Confusion about Photosystem 2 with regards to lysis of water

Question: I am slightly confused about the role of $\ce{H2O}$ lysis in PII. I know that this releases $\ce{H+}$ ions, which I think are important because they drive the production of $\ce{ATP}$ through F-Atpase across the thylakoid membrane. But I don't understand how else this is important? With my current understanding, I would think that it is perfectly sufficient for PII to receive photons to excite an electron in the primary pigment reaction centre, which goes along the electron transport chain to PI. Is the water lysis there to replace electrons lost by photosystem 2? If so, how is it controlled that the correct number of $\ce{H2O}$ molecules are lysed so that excess electrons aren't generated?
Answer: Generation of ATP via photons is the primary aim of the photosynthesis pathway, which is accomplished by the generation of a chemiosmotic gradient of $\ce{H+}$, which then drives the ATPase pump. All the other enzymatic setups are designed to just let this process run in the most efficient way.

I would think that it is perfectly sufficient for PII to receive photons to excite an electron in the primary pigment reaction centre

While you are partially correct in assuming this, since the ETC also participates in creation of a chemiosmotic gradient (Plastoquinone), such a mecahinsm would not be able to run repeatedly. Without the replenishment of the electrons of the PSII, it will not be able to initiate another round of electron transport. Hence, the oxidation of water is crucial in providing PSII the electrons it passed onto plastoquinone, so as to allow another round of photon-absorption and continuation of the photosynthetic process.

how is it controlled that the correct number of H2O molecules are lysed so that excess electrons aren't generated?

This is achieved by a complicated interplay of the enzymatic components within the PSII. In summary, utilizing the four stable oxidation states of manganese core in the redox center ($\ce{Mn}^{(2-5)+}$, four separate states of the center ($S1\rightarrow 4$) are formed. These states cyclically shunt one electron during each step, until a water molecule is bound to $S4$ which is then directly converted to $\ce{O2}$ by $P680+$, formed in PSII due to photon absorption, which is a strong reducing agent. Since the final step occurs only with water molecule bound to $S4$, which in turn is formed only by the cyclical transition between the various states of the redox center with systematic sequential loss of electrons, the overall process is very tightly constrained to extract only the limited number of electrons preventing any troublesome redox intermediates.
See here for some basic treatment of photosynthesis.
Comment: Thank you for your answer. Your answer and some additional reading allowed me to understand the role of water lysis! However there is one question that has come up for me which I cannot seem to find the answer to: so quinone B, after accepting electrons and hydrogen, transfers electrons to cytochrome b6f as plastoquinone/quinol. These electron are accepted by cytochrome b6f, to re-form quinone B, which is not lipid soluble. How is the quinone B replaced in PSII? It cannot diffuse back in the phospholipid bilayer as it came?


What differentiates a $100 coffee machine from a $1000 coffee machine?

Question: There is a huge amount of price variance for coffee machines. Just a quick look in any shop will reveal two espresso machines, made by the same manufacturer, one in the $100 range, and another in the $1000 range. For the purposes of simply making espresso from ground coffee, what is the difference between them?
Comment: I believe 9 bars of pressure is the industry standard.. If a machine isn't telling you anything about the pressure, its likely not meeting this.
Comment: The 100 dollar model probably does not have enough pressure to make real espresso but instead makes what is technically steamed coffee.
Comment: @JoshuaAslanSmith How can you tell the difference (before you've bought the machine)?
Comment: @JoshuaAslanSmith Even budget machines usually advertise a 15-bar pump, so I don't think it's this.
Comment: Keep in mind that higher priced equipment does NOT always translate into better espresso. The best analogy is in wines, where many $20 bottles are better than wines that are priced over $100. I'm sure there is a higher percentage of $1,000 espresso machines that make really good espresso, compared to the % of $100 espresso machines that make really good espresso.
Answer: More expensive coffee machines typically have better "plumbing", including some and even all of the following:

2 boilers / HX to allow for frothing and brewing at the same time
Preinfusion
Copper boilers vs. cheaper aluminium versions (guarantees better temperature stability)
Larger boilers, allowing for more shots to be drawn/ milk to be frothed
Wider portafilters (which in some peoples' opinion gives better flavour)
3-way valves to allow back-built pressure to evacuate
a real steam wand, no gimmicky plastic ones that promise the world and don't deliver
the ability to be plumbed (connected to your water drain so you don't have to manually clear out the water tray.)
The option of vibration vs. rotary pumps (which are quieter, although I think they are more likely to break if there is no water)
Customisability of technical factors (pressure, temperature) which gives more control for our crazy data-obsessed coffee needs :)

Now this doesn't mean you can't get good coffee on a cheaper machine. You're just going to have to put more effort in it and get more variable results. Which is more than fair for most people.
As for the price difference, most of these features will raise the price by themselves and a lot of the more expensive machines are hand-made as well.
Last point they are also very pretty and a status symbol, not to the extent of let's say a very expensive watch but it does sort of feel that way sometimes.
Answer: Check for coffee related features.
These are things which make your coffee taste better:
Cup heater - if you make your espresso into pre-heated cup, it will taste better
Metal steamer - I know you are going to make espresso only, but if you want to do cappucino, heating milk by metal steamer is better than by plastic one
Pressure control - The expensiver coffee machines can control pressure bit better.
Anyway, in my own opinion, for good coffe is enough even low end coffee machine (I own one for 200 bucks)
If you want to make great cofee then go to higher end. But for beginner or even bit enthusiast as I am, low end should do the trick


How should I clean my focusing screen?

Question: While on holidays I managed to get hair and dust onto the focusing screen of my 550D. How should I clean this off.
I have already tried a normal lens cloth, but that only made it worse.
Answer: Well, first I should mention that dust on the focusing screen has no effect on the image quality or the exposure metering, so for that sake there is no need to clean it. On the other hand the dust may get loose and get onto the sensor, so it's a good preventive measure tog get the worst dust away at least.
To clean it, you should first turn the camera off, to reduce the static electricity. A dust blower is good for removing dust. A brush can also be useful, but the drawback is that they tend to lose bristles now and again, which adds to the matter that you want to remove.
Answer: You can always remove the focusing screen then puff some air on it with a blower or whatever.
Here's a website with instructions on how to remove the focus screen.
http://www.focusingscreen.com/work/550den.htm
You may simply end up with more dust though. Who knows. Good luck!
Answer: Take it to a repair shop. Nine times out of ten you make it worse when trying to fix these kind of things at home.
Answer: i would prefer you take it to a service provider . but if u wanna insist on cleaning it then these steps should help, clean it in a dust free area.
1)avoid blowing directly. User a Blower bulb.Turn off your camera.
2)make sure you have your camera's front side facing the ground. this way, it will make sure your dusts will get out of your camera and not fall back in while blowing .
3)never use a cloth or brush, even if it if just a focusing screen and not a sensor.
they tend to settle dusts and particles in critical internal areas of the camera.
4) i would still suggest you to take it to a service center :)
Answer: I regularly use my air compressor to clean my cameras & enlargers. I also use it to clean dust of the negatives & carriers before printing. You want a blast about twice as hard as you could blow with your lungs. The secret is to just make sure you don't blast it so hard you break something.
You don't want to use a cloth or a brush as the tend to make more of a mess then when you started. Also do not use chemicals as its hard to get in to use them properly with out disassembly & it tends to be more work then its worth to remove them.

How should I clean my focusing screen?


What aspects of linguistics are necessary or good for natural language processing?

Question: What aspects of linguistics are necessary or good to know for natural language processing? What references do you recommend for studying those aspects? Thanks!
Comment: I believe that you don't need to know any linguistics for NLP these days, since everything is done using (nearly) oblivious statistical methods.
Comment: At least when considering what features to be used and interpreting the results of statistical analysis, we do need to understand some aspects of linguistics?
Comment: You are asking for a summary of a whole field -- that's to broad. Can you narrow it down to, say, "What use is linguistic feature X in NLP?" Note that there is [linguistics.SE]; the folks over there may provide a useful additional perspective.
Comment: @YuvalFilmus: That's not universally true, see e.g. [Grammatical Framework](http://www.grammaticalframework.org/). It *is* true that many popular tools rely on "dumb" n-gram approaches, but these have known and severe limitations.
Answer: NLP is a big place, you might want to be more specific.
Within information retrieval, stemming is a linguistic idea that has become useful as a heuristic means of reducing vocabulary size.  As a practitioner I learned about it from An Introduction to Information Retrieval.
Comment: "NLP is a big place, you might want to be more specific." -- good indicator that the question is not suited for the site.
Answer: It depends - generally, if you want to use or implement well known approaches or systems for some specific application, then you can get by without any linguistics, and if you want to improve state-of-art solutions, then you'd need at least a broad overview of general linguistics (things that apply to human lanuages as such), (non-CS) syntax theories, why POS-tags and phrase/dependency structures are chosen to be built that way, etc - but all the neccessary fragments tend to be taught as part of 'NLP courses', so you can get by with a single source and expect whoever is teaching that NLP course to gather up all the various domains.
Ah, and proper knowledge of your target languages - you can do quite a lot of stuff with foreign text you don't understand, but if you have some linguist available for every target language, then it is very useful.
Answer: There is no good answer to your question. Much depends on the kind of
NLP you want to do. Do you want to do man-machine interfaces,
information retrieval, syntax checkers, machine translation, data
extraction from corpora? Do you want to process text or speech? Are
you interested in ill formed sentences? Are you concerned with syntax
or semantic processing? And so on ...
Now, your question is about "aspects of linguistics [...] necessary or
good to know for natural language processing". Is statistics an aspect
of linguistics?  Is formal languages theory an aspect of linguistics?
Or simply, is NLP an aspect of linguistics? If not, where is the border?
Recall that formal language theory started with linguists such as Chomsky or Bar-Hillel.
My suggestion would be to study some of the systems that have been
developed for NLP, at various stages of language processing, and it
will force you to extend your knowledge of linguistics as you go
along. Use call by need when you learn, especially if you do not know
what is essential.
Another interesting kind of systems to study (which are also NLP
topics) are system used to extract linguistic data from corpora,
whether lexical, syntactic or semantic. This data will then be fed to
your NLP systems to process actual texts for whatever purposes.
Statistics and formal languages are important to structure
understanding, but they have to be motivated by linguistic
considerations too. But if you start with linguistics, you may be
bogged down into countless very specific studies.
Comment: Statistics and formal languages are not considered linguistics. Linguistics comes in many varieties, but although ultimately formal language theory arose from linguistics (Chomsky was involved), I wouldn't consider this "classical" linguistics. Hierarchical syntax and morphology are two examples of linguistic phenomena which may or may not be useful in NLP.
Comment: @YuvalFilmus I am aware of what you are saying, but I am also trying to raise
questions without being too assertive. What I am actually saying is
that the border between formal languages as a mathematical body of
knowledge and as a mean (a notation if you wish) of describing
linguistic phenomena has been and is still evolving. Similarly, the
role of statistics may not be as clear-cut as you seem to make it.
To be true, classifications are often only what people make them, and
much subject to change with perspective. And the OP wrote "*aspects of
linguistics*", not "*linguistics*".
Comment: "There is no good answer to your question." -- good indicator that the question is not suited for the site.
Comment: @Raphael Well, my statement is also partly rethorical. The issue is
also, as I tried to state in my answer, that it is not so clear what is
"linguistics" itself. Why should NLP not be part of
linguistics. Linguists may not agree, but I feel that NLP is much the
mathematical theorization of linguistics, not just the engineering
part of the field, and as such it is part of linguistics. Of course,
theorization has a different meaning for linguists. I think there have
been answers with some content, but no list of items to study. The question could
have been moved to SE-linguistics though.
Answer: The answer depends on what you want to do:

