How to Archive All Metadata

Question: A project I'm working on is winding down but may be revived again in two or three years. I need to archive all of the project metadata, including apex, lightning components, workflow rules, process flows and email templates outside of Salesforce as no Salesforce licenses will be preserved. I looked at creating an unmanaged package but there doesn't appear to be a way to download them locally. Is there a standard practice for archiving  an org's metadata or should I just download everything in VSCode and zip it into a single file?
Answer: If you added all the metadata to the unmanaged package you can extract all of its content using the workbench as a zip file.
To do so here are the steps

Log into the workbench(https://workbench.developerforce.com) using your salesforce login credentials
Navigate to metadata retrieve page (https://workbench.developerforce.com/metadataRetrieve.php)

Enter the package name in the package names and click single package checkbox and you will get a zip folder.
The zip folder can be securely stored and in future if you need to restore you can deploy the same using workbench in your org.
Answer: I ended up doing this a different way, mainly because of the time required to create an unmanaged package with thousands of items.
First, I used the packagebuilder tool on Heroku to get the package.xml for my entire org.
Second, I downloaded all of the metadata using the following Salesforce DX command with the manifest I generated:
<code>sfdx force:mdapi:retrieve -r archive -u full_sandbox -k metadata/package.xml
</code>
You can also use the package.xml file to download all of your metadata from VSCode. The advantage of this workflow is that it's then very easy to uploaded all of the metadata to a Github repository, which is ultimately what I need to do as an archiving strategy.

How to Archive All Metadata


Why exactly can't Microsoft Word close if there's a dialogue box open?

Question: I occasionally get the error that Word gives when trying to close a document with another dialogue box open but I've never been able to figure out why it happens.
Comment: The general issue is that stuff in the dialog might become valid,  invalid, or even inapplicable depending on what you do in the main window, and there's often no clear way to resolve this with changes that the user might have made in the dialog in the interim. (I guess this is just another manifestation of the more general principle of "feedback loops can cause problems in a system".)
Comment: They can if you launch Task Manager and tell it to kill the process. =) But this may have unexpected side effects. (There *might* be some rare instances where a file could end up corrupted, but I'm pretty sure they'd be extremely rare. It has to be designed for unanticipated crashes and power outages anyway.)
Answer: Because most dialog boxes are considered "modal" which means that control does not pass back to the main program, or calling container, until the dialog itself is closed.  This is by design and the programmer has the option to make a window modal or non-modal.  Usually, a window is defined to be modal if the main program cannot or should not continue until the opened dialog is dealt-with either through selection (Ok) or aborting (Cancel).
Comment: @LightnessRacesinOrbit I grant you Task Manager is a more "expert" way, but I wouldn't be at all surprised if people thought closing something from the taskbar was perfectly normal. In fact, I now realise, you don't even need to right-click, there's a red [x] button right there if you hover over a group or view the little thumbnail. Different things seem obvious to different people.
Comment: @LightnessRacesinOrbit There are many ways of closing a program, not all of which require clicks on the main window. For instance, you can right-click on a taskbar entry and select "Close", or pull Task Manager up with Ctrl-Shift-Esc and attempt to close from there. Shutting down Windows will also attempt to close applications gracefully initially, although may then "kill" them after a timeout. These send a signal to the program to close without it actually having focus, hence [Bob's screenshot](https://i.stack.imgur.com/hTITH.png) saying "Click OK, switch to Word" in that order.
Comment: But if the dialog were modal, how did the OP instruct the program to close? Might something else be going on here?
Comment: @IMSoP: I am aware that there are more "engineering" ways to ask an application to close, but I'd mentally drawn a line where I think "common usage" ends, because I'd have expected the OP to specify exactly what they were doing if it were beyond "common usage".
Comment: @IMSoP: That is true.
Answer: The dialog box might be saying something like:

You have made changes to your document, do you want to save them? (Yes) (No)

There is no obvious right answer here. You may have accidentally corrupted your document (for example, the cat walked over the keyboard) in which case the answer is "No", or you might have spent hours typing in changes in which case the answer is "Yes".
The safest thing for Word to do is is refuse to close until you answer the question.
Comment: OK, but the question didn't mention any particular dialog box. I'm a programmer, I understand what a modal dialog box is, however I tried to answer the question of *why* it happens.
Comment: I'm pretty sure the question is about [this](https://i.stack.imgur.com/hTITH.png) error specifically.
Comment: IMHO gotta keep in mind that people who aren't programmers use programs.
Answer: Because the program is designed this way, to avoid taking action the user might not want.
Usually, a dialog box is displayed when the program needs the user to guide some action. Closing an unsaved document is excellent example: a dialog offers to save the changes, discard the changes or abort closing and return to editing. The program intentionally refuses to close without answering this question because closing will force SOME action to be taken. The program can't decide on it's own to eg. discard recent edit, or on the contrary, overwrite correct version with cat-on-the-keyboard typing.
Even if we consider a dialog that's not related to closing, it usually means that some process is underway, it hadn't completed yet, and the user must decide which way to go. It cannot be "simply aborted", because aborting is also an action that the user might not meant.
It also simplifies design of the program, as it's creators don't have to create "a safe way out" of every function.
Today, most dialogs are not modal in the technical sense (the program remains responsible), but it's still easier to make them modal in a wider sense of logic flow of the program.
Answer: I could be mistaken, but I suspect this goes back to the old common dialog control behavior.
Several of those if killed abruptly without returning had unpleasant side effects, sometimes even outside the now-dead program and there was not a way to escape from them politely in all cases if they were doing something at a system level that required user input.
As to why it still is that way, people grew used to it, developers programmed with that assumption for decades and more importantly non-programmers used those dialogs in their office automation scripts and Microsoft is nothing if not a strict adherent to the goals backwards compatibility.
Answer: Behind the curtains, the program (in our case it's MS Word) creates a "X button click event handler" when creating the window. When there's a dialog window, Word records that. Then, in the X button handler, when the X button clicked, it checks for recorded open dialog windows. If there are some, the handler aborts the close operation. If there are not, it terminates the program and the OS cleans up the memory taken by the program. This is how it works.


Is there a material with work function less than 1 eV?

Question: There are lots of problems related to photoelectric effect, which, for example, use, or have as answer, a work function of less than 1 eV. But when I search on Google, I found out that most metals have work functions greater than 2 eV, let alone reach between 1-2 eV. So is the work function in the problem just made-up, or is there a material with work function less than 1 eV? I also found this but it was released 8 years ago, so I don't know if it's outdated.
Comment: Maybe a highly charged metal? Coulomb repulsion of all the extra electrons would reduce the energy needed for an electron to escape.
Comment: https://pubs.acs.org/doi/pdf/10.1021/acsenergylett.9b01214  Abstract talks of below 1ev.   2019 paper . But it is not a metal.
Answer: I think most of the materials have work function above 2 eV (most common materials). The poster you shared, I don't think it is outdated. Of course, a lot of materials can be made and synthesized with different work function values. And as I see on the poster, there is no material with work function less than 1 eV. The plot has a minimum of ~ 1.8 eV.
P.S.: in (especially, theoretical) physics problems, of course, any work function can be used.
EDIT: Here, one with less than 1 eV (it is a bit old): https://aip.scitation.org/doi/abs/10.1063/1.1652810?journalCode=apl and pubmed.ncbi.nlm.nih.gov/28681728
1.5 eV also exists. But less than 1 eV work functions, sounds unfeasible. That means that a material should have very weak bound electrons, which can easily be rejected from the material
Comment: I'd suggest to edit your second reference into the main text as well. (Also `EDIT:` markers are not really common on physics.SE, we can see the edit history of a post, so it doesn't need to be marked in the text IMO).


Notions of "confined" and "metastable" states?

Question: What is the exact definition of terms "confined state" and "metastable state", in the context of quantum mechanics?
Can we also have a "confined metastable state"?
Can we somehow easily link these terms to the character of the potential?
Answer: There are no exact definitions in that particular corner of quantum mechanics; people will use those words (and other words like "squeezed") to mean a lot of different things in different contexts.
A wavefunction is generally held to be "confined" if it's more or less "stuck in a location for a human-observable amount of time." If you've got a 1D square well, for example, there are two classes of solution: ones that look like sinusoidal waves off at infinity ("free" states) and ones that attenuate exponentially as space goes on to infinity ("confined" states).
A state is metastable when you've got a shallow potential well connected to a deeper potential well with some "barrier energy" between them.
It is a feature of quantum mechanics called "tunneling" that a particle which is confined to a metastable state will eventually, as if by magic, find itself in a stable state with the associated energy dissipated into environmental degrees of freedom, even if it does not have enough energy to jump over the barrier "classically". In some sense it is like there is an energy-conserving quantum noise which offers short "kicks" to the particle which it immediately "takes back". These kicks will occasionally be enough to knock a particle over any barrier.
So, if you "confine" a particle to a "metastable state", such a particle is not really "confined" in the sense that it will not stay in the well as $t \rightarrow \infty$. But you could still speak of it and most physicists would understand that you mean that the barrier energy is being held high enough to prevent both classical transitions and quantum tunneling over the course of the experiment -- in which case, yes, you can be confined in a metastable state.
You could also have "free states", which are needed to really get a meaningful "confined" state. A good example of how this happens is the sorts of Hamiltonians you see for molecular motors, which can have some $H(\theta) = A \cos \theta + B \cos (2\theta + \phi)$ behavior. There are states where the motor is just rotating mostly-freely, but there are also states where you are "bound" to one of two potential wells, one of which might be "lower" and the other of which might be "higher".
Comment: Thanks, this clears a lot. The thing is that I've seen physicists to speak about confined states when metastable would be a much more appropriate term.
Answer: It is not so clear what you mean by confined. Maybe you mean "bound states"?
Anyway, about the state of a particle in a potential well, we can have bound states, scattering states, and "resonant states. (People speak also about anti-resonant states but I am not sure whether it is relevant to your question).
1) Bound states are first of all integrable in absolute square. Their intensity tends quite rapidly to zero as $r \to \infty$. In short, they are mostly confined to a small volume. A good example is the ground state of an atom. The electrons of an atom in the ground state remain forever in the atom if we don't disturb them by bombarding with particles, by placing in all sort of fields, etc.
Usually, in a given potential well, the bound states have a discrete spectrum of energies, e.g. cosine waves in a square well of infinite walls.
2) Scattering states, are not integrable in absolute square. They resemble very much with the Fourier functions and are even called sometimes generalized Fourier functions. The scattering waves come from $r \to \infty$ and going to $r \to \infty$ after passing through the potential well - this is why they are called scattering waves, because they come and go. Such states can be found when the potential well has a finite maximum.
Their energies have a continuous spectrum. Many times (but not always) greater than the peak energy of the potential well.
3) Resonant states, are a class of states that comprises the metastable states of which you ask. They are in between the scattering and the bound states. A particle won't remain in such a state forever. The probability to find in inside the potential well decreases in time, in most of the cases as $e^{-\Gamma t/\hbar}$. Typical such states are the excited states of an atom. They live for a while, then they decay with the emission of a photon. When the half-life of such a state is very long (which implies small $\Gamma$) the particle, the electron in the case of the excited atom, has a very big probability to remain for a long time in this state. This is the metastable state.
The resonances also have a discrete spectrum. As to your question, they are confined, but not completely. For example in an atom, short time after an electron rised to an excited state, its wave-function is quite confined to the atom. But immediately, the wave-function begins to expand in space. Outside the atom we get a wave that all the time expands. So, after a time much bigger than the half-life the biggest intensity of the wave is out of the atom, not inside.
Comment: Thank you. Well, on a daily basis, I use the term "bound state", but I am not very familiar with the term "confined state", that is why I am asking to give me a definition, because I saw it recently in a strange context which I think is wrong.


