $f$  The book got the answer $$\frac{\pi}{4}\biggl(sin\frac{3\pi}{8}\biggr)^{-1}$$  Any help would be appreciated.

Compute the integral.   $$\int_{-\infty}^\infty \frac{x^4}{1+x^8} \, dx$$  The answer at the back of the book is  $$\frac{\pi}{4\sin(\frac{3\pi}{8})}$$


I want to save or copy the data which is displayed at the command prompt while compiling a process.  For example, if I want to install a tool like LIGHTTPD, I want to save whatever I do and see in the terminal to a file..

I viewed  to redirect text to file while displaying the output. My question is how can I redirect it while working AND without constant | tee command.  My plan is to use  to identify terminal (Gnome or Guake) and record only Gnome for my Linux commands testing. So I need constant and immediate redirecting of commands and their outputs (with errors) to a file (say cmdlog.log).


In the book HTML and CSS, I came across the following quote:     The web browsers on most desktop computers display images at a resolution of 72 pixels per inch (ppi).    So is it really useless to create an image larger than 72 ppi if the browser will only render it at 72 ppi? After all, the larger the file, the slower it is to load and don't want to slow load time for nothing.   My monitor has a resolution of 1680 x 1050 yet according to this book, when I open up Firefox and view images, they will only be viewed at 72 ppi.

I have been designing web banners for more than a year but never considered the DPI. I was using the default 72 dpi, but now I want to know is it necessary to create web designs in 72 dpi? What if we use more than that, for example 200 dpi? I know that more DPI means more quality image and that's why I want to use high DPI, but recently I read somewhere that for web banners we should use 72 dpi. I just want to know if it is mandatory and if it affects negatively in any aspect?


Could anybody possibly kindly explain me what is the difference between these?- in meaning.  They are all 10 years old  They are all ten-year-olds

1) a ten years old boy is sitting on the couch.      2) a ten year old boy is sitting on the couch.      3) a ten-years old boy is sitting on the couch.      4) a ten-year old boy is sitting on the couch.   Which is correct?


Find a combinatorial argument to prove that for all positive integers $k \leq n$,$${k\choose 2} + {n - k \choose 2} + k(n - k) = {n \choose 2}$$  I'm recently new learning combinatorics and having trouble understand the intuition behind this. I don't either know what's combinatorial argument, but it looks like I have to show the LHS counting is equal to RHS by some tricks. Any suggestion ?

${n\choose 2}$ counts the 2-combination $(a,b)$ where    $a\,\in\,\{\text{Set with n-k elements}\}\,b\,\in\,\{\text{Set with n-k elements}\}$ $a\,\in\,\{\text{Set with n-k elements}\}\,b\,\in\,\{\text{Set with k elements}\}$ Order trivial here? $a\,\in\,\{\text{Set with k elements}\}\,b\,\in\,\{\text{Set with k elements}\}$   ${k\choose 2}$ counts the 2-combination $(a,b)$ where    $a\,\in\,\{\text{Set with k elements}\}\,b\,\in\,\{\text{Set with k elements}\}$   ${n-k\choose 2}$ counts the 2-combination $(a,b)$ where    $a\,\in\,\{\text{Set with n-k elements}\}\,b\,\in\,\{\text{Set with n-k elements}\}$   $k(n-k)$ counts the 2-combination $(a,b)$ where    $a\,\in\,\{\text{Set with n-k elements}\}\,b\,\in\,\{\text{Set with k elements}\}$ First question, is that because the order is trivial, either $k(n-k)$ or $(n-k)k$ would suffice? Second question, under what circumstances will both $k(n-k)$ and $(n-k)k$ have to be counted?


I was just playing around with python, take this code:  a=[[-1,-1,-1],[-1,-1,-1],[-1,-1,-1]] b=[[-1]*3]*3 print(a) print(b) a[0][0]=6 b[0][0]=6 print(a) print(b)   As I would expected it, both lists most be the same at the end, but they don´t, it looks like doing [[-1]*3]*3 creates by reference the lists, you can see that all first values from the list are change On console:  [[-1, -1, -1], [-1, -1, -1], [-1, -1, -1]] [[-1, -1, -1], [-1, -1, -1], [-1, -1, -1]] [[6, -1, -1], [-1, -1, -1], [-1, -1, -1]] [[6, -1, -1], [6, -1, -1], [6, -1, -1]]   is it a bug or is it just a normal behaviour? I'm using python 3.7

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?


I have a city or normal bike and I want to ask, that with the necessary modification except the frame, is possible to convert this bike in a road bike?

I'm fairly certain that the bars should change out quite easily; I'm more concerned about the shifters and brakes. Currently I have a hybrid 18 speed with cable disc brakes and Shimano Deore XT derailer. I know that these are typically mountain bike parts. I'm eyeing up the Shimano 105 STI dual control shifter/brake. Is this even going to work?   My main reason for wanting the change is after riding the road for quite a few years with flat bars my wrist are starting to take a bit of a beating. I put some bar end on the flat bars to change my grip position, which helped my wrists, but now I feel my grip is too wide.   If pictures would help i can try to upload some tonight, any advice would help.


I just installed ubuntu 11.10 on a laptop of mine. Where do you turn on window autofocus on mouse hovering in this new version?  I used to be able to do it very easily in 11.04.  UPDATE: I'm looking for "Select windows when the mouse moves over them"

Is there a way to set up "focus follows mouse" behavior in Unity?


I have a form that includes many checkboxes with the same name but with different values, when the form is submitted I get a single variable that has the name of the checkboxes and it contains a comma separated list values of each checkbox that was checked.  All this is OK, however, I have modified the form to disable some of the checked checkboxes which means that we cannot uncheck the checkbox, again this is OK and working. The issue that I have is that disabled checked checkboxes do not have a value when submitted.  Is there another property I can use that will include all checked checkboxes?

I thought they could be, but as I'm not putting my money where my mouth was (so to speak) setting the readonly attribute doesn't actually seem to do anything.  I'd rather not use Disabled, since I want the checked check boxes to be submitted with the rest of the form, I just don't want the client to be able to change them under certain circumstances.


From :  Photons - those fundamental particles of light - have a slew of interesting properties, including the fact they don't tend to crash into one another. That hasn't stopped physicists from trying, though. University of Chicago physicists have now come up with a new, highly flexible way to make photons behave more like the particles that make up matter. It might not give us lightsabers, but making photons collide could still lead to some fantastic technologies. The trick to getting particles of light - which have no mass - to acknowledge one another's existence is to have them meet in the quiet confines of an atom, and combine their properties with those of an electron. Researchers have been studying these interactions in the lab for several years now. The electron-photon partnerships form a kind of 'hybrid' quasiparticle called a polariton.  [...]  "But we were running into a problem because the photons only interact with atoms whose electronic orbitals are at very particular energies," says University of Chicago physicist Logan Clark.  What does the above statement means? What are those very particular energies? Why photons only interact with atoms whose electronic orbitals are at very particular energies?

This might be a stupid question, but nonetheless, it has been bothering me.  If you take a photon, make it go through some atoms in a solid, liquid or whatever, then you have the chance of this photon being absorbed by an electron, and thereby exciting the electron. This requires the photon to have enough energy to actually excite the electron to another energy level.  My question is then: How does the photon know if it has enough energy or not? Do they interact very quickly to determine if it's okay or not, or is it just something it "knows?"


I submitted a manuscript through ScholarOne two months ago. During the first week they asked me a few doubts and once they were answered, the manuscript status appeared as "awaiting reviewer selection". Then they change the status to "awaiting ME decision" and stayed this way until a week ago, when they changed iy back to "awaiting reviewer selection" I'm a bit confused. Can anyone give me an explanation? Thanks

What steps does a manuscript typically go through from submission to publication (or rejection) in a typical journal? How are these steps referred to, in particular by editorial systems, and how long do they each typically take?  Note that this question is about the typical situation and hence not about:   Journals with an atypical workflow, e.g. those that allow for an instantaneous reviewer–author interaction. Exceptional steps or rare occurrences such as withdrawal or .   This is a canonical question on this topic as per . Due to its nature, it is rather broad and not exemplary for a regular question on this site. Please feel free to improve this question.


I'm using Android App v1.0.23 on a HTC Velocity 4G running Android 4.0.3.  In  I've noticed that tapping the comment from user660 instantly crashes the app. I suspect it is because they don't exist any longer!

Steps to reproduce:    Find a comment owned by a deleted user, like . Touch it (as you normally would when trying to upvote or flag). Observe as app stops responding. Wait about 8-9 seconds. Observe crash. Look up to the sky, throw your hands in the air, and scream "WHY???!!!" because you really wanted to upvote that comment. * optional   Could this be unborkified?


If I have 3 rods in a circle and it is allowed to move the disks only in the clockwise direction. How many moves is necessary to move n disks from first rod to the third rod?