For speech recognition: Phonetics and phonology
For tagging and parsing: Morphology, syntax.
For language understanding: Semantics and pragmatics.


What does chamushim ("fifties") mean in Exodus 13:18?

Question: It is easy to imagine that this word would suggest "by fifties" or, more generally, in large groups, or even "in an regimented way like an army," but on what grounds do so many English versions turn this into "equipped for battle,"armed," and "ready for battle"?
Comment: Chamisjim is a modern word, check that on . But curiousdanni is right, today nobody knows exactly what that 3000 year old word in Exodus 13:18 means. Without vowels, dots or capitals the original Hebrew text gives translators an enormous freedom. Whitin the limits of that freedom it is highly unusual to read the word as part of the name of the desert and to write it untranslated with a capital first letter. I will appreciate all good arguments that show that those suggestions are incorrect. Simple opinions add little to a good answer to the question of Robert Koops.
Answer: The basis for those translations is that that's what the word means. Au contraire, "fifties" is a tenuous-at-best translation that is grammatically unnatural and contextually unnecessary.
The only appearances of the word in this format, all of which clearly mean "armed" are:
Joshua 1:14, 4:12 (contextually draw from Numbers 32)
Judges 7:11
It's worth mentioning that other uses of a potentially related root can be found at:
Samuel II 2:23, 3:27, 4:6, 20:10
There is room to look for a connection to the root "five" (probably not "fifty" though, despite the fact that there are military titles referencing the leaders of "fifties" in the Tanakh). Gesenius presents such a connection but favours the similarity to other words in both Hebrew and other languages that have no connection. He has a lovely line where he laments that the "etymology ... has been long sought for".
Answer: Because the word "chamisjim" is translated by Google Translate as "fifty" it has exactly the same meaning as the Arabian word "chamsin", that is the modern name for the eastern desert storm over Sinaï. The number fifty refers to the period in days when that Chamsin can be expected each year. Assuming that in Biblical times that storm was also known under that name in  Hebrew language, the road of the Exodus  was indicated as "the road of the desert of Jam Suf and Chamisjim (or the Reed Sea and the Eastern Storm)". Because the Hebrew text has no dots or comma 's to separate the two sentences of Exodus 13 : 18 this looks like a correct translation, even if it does not fit to the traditional interpretation of this text.It indicates that the children of Israel traveled in eastern direction, not through the Red sea, but through Lake Bardawil at the Mediterranian coast.
Comment: Can you use a more reputation source than Google? And I'd prefer more evidence that a word from a 3000 year old document has **exactly** the same meaning as another word in a different language now than just your assertion that it does!
Answer: Friedrich Weinrebb also tells chamushim must literally be translated as 'with five' or 'one fifth (1/5th).
he suggest that Jewish oral traditions speaks of only 1/5 of all Israel exits Egypt en 4/5 of them staying there.
he suggests that 80% thaught egypt was better than the desert and a unknown future.
this 1/5th is also the ratio which Joseph applies to save egypt from starvation. he puts aside 1/5th of all grain.
...
Answer: If the Israelite's were prepared for battle they must have had weapons. Unless we can establish that they had such, translating the word chamushim as battle may be erroneous unless the intention was to declare a spiritual war in that God intervened in the natural order and showed HIS power through the Israelites. As they were slaves we are to assume that they did not have weapons. There is the possibility though that they took weapons when they plundered the Egyptians. Did this plunder include weapons?
Exodus 12:35-36 The Israelites did as Moses instructed and asked the Egyptians for articles of silver and gold and for clothing. 36 The Lord had made the Egyptians favorably disposed toward the people, and they gave them what they asked for; so they plundered the Egyptians.
To be prepared for "Battle" one must have weapons, but it is not clear from the context here whether they did or not.
In Exodus 12:40 we read:

40 Now the length of time the Israelite people lived in Egypt was
  430 years. 41 At the end of the 430 years, to the very day, all the
  Lord's divisions left Egypt. 42 Because the Lord kept vigil that night
  to bring them out of Egypt, on this night all the Israelites are to
  keep vigil to honor the Lord for the generations to come.

The word divisions here in verse 40 may shed some light on the translation of Chamushim. Or it may not. Does the word divisions indicate a milatary type of state or is it just a reference to the nature of the company leaving Egypt i.e the families of the Israelites(the twelve tribes) and the others that went with them

There were about
  six hundred thousand men on foot, besides women and children. 38***
  Many other people went up with them***, and also large droves of
  livestock, both flocks and herds.

Again here we have a military type statement, "There were six hundred thousand men on foot", is this a statement of strength, then  a statement of battle readiness! So, The Israelites went up out of Egypt ready for battle.
So we have a number of scriptures that together give the impression that the Israelites were set up for battle and were about to engage other nations in Battle. Indeed when we trace the wanderings of Israel in the wilderness we see that they were a battling nation.
The question then is, did the translators base their translation of this word 'chamushim' on what they understood of the whole context of Exodus and Israels mission or did they find justification for the word, battle, as an accurate translation from the context of this single verse, where this word in hebrew, 'chamushim', is in dispute, namely Exodus 13:18.
The language experts may shed some light for you and me.
Personally I believe from the context that the Israelites were armed. As well as Gold and other articles they plundered weapons and Armour. So they were armed and ready for therefore for battle. This taken with the fact that we know what transpired in the rest of their time in the wilderness, whereby they did concur nations and subdue peoples, compels us to believe that when the Israelites  left Egypt they left ready for battle!
We could say also that the battle that ensued with  Israel leaving Egypt was the battle of all battles for God did raise up a people His own people to declare the Law and will of God as preeminent in creation. It was the beginning of the fulfillment of the promise to Abraham, that his descendants would be as the stars of the heavens for number. In Egypt under slavery the Lord had built his weapon to destroy the evil one and at the exodus that weapon went forth to display the will and power of God Almighty. When the red sea parted God declared His sovereignty over all things. It was a battle cry from the Hight of Heaven to the depths of Earth when Israel stepped into the sea on dry land, they walked with God and any man that walks with God does make war in this World for He "Did not come to bring peace but a sword"
Matthew 10:34
New International Version (NIV)
34 "Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword.
So yes when Israel left Egypt they went out ready for battle
Comment: What does Jesus's statement in Matthew's Gospel have to do with this passage in Exodus? Please connect the dots.
Comment: @Dan When Israel left Egypt they went out with Christ as head to do battle with the Nations.
Comment: @GoneQuiet So you do not believe that God led the people out of Egypt? Crossing the Sea

17 When Pharaoh let the people go, God did not lead them on the road through the Philistine country, though that was shorter. For God said, "If they face war, they might change their minds and return to Egypt." 18 So God led the people around by the desert road toward the Red Sea.[a] The Israelites went up out of Egypt ready for battle.
Comment: God is always Head ..."This was to fulfill what had been spoken by the Lord through the prophet: 'OUT OF EGYPT I CALLED MY SON'"      If you chop it up too much you will kill it. Thats if its not already dead!


