Is Creatine bad for you?

Question: Hey I'm relatively new to weight lifting and I have friends who take Creatine before working out. They said it really helps build muscle. But I've also heard it can be bad for you. How true is it, and is it worth the risk?
Comment: It's pretty bad. I get painful cystic (deep) acne on my face. I do not know the cause, but I have read others stating similar side effects. One theory is not enough water intake, but I've tried guzzling water while on it with the same results. I would recommend buying the smallest possible amount to test. You could ask one of your friends if you can try a couple doses before making a purchase. I noticed side effects within 2-3 days of being on it.
Comment: As always, if ONE person tells you they have a bad experience with it, don't let that make your decision. And at the same time, if ONE person says they have a good experience, don't let that make your decision either. Creatine is something a lot of people use, and it's legal because most people don't experience adverse effects. So yes, you should at least give it a try. And if you're still unsure, consult a doctor.
Comment: Also, as I noted down in my answer, the supplementation industry is highly unregulated, so a bad reaction to one batch of creatine may not mean that you'll react the same way to another batch.
Comment: Makes some people, including myself, break out badly.
Comment: @TestWell
How sever is it when you break out, and do you know why?
Comment: @TestWell Yeah I'll do that. Thanks for the advice.
Comment: And it is Creatine Monohydrate, with nothing else in the supplement, correct?
Comment: @BerinLoritsch monohydrate and micronized is the same creatine right?
Comment: **Creatine monohydrate** is a chemical compound, **micronized** is a process.  Creatine monohydrate is the most common (cheapest), researched, and useful form of creatine on the market.  Chances are good, but you can micronize anything.  Double check your label.
Answer: TL;DR: There don't seem to be many negative side effects besides water retention and the need to take in more water, although the benefit is limited for people who aren't already up against their limits and it doesn't seem to help for endurance training.
Per WebMD:

Creatine is LIKELY SAFE when taken by mouth appropriately for up to 5 years.
When taken by mouth in high doses, creatine is POSSIBLY UNSAFE. There is some concern that it could harm the kidney, liver, or heart function. However, a connection between high doses and these negative effects has not been proven. Creatine can also cause stomach pain, nausea, diarrhea, and muscle cramping.
Creatine causes muscles to draw water from the rest of your body. Be sure to drink extra water to make up for this. Also, if you are taking creatine, don't exercise in the heat. It might cause you to become dehydrated.
Many people who use creatine gain weight. This is because creatine causes the muscles to hold water, not because it actually builds muscle.
There is some concern that combining creatine with caffeine and the herb ephedra (also called Ma Huang) might increase the chance of having serious side effects such as stroke.
There is concern that creatine might cause irregular heartbeat in some people. But more information is needed to know if creatine can cause this problem.
There is concern that creatine might cause a skin condition called pigmented purpuric dermatosis in some people. But more information is needed to know if creatine can cause this problem.

BodyBuilding.com comes up with similar results:

Creatine does not cause damage to skeletal muscle or the heart, liver, or kidneys.
Creatine, at this moment in time, seems to be fine for kidney disorders that are not characterized by edema and tissue swelling.
Based on limited research, it is probably wise to avoid creatine supplementation if you have polycystic kidney disease, focal segmental glomerulosclerosis, or another kidney disorder characterized by tissue swelling.

Lastly a medical study found the same things, but also warns that commercial supplies may have other additives due to how badly regulated the supplementation industry is.
Comment: Ok that makes sense. As long as I stay hydrated there's not real problem.
Comment: This is the best source for creatine: http://examine.com/supplements/creatine/  That link gives you the actual studies (plural) ranked by quality, and a lot more detail of the information.  In the doses highly recommended in most cases, there is no issues with creatine.
Comment: _water retention_ and _take in more water_. Doesn't is sound illogical? If creatine causes water retention, why do you need more water? There is extra water in your body, why do you need more?
Comment: @Green: It makes more sense when you consider that creatine causes the water to migrate to your muscles rather than all of the spots where your body also needs it. It's a bit like planting a water-hungry plant in your yard. You'll have to water your yard more, because that plant is drawing in more water, and meanwhile, your lawn will be boggier because of that added water, and that the plant keeps it from escaping.
Comment: @SeanDuggan Thanks! This is one good association for understanding.
Answer: most people resort to creatine after an extended period of training where they're not getting bigger, or stronger, or both. as a beginner, you should see pretty rapid gains in both size and strength as long as you've got a solid workout plan and you're eating a ton. i don't think it makes sense for a beginner to take it. creatine isn't that risky compared to, like, anabolic steroids...but way, way riskier than a bunch of chicken breasts and whole milk.
if you do choose to try i would recommend against a "loading phase," which is several weeks of very high daily creatine intake (around 20 grams), followed by a moderate daily dosage (some call it a "maintenance" dose) of 5-ish grams, continued indefinitely. most of the creatine horror stories i've read are dosage-related.
Comment: Do you have any evidence that creatine is "way, way riskier than a bunch of chicken breasts and whole milk" ?
Comment: http://www.ncbi.nlm.nih.gov/pubmed/25984094
Comment: http://www.mayoclinic.org/drugs-supplements/creatine/safety/hrb-20059125
Comment: You have misinformation and one isolated case study. Yes, there are people with sensitivities or preexisting conditions that may react badly to creatine. However, the loading phase is 5-7 days, not "several weeks".
Comment: 'several weeks' was sloppy on my part, you're right about that. thanks for the correction. is that the misinformation you're referring to, or the mayo clinic site, or something else?

Is Creatine bad for you?


How to export all my pins and boards from Pinterest?

Question: Pinterest does not provide a proper export feature. How can I export all my pins and boards from Pinterest, in order to move to another bookmark manager such as Raindrop.io?
Answer: Update
I forked the Pinback tool and made the changes I describe below, so you can simply use my fork and it should work immediately.
Original Post
Raindrop advises that those wanting to migrate from Pinterest should use the Pinback tool, and my searching was unable to locate any other option.
However, when I tried to use Pinback to export my pins, I received the following message, even though I was on my profile page:

Log in and visit your profile (pinterest.com/username) or board to
start.

Looking through the code, I discovered that it contains a regular expression to extract your username from the web address. That regular expression would have worked if I was using pinterest.com, but it did not work because my account is on pinterest.com.au. The way I got it to work was to:

right-click the bookmarklet on my bookmarks bar and select Edit
copy the code into a text editor
locate the URL-encoded regular expression near the beginning

%2F%5Ehttps%3A%5C%2F%5C%2Fwww.pinterest.%5Ba-z.%5D%7B2%2C5%7D%5C%2F%28%5Ba-z0-9_%5D%7B1%2C30%7D%29%2Fi

decode it

/^https:\/\/www.pinterest.[a-z.]{2,5}\/([a-z0-9_]{1,30})/i

modify it for more relaxed matching

/^https:\/\/www\.pinterest\..*?\/([a-z0-9_]{1,30})/i

encode it

%2F%5Ehttps%3A%5C%2F%5C%2Fwww%5C.pinterest%5C..%2A%3F%5C%2F%28%5Ba-z0-9_%5D%7B1%2C30%7D%29%2Fi

replace the relevant section of the code in the text editor
copy the new code back to my browser as the new code for the bookmarklet

After I made these changes the bookmarklet worked properly, generating a downloadable HTML file containing all my pins, arranged into groups representing my boards. I was able to import this file straight into Raindrop.
Answer: You can request a copy of your data from Pinterest https://help.pinterest.com/en/article/download-your-pinterest-data

Go to settings https://www.pinterest.com/settings
Go to "Privacy and data" https://www.pinterest.com/settings/privacy
In the "Request your data" section, click "Start request"
They will send you a link to the file with your exported data

By the looks of the exported html, it looks that you get a list of boards and a list of pins, but no information about which pin belongs to which board.
Comment: *no information about which pin belongs to which board*, which makes it completely and totally useless.


Independent from others?

Question:
In a semi-direct consensus democracy, on the other hand, party
competition is low because elections cannot lead to a change of roles
between government and opposition. The system places its trust in the
final control by the people over all important issues. Legitimacy
comes from the most important decisions being taken by the people
directly. Proportionality in elections and mutual adjustment in
legislative decision-making favour the idea of 'no single winner takes
everything, everybody wins something'. In direct democracy, voting is
on a single issue at a time, and each case produces different winning
coalitions, which are barely foreseeable by the political elites. A
popular vote, even when settling a fundamental issue, involves just
one clear decision independent from the others. The Swiss government,
free from the fear of not being re-elected, will not spend much time
on programmatic strategy. The narrow limits of manoeuvre imposed by an
all-party government and the permanent risk of a referendum defeat
drastically curtail any effort to design comprehensive programmes and,
at least in domestic policies, allow for incremental progress only.
- Swiss Democracy bu Wolf Linder

In the sentence I emphasized, what does "others" refer to? To other decisions? Or what? I cannot understand.
Answer: "Others" refers to "other decisions". The sentence in bold could be expressed:

A popular vote, even when settling a fundamental issue, involves just one clear decision independent from the other decisions.

That is, a popular vote could be a "yes" or "no" choice, resolving one issue, which is therefore independent from other decisions on other issues.
Comment: I also went through the same thought process, but landed on **other decisions** which could be extended to **other decisions on (other) issues** essentially.
Comment: I agree, although I did wonder whether the sentence could be interpreted to mean **other issues**.

Independent from others?


What property of Typescript's number or Math.ceil() causes this arithmetic error?

