When are p-values deceptive?

Question: What are the data conditions that we should watch out for, where p-values may not be the best way of deciding statistical significance?  Are there specific problem types that fall into this category?
Comment: Just throwing this out there, but wouldn't this sort of question best be posed on [Cross Validated](http://stats.stackexchange.com/)?
Comment: Snarky answer: almost always. There's a huge incentive to create Type 1 errors (i.e., "false alarms") when analysts examine data, so almost all p-values you'll encounter are "too" small.
Comment: @buruzaemon: Maybe.  I did a search, this is the closest match: http://stats.stackexchange.com/questions/67320/hypothesis-testing-with-big-data  There don't seem to be more than a handful of questions that touch on this.
Comment: goodness of fit (p value) measure of raw data and measure of difference between two statistics e.g. mean values - statistical significance are two different concepts.
Answer: You are asking about Data Dredging, which is what happens when testing a very large number of hypotheses against a data set, or testing hypotheses against a data set that were suggested by the same data.
In particular, check out Multiple hypothesis hazard, and Testing hypotheses suggested by the data.
The solution is to use some kind of correction for False discovery rate or Familywise error rate, such as Scheffé's method or the (very old-school) Bonferroni correction.
In a somewhat less rigorous way, it may help to filter your discoveries by the confidence interval for the odds ratio (OR) for each statistical result.  If the 99% confidence interval for the odds ratio is 10-12, then the OR is <= 1 with some extremely small probability, especially if the sample size is also large.  If you find something like this, it is probably a strong effect even if it came out of a test of millions of hypotheses.
Comment: While Bonferroni is definitely old-school it is still pretty popular. Related to it is a method called Šidák correction ( https://en.wikipedia.org/wiki/%C5%A0id%C3%A1k_correction ). I am calling it out, because in a large scale targeting advertising system I worked on we were able to implement this approach as a UDF in Hive. However this only works better when you have independence between tests. If not you have to fall back to Bonferroni or another method.
Answer: You shouldn't consider the p-value out of context.
One rather basic point (as illustrated by xkcd) is that you need to consider how many tests you're actually doing.  Obviously, you shouldn't be shocked to see p < 0.05 for one out of 20 tests, even if the null hypothesis is true every time.
A more subtle example of this occurs in high-energy physics, and is known as the look-elsewhere effect.  The larger the parameter space you search for a signal that might represent a new particle, the more likely you are to see an apparent signal that's really just due to random fluctuations.
Answer: One thing you should be aware of is the sample size you are using. Very large samples, such as economists using census data, will lead to deflated p-values. This paper "Too Big to Fail: Large Samples and the p-Value Problem" covers some of the issues.

When are p-values deceptive?


What is 2 $\theta$ in X-ray powder diffraction (XRD)?

Question: Why are we taking 2$\theta$ instead of $\theta$ in X-ray powder diffraction (XRD). I have found the forum post 2 theta in X-ray Powder Diffraction (XRD),  but there is no answer. What is the explanation?
Answer: When you do diffraction, $\theta$ is the angle of incoming EM wave, as well as the angle of difracted EM in regard to Bragg's planes.  So the total change in angle of the EM wave equals $2\theta$.
See images at http://en.wikipedia.org/wiki/Bragg%27s_law.
If this is not the answer you're looking for, maybe you should specify your question more clearly.  (I was doing Bragg's experiments as a student decades ago, I naturally always halfed the angle, so I do not quite understand what is your problem.)
Answer: For the $\theta : 2\theta$ goniometer, the X-ray tube is stationary, the sample moves by the angle $\theta$ and the detector simultaneously moves by the angle $2\theta$.  At high values of $\theta$, small or loosely packed samples may have a tendency to fall off the sample holder.
Answer: In x-ray powder diffraction, you have crystallites in all possible orientations. Only those crystallites whose bragg planes are at an angle θ with respect to the incident angle will diffract at an angle 2θ with respect to the incident beam (or at an angle θ with respect to the diffracting planes). So that is the reason, you always use 2θ instead of θ.
Answer: I think the angle $2 \theta$ is used because we can see diffracted pattern from incident beam so the angle of incident and reflected are combine to become $2 \theta$.


Can someone explain uncertainty in measurement?

Question: I really cannot get how a measuring instrument with the smallest division of let's say 20 has an estimated uncertainty of half that value. Firstly, why half, and secondly, why the smallest division? Can't the instrument be more precise than that? If possible, kindly explain with diagrams, thank you a lot.
Answer: Uncertainty appears because of the limits of the experimental apparatus. If your measuring device can measure up to 1 unit, then the least count of the measuring device is said to be 1 unit. You cannot get any more accurate than the least count.

Suppose your scale showed a reading as shown above. It obviously lies between 2 and 3 but can you get more accurate? Yes, you can get a more accurate value. The pointer lies between the 2nd and the 3rd lines after the 2. It lies somewhere in the middle, you don't know where. Your instrument does not let you measure more accurately. As it could lie anywhere between the two division lines, the uncertainty is said to be the width of the division lines. In our case, it is $0.2$ units. This is also known as the least count of the instrument.
You will report your reading as $2.4 \pm 0.2$ units.
However, there is a smarter way to report the value but is generally not preferred. You can approximately guess which side the pointer leans to, i.e: to $2.4$ or $2.6$. If it leans more towards $2.4$, you can report the value as $2.45 \pm 0.01$ and if it leans more towards $2.6$, you can report the value as $2.55 \pm 0.05$. Your professor would probably hammer you for reporting the values that way.
A better way to report the value is $2.5 \pm 0.1$.
You can reduce the uncertainty even further by buying better equipment which can measure the quantity more accurately (smaller least count).
Comment: I would have reported the value as 2.5, plus or minus 0.1
Comment: Good point. Will add that to the answer.
Comment: I think the total uncertainty of that rule is 0.2 because we have to consider 0.1 on both sides of the object being measured. See my reply
Comment: In most cases, it is possible to align the scale and object accurately. Your point is valid though. There will some uncertanity at the start but that is very small in most cases.
Answer: We have to make a distinction between analog instruments and digital instruments.
For digital instruments the uncertainty is usually $\pm1$ of the last significant figure (unless you're told otherwise by your instrument sheet). When I had to measure mass in my laboratory course, if the resolution of my instrument was 1 g, I had to write $m=(125\pm1)$ g. Sometimes my error was higher than the instrumental resolution (due to specific note of the manual), but never smaller.
For analog instruments with graduating scales usually your uncertainty is half of the smallest increment you can measure. For example, consider a ruler. You're measuring a pencil and, by sight, you can see that the pencil is closest to 36 mm than it is to 35 mm or 37 mm. Maybe it's 36.2 mm, maybe it's 35.8 mm. But you're sure that it's not 35.2 mm, because you actually SEE that the closest tick is the 36 mm one. So you can conclude that your measure lies between 35.5 mm and 36.5 mm. You get $L=(36.0\pm0.5)$ mm.
This are the "rules" we used in every laboratory course. For the graduating scale measure my reference is the $1^{st}$ chapter of "An Introduction to Error Analysis" by J.R. Taylor.
Answer: Think of reading a measurement taken with a digital instrument. Suppose you are watching your weight and when you get on the scale it reads 76.4 kg. The chances you are EXACTLY 76.4 kg are really slim (actually 0). In fact, the scale will tell you that you weigh 76.4 kg if you are anywhere between 76.35 and 76.45 kg. Thus, the error in your measurement is $\pm 0.5$ kg, and you would report your measurement as $76.4$ kg $\pm 0.5$ kg
A more precise scale might tell you you weigh 76.42 kg or 76.40 kg, in which case your error is $\pm 0.05$ kg.
Answer: If you're looking at a pointer somewhere in the smallest division, you may be able to tell what half it is in by sight. But you'll have difficulty telling where it is more precisely than that. So the smallest quantity you can read from the scale is half of the smallest division.
Also, measurement devices can go wrong, so the accuracy might sometimes be less than the scale on the device can in principle register.
Answer: The uncertainty of a rule is the smallest division, because a length is the difference between two points

The right-hand end of the object is $4.35 \pm 0.05$ (in the corresponding units), but the left-hand end is subjected to the same uncertainty. Therefore, the length of the object will be
$$(4.35 \pm 0.05) - (0.00 \pm 0.05)$$
or $4.3 \pm 0.1$. The existence of an uncertainty on both sides of the object becomes more obvious if we measure the length as


SQL Server queries running more than the timeout values set in IIS 7.5 and SQL Server query timeouts

Question: Which time out value does SQL server take into consideration while executing a query or stored procedure? The application timeout is set at 20 minutes.  The SQL query/command timeout is set at 10 minutes.  Then there is an F5 (load balancer) timeout set at 5 minutes. The SQL queries continue to run for around 40-50 minutes bypassing all the timeout values, even after the request has timed out. Afterward somebody has to kill the query. These long running queries are actually killing our system performance and filling up the SQL Server DB transaction log files.
Answer: SQL Server does not enforce any sort of query timeout by default. A query could run forever.
Usually, client timeout values merely mean that the client will give up and return an error. The client might have lost all connection to the database server, and trying to clean up after itself would likely be a lost cause. In the case where a client does try to kill a query, you may run into a situation where rolling back the work that the query did may take a long time. This is often interpreted as the query "still running". This would only occur if you are modifying data (INSERT, UPDATE, DELETE) or possibly if you are running some sort of large aggregations that use tempdb.
10 minutes is a long time for an IIS page.
I would look for blocking between connections first. A delete statement that removes a single row can block any select on a table, in certain circumstances. You should be able to find questions here on ServerFault to help you do that.
I would suggest reviewing your queries, tables, indexes and index maintenance to make sure that everything follows best practices. This is a big topic, but there are resources here on ServerFault and on nearly any SQL Server adminstration site to help you with it.
Answer: Your command timeout is probably signaling an Attention event to the server.  You can verify this with a packet capture or SQL profiler trace.  The Attention event is what normally causes SQL server to abort any activity in progress.
However, if you are signaling an Attention event, this does not always work very well.  You may want to try setting XACT_ABORT for the default connection values, or modify the existing code to use XACT_ABORT.
http://blogs.msdn.com/b/pamitt/archive/2010/11/07/attention-events-causing-open-transaction-and-blocking.aspx


