911 is the North American standard. I was thinking in case something happens and one were to panic that it'd be good to know if dialling 911, in other countries where it is not the primary emergency number, is still set up to go through to emergency services.
I know that the emergency services can be called FREE in the UK by dialing 999 and in the US by dialing 911.   What I don't know is the number to call in other countries and if there is a cost involved. This is something I think most people should find out before travelling but many don't (including me). Hopefully this will help me and other people.
Two homologous but not homotopic loops on a closed surface of genus greater than one Suppose $S$ is a closed surface with genus greater than $1$. Give an example of two loops on $S$ which are not homotopic, but are homologous to each other.   I need help solving this question. I have read the Wikipedia page on it and I realize that it does not contain the necessary knowledge to visualize this problem.  And I was also wondering the relation between the fundamental group $\pi_1(S)$ and the first homology group $H_1(S)$? Some restrictions is that $S$ is a closed surface and the genus is greater than $1$. What is this shell/Bash syntax: someVariable=someValue someCommand One of my coworkers has provided me with a Bash syntax that I am unfamiliar with.  My Google foo has failed me on figuring out what it does and why/when I should use it.    The command that he sent me was of this form:  someVariable=something command   Initially, I thought that this was equivalent to the following:   someVariable=something ; command   Or  someVariable=something  command   But this doesn't appear to the be case.  Examples:   [Jan-03 11:26][~]$ # Look at the environment variable BAZ. It is currently empty [Jan-03 11:26][~]$ echo $BAZ  [Jan-03 11:27][~]$ # Try running a command of the same format     [Jan-03 11:27][~]$ BAZ=jake echo $BAZ  [Jan-03 11:27][~]$     [Jan-03 11:27][~]$ # Now, echo BAZ again. It is still empty:     [Jan-03 11:27][~]$ echo $BAZ  [Jan-03 11:27][~]$     [Jan-03 11:28][~]$     [Jan-03 11:28][~]$ # If we add a semi-colon to the command, we get dramatically different results: [Jan-03 11:28][~]$ BAZ=jake ; echo $BAZ jake [Jan-03 11:28][~]$ [Jan-03 11:28][~]$ # And we can see that the variable is actually set: [Jan-03 11:29][~]$ echo $BAZ jake [Jan-03 11:29][~]$   What does this syntax do?  What happens to the variable that has been set?  Why does this work? Can you be tripped by an AoO while standing up? Why the middle mouse button in Blender 2.80 changes the orthographic view to perspective? If I choose an orthographic view by using the numpad and then try to orbit the geometry by clicking the middle mouse button Blender goes from orthographic to perspective. Why is that the default now? Wouldn't it be more logical if instead of that Blender kept the orthographic mode? In other words: Why Auto Perspective is turned on by default? Trigger Task Scheduler in Windows 7 when computer wakes up from sleep/hibernate I don't want task scheduler or whatever to wake the computer, but when I open the laptop back up and the machine wakes I'd like that to be the trigger that task scheduler or something uses to run an app. Newtonian mechanics: massless particles Why didn’t anyone dial Abydos before Daniel solved the mystery of the seventh symbol? From what I recall from the movie, Daniel only finds the seventh symbol... however when he explain they give way to show him the star gate and they put their sequence in the dialing computer. This proves the dialing computer was prepared to dial 7 chevrons.  It’s also stated they’ve also tested the 6 previous symbols in the order they appear on before, one has to assume only to fail when they insert the 7th, making them aware of the fact you can, at least dial 7th chevrons.  With 39 chevrons on the gate and 6 already locked in, that leaves 33 to try to get a lock. Those are not that many not to go and simply try one by one so... how come nobody brute forced the thing? What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)? I'm having trouble understanding the ROC curve.  Is there any advantage / improvement in area under the ROC curve if I build different models from each unique subset of the training set and use it to produce a probability? For example, if $y$ has values of $\{a, a, a, a, b, b, b, b\}$, and I build model $A$ by using $a$ from 1st-4th values of $y$ and 8th-9th values of $y$ and build model $B$ by using remained train data. Finally, generate probability. Any thoughts / comments will be much appreciated.   Here is r code for better explanation for my question:  Y    = factor(0,0,0,0,1,1,1,1) X    = matirx(rnorm(16,8,2)) ind  = c(1,4,8,9) ind2 = -ind  mod_A    = rpart(Y[ind]~X[ind,]) mod_B    = rpart(Y[-ind]~X[-ind,]) mod_full = rpart(Y~X)  pred = numeric(8) pred_combine[ind]  = predict(mod_A,type='prob') pred_combine[-ind] = predict(mod_B,type='prob') pred_full          = predict(mod_full, type='prob')   So my question is, area under ROC curve of pred_combine vs pred_full. Moving tfrom Shimano 9- to Shimano 10- speed I'm thinking of changing the 9-speed Tiagra rear mech on one of my (road) bikes to something, still Shimano, but 10-speed.  The obvious replacements I'll need are cassette, right-shifter and chain. But I reckon because of the narrower chain I'm also looking at a new chainset and rear derailleur. However I think the front derailleur and left-shifter should be safe (still keeping the front mech the same). Ditto the bb, regardless of whether I need a new chainset  Has anyone actually done this conversion and is able to confirm (or put me right)?  Thanks  Update  Decided in the end that going from 9- to 10- was too much to spend all in one go. But I used a service as an excuse to change the cassette (to a 9-speed ultegra) and the chain (dura ace) at quite minimal cost. Can upgrade other parts as and when, although I'm basically looking at Shim's 6500 range here so all quite dated now. Why are dot underscore ._ files created, and how can I avoid them? I am using different operating systems on different machines on different locations. I am using a USB flash disk to keep my files (source codes etc.).  