Drum techinique - Arm and wrist questions

Question: I'm having trouble understanding when I should play with just wrist and when I should incorporate arm movement when playing traditional. I am also having trouble letting my wrist move when I use arm even when I'm totally relaxed. When I try to incorporate both wrist and arm, it feels like an unnatural movement and it doesn't feel accurate.
Comment: What are you looking advice on? Technique suggestions? Or explanation of when you should play wrist vs arm?
Answer: Drumming should be a very organic thing, meaning movements happen in a natural manner. With the exception of really big and loud passages where you have to incorporate a significant amount of arm to achieve height and dynamic or fast rolls in which you must pump your arms, your arm should generally move as a reaction to your wrist moving rather than you consciously moving  Think about it like this. There's a toy boat sitting in a pond. You toss a rock into the pond and it creates ripples that travel and move the boat. Your wrist is the rock, the ripples are the motion of your wrist, and the boat is your arm. If we were to do this in slow motion, on the upstroke we would see your wrist turn and your arm move slightly. On the downstroke we would see the reverse with your arm coming back down returning to its set position, then your wrist following and playing the note. The point of your arm moving is to add mass on the top of the stick to give a fuller sound. Try removing the sticks from your hands. Raise your hand above the drum, limp, and then just let it fall onto the head. Feel how much weight your arm has. The motion of your wrist is causing this weight to move, then when the weight naturally comes back down with your wrist, it adds sound.
Answer: Look up and study the Mueller technique. This a technique that focuses on efficient strikes by developing a smooth flowing movements from your wrist to your arm.
Comment: Yes, that's a good tip, actually. Jim Chapin demonstrates it well here: https://www.youtube.com/watch?v=7yNb-kUPwMI, for example.


Why are converts to Islam called reverts?

Question: I have noticed that when a person converts from one religion to Islam it is said that he or she reverted. This is said even when it is the first time he or she embraces Islam as a religion. Why is this?
Answer: In Islam, we have a concept called mithaaq, which means "heavy covenant/contract." According to this understanding, all of humanity met Allah (God) before we were created, and we agreed to follow His rules.
Therefore, we all have a fitrah (innate nature) to the values of Islam, because we are all born as Muslims.
More specifically, this can be extracted from the narration of our prophet (peace be upon him):

No [child] is born but upon Fitra (natural inclination to Islam).
  It is his parents who make him a Jew
  or a Christian or a Polytheist. A person said: Allah's Messenger, what
  is your opinion if they were to die before that (before reaching the
  age of adolescence when they can distinguish between right and wrong)?
  He said: It is Allah alone Who knows what they would be doing.

Source: Saheeh Muslim
Answer: Good question. The origin of the term comes from something the Prophet Muhammad (saws) said about everyone being born "on their nature" (the word used in the hadith is "fitrah"). Meaning that people are born with an innate ability to recognize their Lord and to submit to Him. The hadith continues by saying that after birth, it is the parents who make the child a Christian, Jew or Magian. So the people who like to use the term "revert" say that when one recognizes Allah as their Lord, they revert to their original state at birth.
I personally avoid using the term because a Muslim is something that someone is consciously, something that they believe in from their own intellect, something that they say and act upon. This is not the same state as a newborn baby.
Comment: This should probably be a comment. Please cite your sources bro :)
Comment: You shouldn't hate so, It's what new Muslim is :)
Answer: No Arab calls them reverts. This term was "deduced" by English speaking converts. Arabs refer to a person who has embraced Islam as "hadeeth al-'ahd bil-Islam" (recently come  to Islam) or "Muslim jadeed" (new Muslim). There is no Arabic equivalent of the term "revert".
Answer: To cover the opinion side of this question, temporarily without citations, let me tell you what I know of this personally. Though logic should count for something right?
The first time I heard of this was after telling another Muslim that I dont feel like I changed my religion as much as I have simply increased my knowledge of religion. The term better characterizes this feeling then convert. After all, I truly desired to be a Muslim by definition when I was Christian, so I didnt necessarily feel like I changed my religion. I still believed in One God as a Christian.
Alot of people I've met say the same thing. Eventually I'll find people saying the same thing in quotable formats and I'll start adding references to this to back up my statement. God willing.
The other funny thing is, just to highlight the ideal, that I dont really see other Christians as being non Muslims. People care about the prophet Jesus, the Bible, church, the pope, etc because of a simple belief in a Creator who Sustains and Provides for us every day.
Comment: nice admirable answer. Jazak Allah khaira
Answer: In my own case I try to avoid the whole question of 'revert' versus 'convert'.
Pretty much every day in my time in Saudi Arabia I was asked if I was a Muslim.
In answer I stated the Shahada in English in a very serious wholehearted way: "There is one Allah, and Mohammed is His prophet".
I have never recited this in Arabic, because I know neither the language nor Arab culture from many centuries ago.
In contrast I can be very clear when I say this in English.
So for most questioners this satisfied them, but not all.
Interestingly, my Muslim academic colleagues from Europe, who also taught at my university, were the least satisfied!
So for me this statement of the Shahada is completely true for me, and also in no way excludes the pearl of truth at the heart of many if not all religions.
To me this statement of faith on the biggest issues is far more important, than any business of categorising or identifying myself as a 'convert' or 'revert'.
It's all a question of priorities.
Let the others judge!
Let others risk the sin of TAKFIR accusing another Muslim of not being a Muslim!
Comment: Salam and welcome to Islam SE teh Q&A site about Islam. Please consider taking some time to learn more about this site and our model by taking our [tour] and checking our [help].


Where did the horses come from?

Question: In Tim Burton's Planet of the Apes, apes and humans are decended from those aboard the Oberon.
Where did the horses come from?
Answer: To be frank there is no explanation in the film itself. Looks like a plot-hole to me.
Or we can assume that the planet they land on always had horses. Same question is asked on many other sites too with no results.
Like from IMDb

Where did all the horses come from?
This is a tricky question to answer. It seems unlikely that horses would be brought on the Oberon for experimentation. It is up to viewers to come up with their own explanation.

So if I have to make guess I will say that planet was always inhabited with other animals like horses.
This is also got discussed over reddit and this is what a user came up with his speculation:

The easiest "consistent" explanation for horses is to assume that the animal facility just had horses too (in a different part of the station that wasn't on film). For whatever reason. I mean, there isn't really a good explanation to have every primate species on space station anyway.
Maybe we can pretend they were doing terraforming somewhere (they have gravity control, so they should be to pull it off). Horses were being exposed to "space conditions" to see what modifications were necessary to allow them to live on a new world, and so many primates were around to give the best possible sample of near-human studies in order to make sure there was no danger at all.

Which is not that convincing to me.
Answer: They were on earth the entire time. Horses were one of the few animals that didn't die off due to a disease. This is the same plot point from the original series, where time travelers introduced the virus that  killed off pets and animals,  leaving just mostly just Apes and horses.
Comment: In Tim Burton film they were on different planet. Kindly recheck the facts

Where did the horses come from?


Should your client know that you intend to outsource several parts or the whole project

Question: I have always wondered that people who outsource their work, meaning pay someone here or someone in another country. Do their clients need to know that it was outsourced even if they take a look at it work themselves and work with others who they have outsourced to make sure that work is of the quality they expected.
Answer: This all depends on your relations with the client and your own professional conduct.
Many contractors will simply take and pile up jobs and subcontract them without informing clients or taking care about quality of such product. Those people may have elevated progress of their business, but in long term, they will fail.
I personally tell my clients if I will outsource some part of the project (design, audio overlay, etc.) because that way my client can communicate with my subcontractor directly which makes my life easier and I don't have to spend time passing messages between them (Basecamp room is great for such conversations).
Then again, there were times when I had to code some nasty logic which was boring and I simply was not in mood to do it. So I outsourced it and closely monitored the output and the code so it fits my quality standards. A client was not aware of this. Not because I did not want to tell him or something, but because he did not need such information.
So I am always to tell your clients. If you're afraid that subcontractor may steal your client, then you're subcontracting the wrong person or team.
Comment: I would just like to add, when I was a subcontractor, I've **always** had to sign a non-compete agreement, that made sure I couldn't make contact to the client in regards to ANY other work for either 6 months, or a year, after the project was completed
Comment: When you outsource to foreign country such agreement does not mean anything. It's much better to find a good and honest team.
Comment: Canadian luke how could one enforce that contract or even find out it was being violated...in USA or outside.
Answer: I agree with Peter, if you are outsourcing your work without telling your client, how you can be a great service to them if you don't know/can't explain what your outsourced contractor has done? How can you fix the issue?
I am sure there are a lot of clever ways to deal with that kind of situation but it seems that the best way is to be honest and do the work yourself/with your team so you offer the best product and service to your clients. (All this said and done, I don't have anything against outsourcing but informing your client is a good idea. Build and maintain trust. )
Comment: you could stay in direct contact with outsourced designer multiple times a day. He would be like your distant employee.
Comment: You are right Muhammad Umer, but I am referring to being in that moment in person with a client and getting a direct question to which you don't have the answer to, because you didn't do the work. People are savvy at explanations, but I know I personally would rather be straight forward. I am not implying that people who outsource do lie but I am saying there are those that do. My apologies, I digress...
Comment: no i think you make a valid point, it's just i thought my communication medium would be email..


Combat Skill Challenges

Question: I've seen a combat run as a skill challenge before, and it worked quite well. I'm wondering, though, if anyone has made more formal rules for a combat skill challenge, beyond "pick main skills and set DCs", particularly when it comes to incorporating powers, HP, and healing surges.
Answer: I've seen combat skill challenges for things like riots and obligatory thug attacks. Any skill was usable as long as we could come up with a description of how we might use it.
For example, a riot breaks out in the marketplace the players must put down the riot and keep the innocents safe. Heal was used to tend the wounded, insight to gauge the intent or morale of the rioters, subduing the rioters called for athletics, endurance, or intimidate rolls.   Etc...  A failed roll usually cost a healing surge from being beaten by the rioters.
Sometimes, a well timed or very suitable power could gain a automatic success.  But it had to be a really creative and effective application of said power.  Usually powers would provide a circumstance bonus to a skill check.
I've never seen anyone track hp or healing powers in a skill challenge.  I guess because you might as well run a full combat then.  The healing surge penalties for failed checks usually seems to be sufficient to capture the consequences of a fight.
Failing the skill challenge sometimes has additional consequences, such as capture, etc.  But death seems too severe a penalty.  If it's a tough enough fight to kill a PC then I think it would be better run as a combat.
Comment: That sounds about right. And I agree about death. I'm digging the idea of skill challenges which make things more interesting on failure.
Answer: I recommend looking at the "Dungeon Reality Show" adventure from ChattyDM and his other writings for skill challenges. The rough change is that failures should cost the party surges and 3 failures gets them into a (probably quite nasty) combat.
Comment: I love Chatty's stuff! Healing surges are one thing that a friend DM has implemented, and I like 3 failures --> combat.
Comment: Actually, now that I think about it, try to get your hands on Baker's Poisond by lumpley games. It has what amounts to skill challenges that, when failed, always lead into fights. It could be well worth the time porting some of the conceptual framework to 4e.

