How to use Google Music MP3s to set a ringtone/alarm?

Question: I have bought various albums through Google Music cloud service and they are downloaded for offline use on my device. How can I use one of these MP3s as a ringtone or an alarm?
It seems that the standard picker is not able to find them.
Comment: Isn't this a duplicate of http://android.stackexchange.com/questions/21293/how-can-i-turn-songs-from-google-play-music-into-ringtones ?
Comment: Could be a workaround but I would like to do it from Android, not using a PC in the middle.
Answer: If you are comfortable with copying files in a file explorer

Go grab ES File Explorer if you don't have a file manager already.
Make sure that root browsing is enabled and navigate to /sdcard/Android/data/com.google.android.music/files/music.
Hopefully you don't have too many songs stored locally, cause this is the not-so-fun part.  Go through song-by-song by selecting one and using Google Play Music to complete the action.  When you find which file is the right song, copy it (for ES, long press then select copy, could be different for other apps).
Now navigate to /sdcard/media/audio/<whichever_folder_applies_to_you> if you are on pre-ICS or /sdcard/<whatever_applies_to_you> if on ICS or Jelly Bean.  Paste it in (Hitting Paste on the status bar for ES) and you should be good.

If you aren't comfortable with copying files in a file explorer
If for some reason you don't want to copy, then still figure out which song is the right one.  Then when you go to set your ringtone/alarm/notification use the ES File Explorer entry that pops up.  Then navigate to /sdcard/Android/data/com.google.android.music/files/music and select the right song.
Comment: Only problem with this is you cannot specify which part of the song you want as a ringtone/alarm/notification. It's much better to crop the desired song into an appropriate length at the desired part of a song.
Comment: @ElefantPhace Nice point (+1), I don't know of any straightforward way to do that. :(
Comment: Read my answer.
Comment: Thank you for the info, but the ogher main problem is that all my mp3 files are named like 1.mp3, 2.mp3, 3.mp3 and I have hundreds of them. How can I identify the one to use?
Answer: You'll need to either use a different media player

Player Pro
Winamp
MX Player

I'm pretty sure all the above, plus others, can set ringtones from mp3 files directly from the player app itself.
Or, you can use any of the many different ringtone makers freely available on the Play Market.
I like Ringtone Maker
You'll just open the MP3, find the section you want to save as a ringtone and crop it, save it, then set it!
You will need to do some searching around your file system first to find out which songs are which though. As I remember, when you download audio from Google Play Music for offline use it doesn't save them with titles or anything really identifiable :/
EDIT
That's the problem with Google Play Music. You have to open them and listen to them. If you use one of the above mentioned players it should load the metadata for you, telling you the artist, album, title etc.
I know Player Pro will show you the path of the given file by long pressing it and choosing View Details. I'm sure the others would have similar functionality.
However, using these players to set ringtones does not allow you to crop and choose which part you want saved, they will just set the entire song as the default ringtone, which is probably not what you want.
Most likely you'll need a combination of the two:

Open Player Pro (or whichever other media player) and find the song you want, view details/properties and note the file path.
Open up Ringtone Maker (or whichever you choose) and navigate to that path, and open the file.
You'll then be able to select which portion of the mp3 you'd like to set as a ringtone.
You can then save the ringtone as either an alarm, ringtone, or notification to be used respectively.
Comment: That is the main problem I think, all my Mp3 are name like 1.mp3, 2.mp3, 3.mp3 and I have hundreds of them. How can I identify the one to use?
Comment: This comment is too long, I'll add to my answer
Answer: Just open google play with chrome browser (request desktop site)  goto my music find song and tap the 3 dots over by the tracks time click download it is now an mp3 you can add in the ring tones.
Comment: It's amazing to me that it's been more than four years, and the Goog still hasn't figured it out. Your answer works perfectly.
Answer: I went to the Google Play Music desktop site, found the song, clicked on the 3 dots by it, downloaded it, then emailed myself the mp3 file, then opened it in ES File Explorer, selected to open it in ES Media Player, clicked the 3 dots > Set Ringtone > Set alarm, voila.
Answer: Why not drop the mp3 directly into a directory either ringtones or alarms within the subdirectory of /sdcard/media/audio/notifications (this is for earlier than ICS)?
IIRC ICS had this directory structure on the SDCard, aptly, /sdcard/alarms or /sdcard/ringtones. Drop the appropriate mp3 in there, and it should be picked up the Android's Media provider and away you go.
If Google Music does not have any identifiable information pertaining the MP3, the filename will be used instead.
Comment: the directory hierarchy does not matter, as long as the base folder is `alarms`, `ringtones`, or `notifications` the MediaScanner will pick up it and place it accordingly. Also if you just placed it in notifications you'd only be able to use it for notifications...


Is it advisable to report a 56 percentile in GRE maths subject test if i am applying for Phd in neuroscience?

Question: I am an undergrad from biology background. I want to pursue a Phd in neuroscience and would be applying by the end of 2017. I read in FAQs of many graduate programs that they recommend taking a subject test but it's not compulsory. I prepared for two months and took the GRE maths subject test. I was able to solve all the calculus problems but couldn't do other topics like group theory and abstract algebra. I ended up with a score of 680 and 56 percentile. I have a good research background in this field and i am hopeful of a publication by next year. I don't want my 'non-math' background to hinder my application from getting selected for computational labs. Should I report this score?
Comment: The problem is similar but the context is different. I am asking specifically for neuroscience
Comment: I think this is a duplicate to [this post] (http://academia.stackexchange.com/questions/32171/should-i-report-a-48th-percentile-math-gre-subject-exam-score-for-programs-where?rq=1)
Comment: Well, the 56th percentile means you did better than half the people who took the exam.  IMO, that's nothing to sneeze at since you are not applying for a math program as such; I would think this could strengthen your application.  (If I were on a neuroscience admissions committee, I would simply set aside application components that don't help your case.  BUT I don't know if this is what is actually done.)
Answer: I am in your field, and I think the answer Peter L. Clark gave in the linked post is a good answer. My sense is that most Neuroscience programs don't take the subject exams too seriously. If you have a great score, then send it. But, if not,

A missing subject GRE score just means that we don't take this part of the application into account.

Personally, I would not send it.  That said, with a publication forthcoming and a strong research background, you will still be a competitive applicant, even if you do not send in subject scores. For reference, I had a strong research background and did not even take the subject matter exams. I do not think this hindered me in the application process at all. I applied to 10 schools and got interviews (and subsequent offers) from 5. I'm a second year Ph.D. student now.
Hope this helps.


