Weird color on texture painting with brush

Question: I'm new to Blender and was hoping someone could help me with this. I was watching a tutorial on youtube to learn texture painting in version 2.79 (as you can clearly see by incredibly amateur work, LoL) when all of a sudden the white color turned pinkish. I tried reloading a previous save, restarting blender, but unfortunately it didn't work. I checked if I'd changed the sliders by mistake, but no. Everything was as it supposed to be. I even went as far as reinstalling my gpu drivers. I've posted a picture. I hope you can see the slight difference. I know, it probably sounds like nitpicking on my side, but I can clearly see the difference in color. I'd appreciate any help. Thx in advance.  .
Comment: maybe pack your images and share your file: https://blend-exchange.giantcowfilms.com/
Answer: I think you tapped it. I've been trying to recreate the pink and RED is the direction any change in Saturation goes. As I approach .03, the pink begins to stand out if I see all your other settings correctly.
I'm not sure about creating palettes and how much protection that affords from changing colors. In my opinion you took the right steps by restarting and opening a saved version. I almost want to point some blame toward the alpha but that seems pretty locked in.
Triple check that color swatch and don't get fancy with any button shortcuts while painting in case one of them toggled some setting we're not thinking of. Checking Accumulate and Add for the Blend mode might also restore white where you need it if things are still rosy.


How should we include paper references?

Question: I recently included a few paper references in my answers (in the MCMC convergence question, for instance).  Should we include footnotes with the full citation when we reference papers?  That might be hard to enforce, but it would certainly be a good thing to do in my opinion.
Answer: To provide a complete reference while minimizing the amount of work:

For papers that have a DOI, always link to http://dx.doi.org/thisisthedoi.  Otherwise, link to the publisher's page for the paper, or some other source that provides a full citation and (if available) a link to the PDF.
Clicking on the link will give the reader a full citation, so providing the full citation (author, title, journal, etc.) in the answer should not be required.
Optionally, add a second link with the text "(PDF)".  This link should be to a free verison.
We shouldn't expect the answerer to dig up a link to a free PDF.  Given a full citation, it is not too hard for the reader to Google for that himself if he doesn't have access to the publisher's version through his institution's library.  It's ok to offer a link to a free PDF in a comment.
Incorporate the link into the answer informally, in whatever way makes sense.
If you want to include a full citation, feel free, but I don't think it's necessary to prescribe a format.

Examples of fine ways to incorporate links:

"If you use random kitchen sinks (PDF), you can …"
"Boosting seems to work well for protein subcellular localization patterns and cellular morphologies."
"You may want to try Cheeger regularization."
"Friedman, Hastie and Tibshirani show that boosting can be understood as additive logistic regression."
Comment: I agree, the default should always be if a paper has a DOI, link to that.
Answer: I would prefer that the cite should ideally be a link to a free version (e.g., on SSRN, arxiv, on author website etc) and if a free version is not available then link to the publisher version.
Comment: I would always suggest to use the DOI instead of the direct link to the publisher. Of course free versions are (imho) always preferable.
Comment: I can agree on that; I just got used too much to VPN.
Answer: I don't think it should be enforced, but we can indeed encourage people to do it. When we start with some unified format, people will quickly pick that up. And high-rep users / moderators can always edit it in.
I would suggest the following guidelines:

Using the Parenthesis Name Year format as proposed in (Smit, P., 2010), immediate linked to either doi or free pdf
Putting the actual references in sup tags (hopefully small tags in future, vote it up!)
Including at least the doi link, and if available a link to a free pdf.

Smit, P. (2010) Including references in answers Meta Stats Stackexchange, doi, free link
Comment: It's a lot of work... people pick things up, but (as in Metropolis method) rather those which make them work less.
Answer: Whatever we agree on should go into the FAQ. I support the use of DOI links where available. If not, I think we should encourage links to a standard open access repository such as ArXiv, RePEc or SSRN. As a last resort, link to a personal website.
Answer: I vote for URLs to the publisher site. This will work in a majority of cases, and gives a fast access to the paper. I just hate copying references to Google.

How should we include paper references?


Gimp - how to make entire layer transparent

Question: I'm trying to create watermark so I want my logo layer to be transparent. How do I achieve this? I tried all the existing guides but they aren't working. The layers are in JPG format by default when I import them. Can someone give me the step by step directions?
Answer:
Drag general picture to a empty Gimp window or open it from File dialog (Ctrl+O).
Drag second picture (watermark) to already opened image document or Open as Layers.. from File dialog (Ctrl+Alt+O). Now you will see 2 layers in Layer tool (Ctrl+L). Make sure than watermark image is above of layer of general image.
Right click on watermark layer and select Edit Layer Attributes...
In Layer Attributes set Opacity to 20-25 or smaller.
Optional: move your watermark layer or duplicate it.
Answer: There is no transparency support in the JPG format. When you open a JPG in Gimp (and in Gimp 2.10, when use File>Open as layers), the layer has no alpha-channel, which is how you control transparency of pixels. This is easily checked, when there is no alpha-channel on a layer:

the layer name is in boldface in the Layers list
the menu Layer>Transparency>Add alpha channel is not grayed out (when that mayer is active).

To add an alpha channel, you of course use Layer>Transparency>Add alpha channel.


Difference between Vampire and Noble in Noblesse?

Question: What is the difference between a vampire and a Noble in Noblesse?
Answer: Both terms were used by humans to describe the same species. The species refers to themselves as Nobles, and that's the name used for them throughout much of the series. "Vampire" was used for a relatively short time in the first issues, when the lore was yet being established.
The humans refer to Nobles as vampires because, as Frankenstein explains, Nobles can, and maybe did, consume human flesh and blood. In the series' universe the term "vampire" likely originated from Nobles, as well as the term "Noble" and "nobility" itself.
The term vampire was also used for the humans who were turned into zombie-like creatures by the humans who had obtained powers by making a contract with a Noble. One of those is seen early in the series, when he is turned by M-22.


What is convergence in machine learning?

Question: I came across this answer on Quora, but it was pretty sparse.  I'm looking for specific meanings in the context of machine learning, but also mathematical and economic notions of the term in general.
Comment: I would encourage you to limit the scope of this question to just machine learning to avoid making this question being possibly too broad.
Answer: When formulating a problem in deep learning, we need to come up with a loss function, which uses model weights as parameters. Back-propagation starts at an arbitrary point on the error manifold defined by the loss function and with every iteration intends to move closer to a point that minimises error value by updating the weights. Essentially for every possible set of weights the model can have, there is an associated loss for a given loss function, with our goal being to find the minimum point on this manifold.
Convergence is a term mathematically most common in the study of series and sequences. A model is said to converge when the series $s(n) = loss_{w_n}(\hat y, y)$ (Where $w_n$ is the set of weights after the $n$'th iteration of back-propagation and $s(n)$ is the $n$'th term of the series) is a converging series. The series is of course an infinite series only if you assume that loss = 0 is never actually achieved, and that learning rate keeps getting smaller.
Essentially meaning, a model converges when its loss actually moves towards a minima (local or global) with a decreasing trend. Its quite rare to actually come across a strictly converging model but convergence is commonly used in a similar manner as convexity is. Strictly speaking rarely exists practically, but is spoken in a manner telling us how close the model is to the ideal scenario for convexity, or in this case convergence.
Answer: This is actually a highly technical term, which has been kind of misused and overgeneralized in many places.
What does 'convergence' mean in a literal sense? It simply means that a sequence of terms indexed by $\mathbb{N}$ ($X_1, X_2, X_3,..$) tends to a certain fixed value say $X$ as $\mathbb{N} \rightarrow \infty$, but may not achieve the fixed value. (there are a few technical details associated with this definition but I won't go into it as it requires some analysis)
When it comes to ML we are looking at probabilistic or stochastic models. When we talk about convergence in ML, we generally mean 4 types of convergence:

Convergence in Probability: This means that $\mathbb{N} \rightarrow \infty$ your likelihood of $X_N$ (a sequence of random variables) being very close to $X$ also increases i.e $P(\omega:[|X_N(\omega)-X(\omega)| >\epsilon]) \rightarrow 0$ as $N\rightarrow \infty$. This type of convergence is mostly used in Statistical Learning Theory.

Almost Sure Convergence: This means that $\mathbb{N} \rightarrow \infty$ your probability of $X_N$ (a sequence of random variables) being very close to $X$ is $1$ (NOTE: Here there is no likelihood of being close to $X$, we straight up say it must be close to $X$) i.e $P(\omega:[|X_N(\omega)-X(\omega)| >\epsilon]) = 0 $ as $N\rightarrow \infty$. This is a stronger verision of the previous convergence, and this is the type of convergence I have seen being used in RL.

Convergence in Distribution: This means that the distribution of a sequence of random variables tend to a certain distribution i.e
$$\lim_{N\to \infty} F_{X_n} = F_X$$.

Convergence in $r$'th moment: This means that a sequence of random variables will converge to a certain mean as the sequence goes to infinity or simply put:
$$\lim_{N\to \infty} \mathbb E[|X_N - \mu|^r] \ 0$$ where $\mu$ is the value to which the random variables in converge in $r$th moment.