Doorbell Voltage Drops at Transformer

Question: All, I replaced my doorbell transformer and got 22V (which was odd since it is supposedly a 16V transformer) with no wires connected to the transformer.  As soon as I connect the wires to the transfomer that run to the chime the voltage drops to 2V or so. What would that indicate?
Comment: short circuit in the doorbell wire, or a bad multimeter  ..... why did you replace the transformer?
Comment: I thought it was the transformer because when I checked it showed zero voltage.  Probably didn't need replacing.  I think the multimeter is okay so it must be a short.
Comment: remove the door bell from the wall and bring it to the transformer and connect them together briefly ..... or run a wire pair from the transformer to the bell if you happen to have enough wire .... you could also use a long power cord for testing, as long as someone does not plug it into a wall outlet
Answer: Assuming you have a full mains voltage going into the transformer, then there is a short-circuit in the wiring (or, much less likely, the transformer is vastly underrated for the current drawn).
"Bell wire" has thin insulation, compared to mains wiring. A staple may be pinching the wires, or wires could have rubbed together, tearing the insulation. Sometimes mice or squirrels can cause this. Such a short could have burned out the old transformer.
Another possibility is a short in the chime, which then caused the contacts of the doorbell switch to fuse together.
Also, inspect your connections to the transformer. If there are multiple wires, e.g. from both a front and a back door switch, they could be misconnected.
If you can, check the resistance between the bell wires going to the transformer secondary. The resistance should be greater than 16 divided by the current rating of the transformer, or (16 x 16) divided by the VA rating. For example, if the transformer is rated 10 VA, then circuit resistance should be greater than 256/10, or ~26 ohms. (Not to worry if it's just a bit lower, though: you're measuring DC resistance, while AC reactance across a coil is higher.)
Don't be concerned about the 22 VAC open circuit output because the nominal voltage, 16 VAC, is at the rated load.
BTW, my compliments on checking the voltage on installation! Had you not done so, the transformer would have burned out again, or there is a small possibility of fire if a "short-circuit" is a few ohms and is by something flammable.
Comment: could it still show 2v if there was a short? I would expect very close to 0, unless the wires are way too thin...
Answer: 1: Your Transformer is rated at 16VAC for what input Voltage ? It is Normal to have a higher voltage than rated output if the Xformer is rated 110V input and your home has 130VAC. Perhaps the xformer is really an 18VAC output and you have 130VAC feeding it?
2: Connecting the xformer to the chime and you get an immediate voltage drop. Means you have a load on that transformer, you should not have any load until your door bell switch makes the connection. Your door bell switch might be stuck in the always made position (shorted On), you might hear a small chime when you first connect the transformer wire - but that is all you will hear maybe a quick low bing at first.
Disconnect your door bell switch - check the power from your transformer with it disconnected and then if your power is ok - you know the switch is most likely the culprit. I would verify that by ohming the switch - and also tapping my two wires (at the switch) together (making like a momentary switch) to see if I get chimes.
3: Other than that you have a short - that is PRIOR to the switch.
4: 3rd possibility is both switch and chime are bad but I highly doubt that scenario - I am just listing it as a possibility because it is possible however rare.
Answer: If you have an illuminated bell-push, the globe would be drawing current through the circuit while the button is not being pushed, or if it's not an illuminated model then it could indicate a faulty bell-push. Check the voltage drop across the bell push at your front door.

Doorbell Voltage Drops at Transformer


Why does pair production cross section increase with photon energy?

Question: The formula given by Born approximation for differential cross section shows the photon energy $h\nu $ appearing in the denominator with cubic power; however most graphs show the cross section increasing with energy until it reaches a constant value. What is the correct energy dependence of cross section on photon energy in pair production?
Answer: The Born approximation is only the first term in an expansion that has higher-order corrections. These corrections are rated by the number of closed loops they have in their Feynman diagrams. I don't know how many loops are included, because the pedigree of this expression goes back to a textbook and not a paper that's available online, but this expression is the total cross section for electron/positron pair production [Gould and Schréder (1967)]:
$$\sigma = \frac{\pi r_0^2}{2} (1 - \beta^2) \left[(3 - \beta^4) \ln \frac{1+\beta}{1 - \beta} - 2\beta(2 - \beta^2)\right],$$
where $r_0 = \frac{e^2 }{ 4 \pi \epsilon_0 m_\text{e} c^2}$ is the classical electron radius, and $\beta c$ is the electron/positron velocity in the center of mass (CM) frame of the collision. I don't know how many loops were used to calculate this expression. The presence of the logarithm means they used at least one, but I've never done the calculation myself, so I don't know if higher-order loops will have a square of the logarithm or just more factors of $\beta$ times the logarithm.
The above expression can be reformulated in terms of the relativistic kinetic energy $E$ of the electron/positron in the CM frame:
$$\beta \equiv v /c = \sqrt{1 - \left( \frac{m_\text{e} c^2}{E + m_\text{e} c^2} \right)^2} \text{,}$$
where $m_\text{e} c^2$ is the rest mass-energy of the electron/positron. This satisfies the requirement that $v = 0$ gives $\gamma = 1$, which results in $E = 0$.
Comment: Thank you for answering this question. I've been looking high-and-low for a usable expression for $\sigma_\text{PP}$.


What if I find my password, and not the wallet

Question: what if I find my password, that I wrote down many years ago, but the PC, and so the wallet is gone. can I use this password on a new wallet.dat and get accseess to my coins ?
Answer: It sounds like you are confusing two distinct objects: a password, and a seed phrase.
A password is used to encrypt a file, so that if you have the encrypted file but not the password, you cannot read the file's contents.
A seed phrase is used to derive a master private key that the rest of a wallet's keys will be based upon. So if you have the seed phrase, you can recreate the wallet.
From the sounds of it, you likely have a password that can be used to decrypt a specific wallet.dat file, not a seed phrase. A seed phrase will most commonly be a set of 12-24 words, while a password will be a (hopefully highly entropic) string of characters. If you created the wallet file many years ago, chances are the BIP 39 standard for creating HD wallets from a seed phrase was not widely used yet, furthering my suspicion that you indeed have a password, and not a seed phrase.


LGPL-licensed code reuse in MIT-licensed project

Question: I have an MIT-licensed (in plans, currently it's not published) project. And I've found an implementation of the required algorithm in an LGPL-licensed project. Am I allowed to include that code in my project? And if so, how exactly do I state that code is copied from that file?
Answer: IANAL/IANYL.  That said, it seems to me that yes, you may, provided you conform to the GNU LGPL's obligations.
In brief those seem to me to be

That you license the modified LGPL work under LGPL (or GPL3, but that would interfere with your desire to distribute the rest of the work under an MIT licence)
That you include copies of the GPL and the LGPL with the work

The other obligations seem automatically fulfilled by your distributing the rest of the work as source.  The easiest way to handle the code and its copying seems to me to be to keep all the LGPL-derived code in separate source file(s), which clearly state at the top the original authors' and your copyrights, and that the files are licensed under LGPL.
If your code as written displays any kind of copyright notice at runtime, you must also

include the copyright notice for the Library among these notices, as well as a reference directing the user to the copies of the GNU GPL and this license document.

I note in passing that one of the main ideas of distributing something under an MIT licence is to permit later use in proprietary software.  In the case of your project, such later use will be made much more difficult by the presence of LGPL'ed content (it's possible, but complying with the LGPL gets more onerous when there's no general source distribution).  This makes the choice of MIT a bit perplexing; do consider, however briefly, distributing your project under GPL3 instead, as you could then relicence the LGPL-derived content under GPL3 (LGPL s2b) and the whole project would be under a single licence.
If the amount of code you're taking is too small to be independently copyrightable, you may be able simply to reuse it.  I would advise getting a real legal opinion before you do that.
Comment: Thanks! I'll probably consider redistributing it under LGPL license because it's a library (if i'll not find a MIT-compatible implementation or not manage to write my own)
Comment: By the way, you can see amount of code by clicking on the link. (swap() and swap_adjacent() functions)
Comment: @Ancient It is probably more practical just to copy the whole file (implementation file, list.c) and then #include "list.h" in your own code to use it. Then you can simply say "list.h and list.c are from  and are licensed under ." If it is LGPL, and you modify it (including taking a subset of the library), then you will also need to redistribute your modified version of the library under the same terms.