Combat Skill Challenges


how to login with previous open programs when ubuntu is log out or shutdown like in kde

Question: if you open some applications in kde and log out or shutdown your computer or device you can when log in again it automatically open the last open applications.
is that possible on unity 2d and 3d ?
Comment: This sounds like suspend/hibernate to me, not shutdown. Am I right?
Answer: Im afraid the ability to save sessions was dropped in Ubuntu 11.04 due to numerous side effects. There are currently no plans to re-enable it, which is a shame. Source.
Comment: it would be nice to be enable again
Answer: There are three different general ways to accomplish something generally like this:
Firstly, suspend.  This puts the computer into very lower power mode, but it isn't truely shut down.  When you return from a suspend, everything is the same.  NOTE: if power is totally lost, the state is also lost.
Secondly, hibernate.  This takes the RAM and saves it to the swap space on the harddrive, enabling the computer to be fully shut down.  When a computer is turned back on after a hibernate, the state is loaded back into RAM, and everything continues the way it was.
Thirdly, saved sessions.  (FWIW, I suspect this is what you're referring to)  This is when the desktop environment saves which programs are open upon log out so that when you log back in, it automatically starts up those programs.  NOTE: the programs won't necessarily be in the same state they were before.
The answer depends on which of those you're wanting, and what version of ubuntu you're using.


How do I make article images that can be enlarged on mobile devices?

Question: I'm trying to enter lessons with images on my website, but the images are too tiny on mobile devices.  Is there any way to make it so they can be enlarged by clicking on them rather than trying to expand the screen?
Comment: So you are wanting a clean, screen-filling modal popup?  Not just for mobile, but for all devices?  Are your images a high-enough resolution for an enlarged view?  What are the dimensions of your original images, if I may ask?   (Generally questions that ask for coding a solution must present some effort.)
Comment: Sorry for the simplicity of the question.  I am a volunteer on a community site and know only what I have taught myself.  Yes I am looking for a screen filling modal popup ( I couldn't remember the name), and on all devices is fine since I know specifying mobile devices would be extremely difficult.  My images are approximately 750 x 500 px in their original with fairly high resolution since they are screen captures.
Answer: If the images are tiny on mobile, then an alternative (and possibly) better solution is to use CSS media queries.
For example, you can have the following CSS rule that gets triggered when the width of the screen is 360px and up:
<code>@media screen and (min-width: 360px) {
    .image-class{width: 300px; height: auto;}
}
</code>
You should then add additional rules for upper resolutions:
<code>@media screen and (min-width: 768px) {
    .image-class{width: 600px; height: auto;}
}
</code>
etc...
Note that I am assuming that your images have a width of at least 600px.
Comment: OP is seeking an onclick feature.
Comment: @mickmackusa Correct! It's just that I think there is a better method to accomplish what he wants, which is ultimately viewing non tiny images.
Comment: Sure, but this may break the intended page layout / UX on mobile. (Of course, I don't know this to be true.)
Answer: What I actually ended up doing was installing JCE MediaBox and turning all of my images in to modal image popup links.
To be clearer what I was doing was adding a lesson on using a forum with example screenshots, unfortunately I took the screenshots on the desk top version of the website so on mobile devices the text in the images was too small to read without so horrible resizing.  By turning them in to popup modals they were viewable again.


What is the best order to watch LotR/Hobbit franchise?

Question: I have not watched any of the entries in the Lord of the Rings/Hobbit franchise and as per my knowledge The Hobbit's story occurs before LotR but the release order is different. So for better understanding should I go with the Hobbit trilogy first or should I go with release order?
Comment: The only possible answers here are: "Lord of the Rings, then the Hobbit" or "Hobbit, then Lord of the Rings". Both are entirely opinionated. Sorry, but this question just doesn't work for me.
Comment: @AndrewMartin I agree with your logic. I can use facts of the movie to form my answer, but at it's core, my answer is just an opinion. Someone else that saw the movies in the same order as I did could feel that the tension does exist in the scene I describe. I'm just glad that Ankit didn't ask us "I saw a movie some years ago with a guy that has a precious ring and stringy hair. And something about a fiah...What movie did I watch?" ;) Another problem is that there isn't a definitive answer.
Comment: True - although I'm actually more than happy to *allow* this type of question. But if we do, we should change our rules to get rid of the opinion section. I think questions like this *are* a lot of fun. But as I said, if we allow them, then change the rules to allow them instead of creating one-off exceptions.
Comment: @AndrewMartin We already have rules to allow them. Remember that fuss about *"good subjective vs bad subjective"* going around now and then?
Comment: On [scifi.se]: [Should I watch the Hobbit trilogy before the LotR trilogy?](http://scifi.stackexchange.com/q/77486/10622)
Comment: Perhaps a better question is, which combination of extended and theatrical editions should one watch? (My personal take: extended Fellowship and Two Towers, theatrical Return of the King, and run run run run away from the Hobbit movies.)
Answer: I saw the films in the order that they were released and I have read the Hobbit and halfway through the LotR tome. Here is a personal opinion:
Suggested ordering:

Read the Hobbit
Watch LotR films (perhaps many times each!)
Read the LotR book
Watch the Hobbit films if the nostalgia is unbearable.

(Switching (2) and (3) can also be recommended.)
My Reasons:

The Hobbit serves at least 2 purposes: laying some foundation for the important events that take place in LotR and being a gentle introduction to Middle Earth. ME is a complicated universe with its rich history, diverse geography, many races, many languages and many maps. If you are somewhat familiar with those things, LotR (the films and the book) will be much easier to follow.

Because they are made after LotR, the Hobbit films strive for continuity and providing fan services by bringing back many elements of the first 3 films. The score, several actors, the filming angle, certain emphatic quotes and many subtle hints for the people who have seen the first 3 films. The problem is important elements such as the score and the characters (played by the actors who have aged noticeably since the first 3 films, who have to play younger versions of the characters, and who are now given a much less rich source material to work with) appear in the Hobbit trilogy as lesser versions of themselves in the LotR trilogy. So if you watch the Hobbit first, you will meet those elements for the first time in less positive light than they deserve. That will spoil your LotR enjoyment when you later watch the original trilogy.

While inferior in important ways compared to the LotR trilogy, the Hobbit films are arguably more technologically advanced and flashier. Not surprising considering they arrive a decade later. Thus, if you see the Hobbit films first, they may make you feel disappointed in certain visual effects in LotR.

Finally, LotR are universally hailed as cinematic masterpieces whereas the Hobbit films are at best good and entertaining films. If you see the latter first, you may encounter disappointments that leave behind a bad taste that hinders your LotR enjoyment.
Comment: @algiogia I normally would agree, but the LoTR series are on my list of the very few exceptions, the movies do not deviate enough from the books to create a fundamentally different or disappointing story. There are deviations and cinematic license, yes, but in this case I didn't mind and it didn't spoil it for me. Ender's Game, on the other hand, or Hunger Games: grrr. IMO, read the books first, always.
Comment: The Hobbit films arrive a decade later mainly due to legal wrangling over rights.
Comment: I suggest you either read the books after watching the movies or don't read them at all. Or just read the books. I personally don't like when directors introduce so many changes to an already good story and end upset. I could only bear to watch the first episode of LotR (had not read the book yet) and half of the Hobbit. But maybe you are not so picky :)
Answer: I would start with the Hobbit first. Some things that happen in the Hobbit franchise have no "stakes" if you watch the 3 LotR movies first. The Hobbit also gives back story for the main LotR story.
There are risks that characters in the Hobbit take. If you watch the Lord of the Rings first, you'll know the outcome of the risks, and the tension in the Hobbit is reduced.

 specifically Gandalf fighting a huge amount of Orcs in The Hobbit. Since he's in Lord of the Rings, if you see that first, when you watch The Hobbit you know that he wins the battle against the Orcs.

I found myself less invested in The Hobbit as a result.
So I guess I should specify the order I recommend:

The Hobbit: An Unexpected Journey
The Hobbit: The Desolation of Smaug
The Hobbit: The Battle of the Five Armies
The Lord of the Rings: The Fellowship of the Ring
The Lord of the Rings: The Two Towers
The Lord of the Rings: The Return of the King
Comment: The Fellowship of the ring came out in 2001, which is the point at which this particular spoiler would have been very well known, even if we ignore how well known the books are. But as I said, I agree with your overall point, just not this particular example. I suppose it would work for someone with no knowledge whatsoever of LoTR.
Comment: I take your point generally, but I think the thing in your spoiler block is so well known, I can't possibly imagine anyone going into the movies without knowing it.
Comment: The answer was written 6 years ago, in 2014, around the time the movies came out.
Answer: Watch them in release order.
It is true that The Hobbit series happens chronologically before the LotR series and that there are some characters that are in both, which can lead to some spoilers:

 For example you will know that Gandalf, Legolas, and Bilbo survive the Hobbit movies.

However, if you do anything other than just open the boxes and watch them immediately without knowing any background on the series you are probably already know that already!
Due to the Jackson additions to The Hobbit movies that directly foreshadow events in the LotR, I think there are scenes in The Hobbit that ruin parts of the LotR series.

 For example, you know the importance of Strider as a character in LotR and that Sauron's power is growing, making much of the mystery and knowledge discovery Frodo and the gang face in The Fellowship of the Rings redundant/less significant.

Further, watching LotR first has the beginning and ending of the marathon end spectacularly.