Question: I'm trying to create a function to generate a unique number every time using Typescript. The arithmetic is often incorrect for some reason. I've expanded the logic below and suspect that it has something to do with Typescript/Javascript's number type or Math.ceil(). I'd be grateful if someone could educate me.
function nonce(){
    const millidate = (new Date()).getTime();
    const factor:number = 10000;
    const codeTime:number = +millidate*factor;
    const codeEnd:number = Math.ceil(Math.random()*factor);
    const codeMult:number = Math.ceil(Math.random()*10);
    const codeBody:number = codeTime+codeEnd;
    const code:number =  codeBody*codeMult;
    console.log("Breakdown of " + code + ": ", codeTime, codeEnd, codeBody, codeMult);
    return code;
};

nonce();

Image of some tests in Playground

I was using Typescript's Playground to test this, but its performance seems to be the same across different environments.
Comment: You are of course aware that JS integers only go up `Number.MAX_SAFE_INTEGER`, right?
Comment: `(Date.now() * 10000) > Number.MAX_SAFE_INTEGER`
Comment: (also note that unless you're doing this purely to "see if you can", you almost certainly want a uuid library instead, like https://www.npmjs.com/package/uuid)
Comment: [Please consider replacing or supplementing images of text with a plaintext version.](https://meta.stackoverflow.com/a/285557/2887218)
Answer: As pointed out in the comments, your numbers are way over the system limit. Number.MAX_SAFE_INTEGER on my 64-bit system:
9007199254740991 <- MSI
163469121917820770 <- your number

Dial it down, or make strings.
Answer: To work with large numbers (more than Number.MAX_SAFE_INTEGER), you need to use BigInt()
Without BigInt:
9007199254740991 + 1 = 9007199254740992 // Right
9007199254740991 + 2 = 9007199254740992 // Wrong
9007199254740991 + 3 = 9007199254740994 // Right

Using BigInt:
9007199254740991n + 1n = 9007199254740992n //Right
9007199254740991n + 2n = 9007199254740993n //Right
9007199254740991n + 3n = 9007199254740994n //Right


Compton-like scattering for protons

Question: Why don't we usually calculate scattering cross sections for Compton scattering of photons (gamma rays) off protons? After all both electrons and protons are fermions. Hence shouldn't the amplitude be identical for both type of scattering?
Answer: Two reasons.
Firstly the proton has a much higher mass than an electron. What this means in practice is that for a given photon energy in the fermion rest frame,  the proton has a lower recoil speed after energy-momentum conservation is considered, which means the photon loses much less energy. So basically the cross section stays in the low energy Thomson limit. And the Thomson cross section is proportional to $\frac{1}{m} $ so actually it is lower for a proton tan for an electron
Secondly, and more importantly, an electron is a point charge (as far as the calculations go), while a proton is made up of other stuff and has a spatial extent. The internal structure means that the photon may be exciting internal states of the proton, which is a completely different proposition. Or interacting with the partially charged quarks inside individually. Obviously there is some threshold below which this becomes less relevant, but then you're back to dealing with the Thomson limit worth a cross section reduced by a factor of $\frac {m_e}{m_p}$ compared to am electron.
Comment: It means one can and should calculate cross section for Compton like processes for protons but then we will have to take into strong interactions which is nothing but interaction of quarks with radiation.

Compton-like scattering for protons


How to stop acceleration on AddRelativeForce Unity 3D?

Question: I'm a very new game developer, and I was making a simple first-person script using AddRelativeForce. However, when I go forward(or any direction), I slowly accelerate instead of going at a constant speed. Does anyone know how to fix this?
Comment: [Consider using a trick like the one shown in this answer](https://gamedev.stackexchange.com/a/191346/39518). Instead of applying a thrust in your chosen direction as if the character were a space probe firing attitude jets, compute a target velocity (limited by your max speed), then accelerate to match that target.
Answer: Ok, I found something that works. I basically kept my entire old script, but in every frame I set the velocity to 0 and then added the relative velocity. This caused AddRelativeVelocity to essentially be the same thing as SetVelocity, but instead it set the relative force. While this worked in my situation, it might not work in others. Thank you to all of the helpful people who answered my question, though!
Comment: If you just want to set the velocity, don't add a force, just set the velocity. If you want to make it relative to the object's orientation, just transform the vector first: `body.velocity = body.rotation * localVelocity;`
Answer: If you want to move your character using the AddRelativeForce-Method you need to keep track of the current velocity to prevent applying a force when the limit is reached. Something like this could be a solution:
public float yourMaximumMovementSpeed = 10f;

// we use velocity.magnitude to get the length of the vector
if (rigidbody.velocity.magnitude < yourMaximumMovementSpeed)
{
    rigidybody.AddRelativeForce(yourDirection * yourForce);
}

Instead of adding force you also could just set the velocity directly:
rigidbody.velocity = yourMovementVector * yourMovementSpeed;


How to clean wood stain off of vinyl porch?

Question: I refinished our dining room furniture out on the porch, and stupidly didn't put a tarp or anything down. Now there is woodstain all over. The porch is plastic (maybe vinyl, not sure what the difference is). Is there any way to get it out?
Answer: The exact fix depends on the stain, but try a few common solvents like rubbing alcohol, wd40, and acetone (nail polish remover). Be sure to try them first in an inconspicuous non-stained area with a cotton swap, as some solvents can etch some plastics, e.g. acetone and ABS.
You might also try steaming through a towel; that can remove some things solvents have trouble with.
If all else fails, you might be able to carefully bleach the stains to reduce their appearance. Regular bleach or the hydrogen peroxide gel packet from a cheap blonde hair-coloring kit would be my choices for that.


Give some examples of additional work in thermodynamics

Question: dU=dq + dW(expansion) + dW(additional), give some examples of additional work...
Comment: and gravitational, and magnetic work
Answer: Firstly, dq= du + dw. In thermodynamics, we assume all thermodynamic processes to be quasi-static (i.e. very very slow process). Assuming a process to be very very slow, you won't have any extra addition work done i.e. whatever heat you supply to the system is used up for increasing the internal energy of the gas and for work done by the gas against the external surrounding.
Now lets say if we didn't assumed thermodynamic process to be quasi-static. In this situation, if you apply heat to the system, it would increase the internal energy of the gas, and some part of the applied heat will be used up for the work done by gas against surrounding , and now as the process is not quasi-static, when the gas starts doing work by expansion of the piston, as the process is no longer slow, the piston will acquire some velocity and hence it would acquire a kinetic energy. And hence you will now have another work done. This additional work done is work done for the movement of piston. So if the process is not quasi-static, whenever you apply heat, that heat is used up in increasing the internal energy of the gas, used for work which is done by the gas against the surrounding and also an additional work which is work done to move the piston.
If you assumed the process to be quasi-static, then velocity of the piston during the expansion is approximated as zero and hence no kinetic energy of the piston and hence work done for the movement of piston is neglected. So whatever heat you applied will be utilised for increasing the internal energy of the gas and for the work done by the gas against the surrounding (and no extra additional work done)


Compactness of a set of functions on an infinite-dimensional function space

Question: Let X be the space of functions $f:\mathbb{N}\to\mathbb{Z}$, endowed with the metric $d(f,g)=\sum_{i=0}^{\infty}{\frac{1}{2^{i}}\mathbb{I}(f(i)\neq g(i))}$, where $\mathbb{I}$ is the indicatorfunction. Now fix $L\geq 0$ and let $K=\{f\in X:f(0)=0, \lvert f(i+1)-f(i)\rvert\leq L\}$. Does anyone have any ideas how to show that $K$ is compact in $X$? Probably the sequential definition of compactness is the way to go but how?
Comment: Isn't this a particular case of the Arzelá-Ascoli theorem where $\mathbb N$ and $\mathbb Z$ are endoed with the discrete metric? The metric $d$ desribes the topology of uniform convergence on compact (=finite) subsets of $\mathbb N$.
Comment: The correct accent is Arzelà.
Answer: Let $f_n$ be a sequence in $K$. We will we find a subsequence that converges by a diagonalization argument. Evidently $f_n(0)=0$ for all $n$. $f_n(1)$ is contained in a finite interval $[-L,L]$. Since the $f_n$ are integer valued in a finite interval there must be some constant subsequence $f_{n^1_k}$ of $f_n$, e.g. $f_{n^1_k}(1)=C_1$. Now $f_n(2)$ is contained in the finite interval $[-2L,2L]$. Again take a subsequence $n^2_k$ of $n^1_k$ such that $f_{n^2_k}(2)=C_2$ for all $k$. We continue in this fashion.
Take $g_j=f_{n^j_j}$. If we fix $i$, $g_j(i)$ is a constant sequence for $i\leq j$. Take $g(i)=g_i(i)$. Now
$$d(g_j,g)=\sum_{i=0}^{\infty} \frac1{2^i}I(g_j(i)\neq g(i))=\sum_{i=j+1}^{\infty} \frac1{2^i}I(g_j(i)\neq g(i))\leq\sum_{i=j+1}^{\infty} \frac1{2^i}$$ which goes to $0$ as $j\to\infty$. It is not hard to show that $K$ is closed which implies that $g\in K$.


How in laymans terms do I restore a .dat BTC backed up wallet file on my mac please?

Question: the bitcoin wallet backup.dat file is in my documents
but I'm not an advanced computer user
I have the complete bitcoin qt on my computer but don't know how to restore from the backup
Answer:
Close Bitcoin core so that the program is not running.
Go to /Users/{yourusername}/Library/Application Support/Bitcoin/ and there you will see much of the blockchain data, and a wallet.dat file.
If there is a wallet.dat file here that you also need, save it elsewhere by copying and pasting.
Put your backup.dat in this directory, and rename it to wallet.dat.
Start Bitcoin-QT with the -rescan option so that it will go and look for any coins that your received in the blockchain.

That's it!


How to prohibit some words and letters to use as a Drupal password?

Question: I need to prohibit a user from using a few words as a password. E.g I don't want to use these words as a password. Drupal, 123456, Microsoft. When a user submits the registration form with the above terms in the password field then they get a message about the prohibited password.
Answer: This module should work. I have never used it before, but it should definitely have the feature to prohibit certain password strings.
Password Policy Module
Answer: You may also want to consider the Password Strength module. Some details about it (from its project page):

... provides realistic password strength measurement and server-side enforcement for Drupal sites using pattern-matching and entropy calculation. Almost any type of password can be allowed so long as the password proves to be of high enough entropy. For inspiration see the XKCD comic on password strength.

PS: Here is how the linked comic looks like:


Is it possible to recover deleted responses from Google Forms?