How do I fix this rigging issue on a character?

Question: So I have been using Blender for a bit, but this is my first rigging project. I knew this was going to be uncharted territories, so I looked up some guides. After feeling comfortable with the process, I tried it out on my first character. I know this character has a lot of issues, but I said why not, its part of learning. I applied the rig, parented it to the character and moved it around to check. I noticed a small issue as I moved around the character. There is some clipping issue because I got lazy in the past and didn't fully create a body under the clothes (I couldn't find a good way to make clothes back then, and kinda still can't). So is there a way to fix this? I'll post the pictures. In it, you can see that the hand when rotated is obviously hollow. This is more of a learning thing, as I am really new to the rigging scene. I know its a rookie mistake to be lazy, so any ideas would be appreciated. I'm using v2.83.3
Comment: I think I figured it out. I'll try attaching the vertices to each other.
Answer: Merging the vertices worked. Just went to a previous save, and merged the vertices via edit mode for each object.


command/object option window - how to recover

Question:
The small window which opens up when i execute a command goes off if i click anywhere else in the window and is not recoverable (screenshot attached). how can i get this back.
Answer: I am still a noob so forgive me if I'm wrong, but as far as I know, you can, but not for the operation you just completed (by clicking).
This command window appears after doing an operation (scale, add mesh, in your case move, etc) and allows you to set the parameters of the operation precisely by inputting numbers. When you click anywhere you complete the operation and can't adjust it anymore. But you can ctrl+z and try it again of course.
So if you want this window to reappear you select the object and hit G (for move), but then the move parameters will be based off the current position. If you put in numbers and click, you can hit G again, but now the move parameters will be based off the new position.
I hope this helps.


Why do so many Bitcoin websites have such bad reviews

Question: I'm very interested in starting out trading with a cryptocurrency but I've noticed every single website seems to have a low Trustpilot rating, full of one stars claiming the website is fraudulent etc. Is this just a common, untrue thing amongst Bitcoin trading sites?
Comment: You might also want to ask yourself if you really want to buy bitcoins, or if you might as well buy a certificate or future through a traditional stock trading platform. Personally I can't really see any benefit to going through the hassle and risk of using a crypto currency exchange site, unless you're planning on using your bitcoins as payment or holding on to them for a long time. These platforms are generally secure, easy to use, easy to deposit and withdraw funds from and have less fees than crypto currency exchanges.
Answer: There are indeed a lot of fraudulent online exchanges and wallet providers. The same is true for displeased customers.
I suggest you take a tour at https://bitcointalk.org and get to known which providers are trustworthy.
For trading cryptocurrencies, I'll suggest you start with Coinbase/GDAX or blockchain.info. Then based on what coins you are interested in, find another exchange that support them.
This page is also very helpful, it list the biggest online exchanges.
https://coinmarketcap.com/exchanges/volume/24-hour/


Problems with a CD4060BE ripple counter not counting

Question: I have been trying to trace the fault in the circuit in the image below for the last 3 hours and I have exhausted the possibilities. The problem is that the CD4060BE ripple counter is not counting. The crystal clock signal fed to pin 11 on the chip is fine and is oscillating at 1 Hertz, but I get no output from the binary count pins. My question is: Do I have the chip connected up incorrectly? Also, should pins 9 and 10 be left unconnected?
Comment: Inputs shud never be floating
Comment: What is the state of the reset input? It is active high.
Comment: I2OUT? I1OUT?  Measure all outputs and inputs
Comment: Have you searched how other designs use the CD4060? In Google search for "4060 circuit" then press the **Images** tab. Now see plenty of circuits using the 4060. Look at how they use it, then do the same.
Answer:
Do I have the chip connected up incorrectly?

Since we have no idea where the clock and reset signals come from, we cannot comment on their timing as a possible problem.
But . . .
Yes, you are driving the 4060 incorrectly.
If you want to bypass the 4060's internal oscillator, connect the external clock signal to pin 11.  Of the three oscillator pins, only pin 11 is a simple input; 9 and 10 are points between an input and output, and as such they never should be driven by an external logic signal.  This is shown clearly on the 4060 datasheet, looking at the its internal schematic.
Because pins 9 and 10 are connected internally to output stages, they should be left floating in this application.
Since you are not using the oscillator, an alternate solution is to use a CD4020, 4024, or 4040.  Each of these has the four counter stages you use, Q4 - Q7.
Answer: Pin 12 has to have +Vdd applied to it then driven to a steady gnd or else it will not count. It triggers the count on a negative transition pulse. You can manually trigger it with a switch between pin 12 and Vdd that also has a 1.0K resistor going from pin 12 to gnd. The switch applies the 5VDC to pin 12 and when you release the switch, the 1.0K resister connects pin 12 to gnd.
Comment: Pin 12 is the Reset input, not the Clock input.  Toggling it will not advance the count.  A negative transition pulse will not "trigger the count".  A steady state low level at pin 12 enables counting when the clock input is pulsed.


Aliases on Dreamhost, general management of http request / server errors

Question: I had a hard time deciding how I should manage these errors (404, 500, ...) and when I finally decided, I am encountering problems. This is a reeeeeally long question, I appreciate anyone's attempt to help!
Let me first describe how I decided to set it up. I have several sites hosted on a shared Dreamhost account. In the folder structure that I see, everything of mine on the server is under /home/username, and for example, site1.com's web root is at /home/username/site1.com
I am creating a generic error handler (php script) for errors like 404 not found, 500, etc. that I want to store above the web roots of my sites at /home/username/error_handler/index.php so that I can use an .htaccess file at /home/username/.htaccess which includes something like the following:
ErrorDocument 404 /error_handler/index.php
ErrorDocument 500 /error_handler/index.php
...and many more
When these errors occur on any of my sites, I want it to be directed to /home/username/error_handler/index.phpThis is the problem I'm having a hard time figuring out. The ErrorDocument directives above will actually cause Apache to look for /home/username/site1.com/error_handler/index.php
Anyway, the errors should be redirected to my error handling php script. The script will use $_SERVER['REDIRECT_STATUS'] to get the error code, then use $_SERVER['REDIRECT_URL'] and $_SERVER['HTTP_HOST'] to decide what to do. It will check if an error handler specific to that site exists (for example: site1.com/errors/404.php). If this custom page doesn't exist, it will output a generic message that is slightly more user-friendly and styled, and perhaps will include some contact info for me depending on the error.
Doing it this way lets me funnel all these errors through this 1 php script. I can log the errors however I like or send email notifications if I want. It also lets me set up the ErrorDocument Apache directives once for all my sites instead of having to do it for every site. It will also continue to work without modification when I move the site around, since I already have a system that scans the folder structure to figure out where my site roots are when they really aren't at the web root technically speaking. This may not be possible with other solutions like using mod_rewrite for all 404 problems, which I know is common. Or if it is possible, it may be very difficult to do. Plus, I have already done that work, so it will be easy for me to adapt.
When I am working on sites for which I don't have a domain name yet (or sites where the domain name is already in use at the moment), I store them temporarily in site1.com/dev/site3.com for example. Moving the site to site3.com eventually would cause me to have to update the htaccess files if I had one for each site. Changing the domain name would do the same.
Ex: a site stored at site1.com/dev/site3.com would have this in its htaccess file:
ErrorDocument 404 /site1.com/dev/site3.com/error/404.php
And it would have to be changed to this:
ErrorDocument 404 /site3.com/error/404.php
Obviously, this isn't a huge amount of work, but I already manage a lot of sites and I will probably be making more every year, 95% of which will be hosted on my shared DreamHost account. And most of them get moved at least once. So setting up something automatic will save me a some effort in the long run.
I already have a system set up for managing site-relative links on all my sites. These links will work whether the site exists in a subdirectory of an existing site, or in their own domain. They also work without change in a local development server despite a difference in the web root location. For example, on the live server, the site-relative http link /img/1.jpg would resolve to the file /home/username/site1.com/img/1.jpg while on my local development server it would resolve to C:\xampp\htdocs\img\1.jpg, despite what I consider the logical site root being at C:\xampp\htdocs\site1.com. I love this system, and it is what gave me the idea to set up something that would work automatically like I expected it to, based on the file structure I used.
So, if I could get it to work, I think this seems like a pretty good system. But I am still very new to apache configuration, mod_rewrite, etc. It's possible there is a much easier and better way to do this. If you know of one, please let me know.
Anyway, all that aside, I can't get it working. The easiest thing would be if I could have the ErrorDocument directive send the requests to folders above the web root. But the path is a URL path relative to the document root. Using the following in /home/username/.htaccess,
ErrorDocument 404 /error_handler/index.php
a request for a non-existent resource causes Apache to look for the file at
site1.com/error_handler/index.php
So I thought I should set up a redirection (on all my sites) that would redirect those URLS to /home/username/error_handler. I tried a few things and couldn't get any of them to work.
Alias seemed like the simplest solution, but it is something that has to be set at server runtime (not sure if that is the right terminology - when the server is started). On my local server, it worked fine using:
Alias /error_handler C:\xampp\htdocs\error_handler2
I changed the local folder to test that the Alias was functioning properly. (On the local server, the URL path specified by the ErrorDocument directive is actually pointing to the right folder, since in my local server the web root is technically C:\xampp\htdocs and I store the error handler I want to use is stored locally at C:\xampp\htdocs\error_handler\index.php)
Dreamhost has a web client that can create what I am guessing is an Alias. When I tried to redirect the folder error_handler on site1.com to /home/username/error_handler, it would seem to work right if I typed site1.com/error_handler in the browser. But if I typed site1.com/test1234 (non-existant), it would say there was a 404 error trying to use the error handler. Also, I would have to login through the web client and point and click (and wait several minutes for the server to restart) every time I wanted to set this up for a new site, even if I could get it to work.
So I tried getting it to work with mod_rewrite, which seems like the most flexible solution. My first attempt looked something like this (stored in /home/username/site1.com/.htaccess for now, though it would eventually be at /home/username/.htaccess:
RewriteEngine On
RewriteRule ^error_handler/index.php$ /home/username/error_handler/index.php
The plain english version of what I was trying to do above is to send requests on any of my sites for error_handler/index.php to /home/username/error_handler/index.php. The mis-understanding I had is that the subsitution will be treated as a file path if it exists. But I missed that the documentation says "(or, in the case of using rewrites in a .htaccess file, relative to your document root)". So instead of rewriting to /home/username/error_handler/index.php, it's actually trying to rewrite to /home/username/site1.com/home/username/error_handler/index.php.
I tried including Options +FollowSymLinks because in the Apache documentation it says this:
To enable the rewrite engine in this context [per-directory re-writes in htaccess], you need to set "RewriteEngine On" and "Options FollowSymLinks" must be enabled. If your administrator has disabled override of FollowSymLinks for a user's directory, then you cannot use the rewrite engine. This restriction is required for security reasons.
I searched around for a while and I couldn't find anything about how Dreamhost handles this (probably because I don't know where to look).
I experimented with RewriteBase because in the Apache documentation it says this:
"This directive is required when you use a relative path in a substitution in per-directory (htaccess) context unless either of the following conditions are true:
The original request, and the substitution, are underneath the DocumentRoot (as opposed to reachable by other means, such as Alias)."
Since this is supposed to be a URL path, in my case it should be RewriteBase /, since all my redirects will be from site1.com/error_handler. I also tried Rewrite Base /home/username and RewriteRule ^error_handler/index.php$ error_handler/index.php. However, the Rewrite Base is a URL path relative to the document root. So I need to use something like an alias still. The implication in the quote from the documentation above is that it is possible to use mod_rewrite to send content above the web root. One of the many things I don't know is what the 'other means' besides Alias might be. I believe Alias might not be an option on Dreamhost. At least I couldn't make sense of it.
Answer: Why not use error pages in the site root, then include the actual file from the shared section?
Comment: Thank you for the response. I thought of that, but it's an extra step I would like to avoid. Perhaps  at this point it's not actually saving me time to figure this out, but I really want to solve the puzzle and fill the gaps in my knowledge. From what I read, I thought it should be possible for me to do this.