I am new to Mac OS X and now I realize there are lots of files created with a dot underscore ._ prefix.  Questions  Why are ._ files created?   What are their purpose?   How can I avoid them? What happens when you run out of movement while jumping? How is acceleration measured if there is change only in the direction of velocity & not magnitude? The formal definition of acceleration is      It is the measure of how fast the velocity changes with respect to time.   Now, when the magnitude of velocity changes, acceleration $$\vec{a} = \frac{d \vec{v}}{dt}$$ and its unit is $m.s^{-2}$ .  But what about the case where the velocity only changes its direction keeping its magnitude constant? The definition can then be      Acceleration is the measure of how fast the velocity changes its direction with respect to time.   But how can I calculate the acceleration then?? What should be the unit then??? Please help. What if the universe is rotating as a whole? Suppose in the milliseconds after the big bang the cosmic egg had aquired some large angular momentum. As it expanded, keeping the momentum constant (not external forces) the rate of rotation would have slowed down, but it would never reach zero.  What implications would that have to measurments to distant supernova and CMB radiation? Do we have any experimental data that definitely rules out such as scenario? And to what confidence level?  Edit A  suggests that the universe might indeed be spinning as a whole. Anyone care to poke holes at it?  Edit 2 Even more  places limits on possible rotation. I am using 15.04.   So I'm working with git and I installed the standard version. I set up the ssh keys and was able to clone one of my repositories to the correct folder. Everything was working great and then I decided it was a good idea to install more packages. I ran sudo apt-get install git-all. I'm looking at error codes now having to deal with upstart.  start: Unable to connect to Upstart: Failed to connect to socket /com/ubuntu/upstart: Connection refused No apport report written because the error message indicates its a followup error from a previous failure. dpkg: error processing package runit (--configure):  subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of git-daemon-run:  git-daemon-run depends on runit; however:   Package runit is not configured yet.  dpkg: error processing package git-daemon-run (--configure):  dependency problems - leaving unconfigured Errors were encountered while processing:  runit  git-daemon-run E: Sub-process /usr/bin/dpkg returned an error code (1)   This is what happens when I even update/upgrade my system. At this point all I'm looking to do is be able to install software and update my current software. Is there any way I can potentially reverse this issue or at least correct it?   Edit: Thankfully this issue was solved only a day or two after it happened. The accepted answer worked perfectly and took care of my issue Undo git pull, how to bring repos to old state What's the best way make an "augmented" coefficient matrix? When studying systems of linear equations, it's nice to remind people that the last column of the coefficient matrix holds the constants.  This is often done in books by putting a vertical line between the last column and the next to last column.  What is a good way to do this in LaTex? Is the following scheme for generating $p_n=(1/3)^n$ stable or not. $p_n=(5/6)p_{n-1}-(1/6)p_{n-2}$. The novel centers around a man living a comfortable existence in the pretty distant future.  To support himself, he is occasionally asked to enter a box which will copy his entire body, and send it out faster than the speed of light to some developing world, to work.  His copy on this world wakes up and realizes what a big mistake he's made.  The copy does grueling work, feels lonely, and eventually just dies of radiation sickness.  Back on earth, the man never realizes how bad it is out there, and keeps sending out more copies.  I think the story is probably 80s or earlier - not sure if it's a short story, or the beginning of a novel which I lost &amp; never finished. Mechanism to prevent edits without approval? I would say a quarter to half my questions end up getting edited the vast majority of which end up dramatically changing the context of my question. I'm not against good advice (I've acted on about 2% of all the criticisms I have ever had about my work since they were actually thoughtful) though I think since I joined overflow sites years after I've had a good grip on most of the material I work with people are seeing low reputation and presuming that equates to low levels of comprehension.  Regardless of the reasoning behind people making edits is there an option I can use that would require my approval in order to commit an edit to my questions?   I have no interest in spamming questions in order to artificially boost my reputation. I am getting tired of having to add bullet points telling people to ask for clarifications instead of editing my posts. Having to correct my posts so often reduces my desire to ask the question if I have to review the question again (even with the revision pages available). As this is a discussion there is no reason to edit this post, I will be happy to revise my own if you leave comments as I actively follow questions I participate in though the office of redundancy redundancy requires that I state I know what I am asking.   For example, say I post about Kubuntu (which by default uses KDE) and someone edits it changing the OS to Ubuntu (which uses Gnome by default). Then, answers become Gnome-oriented for a KDE question and the entire context has been changed--negating the point of asking the question in the first place.