This is from one of the exercises in "", and is something I'm doing privately, not homework.  This is a variant on the classic towers of Hanoi, where all moves must be made clockwise only. The recursive solution is to consider $Q_n$ to be the number of moves to move a tower size $n$ one step across (e.g. from start $\rightarrow$ end post), and $R_n$ to be the number of moves to move it two (e.g start $\rightarrow$ end $\rightarrow$ spare).  The recursive solution is (sorry about the formatting, just getting to grips with tex):  $Q_n = 0 \quad \text{if n = 0}$  $Q_n = 2R_{n-1} + 1\quad \text{if n > 0}$  $R_n = 0 \quad \text{if n = 0}$  $R_n = Q_n + Q_{n-1} + 1 \quad \text{if n > 0}$  How can I prove these? I presume an inductive proof is required but everything I've tried to do just gets garbled into a mess of further decreasing $n$ values.  Explaining why these work is simple enough: $Q_n$ can be explained by the fact that you need to move a stack of size $n-1$ two steps forward followed by the $n$ piece, followed by moving the $n-1$ stack two steps again onto the $n$ piece=> $Q_n = R_{n-1} + 1 + R_{n-1} = 2R_{n-1}+1$.   The wordy proof for $R_n$ is similar: It consists of moving $R_{n-1}$ then 1 followed by $Q_n$, 1 and $R_{n-1}$ which will end us up with   $R_n = 2R_{n-1}+1+Q_{n-1}+1 = Q_n+Q_{n-1}+1$  But these are all just words that don't form any real proof... I've gone over the leading chapter and looked up some resources on proof by induction, but doing it with a recursion with two components has put me for a spin (having forgotten a lot of the math studied in the past certainly isn't helping either). If someone could run me through a rigorous proof for $n > 0$ it would be much appreciated.  As an aside, any recommended learning resources on proof by induction would be appreciated as I'm still barely "getting it".


I've been perusing the questions on this forum for sometime now and I think I'm developing an interest in taking part in an adventure.  I see a lot of people take part online or over Skype.  Would anyone have any suggestions on the best way to get started?  I'm a 100% novice, other than playing Baldur's Gate and similar games. Are there any websites / forums that could help me out?  I'd like to meet some people, develop a character and take part in an adventure.

I have been told that roleplaying is great fun. I've looked and looked and it all seems so complicated. Could anyone tell me a good place to start, and what sort of things you end up doing in roleplaying?


I have 2 quests filed under the Miscellaneous category of my journal in Skyrim (talking to Greta about going back to the Temple of Divines and Bring a dragon scale and a dragon bone to Esbern) that I cannot complete. I tried a lot of things to fix them but I could not succeed. First I enabled the tracking to get a hint of where to continue the quests, I tried the CompleteAllObjectives command, ShowQuestStages command, SetStage, CompleteQuest... And then I tried ShowQuestTargets. The sqt command shows the targets of all currently started quests, and also the ID of the next doors leading to these targets. By issuing consecutive sqt and Player.MoveTo <DoorID>, I tracked down all of the targets shown by sqt, and guess what: the doors I took led me to places where I could find all of the targets of my other quests. Just not these specific two misc quests. Also, when I open the journal, the Miscellaneous section displays 6 objectives, for which I can open the map and get a hint of the location, except these two quests again, for which the the key to open the map is greyed-out. Additionally, the sqs command for the "Speak to Greta" quest shows 5 stages, and the 3rd and the 4th of them are shown not completed (0-state) while the 5th is actually completed (1-state). For the "Esbern" quest, it shows 2 stages which are both completed...    Any ideas ? :c

I have a number of quests in my journal that are already done but got put in a second time due to an unfortunate conversation option. Does anyone know a way to clear these types of quests out of the journal or just drop a quest if necessary?


I installed windows 10 in 50% of my SSD Then, i installed linux in other 50% (OS Only)  And i have 75% HDD for Linux + 15% for windows (Data only)  Everything worked fine until Windows update broke windows: blue screen at boot, "inaccessible boot device".. A classic problem in dualboot with windows.  Now, I would like to reinstall w10 in it's partition. I don't want to break my linux installation, so i prefer asking here:  Can I clic "Next" here ?    The partition selected is the windows partition is my SSD. I hope it will not recreate shemas of disk, destroy other partitions, or something else  Thanks !

I've been reading a lot about dual-booting, and it seems as easy as loading Windows and then loading Linux with GRUB, but everybody says that Windows loves to trash GRUB when it gets the opportunity. What are some steps I can take to prevent this from happening (other than using Windows' bootloader, I want to keep this as simple as possible)?


I was trying to solve the problem :   The function $f : \mathbb{R} \to \mathbb{R}$ satisfies $f(x) f(y) = f(x + y) + xy$ for all real numbers $x$ and $y.$ Find all possible functions $f.$   I started by substituting in $0$ for both, to find that $f(0) = 1$, as it becomes $f(0)f(x) = f(x)$ which can only mean $f(0) = 1$. However past this point, I started struggling, as setting both to $1$, or $1$ and $0$ doesn't reveal anything new about the problem. Trying to set both $f(x)$ terms equal to each-other didn't help either. Thanks!

Find all functions $f$, defined on the real numbers and taking real values, which satisfy the equation $f(x)f(y) = f(x + y) + xy$ for all real numbers $x$ and $y$.  I worked out $f(0)=1$, and $f(-1)f(1)=0$, but then I hit a wall.


I believe, both variants are possible:   friendlier / more friendly; and   the friendliest / the most friendly.   I'd like to know what is used in every day speech more often and which is more formal.

I know the rule for making the comparative and superlative form for two-syllable words ending in y, replace the -y with i and use -er and  -est:    hap.py → happier → (the) happiest ti.dy → tidier → (the) tidiest fun.ny → funnier → (the) funniest  Instead for two-syllable adjectives which do not end in -y, use more and most:    bor.ing → more boring wor.ried → more worried care.ful → more careful tra.gic → more tragic  However, there are inexplicable exceptions: The Free Dictionary says the comparative and superlative form of  is cleverer and cleverest. Yet to my ears     He's more clever than I thought   sounds more formal and correct.  Google produces a total of  for “he is more clever than” and  for the contracted form,  “he's more clever than”. Similarly, Google yields  and  for “he's cleverer than” and “he is cleverer than” respectively, which suggests there is very little to choose between the two comparative forms.  Meanwhile, TFD insists that the comparative and superlative form of  is  simpler and simplest. Google seems to concur and produces  for “it is simpler” compared to only  for “it is more simple”.  The two-syllable adjectives that I am aware of, which have both kinds of comparative and superlative forms are:   clever → cleverer/more clever → cleverest/(the) most clever common → commoner/more common → commonest/(the) most common gentle → gentler/more gentle → gentlest/(the) most gentle humble → humbler/more humble (etc.) hollow → hollower/more hollow  narrow → narrower/more narrow  polite → politer/more polite quiet → quieter/more quiet simple → simpler/more simple stupid → stupider/more stupid subtle → subtler/more subtle   Etymologically speaking, is there any explanation for this?  Is it a recent trend?  It seems to me that the number of two-syllable adjectives that add the suffix -er and -est are increasing.   And finally, is there a trick or rule which I can teach my advanced private students? With younger learners and beginners I teach the “rule” that I mentioned at the beginning—so much simpler! :)    EDIT  December 11, 2019     I shall never ever understand Google's algorithms and how they produce their statistics. In the end, for the sake of clarity, the number of results have been substituted and updated with the number of pages each search produced.


I have a US transit visa. I am travelling from India to Jamaica. Will I need a UK transit visa as well? My flight goes from Mumbai to LHR to Miami to Montego bay.

I am travelling to Budapest and therefore have a Schengen Visa. I hold an Indian passport and a valid US visa. I'm travelling from Chicago-Heathrow-Budapest and returning by Budapest-Dublin-Chicago.  Would I need a transit visa for UK/Ireland?  UPDATE  Hoping this will help someone someday.   I was not allowed to board my return flight (BUD-DUB-ORD) because I do not hold an overnight Irish Transit Visa. They said I could have transited happily if the connecting flight was in the same day, but because I would have to originally land at 10 PM and catch the connecting flight next morning at 10 AM, I needed a transit visa. Well, I thought it was BS, but couldn't help comply with the rules. I booked another last minute ticket and flew via Warsaw via LOT.


I wish to display some animations in my beamer presentation. The most trivial way that comes to my mind is to use a gif image. How can I put it in the presentation and what should I use to display it? Is there any other way of doing it?

I'm very new to presentations in LaTeX (I've been using PowerPoint for years but have finally converted). I am wondering how to get a GIF into a section. If need be, I can convert a GIF into lots of pictures and have them overlay to give the impression of movement.


