What can an individual do to meaningfully practice carbon capture?

Question: There is a lot of information on the Internet about how an individual can lower or negate their carbon usage through various techniques and strategies but much less information on what a person can do actively practice techniques of carbon capture to offset their emissions. The obvious example here is planting tree's but are there any other carbon negative practices that are reasonable for an individual to engage in given a fairly standard income?
Answer: It is much easier to avoid emissions than to capture CO2. Anyway, one can roughly prioritize as follows:

Leave it to professionals.
There are expert organizations that focus on CO2 reduction. This is where you have the highest impact per dollar. They mostly work in developing countries, where the reduction per dollar is biggest. Here is a ranking for US-based organizations.
Avoid personal emissions.
Air travel and meat are the most relevant activities, you probably already know about that, but here is a link with tips for a lower carbon life anyway.

This is where the answer to your question starts, since these points actually capture carbon.

Reforestation, plant trees.
There are studies which show that reforestation has a huge potential. Scotland, for example, does a large scale reforestation, almost any country has its own tree-planting-events. You can certainly find one nearby and contribute personally.
Create/protect wetland.
Bogs capture and store huge amounts of CO2, but are often drained for land use. In the process, they emit CO2, roughly 0.5 t per hectare and cm water column.
Prefer (local) wood as a construction material. - The carbon captured by the trees gets sequestered away for 50-odd years as building materials. It also helps to source materials locally as this will minimise the emissions from transportation.
Farm Shellfish
Large amounts of CO2 can be captured by shellfish, who build their shells with calcium carbonate, where the carbon comes from CO2 from the atmosphere (scientific, entertaining) As an individual you could make farmed shellfish a part of your diet, although frankly I doubt that this has a significant effect, also accounting for transportation and such.

This list is by far not complete, please feel free to edit, extend and elaborate.
Comment: I'm doubtful of the claims about shellfish. Our World in Data looked at [impact of transport on GHG emissions from food](https://ourworldindata.org/food-choice-vs-eating-local), and included farmed and wild caught fish. Most of the impact of farmed fish is due to fuel use by fishing vessels. Farmed shrimp/prawns have over double the impact of farmed fish. Wild caught shrimp aren't included, but we can assume fuel use during fishing would be similar. So the shells would need to sequester ~2.5kg CO2 for each kg of food product to break even.
Comment: That's why it is the last point. 1kg of calcium carbonate CaCO3 corresponds to 0,44 kg of captured CO2, stoichiometric-wise. I'm fine with removing this info or labeling it a fun fact.
Answer: I suggest a variation on juhist's forest landfill proposal:
Assuming budget isn't an issue, and you're very patient, I'd suggest: buy land adjacent to a viable (native or at least non-monocultural) forest. Encourage the forest to expand onto it. Remove trees at a sustainable rate (you'll need to study forestry a little, did I mention that?) and use them for some long lasting purpose (i.e. not firewood or paper). Then when you don't need more any wood cut down trees and convert them into biochar. Bury the biochar into soil (good for soil fertility). You may even be able to sell it.
You don't want to do this in an area where you're going to cause significant carbon release from the soil if the trees dry it out - so don't reforest waterlogged peatland! Grazing pasture adjacent to woodland is probably a good bet.
In terms of what one person can do, this is a lot of work to provide a not hugely significant offset for a high carbon lifestyle, so addressing that should of course be the first port of call.
Looking beyond strictly individualistic action, getting involved in restoration of peatland, as Rainer Glüge suggested, or of native forests (e.g. Trees for Life) is a good option.
Answer: You can start growing an exploiting a Moso bamboo forest.
Bamboo is known for growing fast and storing a lot of CO2.
It is said that one hectare of Moso Bamboo can store up to 250 tons of carbon.
Each year, a hectare of Moso bamboo absorbs 5.1 tons of carbon.
Source: matteroftrust.org/what-can-bamboo-do-about-co2
Answer: Well, planting one canopy shade tree in the front yard requires a careful mapping of the utilities. But an individual could offer a service of planting front yard trees. One note, in many climates a hardwood tree shades the house in summer but lets sunlight through in winter.
The individual could become an advocate of industrial processes that make plastic from carbon-dioxide captured at fossil-fuel powerplants. Then that plastic could be used in long-term building materials that are then required by legislated building code.
Furthermore, the individual could become a farmer of Empress Splendor tress for lumber since the lumber can have long term use as a building material. (I like sorghum for carbon-neutral energy but that's carbon-neutral not carbon-capture.)
Answer:
The obvious example here is planting trees.

No, planting a tree is not a good example of carbon capture.
There are not one but two flaws in it:

Firstly, if you don't plant a tree in some place, and the place could support the growth of a tree, then a tree will actually naturally appear in this very location! Trees, like all other species, are efficient in reproducing. Forest grows without being planted.
Secondly, what will you do when the tree reaches an old age? Many ecofascists think it should be left there so you don't chop it down. Unfortunately, when the tree is large, it will not anymore act as an efficient carbon sink. The carbon sink stage is during the fastest growth stage. When it is fully grown, the carbon flows are in balance.

If you want to capture carbon, you should not plant trees but chop down and bury trees into anaerobic conditions.
When you chop down trees, you create room for more forest to grow. In the fast growth stage, the forest will act as a very efficient carbon sink.
That leaves the problem of the fact that the chopped down trees will naturally decompose, releasing the carbon back to the atmosphere. To prevent this, you need to make something that is long-lasting from it.
One obvious choice would be constructing a wooden house. However, someone will move to the house, start to consume heating energy, etc. so it is not really sustainable business to construct houses for people.
The pulp and paper industries will happily accept each and every tree you chop down. However, their products like toilet paper will store the carbon only for very short periods, releasing it back to the atmosphere very quickly. Not acceptable.
So, the chopped tree should be ideally stored in anaerobic conditions so that it will not decompose.
Solution: dig a large hole to the ground and store the chopped trees there.
This is not my invention. Apparently someone else has discovered it too. Even tried to patent it, unsuccessfully!
Comment: or convert it to bioChar?
Comment: not very "sustainable" to destroy forests where "things" live. See this bat-pangolin story?
Answer: Let them live
A livable solution to re-store carbon (who also avoid releasing some more in the process) would be to let wildlife to develop itself without too much disturbance. In my view, this is far more ethical than converting existing land to something agricultural.
Terrible de-growth
Keep this in mind: the fewer you earn, the fewer you destroy life space for wildlife. But if your goal is (food, body, health, sex) security, then you must capt more energy than the others (life forms, peoples, computers, robots, you name it).
An example of this is agriculture on living soil: instead of using huge machinery and chemicals to grow food with very low Energy Return On Invest [EROI], you let the soil live and use manual work to produce reaching EROI>>1, like it necessarily was in the old time where there was no fossil fuel use.
Sure this is not the happy life most of Internet people like us live, but if you include all earth people, then it is what lot of them already do with "standard income" (think of people with less than a 1$ a day). But the idea is the same with this answer (with this reference): store carbon in your backyard if you have one.
Answer: Don't forget that a tree's leaves that fall and the grass clippings you collect when you mow your lawn also contain carbon.
If you leave them alone, they will rot and all their carbon content return to the atmosphere. However if you turn this material into biochar, the resulting pure carbon is not bio-available and therefore won't return to the atmosphere.
Biochar retorts can be built from barrels and pieces of pipe. You burn 70% of the collected material to decompose the remaining 30%, the combustible gases that form in the process is also burned.
All carbon that burns in the process came from the atmosphere when the plant grew and part of it is permanently stored in a form of char.


Cannot upgrade Galaxy Y GT-S5360 with new firmware using Kies

Question: Whenever I try to click "upgrade", my phone suddenly disconnects from Kies but the download prompt still runs. After the download process completes, Kies suddenly closes and there are no changes with my phone.
Comment: Try putting you phone in Download Mode and try again.
Comment: There are quite a few [tag:samsung-kies] questions here, and many of them have to do with update issues. Have you checked to see if any of them are similar to your issue?
Comment: Are you running the latest version ok kies?
Answer: If the answer to my comment is No, then update Kies, and try again.
If the answer to my comment is yes, then try the following:

Place your phone manually into download mode, and attempt the update again.
Kill all Kies processes using the task manager, and then open the program again.
Ensure your USB cable and USB port are working properly (sometimes a weak connection can cause issues)
Erase all the data on your android (do a factory reset) and try again (I put this last, as you lose all your data, so should only be tried AFTER you have tried everything else you can think of).


ArcGIS 10.2 Modelbuilder Spatial Join is not generating an output

Question: I have a model that runs spatial joins in a lines to points relationship and then adds and calculates fields to that join. The parameters are one to one and intersecting at 1 foot.  The search distance is so low because the points are already snapped to the lines. During my initial test run, the spatial joins worked fine in the model, but I realize that the difference here is that I was working in a local environment. This time, I am required to run the model using inputs from a network drive. Could this be my issue? Or am I missing something really obvious here? The spatial join is on a dataset of at least 20,000 lines, so it should be taking around 20 minutes to complete.  IN this new model, the operation is done in mere seconds, so I know its not doing what its suppose to be doing.
Comment: Is it creating any output? Do the input layers have common coordinate systems?
Comment: I have verified the projections and the GCS. Also, there is no output whatsoever being created even though the workspace and layer name are all correct. Yet, the model is saying that it ran successfully.  Here is the weird thing: When running the model in model builder in edit mode, the outputs generate and are added to ArcMap.
Comment: So you say when model builder is open the model runs as expected? Was is the alternative you are running this model, as a tool from toolbox or from a script? Are you putting the same datasets in to the model when you run it this other way? Are there selections or does model logic expect a selection to exist?
Comment: Yes when in edit mode, the operation will write to the output location and add the result to the map display. But, when running as a tool with input parameters (like every other tool in the ArcToolbox) it does not write a new dataset to an output location. This model is part 2 of a custom toolbox and depends on the results from the first model. However, after checking and rechecking, changing the input feature class (as a parameter) does not affect the results of the model (when performed in edit mode).
Answer: This question has been resolved. In order to generate an output for spatial join, the output dataset has to be set as a parameter and the workspace of the model tool must match the workspace of the map document. If they match, the output is generated and added to ArcMap TOC upon completion of the model.