Why does the word "emcee" exist?

Question: I encountered the word "emcee" in written form for the first time this week and was surprised to find that it was not simply written "M.C." (short for Master of Ceremonies). Why does the "emcee" form exist?
(It's found in most dictionaries at this point- see Merriam-Webster, for example.)
Comment: Words like *deejay, okay, emcee,* etc. exist because we need real-world referents for wim's excellent coinage [acronomatopoeia](http://english.stackexchange.com/questions/53567/is-there-a-term-for-words-that-are-sounded-out-initialisms/53653#53653)
Comment: This reminds me: in the novelization of the movie *Star Wars* the droids are named something like artoodeetoo and ceethreepeeyo. I had to stop and think for a moment when I saw those for the firs time.
Comment: @FumbleFingers: Great reference.  That link is aitch-ess!
Comment: I've always known it to be M.C. Never seen "emcee
Comment: Interestingly, [Google Ngram](https://books.google.com/ngrams/graph?content=emcee%2CM.C.&year_start=1800&year_end=2019&corpus=en-2019&smoothing=3&case_insensitive=true) reports that "M.C." is more common (but perhaps due to [other senses of the word](https://en.wikipedia.org/wiki/MC_(disambiguation))
Answer: Per @Sarah's answer in this related question, the coinage vocologue was proposed for such "words" (made by spelling out the name sounds of an initialism's letters) over a decade ago. But it seems to have no currency as yet, and personally I much prefer acronomatopoeia as suggested by ELU's @wim in a comment to that question.
There aren't actually very many in common use. By far the most common is okay, which is one of a very few where the longer "phonetic spelling" form occurs more often than the short form (possibly because people aren't sure whether "ok" should be in capitals or not, and they're not sure what it stands for anyway).
A couple more where we very often see the longer form are emcee (MC, Master of Ceremonies)) and Dubya (ex-president George W Bush).
Others, such as teevee (TV, television),  deejay, (DJ, disc jockey), See-Threepio (C-3PO, Star Wars robot) are easily understood, but the spelled-out versions aren't as popular as the initialisms. I assume people calling themselves dj Pee Tee, dj Jay Kay, etc. are bored with "deejay", but still like using the technique on their own names.
Turning to OP's specific question (why does the "phonetic spelling" form exist at all?), I would say okay is a special case for the reasons given above. I think for the rest, it's a mild form of "linguistic subversion" (cf Old Skool, honest injun, Windoze, k.d. lang, etc.).
Effectively, we like them because they suggest we're part of a "counter-culture", kicking against the bland orthodoxy of correct spelling and grammar. That's why they rarely become dominant - if they did, they'd no longer have the slight "edginess" that justified using them in the first place.
Answer: Hip-hop and rap is characterised by creative lyrical wordplay, and in addition to abbreviating master of ceremonies -> MC -> emcee, you'll see disc jockey -> DJ -> deejay.
Another important part of hip-hop is individuality and rejection of the status quo.  Putting all this together may explain how new generations have changed and switched it up to end up with phonetical spelling.
Fluther.com answers to this question include this from CyanoticWasp:

Well, we know why the shortening
  happens: it's a natural enough thing in
  our language to shorten phrases into
  acronyms that there's surely no surprise
  there.
Maybe the progression from there is
  that the acronym becomes so successful and well-accepted that people start
  thinking of the acronym itself as the
  word. For example, a lot of younger
  people don't know the term "Master of
  Ceremonies", but they do know "MC",
  and they think that is a word: emcee, that means "the guy who sort of runs
  the show on stage".

Kayay8 continues:

It is entirely possible that the current
  generation is unaware of the original
  words, only learned the abbreviations
  and decided to make them into words.
  There is info on wikipedia to support
  this for MC and deejay has a completely different meaning than what we
  (oldsters) think of as a disk jockey per
  the wiki entry.

And roundsquare says:

I agree with [CyanoticWasp and Kayak8] that this is a
  generational thing. However, I think it
  might also just bee that each
  generation likes to change things up. At
  some point, someone made a decision
  to write "deejay" and it caught on. It probably came about as a current style
  but may eventually become all people
  know.

We can see more of this kind of wordplay in Eric B & Rakim's "I Ain't No Joke" where emcee itself is spelled out in letters:

The E-M-C-E-E don't even try to be
Comment: Except that *emcee* predates hip-hop by almost half a century...
Comment: Agreed. http://bit.ly/wD3Ps1 - seems to have been most popular, in print at least, in the 1950s ...
Answer: One online dictionary I consulted said:

Origin: 1930s (originally US): representing a pronunciation of MC

Considering that the letters of the alphabet have phonetic pronunciations (in other words, em and cee are already in the dictionary), it's not hard to imagine how MC would therefore be spelled emcee.
Comment: Well, we already know *how* they got the form, but not *why*.  The OP was asking *why* they chose M.C. and not, for instance, B.A.
Comment: The OP already knows that *emcee* comes from the pronunciation of *MC*.  What he doesn't know is why MC was chosen for acronomatopoetization (emcee), and e.g. MA (emmay) was not chosen.
Comment: Sometimes the _how_ is the _why_.  Why else would it be?
Comment: (MC=Master of Ceremonies, as the O.P. aptly noted...)
Comment: @Daniel: I don't follow you. OP says he knows they chose "M.C." because it's short for Master of Ceremonies. He's asking why "M.C." is often written as "emcee" - but it's hardly likely he'd be wondering why it's not written as, say, "B.A.", is it?
Comment: Oh, you're asking why there aren't **more** acronomatopoeia than the few examples that exist... I see... Like, why don't we write "_It doesn't take a pee-aitch-dee to figure that out_."
Comment: Yes, or less.  Why do they exist at all?  FumbleFingers' comment to the question (though a joke) is the only post to actually address it so far.
Answer: In addition to several points made already as far as acronyms becoming so widely used as to be words in their own right, use of M.C. could easily be confused with post-nominals.  For example, the sentence:
John Doe, M.C., called the next act to the stage.
M.C. looks like a post-nominal (think M.D., Ph.D., or in countries with orders, you'll find things like KBE, OBE, etc.  More here.).
Making a separate word for such a common title is, as mentioned, reasonable, and at least as a side benefit it avoids confusion with such post-nominal letters.
Comment: Actually MC *is* a post-nominal in the UK at least. It's for the Military Cross (medal).

Why does the word "emcee" exist?