 There and back again!
Answer: There are a few interesting orders in which you can watch the six movies

The usual Hobbit trilogy first and then the LOTR trilogy.
Following the story of the one ring (lets you keep track of the one ring)
a. Watch just Galadriel's opening "The Fellowship of the Ring"
b. Then just the opening Smeagol and Deagol scene from "The Return of the King"
c. Then the entire "Hobbit" trilogy
d. Finish off with the remaining original LOTR trilogy
Following the stories of the two kings (for the best epic feel)
a. Watch the first two "Hobbit" films
b. Then the complete LOTR trilogy
c. Finally "The battle of the five armies"

Take a look at this following blog.
    https://medium.com/@rjmarvin1/the-hobbit-lord-of-the-rings-marathon-to-end-all-marathons-a-binge-watching-guide-c44f61239c4
Answer: Read the books, including Appendix A to LotR.  Many times if you like them.  Then watch the movies if you want to take the risk of having your experience ruined.
Tolkien crafted the books -- even The Hobbit -- very carefully.  The movies have minced and mangled that.  I would have understood if they had left out some characters and scenes from the books, but they have 'combined' characters in spite of at one point promising not to, and then they have added a lot of their own inventions, sometimes based on misunderstanding of the books, but more often for no good reason, and in every case disrupting Tolkien's careful narrative and world-building structure. I won't even go into the subject of making eight hours of movie from less than 300 pages of children's book on top of all that. If you think that that is OK in a movie -- after all all movies made from books do that to some degree -- then by all means see the movies in the order in which they were made -- after reading the books in the order in which they were written at least once.
Answer: I would say watch LotR and then the Hobbit. PJ added so much additional crap to the story in the Hobbit movies that I don't think it would make as much sense, or understand the importance, if you watched it the way JRRT intended it.
Which is a shame but neither here nor there....
But if you want a real adventure, I would say read the Hobbit first(it's only 270 pages or so) then watch LotR and then watch the Hobbit. Then read LotR since PJ omitted some things in that. That would be the most bang for your buck, and allow you to fully comprehend where the stories were going as you watched the movies.
Either way, enjoy!
Answer: I have a strange tip, but I hope it makes sense to others too. For this, I suggest you to watch the series in short time (less than a week for example).
In LotR there are many mention from The Hobbit.
So start with The Fellowship of the Ring. Than ask a friend about the parts that were interesting, but not clear at all. I don't suggest to Google it because of accidental spoilers. If it was in the first Hobbit movie, watch it. If in the second, watch them both, and if  in the third, watch all the Hobbit series. If the interested part wasn't in the second or third Hobbit movie, watch the Two Towers. After that, watch the rest of the Hobbit series, and close it with the The return of The King.
This way you get the partly told stories completely, and when you reach the ending film, you already know everything about Middle Earth.
Comment: "... you already know everything about Middle Earth." ... or so you think ^^. Then if you read both books, you discover much more details (and a grandiose sense of the passing of time, and of Beauty [and its loss]). And then you discover "The Silmarillion" (which regroups lots of what Tolkien wrote over much of his adult life, starting *many* years before The Hobbit/LotR) and your mind is blown as you see that everything was but a tiny part of the overall setting. I suggest anyone to read the books (Hobbit, then LotR, then the Silmarillion [don't worry about the many names, keep reading ^^]).
Comment: I agree with you about "everything" is an overstatement if you haven't read the books, but please note this site is about movies. But the correct statement really like **"you know everything that the movies can tell you about Middle Earth"**


Short story/teaser in Asimov or Clarke book

Question: I am trying to find a short story/teaser that I read in a book by (I think) either Isaac Asimov or Arthur C. Clarke. Basically, a spaceship visits a planet to resupply or something similar. They met a tribe of primitive aliens and one of the visitors thinks to himself that earlier, they would have helped the aliens to accelerate their development but now they will not be able to do that since they are fighting a war that is tearing apart their empire and civilization. Unfortunately, that is all I can remember. Any thoughts?
Comment: And is this a last ship? Or simply an expedition one in space? And what approximate time ago you read?
Comment: I think it's an expedition. They might be on their way to join the war or on some other mission. I don't remember much at all, but it's implied that the war is ongoing or just starting.
Comment: About the time: maybe five years ago.
Comment: Maybe this is a ["Green Patches"](https://en.wikipedia.org/wiki/Green_Patches) by Asimov?
Comment: That's not it, no. I read Green Patches recently and the one I'm looking for is another story.
Answer: Thoughts I certainly have, although I don't have a full answer (yet).  I've read a story somewhere in the past two months that fits the description.  I'm pretty sure it was in a Clarke collection.  I've done a bit of looking around but haven't found it yet; I'll continue hunting for that collection and update this answer when I've found it. In the mean time, though, I'd be interested to hear if this fits with the story you're looking for.
As I remember it – but this is bound to have some inaccuracies – the story I read concerned a trio of aliens who were forced to land on (what eventually turns out to be) primitive Earth for repairs, while being on their way back to their collapsing society.  They have a big, remotely controlled robot that takes care of most of their exploring, to avoid having to take risks on the unknown planet themselves.
The robot encounters a primitive human hunter.  A level of trust is established and the robot provides the hunter with meat, such as (if I recall correctly) a freshly killed sabre-tooth tiger.  The hunter takes this back to his village and his reputation soars.
Eventually, the alien crew member himself establishes contact with the hunter, and after a while even accompanies him into the village.  Not much later, however, the repairs are complete and the ship must depart.  The aliens, who would normally have nursed primitive humanity to civilisation within a relatively short time (this may have been anywhere between a couple of years or two generations), instead leave some of their high-tech tools to aid their development and increase the probability of their survival.

Edit: Indeed, as noted by Hans, this was Encounter in the Dawn. I also know now why I couldn't find it: it's not in one of my two collections of Clarke's short stories, it's contained in my edition of 2001: A Space Odyssey (after the main story) – which I recently lent that out along with six other books to a colleague who's just taking his first steps into SF. :-)
The other short story included in that book is The Sentinel.  Both of these served as inspirations to 2001: A Space Odyssey, and I found it nice to read them together and note the parallels.
Comment: This sounds very much like the one I was looking for. Will try to find a copy and have a look.
Comment: Found it! It was indeed Encounter in the Dawn.
Answer: Arthur C. Clarke, Encounter in the Dawn, first published in 1953. No, my memory isn't that good, but I do own ACC's The Collected Stories. All his short stories, chronologically. Some quotes from the story.

It was in the last days of the Empire.
The ship held only three occupants, ...
The swaying motion of the picture as the robot walked forward...

Village, primitive native, all as you described. The story ends with a revelation that it was Earth.
Edit: Oliphaunt's description is a perfect match. My compliments on your memory. Your user name is well-chosen. ;-)
Comment: That's the one!


Why is the bottom of my cactus discolored and soft?

Question: I got this cactus a couple of years ago but in the last few months I have noticed the bottom half getting brownish and soft. I water the cactus about once every 6-8 days and it gets a lot of direct and indirect sunlight as it sits on a SE facing windowsill. I have fertilized the cactus once with a cactus and succulent fertilizer. I also repotted it and the roots looked healthy (a white creamy color). I live in the Baltic.
Answer: It's not clear from the photos, but cactus often have corking or browning of the lower stem near the soil line. It is not normally soft, so that is a concern.
If you could take a picture or two with better light on the lower stem that would be helpful in determining if you have normal corking or if something else is going on.
Your cactus is a Echinocactus grusonii which are fairly robust. Unfortunately, it won't flower until it gets bigger than your head.
Do you know why the lower spines look stained red? I've never seen anything like that.
I caution you to water when the soil is mostly dry rather than on a time table. When it's cold and/or humid the time between waterings should be greater.
It's a good looking plant, I hope it's just corking.
Comment: The spines have always been red, thats why I got it in the first place. Unfortunately I don't think it's normal corking. In better light you can see how there is a very visible line between nice bright green and the slightly brownish green.  I will get a better picture in the morning.
Comment: Oh, I got a better picture, ill add it.
Comment: Yeah, slightly brownish green doesn't sound good. I can sort of see it in the current photos. The red spines are weird. Here in the US. some stores paint their cactus (mostly the spines) for marketing (?). If it is rotten, cutting the rotten parts off ASAP is the way to go. You may be able to root what's left. If you cut the rotten off at the line and the rot goes up into the plant body, you'll have to keep cutting until you don't see rot and/or toss the whole thing.
Comment: I don't think it's rot. I water it after the soil is bone dry, is it possible for rot to develop like that? Only maybe the bottom 1/5 of the cactus is soft, some of the discoloration is hard as well, just like healthy tissue. And yes im pretty sure the spines were just painted I remember when I got it the red spines were up to the half way point but now those have gotten replaced with new ones.
Comment: Cactus like that, I'd water once a month.
Comment: @WayfaringStranger It depends entirely on what conditions it is in and how fast it is growing. If it really likes the temperature and light levels you could water it every day and it would love it. On the other hand when it was in its dormant period over winter, I wouldn't water it at all for 5 or 6 months if it was mine!


Are there any tools to throttle/aggregate multiple outgoing emails into a single email within some time window?

Question: We're developing an application that runs on multiple hosts and emails
notifications to us (the developers @gmail.com) whenever something
goes wrong, via a postfix server.  However, we've run into issues
where the application spews hundreds of such errors in rapid
succession, leading Gmail to bounce our messages.  This is why we're
interested first and foremost throttling messages, but ideally also
aggregating messages together into a periodic digest that is emitted
at most once per minute.  Are there any tools or Postfix extensions suitable for us?  Thanks.
Answer: Mailing list software like maiilman is capable of sending out message digests, but I guess those are intended for daily sending, not once a minute.
What about running your own server for this purpose that accepts as many mails as necessary?
Answer: Error reporting via email is a quick hack - but as you're discovering its far from an ideal solution.
At best, the solution you propose will delay sending out notifications.
I'd recommend having a look at Nagios. In addition to scheduling checks to run on systems it can also be cofigured to accept notifications about system status from other sources (e.g. email) then make intelligent decisions about notifications, automated responses and escalations.
Comment: +1 for addressing the real problem
Answer: Could you not write your application to send errors to a log file and then send that file to you via email periodically if it is not empty?
It may be preferable to handle these errors at this level as you will have more control over the processing.
Answer: Usually I prefer mailing list software such as Mailman or Majordomo, or Policyd for implementing sender quotas etc in Postfix, but just to be different this time:
If you're willing to write some Perl, qpsmtpd can be hooked to Postfix by using the content_filter parameter in Postfix. Just write your own qpsmtpd-plugin which keeps track of throttling and/or queues the messages and combines them as a single message before finally sending them out.
This might sound like a lot of work, but should actually be surprisingly easy. Couple of years ago I wrote a plugin which throttled mail sent via PHP and started to quarantine them after a certain threshold to prevent script-kiddies spamming. The threshold bookkeeping was done in MySQL. The whole script, including comments and a short help section, was only 132 lines of code.
qpsmtpd is bundled with many plugins already, so just learn the basics from those and write your own. This might lead to reinventing the wheel.