Root locus, where do they leave the line parallel to imaginary axis

Question: I know how to sketch by hand root locus of simpler systems. Consider the root locus which Matlab gives for:
$$G(s) = \frac{1}{(s+4)(s+6)(s^2 + 10s + 100)}$$

I've marked the points of interest P1 and P2. When the following task was done during class the points were determined by solving for the breakaway point:
$$\sum_{j=1}^{n} \frac{1}{\sigma - P_j} - \sum_{i=1}^{m}\frac{1}{\sigma - N_i}  = 0$$
Which when solving yields a real solution and two complex conjugate solutions:
$$\sigma_1 = -5, \sigma_2 \approx -5 + j6, \sigma_3 \approx -5 - j6  $$
Obviously the breakaway point from the real axis is the real solution, however for the points P1 and P2 the two complex conjugate solutions were taken, respectively. I have been unable to find the reasoning behind that in my books and on the internet. My question is how do we determine the points P1 and P2 and why?
Comment: So your question is why the formula works? If so, I'm pretty sure you will find it in the book or take a look at control systems engineering by nise. Also, you will find another formula for determining the breakaway points.
Comment: The stability margin is a function of closest distance to axis, that's why
Answer: First, maybe you should not use \$P\$ as a notation for the breakaway points, since your formula use it for the transfer function poles. The poles are the value for witch the denominator is 0. Let's call your breakaway points, the "points of interest", \$B_1\$ and \$B_2\$ (and \$B_3\$ for the real one).
\$G(s)\$ has 4 poles:

\$P_1=-4\$ for \$(s+4)\$
\$P_2=-6\$ for \$(s+6)\$
\$P_3=-5+j\sqrt{75}\$, \$P_4=-5+j\sqrt{75}\$, the roots of \$(s^2+10s+100)\$.

\$G(s)\$ has no zeroes, there is no \$N\$.
To get the breakaway points, you need to solve:
$$
\sum_{i=1}^4 \frac{1}{\sigma-P_i}=0
$$
That is also:
$$
\frac{1}{\sigma+4}+\frac{1}{\sigma+6}+\frac{1}{\sigma+5+j\sqrt{75}}+\frac{1}{\sigma+5-j\sqrt{75}}=0
$$
$$
\frac{2\sigma+10}{(\sigma+4)(\sigma+6)}+\frac{2\sigma+10}{\sigma^2+10\sigma+100}=0
$$
$$
(\sigma+5)\left[\frac{1}{(\sigma+4)(\sigma+6)}+\frac{1}{\sigma^2+10\sigma+100}\right]=0
$$
$$
(\sigma+5)\left[\frac{\sigma^2+10\sigma+62}{(\sigma+4)(\sigma+6)(\sigma^2+10\sigma+100)}\right]=0
$$
The solutions to that equation are \$\sigma_1=-5\$ from \$(\sigma+5)\$, and \$\sigma_2=-5+j\sqrt{37}\$, \$\sigma_3=-5-j\sqrt{37}\$ from \$(\sigma^2+10\sigma+62)\$. Note that \$\sqrt{37}\approx6.0828\approx6\$.
Here you go, the coordinates of \$B_1\$ are given by \$\sigma_2\$, the ones of \$B_2\$ are given by \$\sigma_3\$.
Answer: The poles for determining the root-locus for an open-loop transfer-function \$H(s)\$ are found using
$$1 + K\cdot H(s) = 0 \Rightarrow K = \frac{-1}{H(s)}$$
The equation holds for any \$s\$ that solves the equation. If \$N > 1\$ poles are hugging in a single point \$\sigma\$, then that means that locally, \$K\$ changes proportionally to \$(s-\sigma)^N\$. This means that the first derivative of \$K\$ will be \$0\$ in this point \$\sigma\$. So we can find these points by solving for
$$\frac{dK}{ds} = 0$$
or similarly
$$\begin{align}
\frac{d}{ds}\left( \frac{-1}{H(s)} \right) &= 0 \\
&\Downarrow \\
\frac{1}{H(s)^2}\frac{dH(s)}{ds} &= 0 \\
&\Downarrow \\
\frac{dH(s)}{ds} &= 0
\end{align}$$
A break-away point is defined as the point where the poles leave the real axis. Similarly, a reentry point is where the poles enter the real axis again. However, complex poles can still be kind of "breakpoints" elsewhere on the complex plane, and the above relation will still hold.

Appendix
For rational transfer functions, you can get to the equation in the question by calculating the derivative.
$$H(s) = \frac{\prod_i (s-z_i)^{m_i}}{\prod_k (s-p_k)^{n_k}}$$
With \$k\$ and \$i\$ indexing all poles and zeroes respectively. \$n_k\$ and \$m_i\$ are the multiplicity of their respective pole or zero.
$$\begin{align}
\frac{dH(s)}{ds} &= \frac{d}{ds}\left(\prod_i(s-z_i)^{m_i}\right)\prod_k\frac{1}{(s-p_k)^{n_k}} + \frac{d}{ds}\left( \prod_k\frac{1}{(s-p_k)^{n_k}} \right) \prod_i (s-z_i)^{m_i} \\
&= \left( \sum_i \frac{m_i(s-z_i)^{m_i}}{s-z_i}\prod_{j\neq i} (s-z_j)^{m_j} \right) \prod_k \frac{1}{(s-p_k)^{n_k}} \\
&+ \left(\sum_k \frac{-n_k}{(s-p_k)(s-p_k)^{n_k}}\prod_{l\neq k} \frac{1}{(s-p_k)^{n_k}}\right) \prod_i (s-z_i)^{m_i} \\
&= \left( \sum_i \frac{m_i}{s-z_i} -
\sum_k \frac{n_i}{s-p_k} \right) \frac{\prod_i (s-z_i)^{m_i}}{\prod_k (s-z_k)^{n_k}}
\end{align}$$
So you finally get
$$\sum_k \frac{n_k}{s - p_k} - \sum_i \frac{m_i}{s - z_i} = 0$$


How does a giyur m'safek differ from a giyur l'chumra?