Cobalt problems

Question: I have an 06 cobalt 2.2. The po420 code came on a couple days ago. The cat and both sensors were replaced about 3 months ago by a licensed exhaust specialist/mechanic. What else could be the problem?
Answer: Which sensors were replaced? If the downstream O2 sensor wasn't, it may need to be. If that's not the problem, it's probably as simple as it looks: the catalytic converter isn't performing up to snuff. This could mean the new cat that's in there is a low-quality unit that isn't performing to spec, or the it's been ruined like old one was. Was any additional work done to the car when you had it replaced?
Catalytic converters don't go bad on their own. If everything upstream of them is working as it should be, they should outlast the car. However, if something else is happening like the mixture is too rich (too much fuel), they can quickly get destroyed. I don't know how soon, exactly, so I can't say if 3 months is surprising or not.
I'd bring it to a shop and have them give it a good look-over and see what they say. If you're interested in doing it yourself, start looking for the causes of things like smoke out the tailpipe, rough idles, hard starts...anything out of the ordinary.
Answer: The fuel system, combustion chambers and valves are dirty.
Start by changing the motor oil and filter with a top synthetic oil like Mobil 1.  Substitute one quart of oil with Marvel Mystery Oil (or automatic transmission fluid).
If the car has a PCV valve and EGR valve, make sure both have been replaced and the tubing cleaned with carburetor cleaner.  Replace the air filter and spark plugs.  Check the intake manifold and vacuum hoses for air leaks.
Add Marvel Mystery Oil (or automatic transmission fluid) to your gas tank at fill-up at a treat rate of 1 oz. per gallon.  Drive the car immediately in stop-and-go traffic for 10 minutes, shut off engine for 10 minutes, then drive on the highway at 70 MPH for 10 minutes.  Repeat this cycle multiple times, for at least an hour, and allow the mixture to penetrate at least two days.
When your tank drops to 10 gallons of gas, add one can (15 oz.) of Berryman B12 and one can catalytic converter cleaner.  Immediately drive the car on the highway for 30-60 minutes, then "floor" the car at wide-open-throttle (WOT) from 50-80 MPH.  Repeat the full throttle blasts at least six times, but up to 30 times if the cat. & sensors are very dirty.  Be sure the cooling system and transmission are flushed and working properly beforehand.  Turn the heater and fan on maximum, with windows open, when performing the WOT blasts.
The Berryman's and cat. cleaner evaporate out of the gas tank after about 24 hours, so be sure to run the car hard right away.
When the problems are resolved and you refill the tank, add Marvel Mystery Oil at a treat rate of 4 oz. for every 10 gallons of gas.  It will continue to clean deposits.  Every fourth fill-up, add one can of Berryman's and drive at highway speeds.
Comment: Good call that it may be possible the cats are plugged up and it's possible to unclog them. The only objection I have is to using automatic transmission fluid to the oil. I had heard that recommendation for a while too, but looked it up the other day and it seems to be (at least mostly) bunk https://bobistheoilguy.com/forums/ubbthreads.php/topics/560114/Re:_Using_transmission_fluid_t
Comment: I have seen the page you linked.  There are indeed no detergents in ATF, but it is not the supposed extra detergents that make it effective.  ATF has shorter carbon chains than motor oil, so it penetrates varnish in a way motor oil cannot.  It thus softens carbon and varnish buildup, allowing deposits to gradually flake away.
Comment: Interesting. Good to know!

Cobalt problems


Two finger vs Three finger Power chords on guitar

Question: What are the pros and cons of the two finger and three finger power chords on guitar? Is one faster? What I think I know is that the three finger power chords are more pronounced and powerful than the 2 finger one. Please correct me if I'm wrong please
Answer: I'd say three fingers can be a bit messier if you're using more gain, but also adds some brightness. Fast, low, chunking/palm muting is usually better done with two fingers. Punk-style chord progressions with no major/minor tonality desired will come alive a bit more with three fingers
Answer: Neither is faster than the other with enough practice. Typically it comes down to preference, but there are subtle differences for each fingering that can be taken advantage of especially when going from power chord to barre chord. You can and should take advantage of the different types of fingerings and use a combination of both here.

The three finger power chords, specifically 1,3,4, let you take advantage of the E major, E minor, A minor, D major, and D minor shaped barre chords.
The three finger power chords, either 1,3 or 1,4 , let's you take advantage of the A major shaped barre chords and making a mini G shaped barre chord.

So if you know you're going to be playing a mix of barre chords and power chord the fingering you use can help you greatly. I know out of habit I always finger power chords on the E string as 1,3,4 and on the A string as 1,3. Other than that, the are pretty much the name
Answer: Good answers above.  I'd like to add that maybe the sound you're looking for with the three-finger chords is playing a two-finger octave by taking the middle string out of the power chord.   I prefer two finger power-chords and two-finger octaves myself, especially when I'm playing with distortion/overdrive.  I find that the three-finger power chord sounds a bit muddy compared with the two-finger chords.
Answer: It all depends on the tone you're looking for:

Two finger power chords sound very energetic and fast, so they are great for fast passages.
Three finger power chords sound a lot fatter and powerful, so they are great when you want the song to sound a lot more brutal (\m/) or more primarily when you want the power chord to ring out.

None of them should be faster when your technique is good and you have no tension in your left hand.


How can we store EXIF-type metadata in renders?

Question: I used Blender this afternoon to turn a panorama into an extremely wide-angled photograph. This got me wondering: would it make any sense to store EXIF data in images generated by Cycles so you get the FOV, ISO, Arpeture, and so on? Especially since HDR formats are like the digital equivalent to taking a picture, I can see it being useful for making accurate composites, faking camera shake, and other things. Do Radiance HDR or OpenEXR keep track of that sort of metadata? I tried looking around and couldn't find anything. How do professionals keep track of that meta data in their renders or does nobody care?
Comment: related: http://blender.stackexchange.com/questions/463/logging-renders/464#464
Comment: You can now store metadata in renders this way: https://docs.blender.org/manual/en/latest/render/output/properties/metadata.html
Answer: I don't know of any option to add this data from within Blender, but I would think an extension would be the best solution (there are already options for timestamps and other such simple info IIRC).
For now, a possible solution would be to use a 3rd party application such as GIMP to add this information to the file.
Comment: That link to the other stackexchange question on logging was a good enough resource! It seems that saving to EXR saves the camera, lens, and scene metadata along with other kinds of useful information whether or not you stamp it onto the image itself. Thanks guys!
Answer: Blender can handle the complete pipe line from modelling to video editing. In such a workflow the data is always available and doesn't need to be exported elsewhere. For comparing renders the norm is to just Stamp the images.
Let me quote ideasman42:

stamp options are written into metadata of EXR/JPEG/PNG files. So if you dont want to see them, you can use a tool to read them back (exrheader command for openexr for example).

There isn't yet a standard for storing EXIF data in the OpenEXR format, so it's unlikely this data will show up in other applications.
Answer: For me I find exiv2 command line works fine to add needed fields. EX:exiv2 -M"set Exif.Image.Model RICOH THETA S" untitled7.pngexiv2 -M"set Exif.Image.Make RICOH" untitled7.png
Then can confirm / view it like:exiv2 untitled7.png | less


Can I locate a junction box in a wall that will be accessible through a vanity cabinet?

Question: I am remodeling a master bath and I have removed a knee wall that contained an electrical outlet. I have rerouted the wiring up next to the drain stack. I would like to locate a junction box in the new drywall behind the new vanity. I will make it accessible inside the cabinet. I will route wiring up and over about 3 feet to put an additional outlet in the wall above and to the right of the vanity.My question is..Can I locate a junction box within a foot of the under sink plumbing.
Comment: Hello, and welcome to Home Improvement. Good question; let's see what our pros respond with. And, you should probably [take our tour](//diy.stackexchange.com/tour) so you'll know how best to participate here.
Comment: I have an outlet under my sink, this seems like the same thing.
Answer: It looks good and accessible. The NEC doesn't say it must be readily accessible only accessible, in case you need to inspect or maintain it. If you are feeling like you want to help another owner or an electrician later on down the road, you might even put a label on the panel saying there is an electrical junction box behind the panel. It could save some time in the future.
Good luck.


FastICA - Purpose of centering and whitening the Data

Question: I'm learning about ICA, but dont know whats the purpose of centering the data (making each component have zero mean)and whitening the data (not sure what is this for, is it the same as PCA?), I'm following FastICA algorithm for wikipedia
FastICA
Answer: The goal of FastICA is to rotate your data (unitary transform) so that each axis looks as non-Gaussian as possible.  Gaussian data still looks Gaussian when you rotate it.
If you don't "sphere" the data, all the algorithm can really do is rotate the whole block to one axis.  By bringing the mean to zero (centering), and normalizing the variance in all directions (whitening), you give the algorithm freedom to rotate in all directions.
This lets FastICA find the rotations that correspond to non-gaussian data.  All of the rotations it tries will leave the Gaussian components of your data as zero-mean and unit-variance, but non-gaussian components can be optimized.
Answer: Given a set of signals(observation in the ICA/BSS context) with a covariance matrix M, whitening transform is basically a de-correlation transform that converts M into an identity matrix. Whitening ensures all the source signals(or dimensions) are treated equally before the algorithm is run. Centering is nothing but removing the DC offset from the observations.
This page gives a good graphical explanation about how the Whitening process and ICA transform the joint distribution of the observations.
Answer: Centering is usually conducted at the very beginning step before whitening. It would make the follow-up theory and computation easier.
The behave of centering is shifting the original X, and thus it won't change other statistics, e.g. variance is not changed after centering.
Answer: ICA finds the independent components and PCA find the uncorrelated components. ICA cannot distinguish the strength of the components i.e. ambiguity so whitening does not loose any information but fast to converge.


How to play together online?

Question: We had a band of musicians but unfortunately, my partners went abroad for further studies. Currently we're far away. We want to meet at some time in a week and  play together online. We've tried Skype but it doesn't work OK when we all are active at the same time. Did you try it before? Which software do you recommend?
Comment: That sounds like a very costly practice session.They could try with a couple of bags of telephones, but we don't know if there are two sax o'phones in the band..............
Comment: I'm not sure there's any chance to have a latency that would allow you to play together as a group. I would just work colaboratively on a track, shared via Dropbox for example, and would keep the cam sessions to share riffs, ideas and suggestions and talk about each others works and versions.
Comment: Have you tried a telephone?
Comment: Most online Skype-type apps just can't physically be synced close enough for you to play together.
Comment: We would like to see each other via cam. Sometimes one of us shows something visually to others.
Comment: I know that a paid version of skype allows for conference calls, which would be sort of what you're looking for.  Another alternative might be Google Hangout, which I believe is free.  I do not think the video quality is as good, but I believe more that two of you would be able to get together and see one another.
Comment: Skype conference calls are free but video conference calls are not.
Comment: You probably can't really do it due to latency, but there's [ninjam](http://www.cockos.com/ninjam/), which synchronizes you measures apart instead of milliseconds.  That can be kind of fun, though it might be useless for what you want to do…
Comment: You could try https://jamkazam.com/
Answer: I would recommend you avoid trying to use video. Unless you are 'local' to each other the latency and jitter makes it very difficult to play together.
Audio can be encoded with much lower latency and is typically a fixed bandwidth requirement so this copes better with connection issues.
Tools like Jamulus (http://sourceforge.net/projects/llcon/) are designed for real time jamming, with one machine taking feeds from all players and then sending the mix back out to them. It seems to be better than just using a google hangout or chat type scenario.
Answer: Old-fashioned analog landline telephone circuits had many limitations, but there is very little delay between when a party at one end says something and when the party at the other end hears it.  Other technologies often involve trade-offs between audio quality and delay; for most purposes, a delay of 100ms or even longer would be barely noticeable, but adding such delay between when one performer plays something and another performer, who's supposed to be playing simultaneously, hears it, would render simultaneous performance impossible.
The only remedy I can see would be to have one person who sets the tempo, oblivious to what anyone else is playing.  Audio from that person could be sent to a second person who would play along with it.  Audio from both of those people could then be sent to a third person, who could play along with them, etc.  At the end of the chain, have a listener who would use a separate connection to let the different performers if they need to do anything to work better with what people are doing downstream.
Answer: It depends on how you want to make this work, what kind of grade your internet connection is, if you all live in the same city and have the same ISP as these factors will decide the audio quality and latency.
Audio:

Use Skype audio (conference) calls. These are free, or
If all of you guys use DAW's for recording then you could try VST's like ReaStream (http://www.reaper.fm/reaplugs/) or Source-Live (http://source-elements.com/) which allows to transmit a specific track or mix down of tracks. If you guys have a very good internet connection then this can work out if you know how to configure all related network settings.
Use a service like http://www.ejamming.com/ but I do not have any experience with it.