A simple useful reference for all the aforementioned modes of convergence.
As a side note, this is meant as an informal reference, there is a lot of mathematical analysis involved in getting conditions for when these hold for a sequence of random variables.
In the context of ML, one can think of $L(w_N,y_N,x_N)$ in place of $X_N$ where $w_N, x_N, y_N$ will be the one deciding on the next step, and one can check if it satisfies any of the aforementioned convergence using some sufficient conditions. Note that when we do convex optimization we are talking about almost sure convergence (if the method used works), while for SGD due to stochasticity one might formulate it in the convergence in probability setting.
As a concrete example, the PAC learning paradigm uses the convergence in probability framework (without going into details the idea of PAC learning is that with increasing size of dataset your confidence about your classifier increases which can be interpreted as some sort of convergence in probability with the actual loss as the random variable, check the PAC learning framework here), while the Q-learning convergence (proof as suggested in the comments) is an almost sure convergence under some assumptions (probably proved by Bertsekas and Tsitsiklis), CLT is an example of convergence in distribution.
Comment: I would suggest that you use a consistent notation for all types of convergence. For example, use the "limits notation" when they are applicable. For example, in the last 2 cases, you use limits, but in the first 2 cases, you use "$\rightarrow \cdots $ as something $\rightarrow$", i.e. use the notation used by the reference https://www.probabilitycourse.com/chapter7/7_2_5_convergence_in_probability.php in all cases. I would also suggest that you use double `$$` to emphasize the formulas and their differences.
Comment: As an example of "convergence being used in RL", see e.g. http://users.isr.ist.utl.pt/~mtjspaan/readingGroup/ProofQlearning.pdf, which you can add to your answer as an example. I would also suggest that you provide the links to the references that support your other claims, like "PAC learning paradigm uses the convergence in probability framework". This answer can also be improved by distinguishing between r.v.s and realizations of r.v.s, etc. Convergence series is not exactly the same thing as the convergence of r.v.s., but you use "series of terms", which may be misleading.


What happens if I change the password of the Sales Cloud Connector User in SFMC?

Question: I need to log in as the Sales Cloud Connector User that is set up in the Marketing Cloud. I will need to reset the password for this user to do this.
What happens if I do this? Will my established journeys still run? Will my data stream sync continue to run? Are there any other negative outcomes? Does the Contact Model fall over?
Answer: To answer my own question - in my case (YMMV) it didn't break anything.


Single wide table performance in a column oriented database (Vectorwise)

Question: I am performing some tests on vectorwise using a star schema and a single denormalized table. In the denormalized table I have 5 extra columns which are > varchar (100).
I am new to the column oriented world and hence want to understand to get my facts right.
Few facts :

Query memory = 20G, Cache Memory is set to 7G
The size of name columns alone is around 6G, 6.5G, 2.6G and 650M. Now obviously these can't fit in my cache memory so system is I/O bound.
If I use a star schema approach it is working faster as then it has to cache integer columns from fact all of which can easily fit into my main memory cache.

I have a few questions surrounding this:

If I have to use a single table I need to increase my RAM to make sure all these columns to fit into memory ? I would like to know if someone else has done this kind of structure using Vertica or any other column oriented databases. If yes are you using the same approach all varchar columns should fit into RAM ?
The simple star schema query
select col1,col2, col3, sum(col4), sum(col5) from fact_table join tabl1 on condition join tab2 on condition where tab1.col1 = 1234 and tab2.col2 = 6789
Works slower than:
select col1,col2,col3,sumcol4, sumcol5 from
(select col1,col2, col3, sum(col4) as sumcol4, sum(col5) as sumcol5 from fact_table where fact_table.col1 = 1234 and fact_table.col2 = 6789) as facts
join tabl1 on condition join tab2 on condition
Why?
Note : Master Tables tab1 and tab2 are main memory resident.

I am using Vectorwise but just want to know if these observations are true for Vertica as well?
Answer: Vertica does not have the idea of keeping tables resident in memory. In some cases and in some kinds of joins, table data might already be in memory or get put there. But ultimately, Vertiac performance is dependent on how you store things on disk.
I would not expect the performance of thoe two queries in Vectorwise to have any bearing on how similar queries and tables would perform in Vertica. That said, the fewer number of rows involved with the join in the 2nd query suggests it would do better in various query execution engines.


How to make a website with two types of logins , Sellers and buyers?

Question: I need help please finding out how to make an E-commerce website with two different types of logins Some users will submit their products and others can login to purchase. something like Ebay.
I heard that wordpress is not the right solution for that, but I really love WP and hope that you can guide me if that is possible here on wordpress? if yes .. What themes/ plugins can be used to acheive that please.
Thank you very much in advance.
Comment: The important part here is that they both use the same login, they just have a flag on their account that indicates if they're a seller or a buyer. It's certainly possible with WordPress, but I sense what you need is much broader in scope
Answer: Use a single login, and tag each user as either a buyer or a seller using user meta
e.g. lets use a user meta field called shireefs_login_tag
To set the tag:
update_user_meta( $user_id, 'shireefs_login_tag', 'buyer' );

To read the tag:
get_user_meta( $user_id, 'shireefs_login_tag', true );

To redirect on login:
function my_login_redirect( $redirect_to, $request, $user ) {
    if ( !empty( $redirect_to ) {
        return $redirect_to; // dont mess with existing redirects
    }
    //is there a user to check?
    if ( isset( $user->roles ) && is_array( $user->roles ) ) {
        //check for admins
        $login_tag = get_user_meta( $user->ID, 'shireefs_login_tag', true );
        if ( 'buyer' === $login_tag ) {
            return home_url( 'buyers' ); // example.com/buyers
        } else if ( 'seller' === $login_tag ) {
            return home_url( 'sellers' ); // example.com/sellers
        } else {
            return home_url( 'choose' ); // example.com/choose, we dont know if they're a buyer or a seller yet
        }
    } else {
        return $redirect_to;
    }
}

add_filter( 'login_redirect', 'my_login_redirect', 10, 3 );

With this information you now know how to:

store if a user is a buyer or a seller
retrieve that information so that you can do things with it
redirect users to a location based on that info when they log in

Everything else can be built off of those
Comment: While using meta for this can be ok for very simple cases, using custom Roles and Capabilities is much better and generally the only way to go.
Comment: @IhorVorotnov I look forward to your answer
Comment: The exact *proper* implementation is far beyond the SO answer format and involves many moving parts. I've added a more general answer below.
Answer: While Tom J Nowell's solution will work for pretty simple cases (and definitely will work for the simple case of redirecting users after registration), for more complex things a simple flag in usermeta table will introduce more problems than will solve. Most importantly, you'll need to handle somehow permissions and security.
First, you need to understand that you will need much more than just a simple redirect. Sellers must be able to create and manage custom post type entries (products), see and manage orders of their products etc. Buyers must be able to create and manage their orders. They will have different menus, different actions on items available for them, access to different areas of the site etc. Not to mention lots of transactional emails and other "internal" components. And I'm just scratching the surface here.
Basically, you're introducing two different user roles, and both require more capabilities (permissions) than a default "Subscriber" role (for example, subscribers can't create post type entries, in your case - products). WordPress has a built-in API for Roles and Capabilities. The API itself is on a code level and intended to be used by developers. However, there's a lot of plugins that can help with that, for example, User Role Editor.
I will not dive deeper into the exact implementation as it would take a lot of time and effort and will not fit into the simple SO answer. There are some plugins that can handle at least part of what you need. But if you're going to build a UGC site, you'd better be a developer yourself and spend a lot of time learning all underlying WP APIs, or hire an experienced team that will do it properly.


Which is faster: A math node tree or an OSL shader?

Question: In terms of render times for Cycles materials, which is faster? A material node tree containing many (~20-50) math nodes or a single OSL shader script node performing the same calculation.
Comment: OSL isn't supported on the GPU, so I'd say nodes are faster if you have a GPU to render on.
Comment: This question has no real possible good answer.
because it depends on what you want to do in OSL or cycles
OSL scripts can be large and node systems too. so in comparing apples and pears, we cannot tell anything about weight if we don't know their size.
Comment: Thanks, @gandalf3. I usually use large image textures so GPU isn't an option for me. But that OSL limitation is an important one.
Comment: I would still be interested in the answere.
Comment: why not simply test it ?.
Answer: Answer is hard to give, so I will rephrase the question to will an OSL script node eventually be faster than an SVM node graph with math nodes. The answer to this question is yes. Then the next question, when will this benefit happen. this one depends on many parameters. Would I recomment to migrate to OSL script fore solely this reason? No.
I did a test on this subject. As GPU depends on many other stuff I will stick to a SVM CPU vs OSL CPU comparison.
Specs of my test machine:

Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz (8 cores)
Running on Linux
Using official Blender 2.79 release

Test scenes
I constructed 5 scenes for this test.
SVM-0: SVM without the math nodes

SVM-math: SVM with the math nodes

OSL-0: OSL without the math nodes

OSL-math: OSL with the math nodes

OSL-scipt: OSL with the script node

The scene uses around 12 math nodes. I used the emission shader as it will not scatter new rays.
SVM-0  SVM-math | OSL-0  OSL-math OSL-script
------ -------- | ------ -------- ----------
22.90  25.86    | 25.47  27.70    26.05
22.87  25.80    | 25.40  27.64    26.01
22.86  25.84    | 25.38  27.68    25.99
22.92  25.84    | 25.42  27.65    26.04
22.91  25.79    | 25.44  27.63    26.04
-----  -------- | ------ -------- ----------
22.892 25.826   | 25.422 27.660   26.026

What is important in these numbers:
 - SVM average time in the math nodes is 2.934
 - OSL average time in the math nodes is 2.238
 - OSL average time in script node is 0.604
SVM math nodes scales linear. Meaning adding more math nodes will add on average a constant performance penalty.
There is a positive effect on using script nodes. Where is the theoretically break even?
((26.026-22.892)/0.604)*12=62.2649

But different scenes will have different results. For example: the test scenes are constructed that the shader is full screen. Normally you have many different objects and materials in the scene. So let's calculate the number of samples that are needed.
1920*1080*128*62.2649 = 16526399569.92 # resolution * samples * breakeven

On my machine the benefit would happen around 16,526,399,569.92 samples that pass though a node graph where 62 mathnodes were replaced with a single script node.
Note: on different machines different things will happen and that can influence the results.
There are also other stuff to be aware off: SVM codebase is fully shared between CPU/Cuda/OpenCL. As GPU's don't have the ability to have a stack the cycles developers
came up with an idea to implement a fixed stack that could compile on all devices. This stack is limited to 256.
When node graphs get too large SVM will not become an option anymore so the artist might want to switch to OSL.
Would I still recommend it?
No. reason: other materials setup have other cost penalties in OSL. So this theoretically benefit in practice might be much higher. So for this reason I would stick to SVM.
Answer: For most use cases, OSL will be faster because it is compiled.
Comment: can you provide any examples?
the math nodes are compiled as well, so im wondering how you draw that conclusion.
Comment: Math nodes are not compiled, they are interpreted and stacked. Depending on the function you're executing, you'll get different results using SVM or OSL (both in cpu). OSL has the particularity that it optimizes calculations whenever they can be optimized, but in SVM every node is calculated even if the end result doesn't depend on the node's result.
Answer: It depends on the specific case.
Of course OSL is powerful tool for pattern generation in comparison with cycles' build in math node but you should realise that it doesn't support GPU rendering and it also increases your render time if you use non .tx format textures.
ps.
Remember that sometimes it's much faster to write a couple of lines of code instead of making a large node tree.