Question: Is there any difference betweeen a giyur m'safek and a giyur l'chumra? In either scenario is a female who undergoes either of these conversions prohibited from marrying a kohein?
Answer: One diffrence would be if we have doubts about the conversion such as if we don't know if the mikva the person immersed in had the proper amount of water. This would make the person a safek jew and require them to dip again, a giur misafek. Wheres a situation where there is an argument concerning a certain law of conversion and we try to be stringent and the person converted according to the lenient opinion and we wanted them to convert again according to the stringent opinion, that would be a giur lichumra. But in all probability whatever case you are talking about is probably an interchangeable term as Yishai said.
Answer: The terms are used interchangeably (see e.g. here). So you can't determine anything from the usage of the term.
In terms of prohibition to marry a Kohen, that will depend on the individual circumstance which required the conversion. Sometimes it is recommended out of an abundance of caution (e.g.), but that would not invalidate marrying a Kohen. On the other hand, if the doubt were greater it may.
So it is really a case-by-case thing, and no conclusion can be drawn from the specific phrase used to describe it.


iPad won't accept Verizon SIM

Question: I have an iPad 4 model #1459(wifi/cellular) tied into AT&T/T-Mobile
 my carrier is Verizon. Is there anyway to change my ipad to Verizon?
I dropped in a Verizon sim card but got an error message "Sim is not Valid". It states insert SIM card from a supported carrier or request that this iPad be unlocked by your carrier and to contact Apple for more info.
Comment: No iPad is carrier locked. What happens if you remove the SIM card and connect it to iTunes? Also, please edit in the version of OS on the iPad - it might just need an update to a more recent version of iOS. Lastly - ask us a specific question. Tell us what you want the end result to be - even if you don't know how to get there. Cheers and Welcome to Ask Different.
Answer: Why not work through this checklist from Apple before contacting either the Carrier support or Apple Support?

https://support.apple.com/en-us/HT201415

Since you have a specific error message, you might also jump to one of the last steps first. Back up the iPad and restore it to factory new settings and re-test the SIM card that you think should be active.

https://support.apple.com/kb/HT201252

I've needed to call Verizon to get a SIM card to be part of a shared pool of data, but any active Verizon SIM should work, so once you rule out the iOS software - re-verify that the SIM you have is truly active.
Answer: Try a settings reset  or set your carrier to custom  it may be a locked or un activated sim card.

iPad won't accept Verizon SIM


is it possible for covalent compounds to produce colour during flame test?

Question: I have heard it is the metal ions that are the reason for flame colour during a flame test. so in covalent bond, there are no metal ions does that mean covalent compounds don't produce flame colour. if not what is the reason, if yes why doesn't glucose produce colour. Also is it possible to identify whether a substance is ionic, or covalent with just the flame test. I have searched the web but there are no clear explanations.
Comment: When a compound is put in a flame, pretty much all bonds are broken, so it makes no difference whether they were ionic or covalent.
Comment: Glucose does not produce a distinct color because it is a hydrocarbon, so in combustion looks pretty much like other hydrocarbons. So, somewhere in your question is a conflict between compounds, metals, and how colors are made in the flame.
Comment: You have wrong assumption - there's no real connection between degree of covalence and  flame colour. Also most compounds of metallic elements is in fact primarily covalent.
Answer: The colors produced in flame tests are the result of electrons becoming excited and returning to their ground states, releasing photons of characteristic colors. Different colors from flame tests result from different energy gaps between the electron shells in different atoms. Since flame tests determine properties of individual atoms, they cannot be used to determine if a compound is ionic or covalent. In fact, bonds are normally broken when a compound is placed into a flame, so it would be nearly impossible to use a flame test to find anything about the bonding nature of a compound. Glucose does not produce a color when it is burned because it just undergoes combustion - more or less the same reaction that is creating the flame in the first place.
On the other hand, there are other ways to determine if a compound is ionic or covalent. Ionic compounds normally have ridiculously high melting points, and if you put an ionic compound into distilled water, it will conduct electricity. There are lots of tools to determine if a compound is covalent or ionic; however, a flame test is not one of them.


How do Accepted Answers work on User Experience?

Question: What are Accepted Answers and how are they different on User Experience?
Should I accept answers to my questions?
Should I refrain from answering a question with an accepted answer?
Answer: What are Accepted Answers and how are they different on User Experience?
Accepting an answer basically marks it as "This works for me!" and gives the accepted answer a green check mark to note it as accepted, and also gives a 15 rep bonus to the answerer.
Unlike many sites, on User Experience there's often no one acceptable answer however. Some users almost never accept answers to avoid giving the impression that only one answer is acceptable, and many of us wait a fair amount of time before accepting to see what other answers come in.
Should I accept answers to my questions?
Yes, accepting shows either you consider a solution to be "the best" or you have decided to go with a particular solution provided in an answer.
However, since there's often no one right answer, you should wait at least a day or two to accept an answer to see what other answers pour in; don't just accept the first answer. Accepting an answer gives the unfortunate impression that a question is "finished". Give the answers and answerers the respect they deserve by giving everyone time to answer and give the community time to evaluate and point out strengths/weaknesses in the answers to your question.
The first answer to your question might work, but if you wait until a couple more answers are added you can pick the solution that works best. If there really is not a best solution, not accepting an answer is also okay; you don't have to accept an answer for every question you ask.
Should I refrain from answering a question with an accepted answer?
Certainly not! As mentioned above, accepted answers mean a little less on User Experience. That doesn't mean an Accepted Answer is meaningless, but if you have an answer that's different from all that is posted that you think is valuable enough to post, by all means do.
Community voting will help show the worth of your answer and users of this site tend to read past the accepted answer to see all solutions. Don't be discouraged by the accepted answer, as long as you have something valuable to add, add it.
Comment: "However, since there's often no one right answer" - right, and the very quiet weekends :-)


Any link between Cubital Tunnel Syndrome and "chronic" tendonitis?

Question: Is there any evidence linking Cubital Tunnel Syndrome to "chronic" (persistent, non-healing) tendonitis or any other long-term/chronic issues with connective tissue in the elbow region?
Comment: I guess I'm wondering if Cubital Tunnel somehow causes swelling/inflammation around certain nerves that either cause tendonitis or the sensation of tendonitis...
Comment: +1 Great Question -- When I get some time I will answer this for you
Comment: Just a gentle *nudge* @Mike-DHSc... bounty ends in 3 days, after that I can't assign it to you even if you answer!
Comment: @Mike-DHSc Another ping. The only thing I came across was [this article](https://www.ncbi.nlm.nih.gov/pubmed/18210793) discussing causes of carpal tunnel syndrome and not mentioning tendonitis. It claimed that 15 cases of CTS out of those discussed were caused by tendon compression. [Full source](http://188.8.131.52:81/ch/reader/create_pdf.aspx?file_no=200491313&year_id=2004&quarter_id=9&falg=1). That's not really a lot, but it might help. If  no one answers this question, I might give it a shot, but I'm just a layperson in this area and don't want to rely on my google skills...
Comment: @smeeb My apologizes, a busy couple of weeks coming up.  Just a matter of putting together my thoughts and information I already have on this. If anyone else has anything to add in the mean time that would be great. Don't need a bounty to help you out. I'll gladly help out soon as I get some time!   Really sorry to keep you waiting.
Comment: @Narusan-in-coma - I believe in your "google" skills -- LOL.  Not like you need my permission but add on anything you feel would help!  Not sure when I'll get time to post but the more information the better!!!
Answer: Sorry for the wait!