Arduino resets when I call network.begin()

Question: I have included the RF24Network library in my project. I tried to use the Simple Transmit/Receive example from here but when it calls the network.begin() my arduino restarts. I placed some Serial.println() in order to understand where is the problem. This problem appears only in my Arduino Mega 1280. I tried the same code on my Arduino Pro mini and it works like a charm. What causes this? How to fix that? It is very important to use the specific library. Thanks in advance.
Comment: tmrh20.github.io/RF24 is the new and updated library that should fix the problem.
Answer: The problem was that the RF24Network library is not compatible with the version of Arduino IDE I have. I downloaded Arduino IDE v1.0 and now it works like a charm. I will send an email to maniacbug to tell him about the problem.
Comment: tmrh20.github.io/RF24 is the updated fork.


Post-Doc topic VS PhD topic

Question: Is the topic research for a post-doc position supposed to be more general than the research conducted towards a PhD degree? Or rather the opposite?
Comment: I think if you ask five people, you'll get six different opinions. Mine is that it doesn't have  to be more specific or more general; it just has to be **different**.
Answer: Getting a Ph.D. is establishing that you are capable of doing a significant piece of research.  A postdoc is then your opportunity to start defining the direction in which you are going to take your research, professionally.
As JeffE says, it is usually (though not always) a good idea to be doing something different in your postdoc than you were for your Ph.D.  The reason for this is that otherwise you risk getting "stuck" in your little niche and never really moving beyond whatever happened to be your thesis and into the wider worlds of research.
A postdoc, then, is a chance to broaden yourself, to shift your direction (within reasonable bounds), to build momentum in a direction, and generally to start spreading your wings and leaving the nest.  How exactly one does that is as varied as are the people who pursue science as their career.
Answer:
Is the topic research for a post-doc position supposed to be more general than the research conducted towards a PhD degree? Or rather the opposite?

Great answer by jakebeal, of course, but I will offer a slightly different approach to answering the question.
The postdoc has three main functions, in my opinion:

transition to independence
stepping stone to stable employment
opportunity to build up your publications list

It might last a year, it might last two.  Because of this more limited time frame (compared with the PhD), you will probably spend less time delving deeply into the postdoc project area, perhaps because you are not working on something drastically different from your PhD area, perhaps because you (wisely) embark on something more narrowly focused (so that you can complete it in a shorter amount of time).
Therefore my answer to your question is

The topic research for a postdoc is more focused, and less general, than the research conducted towards a PhD.

Post-Doc topic VS PhD topic


What was Aizen's plan?

Question: In Bleach, Aizen had an incredibly complicated plan that seemed to span decades and that involved a lot of people he had no control over doing what he wanted them to do? I found it pretty difficult to follow what was going on in terms of what exactly his plan was. Can someone summarize it for me?
Answer: Aizen wanted to create the Ouken, the key that opens the door to the Soul King who rules Soul Society.  In order to be able to keep increasing his power he wanted to merge the powers of Hollows and Soul Reapers, this was his experiment with the Visoreds.  Aizen had made his own version of the Hogyoku to do this but it was incomplete, he merged it with the one Urahara made and with that he had the finished one that allowed him to increase his power and become the ultimate being.  Aizen said himself that only Urahara was the only intellectual challenge he might have had.
Remember though that Aizen had his hypnotic power that allowed him to control many of those within Soul Society, those he did not control he tricked.  He was able to get many to do his bidding, knowingly or not, only Ichigo was not under his control since he had never seen the sword release.
Ichigo made a statement after killing Aizen that Aizen was so powerful that having no equal he felt there was no one to challenge him and was somewhat lonely; the part about crossing swords where all Ichigo felt was lonliness.  It's possible to look at this as the only one who could be a challenge to Aizen was the Soul King, so creating the Ouken using Karkura Town would allow him to open the gateway to where the Soul King lived and possibly fight him and find an equal.
Comment: Something to bring up, Now that Bleach ended, we did find out Aizen does not like being Ruled over by anyone, which includes the Soul King. Part of his plan was likely related to fixing this.
Answer: Aizen wanted to merge the power of Hollows and Soul Reapers because he wanted to gain more power as he reached his saturation point of Soul Reaper powers. For this, he needed the Hogyoku. And he wanted to go to the Soul King Palace. But Ichigo even surpassed him and failed him.
Answer: Yea he used the vicerds (can't spell it) to test the hollowfication and then his comrades such as kaname tozen. When it was perfected on tozen he used it on himself because a mere human can't handle the power of the hogyku so he has to be the best of both worlds or something

What was Aizen's plan?


Database Backup using jenkins

Question: I would like to take MSSQL server db backup. Is there any plugin available for it.
Answer: I don't know of any current plugins for doing this.  That may because a lot of backup functionality is built into MSSQL.
The easiest way to automate a backup via Jenkins may be to use a command line script to use a sql command:
Sqlcmd -E -S touch -Q" BACKUP DATABASE [DBName] TO DISK = 'C:\artifact_directory\my_db_backup.BAK'
You could also also avoid automating this via Jenkins and just create a scheduled backup directly within SQL Server.

Database Backup using jenkins


Do I have to use Link monsters on my Yu-Gi-Oh! Deck?

Question: Like the title reads, I was just wondering whether or not I need a link monster in my deck to play Yu-Gi-Oh! at tournaments or my local game store.
Answer: Using Link Monsters is optional.
It's the same case if you decided to, say, build a deck without any Trap cards.
If your deck or strategy doesn't require them, you can play without having to have one.
However, if you plan to play in tournaments, or play competitively, I'd suggest you include or at least considering using Link Monsters, as your options could improve (and because the meta game is tending towards using Links).
Answer: You don't need them. A reason someone might say they 'need' them is because their strategy relies on swarming cards from the Extra Deck.
They're absolutely optional, but I highly recommend looking into how the new Master Rules affected the decks you're currently playing, and see if Link Monsters would help your strategy.
There are still decks in the format that work fairly well without any cards in the Extra Deck, like True Draco, for example.


Offline move trainer software

Question: I am looking for an offline move trainer software like the one chessable has. I am currently looking at PGN's with same opening and I would like to practice these games. For instance, I am looking at Sicilian Najdorf Scheveningen style and have collected Kasparov's game (roughly around 40 of them). I would like to faithfully repeat the moves made by Kasparov in each of these games, while the White's move is made by the computer. I would greatly appreciate suggestions. It need not necessarily be spaced repetition though it would be great.
Comment: What kind of training do you have in mind? Do you specifically want spaced repetition, or just a a software which allows you to follow a specific opening (e.g. versus a computer which plays a random line from the opening)?
Comment: @ATLPoly Added details to clarify.
Answer: Check out Chess Position Trainer. Also Chessbase has a training mode where you can create quizzes for certain moves.
Answer: One piece of software that you might find useful is called Chess Hero. It takes a pgn file you supply and will have you do guess the move training, with it making the move for the other side. It also has an engine running and will tell you if it considers your move better than what was actually played or worse if you chosen something different, and keeps a score of how well you do. Chessbase 15 also has the new replay training feature, which basically does the same thing.
Answer: You can do something like this with LucasChess, option "Play like a gradmaster".
Though you can't provide your own pgns, you can select the player and the opening.

Offline move trainer software


how electromagnetic fields affect brain activity?

Question: I have been investigating for an half hour in the Internet and I think there are not many reliable pages in my ignorant opinion so this is my question: is it possible to have hallucinations caused by electromagnetic fields? Are electromagnetic fields capable of modifying normal brain activity? How do electromagnetic fields affect brain activity? If possible, could they be related in any way to the people that claim to have seen a ghost or similar?
Answer: Transcranial Magnetic Stimulation (TMS) produces electrical currents in the brain through EM induction. It can do all sorts of temporary things to the brain including inducing hallucinations. See for example https://www.technologyreview.com/s/418887/magnetically-induced-hallucinations-explain-ball-lightning-say-physicists/


Can't we delete directly delete/vote to delete before closing a question?

Question: Can't we just delete/vote to delete before even closing a question? Especially those spam question and questions from a junk user?
Comment: Voting and down and running away witout comment is new kind of heroism :P
Comment: -9 ?? one more -1 please ;)
Answer: The process is to flag spam to delete it rather than voting.
The flagging process imposes a -100 rep penalty on the spammers account and also provides data for the anti-spam processing systems. It can also lead to the spammers account itself being deleted if it's only been used for spamming.
So it's much better to flag.
Answer: Only moderators have that power.  Only moderators should have that power.
This isn't to say that I don't agree with the premise - that content that is purely spam should be deleted on sight - but there's a lot of room for abuse.  I wouldn't feel entirely comfortable with someone being able to blanket delete stuff without them being very sure that it should go.  Only people right now that can do that are the moderators.
If you flag content as spam that actually is spam, then it will get acted on much faster, and given enough flags, the content may be deleted automatically by the system.
I see no reason to rush the process, since crap content doesn't stay up for very long at all.


(NT AUTHORITY\authenticated users) login to subsites-SP 2013

Question: intranet has department subsites (HR,IT,sales,..). i break inheritance at each subiste and grant access to (HR group to HR site, IT group to IT site,.,.)
when I add "NT AUTHORITY\authenticated users" to "intranet visitors" group at top-level site, users can see the link of the other departments with it's contents.
However, I want all users to see the links for other departments (HR,IT,..) without been able to see contents (doc libraries& subsites) in other departments.
Answer: If you want the navigation to display without regard for security, then you will need to maintain the navigation manually instead of relying on the automatic "Show sites" capabilities.
However, I would suggest that links to site for which you do not have permission be hidden. This will reduce the number of times users will get the Access Denied page.


Use custom values as units?

Question: Does Blender have any way of using custom units? Say I create a "unit" called depth and set it to equal 5mm. I set an object to have the dimensions (1 depth, 5 depth, 3 depth) which would equal (5mm, 25mm, 15mm). Then I change depth to equal 6mm. The object dimensions would change to (6mm, 30mm 18mm). Does blender have anything like that?
Comment: [Drivers](https://docs.blender.org/manual/en/dev/animation/drivers/index.html) might take you part of the way, but Blender doesn't really have any procedural or editable objects, so unless you can do it all with modifiers you will probably have a hard time achieving this.
Answer: Blender only has 1 unitless unit: the Blender Unit.
You can't create any others, but that doesn't matter, since it does exactly what you want.
At first your BU equals 5mm. Enter 0.005 in the Unit Scale checkbox.

