Turns in beta-alpha-beta loops (protein motifs)

Question: In the context of protein secondary structure, do the loops between strand and helix in a beta-alpha-beta motif form into the conformation known as a beta turn?
Comment: @gilleain It's easy to close this question as off-topic. The explanation you gave should probably be in the body, so that people who are not familiar with proteins would at least have an understanding as from where any confusion is coming from. In its current form the question is only helping people who already know the answer, hence don't need the question. // I downvoted, but I will not dequeue the question. Please [edit] the question to give some more context.
Comment: Why is this on hold as unclear? Both Beta-Alpha-Beta motifs and beta turns are well defined concepts. This is also quite a frequent source of confusion, as the names are similar enough that many students assume that beta-turns are only associated with BAB units. Of course, it's on the edge of chemistry, and more structural bioinformatics...
Comment: I thought I vtc'ed as homework, but I can't remember any more. I will try and edit later to improve the quality of the question.
Answer: So a beta-alpha-beta structure will have two loops that could be turns - between the first beta strand and the alpha helix, and the helix and the second strand. They might be beta turns, but they might not.
Although there are different definitions of beta-turns, one common one is the presence of a hydrogen bond between the carbonyl of residue (i) and the amino of residue (i+3). I'm not actually sure how frequent this is, but you can see this from a search on PDBeMotif. There is also Motivated Proteins, which gives nice 2D (and 3D) images of motifs.
However, you could get other conformations of these loops that are not beta-turns, especially if they are quite long.


Competitor is somehow accessing MetaData on a hidden Wordpress site

Question: We have a Wordpress site that is intended for direct traffic only - it has no main page or category pages etc., just individual pages that people are linked to directly.  They're not password-protected, but the site is set not to be indexed by search engines.  Recently a competitor gloated that he had been able to access metadata, including a list of all pages on the site and the site authors.  I just went through and did an audit of the site.  I've verified that the search query is deactivated and that none of the pages are showing up on Google.  How else might the competitor be getting access to our metadata?  Any and all help is appreciated.
Answer: Well we found one reason anyway - it looks like you can bring up a list of authors using ?author=1 query, which I hadn't even known existed.  Here's an article that explains how and how to fix it:
https://www.wp-tweaks.com/hackers-can-find-your-wordpress-username/


Multiple desktops on a Belkin Router

Question: I have a Belkin wireless router hooked up presently to a desktop. I just purchased a new desktop and would like to use the same router. I have connected a ethernet cable directly to a port on the router to the desktop. However on the new desktop it states that the cable is not connected/no good and try a new one. I know the cable is OK.Is there something that has to be installed on the new desktop to recognize the router. I also checked for devices on the new desktop and cannot see an ethernet connection????
Answer: sounds to me that the ethernet port is either disabled, or you have the cable plugged in wrong.
Go to your networking center in windows, then go to Adapter Settings --> see if its disabled in there, if so, enable it.
If nothing is there, then there's a problem. Either your device is disabled in the Device Manager, or is uninstalled (no driver), or is busted.
Right click on "Computer" then go to "Manage" --> go down to Device Manager and expand the tree for networking devices. See if you have your ethernet port there.

Multiple desktops on a Belkin Router


Allowing sudo privileges, but not access to sites

Question: Is it possible to make it so a user can use the sudo command in terminal, but not have access to sites other then those allowed through parental controls, without a third party system?
Comment: i think the real question should be why you trust one this much so you thinking about giving them sudo powers but don't trust them to not go on certain websites?
Answer: By adjusting the sudoers file (/etc/sudoers) with sudo visudo it should be possible to accomplish this. It is a hell of a job and you need a profound knowledge of all commands to fine-tune this while avoiding errors and loopholes though.
You have to add the user to the User privilege specification section
...
# User privilege specification
root    ALL=(ALL) ALL
%admin  ALL=(ALL) ALL
...

Then use a whitelist (or a blacklist) of allowed (or disallowed) commands:
Examples:
whitelist
# User privilege specification
root    ALL=(ALL) ALL
%admin  ALL=(ALL) ALL
user    ALL=/usr/bin/nano,/usr/bin/opensnoop

blacklist
# User privilege specification
root    ALL=(ALL) ALL
%admin  ALL=(ALL) ALL
user    ALL=!/usr/libexec/PlistBuddy,!/usr/bin/passwd,!/usr/sbin/*

You may mix whitelist and blacklist.
Please check man sudoers how to simplify things or narrow things down by configuring User, Runas, Host and Cmnd alias specifications.

Check the accepted answer to the question How to prevent sudo users from running specific commands? for the pitfalls of configuring a simple command like rnano in the sudoers file.
Answer: The two concepts are mutually exclusive.
Adding someone to the sudoers list effectively gives them the power to bypass any restriction you wish to impose on them.


How to reverse mistaken flag and downvote

Question: I was reviewing a bunch of questions, and by mistake flagged an answer as... not a question and downvoted it. I'm very sorry, I didn't notice it was podted as an answer, and now can't reverse my flag nor downvote. What can I do now to make things right?
Comment: Wait--we can actually flag *answers* as "not a question"!? `:)`
Comment: That's nothing. I once flagged a question as "migrate to crypto.SE"... while _on_ crypto.SE. (I just left a comment on the question explaining my lack of sleep.) And speaking of confusing the mods, there's always the time I found a way to [cast a "disputed" flag on a post with no other flags](http://meta.stackexchange.com/questions/215229/i-can-dispute-flags-without-10k-rep-and-so-can-you), although that was kind of deliberate.
Comment: @anorton, `xD`. Actually, I wrote that in the part that says "other". I usually describe the problem instead of using standard flags.
Answer: Unsurprisingly, a moderator has already declined your flag; actually two of these.
As for the downvote, it is likely locked in right now, but if an edit is made to the post you may be able to undo the downvote (by re-clicking the downarrow next to the answer). Now just find a way to have that post edited....  (The other answer you mistakening flagged as "not a question" has received no downvotes.)
Please be more careful when you are flagging posts.

Added to completely answer the question
Once a flag has been raised, there is no way to undo it and call it back. In such cases it is probably advisable to keep an eye on the question/flag to see how we handle it.  If we do act on your incorrect flag, you can always flag the post again* and, using the "other" option, explain why your original flag was wrong.  (You cannot have multiple active flags on the same post, so you have to wait until something is done with your original flag.)  If you can find one of us, e.g., in the main math chat room, you can explain your error there as well (though I guess you will lose your flagging anonymity to regular users in this way).
* Unless you are <10K and we deleted the post. In these cases you'll have to be a bit more creative.
Comment: That's fine, but how to reverse flags that weren't declined/accepted yet?
Comment: When I was reviewing I just assumed they were all questions, it didn't occur to me they could be answers. I promess not to make the same mistake again.
Comment: A hint for people with sufficient rep that have accidentally downvoted: the modification that allows the downvote to be undone _may_ come from the downvoter himself. I'm not sure how moral it is to randomly modify a post just to be able to undo a downvote...
Comment: I suggested an edit using markdown, and could reverse the downvote. Again, I'm sorry this happened. I also upvoted the other answer I flagged.
Comment: @IanMateus: Once a flag is in the system, there is no way to undo it.  Watch it and see how the moderators handle it.  There is also usually a moderator around, so you can try to ping one of us in the main math chat room if you have reason to believe that we'll act incorrectly.  I'll add the first bit of this to my answer.
Comment: @MarcvanLeeuwen: I personally don't see anything too immoral about this: as long as it is not an unreasonable edit, you're essentially just undoing the "harm" you've done another. (I freely admit that I might be overlooking some important subtlety.)  I would find editing a post to remove an _upvote_ infinitely more troubling.
Comment: @ArthurFischer: There is the subtlety that any third-party edit counts towards the auto-CW-ification limit of the post, which is why it is polite to refrain from edits that aren't really needed. (Yes, someone whose post is pushed over the limit can ask a moderator to un-CW the post, but not all are aware of that).
Comment: @MarcvanLeeuwen, I did that by replacing bare links by markdown.
Answer: Most of the time, there's probably no need to do anything.  If your flag obviously makes no sense, then the moderator handling it will presumably see this, and will decline it.  At worst, they might scratch their head wondering what kind of temporary insanity you were suffering from, but I suspect they've seen enough silly flags before — we're all just human, after all, and prone to occasional mistakes.
That said, if you really feel that your flag needs a follow-up message to explain or clarify it, probably the easiest way to send one is just to post it as an ordinary comment on the flagged post.  Just start your comment with something like:

"To the moderator handling the flag I just sent: ..."

to avoid needlessly confusing other users.  Also, once your flag has been handled by a mod (which you can see in your flag summary, linked from the "helpful flags" number in your user profile), please consider going back and deleting the now-obsolete comment (if it hasn't already been deleted) to keep the site clean and tidy.
Comment: This certainly is possible, if the user doesn't mind revealing him-/herself (which may not always the case).  Even pinging one of us in chat may be similarly problematic, but at least the user who created the post wouldn't be automatically notified.
Comment: Yes, one moderator must've been a bit confused, the flagging was: «Please see my comment, this is not a question. – JMCF125 Jan 12 at 13:33   declined - Why should something being posted as an answer be a question?». Also +1 for the notification you recommended, good idea. Thanks!