Simple C program in Elastic beanstalk

Question: I think what I'm trying to do ought to be trivially easy for anyone who knows what they're doing, but the only language almost without exception that I've ever programmed in is C.  I do so poorly.  I'm trying to create a webapp on elastic beanstalk that talks to a C program.  My current plan is to use JNI to create a native function that I can call on the main jsp page when someone fills out a form and presses a button.
So far on the C end I've written a function that contains the 7 input variables and the 7 output variables needed for the C program to do everything it needs to do.  I don't need to access a database or do anything hard, I just need to pass 7 variables in and 7 variables out.
I've set up a java class that has a native method.  I gave it a main function that sticks in dummy variables and prints out the results.  The JNI works when I compile it all in one directory without any package names or anything that complicates it (I can't get it to work with package names.)  So I have a .so file, and a .class file and that all works.
On the other end I've taken the initial introduction webapp that AWS gives you.  Downloaded it to my machine and unpackaged the war file (Eclipse adds a bunch of boilerplate and structuring and I have no confidence in my ability to further complicate it with new tools like ant or something to do the compiling (I'm very comfortable with javac, javah and jar, thank you very much)). I've created a form on the index .jsp page and some javascript which takes input variables performs a function on them then sticks output data on the form.
As far as I can tell all I need to do now is call the java class from .jsp and that should link the whole thing together. I understand that there may be a better way to do this.  If I'm violating some deep principle of webapp programming or there is a security problem, let me know.  (I'll go ahead and sanitize my data inputs for example).   I can't seem to figure out exactly how to do it.  An example of a hello world doing this would be very helpful.  Do I need to stick anything in the web.xml file?  I kind of vaguely know that the .class file goes in the classes directory.  Where does the .so file go?
In summary:
Is there a simpler way to do what I'm doing (fewer languages/programs/lines of code?)
(I know there are better ways)
Is what I'm doing dangerous in some fashion?
How do I call a java class from index.jsp?
Does web.xml have to have anything?
How do I compile the JNI to find the .so file somewhere other than the .class file?
Can I stick the .so file in with the class file?
Answer: I'd put the .so file inside  $CATALINA_HOME/shared/lib folder wherever that may be.
If you don't want to put it there, maybe you want to specify the value of java.library.path as one of the options passed to the java runtime environment (e.g. java -Djava.library.path=/path/to/my.so ... ), this means you probably need to hack the tomcat launcher, or you could add this option to the JAVA_OPTS environment variable.

Simple C program in Elastic beanstalk


Dripping question

Question: Two taps drip together at exactly 1:00 p.m. One tap then drips again every 68 seconds, while the other tap continues to drip every 72 seconds. At what time will the two taps both drip together again?
Answer: HINT: If they drip together after $t$ seconds, it must be the case that $t$ is a multiple of both $68$ and $72$. What is the least common multiple of $68$ and $72$?
Comment: Thanks for your help. I appreciate it.
Comment: @Perry: You're welcome.
Answer: Find the smallest $T$ such  that $T=68 m = 72n$ for some $m,n >0 $.
$\text{lcm} (68,72) = 1224$ (seconds), so the time at which they are the same again is 1pm+1224 seconds, which is 1:20:24pm
Answer: LCM of 68 and 72=1224
Therefore, time in minutes=1224/60=20 min 4 seconds
That's why another drip with the two drops together will be at 1:20:4 pm
Answer: HINT: if they want to drip at the same time, it needs to be:
72*x mod 68 =0.
72 mod 68 = 4
4 * ? =68
if you solve the "?" you need to multiply the value of "?" with 72.
Then u got the seconds to the next drip together.
transorming to minutes etc should be easy

Dripping question


Can the Shut Down button be removed from the Start Menu?

Question: I often have to remote onto live servers. When I'm done, I go to the Start menu to log off, but the Shut Down button is always lying in wait for me and trying to get me to shut down a live server. Is there any way that it can be removed from my Start menu e.g. registry switch? If it could be removed on a per-user basis, that would be even better.
Answer: Here's a good Microsoft KB article that describes what you are after.
Lock down Win2k3 Server using group policies
Relevant section:
<code>[User Configuration\Administrative Templates\Start Menu & Taskbar]
* Disable and remove the Shut Down command or Remove and prevent access to the Shut Down command
</code>
Comment: The problem here is that disables shutdown, and doesn't just hide the button.  :|
Answer: As it 1) brings up a dialog with options to log off, restart, shut down or disconnect and 2) if you select shutdown it will warn you and require another confirm - doing it by accident doesn't seem too likely...
...if the user is not an administrator, only the log off and disconnect options will be enabled.
Update: dkbits answer would be the best way to go if you really want to remove the button ^^
Answer: It can be removed using group policies. Either with a domain controller security policy or a custom one applied to the server or user.
Expand, Configuration>admin templates>start menu and taskbar and choose the remove and prevent access to the shut down command and enable this policy.
if you need to shutdown the server with the button missing you can use "shutdown -i" from the command prompt


Volume Button (Lumia 535)

Question: My device is a Lumia 535. It has a about 5 inch screen. This makes it a bit difficult to take selfies  because you have to click the click option to take a picture. Isn't there a feature of clicking a picture with the help of the volume button. Is this only with my device or is it the same for such a model?
Answer: I would like to suggest an easier option to counteract the need of pressing the screen, which often results in blurry or shaky photos.
Go under the Lumia Camera and switch to the front camera, then click the gear icon to view the camera settings, then under that, you will see a timer option:

Change the option to the number of seconds you prefer.
Alternatively, you can download the Lumia Selfie app, which virtually has the same option of taking selfies using a timer.
Answer: You can take photos while taping anywhere on screen. such a feature is available on inbuilt camera app as well as on lumia camera. i guess, its more easier than pressing volume down button. give it a try
Comment: The inbuilt camera app does not support this feature you are saying.
Comment: Yeah...."I can't tap anywhere on the screen to take photo" for inbuilt camera app on my 535 as well. Please rectify it.

Volume Button (Lumia 535)


What is preventing the United States from printing USD to buy up prized assets from foreign countries given that USD is the world's reserve currency?

Question: USD is accepted all over the world. U.S can easily print USD to buy up the most valuable assets from all over the world. Ethics aside. What is preventing the U.S from doing so? What did I miss out?
Answer: To a certain extent it can.  But not too much, else it will create a run on the dollar.  If speculators no longer trusted the dollar, they would sell it for other stores of value (like Euros, gold, etc...).  Foreign dollars would have to come home and be redeemed by real wealth which means less real wealth for the US domestic economy and inflation.  This can feed on itself and cause a self-reinforcing inflationary fire that would be difficult to put out.
Answer: Any increase in the money supply causes an increase in prices (inflation), which is exactly the same as saying a reduction in the purchasing power of the currency. If foreigners believe the USD to have lower purchasing power, then they'll want more USDs in exchange for a unit of their currency (or in exchange for their stocks, bonds, physical assets, goods, services, prized assets etc).
If the federal reserve printed a LOT of new USD, then the effect would be very noticeable.
In case you're wondering why the USD hasn't depreciated a lot since 2008 (when the fed began very loose monetary policy including huge amounts of quantitative easing, i.e. printing more money), that's because other countries (especially US trade partners) were affected by the global recession too; so their central banks engaged in similar policies causing the USD to appreciate back up to pre-2008 levels.


Domain-member Win7 system can't access Ubuntu share

Question: I have a home network with the following computers:

Windows XP SP3 (workgroup: MSHOME)
Ubuntu 10.04 LTS (Samba, workgroup: MSHOME)
Windows 7 Ultimate company laptop (domain: XYZ)

XP <--> Ubuntu works fine
Both XP and Ubuntu are on the same workgroup, and they can access each other's shares just fine.
Win 7 <--> XP works fine
My Win 7 work laptop (member of a domain) can also access shares on the XP box (using credentials <hostname>\<username> and <password>), even though the laptop is not a member of the MSHOME workgroup.
Win 7 <--> Ubuntu ... not so much
For some reason, I can't access shares on the Ubuntu box from my laptop. I can see the shares if I type \\<hostname>\ into Win7 Explorer. However, clicking on a displayed share in Explorer produces a credentials prompt, and no matter what I enter, I get a permission denied message.
Interestingly, I get a slightly different error message if I type in an intentionally incorrect password, so I believe things are working up to a point...
The Samba Server Configuration app in Ubuntu has some different Authentication Mode settings. The default is User, and I haven't changed it.
Has anyone dealt with this configuration (Win7-domain / Samba-workgroup)?
Any help would be greatly appreciated. I've been searching online and trying various things, but no joy. I don't know how to see what's actually happening behind the scenes, so it's just down to trying every combination I can think of until it works...
Answer: I suspect the Windows 7 laptop is automatically adding domain XYZ to the username.  Have you checked the logs on the Samba server to see what it's reporting?


Revolving the area between two functions about an axis

Question: I'm trying to graph the revolution of the area between two functions about an axis, but I'm new to Mathematica, and not sure how to proceed. My area is defined by
Plot[{x^2,x},{x,-5,5}, Filling -> {1->{2}}]

Just to clarify, the figure I'm looking is 3-dimensional, and could loosely be called a toroid.
How could I model this in 3D?
Comment: [closely related](http://mathematica.stackexchange.com/a/27649/5478)
Comment: @Kuba somewhat related; I'm just trying to graph the toroid (and not the actual curves), not calculate the area.
Answer: Show[Plot3D[{(x x + y y), -Sqrt[(x x + y y)]}, {x, -5, 5}, {y, -5, 5},
            RegionFunction -> (#1^2 + #2^2 < 25 &)],
     RevolutionPlot3D[{5, t}, {t, -5, 25}, Mesh -> None,
                      PlotStyle -> Directive[Orange, Opacity[.5]]]]


Backup before installing Windows Vista SP2?