Switching between metric and None will you either Dimensions of (1, 5, 3) or (5mm, 25mm, 15mm).
Changing the translating to 1 BU = 6mm seems pretty straightforward. Simply entering the new value 0.006 produces dimensions of (6mm, 30mm 18mm).

Use custom values as units?


Morality, Animal Cruelty, and Non-Vegetarianism

Question: This is a very common question, but I've always been torn about how I can give a rational moral justification for being a non-vegetarian. Is it not hypocritical for me to condemn other acts of animal cruelty (like the animal skin clothing) if I myself eat animals that have been killed for that specific purpose? What are some philosophical schools of thought on this subject, and what does this debate in moral philosophy generally turn on?
Comment: See [SEP Moral Vegetarianism](https://plato.stanford.edu/entries/vegetarianism/) and [Moral Status of Animals](https://plato.stanford.edu/entries/moral-animal/).
Comment: From an evolutionary point of view, being domesticated by humans is often the best thing that can happen to a species.  It pretty much guarantees that it will not go extinct until we do, and most species are not that lucky, we are ending their lines in droves.  The moral guilt of eating an animal is just anthropomorphism and sentimentality.  Animals don't have it.  If your cats get hungry enough, they will happily eat you.  Kant has suggested that what matters is not the act that matters in this case, but whether it challenges sentiments in a way that coarsens empathy.  Factory farming does.
Answer: Many people tend to conflate all human/animal interactions into a single idea, and that makes it easy to see other people (or even oneself) as being inconsistent or wrong.
It helps to separate the issues into independent questions, such as:

Purposeless cruelty (kick the dog, because you can).
Useful cruelty (force an ox to pull a plow).
Humane killing for clothing.
Humane killing for food.

This list is hardly collectively exhaustive and mutually exclusive, and your list might very well be different.
You can assign a justification for your feelings about each individual item.
You can then order the list, and "draw a line" between what practices you personally feel comfortable or uncomfortable with.
Note that even if two people have the same list, they might order it differently.
For instance, I find forcing an ox to work all day long to be more objectionable than letting it graze and then one day killing and eating it.  But a vegetarian would object to the killing and eating, but find forcing an ox to plow a rice field perfectly acceptable.
Unless it is handed down from a god, morality is subjective.  It is what you believe to be right or wrong, and that won't necessarily be what I believe.
As long as you consistently follow your own justifications, you aren't hypocritical.  It's only when you apply your morality to someone else's actions (or their morality to yours) that such problems arise.
Comment: There is a topic in philosophy called normative ethics.   It doesn't suggest or imply subjectivity is included.  Morality would not be a topic if any thing goes and any opinion was valued.  Do you co sider the field of normative ethics subjective? Perhaps distinguishing the differences in types of ethics would help if you mentioned many. What o find is people confuse ethics with morality and DESCRIPTIVE ETHICS and NORMATIVE ETHICS. Descriptive ethic is closer to Psychology and characterized by people thinking all is subjective.


Micro/nano skin implants to signal hole cards at the WSOP?

Question: Given that it is possible to send remote electric shocks, skin itches and muscle twitches to specific areas of the body using nano/micro-implants, is it possible to rig the WSOP which uses cameras and broadcasts hole cards live?
Comment: How would *you* do it? I'd be interested to see your personal answer.
Comment: Really, they broadcast the hole cards live?
Answer: Interesting thought, I think it is possible but it would be very difficult to pull off depending on the method used.

I believe the WSOP now uses RFID cards instead of hole cams to show the player cards on the live broadcast. Using a nano/micro-implant, one could imagine that a player could get information about other players cards. This is impossible at the moment because RFID is not a very long range signal, so the player would have to get very close to an opponents cards to read them (assuming this player can read the card's RFID signal with an implanted micro chip, a big challenge in itself.)
As far as cheating by watching the live broadcast goes, there is usually around a half hour delay between the actual tournament and the live broadcast. I watched the 2018 $100k PCA Super High Roller (https://www.youtube.com/watch?v=hHVHqc9rrF0) and players at the table actually had their phones out and were watching the live broadcast as it was happening. This was not the WSOP but I imagine that they have a similar delay set up.

I do not think it is impossible to cheat with all of the signals that are being sent due to the live broadcast. It would be very difficult to do so because a player is not able to tamper with any broadcasting equipment, and a player obviously can not be seen receiving any information.


What was the period when vedic scriptures were put in written form?

Question: Vedic scriptures were originally in oral form only. In which period were the scriptures put in written form?
Comment: [Timeline of Hindu texts](https://en.wikipedia.org/wiki/Timeline_of_Hindu_texts)
Comment: As far as I have seen the time line refers to (oral) composition. My specific focus is when Vedas was put in written form? Only in the case of Mahabharatha, we have this notion of Ganesh writing it? How historical is it?
Answer: The pre-Classical form of Sanskrit is known as Vedic Sanskrit. The earliest attested Sanskrit text is the Rigveda, a Hindu scripture, from the mid-to-late second millennium BCE. No written records from such an early period survive if they ever existed. However, scholars are confident that the oral transmission of the texts is reliable: they were ceremonial literature where the exact phonetic expression and its preservation were a part of the historic tradition.
The formalization of the Sanskrit language is credited to Pāṇini, along with Patanjali's Mahabhasya and Katyayana's commentary that preceded Patanjali's work. Panini composed Aṣṭādhyāyī ("Eight-Chapter Grammar"). The century in which he lived is unclear and debated, but his work is generally accepted to be from sometime between 6th and 4th centuries BCE.
So we can safely conclude that during this period, ie., 6th and 4th centuries BCE, the Vedic Scriptures were put in the written form.
Answer: This question was dealt as early by the scholars of the Veda as early as 1889.
Also, Yaska the author of Nirukta also alludes to this issue in that codification took place when the power of oral reproduction began to decline (see Nirukata 1.20).
The scholars of the Vedas agree that in all probability the codification took place before 600 BC.
For an extensive discussion on this matter, one can refer to the works of 1. J. N. FARQTJHAR, An outline of the religious literature of India, Oxford 1920,
2. K. R. POTDAR, at Oriental Thought 3 (1957),
3. BERGAIGNE, in JA 1889 I, p. 172 );
4. D. D. KOSAMBI, at JBBRAS 27, p. 12


Is there a way to stop receiving iMessages on OS X when the Messages application is closed?

Question: After I quit the Messages application, I will still receive my iMessages on my Mac. I don't want to disable my iMessages completely but I'd like them to stop bothering me when I've closed the application.
Answer: Yes, you can achieve your desired behavior without disabling Messages on your Mac.
If you turn off notifications for Messages from within System Preferences, you will still receive the messages, but will not be notified that they came in.
You can turn notifications off on the following screen.  Simply click on "None", and deselect all the checkboxes, as illustrated below:
Comment: Similar to @ryebread 's answer, you can also turn on Do Not Disturb when you want to disable notifications.
Comment: Thanks for the answer! It's unfortunately there isn't a way for me to only receive messages and get notifications when the application open but this seems to be the best workaround.
Comment: Good point; though it is worthwhile to note that doing so will disable notifications from **all** applications.
Answer: There is no way to leave it on but not receive the messages.
The only real way is to Disable the account (untick "Enable this Account") in the Messages Menu > Preferences > Accounts.


Piano and Guitar are the same music sheets?