MacBook Pro and external monitor compatibility

Question: I just bought my first Mac (to learn to build apps!). I have the June 2012 non-retina display 15 inch MacBook Pro. Does any 16x10 aspect ratio montior technically work (monitor with VGA and DVI jacks)?
Comment: You will be hard pressed to find a monitor that will not work with the current thunderbolt ports. Since any Mini DisplayPort adapter will work you can start with VGA and work up to DVI/HDMI as well as other more exotic displays with more expensive adapters if needed.
Answer: The Apple 15" MacBook Pro specification about Graphics and Video Support says:

Dual display and video mirroring: Simultaneously supports full native
  resolution on the built-in display and up to 2560 by 1600 pixels on up
  to two external displays, at millions of colors Thunderbolt digital
  video output
Native Mini DisplayPort output DVI output using Mini DisplayPort to
  DVI Adapter (sold separately) VGA output using Mini DisplayPort to VGA
  Adapter (sold separately) Dual-link DVI output using Mini DisplayPort
  to Dual-Link DVI Adapter (sold separately)
Answer: I have a late 2011 15 inch MBP and have successfully used Thunderbolt adaptors to connect to monitors via DVI and TV via HDMI with excellent results. You don't need a 16:10 screen - the display will adapt to various screen dimensions.
I think you can plug just about anything in with a very high chance of success.


Why is differentiation called differentiation?

Question: What is the etymological link between the word 'differentiation' and the procedure it describes?
Comment: Why would "differentiation" be the dual of "integration" (as a word)? Also, the before *needs to be proven* and does not necessarily hold for any integration theory (it does for the Riemann integration).
Comment: related: https://xkcd.com/626/
Comment: I suspect that its called differentiation as it is the dual of integration.
Comment: The result of differentiation is called the *derivative*, which causes many students (and some teachers) to refer to the procedure as "[deriving](http://www.instantattitudes.com/shirts/t068.html)".  However, *to derive* in math refers to a more general process of deducing an equation from certain principles.  So there is a need for a more precise verb.  I suspect that's why we keep *differentiation* around.
Answer: The derivative (differential) is defined as the limit of the difference quotient
$$f'(b) = \lim_{a \to b} \frac{f(b) - f(a)}{b-a}$$
where difference quotient refers to the difference of $f(b)$ and $f(a)$ in the numerator and the difference $b$ and $a$ in the denominator.
The derivative is also defined (per Leibniz) as the ratio of differentials $dy$ and $dx$,
$$\frac{dy}{dx} = \lim_{\Delta x \to 0} \frac{\Delta y}{\Delta x}$$
where $dy$ and $dx$ represent infinitesimal changes (differences) in $y$ and $x$, respectively.
As far as history of the term goes, differential was coined by Gottfried Leibniz as described here.

1684 G. Leibniz Acta Eruditorum 3 469 Ex cognito hoc velut Algorithmo, ut ita dicam, calculi hujus, quem voco differentialem, omnes aliae aequationes differentiales inveniti poſſunt per calculem communem, maximaeque & minimae, itemque tangentes haberi
[Just by knowing the algorithm, as I call it, of this method, which I call differential, all other differential equations can be solved by a common method, and maxima and minima, and tangents too, can be found]

Isaac Newton used the notation $\dot{y}$ to denote the generated rate of change in $y$, which he called a fluxion. Leibniz's notations are generally what are used in calculus today, though Newton's dot notation is still sometimes used for derivatives with respect to time, particularly in physics.
Comment: This "difference quotient" suggestion may be an anachronism, in that I think the term "differentiation" was used long before the modern approach of limits and difference quotients (rather than infinitesimals) was invented.
Comment: @MitchellSpector That's definitely a possibility. I'll do a little more digging on the history of the term.
Comment: @JeppeStigNielsen Lagrange was certainly aware of Newton's notation, and I think even used it in his work at some point. The closest reference I can find is p. 230 of _A History of Mathematica Notations: Vol II_ which states "the Lagrangian $f', f'', f'''$ bears close resemblance to the Newtonian $\dot{x},\ddot{x}, \dddot{x}$, the stroke again replacing the dot. We shall point out that certain English and American writers shifted the Newtonian dots to the position where exponents are placed".
Comment: Very good answer.  Would you know where the prime notation for derivative comes from?  I've been told it's also Newton's.
Comment: Nice answer! Also keep in mind the fundamental principle *"differentiation means linearization"*, since - in school - the differential quotient is commonly established as the solution of finding the slope/incline of the tangent at a certain point $x_0$ of a real-valued function $f$, and the tangent is the *linear* approximation of $f$ in a neighborhood of $x_0$.
Comment: @MatthewLeingang The prime notation is due to [Lagrange](https://en.wikipedia.org/wiki/Notation_for_differentiation#Lagrange.27s_notation).
Comment: @AlexisOlson I have always thought that the prime notation $y'$ is a simple modification of Newton's notation $\dot{y}$. Your good reference (link) does not address whether this is correct. But Lagrange (to whom the prime notation is attributed there) lived after Newton and must have known Newton's dot notation well when he introduced the prime notation.
Answer: The etymological root of "differentiation" is "difference", based on the idea that $dx$ and $dy$ are infinitesimal differences.
If I recall correctly, this usage goes back to Leibniz; Newton used the term "fluxion" instead.
Answer: According to the Collins English Dictionary, if you "differentiate" between things or if you "differentiate" one thing from another, you recognize or show the difference between them. For a random example, one can say that people have the ability to "differentiate" one person from another.
Although the English definition of the word is different from the Calculus definition, I think that they share the same idea. This is why I think they do:
The derivative of a function f'(x) takes as input any point x that exists within f(x) and outputs the slope of the tangent line at x (the rate of change at x, the rise/run at x). Remember that a derivative is a function and a slope is a number.
Since all curves are made of infinitely many points and since every one of them has its own tangent line with the slope of the tangent line, the action of finding its derivative (finding the line equation of the tangent line) and using that tangent line equation to compute ONE slope among infinitely many other slopes that exist for every point on the curve means to take special note of that one slope. You can say that one slope is distinguished, noticed, recognized, set apart, differentiated from all other slopes. Therefore, I think the English definition, in some ways, captures the Calculus procedure of differentiation.
This is simply my personal intuition and there is definitely a possibility of error in my interpretation and would love to hear any comments or criticisms. This is a supplementary answer to the previous ones and I think they better answer the original question than I do.


Do Indians need transit visa to stay in Jeddah for 13 hours?

Question: I am travelling to USA in December from India (Indian citizen) through Saudia Airlines. Unfortunately, I have a layover period of 13 hours in Jeddah. Even though I dont have any plans to leave airport do i still need to apply for a transit visa?
Comment: What is your destination airport?
Answer: From this question:

Airlines use Timatic to display information about visas necessary for particular travelers going (or transiting in) a specific place.

Whilst I don't know your destination, the information on transmitting will be the same for most countries.
Putting in your information with a random destination gives this:
TWOV (Transit Without Visa):
Visa required, except for Passengers transiting through Dammam (DMM), Jeddah (JED) or Riyadh (RUH) with a confirmed onward ticket for a flight to a third country within 12 hours. They must stay in the international transit area of the airport and have documents required for the next destination.
As your connection is 13 hours, you will need a visa.


how can I numerically calculate all eigenvectors of a $n \times n$ complex tridiagonal matrix?

Question: I have tried matlab eig command, it results true eigenvalues but wrong eigenvectors.
I also tried direct iteration with rayleigh qotient which is better but doesn't give all eigenvectors
also I have tried  QR method which gives eigenvalues but not eigenvectors
is there any algorithm that i can use to find eigenvalues and corresponding eigenvectors?
Comment: In what sense are the eigenvectors returned by eig wrong?  Is $\| Ax - \lambda x \| $ large?  Is there something else about the eigenvectors that you don't like?  Can you give us a specific example of this behavior so that we can reproduce the problem?
Comment: How "wrong" were the eigenvectors returned from Matlab's `eig`? If they were just imprecise, you could use the corresponding eigenvalues and the Inverse Iteration Method to refine them.
Comment: How big is $n$? Are you sure that you need *all* the eigenvalues and vectors? What underlying problem does your matrix come from? People will be better able to answer your question if you enhance it with this information.
Answer: MATLAB's eig() function normalizes the eigenvectors to have unit norm; it doesn't normalize the eigenvalues.  You can check the norm of the vectors to verify their correctness.  Remember, if $\bf x$ is an eigenvector of $A$, then so is $c\,\bf x$.
You can "turn off" the normalization by using
<code>[v,d] = eig(A,'nobalance')
</code>
but this also disables preconditioning and may give less accurate results.
Comment: I'm often annoyed by the "wrong" choice of signs even for real eigenvectors (wrong = not what I want aesthetically), and of course normalizing what might well be complex-valued eigenvectors is further fraught with surprise.
Answer: "Wrong" eigenvectors is a poor problem statement in terms of how it helps us to help you. Are they merely of the wrong sign? Since the sign is arbitrary, that is impossible to control, but you can easily flip the signs if you don't like them.
One not uncommon convention is to always force the sign of the first non-zero element to be positive, but that too can be sometimes an issue if the first element were very near zero. How close is close enough?
Are there replicated eigenvalues? If so, then the eigenvectors for that set of replicated eigenvalues are not unique. You can essentially rotate the eigenvectors that span that subspace arbitrarily and they will still be equally valid eigenvectors.
So unless you give us more help as to why eig produced the "incorrect" eigenvectors, we can at best guess at the real problem.


Why is there a sharp and a natural over this Bb?