To orient ourselves first trace the Ulnar Nerve distally to the hand from the Brachial Plexus (BP) and then review how Cubital Tunnel Syndrome ties in (it's neurological relation).
Let me know if you have a more specific question (this is most commonly what is seen -- can go into other areas.  Sorry for so many abbreviations - these are old ortho notes.

Nerve Entrapment - UE
Ulnar Nerve (C7, C8, T1)
1.) Arises from medial cord of BP
2.) Travels down medial arm (anterior compartment)
3.) Once it reaches the medial epicondyle run b/n brachalis and the medial head of the triceps.
4.) Crosses elbow on medial under ulnar groove.
5.) Right after it crosses the elbow It's travels b/n the heads of the FCU (called the cubital tunnel) then it.  Innervates FCU ulnar (humeral and ulnar) heads and FDP (Medial Part) (MOTOR)
6.) In the forearm it travels b/n FDS and FDP.
8.) Exits forearm medial to FDP tendons and just before it crosses wrist gives off a branch Dorsal Brach (SENSORY)  Dorsal side sensation to medial ½ 4th finger and 5th finger
9.) Travels through Guyon Tunnel (or Canal) at wrist above flexor retiaculum and gives off 2 branches:

Deep Branch Supplies (MOTOR)

Oppones Digiti Minimi
Adductor DM
2 Lumbricals (on ulnar side)
Dorsal and Palmar Interossi
FPB

Superficial Branch (SENSORY)

Palmar side sensation to medial ½ 4th finger and 5th finger

Ulnar Nerve Compression Syndromes
Cubital Tunnel Syndrome:

Compression Sites:

Ulnar groove
Cubital tunnel (where nerve passes b/n 2 heads of FCU)
Medial head of triceps – seen as a result of hypertrophy of that
muscle
If nerve is unstable in ulnar groove and it starts subluxing, can result in neuritis, but overtime with scaring can lead to compression.

Etiology:
Syndrome associated with frequent elbow flexion (ulnar nerve on stretch).

Weight lifting
Constricting fascia bands (ligament of strutres)
Masses (bone abnormalities, swelling and ulnar nerve subluxation)

Clinical Picture:

Will be medial elbow discomfort (similar to medial epicondyltis)
Parastesis of the medial ½ of the ring finger and 5th finger
Repetieve flex/ext activites may excepabte these symptoms
Orthopedic Testing /  (+) tinnel
Atrophy of hypothenear group
Decreased grip strength

Treatment:

Night splints to help keep elbow extended (to avoid stretching of
that nerve)

Surgically:

Decompression, medial epicondyleptimy or transposition ulnar nerve
more anteriorly. (so flexion will not stretch nerve)
Ulnar Nerve Transposition

Images From: https://www.physio-pedia.com/
Comment: Thanks so much for this @Mike-DHSc (+1) - so in layman's terms (I'm a software guy, so a lot of the above is greek to me!) when I do a bicep curl, it feels like someone is stabbing my *cubital fossa* (elbow "pit"?!). After a few sets + reps, the pain goes away entirely (but only temporarily). My *theory* is that my Cubital Tunnel Syndrome (I was diagnosed by a neurologist a few years back before I had symptoms) is causing the pain but that doing a few sets of curls somehow pumps blood into "the right places" and relieves whatever compression/pain might be going on. Any thoughts/insights there?


How do I install floating shelves on drywall using a drill?

Question: I am installing some some floating shelves on drywall using a drill. What's the best way to ensure the shelves are a sturdy foundation that can support stacks of heavy books? Should I use a stud finder and attach the shelf bracket directly to a wall stud? Or will the shelves be sturdier if I use wall anchors? If so, to determine the appropriate wall anchors, should I take into account the weight of the shelves and the contents I intend to store on the shelves? Finally, are butterfly or toggle anchors preferred for this project?
Comment: Did the floating shelves come with installation hardware?  That's usually your best bet.
Comment: The way to use a drill to attach floating shelves to drywall is to use the drill to drill through the drywall so you can attach to something behind it that will support it, like studs.  Floating shelves have a lot of leverage, which stresses the attachment with torque as well as just supporting the weight.  Drywall doesn't have the strength for that.
Answer: Attach the shelf brackets directly into the studs, no ifs, ands, or buts. Wall anchors are OK for light loads, but I wouldn't use exclusively them for a floating shelf, even if you weren't putting books on it. I would use at least 2" #8 screws, so you have at least 1.25" going into the actual stud. If your shelf bracket is rather thick, go with 2.5" screws.
If your shelf is short, or you want it positioned such that you'll only hit one stud, you should use wall anchors on the ends in addition to screwing into that one stud. The wall anchors in that case would be more to keep the shelf from rotating. Toggle anchors are certainly appropriate for this case, but the plastic anchors would be OK as well, since they're not intending to support much weight in this scenario.
I like a magnetic stud finder such as the StudBuddy, as it's dead simple to use.


Rails many-to-many :through association: associated object is not updated after destroying the association object

Question: As I am new to Rails, there is may be a trivial solution. But I could not even find this exact issue somewhere. Other posts deal with destroy vs. delete (I tried both with the same result) or just do not mention how the associated object behaves.
My problem: I want to create a many-to-many association via :through. When I delete an association (i.e. the relation object, not the related objects) I expect that this association is removed (updated) in all model instances of the associated objects. But this does not fully happen.
My example:
Meeting < ActiveRecord::Base
  has_many :participations
  has_many :users, :through => :participations

User < ActiveRecord::Base
  has_many :participations
  has_many :meetings, :through => :participations

Participation < ActiveRecord::Base
  belongs_to :meeting, :foreign_key => :meeting_id
  belongs_to :user, :foreign_key => :user_id

When I create a new association, the associated objects are updated accordingly:
u = User.find(...)
m = Meeting.find(...)
m.users<< u

The same when creating the association this way:
m.participations.create(:user_id => u.id)  # this requires to make the user_id attribute accessible

When I now look at the associated user model instance, it got updated as expected:
u.meetings >> contains the newly created association to the meeting m

When I destroy (not delete!) this association, the associated object is not updated as I expect it:
m.users.find_by_user_id(u.id).destroy
m.users >> []
u.meetings >> still contains the destroyed association to meeting m

I would have expected that u.meetings is updated and empty ([]). Adding validations didn't help to solve this:
Meeting < ActiveRecord::Base
  validates_associated :contacts
or
Participation < ActiveRecord::Base
  validates_presence_of :contact, :interview

What am I doing wrong or what am I missing here?
I am using Rails 3.2.8
Thanks to everyone who is willing to help me.
Answer: You should be doing :dependent => :destroy.
Meeting < ActiveRecord::Base
  has_many :participations, :dependent => :destroy
  has_many :users, :through => :participations