Do nuclei emit photons?

Question: Generally in text books they say that when a electron goes from high energy state to a lower energy state it emits photons.
My question is, it is possible that a proton that goes from high energy state to a lower energy state emits photons too?
Comment: I've removed some comments that should have been posted as answers.
Answer: Nuclei emit gamma rays, which are high energy photons. The photons emitted when electron in an atom changes its energy state are usually in optical spectrum, which are more frequently encountered in technology and real life, which is why they receive more attention in textbooks.
Remarks
To underscore why photons are less "important" for nuclei than for atoms:

Nature of interactions It is worth noting that atoms, solids and molecules are held together by the Coulomb interaction (i.e. by electromagnetic forces), which is why their structural dynamics is strongly coupled to photons - the particles carrying this interaction. Nuclear forces are of different nature - although photons play a role, they are but one of many particles involved.
Size Being charged particles protons should be coupled to EM field. The strength of this interaction is proportional to the dipole moment $d=r_ne$, where $r_n\approx10^{-15}m$ (one Fermi) is the nuclear radius that is much smaller than the radius of an atom $r_a\approx10^{-10}m$ (one Angstrom). In other words, the coupling of protons to photon field is $10^{5}$ times weaker.
Mass protons and neutrons both carry spin and could couple to electromagnetic field via Zeeman coupling. However, their mass is about thousand times bigger than that of electrons, resulting in a thousand times smaller gyromagnetic ratio (i.e. nuclear magneton is a thousand time smaller than Bohr magneton), i.e. the coupling is weak.
Finally, here is an authoritative reference on the subject: Interaction of nuclei with electromagnetic radiation

Quote
The following quote is from book "Fundamentals in nuclear physics" by Besdevant, Rich and Spiro:
<code>While the numbers (A, Z) or (N, Z) define a nuclear species, they do not
determine uniquely the nuclear quantum state. With few exceptions, a nucleus
(A, Z) possesses a rich spectrum of excited states which can decay to the ground
state of (A, Z) by emitting photons. The emitted photons are often called
gamma-rays. The excitation energies are generally in the MeV range and their
lifetimes are generally in the range of 10^{−9}–10^{−15} s. Because of their
high energies and short lifetimes, the excited states are very rarely seen on Earth
and, when there is no ambiguity, we denote by (A, Z) the ground state of the
corresponding nucleus.
</code>
Comment: Notice that the question mentions _proton_ going from high energy state to a lower one. This doesn't look like a talk about nuclear physics, but rather changes of atomic nucleus-electron system's state.
Comment: @Ruslan you are right that many different things happen in nuclei, and I am not an expert in this respect. However I doubt that the intention of the question was to go into such details. I also took liberty to assume that electron is in an atom, although one could also talk about solid state, molecules and even vibrational transitions in molecules.
Comment: you are right @Vadim your answer is satisfactory
Comment: True, outer shell electron transitions tend to involve visible photons or UV, but inner shell transitions can involve higher energy photons, even X-rays, especially with heavy nuclei.
Comment: @Ruslan i will pose another question related to your comment
Comment: @Vadim - is there a minor typo?  "their structural dynamics is .." should be "are" ?  (or some other tense change)
Comment: @Fattie *Dynamics* can be used as either singular or plural: https://ell.stackexchange.com/a/59384/118488 I think singular is more appropriate in this context... but I am not a native English speaker, so I might be mistaken.
Answer: Yes, excited nuclei emit photons in the form of the highly energetic $\gamma$-rays.
That these emissions are much more energetic than the VIS photons emanating from excited electron clouds can be somewhat heuristically understood by looking at the energy spectrum of a particle in a closed $\text{1D}$ box, of length $L$:
$$E_n=\frac{n^2h^2}{8mL^2}$$
So the emission energies are inversely proportional to system size:
$$\Delta E \propto \frac{1}{L^2}$$
It follows that smaller systems, like nuclei, will emit much more powerful photons than atoms (electron clouds).
The energy content of a VIS photon is about $2\text{ }\mathrm{eV}$, that of a mid-range $\gamma$-photon about  $1.2\times 10^6\text{ }\mathrm{eV}$.
Of course neither system above are $\text{1D}$ boxes and in reality it is just a useful analogy.
Comment: The nucleus is a mere speck, compared to the rest of the atom. See Rutherford's famous experiment.
Comment: Oh, I know. But in solid-state physics you focus on the *mass* rather than the volume, and the nucleus is vastly more massive than the electrons.
Comment: It's strange to think of a nucleus as smaller than an electron cloud, but I suppose I'm thinking more in terms of mass than physical volume. (comes from working with solid-state physics, I suppose!)
Comment: @Hearth 'It's strange to think of a nucleus as smaller than an electron cloud' Not since Rutherford's experiment.
Comment: @my2cts I know that, I was talking about how it's way bigger than the electron cloud in terms of mass, which is what's more important in my field.
Comment: @Hearth Rutherford's is experiment is also very relevant to solid state physics.
Answer: When nuclei are in an excited state and decay, they often release photons (almost always in the gamma/X-ray energies).  A good example of this is the decay of metastable nuclear isomers.
For instance, the decay of Hafnium-178m2 (the 'm' represents a nuclear isomer of Hafnium-178) yields a photon of 2.5 MeV.  There are attempts to use this isomer as a weapon.  One of the lowest energy nuclear isomers is Thorium-229m, which decays to Thorium-229, releasing a photon with only around 7.6 eV(far ultraviolet!)
Another interesting nuclear isomer is the exceedingly long-lived Tantalum-180m.  It is a primordial nuclei (i.e. if you get a sample of Tantalum, it will contain some Tantalum-180m), and has a half-life of over $10^{15}$ years.  One decay mode is to drop to Tantalum-180, releasing a 77 keV photon.  What is funny about this isomer is that once it drops to the ground state (Tantalum-180), the ground state nucleus is less stable than the excited state isomer, with a 8.1 hour half-life!
Comment: Also, many beta emitters have excess energy after emitting the beta particle and that excess energy is released as a gamma. Thanks for that example of Th-229m. I was looking for very low energy gammas for [this answer](https://physics.stackexchange.com/a/561217/123208), but I missed that one.
Comment: Note that the singular form is nucleus, while nuclei is plural.
Answer: The simple answer is yes. Here is a real life example where this is important.
To produce 'signal', the MRI scanner interacts with protons in the body. Randomly orientated protons become aligned with the powerful magnetic field in the bore of the scanner. A rapidly repeating sequence of radiofrequency pulses – produced by the scanner – then causes 'excitation' and 'resonance' of protons. As each radiofrequency pulse is removed, the protons 'relax' to realign with the magnetic field, and as they do so they give off radiofrequency 'signal' which is detected by the scanner and transformed into an image.
Source: https://www.radiologymasterclass.co.uk/tutorials/mri/mri_signal
It may be interesting as well to mention as an additional layer of information that quarks inside the proton also excite similar to an electron. They don't carry the same SPDF class, but instead form [Nucleon] Resonances which are excited states of protons/neutrons. This was the basis behind my PhD work. In this case they will primarily emit particles instead of photons (so pions, Kaons, new nucleons, etc)
Answer: Yes, many experiments of the form X(n,n'g)X are performed as a way to measure the energy levels of a nucleus. An incident neutron scatters off the target nucleus and if the incident neutron energy is high enough energy it will leave the target nucleus in an excited state. These states will often decay by emmision of a gamma-ray.  The energy level of a nucleus can be determined by measuring the gamma-ray energies.
Answer: It is good to say that nuclei emit not just photons, but also in some cases, their pretty close relatives - W bosons. That's how beta-decay happen (W boson is quick to decay into electron and neutrino).
Comment: Well, this is short of also mentioning alpha decay, fission and loads of other ways a nucleus could emit something. At least in the case of photon-only emission the nucleus remains the exact same isotope, albeit a different isomer.
Answer: This answer addresses the title rather than the comment text, but all nuclei, regardless of state, emit photons, as they contain charged particles, which create electric fields, and (sometimes harder to measure) magnetic fields.
Electromagnetic interactions are mediated by photons, so anything that contains charged particles will emit photons.
Comment: Photon emission does not include _virtual_ photons.

Do nuclei emit photons?


Are the following two compounds isomers or not?

Question: Are the following two compounds isomers or not?
I feel they are enantiomers(non-superimposable mirror images) however my book states that they are not isomers?
I cannot understand why?
Comment: Probably a typo. You are correct that they are enantiomers.
Comment: This is an example of a compound with no chiral center, but it is chiral.  Compare 1,1-diethyl 3-methyl propa-1,2-diene (did I get the substituents in the right order?).
Comment: http://chemistry.stackexchange.com/q/42999/16683 #3
Answer: You are right, these two molecules are enantiomers. If you rotate the bottom molecule 180 degrees, you can see that it is the mirror image of the top molecule. Enantiomers are stereoisomers, so the only reason your book would say they are not isomers is that it (unfortunately) contains a typo.
Comment: Or possibly they missed the concept that a molecule can have not a (single atom) chiral center and yet be chiral.