Question: I'm studying a piece by palestrina (Agnus Dei is the title of this piece, but I'm not sure of the name of the work) and in this 3rd bar we have a sharp in the parenthesis and a natural over the B, which from the key signature is flat. I'm pretty sure that it's supposed to be played as B natural, but would the editor include the sharp as well as the natural accidental?
Comment: It's *Agnus Dei*. *Angus* is a different kind of animal... :)
Comment: @federicopoloni i might have been hungry when i posted this
Answer: In Palestrina's time, the "rules" for writing accidentals were different from the current conventions.
Even as late as CPE Bach, sharps and flats were sometimes used to change the pitch of a note by a semitone up or down, not to indicate the absolute pitch as they are today. So the sharp in front of a B flat would actually mean "B natural".
Also, the rule that "accidentals remain in force to the end of the current bar" was not strictly followed - especially since at this period, bar lines were often placed in an irregular pattern and the modern concept of "time signatures" did not yet exist.
In your example, it was probably "obvious" to Palestrina's contemporaries that the second B in the word "mun-di" should be the same pitch as the first one, and they didn't bother to notate things that were obvious! In fact, writing a natural before the second B could have been read as returning to the pitch in the key signature (i.e. B flat), and writing another sharp could have mean raising the pitch by another semitone (i.e. from the previous B natural to B sharp, which clearly doesn't make any musical sense) so they didn't really have a style of notation that matches the modern style of writing accidentals.
In some early notation, it was generally assumed that in scale passages in minor keys, the "melodic minor" was intended when no accidentals were written - so the notes E F G A G F E with no accidentals might mean E F# G# A G-natural F-natural E. Since modern performers have inevitably heard a lot of tonal music written after this period, it can often be hard to decide what pitches the composer originally intended. One valuable source is contemporary transcriptions made for instruments that used tablature notation (e.g. the lute) where there is no ambiguity about the pitch of the notes - at least, so long as it is clear what tuning system was being used!
This rather careless (by modern standards) notation resulted in some long-standing mistakes when "early music" was being rediscovered in the 19th century - including some in J S Bach.
The small naturals above the stave were added by the editor to show the modern notation for the accidentals. Similarly, the parentheses ( ) round the sharp were added by the editor to show that this was the original notation, but it doesn't have the same meaning as it does today.
Comment: @TonyK: because _what the composer originally wrote_ remains the most important piece of information regarding what the music should be like. Sure, it's important to note that this notation is not compatible with modern standards, but it's also important not to lose ever more details in translations to newer standards. Sure, this particular example is reasonably clear-cut, but in many other older works a pure modern-standardised transcription can leave lots of questions open. The Bach Cello Suites have a lot details where cellists keep looking into the facsimiles for subtle hints.
Comment: On the upside, you're unlikely to find so atrocious things as A♭ in an Emaj7 chord in baroque music...
Comment: That makes sense in a historical context. But why would they print it that way in a modern edition?
Answer: The original music had a sharp printed as an accidental (that's why it's in full size).  Which is a quaint way of doing a B natural.  The editor(?) put it in parentheses (though they should have been small-sized then) and placed the "musica ficta" natural over the note (small size, so usually added after the fact).


When to close the ark after putting away the Torah

Question: On shabbat morning when putting away the Torah, many chazzanim like to draw out different tunes for the verses recited then. Should the one honored with putting the Torah back wait until after the singing to close the ark? Should he close it when he's done putting the Torah back? Should he half close it, and complete the closing when the chazzan is finished? I have seen all three of these options done. Which is most popular/preferable?
Comment: What I've seen in the two congregations I frequent (one for Shabbat, one for weekdays) is that the curtain gets closed right after the scroll is put away and the doors get closed at the end of the singing.  I don't know why (which is why this is a comment and not an answer).
Comment: Is there a reason to think that it matters?  Although my Rav was makpid that uvnucho yomar should be done simultaneously with putting the Torah in the ark.  It shouldn't be started while the shatz is carrying it.
Comment: @YDK No particular reason why it matters. I was doing it last shabbat and wasn't sure if there should be some preference.
Comment: @YDK Just as a thought, you might think that Kevod haTorah dictates not leaving it open needlessly, or perhaps not leaving it open when it is not for the Torah's needs but ours. Alternatively, you might feel that saying those pesukim needs to happen while it is open (I have no idea why you would say that though).
Answer: I have seen the ark kept open until the singing is concluded.
The Koren Siddur says that the ark should be closed after the u'vnucho yomar verses are concluded. It shouldn't really make a difference whether they are being said quickly or drawn out.


Are election boycotts effective against an authoritarian regime?

Question: If there are no fair elections in a country, the opposition may choose to still participate and try to defend its result or to boycott an unfair election altogether. Are election boycotts effective against an authoritarian regime (by 'effective' I mean "effective in expediting a transition to democracy")? What do studies show?
Answer:
Are election boycotts effective against an authoritarian regime?
What do studies show?

In her PhD dissertation, Protesting the Contest: Election Boycotts around the World, 1990-2002, 2006, Emily Ann Beaulieu1, concludes:

The main themes and findings presented here take us a great distance in understanding the causes and consequences of election boycotts, but they beg the question of how we are to understand countries that hold problematic elections where the incumbent commits fraud and the opposition boycotts. Are such countries democracies? Are they democratizing?
Certainly countries experiencing major election boycotts have not yet attained the "gold standard" of democracy—although even countries who are considered to have reached this standard continue to face problems such as election fraud. And yet, the findings of this project suggest that countries holding fraudulent elections and experiencing major election boycotts are not hopeless autocracies. They are clearly in a state of flux, which is not to say that they are on an automatic path to democracy (or dictatorship) but that they are still engaged in some process of better-defining how their country will be governed to the satisfaction of its citizens. Furthermore, boycotts, although they carry some negative short-term implications, appear to help such countries proceed in a more democratic direction.

For specific effects, see these chapters:

THE IMMEDIATE EFFECTS OF MAJOR ELECTION BOYCOTTS

THE LONG-TERM CONSEQUENCES FOR DEMOCRACY

——
1Doctor Emily Beaulieu Bacchus, Associate Professor in Comparative Politics in the department of Political Science and Director of the International Studies program at the University of Kentucky and author of Electoral Protest and Democracy in the Developing World (Cambridge University Press), 2014.
Answer: Short answer: No.
Firstly you would have to achieve sufficient (non-)participation as to put the turnout far beyond some normal variation as to substantially undermine the result. Not least  because boycotts can be a tactical way to explain an expected loss while claiming popular support.
Secondly, it has to be effective. The meaning of the turnout will always be contested so a lot would depend on the wider domestic and international backing achieved by the opposition - which is the boycott is probably not the key factor.
The Brookings Institute published a paper on the analysis of 171 boycotts around the world, of which 4% were classified as effective - and then they were accompanied by other factors that may have been more influential.
Brookings Institute - "Threaten but Participate: Why Election Boycotts are a Bad Idea"
Answer: It is by its nature difficult to define whether a non-action has causal impact. There are many things to consider, and to my knowledge "election boycott" as a means of exercising democratic freedom, is not considered standard, normal or effective in general.
From a principal point of view, boycotting an election has consequences firstly for actual election turnout. In semi-free autocratic states where elections happen, but fraud is present or strongly suspected, for instance Belarus in their recent election, turnout is nominally high, and ostensibly in favor of the incumbent.
As such, abstaining from the vote itself, without being part of a chain of political action, would not tip the scale other than to legitimize the incumbent, whose job of fabricating a credible result is made easier the fewer instances of actual voting do occur.
The more evidence, the harder to hide the crime.


What are the 'natural flavors' in a fruit drink that contains no juice?

Question: When a fruit (flavored) beverage says it contains all natural flavors but no juice, where is the flavor coming from? Is it possible there are man-made additives being thrown in that can be technically considered "natural"?
Comment: Better to take into account that different regulations may exist. Natural refers to the fact that the same molecule does exists in the natural realm. Plus, regulations might require that the molecule does come - through different procedures - from a real natural fruit or seed etc. Sometimes the difference is given by natural flavour and natural-identic. Artificial or synthetic flavours are those created by us, not naturally occurring. Anyway subtle differences might exist in different countries. EU recently updated the classification using a more operative approach, and referring to % comp.
Answer: Ok... I'm going to ruin your day with this.  In orange juice for instance, the process of homaginization and storage kills the flavor of orange juice, so the industry has enlisted the help of the perfume industry to help them.  Each orange juice company has basically a perfume of orange flavors that it uses from the peels and rinds and biproducts that it uses to try to recreate the taste of real orange juice... It's why every orange juice brand tastes slightly different even though they are all "fresh squeezed" (btw, they are technically fresh squeezed, they're just then stored :))
If you google "orange juice flavor packs" you can see what this is talking about.  The flavor packs are incidentally made out of parts of the orange, so the fda has no problem with them (sadly).
http://consumerist.com/2011/07/oj-flavor-packs.html
So to directly answer your question, you can flavor something with fruit derived perfume and call it "natural flavors"
Here's a quote from the site:

Juice companies therefore hire flavor and fragrance companies, the same ones that formulate perfumes for Dior and Calvin Klein, to engineer flavor packs to add back to the juice to make it taste fresh. Flavor packs aren't listed as an ingredient on the label because technically they are derived from orange essence and oil. Yet those in the industry will tell you that the flavor packs, whether made for reconstituted or pasteurized orange juice, resemble nothing found in nature. The packs added to juice earmarked for the North American market tend to contain high amounts of ethyl butyrate, a chemical in the fragrance of fresh squeezed orange juice that, juice companies have discovered, Americans favor.
Comment: To be fair, many of us essentially use oils derived from oranges when we use orange zest, and orange extract and essential oil are reasonably common things in kitchens too. Those are pretty much the same kinds of things that are (hopefully) meant by "natural flavors". Sure, they select for the particular components of the fragrance they really care about, but... it's not that big a leap.
Comment: Agreed... I haven't stopped drinking oj because of this :)
Answer: Both natural and artificial flavors are "man-made", or manufactured. The difference is, essentially, in which chemicals are used in the process. For "natural" flavors, alcohol or oil extracted flavors are generally permitted, and heat or enzymes can be used to extract the flavors. For "artificial" flavors, solvents with a shorter history, created since the industrial age, and petroleum products may be involved. But either way, "flavors" are just chemicals, or mixes of chemicals. The rules that define the differences are fairly arbitrary. The same companies that make artificial flavors and fragrances make "natural" ones.
Once flavor compounds are discovered and isolated by flavor manufacturers, they can produce them using techniques considered natural or artificial. Some "natural" flavors may actually come from sources that don't match their namesakes; cherry, almond, peach, and apricot flavors are essentially made from the same source, as I recall, and different concentrations and contrasting items (including citric acid) affect your perception of the flavor. There's no guarantee that "natural" means "safer" or "healthier"; "natural" peach flavor may contain trace amounts of cyanide, for example, but "artificial" versions won't.
If something tastes juice-like but isn't "juice", chances are it has added citric acid (which is "natural", even though as an isolate, it, too is an industrial product), in addition to small quantities of flavor compounds, and sweeteners of some sort.
In home cooking, I've used citric acid to make some items taste brighter or more intense than they would otherwise, especially if I had some sort of fruit syrup that I considered too sweet for my purpose.
Comment: I think you're misunderstanding. "Derived" means "manufactured." A "natural flavor" is extracted, generally using heat, bacteria, enzymes, or alcohol; someone actively turns those "natural" products into concentrated isolates that can be used by food product companies. Just because it's a "natural flavor" doesn't mean it has very much to do with the fruit, animal product, spice  that it was extracted from. The same New Jersey plants make it, regardless of whether the source is "natural" or "artificial."
Comment: Incredibly helpful answer, thank you for taking the time to elaborate!
Comment: FDA seems to think [otherwise](http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.22). "Artificial flavor includes the substances listed in 172.515(b) and 182.60 of this chapter except where these are derived from natural sources.". I.e. a manufactured substance is artificial, because it is not derived from natural sources.
Comment: @jasontrue this isnt quite the whole story either. If we are concerned about the labeling law, which seemingly would be what matters-consumer protection and broad industry enforcement- instead of just some street lingo that people are saying that's trendy today, then the law is that it has to be labeled artificial if it doesnt taste like what it comes from which is a huge difference, everytime you use orange citric acid to brighten something that has absolutely nothing to do with oranges like apple pie; and the orange zest is absolutely natural, the label has to say artificial flavor
Comment: It's worth noting a natural flavor must be labeled as an artificial flavor, even if it comes from natural sources, if it is added to a product to impart a flavor that isn't already present.  https://www.thoughtco.com/difference-between-natural-and-artificial-flavors-607435
Answer: While they may employ scientists from the perfume industry, there's an important point missing here that might impact how you feel about flavor packs. As orange juice is heat processed, aroma and flavor compounds, which are volatiles (they evaporate easily, or are fat-soluble and don't stay in water based solutions well) are collected. These compounds are worth their weight in gold, basically. The orange juice right after pasteurization is pretty bland and terrible, but these volatiles are added back as a "flavor pack" to reincorporate the flavor and aroma of orange juice. and yes, the flavor packs are standardized (mixing of lots of different flavors and aromas to make sure none are really far off the ideal orange juice flavor/aroma combo), because there's a lot of variation in crops season to season because of weather, soil, other growing conditions, etc. Consumers wouldn't like it if their orange juice might be kind of good or kind of bland or flat or just different between cartons. So in my mind it's just separation of food components and then putting them back where they belong, but I come from a mindset that's kind of...pro-food processing. See below.
Source: I'm a junior level food science undergraduate student at a top ten university in the U.S. Orange juice is one of the products we talk about a lot, in terms of processing, food characteristics, and food safety. Pepisco (which owns Tropicana) is one of our primary industry connections and industry reps come talk to us about their products fairly frequently.


Is it better to have links open in the same window, or a new window?

Question: Are there best practices around when it's ok to open links into a new tab and when it's best not to?
Answer: I would refer to this article on CSS Tricks. It list both good and bad instances to open links in a new window (i.e. use target="_blank")
Bad reasons

Because you like it that way
Because you don't want users to ever leave your page
To differentiate between "internal" and "external" links
Because it links to a PDF
Because a client wants it that way
Because it's on an infinite scroll page

Good reasons

When a user is working on something on the page that might be lost if
the current page changed
Because there is user-initiated media playing
For some technologically obscure point.

Essentially, changing the default behavior of something should generally be avoided, unless you have an iron clad reason to do so. Remember that users can always open links in to tabs if they want to (⌘-Click), but if you force them to, it takes away that choice.
Answer: For me it depends on the needs.
There are generally two scenarios..

I want user to continue on another article.
I want user to take reference from another article.

If its 1st then he is done with current page and so the link should be opening in same tab.
If its 2nd then he should be coming back to the current article after taking reference so, the link should be opened in new tab.
Example:
1. Youtube videos. (Done with current video interested in watching new one)
2. Ads on youtube. (Preserves current experience)
Sometimes exceptions are there user may want to goto another article but wants the current article left open too then they can open the link in new tab via context menu.
Just a general sense.


Is it possible to ping a LAN card through its MAC address?

Question: As you can start a PC through its 'WAKE ON LAN' feature on private networks, can you trace someone's online status through their MAC address over the internet ?
Answer: The MAC address is link-local. When a machine emits an ethernet frame, that frame is tagged with the MAC addresses of the source and destination hosts, which are both connected to the same local link (plugged to the same LAN, associated with the same WiFi...). Normally, (at least) one of the two machines is a router: the frame contents are an IP packet, and the router will put that IP packet in a new frame on another link, and send it on its way. Only the IP packet thus travels; the original frame header, including the MAC addresses, remains local.
Thus, the MAC address of a machine cannot be viewed from other machines which are not part of the same LAN. It cannot be seen, and therefore cannot be used for tracking, from remote Internet places. Similarly, you cannot send a packet meant for a specific MAC address if you are not already on the same LAN. Global routing works on IP addresses, not MAC addresses.

Now there are exceptions to all rules. IPv6 is the next version of the Internet protocol, waiting to be widely adopted (I am not sure it will ever happen, but hey, one can only hope). The relationship between ethernet frames and IPv6 packets is still as I explained above; however, IPv6 may imply a leak of MAC addresses.
Indeed, most user systems nowadays (as opposed to servers and routers) obtain a dynamic IP address when they connect their LAN or WiFi access point. With IPv4 DHCP is used, and, usually, the user's machine is allocated a "private" IP address, that will be converted with NAT when external systems must be contacted. With IPv6, the IP address space is much enlarged, so that NAT is no longer necessary, so the machine's IP address will be visible from the outside; furthermore, IPv6 dynamic address attribution is done with NDP, and (pay attention, that's the important point here) the machine's dynamic IP address will include, as a subfield, its MAC address (the MAC 48 bits are reused as part of the 128-bit IPv6 address).
A consequence is that, from an IPv6 server's point of view, client machines can be tracked. Not that the server would somehow know if a given machine is up and running; but in the sense that the server may notice when two client connections, from distinct IP address, are really from the same hardware (e.g. a laptop, the user having just moved from his office to his home). This is not the kind of tracking which would allow a "ping" request (the tracking server must wait for the system to connect to it), but it is a privacy concern nonetheless.
Extensions to the protocol have been defined, to generate IPv6 addresses differently, in a less trackable way. Most modern desktop/laptop OS implement these extensions, so the tracking explained above does no longer work, or will cease to work in the near-term future (and nobody uses IPv6, anyway).
Answer: No, MAC Addresses are not routed across the internet.
There is no way to get the MAC address of a computer that is not on the same subnet without some sort of software installed on the computer.
If you are wanting to know the status of a device on the public internet, you should be checking their IP address instead.


Should I flag comments posted by a user trying to draw attention to their answer?

Question: On an old question from 2011 with 20 answers, a user has posted a new answer and then immediately left a comment on the question directing users to their answer. A "check this answer out for a new way to do it" type thing. The answer is from a high-rep user and presents a novel way of solving the question but I was thinking the comment should be flagged as "no longer needed." Is this an appropriate flag to raise on the comment or should I just ignore it?
Comment: Yes, flag it as no longer needed. The OP would have got a notification about the answer anyway.
Comment: I'll argue it depends on the type of comment. if it's clear it's a massively pointless comment, flag. If it, however, points out specific flaws with the answer(s) it's posted to, that's more in the realm of accepted comments
Comment: @VLAZ I don't think it was ever needed. The OP will be notified of new answers and – according to SO prophecy – good answers will always rise to the top
Comment: Is it a "new" way just because the answer is new, or because the content of other answers is outdated? The latter can be quite helpful on Q&A that have accumulated votes over the ages.
Comment: The problem with 'The OP will be notified' is that the OP might not be on SO anymore or lost interest. SO is not answering questions to SO only it is answering to _all_ users searching for answers to equal or similar questions. (Actually this is one of the flaws of SO: answer-rot.
Comment: Comments on such old answers should not be for the benefit of the OP but for anyone who happens to come across it.
Comment: @miken32 I think you answered your question for whether to flag NLN, in that case.
Comment: @MisterMiyagi that's what gave me pause. But at the same time, there is a sort option for showing new answers first. The older answers are outdated and more verbose, but still functional.
Comment: Do you think the comment is needed any longer? I'd say "no" but I'm open to reasoning for the opposite.
Comment: @CaiusJard it will when the answer got some upvotes but when the answerer posted the comment immediately after posting the answer, the answer obviously has no upvotes at this point and the purpose of the comment is precisely to solve this (a kind of bootstrapping of the "trending" feature)
Comment: Wouldn't the comment help to point users to a newer, more updated answer at least meanwhile their question does not get to the top? At the end of the day, SO is supposed to leave those questions there for more people to find.
Comment: I'm sure the new trending sort will bring this awesome new answer to the top anyway?
Comment: @S.Dre where does that leave us when every new answer to a question gets its own comment saying "me, me, look at me!"
Comment: If it is not a case where it is useful, I would flag it @miken32 . But there are cases where they can be useful.
Answer: Depends on usefulness of the comment - it is not against the rules to bring up attention to flaws of answers (either due to changes in tech or any other reasons).
If comment is more like "I posted new awesome answer - check that out and upvote" - flag as "no longer needed" and move on. On other hand a comment highlighting changes in tech like "Most answer suggest approach using Foo.123, but now with Foo.456 there are alternatives - make sure to review all answers (I provided one)" worth keeping for some time.
I would check if "the new answer" shows high enough with whatever default sorting is at the moment (I think trending eventually will be default) and include that information to decide when to flag. I personally expect people to review at least first 2-3 answers so the comment suggesting to read one of those is NLN for me.
Note that it may be good idea to add comment (or even edit) to the top (by sorting) "old" answer to specify that it is no longer the only option with comment/edit similar to "This answer uses Foo.123 which was only option prior Bar.2.3, if using Bar.2.3+ review other answers".
Comment: Yes, very much in the "I posted new awesome answer" category. Flagged and removed.
Comment: Related meta question, [Good question, old version-dependent answer - Meta Stack Overflow](https://meta.stackoverflow.com/questions/265433/good-question-old-version-dependent-answer) -- there's option to edit the old answer to say "This answer is only applicable for version X." if that's the case
Answer: Offhand I'd say this is not the kind of thing we'd like to encourage on the site by way of example, so I'd be inclined to flag it.
I can think of two exceptions though.  If the comment was directed to a specific user via <code>@</code> it could be useful until you know that user had seen it.  And if the underlying technology has changed in a way that affects the existing answers, that could be worth drawing attention to.
Answer: I generally don't comment to "go read my answer", though I will credit other folks' answers if referenced in my own posts. This is doubly true if the other answer on the same question is well written, expounds further than my answer does (in this case I've likely edited in a recommendation to read the other answer if I feel it complements my own), or if I'm providing an extension of another answer (e.g. "To expound further on @Soandso's helpful answer...." with a link of course). I will also sometimes link to another answer of my own in a post if I feel it will offer additional clarity, making sure to be clear that it is also my answer.
If the answer if a community wiki, I don't think I've even come across any community wiki answers on the main site myself. I suppose in that case I think I would simply edit the wiki-answer with any additional relevant information, making commenting about the new information a moot-point in that case.