Say, an equation is given below \begin{equation} 2\pi(x) - \pi(2x)=\omega(x) \end{equation}  where $x$ is a positive integer, $\pi(x)$ is the prime-counting function, and $\omega(x)$ is the number of distinct prime factors of $x$.  I would like to know if this equation holds for finitely many values of $x$ or infinitely many.  If one uses asymptotic formula (from number theory) it can be written that \begin{equation} \omega(x) \sim \ln x / \ln \ln(x) \end{equation} (from )  and  \begin{equation} \pi(x) \sim x/\ln(x), \end{equation} so the above equation can be rewritten (after simplification) as \begin{equation} 2x\ln(2)=\ln(x)\ln\ln(x)\ln(2x) +f(x) \end{equation}  where $f(x)$ is an error term.  If I plot the left side (which is linear, supposed to be a straight line) and the right side (a curve), assuming $ f(x) $ is 100% accurate, then the equation implies(?!) that the right will intersect left side. Since line can intersect a curve ($ln  $ function) finite times, so there are finite intersection points. So, can I say that there are only finitely many values of $x$?

Say, an equation is given below \begin{equation} 2\pi(x) - \pi(2x)=\omega(x) \end{equation}  where $x$ is a positive integer, $\pi(x)$ is the prime-counting function, and $\omega(x)$ is the number of distinct prime factors of $x$.  I would like to know if this equation holds for finitely many values of $x$ or infinitely many.  If one uses asymptotic formula (from number theory) it can be written that \begin{equation} \omega(x) \sim \ln x / \ln \ln(x) \end{equation} (from )  and  \begin{equation} \pi(x) \sim x/\ln(x), \end{equation} so the above equation can be rewritten (after simplification) as \begin{equation} 2x\ln(2)=\ln(x)\ln\ln(x)\ln(2x) +f(x) \end{equation}  where $f(x)$ is an error term.  If  I plot left side (which is linear, supposed to be a straight line) and right side(a curve),assuming $ f(x) $ is 100% accurate, then the equation implies(?!) that the right will intersect left side. Since line can intersect a curve ($ln  $ function) finite times, so there are finite intersection point. So, can I say that there are only finitely many values of $x$?  graph example-   here f(x) is assumed as x + sinx  without the f(x)-


What happens if I answered my own bounty, and no one else's answer fit my question?  When the bounty expires, I can't award it to anyone. What will happen?

It's possible to offer and award bounties of reputation on questions.   What is a bounty? How can I find questions that have a bounty attached? How do I start a bounty? When can I start a bounty? Why is the system requiring me to choose a bounty amount that's higher than the minimum? Can I use Markdown formatting in the bounty remarks? Can I edit the remark? How long is the bounty period? How do I award a bounty? Can I award a bounty to my own answer? Can I award a bounty to an old answer? If I offer a bounty on someone else's question, can I award the bounty to their answer? After awarding the bounty, can I remove it or move it to another answer at a later time? What happens if there's no answer after the bounty period? What happens if I feel my question is still unanswered? What is automatic awarding? Are bounty awards exempt from the 200 points/day reputation limit? How does Community Wiki mode affect bounties? How does user deletion or post dissociation affect bounties? Can I award a bounty to an answer from a deleted user or one where the author was dissociated? Can I offer a second bounty after the first one has expired? Can I raise my bounty? What happens if a bounty question is closed or deleted? Why can't I vote to close or migrate a bounty question? What happens if I delete my account while I have an active bounty? Do I keep an awarded bounty when I delete my answer? What happens if a question where I awarded a bounty later gets deleted or migrated? Can I cancel my bounty? Can I affect / divide / share part of my bounty to two (or more) users? How many outstanding bounties can a single user have?      See also:  in the Help Center


I'm trying to display just the top two rows in Oracle, however I've not been able to come across anything that works.  I currently have   SELECT BRANCH.BRANCHID, BRANCHNAME, AVG(SESSIONPRICE) FROM BRANCH, SESSIONS WHERE SESSIONS.BRANCHID = BRANCH.BRANCHID GROUP BY BRANCHNAME, BRANCH.BRANCHID ORDER BY AVG(SESSIONPRICE) DESC   Which returns this  B2      A     18.67 B4      B     17.57 B3      C     15.44 B1      D     13.99   However, I only want the top two rows of this table.  How on earth do I do this?

Is there a way to make an Oracle query behave like it contains a MySQL limit clause? In MySQL, I can do this: select *  from sometable order by name limit 20,10  to get the 21st to the 30th rows (skip the first 20, give the next 10). The rows are selected after the order by, so it really starts on the 20th name alphabetically. In Oracle, the only thing people mention is the rownum pseudo-column, but it is evaluated before order by, which means this: select *  from sometable where rownum <= 10 order by name  will return a random set of ten rows ordered by name, which is not usually what I want. It also doesn't allow for specifying an offset.


I had a Debian Jessie installation on my laptop. I tried to boot live from USB a Kali linux distro and I lost grub.  I have a very important project on this drive. I tried to reinstall grub but failed. Can anyone tell me a way to either reinstall grub correctly or just get the two files from the disk and then format it?  My (non-root) user is password protected, will this cause any problems? Of course I remember the password

After successfully updating my bios,  and I ended up with a blinking cursor on the top left corner of a black screen. No errors, no nothing. The bios now only listed a SATA: <disc name> boot option in place of the usual UEFI ubuntu one. I'm using a GPT partitioning scheme.  I eventually found that the working solution was to properly reinstall grub-efi-amd64. So, how do I do this ?  PS: Actually, i succeeded to reinstall GRUB2 EFI on my own and will post my answer here as I was unable to find any complete how-to on this.


Intuitively I would think that long doubles have more decimal places than doubles and doubles have more decimal places than floats, however, if so why does std::cout print out floats, doubles, and long doubles at the same decimal precision, even when they have overloads for all primitive data types? C++ source code: #include <iostream>  #define PI 3.1415926535897932384626433832;  int main() {     float f = PI;     double d = PI;     long double ld = PI;      std::cout << f << std::endl;     std::cout << d << std::endl;     std::cout << ld << std::endl;      return 0; }  output: 3.14159 3.14159 3.14159

In my  I was printing a double using cout that got rounded when I wasn't expecting it.  How can I make cout print a double using full precision?


I would like to have shared home directory (or it's subdirectory) under dual boot Windows/Linux. I know I can how to mount NTFS under Linux, but I don't like it has different file permissions. So, I would prefer reverse: mount ext4 under Windows. Is it possible?  UPDATE  I don't want to READ ext4 partition, I want to read it AND WRITE.   Documentation for newbies:

Is there a way to read ext4 partitions from Windows? If so, what can I do?


I often see in particular Americans use the words "he/she" (also sometimes "he or she") as a gender-neutral pronoun.   This is grammatically incorrect (the sentence "he/she" makes no grammatical sense), it's clumsy, it's long (two syllables), and, to be a bit pedantic, it doesn't even solve the problem of gender bias, because why is it "he/she" and not "she/he"?   On the other hand, we have the perfectly viable alternative of using "they". It's short, it's grammatically correct, it's completely neutral, it just works.   So why do so many speakers use the clumsy "he/she" rather than the elegant "they"?

I know there are different opinions on this issue. My question: Is using "he" for a general, gender-neutral third person still in common use for formal writing? By common use I mean, can I expect my paper not to be penalised because I use "he" as pronoun for "a student", etc.?   I think "he/she" is too clumsy and I am not comfortable with singular they.


I am not at all experienced with regex, so please bear with me.  I am building a simple content markup language for an admin.  I want for the admin user to be able to create a link by specifying the following within an admin;  [link="http://www.google.com"]Google[/link]  From this, I need to basically get the value XXX in [link="XXX"] and the value between [link="abcd"]XXX[/link]. So for the above example I'd want to extract '' and 'Google'.  I am working with PHP.  Any help would be greatly appreciated.

I'd like to work on a bbcode filter for a php website. (I'm using cakephp, it would be a bbcode helper) I have some requirement.    Bbcodes can be nested. So something like that is valid.  [block]       [block]       [/block]       [block]           [block]           [/block]       [/block]   [/block]     Bbcodes can have 0 or more parameters.     Exemple:     [video: url="url", width="500", height="500"]Title[/video]   Bbcodes might have mutliple behaviours.     Let say, [url]text[/url] would be transformed to [url:url="text"]text[/url] or the video bbcode would be able to choose between youtube, dailymotion....  I think it cover most of my needs. I alreay done something with regex. But my biggest problem was to match parameters. In fact, I got nested bbcode to work and bbcode with 0 parameters. But when I added a regex match for parameters it didn't match nested bbcode correctly.   "\[($tag)(=.*)\"\](.*)\[\/\1\]"  // It wasn't .* but the non-gready matcher  I don't have the complete regex with me right now, But I had something that looked like that(above).  So is there a way to match bbcode efficiently with regex or something else.  The only thing I can think of is to use the visitor pattern and to split my text with each possible tags this way, I can have a bit more of control over my text parsing and I could probably validate my document so if the input text doesn't have valid bbcode. I could Notify the user with a error before saving anything.  I would use sablecc to create my text parser.   Any better idea? or anything that could lead to a efficient flexible bbcode parser?  Thank you and sorry for my bad english...