Using a schema other than 'dbo' in LinqToSql Designer

Question: Is there a way to specify in a data connection or the LinqToSql Designer a schema?
Whenever I go to setup a data connection for LinqToSql there doesn't seem to be anyway to specify a schema and I get 'dbo' by default.  I figure that I can't be the first person to use a schema other than 'dbo' with LinqToSql, so I must be missing something obvious.
EDIT: Maybe a little clarification is in order.  Let's say that my database is such:
<code>MyDatabase.dbo.Tables
MyDatabase.MySchema.Tables
</code>
I can create a connection to MyDatabase.dbo (by default) and thus get a nice listing of tables that I can drag on to the designer.
What I can't seem to do is create a connection to MyDatabase.MySchema to get the nice table listings etc. of which I could drag on to the designer.
Answer: In the properties of each of the data classes inside the dbml the "Source" would usually point to dbo.TableName you should be able to change dbo to your schema name.
Edit:
If you are saying that your having to build the dataclasses manually... then with in the dbml designer you right click and say add, then select dataclass, then right click the new dataclass and select properties. Inside the property window of the dataclass there is a property call Source with is . it is at that point you would specify the schema name.
Comment: There is an attribute for each data class of [Table(Name="dbo.Queue")], but modifying this wouldn't help because I can't drag the tables from the schema I want in to the designer to have it generate the data class.
Comment: I guess this is the lesser of two evils. :)  I just find it hard to believe that MS doesn't think that anyone would want access to a schema other than dbo.
Comment: I am not sure we are on the same page yet. I have 3 production applications that use SQL2005 and have schemas other than dbo (CAPS, CSI, SAMS, etc.) and in the LinqToSql dbml is has my schema and not dbo...
Answer: Try creating a user with a different default schema and setting that up in Server Explorer- it shows all the objects in the user's default schema (bonus- I saw all the dbo objects the user could see as well, with a (dbo) suffix).
Comment: Thanks, but it's rather impractical to create a new user just to gain access to that schema.


Is there a Tridion Default Components Library?

Question: Components like navigation, breadcrumbs, toolbar, table, login, search are the components mostly used in every web portal. Does Tridion has its default set of library providing these components OOTB, that can be leveraged/re-used/extended for any new website based on Tridion?
Comment: At the recent SDL Innovate conference, the Web roadmap session described more examples in a future version of Tridion. But since this isn't in the product now, we will have to wait to see what features will be available. Professional Services has also provided example or starter features [see PDF](http://tridion.stackexchange.com/q/2947/46), but this wouldn't be part of a free library. I have submitted an idea for such a library (a TBB exchange of sorts), consider voting for it on [Tridion Ideas](http://ideas.sdltridion.com/ideas/detail.asp?i=4852). :-)
Answer: Tridion does not provide OOTB components.
However, there does exist a "Default Schemas for Tridion" github project which can help you at least get started on making some of the most common components for your clients: https://github.com/paceaux/Default-Schemas-for-Tridion
You'll have the option to select either PascalCase or camelCase schemas.
Answer: Tridion default installation do not provide OOTB components in question. But if you follow blogs and SdL tridion world, you will find lots of examples and code you need as per your requirement.
Navigation: you can publish sitemap xml and use asp.net controls to render navigation and breadcrumbs.
Help Link: http://www.tridiondeveloper.com/web-sitemap
Login: you can use default .net login controls.
Search: Google search appliance / SOLR etc are integration points.
Help Link:Search products and SDL Tridion 2011
In Tridion Content management & Content Delivery are decoupled. CM is used to manage content, which you publish to disk/db & use  choice of your technology stack e.g net/java. Above facilities comes in purview of your Content Delivery website not CM. CD you can consider it like any .net/java site where you need separate effort to implement/integrate those features
Comment: Check out SI4T for search.  Will Price did a 15 min talk at the TridionDeveloperSummit on it


How can I create a shape in Illustrator which follows a path in descending order size?

Question: I want to create something similar to the first image, but the angle of the star should be same.
Comment: Please share what you have tried and where it is failing.
Comment: Also note that it's better to take screen shots rather than take photos of your screen.
Comment: i uploaded the image how far i have done it.
how can we add image in here comment box?
Comment: You can't add images in the comments, but you can upload images to imgur(dot)com or other image sharing sites, and copy and paste the link in your comment.
Answer: In case you don't have access to a pressure sensitive device....
This is somewhat possible via a blend. But due to how blends behave, in many cases spacing will require manual refinement.

Create a blend, specified steps
Replace Spine
Alter blend options to set blend to be Relative to path and then increase steps to space the small end better
Expand the blend
Manually remove superfluous objects and then manually reposition a few objects for better spacing

This is far from perfect, but may offer a relative shortcut by supplying overall rotation and sizing to follow the path desired.

If you wish to achieve precision, then there's really nothing "automated" that will accomplish that which I am aware of. You would need to manually determine sizes, positions, and rotation degrees if you want things to be precise.
Answer: Assuming I've understood your question properly, it is kind of possible.
Here's one method which involves the use of a graphics tablet and pressure sensitive stylus, such as a Wacom.
Draw a star, and use it to create a Scatter Brush, with settings as shown below. When you use the Brush Tool, press harder at one end and release the pressure gradually as you draw. It might take a couple of attempts to get the pressure right.


Why is a spin network a spinfoam's boundary?

Question: i read in Wikipedia that spinfoams boudaries are spin networks, but nothing is said about what is a boundary in this case.
i know that a spin foam is a spin network where other colours and intertwiners are added to faces and edges. are boundaries of a spinfoam a part or them where these colors are neglected?
Answer: Sorry this answer is a bit late. This is pretty trivial, actually.
A spin network is a graph with the following data associated to its nodes and links (note the terminology here - we've reserved terms vertex and edge for the components of spinfoams):

To a link we associate an irreducible unitary representation of the gauge
group $G$ (in LQG this is $G=SU(2)$).
To a node we associate an intertwining tensor between the representations of incident links.

A spinfoam is a 2-complex with the following data associated to its vertices, edges and faces:

To a face we associate an irreducible unitary representation of $G$.
To an edge we associate an intertwining operator between the representations of incident faces.
To a vertex we don't associate any data. Instead, each vertex contributes with the spinfoam amplitude evaluated at the vertex which depends on the data associated to incident edges and faces.

Now imagine a spinfoam to be "cut" by a sphere which never passes through vertices. Each face will be cut in two halves separated by a link, and each edge will be cut in two halfs separated by a node. Moreover, the incidence relation between edges and faces becomes the incidence relation between nodes and links.
Thus, the boundary of a spinfoam is a spin network.
Comment: I see how a spin network can be built from a spinfoam. it is a choice. a spinfoam has no naturel boundary. suppose that the spinfoam is not embedded in a manyfold you have no sphere cutting rhe edges. what are the rules for a good choice of faces? (only one face is not a goof choice)
Comment: @Naima I'm not sure I agree with "spinfoam has no natural boundary". Maybe not in the mathematical sense, but in quantum physics we are always looking to find quantum states associated to the boundary. Try reading about the boundary formalism in any of the LQG textbooks or seminal papers e.g. https://arxiv.org/abs/gr-qc/0604044. It's probably one of the deepest and most general insights of QFT and especially TQFT – that Hilbert spaces are associated to boundaries, and evolution operators are associated to sums over the bulk objects of some sort.
Comment: thanks. i understand now that not  having a unique boundary is not a problem. you give a great tool to get spin networks of a spinfoam!


Rendering: Excluding a layer while keeping it's influence (Masking?)

Question: I am making this Christmas Tree but the problem is that I can't render the whole scene in one go because of too many particles. So I have rendered my tree and now I want to render only tinsels wrapped around the tree but I want it as png with alpha so that I can add them together as layers.
So how can I do this?
Thanks.
Tree

Tinsel
Comment: This works perfectly. Thanks. Can you write it as an answer so that I can accept it?
Answer: It should work if you replace the transparent with a holdout shader. However that doesn't solve the Memory issue.
There's a fairly easy solution, which of course doesn't work in all cases.
In post you can use the Z-pass in order to combine renderlayers.
Compositor -> SHIFT A -> Color -> Z-Combine.
It is intended to do what you want, but it will produce strange results when MB or DoF is involved.
Comment: Thanks for the answer. An example would be really helpful.
Comment: Did you get the notification that I edited my original answer as for your request?
Answer: In my own opinion the only way do so in Blender 2.8* is to override the hidden but influencing materials with Camera ray to Transparent setup:

Diffuse BSDF must be replaced with your Node setup.
Comment: Tried this. Doesn't seem to be working. A example would be really helpful. Also, in this method I would have to render the Tinsels and Tree together which will defeat the whole purpose of this question. https://imgur.com/39Dn9yU


Why don't spacecraft accelerate to the speed of light, or just fractionally below that?

Question: In space there is almost nothing to slow you down, and your proppelent/S will always be traveling relatively faster than your craft so you should accelerate infinitely close to the speed of light assuming you have enough proppelents. Why don't we though?
Comment: Your assumption is wrong.
Answer:
so you should accelerate infinitely close to the speed of light assuming you have enough proppelents.

That's correct, but only for unreasonably large values of "enough".  In practice, it is not possible to carry enough fuel/propellant.  It has to be stored in a tank, and building the structure for the tank is expensive and difficult.
The way to see this is via the Tsiolkovsky rocket equation
$$\Delta V = v_e \ln \frac{m_0}{m_1}$$
Let's say that we want to reach 50% of the speed of light and we have a fuel that has an exhaust speed of $300\,000 \text{m/s}$ (faster than we have today, but not far from some technologies).  Then we just rearrange to solve for the mass fuel fraction.
$$\ln \frac{m_0}{m_1} = \frac{\Delta V}{v_e} = 500$$
$$\frac{m_0}{m_1} = e^{500} = 10^{217}$$
This means to reach half the speed of light (ignoring relativistic effects) with a realistic engine, the ship has to carry $10^{217}$ grams of fuel for every gram of non-fuel (like the engines, the ship itself, etc.)   That ratio is much greater than the ratio of the mass of the galaxy to a proton.
Comment: Then you need a stage 2 somewhat smaller amount to slow down so you don't smash into your destination at relativistic speeds.


How to make a function that returns all super distinct partitions?

Question: I am working on distinct partitions. I recently created a function StrictIntegerPartitions.
This is from the book Integer Partitions by George E. Andrews at Pennsylvania State University and Kimmo Eriksson at Mälardalen University published by Cambridge University Press in 2004 with ISBN 978-0-521-84118-4.