The one exception for me is that I will sometimes comment under a question or answer to one of my own answers on another question if it expounds further on some detail (and wouldn't qualify as a duplicate of the question), explaining why they may want to review it. I generally do this rarely and only if I feel the additional information might help the poster. This is especially true if I feel the information isn't at the core of the question or answer but the poster demonstrates a fundamental misunderstanding of how the subject works.
I can't find examples of any comments where I've done this as I don't do it very often. To offer an example context though, I do sometimes share this answer in comments when I feel the user could use an explanation of how redirection and output streams work in PowerShell, and I have not or would not be able to provide an answer to the poster's question. And again, the case for doing so hinges on whether the post author demonstrates a fundamental misunderstanding of redirection or output streams in the first place.


Do I have to pay a capital gains tax if I rebuy different stocks?

Question: If I sell stocks and bonds and have a capital gain, and rebuy different stocks within a certain time frame, will I still be paying the capital gains tax from the original sale? ( just want to change my portfolio   Thanks
Comment: What country are you in? What kind of account are you trading in?
Answer: Yes- you do not realize gains or losses until you actually sell the stock.  After you sell the initial stocks/bonds you have realized the gain.  When you buy the new, different stocks you haven't realized anything until you then sell those.
There is one exception to this, called the "Wash-Sale Rule".  From Investopedia.com:

With the wash-sale rule, the IRS disallows a loss deduction from the
  sale of a security if a 'substantially identical security' was purchased within 30 days before or after the sale.  The
  wash-sale period is actually 61 days, consisting of the 30 days before
  and the 30 days after the date of the sale. For example, if you bought
  100 shares of IBM on December 1 and then sold 100 shares of IBM on
  December 15 at a loss, the loss deduction would not be allowed.
  Similarly, selling IBM on December 15 and then buying it back on
  January 10 of the following year does not permit a deduction. The
  wash-sale rule is designed to prevent investors from making trades for
  the sole purpose of avoiding taxes.
Comment: While this is accurate, I think it's a bit misleading - if you buy stock on 12/1 and sell it on 12/15 at a loss, you can claim the deduction from the loss - it's just a short-term loss and that's fine. It's designed more to prevent people from selling (at a loss) and immediately re-buying a stock right at year end, counting the loss as a deduction (though they're essentially lowering their cost basis, meaning they'll just pay the same taxes later).
Comment: @SqlRyan - in your example, a broker may very well report this as a wash sale which only is avoided with the passing of 30 days, i.e. 1/15. I personally find this a bit convoluted, my own claim is that a buy/sell isn't a wash unless the new purchase is made, but it's a matter of semantics, I recognize when actual wash sales occur.
Answer: Yes. As long as the stock is in a taxable account (i.e. not a tax deferred retirement account) you'll pay gain on the profit regardless of subsequent purchases.
If the sale is a loss, however, you'll risk delaying the claim for the loss if you repurchase identical shares within 30 days of that sale. This is called a wash sale.
Answer: Probably.  It sounds like you're looking for a 1031-exchange for stocks and bonds.  From the wikipedia page for 1031-exchanges:
To qualify for Section 1031 of the Internal Revenue Code, the properties exchanged must be held for productive use in a trade or business or for investment. Stocks, bonds, and other properties are listed as expressly excluded by Section 1031 of the Internal Revenue Code, though securitized properties are not excluded.
1031-exchanges usually are applicable in real estate.
Answer: Yes (most likely). If you are exchanging investments for cash, you will have to pay tax on that - disregarding capital losses, capital loss carryovers, AGI thresholds, and other special rules (which there is no indication of in your question). You will have to calculate the gain on Schedule D, and report that as income on your 1040. This is the case whether you buy different or same stocks.
Comment: You are correct; there is a "wash sale" rule that applies to capital _losses_. But OP gives no indication of that in his question.
Comment: No, this is **not** the case if you buy the same kind of stock (including the same stock), within 30 days before or after the sale, if the sale was at loss.


Does repeated flashing cause degradation NXT

Question: I have a Lego Mindstorms NXT 2.0, which I'm tinkering around with, writing a custom firmware for. I just want to know if repeated flashing could damage the flash memory.
Answer: LEGO Mindstorms all use flash storage which does have a limited number of write cycles, so the answer is technically yes in some capacity, but it's probably not something you need to worry about.
A LEGO Mindstorms NXT 2.0 uses a Atmel AT91SAM7S256 microcontroller. This board has 256 KB flash memory, which is roughly the size of the latest firmware image.
According to the datasheet for this board, it should be good for 10,000 write cycles.

256 Kbytes of Internal High-speed Flash, Organized in 1024 Pages of 256 Bytes

Single Cycle Access at Up to 30 MHz in Worst Case Conditions
Prefetch Buffer Optimizing Thumb Instruction Execution at Maximum Speed
Page Programming Time: 4 ms, Including Page Auto-erase, Full Erase Time: 10 ms
10,000 Write Cycles, 10-year Data Retention Capability, Sector Lock Capabilities, Flash Security Bit
Fast Flash Programming Interface for High Volume Production

10,000 is actually quite a bit, and would take a very long time to reach intentionally, even if you automated it to run 24/7.
I'm not sure how fast you physically can flash the firmware, but if you did it once every 10 minutes 24/7, it would take you almost 70 days to reach that limit.
If you flashed it a still-unrealistic 10 times per-day, it would take you 1000 days to reach that limit.
And of-course, if you did it once per-day, it would take you over 27 years.
In practice, I think it's much more likely some other hardware component will fail first.
Comment: Not particularly reassuring. Thanks anyway.
Answer: I've found a very old NXTasy thread that answers this question definitively.

Flemming Bundgaard, from LEGO, ran two or three test-to-failure runs with my NXTTools utility repeatedly setting the brick into firmware download mode and downloading the standard NXT firmware to the brick. In each of his tests the brick failed, if I recall correctly, after ~7000-8000 iterations. There is no doubt that if you put your NXT into boot mode somewhere in the neighborhood of 8000 times your brick will no longer accept a new firmware download. You can test this yourself if you like using NXTTools undocumented iteration count switch and a brick running on an external power supply. Each iteration takes about 30 seconds so the test will run for ~67 hours. Of course, your brick could have a different lock bit lifespan than Flemming's bricks had. It is also worth pointing out that if you reflash or reset your NXT once a day 365 days a year it will probably take you almost 22 years to wear out your lock bits. If you do it 10 times a day, everyday, then your brick should last 2.2 years.


Question about "mining" in bitcoin

Question: Hello I am a student who is trying to understand bitcoin mining and block chain technology. As I read the articles and papers about bitcoin mining, mining is the process of adding transaction records to Bitcoin's public ledger of past transactions. And its average solving time is around 10 minutes and whoever solve the fastest will be awarded to 25 BTC. So if there are more and more people using bitcoin and sending their bitcoin to each other, then more and more bitcoin has to be awarded to whoever solved it right? Is that why the predicted time for last Bitcoin to be mined is becoming sooner and sooner? If Bitcoin becomes a major currency and millions and millions of people use bitcoin everyday then are there any possibility that the last bitcoin will be mined way sooner than expected date which is May 7th, 2140? Thank you
Answer: Mining is the process of extenting the chain with new blocks containing (or not) new transactions. The block reward and any tx fees for that block goes to the miner, who found  a nonce such that the hash meets that block's difficulty target.
In Bitcoin the difficulty retargets every couple weeks I believe. This means that if more miners start mining, they will indeed cause blocks to be found faster than the 10 minute starget on average, until difficulty retargets, where it will go back to about 10 minutes (and possibly go up or down depending on whther new miners arrive, or existing miners leave).
Due to thus two weeks retargetting, there should be only minimal change to the expected time of the last block reward (accumulation of each two weeks period's drifts).
Last, the number of txes do not influence the number of blocks. The miner does get a bit more due to the tx fees, but whether blocks are full or empty or the the middle, the target is still 10 minutes.
Answer: As more hashing power is put towards mining, the faster a block is solved.  Every 2,016 blocks, the difficulty of mining a block is re-targeted so that on average, blocks will still be found every 10 minutes.  This means that it will be roughly every 14 days (<code>((10 minutes * 2,016 blocks) / 60 minutes per hour) / 24 hours per day = 14 days</code>).
However, when the hashing power of the network over time is sloping upwards, this means that there is a 14 day lag before recalculation.  As the hashing power increases over these 14 days, blocks are mined less than 10 minutes on average, thus bringing the date of the last mined coin sooner than predicted.
However, the opposite happens if hashing power is trending downward.  During the 14 day period, blocks will start to take greater than 10 minutes, thus pushing back the date of the last  mined coin.
Seeing as we are only 7 years in, out of a 131 year time span, it's hard to predict whether hashing power will slope upwards more than it will slope downwards during the next century or so.  If it slopes more upwards than down, then all coins will be mined prior to 2140.  If it slopes more downwards than up, then we may still have coins to mine after 2140.  We all expect it to slope upwards, but there is probably a limit at which point it never goes much higher, and may even trend downwards.
I think it is far too soon to predict an actual date.

