Why do all atoms follow the same $n$ and $\ell$ quantization conditions as hydrogen?
Why do non-hydrogen atomic orbitals have the same degeneracy structure as hydrogen orbitals?
How do I find least cost path over a DEM based on slope magnitude and direction? What sort of algorithms can I use to find a least cost path through a DEM where it costs more to traverse a cell going downhill or uphill than it does to follow the contour of the land?  All the examples I've seen involve creating a least cost surface where the magnitude of the slope is part of the cost - but the direction isn't.    Additionally, the examples assume the cost to travel through a cell does not depend on the direction of travel. Difference between pre-increment and post-increment in a loop? Is there a difference in ++i and i++ in a for loop? Is it simply a syntax thing? Some lands have an ability to become a creature, but they usually say they are still a land. If a land is a 3/3 creature and a land, can you target and kill it with a  to send it to the graveyard, or does it remain in play as a land? To make it simple, I want to highlight a group of tikz nodes like in the following picture    It was borrowed from the . I would like to know which Tikz commands I can use to do the job in order to automatize this task for several trees I have to make. It is important to keep the blending effect of colors like in node g. Here is the MWE also borrowed from :  \documentclass{article}  \usepackage{tikz} \usetikzlibrary{arrows,backgrounds,calc,trees}  \begin{document} \thispagestyle{empty}  \begin{tikzpicture} \node (f) {f}     child { node (g) {g}       child { node (a) {a}     }       child { node (b) {b}     }   }     child { node (h) {h}       child { node (c) {c}     }   }; \end{tikzpicture}  \end{document} crossfade between 2 videos using ffmpeg Fake News Detection problem I would like to work on a project for Fake News Detection especially for Indians news which are in different languages and different formats.   Fake news as image with no or very less text Fake news on a blog site Fake news as Tweets Fake news in Hindi Fake news in the watsapp group and shared across.   Need your help on the approach. One approach I can think of is using OCR we can read the content of the post, then search those content in the google. If the news is not present in any of the famous print media then we can tag it as fake. However there can be many challenges in this. What if the print media itself gives any fake news shared by someone.  How to handle the scenario where there is no text in the image but the information shown as image is fake.  How to handle posts written in Hindi. ?  And even if we detect fake news, is there any way to make the person accountable for sharing it. ? I know it is little difficult problem to solve. But is there any work currently done by any company on this. ?  Any starting point for me to get into this domain ? Let $G$ be a finite semi-group with identity such that it has only one idempotent.Is $G$ a group?  It only remains to show that for any $a\in G$ $\exists b\in G$ such that $ab=ba=e$ where $e$ is the identity of $G$  Also $e$ is the only idempotent of $G$ .How to proceed next? ViewPager as a circular queue / wrapping Recovering data off of a dead hard drive My hard drive died in my macbook and it no longer will start up. It will not mount in an external enclosure but disk utility is still reading that the hard drive is there, and I tried to repair disk and I am getting this error: (Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.) So my question is how do I backup my files if the hard drive won't mount? The only way that I have been able to see the hard drive is through disk utility. I just want to be clear that I am using mac os x snow leapard. Can some metadata about deleted posts be included in Data.SE? Does personified Death really exist in Harry Potter? I went through the last book, Harry Potter and the Deathly Hallows, yesterday and a question popped in my mind: Does Death, the supposed creator of the Deathly Hallows, really exist in the Harry Potter universe? Dumbledore thought otherwise and I am with the same school of thought.  By the way who created the deathly Hallows actually?  Update:  1) Why were the brothers so sure that the hooded figure was death(couldn't it be a more powerful wizard playing with them)  2) Couldn't, Beedle and the brothers create this story? Where such a term would reference the location/time of an object, almost like it was of a property of the object. That is to say, if a duck is red, blue, yellow etc, we describe it has having a certain colour. If it's a nanometre, or 10km big, then it's property of size.  Now I know that where/when an object exists an object isn't a property of an object, but it is something unique to that object, so I think it would be useful to have a shorthand for 'geographical location', and 'time of existence'.  There are terms describing both time and location, such an event, or rendezvous (which I think is used to describe the when and where of a meeting between two humans) but I wan't a term that just describes one of each. How to update Ubuntu terminal? How to update Ubuntu terminal? Does it exist a free interactive geometry software, like GeoGebra, which works for 3D geometry? I would be able to draw spheres, great circles, and so on. Generalized Tube Lemma Reference for the subgroup structure of $\rm{PSL}_2(q)$ This material is covered in detail in Dickson's "Linear Groups with an exposition of the Galois Field Theory", chapter XXII and Huppert's "Endliche Gruppen", chapter II, paragraph 8. Since I don't speak german and Dickson's treatment often requires deciphering, I was wondering if there is a "modern" account of this somewhere. Flawed proof that all positive integers are equal How to distribute the objects on a sphere evenly? I want to replicate this mesh -    I think the best way is using a particle system of cubes. So I need to create a sphere of simple circles. It is necessary that in each circle the vertices are at equal distance from each other. But I don't know how to create those circles. Problem to launch java at Debian: "error while loading shared libraries: libjli.so" Can't format my usb drive. I have already tried with mkdosfs and gparted I have a MicroSD card in a USB adapter (which plugs into a USB port on my machine, and acts like a USB flash drive). I was using Unetbootin to make this a bootable USB flash drive with Kubuntu. But I needed to cancel while it was working. So I killed the Unetbootin process from the console.  Since then, I can't format the MicroSD or delete the folder that Kubuntu made. I have also tried mkdosfs, with no success. I can't mount the drive anymore either? What can I do to make this drive usable again?  Trying to create a new partition table in GParted, as described in Eliah Kagan's answer, does not work. It fails with the error message "imposible crear tabla de particiones" ("unable to create a partition table").