How can I improve the sharpness of my Sigma 50mm 1.4 DG HSM lens?
Why are my photos not crisp?
What is the best way to determine the number of days in a month with JavaScript? I've been using this function but I'd like to know what's the most efficient and accurate way to get it.  function daysInMonth(iMonth, iYear) {    return 32 - new Date(iYear, iMonth, 32).getDate(); } We have a pool of N number of balls.  There are: A number of white balls (W), B number of green balls (G), C number of blue balls (B), and D number of pink balls (P)  In how many ways (combinations) we can pick X number of balls from this pool? Is there a formula for something like this?  This is similar to combinations with replacement, but there are limitations to how many times a certain object can be replaced. What happens when a moderator clicks 'leave open' in the close-vote queue? It takes  clicking "leave open" in the close-vote queue to remove the question from the queue.  How about diamond mods?  Do they remove it from the queue in one click, or not? How to evaluate $\int_{0}^{\pi }\theta \ln\tan\frac{\theta }{2} \, \mathrm{d}\theta$ Under what assumptions can a semigroup $(S,*)$ be embedded into a group? I have just started studying implication in mathematics. So, you'll probably have an idea of where my confusion lies right from the get go.  In the truth table, where $A \implies B$ we obtain this result:  A   B   T/F ___________ T | T | T T | F | F F | T | T F | F | T   Now, my confusion here is regarding why $A\implies B$ given A is false, and B true. The others I understand. The first and last one are obvious, the second one implies, to me anyway, that given A implies B, the truth of B rests upon the truth of A, B is false, A is True, which cannot be, thus not B given A is false.  Now... then, why is B true despite the fact that A is false? Or rather, why is the statement B given not A, True. The truth of B is implied from the truth of A, but A is a false statement. So it's very contradictory that this may be, and in fact, if you go through a real life example, you would find that the third statement seems to be false.  Say $A$ is the statement that it is dark outside, and $B$ the statement that the sun is not on our side of the earth. If it is not dark outside, than stating that the sun is on the other side of the planet must be wrong (in my example i'm going to claim that the sun is the only light source).  Side note:  I just had a thought, if A is false, does that mean you can conclude... mmm, whatever? I mean, B is implied via the truth of A, if A is false, B is NOT implied, but then B could be EITHER true or false, I suppose. Is this correct?  However, would that not mean that A does not imply anything when false. Would that not set the 3rd and 4th statement to be undefined? I did not create a swap partition during Ubuntu installation.  Later, I freed up some space and made a swap partition.  Now after each boot up, I am manually opening gparted to right-click the swap partition to turn on the 'swapon' option.  How can I automatically enable the swap partition at boot?  Also, if I had not created the swap partition, what are my other options? I have read the first five Dune novels and after the first I do not recall any further mention of Imperial conditioning. In the novels written since Frank Herbert's death, were any further references or details given about what this process actually involved and why it was considered virtually impossible to remove? Terminal not displaying colors for directory listings I don't know why my bash session doesn't show colors. I have tried Terminal as well as iTerm.  I have tried:   ls -G Setting export CLICOLOR=1 and export LSCOLORS=GxFxCxDxBxegedabagaced Using different themes such as solarized and something else   The versions of my software are:   bash: GNU bash, version 3.2.51(1)-release (x86_64-apple-darwin13) osx: 10.9.2   I have Homebrew installed  I don't know what other information might be helpful. I spend a lot of time on the shell, this problem is becoming very annoying :)  edit: in terminal preferences, I have 'Declare terminal as: xterm-256color' and 'Display ANSI colors' along with 'Use bright colors for bold text' I just updated all my sites using the patch method of resolving the Drupal SA-CORE-2014-005 exploit. I just read reports that just yesterday there is someone from a Russian IP infiltrating drupal sites.     