Video:

Use a seperate laptop, tablet, smartphone to set up a video as video encoding is pretty heavy and will cause latency issues on your DAW system.
Use video conference via Google Hangout
Use a live broadcast platform like UStream, YouTube, LiveStream or one of the many other available services.
Answer: Jammr is your best bet for rehearsing.  There's no latency because each player is synched to click and the other player's tracks play at different times in real time but the same time on your machine.
From the FAQ:

jammr sends your audio to other users and receives their audio. In order to avoid lag, jammr is "live" but not "real-time". This means other players hear you after a fixed amount of time. This fixed amount is called the interval and can be set to fit the chord progression you are jamming to. This allows you to jam synchronised with people from all over the world.
Why is jammr not real time?
At the speed of light it takes 67 milliseconds to go half-way across the world. This means jamming with someone halfway across the world would be noticably laggy. Therefore, to ensure that you can jam with people from all over the world without delay we use intervals.
How many musicians can jam together in one session?
The limit is set to 10 jammers per jam session, this should cater to most small orchestras. If you are talking rock however, from experience, we advise not to have more than 8 people in a jam, as this gets very messy otherwise.

You can make your session ("jam") private by installing the Premium version which for the moment appears to be free.
Comment: From the Jammr web site,  they attempt to solve the latency problem by delaying the playback to one full time through the form.   In another words, you play against what everybody played the last time.    They claim all G chords are the same.   That is ridiculous, and false of course.   Besides that,  the approach is counter to what you should be doing in any ensemble - listening and interacting with what you hear.

How to play together online?


Sort careers.stackoverflow.com/jobs/feed RSS feed by date?

Question: I'd like to scrape data from the Stack Overflow careers RSS feed, and I would like to receive the RSS feed entries sorted by date, with the most recent entries first. Is there a way to accomplish this? More generally, is there any official documentation that describes all the parameters that can be passed to the RSS feed? Thanks.
Answer: I tinkered around with this a little. There is a tab on the main Jobs listing page which is labelled "most recent" which would be the sorting option you want. Choosing this tab adds <code>?sort=p</code> to the URL, so I just copied that and plugged it into the RSS feed URL, like so:
http://careers.stackoverflow.com/jobs/feed?sort=p
Seems to work correctly.


How can I move a OneDrive folder to external hard drive?

Question: I'm running out of space in SSD and have bought external hdd, but there is no section showing where to move to
Answer: One of the easiest ways to do it is by:
First ensure that your OneDrive is Up-To-Date synced with local.

unlinking your drive to OneDrive
Move the folder you want to the desired location
Re-link the folder to OneDrive account

It's ok to merge, as the sync will read all your files as being the latest ones in the cloud. It does this by checking the MD5/SHA hashes of the files and ensures they are the same that is on the cloud.

That's the easiest way!
Answer:
download OneDrive for Desktop - https://onedrive.live.com/about/en-en/download/
install it
a folder shall be created where you can drop your files
Comment: I already have files on computer, just tried re link file after unlink. Seemed to work good


How to know for sure if we can learn from a given data or not?

Question: I want to know that given a set of data and a target, how we can know for sure whether we can learn from that data to make any inference or not?
Answer:
how can we know for sure

We can't.
A toy example to show why even humans can not do this for sure:
Assume you get the number 2, 4, 8, 16, 32, ?? and want to extrapolate to the next number ??. A natural extension of the series would be 64, but we can not take this for granted. The next number can just as well be 0. You can not be sure.
Only given the data and without additional assumptions about what you would expect to see, you can not learn a correct model per-se. You always have to be critical about your data.
Comment: I like to troll puzzles with such "guess the next number" questions, by answering π and providing a function which really does that.
Answer: With respect to the presented answers, I want to add an extra explanation. Basically, what ML approaches do is approximating a mapping from inputs to outputs. This function usually should be well-behaved 1 otherwise you should have so much data to enable your model to learn it in the current feature space. To be more specific, you should find the distribution of your training data in your current feature space. It helps you investigate how much the distribution of your different labels overlap, for classification tasks. By doing that, you'll be able to figure out the best performance your best ML approach can have. The distribution of your data in your current feature space can show you the Bayes error of your model.
If you find out that the current Bayes error is a large value, then you can be sure that your data cannot be learned in the current feature space and you have to change the current features.
Answer: The current standard is essentially:

Given this input data, can any other system or approach classify it or estimate a quantity of interest? If so, then a machine learning approach may be able to achieve the same.

This is basically how machine learning challenges in computer perception can be treated as tractable. We have humans and other animals as working models, and make the assumption that the process can be automated. A similar approach can be made on any machine learning system which attempts to re-create the behaviour of an expert - provided we use the exact same input data, and enough of it, the ML system can learn what the expert does through statistical approximation.
The "expert" can be a statistician/data scientist looking at the data, using any tool. Exploratory plots of features and measures of correlation are a good way to assess whether a data set might be amenable to training a ML model for prediction. If you can visually separate classes on a scatter plot using some combination of features, then it is likely that a suitable ML model will be able to separate those classes too.
There are hard cases, where it seems on the surface like there is no pattern. Perhaps a relationship could be teased out and shown to exist with statistical analysis, but you could eschew that and directly throw some non-linear ML model at the problem in the hope that it finds it for you with the correct hyper-parameters. Of course you don't know in advance whether that is a worthwhile approach, and this carries some risks. But it is not that expensive to do once you have some data - just throw a fairly robust non-linear model at the problem, like XGBoost, and see what happens.
Of course, ML is not magic. If there is nothing to find, it will tend to find nothing. Worse than that, it can find spurious correlations, or patterns due to prejudice inherent in the data collection or labelling. Those issues are a problem regardless of evidence on whether it was theoretically possible to achieve a result at all. However, the kind of thinking that drives "let's throw some neural networks at this" has led to some published works which are quite terrifying and wrong on many levels. An example of such a system was a NN which classified a person as criminal or not according to a picture of their face - luckily flaws were pointed out in data collection on that one, but the original story made headline news in many places, despite essentially being a modern re-birth of Phrenology.
Answer: One cannot evaluate ML models using deterministic approach. ML models do not simply follows if else statement where one can verify whether the model predict the outcome correctly or not. Majority of ML algorithms work on probabilistic approach that predicts the most probable or near class.
In addition to this, distinguishing boundary between different classes are not simple and linear always and in majority of the cases the class boundary that separates the data points follows the higher order of differential functions.
Many a times, noise data leads the separating  boundary more complex and leads to deteriorate the performance of the model. Bias- variance trade off is the important concept one should learn in order to make the model work as intended.


Why does my iPhone 7s keep losing Wi-Fi since I installed iOS12?

Question: I can connect the phone to Wi-FI manually, but after several minutes, it loses the connection, and I have to restore it manually. This did not happen before I installed iOS 12.
Answer: Before doing anything, have you erased network settings and verified WiFi is stable?
Next, erase all content and settings and retest on a new network.
Apple typically stops signing the previous release within a week of a new iOS, so you could try restoring back to iOS 11 to rule out a hardware failure that was a coincidence. At that point you can decide to see Apple service before upgrading to understand if you have any recourse from them in case a second upgrade also fails.
Many many iPhone 7 era devices work fine, so it's almost certainly not a widespread bug. If you're sure you want iOS 12 I would erase and restore the device and then connect to a Mac to look over the system logs if the failure continues.
Answer: Thanks, the reset of network settings did it.  I'm annoyed at myself because I was so sure it was duet iOS12 that I didn't do theobvious.
Comment: Bob - thanks for confirming. If you use the "contact us" link - you can merge your two accounts and then tick the "solved" check mark so others know it worked. I'm super glad it was not anything hard like a failure / repair. It's natural to try and think what changed last when things break.


