Are there any medicinal uses for beer?

Question: Are there any common medicinal uses for beer? I'm thinking along the lines of how liquor can be used as an antiseptic and less of how red wine can improve your heart health.
Comment: I think this question would be better phrased "alternative uses" rather than "homeopathic uses." Homeopathy is specifically a system of alternative medicine developed in the 18th century—and widely considered a pseudoscience.
Comment: I changed it to say medicinal instead of homeopathic.
Comment: This question appears to be off-topic because it is about medical advice.
Comment: Voted to close with reason "too broad". There are multiple answers to this question, all of which are equally valid.
Comment: So, are questions about pairing off-topic because it's "about food?" This is about medicinal advice, but also about beer. And why is this too broad? The answer is _"Yes, there are medicinal uses[, and here are some examples.]"_
Comment: I would use caution referring to a question on Stack for the medicinal properties of beer. While some journalism will tout health benefits of drinking alcohol, it can often be for page views, and may not always be based on sound science. For this, people should rely on Google Scholar, and scientific source papers.
Answer: Just like wine, absolutely! I'm not a doctor and I am not giving medical advice; I am not liable whatsoever for your drunken antics.
With that said, in addition to kidney benefits:

Beer contains high amounts of silicon, which makes bones stronger
In moderation, it has been shown to lower the risk of cardiovascular problems. However, when abused, cardiovascular problems spike instead. It helps to raise levels of "good cholesterol" which helps to keep arteries free of blockages.
It may help out your brain, keeping Alzheimer's disease at bay.
It is high in antioxidants and helps reduce your risk of cancer.
It is high in B vitamins, namely B6 and B12
Moderate amounts of any alcohol, beer included, may help decrease your risk of stroke by reducing the chance of blood clotting in the cardiovascular system.
I highly doubt this one, but apparently, studies have shown a reduced risk of diabetes among men who drink occasionally.
Studies have shown that it has been linked to lower blood pressure.
It contain fiber! Beta-glucans in particular, which are a soluble type of fiber.
Like sauerkraut, pickles, kimchi, yogurt, miso, and kombucha, beer is a fermented food, so many of the benefits of fermented foods such as aiding in digestion may apply to beer as well.

Yahoo Beauty
4 Health Benefits Of Beer Drinking: Antioxidants, B-Vitamin, And Protein Are There... But Don't Overdo It
Answer: Beer apparently not only lowers the risk of kidney stones, but also helps dissolve and pass existing kidney stones (additionally by dilating the ureters—the tubes connecting the kidneys to the bladder).

Beer consumption was inversely associated with risk of kidney stones; each bottle of beer consumed per day was estimated to reduce risk by 40% [...]

Hirvonen, T. et al. Nutrient Intake and Use of Beverages and the Risk of Kidney Stones among Male Smokers. 1999. [PDF]
Answer: There are a number of uses I have heard of people using beer for.  I will add a personal experience below as well.

I have heard of people washing their hair with it, believing it helps promote healthy hair and scalp.
Heavy, high starch beers, have long been used as a food source for fasting monks, sort of a liquid bread.
Beer is commonly used for cooking certain things because the alcohol (as with wine) helps bring out certain flavors.

Additionally I want to mention something I use it for.  This works for me because of very specific reasons and I am not recommending that anyone else try it.  However, I get asthma frequently following upper respiratory illnesses (I have since I was a teenager).  I have a couple of alternative medical strategies for dealing with this depending on what is available.  Note, if you have asthma, don't take medical advice from me: asthma can be life threatening.  Work with a doctor.   However, among other things, I find that drinking a number of drinks of beer or wine for two nights in a row will cause the asthma to clear up until I get sick again.  This naturally works best when I am not otherwise consuming alcohol, but it allows me to be mostly medication free regarding my asthma (doing this two to three times a year).  Again this has a bunch of risks, so I am mentioning it just for informational purposes.  In general anything medical deserves a great deal of respect because what can cure can kill.
Also some kinds of traditional beer have very specific health benefits.  In Indonesia, "tape hitam" (black rice beer, consumed with the lees as a sort of soup) is generally understood to reduce blood cholesterol.  As it turns out the helper cultures used are extremely close (and sometimes the same) as those which produce lovostatin.  In fact lovostatin was originally found in Chinese fermented rice products.
Answer: Not to be snarky, but there are as many uses for beer as there are people who use it.  I'm here because I use it, specifically high-hop/low alcohol (IPAs) as an alternate for sleep medication, since I don't want to be taking the same ones all the time.  (And though it's impossible to separate the sleep benefits, I think it helps with anxiety, not just at consumption time, too).
Beer, particularly the hoppy stuff, is known to raise blood estrogen levels. http://goo.gl/qctfH3.  Frankly, though I'm no expert by any stretch, I'd say a (that's one) bitter IPA at bedtime is the perfect prescription for menopausal insomniacs.
There's so much to read about beer and hormones.  To each his (her) well-read own.
Answer: Beer is alcohol no matter what people may think. Alcohol is a dangerous drug that happens to be legal right now.
There are no proven benefits to drinking, bathing, washing hair or dishes in beer.
Beer has a reputation of being safer than whiskey, but the opposite is true.
Both can kill you.
Comment: This is factually, scientifically incorrect.  There are many well respected studies that have shown there are positive health effects from alcohol consumption.

Are there any medicinal uses for beer?


Are black holes hot?

Question: If no light can escape black holes, in my mind they would act as a greenhouse, collecting radiation from the stars or CMB or anything. Or is all this energy just absorbed by the black hole?
Answer: The energy of any infalling mass is absorbed by the black hole.  Classically, the temperature of a black hole is absolute zero, since it is a perfect absorber.
If you include quantum mechanical effects, as Stephen Hawking did, you can show that black hole horizons will emit radiation in such a way that is consistent with the horizon being a hot body with a given temperature which is proportional to $\frac{1}{M}$.  So, small black holes are hotter than large ones.
Answer: Simply because the Second Law of Thermodynamics states:
<code>Entropy > 0  (always)
</code>
(think of taking a basketball and squeezing it into a golf ball)
so that the density gets larger as the mass gets smaller.
therefore,
Entropy will always increase in a black hole, gaining Entropy [heat] as it gets smaller.The stars reaching critical mass(limiting mass) ~ 1.4 solar suns and the star either becomes:
A Black Hole  =  [ M > 1.4  Solar suns] (very active)
Dead Neutron Star = [ M < 1.4 Solar suns] (not active)
There can be no loss in bits of information (Entropy) based on a congruent partition function as beta gets bigger with more "time" so-to-speak. also see Law of Conservation. So if you treat Entropy as Heat then yes it is very very HOTTTT!!!

Are black holes hot?


Why are visualforce pages served from a different domain?

Question: There are a number of reasons why this is frustrating. The biggest for me is that embedded visualforce pages can't use JavaScript to access the parent frame.
There doesn't seem to be any benefit serving visualforce from a separate domain, is it a security decision? I am sure there are still plenty of ways to use the platform for something evil.
I am not looking for a solution to a specific problem just a better understanding of why visualforce was implemented in this way.
Comment: If it is of interest, I was able access an element from the parent page okay using javascript - eg alert(jQuery('#acc2_ileinner', window.parent.document).html()); displays the company name from an embedded vf page on an Account Detail page.
Answer: While I've never seen this information in an official Salesforce document, Doug Chasman answered this on the developerforce boards back in 2009:

The move to separate domains has one very specific purpose: leverage the browser security model (same domain policy) to protect our customers and the salesforce.com service from cross site scripting and cross site request forgery attacks.
Moving to the serving pages from separate domains is a critical component of our ongoing commitment to insure the highest level of security and availability for everyone.
In the world where everything is served from the same domain any custom page that you visit had full access to any other page in your org and also any page served from salesforce.com itself. This included potentially malicious code that was installed as part of a force.com package.

The original thread can be found at:
http://boards.developerforce.com/t5/Visualforce-Development/Please-explain-cs2-salesforce-com-vs-c-cs2-salesforce-com/td-p/110601
Comment: I verbally heard the same comments for a senior product management director as well.


Is there a product(s) to stream recorded videos, all at same given point in time

Question: I've been searching for a hardware or software product that can stream up at least 17 time stamped video recordings, all at the same point in time.  If I had 17 separate recordings of 17 different flight simulations for example, I would like the ability to fast forward/rewind to a given point in time and have these channels all stream the recordings from that point in time.  Any products I've come across so far can only work with a small number of channels.
Answer: I did find a product called Calypso by Haivision
http://www.haivision.com/products/record-stream/calypso
I've spoken with their tech support and they claim it can do the time sync functionality I desire.
I recognize this product will be out of the price range for some looking for the same sort of thing.  The multiscreener app screaming drills mentions above looks promising, as does some other software products that website mentions.  I just do not have the time to check them out.
Answer: Adobe Premiere and Final Cut Pro X can. Final Cut is particularly good at this. Look up multicam FCPX for some demos.
Comment: I see the multicam feature is able to sync multiple imported streams for editing in these products, but what about exporting?  I've started researching both Adobe Premiere and Final Cut Pro and haven't found anything yet that says either product will stream multiple sources to multiple destinations, all sources starting at a given point in time.
Comment: You're right about that, its great for syncing and viewing, but most editors assume you would want to watch one stream at a time. Can you tell me more what you're trying to achieve? How would you like to watch the video? What player would you use (QuickTime, VLC). What's the max resolution you'd want?
Comment: I would like to be able to play back training sessions that took place on multiple computers simultaneously.  I am flexible about what video format the recordings would be in.  The recordings would all be time synced.  The idea is that I could jump to x minutes after start and have each of these recordings streamed to a separate display for review at the same point in time.  I'd then proceed to fast forward/rewind, and have all the streams jump to that time.  I'd like to view each of the recordings on a separate display.  I am flexible about what player to use.  I'd prefer full HD res
Comment: Gotcha, this a really interesting problem. I'm sure there is a good very expensive broadcast solution but I'd like to research and see if I can figure this out. Now that you've got me thinking I can think of a dozen applications for this.
Comment: I found this multiscreener app: http://www.ucl.ac.uk/slade/know/3447. This looks promising. I would prep the videos by using the multicam FCPX function to synchronize and create several "tracks" with the exact same start and end time. It would be just as simple with Premiere. Ill have to test it out when I get home.


