I would like to know where this color aberration comes from in my pictures, so that I can avoid it wherever possible.  Here is a picture I took in the sunny afternoon with my 50mm 1.4G (nikkor) wide open at 100iso:     If this comes from the lens, how the professional photographers do to avoid it? (I assume my lens is quite good :-) but I may be wrong).  And here is a close up of the color aberration that I'm talking about :
What is Chromatic Aberration? Is it a physical part of the lens, or just an optical illusion?
Is just after your PhD a good time to switch your research area? I am finishing my PhD soon. The area in which I pursued my PhD is very challenging as I was only able to publish couple of papers even after spending many years. I want to switch into other research are due these reasons   to attract more students  to be comfortable to do research (along with teaching, I should be able to do research)   Even though I like the research I am doing right now, I seem to be isolated in my university. If ten students join my university for a PhD, hardly one student takes this area. My research area is not like machine learning or deep learning etc, so researchers of my domain are also not that much interested in my work.   The thing is I can work different research area but: Is this the right time? I am heading to a post-doc and learning a new area will probably take several months. Although my switch is not 180 degree, I am still worried. How to detect if a function is called as constructor? Given a function:  function x(arg) { return 30; }   You can call it two ways:  result = x(4); result = new x(4);   The first returns 30, the second returns an object.  How can you detect which way the function was called inside the function itself?  Whatever your solution is, it must work with the following invocation as well:  var Z = new x();  Z.lolol = x;  Z.lolol();   All the solutions currently think the Z.lolol() is calling it as a constructor. Is there a way to make PythonTEX compile as of today in Overleaf V2 ?  \documentclass[]{article} \usepackage[utf8]{inputenc} \usepackage{pythontex}  \begin{document} \begin{pyverbatim} def calc_ellipticity(theta, delta):     theta = np.deg2rad(theta)     psi = np.arcsin(np.sin(2*theta) * np.sin(delta))/2     return np.tan(psi) \end{pyverbatim} \end{document}   Compiling gives : ? PythonTEX ? How to install Windows 7 after Ubuntu and dual boot? I just installed Ubuntu, a full install removing the prior OS. I was forced to remove  from my  because of the max four partitions already being there. I didn't lose anything, all backed up. However, now I am looking to create another partition and install Windows&nbsp;7 on it.   Do I also need some sort of boot loader that lets me choose which to boot? A   B   C   D   E   F             I don't even know. It just seemed weird.  Yes, I understand I could just avoid doing something like that. But the problem already exists with a single level.   Consider having 2 images in a post. Both exceed the maximum width of a post. One is nested in a list. Key to this issue is that my original images were much larger. They were automatically resized.  Image    List      I think it looks weird. I'm trying to mount my HDD,  /dev/sdb, which is connected via an enclosure but every time I try do so I get an error message   mount: /dev/sdb: can't read superblock   How do I solve this problem and mount my HDD? Is my phone liable to explode if I charge it with a charger that came with a different phone? Any open subset of $\Bbb R$ is a countable union of disjoint open intervals I would be happy to get some hints on the following integral: $$ \int_0^1\frac{x^{19}-1}{\ln x}\,dx $$ hyperlink name with biblatex authoryear (biblatex 1.4b) Is it possible to reference an excel cell in a comment? I have an Excel balance sheet with a total at the bottom. On that cell I have a comment that says that the reason the total is X is because of what happens in J2. What happens if I insert another row before that, now my comment is wrong because all the rows jumped up a value.  Is there any way to reference a cell dynamically in an Excel commment? What kind of material is the Robert Downey Jr. Iron Man's armor supposed to be made from? I know he crafted the prototype from the things he had on hand, but once he was able to build the next one(s) in his own lab, what hi-tech material did he use for the movie armor? Can I register a retail boxed copy of a game with Steam? I personally do not like to purchase games digitally.  