I buy and sell used bikes some have been repainted how can I find manufacturer if there are no identifying marks

Question: Need help identifying frames to make sure make model and possibly year
Comment: You can't, in any general case.
Comment: Suppose you convince yourself that this repainted, unbranded frame is actually from Brand X. Are you going to be able to convince your buyer of that? If not, it's made zero difference. Ditto the year: great, it's a 2009 rather than a 2008. Does your buyer care about the difference between a ten-year-old bike and one that's eleven years old? Probably not, and even if they do, what's your time worth? Three hours of research for an extra ten bucks on the price is a lot less than you could earn in three hours stacking shelves at your local supermarket.
Comment: Ask your suppliers to not repaint them?
Answer: The short answer is that it's a lot of work and there is no one way of identifying every bike. Sometimes a bike impossible to identify.
Documenting all the things to look for that might help ID a bike would take a large book. Here is some high level information to get you started.
As a rule of thumb
The less information you have to start with the less likely it is that you will be able to identify the bike.
Per the original question - there are no identifying marks.
Is it worth identifying?
Some bikes are not worth the effort of identifying.
If it's a department store bike it does not matter which brand of department store bike it is.
Here is a link to a previously asked question on how to identify department store bikes.
Let's assume it's not a department store bike - what are next steps.
What kind of bike is it?
For a BMX / Freestyle bike BMXmuseum.com is a great place to do research.
Mountain, Gravel, Hybrid, Road and touring bikes - with a little experience you can roughly identify a year range the bike may have been made and then work with Google images to find a picture of a bike like the one you have. If the frame you has no distinctive features it will be very difficult to identify.
Possible distinctive frame features.

lug work
frame design - anything besides the standard diamond frame.
tubing - oval shaped, tapered etc.
fork crown
Fork or frame drop outs

Here is a forum thread discussing a wide variety of ways to identify a bike.
Bike parts
If the bike has parts on it the brand / model names of the parts can help you identify a bike. You can search for bike makers that used the brand / model of part that is on the bike. The newer the bike is the less distinctive parts are to particular bike makers. There just aren't as many bike parts makers as there use to be.
Stolen bikes
Finally, there are many stolen bikes out there. It's always good to run a serial number through the Bike Serial Numbers database to see if it's stolen.
This answer is intended to be a start on the answer. I'm sure others will have valuable tips and tricks.
Answer: Don't bother - go on overall build quality and to some extent weight, then mitigate that with an allowance for wear and mileage.
A nice road/race bike that was expensive new will be light, and specced with higher group parts.   That's Dura Ace and Ultegra and the comparable SRAM.  However if its done 20,000 km then there will be a heap of worn parts, which won't work that well together.
On the other side, a bike that has 3x7 gears, a Tourney groupset or unlabelled Shimano parts, and plastic gripshitters will be a low grade BSO no matter how much or little its been ridden.
If it was a good high-quality brand, the previous owner is less likely to have hidden that by stripping or painting.   Ask for any documentation, warranty form, sales receipts etc.
If it was a BSO, then anything could have happened, but they tend to be obvious to the trained eye, and not worth a lot.


Why didn't they use Hitler as one of the six ghosts?

Question: The Exorcism of Emily Rose is based on the real story of Anneliese Michel. In the real story, two priests claimed that there were six demons including Adolf Hitler, Judas Iscariot and Nero. But in the film version the six ghosts are  Cain, Nero, Judas Iscariot, Legion, Belial and Lucifer. Why did they not use Hitler's ghost?
Answer: I would guess that the most likely reason was to avoid the possibility of causing upset or offence.  Hitler's actions are still within living memory and some people (mainly in Europe) are very sensitive about the issue and do not even like discussing it or even having it mentioned.
Sometimes it is because their families might have suffered in the atrocities and sometimes it is because their families might have been involved in inflicting it etc.  Whatever the reason it is usually best to simply avoid the issue unless you are going to handle it in a very specific way.  That is not the angle the film makers wanted to go down so they avoided it entirely, it is not as if there are not plenty of other horrible ghosts you could use.
For example in Germany a friend was stopped and questioned at an airport because a tattoo he had resembled (if you squinted) an eagle symbol which is associated with the Nazi party.
Comment: +1, nice answer, also thought the same but looking for some source to know the official reason for this change.
Comment: Fair point, I am afraid I am not aware of any official statement on the issue.


What modifications are necessary to the airframe and or instrument panel to add an autopilot to a light airplane (like a Cessna 172 or 182)?

Question: If you were going to add an autopilot to a light airplane that never had one, what all needs to be done? I know they need to connect servos somewhere (where exactly), and add instrumentation to the panel, but how invasive is the installation?
Comment: What kind of auto pilot? Single axis? Two Axis? Is it coupled to the GPS?
Comment: @RonBeyer I'm sure a good answer can cover all. Otherwise you'd have to ask three separate questions for incredibly similar topics.
Comment: I'm particularly interested in a two-axis autopilot coupled to the GPS. From the only answer (so far) it looks like it is very specific to each airplane. I guess I was looking for some general "servos for the ailerons are typically mounted here..."
Answer: I participated in a project to do this to a light aircraft some time ago. The requirements will vary on the basis of the type of autopilot you select and the requirements of the STC that comes with it, and which allows it to be installed on your aircraft. There might (and likely will be) one or more of the following requirements: panel mods, electrical mods, servos need to be installed (type, placement and installation procedure as per the STC), there will also have to be ground and flight testing, and if you intend to interface the unit to navigation equipment, then it gets really interesting. It all depends what other avionics you already have in your aircraft. You may or may not have to upgrade your existing equipment to achieve that.
To get a complete answer to your question for a specific aircraft you need to go to a reputable avionics shop that has done the work before (read: has references) and pose the question to them.
You should also expect to have to pay for a detailed quote and time estimate -- it takes quite a bit of work to prepare that, and avionics shop owners have to pay bills and put food on the table, just like you. :)


Missing uv textures

Question: So trying to get this wolf I did finished but I can't paint on it as it keeps saying missing uv maps! Any help please with this?
Answer: In order to paint on a 3d object,first Uv maps and paint/texture layers need to be created and saved and only then one can paint on it.There are many other ways to do this but the one below, is by far the simplest.
I am demonstrating the procedure on this monkey ,you can follow the same steps on for your  model.
1 .After creating/adding monkey in object mode, select the monkey and  switch to texture mode.Also open a side window and open the Uv/Image editor.
2 . Once in texture mode -tools panel(T),click   on  add simple Uv's button.This will create a Uv map of the object in Uv/Image editor. Save this Uv map as a Png on your computer by clicking Image->New Image->Create 1024x1024 png.
3.Going back to 3dview,click on Paint Slot dropdown menu and select the type of Paint Slot you want.For general purpose,DiffuseColor =1024x1024 should suffice .

4.Save these newly created Uv map and Paint Slot/layer as a Png Image by going to the Uv/Image editor ->Image->Save as Image.This is done by individually selecting the Uv map and Paint layer from the Dropdown menu.

5.Start Painting by going to the texture paint -tools panel and under brushes selecting the TexDraw brush and the required color.
6.IMPORTANT -Save the Paint layer frequently as Blender does not Autosave.
Comment: Even if Blender version's are different ,the procedure is the SAME.Simply go to textures panel (top) with your model selected and follow the above steps.You should be able to get the above shown results.
Comment: That's different from my blender
Answer: To texture paint, you need to set up a material, an image texture, and a UV map.

To make Ctrl+T work Node Wrangler add-on should be enabled.

Missing uv textures


Can cameras set exposure in more precise increments than third stops in automatic exposure mode?

Question: If I shoot in manual I set the exposure to the nearest 1/3 stop. If I use one of the automatic modes does the camera do the same thing or can it set the dependent variable to a resolution finer than 1/3 stop?
Comment: Which camera are you interested in? The answer can (and almost certainly does) vary between cameras.
Comment: @mattdm On the low end Canons (up to the xxxD), you can set ISO only in full stop increments, but auto ISO will use 1/3 stops.
Comment: @PhilipKendall I'd be curious to see an example of a camera which uses smaller fractional stops in automatic modes.
Comment: @PhilipKendall Thanks. I guess that's either simplification for entry-level users or deliberate market segmentation via withholding features, depending on how cynical you are. :) Do you know of any that go _more_ precise than third stops, though?
Answer: It can depend upon the camera and lens you are using, but the vast majority of cameras use the same step sizes whether shooting in manual mode, a semi-automatic mode, or fully automatic mode.
Answer: In manual, cameras have 1/2 and 1/3 stop increments because it is difficult to discern 1/3 of a stop, much less a finer resolution than that, and smaller increments would simply mean having to spin a thumb wheel that many more times to get to the setting you want.
In an auto mode you would think the camera could freely choose any intermediate value it wanted.
However, with ISO, best results often come at specific multiples of the base ISO, so finer tuning might yield poor results.
And there is no doubt a limit to how finely the camera can control the lens aperture.
Depending on shutter design, I would expect the camera could achieve shutter speeds finer than 1/3 stop increments.
But in the end the camera has to calculate exposure, write EXIF data, and display the aperture, shutter speed and ISO in the camera's displays, and it may just simply the onboard processing to keep things consistent to how they are in manual mode, in those discrete 1/3 stops.
In a practical sense, it really doesn't matter because you really won't be able to tell, even in a precisely controlled experiment, for example a 1/6 stop difference. You probably can't tell a 1/3 stop difference.
Comment: _"...it may just simply the onboard processing to keep things consistent to how they are in manual mode, in those discrete 1/3 stops"_ It also simplifies things for the _photographer_. I can think of times when I'd be annoyed if I couldn't replicate the camera's program mode settings manually.
Comment: For whatever it's worth, while I've not seen a camera use finer steps, it's common for TTL flashes to have finer increments in full-TTL auto modes than are accessible via their manual settings.
Answer: For usual photography (i.e. not high precision scientific measurements), there is no point in setting it in finer increments.  The mechanical shutters and mechanical apertures used in these cameras are simply not that accurate.  You can try this by firing off a few shots in continuous mode, and looking at the histogram of each shot. Set your camera to display the histogram in playback mode, and flip through the images.  You will see obvious variations between the shots.
Comment: Be sure to use a reliable continuous light source, like sunlight, when trying this. If you do it under fluorescent lights the variation you see will most likely be due to the lights flickering.
Answer: Yes they can and many but not all do. It depends on the camera model but often cameras with manual controls use the same step sizes which makes it simple to switch between the automatic and manual exposuse and get the same results.
On digital sensors ISO can almost be continuously variable but some sensors have dedicated circuits to provide better gain and a cleaner signal at some multiples of the native sensitivity. This is why some cameras have better performance at ISO 800 than 640, for example. Yet some cameras do it. You can check EXIF to see what happens, I have seen some ISO 158 shots!
Shutter-speeds are also easily divisible in small increments and many cameras take advantage of that to compensate for a lack of aperture or simply because they can. On the Fuji X-Pro2 for example that I was shooting with on the weekend, metering at ISO 200 and F/5.6 gave a shutter-speed of 1.1s which is not possible to select manually, so I settled for 1s which is close enough and reduces the risk from details burning out.
The most restrictive component is the lens. Not all have a continuously variable aperture, so they may have set stops built-in, in 1/3 or 1/2 increments usually. There are continuously variable ones which are advertized as better for video as they create a smooth transition when a scene changes. I guess that electronic aperture control has a set number of bits to select aperture so that might also add yet another limit to increments.