Set an alias on Bourne shell

Question: I am using a scrtipt with instruction 'SH -c command', where command is an alias from bash, this alias can not be interpreted into Bourne shell. ¿Do you have any idea for set this alias into Bourne shell and getting that it works in the new shell? Thanks everyone !
Comment: The new shell does not have an alias defined in the current shell, otherwise aliases would make things extremely confusing.  Aliases are meant for interactive use not for scripting.  Make a procedure instead of an alias, call it to produce the desired command (without aliases) and only then pass to a second shell.
Comment: As a minor thing, commands in Unix-like systems are usually case-sensitive, so you're likely not running `SH`, but `sh`.
Answer: I would be surprised if it's a real Bourne shell you have on Linux. Though the Bourne shell has now been ported to Linux, it's generally not installed or even packaged by default.
You'd only install it for archaeology purposes.
Maybe you're confusing sh (which nowadays refers to an interpreter or another of the POSIX sh language) with the Bourne shell (an ancient shell that also used to be called sh (and from which modern shs descend, but also differ)).
The Bourne shell didn't have aliases. Modern sh do.
Aliases however are local to the current shell. If you execute a new shell (whether it's bash, sh, csh, zsh...), that new shell will not inherit those aliases.
You'd need to redefine those aliases in the new shell.
bash has a way to dump the definition of one of its alias in a syntax that is compatible with that of sh. So you could do:
alias foo='echo foo' # alias defined in bash
foo_definition=$(alias foo)
sh -c "$foo_definition
foo"

Or simply:
sh -c "$(alias foo)
foo"

Now, there's a catch in that it doesn't work in all implementations of sh. First you'll noticed we didn't do:
sh -c "$(alias foo);foo"

Which would have worked in no sh implementation.
That's because aliases are really like some form of macro expansion. Because alias expansion is done prior to parsing, in alias foo='echo foo'; foo, by the time the alias command is run, the line has already been parsed.
Putting the alias definition on one line and its usage on the next works around that for some shells, but some others (like yash or zsh) parse the whole sh -c code as a whole, so alias expansion won't work there.
However because aliases are more or less macros, that is the substitution of some text with some other text, you might as well do the substitution by hand.
You can get the value of an alias by doing:
eval "$(alias foo | sed '1s/ /_/')"

Which would store the definition of the foo alias into the $alias_foo variable.
Then, you can do:
sh -c "$alias_foo"

To have the value of the foo alias passed as shell code to sh.
You may prefer using functions than aliases for that purpose. Like for aliases, functions are local to the current shell. Some shells like rc or bash can export functions to other invocations of the same interpreter.
foo() { echo foo; }
export -f foo
sh -c foo

Would only work on systems where sh is implemented with bash (mostly only Apple OS/X and some Linux-based systems).
A more portable approach would be like for aliases to dump the definition of the function into the code passed to sh -c:
sh -c "$(typeset -f foo); foo"

This time, no problem with time-of-expansion, time-of-parsing as functions as opposed to aliases as functions are real structures of the language.
However, you need to make sure the definition of the function contains code that is valid sh syntax and doesn't use any bash extension.
Comment: I definitely, I referred to the modern sh shell, your response has give me many posible solutions. Thanks!
Answer: Speaking about Bash in particular-
That happens because when Bash is given a command using -c, it starts in non-interactive mode, and in particular, alias expansion is disabled.
In general, you shouldn't use aliases in scripts, but instead you should use shell functions or other scripts. If you really want to use aliases, try bash -ic <alias_command>. The -i will start the shell in interactive mode, read your configuration files such as /.bashrc, then alias expansion will be enabled.
Note- Aliases that Bash sees will come from the configuration files, not from the parent shell.
Comment: Alias expansion is done in `sh -c`. It's only in `bash` (when not called as `sh`) that aliases are not expanded when the shell is not interactive.
Comment: ` -ic ` will not cause the aliases to be magically passed to the new ``. However, with some shells, that will cause the `~/.bashrc`/`.zshrc` to be sourced and then the alias definitions in there being loaded.
Comment: Thanks, I edited to talk about `bash` only.

Set an alias on Bourne shell


Why doesn't my TRUST GXT 560 Nomad controller work on my xbox 360?

Question: I have found a good controller, it is a controller from Trust and it is called Trust GXT Nomad. It works when I plug it into my computer, but when I plug it into my Xbox 360 it does not work, even though it has xInput. Any ideas why it isn't working when it should be? Thanks!
Answer: XInput and Xbox 360 Compatibility are two different things.
Any controller can be made XInput compatible on Windows either in Software (eg. the DS4Windows program for an XInput DualShock 4) or Hardware (flashing a different firmware or a physical switch), but they need to be specifically tested on an Xbox 360 due to the console checking for the device information and refusing to connect if it doesn't matches.
The Trust page for the GXT Nomad never mentions Xbox 360 compatibility because it was not designed and/or tested for it:


Apply Transformation Matrix To Circle

Question: I'm building a 2D level editor for my game, and you can deal with two types of geometries which are circles and polygons.
I've got it working so I can apply any transformation matrix to the polygons, and the vertices will transform correctly. I'm now thinking about how to apply the transformation matrix to a circle.
My circle is defined by a center position and a radius. The problem is that because the circle is only defined by one point, a matrix scale operation will result in the circle just being translated, not being scaled.
I'm not sure if this would work, but my solution was going to be when the circle was transformed, place two temporary vertices on the edge of the circle on opposite sides, apply the transformations to those vertices, and then recreate the position (midpoint between the two vertices) and radius (distance between the two vertices divided by 2).
Is there a better / easier way to transform a circle using transformation matrices?
Answer: I would take two points: the center of the circle and any point on the edge. That way, you already have the new center, and you just have to calculate the distance to get the radius. It's like you proposed, but slightly simpler.

Apply Transformation Matrix To Circle


How to get all videos uploaded by a specific user via YouTube API

Question: This is a simple question. We need to get all the videos uploaded to our channel in our Android application using YouTube API. According to the YouTube API v2.0 documentation this is a really easy case - https://developers.google.com/youtube/2.0/developers_guide_protocol_video_feeds#User_Uploaded_Videos.
They say that:

To ensure that the API response contains the most up-to-date
  information available for the user's videos, do not use any parameters
  other than start-index and max-results in your request. Requests using
  other parameters, such as orderby, will return cached results.

Great! According to the above doc the URL is https://gdata.youtube.com/feeds/api/users/itcuties/uploads, but the returned result doesn't contain all of our videos. What's going on?
The question is, how to get all the videos uploaded by a given user using YouTube API?
Answer: Ok, case solved - YouTube API - Get All Videos From User limits? :)
We need to add max-results paramter - https://gdata.youtube.com/feeds/api/users/itcuties/uploads?max-results=50
Back to coding! Have a nice day!


Do we have binary dividers cicuit on cisc computer?

Question: Just like we have binary multipler circuit in cisc computer so do we have binary divider circuit in cisc computer? Or it is just like we use algothrims instead of having a real divider circuit? (Just like risc don't have multiplier circuit so it use adders circuit instead of multiplier circuit).
Comment: Some RISC devices do have a hardware multiplier. ["· Advanced RISC Architecture — \[...\] — On-chip 2-cycle Multiplier"](http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-42735-8-bit-AVR-Microcontroller-ATmega328-328P_Summary.pdf)
Comment: Wait. A copy of your own question that you accepted an answer to? That's basically an insult to me spending time on your question. How very rude of you, alphabet.
Comment: Yeah i am because my post is being put on hold i just help you get more reputation and it help me a parts not all
Comment: @AlphaBetA you've asked a question again that you marked as "I've gotten an answer to this", and I spent time on that. Obviously the message you're transporting is that our time is worth nothing to you. And believe me, once you've got a couple hundred points of reputation (which happens really fast if you, you know, ask good questions instead of such that get closed!! Or at least, incorporate the feedback you've gotten), you really don't care about the one or two additional upvotes. So, please, don't be rude.
Comment: Ok i know but everyone put my post on hold while i edit it again
Answer: You're confusing things:
CISC or RISC says something about the instruction set.
Nothing about how instructions are implemented. You can have a RISC  with barrel shifters, hardware single-clock floating point multipliers and dividers, and you can have a CISC system that implements rotational shift under the hood in multiple single-bit-shifts with a carry register, and can't do any floating point in hardware, but does all floating point in slow fixed-point microcode.
CISC and RISC are unrelated to the question of how (and how fast) things work!
Generally, hardware dividers are rare:

because division is surprisingly seldom useful and
because a hardware divider is humongous to implement. I'll invite you to look at the "small" images in this answer of mine about why division is slower than multiplication in hardware.
Comment: I was just about to comment on the instruction set lol. Thank you for saving me the trouble ;)
Comment: @KingDuken this started as a comment. Then it got so long that I ctrl-c/ctrl-v'ed it into an answer.
Comment: I was about to provide an example with MIPS since that instruction set is for x86 architectures. From what I remember, MUL and DIV were pseudo instructions.
Answer: RISC versus CISC has nothing to do with which raw machine capabilities are included, like whether there is a multiplier, divider, barrel shifter, etc.  A hardware divider is a particulary heavyweight computational block to implement, so fewer processors have them than the more simple multipliers and even simpler adders.
The distinction is more about addressing modes, and what parts of the processor data can be moved between during individual instructions.  This distinction was always somewhat blurry, and of course with marketing involved, it got even blurrier.  For a while, everything was labeled RISC because the marketers thought it sounded more cool and modern.  Neither is true, but some of that has left the impression that RISC is somehow more advanced.  That's not true either.
In my opinion, the drive towards RISC or CISC had more to do with the relative speed of main memory compared to the combinatorial logic to implement instruction decoding and data manipulation.  Consider that main memory and logic gates are implemented with different technologies.  It should be no surprise that the relative speed of each therefore changes as different technologies advance and new ones emerge.
Back when main memory was core and logic was TTL chips, main memory was relatively slower than it generally is today.  It therefore made sense to highly encode instructions, then perform lots of logic operations as a result of each, since you'd be waiting around a while for the next instruction anyway.  When main memory is relatively faster, then you can fetch instructions more often, or put another way, you have fewer gate delays to do anything with a instruction before you need to process the next one without stalling the pipeline.
Back in the 1980s when core memory as main memory was being phased out in favor of dynamic RAMs, various new machine architectures emerged based on the "RISC" philosophy.  This was over-hyped to make RISC sound like some breakthrough, as apposed to the logical evolution of faster main memory relative to gates.  The relative speeds of memory and logic continue to waffle back and forth, so there are machines with tradeoffs all along the CISC/RISC spectrum.
Actually, parts of common computers from the 1960s and 1970s were way off at the RISC end of the spectrum, because microcode is in some ways the ultimate RISC architecture.  CISC machines of the time had so many logic delays available to them per main memory instruction fetch that the complicated instructions were actually performed by a fast internal RISC machine running from a small (and much more expensive) gate-like memory.  These micro-instructions were typically very wide, with individual bits directly controlling buffer enables controlling the source of data onto internal busses, the ALU functions, and the like.
As a result of all this, CISC instruction sets generally have lots of possible addressing modes for the sources and destinations of operands.  RISC instruction sets are simpler ("reduced") by generally performing operations only between a limited set of special hardware registers.  The source values have to be moved into the registers from memory and the results written back to memory (when these are required) by separate instructions from those performing the computations.
However, back to your question, none of this says whether a machine has native divide hardware, or whether divides must be done in software.
Comment: That what i ask for : do we have hardware that can divide in cisc instead of using software like risc (the complex is in software not hardware)