Can we see the south Pole of the Moon standing on North Pole of the Earth

Question: As the Moon's orbit is inclined to Earth's Equator and radius of earth is only 6350Km but Moon is 385000Km away, we should be able to see the south pole of the Moon from below- i.e standing on North Pole of the Earth
Answer: No, people at the North pole (of Earth) cannot see the South Pole (of Moon).
We can actually find this by some basic trigonometric relations and considering the orbits of Earth and Moon: ( taken from Orbit of the Moon)

Since, the south pole of the moon can be viewed only at an angle that is tangential to the moon like:

Here, the south pole of the moon can only be viewed below the red line: that is the yellow region on the Earth. Note that this image is not scaled and hence the scaled image might be quite different. But if we solve it, we can find the yellow region mathematically just like below:

We have:

$D_m$ = Distance between Earth and Moon
$R_e$ = Radius of Earth
$r_m$ = Radius of Moon
$\theta = 5.14^{\circ}$
$\phi = 23.44^{\circ}$
$\alpha = \angle ACB$

In triangle CDF: we have $sin \theta = \frac{r_m+a}{D_m}$. Using this we can find the value of a.
In triangle AGC: we have $sin \alpha = \frac{R_e}{a}$. Using this we can find the value of $\alpha$.
Solving these equations, we get $a$~$34000$ Km and $\alpha$ ~ $10.775^{\circ}$.
Hence, anything above $\phi + \alpha = 34.215^{\circ}$ above the Earth's equatorial plane cannot see the south pole of the Moon directly.
Comment: Nice pictures, but note that while in the first image, the south pole is pointed away from the Earth, at other times it points towards the Earth
Comment: Its actually pointing towards the Earth in the first picture (The bold line is the lunar axis). Hence, this limit is on the best case scenario side. The angle of 34 degrees is around the best we can expect. Of course, this also depends on the distance between Earth and Moon and some other factors.
Answer: The moon rotates at exactly one revolution per orbit.  This keeps the same side of the moon facing the Earth. The moon is indeed inclined to the Equator (in fact it orbits close to the plane of the ecliptic) But this fact is not very significant to the answer to the question.  The moon could orbit in any plane in such a way that the same face was always pointed towards the Earth.
However, as the moon does orbit in the ecliptic, it is visible from the North Pole.
Now there is a 6.7-degree axial tilt between the moon's orbit and its equator.  This means that at some points in its orbit the South pole of the moon is tilted by 6.7 degrees towards Earth.  It is visible from the North Pole as well as everywhere else on Earth.  At the north pole, the Earth's radius reduces this to about 5.7 degrees From the South pole it would increase to 7.7 degrees.  But 7.7, 6.7 or 5.7 is still a very difficult observing angle.  You can't see easily what the polar regions are like, even at times of maximum tilt.  You can't see the South pole of the moon "from above" from anywhere on Earth.
I think your misconception is that you think that the North pole of the moon points in the same direction as the North pole of the Earth. It doesn't.  It is tilted so that it is nearly perpendicular to the moon's orbit in the plane of the ecliptic.
Comment: Can you show how you got $\pm$0.5°? I think it's more like $$\pm\frac{180}{\pi} \frac{\text{6378}}{\text{384400}} \approx \pm \text{0.95°}$$
Comment: I think you;re right.
Comment: I do not know how to post the photo here?  So I will as new question


Why does nation's total debt matter and not NIIP?

Question: Most people in the media talk about how the total debt level of a nation relative to its GDP is a measure of how "screwed" the country is. For example, see this: http://www.zerohedge.com/news/goldmans-sigma-x-hints-who-next-contagion-target
It seems to imply that UK is in bad shape but nobody seems to pay attention to it?
Japan also not looking good.
However, look at the Net International Investment Position (NIIP) of these countries:
UK: about 0% of GDP (equal amount of debt and assets)
Japan: >50% of GDP (Japan holds more assets than debt)
"A country's external debt includes both its government debt and private debt, and similarly its public and privately held (by its legal residents) external assets are also taken into account when calculating its NIIP"
If Japan needed to pay back its debt, couldn't it just sell some of the assets it holds and repay that way?
Is there something I'm missing here? Which is the right way to look at things?
Answer: NIIP includes (and in fact is predominantly) personal assets.
The government of Japan could not sell the assets of its citizens to satisfy its sovereign debt.
Comment: The zerohedge.com graph is a bit misleading then as it includes private debt, right? Where could I find information on sovereign assets?


Horn transposing

Question: I need help transposing a piece for the horn. I do not play it so therefore it is very difficult getting my head around this. I originally play the violin so brass instruments are totally diff. world to me.
I am writing a piece for orchestra in G minor and I have two different sections for horn - G and D horn. However the software I am using only has the F horn option. Your help transposing the piece to both G and D would be very helpful.
Comment: Just to clarify, you want it played using the Horn in G and Horn in D, not the standard Horn in F? Have you considered whether such instruments are available? I assume that you're aware that the Horn in F can play in all keys, not just F.
Comment: Apart from writing the dots out bearing transposition in mind, also be aware of the range of each instrument.
Answer: Unless you're purposely writing in an antique style, for players who you know possess antique instruments, write for Horn in F.  The instrument is fully chromatic.  The player will very likely switch freely between the Horn in F and Horn in Bb which are combined in his modern 'Double Horn'.  This is not your concern.  I repeat - write for Horn in F.  That means notating a perfect 5th above the required piich.  If you want middle C, write the G above.  The convention in horn parts is not to use a key signature, just accidentals for everything.  Silly, really (if the music IS tonal).  But horn players cling to the tradition.
Very likely your notation software has the option of composing in concert pitch, then automatically switching to a Transposed mode where Horn in F, Clarinet in Bb etc. see the right notation.  Confusion is possible :-)
Comment: 'The convention in horn parts is not to use a key signature' - Is this really the case nowadays? I would not recommend writing a new part without a key signature, unless you want to annoy your horn players. Which is a noble goal, but less than productive :-).
Comment: Actually, "natural" horns were almost fully chromatic (apart from a few notes at the bottom of the range) by the 19th century, when players had discovered how to "hand-stop" notes, which wasn't possible while the playing technique was the same as for a "hunting horn" played while riding a horse! Some composers (e.g. Brahms and Wagner) considered valve horns to be an inferior instrument with a poorer tone quality.
Comment: " Silly, really (if the music IS tonal)" - sometimes there was *really* evil logic in 19th century horn notation, where the music was written without accidentals but the written transposition of the horns sometimes changed bar-by-bar, with no time for any physical changing of instruments or inserting/removing tuning crooks!

Horn transposing


Default Values do not get applied to new versions of documents

Question: Default values work correctly when a document is first uploaded to a library.  But when that document is modified and re-uploaded to the library, the default values are not applied.  I've tested this on regular default values and those put in via "Column Default Values" via Library Settings.  This library has Major and Minor versions and also requires content approval.  How do I ensure that the default values work on updated documents?
Comment: Isn't this per design though? That default values should be used when the document first get the content type of the library but that the user should be able to change them (so in your case, since you upload a new version, SP does not see this as a new document but rather one where the user has "changed" the default values to blanks)
Comment: If a user drags-and-drops a document into a library, he or she hasn't changed anything but the file itself.  I struggle to see the design benefit...
Comment: What I mean is that, it is only set on new list items, since it should be possible for users to override the values. The real problem here, if I comprehend you correct, is that these default values where added when list items already existed in the library and therefore those documents will never get the default values. Default values are just that: default values, they are not (in programmer lingo) statics
Comment: If you want values that can not be updated, but that should be set to default on every update, you could hook on a workflow or ItemUpdating event receiver to "reset" the value. If you just this once want to set the values to the default ones, you could write a PowerShell script making sure that the old document get your new default values
Comment: Thank you for the options. I'm not looking for statics; if the user purposefully changes the value, then that makes sense.  Instead, I'm just trying to get around this unintended behavior that completely defeats the purpose of document versioning.  I am using 'Column Default Settings' in the Library settings.  I have dozens of defaults and it would be difficult to also have to manage these defaults in a workflow.
Comment: When the defaults were put in place, the document library was empty...  This affects all documents in the library.
Comment: Ok, so it documents downloaded from another library in SharePoint and then uploaded in this one? You should probably clarify that in your question
Answer: It has come to my attention that as long as a file is downloaded from SharePoint, modified and re-uploaded, the values remain the same. This issue only occurs if someone has retained the original version, made edits, and re-uploaded the changed file to SharePoint.


What's the temperature of Pluto's core?

Question: The surface is freezing-nitrogen cold, but it's typical for the temperature to increase towards the core. What's the temperature of the core of Pluto? Is the planet icy and rocky all the way through? I wonder at the possibility if that frozen ice ball could have any internal heat at all?
Comment: [Life inside Pluto? Hot birth may have created internal ocean on dwarf planet](https://theconversation.com/life-inside-pluto-hot-birth-may-have-created-internal-ocean-on-dwarf-planet-140976) They don't mention a temperature and the cited paper is paywalled.
Comment: A couple more speculative papers: https://arxiv.org/pdf/1510.06604.pdf , https://www.popsci.com/pluto-ocean-insulation/
Comment: @CriglCragl The Sun cannot explode because it by far hasn't enough mass to go supernova. You probably mean the ejection of its planetary nebula, becoming a white dwarf.
Comment: Remember, Pluto isn't very big. Its mass is < 0.18 the mass of our Moon, and its radius about 0.67 the Moons radius. And of course it gets much less solar heating.
Comment: The core of the moon is about 1400C https://www.space.com/18175-moon-temperature.html You might expect Pluto's to be above vacuum temp. But at 0.2 of Earth rather than 1.2, & with much less heating, proportionately lower. I remember reading that when the sun explodes Earth's core will have only cooled a few degrees, so there will still be seismic activity. Because the mantle acts as a great insulator, & the core is very dense & hot to start with. But that will vary with the cube of radius..
Comment: @CriglCragl I though the moon's core was hotter but that's still quite hot
Answer: TL;DR: 1000 K (according to differentiated model of Pluto)

According to the density value of Pluto, astronomers proposed three types of structural models:

Undifferentiated or "cold" model: rocks mixed with water-ice
Differentiated or "hot" model: rocky core and water-ice mantle
Rocky core only (temperature high enough to boil off water-ice.

