My mom came from Venezuela to visit my sister and my family and after 6 months we applied for an extension of stay, she went to Mexico to visit my nephew and his wife but I want her to come back to the USA; how long does she need to be outside before she can re-enter the state?
I entered the USA on a three month visa waiver program from Australia. I am about to return to  Australia and would like to come back again to the USA. How long do I have to wait until I can re-enter the USA for another 3 months?
The set of homotopy classes Using the Pigeonhole Principle to show that $2$ of any $n+1$ numbers from $\{1,2,\ldots,2n\}$ sum to $2n+1$ Quantify Difference/Distance between Lognormal distributions I am trying to determine a metric that quantifies the distance between two continuous lognormal distributions. The data is actually a mixture of two lognormal distributions (I am not sure if this can be called bimodal). The individual distributions have different means but the same standard deviations. I have 20 data sets that can be divided into 4 groups, with each group having a constant standard deviation, but the 5 data sets in each group are made up of two distributions with different means. Some examples:      I am in search of a metric that accounts for the contrast (difference in means) and the standard deviation. I have tried out some parameters like coefficient of variation (of the mixture), Ashman's D etc. I have also tried percentage of overlap. However the problem always is that, at the end when plotted against the results I end up with 4 trend-lines again, corresponding to the 4 different standard deviations. Is there some other way I can quantify this?  Just to make myself clear, I want to quantify the difference between two distributions in a single case (between the red and green PDFs in the above image). Show that a ring is commutative if it has the property that ab = ca implies b = c when $a\neq 0$ Show that a ring is commutative if it has the property that ab = ca implies b = c when $a\neq 0$.   This is my proof to show that a ring is commutative if it has the property that ab = ca implies b = c.  We need to show that if x, y ∈ R then xy = yx. Let a = x, b = yx and c = xy. Then ab = x(yx) = (xy)x = ca. Thus, by the hypothesis, b = c, or xy = yx. Thus, for x, y ∈ R we have xy = yx.   How would I show when $a\neq 0$? The junction has a stop sign on each of the four entrances.   The junction has a stop sign on each of the 4 entrances.   The first is preferred, for some reason, by many English texts. Why? I haven't seen this phenomenon in other languages. Disable the "You've gone full screen" notification in Chrome Is it possible to recover original content from an edited image file? OK possibly a random question here, but one that is relevant to the site and regarding a hot topic nowadays: privacy.  If I load an image file (in my case a PNG photocopy of a document which contains some personal details) into Gimp, and I 'fill' with black (i.e. as if to redact) the areas of the image that contain sensitive information, and I then overwrite the original file, is there any way that the original untouched image can be recovered or gleamed? Such as low level bit analysis or...?  If so what tools and techniques are behind that, and how can I mitigate this? Is it a simple case of not overwriting the original but simply creating a new file with the changes? Proof of the formula $1+x+x^2+x^3+ \cdots +x^n =\frac{x^{n+1}-1}{x-1}$ Possible Duplicate:          Proof to the formula  $$1+x+x^2+x^3+\cdots+x^n = \frac{x^{n+1}-1}{x-1}.$$ Is "a total of 10 payments" singular or plural? A total of 10 payments were made.   OR     A total of 10 payments was made.   Which is correct? Or can both be correct? The expression 'not that bad of a' In an essay, a friend used the expression:       It wasn't that bad of an idea.    I think that it would be preferable to write       It wasn't that bad an idea   However, I can't explain why. When is unbalanced data really a problem in Machine Learning? Why didn't the Ministry use owls to find Sirius? Harry, before the Triwizard Tournament, was able to send owls to Sirius when he was in hiding (not at Grimmauld Place) just by telling them "just find him, will you?", and the owl would come back a few days later with an answer. This doesn't happen with Hedwig only, because, if I recall correctly, he uses school owls as well.  