Question: I want to start learning piano.  My friend said all my guitar lessons sheets can be played on a piano and that I would not have to buy sheet music for the piano. Is this true?
Comment: Hello Sammy! Could we see a typical guitar lesson sheet?
Answer: It depends on the music sheet. Piano music often has guitar chords listed above the grand staff, so you could have been using piano music for guitar. If you're using made-for-guitar lessons or lead sheets then its probably not appropriate for piano, though you may have some melody lines you could play there.
As a very rough approximation, if you have a grand staff (both treble and bass clefs) it may be designed for piano. If you have only treble clef then it's not designed for beginner piano: it can be played on piano, but that requires more advanced improvisational technique. If you have tab or just chords and lyrics then it's really not designed for piano. Again: advanced players can improvise it, but it's not a good place to start for beginners.
Whatever you do have, if you're just starting piano you'll probably want music designed for beginner pianists. Getting both hands coordinated will take some practice and you'll want to ease into that!
Comment: If you have the melody in treble clef and chords and use an e-piano, you can usually get something decent sounding using the auto-accompainment feature. You play the melody with your right hand and the chord (or sometimes just the base note or base note plus third for minor chords) with the left hand and the e-piano turns your chord into accompaniment. You can play around with different styles ... It's quite fun to do when you're a beginner on piano, because you get results fast. But it's not a technique for learning to be a better piano player.
Answer: In addition to the other answers, I would say that music written expressly for guitar is usually going to be different from music written expressly for piano, even in the same piece of music, because the instruments are different.  Guitar and piano have different strengths and weaknesses, and this is reflected in the music written for them, if it's at all idiomatic (fitting the particular instruments).  Therefore, while you might be able to play and get some of the same effect from music written for another instrument, you will use the characteristics of your instrument best with music written (or arranged) expressly for it.
Answer: Piano music is written using both G (or treble) clef and F (or Bass) clef.  Because of this you can absolutely play your guitar music on the piano.  Guitar is written in treble clef but in a different octave than the instrument is played in.
The problem you will run into is that you will not have anything for the left hand to do, or you will have to try and split the task of playing complex songs between your two hands.  This is a added burden.  If you are a beginner you're better off learning to read both clefs.  The same could be said of violin music or bass music, they can all be played on the piano but you have some missing information to figure out.  If the songs are mostly single lines then you won't have a problem.  If you have single lines with box chord charts above then as long as you know how to play the chord on the piano you can get by.  But classical guitar music will have as many as 6 notes at once and possibly spanning a few octaves.  Here you will need to figure out what to play with the left hand whereas in a piano arrangement this would be in the bass clef.
Answer: Two separate issues here.   LEARNING guitar and piano and PLAYING 'songs'.
Guitar and piano have different techniques, different hand positions, different approaches to playing scales, chords, melodies...   You need to learn guitar from a guitar tutorial, piano from a piano tutorial.
Once you have some fluency on each instrument and want to play 'songs' the same music copy will very likely do for both.  Popular music is normally presented in 'Piano/guitar/vocal' format.    You get the melody (and words).  You get a rudimentary piano arrangement.  You get chord symbols so a guitarist can strum along.
But there's 'songs' and there's music specifically for each instrument.  If you want to play classical guitar, or even to play the exact 'licks' used on a pop song, music written specifically for guitar will be needed.  Tab notation might be used.
And if you want to play Beethoven's piano sonatas, or Fats Waller 'stride' or the exact piano part from a Coldplay song, you'll need music designed for two hands on a keyboard, not one hand on a fretboard.
Answer: Beyond the answer of Rob (upvoted), I want to add that especially for beginners for piano, for melodic parts (so separate notes, not chords), have a number denoting the finger number (1-5) to show which finger should be used. This is especially useful when more than 5 notes are played which go up and/or down more than 5 (semi) notes. So one knows where to place one finger up or down another.
Of course this technique is not used (or at least different) for guitarists and not denoted on (beginner) guitar music sheets (neither on normal or advanced piano sheets btw).
Answer: Guitar music is essentially written on treble clef only, actually an octave higher than it sounds when played on guitar.
Of course this music could be used when piano playing - just bear in mind it will sound an octave out from the guitar. This can easily be remedied by playing the piano an octave lower.
Piano music essentially uses two staves, called the grand staff, so there's something to play with the left hand. That won't be present on guitar music as a rule, so you'll end up playing something like a melody line, if single notes, or a more complex right hand piano with up to six notes simultaneously. Quite a feat with r.h. piano!
So, yes it'll work but not be very satisactory except for the very beginning of your piano playing career. There's plenty of piano music available to download, and that, or other stuff you obtain, will be far more apposite for you as a piano player.
Answer: An example of your guitar 'sheets' would help, but I think some general comments can be made.
Guitar clef is normally treble or "G" clef. A pianist can read that clef. Well... a good pianist should be able to read various clefs.
Your sheets may use the G clef and be readable by a pianist.
Your sheets may be guitar tab or lead sheets both of which can provide chord symbols. A pianist could ad lib from those sheets.
If the melody is included - like on most lead sheets - then the pianist can play the melody with an ad lib accompaniment.
If the sheet is only tab with chord symbols, that's a hard case. I think most pianists will not be able to read tab and the best they could do is ad lib from chord symbols. They could take some queues from the tab in terms of rhythm and general figuration (scalar versus broken chord figures.)
I think these possibilities cover the typical guitar sheet music I have seen and you might get some use out of your guitar music on the piano.
Having said this, you really should get specific piano music. You can get either some method books or albums of beginner level material. The point of such material is to give you standard fingerings and to train the hands to play separate parts. You won't get those training specifics from guitar music.
Pick things according to the style you are interested it. If classical, there are lots of methods like Clementi's Introduction to the Art of Playing the Pianoforte. For pop styles look for books like those from Mark Harrison. Of course you don't have to use those particular books. My point is don't just buy any old sheet music. Look for stuff that matches your goals and suites your taste and learning style.
Comment: Not sure a pianist would be ad libbing guitar tab..!
Comment: @Tim, I'm just running through the likely guitar "sheets" because the OP didn't give an example of what exactly the sheets contain. Reading tab on piano isn't practical - not at all - but if chord symbols are above the tab, you might be able to work from that. The OP might get some use out of their existing guitar material.
Comment: Just being jocular! As someone who hasn't even started playing piano, he maybe wouldn't even find the chord symbols which may/not be included in tab. And so much tab is - shall I say - not that good...
Comment: Ah, OK. Smiley :-) But I did edit my answer a bit accordingly
Comment: Now, I'm smiling. Who is waiting in those queues? Cue an answer...
Answer: To be simple, piano and guitar shares same clef (treble clef). Apart from that piano has bass clef too. I hope the pitch matters here for clef. Playing way might differ by instruments.


What does lens flare from a catadioptric (mirror) lens look like?

Question: Can one get lens flare with a mirror lens? What does it look like?
Answer: Catadioptric lenses are lenses that combine both refractive and mirror elements. A simple mirror lens with no refractive elements is not a catadioptric lens. I've never seen a commercially available photographic lens with only simple mirrors, though.
Simple front coated mirror lenses, such as those used in reflector telescopes, that are clean do not demonstrate flare. Off axis light is, by definition, reflected outside the lens' field of view. Light from within the FoV is only reflected to a single point (or a blur circle for out of focus light sources) at the lens' focal length. The reason many simple reflector telescopes have barrels is to protect the mirror from condensation, dust, and damage. Dust and condensation on the surface of a mirror lens have optical properties than can, in the presence of off-axis light, reduce the contrast of the image projected by the mirror in a way that resembles veiling flare, but that is due to the nature of the substances on the mirror, not to the nature of the mirror itself. If the barrel of such a telescope is reflective, the reflections from the inside of the barrel can fall on the mirror and cause flare.
Any flare created by a catadioptric lens is caused by its refractive elements. This could include corrector plates, the glass in front of a back coated mirror, or even flat protective plates at the very front of the lens. Because most catadioptric lenses used for photography have fewer refractive elements than typical refractive lenses created for creative photographic use, most catadioptric lenses demonstrate less flare than many refractive lenses used in creative photography. But what flare they demonstrate is caused by the same properties of refractive lenses as the flare produced by a non-mirror lens. Thus any flare demonstrated by a catadioptric lens would be similar in nature to flare demonstrated by a refractive lens.
Catadioptric lenses with fewer refractive surfaces are more resistant to flare. In shooting situations that would induce ghosting with many conventional lenses, a mirror lens does not show the same tendency:

Normally we would expect to see some ghosting in the area, indicated by the yellow oval, directly across the center point in the photo from the brightest light source in the scene. Yet there's not even a hint of ghosting in this image taken with a Nikkor 500mm f/8 Reflex.
If you overexpose the scene enough, you'll get ghosting that looks exactly the same as ghosting with a typical refractive lens, other than the higher difference in brightness between the primary image and the ghost refelection:

The moon is well beyond totally blown out before we see a ghost reflection against the dark empty sky. Image taken using an Opteka 500mm f/6.3 + 2X teleconverter.
This image was taken with a Samyang 500mm f/8 mirror directly into the setting sun with enough exposure to see some flare. It's fairly conventional looking flare.

The veiling flare in this image from a 500mm f/8 mirror is very well controlled but otherwise the same as what one would see with a more conventional telephoto lens. The bokeh, however, is not!

We see the same thing in this one from a Minolta RF Rokkor 250mm f/5.6. Other than the degree to which the flare is controlled, there is no difference from a non-mirror lens under similar conditions.

(source: staticflickr.com)
Taken with a Walimex 300mm f/6.3 mirror, this sunset shows no obvious flare. A regular refractive lens of this focal length placed in the same situation almost certainly would.
Comment: This may be my phone, but why are the images at the bottom stretched? Nice answer btw
Comment: @10Replies They don't look stretched to me. It must be your phone.
Comment: You are right. .
Answer: Optical flare is caused by image forming light rays that are misdirected by the optical system. We are taking about rays that are reflected from polished surfaces and rays from the mirror or upfront glass corrector lens. The stray rays bounce and rebound about. Eventually some will intermingle with the image forming rays at the focal plane and induce some unwanted exposure. This results in an overall reduction in the contrast of the image. Flare can be devastating. Opticians do everything in their power to mitigate flare. They make sure the insides of the lens tube are painted or otherwise coated so the surfaces are anti-reflective. Polished glass lenses are mineral coated. This is a transparent coat with a specific thickness. This is ¼ wavelength of the color of the light to be mitigated. Often the lenses are multi-coated so that reflections are deadened. Let me add that the first-surface mirrors are coated with transparent quarts. This preserves the mirror finish by forestalling oxidation. Some mirror designs use thin wires or tubes to support the upfront secondary mirror. If used, they add a star-like pattern to the     bokeh. A catadioptic design uses a primary mirror that is more spherical, it should be parabolic. This induces spherical aberration. This aberration is mitigated by a thin low power corrector lens upfront. The secondary mirror is supported in the center of this corrector lens, this avoids the need to support the secondary via a spider web of wires or tubs. Most mirror camera lenses are of the Russian Maskutov design. In this design the upfront correct lens has more power and secondary silvering is applied directly to center of the corrector lens.
Comment: So, [What does lens flare from a catadioptric (mirror) lens look like?](https://photo.stackexchange.com/q/95006/15871)
Comment: My take is that this is a partial answer.  It does seem to drift off topic and doesn't fully answer the question, but it does seem to be making an effort at answering the first part.


When we go to Jannah, can we have children?