Another way of describing that the numbers in a set are distinct is
that every pairwise difference is at least one. Let us say that parts
are super-distinct if every difference is at least two. We shall now
present a relatively modern bijective proof of a partition identity
concerning distinct and super-distinct parts. Since
every partition into super-distinct parts is also a partition into
distinct parts, there must be more of the latter kind. For example,
there are seven partitions of eleven into super-distinct parts: 11,
10+1, 9 +2, 8 +3, 7 +4, 7 + 3+1, 6 + 4+1 . There are a few more
partitions where the parts are distinct but not super-distinct: 8 +
2+1, 6 +5, 6 + 3 +2, 5 + 4 + 2, and 5 + 3 + 2+1 . We shall prove the
following strange-looking theorem: Theorem 3 p(n | super-distinct
parts) — p(n | distinct parts, each even part > 2(# odd parts)). For n
= 11, the right-hand expression counts the seven partitions 11, 10 + 1, 8 + 3, 7 + 4, 7 + 3 + 1, 6 + 4 + 1, and 6 + 5. The bijective proof
of David Bressoud (from 1980) goes as follows: Take the Ferrers graphs
of partitions into super-distinct parts and adjust the left margin to
a slope of two dots extra indentation per row. Draw a vertical line in
such a way that the last row has one dot to the left of this line, the
next-to-last line has three dots to the left, etc. Thus, for 14 + 11 +
6 + 4 + 1, the graph looks like:

To the right of the line, we have obtained a new Ferrers graph, and we
now rearrange its rows, starting with the odd rows in descending order
followed by the even rows in descending order

Ignoring the line and taking the rows of this graph as the parts of a
partition, we get 14 + 8 + 6 + 7 + 1, a partition into distinct parts
with each even part greater than four (i.e., twice the number of odd
parts).

I would like to design a function SuperDistinctIntegerPartitions. For example, SuperDistinctIntegerPartitions11 would return {{11},{10,1},{9,2},{8,3},{7,4},{7,3,1},{6,4,1}}.
How can I use this to design a function to returns SuperDistinctIntegerPartitions? There is a Resource Function Ferrers Diagram that could be useful. The Resource Function uses a different orientation. Wikipedia states,

[Young diagrams and Ferrers diagrams] have several possible conventions, here we use English notation,
with diagrams aligned in the upper-left corner.

This is related to this exercise.
36. Explain why the procedure is invertible, that is, why every partition into distinct parts with each even part greater than twice
the number of odd parts is obtained exactly once. (Difficulty rating:
2)

I also found something helpful in this slideshow on slides 16 and 17.

I downloaded the presentation from http://player.slideplayer.com/download/10/2772378/g2qgMmjeKt8WgGBgww8Hdg/1691086330/2772378.ppt. Here are some more screenshots.

How do we know where the draw the line? How would I calculate the line should be drawn at the 9th position from the left and 8 positions from the right?
Here is another picture I drew for {14,11,6,4,1}

Here is a picture I drew with indentations for  {14,11,6,4,1}:
Answer: You want to use Mathematica to demonstrate the bijection between these 2 cases:

Integer partition of $n$, all parts differ by $\geq 2$,  i.e. The so-called super-strict integer partition
Integer partition of $n$, $\text{  distinct parts }$, $\text{each even part}$ $>2\cdot (\# \text{odd parts})$.

SuperStrictIntegerPartitions[n_Integer] :=
 Module[{partitions, validPartition},
  partitions = IntegerPartitions[n];
  validPartition =
   Function[partition, Min@Abs@Differences@Sort[partition] >= 2];
  Select[partitions, validPartition]]

superStrictIntegerPartitionsOf11 = SuperStrictIntegerPartitions[11]

DistinctEvenOddPartitions[n_Integer] :=
 Module[{partitions, validPartition},
  partitions = IntegerPartitions[n, All, Range[n]];
  validPartition =
   Function[partition,
    With[{evens = Select[partition, EvenQ],
      odds = Select[partition, OddQ]},
     Min[evens] > 2*Length[odds] && DuplicateFreeQ[partition]]];
  Select[partitions, validPartition]]

distinctEvenOddPartitionsOf11 = DistinctEvenOddPartitions[11]

Length /@ {superStrictIntegerPartitionsOf11,
  distinctEvenOddPartitionsOf11}     (*{7,7}*)

case 1 to case 2
helper[lst_List] :=
 Module[{odd, even}, odd = Sort[Select[lst, OddQ], Greater];
  even = Sort[Select[lst, EvenQ], Greater]; Join[odd, even]]
case1TransformToCase2[partition_] :=
 Module[{n, part1, part2}, n = Length@partition;
  part1 = Reverse@Array[#*2 - 1 &, n];
  part2 = helper[partition - part1]; part1 + part2]

generatedDistinctEvenOddPartitionsOf11 =
 case1TransformToCase2 /@ superStrictIntegerPartitionsOf11

Sort[Map[Sort, generatedDistinctEvenOddPartitionsOf11]] ==
 Sort[Map[Sort, distinctEvenOddPartitionsOf11]]

case 2 to case 1
helper1[lst_List] :=
 Module[{odd, even}, odd = Sort[Select[lst, OddQ], Greater];
  even = Sort[Select[lst, EvenQ], Greater]; Join[even, odd]]
case2TransformToCase1[partition_] :=
 Module[{n, part1, part2}, n = Length@partition;
  part1 = Reverse@Array[#*2 - 1 &, n];
  part2 = Sort[(helper1@partition) - part1, Greater]; part1 + part2]

generatedSuperStrictIntegerPartitionsOf11 =
 case2TransformToCase1 /@ distinctEvenOddPartitionsOf11

Sort[Map[Sort, generatedSuperStrictIntegerPartitionsOf11]] ==
 Sort[Map[Sort, superStrictIntegerPartitionsOf11]]


How I/O channels are implemented in Linux kernel?

Question: stdin, stdout, stderr are some integers that index into a data structure which 'knows' which I/O channels are to be used for the process. I understand this data structure is unique to every process. Are I/O channels nothing but some data array structures with dynamic memory allocation ?
Comment: @strugee I am talking about Linux kernel. I meant streams by I/O channels. How these streams are implemented in linux? some array or something?
Comment: by I/O channels do you mean streams or pipes? also, this probably varies by kernel. you'll probably need to ask about a specific kernel.
Answer: In Unix-like operating systems, the standard input, output and error streams are identified by the file descriptors 0, 1, 2. On Linux, these are visible under the proc filesystem in /proc/[pid]/fs/{0,1,2}. These files are actually symbolic links to a pseudoterminal device under the /dev/pts directory.
A pseudoterminal (PTY) is a pair of virtual devices, a pseudoterminal master (PTM) and a pseudoterminal slave (PTS) (collectively referred to a s a pseudoterminal pair), that provide an IPC channel, somewhat like a bidirectional pipe between a program which expects to be connected to a terminal device, and a driver program that uses the pseudoterminal to send input to, and receive input from the former program.
A key point is that the pseudoterminal slave appears just like a regular terminal, e.g. it can be toggled between noncanonical and canonical mode (the default), in which it interprets certain input characters, such as generating a SIGINT signal when a  interrupt character (normally generated by pressing Ctrl+C on the keyboard) is written to the pseudoterminal master or causing the next read() to return 0 when a end-of-file character (normally generated by Ctrl+D) is encountered. Other operations supported by terminals is turning echoing on on or off, setting the foreground process group etc.
Pseudoterminals have a number of uses:

They allow programs like ssh to operate terminal-oriented programs on a another host connected via a network. A terminal-orientated program may be any program, which would normally be run in an interactive terminal session. The standard input, output and error of such a program cannot be connected directly socket, as sockets do not support the aforementioned terminal-related functionality.
They allow programs like expect to drive a interactive terminal-orientated program from a script.
They are used by terminal emulators such as xterm to provide terminal-related functionality.
They are are used by programs such as screen to multiplex a single physical terminal between multiple processes.
They are used by programs like script to to record all input and output occuring during a shell session.

Unix98-style PTYs, used in Linux, are setup as follows:

The driver program opens the pseudo-terminal master multiplexer at dev/ptmx, upon which it receives a  a file descriptor for a PTM, and a PTS device is created in the /dev/pts directory. Each file descriptor obtained by opening /dev/ptmx is an independent PTM with its own associated PTS.
The driver programs calls fork() to create a child process, which in turn performs the following steps:

The child calls setsid() to start a new session, of which the child is session leader. This also causes the child to lose its controlling terminal.
The child proceeds to open the PTS device that corresponds to the PTM created by the driver program. Since the child is a session leader, but has no controlling terminal, the PTS becomes the childs controlling terminal.
The child uses dup() to duplicate the file descriptor for the slave device on it standard input, output, and error.
Lastly, the child calls exec() to start the terminal-oriented program that is to be connected to the pseudoterminal device.

At this point, anything the driver program writes to the PTM, appears as input to the terminal-orientated program on the PTS, and vice versa.
When operating in canonical mode, the input to the PTS is buffered line by line. In other words, just as with regular terminals, the program reading from a PTS receives a line of input only when a newline character is written to the PTM. When the buffering capacity is exhausted, further write() calls block until some of the input has been consumed.
In the Linux kernel, the file related system calls open(), read(), write() stat() etc. are implemented in the Virtual Filesystem (VFS) layer, which provides a uniform file system interface for userspace programs. The VFS allows different file system implementations to coexists within the kernel. When userspace programs call the aforementioned system calls, the VFS redirects the call to the appropriate filesystem implementation.
The PTS devices under/dev/pts are managed by the devpts file system implemention defined in /fs/devpts/inode.c, while the TTY driver providing the the Unix98-style ptmx device is defined in in drivers/tty/pty.c.
Buffering between TTY devices and TTY line disciplines, such as pseudoterminals, is provided a buffer structure maintained for each tty device, defined in include/linux/tty.h
Prior to kernel version 3.7, the buffer was a flip buffer:
#define TTY_FLIPBUF_SIZE 512

struct tty_flip_buffer {
        struct tq_struct tqueue;
        struct semaphore pty_sem;
        char             *char_buf_ptr;
        unsigned char    *flag_buf_ptr;
        int              count;
        int              buf_num;
        unsigned char    char_buf[2*TTY_FLIPBUF_SIZE];
        char             flag_buf[2*TTY_FLIPBUF_SIZE];
        unsigned char    slop[4];
};

The structure contained storage divided into two equal size buffers.
The buffers were numbered 0 (first half of char_buf/flag_buf)
and 1 (second half). The driver stored data to the buffer identified
by buf_num. The other buffer could be flushed to the line discipline.
The buffer was 'flipped' by toggling buf_num between 0 and 1.
When buf_num changed, char_buf_ptr and flag_buf_ptr
was set to the beginning of the buffer identified by buf_num,
and count was set to 0.
Since kernel version 3.7 the TTY flip buffers have been replaced with objects allocated via kmalloc() organized in rings. In a normal situation for an IRQ driven serial port at typical speeds their behaviour is pretty much the same as with the old flip buffer; two buffers end up allocated and the kernel cycles between them as before. However, when there are delays or the speed increases, the new buffer implementation performs better as the buffer pool can grow a bit.
Comment: Answers as knowledgeable as this are extremely hard to come by.
Answer: From the man pages for any of the three it explains the answer:
   Under  normal circumstances every UNIX program has three streams opened
   for it when it starts up, one for input, one for output,  and  one  for
   printing diagnostic or error messages.  These are typically attached to
   the user's terminal but might instead  refer  to  files  or
   other  devices,  depending  on what the parent process chose to set up.