Question about "mining" in bitcoin


Twelve Weeks on and One Female Cucumber Flower

Question: I have straight eights planted in a raised with tomatoes planted late April.  So far only one female flower it went unfertilized although I have lots pollinators of different kinds all over the perennials planted near by.  The vine looks great and I tossed in some slow release balanced fertilizer.  Any ideas or is this just a bad cucumber year in Northern Virginia?
Comment: Having similar issues in Zone 9b but I think it is because of soil issues.  Looking forward to the answers
Answer: Female flowers are the fewest on the main stem and their number is greatest on 3rd level of ramifications.
Also, when the plant is young it will produce a female flower for every 10 male flowers, and the number of female flowers grows with the plant's age.
Drought results in more male flowers. Low temperatures results in more female flowers.
Update: As suggested in the comments, I'm adding the source of the above info. It's a book called "Cultivation of vegetables", 3rd edition (2012), coordinated by D. Indrea. The chapter regarding cucumbers is written by D. Mănuțiu and he provides a table for causes of the variation of flower gender. This table has a citation that states the info came from an old book "Legumicultura" by M. Bălașa, published in 1973.
Unfortunately, I don't have an English version of the book.
Comment: @Shule The branch that is attached on the main stem is a first level (or first order, first degree) of ramification. A branch that is attached to a first level ramification branch is called a second level ramification, and so on. The idea is that all branches that come from the main stem are first level ramifications, and all branches that come from these first levels are called second levels. All branches that are attached to second levels are called third levels. I have also updated my answer to provide a source for the info. Thank you for pointing that.
Comment: Temperature has quite an effect as Alina mentioned.
Comment: No doubt it's hot here.  Our July days are often in the 90's approaching 100, and while it has been dry, i water on a fairly regular basis as the tomatoes are growing in the same raised bed.  Thanks for your ideas.
Comment: Alina, what's the '3rd level of ramifications'? Do you mean third branches away from the main stem? Where did you get your information? Technically, we're supposed to say our sources, even if it is personal experience/observation, something we read online and don't remember where or what-have-you. A lot of people (including myself) forget to do it sometimes, though (so feel free to remind me if I need it, also).


Removing finger oil and finger prints from photographic prints

Question: Is there a way I can inexpensively remove finger oils and fingerprints from photographic prints (we're not talking about slides or negatives here) without doing any damage to the photo? Or is a conservator my best bet?
Answer: It depends on what prints you have. My prints made from digital photos don't need cleaning. Some old which  I made from analogue negative long long ago, do need.

Old prints with gloss coating I've made using an hand-made gloss device: I use a mixture of glycerol (90%), isopropyl alcohol (10%) and a dash of Trilon B (Na2EDTA or (NaOOCCH2)2N(CH2)2N(CH2COONa)2).
Old prints with mat(e) coating: the same mixture as above but without Trilon B.

Applying: put this mixture on your print using non-woven cloth, keep covered about 30-40 minutes, then remove accurately. Sometimes you have to use pure isopropyl alcohol to remove remains of mixture.
Be careful! Various kinds of photo paper have various properties. I've developed this method for certain kinds of soviet and chech photo paper I've use. For your prints this approach may be dangerous!!! First, try this on a small piece, wait for week or more to be sure all is OK.
Answer: Cleaning an old photo is risky if you can't identify the print. Most old photos will be conventional prints on photo paper. I am talking about chemical based photo prints. As you said, these have oily finger prints. First try to wipe off the smudges using absorbent cloth like a "T" shirt. OK to be a bit aggressive.  If this does not work, wet a Q tip and test one print that is relatively unimportant. You are testing to see if the dyes that make up the picture can tolerate being wet. If the print passes the Q tip test, soak in water; add a few drops of Dawn dish washing detergent. Scrub with your fingers, the soiled places. Rinse off with running water and lay the wet print on a towel and allow to air dry. Of course, test the print before you attempt such rigorous cleaning.
It is likely that you can overspray the print with clear lacquer. Most craft shops plus on line, purchase a can of Krylon clear spray paint. You can get gloss or matte. It is very likely that you can overspray the prints with Krylon and the spray coat will hide any and all oily finger prints. In other words no need to attempt to clean.


why is a lamp socket labeled "FOR TEMPORARY USE ONLY"?

Question: i am hanging a ceiling lamp which came with an cord set only rated 60W -- insufficient for my purposes. poking around in my parts bins, i found a rubberized E26 socket rated something like 660W, but labeled "FOR TEMPORARY USE ONLY". what does this rule mean, and can i use the socket anyway?
Comment: It's frequently the rest of the lamp that can't take the heat, not the cord.
Comment: I have flagged this to be migrated to DIY.se, the home improvement stack exchange.
Comment: @IgnacioVazquez-Abrams agreed, but I assert that it is not the case with this lamp. i won't install anything underrated, of course.
Comment: This is common on temporary outdoor lighting strings and their replacement sockets. It's a reminder to the user that they are not designed or approved for permanent outdoor installation.
Answer: It likely means that it is NOT designed or constructed for CONTINUOUS use and/or to be built INTO some kind of fixture.  It can handle the heat dissipation only when out in the free air, and with intermittent use. Perhaps no more than 2 or 4 hours at a stretch, etc.
Comment: i have seen the label "not for continuous use" plenty of times on machines with moving parts, but never on electrical parts; you think this is a synonym?


Good lightweight web server framework?

Question: Which web servers and frameworks work well on the RP? Are there tweaks which can be made to the web server config files that will make it run better given the limited RAM?
Comment: Voted to close. This is too subjective and many answers can be found elsewhere.
Comment: I'd suggest making this a community wiki and we'll start listing options. There isn't a single good answer, but it would be nice to have a list that people can refer to here.
Comment: @silent__thought, making it community-wiki will not change the fact that it is a poor fit for the Q+A format.  This mistake was made often in the early days of StackOverflow.
Answer: There won't be a universal answer to this as there are too many different requirements from web servers for different applications. Questions that will get more refined answers will be along the lines of: I want to host a small Ruby on Rails application on the Pi (instructions at: RPi Ruby on Rails).
The Pi will be able to host most web servers and/or frameworks as both try to keep their memory requirements minimal so that they can support more end users with less server resources. Web servers designed to push the lower bounds of server resources would be useful if the maximum number of clients is desired, trying checking out many of the options listed in Wikipedia's comparison chart of lightweight web servers.
For users wanting more full featured web servers the normal suspects like Apache will work well, but you'll want to spend quiet some time tuning all the options to use the minimal options required by the specific application being used.
Answer: As already stated, there isn't a single good answer to this question. There are many web frameworks that will run just fine on the Pi. However...
I'm planning to run a Node.js application on my Pi. Installing Node.js on Arch Linux ARM is as easy as pacman -Sy nodejs. Using Express and Sqlite you should be able to make a pretty snappy web app that has no problem on the Pi.
Answer: I agree it's not possible to give a single good answer to this question.
However, some time ago I asked myself the same question and I tried with nginx on the Pi.
I wrote a very simple tutorial on how to install it. Here it is: http://www.joscandreu.com/post/22439909883/install-nginx-on-raspberrypi
I also tried with node.js, however as I wasn't running arch linux but Debian I had to compile node from source with some config hacks, which took around 1 hour. This is the tutorial that worked for me for installing node: http://blog.tomg.co/post/21322413373/how-to-install-node-js-on-your-raspberry-pi
Comment: This is what happens to link-only answers. Both links are dead as of Dec. 2016. Remaining words do not provide any value.

Good lightweight web server framework?


Did we ever see any civilian contractors working within the StarGate program?

Question: I'm working on a Stargate story, and I've been wondering about Civilian Contractors.
In our real-world military, civilian companies are playing an ever-increasing role in the military, performing all kinds of technical and logistical roles on bases, and even very near the front lines.
Did we ever see that happening in the SGC?
That's an operation that has to be WAY outside the usual role of the Air Force--they're exploring worlds with strange plants and animals, weird tech that's either primitive or hyper-advanced, deciphering alien computer code, circuit schematics, and medical techniques... they can't have been doing all that with personnel who had spent most of their time training to fly and maintain aircraft, could they?
Did they ever show specialist civilians inside the SGC?
Would it be that much more dangerous to trust a civilian (bound by every Non-disclosure agreement imaginable) than to trust an airman who has sworn an oath to keep those secrets?
Comment: http://www.stargate-sg1-solutions.com/wiki/Stargate_Universe:_Major_Characters#Civilian
Answer: Yes, at least on individual levels.  The most prominent example, beyond Dr. Jackson himself (who is of course, a civilian, although you might consider that a special circumstance) and pretty much all of the alien members of SG-1 who don't fit into the existing military structure, is Dr. Rodney McKay, who has pointed out on several occasions that he's a civilian, including in his first appearance, the episode "48 Hours."  At the end, they suggest that they're reassigning him to Russia.