Question: When we go to Jannah, can we have children?  I.e., have a family, not just be with your family. If not then why?
Answer: There is a difference of opinions on the interpretation of the hadiths on this topic. The strongest opinion is that one may have one's children in Jannah that one had during one's life on Earth, but not give birth to a new offspring therein, and no reason was given in any hadith as to why.
In one hadith, the Prophet ﷺ said that if a believer desires a child in Jannah, one's wish would be granted:

عن أبي سعيد الخدري، قال قال رسول الله صلى الله عليه وسلم: الْمُؤْمِنُ إِذَا اشْتَهَى الْوَلَدَ فِي الْجَنَّةِ كَانَ حَمْلُهُ وَوَضْعُهُ وَسِنُّهُ فِي سَاعَةٍ كَمَا يَشْتَهِي
Abu Sa'eed Al-Khudri narrated that the Messenger of Allah (ﷺ) said: "The believer, when he desires a child in Paradise, he [the baby] shall be carried [in pregnancy], born, and complete his aging in an hour as he desires."
— Jami' at-Tirmidhi, Vol. 4, Book 12, Hadith 2563

In a continuation on the same link above (in the Arabic text only, not translated on Sunnah.com) Is'hāq ibn Ibrāhīm said the believer would give borth if he desires so but he would not desire so. Note that the word "itha" (Arabic: إذا) in the hadith was translated in the link above as "when" rather than "if". "Itha may be used to mean "when" but the typical use is that it means "if".
In the same link, there is a reference to another hadith:

وقد روي عن أبي رزين العقيلي، عن النبي صلى الله عليه وسلم قال: إِنَّ أَهْلَ الجَنَّةِ لاَ يَكُونُ لَهُمْ فِيهَا وَلَدٌ
NOTE. My own translation, so treat with care.
It was narrated through Abu Razīn al-'Uqaily that the Prophet ﷺ said: "The dwellers of Jannah will not have children therein."
— Jami' at-Tirmidhi, Vol. 4, Book 12, Hadith 2563

This other hadith and the concept that there will be no giving birth in Jannah are further strengthened through another long hadith in Musnad Ahmad (partially quoted):

قال رسول الله صلى الله عليه وسلم: َالصَّالِحَاتُ لِلصَّالِحِينَ، تَلَذُّونَهُنَّ مِثْلَ لَذَّاتِكُمْ فِي الدُّنْيَا، وَيَلْذَذْنَ بِكُمْ غَيْرَ أَنْ لَا تَوَالُدَ
NOTE. My own translation, so treat with care.
The Messenger of Allah ﷺ said: " The righteous women will be there for the righteous men to enjoy as you enjoyed in this world, and they will enjoy you, but there will be no giving birth.
— Musnad Ahmad, Vol. 27, pp. 126 (Arabic only)

Ibn Qayyim al-Jawziyya in Hādi al-Arwāh Ila Bilād al-Afrāh 249 (Arabic only) said that what goes on in Jannah is a matter of the unseen, so we do not know for sure what will happen there. However, he added that it was his opinion that there will be no giving birth in Jannah because:

The hadith of Abu Sa'īd al-Khudri is conditional as it said that "if a believer desires a child", and it may be the case that no believer would desire so in Jannah.
The hadith of Abu Sa'īd al-Khudri was narrated through Abu as-Siddīq an-Nāji, who had poor command of words that he memorized (hence, the hassan or good grade of the hadith). He narrated the same hadith in three different forms that the believer will have children in Jannah (a) and he will desire so, (b) when he desires so, or (c) if he desires so.
There is more than one hadith, although they have their own issues in their chain of narration, that point to the option of no giving birth in Jannah.

You may refer to Islam Q&A's article "Will there be pregnancy and childbirth in Paradise?" for more information.


What causes a code po300

Question: 2003 chevy Silverado has check engine light on but it flashes and won't go solid. It use to happen when it was wet or raining out but now its all the time. Could it be a ground issue
Comment: A flashing CEL usually means a misfire or other serious issue is happening and the truck shouldn't be driven until you know what it is.
Comment: Welcome to the site. What engine is in your truck? Were there any other codes? How does it run?
Answer: The P0300 code means "random misfire".  Some misfires are isolated to one cylinder and have different trouble codes, but this means that multiple cylinders or random cylinders are misfiring.
Misfiring will cause a loss of power, but it can also cause damage to the exhaust system if unburnt fuel enters the catalytic converter and burns inside.  Other types of damage can occur, so the flashing light is trying to tell you "this is serious, please stop driving".
It looks like your engine probably has a separate coil for each plug with short plug wires going to each plug.  Since you say it was happening on wet days, I'd focus on the ignition system first.  Look at the coils and see if they are cracking.  On some vehicles you can run the engine in the dark and look for sparks coming out around the coil as an indicator of damage.  Each coil also has control wires that hook into them.  Make sure these connections are good, and also check the main harness that these wires go to.
Someone with experience on your engine might have a better answer - I just want to point you in the right direction since a misfire should be fixed as soon as you can.  It's not like an emission error you can drive around with for months until you get around to it...

What causes a code po300


Completeness relations of eigenstates in the Heisenberg picture

Question: I've been reading Srednicki's introduction to path integrals and I'm slightly unsure of the notation that he uses for the completeness relation of position eigenstates in the Heisenberg picture. In particular, when he writes $$\mathbf{1}=\int_{-\infty}^{\infty}dq_{j}\lvert q_{j}\rangle\langle q_{j}\rvert$$ is this the instantaneous completeness relation for the position eigenstates in the Heisenberg picture? i.e. Given the instantaneous position eigenstate $\lvert q_{j},t_{j}\rangle =\hat{U}^{\dagger}\lvert q_{j}\rangle$ at time $t_{j}$, then we have $$\int_{-\infty}^{\infty}dq_{j}\lvert q_{j},t_{j}\rangle\langle q_{j},t_{j}\rvert =\int_{-\infty}^{\infty}dq_{j}\hat{U}^{\dagger}\lvert q_{j}\rangle\langle q_{j}\rvert\hat{U}= \hat{U}^{\dagger}\left(\int_{-\infty}^{\infty}dq_{j} \lvert q_{j}\rangle\langle q_{j}\rvert\right)\hat{U} =\hat{U}^{\dagger}\hat{U} =\mathbf{1}$$ where $\lvert q_{j}\rangle$ are the constant position eigenstates corresponding to those in the Schrödinger picture at time $t_{j}$, and thus satisfy the completeness relation $\int_{-\infty}^{\infty}dq_{j}\lvert q_{j}\rangle\langle q_{j}\rvert =\mathbf{1}$. (We've also used that $\hat{U}^{\dagger} \hat{U}=\mathbf{1}$.)
Comment: $\uparrow$ Which page?
Comment: @Qmechanic     page 57, Chapter 6 ("Path integrals in quantum mechanics")
Answer: I) Let us for clarity use a subscript "$S$" (and "$H$") to denote the Schrödinger (Heisenberg) picture, where bras and kets evolve (are unchanged) and operators are unchanged (evolve), respectively.
Moreover, let us assume that the two pictures coincide at the instant $t_0$ (which Ref. 1 assumes is $t_0=0$).
II) Recall first of all the possibly confusing fact that the Heisenberg instantaneous position eigenstate $|q,t\rangle_H $ does not evolve in time but does depend on the time parameter $t$, such that
$$\hat{Q}(t)_H ~|q,t\rangle_H~=~q~|q,t\rangle_H , \qquad \hat{Q}(t)_H~\equiv~e^{i\hat{H}(t-t_0)/\hbar} \hat{Q}_S ~e^{-i\hat{H}(t-t_0)/\hbar}. $$
The Heisenberg instantaneous position eigenstates satisfy
$$\int_{\mathbb{R}}\! \mathrm{d}q~| q,t\rangle_H ~{}_H\langle q,t|~=~{\bf 1}$$
for all $t$. Moreover
$$|q,t_2\rangle_H~=~e^{i\hat{H}(t_2-t_1)/\hbar} |q,t_1\rangle_H.$$
III) Let us now return to OP's question about whether the ket $|q\rangle $ in Ref. 1 is in the Schrödinger or in the Heisenberg picture? The ket $|q\rangle $ satisfies
$$ \hat{Q}_S~|q\rangle~=~q~|q\rangle. $$
The ket $|q\rangle $ does not evolve in time. Hence it is by definition in the Heisenberg picture. In fact, it is the Heisenberg instantaneous position eigenstate $|q,t_0\rangle_H $. Be aware that $|q\rangle $ often is called a Schrödinger picture position eigenket, cf. Ref. 2, because ... that's what it also is!
References:

M. Srednicki, QFT, 2007; Chapter 6. A prepublication draft PDF file is available here.
R. Dick, Advanced Quantum Mechanics: Materials and Photons, 2012; p.243.
J.J. Sakurai, Modern Quantum Mechanics, 1994; Chapter 2.
Comment: Ah OK, so is it that the instantaneous eigenstates satisfy the completeness relation I gave in my post? I'm just confused by Srednicki's notation of $\lvert q_{j}\rangle$, is this shorthand for $\lvert q_{j}, t_{j}\rangle$? Also, I thought that in the Heisenberg picture the eigenstates of a given basis evolve in time, i.e. $\lvert q_{j},t_{j}\rangle =e^{i\hat{H}t_{j}/\hbar}$, such that the state vector of the system $\lvert\psi\rangle$ remains constant in time?
Comment: My question arose in particular after reading page 242 in Rainer Dick's book, "Advanced Quantum Mechanics: Materials & Photons: https://books.google.co.uk/books?id=gmss64mGm2IC&pg=PA242&lpg=PA242&dq=completeness+relation+in+heisenberg+picture+quantum+mechanics&source=bl&ots=Bew7BwEe_u&sig=NLTiMWmspWzWvfVfWG9F2LGXt9w&hl=en&sa=X&ved=0CC8Q6AEwBmoVChMImovm4LjOxwIVoxTbCh0rKA4-#v=onepage&q=completeness%20relation%20in%20heisenberg%20picture%20quantum%20mechanics&f=false
Comment: I updated the answer.
Comment: Thanks for the updated answer. So is what I put correct (according to what R.Dick has put in his book) about the instantaneous completeness relations? In the Heisenberg picture does $\lvert q_{j},t_{j}\rangle$ simply mean that the system is in a fixed state at the point $q_{j}$ at time $t_{j}$? Is the notation $\lvert q_{j}\rangle$ shorthand for $\lvert q_{j},t_{j}\rangle$?
Comment: ... Also, in Srednicki's book (chapter 6, page 159) he goes on further to talk about the transition amplitude $\langle q'',t''\lvert \hat{Q}(t_{1})\rvert q',t'\rangle$ introducing a factor of $q(t_{1})$ in the corresponding path integral. By this is it simply meant the eigenvalue $q$ of the position operator $\hat{Q}$ at time $t_{1}$, i.e. $\hat{Q}(t_{1})\lvert q_{1}\rangle = q(t_{1})\lvert q_{1}\rangle$?


Time series decomposition

Question: For me, the original data looks to have like a decreasing or constant trend but stl() is giving a different trend altogether. Can someone here please explain why?
The decomposition plot is as follows:
Answer: To my eye, the second half of 2018 is substantially higher than the prior two years, so the trend that stl() is giving seems not unreasonable.
Trying to fit a time series model to only three years of data is going to require you to take a pretty strong hand guiding the model; I wouldn't expect a turn-key solution to give satisfactory results.
One obvious problem with the decomposition from stl() is that the seasonal figure is wildly overfit.  I would try using the Fourier series approach to fitting the seasonal figure that Rob Hyndman describes in this blog post.  I have applied that technique in exactly your situation and gotten decent results.
The closest to a turn-key solution is probably going to Facebook's prophet library.  But with only three years of data, I still suspect you'll overfit the seasonal component if you call it with the defaults.
If you post your actual data and describe your goals more completely, folks might be able to help more.