There is this .  This is in the .     Edits are expected to be substantial   Now I am in discussion with another user:        .  Can we have an authoritative link to give to users regarding minor suggested edits. It would stop needless discussion and wasting of time.    The issue here, is not this user in particular, but the whole minor edit debate  Whether the suggested edit is valid or not, it would be good to know either way.          I have added images, as the question in this example is so badly downvoted, I would not be surprised if it is deleted by the owner, in which case links would be useless

At the moment the reviewers are split into two camps, one is accepting minor edits, the others don't. But first, let's start with some basics:     too minor      This edit is too minor; suggested edits should be substantive improvements addressing multiple issues in the post.   And now we'll look at . In my opinion this is way too minor to be approved, but the . Though, .  From an editors point of view, it's a little bit confusing, because some people are accepting those edits, some don't...so it's pure luck based on who sees it first if it is accepted or not. In theory an editor could even do the same edit multiple times until it is accepted.  That's a very big hole of inconsistency there, which should be plugged. Either the rejection reason should be refined and clearer outlined what is "too minor" or, if those edits are valid, it should be removed altogether (because in that case minor edits are already caught by the system).


Question: Let $a_1,a_2,\cdots,a_n$ be positive real numbers and $\lambda_1,\lambda_2,\cdots,\lambda_n$ be non-negative real numbers such that $$\sum_{k=1}^n\lambda_k=1.$$ Prove that $$\prod_{i=1}^n a_i^{\lambda_i}\le \sum_{i=1}^n\lambda_i a_i.$$    Solution: Observe that for each $a_i$, $1\le i\le n$, we have an unique $y_i\in\mathbb{R}$, such that $a_i=e^{y_i}$. Therefore, we have $$a_1=e^{y_1},a_2=e^{y_2},\cdots, a_n=e^{y_n}.$$  Discrete Jensen Inequality: Let $f$ be a convex function defined on an interval $I\in\mathbb{R}$. Assume that $x_1,x_2,\cdots,x_n\in I$ and let $\lambda_1,\lambda_2,\cdots, \lambda_n$ be non-negative real numbers such that $\sum_{k=1}^n\lambda_k=1$. Then, $$f\left(\sum_{i=1}^n \lambda_i x_i\right)\le \sum_{i=1}^n\lambda_if(x_i).$$   Now $f(x):=e^x, \forall x\in\mathbb{R}$ is a convex function. Also we have $a_i=e^{y_i}$, $1\le i\le n$, where each $y_i\in\mathbb{R}$ and $\lambda_1,\lambda_2,\cdots,\lambda_n$ are given non-negative real numbers such that $\sum_{k=1}^n\lambda_k=1$. Thus, applying Discrete Jensen Inequality we have $$e^{\sum_{i=1}^n\lambda_i y_i}\le \sum_{i=1}^n\lambda_i e^{y_i}\\\implies \prod_{i=1}^n (e^{y_i})^{\lambda_i}\le \sum_{i=1}^n\lambda_i e^{y_i}\\\implies \prod_{i=1}^n a_i^{\lambda_i}\le \sum_{i=1}^n\lambda_i a_i.$$ Hence, we are done.   Is this solution correct and rigorous enough? And, is there any other way to solve the same?

Let $a,b,c,x,y,z>0$ and $x+ y+ z= 1$. Show that $$ax+ by+ cz\geq  a^{x}.b^{y}.c^{z}$$ I have found the generalization of this inequality: For 2 sets of numbers $\left \{ a_{i} \right \}, \left \{ b_{i} \right \}> 0$ and $\sum_{1}^{n}b_{i}= 1$, we have: $$\sum_{1}^{n}\left ( a_{i}b_{i} \right )\geq  \prod_{1}^{n}\left ( a_{i}^{b_{i}} \right )$$ First solution Simply compare the logs: as the natural logarithm is a concave function, one has $$\ln\bigl(a^x b^y c^z)=x\ln a+y\ln b+z\ln c\le \ln(ax+by+cz)$$ for all non-negative $x,y,z$ such that $x+y+z=1$. How about another solution? I really hope to see that. Thanks!


I import a CSV File and for each coordinate, I get a point in the map. Can I set a column for the value. Then the size should based on the value have a special size. Or based on all values, it should display from max to min value.

I am trying to plot sales data on a map using QGIS. I will add the disclaimer that I am a rookie at using the program. I added the different sales types by adding delimited text layers (utf16). The data included Longitude, Latitude, and Amount. I want to make the dots on the map scale with the value of the sale. Ive had no luck with trying to use Simple Marker->Data defined properties-> size and writing case functions. Some data points show up at different sizes while others show up at all data points. Here are my functions under different simple markers:   CASE WHEN Amount <= 10000 THEN '.2' END CASE WHEN 10000 < Amount < 75000 THEN '.4' END CASE WHEN 75000 < Amount <= 250000 THEN '.6' END CASE WHEN Amount >= 250000 THEN '1' END   The majority of my data set falls into the 10-75k range. However the .4 and .6 size circles show up at every data point on the map, while the .2 and 1 sizes only show up where the data specifies (along with the .4 and .6 sizes). At this point I am trying to figure out what is wrong with the equations, however I am stuck.   Is there a better way to go about this or am I just simply messing up the equations?   I wish I could share my whole map with you but it is looking great. I went with U/Joseph 's solution and here is an excerpt of the results for those interested.


$$\overline{z}=z^n$$ where $n\in \mathbb{N}$   So I have started with moving the polar representation as the expression is in the n-th power  $$rcis(-\theta)=r^ncis(n\theta)$$   I can not multiply both sides in $r^{(-n)}$ as $n\in \mathbb{N}$ how should I continue?


Been doing html dev for 15 years and manage a ton of sites.  These tags functionally do the same thing to words.  I can style each similar in css.  I have even found uses for strong and bold by doing stuff like making strong show block lettering or a different color... but really I could have added a class for that.  Why do these exist?  How can I explain this to a new coworker learning html beyond "It's just another whacky/stupid thing you have to deal with and they are in effect the same thing?"  There is already a question- What's the difference between <b> and <strong>, <i> and <em>?   - This question is too old and references and answers are made using old html/css standards that no longer apply.  But this question has an answer that has 425 vote ups that is more or less marred with mistakes.  B and strong are not styles and are just tags that can be styles.  I understand the aspect of handicap reading but that didn't need a new formatting tag to accomplish that.

What's the difference between <b> and <strong>, <i> and <em> in HTML/XHTML? When should you use each?


I'm trying to understand the Kolmogorov-Smirnov test using a very simple example. I generate a set of random, uniform values between 0 and 1.0. I then test that these values are from a uniform distribution by using the . I'm expecing a very small D value and a pvalue close to 1.0, but instead I get wildly varying pvalues every time I run the code. What am I missing?  import numpy as np import scipy a = np.random.uniform(size=4999) print(scipy.stats.kstest(a, 'uniform'))   Here are the outputs of a few consecutive runs:  (0.0075523161200627964, 0.93798952050647577) (0.013787195268362473, 0.29799260741344774) (0.014359046616557847, 0.25402403230845855) (0.012521820948675988, 0.41329007558099806) (0.011159003477582918, 0.56216895575676396)

Recently, I have found in a  a statement that p-values should be uniformly distributed. I believe the authors, but cannot understand why it is so.   Klammer, A. A., Park, C. Y., and Stafford Noble, W. (2009) . Journal of Proteome Research. 8(4): 2106–2113.


She's got a ticket to ride,   She's got a ticket to ride,   She's got a ticket to ride,   But she don't care.     It sounded odd to me. So why is it used that way?

I was listening to Eminem's song Stan. I noticed in one verse he says:        But she don't know you like I know you Slim...      At first I didn't believe my ears, but when I read out the lyrics I got astonished. I further searched on Google and found on some other forums that this type of incorrect grammatical usage is either intentional (for some linguistic reasons) or the speaker is uneducated!       So my question is:      What is the purpose of this type of intentional misuse of grammar? How does it appear to native English speakers?      Thank you.


I need to reproduce an animation-like effect on the browser (mobile and desktop), this effect is just a procedural changes on the background color from black to white.  The timming is important, since a black background for a short time means "0" and a longer time means "1" (is like a binary Morse code). This information is interpreted by a light sensor in front of the screen. The sensor is very fast, and if we use a lower frequency we wont have problems with the screen (assuming a maximum refresh rate of 50Hz).  This is the script im using:  var i = 0; var b0t = 100; var b1t = 3.5 * b0t; var wl = 100;  function pulses (){     bytes = "1001101010110101001000100";          bit = bytes[i];          i += 1;          document.body.style.backgroundColor = 'white';         document.body.style.color = 'white';          setTimeout(toblack, wl);          if(i <= bytes.length) {             if (bit == 1)                 setTimeout(pulses, b1t + wl);             else                 setTimeout(pulses, b0t + wl);         } }  function toblack() {     document.body.style.backgroundColor = 'black';     document.body.style.color = 'black'; }  pulses ();   And a  (Do not open if you suffer any epileptic syndrome)  The problem is, 1 out of 20 the browser mess the timing, of course in the sensor side i have a tolerance range, a very tolerant range, but again the browser some times is out by several milliseconds, and this is no surprise, if your computer of cellphone is doing something in the background the performance of the browser is severely affected.  Is there a software solution for this? I was thinking using flash to do the flickering with more precision, but i really like my app to be accessible also from IOS. Or i can make a native app that for sure will be more precise than the browser, but then again, i will like to know if i can make it work on the browser.