Bringing the Realism

Question: As I have played D&D we have come to many points on the road where things don't seem quite fair and as the DM I have to be the arbiter of sticky wickets. For example: If you have a situation where the player has the blade of his knife to the throat of the evil baddy and there is no realistic reason the evil baddy wouldn't die in the next minute, but the rules tell you that a dagger in D&D 3.5 at most (meaning with a crit) can deal 8 + STR (mod) x2 damage, and the baddy is a level 3 fighter and thus beyond that spectrum how do you handle it? And moreover how do you handle it fairly? Sure for story's sake you allow the player to kill the evil baddy, but what happens in the next encounter when the roles are reversed and there is no reason the enemy shouldn't be able to end the life of the player? How do you make these decisions and make them feel real and somewhere in the realm of fairness, taking a step away from dice rolls and getting into the moment? The goal here is to find a way to make high level players afraid of things that are still dangerous. Even a massively high level fighter as a CHARACTER should consider the danger of a fight that the game would say "isn't dangerous"
Answer: Dungeons & Dragons is not a realistic game
It's not intended to be. It is designed with a large number of abstractions and it is designed for larger-than-life, superhuman heroes. A first level human barbarian can break Usain Bolt's world-record sprint time – and then keep up the pace for several minutes, and do it while wielding a battleaxe, wearing a chain shirt, and carrying fifty or more pounds of assorted other gear.
It only gets worse from there. A character limited by the realistic limits of the human body cannot reasonably challenge much of anything above first level, and even that is pushing it. Someone limited by realistic laws of physics caps out around being a challenge for roughly eighth-level characters; after that, things like flight or invisibility or whatever become so common that creatures with no answer to them are non-threats, regardless of how strong they are (see the Tarrasque, which is actually a fairly trivial fight for an intelligent eighth-level party, and can be taken down as early as third level if you're clever and can justify some enormous knowledge checks).
HP is the biggest abstraction in the system
HP is not really (necessarily) "health," and loss of HP is definitely not (necessarily) "wounds." HP is more like "plot armor," and can represent morale, determination,                                                                                luck, blessings of the gods, magic mojo, and any number of other things, or more likely multiple things in combination. Just looking at some of the effects that can restore HP makes this rapidly clear; there even exist Extraordinary (read: non-magical) forms of HP healing based on being inspiring, rallying your allies to push on and fight through the pain. That couldn't be possible if HP were strictly wounds.
So ultimately, the way D&D works, your players shouldn't have been able to get a knife through an enemy's throat unless the die rolls had already shown it was a killing blow. That's how the game works: you roll the dice to see how well you do, then describe what you did to achieve that. You don't get to describe a killing blow unless you actually score one. If they came up short, that should have been described accordingly; the enemy writhed out of the way or they messed up and only nicked him or whatever. And if that seems implausible given the circumstances, then they probably should have been using a Coup de Grace (and surviving a Coup de Grace is fairly implausible; that is a very difficult Fortitude save).
You might consider another system
But I honestly think this probably is not a very satisfying answer for you. Unfortunately, it's the answer that D&D has, and trying to shoehorn realism into a system that is so fundamentally designed from the ground up with huge abstractions and intended for larger-than-life fantasy heroes, is just trying to force a round peg through a square hole. I've seen it tried, and it just does not work well at all: it's a lot of work, lots of rules end up being really wonky, and I generally haven't seen people with your interests actually be satisfied by it. If this is what you and your group is interested in, there are games that are more lethal and aim at greater levels of realism that may suit you better.
Comment: -1, Admittedly, you give a possible solution (Coup de Grace), but you've hidden it within an answer that is effectively just, "play a different system".  We need to attempt to answer the question within the frame it was asked before suggesting alternatives outside of that frame.  Relevant: http://meta.rpg.stackexchange.com/questions/3318/how-do-we-handle-a-desire-to-challenge-the-frame-of-a-question
Answer: For the knife thing, there's always Coup de Grace
A Coup de Grace can happen in a situation where one character has another - PC or NPC - helpless. They normally take a full-round action to happen, and automatically deal damage as a critical hit, followed by forcing a fortitude save vs. death. While this isn't a certified kill, I should note for you that people in real life have survived having their throats cut - and none of these people could wrestle bears with their bare hands.
But...
3.5 is just straight bad at realism. 10th level characters can swim, unaided, through lava and come out the other side alive. An untrained shopkeeper can run for miles in full plate through the high heat of summer and the worst thing that happens is he gets tired. These catches, these areas that utterly lack resemblance to real life, are built into every facet of the system and it's too integrated to really remove. You can house rule it every time, of course, but you may be better served finding another system.
Answer: Fight Dirty D&D vs. High Adventure D&D
The real question is what kind of game do you (the group) want to play?
There is a style of D&D where the knife to the throat is just ruled a kill and done.  And yes, the bad guys can do it too.  So a lot of play becomes finding ways to fight dirty and eke out victory.  This is where "throw lantern oil on the bad guys and throw a torch" came from.
There's also D&D that's aimed at being more like a lot of fantasy fiction - where the characters are heroic and not ruthless murderers - they may kill someone in the heat of battle, but not someone helpless.  If you want to do this kind of play, then you have to agree as a group that this is what works for you.
If you want something that supports more realistic play on it's own, a different system is the best answer.
Keeping the tension
The second question - how do you make things scary for high level players?  It's hard, because D&D magic effectively removes a lot of the fear for PCs quickly - heroes heal in 1-2 days maximum, raise dead eliminates fear of death, etc.  Other games like Burning Wheel can leave a character laid up for weeks or months with injuries - you just don't want to get hurt at all in those games, so every fight has an element of danger.
With D&D, it's really hard.  I think WOTC did a study of play and saw when most parties died, the players never realized they were losing until it was too late.  So, the thing is that what is actually combat effective, may not put fear in the players' hearts.  In one game, I gave a character a "Midas Touch" attack - on a critical, the target would turn to gold.  Someone had a hawk animal companion they sent to attack the guy first, and he happened to roll a critical.  Everyone freaked out and ran after that.  Even though the odds were low, they didn't know that and the potential consequences were high.
You can try to do cheap tricks like that, but players will get tired of them if overused.  Otherwise, it's a lot of stacking together several monster powers/spells in combos to hit hard and fast.  Which is a lot of work, because the players have had many, many sessions to master their combinations of powers, while you will be putting together new monster sets regularly and having to figure out how these new sets work together.  It makes high level play very swingy - sometimes you miss something crucial or the players play a little different and they steamroll your encounters, sometimes they miss something crucial or you actually put together something terribly mean and they don't run, and you steamroll them.
The only sorta-useful trick I have in that case is to try to make a combo that takes out one PC really hard.  "Wait, the Barbarian is down to 3 hitpoints, already?!? Oh crap." It keeps the party up to win the fight, but that one PC who gets hit freaks out, and if everyone else sees someone go down quick, they realize they might be next.
Answer: Use Vitality/Wound points. Higher level characters can shrug off most would be injuries with vitality points. But even high level characters can accidently die quickly with a loss of wound points. For example, a gun pointed to the head, or the knife to the throat, would be an automatic critical damage, which would directly affect Wound Points rather than Vitality points. Now the possibility of surviving the slash to the throat is still there, but so is the instant death. In "real life" some people have survived gun shtos to the head, or having their throat cut. Is it common? No. But the Vitality/Wound Point system will bring that "fear of death" into your game.
Example in a Vitality point system:
A person fresh out of high school would be a level 1 character. Low Vitality Points/Low Wound Points. Someone pointing a gun at their face should scare them. The threat of death is there.
A 20 year soldier/combat veteran would be a level 15-20 character. High Vitality Points/Moderate Wound Points. Someone pointing a gun at their face should scare them. The threat of death is still technically there.
Example in Hit Point system:
A person fresh out of high school would be a level 1 character. Low Hit Points. Someone pointing a gun at their face should scare them. The threat of death is there.
A 20 year soldier/combat veteran. High Hit Points. Someone pointing a gun at their face wouldn't scare them in the least. They have so many hit points the damage from the gun wouldn't be a scratch. Even if it would be an automatic critical, and even using coup de grace rules, their fortitude save would be so high that unless they roll a natural 1, their chances of death is just so low there would be no way to effectively roleplay the fear of death.
Remember, in a Vitality Point system, higher level character get more vitality points, meaning through their experiences in life they learn how to avoid many dangers that would kill others without that sort of life experience. But wound points always stay sort of relative. In other words, some dangers can't be avoided and everyone would have a fear of death. It would add a whole new level on how characters conduct themselves, and you may find yourself DM'ing a lot less charge attack barbarians. You may also find yourself with people using combat as a last resort, which in real life, it often is.

Bringing the Realism


Does Nisan's pseudo-random generator relativize?

Question: Nisan proved in "Psuedorandom Generators for Space-Bounded Computation",
that there exists a pseudo-random generator which "fools" space-bounded computations.
Does this construction hold for every oracle (at least for non-adaptive queries) ?
Comment: I can't answer this question, yet I wanted to point to a related paper titled "Hardness vs. Randomness" (http://dx.doi.org/10.1016/S0022-0000(05)80043-1), which you may find useful.
Answer: It depends on whether in your definition of the Oracle TM, the oracle query tape is also bounded to be of logarithmic size: if it is bounded then the PRG fools also L^A for any A too, if it is not bounded then A can contain the list of "pseudorandom strings" and thus L^A will not be fooled.
Comment: Since this PRG is completely specified (ie not based on some other "hard function f"), it's not clear how to use the oracle in the relativized setting.
Comment: This is true for all pseudo-random generators, however, for example, NW generator does relativizies if we assume hardness against the oracle we want to fool. I  was wondering whether we can do something of this kind also for this generator.


How to setup shared folder as virtual directory in IIS 7.5 (cross-domain)

Question: This is my current understanding of how this should be done:
(TL;DR for the actual problem, please see the bold text.)