Time series decomposition


iPod Nano 6th Generation stuck power button

Question: I heard that you can start the iPod Nano using the volume keys in lieu of the stuck power key. Is this true? Any other way around the stuck power button?
Answer: Yes there is. Plug it into your computer or a power source. It will power up; unplug it  and you can start the music or audiobook or whathave you. When you want to stop, you can pull out the headphone which shuts it down. To restart, you'll have to do the same and it won't start at the point where you stopped. I know it isn't great, but it is something. I will eventually take it apart and try to do the repair that is posted on the internet.


How to filter an array of objects?

Question: I have an array of objects that have been pulled from a web service that look something like this.
{
  ArticleID: "ABC123",
  Region: "US",
  PubTypeID: "EO",
  PubType: "Europe Order",
  Created: "01/01/2013",
  Scheduled: "03/02/2013"
}

The ArticleID, Region & PubTypeID make up a composite key. The datasource is one table and cannot be changed but I need to get Unique items to display a dashboard like interface. So Show Unique ArticleID's but group the articles under them. The interface should look something like this.
ArticleID      Status
----------------------
ABC123          Scheduled
    Region:US       Scheduled: 02/02/2013
    Region:JP       Scheduled: 05/02/2013
    Region:OE       Scheduled: 03/02/2013
    Region:EU       Scheduled: 04/02/2013
ABC456          Ready to Schedule
    Region:US
    Region:US
    Region:US
ABC789          Sent
    Region:EU       Sent On: 01/02/2013
    Region:EU       Sent On: 01/02/2013
    Region:EU       Sent On: 01/02/2013
    Region:EU       Sent On: 01/02/2013

The status is determined by the date. I also have the dilema of what the status will be if one item under an article has a date and one does not, what will the status be?
If the data was normalized I would have no issues here as I could do multiple selects and build the output but I only have a flat result set so need to do the "selecting" in Javascript.
Can someone help me on how I would do this in Javascript please?
Answer: In order to build this data out to go into a table as you describe, I would first organize the data so it matches what you want to do.  So instead of having individual objects, I would iterate through the returned data and convert it into:
{ArticleID: "ABC123",
Status: "Scheduled",
Articles: {
  ArticleID: "ABC123",
  Region: US,
  PubTypeID: "EO",
  PubType: "Europe Order",
  Created: "01/01/2013",
  Scheduled: "03/02/2013"
  },{
  ArticleID: "ABC234",
  Region: US,
  PubTypeID: "EO",
  PubType: "Europe Order",
  Created: "01/01/2013",
  Scheduled: "03/02/2013"
  }
}

Then build the table based on this structure.  You will need to have some calculations in your function to determine the status.  I don't understand this one enough to give you a specific answer, but it looks like all common article ID's have the same status, so this could be ignored while restructuring the objects, and inserted while building the table.
If you have any control over the server side code, it would be much better to do this object restructure work before passing it to the client.
Answer: You could use Array.prototype.filter, to sort all entries, given the fact you know all the article IDs (If not, you would have to iterate over the input and collect them).
var input = [{
  ArticleID: "ABC123",
  Region: "US"
},{
  ArticleID: "ABC456",
  Region: "US"
}];

var regions = ["ABC123","ABC456"];

var articles = [];
regions.forEach(
    function(reg,i){
        articles[i] = input.filter( function(el){ return el.ArticleID == reg} );
    }
);

console.log(regions);
//regions[0] <= array with all articles with regionID "ABC123"
//regions[1] <=                   - " -               "ABC456"

now articles holds an array with all articles sorted by ArticleID.
Beware, this is IE9+ code, in order to make it work in IE8 and below, you need a shim for filter and forEach which you can find on the according MDN-Articles.
Answer: I think that you need to re-arrange the data having it ordered by ArticleID. And assuming you are going to have many articles. Something like this iteration could do the re-arranging task. Then you can easily iterate trough the new object printing the useful information
var x
var y = 0;
var newArray = new Array();
for(key in data){
   x = data[key].articleID; //The value of the key you want to use (ArticleID)
   newArray[x] = newArray[x] || []
   newArray[x][y] = data[key];
   y++
}
console.log(newArray)

Here you have a fiddle. Look into the resulting object (using the chrome or other console), and you are going to see how the data is now grouped by ArticleID;
EDIT: I've replaced the code with a cleaner version.
Comment: So in the fiddle Os the key the field name or the value in the field? Thanks by the way
Comment: Sorry, what you mind by Os?. I don't understand the question. Can you explain a bit more what problem are you having? :)
Comment: Sorry I was typing on my cell... I meant In the SQL that you posted is the key the field name or is it the value of the field?. so for instance is it data["ArticleID"] or is it data["ABC123"]?
Comment: In the new Array we are generating, the key of each group of objects is the value shared by the objects, for example ["ABC123"]. Where we are using the key (articleID) is where we defined the X variable. But we using "key" as a variable inside the for loop which let us select each object, maybe is a bit confusing. I've made this kind of debugging fiddle, so you can read on the console, the values of those variables and keys. http://jsfiddle.net/Ltemt/5/  And at the end I also incorporate a printing in console of the desire result, let's say a way of using the newArray.

How to filter an array of objects?


Trop (cantillation) for leining

Question: Who created the trop (cantillation) for leining? Is it a Mesorah from when the Torah was written?
Comment: http://www.chabad.org/library/article_cdo/aid/817346/jewish/Who-made-up-the-way-we-sing-the-Torah.htm
Comment: dupe? http://judaism.stackexchange.com/q/22586/759
Answer: The te'amim (trope) symbols are about 1,000 years old and are pretty much universal within the Jewish world. They replaced earlier (and probably less efficient or more confusing) systems of notating the grammatical breakdown of verses. The actual parsing of each verse into clauses and sub-clauses is, of course, a much older oral tradition.
The melodies we assign to the trope symbols are harder to track down. They are certainly old, but have clearly changed over time, and differ from community to community. Ashkenazi, Sephardi, Mizrachi and Yemenite Jews all have different sets of melodies and use them in very different ways, and there is a huge amount of diversity within each of these major groups.
There are a few older examples (perhaps 400-500 years old) of the tropes written out in something like modern musical notation. These come from a German Christian work of that era. From what I recall, the melodies indicated sound very little like either our modern day Western Ashkenazi or Eastern Ashkenazi trope.
Comment: Here is a relevant article from the Jewish Encyclopedia online.
http://www.jewishencyclopedia.com/view.jsp?artid=109&letter=C
Comment: Jordan, the Christians always considered the Sefardic traditions more accurate. 400-500 years ago in Germany there were transplant communities of Sefardim in Germany. (Such as in the Altona-Emden-Hamburg region.) Compare those melodies to the Sefardic trop and see if there are any resemblances.
Answer: In all systems of trop there is a typology regarding the functions of the trop. Some are full stops, partial stops, assistants, etc. that all lend assistance in understanding the text. There is no need for a source to prove that we as Jews have known how to read the Torah and understand it since we received it.
What is not clear is the various styles of trop and the way they tend to sound like the musical cadence and scales of the host countries of the Jewish communities that they stem from.
A fair assesment could be that the style, inflection, and actual musical intonations always changed depending on the native language of the Jewish community. The pauses and other tones used may have made sense to those who spoke the language of those host countries.
Answer: Wasn't it Moshe Rabbeinu who instituted reading of the weekly Torah portion every Monday and Thursday so we not abandon Torah for more than two days? Wouldn't you expect therefore that "trop" was devised back then and its מסורה handed down -- since then? And just like trop, wasn't it since then that also handed down were  the "psikim" (or whatever they're called), those bar-like separators between two words (looks like this: | ), which tell us that a separation between those two words is needed?
Comment: You're asking a lot of (unsourced) questions in a space reserved for answers.
Comment: The Talmud (Nedarim 37b) indicates that trop was given to Moses at Sinai.
Comment: Edit that into your answer! Your answer would be more valuable and useful with declarative statements with sources.

Trop (cantillation) for leining


Can we use PHP inbuilt function inside Twig File in Symfony

Question: Hi Can anyone Please let me know can we use php inbuilt function inside a twig file.if not then why.
What is the way then to access php inbuilt function inside a twig file.
Because in a application in 100 of time we need to check many conditions basis of php inbuilt function.I have tried in_array() function to check multiple vaslue selected in a multiple dropdown  list but i am getting error Is_array() not defined.
Please help
Thanks
Answer: As @DonCallisto Said, There is some PHP equivalent function exists in twig not all. So you cant call a php function from twig template. You may have to use a existing equivalent or need to create one if not exists.
Why?
One of the main reason is SoC. Template is for presentation layer of your application. So twig made available tools(filter,functions, global variables) to do that.
Know the differences
Though you have date function in twig. its not the same date function you have in php. To achieve a similar functionality you may have to use same or different approach in twig then php. for instance you can achieve php's in_array functionality using the twig's Containment Operator
What is the way
Now come to last part of your question:

What is the way then to access php inbuilt function inside a twig file?