User < ActiveRecord::Base
  has_many :participations, :dependent => :destroy
  has_many :meetings, :through => :participations

Participation < ActiveRecord::Base
  belongs_to :meeting, :foreign_key => :meeting_id
  belongs_to :user, :foreign_key => :user_id

This will make sure to destroy the participation if either of the associated user or meeting is destroyed.
Comment: Sorry, I didn't mention it. But I tried that, too. I also checked all callbacks and participation.before_destroy and participation.after_destroy were triggered. But still, if I call u.meetings it is not empty as expected. It still contains the just destroyed association. It is deleted within the db but not removed from the meetings enumeration of the u instance.
Comment: I think you are looking at the cached data then. Try doing `u.reload` and then try `u.meetings`.
Comment: Ok, thank you a lot. Both approaches `u.reload` and `u.meetings(true)` work as expected and do refresh the (previously instantiated) user object `u`. Just to learn about Rails: why is the `u` instance being updated after the association was created but not after it was destroyed. Is there any meaningful reason? This way, I always have to refresh instances to make sure not to show outdated information.
Answer: You should update your model with the following relationship option:
dependent: destroy

Which will call destroy on the associated objects.
Reference: http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#label-Deleting+from+associations
Answer: I guess the problem could be like this. In your example,
m.users.find_by_user_id(u.id).destroy
m.users >> []
u.meetings >> still contains the destroyed association to meeting m

u and u.meetings were already loaded before m.users.find_by_user_id(u.id).destroy. Then u.meetings output the cached data.
You can try u.meetings(true) or u.reload; u.meetings to see if there are any difference.


Removing noise coming from 3.5mm audio jack

Question: I see there is a question similar to this here. However its solution was not for everyone, and doesn't help me. Any time a key is pressed either remotely through ssh or directly connected there is a noticeable click sound from the speakers like the information is being processed. Also when i install something or run a program that displays text it will make a louder noise from the other background noise. I already tried going into config.txt to make some changes i read about but that doesn't help at all. Is there something i can change here on the pi or do i need to settle with an hdmi to aux adapter. Also my speakers are 3W 4 Ohm and i heard there may be problems with low impedance speakers to begin with but i will try and report any solution.
Comment: I think using USB sound card, and digital power amp might be more quiet. https://raspberrypi.stackexchange.com/questions/96756/how-can-i-amplify-my-voice-in-real-time-just-like-a-microphone-does
Comment: You can't, use a USB sound card or HDMI. See my explanations of the output circuit for why that is the case https://raspberrypi.stackexchange.com/a/72599/71180
Answer: Sounds like you have embedded noise sallying your acoustic pathway.
The ultimate solution is to have an isolated sound card installed on your GPIO header. An isolated sound card breaks any chance of currents flowing from the Pi through the acoustic pathway. For that reason, as no noise can flow to your acoustic pathway, you will not hear the embedded noise any more.
Probably the highest quality sound will be when the isolation is just after the GPIO header. In this case the isolation is between the Pi and the audio codec.
Some sound cards are well designed and don't require complete isolation, however it can be a case of purchase and test to find out.


My kitten was desexed young?

Question: I got my 10 week old kitten yesterday and he was desexed 3 days before that. That seems too young. Wondering what effects this could have on his hormones, personality and development?
Comment: While the question http://pets.stackexchange.com/questions/1848 is similar, it's about the *recommended* age for desexing a cat. This question is about the effect of early desexing. Since early desexing is becoming common in shelters, I think it's good to address this issue.
Answer: I don't think you need to worry. The ASPCA says:

It is generally considered safe for kittens as young as eight weeks
  old to be spayed or neutered. In animal shelters, surgery is often
  performed at this time so that kittens can be sterilized prior to
  adoption.
Answer: All is good! SPCA's spay/neuter the kittens super young, this helps them to be adopted MUCH faster. The surgery is more risky but you won't have any bad side-effects from it.
Comment: If you get a chance may post an answer at [the dupe](https://pets.stackexchange.com/q/1848/13) where the answers talk about months of age as opposed to weeks of age.
Answer: One of the biggest effects of this is that he will (hopefully) never develop a marking habit. Cats usually start marking around the time that they go through puberty and it's more common in male cats, so it's definitely a good thing that he's fixed already

My kitten was desexed young?


Word/phrase for the activity of hiding mistakes

Question: What word/phrase can I use to describe the activity of hiding a stupid mistake/incident, such as quickly cleaning up tea spilled by accident before anyone could notice?
Comment: What about 'concealer'?
Answer: This is called a:

cover-up : a usually concerted effort to keep an illegal or unethical act or situation from being made public

The definition in Merriam-Webster talks about illegal and unethical acts but this can be more widely used to "cover up" anything from small to large.
Note that "cover up" can also be used as a verb which I think is what OP is looking for.
Comment: While my answer can also be associated with hiding illegal or unethical activity, my impression is that your answer is almost always used in this way and might not fit with the example of spilled tea.
Comment: Hmmm, The fact that you are sweeping something under the rug means that you are trying to hide it from someone who presumably won't be happy to see it.  Therefore I'd call that unethical.
Comment: _Sweeping it under the rug_ works if all you're doing is attempting to avoid temporary embarrassment over a mistake you've made (like spilling tea). I'd still reserve _cover-up_ for actual wrongdoing.
Answer: Not a single word, but one phrase used for this situation is to sweep it under the rug.
Comment: @shampa - don't forget to accept the answer. Voting up is not enough if you think that who answered your question  has given to you the correct answer.
Comment: This is a good phrase for fixing something quickly, but it's worth noting that it carries the additional meaning of an attempt to prevent discovery of a problem rather than a genuine solution that happens to happen before someone finds it.
Answer: You might use furtive, an adjective, or furtively, an adverb, to describe to wiping up.

Since this was the second time this week I had spilled red wine on her carpet, I furtively blotted with a paper towel. I could hear her footsteps approaching.

or

Since this was the second time this week I had spilled red wine on her carpet, I made a  furtive attempt to blot with a paper towel. I could hear her footsteps approaching.

This carries the sense of being done secretly or by stealth.
Answer: I don't think there is a single word or common phrase for what you are describing that doesn't also carry additional meaning that you may not want.
The other solutions offered so far (cover-up, sweep under the rug) carry the added implication of impropriety, and in fact, neither one necessarily means the problem has even been truly solved, only hidden.
The closest words that I would recommend would be those that mean to fix the problem that carry the added connotation of putting things back to the previous state, making a perfect repair.
These would include (depending on the kind of problem):

rectify
fix
clean up
make right
remedy
repair
right
straighten out
put back

I would couple one of these words with something that indicates that it's happened before anyone else can see it.