McKAY: I am not going to Russia. Do you know what the food is like in Russia? Besides I'm a civilian, I don't have to do what you say.
CARTER: Well as long as you're on the Air Force payroll.
McKAY: Oh.. this really sucks.

We've also seen on several occasions individuals who are asked to sign an NDA so they can consult on one issue or another, or be approached for a more extensive job.  McKay's sister Jeannie is one who didn't want to sign the agreement (until she was just told what it was for).
As for companies, it depends on what you mean by "working within the Stargate program."  We have seen several instances of civilian companies that work on technology related to the overall defense of Earth from alien threats (and the cover-up involved), such as Coulson Industries, which both cleaned up Antarctica from the battle over the Atlantis outpost, and developed an engine control system for the F-302s.
There was also Devlin Medical Technologies, which kidnapped Rodney and his sister.

McKay: They're a predominantly government funded contractor and, unfortunately for us, they manufacture our subcutaneous transmitters."

"Government-funded" is a little ambiguous and so may arguably be not "civilian," but I think it counts.  In any event, they, and other companies, are often used to get alien technology out to the public (once suitably sanitized and a paper trail supporting their "discovery" is created), and although they often have access to some information that is classified, usually they're not told the whole story and do not know of the Stargate itself.
It seems that the general pattern is that they'll hire civilian contractors on an individual basis and give them fairly high access (contingent on NDAs being signed, etc), when needed for their expertise on the front-lines but for companies they'll keep them on a need-to-know basis and keep them working on pieces of a larger whole, like for supporting their space-vessel construction.
While there may be contractors companies who are more in the know, and it's possible some are even working directly at the SGC in Cheyenne Mountain, we don't seem to see any direct evidence of this.
Comment: Ah, your initial question seemed like it asked about either individuals or companies (either of whom can legitimately be called Civilian Contractors).  I've added a bit more information on companies.
Comment: http://www.stargate-sg1-solutions.com/wiki/Cameron_Balinsky
Comment: Ah, that's a good point about McKay, but that puts him in the same category as Daniel, which isn't --quite-- what I was asking. I meant something more along the lines of a civilian contractor--a civilian COMPANY who does work for the military. In the same way that civilian trucking companies sign on to do transport for American forces in Iraq or Afghanistan, or civilian construction teams are now often the ones who actually build forward bases for the military, or do vehicle repair, or operate the generators or other support facilities. Did we ever see signs of that, in the Stargate verse?
Comment: Along with these is the NID not independently funded and not under government jurisdiction?
Comment: No, I'm pretty sure the NID is an intelligence agency (albeit secret) and civilian in the sense that it's not an arm of the military, but still actually a government agency.  They're not under the jurisdiction of the STARGATE program, much like the FBI isn't under the jurisdiction of the NYPD, there may be times where they overlap or one has priority of the other.  If the NID was non-governmental, having so many "rogue elements" within would likely have been cause to terminate any relationship and clearances they had.
Comment: We never saw any but the CIA and SIS both have teams of normally ex military contractors the CIA's is SAD and the UK eqvielent is called the Increment I would assume the US and UK intelligence agencies would want to have stargate teams


Where does the colour-coded item rarity come from?

Question: In most new titles, especially RPGs, item rarity is colour coded in an easy to remember white-green-blue-purple-orange progression, sometimes with omissions (no green, no orange) or additions (extra silver or neon blue as ultra-rare). Why and how was this introduced in gaming? Does this trend come from outside gaming? How did this evolve to become a trend that almost all games began to follow?
Comment: After much deliberation I have decided to undelete this question. My reasoning is threefold: 1) So community members with <10k votes can view it ([as currently lamented](https://gaming.stackexchange.com/questions/352554/what-is-the-origin-of-the-standard-color-coding-scheme-for-item-rarity#comment495933_352554)), 2) It becomes a valid duplication target for [this question](https://gaming.stackexchange.com/q/352554/28182), 3) This week's [Historical Trivia Meta](https://gaming.meta.stackexchange.com/questions/13431) puts community support currently behind this type of question
Comment: Not really a cross-site dupe, but an interesting read nonetheless: [Should I use conventional colors to represent item rarity?](https://gamedev.stackexchange.com/q/140586/70488)
Answer: The Meaning of Colors
While doing research on why the color-coded system came to existence, I remembered that each color is perceived to have a few meanings.

Looking at this list, there could easily be some links to why they picked certain colors. For example, in Star Wars the Old Republic, the ordering of items is White (standard), Green (premium), Blue (prototype), Orange (custom), Purple (artifact), Deep Purple (legendary), Light Yellow (legacy), and Yellow (mission).
The Purple and Deep Purple items are very rare and powerful, which could easily be traced back to the meanings that purple has, sophistication and power.
Besides just this, these more rare and vibrant colors pop out more, and are more likely to draw a players attention. Mix this with making them rare, and these exotic and new colors will easily grab a players eye while they are playing as they are rare and new.
Color Psychology
Gaming History
Going from the history of gaming and seeing where it was used, an early contendor is Diablo 1, which came out in 1997. However, the best contender I could find for setting the trend in motion early was Diablo 2, which came out in 2000. Here they used a myriad of colors to clarify between different types of items.
They used White for Normal items, Blue for Magic items, Yellow for Rare items, Green for Set items, and Gold for Unique items.
Which is easier to see in a gloomy crypt, a dark gray glow or a bright yellow one?
After Diablo 2, World of Warcraft (released in 2004) was the next major game that I could find that started using color coding for it's loot system, and it was very easy to see it was based off of the Diablo 2 coloring system, which is the same for every game that uses the coloring system. Gray for junk, white for common, green for uncommon, blue for rare, purple for epic, orange for legendary, gold for artifact, and cyan for heirloom (with the latter two only being added in later additions to the game).
While Diablo 2 started the trend, I think it would be safe to say World of Warcraft really set it into stone.
Note: Both of these games were made by Blizzard Entertainment.
Non-Gaming History
Outside of gaming however, color coding based on value or rarity probably dates back a long time. Just one that is coming from the top of my head is the color of coins. Gold coins are made of a valuable metal, meaning a gold coin would be worth more than a silver coin. While this is not directly making lists based off of value, the value of the coins made their own color list, associating gold with value and silver with less value.
Coins in the Byzantine Empire
I refer to both the Solidus(gold coin) and the Follis(silver coin).
Much like the coins, indigo was another instance of color being related to value. The dye itself was rare in Europe at one point, so the mere use of the color dictated value. It might just be a color, but because it was different and rare, it had value.
Indigo Dye
Conclusion
There are multiple reasons to why I believe colors are used to denote rarity in games.

Unique colors stand out: on an ease of access standpoint, developers would choose colors that stand out somewhat and grab players attention, so they do not miss them.
Colors have meanings: with colors having meanings, different colors would subconsciously associate with how society has formed them. Purple being rare and royal, while gray being bland.
Consistency: once it was solidified by Blizzard in Diablo 1 and 2 and World of Warcraft, all of the other games that would use similar loot systems probably followed in suit. This would make the games friendlier to players who were coming from the Blizzard games. Even though some companies would make changes, they would remain generally similar.
Colors Have Had Value: Even though coinage does come with some real value tied to it (gold physically being worth more than silver), it still has been shaping society to understand that gold is more valuable. The same is for indigo.
Scarcity: The rarer items are usually the ones with colors that was once considered valuable, such as gold or purple, which could be a reason to why they are used for valuable items commonly.

Simply put, the color rarity system was re-adapted for games by Blizzard Entertainment with Diablo and World of Warcraft. As a basic concept however, it has been around for a while. It is all balanced deep in the human mind, and how we perceive colors and how scarcity works.
Comment: @ShadowZ. What sort of coverage do you mean? Angband is open source and you can access a historical changelog going back to 1983 at [1]. Version 2.8.2 (released in late 1997, after Diablo) mentions changes to how inventory colours are handled, so presumably the feature was in there for a while before that. (That said, it looks like Angband used colour to primarily denote item types, e.g. rings vs. potions -- it didn't really have a concept of "rarity" like Diablo.)

[1] http://www.thangorodrim.net/history/version.txt
Comment: While Diablo did use the system (gold for artifacts, blue for enchanted non-artifact items, and white for everything else), Angband was a major influence on Diablo 1 (it was originally pitched as "user-friendly angband with graphics", basically) and I believe it had a similar colour-coding system in place at the time, although I haven't checked the revision history to verify this.
Comment: You might want to check on your Diablo 1 colors. There was only, as far as I remember, white for normal items, blue for magic items, and gold for unique items. There were no "rare", "legendary", "set" or "junk" items. Rare and Set items were introduced in Diablo 2, and legendary only in Diablo 3. Not sure if "junk" is a thing and where it was introduced.
Comment: @kutschkem I edited the question. I did some more research and saw that Diablo 1 did not really utilize the color system, while Diablo 2 did. I modified my answer accordingly.
Comment: @ToxicFrog I am doing research in to Angband. Sadly, that game did not get as much coverage as other games, so it is harder to research in to it.
Answer: The other answers mention the origins tracing back to Diablo. According to Diablo designer David Brevik (on the May 16, 2019 Game Informer show):

Angband was a game that I played literally thousands of hours of ... there were different random items that you could get in the game and they had different colors ... if you found a rare one the text wasn't just gray it was blue text and that meant it was like magic ... we expanded on it but originally the idea came from Angband
Answer: The trend is coming indeed outside gaming. It is a mix of psychology and ranking (but ranking is also based on psychology). So the short answer is it is psychological trick.
If to talk about which game first used colored tiers/ranks I think it was FF, but I might be wrong according to this article:

Diablo:
The first game's division between standard (white) items, enchanted (blue) ones and uniques (yellow), may be considered an Ur-Example. The sequels add the green "set" category, where items from the same set are more powerful when used together, and gold or orange tier for uniques, while yellow items become a more powerful tier of "randomly enhanced" blue items.