I think you already know the short answer from @DonCallisto. You can create your own extension. And define what function you needed. Or if you are crazy enough to access all php builtin function from your template, you can use this Extension. It will allow you to call any php functions by prefixed with php_. for example if you like to call in_array function, then you can call like php_in_array() from your template.
Happy coding!
Answer: Twig have some php builtin functions equivalent. For instance in_array() php function is in twig function. Check it out
If you don't find some builtin, you need to write your own twig exstension
Comment: Thanks there is In function which we can use as in_array() of php in twig file.
Comment: @user3458514: told you :) there is and is linked above


GNUPLOT on Lion using Homebrew

Question: After upgrading to OSX 10.7.4 I had to reinstall GNUPLOT which is always a hassle. I decided that I would try Homebrew instead of Fink or MacPorts.
Ofcourse, before installing Homebrew one needs the Xcode application and together with it the Xcode CLI kit (I first installed the latter one as it looked as if that would suffice, but the Homebrew doctor recommended installing the XCode app also...).
After some reading I got the impression that when installing GNU Octave (which I might also need later on), Homebrew would also install GNUPLOT. This did not happen and after an hour or so the Octave installation also failed. Then I decided I was not interested in Octave itself at the moment, but only in GNUPLOT and installed that by doing 'brew install gnuplot' which was rather quick as most of the dependencies were already there.
Anyway, when using GNUPLOT (with Apple's native X11) I can plot a few things, but when exiting or when replotting some data files I get the following error:
<code>gnuplot> exit
gnuplot(406) malloc: *** error for object 0x6d72657420746573: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6
</code>
I'm not sure how to debug this, tried reinstalling with brew (and also checked the deadlines installation), but without any result.
Any input on this?
Cheers,
Answer: Try switching the readline to the built-in readline:  http://head-lights.blogspot.com/2013/09/gnuplot-mountain-lion-and-malloc-errors.html

GNUPLOT on Lion using Homebrew


Mac App Store apps without internet connection

Question: I want to set up a Mac running a recent version of OS X but I don't want it to be connected to the internet because of security reasons. Is it possible to copy and activate apps bought and installed from the App Store on an other computer to the one with no internet connection? I know that the App Store validates the license to install such apps and it actually needs an internet connection to do so. But maybe there is a kind of license key file that can also be coppied over to the air gapped box.
Answer: YMMV. Every once in a while when the transferred app is opened for the first time, it will need to validate the Apple ID which the app was downloaded with, so most of the time it will work, but sometimes it won't.


Planting non organically grown plants in organic garden

Question: I have some raised beds that I use for vegetable gardening. I don't put any fertilizers or pesticides and I grow all vegetables from seeds. Lately I have been thinking of purchasing young vegetable plants from a big box store to do winter vegetable gardening and planting them in the same raised beds. I would only plant the seedling and throw away the soil that comes with it. I realize the produce will not be organic but any other downside I am missing. Note that I am growing for personal use only and not a strict organic consumer.
Comment: J. Start looking for labels and asking the dang employees whether or not the plants you want to purchase are NON-GMO.  That is the big thing.  The biggest thing.  Pretty soon it will be impossible to get NON-GMO seed or purchase vegetables declared to be NON-GMO.  The Organic or Natural label is often abused.  Don't accept plants from friends. To get Sclerotinia sclerotinorum...or white mold is a death Knell for your plants. But RARE.  You'll be fine if you use starts that are in fluffy potting soil.  And as long as you have an outside garden...no problemo.
Comment: I edited the title - 'inorganic' means inert or lifeless (as in gravel for instance)
Answer: Really all plants are organic (and by the way also few fertilisers and pesticides). The definition is about using product produces (by humans) with chemical synthesis.
On your garden, you know how you produce things, so you don't need any label (and strict rules).
For health, I don't think it matter so much: existing part of seedlings will be a tiny part of yield.
Anyway I would discard flowers and fruits, and possible I'll mark the leaves, so that I'll not eat the existing leaves.
Organic fertilisers and fungii affect much more the consumer health. For the first, try not to over-fertilize (manure tend to concentrate minerals and metals, and few metals are good for plant, too much could be toxic). For the fungii: I assume you don't harvest with machines, so you will see and discard bad fruits.
So it is more about ethics and personal choice.
Answer: I think you are a bit too far into the purist spectrum? All plants need additional fertilizer.  A natural ecosystem is where all the plants are part of the system and over time all nutrients are actually in the plants.  When those plants die they are then decomposed and the chemicals are released back into the ecosystem to be immediately taken up into the live plant material and micro/macro organisms that are part of the ecosystem.
Our gardens, plants in pots, rely on us humans to replace chemicals those plants need that were mostly stripped away during construction.  Fertilizer is not pesticide.  All pesticides aren't all BAD.  All pesticides include herbicides.  Pesticides/herbicides are BANDAIDS for problems we humans made.  When we get better we know how to prevent ever using pesticides...well, almost. When we mix milk and water 1:9 and spray plants for powdery mildew...THAT IS a pesticide (fungicide).  Soap and water is a pesticide.  Scissors and cutting slugs in half at night is also a pesticide.
More importantly one should know the pH of the soil and what the plants we want to thrive in that soil love that pH.
I assume this is not a greenhouse/hermetically sealed environment.  Raised beds are great (there isn't concrete or gravel below that soil, yes)? If these beds are garden soil over concrete or gravel...we need to talk.  If you've made raised beds over concrete I hope you've used sterilized soil.
If you were trying to grow in a greenhouse we might be talking about foreign soils/plants/problems being introduced.  But we are not.  Do not throw the soil away.  Starts you purchase are always done in sterilized potting soil.  There can be problems when bringing purchased plants into the garden even an outdoor one but usually that is when we bring starts home from our friend's homes/gardens.
Do begin to imagine how you will rotate your 'crops' the next year.  Do add decomposed organic matter whenever you are able, just to the top of the beds.  It will be mixed for you by the organisms coming up out of the soil to eat the decomposed organic matter. They then go back into the soil profile and poop it out mixing this decomposed organic matter into the soil without you spending any calories!  Be vigilant to see problems before they become a problem.  In every sense gardening is organic, flexible, complex yet simple.
Comment: And I forgot to add if you are thinking growing via seed is a good thing YES it is BUT, you have to make dang sure NON-GMO is on that package.  If not don't buy it!!


Can I turn off Discussion Forum Administrator notifications?

Question: I'm set as the Administrator on a client's discussion forum. Certain employees are set as moderators and receive email notifications. I don't want to receive the notifications as the administrator. Any way to turn this off? I searched through the menus and couldn't find anything. Thanks!
Answer: Are you talking about the "New Topics" / "New Reply" notifications? If so, just don't specify your email in "Admin Notification Preferences" when you "Edit" the forum in question in the CP. See screenshot.
Comment: Bjorn, my email isn't in there. I have added a couple email addresses of my client in there.
Comment: Then it's probably the "webmaster email" setting - I'd just change that email to your clients'. https://ellislab.com/expressionengine/user-guide/cp/admin/email_configuration.html or https://ellislab.com/expressionengine/user-guide/general/system_configuration_overrides.html
Comment: Thanks Bjorn, this is probably the answer. It's a slow board so I'll have to wait a few days to see if it worked. If you update your answer above with this info I'll mark it as the answer. Thanks!


Brexit: EU citizen moving to UK under current laws?

Question: If I understand correctly, EU citizens can move to the UK under the current laws and they will get same status after the Brexit. For how long they can move to UK under the current laws and when will be the new immigration law enforced?
Comment: The eventual outcome will likely depend on whether you're working, student, on welfare, retired, joining other family members and what their status is, etc.
Comment: note: until we know more any Brexit questions referring to EU nationals are duplicate of the canoncial one. Please edit the CW answer there to add new details.
Answer: (Answer up-to-date as of 2017-03-22)

If I understand correctly, EU citizens can move to the UK under the current laws

Correct.

and they will get same status after the Brexit.

Wrong.
The post-Brexit status of current or future EU citizens in the UK is currently unknown.  Analists consider it likely that their status will eventually be guaranteed, but currently this is speculation.

For how long they can move to UK under the current laws and when will be the new immigration law enforced?

Unknown.
The uncertainty facing EU citizens in the UK is one among many political issues in the UK.  The House of Lords tried to pass an amendment guaranteeing their (our) rights, but the House of Commons effectively overruled them (BBC News).
Answer: Current EU law still fully applies and the UK hasn't made any major change to its immigration regime since the Brexit referendum.
As far as EU law is concerned, freedom of movement should apply until the actual Brexit happens, which should be two years after the UK triggers article 50 of the Treaty on the European Union. The British government stated plan is to notify the Council of its intention to withdraw from the EU on March 29, 2017.
Legally, two things could alter this timeframe. Firstly, article 50 provides that the treaties cease to apply once the withdrawal agreement enters into force. So the UK could leave the EU before March 2019 if an agreement is reached earlier. Secondly, the same paragraph also allows the EU to extend the deadline of negotiation if all EU countries agree. Both of these presently seem unlikely.
Furthermore, the UK could also conceivably cease to apply EU law unilaterally, for example by introducing some new restrictions or requirements on EU citizens' residence. I recall that some MPs toyed with the idea but this would force the EU to retaliate and make negotiations even more difficult so I don't think it's very likely.
After that, what will happen is even less clear. It's possible, although not particularly likely at this stage, that the EU and UK will enter some sort of Swiss-style association agreement with minimal changes to the immigration regime. It's also possible that it would create a completely different immigration regime but allow EU citizens currently in the UK to stay under EU rules, perhaps in exchange for reciprocity for the British citizens living in the UK.
In that case, something like the current rules would still apply to some people for many years. It's also conceivable that this would only apply during some sort of transition period or perhaps only for people who already lived in the UK before the referendum or some other specific date set during the negotiation. But all this is obviously very speculative, there is no way to know at this stage.
Comment: "...for the British citizens living in the UK." should be in the EU I assume.


Which chess site has the most rapid players?

Question: It is common advise that a chess player trying to improve should limit their blitz chess. Online chess is filled with people playing blitz and bullet and I often have trouble finding players to play longer time controls. Is there a chess site with a lot of rapid players? I'm thinking that unfortunately, chess.com is the best option, but sometimes I feel like it takes too long to pair up, and the opposition is not so strong. I've heard that ICC isn't too good for long time controls either. Anyone have any information?
Answer: The vast majority of online chess games played on any site are played with very short time controls. Because of this fact, if you want to play longer games, you will have to wait longer, on average, than you would for a game shorter time control.
If you are looking for quality chess games and you want relatively long time controls and decently high-rated players then you can try limiting your searches to high rated players.
You can select custom rating ranges on lichess and on ICC. This will allow you to, for example, filter out lower-rated opponents if you want a strong opponent.