Create a folder on you storage server, henceforth known as B.
Create a local user account on B, henceforth known as BUser
Share that folder

In folder properties>sharing>advanced sharing>permissions, add BUser and give full control
In folder properties>security>Edit... , add BUser and give full control

Create a local user account with same name/password on your web server, henceforth known as A
In IIS settings, navigate to the node under which you want to create virtual directory
Right-click > Add Virtual Directory...   --In Alias, put the name that you want the directory to appear as

In Physical Path, put: \B\shared-dir
Click Connect As...

Enter the username and password of the local account(s) that you created earlier.

Click Test Settings...

Green check icons on both items indicate that your share is accessible and fine.

- Right-click the virtual directory > Explore
- Get error, either: "the specified network password is not correct."
- Or: "Logon Failure: Unknown username or bad password."
It appears that the errors above are selected at random, but the second one seems to be a bit more common when trying the last step multiple times. I am totally stumped as to why. Any ideas?
Answer: It's because when you click 'Explore' in IIS Manager, you are using IIS Manager with a user account (most likely the local Administrator) of that box that does not have access to the share. You can fix this by synchronizing the Administrator passwords on both the web server and the storage server.


Does sound come out of both audio ports?

Question: My computer has two headphone jacks, and I haven't been able to listen to both of them at the same time. Do both of them output the same sound?
Answer: Assuming that both headphone jacks are from the same audio card, and the default sound balance settings have not been changed, then yes, the outputted audio should be the same from both jacks.
Answer: Though the same connectors are used for a variety of applications, it is very uncommon to have more than one headphone jack on the same audio card. It is more likely the second output is actually a line out, designed to carry a signal to another audio device's 'line in', whereas the headphone jack is designed to drive headphones.
Though headphones hooked up to either port will produce sound, there are functional differences. The line out port may bypass volume controls, as well as having a different volume level altogether. The sound card may also adapt its behaviour, such as muting the speakers when headphones are connected, but not when something is plugged into the line out. Playing individual songs on both ports is generally not an option, however.


Acidic Wort Affect on Immersion Chiller and Flavor

Question: I am looking into building a copper immersion chiller for use on my next batch of beer. I plan on doing a sour ale. Will the low PH of the wort have any negative affect on the chiller? Will it cause the metal to leech extra particles, possibly causing off flavors?
Answer: No. The comparatively low pH will not leach the copper in any appreciable way into a wort solution.
Comment: Even if the ph drops below 4
Comment: A pH below 3 is not a particular problem,  per se. High pH levels can be more problematic.
 "Galvanic corrosion" can also be a problem if there are two different metals in contact with the wort
Answer: I think that the acidity does not have an influence on copper, but it does on copper oxidation, which you do not want in your beer. Always clean and dry your chiller very well, and store it dry so that it does not oxidise (turns green).
Answer: If you're concerned with the oxidation effecting the wort. Simply give it a 5 minute starsan soak before using, it will be bright and shinny.
Yeast actually use a little copper as nutrients.


Where can I get the images data set of skin diseases?

Question: I want to search on images of skin diseases corpus. I need this dataset to index images in my search engine. Please suggest me how and from where i can get those images.
Answer: We have made available some publicly accessible skin diseases images collections here: https://datasn.io/p/528
The APIs are all open. No registration required:

http://n3.datasn.io/data/api/v1/n3zm/image_of_skin_disease_dermatology_1/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3zm/image_of_skin_disease_4/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3_chennan/skin_disease_3/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3zm/image_of_skin_disease_5/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3_chennan/skin_disease_7/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3zm/image_of_skin_disease_3/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3_chennan/skin_disease_1/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3_chennan/skin_disease_4/main/list/?app=html-bunker
http://n3.datasn.io/data/api/v1/n3_chennan/skin_disease_6/main/list/?app=html-bunker
Answer: Wikimedia Commons has a few images: Start from the top category here: https://commons.wikimedia.org/wiki/Category:Diseases_and_disorders_of_the_skin
An API is available here: https://commons.wikimedia.org/w/api.php
The files are quite heterogeneous. Some are drawings. I suspect they are not optimal, e.g., for training a machine learning classifier.
Besides the category system, the skin disease image files on Wikimedia Commons may also be identified with Wikidata through the Wikidata Query Service at https://query.wikidata.org, for instance, with the following SPARQL query:
<code>#defaultView:ImageGrid
SELECT ?disease ?diseaseLabel ?image WHERE {
  ?disease wdt:P279+ wd:Q949302 ; wdt:P18 ?image .
  SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}
</code>
The result is available at this link: http://tinyurl.com/ya3ogyq7
However, this query only identifies 75 images.
Answer: ISIC (International Skin Imaging Collaboration) - but with a focus on melanoma
https://isic-archive.com/

ISIC has developed and is expanding an open source public access archive (ISIC Archive) of skin images to test and validate the proposed standards. This archive serves as a public resource of images for teaching and for the development and testing of automated diagnostic systems.

Image browser
API


Derive OIS rate from IRS rate and Fed Funds/Libor basis spread

Question: For example I have 7Y interest rate swap rate and 7Y Fed funds/Libor basis spread. What is the step-by-step procedure to derive OIS rate from these two?
Comment: Hi andr111, welcome to Quant.SE! Please add the self-study tag if it applies. Can you tell us what you've found already and where exactly your stuck. The question in its current form would require quite a big answer.
Comment: Hi Bob, I originally assumed that this can be done through a simple closed-form formula. But as I did more research I realized that this is more complex. I'll publish as I get more understanding.
Answer: If you're lucky enough that the payment schedules (start/end dates, frequency, day count, business day adjustment etc.) are the same between the fixed leg of the interest rate swap and the "spread" leg of the basis swap, then you can simply use:
OIS rate (%) = IRS Rate (%) - 0.01 * (basis spread (bps))
Otherwise, to do it accurately, you'll need to do a bootstrap the two term structures (possibly simultaneously if there is mutual dependence between them).
[In fact, in the USD case, there is an added complication that comes from the OIS rate being a compounding rate, while the FedFunds rate is an arithmetic average.]
Comment: Yes, this is what I found out. I read a bloomberg document explaining how  to do the conversion. Unfortunately, I don't think I can publish it here :(


Are there any rules for OOP?

Question: Recently I heard that there are 9 rules for OOP(Java). I know only four as Abstraction, Polymorphism, Inheritance and Encapsulation. Are there any more rules for OOP?
Answer: Seems like what you're looking for are the Principles of Object-Oriented Design.
Summarized from Agile Software Development Principles, Patterns, and Practices. These principles are the hard-won product of decades of experience in software engineering. They are not the product of a single mind, but they represent the integration and writings of a large number of software developers and researchers. Although they are presented here as principles of object-oriented design, they are really special cases of long-standing principles of software engineering.
SRP The Single Responsibility Principle A class should have only one reason to change.
OCP The Open-Closed Principle Software entities (classes, packages, methods, etc.) should be open for extension, but closed for modification.
LSP The Liskov Substition Principle Subtypes must be substitutable for their base types.
DIP The Dependency Inversion Principle Abstractions should not depend upon details. Details should depend upons abstractions.
ISP The Interface Segregation Principle
Clients shold not be forced to depend upon methods that they do not use. Interfaces belong to clients, not to hierarchies.
REP The Release-Reuse Equivalency Principle
The granule of reuse is the granule of release.
CCP The Common Closure Principle
The classes in a package should be closed together against the same kinds of changes. A change that affects a closed package affects all the classes in that package and no other packages.
CRP The Common Reuse Principle
The classes in a package are reused together. If you reuse one of the classes in a package, you reuse them all.
ADP The Acylcic Dependencies Principle
Allow no cycles in the dependency graph.
SDP The Stable Dependencies Principle
Depend in the direction of stability.
SAP The Stable Abstractions Principle
A package should be as abstract as it is stable.
Comment: The first link hangs. Fortunately, there are other sources, i.e http://wiki.c2.com/?PrinciplesOfObjectOrientedDesign. This answer puts together principles of class design, principles of package cohesion, and principles of package coupling.
Answer: Not sure about any rules. All these mentioned things are more like OO paradigms to me. There are few advices we follow like,

Separation of Concern
Single Responsibility per Class
Prefer Composition over Inheritance
Programming to Interface
Plus all mentioned by Billybob, already
Answer: These OO principles are straight from Head First Design Patterns:

Encapsulate what Varies
Program to an Interface, rather than an Implementation
Favour Composition over Inheritance
A Class should have only one reason to Change (Single Responsibility Principle)
Sub-Types must be substitutable for their Base (Liskov Substitition Principle)
Classes shoule be Open for extension, but Closed for Modification (Open-Closed Principle)
Answer: These are concepts, not rules. There are no rules really, just decisions to make, some designs are better than others, some much better than others :-)
There are plenty of guidelines though :-) Some are language specific (C++ is riddled with them) others are OO specific. Too many to list though :-)
Off the top of my head, important ones are:

Loose coupling, high cohesion
Write testable classes, which you test
Use inheritence sparingly and only where it makes sense (prefer composition)
Try stick to the open/close principle.
(most important) KISS

Plenty to expand upon and add :-)
EDIT: I should add, the rules which you listed are not unique to OO
Comment: Neither yours :). By the way, how would we practice Inheritance, Polymorphism, etc. in a non-OO language. I believe all these 4 are OO paradigms.
Answer: According to the Pragmatic Programmers - the rules are:

Keep it DRY (Don't Repeat Yourself)
Keep it SHY (Ensure that your classes have high cohesion and low coupling)
and tell the other GUY (Separation of concerns)

http://media.pragprog.com/articles/may_04_oo1.pdf
Answer: There are no "Rules" to OOP.
There are 4 language properties that make a language object-oriented or not (these are the things you listed in your question).
The rest of the material out there are guidelines.  The best/most helpful guidelines I've read are GRASP
Many of the suggestions are not readily understandable by laymen (non-CS majors).  I thought GRASP was pragmatic and approachable.
I think GRASP is nice because it suggests the most critical part of OO in its name - Assignment of Responsibility (to objects not programmers).
The two most critical GRASP concepts from which everything else derives are coupling and cohesion.  These two concepts/principals drive all other patterns and approaches.
BTW - did I just interview you?  You transcribed the question incorrectly...

