I am an undergraduate pursuing mathematics and computer science in the research university at U.S.  Inspired from the applications of algebra to math and statistics, I have been trying to find a suitable project in the mathematics with supervision from a faculty member, or a reading course in some topics of the pure mathematics.  I have been sending emails to professors at the math department for either a reading course or a project (regardless of the difficulty) I can pursue, but they are either not interested or ignoring my emails and corresponding followup reminders.  When I visited one of faculties during her office hour, she told me that she have been ignoring my emails since she is not interested in my proposal of research idea (I felt sad for a while as I hope she just informed me she is not available).    The general outline is that I approach professors doing research similar to my interest, and ask them if they have any available project.  If they do not have projects, then I ask them if they are interested in hearing about my own ideas.  I am started to feel anxious about it as I really like to work with professors in the mathematics (my interests are not really in the domain of CS, but more or less the pure mathematics and its applications in theories of CS); I am interested in their research, but they are not interested. I understand the busy schedules of professors, so I am curious if there us any way to approach them to acquire the opportunities of project or reading course. So far, none of the professors at the department is interested or available...
Dear Academic SE advisers,  I am a college sophomore in US with double majors in mathematics and microbiology. My algorithmic biology research got me passionate about the number theory and analysis, and I have been pursuing a mathematics major starting on this Spring semester. I have been independently self-studying the number theory textbooks written by Niven/Zuckerman/Montgomery, Apostol, and Ireland/Rosen on this semester. As this semester progressed, I discovered that I am more interested in the pure mathematics than applied aspects (computational biology, cryptography, etc.). I want to pursue a career as analytic number theorist and prove the Collatz conjecture and Erdos-Straus conjecture.   I have been thinking about doing the number-theory research on my university (research university; huge mathematics department). I have been self-studying the NT by myself and also regularly attending the professional and graduate seminars on number theory but I did not do any pure mathematics research as an undergraduate. Should I visit NT professors in my university and ask them about if I can do undergraduate research under them? If research is not possible (perhaps due to my lacking maturity), should I request of doing independent reading under them and later proceed with the research? How should I ask them? What should I address? If even independent reading is not desirable to them, what should I ask to them or do in my own?   As for my mathematical background, I have been taking Calculus II (computational) and discrete mathematics. I will be taking calculus III (vector calc.) on Summer, followed by Analysis I, Probability, Theoretical Linear Algebra on Fall 2015. As for my self-studying on this semester, I have been studying NT textbooks (mentioned above), proof methodologies, and basic linear algebra.   Thank you very much for your time, and I look forward to your advice!  Sincerely,  PK
Looking for the proof of the lemma asserting that the conical surface (envelope) is a closed space. Thank you. How many numbers of 6 digits, that can be formed with digits 2,3,9. And also divided by 3? How many numbers of 6 digits, that can be formed with digits 2,3,9. And also divided by 3?  $$$$ I was trying to to add 2^6 (when there is no 2)+ C(6,2)2^2 (when 2 can be in two places)+C(6,3)2^3 (when 2 can be in three places)... I am wondering how to differentiate all these different joins ... What's the application extension? (aka .exe, .app, etc.) I'm new to Ubuntu. What's the application extension for development reasons? I know Windows is mainly .exe and Mac is .dmg or .app. Does Linux have an unique one? How do you associate the .exe file extension with a program in Windows? "Questions like this" or "questions like these" Assurance that ST_Envelope works with geography as expected Using PostGIS, I have a table of data with geographic points defined as last_known_coordinates GEOGRAPHY(POINT,4326). I want to find all of these within a geographic bounding box with given top left and bottom right geographic coordinates, and be sure that the calculations are geographic, not geometric, e.g. that the results account for the curvature of the earth. The query I'm using contains the fragment: last_known_coordinates &amp;&amp; ST_MakeEnvelope(?, ?, ?, ?, 4326)::geography As you can tell I'm a bit new to this, and I know what I want, but not necessarily how to do it correctly. Other answers hint that this is correct, but I'd like to know for sure: Will this point data and SQL fragment take into account the curvature of the Earth in the bounding box? Why doesn't an orbiting body keep accelerating? As a physics newbie I'm trying to get a grip on basic orbital mechanics. I think I'm beginning to get grasp on how bodies interact with each other. When a body approaches another body it accelerates due to gravity. It can reach a point where its velocity is high enough to keep falling but also keep missing the object it is falling towards. What keeps it from accelerating (because of gravity) and eventually reaching escape velocity? I feel like I'm either looking at things the wrong way or I have the entire thing wrong. Assume  $$\lim_{n\to \infty}  (y_{2n} - y_n)=0$$  then  $$\lim_{n\to \infty} y_n$$  exists.  