Question: Here is the context of this question. We used Google Forms for an election of 6 people. I want to know if it is possible to delete individual responses and then recover all responses (deleted and not deleted). For example, on Google Docs you can look at everyone's edits and recover deleted items from previous dates. Is this possible with Google Forms and if so, how can I get all of this information.
Comment: did you try **Version History**?
Answer: If you didn't save the form responses to a Sheet before deleting them, they cannot be recovered after deletion.
I contacted Google support about this issue in the past and they told me the same thing - they don't have an undelete button for Forms.
Answer:
Yes you can get back deleted form Responses

i know this is an old post but this answer is for anyone else looking for the same solution to a similar problem quite recently.
You might have some luck here- google has quite a good auto backup system when it comes to sheets
Login on your desktop browser for easier access
Your form responses are generally linked to a google sheet someplace - if you want to know which sheet name click on the green sheet logo on the right hand top corner of your google form settings  - it will ask you if you want to change the location of your responses "dont click anything " just make note of the sheet name that you see auto populated there.
Go to your google sheets in your google drive account & select that sheet that your form is linked to.
Click on "file" on the Menue
Click on "Version History > See Version History "
let it load
on the right hand side of the page you will see the diffrent auto saves done by google sheets - it includes everything that was inputed onto the google sheets -all data including that of the form, since the last time you accessed it.
Just tick the option "see changes" you will see all the changes done across the sheet in each and every timestamped version.
when you found what you looking for -clcik on "restore this version" get the data you need or deleted etc - it will all be saved here
take note this will restore your sheet back to the version you have selected based on the date & time of that auto backup you selected
Answer: If it has been deleted from the bin. The only way to have access to the response is to recreate another one. It is done by clicking the three-dot button and selecting 'Select Response Destination' from here you will be offered to Create a New Spreadsheet or add the response to an old response database.
Answer: If you still have the Form but without the Google Sheet response (deleted from trash), you may unlink the form and get a new spreadsheet later on with all the submitted response (Please know that the new spreadsheet will only contain response submitted from the latest version of Google Form).


What is the meaning of "chmod 666"?

Question: I am using Linux. What is the meaning of chmod 666?
Comment: aka, the Satan command.
Comment: If that bothers you (or if you can't be bothered to remember those numbers) you can also write it as `chmod a=rw`.
Comment: useless command, since the third argument is not given ^^
Comment: also it can produce security flaws (all users can write the file/folder) or useless file/folder permissions
Answer: chmod command change attributes from a file/folder:

chmod 666 file/folder means that all users can read and write but cannot execute the file/folder;
chmod 777 file/folder allows all actions for all users;
chmod 744 file/folder allows only user (owner) to do all actions; group and other users are allowed only to read.
permission to:  user(u)   group(g)   other(o)
                /¯¯¯\      /¯¯¯\      /¯¯¯\
octal:            6          6          6
binary:         1 1 0      1 1 0      1 1 0
what to permit: r w x      r w x      r w x

binary         - 1: enabled, 0: disabled

what to permit - r: read, w: write, x: execute

permission to  - user: the owner that create the file/folder
                 group: the users from group that owner is member
                 other: all other users

Alternatively, you can execute the command with a more intuitive syntax, without needing to think in binary or octal (but the knowledge of numeric syntax is so important): chmod u=rw, g=rw, o=rw file/folder
Remember that the permission changes with chmod command requires at least 3 arguments, so chmod 666 does nothing without explicit file/folder to change permissions.
Also be sure to criticize if it does not produce insecure issues or simply if it is an useless permission change, because chmod 666 will allow file/folder write to all and the execution to none.
Comment: Only it's "octal", not "decimal".  +1 anyway.
Comment: It only goes to 7 anyway, so there's no difference between octal and decimal in this case. :/
Comment: The third point mentioned in the first post is incorrect - chmod 711 allows only owner to do all actions, group and other are allowed only to read
![enter image description here][1] This is the table for rwx for octal rwx 000 001 010 011 100 101 110 111 Octal 001, or 1 denotes execute permission Octal 7, 111 denotes read write and execute permission hence 711 denotes, rwx for owner, and x for groups and others.
Comment: @KyleVassella, `owner` is the owner of file or folder, generally the one that created it. `group` is the group of users associated with that file or folder, generally the group that owner is in. So imagine that I am rootbira and my groop is rootusers and you are on that group too, and all other SU forum members are in other group. If I create a file and do a with chmod 750, I would read, write and execute it, you would only read and execute and SU users won't do anything - it is our secret ¬¬
Comment: yeah, @Yash, and after 1 year, 2 months and 18 days after the original post someone saw that error :) I'll correct it to 744 on example.
Comment: @Rob, you are right, but I do it to explicit that is a number from 0 to 7 :) as suggested by ben
Comment: http://en.wikipedia.org/wiki/Chmod
Comment: What's the difference between an `owner` and a `group`?
Answer: As mentioned in other answers, chmod means change mode. It affects the read, write and executable permissions for the owner, group and other categories of users. The numbers that follow the command (in this case 666), indicate how those permissions are modified for the file the command is run on (for 666, it means that owner, group and other have read and write permissions, but no executable permissions).
By changing the numbers to different values you effectively change the permissions for the file. The link I've referenced above has a little tool for figuring out what values you need to put in to get the permissions scheme you're after. It also goes over the switch options available for the command and some examples to help you understand better how it works.
Comment: That is a great site. It's going in my bookmarks. Thanks!
Answer: In really plain speak: it makes a file read- and write-able by the file owner, the file owner's group and every one else using the machine (all). Applied against a directory it lets everyone read (get file contents lists) of a directory and write (create, edit files in the directory) but not execute files from the directory.
For more detailed information how chmod works check out this handy tutorial.
Comment: ...Don't you mean lets everyone read/write files but not execute, and let's everyone read/write files in a directory, but not list all of the files?
Comment: what @earlz says, plus write on a dir does not mean you can edit files there (write perms on a file does) but solely means you can create new entries (dirs, files, symlinks, etc.). Also, its nice of you to mention dirs for completeness, but 666 doesn't make sense for a dir; you'd never eliminate x for owner.
Comment: @Earlz: thanks for that. I always forget what 666 does for dirs because, well, I never set rw- for a user on a dir. :)
Answer: The chmod command (abbreviated from change mode) is a Unix command that lets an operator tell the system how much (or little) access it should permit to a file. Command chmod 666 means that all users will have read and write permissions.
Answer: If your questions is more about the 666 part than the chmod part, I would refer you to The Linux Documentation Project where is a decent explanation of how file permissions work in Linux.

What is the meaning of "chmod 666"?


Do nickel-free bassoons exist?

Question: I am allergic to nickel. I come up in itchy bumps after contact.
I would like to try playing bassoon but all the ones I have looked at have nickel silver keys, which isn't silver at all but is nickel.
Does anyone make bassoons with a different metal for the keys?
Comment: Are you allergic to actual silver, because you can get silver-plated keys.
Comment: "I imagine they can't be replated the way a mouthpiece can": I suspect that removing, restoring, and replacing the keys of a bassoon is a standard maintenance service.  Surely pad replacement must be common.  Replating is likely to be far less common, but it ought to be possible.  You might also consider baroque bassoon, which has fewer keys that are typically made of brass.
Comment: @phoog Silver plated keys are sometimes replated when the instrument is dismantled for maintenance. It's quite expensive, so it's not done very often.
Comment: Thanks, that might work, as I use a silver plated mouthpiece for brass. Do you know which brands do that?
How long does the plate take to wear through? I imagine they can't be replated the way a mouthpiece can.
Comment: What is your price range?   As you can imagine, silver is unlikely to be used in student-level axes, expensive though those may be
Answer: Could you use clear nail varnish so your skin doesn't touch metal? This is common practice for brass players who would otherwise have an adverse reaction to their mouthpiece.
I also did a web search for bassoons and some of the non-student models do feature silver-plated keys. Looks like only the cheaper (no such thing as a cheap bassoon!) models feature nickel-silver keywork without plating.
Answer: Starting from middle price level, the mechanics of a bassoon is silver-plated. Two issues I know for sure:

for a general maintainance (for non-professional use required maybe all 8 years) all metal is removed from the instrument to receive a new silver-plating
to judge from the amount of darkening which can be removed with a silver-polishing cloth I would assume there is still silver present then, but the keys do not darken due to frequent contact with the fingers anyway.

Do nickel-free bassoons exist?


Good way to learn Ramsey Theory

Question: What are some good books on Ramsey theory? I have Van Lint's book on Combinatorics: is this enough preparation to start reading about Ramsey theory? I want a book that includes important results and has good proofs.
Answer: This is a list of some resource material on Ramsey Theory:

Expository note on Arithmetic Ramsey theory by Terence Tao. This contains the basic theorems and proofs presented in a very nice manner.

Ramsey Theory by R.L. Graham, B.L. Rothschild, and J. Spencer is a book which contains an introduction to nearly all areas in finite Ramsey theory. It contains proofs of all the basic results: Ramsey's theorem, van der Waerden theorem, Hales Jewett theorem, Schur's theorem, Rado's theorem, Graham's theorem etc.

Ramsey theory on the integers by Landman is a book accessible to undergraduates. It is unique in the sense that it uses only elementary mathematics and describes many research problems. Most of the book deals with variants of the van der Waerden's theorem.

Mathematics of Ramsey theory by Nesteril & Rodl is a book which I haven't read but is supposed to contain many advanced techniques.

The ebook Introduction to Graph Ramsey Theory by Yusheng Li and
Wenan Zang available here.

Elemental methods in Ergodic Ramsey theory by McCutcheon introduces one of the current approaches to Ramsey theory (via Ergodic theory). I have only read the first chapter but it seems an accessible and well written book.

Erdos' book Partition Relations for Cardinals (Infinite Ramsey theory). I haven't read it.
Comment: Plus: The beautiful "The mathematical coloring book" by Soifer, http://www.amazon.com/Mathematical-Coloring-Book-Mathematics-Colorful/dp/0387746404, contains a very nice introduction to several of the standard topics, and many historical references. Soifer later edited "Ramsey theory: Yesterday, today, and tomorrow", http://www.amazon.com/Ramsey-Theory-Yesterday-Tomorrow-Mathematics/dp/0817680918/ And I know of several books in preparation. See also http://www.cs.umd.edu/~gasarch/ramsey/ramsey.html and http://math.stackexchange.com/questions/14020/known-bounds-and-values-for-ramsey-numbers
Comment: The "Partition relations" book also discusses finite Ramsey theory. For additional results on partition calculus (the infinite version of the theory), see also "Combinatorial set theory", by Williams, http://www.amazon.com/Combinatorial-Theory-Studies-Foundations-Mathematics/dp/0720407222, and the relevant chapter in the Handbook of set theory, http://www.amazon.com/Handbook-Set-Theory-Matthew-Foreman/dp/1402048432
Answer: I still like the first edition of R.L. Graham, B.L. Rothschild, and J. Spencer, Ramsey Theory, from 1980. There was a second edition in 1990 that I've not seen but which I believe added quite a bit of new material. Unfortunately, it's obscenely expensive.
I have not seen B.M. Landman and A. Robertson, Ramsey Theory on the Integers, but it's received some very good reviews and sports a much saner price tag.
Answer: You might like Ronald L. Graham's Rudiments of Ramsey Theory, which is quite short, and which I think is intended to be an introduction. I haven't looked at it myself in many years, so I can't provide a more detailed review than that.