In case you'd like to learn more without going too deep in psychology there is a Wiki article (very brief and simple version of psychological effects of colors). For deeper and more exact knowledge, I'd recommend to study psychology and philosophy (at least to read a textbook or attend several lectures in some college or university).
Comment: While these links may answer the question, Arqade requires users to summarize links in the answer body, to avoid an answering becoming useless due to link rot. Feel free to repost your answer with more details in the answer body itself.
Comment: I feel like it is a combination of ranking and better colors. For example, white is bland, while a saturated orange or purple has more appeal, or at least looks more interesting, regardless if the viewer likes the color. I might do research and try my own answer at this.


How to recover files on EFI boot partition

Question: I have a laptop with Windows 7. When I try to install Fedora I delete Efi boot partition. Then I again created it. Then I remove Fedora and now nothings work. How to recover files on EFI boot partition. All Windows partitions are on the disk.
Comment: reinstall grub or try to fix the MBR?
Comment: Disk use GUID Partition Table. MBR is not option. I want to recover my original efi partition.
Answer: It sounds like you deleted your EFI System Partition (ESP) and then created a new ESP in the same space occupied by the original. If so, files written to the replacement ESP may well have overwritten files stored on the original ESP, making recovery of the original files impossible. If you're very very lucky, though, you might be able to recover some or all of the original files with a tool like PhotoRec; however, PhotoRec does a poor job of recovering filenames, so you'll be left spending a lot of time sifting through files and guessing at filenames. There may be a similar tool that does a better job at recovering filenames, but if so, I don't know what it is.
Chances are you'll do better to boot a Windows recovery disc and have it restore the Windows boot loader to the ESP. I can't provide detailed instructions on doing this, since I'm not very familiar with the relevant tools, but I know they can do the job. One caveat: Before you begin, be sure that the ESP uses a FAT32 filesystem. Fedora often creates a FAT16 ESP, and the Windows installer doesn't much like that. I imagine that the Windows recovery tools might also dislike a FAT16 ESP.


What introductory book on Graph Theory would you recommend?

Question: I'm looking for a book with the description of basic types of graphs, terminology used in this field of Mathematics and main theorems. All in all, a good book to start with to be able to understand other more complicated works.
Answer: Diestel's book is not exactly light reading but it's thorough, current and really good. Also in the GTM series is Bollobas' book which is very good as well, and covers somewhat different ground with a different angle (Diestel emphasizes the forcing relationships between various invariants which is a nice unifying theme).
There are hundreds of other introductory texts, but I would go with one of these two (or both).
Comment: Diestel's book _Graph Theory_ is also freely available to view online.  http://diestel-graph-theory.com/
Comment: And it has a German version!
Answer: Introduction to Graph Theory by D.B. West. The book homepage is maintained by the author. Well written, with plenty of exercises.
Comment: I was starting to think nobody would mention it!
Answer: 1) Harary's book is great - and he's a hoot.
2) Ringel and Hartsfield's Pearl in Graph Theory is great, lovable and has lots of pictures and excellent exercises - ideal for an undergrad class that's not geared towards prepping students towards a grad course.
3) Gross and Yellen's book is probably the best introduction if you're a "mature" math reader and want to really learn stuff - this is what I would buy.
4) Applied Combinatorics by Tucker is phenomenal - but graph theory is only 4 chapters out of 11. Nonetheless, I'd strongly consider this one.
Comment: There is also "Extra pearls in graph theory" https://arxiv.org/abs/1812.06627, it is a  supplement to "Pearls in graph theory" covering a few additional topics.
Comment: Ringel and Hartsfield's Pearls in Graph Theory is indeed a gem.
Answer: Robin Wilson's Introduction to Graph Theory is very easy to read - I read it over a weekend. I definitely recommend you give this a quick read before plunging into Bondy and Murty, Diestel or West.
Answer: The classic Graph Theory with Applications by Bondy and Murty is available online.
Comment: I would recommend the new edition of their book also.
Answer: Graphs & digraphs by Gary Chartrand and Linda Lesniak is very well written.  The organization is nice and the proofs are very clear.  Moreover the exercises are concrete and to the point.
Comment: I'd second this one!
Answer: Pearls in Graph Theory: A Comprehensive Introduction by Nora Hartsfield and Gerhard Ringel.  This is a great introductory book and is one of the better dover books out there in my opinion.
Comment: I used this book to teach a course this semester, the students liked it and it is a very good book indeed. [The book includes number of quasiindependent topics; each introduce a brach of graph theory and avoids tecchnicalities. I would include in addition basic results in algebraic graph theory, say Kirchhoff's theorem, I would expand the chapter on Algorithms, but the book is VERY GOOD anyway.]
Answer: graph-theory-algorithms-book A GNU-FDL book on algorithmic graph theory by David Joyner, Minh Van Nguyen, and Nathann Cohen.
Answer: There are lots of terrific graph theory books now, most of which have been mentioned by the other posters so far. I would particularly agree with the recommendation of West; one of the most complete and well-written texts there are.
But to me, the most comprehensive and advanced text on graph theory is Graph Theory And Applications by Johnathan Gross and Jay Yellen. Crystal clear, great problems and contains probably the best chapter on topological graph theory there is in any source by 2 experts in the field. It's pricey, but well worth it.
And of course, anything by Bollobas is beautiful. The problem with Bollobas, though, is that it treats graph theory as pure mathematics while the books by Gross/Yellen and West have numerous applications. Like linear algebra, the applications of graph theory are nearly as important as its underlying theory.
Answer: Graphs and Applications: An Introductory Approach
Answer: I know only one book on graph theory, Wagner, Bodendieck "Graphentheorie". It contains detailed introductions of the basic concepts and theorems and independent chapters on interesting special topics, the 3dr vol. is independent and on games, many exercises.
Who dislikes that may comment, because I use it for tutoring, math-circle-like groups etc.
Answer: Different peoples need different introduction. If anyone want a light weight smooth reading I'll recommend Wilson. Although it is easy read, it'll take you even to the matroids.
If anyone want a proof based intro, research paper like, then West is the best choice.
Diestel, Harary are to some extent for intermediate/advanced readers.
Some encyclopedic resources are Handbook of Graph Theory, Handbook of Discrete and Combinatorial Mathematics, and are easy read.
By any means bondy-murty ranks first, assumed that readers are not below average.
Answer: I heard good things about Combinatorics and Graph Theory by  Harris, Hirst  and Mossinghoff  (Springer Undergraduate Texts in Mathematics).
It's easier to read than Diestel or Bollobas, but not dumbed down. But of course, it's neither thorough nor exhaustive.
Answer: Hajnal Péter, ''Gráfelmélet'' (Polygon, Szeged, 1997) is a very good introduction to graph theory.
Comment: See also a more specific question with this answer: http://mathoverflow.net/a/95565/5340


How does Google Analytics define a new vs returning user?

Question: Google Analytics support page does not provide specifics on how new vs returning users are defined.
https://support.google.com/analytics/answer/1012034?hl=en#Behavior
Answer: ga.js and analytics.js user tracking. The first time a user visits your site, a _ga cookie is set to help distinguish the user. The cookie has a 2 year expiration date from the time it is set.
If the user visits your site within the 2 year period, they will be marked as a returning visitor. On the return visit, the expiration date for the cookie will be updated to be 2 years from the latest visit.
User clears cookies. If a user clears their cookies, they will be marked as a new user on their next visit.
Answer: Using the New vs Returning reports will help you realize the potential for different types of visitors to your website and how you can best make the most of your traffic. Adding custom variables will take this analysis to the next level and really make the data matter more to you.
Comment: How is this answering the question?


Delete post after x minutes if user role is

Question: If a user has contributor role (or role of my choice) then delete his posts older than x minutes. How to?
Comment: Subscribers cannot write posts.
Comment: Well it was just a example for a user role. I edited my post.
Answer: This is a simple question, but it involves quite some work, so I'll just give you an outline:
First, you need to define a cron job that runs every minute or so. This will allow you to define an action that is run automatically. Beware that this will run only when the site is visited, because otherwise WP is just a bunch of files that sit on your server's hard drive. Now, you have a hook that fires every minute when your site is indeed visited every minute, but less if you get less visits.
Second, you will have to write a function that deletes posts based on the user role of its author. Get all users with a certain role using get_users. Feed the result in a query in which you also specify posts older than the X minutes your want. Then loop through all retrieved posts and delete them.
If you're actually going to do this, you're putting quite a load on your server, so don't expect it to be fast. Doing this max every hour might be a better idea.


OSX ssh server disconnects after 15 minutes

Question: I have a Mac mini running MacOS Sierra, with Remote Login turned on. I can ssh into the mini just fine (Cygwin's SSH client), but if I issue a long-running command (e.g. building clang from source) it doesn't complete, because the ssh connection gets disconnected. This is the end of the output of the ssh client when invoked with the -vvv switch:
debug3: send packet: type 1
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i0/0 o0/0 fd 4/5 cc -1)

Connection to mini11 closed by remote host.
Connection to mini11 closed.
Transferred: sent 3712, received 129732 bytes, in 735.3 seconds
Bytes per second: sent 5.0, received 176.4
debug1: Exit status -1

I tried running the build command from caffeinate -i, but it didn't seem to help. What now?
Every OS/X SSH article I found was about OS/X SSH client being disconnected.
Comment: I would check to see if you have a firewall somewhere inbetween that is cutting the connection off after x amount of minutes
Comment: Nope. Both machines are on my local network with fixed 192.168.x.x addresses.
Answer: You should be able to force the client to send keepalive messages if there is no activity by setting TCPKeepAlive yes (should be default) in ssh_config.
If it will not help, you can try to set
ServerAliveCountMax 5
ServerAliveInterval 600 # seconds = 10 minutes