"Immediately rectify"
"Make it right before anyone notices"
"Hurried to fix it"
"Put things back before the mistake was discovered"

In a more corporate/organizational context, you may want to use something like "damage control" or "disaster management," but that doesn't necessarily imply fixing the problem before it does any damage, more about just minimizing the damage and fixing things as well as possible as fast as possible.
Finally, for something like spilled tea, you could use descriptions of the action of fixing it to suggest the kind of immediacy you are looking for. If this is a narrative, you could say that he used his shirt to wipe it up and then looked around to see if anyone noticed, as an example. Whatever the particular problem, there are going to be options like this.


What is the difference between differentiation and phenotype switching?

Question: I am trying to model bone remodeling process and I wonder what is the difference between phenotype switching and differentiation. I am relatively inexperienced in biology. Please explain me with examples related to this context. Thanks in advance.
Comment: Welcome to Bio.SE! What attempts to answer this question have you already taken? We ask that all question posters here attempt to search for an answer to their own question and explicitly indicate what research they've already done, what they learned, and what is still confusing or unknown to them. Our goal is not to simply be an answer site, but rather a site that promotes self-learning with some expert help along the way :). Please take a moment to edit your post with this additional detail, and it will likely be received more positively by our community. Thanks!
Answer: Differentiation is a process which occurs in multiple steps. A precursor cell for example a mesenchymal stem cell can proliferate (divide/multiple).  The stem cell can commit to become a progenitor cell (osteoprogenitor cell) which can still proliferate but has acquired the possibility to differentiate to a different cell type. In some cases or when specific conditions are met,the progenitor can differentiate to a pre-osteoblast and finally to a mature osteoblast.
The differentiation process require the activation of a specific transcription program and leads to large changes in the cell like morphology, size, and function. Once differentiated, the cell cannot proliferate anymore and loss the capacity to divide.
Phenotype switching can be broadly defined as any change in the phenotype like morphological change, expression of specific biomarkers, etc. In the context of differentiation phenotype switching refers to the acquisition of a specific differentiation marker usually a transcription marker like Runx2. While they might not be a large morphological change, the fact that the cell express this transcription factor indicates it is switching phenotypes and starting differentiation.
In summary: differentiation is process which occurs in multiple distinct steps. Differentiated states are characterized by a specific morphology, acquisition of key bio markers (usually transcription factors), loss of the capacity to proliferate, and a cellular specific function. Phenotype switching refers to the time frame when a cell changes from one phenotype to another; when it acquires or loss a defined morphological state or key markers.
Comment: Both differentiation and phenotype switching are terms which are used in intense research areas. Their definition will get revised in the next decade for sure. The definitions I have highlighted are what you will classically find in most publications but in reality it is difficult to define specific steps in a differentiation process because it is usually a continuous process.  Phenotype switching is even worse to define as it assumes that once classified to a category a cell does not have a dynamic phenotype: a cell which proliferate change phenotype as it goes through the cell cycle.
Comment: Thank you very much for the response. Differentiated cells lose the ability to proliferate. Does that mean they don't divide forever? Do they die?
Comment: Technically yes they should not divide. Theoretically, these cells could accumulate genomic mutation (UV, chemical environment, etc) and become cancerous but I'm unsure if this has been convincingly shown in the literature.
Yes differentiated cells can die by different mechanisms including apoptosis and necrosis, and be replaced by others cells. A good example would be neuronal cells.


Has there ever been a successful copyright infringement suit against someone using a small amount of a protected work in an academic publication?

Question: I am familiar with what the US Code says about copyright and fair use, and am specifically interested in actual practice regarding academic publications which use small amount (under 10% of the original) of a protected work, without obtaining permission. Specifically, I would like to know if an infringement suit has ever been successful when the amount of copying has been under the prevailing "substantiality" threshhold, and the copying was in an academic publication. I'm not asking what might happen or whether I should ask permission. U.S. cases and non-U.S. cases would be relevant (to the extent that "fair use" concepts exist in other systems). Alternatively, if you know of a case where the copier prevailed specifically because the use was in an academic publication, that would be relevant.
Comment: +1, I would love to see if any examples can be given. That being said, the case doesn't have to be successful against the alleged infringer to be damaging to them. Depending on their agreement with the publisher, it might be very costly to defend the suit, and/or the article might be withdrawn. These possibilities might occur independently of whether the author ultimately wins the lawsuit.
Comment: What's your underlying question here? What difference will the answer make to you? As it stands, this is very broad, and it's hard to see the usefulness of an answer that says "in Judisdiction X, Y happened" if you're not in Jurisdiction X. NB "under 10%" is not necessarily a "small amount": to reuse one single image from a protected work without permission is going to raise concerns.
Comment: Even if there has never been a lawsuit over academic fair use, I wouldn't consider that as strong evidence that it is a good defense.  My impression is that academic publishers are extremely risk averse regarding fair use.  If they see even a small chance of being sued (and even if they think they would likely win), they typically insist on getting permission in advance from the copyright holder.  This means fair use never even comes up in more than a small fraction of the cases in which it might have been relevant, so it hasn't been tested as thoroughly as one might wish.
Comment: EnergyNumbers, the underlying question is whether academic publication is *de facto* if not *de jure* a bullet-proof defense against infringement. If the courts have ever found a journal / author of an academic work to have infringed, given an "insubstantial" amount of copying, that would argue against this hypothesized "rule"; if this has happened many times, it would refute the conjecture, and depending on the cases, could obliterate alternative conjectures. Available evidence so far shows a lack of decisive cases. I'm trying not to separate text and image right now.
Comment: This is not an answer to your question, but two considerations are still in order: * What matters is not whether you copy a certain *fraction* of the original work (say, 10%), but instead the amount you copy. If you copy half a page without attribution from a 500-page book, then that's just as wrong as if you copy half a page from a 6-page conference proceedings. * There are doubtlessly far fewer legal actions about copyright infringements than  cases of *academic misconduct* investigations because someone points out that you copied a page from somewhere else without attribution.
Comment: Bill Barth, I did want to exclude settlements and withdrawals, because I'm looking at the legal issue and not the practical "what should I do" question.
Comment: AnonMath, that is absolutely correct. I'm basically asking for any amount of high-hanging fruit. This is a situation where silence is uninformative, and only specific decisions for or against reveal anything about the nature of the legal rule.
Comment: As you say, this isn't an answer to the question.  You are addressing plagiarism, not copyright.
Answer: One case in a similar direction is Sundeman v. The Seajay Society.  A researcher included quotations from an unpublished work in a presentation; this was upheld as fair use.  There's some discussion of the case and the outcome from the Columbia copyright office (have to scroll down a little bit).  There are some other related cases listed on the same page, e.g. involving fair use of copyrighted images in less academic publications.
Answer: Half an answer...
I no longer have a copy of Permissions: a survival guide (lent it to someone and never saw it again) but from memory, it discusses a few cases along these lines, particularly from the scholarly-art-monograph world.
(While the XYZ estate can't stop you writing about XYZ, they can make it very difficult if they refuse you the rights to use any of their visual artwork... and publishers get nervy about claiming fair use on things they would normally expect to pay fees for.)
Unfortunately, it's been a while since I read it and so I don't recall if any of them got as far as a legal case; I suspect the publishers usually folded. Worth taking a look if you can find a library copy, and seeing if it names specific cases, as these might be just what you're after.