Do I have battery or engine problems?

Question: Yesterday, I used my car to drive literally 2mins. Away from my dorm building to get to my class building and back because of bad weather. 30+mins. Later I come back outside and use my remote to unlock my car door and it unlocks but as soon as I try to start it , it doesn't turn on . So automatically I think it's the battery . I found a campus police and he jumped it for me and it started to crank up , and he told me it could possibly be a light that was left on . Mind you the light in my car when you open and close the door does not work we have to get new light bulb for it , so I don't know if a door is closed or not . The handle that controls the lights were off too . Then a friend told me it could also be either the battery or the alternator. However, the police told me to leave alone for a good 15mins. And that I did . In fact I waited longer than 15mins to check the car . And it cranked up fine , so I left it alone for the rest of the day. This morning, i go check on it and see if it's driving normal and it shows that the engine was on C . I did research and it says it is suppose to be in between the H and C . As I drive it goes up slowly . When I used the break it made a noise then stopped , then it started shaking a little as I used the break. So i have no idea what is wrong with the car . Does anyone know what it could be so I can take care of it immediately because I'm a college student away from home. Thanks
Comment: In the future, could you please be more specific with your questions? This question is fairly broad and covers three very unrelated topics. For this website, we generally look for information about the car (year, make, model), the specific problem(s) you are having, and anything you have already tried to diagnose or fix the issue. This allows other people to refer to this question for help instead of needing to post another similar question, which will likely get similar answers. Thanks!
Answer: You seem to have several concerns here, so let me try to address them one at a time.

You are worried about the car starting up properly. Since the engine would not turn over when you tried to start it, then it started right away with a jump start, it sounds like it was only the battery you need to worry about. Either you left a light on or something else that drained the battery or the battery is old and is having trouble keeping a charge. If you experience this issue again and are convinced you didn't forget to turn off a light, replace the battery. It is likely not the alternator as this doesn't have any effect on starting the car and the car would have died soon after starting it up.
As for the temperature gauge being between C and H, you are correct. At normal operating temperature, the gauge should be just below the halfway mark between Cold and Hot. When you first start the car, the gauge will stay at C for a few minutes, then creep up to the halfway mark as you drive it. This is completely normal and is what you want it to do. It doesn't sound like you have anything to be concerned with here.
There could be many reasons for there being a sound when you hit the brakes. If it made a noise briefly, stopped, and hasn't done it ever since, you probably don't have anything to worry about. As for the shaking when braking, you should get it checked out immediately by a mechanic if it is severe. Check out this question for potential causes of shaking while braking.
Answer: As far as the battery issue goes - one other thing to check is the battery connections. Open the hood and look at the battery connections and feel with your hand if the two wires (positive and ground) are fixed securely to the terminals. A loose cable can cause intermittent problems because the normal motion of the car (going over bumps, etc.) can move/jog the cable enough to prevent starting the next time you try to use the car. This problem could lead to the symptoms you describe (unable to start, even though you didn't leave lights on or anything). Jumping the car would potentially work in this case because it could jog the cables enough to cause a better connection. I had this exact problem last weekend :)  The solution is to remove the battery cables, clean the terminals and connectors (sandpaper works for this) and reattach the cables, making sure they are nice and tight.
If you do this, wear eye protection because the battery often sparks when you reattach the cables and this can (very rarely) lead to explosion of the battery gases.
Answer: After jump starting the car, turn on the head lights, heater, rear windscreen heater etc.  if they all operate correctly, e.g the lights are full brightness and the heater fan sounds like it is running at normal speed, then your alternator is fine and the problem is your battery.  If the lights are dim, then the fault is the alternator.  After totally
flattening your battery due to a faulty alternator, there is a good chance your battery will also be damaged now.

Do I have battery or engine problems?


Does ATC prefer ILS over RNAV?

Question: Listening to APP for several major (US class B) airports, it seems that every flight is vectored to intercept the localizer.  Is it really possible that 100% of flights filed an ILS approach?  If so, why?  It seems like at least some (perhaps small) fraction would have filed an RNAV approach.  Can someone with only GPS still "intercept the localizer" by flying the given vector until the runway is in sight and then get cleared for visual approach, so actual ILS doesn't matter?  Or does that case just never come up because ATC knows (via the equipment code in the flight plan) who has ILS equipment available and makes them use it even if that's not what they filed?
Comment: This might just be a terminology thing, but flights (pilots) don't _file_ approaches, they can optionally _request_ them. ATC otherwise chooses the approach that suits conditions and that allows the most aircraft to land per hour.
Comment: If you are instructed to "intercept the localizer" and you are GPS only then you do NOT have the equipment and means to comply.  Actual ILS does matter in this case.  Flying an assigned vector in IMC hoping to get VMC and runway in sight is not an acceptable means of getting around the issue.  Simply reply "unable, request vectors to visual..."  (or RNAV)
Answer: As egid pointed out, pilots typically do not file a specific approach as part of their flight plan. ATC will decide what runways and approaches are in use based on the weather. As the pilots are on their descent to the destination, they will be told which approach to expect. Pilots can always request something different but ATC is trying to get everyone to their destinations as safely and quickly as possible.
It's easier to space and sequence aircraft if they are all on the same approach, rather than trying to get aircraft on multiple approaches to mesh together just right. It's also easier to sequence them if they are all on the same approach course along the localizer, where an RNAV approach may have multiple initial fixes that follow various paths to get to the same final approach fix.
An ILS approach gives ATC more control over the spacing and sequencing of aircraft onto the final approach course. Aircraft can be vectored in anywhere along the localizer. RNAV approaches have more locations where aircraft can join them, which may be inconvenient depending on the direction from which an aircraft is arriving. Not all aircraft may be able to join an RNAV course by vectors, but pretty much any airliner can intercept an ILS localizer.
The same benefits can apply even in visual conditions. The localizer provides a common reference that all pilots can join and follow while they can maintain visual separation from each other, allowing closer spacing of aircraft. It's easier to say "join the localizer" than "join the RNAV RWY 17 final approach course."
Comment: Looking at KDFW, the RNAV and ILS approaches appear to have the same fixes, descent profiles, etc. for each runway.  They do have different minima, of course, but I assume that doesn't matter in VMC.  However, the ILS approaches say SPECIAL AIRCREW & AIRCRAFT CERTIFICATION REQUIRED, so why wouldn't RNAV be preferred as more generally applicable?  Or is it assumed that anyone landing there would have the appropriate certifications?  I do notice the missed approach is different, but in the normal case, how would ATC even know which you did?
Comment: @StephenSprunk the basic ILS doesn't have the extra requirements. I'm going to try to update my answer as well with more accurate info that might address the rest of your comment.

Does ATC prefer ILS over RNAV?


Should we have a 'closed' tag?

Question: I would not mind tagging questions as closed, so that I can put closed in my 'not interesting list' and ignore them. It's kind of a hack to save those micro-seconds I spend on closed questions. What do you think?
Comment: The MSO question on this subject (with a Jeff answer) - [Can Closed questions be hidden/filtered?](http://meta.stackexchange.com/questions/83213/can-closed-questions-be-hidden-filtered) - its also not difficult to do via search: [is:question closed:no \[java\]](http://codereview.stackexchange.com/search?q=is%3Aquestion+closed%3Ano+%5Bjava%5D) and variations on that.
Answer: What if a closed question already has 5 tags?
Tags are for categorizing questions, not to filter them by status. If we go forward with this, soon we'll want a on-hold, a protected and then a locked, migrated and why not a deleted...
These things belong in the question's title, like blablabla [on hold].

Since the idea is to have these questions show as "not interesting", perhaps there could be a feature-request made, to make questions with one of these statuses show up faded in the questions list, like questions tagged with "ignored tags"?
Comment: I'd actually upvote such a feature request. I did downvote this one though, because of the idea of introducing these tags. I think it should be posted on MSO though (wouldn't it be SE-wide?).
Comment: I'd agree, if I could filter on titles.
Comment: The difference is that there's no tag involved, rather just the question list made a little bit "smarter".
Comment: That could work as well, and we would avoid the extra tagging.
Comment: Not to go meta on meta, but I think down-voting means that the style of the question is bad, not that you disagree with the content ;)
Comment: @tomdemuyt how about simply having them show up as "not interesting", as if they were tagged with one of your "ignored tags"? (see edit)

Should we have a 'closed' tag?


Who can vote in Tibet elections and where would it take place?

Question: The Tibet government in exile is about to have their elections soon. Tibetans staying around the world would go to India (correct? or can they vote in their countries too?) and would vote for their top political leader (Sikyong in Tibetan) and members of the Exile Tibetan Parliament. It seems it might not be legally allowed for the people staying at Tibet, but is it allowed in theory? So, my two questions are- is the voting center only in India and who are eligible to vote? Let's say there might be other non-Tibetan people who fled from Tibet or are staying in Tibet.
Answer: According to a NYT article about the 2016 election

A democratic election for a people without a country is a complicated affair, with voting in more than 40 locations in India, and dozens more around the globe. Registered voters number about 88,000, fewer than in most mayoral elections in the United States.