Something that has always bugged me is how unpredictable the setTimeout() method in Javascript is.  In my experience, the timer is horribly inaccurate in a lot of situations. By inaccurate, I mean the actual delay time seems to vary by 250-500ms more or less. Although this isn't a huge amount of time, when using it to hide/show UI elements the time can be visibly noticeable.  Are there any tricks that can be done to ensure that setTimeout() performs accurately (without resorting to an external API) or is this a lost cause?


If $M$ is the sigma algebra generated by $E$, then $M$ is the union of the sigma algebras generated by $F$ as $F$ ranges over all countable subsets of $E$.   (Hint: Show that the latter object is a sigma algebra)

Given a collection of sets $\mathcal{C}$ and $E$ an element in the $\sigma$-algebra generated by $\mathcal{C}$, how do I show that $\exists$ a countable subcollection $\mathcal{C_0} \subset \mathcal{C}$ such that $E$ is an element of the $\sigma$-algebra, $\mathcal{A}$ generated by $\mathcal{C_0}$?    The hint says to let $H$ be the union of all $\sigma$-algebras generated by countable subsets of $\mathcal{C}$....although I don't know why.


MWE:  \documentclass[]{article}  \usepackage{xcolor} \usepackage{color} \usepackage{listings}  \definecolor{maincs}{RGB}{255,0,0} \definecolor{secondarycs}{RGB}{255,179,246} \definecolor{tertiarycs}{RGB}{79,139,87}  \lstset{ language=[LaTeX]TeX, basicstyle=\ttfamily\normalsize, columns=fullflexible, breaklines=true, texcsstyle=*\color{maincs}, texcs={documentclass,begin,end,chapter,section,subsection,label,alpha}, moretexcs=[2]{usepackage,input}, texcsstyle=*[2]{\color{secondarycs!80!black}}, moretexcs=[3]{\n,\,renewcommand,tablename,contentsname,indexname,chaptername, figurename,listfigurename,listtablename,hyphenation,sin,cos, index,printindex,item,jobname,date,makeindex,maketitle,title,author,tableofcontents}, texcsstyle=*[3]{\color{tertiarycs}}, inputencoding=utf8, extendedchars=true, literate={ö}{\"{o}}1 {ü}{\"{u}}1 {Ş}{\c{S}}1 {ç}{\c{c}}1 {İ}{\.{I}}1 {ı}{\i}1,}  \begin{document}  \begin{lstlisting} \begin{eqnarray*} x + y &=& z + t\\ &=& u + 6\\ \end{eqnarray*} \end{lstlisting}  \end{document}   and displaying    But that I want    That is, \\ add to list. What will I do?

I've got a question (it's in the title) about listings that I do not believe have been answered anywhere (either that or my Google-fu isn't that sufficient). Before I knew of texcsstyle's star option, I tried to highlight double backslash (\\) by using the literate option (how monstrous):   literate=*{\\\\}{{\textcolor{red}{\textbackslash{}\textbackslash{}}}}{1}   With this I used to be able to highlight double backslash but since I didn't use texcsstyle I could not highlight the backslash that comes before all LaTeX commands. But when I finally DO use texcsstyle, the literate option suddenly no longer works for double backslash, even though all the other literate replacements (for &,[,],{,},...) still work. I guess texcsstyle is interfering with the literate option? How do I resolve this? Is it even possible to have both texcsstyle and double backslash highlighted?  Edit: added an example, sorry. Uncomment the line with texcsstyle and you will see the double backslash stop getting highlighted.  \documentclass{article} \usepackage[T1]{fontenc}   \usepackage[usenames,dvipsnames,svgnames,table]{xcolor} \usepackage{listings} \usepackage{charter} \definecolor{lightgrey}{rgb}{0.9,0.9,0.9} \definecolor{darkgreen}{rgb}{0,0.6,0} \definecolor{darkred}{rgb}{0.6,0,0} \definecolor{myblue}{RGB}{20,105,176} \definecolor{darkgreen}{rgb}{0,0.6,0} \lstdefinelanguage{mytex}[LaTeX]{TeX}{   moretexcs={includegraphics,multicolumn,multirow,newcolumntype,intertext,},   morekeywords=[2]{figure,tabular,tabulary,document,minipage,verbatim,table,     enumerate,tikzpicture,preview},     % texcsstyle=*\bfseries\color{darkred},   literate=             *{\{}{{\textcolor{myblue}{\{}}}{1}             {\}}{{\textcolor{myblue}{\}}}}{1}             {\&}{{\textcolor{red}{\&}}}{1}             {\\\\}{{\textcolor{red}{\textbackslash{}\textbackslash{}}}}{1}             {[}{{\textcolor{myblue}{[}}}{1}             {]}{{\textcolor{myblue}{]}}}{1}, } \lstset{language=mytex} \lstdefinestyle{mystyle1}{ basicstyle=\small\ttfamily, keywordstyle=\color{purple}\bfseries, keywordstyle=[2]{\color{magenta}}, commentstyle=\color{darkgreen},  stringstyle=\color{orange}, identifierstyle=\ttfamily, showstringspaces=true, breaklines=true, tabsize=4, columns=fullflexible, keepspaces=true, } \lstset{style=mystyle1} \begin{document}    \begin{lstlisting} \begin{alignat*}{4}    y & = -4   & + 3 & +4     & -7      \\    y & =      & + 3 &        & -7      \\    \intertext{therefore}    a & = b    & d   & = cccc & e & = d \\    a & = bbbb & d   & = c    & e & =   \\ \end{alignat*} \end{lstlisting}  \end{document}


Am flying into Newark EWR from Ireland en route to Vancouver, Canada, all on United.  Will I have to clear Customs, pick up my bag and recheck it?  Will I also have to change terminals?

In Europe usually you don't need to go through immigration to change planes (unless you are entering/exiting Schengen). Is it the case in the US as well? May I catch a connecting flight on one of the US airports if I don't have US visa?


Considering ditching windows 10 altogether..  But one of my main concerns is losing adobe acrobat.  What is the best free and paid pdf editors for ubuntu? Need to be able text. Also is there anything that can compete with photoshop?

I was wondering if there is a pdf reader-writer-publisher-editor that can add text, highlight, shapes and general edit an existing pdf document.  Something like Nitro in windows.


I am looking for some way of putting a tick and cross marks above a word or a letter. Something like this

I've seen an equals sign with a small exclamation mark on top being used to say "equals because of data that was given in the problem", for example for a boundary condition or initial value in a differential equation.  A rough picture of what I mean:       ! f(x) = 4   How do I typeset this in LaTeX? I've tried $=^!$ (which doesn't produce the desired result) and looked through the "relations" section of the  without success.


I usually preferred some fonts which are not available in Ubuntu 14.04 viz. Times New Roman, Arial etc. How these fonts can be installed in Ubuntu 14.04 environment ?

I don't have these fonts:  times new roman, arial and calibri..., like in microsoft office? What can I do?


Is there a way that when you cycle through the last Space, it cycles you back to the first one?  And, if you cycle backwards and get to the first space, have it cycle back to the last?  Right now, it stops as at the end and beginning, and I'd love to just keep on swiping to cycle.

On Snow Leopard you could "jump" from the last space to the first space by hitting cmd+right arrow.   How to do this in Mavericks?


I'm trying to match (.)\1+ in google. This works just fine on , but when I try this code in Python, r.match(s) returns None.  import re  s = 'google'  r = re.compile(r'(.)\1+')  print(r.match(s))

What is the difference between the search() and match() functions in the ?  I've read the  (), but I never seem to remember it.  I keep having to look it up and re-learn it.  I'm hoping that someone will answer it clearly with examples so that (perhaps) it will stick in my head.  Or at least I'll have a better place to return with my question and it will take less time to re-learn it.


This is probably stupid, but like an isolated tank which is completely filled with some liquid or stuff can't have any more entropy on its own right?

In any sizable system, the number of equilibrium states are much, much greater then the number of non-equilibrium states. Since each accessible micro state is equally probably, it is overwhelmingly likely that we will find the system in an equilibrium state.   However, for a closed system, one that does not interact with any external system, the number of micro states is fixed. Therefore the entropy is fixed.  At any given time, the system will be in one of its micro states. Even if the system is in a micro state that does not look like equilibrium from a macroscopic point of view, its entropy will remain the same, since entropy is a property of all the micro states, not just a given micro state.   So, are the number of accessible micro states (and hence entropy) of an isolated system constant?