Can you tell how ripe a banana is by the actual fruit not the peel?

Question: Hi I am doing a research project on banana ripeness and cannot find a way to tell the ripeness of a banana from the inside of it. I cannot use taste to measure the ripeness but I would really like to have a chart of some kind and if possible a url where you found the chart. Thank you!
Comment: Can you explain what you're actually trying to accomplish? Why would a chart be necessary?
Answer: Ripe bananas are softer and sweeter. You can pretty easily tell how ripe a banana is simply by biting or cutting into it, or even poking it with a finger. Ripe bananas are also more prone to bruising, which is visible on the inside of the banana as well.
If you really want to try to measure, you could indeed try to measure the sugar content. As bananas ripen, they get sweeter because starch is converted into sugar, so the sugar content should indicate ripeness. You'd need a refractometer to do that, not generally an everyday household item.
Comment: Wouldn't you need to know the ratio of sugar to starch rather than absolute sugar content?
Comment: @Carmi I don't think so. The sweetness you're tasting as it ripens is just the sugar, not the lack of starch. And in any case, yellow bananas are all the same variety; the starch content is not really going to be particularly variable. I don't know exactly how constant it is, but it's definitely close enough for a first approximation, especially for a research project like this.
Comment: The sweetness is certainly just the sugar. However, with regards to ripeness, it seems to me best defined as how much of the starch was converted. Wouldn't the starch content vary by soil, latitude and season?
Comment: @Carmi I know that the ratio of sugar to sugar plus starch (lower error than sugar to starch) might be a better measurement. But just measuring the sugar is probably good enough, and way better than anything else you can do that easily. Bananas really aren't very variable.
Answer: I think that the best, most accurate, measure of the ripeness of a banana is the ratio of sugar to starch.
The absolute sugar levels (ratio to mass) may be misleading, as only starch is converted to sugar, and the amount of starch is variable.
If you don't need very high accuracy, you may be able to use colour as a proxy for sugar content. The banana flesh will turn darker as it becomes sweeter. I know that hospitals use a device for checking if newborns are jaundiced. It basically measure the "yellowness" of the skin. Something like that would work well here. At the very least, a digital camera and computer will give you a decent sense of relative yellowness.
Comment: A digital camera and computer and very very controlled lighting will get you started, maybe, but the difference in color is fairly small and digital cameras aren't that precise.
Comment: @Jefromi Agreed, the difference is fairly small until the banana goes a little over-ripe. I did recommend professional equipment too, but it's probably a bit much for this project, which sounds suspiciously like homework.


Different versions of libdc1394?

Question: I'm working on a project that uses libdc1394 to interface with Point-Grey Firewire cameras. We build the code on Ubuntu 8, Timesys, and Ubuntu 9 primarily. We usually use the package manager for most dependencies on the Ubuntu's, and the Timesys installation seems to be compiled from source.
Now here's the part that confuses me. I can't figure out what version of libdc1394 is on the Timesys installation. Looking at the library files, I can find a file named libdc1394.so.20.0.0. But these are the header files that I have:
dc1394_control.h      dc1394_register.h  dc1394_vendor_avt.h
dc1394_conversions.h  dc1394_utils.h

They're in a folder named dc1394. From what I see on the Ubuntu 8 package (which is libdc1394 version 1), I only see dc1394_control.h. And it's in a libdc1394 folder.
From what I see on the Ubuntu 9 computer, which uses libdc1394 version 2.2 (that's the version in the repository), I have a dc1394 folder and then an include directory that looks like the copy I find here: https://libdc1394.svn.sourceforge.net/svnroot/libdc1394/trunk/libdc1394
I can't find anything about a major change between version 2.0 and 2.2. From the sourceforge page, it looks like the 2.0 version is similar to the Ubuntu 9 version.
Any idea why it seems I have 3 different versions of the library? I understand why Ubuntu 8 and Ubuntu 9, but not why the copy that we have installed on Timesys is different.
Once again, I'm decently sure the one on Timesys was compiled from source. I wasn't around when they did that though, so I don't know for certain.
Answer: Use ldd to see the dependencies on the Timesys executable. That'll tell you WHICH ONE it's loading.

Different versions of libdc1394?


What is the name of the movie where a guy gets a bullet to the head, and survives because of a gel like gauze?

Question: Does anyone know the name of the movie where a guy gets shot in the face, but his friend immediately puts a weird gauze-like gel on that stops the bullet from going any further? The gel wraps around the wound and stops the damage.
Comment: Please go to https://scifi.stackexchange.com/tags/story-identification/info and answer as many of those questions as you can, editing them into your question. It will help us help you.
Comment: Under easy questions, when did you see it? In what country? What language? Live action or animated? In theaters? On TV? Online? Did it seem like it was originally made in a different language? Do you remember why the guy got shot in the face, or by what sort of weapon? Do you remember if the gel was magic or science? Do you remember anything else that happened?
Answer: Could it be Kingsman: The Golden Circle?

 Audiences believed Hart was a goner at the end of Kingsman: The Secret Service, but a flashback sequence in The Golden Circle reveals that two members of the U.S.-run Statesman agency swarmed onto the crime to investigate after Hart was left for dead. The American spies, played by Channing Tatum and Halle Berry, go into first-aid mode by wrapping a plastic-like shrink-wrap around Hart's injured head.

When it's activated, the shrink-wrap rapidly inflates with a swirl of orange and blue gel, which then fills in the hole in his skull. This "bio-foam" is what keeps [the victim] alive until nanites (nano-scale robots) rush in to repair the damage. It may seem like another ridiculous made-up tool in the super-spy toolkit, but its premise is something actual scientists have already considered.