There are two types of rocks to consider i.e. CI rock- carbonaceous chondrite($\rho$ = 2.66g/cm3) for undifferentiated models which is $\approx$13% by wt. eposomite(MgSO4) and Prinn-Frigley rock($\rho$ = 3.262 g/cm3) for differentiated models which is sulfide-rich rocks like troilite(FeS).
McKinnon and Parmentier(1986); McKinnon and Mueller(1988) correctly predicted the structural model of Pluto to be differentiated one. During initial formation of Pluto, radiogenic heating was the only source of heat, hot enough to melt the outside part of the undifferentiated core consisting of hydrated CI-rocks to form liquid matter of what is known today as water-ice in the mantle (water-ice melting temperature was 251 K at 0.21 GPa). During that time, 80% of core was at above 500 K . The anhydrous silicate core at the center was still rigid resisting the outside flow (the temperature of core was 500 K). Convection through heating allowed steady-state heat flow to form water-ice in the mantle, some of which erupted into the surface. Although the gravitational potential energy was modest, the process become self-accelerating.
This process was also accelerated by the "accretion process" due to a large-body impact that resulted in the formation of Charon. This collision heated up the core by 100 K and also resulted in several differentiation of Pluto that made the surface level ice layer mixed with organic compounds.
Present day scenario: Pluto is a rock-rich world with rock mass fraction $\gtrsim$ 60%. Core temperature is 1000 K, surrounded by 250-300 km thick mantle shell of predominately water-ice and mixed liquid rock. Surface temperature is 40 K. Core pressure is 1.1-1.4 GPa. Rock fraction (rock/rock+H2O+ice) for differentiated Pluto is 0.69-0.79(mainly PF-rock). There is also an extra thermal boundary layer between the ice-mantle and the ice-rock layer just outside the core. There might also be an organic layer in between the core and mantle but it hasn't been proven yet. The water-ice mantle is differentiated into several layers based on its transitions. You can check the details and calculation in ref.2

Fig. 1: Temperature of Pluto at several Pressure value

Fig. 2: Temperature of the mantle and outside layer

Fig.3: Differentiated model of Pluto
References:

http://articles.adsabs.harvard.edu//full/1988LPI....19..764M/0000764.000.html
Pluto and Charon, Alan Stern, David James Tholen, University of Arizona Press, 1997
https://arxiv.org/ftp/arxiv/papers/1510/1510.06604.pdf (This paper discusses the possibility that Pluto might have an iron core)

What's the temperature of Pluto's core?


Which human rights are officially supported and recognized by the Chinese Communist Party?

Question: The Chinese government has always been extremely skeptical of the Western definition of human rights. For example, they refuse to implement a democracy, reject the freedom of speech and assembly, prevent citizens from freely moving around the country, controlled the population growth when necessary, etc. But are there any human rights which are officially recognised, implemented and supported the the CCP? What is the official view on the subject?
Answer: I think the subject is covered pretty well on Wikipedia which provides some insight about human rights implementation in China:

Human rights in China is a highly contested topic, especially for the
fundamental human rights periodically reviewed by the United Nations
Human Rights Committee, on which the government of the People's
Republic of China and various foreign governments and human rights
organizations have often disagreed.

According to Chinese Constitution, the most if not all human rights as are ensured (Chapter II):

right to vote (18+)
freedom of speech, of the press, of assembly, of association, of procession and of demonstration
freedom of religious belief
freedom of person inviolability
freedom and privacy
right to rest
right to material assistance
right to receive education
women enjoy equal rights with men
etc.

So, officially (by law) all these rights are recognized.
Also, it is important to notice that the Chinese Government officially recognizes that human rights cannot be applied in China in the same way as in Western countries due to "political and economical" differences:

The PRC government repeats the often ambiguously and confusingly
stated opinion that human rights should encompass what its officials
have labelled as 'economic standards of living and measures of health
and economic prosperity'. It insists that as economic, cultural and
political situations differ substantially between countries, a
international definition of human rights literally cannot apply to
China.

Rights that seem to have some support

religious freedom

Members of the Communist Party are officially required to be
atheists,[68] but this rule is not regularly enforced and many party
members privately engage in religious activities.

political freedom

Legally, all citizens of the People's Republic of China who have
reached the age of 18 have the right to vote and stand for election,
regardless of ethnicity, race, sex, occupation, family background,
religious belief, education, property status, or length of residence,
except for persons deprived of political rights according to laws
imposed by CPC regulations.

sexuality related rights

In 2001, homosexuality was removed from the official list of mental
illnesses in China.

"they refuse to implement a democracy"
China is a democracy, although its form, definition and implementation was debatable. According to its Constitution China has a "democratic dictatorship":
People's democratic dictatorship is a phrase incorporated into the Constitution of the People's Republic of China by Mao Zedong, leader the Communist Party of China (CPC). The concept, and form of government, is similar to that of people's democracy, which was implemented in Eastern Europe under the guidance of the Soviet Union.
Comment: I note it says rights should encompass living standards, which suggests that there should be a right given to the needs of life; however then what is the other stuff on there about with free speech and all which has nothing to do with that? Is that just a salve to make it "look good" to the west, as a cynic might say, or what? Or is it there's just so much Corruption the rights can't be implemented because everyone in the government has a corrupt agenda? I find the right to vote puzzling even more because China does not elect its leaders. What is this meant to apply to? What vote?
Comment: The question I wonder then is what logic does China use to justify the barring of free speech (through the use of extensive censorship of the internet and media, the deployment of state-sponsored propaganda ads and loudspeaker announcements, and hefty penalties for violation of any of these measures) given that it puts it right there in its Constitution, and furthermore nobody within the party seems to protest this? Why don't they just strike that portion altogether and say the opposite, that what speech is to be allowed and not is the sole right of the State to determine at its discretion?
Comment: And if just a "salve", what then is the purpose of the Constitution itself, in general? The whole thing just a salve? It seems fairly useless if it can just be totally ignored - heck, not only "can be" but it is actually standard and official (as exemplified by censorship bureaus being made explicit, formal organs of the government) operating procedure all the time, continuously, to not follow it?
Comment: @The_Sympathizer I would encourage you to ask your question(s) as a question; it may need a little adjustment to be answerable on this site, but it definitely can't be answered as a comment.
Comment: On religious freedom: https://en.wikipedia.org/wiki/Freedom_of_religion_in_China - the Holy See and the Dalai Lama certainly don't believe that there's religious freedom in the PRC.
Comment: @MartinSchröder - I think most, if not all the Western world would agree with them. I would say there is a minimum religious freedom: you can be a religious person and there is chance to get away with it. Otherwise, the list of religious persecutions is too long to be included in any reasonable sized answer.
Comment: @The_Sympathizer, re your first comment question. Although China is a "democracy" as in it allows its citizens to vote, there is very little separation of power (executive/legislative and judicary). It means there is no independent "supreme court" to who you could bring your claim that the government curtailled your right written in the constitution. In effect, if there is no way to get it *enforced*, the constitution is not worth the paper it is written on. So for the party in power, why not use it as a pretty looking storefront to answer(squash) the negative comments of foreign countries.


What is the most economical way to file a US patent

Question: I have a product that I am confident will be granted a patent. I am also confident that it is worth patenting from a commercial point of view.
Whilst being very different and not obvious, the product is an improvement on a previous lapsed patent that carries out a repair in domestic homes.
I would like to outline and file my patent application, then launch the product, and complete the patent process with a relevant patent lawyer, whilst the product is selling.
The question I would like to ask is; what is the best and most economical way of achieving this?
Comment: The original question was regarding a world-wide patent. Wile there is no such thing as a WW patent there is an almost WW patent * application* process. It is called a PCT application. To actually eventually get coverage in each country will be very expensive.
Answer: My overly-simplified view. There are two broad ways to file a utility patent application (I do not know what the title "WW patent" means). Option (a): file the application through a professional (patent lawyer or agent); the "best" option but not the cheapest. Option (b): file it yourself; NOT the "best" but it will the cheapest and will also be unlikely to result in the protection you want.
There are two applications paths available, regardless of the options above. A "Provisional" application will establish your priority date (giving you a year to get things together, incorporation, funding, etc); or a "Non-Provisional" application will begin the actual patent process. If using a Provisional, be aware that your final Non-Provisional will only get the benefit of the earlier
filing date of the provisional application for content that was well covered in the Provisional. Thus the effort and cost of a really solid Provisional application could be almost equal to the filing of a Non-Provisional application. I have observed that Provisional applications are often used to spawn a series of similar/related Non-Provisional applications, thereby providing a wider range of claims that may collectively provide greater protection to the inventor (or, an wider net for patent trolls to cast).


How do you configure Mathematica 9 to automatically evaluate all notebooks?

Question: I have a Mathematica 6 course that I am using in Mathematica 9; there is no updated version. Every time I open a notebook I have to go to the Evaluation menu and click on "Evaluate Notebook". Is there a way for me to set it so that it automatically evaluates a notebook upon my opening it? I keep getting answers on shortcuts I can use once the notebook is open or pressing shift-enter on a cell but that's not an answer; I would like not to do anything at all other than open the notebook and have every cell evaluated already since the tutorial course is long and contains a ton of notebooks.
Answer: One thing you could do would be to make a master notebook with lots of
NotebookEvaluate[notebook]

commands. Then execute all the ones you'll need at the start in one group. Then when you open them, they'll already be evaluated. You could do this programmatically by reading in and evaluating all the notebooks in a directory.
Comment: But this option would require a lot more work than simply evaluating a notebook myself.
Answer: With the option inspector (shiftctrlO) you can set the value of the option InitializationCellEvaluation to True (make sure that you select "Global Preferences"). Setting InitializationCellWarning to False suppresses the dialog you would normally get. Please note that this may entail a potential security issue.

You can do it programmatically as well:
SetOptions[$FrontEndSession,
  InitializationCellEvaluation -> True,
  InitializationCellWarning -> False
]

I used$FrontEndSession here, so that the effect lasts for the session  only (safer), but if you want to make this more permanent you could change that to $FrontEnd.