Cellular signal handoff

Question: In a cellular network like T-Mobile, Sprint, etc. if one sector of a tri-sector tower is maxed out and can't accept new calls, will a new call request normally served in that sector be handed off to another sector (or another tower/sector) with the next best received signal strength? Or will the call be blocked?
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
Answer: It depends on user location. If user moves in the central location of utilized sector call will dropped till free channel receive. If user moves at border of covered area by utilized sector then call handover. Nowadays, calls are matured by using roaming networks like other cellular operator as UE are very smart.
Answer: To be honest, a lot of this depends on the configuration adopted by each carrier.
 Having said that, most carriers will try to hand the call off to another tower or another contracted carrier. Dropped calls are something to be avoided.

Cellular signal handoff


Account and Contact Query

Question: In an update trigger, how can I query all contacts related to an account where the record type of the account should be 'AnyString' and Shipping Address is being updated?
Comment: Please post the code you've tried already and where exactly you're experiencing problems.
Comment: after Update trigger on Contact? or Account?
Answer: In your trigger,:

Identify when Account records have had the address updated and store the IDs
At the end of the trigger use the ID's from #1 and query the contacts where the AccountID IN the IDs from #1.
Answer: Some rough code to get you started. First you need to find the list of account IDs where the address has been changed, then you need to query for the contacts after. You can do this by querying accounts and getting the children to save you having to map them out manually.
trigger Account_BeforeUpdate(before update)
{
  set<id> accountIds = new set<id>();

  for(Account a: trigger.new)
  {
    if(a.ShippingAddress != trigger.oldMap.get(a.Id).ShippingAddress)
      accountIds.add(a.Id);
  }

  for(Account a : [select Id, (select Id, Name from Contacts)
      where Id in : accountIds and RecordType.DeveloperName = 'AnyString'])
  {
    // do stuff with the accounts & contacts
  }
}

Note that when working with record types it is important to use the DeveloperName field as the label of the record type could be changed at any time by an administrator. The DeveloperName is the equivalent of the API name on an SObject or field, i.e. it can't be changed as easily as the label can, meaning your code is less likely to be broken later on.

Account and Contact Query


Linux icon appearing in rEFind even after uninstalling Linux

Question: I installed Ubuntu 12.04 on my mac.and I uninstalled it and but after that when I boot up using rEFind. it shows me an Linux icon saying that boot Linux from whole disk space.how can I get rid of it?.
Answer: There are several ways to do what you want:

In refind.conf, uncomment the scanfor line and ensure that it does not include the hdbios option. This will also have the effect of removing any other BIOS-mode boot options from the menu (at least for your internal disk), so if you're dual-booting Windows, this option may be undesirable.
In refind.conf, use the dont_scan_volumes option, and specify any unique subset of the description you want to remove, such as dont_scan_volumes "whole disk", assuming no other entry you care about includes the string "whole disk".
Using a Linux emergency disk, wipe GRUB from the MBR of the hard disk by doing something like sudo dd if=/dev/zero of=/dev/sda bs=440 count=1. This command is potentially quite dangerous! If you get any of the options wrong, you could seriously damage your partition table or even permanently destroy data on your hard disk. This command should take a fraction of a second to execute. Also, you must NOT issue the equivalent of this command in OS X, since OS X's version of dd doesn't let you specify partial-sector block sizes (bs=440).

If you opt to edit refind.conf, you must locate it. If your rEFInd installation is an old one or if you used the option to install it to your OS X root (/) partition, it will be /EFI/refind/refind.conf. If your rEFInd installation is newer, it's more likely to be in that directory on your ESP, which you'll need to mount:
mkdir /Volumes/ESP
sudo mount -t msdos /dev/disk0s1 /Volumes/ESP

refind.conf will then probably be at /Volumes/ESP/EFI/refind/refind.conf.


How to run two scripts at the same time

Question: In line x in script A, I want to start running script B, which takes 10 seconds. However, I do not want line x+1 to be executed 10 seconds after line x. Is there a way to fix this?
Script B is simply an independent series of command sent to another external device. Script A is used to monitor that device. Script B does not have any return, and code after line x in script A does not rely on script B.
Overall, I want to trigger the start of Script B and let it run independent of Script A. While script A is kept running continuously.

Thanks to the comment, I found subprocess.Popen() can do the work.
Actually, Script B can be simplified into one single function (Function B). In this case, shall I create one Python script as Script B that only calls Function B, and use subprocess.Popen() to call Script B in Script A?
Or, is there a better way to call Function B, rather than Script B, in a similar fashion as in subprocess.Popen()?
I am trying to call Function B directly because my task is very time-dependent, and half a second of delay may be significant. I have measured the delay from the line x-1 in Script A to line 1 in Script B, if I call Script B in Script A. The delay is ~450 ms. I suspect the delay is from the time for the interpreter to compile Script B and execute it, even though Script B is one or two lines long.

Thank you very much!
Comment: Possibly a duplicate of:  https://stackoverflow.com/questions/636561/how-can-i-run-an-external-command-asynchronously-from-python
Answer:
How to run two scripts at the same time:

Use the GNU parallel ( sudo apt install parallel if not already installed on your system )
Alan@Enigma:~$ parallel python ::: TheScript_A TheScript_B [ TheScript_C [ ... ]]

This way is way cheaper, than trying to orchestrate process-spawns from inside the first python session. It is possible, yet the processing costs and latency side-effects and software engineering costs are way higher, than using the smart O/S services present right for this simple problem-definition.
Reading man parallel you get all the smart bash-scripting options to add for flexible, parametrised process-options, as one may need and wish
...
total_jobs()         number of jobs in total
slot()               slot number of job
seq()                sequence number of job
...

How to run two scripts at the same time


Show that the one point compactification of $\mathbb{Q}$ is not Hausdorff

Question: https://en.wikipedia.org/wiki/Alexandroff_extension
Definition: one point compactification

Let $X$ be any topological space, and let   $ \infty$  be any object
  which is not already an element of $X$. Put $ X^{*}=X\cup \{\infty
 \}$, and topologize $X^*    $ by taking as open sets all the open
  subsets $U$ of $X$ together with all subsets $V$ which contain $\infty
 $  and such that $X\setminus V$ is closed and compact

Show that the one point compactification of $\mathbb{Q}$ which is $\mathbb{Q}^*$ is Not Hausdorff.
What to do? What...
My Attempt:
Suppose to the contrary $\mathbb{Q}^*$ is Hausdorff, then we take two points $x$, $\infty \in \mathbb{Q}^*$, $x \neq \infty$, and produce disjoint open sets $U,V$ such that $x \in U$ and $\infty \in V$
By definition, we know that $\mathbb{Q} \backslash V$ is a closed and compact space such that $x \in U \subseteq \mathbb{Q} \backslash V$
We wish to produce a contradiction such that $\mathbb{Q} \backslash V$ is not closed, or not compact. But we know that $\mathbb{Q} \backslash V$ has to be closed since $V$ is open, therefore we need to show $\mathbb{Q} \backslash V$ is not compact.
Let $\mathcal{U}$ be an open cover of $\mathbb{Q} \backslash V$. Since  $\mathbb{Q} \backslash V$ is claimed to be compact, then $\mathcal{U}$ has a finite subcover $\{U_i|i \in F\}$, $F$ is finite in  $\mathbb{Q} \backslash V$. Then for all $x \in \mathbb{Q}\backslash V$, $\exists i \in F$ s.t. $x \in U_i$ (...Ugh everything seems fine...)
Can someone provide me with some help as to how to go on with this proof? Thanks a bunch.
Comment: Related to http://math.stackexchange.com/questions/231509/what-do-compact-sets-look-like-in-the-rationals
Comment: More generally, one can show that $X^*$ is Hausdorff iff $X$ is Hausdorff and locally compact.
Answer: Given your open sets $U$ and $V$ in $\Bbb Q^*$, you can continue the argument as follows.
$U$ is an ordinary open nbhd of $x$ in $\Bbb Q$, so it contains an open nbhd of $x$ of the form $(a,b)\cap\Bbb Q$ for some irrational $a,b\in\Bbb R$. Let $W=(a,b)\cap\Bbb Q$; clearly $W\cap V=\varnothing$, so in particular $\infty\notin\operatorname{cl}_{\Bbb Q^*}W$. Thus,
$$\operatorname{cl}_{\Bbb Q^*}W=\operatorname{cl}_{\Bbb Q}W=[a,b]\cap\Bbb Q=W\;.$$
But this is clearly impossible, since $W$ is not compact.
If you want an explicit example of an open cover of $W$ with no finite subcover, let $\langle a_n:n\in\Bbb N\rangle$ and $\langle b_n:n\in\Bbb N\rangle$ be sequences in $(a,b)$ such that

$\langle a_n:n\in\Bbb N\rangle$ is strictly decreasing and converges to $a$,
$\langle b_n:n\in\Bbb N\rangle$ is strictly increasing and converges to $b$, and
$a_0<b_0$.