Question: Is it necessary to back up data before installing Windows Vista Service Pack 2 (SP2) from online updates?
Answer: No, it is not necessary, but it is recommended.
Service Packs are many updates all packaged together, and it only installs the updates in the SP that are not already installed or up-to-date.  However, there is always the chance that an update can mess up your computer, etc, and with a SP, you should backup, just in case.
Answer: You should always back up important data before critical system updates. That's what they tell you anyway. It's better to make a complete system backup in case you are left with an unstable system rather than backing up just single files.
That said, I think that 99% of people do their service pack updates without backups and it should be fine.
Comment: Good answer. Think broader - you should ALWAYS back up important data, certainly before a major system update but really you should do it on a regular basis anyway!
Answer: Yes, this site and other forums are full of posts about lost data for one reason or another.
You should Always have a recent backup of your important data.
In addition to a backup of your data you could make a system image of the hard drive before you install a Service Pack as suggested by  member slhck.
Vista Business and Ultimate have this ability to make a System Image built in, otherwise you would need to install software to make a system image, something like This Software
When windows installs a service pack it automatically creates a Windows Restore Point, which can be useful to roll back the service pack install if things go wrong, but should not to be relied on as a replacement for data backups or system images.
System Restore in Windows Vista
System Restore from a Vista Install disc or by using F8 at boot time


How can I import the accounts from truffle develop into MetaMask?

Question: I use truffle develop. It seems to me that the accounts in truffle develop are persistent. Pleas correct me if I'm wrong. How can I import the accounts from truffle develop into MetaMask?
Comment: How do you connect to your node with truffle ? is it testrpc or mainstead  ?
Comment: I use truffle develop which was introduced in truffle 4.0.0 instead of tesrpc. It has the same functionality like testrpc but it runs on port 9545.
Comment: yup,if its testrpc it does not mean persitent,every time you run truffle develop a new node is created for you to deploy changes and deployed contract address would also change. Your question seems like you want to import between nodes i.e from testrpc to metamask which i think is not feasible.  TestRpc has its own node setup and account while Metamask has its own account and node setup. One possible way is to make Metamask point to your testrpc account but not the reverse.
Answer: With release V4.0.x of the Truffle framework, whenever you start Truffle using truffle develop it starts a new local in-memory Ethereum private network using the same 12 word mnemonic:

candy maple cake sugar pudding cream honey rich smooth crumble sweet treat

It is, therefore, possible to import the accounts into MetaMask by following the following simple steps.
When you open MetaMask in your browser, there is an option to "restore from seed phrase":

Enter the truffle develop phrase and then click on okay:

Press the "create account" up to 10 times (as many as you want access to) - it will generate the same addresses as seen in the truffle develop console (it's a deterministic process):


What is a code-kata and what is it good for?

Question: in the past few weeks I have heard about a phenomenon called 'code-kata'. When I get it right, it means coding an exercise again and again. What is its point? Does it improve your abillity to design better software? If yes, why does it do so?
Comment: For more info see this question: http://stackoverflow.com/questions/1432485/coding-katas-for-practicing-the-refactoring-of-legacy-code
Comment: I've heard that Robert C. Martin has blogged about this topic: http://blog.objectmentor.com/articles/2009/11/21/whats-all-this-nonsense-about-katas
Answer: This was the first time I've heard of this, so after a quick google, here's my gut reaction:
Code Kata is not repeating an exercise over and over again.  Rather it's about constantly expanding your "comfort zone" so you can grow as a developer.
Simply working on projects that you know how to do won't help you.  You need to try and tackle projects that you would most likely fail at on your first attempt.
The end goal is that if you continuously try, fail, try again, fail again, etc, sooner or later you will succeed.  When you do, you've mastered some new knowledge, and become a better developer.
Enough repetition of this will obviously improve your skill.
(Sorry if it's a bit of a brain dump)
Answer: I collected a bunch of references here: http://slott-softwarearchitect.blogspot.com/2009/08/code-kata-resources.html
The most important of these is http://codekata.pragprog.com/
Comment: The second link points to a good explanation - thanks.
Comment: @Roland - I agree, really explanatory link. I found this link for some hands-on - http://tddkatas.codeplex.com/
Comment: Codeplex repository moved to Github: https://github.com/garora/TDD-Katas
Answer: It's not primarily to improve your design skills, rather it is a way to improve your productivity in your chosen IDE.
Repeating a familiar task over and over again allows you to watch out for and take advantage of IDE shortcuts and features that you were previously unaware of to shave seconds from your time. It will also help you find any unnecessary steps you take out of habit so you can cut them out of your routine.
Answer: We tried a few of these at my company, our thoughts were to develop a simple game (obviously something with a bit of logic we'd not know how to do). We'd all have a go at doing it, then we'd keep improving it as much as we could until we thought we had the best way to do things, then we'd meet up again maybe a week later and compare our results. It's interesting to see how different people come up with different solutions, and everyone learns from the experience. Maybe not a proper kata, but we always try and bend these things to something we'd find useful :)


Forgot to add spices to curry

Question: I made a jalfrezi today for tomorrow and I forgot to add spices, (cumin, tumeric, paprika).
Is there a way I can add them now getting the most from them?
Answer: You will need to cook the spices before adding them, but you can add them in now and it will be fine. You can either dry-roast the spices in the pan or cook them in a little oil like making a tadka.
Probably if the cumin is whole, dry roast it until it starts to turn golden then add the turmeric and paprika and cook it for just a few seconds more. If everything is powder, I'd heat a bit of oil and add all the spices at once and cook for a few seconds.
If there is coriander, too, though, I feel that needs a bit more cooking.
The flavors will blend overnight in the fridge, and further when you heat it before serving, so as long as the spices are cooked, it is fine to just mix them in.
Comment: @Lilienthal, one reason is that cooking spices in oil can help release their flavors and distribute them through the dish. For example, 3-5 sprinkles of cayenne pepper cooked briefly in oil is enough to spice up three good servings of bhindi masala. Those same three sprinkles would probably only be good for one serving uncooked, and would give it a harsher flavor.
Comment: I agree with using a tadka; try as much as possible to replicate the cooking conditions of the recipe for the spices - e.g. if the spices are added in several different batches, with the first batch cooked in oil, do that as much as you can.   The spices alter in flavour depending on whether they are cooked in oil or water (different flavour compounds are extracted) and for how long.  An essential part of most Indian recipes is "bhuna"; dry frying the spices in oil, and is crucial.   Letting it sit overnight after blending will also help.  It will never quite be the same, but it may be close.
Comment: You cook the spices because they would have been cooked in the normal cooking process and their flavor changes in cooking. If you add then without cooking they will taste raw.
Comment: Why do you need to cook the spices though? To enhance the flavour? Make them palatable? Render them safe for consumption? Make the absorption of flavour in the final dish easier?
Answer: Use one of these small pans to add spices later on. You can use it directly over the flame. Pour some oil in it and bring it to heat, add cumins and other spices and cook it for some time. Then add the cooked spices in your jalfrezi.. :)
Answer: I'm wondering what you did cook. Spices are such an integral (and usually fundamental) part of Indian cooking that omitting them is going to leave you with a completely different dish.
So take out those spices and you're left with:

Meat
Onion
Tomatoes
Chilli
Garlic

So yes, you could fry up some spice in some more oil and mix that through your existing batch. There are food-safety issues here so if your meat-and-tomato dish is already cooled, I'd probably save this step for when I was reheating it for serving.
Don't add a hot oily spice mix to a cooled meat dish and then cool the whole lot again.
But will it be good? Again, with a Jalfrezi, you'd start by frying off the spices on the meat. I assume your meat wasn't pre-prepared (eg tikka'd) so adding the spice now is going to see very limited flavour penetration.
What you do have is a fairly solid base for a lot of Italian dishes. Stir in a bunch of fresh herbs (oregano, basil, parsley, thyme, etc) as you're reheating and it'll likely take on enough flavour for an Italian style dish.
Comment: Thanks for the info. There is no meat, and the sweet potato and chickpeas take some of the Italianness from it

Forgot to add spices to curry


Mixing Windows and Forms Authentication in ASP.NET MVC

Question: I'm currently trying to set up a website that uses both windows authentication and forms authentication.  I am using ASP.NET MVC and both IIS6 and 7 need to be supported.  How would I go about letting known AD users into the app (their AD id is stored against their user record in the application database) and directing everyone else to a standard username/password page.
Answer: It seems the answer is no.  We've had to set up 2 sites, the main application with forms authentication and a separate windows authenticated site which redirects to the forms site with a token which expires quickly telling the forms site that an authenticated user is incomming.
Answer: What about the option using custom 401 redirect at IIS level outlined in this article


Basic properties of symmetric difference in sets: $A \Delta B=A \Delta D$ implies $B=D$