   The input stream is referred to as "standard input"; the output  stream
   is  referred  to as "standard output"; and the error stream is referred
   to as "standard error".  These terms are abbreviated to form  the  sym-
   bols used to refer to these files, namely stdin, stdout, and stderr.

   Each  of these symbols is a stdio(3) macro of type pointer to FILE, and
   can be used with functions like fprintf(3) or fread(3).

   Since FILEs are a buffering wrapper around UNIX file  descriptors,  the
   same  underlying  files  may  also  be accessed using the raw UNIX file
   interface, that is, the functions like read(2) and lseek(2).

   On program startup, the integer file descriptors  associated  with  the
   streams  stdin,  stdout, and stderr are 0, 1, and 2, respectively.  The
   preprocessor symbols STDIN_FILENO, STDOUT_FILENO, and STDERR_FILENO are
   defined  with  these values in <unistd.h>.

Comment: This answer describes the implementation of `stdin`, `stdout` and `stderr` from the point of view of the C library, but the question is explicitly about the kernel implementation. I tried to account for the kernel point of view in [my answer](http://unix.stackexchange.com/a/102777/43779).


Can you explain glottal stop?

Question: It doesn't sound like a consonant. Especially at the end of words. It sounds like a shortened vowel which it follows.
English word "cat" for example [kʰæʔ]
Comment: What do you mean by "explain glottal stop"? Are you asking how they are produced? Are you asking how they behave phonologically? Are you asking for an explanation for why you don't think they sound like consonant?
Comment: It's called a "stop" because it stops the breath flow. That's what "shortens "the vowel preceding it. You experience the  cessation.
Answer: In some languages, glottal stop is associated with shortness of vowels, but so far as I know, this is not the case in English, except perhaps indirectly.
In English, vowels are shorter before a voiceless sound in the offset of a syllable, and also, the voiceless stops p t k are glottalized (said with glottal closure) in the offset of a syllable before a consonant.  Then, in some circumstances, the glottalized p' t' k' lose their oral closure, leaving behind the glottal closure alone, which is a glottal stop.  This loss of oral closure happens before a homorganic consonant (i.e., with the same place of articulation), or for t', before any consonant.  These things happen only in some dialects.
So there is a relationship between the shortening of vowels and glottal stop (vowel is shortened before p t k, p t k are glottalized to p' t' k', which then turn into glottal stop), but it's coincidental.
In some other languages, glottal stop has more directly to do with vowel shortness.  There is a language of Brazil, Shavante, which has "clipping" of word final vowels, which consists in shortening the vowels and appending glottal stop.
Some examples from Danish make it appear that glottal stop has something to do with vowel shortness: læser /ˈlɛːsʌ/ "reader", læser /ˈlɛˀsʌ/ "reads" are cited in the Wikipedia article on stød.
Although this is not so in English, in many languages, glottal stop is a phoneme -- just another consonant in the language's phonemic system.  I'm not aware of any shortening of vowels in such cases.
Answer: It is a stop consonant, as it stops the airflow in the glottis.
The fact that you can't differentiate the sound doesn't mean it isn't a consonant - there are many, many, many consonants which sound indistinguishable if you don't have the right mother tongue. But they are distinguishable if you do speak the right language.
For example, semitic languages are languages in which the glottal stop is a consonant.
Comment: BTW, in the production of a vowel, airflow through the glottis also stops briefly, every cycle (though perhaps not in the case of breathy vowels). The concept of "stopping" transglottal airflow has to be relativized to some minimal time period, in the definition of "stop". It turns out that glottal "stop" frequently just introduces irregularities in transglottal airflow, without bringing airflow to a halt as you find with /p b/ etc. In fact, a characteristic of full voicing of /b/ as opposed to English-style *b* is that the vocal folds continue to vibrate.
Comment: @user6726 really? What is an english-style b then?
Comment: it varies by speaker, but voicing dies early during the closure and it is a voiceless unaspirated stop thereafter.
Answer: Well, it is a consonant.
It is produced by stopping the airflow in the same way as in producing [p],[k] or [t], it is just made in different place. While the aforementioned obstruents are articulated by stopping the airflow respectively between lips (bilabial stop), root of the tongue and velum (velar stop) and tip of the tongue and alveolar ridge (alveolar stop), glottal stop is produced by stopping the airflow with glottis.
In English glottal stop function merely as an allophone of /t/ word finally, and (in some dialects) intervocally. But there are languages where glottal stop is a distinct phoneme. The example would be the Semitic family where it is written with letter aleph.
Answer: Let's use "uh-oh" as an example, right after you say the part "uh" and before you say the part "oh", that's a glottal stop.

Can you explain glottal stop?


How can I make search with a substring of a word?

Question: I would like to search with only part of a word,not the whole word.For example when I search name of people,I would like to search only the first 3 letters of the Last Name,not the whole name.Now if I put on  search only the first 3 letters I take no results.For the moment I am using the search api with apache  solr(and perhaps views).Any suggestions please?
Answer: Add ngramfilter to text type definition in schema.xml in solr config directory.
<code><fieldType name="text" class="solr.TextField" positionIncrementGap="100">
  <analyzer type="index">
    <filter class="solr.EdgeNGramFilterFactory" minGramSize="3" maxGramSize="25" />
</code>
Comment: :I added it but its failing because there is no tokenizer..which class should I add for my tokenizer?


What exactly is the meaning of the phrase "county courted"?

Question: I come across this phrase very rarely, most recently in a Wodehouse story. It seems to mean something like "brought as defendant before a county court", e.g., sued. Is there a more precise meaning? In Wodehouse it arises when a character fails to pay his bills and is county courted by his tailor, or something like that. Is a county court something like a small claims court? Can one be county courted for theft, for nonpayment of taxes, for speeding, for murder? What is the level of such a court in the hierarchy?
Answer: The Victorian weekly literary magazine All the Year Round, edited by Charles Dickens, has an interesting passage found here:

The fact is, that Growler had been "County Courted." ("To County
  Court," I may observe in parenthesis, is a verb only admissible into
  dictionaries of recent date.

I am not sure which dictionaries are meant here, since none of those I checked have such entry. Still, the meaning is clear from the context, as well as from other occurrences of the same phrase found on Google Books, e.g.:

Let it once be known that a trader has been "County Courted " and his
  destruction is inevitable,
Otherwise, he remarked, he might be "county courted" for a debt he
  could not pay. There was also a great deal of evidence as to the
  inferiority of goods supplied by tallymen upon the credit system, and
  among the witnesses was Mr. Commissioner Kerr,
Some debtors talked of being 'county courted'. For instance, Debtor 11
  said, 'I knew you'd get county courted. That's obvious, everybody
  knows that.'
The reason why one debtor can be county courted and another cannot
  lies in the amount of the debt;

The nature and jurisdiction of county courts is IMHO adequately covered by Wikipedia.


Holomorphic h-principle for compact manifolds

Question: The Oka principle for Stein manifolds says (roughly) that the only obstructions for "things" are topological obstructions (for instance every smooth complex vector bundle admits a holomorphic structure, etc). Is there a similar principle (atleast in some cases) for compact complex manifolds? Or atleast some version of a h-principle for compact manifolds?
Comment: Hi Vamsi,

As Johannes states, of course the answer is "no" in general.  However, for fiber bundles of very special type, and up to replacing holomorphic section by meromorphic section, there are some such results in the compact case.  The basic example is Tsen's theorem: a $\mathbb{P}^1$-bundle over a Riemann surface always has a holomorphic section.
Answer: I don't think you get an $h$-principle for compact complex manifolds.
Example: Given a complex line bundle $L \to M$, it admits a holomorphic structure iff the image of its Chern class in $H^2 (M;\mathcal{O})$ is zero.
Similarly, the group of holomorphic line bundles which are topologically trivial is the cokernel of the homomorphism $H^1 (M; \mathbb{Z}) \to H^1 (M;\mathcal{O})$. Complex tori show that Oka's priniciple fails for compact complex manifolds.
The Gromov-Phillips h-principle for closed manifolds is false as well, immersions are the only special case which applies to closed manifolds I am aware of. All other versions (e.g. submersions, symplectic structures, positively or negatively curved metrics) fail, and each of them fails in a fairly spectacular manner.
There are some exceptions to the rule, but in general I would say that one needs noncompactness to push away all possible obstructions to infinity.