Good way to learn Ramsey Theory


When formatting an oEmbed iframe, how (and where) does WordPress determine the height value?

Question: When formatting an oEmbed iframe, how does WordPress determine the height value? A pointer to the code that does the working out would be good too.
Comment: which OEmbed? Normally OEmbed HTML markup is generated by the OEmbed provider, not WordPress. What's the context for this? What problem requires this knowledge?
Comment: because that's what that instance returns, you'd need to ask the instance maintainers what software they use then follow through to the vendor. I tried using the iframely debugger on a toot and it gave me 479px as the height, and another toot gave me 900px+ so it's content dependent. It may be that what you're seeing is determined by javascript that runs in the browser when the embed is loaded. It's extremely unlikely this is something you can change using WordPress APIs, and you may need to resort to JS and CSS on the frontend or reporting this to Mastodon on GH
Comment: e.g. for the toot I chose to test with I got this response in the iframely debugger: `` so the height is determined at runtime, see http://debug.iframely.com/
Comment: I'm trying to figure out why oEmbeds from Mastodon have a height of 960 which looks really silly.
Answer: It doesn't, that's not how oEmbed works.
WordPress doesn't generate or format the HTML for an OEmbed, the OEmbed provider is responsible for that. It's not even responsible for the creation of the iframe tag. The most WordPress can do is suggest a maximum height and width, but it's nothing more than a suggestion.
So if you embed a youtube video, WP will go to youtube and ask it for the embed code.
As for where WP gets that suggested max height and width, it gets it from the defaults function/filter:
https://developer.wordpress.org/reference/functions/wp_embed_defaults/
Remember, this is sent to the oembed provider, but is not used to generate the HTML, modify the HTML, validate the response, or for enforcement.
If you use an embed block or shortcode then the height/width used there will override those defaults e.g. [embed width="900" height="600"]https://youtu.be/6LwWumPeues[/embed] will pass 900 and 600 to Youtube when it asks for the embed.
Note that as an OEmbed provider, Youtube can choose to ignore this. WordPress doesn't interfere with what Youtube returns to enforce this, and can't as an OEmbed may return a script tag. Some embeds have dynamic heights too that change based on user interaction or the device.
There is the edge case of when you yourself register an OEmbed provider that has a local source. In this case you are the source of the height as the code is entirely local and written by yourself. If this is your situation and you cannot find where the height is set, it may be because your code does not set the height.
Most of the time, the browser will render the iframe, then the iframe has JS that sends a message to the parent frame containing the height of the content, and JS in the embed code receives it and resizes the iframe to match
E.g. this OEmbed response from a toot on mstdn.social:


Is there a reliable autosave function for nodes?

Question: We're working with dirty forms to at least warn users before they leave an unfinished page before they save. It kind of works.  Would enabling revisions control work? At least in that case an admin could recover the last version.  Is there an automatic autosave ... say every 30 sections -- to be sure work is properly saved even if the user forgets to hit save?
Answer: Autosave

The Autosave module automatically saves a snapshot of your content
  type form using AJAX. If the user's browser or machine dies while
  editing a node; the edits will be presented to the user the next time
  they return to the node. The user may toggle back and forth between
  the last saved version and the version with the edits that were lost
  and select which of these they would like to continue with.
How often a form is autosaved as well as which content types to enable
  autosave for are admin configurable.
Answer: There is a Drupal 8 module: Autosave Form
We have tested it. It basically works, but is not stable and has open bugs for complex forms.

The "Autosave Form" module provides an autosave feature for all forms
  (entity forms inclusive). Currently the autosave submit will be
  triggered every 60 seconds, but this approach might be exchanged later
  through a solution listening for DOM changes.
Comment: Hm, no stable release, last update 3 months ago, tests failing. Is it any good? Have you tried it in production yourself?
Comment: @leymannx we are not using it in production yet, But we might soon. We are still testing it, but the module looks very good so far. See also https://www.drupal.org/project/autosave_form/issues/2990885
Comment: It has issue https://www.drupal.org/project/autosave_form/issues/3004984


Change date format in forum

Question: Is there a way to change the date format in main forum table? I changed the date format in views for topic list, but the date format wasn't changed on main forum page
Answer: What I did to change the date format. In modules/advanced_forum/includes/theme.inc I found the function advanced_forum_preprocess_forum_submitted(&$variables) and changed line 249 to $cutoff = variable_get('advanced_forum_time_ago_cutoff', 0) * 60 * 60; and line 254 - to $variables['date_posted'] = format_date($timestamp, 'custom', 'j M Y,    G:i');
Answer: You generally don't want to edit Core or contributed modules but instead make a module that implements a hook to get your changes to work without effecting your ability to update.
To make this change I created a custom date format via the UI in Drupal 7 at 'admin/config/regional/date-time/formats'
Then I set my module's weight to 1 higher than the advanced forum module's weight in the drupal_system table via direct database manipulation. This allows your module's hook to run after the advanced_forum module's hooks.
I then added a function to a custom module that implements hook_preprocess_HOOK
/**
 * Implements hook_preprocess_HOOK().
 *
 * Changes date format for latest posts on forum listing page "/forums"
 *
 * requires module to be set as higher weight than the advanced_forum module (default 15) in drupal_system
 * this module must be set to weight 16 to make sure the preprocess functions happen after advanced_forum
 */
function forum_enhancements_preprocess_forum_submitted(&$variables) {
  if (isset($variables['topic']->created)) {
    $timestamp = $variables['topic']->created;
    $interval = REQUEST_TIME - $timestamp;
    $variables['time'] = format_interval($interval);

    // For items posted more than $cutoff hours ago, offer an actual date.
    $cutoff = variable_get('advanced_forum_time_ago_cutoff', 48) * 60 * 60;
    if ($interval > $cutoff) {
      $variables['date_posted'] = format_date($timestamp, 'forum');
    }
    else {
      unset($variables['date_posted']);
    }
  }
}

Answer: You can accomplish this task in multiple ways. The easier is to override forum-list.tpl.php or forum-topic-list.tpl.php and change the date format directly from the template file.
Answer: In order to change date format for main forum table, you need to override template_preprocess_forum_list by placing it in your Drupal custom theme or Drupal custom module
function MODULE_NAME_OR_THEME_NAME_preprocess_forum_list(&$variables) {
  foreach ($variables['forums'] as $id => $forum) {
    $variables['forums'][$id]->last_reply = format_date($forum->last_post->created);
  }
}

For more details check Drupal formate_date
Answer: One thing you should keep in mind while working with Drupal is that you should Never hack Core and its features. You should not be looking at a way to change the date format in table, instead, you should be looking towards a way to manipulate the template where you need to show.
Currently, you should change the way it is shown while rendering in the template file.

Change date format in forum


What causes "The Finder can't quit because some operations are still in progress" error message?

Question: I am receiving this message when I'm trying to shut down my computer and I don't have any Finder windows open. What could be causing this message and how do I fix it so that I don't have to perform a hard shutdown?
Comment: I ended up force quitting Finder but then I still have to push the power button to shutdown.
Comment: Same here.  Happens seemingly randomly and requires the hard "hold the power button down for awhile" operation to get the thing to shutdown.
Answer: Here's another way to Force Quit an application:

Click the Apple Menu
Hold Shift, and notice that the 'Force Quit...'
menu item has changed to 'Force Quit [frontmost app name].'
Select 'Force Quit [frontmost app name]' to force quit the Application.
Comment: Alternatively, press ALT+CMD+ESC to bring up the Force Quit dialog (akin to CTRL+ALT+DEL on Windows), or press ALT+SHIFT+CMD+ESC to Force Quit the frontmost app
Answer: It usually happens when it's trying to synchronize or back-up IOS devices.  Sometimes it happens when it's doing mail.
What's bad is when the computer is doing its regularly scheduled shut-down and the message comes up, but I have already left.   It stops the shutdown waiting for me to respond to the message and I don't discover it until the next morning, even though the cause of the message is no longer valid.
This is a real security issue.
Answer: This usually comes up when the Finder is doing a long copy or emptying the Trash. Are you sure you don't have a progress window minimized to the Dock or on a different Space?
Answer: Network errors can cause Finder to hang at Shutdown.
Sometimes you can get around pressing the power button by quitting network manually before trying to restart.
This MacOS hint doesn't cover your exact situation, but may well provide a workaround for your hung shutdown:
Making Finder BeachBalls go away without rebooting System

Turns out that using that to turn off Wi-Fi, then waiting for a bit, and turning Wi-Fi back on clears the Finder's beachball
Answer: I found that opening Force Quit (with no other apps running except Finder) then relaunching Finder allowed me to Restart my Mac Pro.


How do you find inspiration without copying someone's work

Question: Say you want to design a mobile app and the like a few stuff about some design choices and decisions on similar apps designed... You'd like that in your app design wouldn't that be copying
Comment: Does this answer your question? [Is copying other app's UI okay?](https://ux.stackexchange.com/questions/88671/is-copying-other-apps-ui-okay)
Answer: Easy steps:

Get familiar with the platform specific design guidelines. It will make you to know all the rules, constrains, etc. There are official guidelines for iOS, Android, Web etc. iOS: Human Interface Guidelines. Android/Web: Material Design. Web: The best one currently is Fluent Design System by Microsoft.
Do best practice research.
Do not open Dribbble, Behance to find inspiration if you are not familiar with the rules and constraints of the UI design.