Question: How can I prove that for any sets $A,B,C,D$
if
$$A \Delta B = C  $$
and
$$A \Delta D = C  $$
then $B=D$.
Where $\Delta$ denotes symmetric difference.
Comment: Sorry, I mixed it up with something else.
Comment: Related question: http://math.stackexchange.com/questions/537172/a-oplus-b-a-oplus-c-imply-b-c
Answer: First show that $\Delta$ is associative and has inverses; namely, every set is its own inverse. Then apply $A$ from the left to both equations and use what you proved in the first step. In doing this, it may help to think of the symmetric difference as XOR.
Answer: The probabilist in me cannot resist mentioning that symmetric differences can (and maybe they should) be approached through indicator functions modulo 2.
Recall that, for every $A\subseteq E$, the indicator function $\mathbf 1_A$ is defined on $E$ by $\mathbf 1_A(x)=1$ if $x$ is in $A$ and $\mathbf 1_A(x)=0$ if $x$ is in $E\setminus A$.
Then, for every subsets $A$ and $B$ of $E$, the set $C=A\Delta B$ is uniquely characterized by the fact that $\mathbf 1_C=\mathbf 1_A+\mathbf 1_B\pmod{2}$ (can you check this?).
A host of properties of $\Delta$ become obvious with this approach since $\Delta$ is simply the sum in the group $\mathbb Z/2\mathbb Z$. For example, your hypothesis is that $\mathbf 1_A+\mathbf 1_B=\mathbf 1_C=\mathbf 1_A+\mathbf 1_D\pmod{2}$ hence $\mathbf 1_B=\mathbf 1_D\pmod{2}$. And this is enough to guarantee that $B=D$ (can you check this?).
Note equivalently that, in every group $(G,\ast)$, the identity $g\ast h_1=g\ast h_2$ for some $g$, $h_1$ and $h_2$ in $G$ implies that $g^{-1}\ast g\ast h_1=g^{-1}\ast g\ast h_2$ hence $h_1=h_2$. Homework: what is $g^{-1}$ in the setting of the exercise?
Comment: Seems an expansion of @joriki's suggestion to see $\triangle$ as XOR.
Answer: $$B=\emptyset\Delta B=(A\Delta A)\Delta B=A\Delta(A\Delta B)=A\Delta C=A\Delta(A\Delta D)=(A\Delta A)\Delta D=\emptyset\Delta D=D$$
Answer: Assume $x$ is in $B$, and deduce from the given equations that it must also be in $D$. Then assume it's in $D$, and deduce by symmetry that it's in $B$. That will prove $B=D$.
Answer: Take $b\in B$:
1.: $b\notin A$. This means that $b\in C\setminus A=D\setminus A$ and hence in $D$.
2.: $b\in A$. This means that $b\in A\setminus C=A\cap D$ and hence in $D$.
This proves that $B\subseteq D$ and for the other inclusion just swap $B$ and $D$.
Comment: How do you know that $C\setminus A = D\setminus A$ ?
Comment: @Sunny88: $A\Delta D= C$ are the elements that are either in $A$ or $D$ but not in both. So if $c\in A\Delta D$ but not in $A$ it must be in $D$ (and still not in $A$, so it's in $D\setminus A$).
Answer: $
\newcommand{\calc}{\begin{align} \quad &}
\newcommand{\calcop}[2]{\\ #1 \quad & \quad \text{"#2"} \\ \quad & }
\newcommand{\endcalc}{\end{align}}
$As a first simplification, we can take out $\;C\;$ and rephrase your theorem as
$$
\tag{0} A \Delta B = A \Delta D \;\Rightarrow\; B = D
$$
The proof depends on your definition and the laws of logic that are available.
In my favorite setting the proof would go something like this:
$$\calc
A \Delta B = A \Delta D
\calcop{\equiv}{set extensionality; definition (1) of $\;\Delta\;$, below, twice}
\langle \forall x :: x \in A \not\equiv x \in B \;\equiv\; x \in A \not\equiv x \in D \rangle
\calcop{\equiv}{logic: $\;\equiv\;$ is symmetric}
\langle \forall x :: x \in A \not\equiv x \in A \;\equiv\; x \in B \not\equiv x \in D \rangle
\calcop{\equiv}{logic: $\;\not\equiv\;$ is anti-reflexive}
\langle \forall x :: \text{false} \;\equiv\; x \in B \not\equiv x \in D \rangle
\calcop{\equiv}{logic: the negation of $\;\not\equiv\;$ is $\;\equiv\;$}
\langle \forall x :: x \in B \equiv x \in D \rangle
\calcop{\equiv}{set extensionality}
B = D
\endcalc$$
This completes the proof of (a slightly stronger version of) $(0)$.
Above we used the fact (or alternative definition) that for every $\;x\;$
$$
\tag{1} x \in X \Delta Y \;\equiv\; x \in X \not\equiv x \in Y
$$
Also, we implicitly used the fact that $\;\equiv\;$ and $\;\not\equiv\;$ are not only both associative but also mutually associative.


A mythical/legendary/demonic creature that steals talents or abilities

Question: I swear I heard about this a long time ago but I can't remember it for the life of me (to the point that I am beginning to doubt if it exists). I faintly remember some type of monster that was able to mimic or outright steal the abilities of other people... Can anyone help me out here?
Comment: @SemperAmbroscus But just because we haven't found anything yet, doesn't mean it isn't there.  I'm going to do a little answer from Norse Mythology.
Comment: @LaurenIpsum I didn't think it wasI was just saying in general
Comment: @Gibet as I remember it it was more like stealing talents than superpowers, like if you were good at basketball and they touched you then they stole your basketball skill
Comment: There is a theory that defeating an enemy (and possible eating body parts such as the heart or liver) confers the power of the fallen to the victor.  Not a specific entity, but give some weight to your claim.  (However, it is possible you are conflating this with some contemporary source that took the form of canonical mythology...)
Comment: @DukeZhou yes I must be remembering a fiction rather than a myth
Answer:
The Mead of Poetry is a prime example.  The power is transferred not once, but twice:

Kvasir was a man considered most wise, who is murdered by a pair of dwarves.  The motivation of the dwarves is to create a magic potion that would confer this wisdom to any who drank it.
Odin, likely not content to allow such a power to be freely accessed, uses trickery to steal the mead, and is mostly successful.  (The part that spilled confered a lower form of capability in simple rhyming, while Odin himself keeps the greatest form of the gift to bestow at his discretion.)

Mimir is another such example:

When Mimir's severed head is sent to Asgard, Odin uses magic to re-animate it, and afterwards benefits from Mimir's knowledge and secrets.
Comment: @SemperAmbroscus  I'm far from the leading Norse expert here, but this material is very well known in that canon.  *(I was lucky to have very good teachers--the way they trained me to analyze stories from a fundamental perspective has been useful in a number of endeavors.)*  I suspect there are other examples from other canons, and I will keep this question in the back of my mind and add more examples should they occur to me.
Comment: This is more than I could have hoped for, I find it interesting how you immediately knew to look in Norse Mythology
Answer: "If that's what you want," the Patriarch replied, "come here and I'll teach you the spells." Thereupon he
whispered into Sun Wukong's ear, and who knows what miraculous spells he taught him? The Monkey King
was the sort of person who understands everything once he is told a tiny part, and he learned the spells on the
spot. He practiced and trained until he had mastered all seventy−two transformations. One day the Patriarch
and all his disciples were enjoying the sunset outside the Three Stars Cave.
Journey to the West-Chapter 2
Things like Sasuke's Sharingan come only from this part of Journey to the West.
And all the 'eyes with powers' and power to 'copy abilities'
here, 72 is not an assigned limit to Sun Wukong's power, but a number often used to denote infinity.


Membrane jacket rises up when crouching

Question: I have a trouble with my membrane jacket. When I am crouching or moving around, my jacket rises up in the back and doesn't go down when I stand up straight again. How can I prevent the jacket from doing this?
Comment: The jacket probably isn't a proper fit.
Comment: If the jacket has some way of tightening the lower hem, then if the hem is too tight, it will rise as you crouch or raise your arms but remain in place when you stand up or lower your arms.
Comment: @Austris is this problem specific to membrane/nylon jackets? It seems vague and unrelated to outdoor clothing.
Comment: What is a membrane jacket?  Is it like Gortex?  Is it friction that prevents it from falling back in place?  Is the jacket perhaps too tight?
Comment: Buy a bigger jacket?!
Answer: Sew a crotch strap: one end on the back, one on the front with quick release fittings, and length adjustable allowance.
Comment: I am perfectly serious, and have used the device. I own Musto brand foulweather gear for extreme sailing conditions; the "float coat"/PFD liner has a crotch strap to prevent the jacket from going up over my head in the event of going overboard. Also certain stand-alone PFD's use a crotch strap.

Membrane jacket rises up when crouching


Are curve physics possible?

Question: For example, I'm using a tree generator addon that creates trees in curve form. I have a strong wind forcefield in the scene as well for the grass. Is it possible to apply the curve to the physics?
Comment: It seems I was wrong, answer updated below, if it still matters
Answer: Physics and simulations generally only affect mesh or particle objects, you often have to convert your curves to a mesh.
If you are using the builtin Blender tree generator Sapling Addon it even has an option to create an animated armature with wind animation, but even then, has far as I know you will have to convert it to mesh to work.
You may keep a copy of the original curve object in a separate scene or another layer in case you need to go back and change something.
It is however possible to use some basic soft body physics on Curve objects if it is well subdivided, although it does not work very reliably.
It seems most settings don't have any effect, except for the Self Collision options, as stated Quick Noodle Physics in Blender Tutorial Youtube Video
The trick is using a highly subdivided curve, there must be lots of actual vertex (display subdivisions are insufficient), then tweak the parameters under Soft Body Self Collision like *Ball Size and Stiffness and turning off Soft Body Goal.
Some other objects set to Collision Physics type must be present at the scene for interaction.
Comment: Maybe it will be within a few updates. In the game-engine, empty physics are already possible.

Are curve physics possible?


LEXUS ES300 '99

Question: Ok so im having a problem that been happening for about 3 weeks. At one time we were at the movie drive in and my car died after 10min. Lights were all coming on and it would make several clicking sounds when you tried to turn it over. Did it again an hour later. Had to get a jump by movie workers (twice). Then it happened a few days later. We thought it was my alternator. Switched it out since i had warranty. Still the same. Thought it was my battery but it had 100% charge. Changed the terminals and it seemed to be the problem. Til yesterday... It was dying on us just sitting at pizza hut waiting for our food. We got it home as soon as we did it died and didnt turn on. We got a jump several hours later.. On our way to my moms it died at a stop light. Tried turning it over but the lights were dimmed out almost completely and it wasnt even making that clicking noise. Got a jump and as soon as i put it in R it died again. Got a jump let it sit n charge a bit and gt the car home. Now it turns on like nothing happened. while at pizza hut.. Stepping on the gas and lettin it go the battery light would come on but if we didnt the light didnt show SOMEONE please help!
Comment: How did you check to see if your battery was "100% charged"?
Comment: Took it to autozone
Comment: Does the alternator squeal at all when you first start it up?
Comment: No it doesnt do that either.
Comment: When was the last time the serpentine belt was replaced?
Comment: That i actyally dont know. Everyone keeps saying it something eletrical or one the wires or  something wet?
Answer: I think there may be one or two things happening here (but this is more of a gut check than anything):

The serpentine belt is worn out, causing the battery not to charge the battery correctly. Usually if the belt is getting worn out, it will cause a chirping sound when it slips, but if the belt is worn and glazed, it could be slipping without you even knowing it, causing a loss in electrical charging ability, and thus allowing your battery to go flat. The jump and subsequent running at a normal level allows it to recharge.
The spring in the tensioner may be weak, causing the same issue as described above. I'm not sure on your specific vehicle, but there could be a tension gauge consisting of an arrow which will point inside a range. This will show if the belt has stretched, but will also show if the spring is weak.

Considering what you said about the dash lights coming on after a rev, I'm thinking scenario #2 is the most likely. This indicates to me the belt may be slipping across the alternator after a rev, which does not allow for proper charging.
Comment: Well im about to try n drive it across town bcuz my baby daddy is my mechanic. So ill let him know wat u posted... Hopefully ill make it there.