Like this, only it doesn't work:  \documentclass{standalone}  \usepackage{tikz}  \begin{document}  \begin{tikzpicture}   \draw [->] (0, 0) ellipse [x radius = 2, y radius = 3];  \draw [->] (0, 0) -- (1, 0) -- (0, 1) -- cycle;  \end{tikzpicture}  \end{document}   (Edited, twice, to include an MWE that actually compiles, as requested).


Could someone help me with the below.  I am a bit of confused regarding URI and URLs. I read somewhere that all URLs are URIs. Now I have the following URL:    Could someone tell me if this URL is a URI as well? If not, how can i convert it to URI.  Thank you in advance.

People talk about URLs, URIs, and URNs as if they're different things, but they look the same to the naked eye.  What are the distinguishable differences between them?


Can someone help me by explaining what imaginary numbers actually are, please?  I know that it is defined as $i = \sqrt{-1}$  and I can find umpteen sources telling me how to calculate with them but I cannot get my head around what they actually represent.  I've seen a number of argand graphs but I just cannot relate what the lines are describing.  Can anyone help?  Thanks

At school, I really struggled to understand the concept of imaginary numbers.  My teacher told us that an imaginary number is a number that has something to do with the square root of $-1$.  When I tried to calculate the square root of $-1$ on my calculator, it gave me an error.  To this day I still do not understand imaginary numbers.  It makes no sense to me at all.  Is there someone here who totally gets it and can explain it?  Why is the concept even useful?


I came across a question ( mentioned below ) which is from a Mathematical Olympiad.  It says,  If $m $ and $n $ are positive integers such that      $n + (n + 1) + (n + 2) +...+ (n + m) = 1000 $   then how many $(m, n)$ pairs exists ?

All the positive numbers can be expressed as a sum of one, two or more consecutive positive integers. For example $9$ can be expressed in three such ways, $2+3+4$, $4+5$ or simply  $9$. In how many ways can a number be expressed as a sum of consecutive numbers?  In how many ways can this work for $65$?  Here, for $9$ answer is $3$, for $10$ answer is $3$, for $11$ answer is $2$.


I've run into a complication when creating one of the trees for a location. I am not sure how to really ask this question without this picture:   As you can see I have a UV leaf texture that I want to apply to the rectangular generated leaves from the tree. When I put this into the texture tab it shows the leaf in the rendering, but keeps the white space that fills the rest of the rectangular shape.   Is there a way to eliminate this white space between the leaf and the edge of the rectangles to have it look like there are leaves on the tree?  Thank you for any help and suggestions.

Whenever I download Nintendo models I come across this texture with the black. I can't transparent it, but how do I use this for stuff in Blender Render mode? If it's possible can you tell me what I do with these kind of textures?


I have a set of classes each with a constructor. These classes are in a folder (lets call this folder ABC). I have a separate python file (lets call this file PROJECT) that is in the parent folder of ABC. I would like to use the constructors of the classes in folder ABC in PROJECT.   I know how this would be done if they were all in the same folder but how would this be done if the classes are not in the same folder.  Thank you very much for your help.

I can't seem to get Python to import a module in a subfolder. I get the error when I try to create an instance of the class from the imported module, but the import itself succeeds. Here is my directory structure:  Server     -server.py     -Models         --user.py   Here's the contents of server.py:  from sys import path from os import getcwd path.append(getcwd() + "\\models") #Yes, i'm on windows print path import user  u=user.User() #error on this line   And user.py:  class User(Entity):     using_options(tablename='users')      username = Field(String(15))     password = Field(String(64))     email    = Field(String(50))     status   = Field(Integer)     created  = Field(DateTime)   The error is: AttributeError: 'module' object has no attribute 'User'


It's a while that I'm trying to create a bootable USB drive with a Windows on it. I first tried with Unebootin unsuccessfully, I reckon the reason is the fact that the last version doesn't support any more the "show all drivers" option, which was necessary for the application to recognize USB drives formatted to ntfs using Gparted.  And apparently to create Windows bootable USB drives the ntfs format is required, otherwise it won't boot...  Then I've tried, carefully following the instructions that I've picked up on the internet, to do it on the terminal using the dd command. But then again, so far no luck.   Here's the details:  dd if=/home/GIGI/Windows/Windows.iso of=/dev/sdb1 ibs=4b obs=1b conv=notrunc,noerror   But here what the terminal then prompts:  dd: failed to open ‘/dev/sdb1’: Permission denied   What permission? Anyone can help telling me what I'm missing?

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


I'm trying to reference the length of three arraylists in another method in a java file, but I keep getting null exceptions when I try to run the code, despite no errors being thrown. What am I doing wrong?  The important parts of my code are below, thanks for any help you can provide    public class Generator extends Application {      ArrayList<String> list1;     ArrayList<String> list2;     ArrayList<String> list3;     Text outputText;      public void readin() throws FileNotFoundException     {         Scanner in = new Scanner(new File("names.txt"));          ArrayList<String> list1 = new ArrayList<String>();         ArrayList<String> list2 = new ArrayList<String>();         ArrayList<String> list3 = new ArrayList<String>();          while (in.hasNext())         {             list1.add(in.next());             list2.add(in.next());             list3.add(in.next());         }     }      // ......  [primary stage code not relevant to this question]      public void handleButton(ActionEvent event)     {         Random generator = new Random();         int l1 = list1.size();         int l2 = list2.size();         int l3 = list3.size();          int lnum1 = generator.nextInt(l1);         int lnum2 = generator.nextInt(l2);         int lnum3 = generator.nextInt(l3);          outputText.setText(list1.get(lnum1) +                             " " + list2.get(lnum2) +                             " " + list3.get(lnum3));     }   }

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?


Evaluate $$\lim_{n \rightarrow \infty~} \dfrac {[(n+1)(n+2)\cdots(n+n)]^{\dfrac {1}{n}}}{n}$$  Attempt: Let $$y=\lim_{n \rightarrow \infty} \dfrac {[(n+1)(n+2)\cdots(n+n)]^{\dfrac {1}{n}}}{n}$$  $$\implies \log y = \lim_{n \rightarrow \infty} \dfrac {1} {n} [\log (n+1) +\cdots+log(n+n)-log(n)] $$  How do I move forward?  Thank you very much for your help.

Evaluate $$\lim_{n \to \infty} \frac{1}{n}[(n +1)(n+2) \cdots (n+n)]^{\frac{1}{n}}$$  We can write as $\displaystyle\lim_{n \to \infty} \frac{1}{n}[(n +1)(n+2) \cdots (n+n)]^{\frac{1}{n}}$ $$= \lim_{n \to \infty}\left[\frac{(n +1)(n+2) \cdots (n+n)}{n^n}\right]^{\frac{1}{n}} = \lim_{n \to \infty}\left[(1+\frac{1}{n})(1+\frac{2}{n})\cdots (1+\frac{n}{n})\right]^{\frac{1}{n}}$$  I have used this result if $\{a_n\}$ is a sequence of positive term which is convergent to $l$ and $b_n = (a_1. a_2 . \cdots a_n)^{1/n}$ ,thhen $b_n$ converges to $l$  here $a_n = 2$, but i think it is not right,how to use this result in this question. Give me hint how to proceed . Thank you


The reason I ask this is because there are several different versions of the Spell Sniper feat, and all of them double range for ranged spells with attack rolls. Most feats that are like this specify they don’t stack, but not Spell Sniper.  I'm not asking how you'd rule it, I'm asking if the base rules allow it. I can't find anything on this. I'm hopeful because this would mean that a sorcerer + warlock could eventually have a range of 9600 feet with eldritch blast.

I was looking at the Player's Handbook and I saw that there are 3 different types for Spell Sniper.   Simply put, does choosing all three of them create an 8 times multiplier?  For example, say that a Level 10 Arcane Trickster rogue were to use the three Ability Score Improvements they had to take three feats instead.   The feats taken (in no particular order) are Spell Sniper (Bard, Sorcerer, Warlock), Spell Sniper (Cleric, Druid), and Spell Sniper (Wizard).  Does the range benefit of each version of the feat stack, multiplying the range of any spell that requires an attack roll by a total of 8?  (I just inputted the values on D&D Beyond, and it seem like they added the multipliers together for 6 times multiplier. Fire Bolt has a range of 720 ft and Thorn Whip has a range of 180 ft. This is increased from 120 ft and 30 ft. Is this correct on their part?)


I want to define a new counter for numbering some headlines. I also would like to reference them. So, if I label the headline 3, then \ref should just return the number 3.   Unfortunately, all other references seem to be broken now. Take a look at the following code:  \documentclass[11pt,a4paper]{scrreprt} \usepackage[utf8]{inputenc}  \newcounter{LPCounter}  \newcommand{\LP}[2]{\refstepcounter{LPCounter}\label{#2} \noindent \textbf{LP \theLPCounter: #1}}   \begin{document}  \chapter{Chapter} \section{Section}  \LP{A}{lpA}  \LP{B}{lpB}  \begin{table}[h]\label{test} \textit{I am a table.} \end{table}  Here is LP 1: \ref{lpA}, and here is LP 2: \ref{lpB}. Here is the table: \ref{test}  \end{document}   The output now looks somehow like     Here is LP 1: 1, and here is LP 2: 2. Here is the table: 2.   So, instead of "1.1" I get "2". Why is that?