Spin matrices in Dirac equation

Question: Why in every textbook when deriving Dirac's equation the smallest possible matrices ($2 \times 2$) are used?
I wonder why one couldn't use spin 1 matrices ($3 \times 3$) and get relativistic equation for spin 1 particle?
Answer: One can write down equations for spin-one particles but they won't be the Dirac equation because the Dirac equation, by definition, describes spin-1/2 particles (i.e. fermions such as leptons and quarks). The equations for free fields associated with spin-one particles are the Maxwell equations (for photons etc.) and/or Proca equations (for W-bosons or Z-bosons).
Comment: @Luboš Motl "by definition, describes spin-1/2" - could you elaborate? Wherever I see Dirac's equation derivation there is only considered the case of 2x2 matrices which obviously leads to spin-1/2 but what about other cases?
Comment: but i think you would agree that its still an interesting exercise to try to obtain the bulk maxwell equations from such a field equation
Comment: Dear @lurscher, the spin-one equation *is* Maxwell's equation. The work needed to get from one to another is zero. Well, at most, you may change a basis or something like that. John: electron has $j=1/2$ because the eigenvalue of $J_z=J_{12}=\gamma_1\gamma_2/2$ acting on the electron state is $1/2$ times the original state. Photon has $J=1$ because when you act with $J_{12}$ on the photon state moving in the z-direction, you get $1$ times the original state. One-half is something else than one. For example, if people only eat 1/2 of a bread, 1 bread may feed 2 of them, not one.
Answer: Particles in the standard model are in principle massless and acquire mass through interactions via the Lagrangian. This poses a problem if you want to use the 3x3 matrix generators of angular momentum because massless particles have different lie group representations as particles with mass.
The 3x3 generators for particles of spin 1 acts on three states, -1, 0 +1. In the massless case only two states remain.
With fermions and the 2x2 SU(2) matrices  this issue doesn't exist. The two chiral components $\psi_L$ and $\psi_R$ propagate lightlike and the two states of each chiral component correspond with spin up and down where the spin is parallel or anti parallel to the direction of propagation.
Hans
Comment: so long story short if I get you right: when it's spin-1/2 both $m=\pm 1/2$ values are ok for particles wheather or not they has a mass, while for spin-1 particles there's a problem with massless particles $m \neq 0$?

Spin matrices in Dirac equation


Confidence intervals for beta regression

Question: I have used the betareg package in R to fit a regression. My question is: how do I calculate confidence intervals for betaregression in R?
Comment: What do you mean by "confidence interval" in this context? Do you want a CI for some parameter? Do you want a conficence *band* for the model? Do you want *prediction* intervals for some y-hat values? Etc.
Comment: Questions solely about how software works are
[off-topic](http://stats.stackexchange.com/help/on-topic) here, but
you may have a real statistical question buried here.
You may want to edit your question to clarify the underlying
statistical issue. You may find that when you understand
the statistical concepts involved, the software-specific elements are
self-evident or at least easy to get from the documentation.
Answer: The beta likelihood is not a regular exponential family, so constructing interval estimates for such two parameter families is not easily done. I think Zeileis was wise not to implement any de-facto methods for confint. The cited article Ospina suggests that bootstrap interval estimates perform best. The package boot has some methods, but bootstrapping is also easily done "by-hand" in R.
Comment: One more comment about `confint`: This is not for confidence intervals of _fitted values_ but for confidence intervals of _coefficient estimates_. The default method works if there is a `coef` and a `vcov` methods (which is the case for `betareg`) and returns Wald confidence intervals based on the asymptotic normal distribution of the maximum likelihood parameter estimates.
Comment: In essence yes. See http://stats.stackexchange.com/questions/230501/variance-vs-standard-deviation-in-beta-regression/230681#230681 for a few more comments.
Comment: (Not sure about the celebrity thing...anyways:) Of course, the maximum likelihood estimates and their associated confidence intervals are biased in finite samples. As Kosmidis & Firth (2010, EJS) showed, the bias in beta regressions can become quite large, especially for the precision estimates. They have suggested a generic approach for reducing the bias and we have implemented this in `betareg(..., method = "BR")`.
Comment: @AchimZeileis A celebrity sighting on my post! Indeed I assumed the OP was asking about CIs for the parameter estimates. Help me understand something: Wald based CIs using `coef` and `vcov` methods are not necessarily asymptotically correct for MLEs unless the likelihood is a regular exponential family. Take linear mixed models from the `lme4` package, they don't recommend creating inference from the information matrix and coefficients from the fixed effects. They use profile/bootstrap CI methods, is this to improve efficiency or reduce bias?


Quick Question - Hot Reboot - Android

Question: Can anyone please tell me what is the difference between the a normal Android boot vs. a hot reboot!? When I toggle the power options on my tablet to turn it off or reboot it... It says on the bottom "hot reboot"!? I have looked it up online, and nothing has giving me an understatement of the difference. Nothing clearly defines it. That would be great thank you! :)
Comment: To quote [Wikipedia](https://en.m.wikipedia.org/wiki/Reboot_(computing)), *reboots can be either cold (alternatively known as hard) where the power to the system is physically turned off and back on again, causing an initial boot of the machine, or warm (alternatively known as soft) where the system restarts without the need to interrupt the power*.
Answer: A cold boot means start a machine from a state where its power is not supplied, and a cold (hard) reboot means completely shut down power then power up as a normal boot. In a cold boot procedure, the BIOS first starts after the machine gets powered, loading the system's loader before actually starting the operating system.
On the contrary, a hot reboot does not cut the power to a machine, but simply shuts down the running OS and re-load it. No hardware components lose their power during a hot reboot. Only the system works as if it's normally booted.
Answer: There are certain software components that don't need to be reloaded to "restart" Android OS. So the hot restart is when only the needed components are reloaded.
You can see it in action if you use the RootTools Android library(developing on Android Studio) with the following code:
<code>RootTools.restartAndroid();
</code>

Quick Question - Hot Reboot - Android


What is Quirks mode in IE8 Developer toolbar?

Question: I am wondering what is Quirks mode in IE8 Developer toolbar? Why page rendering is different in Quirks mode than in IE8 standard mode?
Answer: Simply speaking, it is for really old webpages to show in the way it always has been on IE.  So if a webpage's HTML doesn't start with a DOCTYPE that indicates Standard Compliance Mode, then IE will show it in Quirks mode.  In such mode, IE uses its own Box Model to render the page elements.
A simple example is: IE's box model adds padding to the inside of the width, so a div occupies the width number of pixels, but Standard Compliance mode add the padding to the width, so a div will occupy width + padding number of pixels.
You can try a div with width 300px and padding 100px and click between the modes in IE Developer's bar to see the difference.
More info at: http://en.m.wikipedia.org/wiki/Quirks_mode
Answer: I think it will be useful : http://www.quirksmode.org/css/quirksmode.html.
Answer: Quirks mode is basically a legacy mode that allows IE to render web pages that were written back in the day where no one adhered to html standards.


Android Pokemon go - General vs miscellaneous notifications?

Question: Does anyone know the difference between general and miscellaneous app notifications on Android? I'm assuming general is like for regular reminders for raids and miscellaneous is like event reminders or something?
Answer: The General category includes items like announcements, reminders, etc.  I practically ignore this category, so I do not recall the complete list; feel free to edit and add to this.
The Miscellaneous category includes items like egg hatches, buddy finding candy, and weekly Adventure Sync rewards.  I do monitor this category since I like to know when an egg hatches.


USB drive malfunction

Question: My Seagate free agent goflex 1TB is not getting recognized in my windows 7 laptop.. It was working till yesterday. It is not showing up in device manager. Is there any way I can reinstall the driver? Or any better way to get it working again?
Answer: Before attempting to solve the problem, you have to determine its root.
There are only four possibilities:

Something is wrong with the computer.
This could be indeed a driver problem, a malfunctioning USB host controller, a bad BIOS setting, etc. The easiest way to troubleshoot this is connecting the device to a different computer.
Something is wrong with the USB cable.
Try a different cable.
Something is wrong with the enclosure.
If the drive isn't under warranty, you can open the enclosure and take out the HDD. Depending on the design, this may be possible without damaging the enclosure.
Something is wrong with the HDD itself.
If none of the above helps, this is the case.

The first three cases are easily fixable. If the HDD itself is failing, you're out of luck. Professional data recovery is required and, sadly, very expensive.
Answer: Along with Dennis's cases there's also the case when you file system might have been corrupted due to unsafe plugging of the drive to the devices.
This can be easily solved by plugging the device to some linux system (a live disk will work as well) and rewriting the file system on the device. If GUI is not accessible you can do this via terminal as well.
Comment: As answers go, this is very generalised. How would you "rewrite the file system" on Linux. Please be more specific.
Comment: Simply format the disk drive.
Comment: Linux shell command? GUI? Which utility is easiest? Care to recommend a LiveCD version? Please remember, this user may never have used Linux or may not have access to a Linux PC.
Comment: @tog sorry for skipping that. User can do this via rhe GUI from the live CD of Ububtu or any other Linux file system. Also format it to NTFS.

USB drive malfunction


I own a domain name. Can people view my personal registered info?

Question: Is my information protected?
Or can someone tell where I live by my domain name?
Why do hosting services offer a protected information service for extra money?
How can I view that information?
Answer: You should not use a registrar that charges extra for private registration. A domain owner shouldn't have have to pay off their registrar to keep their private info off of the internet. That's akin to extortion or blackmail ("pay this extra fee or we're going to give your billing address and contact info to strangers").
It costs the registrar nothing to keep your registration info private, thus many registrars provide this option completely free of charge. So why use shady registrars who charge you money just to not give out your personal info? After all, they're liable to screw you over in other ways as well if their ethical standards are that low.
Answer: If you register a domain name without protection, a quick WHOIS search will yield your name, email, street address, and fax. With protection, it looks like this:
<code>Registrant Name:Whois  Agent
Registrant Organization:Whois Privacy Protection Service, Inc.
Registrant Street1:PMB 368, 14150 NE 20th St - F1
Registrant Street2:
Registrant Street3:
Registrant City:Bellevue
Registrant State/Province:WA
Registrant Postal Code:98007
Registrant Country:US
Registrant Phone:+1.4252740657
Registrant Phone Ext.:
Registrant FAX:+1.4259744730
</code>
I recommend you spend the extra few dollars for protection, however if you are a small business or indivual who has no need for it, then don't purchase it. This is more for people to whom security and privacy is a concern.
Comment: Could you please tell how I can get that WHOIS information ? All I can see is my webhosting data...
Comment: @Ted - http://www.ionfish.org/whois You can type your domain name (no http://) into the box, and it will search for available information on your domain and/or owner.
Answer: Without WHOIS protection, not only people can view your personal data when inspecting your domain, they can GOOGLE your personal data by your name - and they can see not only your address but also all the domains you own. That is because some websites cache whois results as web pages e.g. http://whois.domaintools.com (I'm not sure that's even legal)
But it depends on registry (what is the domain extension) - for example my national registry hides WHOIS information for individuals by default and there is no need to pay extra for that.
Also, if you look around, you may find companies that offer WHOIS protection very cheaply or even without any extra charge.
Finally, I would say that today privacy is needed for security.
Comment: I am using mydiscountdomains.com for domain name registry, and with WHOIS I could only get THEIR info. Should I be concerned that there is still a way to get my personal info ?
Comment: Looks like you are safe. But what is the extension of your domain?


