There are black lines on my Nikon D3100 and I'm wondering if it is a problem with the lens or with the body itself.
In my question's preview, the attached image looks rotated. So, assuming you are able to see it in the real orientation, can anyone determine what is that dust flake type thing on the top, slightly towards the left?   One looks like a dust flake and there's another dot to the left of it?  Note: I wont have physical access to the camera until the weekend.  Is it just a dust flake on the lens or can it be some problem with the sensor? Its a 3 month old Canon 1500D.
USB-C Charging Speeds / Charger Outputs I own a 2016 Macbook (with the USB-C charging) - at the time and in response to all of the reports of poor cables and poor chargers, I bought a meter so I could see what the throughput of my cables/chargers was. However, having run some tests I'm now not sure what to consider normal / what is harmless to the battery.   For all tests I used an original Apple C-C cable - though was able to replicate with two third party cables I own.  I have the original Apple block charging at 14.3 V / 1.99 A and a third party block that charges the same.  Another third party block which advertises USB PD and 3 A is currently charging at 20 V / 1.43 A  I've done some research online but I can't find any articles that indicate what a normal USB PD output is relative to the devices that connect to it and would appreciate any guidance / assistance.   TL;DR: Have Apple charger which charges at one voltage/amperage. Bought several others advertised at PD which are higher voltage, lower amperage. Not sure what is 'safe', or 'fast', or does least overall damage to battery. US citizens travelling to Cuba are restricted to a set of "reasons" for travel, of which tourism is not one. I have US-Philippines dual citizenship, and both passports. Would I just buy the ticket using my Filipino passport? What kind of documentation/proof would I need to return back to the US? And as a US citizen travelling with a foreign passport, where would I go for US customs?  Thanks. Image looks embossed when converted to SVG How to prove $\lim\limits_{n \to \infty} (1+\frac1n)^n = e$? $\aleph_0$ is the cardinality of the set of natural numbers, $\aleph_0 = |N|$. $c$ is the cardinality of the continuum, i.e. the set of real numbers $c = |R|$.  I know that $|P(A)| = 2^{|A|}$. This means that the cardinality of the power set of a set is 2 raised to the power of the cardinality of that set.  This basically means that to prove  $2^{\aleph_0} = c$, I need to prove $c = |P(N)|$. I've seen the Cantor diagonal argument, although I have no idea on how to use it to prove this.   Could anyone suggest ideas of the simplest way to prove that $2^{\aleph_0} = c$? What's the difference between "either" and "neither"? Show that if $n>2$, then $(n!)^2>n^n$. Show that if $n&gt;2$, then $(n!)^2&gt;n^n$.     My work: I tried to apply induction. So, at the induction step, I need to prove, $n^n&gt;(n+1)^{n-1}$ Here, I tried to use induction again without any luck. I also took log of both sides, but I did not get anything. Please help! Yesterday I was filming a scene with my phone but suddenly the application crashed and when I try to open the m4v generated it says that is corrupted.  I have downloaded the video files (around 36MB) on my PC and I am trying to open and repair it. Can you suggest me a way to do it?  FFMPEG info  As suggested in comments I try check what FFMPEG says me about that file with this command  ffmpeg.exe -i VID_20120425_144739.m4v -c:v copy -c:a copy out.mp4 2&gt; log.txt   Here it is the result:  ffmpeg version N-40126-ga4b58fd Copyright (c) 2000-2012 the FFmpeg developers   built on Apr 26 2012 03:29:50 with gcc 4.6.3   configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-runtime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libass --enable-libcelt --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-libnut --enable-libopenjpeg --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libutvideo --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib   libavutil      51. 47.100 / 51. 47.100   libavcodec     54. 15.100 / 54. 15.100   libavformat    54.  3.100 / 54.  3.100   libavdevice    53.  4.100 / 53.  4.100   libavfilter     2. 72.100 /  2. 72.100   libswscale      2.  1.100 /  2.  1.100   libswresample   0. 11.100 /  0. 11.100   libpostproc    52.  0.100 / 52.  0.100 [mov,mp4,m4a,3gp,3g2,mj2 @ 003fc940] moov atom not found VID_20120425_144739.m4v: Invalid data found when processing input   Latest two lines are displayed in red. How many ways are there to distribute 5 distinguishable balls between 3 kids such that each of them gets at least one ball?   My approach is $ \binom{5}{3} 3! $ + $ \binom{2}{2} \binom{3}{2}2!