According to a 2016 paper by academics from the Central University of Himachal Pradesh:

TiGE represents over 1,22,000 [sic] Tibetans living exile, perceives itself as the de jure representative of Tibetans [...]
The whole Tibetan population spread world over is organized into small settlements. The settlements are governed by the Local Assembly. Article 78(1) of the Charter of Tibetans-in-Exile has the provision for establishment of Local Assembly in a community having a population of not less than 160. [...]
Voter registration is done at settlement level. Every Tibetan, above the age of 18 years has to voluntarily register himself with nearby settlement office and has to obtain the Green Book. The Green Book is the basic identity proof which has to be produced at the polling station while casting vote.

There are approximately 6 million Tibetans living in China who cannot vote in TiGE elections.
Comment: I'm not sure if you added the [sic] to the quotation or not, but you may be interested in the [Indian numbering system](https://en.wikipedia.org/wiki/Indian_numbering_system) (see Use of Separators section), which puts separators every two digits (except the first three), giving a number like 1,23,45,67,890. I can't confirm the quotation is correct, but I also can't dismiss it out of hand.
Comment: @JoelHarmon: I've added the "[sic]", so that those not familiar with the notation would not think it is a typo.
Answer: The Charter of the Tibetans in exile guarantees equal rights to all Tibetans

Charter guarantees to all Tibetans equality before the law and enjoyment of rights and freedom without discrimination on the basis of sex, religion, race, language and social origin.

The CTA defines a Tibetan as

"any person born in Tibet, or any person with one parent who was born in Tibet"

So, possibly every Tibetan may vote subject to the fulfilment of the eligibility conditions. They must have registered and paid the green book dues.

As per the provisions of Article 18 (4), any Tibetan citizen who completed 18 years of age on 31st October 2020 are eligible to register.

Tibetans don't have to come to India to vote. They can do it in their own places. I'm not so sure about these centres though. The best I could find was about the previous election results page which says

A total of 59,353 Tibetans voted at 85 locations around the world.
Answer: The problem when you talk about "legal" for something like that is the question of jurisdiction. International law assumes that nations are sovereign, but there is no clear mechanism to define when a group-pretending-to-be-a-nation becomes an actual nation.

The Chinese government assumes that Tibet is part of China.
Some Tibetian exiles dispute that.
By and large, the world community accepts Chinese sovereignty over China and at the same time gives asylum and recognition to Tibetian exiles. Not a very consistent position.

So when people currently in Tibet want to vote for the exile government, they have to deal with the Chinese government. Which cracks down on separatism.


Hotplug li-ion in parallel for a custom battery pack

Question: I'm designing a custom battery pack for a computer with 2S1P alignment. However, I want to be able to add batteries on the fly, as the computer is designed to be working at all times without reboots.
Say, I have 3 (for two cells in series) pins to which I can connect an external battery pack for the computer, making the whole arrangement 2S2P. However, I know that voltage difference shouldn't be too low, else the batteries with highest voltage will charge those with lowest with no current limiting whatsoever. So how could I design such a battery pack? Is there something I can do, like circuit which connects the hotplugged batteries through a resistor for some time, or something MOSFET-controlled?
Ideally, my concept would be 4 sockets for removable 18650 cells (2S2P) which I can either remove or add on the fly without interrupting power supply, so I can replace them - or even add an additional battery pack in parallel through a connector - but I somehow have to take into account the possible problems of interconnecting a 3.5V discharged cell with a 4.2V charged one. Any guidelines on what's the simplest way?
Answer: The best scheme would be to not actually be trying to put the battery packs in direct parallel for the reasons that you have cited. A better approach would be to design it so that only one battery would drive the computer through a MOSFET switch. A second battery would be switched in automatically through a second MOSFET switch. A control circuit would manage which battery pack switch was active and auto switch to the alternate battery when the the current battery is depleted. The main point that only one battery MOSFET is ON at a time.
A sensor in the control circuit would provide the indication when the battery became depleted and a switch over was necessary. An LED would be placed by each of the battery packs with it being turned on to alert the user that the battery back that needs swapping out.
You would equip the front end power connection to the computer with some capacitors sized to keep the computer powered through the short time that the control circuit switches off one MOSFET and turns on the other MOSFET.
Comment: Agreed. And for the switchover circuit have a look at these search terms: 'load sharing', 'ideal diode', 'powerpath'. There are also ICs that even integrate some things you might need such as a DC/DC converter and battery charger. Eg. http://www.linear.com/solutions/1652, http://www.linear.com/product/LTC1479, http://www.linear.com/product/LTC3118 (but there are plenty others)
Comment: Thank you for your answer! So I think as for now I'll omit the "connect additional batteries" feature to save time, but I'll definitely look into it later and come back with more questions ;-)


How to retrieve contacts from trash

Question: I inadvertently deleted a number of contacts and sent them to "trash". How do I retrieve them?
Answer: Use the Advanced Search (in the Search menu) and check the box labeled 'Search in Trash (deleted contacts)'. It is a small check box in the Search Settings part of the Basic Criteria section.  Whatever search you do will look in the 'Trash' rather than among active contacts.
Once those search results come up, you can select your desired contacts and, from the Actions list, 'restore' them.
Comment: If you then select the contact you want to do something with, you get the option for your selected contacts to either delete permanently, or restore.
Comment: Thank you Erik, I should have mentioned that. I'm editing my answer to include the last step of the retrieval process.

How to retrieve contacts from trash


VPN with Cisco virtual ASA on Azure not routing correctly

Question: I've deployed a Cisco virtual ASA in Azure to use as a VPN server.  For simplicity, I'm using just the management interface as the lan for the time being (10.2.0.4 is the interface). I want to use the ASA as the VPN server rather than Azure's built-in VPN capability.  I'm able to use Cisco Anyconnect to establish a VPN connection to my virtual ASA.  However, when I then pull up Remote Desktop Client to connect to my virtual client at 10.2.0.5, it fails to make a connection.  Using wireshark, I can see the port 3389 RDC connection attempts coming in to 10.2.0.5 from 10.2.0.10, which is the virtual IP that ASA assigned when I made the initial VPN connection.  However I don't see any traffic from 10.2.0.5 back.  It looks like 10.2.0.5 is trying to use ARP to get the MAC address for 10.2.0.10 so it can respond, but it's not getting any ARP reply.  If Cisco ASA VPN is distributing 10.2.0.10 as a virtual IP, shouldn't it respond to the ARP request?
Comment: You need to set up a separate subnet for the VPN clients and make sure that the Azure nodes have either a specific route to that subnet or that their default gateway has.
Comment: the virtual ASA is deployed with a "management interface" which accepts incomming VPN connections from the internet, and there are 3 additional interfaces, gig0, gig1, and gig2.  So you're saying I need to put all the internal network machines on say gig0, then add a rule to allow traffic to pass from management to gig0, then in Azure add a user defined route of type virtual appliance with 0.0.0.0/0 pointing to the "management" interface?
Comment: great info here https://docs.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview
Comment: Did any answer help you? if so, you should accept the answer so that the question does not keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
Answer: Keep in mind that networking in the cloud works a bit differently than it does in the real world. ARP for instance does not work as you would expect: it's the cloud controller that answers the ARP request, not the device on which the IP address is configured. This means that Azure must know at all times what IP addresses are on what devices.
In order to route traffic to an instance (such as the ASA) on an IP address that is not assigned (by Azure) to the interface, you need to create a User Defined Route in the VNET. So it's best to create a seperate subnet for VPN clients, and add a route to that subnet that points to the ASA appliance.
Also keep in mind you need to enable IP forwarding for the instance, or "transit" traffic will be dropped by Azure anyway.
Comment: I did create a UDR of type network appliance but that didn't work either. I was able to get the ARP failures to go away but I still couldn't ping or do RDC and on the RDC connections, they were being reset, my theory might be that the ASA was killing them due to a missing static route or ACL on the firewall.  After messing with it for about 12 hrs straight, I was finally able to get it to work by trial and error using static NAT to translate the VPN pool address the ASA assigned to the VPN connection to the private interface that Azure sees.  I'll post the solution for others


Appropriate statistical measure for rank correlation

Question: In the course of my work, something of a problem has arisen. It can be summarized like this: there's a large pool of job applicants, let's say N of them. What needs to be done is that these applicants be ranked in order of desirability to the company: 1, 2, 3,... N. Until now, this has been done rather laboriously by discussions (read: arguments) between multiple people responsible for the decision. The idea is NOT to eliminate said discussions, but to reduce the amount of work necessary.
So, the new idea being batted about is that one could introduce a sort of "score" for each applicant... For the sake of argument, let's say that each applicant was rated from a low of 1 to a high of 5 for each of several different dimensions (e.g., raw intelligence, sociability, etc.), and the ratings were simply added up to generate a final score. Then the applicants could be ordered by score. Of course, there will be many many ties with this particular system, but it would reduce the problem of ranking each applicant by creating "bins" that could then be sorted through individually, i.e., independent of those outside a given bin.
But how to convince people that the "score" had any correlation with rankings as done by the old, laborious method? It seems to me that one of the common nonparametric rank correlation coefficients -- Spearman rho, Kendall tau -- should be suited to this purpose. (In particular, Kendall tau-b, as it is designed to handle ties.)
But I am not a statistician, and I wonder if something more appropriate exists. After all, using a nonparametric statistical test ignores the fact that the one of the variables being compared is simply the list (1, 2, 3,..., N)! Or perhaps my understanding of what "nonparametric" means in this context is flawed. Any insight into what methods I can use to attack this problem would be appreciated.
Answer: I am not sure what you mean by "ignores the fact that one of the variables is a list".
You have two rankings, one with ties, one without. A rank correlation seems ideal.
Taking a step back though, if you have a measure of job performance, then, going forward, you could see which method did better as a predictor of performance


Is it possible to pick up a thrown glowstick in Terraria?