Why can't group 2B metals (Zn, Cd, Hg) form complexes with ligands such as CO, nitrosyl (NO), and olefins but do from complexes with NH3, CN- etc?

Question: Why Group 2B metals (Zn, Cd, Hg) can form complexes with Ammonia ($\ce{NH3}$), Cyanide ($\ce{CN-}$) etc. and not with ligands such as carbonyl ($\ce{CO}$), nitrosyl ($\ce{NO}$), and olefins?
What I think is that M(2B)-$\ce{NH3}$/$\ce{CN-}$ complexes are stable without any pi-bonding whereas $\ce{CO}$/$\ce{NO}$ complexes require pi-bonding for stability.  Backbonding (pi-bonding) is what stabilizes Carbonyl, Nitrosyl and olefin complexes. Group 2B metals (Zn, Cd, Hg) have filled 3d orbital and cannot accept electrons from ligands and do not form stable complexes with aforementioned ligands. Am I correct? Please explain this further if possible.
Now, $\ce{Cu (1)}$, group 1B, also has a filled d-orbital (3d10), but its complexes with Carbonyl do exist such as $\ce{[Cu(CO)n]+}$ where n=1,2,3. Why is it so?
Comment: Welcome to ChemSE! Please find guidance for MathJaX / $\LaTeX$ as follows and reformat your post - [Basics](https://chemistry.stackexchange.com/help/notation) // [MathJaX and mhchem formatting for equations and chemical formulae](https://chemistry.meta.stackexchange.com/questions/86/faq-how-can-i-format-math-chemistry-expressions-on-chemistry-stack-exchange) // [Guidelines on which should be upright / italics](https://chemistry.meta.stackexchange.com/questions/443/which-symbols-are-written-in-roman-upright-font-and-which-are-italicized)
Comment: Also you can refer this information bit on [how to use MathJaX](https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference).
Answer: Zinc actually has been incorporated into a room-temperature carbonyl complex embeeded into a zeolite matrix [1]. Ordinarily, G12 metal centers have their $d$ orbitals too tightly bound to serve as pi donors to the pi-accepting carbon monoxide, but in the zinc-zeolite compound the oxo ligands provide that function and thus enable the zinc to accept carbonyl ligands.
Reference

Guodong Qi, Qiang Wang, Yueying Chu, Jun Xu, Anmin Zheng, Jihu Su, Jiafu Chen, Chao Wang, Weiyu Wang, Pan Gaoa  and Feng Deng, "Room temperature stable zinc carbonyl complex formed in zeolite ZSM-5 and its hydrogenation reactivity: a solid-state NMR study", Chem. Commun., 2015,51, 9177-9180. https://doi.org/10.1039/C5CC02601F
Answer: In addition to Oscar's zinc complex, I want to point out the very first thermally stable cadmium carbonyl complex, $\ce{[Cd(CO)3(C6H3Cl)]4·2H2O}$. It has been synthesized with an overall yield of 35%.
Ref.: Subrata K Dey, Shyamapada Shit, Sankar P Dey, Samiran Mitra, K M Abdul Malik, First Report on Thermally Stable Cadmium Carbonyl Complex Containing an Interesting Chloroaryl Bridge: Isolation and Characterization, Chemistry Letters, Volume 40, Issue 8, 2011, Pages 810–812, DOI: 10.1246/cl.2011.810

FWIW, zinc(II) is also shown to form a series of divinylzinc π-complexes, $\ce{Zn[C(Me)CH2]2}$  and $\ce{Zn[C(H)CMe2]2}$, have been synthesized and isolated as white crystalline solids in 66 and 72% yield, respectively.

Ref.: Unprecedented Alkene Complex of Zinc(II):  Structures and Bonding of Divinylzinc Complexes, Alfred Wooten, Patrick J. Carroll, Aaron G. Maestri, and Patrick J. Walsh, Journal of the American Chemical Society 2006 128 (14), 4624-4631, DOI: 10.1021/ja058700x


Travelling out of France with a receipt for first residence permit

Question: As title explains, I am wondering if it is possible for someone to go out and back in to France with an expired long term visa and a receipt for a first residence permit.
The visa is a scientist visa.
Comment: Are you asking what the rules are or whether you might get away with it in practice? What's your citizenship?
Comment: @Relaxed I was thinking about taking a brief holiday in my home country Tunisia, so if there's a remote chance i'll be denied re-entry which might really interfere with my work then it's not worth the risk.
Answer: This receipt (récépissé) is not a valid document to reenter France. I am not sure what would happen in practice if you go to another Schengen country but, if you leave the Schengen area, you may legally be denied entry when coming back and forced to restart the whole process (visa application, etc.) from scratch from abroad.
Answer: It depends on where you go out... If you go out to a country within Schengen area, then since borders control are pretty random, there is a good probability that you won't have any problem to come back. If this involves getting out of Schengen area and coming back into it, then it will probably be more complex as then the visa will be checked...


GRASS GIS module dialog not starting

Question: my module dialogs are not appearing in GRASS 78 (for 76 it is working) e.g. I want to change the colour of a vectorlayer and click on the properties button, but no module dialog will open.
Comment: To receive help you will need to tell us more (please edit your question for that): which operating system, which GRASS GIS version?
Answer: Under Windows, QGIS 3.10 is not compatible with Grass 7.8.0-2, QGIS only works with Grass 7.6.1. The solution is to use the OSGeo4W installer to downgrade to Grass 7.6.1 (I presume you are on Windows, like me). Runs the OSGeo4W installer again and click the Grass 7.8.0-2, changing it to 7.6.1-1. This will install the older version of Grass.  These breaks in compatibility between QGIS and Grass have happened many times before.
Comment: We are close to the GRASS GIS 7.8.1 release which should help in this regards.

GRASS GIS module dialog not starting


Who was Nachiketa's brother Ashtavakra?

Question: Who was Ashtavakra? I have heard that he was nachiketa's brother and was having great knowledge. What is his story?
Comment: The only Ashtavakra I know of is the Rishi who gave knowledge to Janaka (Ashtavakra Gita)
Comment: @AmitSaxena That's the same Ashtavakra that Parth is referring to.
Answer: I do not know that Ashtavakra is the brother of Nachiketa but the story of Ashtavakra is described in Mahabharat :

The sage Uddalaka had a disciple named Kahoda of subdued passions, and entirely devoted to the service of his preceptor and who had continued his studies long. The Brahmana had served his tutor long, and his preceptor, recognising his service, gave him his own daughter, Sujata, in marriage, as well as a mastery over the Shastras. And she became with child, radiant as fire. And the embryo addressed his father while employed in reading, 'O father, thou hast been reading the whole night, but (of all that) thy reading doth not seem to me correct. Even in my fetal state I have, by thy favour, become versed in the Shastras and the Vedas with their several branches. I say, O father, that what proceeds from thy mouth, is not correct.' Thus insulted in the presence of his disciples, the great sage in anger cursed his child in the womb, saying, 'Because thou speakest thus even while in the womb, therefore thou shalt be crooked in eight parts of the body.' The child was accordingly born crooked, and the great sage was ever after known by the name of Ashtavakra.

Who was Nachiketa's brother Ashtavakra?


How to consider capital assets in DCF analysis?

Question: I'm calculating an enterprise value with the DCF analysis.
In DCF I consider revenues - costs, and I also discount reinvestments. These reinvestments are to get more capital. How can I take into account this capital?
Answer: DCF = 'discounted cash flow'.  so, you build a model that has (cash) revenues minus (cash) expenses.  It doesn't matter if the expenses (outflows) are for supplies, labor, or reinvestment of capital. In the end you get a net cash flow (including all cash costs), and you project that forward.  Then discount it back to today.
Comment: Yes you are, in the final year.  You are going to need to make some assumption about what the company would be worth, in aggregate, in some terminal year - say year 20.  But your intuition is right.   if a company had chunky outlays that don't depreciate (a building or land might fit the bill) you might just leave that out of cashflow and final valuation. But, for example, machinery with a 10 year life or office furniture with a 5 year life gets counted, because you expect to @"sell" the business in 20 years with that stuff to get full value.
Comment: What do you mean by project forward ?
Comment: You make an estimate for this year, then for next, then the following, etc., until you have enough.  Then you discount those cash flows to today and add them - hence Discounted Cash Flow analysis (DCF).
Comment: Yes, I know the steps to calculate the cash flow, buy I wonder what is happening with that re-investments you talk about. For example, if at some year the company invest in a building, the cash flow is going to be lower that year. More expensive the building, more negative that cash flow, and sow the EV lower and lower. And we are never taking into account that the company owns a building.


Unable to install auto-bed levelling sensor into my Anet A8

Question: I've been trying to install an inductive sensor for auto-bed levelling into my Anet A8 and I'm having a few issues.
I have been using the wiring diagram provided by Solid Ground Electronics in one of his videos (Cheap 3D Printer - Anet A8: Upgrades, Experience & Thoughts), which I decided to follow as it still uses the Z limit switch, in case the inductive sensor fails to work.
The sensor seems to work when I power the printer on, the red LED is constantly on and when it comes into contact with metal, the LED turns brighter (as shown in the photos).
However, when I set it to auto-home, the Z axis does not move down like it usually does (until it hits the switch), but it moves up a bit. Although when I auto-homed the printer with a piece of metal under the sensor, the Z axis moved down, like it should do. So the sensor is acting in an opposite way to what it needs to.
I believe that it's been wired up correctly with a 10k ohm resistor connected to the base of the transistor and the signal wire of the probe. However the NPN transistor shown in the diagram is '2N4401' and the one I used is 'PN2222A', but I believe this should have no difference in the function of the transistor (only the voltages it can handle).
I initially thought that as the NPN transistor is slightly different, perhaps the polarity of emitter and collector is incorrect, so I switched them around but the problem still occurs.
I would thoroughly appreciate it if anyone can help!
Answer: The sensor is working correctly, but the signal is inverted.
Take the obvious solution: invert the endstop from being normally open to normally closed or vice-versa in your firmware.
If you still want to use your existing limit switch in parallel with the sensor (as shown in the video), you will need to switch that one over as well (usually limit switches have 3 contact points, one common, one NC, one NO, so you'd need to move the wire from the NC contact to NO or vice-versa).