Getting to know the basic rules of the platform is the right start for all UX designers. You will be able to design a completely fine interface. It may not very nice, but aesthetics are secondary. Later you will learn that too. Then you can do a best practice research to find the right solutions and patterns for your specific problems. Unfortunately, most of the UX/UI designers are just copying designs from Dribbble without understanding the context or just understanding that what is uploaded there, 90% of it is not feasible or even may harm the business, as these are just for showing off. So only open these websites, when you are already know how to "read" and understand everything you can find there. Do not copy the aesthetics. Copy the system, how these work instead. But for this, you have to understand them.
Answer: One advice I recently heard is a simple 3 step process:

Find & analyze your inspiration
Sleep on it
Design your thing without looking at inspiration
Answer: When I was a junior, I always draw inspiration from other people's work. But as I grew mature in my field, I realised that our inspiration must and always be our users -- the people who use our products. If you can address their needs, solve their issues, then that's a success from your part.
Answer: You don't have to reinvent the wheel per-se.
If for example, the navigation system is very easy to use and self-evident then by all means implement a similar system.
Many sites/apps follow similar formatting and layouts. There are universal concepts that make websites and apps more usable.
I would make sure you are not copying anything artistic. You can implement a similar structure, but don't copy the exact design.


How to connect a 2 wire light fixture to a 3 wire ceiling box?

Question: How do I wire a light fixture with one white and one black wire to a ceiling box with one white, one black, and one red wire.
Comment: Are those the only wires in the box? Are there two switches in the room, or just one? Some photos would be helpful.
Answer: Usually red is switched, black is hot, white is neutral. However, you should verify this with either a test light or a multimeter ($5).
So the easy way to do this is to connect white to white, red to black, and see what happens when you flip the switch.
However, red might be a second circuit or part of a three way switch -- there's no easy way to tell without testing it.  Write down the voltages between white and ground, black and ground, and red and ground with all switches in both positions -- have your assistant operate the switches while you test them.
Finally, turn off the power at the breaker, connect white to the neutral, black to the hot or switched leg (your preference), turn the breaker on, and operate the switches to make sure everything is working.


If you plan on getting a PhD could you strictly take classes in your field to prove yourself and not get your bachelors?

Question: Could one potentially get into a PhD program if they don't take college graduation requirements and instead take more classes in their field?
Comment: Wait, college graduation requirements - you mean skipping the classes required to get any bachelor at all and apply for a PhD anyway? Of all the graduate schools I've looked into in the US, every single one explicitly required a bachelor's degree to be completed and awarded before starting graduate school, with the stipulation in the acceptance email that you must provide an official verification of that or you won't be allowed to start. If you mean taking additional classes in a field because your major is in a different field, that's an entirely different question!
Comment: you can get BSC or ASS, and than at some uni apply
Comment: Look up the requirements of some PhDs you might apply to and see if they accept applicants without degrees.
Comment: Just to provide a counter to @BrianHall's almost universal rule, I know of a student who was offered admission to a MEng program on the basis of her strong performance in upper division undergraduate work that was not going to lead to a finished degree for a few years due to a complicated cascade of transfers and incompatible curricula. But this was a decision made about a student the department already had significant experience with.
Answer: There's no answer single to whether you can do this: every school sets its own policy, although the overwhelming majority will not allow you to apply for a PhD without a Bachelor's degree.
However, even if it is allowed, you should not do this!

A PhD involves a large amount of reading, writing, and self teaching. Taking a breadth of classes helps to hone your skills in these areas.
Real world papers are often interdisciplinary, so having a breadth of knowledge will be helpful in understanding (and writing!) these
If you have a degree and major in your subject, you will likely have enough knowledge to teach yourself things from the classes you didn't take.
Electives give you a good opportunity to take classes in things you enjoy but aren't related to your future career
Answer: I agree with the previous answers that graduation requirements typically have real intellectual value, but there's another reason why failing to complete requirements in other fields looks bad to admissions committees: it suggests an inability to make yourself do things you aren't excited about.
This is a crucial skill for having a successful career.  You'll periodically have to do things you find uninteresting or unpleasant, and you'll need to do them well enough that they don't stand in your way.  What these things are can vary; they might be perfectly sensible things you just don't happen to enjoy (such as writing or lecturing), or meaningless bureaucratic hoops you are forced to jump through.  Either way, sometimes you'll just have to do them.  If you're lucky this will amount to only a tiny part of your career, and if you're brilliant people might bend the rules for you, but most people are neither lucky or brilliant.
Every so often this derails someone's career.  They enjoy and do well at 80-90% of the job, but they fall apart completely on the remaining 10-20%.  They just can't make themselves do it, and they can't find a way to avoid it.  This doesn't end well.
I don't want to invest years in working with a grad student unless I'm confident they can do what they need to do to have a successful career.  If an applicant is too reluctant to complete graduation requirements (even requirements that I personally agree are excessive), it's a worrisome sign.  I wouldn't consider this factor decisive by itself, but it would make me look at the whole application skeptically for signs of trouble.
Answer: Almost certainly not.  I have only once heard of someone who did not get their undergraduate being accepted.  They couldn't pass the university's swimming requirement, but otherwise met the requirements.  They then won the Nobel.
There is a practical issue too and that is filtering.  In order to winnow out the applications, graduate schools put a variety of filters in so that faculty do not have to review all applications that are submitted.  If you are not getting a bachelors, then you will almost certainly be filtered out and even if you are the best candidate on the planet, no one will read it to know that.
Still inside the practical, your graduation requirements were almost certainly modified by the non-major requirements at your school.  To provide an example, we are preparing to do a program review.  Part of reviewing the graduation requirements is making sure that things that are necessary to learn are either taught in the program or in the core and gen ed requirements.
No academic field is independent.  Within-major requirements are impacted by the courses out-of-major.  Academic departments are not concerned with courses  so much as skills.  If we know some courses teach certain skills in a course, then we do not need to teach those skills within the major.  Core requirements save academic departments effort in that if there is some commonly used skill, it saves money and resources if they are taught as broad skills in a core course rather than as narrow skills in a field course.
By avoiding courses out of your major you may be reducing your skills rather than increasing them.  My school requires everyone to take statistics, for example, so we do not require field specific statistical methods, though you could take that course.
Still in the practical, even if you graduate and are qualified you may not get into graduate school.  There are only so many spots.  You may also hate it.
Outside the immediately practical, it is uncommon to not have to leap across fields in most research.  A PhD is a degree that teaches you how to do independent research.  If you have no knowledge of other fields, you will not know how they think.  If you do not know how they think you will make serious mistakes in your own research.
In my own doctoral work, I had to draw on work from seemingly unrelated fields.  None of these are inside my field.
Although not taught in my doctoral program, I found myself concerned with computational algebra because of issues related to significant digits and a computers ability to properly perform operations on very small numbers.  I found myself drawn into the debate between the Frequentist, Likelihoodist and Bayesian schools of thought in statistics and even ended up doing reading in the now defunct Fiducial school of statistics.  I ended up needing the tools normally taught to historians because I had to unwind how and why things were done the way they were in the past to explain to those in my field how we got to where we are at.  I found myself in the philosophy of model building and in the general philosophy of science.  I ended up needing to learn programming for massive data sets in a supercomputing environment.  I found tools in geology that were very useful in my field, though we do not have anything at all to do with rocks.  The Feldspar jockeys are useful for more than knowing what quartz is.  I had to pull literature from psychology, sociology and biology.  I found myself in neuroscience reading medical journal articles.  My work is not in medicine.
If you go through your undergraduate with the plan of getting a doctorate, then you should take as many in your field as you can.  Be sure to take a philosophy, biology, chemistry, computer science, and French literature courses too.  You may end up stunned that the French literature course ends up being more useful than your field course.
A PhD program will teach you how to think in a disciplined manner and to learn without taking any more classes.  You will want a broad base of knowledge going into a doctoral program.
If it is a choice of graduating or taking field courses, then graduate.


Is it safe to buy 2 times 2x8GB RAM, instead of 4x8GB RAM kit?

Question: It seems to be a stupid question, but on many many website I see that the price for  the 4x8GB RAM is higher than buying two times the 2x8GB, which is supposed to be equivalent.
Of course, the RAM is the same, same brand, same frequency, same model and so on and so forth, since I buy it two times in a row.
Starting from the assumption that I want to fill all my 4 DIMM slots, is it ok to buy 2 times the 2x8GB RAM instead of 4x8 one?
Comment: Using 'twice' might be better, but 'two times' is still perfectly valid in English (just as 'five times' or 'one time' are). Don't overcorrect.
Comment: There are also sellers who price 1x lower than 2x or 4x (per stick costs)
Comment: The modules are identical the only difference is the amount of modules in a kit.  Using the word twice instead of "two times" is proper English.  You definitely shouldn't say "two times" then switch to "2 times".  You could say two 16 GB kits.
Comment: I wrote about buying it two timesin a row, so (2x8)x2=32GB.
Answer: In the all cases that I know about, YES.
If the motherboard supports 32gb of RAM, then you're all set.
Comment: @Vylix I can imagine a really weird edge case. For example, say the manufacturer slipstreams a slightly different memory module with the same part number and you get one set of each type. It might be that the two modules operate at different voltages. It's a defensive thing that there are lots of weird things out there and it's always dangerous to say something is always safe. ;)
Comment: in virtually all cases. What case that cause the answer to be a NO ?
Comment: Well yes, in my case 4 slots and the max is 64GB.
Comment: @user840718  If your motherboard is new enough to support 64gb of RAM (16gb *4) you should have no problem.
Comment: @DavidSchwartz At least when buying on E-Bay, this isn't unheard of. I *have* almost been burned by this. In my case I had two sticks with the same part number but different DRAM chips; in order to get them to work in a dual-channel system I had to transpose them so matched pairs were matched. The person operating purchasing/shipping had no idea of the issue until after I contacted them to clarify.
Answer: Yes, it's very nearly perfectly safe, even if they're different kits from different manufacturers running at different speeds, as long as you follow the directions in the motherboard's manual. The main things you need to watch out for are channels, CAS latency and other timings, and speed.
Motherboards have a lot of flexibility in how they can operate, but one specific design is that there are usually two "banks" for the memory. Within each bank, there must be at least two channels, they must be the same speed, and they must have the same internal timings. It is often a requirement that both sticks also have the same capacity, so you can't mix 4GB with 8GB in a bank (but you could do so between each bank).
Usually slots A and C are a bank, and slots B and D are a bank. Within each bank, you cannot mix single/dual channel, different speeds, or different timings. Assuming the parts are what they are labelled as, this means that if you buy two kits, consider putting each kit in the same bank to minimize the odds of anything happening. Banks on some boards are color coded; if you have two different color slots, make sure that sticks from the same kit end up in the same color.
If you're not sure what I'm talking about, check your motherboard's user manual for the limitations. In fact, there are professionals out there that will tell you that you should always pair up kits in the manner prescribed by your motherboard for the best chance of success.
Note that if you mix and match pairs, all of the sticks will be negotiated to run at the minimum capacity across all of the sticks. For example, mixing PC2400 and PC2666 will likely give much worse performance than using all PC2400 (for now, PC2666 and above is typically single channel, so half-bandwidth).
Do try to keep the sticks from the same kit paired, and do try to get the same type of specs for each kit, and you should be okay.
Comment: This answer needs more attention. Nice job!
Answer: Sometimes the RAMs are produced in modules ( Indicating they are from the same assembly line at the same time) which avoids any types of mismatch among the modules. These are usually a bit higher priced than the individual piece X number of pieces. If you are technical enough to find all the RAM properties(CAS, Frequency, Latency etc) by yourself, then you can choose any size or brand based on those parameters. Otherwise it is safe ti go for a 4 or two module bundle.
Comment: FWIW I'm buying DDR4 at the moment 1x8GB is £42, 2x8GB is £105, 4x8GB is £350. This is for the same brand, same part number from same seller