LEXUS ES300 '99


How to place widget in Joomla 3.0 as module

Question: How to place widget code in Joomla 3.0 site through a module. Earlier in Joomla 2.5, I used Advanced HTML but could not locate in Joomla 3.3.
Comment: What do you mean by `widget code`? Is this short code that is provide by another extension?
Comment: By widget I meant Java Code that is provided for rotating banner by affiliate marketing companies like cj.com, linkshare.com. I have installed sourcerer extension which appears to be serving my purpose.
Answer:
If you want to implement a well-known widget, for instance a Facebook Like, you can find several extensions already developed and tested in Joomla! Extensions Directory http://extensions.joomla.org/
If your widget is not already developed, you look for a similar widget in JED and change the code to match your requirements. All extensions in JED are open source GPL.
If your widget is very simple, you can simply install an extension to add Custom Code in content http://extensions.joomla.org/extensions/core-enhancements/coding-a-scripts-integration/custom-code-in-content or create a module to have the HTML and Javascript code (similar to Advanced HTML), like NoNumber's Sourcerer.
Answer: The built-in Custom HTML module in Joomla can work, but if you're using TinyMCE as your editor, it will try to clean up your code, thus removing code that such Widgets might contain (usually


how can I get my sleeping cycle to normal again?

Question: in my job I have no official known work hours ,when they call I have to go to work no matter what hour it is (should've red the contract before I signed it right :-D ),this make me lose my sleeping cycle and I end up always sleeping during day and can't sleep the night ,my way to fix this is to deprive my self from sleep for 36 hours that way I will sleep during night ,but I always end up loosing that cycle again ,any good way to reverse sleeping cycle to normal without depriving my self from sleep ? is the use of some sleeping pills recommended ?
Comment: I believe that this may be a duplicate of [Reversing sleep cycle](http://health.stackexchange.com/questions/1101/reversing-sleep-cycle)
Answer: Many sleeping pills are addictive.
Many non-addictive sleeping pills can be mentally addictive.
If you do not mind using sleeping pills for the rest of your life, then that is a perfectly fine choice.
Otherwise, you may want to consider other options first.
Exercise will help. Use up your energy and your body will WANT sleep. Exercise is key to your body's cycles.
Your circadian rhythm (sleeping cycle) is largely affected by light. Particularly, artificial light gives off a lot of light in the frequency range that causes your body to think its NOT time to sleep and will screw up your cycles. When you know you have time to sleep, stay away from staring at computer screens as much as possible.
Stay away from stimulants. i.e. caffeine or whatever else you may use throughout the day/night.
The huge factor here is that you said you have no official known work hours and you go in whenever they ask you to. If that means that you never know when you might have a good 6-8 hours of sleeping time, then there really is no way to "fix your cycles" since it is a constantly moving unknown. Sleeping pills MAY be the only realistic answer in that case. However, if you are able to figure out times when you know you will be off work for a certain number of hours more often than not, then you have a good chance of trying to fix your sleeping cycle.
Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression
Evening use of light-emitting eReaders negatively
affects sleep, circadian timing, and
next-morning alertness
The Sleep and Technology Use of Americans: Findings from the National Sleep Foundation's 2011 Sleep in America Poll
Comment: What about 8 glasses of water is common knowledge? Just unsure what you mean.
What is your take, pertaining to melatonin and suvorexant?
Do you deem it as non-addictive, both physically and mentally?
Comment: "Many non-addictive sleeping pills can be mentally addictive. If you do not mind using sleeping pills for the rest of your life, then that is a perfectly fine choice." You really need to back up such statements. It may be "common knowledge", but a lot of "common knowledge" (like drinking 8 glasses of water per day) is not true at all. Look up melatonin and suvorexant, for example.
Comment: the Other options are valuable ,I mean I use computer alot specially at the after noon and night didn't know it was waking up my body because I use it for the opposite (I use computer to make my self tired !)  ,still they are a better option than pills ,I mean those pills will force me to sleep in a way to shutdown I think there is an effect for the long term can't afford the risk ,I will only if the risk of sleep deprivation is higher


My question was closed as duplicate

Question: My question about iOS 11.4 Full Jailbreak was closed as a duplicate although it was asked 1 month earlier than an "original" question. Can someone investigate this?
Answer: When we close as a duplicate it doesn't really matter which question was asked first but which question got the "better"/more helpful answer. I know that the "on hold" reason implies otherwise, but as this site is all about getting good answers the focus is more on the answers than the questions.
If things change (e.g. a jailbreak becomes available) it doesn't matter which of the questions is open or closed. People who want to answer will find the open question easily, and can provide an answer there.
PS: Whether a question about the availability of a specific jailbreak even is on-topic and doesn't qualify for getting closed due to "missing research" or "asking for an external resource" is a different matter...
Comment: Off-topic comments removed, on-topic comments still welcome :-)

My question was closed as duplicate


What kind of wood is this

Question: What kind of wood is this? It is made of a patchwork of wood pieces.
Comment: What is the size of what we are looking at?  width? thickness?  photo is kind of blurry
Answer: From the worktops I have seen that is likely to be beech.
Upside is the surface is less likely to warp over time.
Answer: It looks like finger-jointed and edge-laminated pine. If you look at the edge you can probably see the characteristic zigzag cut pattern.
It's commonly used for "paint grade" millwork such as closet shelf cleat. It's cheaper and more stable than clear pine, but you may see the grain variation through light paint coatings. Try to avoid making any end cuts directly through the joints.
Comment: Those flecks look more like beech to me than pine.
Comment: They look like dirt or mold to me. Oh, for properly focused photos. :)

What kind of wood is this


phpunit in org-mode src block

Question: I'm using phpunit package
https://github.com/nlamirault/phpunit.el and it works great with php files.
But I have a simple php blog about refactoring ex: http://phprefactor.com/refactorings/decompose-conditional and I would like to run phpunit test in org-mode src block. That would be extremely usefull in blogging about php :)
Comment: `(defun org-babel-execute:phpunit (body params)
     "Orgmode Babel PHP evaluate function for `BODY' with `PARAMS'."
     (let* ((cmd "phpunit EmailTest.php")
     (body (concat "")))
       (org-babel-eval cmd body)
       ))`

I find out that this works when I set precise file, But how can it be done to run the code in #+BEGIN_SRC ? Because when i try it gives "Code block produced no output."
Answer: Finally I make it work. The main problem is that org-mode shell source blocks do not capture stderr. You can read more about this here. So normally you will not see output if one of the test fails.
Solution for this is to save code block to temporary file and then running org-babel-sh-command on the file which in case of failure redirect stderr to stdout.
I create new config for phpunit:
<code>   (defun org-babel-execute:phpunit (body params)
 "Orgmode Babel PHP evaluate function for `BODY' with `PARAMS'."
 (let* ((cmd "./phpunithack.sh")
    (body (concat "<?php\n" body "\n?>")))
    (write-region body  nil "/home/slk500/.emacs.d/EmailTest.php")
   (org-babel-eval cmd body)
   ))
</code>
and my script phpunithack.sh looks like this:
<code>exec 2>&1
</code>
phpunit EmailTest.php
:
Example src block:
<code>#+BEGIN_SRC phpunit
use PHPUnit\Framework\TestCase;

class EmailTest extends TestCase
{
    public function testOne(): void
    {
        $this->assertTrue(true);
    }

    public function testTwo(): void
    {
        $this->assertTrue(false);
    }

}
#+END_SRC
</code>

phpunit in org-mode src block


Why 入った and not 入た past tense

Question: I've learned that ru verbs should drop る and replace it with た.
But 入る becomes 入った and I'm not sure why.
The same goes for

食べる → 食べた
しゃべる → しゃべた

Are these irregulars or am I misunderstanding something?
Comment: Note that しゃべる is a _godan_ verb, and the past しゃべった and conjunctive しゃべって both have geminate (doubled) "t" consonants.
Answer: tl;dr
入る hairu is a consonant-stem verb, i.e. hair·u.
Long version
Besides a handful of exceptions, there are two type of verbs

vowel-stem verbs (-e·ru, -i·ru)
consonant-stem verbs (-k·u, -g·u, -s·u, -t·u, -n·u, -(w)·u, -m·u, -r·u)

where I have used an interpunct · to separate the stem from the ending (and the hyphen - means there is more coming before it).
These types follow different inflection patterns.
Of course there are no pure consonants in kana, so written in kana you cannot show where the border between stem and ending is — for example a verb ending in ~く may inflect to ~か (as in 聞く → 聞かない), but written as above, the stem ending in -k does not change (kik·u → kik·anai). (This is why it is called the stem. And the stem of vowel-stem/consonant-stem verbs end in a vowel/consonant, respectively.)
Now, seeing a verb written in kana, there is no way of telling whether a verb ending in -eru / -iru is a vowel-stem verb or a consonant stem verb, i.e. whether it is -e·ru / -i·ru or -er·u / -ir·u.
The following vowel-stem–consonant-stem verb pairs show that this difference simply has to be learned:

着る ki·ru ↔ 切る kir·u
変える kae·ru ↔ 帰る kaer·u

In particular, their past tenses are different

着た kita ↔ 切った kitta
変えた kaeta ↔ 帰った kaetta

Now, 入る is hair·u (i.e. a consonant-stem verb), so its past tense follows the same pattern as 切る, giving 入った.
However, the way the verb is written in kanji gives some way of guessing whether it is vowel-stem or consonant-stem. As a rule of thumb (for verbs of three or more morae), if the -i or -e is part of the kanji, then a verb is more likely to be consonant-stem.
In particular, since はいる is a three mora verb, written 入る rather than *入いる, it is more likely to be consonant-stem. The rule also correctly identifies 食べる as a vowel-stem verb (→ 食べた) and 喋る【しゃべる】 as a consonant-stem verb (→ 喋った).
Comment: Thanks for the explanation! Although @EiríkrÚtlendi his answer was very clear as well, I found your's just a bit easier to understand. But thanks to both of you.
Comment: Jinx!  :) .......
Comment: @EiríkrÚtlendi ハッピーアイスクリームお返しなし! =)
Answer: The name "ru verb" is misleading.
This does not mean that every verb ending in -ru conjugates the same way.
Certain verbs end in -ru, and that final -ru disappears in entirety when conjugating.  These are called 一段活用 (ichidan katsuyō, literally "monograde conjugation" or "one-step conjugation") verbs in Japanese grammars, because there is only one vowel on the end of the verb stem (either -i or -e).  These are often labeled as "type 2" verbs in English texts about Japanese grammar.
One everyday example is 食べる (taberu, "to eat"), where that final -ru just disappears entirely in conjugated forms:

taberu "[I / he / she / they] eat", plain informal
tabenai "[I / he / she / they] don't / doesn't eat", plain negative
tabemasu "[I / he / she / they] eat", polite
tabesaseru "[I / he / she / they] make someone eat", plain causative

... etc.  As you can see here, the -ru vanishes entirely in the conjugated forms.
Other verbs end in -ru or -ku or -su, etc., and that final piece doesn't quite vanish entirely -- the consonant remains, but the vowel changes.  These are called 五段活用 (godan katsuyō, literally "quintigrade conjugation" or "five-step conjugation") verbs in Japanese grammars, because there are five different possible vowels on the end of the verb stem (-a, -i, -u, -e, -o).  These are often labeled as "type 1" verbs in English texts about Japanese grammar.
One everyday example with -ru is 入る (hairu, "to enter, to go into"), where that final -ru doesn't disappear entirely, and only the vowel changes:

hairu "[I / he / she / they] enter", plain informal
hairanai "[I / he / she / they] don't / doesn't enter", plain negative
hairimasu "[I / he / she / they] enter", polite
hairaseru "[I / he / she / they] make someone enter", plain causative

As you can see here, the -r- sticks around, and the vowel changes.
Things ultimately get a bit more complicated than this (such as the conjunctive forms and plain past forms, where you often get geminate [i.e. doubled] consonants instead of the final consonant, as in haitta), but that's the basic framework.  There's good information on Wikipedia, at https://en.wikipedia.org/wiki/Japanese_verb_conjugation.
Answer: The rule for '-ru' (ichidan) verbs and '-u' (godan) verbs is 'anything ending in '-iru' or '-eru' can be a '-ru' verb. But 入る and しゃべる are not; they are '-u' verbs that conjugate as you would expect.
Comment: Thanks for the answer. I guess I missed that they can be godan. Would they count as irregulars? Our does that happen a lot?