\documentclass{article} \usepackage{algorithm}  \begin{document} \setcounter{section}{54} \section{A section with no label} \begin{algorithm} \label{myalg} \caption{An algorithm with the label `myalg'.} \end{algorithm} Reference to myalg: \ref{myalg}. \end{document}   With this code, the reference givens 55 (the section number); if I move the label after the caption command, I get the correct reference (1).  Why should this be the case? I find it confusing: when thinking about an algorithm as an environment, you expect to be able to label it right after you began it. At the very least I would expect some kind of error or "??" to appear, rather than the previous environment or reference-able entity being used.


I have a very peculiar question. We have some categories of substances like transparent, opaque, translucent. My question is when it comes to transparent objects like glass which is solid, how can we see through it. Since matter is made up of atoms which contains electrons, protons, neutrons, etc, is it like are we seeing through them. If yes are these particles like electrons are see through particles. Does the same apply for water(does oxygen atoms and hydrogen atoms can be see-through) and atmosphere(which is combination of lot of gases which contain different particles). Ideally they should obstruct the path like the opaque objects do right? I have seen other questions but could not get proper understanding and those haven't answered my question.

Once I asked this question from my teacher and he replied "Because it passes light.". "And why does it pass light?" I asked and he said, "Because it is transparent.".  The same question again, Why glass is transparent? Why does light pass through it, while for opaque objects, it does not?


I'm looking for a word that describes someone that remains calm when others panic, specifically in a calamity or accident.  Example 1: Someone that is in an auto accident and they remain level-headed when others around them freak out.  Example 2: Someone that hold it together in a natural disaster while people around them break down into hysteria.  Possible sentence 1: "John is a ________. He kept it together when the hurricane hit."  Possible sentence 2: "Devin is a real ________. He was still calm after hitting that vulture with his Jeep."  (Before you ask, yes, I hit a vulture with my Jeep today.)

What is an adjective to describe the duality of a first responder (such as an EMT responding to a terrorist attack) who is terrified for the wounded, yet simultaneously calm, detached, and capable enough to give aid?


How can I install preferably the latest version of MySQL Workbench on Ubuntu 14.04?

I have installed MariaDb as its supported by Ubuntu community , mentioned in release note of latest LTS.  After that I tried to install Mariadb-client , that too installed successfully, after that its good to have GUI tool So decided to install MySql-workbench from both Ubuntu-SOftware-Center and via Terminal but it prompted errors mentioned below-  Error via Ubuntu-Software-Center-   This error could be caused by required additional software packages which are missing or not installable. Furthermore there could be a conflict between software packages which are not allowed to be installed at the same time.  mysql-workbench: Depends: libgcc1 (>= 1:4.1.1) but 1:4.9-20140406-0ubuntu1 is to be installed              Depends: libgtkmm-2.4-1c2a (>= 1:2.24.0) but 1:2.24.4-1ubuntu1 is to be installed              Depends: libpcrecpp0 (>= 7.7) but 1:8.31-2ubuntu2 is to be installed              Depends: python:any (>= 2.7.1-0ubuntu2) but it is a virtual package              Depends: mysql-workbench-data (= 6.0.8+dfsg-2) but 6.0.8+dfsg-2 is to be installed.   Error via Terminal-   The following packages have unmet dependencies:     mysql-workbench : Depends: mysql-client     E: Unable to correct problems, you have held broken packages.   This one has become confirmed bug on launchpad as mentioned   On the official website of My-sql , the versions of workbench are only available till saucy (13.10) , So how can I install it.   UPDATE 1  Added the following lines in /etc/apt/sources.list  # MariaDB 10.0 repository list - created 2014-04-19 11:47 UTC # http://mariadb.org/mariadb/repositories/ deb http://mirror.mephi.ru/mariadb/repo/10.0/ubuntu trusty main deb-src http://mirror.mephi.ru/mariadb/repo/10.0/ubuntu trusty main   No change , still same issue. There is some problems between trusty and version 10.1.10 of Mariadb . So tried  sudo apt-get install libmysqlclient18=10.1.10-mariadb1~trusty mysql-common=10.1.10-mariadb1~trusty   And its output is -  E: Version '10.1.10-mariadb1~trusty' for 'libmysqlclient18' was not found E: Version '10.1.10-mariadb1~trusty' for 'mysql-common' was not found   So the thing is simple it could not find it . though its there on the official website.  UPDATE 2  Removed MariaDB 10.1.10 , but the problem is still same with MariaDB 5.5.37.


The initial question is:  Alan and Barbara play a game in which they take turns filling entries of an initially empty $2008\times 2008$ array. Alan plays first. At each turn, a player chooses a real number and places it in a vacant entry. The game ends when all the entries are filled. Alan wins if the determinant of the resulting matrix is nonzero; Barbara wins if it is zero. Which player has a winning strategy?  Answer: Barbara has a winning strategy by a basic parity argument. Label the rows $r_1,\ldots,r_{2008}$ and partition them into 'slices' of two, say $\{ \{r_1,r_2\},\{r_3,r_4\},\ldots,\{r_{2007},r_{2008}\}\}$. If Alan places an entry in some spot, Barbara places the same entry in the same column in that slice; for instance, if Alan plays $5$ in $a_{332,98}$, Barbara plays $5$ in $a_{331,98}$. This ensures the rows in each slice are equivalent, so the determinant of the matrix is zero.  My question: How can this be modified if instead of a $2008\times 2008$ array, they play on a square array with odd sides ($3\times 3,5\times 5,$ etc., with the $1\times 1$ case discarded)?  I don't know of a winning strategy even for the $3\times 3$ case. I think Barbara's strategy breaks down because Alan isn't forced to complete a row in the same way as he was in the even case, so it isn't clear to me that Barbara can force one row to be a linear combination of another. I also think the strategy of, 'Barbara tries to get a column/row of zeroes,' is easily disrupted, so I don't see that as viable either.

Alice and Bob play the following game with an $n \times n$ matrix, where $n$ is odd. Alice fills in one of the entries of the matrix with a real number, then Bob, then Alice and so forth until the entire matrix is filled. At the end, the determinant of the matrix is taken. If it is nonzero, Alice wins; if it is zero, Bob wins. Determine who wins playing perfect strategy each time.    When $n$ is even it's easy to see why Bob wins every time. and for $n$ equal to $3$ I have brute-forced it. Bob wins. But for $n = 5$ and above I can't see who will win on perfect strategy each time. Any clever approaches to solving this problem?


Is there a flag/option for touch, mkdir, >, or some other command that will allow me to create a file and any non-existent parent directories at the same time?  For instance, let's say I'm in an empty folder. Now I can create parent directories if they don't exist when creating a folder  mkdir -p nested/folder   I can create files in existing directories  touch nested/folder/something.txt   But I can't create a file in a directory that doesn't exist yet  touch nested/folder/deep/more.txt      touch: cannot touch ‘nested/folder/deep/more.txt’: No such file or directory   How would I create that deep folder at the same time I create more.txt ?

mkdir -p will create a directory; it will also make parent directories as needed.  Does a similar command exist for files, that will create a file and parent directories as needed?


First of all, I must say I'm in no way a data scientist or anything; I just happened to come across a problem, and I am attempting to use statistics to find the best solution.  The problem is about splitting each of six sets of items in two, with each combination having four parameters, and finding the split that minimizes four parameters. Specifically, I'm trying to optimize the book schedule, so that my desk mate and I can bring the required schoolbooks to school with the least effort - that is, with   minimal total weight for me $W_m$, minimal total weight for my desk mate $W_d$, minimal swapped books for me $S_m$, and minimal swapped books for my desk mate $S_d$.      How should I seek the best splitting, i.e. the combination that minimizes all four parameters?     My first thought was simple weighted Euclidean distance: simply assign a score $S = \sqrt{\alpha(W_m^2+W_d^2)+\beta(S_m^2+S_d^2)}$ to each combination, and then evaluate the $n$ lowest scores for some weights $(\alpha,\:\beta)$. However, my concern is that such a score would possibly give too much weight to suboptimal solutions, no matter the choice of weights. This seems especially true considering that [I read somewhere that] the Euclidean distance tends to favour closer points much more than farther ones.  Perhaps an improvement could be computing the average weight $W=\frac{W_m+W_d}2$ and the average swap number $S=\frac{S_m+S_d}2$, and then computing the weighted Euclidean distance between these, $S=\sqrt{\alpha W^2+\beta S^2}$.  Any thoughts?

Say there are 3 companies A, B and C. Each company has a quality rating from 0 to 100 and a price in USD.  Company    Quality    Price A          80         7.9 B          70         8.0 C          75         8.1   How do I determine the best quality-price trade-off? What kind of analysis should I use?