Can an encryption key be inferred by knowing the plaintext and the corresponding ciphertext?

Question: Thinking about validation methods for guaranteeing a proper key is used. Will keeping a dummy plaintext value and its corresponding ciphertext in plaintext code expose any risk?
Comment: Key-recovery resistance is a basic requirement in all modern ciphers under the assumption that any practical number of plaintext-ciphertext pair are known by the adversary.
Comment: The title a bit confusing, are you simply asking is there a secure way to see that the key is correct before decryption and validation of the whole file?
Answer: Good thinking!
The good news is that, when you use authenticated encryption, there's no need to keep such "dummy" plaintext-ciphertext pair.
In a typical authenticated encryption, a tag is computed based on the key, the plaintext, and possibly additional data (e.g. AAD, Initialization Vector), so that upon decryption, the tag is verified for correctness. Typically, the tag is 128-bit as is the case with GCM-AES and ChaCha20-Poly1305.
Successful decryption of an authenticated ciphertext indicates that if the correct key had been used then the ciphertext along with other inputs to the encryption algorithm are correct and had not be modified by any man-in-the-middle.
Comment: "Successful decryption of an authenticated ciphertext indicates that both the correct key had been used" is not correct for AES-GCM or ChaCha20-Poly1305. Neither is key-committing, so multiple keys may decrypt to different plaintexts but still have the same tag. If you need key committment, that's easy to add, just stick a hash of the key in the AAD and validate it during decryption.
Comment: What if the file is too long to see that? The proper way is to use the first block as identification and this is still secure since we need at least Ind-CPA secure ciphers.
Comment: @kelalaka You make a good point. For large files, reserving an initial segment of data for key verification using some kind of key derivation function can speed it up a bit. We'll see what OP's use case is and then determine if more details deserve to be added.
Comment: @SAIPeregrinus Updated for the fact.
Comment: FYI: https://eprint.iacr.org/2019/016.pdf is the paper that AFAIK first showed a case where the lack of key commitment caused undesired behavior. https://keymaterial.net/2020/09/07/invisible-salamanders-in-aes-gcm-siv/ is an easy-to-understand writeup (though if you are actually "Danny" Niu Jianfang you probably don't need the blog post).


Canon EOS t3i software on EOS T5

Question: Would it be possible to install the T3i software on my T5 (1200D)? Both cameras have the same Digic-4 CPU. The reason I'm asking this is that the T3i have some features for video my T5 doesn't have.
Comment: Not really because I'm talking about installing an older firmware, not a more recent firmware
Comment: My understanding is you want to install firmware from one more to other model. And I have my doubts...
Answer: No, T3i firmware will not install on your T5.  Firmware is always very specific to each camera model.
Magic Lantern is a free 3rd party firmware add-on that is available for many different Canon DSLRs.  It unlocks many hidden features, but it is not yet fully developed for the T5/1200D.

Canon EOS t3i software on EOS T5


What kind of plant is this? It has maple-like leaves but is a fast-growing weed

Question:
I've scoured the internet but cannot seem to identify this plant. It is growing in the Southeastern United States and is around 3 to 4 ft high. It grows fairly quickly, so I assume it's some kind of weed, but I wanted to be sure of what it was before I pulled it.
Answer: It looks to me like Broussonetia papyrifera the "paper mulberry" which although native to Asia has been introduced elsewhere and in Florida for instance is a Category II invasive:

Brisbane City Council list it as a weed, provide many aids to identification  and have an image that seems a close match despite some variation in the very unusual leaf shape across specimens and age of specimen:

(Image courtesy of Asad Shabbir).
It is fast growing (up to 20 m in height) so should probably be removed as soon as possible, though I would be inclined to keep a little (under control!).
Comment: This is 100% the right answer, for future reference.
Answer: I may be way off target but since you said it's fast-growing, I wonder if it might be a very large vine just getting started. I don't know plants in the southeastern States but when I did some checking (as I find the shape of the leaves very interesting), I came across a wild grape species native to your area - Mustang grape (Vitis mustangensis). Here's the University of Texas site on Vitis mustangensis with lots of photos. They do say that the degree of lobbing in the leaves can vary greatly even in the same plant. http://www.sbs.utexas.edu/bio406d/images/pics/vit/vitis_mustangensis.htm

And from the Lady Bird Johnson Wildflower Center: https://www.wildflower.org/gallery/result.php?id_image=14245
Somehow, I don't think that's what your plant is but who knows.
Comment: I also don't think it is the right plant. Venation is different (and not a like in Vitis), also the original is toothed (and not like in Vitis).,
Comment: Lobing does vary greatly within the plant, some are completely oval! But it definitely isn't a vine, and the leaves are serrated. @pnuts The paper mulberry may be the correct. Could I get an answer with more information?
Comment: Should I delete the answer since it's wrong? I agree with it being paper mulberry. I shouldn't try to look up answer just before bedtime as I miss things sometimes - like the serrated top edges of the leaves. --- Or would it be better to leave the answer (but say it's incorrect) so others wouldn't mix IDing it? Either way is fine by me
Comment: @Jude I would leave it, since it may help others that are trying to identify a mustang grape with similar terms.
Answer: We have a similar plant in the Ottawa area of Canada, but it is definitely a vine, since it climbs everything, and tries its best to strangle everything it climbs! The leaves are definitely like a Maple, and since I live in the heart of Maple syrup (sugar, flakes...) country, I know them well (we have three red maples, as well as a few others). I have a picture, but it is almost the same. I assume that it is Mustang grape.


Air friction at supersonic velocities

Question: I know that if an object moves in the air, it can experience two types of drag, laminar and turbulent. For instance, I have a meteor of ideal spherical shape falling from edge of space, say, 100 km up at the Earth surface with initial velocity of 1 km per second. I would consider turbulent drag, but is it still applicable at supersonic velocities? How do I estimate meteors velocity when it hits the ground?
Comment: Yes, it works better the faster it moves, the effect of the turbulence is to erase the long distance correlations in the flow velocity in the fluid. The faster the object moves, the less the back reaction of the fluid matters, when the object arrives at some spot, the fluid "doesn't know" that it was coming. So, the approximation to just assume that right until the object arrives the air molecules have not yet been affected and they will then bounce off the object is going to work better and better at higher velocities.
Comment: So, you mean, it's just turbulent drag assumption and that's it?
Comment: Yes, the drag formula expresses the resistance as being proportional the cross section and the square of the velocity, which is due to intercepting the flux of molecules scooped up by the meteor and letting the bounce off it. Per unit time the moment transferred to the air. And if the asteroid slams into the Earth, if that happens at velocities much faster than the speed of sound of the solid ground, the ground will behave as a fluid and you can still use that formula.
Answer: The drag force, $F$, on the meteor is given by:
$$ F = C_d \frac{1}{2}\rho v^2 A$$
where $\rho$ is the fluid mass density, $v$ is the meteor speed, $A$ is the meteor cross-sectional area, and $C_d$ is the drag coefficient (discussed below).
The fluid mechanics of meteor reentry is quite complicated.  Over the important ranges of altitude, the meteor is supersonic and a bow shock forms in front of the meteor.  Consequently, the flow adjacent to the meteor is subsonic.  The flow field is therefore non-trivial.
For a quick answer, though, meteor trajectories can be calculated by assuming $C_d=0.7$.  If you want to be more accurate, a plot of $C_d$ vs far-field mach number can be found in this paper:  "ESTIMATING THE DRAG COEFFICIENTS OF METEORITES FOR ALL MACH NUMBER REGIMES" by R. T. Carter, P. S. Jandir, and M. E. Kress:

From the plot, you can see that the rule-of-thumb value of 0.7 underestimates the drag at high speed and overestimates at low speed.
You will also need to know atmospheric density vs altitude.  A NASA report from 1976 defines the standard values for this and is available online here.  There are also online web calculators, such as this one, that are based on the same report.  (For data above 86 km, see this report.)
Comment: I have been looking for that raw atmospheric data for years. Thank you.
Comment: Just to confirm the numbers: that means that 1m^2 body at 800m/s through the atmosphere at sea level would roughly have `0.5*0.9*1.225*640000*1=352800N` drag force? So for 100Kg, 350Gs of (de)acceleration?