Let $U_n=(a_n,b_n)\cap\Bbb Q$ for $n\in\Bbb N$; then $\{U_n:n\in\Bbb N\}$ is the desired cover.
Comment: @John: $a$ and $b$ are irrational, so $[a,b]\cap\Bbb Q=(a,b)\cap\Bbb Q$. \\ I mean that $W$ is not compact. I even exhibited an open cover with no finite subcover.
Comment: Hi, how do you reach the conclusion that: $\operatorname{cl}_{\Bbb Q^*}W=\operatorname{cl}_{\Bbb Q}W=[a,b]\cap\Bbb Q=W\;.$? I understand why  $\operatorname{cl}_{\Bbb Q^*}W=\operatorname{cl}_{\Bbb Q}W=[a,b]\cap\Bbb Q$, but then how does that equal to $W$? And what do you mean by $W$ is not compact? Do you just mean that we defined $W = (a,b) \cap \Bbb{Q}$ but later reached the conclusion $W = [a,b] \cap \Bbb{Q}$...do you mean the latter $ [a,b] \cap \Bbb{Q}$ is compact? How? Thanks for ur help
Comment: I agree, I just wish to understand your top proof. So we let $W  = (a,b) \cap \mathbb{Q}$ which is open and not compact, then we found that $\text{cl}_\mathbb{Q}^* W = W$, which implies it is closed and compact... so we reach a contradiction. I think what I am not getting is why is $(a,b) \cap \mathbb{Q}$ not compact in $\mathbb{Q}^*$, and why if we show that $\text{cl}_\mathbb{Q}^* W = W$ is closed, then it is compact. After all we are not working in $\mathbb{R}$, so the intuition about closed and bounded = compact doesn't hold.
Comment: @John: Every closed subset of a compact space is compact. Since $W$ is closed in $\Bbb Q^*$, it must be compact. But in fact it's just $(a,b)\cap\Bbb Q$ with its usual topology, which is not compact. This contradiction shows that $x$ and $\infty$ cannot in fact be separated by disjoint open sets.
Answer: Let $C$ be a compact subset of $\mathbb Q$. Then because the inclusion map $\mathbb Q\to\mathbb R$ is continuous it follows then $C$ is a compact subset of $\mathbb R$, so it is bounded and has all its limit points.
Let $a,b\in\mathbb R$ with $a<b$ such that $(a,b)\cap\mathbb Q\subseteq C$, then the closure of $C$ in $\mathbb R$ includes $(a,b)$. So by contradiction $C$ has empty interior. Therefore every open set containing $\infty$ is dense.
Finally let $x\in \mathbb Q$ and let $U,V$ be open sets with $x\in U$ and $\infty\in V$, then $V$ is dense so $U\cap V\ne\emptyset$.


Punctuation after "Yes"

Question: A common construction is "Yes, that's right." Is that acceptable, or should a semicolon (or period) replace the comma? If acceptable, how can it be justified grammatically?
Comment: Same thing with "No, you're not!" I like that you opened up constructions (that we take for granted) vs. actual grammatical rules.
Answer: It is correct to say, "Yes, that's right."
This is a particle, which means that you don't inflect it and it's grammatically independent from the rest of the sentence. Interjections like "yes" are an example of this kind of particle.
You can put commas around these and that will be enough because of their independence.
Other examples:
no
wow
ouch
goodbye
hello
Answer: A comma is preferable to a semicolon in cases where the clause is a word or two. Example:
<code>I came, I saw, I conquered.
</code>
As to the choice between a comma, a period, and an exclamation point, that would be an attempt to model the stress and emphasis with which the statement was made.
Answer: This is an interjection. One uses a comma after a mild interjection and an exclamation point after a strong one. "Yes! We won!" Vs. "Yes, we won, but who cares?"

Punctuation after "Yes"


MVVM Light Resharper Templates?

Question: Since mvvm-light's C# snippets will not show if I'm using resharper, and my google skills have failed me... Does anyone know where i can get a set of MVVM light specific templates for ReSharper?  I've found a post from Laurent that says he's working on it, but I've not been able to find them, and the thought of building them all myself seems daunting.
Answer: I'm using MVVM Light and ReSharper. The snippets show up when I press CTRL+J.
Answer: simply type the shortcut of a snippet (for example: mvvminpc ) somewhere in your source code and press TAB TAB
Please make sure that the snippets are available and correctly installed. You could use the Visual Studio Code Snippet Manager (Tools -> Code Snippet Manager) for this purpose. Select the Language (eg. C# ) an then you should see a folder named MvvmLightCSharpSnippets which contains all MVVM Light Snippets.

MVVM Light Resharper Templates?


Amps, Speakers, and power supplies

Question: If you have a 4 ohm speaker and you add a 4 ohm resister to the positive wire. Do you have an 8 ohm speaker?
Is impedence the same as resistence?
I have 2 Scosche HD4004 HD Speakers 4 oms 30 wat RMS. I also have a Lepai LP-2020TI amp, 15 watts per changle.
So, will this amp drive the 2 Speakers?
Speakers 4 ohms 30 watt RMS. So, if you are sending 15 watts at a medium volume. is that OK.
The Lepai LP-2020TI amp has a TPA3118 chip, according to the ad the chip does not have a heatsink. If I add a heatsink and
increase the power from the 12v 3amp power supply to say a 19.5v 90watts on amp, will it heat up that chip? Will it increase the output
wattage of the amp? How do you glue a heatsink on a chip?
Comment: I'm voting to close this question because it is about car audio installation not 'music performance or practise'.
Comment: @Tetsujin - this could easily be a question based on a practice amp and adding speakers. No difference, really.
Comment: @Tim - but it isn't about practise amps, it's about specialist 12v systems used in cars. That is not where this stack's expertise lies. Next we'll be doing home cinema & Powerpoint screen projection tips… got to draw the line somewhere & this would appear to be right there.
Comment: @Tetsujin - whilst you're right, there are more amps now using 12vdc, and people will want to add extra speakers, so the end product would be the same. If that clue was removed from the question, it would boil down to the same.
Comment: Gary,  it's good practice here to ask one specific question.  You are asking about a dozen here, many of which are contradictory.  I would recommend first reading up on audio electronics and what  'resistance,' 'impedance,' and 'watts'  ratings mean in this context.
Answer: Welcome Gary. It sounds like you might like to turn your musical situation into a laboratory situation, as with a list of questions like this you'll either need to have a designer/ engineer redesign your power supply and amplifier or be willing to risk having your whole set-up go up in flames to get the answers you are looking for. As for your question about whether or not your amp in its current configuration will match up with your current speaker set-up, from the information you given us here, I'd say it'll match up okay. And as for the resistor wired in series with the speaker, well it would need to be a 15 watt resistor and it would just convert your output to heat, so I would be more inclined to find another speaker to wire in the circuit in place of that resistor, where the amp output would be converted into sound. Two concepts in electrical circuit operation are resistance, which is not frequency altered, it stays the same rating, which is pretty easy to understand. The other concept is called reactance, where the resistance can be altered depending of the operating frequency of the circuit. This is how a speaker acts in operation, where the resistance of the speaker changes in reaction to the frequency of the signal being presented to the speaker. This type of resistance is referred to as impedance. This is about as simple as I can think to explain it.
Comment: This fails to address the key question of   static resistance vs dynamic impedance
Comment: @Carl Witthoft- I apologize, But I simply didn't recognize that to be the key question.

Amps, Speakers, and power supplies


Is "based on" used as an adverb or in the passive voice?

Question: I'm a little bit confused when I use a sentence like "It is divided based on glasses of milk". I'm not sure, is "based on" used as an adverb or in the passive voice? I want to know for sure whether I'm using it correctly.
Comment: A traditionalist would probably remark that *based on* is adjectival rather than adverbial, and that if you're looking for an adverbial phrase you'd do better to go with *on the basis of*. What about, "The criterion of separation is the number of glasses of milk"?
Comment: There's no way to know if you used it correctly or not without a lot more context.
Comment: Why do you think that matters?
Comment: because I want to know for sure that I used it correctly or not.
Comment: Yes you did. Although I'm not sure what is being divided, nor how its division is related to [the number of ] glasses of milk.
Comment: Thank you so much for your confirmation and ideas. I think I get it now.
Comment: They seem to be used as if they're a single preposition. However, in broader usage, I'm guessing it's idiomatic.
Answer: As Lachlan Dominic observes in a comment above, "based on" is interchangeable with "on the basis of" in many constructions. So, for example, you could say with equal accuracy and clarity

The league determines playoff seedings based on each team's number of regular-season wins.

and

The league determines playoff seedings on the basis of each team's number of regular-season wins.

The "It is divided based on glasses of milk" example is a bit difficult to interpret (because you don't provide a referent for It), but in terms of meaning it is interchangeable with

It is divided on the basis of glasses of milk.

Both the "based on" form of the sentence and the "on the basis of" form are coherent and grammatical, so here (and probably in most other cases) you are free to use the form you prefer.

UPDATE (9/16/2017)
Having described real-world usage fairly accurately in my original answer (above), I feel that I should expand this answer to acknowledge a prescriptive view of "based on" that has existed for many decades.
Theodore Bernstein, The Careful Writer: A Modern Guide to English Usage (1965) gives a succinct account of this view:

BASED ON
A latter-day tendency is to use based on as if it were an absolute participle like considering or given: "Based on future prices today for October delivery, Cuba will pay about $1.5 million for the shipment," This could be corrected to, "Based on future prices ... estimates are that, etc." Another example: "Once fully certified—based on {make it on the basis of} at least four years' carefully observed performance in the classroom—the new teacher would be licensed to teach anywhere in the United States." Some day based on may become an absolute phrase; but as of now, unless it has a clear and present subject, it must be classed as a DANGLER.

In short, Bernstein argues that a teacher may be fully certified on the basis of four or more years' carefully observed performance, but may not be fully certified based on such performance.
Almost forty years later, Bryan Garner, Garner's Modern American Usage, second edition (2003) identifies two appropriate and two inappropriate applications:

based on. This phrase has two good and two bad uses. First, the phrase may carry a verbal force (base being a transitive verb)—e.g. [first example only]: "She said she based her ruling on Xiong's allegations." ...
Second, in a passive sense, it may carry an adjectival force (based being read as a past-participial adjective)—e.g. [first example only]: "A quick calculation based on U.S. data indicates a requirement of $13 billion a year for Afghanistan." ...
But traditionally speaking, based on should have neither adverbial nor prepositional force. Here it's an adverb: "American officials said they attacked the convoy based on intelligence reports." ... (Based on improperly modifies attacked. Try because of or owing to instead.) ...
And here it's a preposition (a DANGLER, to be exact): "Based on those conversations, Riley said he doubts Graham will play." ... (A suggested revision: Riley said that because of those conversations, he doubts ....)