Are there any rules for OOP?


Normality and descent

Question: Let $R$ be a normal noetherian domain. Write it as intersection of discrete valued domains $\bigcap_p R_p$. Assume I have schemes $X_p\rightarrow \operatorname{Spec}(R_p)$. Via the inclusion $B_{p,p^{\prime}}:=A_p\cap A_{p^{\prime}}\rightarrow A_p$, we can consider the structure sheaf $\mathcal{O}_{X_p}$ as $B_{p,p^{\prime}}$-algebra. Assume that for any pairs of such primes $p,p^{\prime}$ we have an isomorphism $\varphi_{p,p^{\prime}}:X_p\rightarrow X_{p^{\prime}}$ as $\operatorname{Spec}(B_{p,p^{\prime}})$-schemes, satisfying the usual cocycle condition. Under which conditions is it true that we can find a scheme $X\rightarrow \operatorname{Spec}(R)$ such that $X_p$ is the base change of $X$ via the morphism $\operatorname{Spec}(R_p)\rightarrow \operatorname{Spec}(R)$??
Answer: I think you may have slightly misstated your question.  I think instead of $\phi_{p,p'}$, it is more natural to assume that there exists a scheme $X_{p,p'} \to \text{Spec}(B_{p,p'})$ and isomorphisms between $X_p$, resp. $X_{p'}$, with the corresponding base change of $X_{p,p'}$.  With your current definition, even the collection of identity morphisms, i.e., $X_p = \text{Spec}(R_p)$, does not give a datum.  In place of the cocycle condition, perhaps you want to insist that for every triple $p$, $p'$, $p''$, there exists a scheme $X_{p,p',p''}$ over $\text{Spec}(B_{p,p',p''})$ and isomorphisms of the base changes with $X_{p,p'}$, resp. $X_{p,p''}$, $X_{p',p''}$ that are compatible with the specified isomorphisms of the further base changes to $X_p$, $X_{p'}$ and $X_{p''}$.  To me this seems like the natural condition to impose if you are trying to get a gluing result out of coproducts $\text{Spec}(R_p\cap R_{p'})$ rather than a descent result out of products $\text{Spec}(R_p\otimes_R R_{p'})$.
Since this is an "under what conditions" question, I cannot give a complete answer.  However, I can give a counterexample.  Let $k$ be $\overline{\mathbb{Q}}$, or any other countable, algebraically closed field.  Let $R$ be $k[t]$.  By Hilbert's Nullstellensatz, the set $M$ of maximal ideals $p$ of $k[t]$ is naturally bijective to the set $k$.  For every subset $S\subset M$,
form a datum, $$\mathcal{X}_S = ((X_{S,p})_{p\in M}, (X_{S,p,p'})_{p,p'\in M}),$$
as follows.  Define $X_{S,p} \to \text{Spec}(R_p)$ to be the open subset $\text{Spec}(R_p) \setminus (\{p\}\cap S)$, i.e.,
either $\text{Spec}(R_p)$ if $p\not\in S$, or $\text{Spec}(R_p)\setminus \{p\}$ if $p\in S$.  For any pair $p,p'$ of distinct primes, we similarly define $X_{S,p,p'}$ to be $\text{Spec}(B_{p,p'}) \setminus (\{p,p'\}\cap S)$.  Then both $X_{S,p}$ and $X_{S,p'}$ are canonically isomorphic to the base change of $X_{S,p,p'}$.
If there were a scheme $X\to \text{Spec}(R)$ satisfying your condition, it would have to be $\text{Spec}(R)\setminus S$ with its natural monomorphism to $\text{Spec}(R)$.  But for most choices of $S$, this is not a scheme.  Indeed, there are only countably many locally closed subschemes of $\text{Spec}(R)$, but there are uncountably many choices of $S$.
There may be a result of the form you ask if you add the hypothesis that every $X_p\to \text{Spec}(R_p)$ is proper.

Normality and descent


How to bypass sites that blocks tor?

Question: Tor has many mechanisms for obfuscating its traffic to prevent packet inspection. The "meek" pluggable transport helps to hide this deep packet inspection and hide it as https traffic. (This works fine for outbound traffic). But the problem is that all the tor exit nodes are available through the TorDNSEL. So reverse proxies like cloudflare still easily blocks tor. (Inbound traffic being blocked here). How do i REALLY bypass any server i want (even if it means chaining tor with something else like a vpn)?
Comment: I don't know your situation, but my opinion on this is that if the site cares so much about your data (as in, *aquiring it*) that it goes out of it's way to block most means of hiding it, it's not a site you want to be using. In worst case, you could spin up generic vm or docker container with VPN that the website doesn't block, coupled with a standard browser, so chrome/chromium or mozilla, then discard it altogether after use.
Answer: As far as I know this is not possible
All tor relay UP addresses are publicly available, including exit ones. Any webmasters that choose to block them can, in fact Tor Project operates a dedicated list for this purpose. Cloudflare also provides an option for sites using their services to block Tor traffic.
Webmasters sometimes block for security purposes (some people do use the Tor network illegitimately, and there is the stereotype that Tor is only for illegal purposes) or occasionally because they cannot appropriately track you for various reasons. Either way, there is zero you can do to get around this, besides maybe politely ask the website owner to unblock Tor users
And as far your suggestions of using a VPN with Tor, this is a very bad idea and the docs recommend against it
Comment: As for "ask the website owner to unblock Tor users", see [Stack Exchange IP Block Exemption Policy (Tor)](https://meta.stackexchange.com/questions/398349/stack-exchange-ip-block-exemption-policy-tor)
Comment: See also [Stop telling Tor users to contact support for registration](https://meta.stackexchange.com/questions/391323/stop-telling-tor-users-to-contact-support-for-registration-if-their-request-wil)
Comment: See also [How to create a StackExchange account on Tor?](https://tor.stackexchange.com/questions/23977/how-to-create-a-stackexchange-account-on-tor)
Comment: Are you a bot @MichaelAltfield?
Comment: No. I'm a human. This human: https://michaelaltfield.net

How to bypass sites that blocks tor?


Finding point coordinates of a perpendicular

Question: Given that I know the point coordinates of point $A$ and point $B$ on segment $AB$ and the expected length of a perpendicular segment $CA$ (perpendicular over $AB$), how do I calculate the point coordinates of the point $C$?
Answer: There are, in general, multiple possible solutions for $C$, depending on which direction you go from A. If you restrict yourself to points on a plane, then there are two possible solutions.
Say that the length of $CA$ is known to be $l$. We want to find a perpendicular to $AB$. Say $B-A = (x,y)$ then we want $(a,b)$ with $(x,y) \cdot (a,b) = 0$. Check for yourself that $(-y,x) \cdot (x,y) = 0$.
But we also want $(a,b)$ to have length $l$. To get something in the same direction as $(-y,x)$, but with length $l$, divide $(-y,x)$ by it's length and multiply by $l$. This gives $(a,b) = \frac{l}{\sqrt{x^2+y^2}}(-y,x)$.
So with this choice $(a,b)$ has both the right magnitude and direction. Since this is the displacement from $A$ to $C$, let $C = A + (a,b)$. As I said above, this choice is not unique; you can check that even in the plane $C = A - (a,b)$ gives another valid solution.
Comment: Thank you for your answers - they helped me solve the problem.
Answer: You have apparently $2$ possible solutions. Consider the vectors $A=(a_1,a_2)$ and $B=(b_1,b_2)$. Then, the vector $B-A=(b_1-a_1,b_2-a_2)$ is the director vector of $AB$. Hence, $u=(a_2-b_2,b_1-a_1)$ is orthogonal to $B-A$. Therefore,
$$C=A\pm|CA|\cdot \frac{u}{\|u\|}$$
are your two desired points.


Apache container cant access php files mounted in /var/www/ - 403 error

Question: I want to run my php website in a container with apache and php7
I am using this docker image : https://hub.docker.com/r/nimmis/apache-php7/
I run Fedora so I enter the example command given in docker hub in my terminal.
docker run -d -p 8080:80 -v {my_php_app_path}:/var/www/html nimmis/apache-php7

The container pull and run fine. But once i try to access the asset (on localhost:8080) I mounted to it, I receive a 403 error. So now i try to connect to the container to see what happens.
I use the command adviced by the author:
docker exec -ti <container id> /bin/bash

Once in it, I cd to /var/www/html all the file are presents but I cant read or ls in the folder. the root of the container cant do anythig with it. Here is what I get :
>>> root@a1f13dc4c29d:/var/www/html# ls
>>> ls: cannot open directory '.': Permission denied

Why is it that way ? Am I missing a step ?
Any help would be loved :D
Answer: SELinux prevent the docker filesystem to work in the intended way, to fix this issue just add the :Z flag at the end of the volume declaration. It goes something like this:
docker run -d -p 8080:80 -v {my_php_app_path}:/var/www/html:Z nimmis/apache-php7


Time of Asr Salah according to Safi'i and Hanafi can I follow both?