UPDATE
Assuming that you have all the notebooks in one directory dir, you could open and evaluate them all at once by using:
NotebookEvaluate /@ NotebookOpen /@ FileNames["*.nb", dir]

Comment: I had already tried this and it didn't work :(
Comment: @anthony I was assuming your notebooks would have initialization cells, but apparently they don't.
Comment: @Anthony Perhaps the update meets your requirements?
Comment: Unfortunately this would open hundreds of notebooks; I only go through certain notebooks as needed.
Comment: @Anthony I suggest that you do a ctrl-a shift-return upon opening a notebook. Those two key presses should be easy to perform. Or is that too much effort for you?
Comment: It's not too much effort, it's just that there are hundreds of notebooks and it would be a nice touch to have it evaluate upon opening; I was wondering if there was a simple option for this but it seems as if there isn't. I appreciate all your help though.


When is a note flat/sharp?

Question: For instance we are playing a B, is the third note of the chord a Eb or and D#? If we play Bm is the fifth a Gb or a F#?
Comment: Possible duplicate of [Why do notes have multiple names?](http://music.stackexchange.com/questions/23976/why-do-notes-have-multiple-names)
Answer: This is one of those questions that seems really obvious once you have a decent amount of experience, but can be a little challenging to explain.
I'm going to try and give you a couple of approaches that might help. All of the three ideas below are explaining the same thing from different starting points. Hopefully one of them makes sense.
After the first section, I've written a few quick comments on other connected ideas, or questions that might result from the other sections.

First idea. Are you familiar with your key signatures? Key signatures always have flats or sharps; never a combination of both. If our chord progression stays entirely within the key signature, we get an easy shortcut. If the key signature has flats, you're going to spell everything as a flat, not a sharp. If it has sharp, you're going to spell everything as a sharp.
Let's take your example. The key of B Major has five sharps. So, we're going to spell the accidentals as sharps, not flats. Which means the notes are D# and F#.
What about Cb Major? It has seven flats. Now, if you play this scale, it will sound the same as B Major (ignoring temperament, which is superfluous to this discussion). We're going to spell the accidentals as flats, not sharps. Which means the notes are Eb and Gb.
Second idea. Every major and minor scale has seven notes. Each of those notes has a name; it's a letter, and sometimes an accidental. Within the scale, we want to make sure that every note has a different letter. We don't want to be seeing Eb and E in the same scale; it makes things messy.
Back to your example. Following this single-letter rule, we can only spell it:
B C# D# E F# G# A# B
If we try to use Db instead of C#, we won't be able to complete the scale without repeating a letter somewhere, unless we spell the B as a Cb. But that's a Cb Major scale, not a B Major scale.
Third idea. Intervals. Each interval will have an associated letter. In a B scale:

The second will be some sort of C
The third will be some sort of D
The fourth will be some sort of E
The fifth will be some sort of F
The sixth will be some sort of G
The seventh will be some sort of A
The octave/unison will be some sort of B

So, the third must be a D#. It can't be an Eb, because that would be a fourth of some type (diminished, specifically). You can apply this pattern to any scale.

Notes and Chords. This all applies equally to both notes and chords of a scale. The third note of B Major is called D#. The third chord of B Major is called D#m (hopefully it's clear why it's a minor chord; if not, comment). The fifth of B Major is called F#. The fifth chord is called F# [major] (not Gb major).

On guitar chord charts. There's a tendency online for chord charts to refer to Bb as A#, and Eb as D#. That's ok, if the piece is in a key like C# Major or F# Major, because those are the correct spellings. It's not ok if the piece is in F Major or Bb Major or Eb Major. Here's some examples:
F Dm A# C (we're in F Major/D Minor, the key signature has one flat, so it should be F Dm Bb C)
Fm D#/F A# Fm (we're in F Minor/Ab Major, the key signature has four flats, so it should be Fm Eb/F Bb Fm)

On 'weird' keys. You may already know this, but once you get up around five, six and seven flats/sharps, you can pretty much choose between a flat key or a sharp key, and it will work either way. That's cool, and confusing.
The equivalences you're most likely to encounter are:

Five Flats == Seven Sharps (Db Major is the same as C# Major)
Six Flats == Six Sharps (Gb Major is the same as F# Major)
Seven Flats == Five Sharps (Cb Major is the same as B Major)

There are other equivalences, but let's not muddy the waters. You can also argue that these scales are not technically the same, but I think that's going way too far for this discussion.
How do you choose the right one? It's pretty much up to you, but you must be consistent. If you're going to call it C# Major, you can't use Ab chords. They are G#s. No mixing and matching.

Out of Key Signature Chords. Still with me? One last point. Sometimes a chord progression uses chords that aren't actually in the key signature. This means you need some extra accidentals. In this case, prefer flats if the key signature already has flats, and sharps in the opposite case. But this isn't as clear cut, and it depends on the chord progression. As you gain experience, you'll learn that people expect to see Bb chords in C Major, not A# chords. There are other theoretical reasons for these conventions, but this answer is far too long already, so I'm going to stop typing now.
Comment: One of the most common accidentals occurs when a dominant chord is required in a minor key.  The 'sharpened 7th' of the Harmonic Minor scale.  And it WILL be a sharp.  Or at least a natural.   But not a flat.
Answer: You've answered the question by calling the intervals a 'third' and a 'fifth'.   Whether perfect, major, minor, dimininished, augmented or anything else, a 'fifth' encompasses five letter names.  If the root is some sort of B, the fifth will be some sort of F.
B, C, D, E, F.
1, 2, 3, 4, 5.
A fifth.
B, C, D.
1, 2, 3.
A third.
Comment: In normal equal temperament, Gb major and F# major are the same chord.  The notes of Gb major are Gb, Bb, and Db, in F# major they are F#, A#, and C#.  As Laurence said, the spelling of a triad by root/third/fifth is conventionally followed.
Comment: I don't quite understand. Okay.. What about chords? It it an Ebm or an D#m and F#maj or Gbmaj? and in this chords are the notes sharps or flats?
Comment: Same difference with chords.  Or (8 note) scales, come to that.   If you root a triad on E - any flavour of E - the notes will be spelled E, G, B.   If you start a scale on F, the notes will be spelled F, G, A, B, C, D, E, F.    If this requires sharps, flats - double-sharps and flats even -  so be it.   That's how the basic spelling goes.    In extreme cases, we can cheat.  But be AWARE it's a cheat!
Comment: @ScottWallace is there any 12-tone temperament in which Gb major and F# major aren't the same chord?
Comment: @phoog- not that I'm aware of.  Gb major and F# major are as two peas in a pod.  Cheers from cold Vienna, Scott
Comment: There are plenty of 12-tone  temperaments where Gb/F# chords are unuseable though.  In fact, just about ALL of them except equal  temperament.
Answer: Try not to mix sharps and flats.Start a scale with whatever note. Count up, in order, T,T,S,T,T,T,S. T=tone, s=semitone. Use the next letter for the next note.
So, in C (no b or #) the order is C D E F G A B. Start on Eb. The order is Eb F G Ab Bb C D. The TTSTTTS is the same. The letter names are alphabetic. It works simply.
Now, to answer. Your B - third letter up - D. It's 2 tones up, so it must be D#. Any sort of E would be 4th.This is fairly straightforward elementary theory, but without it, nothing after will make any sense.
Answer: The interval quantity is always determined by counting the notes. In the key of A: A=1, B=2, C=3, etc.
So if you're in the key of B, all thirds will be some type of D, and all 5ths with be some type of F.
Once you have the interval size, then you determine its quality - sharp or flat, major/minor/perfect/augemented/diminished - depending on the root and the context.
So:
So, if for example, your tonic is B:
D# is the Major 3rd. (two whole tones from the root) Eb would be a Diminished 4th (one semi-tone below the Perfect 4th, E). D# and Eb are called enharmonic equivalents: Different spellings for the same note/pitch.
F# is the Perfect 5th.(3 1/2 whole tones from the root) Gb would be a Diminished 6th (one semi-tone below the Minor 6th, G) - again, enharmonic equivalents.
Answer: Rather than asking "when is a note sharp or flat" the question is more like "how to choose between enharmonic equivalent choises?"

For instance we are playing a B, is the third note of the chord a Eb or and D#? If we play Bm is the fifth a Gb or a F#?

For that particular choice of enharmonic equivalents the thing to understand is those kinds of chords are tertian which means they are built of a stack of thirds.
The gamut of letter, without sharps or flats, in thirds is A C E G B D F A C E....
So, a chord rooted on B, any kind of tertian chord, will be from the stack of thirds B D F A C E G B.
If you already know your choices for the third are between Eb/D# and the fifth between Gb/F#, then that combined with the tertian stack of B D F let's use know the chord is B D# F#.
You can arrive at the chord a different way using fundamental information about intervals and chord types. Intervals are named first by a number for the space of the letters, ex. B D is a third, and then the specific quality by half steps, ex. minor thirds - m3 - are three half steps and major thirds - M3 - are four half steps, and fifths are five letters apart, ex. B F and perfect fifths - P5 - seven half steps B #F. Major triads are a root, ex. B, and a M3 above the root D# and a P5 above the root F#.
Answer: You are dealing with the issue of enharmonic tones in the 12TET tuning system versus the standard naming convention in music.
The Major scale in any key will have the following pattern of steps:
(W - W - H) - W - (W - W - H)
W = whole step, H = half step.  There are 8 notes including the octave, 7 intervals.  The parenthesis separate Tetrachords. The Maj scale is 2 tetrachords separated by a W.
The naming convention for any and all scales is determined by taking 7 consecutive letter names from the alphabet, repeating after G:
A B C D E F G A B C D E F G A B C ...
And applying sharps or flats as needed to get the correct sequence of W and H.  The "degrees" of the scale are just the numbers 1 through 7 starting on the first note (not very exciting).  The correct letter name for a degree is obtained by mapping the degrees to the letter string, or simply counting up from Do, starting at number 1.
In the Key of A the 3rd must be a C, in fact it is C#, but NOT Db despite the two having identical frequencies on a piano or other equal tempered instrument.  In your example, B, the third note would have to be names D, since it is 3rd in the sequence (B, C, D, E, F, G, A), and it does need to be # to get 2 W space between B and its 3rd.  In Bmin the 5th is determined by the same logic, the 5th letter name in the sequence is F, so it must be named F something (in this case F#).
For equal temperament a C# and a Db might be the same note but from a music theory point of view you could not say that the Db is the Maj 3rd of A.  That would get points off on a theory test (I know from personal experience).