At least in the third example—the adverbial one—Garner presumably would have had no objection to "on the basis of" in place of "based on."
Kenneth Wilson, The Columbia Guide to Standard American Usage (1993), however, argues that in practical terms the "some day" at which "based on" becomes an absolute phrase (to use Bernstein's terminology) has arrived:

based on, based upon These combined uses as participial phrases, when they begin a sentence, often turn out to be dangling modifiers, although it is not necessary that they be so: Based upon the facts we have, my conclusion should stand up under scrutiny. But the fact is that based on and based upon, even when they dangle, are idiomatic in all but the most careful Edited English: Based upon {on} what we've heard, the police probably are ready to make an arrest. Most listeners will not notice such danglers at Conversational levels or in Semiformal or Informal writing.

Even fewer listeners will notice the adverbial "bad use" (according to Garner) of the phrase when it appears after the associated verb, as in "They could calculate nearby pick-up and drop-off points for their passengers based on optimized routing."
In any case, Wilson's distinction between Edited English and other forms of spoken and written English is a useful one to bear in mind.
The disapproval of "based on" in adverbial and prepositional settings persists in certain editorial precincts to this day—as I have been made aware repeatedly by colleagues at a company for which I have worked frequently in the past couple of years. But outside the rarefied air of Editorial English strongholds, "based on" used adverbially or prepositionally has overwhelmed any lingering objections to it with the sheer force of its ubiquity.
Comment: "These combined uses as participial phrases, when they begin a sentence, often turn out to be dangling modifiers, although it is not necessary that they be so: *Based upon the facts we have, my conclusion should stand up under scrutiny*." -- How is the participial phrase a dangling modifier here? Isn't it modifying the clause after it? And is the summative non-restrictive relative in "You talk too much, which bothers me." considered a dangling modifier too?
Comment: @MrReality: The example that Wilson gives isn't a dangling modifier; it's an example supporting his assertion that "it is not necessary that [a phrase starting with 'based on' used as a participial phrase] be so"—that is, be dangling modifiers. An example in which "based on" does create a dangling modifier is this: "Based on your argument, I am convinced that I was wrong." Arguably, that sentence asserts that "I" (rather than my being convinced that I was wrong) is the thing based on "your argument." Whether dangling modifiers are therefore syntactically unacceptable is a separate issue.
Answer: your sentence is similar to this: "people are classified based on their characters."
"based on" refers to "classified". as in saying :the classification of people is based on their character".


Overhead garage door opening on its own

Question: I have two, 6 year old Overhead garage door openers. On about 5 occasions in the last couple of months, I have discovered one side has opened on its own. When this has happened, neither of the manual switches will function, but the RF openers will operate the door in either direction. I have checked the Safety Beam for obstructions and found none. Any ideas? I am thinking along the lines of an intermittent short in the circuit board of the opener but would welcome any thoughts or ideas.
Comment: You might be right; rain water or humididty may be finding it's way into the manual switch (shorting - open). But just to offer an alternative theory, maybe someone else in the neighborhood has a similar garage door opener (or TV remote that happens to operate on the same frequency), and they are (unwittingly) opening your garage.
Answer: The fact that it's intermittent makes it hard to prove. I suspect the manual switches you refer to are the type with a separate up button and down button rather than a single button type control. If that is the case then I suspect the up button (or the wires from it) has made a connection (short). That would explain it not working when you push the down button because the up is still in effect pushed. It could also be as you say a short in the board giving the signal to open. Some openers have a push button on the board also. I would try disconnecting the wires at the opener going to the manual controls. If it works for a month or two without any problems then I would replace the switches.
Comment: Well I doubt the theory that someone else is inadvertently operating a switch as one person suggested. For one, this is a "rolling code" so that makes it unlikely. The question of humidity causing the problem is a possibility although that would not explain why neither of the manual (single button type) operation wouldn't function while the RF units will make it work... I could see if one of the switches didn't function but seems unlikely that both manual switches would fail at the same time ... and then both begin working again at the same time... bizzare
Comment: @BGeoffreyBurnham The manual switches may very well be wired in parallel, so that closing either one will complete the circuit.  If this is the case, one bad switch would stop the functioning of the other, and JPC's answer makes sense. Next time it happens, disconnect one of the manual switches and see if the other works.  If not, reconnect the switch, disconnect the other one, and give it a try.
Comment: Great idea... both switches are wired separately to the main unit but I will give that a tray. I called Overhead Door company who wants $110 for the first 30 mins, then $20 for every 15 mins thereafter... with the likelihood of the opener functioning Correctly when they come out, it makes it very likely they would have to come out at least a second time.. for that cost, I can replace the entire unit myself... if it comes to that I am thinking about the Ryobi 2 HP opener... wondering if anyone has any experience with this unit .. Thanks again for your time and thoughts

Overhead garage door opening on its own


KDE Plasma KDialog Issue

Question:
OS was originally Ubuntu Mate 16.04 but I installed KDE plasma 5.8.8. Im having an issue in the Open Files window where all items appear to be selected and possibly the selection text color and background are set wrong. Possibly this issue is unique to chrome as its the only program that I have found to use this dialog. All others are using whichever one this is
Answer: I was facing the exact same problem, here is how I solved the problem.
Go to System settings -> Application Style -> GNOME Application Style (GTK)
"Select a GTK2 Themes" AND "Select a GTK3 Theme" both use "Breeze-Dark"
Problem solved! Apparently, there is a conflict between Ubuntu MATE (GTK2) and KDE (GTK3)

KDE Plasma KDialog Issue


What is your email retention policy?

Question: Drafting up an email retention policy for our MS Exchange 2003 system. Curious as to what other people have as a policy -- how many days to keep online, delete, etc. Thanks!
Comment: I'm tempted to give this a "SFINAL" tag... as in "Server Fault Is Not A Lawyer".
Comment: Yep this would all be run thru the legal team but their hourly rate >> my hourly rate so I gotta get as much down on paper first for them to tweak slightly, rather than write it all themselves
Answer: Legal issues aside, I am in favor of keeping emails as long as I possible can. My own email database go back about a dozen years, and it is quite useful at times to have access to that information. Disk space is cheap, and getting cheaper, and machines are getting faster and cheaper as well.
Answer: It should be part of your overall document retention policy, not just a policy for your Exchange server.  Our document retention policy (drafted by Legal) states that emails older than 90 days must be deleted.  If the information in the email is required past 90 days of receipt then it is to be saved to disk (NOT a .pst file) as a file (rtf, doc, pdf, whatever) at which point it is under the governance of our document retention policy.  Automated archiving mechanisms are not permitted.
EDIT: in response to Evan's comment:
Yeah, good question.  It is draconian to be sure.  However, much time (ugh) is spent here forcing this policy down the organization and policing (ie- auditing), so it is working.  The first attempt at it met with such a rebellion as you describe, then it was reworked again and recently redeployed.  I do agree that email should be included in the overall retention policy and not left to an autonomous policy.  There is still much wailing and gnashing of teeth about not being able to utilize Outlook features to manage email here.  More so the fact that dept heads must annually audit to the retention policy and sign-off their dept's compliance, accountable to internal controls.
There are arguable benefits to your storage solution using such a policy, even when mailbox quotas are implemented.  There are still a lot of questions related to the "useless" that are being met with statments like "do it".
Comment: I did a contract gig at a public company with a policy like that, and users ignored it. I don't want you to "rat out" work, per se, but I'm curious if such draconian policies actually work. The "rebellion" against the policy that I saw directly related to the "useless" that was created when email was moved out of a tool designed to manage email (Outlook) and placed into a container (the filesystem) that was profoundly useless at helping to manage email. I saw a _lot_ of printing and filing of email at this particular company... I believe that trees hate them.
Comment: Thanks for the edit. Is the basis for the policy coming from the legal department, or from IT management, out of curiosity? (I've seen this kind of thing come from legal deparments and I've never been in a position to ask on the lawyers why such policies should apply to email but not, say, to all other types of files, both electronic or otherwise. I'd love to do that sometime... Perhaps we need Jeff and Joel to start, like, a "Affidavit Explosion" site... >smile<)
Comment: The basis is coming from legal.  I think most of it is that they don't want the emails to show up in a court room.  This policy applies to EVERYTHING at our place, paper or electronic.  The annual audit I mentioned covers mail, network shares, local drives, file cabinets, desk drawers, you name it.  Then I have to cross-audit it as a member of the data security organization.
Answer: I agree with squillman in terms of addressing legality obstacles. I would talk to the legal department first and foremost to avoid any headaches later on, and for possible compliance issues (HIPAA/SOX/PCI). Seems to me that industry usually dictates compliance in tandem with legal more than anything else.
From then on I would focus on common metrics within IT such as the total number of users, avg. growth rate per hour/day/week/month, etc. etc. to determine how many days to keep online storage (if legal hasn't mandated anything). From my experience, always leave a little slack too in terms of storage for YOU, not the users. Often users will take as much email storage as they're given (especially Outlook/Exchange shops), so if money is tight and storage is at a premium, lower the retention policy a little to alleviate future financial/technical headaches.

What is your email retention policy?


Derivation and tangent problem set

Question: Problem 1
On the curve $y=\frac{1}{1+x^2}$ find a point in which tangent line is parallel to the horizontal axis.

My idea:

Let's find $y'$.
$$y'=\frac{-2x}{(1+x^2)^2}$$
If we want a tangent line to be parallel to x-axis it must look like this $t...y=kx+l$ such that $k=0$.
Let's find for which $x$ we have that situation.
$$y'=\frac{-2x}{(1+x^2)^2}=0$$
$$x=0\to y=1$$
$$(x,y)=(0,1)$$
Problem 2
Determine the angle of the curve
$y^2 - 3x^2 + x + 1 = 0$ and
$xy^2 - 1 = 0$
intersect in the first quadrant
My work:
$y^2 - 3x^2 + x + 1 =xy^2 - 1$
One solution for $x>0$ and $y>0$ is $x=y=1$.
Let's now find derivative of easch function at that point.
$$2xyy'=-y^2$$
$$y'=\frac{-y^2}{2xy}=\frac{-1}{2}$$
$$2yy'=6x-1$$
$$y'=\frac{6x-1}{2y}=\frac{5}{2}$$
And the angle is $\alpha =arctg|\frac{k_1-k_2}{1+k_1*k_2}|$ where $k_1=\frac{-1}{2}$ and $k_2=\frac{5}{2}$

Problem 3
Find the angle of intersection of the tangents to the curve
$3x^2 - 6x + 2y^2 - 3 = 0$
from the point $T( 1,3 )$?
My work:
First (1,3) isn't on the curve.
We will need that tangent equation:
$$y-y_0=y'(x_0)(x-x_0)$$
From the task we know that $x=1$ and $y=3$.
Let's try to find $x_0$ and $y_0$.
Using implict differentation we will find $y'$.
$$6x-6+4yy'=0$$
$$3x-3+2yy'=0$$
$$2yy'=-3x+3$$
$$y'=\frac{-3x+3}{2y}$$
Plugin that in equation:
$$3-y_0=\frac{-3x_0+3}{2y_0}(1-x_0)$$
$$3-y_0=\frac{-3x_0+3}{2y_0}+\frac{-3x_0^2-3x_0}{2y_0}$$
$$3-y_0=\frac{-3x_0^2+3-6x_0}{2y_0}$$
$$6y_0-2y_0^2=-3x_0^2+3-6x_0$$
But I can't get something nice...Is my problem 1 and 2 ok and please help me with 3
Comment: The wording of problem (3) is odd: what does it *really* mean? "Intersection point of tanget to curve...from the point (1,3)..." Intersection of what with what?
Comment: Tangents must cross point (1,3) and search angle of that tangents
Comment: @Lo "angle..." with *what*? The positive $\;x-$ axis, as usual, or something else?
Comment: @LovroSindičić: I edited the question. Hope that's fine.
Comment: @LovroSindičić: In problem 3, you can draw **two** tangent lines from $(1,3)$ since the curve is an ellipse.
Answer: For problem 1,2 :
They look fine except the following :

One solution for $x\gt 0$ and $y\gt 0$ is $x=y=1$.