Question: I'm confused about which Asr time I should follow. Can I pray in both of these times. If not then which has more evidence to support it, that I should follow it?
Answer: Differences in the Mathab is a mercy for us according to the following Hadith:

اختلاف أمتي رحمة

The only issue is that the above hadith is weak, but I personally think it true since differences give us an exit when we need it. Take the following authentic hadith for example:

أنّ رجلاً أصابه جرح في عهد رسول الله (صلى الله عليه وسلم) فأُمِر بالاغتسال، فاغتسل فمات، فبلغ ذلك رسول الله (صلى الله عليه وسلّم) فقال: قتلوه قتلهم الله، ألم يكن شفاء العيّ السؤال.
A person with a head injury during the time of the Prophet PBUH was asked to wash his head for Wudu, the prophet PBUH later said to the people who told him so "They killed him, Allah may kill them", wasn't it a cure to just ask.

My personal take from the Hadith is that nothing is set in stone and if there is a way something can happen to make things easier for you, you should do as long as you have the correct interruption.
Personally, I think if you need to pray Asr at a certain time and it is convenient for you, go ahead. Allah meant this deen to be easy and not complicated. Sometimes I pray Friday in one Masjid 1 hour before Zhur and sometimes in another Masjid 2 hours after. It is all on what is best to you.
Answer: Well if you want to pray and don't have any headache take the Hanafi rule.
More detailled answer is here: http://www.isgr.org/asrpray.htm
This is also supported by a Hadith in Muwata' Malik

Yahya related to me from Malik from Yazid ibn Ziyad that Abdullah ibn
  Rafi, the mawla of Umm Salama, the wife of the Prophet, may Allah
  bless him and grant him peace, asked Abu Hurayra about the time of the
  prayer. Abu Hurayra said, "Let me tell you. Pray dhuhr when the length
  of your shadow matches your height, asr when your shadow is twice your
  height, maghrib when the sun has set, isha in the first third of the
  night, and subh in the very first light of dawn," i.e. when the dawn
  has definitely come.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَزِيدَ بْنِ زِيَادٍ، عَنْ عَبْدِ
  اللَّهِ بْنِ رَافِعٍ، مَوْلَى أُمِّ سَلَمَةَ زَوْجِ النَّبِيِّ صلى
  الله عليه وسلم أَنَّهُ سَأَلَ أَبَا هُرَيْرَةَ عَنْ وَقْتِ الصَّلاَةِ
  فَقَالَ أَبُو هُرَيْرَةَ أَنَا أُخْبِرُكَ صَلِّ الظُّهْرَ إِذَا كَانَ
  ظِلُّكَ مِثْلَكَ وَالْعَصْرَ إِذَا كَانَ ظِلُّكَ مِثْلَيْكَ
  وَالْمَغْرِبَ إِذَا غَرَبَتِ الشَّمْسُ وَالْعِشَاءَ مَا بَيْنَكَ
  وَبَيْنَ ثُلُثِ اللَّيْلِ وَصَلِّ الصُّبْحَ بِغَبَشٍ . يَعْنِي
  الْغَلَسَ .

But consider that the differences could sometimes come from mistakes in calculation or extreme carefulness. For example in the internet you can find many different calculation methods and many prayer times for the same prayer sometimes with diffrences of an hour or more!
Therefor one should take the one of his/her trust!


How did Germany deal with the East German communist Government structure after unification?

Question: When West Germany annexed East Germany, what happened with the Government structure in the East? For example, were the police, judiciary system and executive branch in the East simply renamed, created from scratch, or merged and their members verified? If verified, how was the verification done?
Comment: See also https://history.stackexchange.com/q/27599/1773
Answer: Technically, West Germany (the FRG) did not annex East Germany (the GDR). Instead, the GDR declared their accession to the FRG. A treaty regulated the details.

The GDR had a post-communist government for about a year. They did disassemble much of the political security apparatus and also acted to prevent the destruction of some documents.
The vetting of personnel was done through the Stasi Records Agency.
The more senior police, military, judiciary, and administrators were pensioned. Their pensions were much less than comparable West German officials would get, but they got some money in D-Mark (and later Euros). It is anybody's guess how the purchasing power compares with what the GDR would have paid in Ostmark.
Juniors could stay on, but their careers slowed down. Recently a former Volksarmee officer made General in the unified German army -- two decades after Reunification.
Comment: Not sure that officer had anything to complain about then. The notorious *Beförderungsstau* (promotion jam) in the Bundeswehr has been a problem for decades, exacerbated by the downsizing of German armed forces. An old acquaintance of mine (fighter pilot) made it to Lt Col in that time and with luck will make it to Col (ret).
Comment: @Marakai, there were plenty of GDR colonels. If it had been an equal merge, one of them would have stayed on and made general. Instead, more than 90% of the GDR officers had to go, including the seniormost ones. I doubt that they all wanted to go to the civilian sector.
Comment: There's some more info I could provide but is too close to family for my wanting to share it here. Doesn't belong in comments anyway. I wasn't disagreeing with you, mow just another data point that promotion in the German AF had been a disaster for decades-and as a result worse for"Easterners" more than its might have been in less clogged up armies.


Advanced rendering data source criterias

Question: Has anyone got any ideas on how to customise the "choose data source dialog" / pipelines; so that only certain items (by tag or otherwise) are available as the selectable data source?
Comment: In your scenario, is the user allowed to create a new datasource item, or must they pick from an existing list?
Comment: You mean having a custom rendering parameters for the datasource?
Answer: Prepare for a huge wall of text here which is not tested, but should work in theory and is a perfect blog post material :)
So the easiest way to do this, is to actually act to the unselectable items in the same way that Sitecore reacts to the unselectable templates - i.e. showing a message and telling that this is not a valid choice.
So the first stop should be GetRenderingDataSource Pipeline and GetRenderingDataSourceArgs.
You need to create a Custom GetRenderingDataSourceArgs (inheriting from the existing ones) that will host your custom rules.
After this being applied you need to create a custom processor and plug it in right before <processor type="Sitecore.Pipelines.GetRenderingDatasource.GetDialogUrl, Sitecore.Kernel"/>.
Here you are going to plug your processor that is going to apply your custom rules.
Next step would be to override the GetDialogUrl processor, which is going to spawn the window with the rules applied to it. The problem here is that it uses SelectDatasourceOptions class which is one more point you will need to extend.
So in the Custom SelectDatasourceOptions you need to add a place for your custom rules, override the ToUrlString method and override the Parse Method, so it can parse correct parameters to the window.
After that you need to go back to the GetDialogUrl Processor and pass the new parameter.
Now we hopefully will have the window opened and the custom rules paramaters are going to be passed, so the next stop would be the SelectRenderingDatasourceForm.
Here you will need to have to use your Custom SelectDatasourceOptions as options. In the parse method (which is actually located in the Property for the Options) I am not 100% sure that you will need to do a new override of the SelectItemOptions.Parse<SelectDatasourceOptions>(), but it is most likely the case that you will.
In theory now the data which is passed to the dialog should be handled and you are ready to apply the filtering.
The final thing that needs to happen is for you to override the IsSelectable method in which the actual filtering will happen.
Hope this makes sense !
Comment: Thanks. Good thorough walkthrough. Should really be a lot simpler than that :-)
Answer: The pipeline that you need to patch is the getRenderingDatasource. Below is the different steps that you will require to implement a custom rendering datasouce:
1. Sublayout
In the sublayout, in the Editor Options Section, there is a field called Datasource Location. In this, you can specify the query you want, below is an example of the query:
query:ancestor-or-self::*[@@templatename='Website']//Catalog Container
Note that the query above needs to have a template called Website then get the Catalog Container.
2. Code
Here, it is where you will insert the logic that you will require to have a custom datasource. As example, the below code will execute and will set the window from where content authors select the item to a specific container. Note that this is dynamic. In other words, let's say you have Site A, B and C and all 3 have a catalog container. The below code will render the datasource and content authors will never be able to select catalog from Site A in Site B or C
public void Process(GetRenderingDatasourceArgs args)
{
    Assert.IsNotNull(args, "args");

    string text = args.RenderingItem["Datasource Location"]; //Get the value from the field
    if (!string.IsNullOrEmpty(text))
    {
        if (text.StartsWith("query:") && !string.IsNullOrEmpty(args.ContextItemPath))
        {
            var contextItem = args.ContentDatabase.GetItem(args.ContextItemPath);

            if (contextItem != null)
            {
                text = text.Remove(0, 6); //remove the query:
                var item = contextItem.Axes.SelectSingleItem(text); //Execute the query

                if (item != null)
                {
                    args.DatasourceRoots.Add(item);
                }
            }
        }
    }
}

To restrict the content authors from selecting other templates, you can set the Datasource Template. This allows content authors to select items which are of the same template as specified in the Datasource Template
3. Config
Now you need to patch the getRenderingDatasource pipeline. Below is how you will need to patch it
<getRenderingDatasource>
    <processor type="YourNamespaceHere, YourAssemblyName"
               patch:before="processor[@type='Sitecore.Pipelines.GetRenderingDatasource.GetDatasourceLocation, Sitecore.Kernel']"/>
</getRenderingDatasource>


If my starter is spinning but not engaging flywheel, what is the issue?