My main concerns are now:   How do I tell if my sites have been comprised? What should I search for in my apache access logs to detect if my site was a victim or not? So far what are these hackers doing to comprised sites? Just want to get clarification on something we're noticing in our org. Its regarding a new integration user we've created for an external application to connect to Salesforce. We also created a Connected App for this application to authenticate using OAuth. All of this is setup and working up to this point.   But one thing that we don't understand is there is a related list on the integration user detail page named "OAuth Connected Apps". We're concerned because although we are connecting fine and data is getting return to the external application no records are showing up in this "OAuth Connected Apps" related list. Should we expect to see Authorization or Access tokens in this list?   We just want to make sure we aren't bypassing the connected app in anyway, which we assume not, but just want to run it by the community and see. All comments are appreciated. Thanks ahead of time for the support. How can I fix "unbalanced brackets" in my data tag? Proving $f(x,y,z)=\big(\frac{x}{a+x+y+z}, \frac{y}{a+x+y+z}, \frac{z}{a+x+y+z} \big)$ is injective Let $a\in \mathbb{R}$, $a\neq 0$, and $E=\{(x,y,z)\in \mathbb{R}^3:a+x+y+z\neq 0\}$ and $f:E\rightarrow \mathbb{R}^3$ defined by $$ f(x,y,z)=\big(\frac{x}{a+x+y+z}, \frac{y}{a+x+y+z}, \frac{z}{a+x+y+z} \big) $$ Show that $f$ is injective.    I've been trying to prove it directly by showing that if $f(x_1,y_1,z_1)=f(x_2,y_2,z_2)\Rightarrow$ $x_1=x_2, y_1=y_2,z_1=z_2$. But I get a system of equations which I'm find difficult to deal with. Any help would be greatly appreciated. Why do diamonds shine? Which tag is used in the title of a question?   It does not seem to be the most popular It does not seem to be the first in the tagging order:   This question   is prefixed with NGINX (which is actually completely fine)  And it is tagged with "php nginx fastcgi magento" in the order of popularity.  Can we choose the tag to use in the title manually? Windows 8.1 fresh install with Windows 8 licence Install Spyder3 without Anaconda on ubuntu 16.04 Do the integral forms of Maxwell's Equations have limited applicability because of retardation? In the usual bookwork treatment, it is easy to show that the differential and integral forms of Maxwell's equations are equivalent using Gauss's and Stokes's theorems. I have always thought that neither version is more fundamental than the other and each has its place in solving problems. (See also  )  But: I have a conceptual problem with applying the integral forms of these equations in cases where there is time-dependence and the "size" of the loop or area means there is a significant light travel time across the regions considered compared with the timescale on which fields vary.  e.g. Suppose there is a time-varying current in a wire $I(t)$ and I wish to find the fields a long way from the wire. My first instinct is that this ought to be solved using the inhomogeneous wave equations to give A- and V-fields that are dependent on the retarded time - hence leading to the E- and B-fields.  But what about using Ampere's law in integral form? What is the limit of its validity? If we write $$ \oint \vec{B}(r,t)\cdot d\vec{l} = \mu_0 I(t) + \mu_0 \int \epsilon_0 \frac{\partial \vec{E}(r,t)}{\partial t} \cdot d\vec{A}$$ then presumably the $t$ that is defined on each side of the equation cannot be the same, since a change in $I$ at time $t$, presumably leads to a change in $B(r)$ at a time $t + r/c$? I suppose one does not care about this so long as the timescale for a current change is $\gg r/c$.  So my question is: Are the integral forms of Maxwell's equations inherently limited by this approximation, or is there a way of formulating them so that they take account of the finite size of a region in cases where the fields are time-variable? Globally disable "include online search results" Test -n gives unexpected result I understand test -n &lt;expression&gt; to return false if the expression evaluates to a string length of greater than 0.  Why then does the following happen?  Macbook:~ echo ${#undeclared_variable} 0 Macbook:~ test -n $undeclared_variable &amp;&amp; echo Foo Foo   Bash 4.x  My expectation is that since test -n $undeclared_variable should evaluate false, that Foo should not be echoed.  If I use [[  ]] instead of test, it works as expected.