I know it's not true, and I can see a sequence that disprove that $(1,1,2,1,3,2,4,1,5,3,...)$ but I want a sequence that has formula.  hint/help?  thanks Underscores in custom fields While trying to perform a WP_Query using meta_query(), I had some trouble because the custom fields created by a plugin had _ in the beginning of its name.   Although I noticed it was stored this way in the database, I had no idea why it was there and thought I had to reference it without the underscore (for the record, that is wrong).  Why do some custom fields start with underscores and others don't? What are the underscores used for? Are they mandatory in some circumstances? is it safe to keep database connections open for long time I have a .net client application which is connected to a remote database. Is it safe to keep a single connection open for the lifetime of the client (hours)? Does the answer hold if I have multiple (10 or 100) clients running? Why do prisms work (why is refraction frequency dependent)? It is well known that a  can "split light" by separating different frequencies of light:    Many sources state that the reason this happens is that the  is different for different frequencies.  This is known as .  My question is about why dispersion exists.  Is frequency dependence for refraction a property fundamental to all waves?  Is the effect the result of some sort of non-linearity in response by the refracting material to electromagnetic fields?  Are there (theoretically) any materials that have an essentially constant, non-unity index of refraction (at least for the visible spectrum)? Short Question:  Why can we manipulate a read-only file in Vim using : + w + q + ! even without being an administrator?  Long Question:  I have a text file (myFile.txt) which is read-only for everyone:  navid@navid-ThinkPad-T530:~/ubuntuTest$ ls -l myFile.txt  -r--r--r-- 1 navid navid 26 Aug 22 21:21 myFile.txt   I can open it with Vim without having admin privileges:  navid@navid-ThinkPad-T530:~/ubuntuTest$ vi myFile.txt    I modify it and press: Esc + : + w + q + Enter and I see this error message:  E45: 'readonly' option is set (add ! to override)   So far, everything makes sense.  But when I press: Esc + : + w + q + ! + Enter, Vim saves the changes.  I'm using Ubuntu 16.04 and VIM 7.4. I can get goosebumps at will, regardless of the environment. Its mostly visible on my arms, and I can feel it on my head. It requires some level of concentration to achieve this.  My questions are : what biological mechanisms are involved in doing this ? Is it common ? Is it useful ? Setting default values (conditional assignment) In Ruby you can easily set a default value for a variable   x ||= "default"   The above statement will set the value of x to "default" if x is nil or false  Is there a similar shortcut in PHP or do I have to use the longer form:  $x = (isset($x))? $x : "default";   Are there any easier ways to handle this in PHP? Custom thumbnailers don’t work on Ubuntu 18.10 and 18.04 Recently I had a bunch of my own scripts for the thumbnails in Nautilus: , , office documents and so on.  Seems like either I’m doing something wrong (thumbnail generation behavior changed), or custom thumbnailes don’t work in latest GNOME at all, even my previous scripts, which worked smoothly on previous versions of Ubuntu.  I’ve done some research, tried to run a simple script (see below) and it didn’t work out.  My test thumbnailer in /usr/share/thumbnailers/z.thumbnailer:  [Thumbnailer Entry] Exec=/home/maximal/thumb.sh %s %i %u %o MimeType=image/webp;image/x-webp   Where /home/maximal/thumb.sh is:  #!/bin/bash echo $0 &gt;&gt; /home/maximal/thumb.log echo $1 &gt;&gt; /home/maximal/thumb.log echo $2 &gt;&gt; /home/maximal/thumb.log echo $3 &gt;&gt; /home/maximal/thumb.log echo $4 &gt;&gt; /home/maximal/thumb.log   Then, when I remove thumbnail cache rm -rf ~/.cache/thumbnails and restart Nautilus nautilus -q, my log file doesn’t contain anything and ~/.cache/thumbnails/fail/gnome-thumbnail-factory contains all the failed thumbs (looks like corrupted/empty PNGs):    So, apparently, Nautilus even didn’t try to execute my thumbnailer script. When I try to run thumb command itself, it works perfectly. For example convert through cwebp|dwebp package:  convert -thumbnail 256x256 file.webp png:file.webp.png   When I wrap this command to a thumbnailer, it looks like it wasn’t even requested to run by Nautilus.  [Thumbnailer Entry] Exec=convert -thumbnail %sx%s %i png:%o MimeType=image/webp;image/x-webp;   Exactly the same situation occurs with other my thumbnailers: audio waveforms, office documents, photoshop files and so on.  