With the sample MWE below, TikZ generates the following diagram:  1. Drawing an arc  \documentclass{article} \usepackage{tikz} \begin{document} \begin{tikzpicture}   \coordinate[label=below:$a$] (a) at (0,0);    \draw (a) arc(0:180:2); \end{tikzpicture} \end{document}      2. Drawing a circle  \documentclass{article} \usepackage{tikz} \begin{document} \begin{tikzpicture}   \coordinate[label=below:$a$] (a) at (0,0);   \coordinate[label=below:$b$] (b) at (5,5);    \draw (a) arc(0:180:2);   \draw (b) circle [radius=2cm]; \end{tikzpicture} \end{document}      With \draw <coordinate> circle command, TikZ draws a circle, with the <coordinate> at its center.  With \draw <coordinate> arc command, TikZ draws an arc, with the <coordinate> as one of its endpoints.  I wish to understand, why this difference of behavior and how is TikZ drawing the arc with \draw (a) arc(0:180:2);.  Why does TikZ does not use (a) as its center point while drawing an arc similar to drawing a circle.  How does TikZ actually draw the arc with point a.  What is the reference and center point, when TikZ draws an arc.

Several questions about how arc is computed:   The start and end angles seem to be defined relative to the y axis, yet in the Tikz manual they are defined relative to the x axis. Is this right? Is the end angle defined between the y (or x) axis and the incoming path, or between the y (or x) axis and the extension of the path beyond the endpoint? Geometrically speaking, providing just the start and end angles (and radius) is not enough to define an arc unambiguously. Is there some other assumption, such as: Arcs must be less than 180 degrees? Or arcs must always curve counterclockwise?


I have a double stroke svg that I want to reduce to a single stroke svg. The area on the svg is defined as some white shapes that are overlayed on a black background, with anchors outlining the shapes and background.     I hope this makes sense  I almost want something like the monoline tool developed for text, so that I can simplify an icon to a single line svg for a lazer cutter.   Thanks.   Here's the closest thing I can get to a single line:

Recently I've been messing with Illustrator/Inkscape and trying to convert something like this:    to a single-stroked path like this:    I've searched a lot and I haven't found a solution.


Since I upgraded to 12.04, I am unable to RDP to a Windows 7 server. All I can see is a pop-up that says "Uable to connect to RDP server ". I am able to RDP using Vinagre, so that rules out any issues with my router or the Windows server. As far as I can tell, there are no logs from Remmina and the Debug window shows a blank. Any one got any ideas? Thanks.

I'm using Ubuntu and I'm trying to connect to another machine in a different network using remote desktop.   In Windows7 I have made the following in order to activate remote desktop:   I've gone to computer -> properties -> remote settings I've selected the option: "Allow connections from computers running any version of Remote Desktop I've opened "Windows Firewall with Advanced Security" In inbound rules I've enabled the rules for remote desktop (public and domain)   I have also installed Remmina in the Ubuntu machine.  For configuring it I did the following steps:   Selected the RDP protocol In the server input I have written the Windows machine public IP. In username / password I have typed my login credentials (the same as my Windows admin account)   But when I try to connect I get this error message:  "Unable to connect to RDP server 89.130.251.160"  If I ping my Windows7 machine, I have a correct response.  Any suggestions?


What will happen if the Initialiazation Vector (IV), i.e, the initial randomness fed in to the first block arrives mangled at receiver end? How will this affect the decryption? Will the receiver be abl to decrypt all blocks correctly? Or none? Or some?

I'm currently practicing on a purposely flawed login page, where I have to change the value of a cookie to enter. The cookie is an encrypted and encoded form of a simple JSON string with fields "admin", "username", "password". The admin field is set to 0, and the user/pass fields accepts anything. To login, I have to change this ciphertext such that the admin field is set to 1 when decrypted.  The encryption function works like this:   A raw string is padded, then encrypted with AES-CBC and a random IV. Then, this cipher text appends the IV (concatenation; IV+cipher).  Then, this is Base64 encoded, and returned.   So, to decrypt, we simply decode it with Base64, and split the result so that the 16 first characters are the IV, and the remaining is the ciphertext.   Now, I want to know the ciphertext when one character of the plaintext is changed.   Specifically, in my example:  The following string is encrypted, appended to the IV, and encoded:  {"admin": 0, "username": "admin", "password": "admin"}  This apparently results in the encoded text (found in cookie):  yMqlNejXMclgcU5+wbL40RY/mvIMW+AvguoMvCv0NemhRYzWzs7EQ2DXpvwsGmFynGpNWNyotYBea+P3Z3XZIvMBoMzdMVb/FtWQ+GV/MmA=  I'd like to know what this encoded text / cookie looks like if the plaintext is changed to {"admin": 1, "username": "admin", "password": "admin"} (note, the 0 changed to 1). The username and password can be anything, only the "admin": 1 part is important.  It appears the key is fixed, but the IV is generated at random every time I try to logout and login again.  Is this possible? If so, how?  Thanks!


During the prequel trilogy, we learn that the predecessor to the Imperial stormtroopers are all clones. Are the stormtroopers of the original trilogy still clones? If not, where do they come from?

Reading this article about , my nerd-rage started flaring as they claimed that Stormtroopers were still Fett-Clones 20 years after the rise of the Empire.  As I started thinking about it, I realized that everything I had read saying that Modern-Day Stormtroopers not being clones was from the EU - C Level books or games.   One of the quotes often cited for backing the idea that the Stormtroopers are clones comes from Princess Leia:     Aren't you a little short for a Stormtrooper?   But through the movie, paying close attention, Stormtroopers are often shown to be slightly different heights. One even hits his head in the doorway while others walk through uninjured.                                  Is there any G Canon fully canon (non-Legends/Infinities) evidence to support the idea that Stormtroopers are, or are not still clones at the time of Episode IV?


I'd like to use Migration Assistant to migrate data from a Late 2016 13" MacBook Pro to a 2009 Mac Pro. The only connection options I see possibly working are gigabit ethernet or USB.  I'm not sure if Migration Assistant will even use USB to connect two Macs. Even if it did, I'm at the mercy of the slower USB 2.0 port on the Mac Pro.  Is it possible to transfer data using USB and if so, is USB faster or is it faster to use gigabit Ethernet?

When using Migration Assistant to move users, files, and folders from an old Mac to a new one, you have a few different choices, depending on the Macs involved. Presuming that both Macs have appropriate ports, which ports should be used in a real-world situation? Please do not provide quotations of theoretical port speeds; I'm looking for real-world experiences as to what will get the job done faster.  Port choices:   FireWire 400 in target disk mode FireWire 400 to 800 in target disk mode FireWire 800 in target disk mode 100 Megabit Ethernet to Gigabit Ethernet in the OS Gigabit Ethernet to Gigabit Ethernet in the OS Thunderbolt cable in target disk mode


I am trying to move equations which i created in equalx equation editor for ubuntu to Libre office presentation. I tried to copy paste the equation code in insert-object-Formula but the size of equation is very small. It can't be readable. Also one can't increase its size. The only way I know is the following:   save it as tex file run it using latex to create dvi and then PDF Then using GIMP-Tools-Rectangular selection Paste the selection in presentation.   I looking for an alternative.

In a LibreOffice Impress presentation (Version 5.1.4.2 on Ubuntu 16.04), when I click Insert -> Object -> Formula, I see a visual toolbar that lets me add elements of an equation such as fractions etc. However:   The inserted formula is in a very small font (18 pt), and I do not find any way to enlarge it, neither within the formula editor nor outside it. Outside the editor, I can enlarge the font of the box, but it has no effect. It is very cumbersome to insert formulas through the visual editor. Is there a way to insert formulas in a plain text markup, like in Writer?


My question is regarding the question posed at the end of the proof.  My answer is that the result does not hold for all $m \ge 7$ because when $m=7$, the result is $343 \le 128$, which is false.  Is there another way to answer this sort of question besides directly trying different values until you get a false result?  EDIT:  Another question I have regarding this solution is:  In the proof for the inductive step, we start by assuming $k \ge 10$. But along the way, the author mentions $k \ge 1$ and $k \ge 7$ to justify the inequality.  Why do we bother to do this instead of just sticking with $k \ge 10$?


Is there a method on Windows or Linux for downloading all files* within an online directory, specifically:    so I have a local repository I can work on? Any browser or command-line solutions would be fine, and I am willing to download any browser.  *recursively

I have been using Wget, and I have run across an issue. I have a site,that has several folders and subfolders within the site. I need to download all of the contents within each folder and subfolder. I have tried several methods using Wget, and when i check the completion, all I can see in the folders are an "index" file.  I can click on the index file, and it will take me to the files, but i need the actual files.  does anyone have a command for Wget that i have overlooked, or is there another program i could use to get all of this information?  site example:  www.mysite.com/Pictures/ within the Pictures DIr, there are several folders.....  www.mysite.com/Pictures/Accounting/  www.mysite.com/Pictures/Managers/North America/California/JoeUser.jpg  I need all files, folders, etc.....