Why 入った and not 入た past tense


Visual Studio 2012 is Missing "Workspace Settings" Tab

Question: On the Team menu, Team Project Collection Settings, Source Control window there should be two tabs, "File Types" and "Workspace Settings".  Some of our developers do not have the "Workspace Settings" tab.  What determines if this tab is available?  Thanks.
Answer: This is a TFS 2012 feature, I think there might be a bug that's causing to appear on TFS 2010 instances. I'm guessing if you have ever connected to a TFS 2012 instance it will appear.
When changing the value in TFS 2010 it won't do anything. You just get the following error:


What's the significance of the roses on Oskar Schindler's grave?

Question: Jews have a tradition of placing stones on the grave. In the Film Schindler's List, in the ending scene everybody places stones on the grave of Oskar Schindler. But Liam Neeson places a pair of roses on the grave and stands over it. What does this signify?
Comment: In the concentration camp Jews were given a stone (instead of bar of soap) before going in to the "shower." They are gassed instead of getting the shower. Perhaps this the reference to why stones are placed on his grave.
Answer: According to the movie's FAQ on IMDB.com, Neeson's reason was "for respect and the fact that he was proud to portray such a historical figure."
Also, the scene shows actual Holocaust survivors as well as the actors who played some of them. I believe it is only the survivors, not the actors, who place stones on the grave. So perhaps it would not have been proper for Neeson to place stones on the grave, leading him to use roses instead.
Answer: The previous answer is good, but for a little more detail of the tradition of leaving stones, here's my two cents.
Jewish people leave stones instead of flowers for a variety of reasons, many with Talmudic roots that I'm not educated enough to explain. For a more complete explanation visit Mi Yodeya, the Judaism SE. However, one of the primary reasons is that stones offer permanence and solidity. They are a standing testament and remembrance. Unlike flowers, they don't wither and need to be removed or replaced. They become part of the monument.
Neeson may have felt that both due to his non-Jewish identity and the fact that he is an actor, not a survivor, that it was inappropriate for him to leave a stone and permanently alter the gravesite. Flowers are a good alternative for him to pay his respects in a less invasive way.
Comment: Good example of multiple answer for single question. +1.
Answer: If you watch the end closely you will notice that both the Schindler Jews and their actor counterparts place stones on the grave. We only see Liam Neeson's forearm and hand as he places the two red roses. I believe Neeson uses roses to show his respect instead of a stone and he knows his portrayal is as temporary as the flowers. Red was used as a connection to the little girl in red who symbolized the innocence and death of the 6,000,000 Jews butchered by the German Nazis.
Answer: The red roses, I think, are supposed to suggest the little girl in the red coat. Much has been discussed, of course, about exactly what the little girl and her coat signify, but whatever that may be, I think the link is obvious.
Answer: Roses are an Anglo Saxon custom.  Stones are a Jewish custom meaning I have been here and I have remembered you.  Ditto for the Anglo Saxons.
Comment: Do you have supporting internet links for these cultural / religious attributes?
Comment: For the Jewish custom of stones there are many sources online.  One I like is at https://www.jcam.org/Pages/Foundation/visitationstones.htm
Answer: The roses places by Liam Neilson are out of respect for the man he portrayed.It doesn't signify much more than that. A man paying his respects, as we all should (and we may even say on our behalf as an audience) to Oskar Schindler.
The stones are stones of rememberance. It is a Jewish custom daiting back to the book of Genesis with placing stones as a marker in a place where something happened to remember the event. They are also placed on graves as a form of rememberance for that person. The stones recall or commemerate a person's life and deeds.
Answer: I think they did it as a proof of respect for his religion, since Oskar promoted space for their faith (Rabbi scene), beyond their survival. Oskar practices catholicism as we can see in his final pray, so I think they show their gratitude as Jews with the stones and then end with the rose in the fashion of Oskar's own tradition.


How did Kate survive being shot?

Question: In The Blacklist, how did Kate survive being shot? I thought that Raymond didn't want to kill her but she said that he shot her in the head, so she couldn't protect herself and he doesn't miss.
Comment: I haven't seen the Blacklist, but in reality, getting shot in the head isn't *always* as fatal as it might seem.  (Not that I would recommend the experience in general.) https://www.reddit.com/r/IAmA/comments/97963/i_was_shot_in_the_head_2_years_ago_this_is_what/
Comment: because not everyone dies when there shot in the head.
Answer:
•Gunshot wound head trauma is fatal about 90 percent of the time, with many victims dying before arriving at the hospital.
  • For victims who survive the initial trauma, about 50 percent die in the emergency room.
  • About 50 percent of surviving patients will suffer from seizures and require anti-epilepsy medication.

According to the American Association of Neurological Surgeons, humans have a 5% chance of surviving a GSW to the head, assuming that medical attention is forthwith (fifty percent of which will have chronic problems afterwards) as "The main cause of death at the scene is usually blood loss".
So, there's a 2.5% probability that she will recover fully. This seems likely as she does not appear to exhibit any signs of TBI.
E.g., there's no loss of "[motor, sensory, cognition, memory, speech, or vision]" (all of which either require one side of the brain or both).
In short, she was extremely lucky and received prompt medical attention. We can blame thank Red for failing to "double tap" and confirm his kill. That would have brought the odds to ~1% or zero, respectively.
Answer: Maybe Red didn't really want to kill her and missed subconsciously, because Kate is injured in the face/temple region... not right in the forehead.
Comment: That's what I think
Answer: Pretty sure they discuss this later in the show.
Red didn't want to kill her and was very shaken by the whole ordeal. She was one of his closest, dearest, most  trusted friends for at least 28 years. Shooting such a friend is very hard emotionally and he was physically shaken by the situation. You can see it in his immediate reaction of hem turning around as fast as possible and just walking away.
This is in stark contrast with pretty much every other kill that Red commits.
All this added up to his aim not being 100% on point so her brain wasn't damaged and thus she survived.
Edit: Few episodes later Red indeed explains how he didn't double-check the body and by that time it is revealed Kate has a metal plate in her head from an earlier accident in the exact same spot.

How did Kate survive being shot?


Is a simplified function the same as the original?

Question: Is a simplified function the same as the original?
Example:
Let $f(x) = \frac{ax}{x}$, and $g(x) = a$
where $a$ and $x$ are real numbers.
Does $g$ = $f$?
Comment: One has a "hole" (a *removable discontinuity*, that is), and the other doesn't have one.
Answer: A common convention for real functions of real variables is that of the "natural domain of a function":

If a function $f$ is given by a formula, and a domain is not explicitly specified, then the domain is understood to be the "natural domain of $f$", which means, all real numbers for which the formula makes sense and yields a unique output.

Another common convention for this type of function is that two functions are considered to be equal if and only if they have the same domain, and they have the same value at each element of their domain.
If we take both conventions, then
$$f(x)=\frac{ax}{x}\quad\text{and}\quad g(x) = a$$
are not equal, because the domain of $f(x)$ consists of all real numbers except $0$; whereas the domain of $g(x)$ is all real numbers, including $0$. Since $f$ and $g$ have different domains, they are not equal as functions.
On the other hand,
$$f(x)=\frac{ax}{x}\qquad\text{and}\quad g(x)=a, x\neq 0$$
are equal, because "$x\neq 0$" after $g(x)$ is specifying the domain explicitly, which means that $g(x)$ now has the same domain as $f(x)$ (all $x\neq 0$), and they have the same value at every point in their common domain.
If you are operating under these conventions (which are the usual conventions in, for example, most calculus textbooks in the U.S. that I am familiar with), then when you simplify the formula for a function, you should check to see if you haven't implicitly changed the domain. Some simplifications don't matter; e.g., $f(x) = (x-1)^2-1$ and $g(x) = x^2-2x$ are equal as functions (same domain, all real numbers; and same value at every real number). Others do (such as the one you did).
Answer: It depends on what you take to be the domain of each. If they're given the same domain (which of course cannot include $0$), then they're the same function. For example, considered as functions with domain equal to the set of positive real numbers, $f=g$.
If you give them different domains, however, they are no longer the same function, though it is still true that $f(x)=g(x)$ for all $x\in\operatorname{dom}f\cap\operatorname{dom}g$, i.e., for all $x$ for which $f$ and $g$ are both defined.
In a first-year calculus course it's often assumed that a function has as its implied domain the largest subset of $\Bbb R$ on which it is defined. With that convention $f$ and $g$ have different domains: the domain of $g$ is all of $\Bbb R$, but the domain of $f$ is just $(-\infty,0)\cup(0,\infty)$. Technically, then, they are different functions.
Answer: In contemporary mathematics, a function should always be defined by means of: (1) a set called "domain of definition"; (2) a set called co-domain; (3) a "rule" or a "law" that sends every element of the set (1) to one (and only one) element of the set (2). If you do not like to think in terms of subsets of cartesian products, a function is a triple. As you have been told, calculus is abundant of functions as they were used by pioneers: just rules.
This can be tolerated at very low levels of teaching, but should be replaced by a more precise definition rather soon. And we, teachers and professors, should stop asking our student "to find the domain of definition of the following function", since there is no function without a domain.