There's just something magical about going to the store, picking up a boxed game, staring at the amazing box art, bringing the game home and putting the disc in the drive.  That being said, I know that several game distribution companies are leaning more toward digital distribution, with[Steam holding a large chunk of that market.  Is it possible to buy a retail boxed copy of a game, but still get the benefits of Steam (automatic updates, install on multiple computers, etc.) ? Can the Earth's magnetic field be used to generate electricity? I need a binary search algorithm that is compatible with the C++ STL containers, something like std::binary_search in the standard library's &lt;algorithm&gt; header, but I need it to return the iterator that points at the result, not a simple boolean telling me if the element exists.  (On a side note, what the hell was the standard committee thinking when they defined the API for binary_search?!)  My main concern here is that I need the speed of a binary search, so although I can find the data with other algorithms, as mentioned below, I want to take advantage of the fact that my data is sorted to get the benefits of a binary search, not a linear search.  so far lower_bound and upper_bound fail if the datum is missing:  //lousy pseudo code vector(1,2,3,4,6,7,8,9,0) //notice no 5 iter = lower_bound_or_upper_bound(start,end,5) iter != 5 &amp;&amp; iter !=end //not returning end as usual, instead it'll return 4 or 6   Note: I'm also fine using an algorithm that doesn't belong to the std namespace as long as its compatible with containers. Like, say, boost::binary_search. How many days a year is a U.S. citizen allowed to stay in Morocco? I arrived in Morocco in October of 2014 and renewed my visa by traveling to Spain by ship for a day and getting my passport stamped again in January of 2015. My question is, am I allowed to leave the country and repeat this process this year by traveling again to another country, other than my own in order to return to Morocco for another 90 days? And if so, how many times a year is this allowed? I have read 180 days on some websites but there is not any clear answers anywhere about this that I can find. I'm doing magnification and lens in class currently, and I really don't get why virtual and real images are called what they are.  A virtual image occurs the object is less than the focal length of the lens from the lens, and a real image occurs when an object is further than focal length.  By why virtual and real? What's the difference? You can't touch an image no matter what it's called, because it's just light. What do you call a person who does/thinks the opposite of the crowd for just that reason? Show vote counts on activity>comments page It would be helpful to show vote counts on the activity > comments page, and also allow sorting by votes.  This would make it easy to see what comments other people thought were valuable or at least amusing. How do I show that if $f : [0,1] \to [0,1]$ is continuous, then there is some $c$ such that $f(c) = c$? Theorem: Let $f:[0,1] \to [0,1]$. Assume $f$ is continuous. Then there exists   $c \in [0, 1]$ such that $f(c) = c$.         For any function $f$, let $g(x) = f(x) − x$. If the theorem is true, what does that say about $g(c)$?   Write a proof of the theorem. Do it by applying the Intermediate Value Theorem   in the appropriate way to the function $g(x) = f(x) − x$ with $a = 0$ and $b = 1$. Clearly state why the hypotheses of the IVT are satisfied here.        Well if the theorem is true, then there exists $c$ such that $f(c) = c$. Then $f(c) - c = 0$. Then $g(c) = 0$. Intermediate Value Theorem: Let $I$ be an interval and $f$ a function whose domain contains $I$. If $f$ is continuous, then for all $a, b \in I$ with $a &lt; b$ and all real numbers $k$, if $k$ is strictly between $f (a)$ and $f (b)$, then there exists $c$ such that $a &lt; c &lt; b$ and $f (c) = k$.   Proof Attempt: Take $a = 0$ and $b = 1$. Then $a,b \in[0,1]$ and $a &lt; b$. Since $f:[0,1] \to [0,1]$, it follows that for all real numbers $k$ such that $f(a) &lt; k &lt; f(b)$, then there exists $c$ such that $a &lt; c &lt; b$ so $0 &lt; c &lt; 1$ and $f(c) = k$. Then $f(c) - k = 0$. Thus, since $g(x)=f(x)-x$, it follows that $g(c) = 0$.   Looking to see if I did this correctly and/or if there is a more elegant way to prove problem 2. I am a little confused why the first theorem is true, but I went with it.