True, but that $(x,y)=(1,1)$ is the only solution for $x\gt 0,y\gt 0$ has to be proven. We have $y^2 =3x^2 −x−1$, and so
$$x(3x^2 −x−1)−1=0⟺(x−1)\left(3\left(x+\frac 13\right)^2 +\frac 23\right)=0\iff x=1$$
For problem 3 :
You have $$3-y_0=\frac{-3x_0+3}{2y_0}(1-x_0),$$
i.e.
$$-2y_0^2-3x_0^2+6x_0=-6y_0+3\tag1$$
Note here that $(x_0,y_0)$ is a point on the curve, so you have
$$3x_0^2-6x_0+2y_0^2-3=0\iff -2y_0^2-3x_0^2+6x_0=-3\tag2$$
From $(1)(2)$,
$$(x_0,y_0)=\left(\frac{3\pm 2\sqrt{3}}{3},1\right)$$
Hence, the slopes of the tangents are
$$\frac{-3x_0+3}{2y_0}=\frac{-(3\pm 2\sqrt 3)+3}{2\cdot 1}=\mp\sqrt 3$$
Now find the angle in the similar way as problem 2.
Comment: @Lovro Sindičić : For problem 3, after having $3-y_0=(-3x_0+3)(1-x_0)/(2y_0)$, you finally have $6y_0-2y_0^2=-3x_0^2+3-6x_0$. But this is wrong. You made a sign mistake at the second line.
Answer: Problem  1 is OK.
Problem  2 ;
First try to find intersection point $(x,y)$
$$ \frac1x - 3 x^2 + x +1  =0 $$
Factorize it
$$ -(x-1) (3 x^2  2 x +1) =0 $$
At $x=1, y= \dfrac{1}{\sqrt x } =1.\; i.e., (1,1) $ is the point of intersection. Other roots are neither in first quadrant nor real.
Now for the slope: $ y^2 = \frac 1x \rightarrow y'= \dfrac{-1}{ x^2 y} \rightarrow -1. $
Problem 3:
not answered.
Answer: The solutions to problems 1) and 2) are correct.
For problem 3) note that you are searching the straight lines of equation $(y-3)=m(x-1)$ that are tangent to the curve $3x^2-6x+2y^2-3=0$. This means that you want the values of $m$ such that the system:
$$
\begin{cases}
(y-3)=m(x-1)\\
3x^2-6x+2y^2-3=0
\end{cases}
$$
has one double solution, and this is done if the discriminant of the second degree equation that we obtain substituting from the first to the second equation is null. This gives an equation ( of second degree) in $m$ and solving this equation you find the slopes of the tangent lines.

Derivation and tangent problem set


FX Price aggregation method

Question: Lets say we are receiving tradable FX market depth(bid/ask prices and amounts for each level) from several Liquidity Providers and we want to aggregate the market depths in to a single bigger market depth. It is possible to sort the bid prices descending and ask prices ascending to give the best price for each but in this case, max(bid) > min(ask) situation can occur.
Sorting the price lists as above seemed trivial to me. Can you suggest another method?
Thanks
Comment: The fact that max(bid) > min(ask) is probably not a real market-based phenomenon but the result of a slight lag in getting information from some of the providers, i.e. a "non-simultaneity" problem. If at a certain price levels there are both bids and offers you then have to decide how to handle that... perhaps you might report the net (i.e algebraic sum).
Answer: Are these tradeable prices or indicative feeds from brokers? Or on different e-platforms? If they are tradeable, what other information do you have, like available size, period of validity...
All of that information is needed to tell you what those numbers mean. From indicative numbers you may only be able to get an indication, so significant analysis might be misleading.
Comment: Brokers send these tradable prices including bid/ask prices and amounts are available for each level. Period of Validity is not available.

FX Price aggregation method


Forcing specific visible symbol export from linked static library with GCC (while excluding other symbols)

Question: I am trying to provide access to a function linked in to an executable from a static library. The original static library defines the symbol with no access specifiers, and I was able to access the function using the method defined here, which works fine using MSVC as linked in symbols are hidden by default.
However, when using GCC, I need to export the function while using -Wl,--exclude-libs,ALL which keeps all other unnecessary symbols from being visibly exported from linked-in static libraries. The symbol in question is not referenced from the main application itself, however third party modules may attempt to dynamically use the symbol externally (ffi etc), hence the use of FORCE_UNDEFINED_SYMBOL.
The only symbols I need exported are those marked visibility default from the main application, and certain imported functions from static libraries (which I may not be able to modify). I know wrapper functions could be used, however I'm wondering if there is any other way.
So, is it possible to export a symbol (visibly) from a linked-in static library, while using -WL,--exclude-libs,ALL, without the use of any additional (version-lists etc) files, or commands/flags? (And without modifying the static library)
Using the following macros (partially) work, however the original function symbol is still .hidden (with __MyFunction_fp exported as visible).
<code>#define APIEXPORT __attribute__ ((visibility ("default")))
#define FORCE_UNDEFINED_SYMBOL(x) extern APIEXPORT void x(void); APIEXPORT void* __ ## x ## _fp =(void*)&x;
FORCE_UNDEFINED_SYMBOL(MyFunction)
</code>
In this instance, the actual definition/declaration of MyFunction would exist in a static library, and cannot be changed.
EDIT: I discovered that the above macro FORCE_UNDEFINED_SYMBOL does not produce the desired symbol visibility under MSVC. It seems that the only working solution is using pragma comments, ie, __pragma(comment (linker, "/export:" #x)). Maybe a similar solution exists for gcc/ld.
Answer: What you're suggesting sounds hard to maintain even if you succeed. You want shared object (DLL) behavior with static libraries.
When I had a similar problem (e.g. 3rd party static lib) I wrapped the lib in a shared object and used that with my application.


HighCharts within JQuery tabs

Question: I am having a strange problem while using HighCharts as ASPX user control within JQuery tabs.
All pages are derived from a Master page. JQuery tabs are working fine in all content pages but when I place my HighCharts user control withing tabs, blank page is displayed with no rendered HTML available (view source). When I remove tabs, charts are working fine as well.
Here is the code:
    <asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">

</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">

Chart

                <control:Chart ID="ChartData" runat="server"></control:Chart>

</asp:Content>

This is driving me nuts. Any help is appreciated.
Best Regards,
Faisal
Comment: Can you provide some example or fiddle ?
Answer: This is a known issue with IE. The link gives a workaround that is a bit cumbersome.

HighCharts within JQuery tabs


"_layouts" pages in Web analytics report

Question: Is there any way that we can exclude the pages in the "layouts" folder from appearing in web analytics reports such as "Top Pages"? I am getting too many hits for the "userdisp.aspx" file and there by resulting in an incorrect report. My site contains mostly article and wiki pages.
Answer: I am not sure if you can exclude them but I think you can filter the reports in the settings in CA.
Comment: Would you care to detail that, please?


Which is correct; "Be not late for school", or "Don't be late for school"

Question: We are taught when you negate a verb, you use "do not", "does not" or "did not" for general verbs, but you only have to add "not" after the verb in the case of Be-verb. If this rule should be applied in all cases, I think "Be not.." is the only correct writing. Please advise me.
Comment: Although do is not normally used as an auxiliary with be, this happens in negative imperatives: _Don't be silly!_
Answer: The correct modern expression is

Don't be late for school.

This is a standard negation of the imperative:

Put on your shoes ➡ Don't put on your shoes.
Run to catch the bus ➡ Don't run to catch the bus

It is the same for the "be" verb:

Be the best student ➡ Don't be the best student

That being said, archaic English does include your negation.  It would not be correct to use it in ordinary conversation, but you might find this kind of expression in things like period dramas, older manuscripts, and religious texts:

Be not so proud as to think yourself wholly without sin.
Trust not those who would wish you ill.

Naturally you can use this if you want to sound like someone speaking old-fashioned English, or making some kind of officious proclamation:

Be not late for school, lest ye be remanded to the Pit of Detention.
Comment: @Tashus [Don't even think about trying to escape.](https://www.youtube.com/watch?v=mBaDcOBoHFk)
Comment: +1 for Pit of Detention.
Answer: Placing "not" after a verb is grammatical but very old fashioned except for the negation of auxlliary verbs such as "do not"(don't), "will not"(won't), "can not"(can't) and so on. It probably hasn't been used in ordinary speech for at least 200 years.
Also when it was current it wasn't limited to the verb "to be", any verb could be negated in that way, a good example is John Donne's famous sentence "Ask not for whom the bell tolls, it tolls for thee". John Donne lived from 1572 to 1631.
The form has been used more recently but only formally and for artistic effect, for instance Go not to the temple by Rabindranath Tagore. This was a late 19th or early 20th century translation of a Bengali poem and the "Go not" construction was used for artistic effect, possibly to make the poem match the feel of the Anglican Book of Common Prayer or the King James Bible and, so, make it more obviously reigious.