Air friction at supersonic velocities


Control different flash projector on the same LAN

Question: Does anyone know how to control a projector on a pc, from another projector on another pc, in the same LAN?
any solution is good for me!
Answer: actually is possible and really easy to do with zinc, wich have a nice custom object called Network.
http://www.multidmedia.com/support/livedocs/index.php?url=class.php?action=class=Network
the user can also listen (connect) to some "server" type of application that could control them remotely (even if within LAN). The similar solutions (that is based on tcp/ip protocols) could be based on Flash runtime built-in supports for sockets connection (xml socket, raw sockets) and locally installed server similar to FoxServer/ElectroServer (or any other solution including open source solution).
source: zinc forums
Answer: Control of projectors is quite easy using a PC, find a copy of "TCPLINE" by Davis Moshenkovs.
Write a batch file include the line "tcpline 192.168.100.100 7142 1000 H:"020000000002" to turn on an NEC projector.
Write a batch file include the line "tcpline 192.168.100.100 7142 1000 H:"020100000003" to turn off an NEC projector.
Just find the Extended rs232 files for the projector you want to control, set the static ip address in the projector to the ip address in the batch file, use the listening port number and insert the control code you want from the extended rs232 codes. Works using rs232 connection and lan connection.
For control of sanyo or eiki projectors I recommend using "TST10" by Albert Yale.
Write a batch file include the line "TST10.exe /r:FISHon.txt /m" you also need a text file called FISHon.txt the /m is (return key).
The Text file should contain 6 lines
192.168.100.100 10000
WAIT "PASSWORD:"
SEND "\m"
WAIT "Hello"
SEND "CF POWER ON\m"
WAIT "000"
Put them all in the same folder.


Should the .gradle folder be added to version control?

Question: Gradle creates a folder called .gradle. Should I track it with my version control (i.e. git)?
More importantly, why / why not?
Answer: Should I track the .gradle directory?
No. It can safely be ignored.

Why should I ignore it?
It's purely for caching information, you don't want it in your repo because:

it can get big and be full of binary files
there can be machine specific data in there
there's a lot of churn in there (you'd be constantly committing changes to files in there)
everything in there can be completely re-generated whenever it is needed anyway

It's basically a temp directory that Gradle is dropping in the middle of your source code (why Gradle thinks that's an appropriate thing to do is a different question).
You can tell the "cache directory" nature of the directory by the name of the switch that lets you change where it goes: "--project-cache-dir".
Though I hate having binary files in my source tree, I usually just end up adding the directory to my ignore file because somewhere along the line I'll forget to use the switch from some command line or from my IDE or something and then end up having to deal with the directory anyway.

How do I ignore it?
Git users can add a line with just .gradle to the .gitgnore file and Git will ignore all files in any directory with that name.
Mercurial users will want to look up the .hgignore file.
For other version control systems, refer to the documentation - they all have a feature to support this.
Comment: All of the world's iOS debs converting to Android, thank you! :)
Answer: The .gradle folder contains different calculated information about your gradle build (e.g. cached outputs/input information). You definitely shouldn't check that folder into your version control system.
Answer: I was new to Gradle and thought that the .gradle folder will contain generic information such as dependency mappings, etc and uploaded it on version control. I then tried setting up a new machine with a different OS flavor and Java version using code from the version control including the .gradle folder and ran into errors. Turned out that the .gradle folder contains machine specific information and is used for caching on local.
Do not include the .gradle folder in version control and try setting up a new machine with the code, the gradle daemon will do the rest.
Answer: You don't need to keep the .gradle folder.
Because once you execute gradle build command again, you can make almost the same .gradle folder again.
But when you use the gradle.setting file under .gradle you might need to move it to root folder of the project.
Answer: when we start the gradle it create the .gradle folder inside your home directory. It consist of native (information about your system) and caches. Caches further consist of plugins and all other jars dependencies.
When we build the the project first time at that time it download dependencies and plugins and cheched them here. next time when we need them it, it get from here. even when we need them in eclipse to compile the code (=>gradle eclipse), its dependencies are added from cache
As it will keep updating and adding when you run gradle. so i guess we do not added it to version control.


Adjusting the color of multiple pictures at the same time in Photoshop

Question: Is there a way to adjust the color, hue, contrast, etc. at the same time in Photoshop?
I need to do a quick optimization on my pictures. For example, inserting 5 pictures at the same time and adjusting them.
Comment: Photoshop can do batch processing on multiple images, but not the way you describe. You can do it in Lightroom though.
Comment: Please do not call out to specific users for help. Besides that it's rude, it's useless as well: as long as a user hasn't posted anything in a Question thread, they won't see your mention. Thanks.
Answer:
Adjust color, contrast & brightness using adjustment layers
Group it using a layer group
Drag & Drop the layer group to other documents
Answer: Actions would be your best bet if you need to change a lot of them.
Open an image, or just a new canvas.
Open the Actions window from Window > Actions
Make a new action folder if you like, then create a new action by using the buttons at the bottom. Making sure the Record button in the action window is red, start creating adjustment layers and setting them to the levels you desire.
Perform a Save as using any file type you want to a common destination and then close the window (not photoshop, just the image). Do not change the filename of the file when saving you may do this later on in the process.
You should still be recording, so press the stop button. What you've just created is the action you'll use to change all of your photos.
Now under File > Automate > Batch..., pick the action folder and action that you just created.
Change the Source to be Folder to batch process all the files from a specific folder. You can also use Opened to apply this action to all tabs within Photoshop. If you have Adobe bridge you can start the batch process from Adobe bridge.

You may also change the File Naming tab in order to add things like Datestamps or sequence numbers. You can check Override Action "Save As" Commands, but it doesn't work for me since they always go to the folder i specified in the action.
When you press OK, Photoshop will open each of the files you specified for the source, apply the adjustment layers, save and then close it again before moving onto the next one. They do not close unless you specify it in the Action, which is why its important to include that step if you don't want photoshop to crash.
Answer: If you know exactly what adjustments you require and they will be the same for each picture then an Automated Batch process would be your best option. Create a Macro and record all your adjustments save that Macro and then head on over to, File > Automate > Batch Select the macro you created with the folder of all your files and hit Ok.


Silence about Syria deafening

Question: With reports claiming that nearly half a million Syrians have been slaughtered since the beginning of the war.
Why did the West including the US not get involved and intervene in the largest massacre in the 21st century so far?
Comment: Curiously enough, some other people [complain that the USA and NATO intervened too much in Syria](politics.stackexchange.com/questions/11302/why-wont-nato-leave-syria). The NATO **did** force Al-Assad to give up his chemical weapons stocks (although with some controversy), and supported with weapons and training opposition groups. But the opposition groups failed to form a coherent alliance, with some of them joining the islamist band after they had been supplied with Western weapons...
Comment: Although we condole with the people of Syria, what answer are you expecting? *"How could the global superpowers sit back?"* is a far too broad and opinion-based question to qualify for StackExchange format.
Comment: The US IS involved (illegally might I add as they are violating international laws). This question has too many moving parts and is very complicated and hard to answer. Be more specific. Simplest answer would be US and Russia are in a proxy war in Syria.
Comment: Your question is about two different subjects. Perhaps you should edit it to focus on either topic? Otherwise the  question is leading and becomes very hard to answer factually.
Comment: Have now edited.
Answer:
Turkey wants a neo-Ottoman realm in north Syria and Iraq, that + stop Syrian Kurds from linking their cantons (note that it cooperates with Iraqi Kurds at the same time)
Qatar, Saudi Arabia & co. want Iran's influence out of Syria and a direct continental pipeline to the EU
Iran wants a pipeline of it's own to the EU and it believes that if Damascus falls then Teheran will be next
Israel just wants every organized army around itself to be super-occupied with something that is not Israel
Russia wants a strategic base smack in the middle of the middle east
US doesn't want Russia's strategic base, wants Iran isolated and supports Qatar, Saudi Arabia & co and their friends (the Idlib jihadi groups, which are actually enemies of the US, but more on them later)
100+ different more Jihadi or less Jihadi groups in Idlib province want slightly different and competing version of this or that califate, more US aligned, more Saudi aligned, more Turkish aligned, more independent, women dressing slightly more, or slightly less etc etc, a clusterfuck of minor interests basically
IS wants global domination :tadadadaaaaam:
Iraqi central government wants control of it's own country in face of US&Turkish backed Kurds, Iran-influenced shia groups and Saudi-influenced Sunni groups
Syrian government wants all of Syria for itself and if anybody will be building any pipelines it better be over the ground they control
Iraqi Kurds want to control the oil rich regions around Kirkuk and Mosul without getting controlled by the central government
Syrian Kurds want to link up their cantons and achieve some sort of independence from whoever wins the war
...

and the list goes on. Which side do you suggest to support? What exactly is the international community supposed to do?
One thing that is certainly not going on is "international community sitting idly by". In fact, it's doing far too much to be good for Syria.
I suggest you follow this for a while https://www.reddit.com/r/syriancivilwar/ and develop a bullshit filter of your own and figure it out for yourself, because almost no source will give you the whole truth of what is going on there.
Answer: The fact of the matter is that the U.S. has been involved since the beginning and has been instrumental in creating the conditions that lead to these deaths. You can think of Syria as a key piece on the Grand Chessboard. The reason Syria is such an important strategic country is because of its geographical position in the region, its relatively secular culture
(when compared to other Islamic nations), and political alliances with certain "naughty" countries -- according to the U.S.'s definition.
Keep in mind that the Obama administration has maintained that if the U.S. can get its allies to be the boots on the ground then they will support them with drones. (I would reference an article here, but my rank only allows 2 links per post)
This is a topic that can lead down many rabbit holes, because of the sheer volume of analysis on the subject. So, let us begin with one important piece of the puzzle: the U.S. government had been planning the overthrow of the Syrian government since at least 2001.
The Plan -- according to General Wesley Clark -- was to take out 7 countries in 5 years: Iraq, Syria, Lebanon, Lybia, Somalia, Sudan, Iran.
Well, that was the goal, of course, but things haven't gone as smoothly as they had hoped -- mainly because of Russia getting involved. Which is why the U.S. got involved with the Ukraine... as retaliation against Russia for getting in our way. Putin's had been working towards absorbing the Russian portion of Ukraine via a Ukrainian succession referendum. But I digress...
How many of these countries has the Bush and Obama administrations successfully or actively attempting to create regime change?

Iraq: COMPLETE
Syria: War In Progress
Lebanon: ?
Lybia: COMPLETE
Somalia: War In Progress
Sudan: ?
Iran: Conducted Media
Demonization Campaign & Cyber Warfare so far. Russia stepped-in
politically and delayed progress.