Question: I'm pretty new to this game and maybe I'm missing something obvious, but is there any way to pick up a glowstick after I throw it (usually accidentally...)?
Comment: I believe it is possible to make them retreiveable by digging out the block they've been lodged into.
Answer: As per the wiki:

The Glowstick is a light source that can be held or thrown, and works underwater, but can not be placed in a wall or floor like the Torch can (though the Sticky Glowstick will stick to surfaces they are thrown against).  Glowsticks will emit light for a lengthy period of time after being thrown, and have a 1:3 chance to be recoverable after several minutes. The Glowstick can be bought from the Merchant, at night, for 20 Copper Coins. Glowsticks are also dropped by all Jellyfish, and can be found commonly in Pots and Chests.

So yes you can pick it back up, only if the Terraria gods feel you should.  This info should be relevant as of 1.0.6
Comment: My experience matches this. After tossing glowsticks around while exploring a cave, I came back and was pleasantly surprised that I could pick them up again, but it seemed like there were fewer than I'd thrown. 1.0.6
Comment: Oops, thanks Raven.  I had mis-typed.
Answer: I wait by doing something else like mining, and I can collect it in around 4-5 minutes.


Mistakes post publication

Question: I just discovered some mistake after the online publication? There are two mistakes- instead of figure S4A (supplementary figure), it says Figure S3A at two places. It's very embarrassing, should I write to the editor about this?
Answer: You should inform your coauthors, use this opportunity to search for other misprints and finally write to the editor.
Answer: This sort of typographical error should be handled with a "Correction". You'd say something like "In the article such-and-such (citation) the text on line x, page y should read "Figure 4A" instead of "Figure 3A". The online text has been corrected."
The details of how that's done depends on the journal, so you should discuss with the editor.
It's quite common to have to issue corrections, it's not a big deal, and aside from being a minor embarrassment an occasional Correction doesn't reflect on you in any way.   I suppose if it were a regular thing it might get noticed, but this should not be a big deal.
Comment: This might be field dependent.  In my field, errors of this magnitude abound in every paper and are rarely formally corrected.  Occasionally someone puts a list on their webpage.  If a reader (who will necessarily be an expert in order even just make heads or tails of the paper) would not be able to figure out the appropriate correction after a bit of effort, then perhaps a correction is issued.
Comment: Sure, I think that's probably true in my fields as well, the author would be fine in letting it go, but since they seemed upset about it a correction is fine too

Mistakes post publication


Can my body touch the table in table tennis?

Question: Suppose I am about to hit a "overhead", then my stomach touches the edge of the table... Is this allowed? Can I "dive" on the table?
Answer: My understanding after reading the rules is: as far as the touch does not move the table it should be O.K. otherwise it's a point to the opponent. The last three (in italic) points govern the "contact":

2.10  A POINT
2.10.01   Unless the rally is a let, a player shall score a point:
2.10.01.01    if an opponent fails to make a correct service;
2.10.01.02    if an opponent fails to make a correct return;
2.10.01.03    if, after he or she has made a service or a return, the ball touches anything other than the net assembly before being struck
  by an opponent;
2.10.01.04    if the ball passes over his or her court or beyond his or her end line without touching his or her court, after being struck by
  an opponent;
2.10.01.05    if an opponent obstructs the ball;
2.10.01.06    if an opponent deliberately strikes the ball twice in succession;
2.10.01.07    if an opponent strikes the ball with a side of the racket blade whose surface does not comply with the requirements of 2.4.3,
  2.4.4 and 2.4.5;
2.10.01.08    if an opponent, or anything an opponent wears or carries, moves the playing surface;
2.10.01.09    if an opponent, or anything an opponent wears or carries, touches the net assembly;
2.10.01.10   if an opponent's free hand touches the playing surface;
Comment: So you may not lean on the table, but touching it (unintentionally) is not a big problem.
Comment: Yes, assuming that you do not move or shake the table (which I guess is pretty hard in itself), intentionally or not...
Answer: No you are not allowed your stomach to touch the table espically when serving. Your free hand is allowed to touch the table but through out the play you are not allowed to touch the table with any body part. But you can lean on the table if you are trying to hit the table tennis ball in play but not when you are serving.
See AU table tennis rules for more information why you are not allowed.
Comment: Welcome to the site. This answer would be much better if you can add a link to the specific part of the rules.


What's the best way to increase my rate of research?

Question: What's the best way to increase my rate of research in Civilization 5? Is it purely a function of population and buildings, or is there something else I can do to speed it up (especially in the early game)?
Answer: There are a number of different ways to boost your research:

Great people can be used to immediately complete a tech or build academies
Research agreements gain you an extra tech for a fee (starting at 200 gold - see comments).  You can have research agreements with multiple players (and it's advantageous to do so, if you have the cash)
Many Wonders will increase research (in their city or in other capacities)
Buildings like Libraries and Universities increase research, and gain further research bonuses when assigned specialists
Policies - most of the Rationalism track improves research, and Scholasticism (under Patronage) grants you research from allied city-states
City production can eventually be set so it all goes straight to research
Comment: @Oak, as far as I know, it's not based on the more agreements you have, but rather the tech level of the more advanced party (i.e., modern era research pact will always be more than a classical era research pact)
Comment: The amount you pay for research agreement is not fixed at 200 gold, it gets higher later in the game. +1 for the last two bullets, however, I completely forgot them in my answer. Scholasticism is especially useful.
Comment: @Raven my bad then, I've fixed my comment (diamond powers! =D)
Answer: I've answered a question asking how to increase production which in my opinion is pretty similar - though science is global, of course, and not local to a city. You basically have the following options:

Increase the science output of your cities.

A lot of building types increase the science output, as you've already mentioned in your question, and they do it in a scalable way - increased science per population or increased science percentage (as opposed to a fixed bonus), very useful throughout the game.
Very few hex types yield science, with the notable exception of the academy, see below. However, many buildings have specialist spots that can improve science. So for example, if you build a university not only is the science output of the city increased, you can also allocate citizens to specialist spots given by the university, and those spots will generate science.

Work towards getting great scientists. You can either just use them to get technologies for free - very useful in the early game when you want to get some of the stronger technologies - or you can create academies, which gives a specific hex a lot more science output - that's basically more of a long-term investment.
Research agreements are a very good way to get new technologies. They take time and money, true, but the monetary investment is not that high and the time it takes is not that bad considering you research your own technology in parallel. You can sign on to multiple research agreements at once, so in effect you can have a large amount of research in parallel. The downside is that you cannot control what technology will be achieved.

The above points are not orthogonal - if you want a lot of technologies you should do all of them; i.e. allocate citizens to specialist slots, use buildings and abilities that increase the speed at which great scientists are born, and sign a lot of research agreements.
Answer: Research Agreements. As many as possible, as often as possible.
If you want to keep a tech lead, you need to spread out who you make the agreement with -- if you only have a single research agreement with the most advanced AI civ, you're not going to make any progress. But if you make a research agreement with the last-place player (perhaps gifting them enough gold so that they can pay their "half) AND the most advanced civ, you're effectively researching three different technologies at once to their two.
Set up those trading posts and get to work!
Answer: The answers already given (summed):

Science buildings (library, university, observatory, public school and research lab)
World Wonders (Great Library and Porcelain Tower) and National Wonders (National College
and Oxford University)
scientist specialists
Great Scientists build Academies (a tile improvement) or Discover Technology (instant science boost)
Research Agreements (available after you research Education)
Social Policies (most of Rationalism, Scholasticism - Patronage, Mercantilism - Commerce)
city Production (after researching Education, you can choose to make a city build science: the science generated is 25% of the production for that city)

Here are 3 additional considerations when maximizing science output, from most important to least.

Population
Tech path
Trade routes

By far the most important is Population. A citiy's base science output for a city is equal to the number of citizens. The science buildings are more effective in larger cities. A city can work more specialist slots with more citizens. If you want to increase your science, anything that increases your population will help.

buildings: Granary, Water Mill, Aqueduct, Lighthouse, Hospital, Medical Lab
Wonders: Temple of Artemis, Hanging Gardens, Petra

Due to the importance of buildings and wonders in science output, your path through the tech tree can also play an integral role in determining how fast you tech up. They don't always have to be the first techs you research (within each era), but waiting too long before picking up these science techs could hurt your overall game.

Writing (Ancient)
Philosophy (Classical)
Education (Medieval)
Astronomy (Renaissance - if you founded a city next to a mountain)
Scientific Theory (Industrial)
Plastics (Modern)

The final consideration is trade routes. Science is transferred via international trade routes (between civs, CS trade routes do not apply) when 1 of 2 conditions are met:

One of the civs have discovered techs that the other has not. If both civs have discovered techs that the other has not, they each receive a science bonus.
One of the civs has achieved partial or full cultural influence over the other.
Comment: Some specific strategies (for BNW?) - In high level AI games, they will often have a huge tech lead until the Renaissance era or later regardless of what the player does, so trade routes grant a lot of science.  Universities grant +2 science per Jungle, and a policy in Rationalism boosts Universities to +50% science and trade posts grant +2 (same policy), so a city with either some river farms or a bunch of bananas in a jungle can become a tech powerhouse (but note that pop is still extremely important, so cut down jungles for a few farms if necessary).


In an isothermal process work is done on/by the system (expansion or compression of the gas) yet still the internal energy remains constant, why?

Question: An isothermal process indicates that $\Delta Q = 0 $ as there's no change in heat energy. But in most text books it's taken as $\Delta Q = 0 $ and internal energy change is taken as a constant. At the same time a 0 change in heat energy implies a change in work done  on/by the system and, by definition work done by/on the system contributes to internal energy $U$ right?
Answer: An isothermal process is not necessarily one in which Q = 0.  In an isothermal process, the only thing we can say is $\Delta T=0$.
In addition, the internal energy is, in general, not just a function of temperature.  It is a function of temperature only for an ideal gas (or for an incompressible solid or liquid).  So, for the isothermal expansion or compression of an ideal gas, the temperature and internal energy are constant.  For a non-ideal gas, the internal energy is not constant.
Answer: The internal energy U is a function of many variables, (temperarure or entropy) , (pressure or volume) and (number of moles or chemical potential) the temperature part corresponds to dQ while the pressure/volume dependence corresponds to dW if dQ=-dW then dU=dQ+dW=-dW+dW=0. Ie the change in internal energy is 0


Visual Source Save Configuration

Question: I'm using VSS version 8.0.5. I've installed it on server. I've added visual studio 2010 project in it.
now on my system, i point the source control vss in my visual studio envionrnment. I configure the project on my working folder and then set the solution file in the IIS. When i open the solution then it was not being configured and not showing checkin/checkout.
Can you anyone give me the idea what can be the issue?
Answer: Not quite sure what you mean by "not showing checkin/checkout". Do you mean the solution is not bound to VSS? If yes, how did you open the solution? Please try to open it from source control and see how it works.