Another possibility is to play in the long-time-control tournaments that most popular chess sites have on a regular basis. Both ICC and lichess have regular tournaments with relatively long time control. The advantage of this is that once the tournament starts, usually the wait time between games is not that long.
Comment: Tournaments don't seem like a good idea in my opinion. You have to play players of all strengths in a tournament, so you don't get to play "strong players" too often. Also, lichess tournaments with rapid time controls is 10 minutes, which isn't very serious, especially with the lack of increment.
Comment: Some tournaments are restricted to rating ranges (e.g. U2000 or 1800+) ... but yes, if I were you, I would just search for high rated games and long time control, and during the long waits just do lichess puzzles (I think they are quite convenient) or chess tempo puzzles ...
Comment: The issue with tournaments is that say if you play a 30 minutes each tournament, and you win your first game in 5 minutes because your opponent blunders or leaves, you (generally) have to wait 55 minutes for your next game to start. Most people don't "play" chess online to sit and wait for a game for so long. (The lichess arena system somewhat circumvents this issue, but for small tournaments with long time controls you'll still have to wait a while to be paired again.)
Comment: Lichess doesn't seem to have the problems mentioned in the comments to this thread, but unfortunately the longest tournaments are 10+0 games.
Answer: Chess With Friends
It is available as an app for android and iOS. There is a time restriction of 5 days per move. Falling foul of the time restriction forfeits the game.
The game has it's own ELO system independent of any official ones and it's not tremendously accurate (I am rated about 200 points higher than my real rating)
But it's matching system works really well and it picks opponents for me who are a good match for my skill level.
I am currently playing about 12 games simultaneously. Each night after dinner I will sit down and play one move in each game. If I miss a night because I'm busy or tired it's no big deal. Sometimes I won't be able to play a move because my opponent has not moved yet, but I will still spend a few minutes looking at the position.
That style of play won't suit everyone, but the app is definitely worth a look.
There is a free version which has 100% functionality but has quite a lot of ads. The paid version is quite cheap and worthwhile in my opinion.


How to decompose a unitary transform into two-level unitary matrices?

Question: I'm struggling to understand the process of how to decompose a unitary transform into two-level unitary matrices. I've been trying to understand the process as detailed in arXiv:1210.7366, but I don't get where those 2x2 matrices in the individual two-level matrices are coming from, or what P actually is. If anyone could walk me through a numerical example of decomposing for example, a 4x4 matrix into two-level unitary matrices, that'd be greatly appreciated!
Comment: what do you mean by "two level unitary"?
Comment: This is how it's defined in the PDF I linked above: "Recall that a two-level d×d unitary matrix is a unitary matrix obtained from the d×d identity
matrix I_d by changing a 2×2 principal submatrix. It is well known that every d×d unitary matrix
can be decomposed into the product of no more than d(d−1)/2 two-level unitary matrices."
Comment: what's the difference between this and the classical [Reck et al. 1994](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.73.58) method to decompose unitaries as sequence of 2x2 ones?
Answer: The basic idea is to multiply $U$ on the left with $2\times 2$ unitaries until the identity is obtained. This method provides a sequence of gates $U_k$ such that $U_1\cdots U_n U=I$, which then gives you the decomposition of $U$ in terms of $2\times2$ unitaries: $U=U_1^\dagger \cdots U_n^\dagger$.
For example, suppose you start with
$$U=\begin{pmatrix}1/2&\frac{1}{2\sqrt3}&\sqrt{2/3}\\-1/2&\sqrt3/2&0\\1/\sqrt2&1/\sqrt6&-1/\sqrt3\end{pmatrix}.$$
We start by finding a matrix which only mixes first and third row of $U$, with the goal of annihilating the $(3,1)$ element.
In general, a matrix $U_1$ mixing only first and third column of $U$ has the form
$$\begin{pmatrix}* & 0 & * \\ 0 &1&0\\ *&0&*\end{pmatrix}.$$
To send $U_{31}$ to zero essentially amounts to finding parameters $a,b$ such that $aU_{11}+b U_{31}=0$, which gives $a=-b U_{31}/U_{11}$ (the case $U_{11}=0$ can be handled separately). You then put the resulting $a,b$ in the third row of $U_1$, and then adjust the rest of the parameters in $U_1$ in order to make it into a unitary. This results in the following $U_1$:
$$U_1=\begin{pmatrix}
1/\sqrt3 & 0 & \sqrt{2/3}\\
0 & 1 & 0\\
-\sqrt{2/3} & 0 & 1/\sqrt3
\end{pmatrix}.$$
Then,
$$U_1 U = \begin{pmatrix}\sqrt3/2 & 1/2 & 0 \\ -1/2 & \sqrt3/2 & 0 \\ 0 & 0 & -1\end{pmatrix}.$$
In this case we were lucky in that we obtained two zeros in one step, but this is only due to this particular choice of $U$. You now need to find some $U_2$ which only mixes the first two rows of $U$, that is, a matrix with the structure
$$\begin{pmatrix}* & * & 0 \\ * &*&0\\ 0&0&1\end{pmatrix}.$$
To send to zero the $(2,1)$ element of $U_1 U$ we can use (again, focus on coefficients that send to zero the elements in the first column of $U_1U$, and put them in the second row of $U_2$, then filling out the rest to make $U_2$ unitary):
$$U_2=\begin{pmatrix}-\sqrt3/2 & 1/2 & 0 \\ 1/2 & \sqrt3/2 & 0 \\ 0 & 0 & 1\end{pmatrix},$$
so that finally
$$U_2U_1 U=\begin{pmatrix}-1&0&0\\0&1&0\\0&0&-1\end{pmatrix}.$$
Notice how some of the signs in the resulting matrix are wrong. This is because I didn't put much care in the signs of the matrices $U_i$. Following the more accurate prescription given in the paper (note how they also include the determinants in the expressions, and take care of the cases with complex numbers) you will always obtain the identity at the end.
Finally, it might be interesting to note that this is essentially the LU decomposition applied to the special case of a unitary matrix.
Comment: Hi, thanks for the very detailed reply, I really appreciate it! If I could ask you a couple of followup questions, that'd be awesome.

**1.** Solving the parameter equation, is this just taking educated guesses at the values of a and b until we have a pair that fit, since we only have a single equation with 2 parameters?

**2.** In the paper I linked, in page 2, in the Step 1 section, it says that det(U_1) = u_bar; how is that calculated when we need u_bar to make U_1 in the first place?
Comment: @Yuerno 1) more than educated guesses, you are solving equations like $a U_{11}+ b U_{31}=0$ for $a,b$, whose solution can always be written down explicitly. 2) I think that's an additional freedom in the way the $U_k$ are chosen. You just need the final matrix to have a fixed identity, so you can tune the intermediate determinants as long as the overall one is correct
Answer: Their approach is more advanced than the simple one, described in the book "Quantum Computation and Quantum Information" by M. Nielsen and I. Chuang, section 4.5.1. It's better to understand it first. Basically we are just making zeros under diagonal step by step, where each step is the multiplication by some two-level unitary. Hence there are only $d(d-1)/2$ steps needed.
In the linked paper, $P$ is just a permutation of $d$ numbers $\{1,2,..,d\}$ represented as a tuple $(j_1, j_2, .. ,j_d)$. For a fixed $P$ we can take two consecutive numbers $j_k,j_{k+1}$  from the tuple $P$ by picking $k$ from the set $\{1,2,..,d-1\}$.
Comment: Thanks for the reply! Would you be able to explain how these approaches are calculating the values of the principal submatrices? I think I'm just missing some linear algebra background here. Like for example, in the PDF I linked, how the entries of the bottom right square of U1 are calculated?


Is there such a thing as Balanced stereo cable?

Question: From the look of it, left and right channels have common ground, but still all the cables I've found so far are just two balanced cables glued together.
Why no one created 5-wires cable and saved 20% of the cost?
Answer: Sound quality is probably the first reason. A balanced audio signal only works when the interference/noise is the same on both signals. After inverting the sound signal, the noises that were identical on both signals will only be canceled out. So if there is any interference on the signal, make it happen that they are the same on both cables. When using a shielded two core cable is more likely to have the same interference than when using a shielded four core cable.
Usability is another aspect in choice of cables. A shielded two core cable is more flexible, especially the dual braid copper wires. When using a shielded four core cable you'll lose flexibility, durability and even the chance of exposing one of the conductors from its shield when flexed (read: more stress inside the cable when flexing).
Price A shielded four core cable is in general twice as expensive as an shielded two core cable. When one core breaks down you need to replace the entire, more expensive, four core cable while using two cables you only need to replace one of the two.
Answer: I use 5-pin XLR ends on a canare starquad cable to carry a stereo signal from my MS microphone pair to my stereo mixer. No problems so far. From my research this seems to be a common method and is supposedly especially safe over short runs. My run is 10 feet and I use y splitters that use mini starquad at both ends.
Comment: Is this the cable: http://www.canare.com/UploadedDocuments/Cat11_p35.pdf ?
They don't mention cross-talk measurement, is it supposed to be used for stereo?
Answer: Yes there is, and it's called multicore, which is a generalized name, and can have as few as 2 cores, e.g.: http://katalog.cordial.eu/catalog2,25,29,mw41.html


How to allow someone to correct their Cognito Form submission

Question: I'm trying to have people go back in after they've submitted the form and fix things.  I've marked the entries incomplete and want to, whenever the form is deemed incomplete, have an automatic email response sent to the enterer asking them to complete other details.  How do I do this?
Answer: Here is a detailed description of how to automatic the process of asking your customers to make changes after they have submitted their Cognito Forms.
Enable Link Sharing
Under Build - Form Settings:

Turn on Entry Link Sharing
Set Allow Edit Links to Always
Click on the email template to customize the email that will be used when you share view/edit links with your customers.
Make sure to specify the field on your form that contains the email address of your customer

Enable Save & Resume
Under Build - Submission Settings, enable Save & Resume:

Share Edit Links
Under Entries, select the entry you want your customer to update and follow these steps:

Click Share above the entry
Under Share a Link - Edit Link, select Link Expires - When Submitted
Click Get Link to mark the entry as Incomplete and create an edit link for the entry

Further customize the sharing message to provide instructions and click Send

You customer will then receive the email asking them to make changes, including a link to edit their submission.  They will be able to edit the entry, including saving incremental changes, until they click Submit.  When they click submit, they will no longer be able to make changes using this link and the normal submission emails and integrations will be kicked off.