Question:
99 Chrysler Concorde, new starter manufactured by Chrysler, Autozone tested the battery and said it had 73% health and was fully charged. What is the reason why my car won't start?
Comment: so the starter just spins and the engine doesn't turn over? are the teeth on the flexplate ok?
Comment: Is your fuel pump ok? Are your sparkplugs sparking? Are the power cables from the starter engine still connected with the battery? Check them. Try to stay in N and go on full throttle then try to start your engine! In the worst case try to make a jump start with a power booster (booster battery).
Comment: if the flex plate teeth are shot you just might get it to go if you put a wrench on the crank and turn the motor by hand a bit.  Presuming the teeth are bad in a spot but not all the way around.  In any case make darn sure the battery is good before tearing into anything. It wouldn't be the first time AZ misdiagnosed a battery.
Answer: To expand on @Draw3D's answer:
If you can hear the starter spinning - and you're sure it's the starter - but the engine isn't turning over, then the starter solenoid isn't working correctly.
The solenoid pushes a little gadget that engages with the flywheel / flex plate, so that when the starter spins, it turns the motor. If you just hear a whirring sound like the starter motor is spinning without affecting the motor, then the solenoid is either broken, or there's a wiring issue on the starter itself.
Options are: have the starter rebuilt, replace the whole thing, or see if you can track down the wiring issue on the starter.
Answer: I can compile those starter problems I have suffered along the way (and possible solutions) as follows:
Starter spins but doesn't engage: you hear it spinning like any electric motor, free spinning sound, no clicks, no grinding sound.
The mechanism to engage the flywheel is faulty, probably the solenoid that activates it is either faulty (it moves its internal parts to make contact and so the motor spins, but it is not pulling the engaging mechanism at all)
Starter spins but doesn't engage. Clicking sound : you hear it spinning with a click sound before it starts spinning. No grinding sound. The mechanism to engage the flywheel is faulty, probably it is seized, or battery doesn't have enough power to make the solenoid fully pull the mechanism (check battery charge). Hit the solenoid "moderately" with a mechanic hammer, one or two dry blows, if next crank try works, then the mechanism is getting seized and needs maintenance.
Starter spins but doesn't engage. Grinding sound: you hear it spinning like normally it should, but it comes with a grinding sound like sprockets not engaging correctly: worn out bendix ("sprocket" that engages the flywheel), and/or the flywheel (replace). In refurbished starters, it could happen that the engaging mechanism is not correctly adjusted/mounted making the bendix spin too early or too late while trying to engage the flywheel.
Battery should be sound and well charged. One of the most power hungry elements in a car is the starter. If the battery is weak, or as you say under 90% charge it may make starting by starter motor very difficult to impossible.
Answer: If the starter is engaging as you say, then either the starter pinion, flywheel ring gear or both are excessively worn.
Answer: My guess would be a bad starter solenoid.
Comment: If you explained *why* you thought this was the starter solenoid over some other problem, your answer would be more widely accepted. You may even want to help the OP understand better how to diagnose the issue.


Sources For Listening To/Not Listening to Non-Jewish Music

Question: What are sources for it being allowed to listen to non-Jewish music and sources for it being prohibited?
Comment: BTW, composing secular songs and poetry is a long-standing Jewish tradition, dating back at least to Shmuel haNagid.  See [JewishEncyclopedia - Poetry](http://www.jewishencyclopedia.com/articles/12223-poetry#anchor25) and [Hebrew Love Poetry](http://www.jstor.org/pss/1486312) for details.
Comment: Which means that you might want to better define what "Jewish music" and "Non-Jewish music" is.  I assumed it was all music that contained secular content and\or was non-Judaism-related.
Comment: Not a duplicate that is the performer Which I still don't understand how he got and this question is the Music
Comment: Related: [Going to Non-Jewish Concert](http://judaism.stackexchange.com/questions/1352/going-to-non-jewish-concert/11799)
Comment: Possible duplicate: [Listening to Christmas Music](http://judaism.stackexchange.com/questions/11938/being-exposed-to-christmas-music)
Comment: Related: [Are jews allowed to listen to music that is performed by non-Jew?](http://mi.yodeya.com/questions/5533/are-jews-allowed-to-listen-to-music-that-is-performed-by-non-jew)
Comment: No sources, but this writer on Chabad's website disapproves: http://www.chabad.org/library/article_cdo/aid/568482/jewish/Is-there-any-issue-with-listening-to-non-Jewish-music.htm
Comment: No sources, but my general experience is that Chassidim are against it, and Litvaks say that music is not "mekabel tumah" and thus okay. (This would be for words without foul language, women singing, etc. E.g. classical music.)
Comment: Extensive article here: http://www.ohrtorahstone.org.il/features/music_berman.htm
Answer:
Rabbi Moshe Feinstein in Igrot Moshe Yore Deah vol 2 no 111 states:

Music (with or without words) performed to honor a religious diety is
  prohibited.
Music with words of religous praise are prohibited even when performed
  in a secular setting. No distinction is made regarding language or
  comprehension.
Religious music without words of praise in a secular setting (aside from any
  problems associated with music in general) is permitted but R. Feinstein
  calls it a "davar mechuar" - an ugly/disgusting thing. The instruments
  used cannot be instruments generally used for religious purposes.

In addition, in responsa #56, R' Feinstein prohibits listening to Christian religious music.

(Source: http://ottmall.com/mj_ht_arch/v9/mj_v9i98.html#CWQ )

The Mishnah Berurah (53 s.k. 82), based on the Bach (Shu"t Bach haYeshanim 127), says it is permissible to listen to the song unless it was composed for\is primarily sung in Christian religious services.

Please see the responsa inside for details, and ask your LOR for an actual p'sak.

See also:
Halachipedia - Listening to Music (especially the "links" section) for the Halachot of listening to music in general.
Rambam's Commentary on the Mishna, Avot 1:17.  Loosely translated and explicated here: http://www.torah.org/learning/pirkei-avos/chapter1-17.html
Comment: I have not confirmed these sources (yet).  I highly recommend that you look up the originals instead of relying on my comments.
Comment: @ElShteiger s.k. stands for *seif katan* (סעיף קטן). That's what the numbers in Mishna Berura are called; the Mechaber (Shulchan Aruch) is arranged by *siman* (סימן) and *seif*.
Comment: Forgive my ignorence, but when you quote Mishnah Berurah (53 s.k. 82) what does s.k stand for?
Answer: This entire post is adapted from Through Music and Song, by Rabbi Elysha Sandler, in which he discusses the deeper aspects of music. In chapter 8 (p. 85-97), he discusses this very point, of being selective of what music one listens to. All emphasis placed in quotes are mine, and are meant to highlight the main points for those who don't wish to read through the whole thing.

The tune
Hachsharas Ha'avreichim 9 (written by the Rebbe of Piasetzna):

Behold, we see great singers and musicians whose hearts are distant from HaShem, without belief and heart, Heaven spare us; and even among idol-worshippers there are musicians. For music is nothing but a form of exposing of the soul and its feelings. Yet, there is no determining what a person will do at the time that he brings out this feeling, and what he will accomplish with the part of his soul that has now become exposed.
Just as there can be two joyous people, one channeling his joy to increase his service of HaShem, while the other just becomes wild, so, too, when it comes to music - one of the keys to the soul, to arouse it and its feelings. It is possible for a person to open his soul and to have some of it come out, yet not only does he not do anything with it, he instead sullies this portion of his soul, whether it is with joy-filled wildness or with the broken-heartedness of depression and despair. This could lead him to fall from his former trust and belief and to do things that may not be done, Heaven spare us.

In Rabbi Sandler's own words:

Therefore, if a person listens to music and song from a musician whose essence is good and pure, he will connect with it and absorb sparks of that goodness and purity into his own essence and being. It will become part of who he is and, perhaps subconsciously, influence him for the better.
Unfortunately, the converse is true as well. If a person listens to music from a musician or singer whose essence is not good and pure, then he will connect with that music and absorb sparks of decadence and impurity into his own essence. It will infiltrate and become part of who he is, and even subconsciously, influence him for the worse. One must therefore be exceedingly selective with the music and songs one listens to, and ascertain that it emanates from a person whose essence will have a positive influence on one's own. (p. 87)

The Rebbe of Modzhitz takes this a step further (Imrei Sha'ul, Inyanei Zimrah V'simcha 41):

My grandfather from Zvohlin, zt"l, used to say, "A person is taking a heavy responsibility upon himself when he makes song heard. For the elevation of the soul and its descent are dependent on music. It all depends on the musician, what he is playing and how he is playing it.

He doesn't just limit the musician: he also limits the song and even the instruments!
Rav Nachman of Breslov succinctly remarks (Likutei Maharan 3:1):

Behold, when one hears music from a wicked musician, it becomes difficult for him to serve his Creator. Yet when he hears it from a kosher musician, then it is good for him.

R' Yaakov Moshe Hillel even cautions that not only the musician, song, and instruments be appropriate, but even the composer (Vayeshev Hayam 2:7):

it is my humble opinion that any tune that was composed by a non-Jew or a Jewish sinner, even if it was not originally accompanied by lyrics - neither of promiscuity nor of idolatry - should not be listened to, and certainly should not be sung or played, for "the force of the workman is in his works."

He proceeds to use this basis to reject the claims that a Jewish singer may take a non-Jewish song and adapt it, thus "purifying" it. However, songs originally non-Jewish that have crept into Jewish society should be permitted:

Regarding songs which stem from the songs of the [non-Jews] of decades and centuries ago, of which we do not know their lyrics nor their scheme, it is beyond the realm of our authority to forbid them. Even the issue of "the effect of the workman is in his handiwork," which should be of concern, is also possibly a non-issue, since they have become sanctified by us over many years, and the memory of their corrupt, lustful source is all but forgotten; they no longer around and remind of those despicable things. It thus appears that there is no basis to forbid them.

(My comment: It seems important that he emphasizes the fact that their origins have been forgotten, as otherwise, the composer's spirit lives on and influences the listener.)
It's for this reason that when Sha'ul's servants sought out a musician, they looked for one who had good character traits (Shmuel 1:16:18):

And one of the youths called out and said, "I have seen a son of Yishai from Beis Lechem who knows how to play music, is of great strength, of profound understanding, a man of stature, and HaShem is with him."