$ which is equal to $66$? Phrase for a situation where a problem disappears when you are about to fix it, but reappears later For example, the car mechanic can't replicate the problem you are having every day, but when you drive it off the service dept, there it is again. Or, when seeing the dentist, the tooth ache goes away, and comes back when you leave. Dual citizenship passports and visas This is about entering the USA. I have   Hungarian citizenship with a 10 year B1/B2 visa in my passport I got before Hungary became part of the VWP. Real soon now, I will become a Canadian citizen (my oath is on April 5th) and will get a passport.   Since I, as a person, have a visa, am I obliged to enter into the USA with that? Or can I just forget it and use my Canadian passport? I know I could do whatever I want if I didn't have a visa but with that in the picture I am unsure.  describes a number of situations but not mine. How to connect Selenium to an existing browser that was opened manually in java or create semi automated tests? I want to achieve some use cases in which:  I want to perform some tasks that require manual intervention before kicking in automation execution. For instance, I need to manually launch the browser, navigate to the desired page, perform some manual tasks like entering captcha manually and then run the automation script to continue from there.  Debugging – Let's say we are working on a test script for a certain page (product checkout) in the application. But the script to reach that page (add to cart) is not ready yet. We can manually launch the browser and navigate to that page and then run the automation script.  Can someone help me to achieve this type of scenario? The definition of "Lie group" typically restricts to a smooth manifold.  If we instead define a "Lie group" to be a topological manifold such that multiplication and inversion are continuous, is the manifold necessarily smooth?  Is the smooth structure unique if we want a smooth Lie group?  I believe the answer is yes, since a connected Lie group structure is determined by the Lie algebra, but my search attempts failed. Clothing store access in Pokémon X & Y Once the player obtains access to Lumiose City for the first time, they'll be able to visit Boutique Couture from the city's Vernal Avenue (South fork, connecting from South Boulevard). Upon entering the store without performing any other actions, the player will be turned away and informed they "aren't stylish enough" and that they should visit more places in Lumiose City before visiting again.  This description is dubious, and doesn't inform the player of what they need to accomplish to gain access. Specifically:  Even beating the game (completing the Pokémon League) fails to allow access, as does modifying the player's look, visiting most shops in all areas of Lumiose City, and performing all hair stylist, PR studio, and associated actions. Completing a set of triple battles in Restaurant Le Wow did set the event flag that allowed access in my copy of Y, but it is not clear if this is the only requirement for access.  So other players may benefit, and so I know how to repeat this process if I obtain a copy of X or the future release of Z, what exact requirements yield access to this store for the first time? When is assembly faster than C? One of the stated reasons for knowing assembler is that, on occasion, it can be employed to write code that will be more performant than writing that code in a higher-level language, C in particular.  However, I've also heard it stated many times that although that's not entirely false, the cases where assembler can actually be used to generate more performant code are both extremely rare and require expert knowledge of and experience with assembly.    This question doesn't even get into the fact that assembler instructions will be machine-specific and non-portable, or any of the other aspects of assembler.  There are plenty of good reasons for knowing assembly besides this one, of course, but this is meant to be a specific question soliciting examples and data, not an extended discourse on assembler versus higher-level languages.  Can anyone provide some specific examples of cases where assembly will be faster than well-written C code using a modern compiler, and can you support that claim with profiling evidence?  I am pretty confident these cases exist, but I really want to know exactly how esoteric these cases are, since it seems to be a point of some contention. Network-wide HTTPS: It's time I have a WinXP installation that is used to only connect to another PC with RDP.   A dummy user account gets logged in automatically, then the user must click a link to start the RDP connection with predefined parameters.  Is there a way to run the RDP client without Windows Explorer being accessible? Using MAX in SQL Expression of ArcMap ModelBuilder Floor function in complex plane My question is very simple. How would one take the floor of a complex number and what is the floor of i? If $(\log_4 x)^2= (\log_2 x)(\log_a x)$ (the $4$ is the little number next to log by the way) , find the value of $a$.