Visual Source Save Configuration


Kalman Filtering with Unknown State Transition Matrix

Question: I'm currently studying the use of Kalman filters for estimating linear systems. My current State Transition Matrix (STM) is the identity since so far I've been dealing with non time-varying systems. However my next step is to extend to time-varying systems and in this case there is no information on how the system varies and so the STM is unknown. And as of my testing so far a wrong STM causes a ton of errors on the Kalman Filter estimations. So my question is if there is a method for circumventing this, be it by updating the STM on the fly or some kind of way of updating the Process Noise Covariance Matrix in order to account for that?
Comment: What do you mean by *my next step is to extend to time-varying systems and in this case there is no information on how the system varies and so the STM is unknown* What information do you mean? As long as a system is characterized by a differential equation you know how the system varies (although you may not solve analytically the equation for a closed form answer)
Answer: In the Bayes Net Toolbox (BNT) for MATLAB, there is an example under Kalman Filter where the EM Algorithm is used to estimate the State Transition Matrix (and the rest).  It is a 2 pass batch algorithm.
http://bayesnet.github.io/bnt/docs/usage_dbn.html#learn
The only problem is that BNT was written for Matlab V5 and the GitHub version (See GitHub Repository - BayesNet BNT) has some updates but under 2017a, there are a few problems, nevertheless I found it useful.
The other limitation is that it is for a strictly Kalman Filter, not an EKF, UKF, or particle filter.
Answer: Unfortunately, in Classical Kalman filter applications you need to have a guess of your state transition model governing the states. Classical choices for such models for time-varying systems are the random walk model, or its generalization, a first-order Markov model. If do not have a clue about which state model you can assume, you can try to extract a trend component from your state time series (via EMD or a moving average filter, for example), and plot it to have an idea of how the first-order moment of your states vary with time, for example. If it decays as a power law with $n$ (i.e. $E[x(n)] \approx \alpha^n$) until a final value, it may be an indication that a first-order Markov model with pole equal to $\alpha$ can serve as a state transition model.
Otherwise, you can treat the transition model for your states as a black box and consider techniques such as the Unscented Kalman Filter, for example.


Is this the correct approach for installing 3/4" Hardwood floor?

Question: So I've been thinking of adding a hardwood floor in my dining room and hallway.  This is what I know as of right now.  I have Hemlock 2x10 Floor Joists spaced apart 16" OC that span 13 feet and the home was built in '71.  The subfloor as it sits right now is 1/2" plywood with what seems to be 1/2" MDF or Particle Board nailed on top.  I've noticed the floor is not perfectly level and might be due to the MDF warping and expanding from moisture.  From what I've been researching it would be best to rip up the MDF (or Particle Board) and gluing the 3/4" plywood and screwing it down to the existing 1/2" plywood (not to the floor joists).  Then lay down a vapor barrier and then the flooring at a right angle to the floor joists.  Is this correct?  I just want to get all of my ducks in a row before I go spend money.
Answer: I have seen 3/4" thick hardwood floors go over 1/2" subfloor with no problem. Your floor structure is plenty heavy to carry any load you apply to it. In many older homes (really old homes) there was no subfloor at all, and the floors held up very well.
Remove the layer of MDF, clean up the nails, and reset all the nails that are in the subfloor. This minimizes the chance of squeaks from the nails that may have risen up as the framing dried and shrunk. Add 1 5/8" screws at all the edges and 3 or 4 more spread across the center of the spans of all the plywood.
In my humble opinion, DO NOT use an underlayment foam under hardwood flooring. This is only intended for floating floors!!!!. The "give" the foam has, is asking for your floor to squeak!!! The only vapor barrier you need is a 5 lb. felt paper. It is much lighter and much thinner than roofing tar paper and will give the resistance the wood needs against moisture rising from below. This is what is used in all new floor applications. Sometimes, on occasion red rosin paper is used too, I believe it is error, it has no resistance to vapor permeability.
After this initial bit of prep, lay your new floor.
Answer: The best idea would to start by ripping up the MDF assuming the plywood underneath is good and not rotten or destroyed, then check the floor to see if it is level again, if it is you can put down new 3/4 plywood and screw it in, there is no need for glue here. I would recommend screwing it into the joists though, not just the plywood! Then lay down your vapour barrier and hardwood foam if you want to (I always do, it's quieter that way) and then lay down your hardwood like any other floor!
Comment: Right that all makes sense! Also I forgot to mention in my first post, run your hardwood non parallel with your joists, meaning the opposite direction! Your welcome, have a good one!
Comment: Yes, I think the plywood underneath is good, at least from what I can tell looking up at it from the basement.  The joists are pretty close to level either dead center or just touching a black line.  I guess that's probably expected from a house that's 44 years old.  Worst case scenario is replace all the plywood with 1 1/4" T&G plywood or I may have to tweak the load bearing beams a little that support the lvl in the basement that the joists sit on.  Thanks for the help!
Answer: I voted up Jack's answer since he is right on with everything.  Just want to add that you are not doing your whole house so you need to figure out if taking out 1/2" MDF is going to affect the height matching of the adjacent flooring.  You may very well have to put back a 1/2" sheet of plywood after ripping out the bad stuff.


How Does a Precipitate Get a Colour?

Question: If you can use precipitate colours to determine an anion, what makes the precipitate have that particular colour?
Like for example what in sodium sulfate or barium chloride makes a white precipitate when these two combine?
Comment: Possible duplicate of [Why is snow white?](https://chemistry.stackexchange.com/questions/26749/why-is-snow-white)
Comment: White is the default color. You don't have to do anything to produce it.
Answer: The 'white colour' is due to the fact that the product does not absorb light in the visible part of the spectrum but forms as many fine crystals which in themselves scatter room lights. So the 'whiteness' is due to the scattering of light back towards your eyes after the light is repeatedly reflected of the many facets of the many crystals in the ppt. If you use red light to illuminate then the 'white colour' will become red. If the ppt is coloured then absorption of light occurs at some wavelengths as well as scattering at all wavelengths.
At the surface of a crystal some small fraction of light is reflected, but with millions of randomly oriented crystals numerous reflections occur. The amount of reflection at each surface depends on the difference in refractive index between the crystal and air for the wavelength of light used. If you could add a solvent say dichloromethane which has  a high refractive index and will probably not dissolve the ppt then the crystals can be made to almost disappear as scattering is now far less.  You can do the same thing with frosted glass beads which, when in air, scatter a lot but in water become virtually invisible.
Answer: The following answer applies to all questions regarding color.
Color is the result of a substance absorbing certain wavelengths of light and reflecting others.
Different molecules have different shapes (geometry). Different shapes absorb/reflect different wavelengths. In addition to the shapes, the other parameter regarding color is the temperature and pressure.
Closely packed molecules will absorb/reflect light different from loosely packed ones.
2 more things that can "produce colour" rather than reflection of photons hitting it, are:
photons generated from chemical reactions and
photons generated from radiation

How Does a Precipitate Get a Colour?


Modelling Pd(111) and Pd(100) Surface Oxides Through VESTA

Question: I want to build unit cells for Pd surface oxide models, but I am not sure how to begin as I am new to using VESTA. On Pd(100), the most stable surface oxide structure is √5x√5 R27o. On Pd(111), the most stable structure involves a √6x√7 arrangement of O atoms with a Pd4O5 stoichiometry. Does anyone have any suggestions for the best way to model such structures? Thank you!
Comment: Have you checked this YouTube channel: https://youtube.com/channel/UCmOHJtv6B2IFqzGpJakANeg He has several playlists (VESTA- Nanostructures, Bulk Crystals, Heterostructures, Slab Models, and VESTA bigginer tutorials). Actually he masters VESTA and he may even do videos on request.
Comment: Yeah I have! Still a little confused about it though.
Answer: Using ASE you can do this simply. Take a look this link: https://wiki.fysik.dtu.dk/ase/ase/build/surface.html?highlight=surfa
Here you can build common surfaces as well as root surfaces.
Comment: Could you expand on this a bit more, summarizing the link and/or adding an example code snippet? As is, this post comes across as more of a comment than an answer.
Answer: This doesn't exactly answer your question but I'd recommend using one of the following Python modules instead of VESTA for surface creation: PyMatGen or ASE.
Comment: At the moment, this looks more like a comment than an answer. If you could expand to explain how one might address OPs problem in either of these programs, I think that would make for a better answer.


Sarbanes-Oxley (SOX) Versioning Strategy

Question: When dealing with publishing SOX application artifacts what is the best strategy for versioning SNAPSHOTS?
I'm currently following the semver pattern <major>.<minor>.<patch> and wondering if it is necessary to get granular with the version strategy and append something like a git hash to the end? e.g. <major>.<minor>.<patch>-SNAPSHOT<githash>
Or can I treat SNAPSHOTS as a SNAPSHOT should be and drop the hash all together?
My argument for the latter is that SNAPSHOTS are not cut as release candidates (rc) until they actually enter the release pipeline and therefore can be clobbered, especially when following a mature CI pattern where changes are continuously merged to master following early testing validation.
In addition to this, typically in an organization, a change request is only opened and tracked at the time you are performing a release.
(additional convo happening here)
Comment: What is the added value of `(additional convo happening here)`? Is this a copy or really additional information?
Comment: Could you indicate whether you solved the issue?
Answer: I suggest to follow the principles that are defined in the Semantic Versioning 2.0.0 documentation.