The lyrics
And we haven't even begun addressing the lyrics. Even when not part of a song, decadent speech is bad enough (Shabbos 33a):

Due to the sin of obscenity of the mouth, many calamities and harsh decrees are renewed, young Jews die, orphans and widows cry out - and are not answered!

Combine it with music, and the results can be catastrophic (Reishis Chachmah, Sha'ar Ha'ahavah 10):

Songs whose lyrics consist of desire and vulgarity cause the soul to become separated from being bound to eternal life. ... Indeed, some people of low worth are drawn after these low songs and destroy their souls.

The Mishnah (Sanhedrin 10:1) lists one who reads "outside books" as one who loses his Olam Haba. What are these outside books? The Bartenura explains:

Included in this category is one who reads...songs of lust and desire, for they contain neither wisdom nor benefit, and are nothing more than a waste of time.

(Presumably, he's referring to poetry, but the point still stands; adding a tune shouldn't detract from its danger.)
With all of this background, it's no surprise that, as Rabbi Gabriel and Avraham noted, Chazal banned music altogether after the Sanhedrin was disbanded (Sotah 48a). As the Yerushalmi explains (Sotah 45a):

Said R' Chisda, "At first, the fear of Sanhedrin was upon them, and they did not use words of vulgarity in their song. Now that the fear of Sanhedrin is no longer upon them, they do use vulgarity in their song."

(As an aside, this could explain Avraham's comment that today things are different. At least in Jewish music, vulgarity is no longer an issue, though non-Jewish music, for the most part, would seem to remain under this ban.)
For one last point, Rav Zilberstein (Barchi Nafshi, Shemos p. 422-423, and Torascha Sha'ashu'ai, p. 212-213) records the following story:
There was once a bachur who attended Beis Midrash Gevo'ah in Lakewood, who suddenly was overcome with a desire to convert to Christianity. Try as they might, nobody could dissuade him, including the Rosh Yeshiva, Rav Aharon Kotler.
Rav Aharon enlisted the help of the Kopishnitzer Rebbe, who asked Rav Aharon to verify how the bachur set his alarm clock. Turns out, the most accurate clock he could find was the Church clock across the street from his dorm room that rings every hour on the hour, and so he had set his clocks according to the Church bell.
Solution: The Rosh Yeshivah bought the bachur a new alarm clock that he personally set based on the Yeshiva clocks, and the Talmid remained in Yeshiva with an urge only to stay with Yiddishkeit, not to stray from it.

Poskim
R' Moshe (EH 1:96) ultimately paskens that listening to music played by a rasha is not an issue of perpetuating the name of the wicked. However, depending on the type of wickedness, a ben Torah should avoid listening to it nonetheless, even if it's technically mutar.
Yabi'a Omer 6 (OC 7) permits songs with impure sources, provides that the words are switched. Contrast to Vayeshev HaYam, quoted earlier.
Rav Moshe Stern (Be'er Moshe 6:74), as well as Rav Menashe Klein (Mishnah Halachos 6:108) are much stricter, and hold that listening to music by a Rasha is even worse than using his Seder Torah!

TL;DR: Music can be an incredible boost to your neshamah, but it can also be an incredible detriment. Be careful how you use it, even if you hold it's permissible.

As I said, this post merely adapts the chapter and its main points. Other sources brought down are Rav Ahrele Roth, Shomer Emunim, Ma'amar Tzahali V'roni 6; Rav Avraham Schrorr, Halelach Vehalibuv 5761, Shemini 2; R' Yisrael Elya Weintraub (quoted but unsourced), Kuzari 2:64-65.
Answer: if I remember correctly, first of all music in general is forbidden because we are mourning for the bet a micdash.
but we are lenient on music that are basically pesukim or praises to hahsem, specially in wedding and such.
maran in shulhan aruch posek and I think in ialcut iosef he simply says that today is different
Comment: The English version of Yalkut Yosef on the Arba Ta'aniyot has an introduction explaining the hashkafah behind only listening to music that is of religious value. Unfortunately, I can't quote it because I don't own a copy. Maybe someone else can???
Comment: I have a copy, but it is some pages long, you sure you want me to copy everything?
Answer: See the Rashi on the Gemara <code>!אחר מאי? זמר יווני לא פסק מפומיה</code> in :חגיגה דף ט"ו  that says that Acher (אלישע בן אבויה) went off the Derech because he was listening to Greek music - and he should have refrained because of [Aveilut on] the Churban.
Comment: Is music nowadays considered greek music?
Comment: I think the comparable music would be Wagner and composers liked by the Nazis ym"sh.
Answer: From a Teshuva on asktherav.com
The concept of connecting to the soul of the composer of non-Jewish music is discussed in various sources. This applies specifically to the composer and not to the singer or the one playing.
Sources:
See Likkutei Dibburim 1, Likkut 4, Sicha of 20 Kislev 5694 ch. 5:  "When one sings a song composed by another, one unites with his Chayah-Yechidah". See also Toras Menachem 5747 II p. 647 about non-Jewish lullabies. See also Hachsharas Ha'avreichim 9 (from the Piasetzner Rebbe). See at length Responsa Vayeshev Hayam (Hillel) 2:7.
Note however that in Imrei Sha'ul, Inyanei Zimrah V'simcha 41 from the Modzitzer Rebbe, he quotes in the name of his grandfather from Zvolin, that a person is taking a major responsibility upon himself when he makes song heard because the elevation of the soul and its descent are dependent on music. "It all depends on the musician, what he is playing and how he is playing it."
See a similar point in Likutei Maharan 1:3.
מִי שֶׁשּׁוֹמֵעַ נְגִינָה מִמְּנַגֵּן רָשָׁע קָשֶׁה לוֹ לַעֲבוֹדַת הַבּוֹרֵא. וּכְשֶׁשּׁוֹמֵעַ מִמְּנַגֵּן כָּשֵׁר וְהָגוּן, אֲזַי טוֹב לוֹ …  מִי שֶׁהוּא כָּשֵׁר נִמְשֶׁכֶת הַנְּגִינָה שֶׁלּוֹ מִן הַשְּׁתֵּי צִפֳּרִים חַיּוֹת טְהוֹרוֹת … וּכְשֶׁהַמְּנַגֵּן הוּא רָשָׁע אֲזַי הוּא לוֹקֵחַ הַנְּגִינָה שֶׁלּוֹ מִצִּפֳּרִים אֲחֵרוֹת שֶׁבִּקְּלִפָּה.
It should be noted that when the servants of King Shaul sought out a musician, they looked specifically for one who had good character traits (Shmuel 1:16:18): And one of the youths called out and said, "I have seen a son of Yishai from Beis Lechem who knows how to play music, is of great strength, of profound understanding, a man of stature, and Hashem is with him."
See Shulchan Aruch Admur Hazaken (Orach Chayim 338:3) where from there one can see that in the past non-Jews would some times play music at a Chuppah that went into Friday night-Shabbos. This deals with the issue purely a halachic point of view and refers to playing music, not singing, and it deals specifically with a case when a Jew is not available (because it is Shabbos). Obviously, where a Jew is available one must always rather employ a Jew, in all employment.
See also Igros Moshe Yoreh Deah 2:56 who writes that it is forbidden to listen to a non-Jew singing verses of Psalms for it is almost certain that their thoughts are to their deities. Based on the Gemarah in Chagigah 15, it can bring to מינות and transgresses a Biblical commandment of לא ישמע על פיך.

(By the way the same concept applies to connecting to the soul of a Jew who is not pious)


How can I find my bitcoin wallet?

Question: I had to update the software on my computer and had to delete everything on my computer. I wasn't aware that my Bitcoin wallet was like a physical wallet. I thought I'd be able to download the wallet and enter my address into it and get everything back. I don't know what to do. I'm freaking out and don't know how and if I can get my Bitcoin wallet back. I know the address of my wallet but I don't have any of the files on my computer.
Comment: TL;DR if you have lost your `wallet.dat`, there is nothing you can do. Try with some recovery software, such as [PhotoRec](http://www.cgsecurity.org/wiki/PhotoRec).
Answer: Unfortunately once you lose your wallet, there is no way of getting it back.
The wallet is so inportant because it contains your private key, this key is used to send money from your wallet to other people. Without it you can't do anything.
Next time consider writing down the private key and keep it locked up, or keep an offline version of your wallet.dat file. however be careful with keeping online versions, since anyone who has your private key can send money anywhere.
Just for clarity, you talk about your 'adress', is this your public or your private key? With other words, did you use it to send money? Or to recieve money?

How can I find my bitcoin wallet?


Facebook Company Page login when info is lost

Question: I'm the new GM for our company -- we have a Facebook page that is very outdated and no one knows how to access it by password or login - do we just abandon it and start over or do you have other suggestions?
Answer: Facebook have a Help page entitled How do I claim a Page that already exists for my business? Can I merge it with my business's official Page? If no one is managing the Page, you can request to claim it:

From the Page, click  below the Page's cover photo
Select Is this your business?.
Add and verify information about your business, like the address and
  website, and click Continue.
Choose to verify your connection to the business by Email or
  Documentation:

Email: Choose this option if you have an email address associated    with your Facebook account that is officially issued to
  you by your    business. Email addresses from generic providers like
  Yahoo! or Gmail    will not be accepted. The email address should
  correspond to your    business's name (ex: email@example.com).
Documentation: Choose this option to upload a scanned copy or photo    of an official document that shows your business's name and
  address    (ex: phone bill, business license, business tax file or
  articles of    incorporation).

Click Submit.