If finding Sirius was as easy as telling an owl "find him", and a 13-year-old wizard could do it, how come the Ministry had no clue as to where he was? They could've sent an owl with a summons and followed it from a distance.  Two theories, neither mentioned in the book, and both a bit unlikely:   He was living as a dog and -hopefully- the Ministry would not be able to recognize him. Unlikely because the owl would have got there anyway, so they would have guessed the dog was Sirius in disguise, not necessarily as an animagus, but maybe he could perform human-animal transfiguration (remember he was brilliant at school).. Kingsley Shacklebolt was already in charge of the hunt and Dumbledore told him Sirius was innocent and all that. Then, Kingsley would have prevented the Ministry from using any method that could've actually worked. Unlikely because they could've used owls before Dumbledore's tip, when Kingsley didn't know Sirius was innocent, and also because Kingsley was quite powerful and had the support of Crouch and others at the Ministry, so if he was in charge, they would probably have succeeded.   Your thoughts? Integral $ \int_{-\infty}^{\infty}\frac{x^{2}}{\cosh\left(x\right)}\,{\rm d}x $ I need to compute the improper integral $$ \int_{-\infty}^{\infty}\frac{x^{2}}{\cosh\left(x\right)}\,{\rm d}x $$ using contour integration and possibly principal values.  Trying to approach this as I would normally approach evaluating an improper integral using contour integration doesn't work here, and doesn't really give me any clues as to how I should do it. This normal approach is namely evaluating the contour integral $$ \oint_{C}{\frac{z^2}{\cosh\left(z\right)}\mathrm{d}z} $$ using a semicircle in the upper-half plane centered at the origin, but the semicircular part of this contour integral does not vanish since $\cosh\left(z\right)$ has period $2\pi\mathrm{i}$ and there are infinitely-many poles of the integrand along the imaginary axis given by $-\pi\mathrm{i}/2 + 2n\pi\mathrm{i}$ and $\pi\mathrm{i}/2 + 2n\pi\mathrm{i}$ for $n \in \mathbb{Z}$. The residues of the integrand at these simple poles are $-\frac{1}{4}\mathrm{i}\pi^{2}\left(1 - 4n\right)^{2}$ and $\frac{1}{4}\mathrm{i}\left(4\pi n + \pi\right)^{2}$, so that even when we add up all of the poles, we have the sum $4\pi^{2}\mathrm{i}\sum_{n = 0}^{\infty}\,n$, which clearly diverges.  Any hints would be greatly appreciated. I have created a logo with pen tool in Illustrator but between lines (where they intersect with each other) there is a gap where it gets the color of the background.  Something like this:  (Black color is the background color) - As you can see where the paths join each other there is a kinda dotted black line. I Grouped them but still the same. I converted to jpeg just to be sure it is not only shown like that but same effect.   NOTE: I want to export that logo as SVG file type and use it in the WEB. I tried some solutions given like anti-aliasing in preferences or art optimize when saving for optimization. But still I have same problem. I want to get that logo in SVG and put it on the web where it will display clean without those strange gaps.  How can i get rid of this? I tried to use my Virtual Box and this is the error I received - (I just updated to the new Ubuntu also) and I am VERY new at this Linux OS.     Kernel driver not installed (rc=-1908)      The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or   there is a permission problem with /dev/vboxdrv. Please reinstall the   kernel module by executing      '/etc/init.d/vboxdrv setup'      as root. Users of Ubuntu, Fedora or Mandriva should install the DKMS   package first. This package keeps track of Linux kernel changes and   recompiles the vboxdrv kernel module if necessary. How to calculate the integer part of the value of the following equation?  $$y=1+\frac{1}{\sqrt{2}}+\frac{1}{\sqrt{3}}+\frac{1}{\sqrt{4}}+\ldots+\frac{1}{\sqrt{1000000}}$$  It should be calculated in a special way, after all the equation is so long. How to remove indentation in footnote? I would like to configure my Ubuntu 12.04 server to synchronize its clock with a specific NTP server. Where to set this up? Is the sentence "There is a large number of labourers who want to migrate to Japan for work." correct? Possible Duplicate:             There is a large number of labourers who want to migrate to Japan for work.   I type this sentence in a word processor, and it reports an error that "is" should be "are" (subject-verb agreement).  I doubt this is a valid error. Could anyone confirm this? What does "Suit yourself" mean?