Now that we have context established, lets go back to your original question:

Why did the West including the US not get involved and intervene in
  the largest massacre in the 21st century so far?

The answer is because the west began the war as a NATO effort to institute regime change in Syria and overthrow Assad. The more death and carnage there is with this conflict, the more pressure that puts on the Assad regime -- with the hopes of leading to his overthrow and/or death.
Luckily for Assad, he has Russia on his side. Russia (Putin) has backed Assad for their (his) own reasons. I think, mainly to push back against the U.S. and assert their regional dominance.
There's also the point that the U.S. wants to run an oil pipeline from Iraq to Europe via a Syria that has a US-controlled puppet-regime.

Silence about Syria deafening


Can someone explain the idea of revenue per "X", from good to great by Jim Collins?

Question: I'm not sure what is meant by improving revenue per "X", does it mean to increase the amounts of "X"? Does it mean to increase the revenue made per "X", and if so, why wouldn't you choose time to be the "X". E.g. what would a lemonade store choose as their "X" and why?
Comment: Can you provide the sentence where you came across this and maybe some context?
Comment: A quote from the book containing this term would be helpful.
Answer: In "Revenue per X" the X is usually the thing sold. For a lemonade stand X might be a glass of lemonade, and you might discuss the revenue as "revenue per glass", which would be the price of a glass of lemonade.
As an alternative you might consider "revenue per customer" which for a lemonade stand is every person who visits the stand.
The difference gives rise to two common ways of a company increasing revenue, for a lemonade stand being increasing "revenue per glass" (i.e. raise the price) or "revenue per customer" (persuade customers to buy more than one glass).
Comment: And I guess per the OP's comment you could choose time to be the "X" - revenue per hour, get more customers into the store per hour.


Argon instead of nitrogen

Question: I read through https://simple.m.wikipedia.org/wiki/Argon it says that argon can be used in doping. If humans have to settle down on a planet, that has the nitrogen of earth swapped for argon, can they or the next generations adapt?
Answer: There shouldn't be a big problem.
In doping, Argon is used to create low oxygen conditions. Athletes train in low oxygen conditions to stimulate overproduction of red blood cells and greater oxgygen carrying capacity. However in the latest version of the doping list, Argon isn't mentioned.  So Argon does not itself enhance performance.
Moreover, unlike Xenon, Argon doesn't have sedative or narcotic properties.  The action of Xenon is directly related to its large molecular weight, not its chemical actions. Like, for example chloroform, gases can induce anaesthesia without any chemical action.  Argon, however is lighter and doesn't have this effect. Lab rats were able to breath 70% argon without ill effects.
An argon-oxygen atmosphere should be breathable, though there may be some difficulties transitioning from nitrogen to argon as the inert factor in the atmosphere, so this should be done slowly.
There are lots of "how ever did it get that way!"  Nitrogen is a pretty common element, more common than Argon. And it is pretty ubiquitous in biological molecules. So, if you are being "hard", you'd need a clever explanation of what happened to all the Nitrogen, and how life exists without it, and if life doesn't exist on the planet, where the Oxygen is coming from.
Comment: /So Argon does itself enhance performance/  typo? Seems like it should be "does not".    But I am not confident enough to correct.    This once.
Answer: Nitrogen is the 4th most abundant element in the human body, after oxygen, carbon, and hydrogen. Every amino acid contains nitrogen, and thus every protein. DNA and RNA both contain large amounts of nitrogen, along with many, many other components of Earthly biochemistry.
We do not obtain the nitrogen we need directly from the atmosphere, we get it from plants capable of fixing that nitrogen in more biologically available form, and from animals that eat those plants. Humans could survive on such a world as long as their food supply lasts, but long-term survival of any form of Earth life would be reliant on recycling and importing of nitrogen or on concentrating what nitrogen does exist there.
Answer: Argon is a noble gas, so it's inert. It wouldn't cause too much trouble, but life would need to adapt to having less nitrogen to work with, as there's only trace amounts of atmospheric nitrogen on that planet.

Argon instead of nitrogen


How to fix braking problem

Question: My Shimano BR-Z57 front side pull brakes. Don't brake smoothly and jerks under braking. Does anyone have any suggestions on why & how to fix this problem?
Comment: Could be several things, though worn-out or dried-out brake pads are the first guess.
Comment: There isn't much here to go on; perhaps you could make it more likely to get an answer by adding a photo?
Answer: Possible issues (probably not a complete list - things I've seen)

Dirty rims - if the rim does not provide a consistent friction surface (there is dirt that makes one part too sticky or too slick - brake pad residue etc.) you will not get smooth braking.
Dents or blips in the rim - if the rim is wider or dented in some places it will affect braking smoothness.
Dirty brake pads - may not affect smooth braking but clean pads will improve general braking.

I'm sure others will have suggestions.
Comment: Point 3, not just dirty brake pads, but old ones go hard over time and produce some horrific grab/release pulsing   This brake dates from the mid 1980s so it could easily have old pads.      Point 2, an untrue rim will feel weird while braking because the caliper has to swing left and right to track it.   Also if the rims are as old as the brakes, they could be steel.

How to fix braking problem


Email addresses showing next to contact name

Question: I moved to a new gmail account. I have set it up on my Samsung S6. However, now when searching through text messages or contacts email addresses are being show next to the contact name. I have tried everything from unsyncing, restarting phone, removing the new gmail account and setting it back up. I have display only phone contacts which does not work since I have everything saved under the gmail. It is very annoying to see email addresses next to contact names when you're sending text. In general it is very annoying to see email address next to the persons name even under contacts. Any help is appreciated
Answer: I finally broke down and deleted the contacts that showed email addresses next to the contact name. Re-entered that contact and saved again and that fixed the problem. Not sure why, only after syncing the new gmail, it showed that way.
Answer: I refused to delete my contacts and history, so I figured it out. Go online to the email that you synced or just created, click the menu button, then click contacts. Somehow all the contacts that got messed up have been edited to the 'last name' being the email. That's why it shows up after the name. So just edit those contacts to have the correct last name or no last name. It worked for me so I hope this helps!


Gravitational potential

Question: As the height from Earth increases, the gravitational potential also increases. If I look at this from the definition of potential (work done in bringing a unit mass from infinity to that point) the potential value would be high for lower distances (from infinity), so does this mean that the Earth will pull the farther objects with more force?
Answer: The relation between force and potential energy is, in general,
$$
{\bf F}=-\nabla U(r)
$$
Using spherical coordinates, the unique component of the force (purely radial) is
$$
F_r=-\frac{{\mathrm d}U}{{\mathrm d}r}.
$$
Therefore, the value of the potential energy does not matter. What matters is its slope. Wherever is the zero of the potential energy, the slope of $U(r)$ decreases with the distance. Forces at larger distances are weaker than forces at smaller distances.
Answer:
As the height from Earth increases, the gravitational potential also increases.

This is not quite true.
First, Let's not make the approximation of constant $g$ which is valid for small distances from the surface of the earth.
$$dU=-\int \mathbf{F}\cdot  d\mathbf{s}=\int \frac{k}{r^2}dr$$
$$U(r_2)-U(r_1)=k\left(\frac{1}{r_2}-\frac{1}{r_1}\right)$$
Setting $U(r_\text{surface})=0$ that is surface of earth is zero potential.
$$U(r)=\frac{k}{r}$$
$$\lim_{r\rightarrow \infty}U(r)=0$$
As expected. The gravitational potential decreases as height increase if the surface is taken to zero potential.

If you make approximation that  $g$ is constant then
$$dU=-\int  -mg\hat{r}\cdot d\mathbf{s}=mg(r_2-r_1)$$
Then it look like  $U(r)\propto r$ but that is not true.
Comment: Wrong answer. If you write explicitly the limits of integration in the integrals, you'll realize that even putting zero the potential energy at the surface of Earth, the potential increases with the distance. If it would decrease, taking into account the relation between force and potential  (${\bf F}=-\nabla U$), there should be a repulsive force.

Gravitational potential


How do I animate a UIButton in a UITableView?

Question: I currently have a UITableView with each cell containing four UIButtons. I am placing an image for each button with a downloaded picture from online. I'd like to have the button fade in when the image is finished downloading. I know I can animate in the viewDidLoad, but I assign the image in the cellForRowAtIndex function. How do I go about animating just the UIButton at a later point in time when I update the UIButton with the image?
Answer: You should probably assign the UIButton a tag, maybe even define an integer tag to make it easy to read when you have four buttons.
#define CELL_BUTTON_ONE 9999

When you build the first button assign this tag:
[myButton setTag:CELL_BUTTON_ONE];
[cell addSubView:myButton];

Since I don't know where or how you load the images it is a bit hard to says what you should do. The idea is you get a reference to the UITableViewCell that owns the button you want to replace by an image. Anywhere you have a reference to a cell you can now go:
UIButton *buttonOne = [cell viewWithTag:CELL_BUTTON_ONE];
[button setImage:loadedImage];

Comment: +1 That's the right way to do. But, shouldn't it be [cell.contentView addSubview: myButton] ? And I think it is [buttonOne setImage:loadedImage forState:xxxxx]
Comment: I think you are right David:)
I usually do custom cells so I don't use the different cell views.
Answer: Do it in -cellForRowAtIndexPath. When your image has finished downloading, you'll call -reloadData on your table view. You can create outlets for each UIButton in your cell or you can just assign them a tag. Set their alpha to 0.0 in IB. Then when -cellForRowAtIndexPath gets called, if the image for that row/button is available, set it's image and then call -setAlpha:1.0 in a UIView animation block. Something like:
- (UITableViewCell*)tableView:(UITableView*)tv
        cellForRowAtIndexPath:(NSIndexPath*)indexPath
{
    // get a reference to your cell...

    // get reference to the UIButton in the cell
    UIButton *button = [cell viewWithTag:tagForButton];

    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.75];
    [button setAlpha:1.0f];
    [UIView commitAnimations];
}

The only issue I can think of is that you will need to keep track of the alpha value for a given indexPath based on your data due to cell re-use. So if your button1 in the current cell has already had it's alpha set to 1.0, you don't want to animate it again, but you will want to animate any other button's alpha that haven't been set yet. This image visibility state is something you will have to keep track of. It's not real hard to do, but there is more to it than just setting the alpha. Let me know if you need clarification.