When is a note flat/sharp?


Breaking doublestops for Baroque music

Question: As a baroque violinist, I encounter double, triple and quadruple stops, like in Bach, Telemann, and Biber, and I want to articulate them correctly. I am looking for advice on how to break them, and how to decide which notes to emphasize.
Answer: I'm only an amateur on the violin, but for simple chords, you break the notes up into two groups, with each group sounding two strings.  For example, a quadruple stop would first be played on the G and D strings, then the A and E.  A triple stop on the bottom three strings would be G and D, then D and A.
For music where some notes in the chord change and some are sustained, it's largely a question of what's physically playable, and where the melody notes are, though it's more difficult to figure out in more complex works.  Bach's unaccompanied violin pieces in particular are interpreted differently by every performer, and there's a lot of nuance that goes into figuring out which notes to emphasize.
Comment: I'm not sure if the 2-2 division of quadruple stops is really idiomatic for Baroque. To me, this goes more in direction of a romantically-dramatic desperately-yearning-from-deepest-heart kind of sensation, as exemplified by the high un-Baroque [Elgar Cello Concerto](https://www.youtube.com/watch?v=OPhkZW_jwc0). For Bach solo stuff, I tend to feel it's more appropriate to only give the bass note a crisp accent that anchors the harmony, then quickly skip over the middle strings and end on a single naturally-melodious top note.
Comment: Maybe it depends on the tempo; or whether the piece is more homophonic or polyphonic...I just looked up the first movement of the first unaccompanied sonata on YouTube, and all but one start with a pair of double stops (one does more or less what you suggested). My favorite recording of the fugue in the same sonata (Szeryng's rendition) does put more emphasis on the theme, with very little sustaining of the other notes.

I'm not versed in more historically-accurate styles (as opposed to modern norms of Baroque interpretation), so if that's what you're referring to then I'm sure you're right.
Answer: You should decide which notes to emphasize by understanding which notes should be emphasized if there were no double or quadruple stops.
For example, if the lowest note is participating in a melodic figure that should be prominent, then it should be prominent in the chord. If the highest note is participating in a figure that is the main part, then it should be prominent (and likewise intelligibly connected to its sister notes in that main part).
If you are not sure what to do, then you ought to study the score more until you are. Or you can try different ideas and see if they make sense.
One approach I would decidedly avoid is to box yourself in with an arbitrary rule, like "in Baroque practice, the bass note should be emphasized." Even if such a statement were penned by a contemporaneous performer, we should step back and realize that A) it's possible people from the time were wrong, or bone-headed, and B) making yourself subservient to a rule that is divorced from the musical outcome or result that you are trying to achieve as a performer transforms you from a creative artist into a boring robot!
So, understand the musical function or role of all the notes in the chords (are they melodic, accompaniment, participating in various step-wise motions in subsequent events?), and then structure the loudness of your playing so that it is aligned with these roles.
In fact, this approach will work very well for all the notes in the piece, not just the double-stops. It bears emphasizing:
Align the loudness of all the notes to fit their role in the musical motion indicated by the melody, harmony, rhythm and texture fixed in the score.
Do this in such a way that the sounds unfold intelligibly, with a musical energy whose increases and decreases are balanced, and a great musical experience might just emerge! Good luck!
Comment: This seems reasonable and musical, the opposite of narrower pedantic approaches. I'm grateful for your time and ideas.  Thank you, Paul Smith. -Lynne

Breaking doublestops for Baroque music


How to choose race in World of Warcraft?

Question: Right after launching World of Warcraft for the first time I have to create a new character, when choosing a race, how are they different and what criteria should I use?
Comment: See also http://gaming.stackexchange.com/questions/10805/starting-out-in-wow - There's a good point there that really the first thing you should consider is which server to play on (PvP vs PvE) - Playing on PvP realms can be more exciting, but open you up to ganking.
Answer: Here is a good answer

Choose a race.

Before choosing, think of the benefits and disadvantages of the
  races    you choose. For example, Tauren has War Stomp, which is a
  good stun    for Warriors, and +5% health, which is also good for
  Warriors.    Because of this, most Tauren players to Warrior, Death
  Knight or    Feral Druid. However, with the case of Night Elves,
  Stealth is a kind    of disadvantage, since it overlaps with rogue and
  panther(feral    druid) abilities. Therefore, it can be seen as
  "wasted". Search on    Google if you want further information.
It's usually better to decide first on a faction, then on a class,
  and last on a race; but it's not necessary. Be aware, however, that
  not all classes are available for each race. An example of this is
  the Druid class. Only Night Elves or Worgen (Alliance faction) and Tauren or Trolls
  (Horde faction) are able to be Druid class. If you have already
  decided to play for the Horde as a Druid, you have no other options
  but to play a Tauren/Troll. Draenei and Dwarves are the only Alliance race that can
  play as Shamans, and Blood Elves and Tauren are the only Horde race that can
  play as Paladins. If you decide on a race before you decide on a
  class, understand that your options may be limited.
Consider how would you feel playing a certain race. Remember that
  you    will spend months and maybe years watching your character from
  his or    her back, so keep that in mind when picking a race. For
  example, you    may find Gnomes' movements and voice a little
  annoying, Undead    characters' bones poking though their armor a
  little disturbing, or    Orcs' roughness a little unpleasant.
Comment: Yeah, it's really about appearance, especially for your first character.  At least when I played the differences were are small and only really significant in the end-game.  I think the differences were bigger then too - eg back then only Dwarf priests had Fear Ward, which made a big difference for various raid bosses.
Comment: The other consideration is where the various races start - some starting areas are more interesting than others, and you're more likely to enjoy yourself. While it's usually not a problem to switch areas, when you're just starting out it can be hard to know where to go. On the Alliance side, I'm told dwarves and gnomes have a really good starting area, while the human one is quite weak (although the second human zone is great, while the draenei one is extremely weak.) Horde-side, trolls and undead have the best starting zones, while orcs are probably the weakest.
Answer: Forget min/max-ing, you'll regret it if you want fun.
Take whatever race you can "identify" yourself with the most or which one you like the most according to your own set criteria.
Answer: There are two ways I use to help me choose a race for a character.

Performance - All races have abilities and passive benefits that make them better at doing a certain job e.g. tanking, At being a certain class, And there are some races that are better at being a certain class spec than other races. This is often quite an advanced way of selecting a race and is focused on being the best at what you do during your end-game experience i.e raids, And I wouldn't recommend it to a new player.
Preference - This is the method that I use more often and would recommend to a new player. This just involves what you prefer i.e character appearance, racial background, roleplaying etc. This method is also helpful when your more focused on questing because the race you pick hugely influences your level 1 - 60 levelling experience for example if you're a Blood Elf it's very unlikely that you'll do your 1 - 10 levelling in Durotar.

For you I would definitely recommend the second method but feel free to use the first one if your eager to level quickly and advance to the later level experience.


How to dissolve water additions

Question: I'm fairly new to water adjustments. This in only my fourth batch with additions. One thing I notice is the additions don't seem to dissolve. I added 9g gypsum, 4 g calcium chloride and 1 g epsom salt to ten gallons while warming the mash water. When I was done heating I could see a good bit at the bottom.
Should I be crushing them finer first?
Comment: Calcium in small amounts is needed for amylase to function efficiently when mashing,  but Mg,  SO4 and Cl are not so important for the mashing process. . IMHO the level and ratio of sulphate to chloride ions in solution is important for taste profile of the final beer,  not so much the mashing. Adjusting the pH of the mash is relatively important.
Comment: The minerals are not really needed during the mash (unless you have very soft water) - so why not add them to the boil. The higher temperature and agitation will facilitate solvation and none will be lost in the grains. .However calcium sulphate (gypsum) is not very soluble so adding it in fine ground form to an excess of wort will help.
Comment: @barking.pete: I suppose this is about kit brewing, not all-grain brewing? Otherwise the statement 'the minerals are not really needed during the mash' do not make sense.
Comment: @chthon I think you're confusing yeast nutrients with water profile building.
Answer: Usually adding to the boil does well to get them mixed.
If you're concerned about clumping you can take some of the hot wort into a cup and slurry the addition to add back to the kettle.
Adjusting strike and sparge water is only needed for adjusting pH. A complete water profile for a specific style of beer isn't critical at this stage.
Comment: Assumption is the death of all logic... :0)
Comment: Well, that is interesting.  I guess I just assumed it was at mash time.
Answer: I believe best practice is to add your minerals the night before brew day, make sure to stir vigorously.  Any minerals that don't dissolve overnight should eventually dissolve as you're heating the water to strike temperature with a bit more stirring.
One notable exception is Calcium Carbonate (Chalk) will not reach desired concentrations in normal conditions.  If you need to add calcium carbonate to achieve your mash water profile, you can dissolve it under pressure of CO2 in a keg.
The "Water" book by John Palmer and Colin Kaminski is really a must for anyone who wants to really understand what's going on with water chemistry in the brewing process.  It's a bit dense, so it'll probably take a few reads through if you don't have a chemistry background.
Comment: So all additions would be part of the mash.  That's counter to the previous answer. A conundrum
Comment: Mineral additions are used for 2 general effects: altering mash chemistry and altering final flavor/mouthfeel.  Usually they do both so they are added before the mash.  It is possible to add them after the mash if you are only going for flavor/mouthfeel effects.  The additions you listed look like they were calculated to enhance mash chemistry, therefore obviously would need to be added prior to the mash.  Mineral additions affect more than just pH.  For example, calcium stabilizes alpha amylase in the mash.
Comment: @GnomeBrewer the grain itself has more than enough calcium that amylase "needs". The "need" of calcium is well documented as just a heat shield to prevent denaturing but is already there through skillful growing and malting of the grains. Additional calcium in a mash only fuctions as a base to adjust pH.

How to dissolve water additions