Arduino starter

Question: I have finished my first year in engineering and would like to do some projects related to arduino. What should we do as a starter?
Comment: What area interests you?
Comment: What do you mean by "feasible"?
Comment: Embedded systems.
Comment: Taking into consideration that I have completed only my first year in engineering , what would be the best course I could do . That's what I meant by feasible
Comment: You're good. Just try to get a balance between circuit design/theory and software in your coursework. In the US, some schools  offer a "computer engineering" major that is a good fit for people interested in embedded systems.
Comment: Books: http://electronics.stackexchange.com/q/616/2028
Comment: @DannyPaul Pretty much 90% of arduino projects are doable at your level.
Answer: The question is a little like: "What field can I specialize in if I am a medical student?"
The answer is: "Whatever you like."
Seriously, doctors aren't forced to become knee surgeons or oncologists. They do so because of their interests, aptitude, and often colleagues or institutions that they know or are familiar with.
Electrical engineers are the same way. If you're interested in cross-country power delivery and generation, focus on transmission lines and high voltage. If you want to develop atom-sized transistors or nanometer-scale integrated circuits, you can specialize in that, instead.
Edit:
Now that you've edited your question to be a little more specific...
The Arduino is a great prototyping and development kit. I skipped Basic Stamps and PIC when they started becoming popular, and wound up getting back into electronics when the Arduino first showed up. From the Arduino, I quickly realized that I wanted to be able to program small microcontrollers without the rest of the development board, and learned how to work with Atmel AVR microcontrollers, which are at the heart of the Arduino.
So, my recommendation is to work on the Arduino more, doing projects that are of interest. You might want to pick up a book like the Arduino Cookbook or any of the thousands of online tutorials from sites like MakerShed and Instructables.
Since you're in engineering, I'll assume you're getting the basic coursework for DC and AC electronics, semiconductors and digital electronics. That will provide a solid background for branching out from the Arduino and developing your own support circuitry, prototyping on breadboards, experimenting with other microcontrollers, and perhaps designing your own boards.

Arduino starter


Evaluation of $\int_{1}^{\infty} \frac{\arctan (x+1)}{x^2+4} dx$ in closed form?

Question: I have used the substitution $u= x+1  $ then $du =dx$ to evaluate the following integral in closed form and since $\arctan$ is connected to $x^2+1$ as it is a derivative of it.
$$\int_{1}^{\infty} \frac{\arctan
(x+1)}{x^2+4} dx$$
But i didn't come up to it's closed form the inverse symbolic calculator doesn't give me the closed form for it , and all my attempts gives me this approach : $$\int_{1}^{\infty} \frac{\arctan
(x+1)}{x^2+4} dx=\frac{\pi^2}{8}-\frac{3\pi}{8}\arctan \left(\frac{1}{2}\right)$$ But this is not the same result with Wolfram alpha, Any way ?
Answer: I suppose a mistake somewhere since
$$\frac{\pi^2}{8}-\frac{3\pi}{8}\arctan \big(\frac{1}{2})=0.687479$$ while Wolfram Alpha returns a value equal to $0.741221$ which is correct.


The inside coil of the A/C unit has ice on it when the temperature outside is cooler than 65 degrees

Question: The inside coil of the A/C unit has ice on it when the temperature outside is cooler than 65 degrees. Freon has been added, but it has iced up again six months later. What is the problem?
Comment: Hello, and welcome to Stack Exchange. What make/model is this? What indoor temperature are you setting it to? Is there anything restricting the airflow?
Answer: Most A/C units do not work well at temperatures below 65 degrees. Years ago, we would install a low ambient control. Ask the HVAC people that service your unit to install a "low ambient control device" to help keep the head pressure up to allow the unit to operate below 65 degrees.
Answer: If just an AC unit that makes sense to me unless set up to make a "cold room" depending on the type of control (capillary tube, orifice) the system may not be able to accurately meter at cooler outside temps as there is no real feedback compared to a system with a throttle valve TXV. With open loop the Freon is compressed and cooled when it expands being close to 20 degrees colder ice will form if there is not enough airflow across the evaporator or the delta of tempature is two low. If trying to make a cold room a shifted temp sensor needs to be used to controll the system and get to lower temps.
Answer: Have a tech check the high and low pressures of the refrigerant before the ice has formed. Low refrigerant pressure (as from a leak) will cause the temperature of the evaporator coils to be below freezing. You want the indicated pressure to correspond to a low side temperature to be 37 - 40 F.


Gaining experience in salesforce

Question: Are there any other projects like "Recruiting app" in salesforce that we can build for practicing admin and developer concepts to gain hands on experience?
Comment: Have you heard of Trailhead? [Click here](https://developer.salesforce.com/trailhead/en)
Comment: https://github.com/choppen5/TwilioSalesforceClick2Dial -- Install this package in your developer org and play with it. I have been working on this from last two days and learnt lot of new things.
Comment: developer.salesforce.com/trailhead
Comment: Ya I have done almost all the project available in Trailhead, currently working on my last project. As I don't have job as a developer, I would like to gain as much as hands on experience over these concepts. Are there any other project other than trailhead that could help achieve this?  Thanks In advance.
Comment: thanks for  the info Javanoob. There seems to be a lot of info regarding this.
Answer: Hands On
As many others mentioned, trailhead is a great way to learn. Other than that, I would suggest taking a look at the workbooks. These workbooks are great step by step guides which walk you through different areas of Salesforce, and personally I found as valuable tools for learning what specifically is needed to pass your certification exams. There are also courses to help you get ready for these exams.
DIY
Depending on if you are a hands-on type learner, I would suggest getting your own dev org, thinking of your own app to build, then build it out on your own. This is great experience as you are defining your own requirements, then building it out and testing it. It's a challenge as it might be hard to identify something to build on your own, but this would be a very close 'real world' scenario. Maybe try an event management application.
Communities
If you want a less hand-on approach, you can always be active in the communities, SFSE, developer forum, and success community. Being active doesn't always mean answering questions - maybe just look through posts and learn what the question is asking and understanding the answer. This gives insight to other peoples issues which you may encounter some day and helps you understand parts of Salesforce that trailhead and other sources don't always let you dive into.
There are also local meetup communities for your to engage and discuss Salesforce. These groups are often run by MVPs or highly engaged Salesforce users. This would get you access to many other users that eat, sleep, and breathe Salesforce as well.
Comment: Thnak you Zainogj. I would start my work on the workbooks. They seem to provide good learnng experience.
Answer: Best way to learn Salesforce is Trailhead - click here
developer.salesforce.com/trailhead
visit , Signup
First go with "Beginner" modules/trails.
Comment: Ya I have done almost all the project available in Trailhead, currently working on my last project. As I don't have job as a developer, I would like to gain as much as hands on experience over these concepts. Are there any other project other than trailhead that could help me achieve this? Thanks In advance.
Comment: For practice purpose - you can go and visit AppExchange - See different apps there - Watch Screenshots carefully - you could install 'Free' of them -- and try to implement functionalities like them. That will be great !  (If you get Unmanaged Package -Apps' there -dont look into the code initially --- Just use your way of implementing things---Then see into their codes and improvise)

Gaining experience in salesforce


Why is pressure an intensive property?

Question: My teacher explained to me that we volume is an extensive property because it is additive in nature. But he also told us that pressure is an intensive property. Now according to the gas law equation $PV=nRT$, pressure is dependent on volume. Increasing pressure should increase volume. So shouldn't pressure be extensive as well.
Comment: Possible duplicate of [How is pressure an intensive coordinate?](http://physics.stackexchange.com/q/201860/)
Comment: Increasing P will decrease, not increase, V for constant T and n.
Comment: Look at the right hand side, $nRT$. It involves a physical constant ($R$), an extensive variable ($n$), and intensive variable ($T$). The left hand side, $PV$ must similarly involve the product of an extensive variable and an intensive variable. The extensive variable is $V$. $P$ must be (and is) an extensive variable. The ideal gas law is a linearized idealization. You'll rarely see the product of two extensive variables in thermodynamics because the result would inherently be non-linear.
Comment: The mistake is that you are expecting $p$ to change when $V$ changes and at the same time assuming that the rest of the parameters ($n$ and $T$) are constant. But why not the other parameters? What if it is $n$ that changes with changing $V$ while the rest ($p$ and $T$) are constant? The point is that this argument doesn't hold. Extensive and intensive properties are not defined by the ideal has equation.
Answer: From the ideal gas equation,
$$P=\frac{nRT}{V}$$
Now assuming the gas is uniformly distributed over space (has constant density for a given temperature), halving the number of moles will divide the volume by the same amount. Essentially, if we divide the number of moles by any number, we will end up dividing the volume by the same number to maintain constant temperature. So it doesn't matter how many moles of gas you take at a given temperature, you will always end up with the same pressure.
You could also look at it as ratio of two extensive quantities will always give an intensive quantity.
Comment: The definition of extensive/intensive property of a system is that the property changes/doesn't change if we take part of it from the whole for a given system. If you vary the density, or the number of moles inside **whole system** then it is no longer the same system. Here, the volume of the whole system is the same throughout our analysis. We're looking at parts of the volume as some fraction, say V/2, and trying to find out what's the pressure in that volume considering it's still the same system. We're not changing the volume, number of moles or the density.
Comment: What if the density varies? Then both pressure and density would be extensive properties?
Comment: If gas is in a box , volume is fixed , and if we decrease moles , pressure decreases. Doesn't that make it extensive?
Answer: Its because if we divide the container in two halves then the volume of the gas will also get half. But the pressure applied on the walls of both the containers will be same.
Comment: But, if volume gets halved, pressure should theoretically and practically decrease.
Comment: @Abhishekstudent Why do you think so?

Why is pressure an intensive property?


Sequence of boxes with a rotating arrow, large (un)shaded circles in the corners, and a small circle

Question:
What is the next image?
The small circle seems to follow the arrow, which would eliminate C and E.
Comment: It seems that you found this puzzle somewhere; could you please add a source? We have an [attribution policy](https://puzzling.stackexchange.com/help/referencing). Thanks!
Answer: I think the next image is:

 B

Explanation:

 I'm going to use W, X, Y, and Z to denote the top left, top right, bottom left, and bottom right corners of each image, respectively.
 The circle with the lines going from the top left to the bottom right moves in each image in the sequence, yielding the pattern WZYXW..., so we can expect it to be in Z next. Assuming your small circle theory is correct (I have no reason to think otherwise), this further eliminates D, leaving just A and B.
 Applying the same rationale to the other circle gives us XYZXY..., so we can expect it to be in Z next, leaving only B as the final answer.
 I can't find an obvious rule for the direction of the arrow, but if it's assumed that its only role is to show where the small circle will be in the next image, than its orientation can be arbitrary.


Are there any references of students (i.e. Hermione) using Apparition outside classes?