Could anyone help? Names of close-voters are not visible in the post notice but in the revision history and timeline I am not a user with close/reopen votes privileges on Travel Stack Exchange, therefore I can't see the names of the close voters :    However, they are visible when going to the revision history:    or the timeline of the post:    This also happens when I am not logged in: I cannot see the banner (and so if the question has been closed), but from the revision history/timeline of the post I can get that information.  Shouldn't names of close-voters be completely hidden from people without close/reopen privileges (even if the revision history is a little hard to find)? I have a typical scientific manuscript in a LaTeX .tex file, and I need to convert it to MS Word .doc file.  The reason for having to convert to MS Word is I'm submitting the manuscript to an academic journal and they only accept MS Word (I know...)  The manuscript includes title page, figures, tables, equations (inline and in their own align environment), footnotes, bibliography, and an annex.  The tables are in their own separate tables.tex file, which I include using the \include{tables} command.  Most tables take up a whole landscape page, and were generated sing the package pdflscape.  I am using Windows 7 Professional.    My plan is to use pandoc to go from .tex to .odt, open the latter in Libre Office, and convert to .doc.  I have read a related  but it is too general.  Similarly the examples in the Pandoc  are too simple.  I have played around but I am unable to accomplish what I want.  This is surprising since converting a scientific manuscript is probably the most common use case for Pandoc. Here are some sample failures:  Example 1  I open a command line in the project folder, and execute the following:  pandoc -s document.tex -o document.odt   I get this error message:  pandoc: figure1: openFile: does not exist &lt;no such file or directory&gt;   where figure1 is the name of a figure file (e.g. figure1.png) in the project folder referenced in a line as \includegraphics[width=5.8in]{figure1}.  I suspect pandoc expects a .png extension but not sure how to provide it.  Example 2  Next I try .html, and excute the following:  pandoc -s document.tex -o document.html   The program executes fine.  I open HTML file.  Footnotes are there but figures are missing, tables are displayed as LaTeX, bibliography is missing, in-line math displays well, but math in align environment does not, section labels are displayed, and some other minor issues.  So given that mine is probably a typical use case scenario, my question is this: What commands should I use to get the .odt file I want?  I could not find a fully worked out example on the web.    Here is a specific list of errors.  I'll update how I corrected them based on community suggestions:   Figures not rendering.  Solved by adding .png extension to .tex file in \includegraphics command.  Now figures are included but they are huge, with half of each figure outside the page. No bibliography.  Solved. First, I have one huge consolidated Latex .bib file where I keep all my citations.  I manage it using .  This was giving me problems as I do not keep the cleanest .bib file in town.  So I reduced the problem by using a neat trick in JabRef that allows you to subset your master .bib file using the .aux file generated by Latex when compiling your manuscript.  In JabRef click on Tools > New Subdatabase based on AUX file.  This way I generated a much smaller biblio.bib file with only the articles referenced in my manuscript.  Running pandoc -s document.tex -o document.odt --bibliography=biblio.bib did the trick. Display math. Math in \begin{align} environment displayed in verbatim \latex;  (A partial solution is to use the  Libre Office extension.  Copy and paste the latex math code in the .odt file created by Pandoc into the equation editor, and so on.  Surely this could be built into a macro that can post-process all remaining math.)  UPDATE: Display math works very well using --mathjax extension. Inline math. Inline equation do not always render properly.  Bold math is a problem.  E.g. $\Sigma=\sigma^2\bm{I}$ displays as $\Sigma=\sigma^2\bm{I}$; Labels are displayed (e.g. section labels show as [sec:empirical] blah blah]; All tables display as raw latex. How do I remove a directory and all its contents? In bash all I know is that   rmdir directoryname   will remove the directory but only if it's empty. Is there a way to force remove subdirectories? First appearance of a predominately black cast in a TV show I was watching MeTV the other day, which is a fantastic station chock-full of old-time TV shows.  In one sitting I saw episodes of Superman, Batman, Wonder Woman, The Rifleman and Star Trek (TOS).  So it got me thinking...  None of these shows has many (if any) black actors.  And now I'm curious as to which TV show was the first to feature a predominantly black cast.  Anyone know?  I'm thinking back to What's Happening, Good Times, The Jeffersons...  But were there any before then?