Question: I'm aware that Apparition is taught to the students, but I wonder if there's any student using this spell besides, for example, Hermione, in The Deadly Hallows if I'm not mistaken, when she takes Harry and Ron with her.
Any mention you can find about this would be much appreciated!
Comment: Did you not answer your question with the example you gave above?
Comment: I want to know if there's any other references of this topic
Comment: http://harrypotter.wikia.com/wiki/Apparition
Comment: Since the Apparition lessons weren't really normal _classes_ as such, I'd say the question is more whether there are any known instances of students using Apparition **in** classes. (The answer is presumably no, since you can't Apparate within Hogwarts except for the Hall during Apparition lessons—not until the 1997/98 year, at any rate.)
Answer: Concentrating only on those who're young enough to be students during the events of the Harry Potter novels;

Both Fred and George Weasley use apparation within the confines of Grimmauld Place in 'Harry Potter and the Order of the Phoenix'

With two loud cracks, Fred and George, Ron's elder twin brothers, had
  materialised out of thin air in the middle of the room. Pigwidgeon
  twittered more wildly than ever and zoomed off to join Hedwig on top
  of the wardrobe.

Harry Potter apparates in Deathly Hallows

Meanwhile, inside number twelve, Harry had just entered the hall. He
  had nearly lost his balance as he Apparated on to the top step just
  outside the front door, and thought that the Death Eaters might have
  caught a glimpse of his momentarily exposed elbow

As does Ron Weasley (and Hermione, obviously)

She was impeded by her own Shield Charm; by the time she had removed it, he had already stormed into the night. Harry stood quite still and silent, listening to her sobbing and calling Ron's name amongst the trees.
  After a few minutes she returned, her sopping hair plastered to her face.
  'He's g – g – gone! Disapparated!'

Graham Montague apparates after becoming stuck in the vanishing cabinet

Montague told me that when he was stuck in the Hogwarts one, he was
  trapped in limbo but sometimes he could hear what was going on at
  school, and sometimes what was going on in the shop, as if the Cabinet
  was travelling between them, but he couldn't make anyone hear him ...
  in the end he managed to Apparate out, even though he'd never passed
  his test.

(h/t to Himarm & Evdzhan Mustafa)

In the film-verse, Draco Malfoy apparates into the Hogwarts dungeon in order to to rescue Goyle and Blaise Zabini in Deathly Hallows, Pt II.
Answer: Graham Montague, uses apparation to escape from the vanishing cabient which was later moved to the RoR. I believe Fred and George stuck him there to retaliate for him abusing his powers during the Umbridge regime.
Comment: @Richard "Montague told me that

when he was stuck in the Hogwarts one, he was trapped in

limbo but sometimes he could hear what was going on at

school, and sometimes what was going on in the shop, as if

the Cabinet was travelling between them, but he couldn't

make anyone hear him ... in the end he managed to Apparate

out, even though he'd never passed his test."
Comment: @Richard it just spat him out in book 5, but in book 6 he apparated out, because she forgot and her editors are bad i guess, and both forgot you cant apparate at hogwarts, whatever,
Comment: Slight inaccuracy: the Vanishing Cabinet wasn't put in the Room of Requirement until after Montague got out of it. It was on the first floor when Fred and George shoved him into it.
Comment: The quote from the book is ***'They've found Montague, sir, he's turned up jammed inside a toilet on the fourth floor.'
'How did he get in there?' demanded Snape.
'I don't know, sir, he's a bit confused.'.*** It doesn't say that he apparated...
Comment: @Richard which makes me wonder how he apparated into a toilet in Hogwarts.
Comment: @Himarm - Ah, OK. I missed that part. I just assumed the vanishing cabinet spat him out.
Comment: @Himarm - Presumably he apparated on the Borgin and Burke's side of the wormhole
Comment: @Richard but ended up in the hogwarts bathrooms
Answer: To complete the good answer from Richard:
There was also :

Percy, after he passed his apparition test, at the Burrow

"Percy only passed two weeks ago," said George. "He's been Apparating downstairs every morning since, just to prove he can."
(Goblet of Fire, Chapter 6, The Portkey)

[Side-Along Apparition] Harry (thanks to Dumbledore) when they went to Slughorn's

Harry gripped Dumbledore's proffered forearm.
"Very good," said Dumbledore. "Well, here we go."
Harry felt Dumbledore's arm twist away from him and redoubled his grip; the next thing he knew, everything went black; he was being pressed very hard from all directions; he could not breathe, there were iron bands tightening around his chest; his eyeballs were being forced back into his head; his eardrums were being pushed deeper into his skull and then--
He gulped great lungfulls of cold night air and opened his streaming eyes. He felt as though he had just been forced through a very tight rubber tube. It was a few seconds before he realized that Privet Drive had vanished. He and Dumbledore were now standing in what appeared to be a deserted village square, in the center of which stood an old war memorial and a few benches. His comprehension catching up with his senses, Harry realized that he had just Apparated for the first time in his life.
(Half-Blood Prince, Chapter 4, Horace Slughorn)

[Side-Along Apparition] Harry (thanks to Dumbledore) when they went from Slughorn's to the Burrow

"This will do, Harry. If you will grasp my arm."
Braced this time, Harry was ready for the Apparition, but still found it unpleasant. When the pressure disappeared and he found himself able to breathe again, he was standing in a country lane beside Dumbledore and looking ahead to the crooked silhouette of his second favorite building in the world: the Burrow.
(Half-Blood Prince, Chapter 4, Horace Slughorn)

[Side-Along Apparition - or something like "Helped Apparition"] Harry (thanks to Dumbledore) when they went to the cave

"It will not be necessary for us to enter," muttered Dumbledore, glancing around. "As long as nobody sees us go ... now place your hand upon my arm, Harry. There is no need to grip too hard, I am merely guiding you. On the count of three--one ... two ... three ..."
Harry turned. At once, there was that horrible sensation that he was being squeezed through a thick rubber tube; he could not draw breath, every part of him was being compressed almost past endurance and then, just when he thought he must suffocate, the invisible bands seemed to burst open, and he was standing in cool darkness, breathing in lungfuls of fresh, salty air.
(Half-Blood Prince, Chapter 25, The Seer Overheard)

[Side-Along Apparition with a student as "leader"] Harry ("carrying" Dumbledore) when they got back from the cave

Sodden and shivering, Dumbledore's weight still upon him, Harry concentrated harder than he had ever done upon his destination: Hogsmeade. Closing his eyes, gripping Dumbledore's arm as tightly as he could, he stepped forwards into that feeling of horrible compression.
He knew it had worked before he opened his eyes: the smell of salt, the sea breeze had gone. He and Dumbledore were shivering and dripping in the middle of the dark High Street in Hogsmeade.
(Half-Blood Prince, Chapter 27, The Lightning-Struck Tower)

[Side-Along Apparition? thanks to Snape? Another Death Eater? or maybe Regular Apparition] Draco when he fled with Snape and the DeathEaters - I can't find a quote telling it, it happened between:

Snape and Malfoy, however, were still running; they would soon be beyond the gates, able to Disapparate--
(Half-Blood Prince, Chapter 28, Flight of the Prince)

and

Snape had managed to Disapparate just beyond the school's boundaries.
(Half-Blood Prince, Chapter 28, Flight of the Prince)

Not to mention of course the Apparition lessons, Apparition Test in Hogsmeade and the many Apparitions of Harry, Ron and Hermione in the Deathly Hallows (some of them being Side-Along Apparitions led by one of them, some others being Regular Apparitions). And also from Dean and Luna, helped by Dobby.
Comment: I didn't count side-along apparition which is what we seem to see from Dumbledore/Harry (the first couple of times) and Snape/Draco (probably).
Comment: @Richard I wasn't sure whether these cases were wished, but since it's Apparition... I'll mark these cases as so for a better clarity;
(For Snape and Draco I'm not so sure... there's a bit of time between these two quotes : Harry runs after them, tries and fights with Snape... I always thought Draco hadn't wait for Snape and had disappeared in the meantime. But no proof. And maybe another DE side-along apparated with him...)


I-formation in doubles tennis

Question: What is the rational behind the I-formation in doubles tennis? What are some considerations when using this strategy?
Answer: Firstly, it can break the return rhythm of your opponents.
Secondly, the return player cannot return the ball cross-court, but only longline. This might force him to errors or a weak return.
Even if he tries to return cross-court, your partner at the net can hit the ball to the open side (cross-court).
Here is a translation of an explanation of the Australian- and the I-formation from a german tennis forum:
Australian lineup
Your opponents are returning heavily and you are having a hard time getting your serves through? In this case it might be worth considering switching to the Australian lineup.
In the Australian lineup, the server stands right next to the center marker (= the tip on the baseline). His partner is in the same half of the court, positioned next to the center line. In the following, the net player is responsible for the left side of the court, the server for the right. So it is exactly the other way around compared to the classic lineup.
The Australian lineup is an effective variation if you want your opponents to
to force your opponents to make more longline returns.
The server typically plays the ball through the middle or to the body. The return player is now forced to return longline if he wants to avoid the net player. This change often throws the returner out of rhythm, especially if he has been returning mainly cross-court. He may make more mistakes now than before.
With the Australian formation, the net player can also intervene by moving diagonally forward to the other half of the court and intercepting the return. This is often even advisable, because the server may not be able to move up quickly enough and would therefore be forced into a difficult volley from the half court.
From a geometric point of view, the Australian formation is slightly disadvantageous compared to the conventional formation. This is evident from the fact that the server has a longer run to cover the court. The advantage of the Australian variation is mainly the surprise effect. It reverses the normal pattern and can thus disrupt the rhythm of the opposing team.
I-Formation
The I formation differs from the Australian formation in that the server's partner kneels crouched over the service line. This variation is also designed to cross the return rhythm of the opponents. Since the net player can intercept returns hit crosscourt, the opposing team may feel compelled to play longline.
With the I-formation, your opponent may be forced to make riskier returns and commit more errors.
For the I-formation to work, your partner at the net must be able to parry powerful returns with reflex volleys. The advantage is that the net player narrows the angles for the return because he is closer to the returner (similar to a soccer goalie moving toward the shooter). A disadvantage could be that with this set-up you give the opposing team more space to lob cross-court.
Translated with www.DeepL.com/Translator (free version)
EDIT:
Here is the source: https://www.saitenforum.de/board/showthread.php?t=25488
Comment: Welcome to Sports SE. Can you also link the forum you got the German text from?
Comment: Of course. I added the source in the post above.

I-formation in doubles tennis