It contains a scene very much like the one you suggest (twice, actually). I came upon it by doing a Google search for film gel cures gunshot wound.
Comment: Huh, I don't usually see "identify" requests for such recent movies. It was released on DVD a little over a month ago.
Comment: Please add a spoiler alert! Too late for me... :-(
Comment: Kingsman it is !! Thanks a lot
Comment: @Offirmo: Oof... that would involve most of the answer, since it's largely quotes.
Answer: This sounds sort of like Kingsmen: the golden circle, in it there's a gel like substance which gets wrapped around a characters head in order to save them from a headshot.
Comment: Omg yes this is it ! It's right when harry gets shot in the front of the church ! Thank you so much


Redesigning h1 headings

Question: I've been given the task of redesigning the h1 headings on a travel website and have no idea where to start with obtaining some kind of secondary or primary research to get some useful data to drive how the redesign should look. Does anyone have any suggestions where to start?
Comment: Redesigning the H1s is a solution to what problem? Without knowing what the problem is, you (and we) can't know how to change them.
Comment: Hi Luke, thanks for your contribution to UXSE :) Can you provide a screenshot or some other information that might help us understand what the problem is with the headings and why you have been asked to address it? This will help inform the people reading the question where to start helping you with this task. Thanks!
Answer: Start with defining the problem. Why are they being redesigned? Legibility? Does the CMS let people but in too much text so they break the rest of the design? Are they confusing (users don't understand them)?
That said, I think you're going to struggle to find much research that's Header specific. I'd look at generic Typography research on ways to improve legibility, proportion and vertical rhythm.
Answer: Like what Luke said, you need first to define the problem. Because what's the use redesigning the H1 Header, is the font size of H1 is too big? I suggest you look for all the elements/words where H1 is being used. So once you've change the size, you make sure that it's appropriate with other pages look and feel
Comment: Header tags are often modified by CSS. H1 has semantic meaning.

Redesigning h1 headings


How can I set the locale and language?

Question: How can I set the keyboard and language in Android, and how can I add more languages to the device?
Comment: possible duplicate of [Install additional language support on HTC Desire HD](http://android.stackexchange.com/questions/5303/install-additional-language-support-on-htc-desire-hd)
Answer: Go to 'settings'-> 'Language & keyboard' -> 'Select language' and select one. If there are only a few available then that was the (awkward) choice of your operator or phone manufacturer.
To solve that problem, an app like CustomLocale solves it only a little. It doesn't work all that well or complete. Rooting and installing a custom ROM with sufficient languages is the only way to fully solve it.
If only the virtual keyboard is bothering you, you can install others, such as the MultiLing keyboard, from the Market. Be careful for malicious apps though. You're granting them access to anything you type in, and since the keyboard is pretty much always loaded, it might render your phone slow or instable if the keyboard app is buggy.
The instructions above might differ per flavour of Android (provided by the manufacturer on top of the stock Android) but will be similar.

How can I set the locale and language?


Single click sound when braking. Sounds like it's coming from the front left. 2009 Toyota Highlander

Question: Braking otherwise works fine, but I hear the click everytime I push the petal. I don't hear it if I'm in a stopped position and pump the breaks.
Comment: Welcome to Motor Vehicle Maintenance & Repair! Does the noise happen in forward and reverse? How much meat is left on the pads?
Answer: I have found a few things that can cause this issue. If the anti rattle springs/ shims are worn or rusted the brake pad can shift forward when the brake is applied. Worn or loose caliper slides can allow the caliper to rock when the pad squeeze the rotor.
Answer: Attention!   sounds like a caliper got loose.. check its two attaching bolts. They should be torqued to about 40-50Nm,  roughly half of force you use to tighten the wheel bolts.
And if they are not rusty,  don't use grease,   factory even uses loctite.


Does it make sense to apply complex mathematics in economics given that the result can be off by substantial percentage points?

Question: Complex mathematics make sense if the results can be calculated with precision. This applies for the physical sciences like physics and engineering. Economics is more of a social science subject. Does complex mathematics make sense in this context?
Comment: I think it is. Complexity of math stems mostly from complexity of the problem. Simplifying the problem (and then using simpler math) will not decrease precision by decimal points. Ignore forward-looking behavior of agents and you will get *qualitatively* wrong results.
Comment: *Complex mathematics make sense if the results can be calculated with precision.* - Whats the reference for this quote?
Comment: By "complex mathematics" do you mean "advanced theoretical mathematical methods", or "complicated numerical computations"?
Comment: "advanced theoretical mathematical methods" are not worse, they are just harder to learn. things that are harder to learn are unfortunately often perceived as "worse" by those who failed to learn them.
Comment: @FooBar, It is from me. Anything wrong with this statement? The reason I said that is that it is a waste of brain cells and time to go through complex calculations if the result is not going to be accurate at all. Why calculate to 5 decimal places if accuracy is +/-10%? Perhaps it is also an excuse for a not-so-smart person like me who can't handle complex math comfortably, at least not without spending lots of time.

Given the track record of economists in making forecasts, I think it makes sense to leave complex math out of economic forecasts.
Comment: Both. But "advanced theoretical mathematical methods" is worse.
Comment: I think you're confusing the difference between using mathematics to express an idea, versus the numerical calculation of the results. Perhaps it's because most people think "math = arithmetic with numbers", which is completely not true...
Answer: In the field of economics complex math is often used for
a) Economic modelling
There are usually tons of factors that influence even the simplest economic event. It is often necessary to resort to complex math to include all the variables that represent those factors in the right way.
b) Analysis of statistical data
It is often very difficult to support economic theories with good data, again because there are so many factors in play. On top of that, many simple mathematical instruments have drawbacks and should not be applied in certain situations. For example, to test relationship between two variables, you can use a simple correlation coefficient, but there are cases where outliers or certain patterns can make it unreasonably high or low. Then you can use simple linear regression, but if you spent months gathering data you may want to spend a few days trying to build a custom regression equation for a better fit. Finally, if you are preparing a paper for publication, you may want to use as many statistics as you can to try to convince reviewers and readers that your findings are actually true.
Drawbacks of using complex math in economics
1) There are not that many readers out there who are proficient in advanced mathematics. Unless you want to limit your target audience to a few math enthusiasts, keep it as simple as possible.
2) If you are preparing a paper for review at a journal, keep in mind that reviewers in economic journals are not necessarily mathematicians. It usually takes longer for math-heavy papers to get reviewed and the quality of those reviews may not be great, unless its a top journal.
Answer: I asked in a comment

By "complex mathematics" do you mean "advanced theoretical
  mathematical methods", or "complicated numerical computations"?

and the OP replied

Both. But "advanced theoretical mathematical methods" is worse.

Well, the use in Economics of "advanced theoretical mathematical methods" has absolutely nothing to do with the accuracy or inaccuracy of numerical calculations/estimations/predictions.
When the mathematization of Economics started back in the 30's and received a critical boost from Paul Samuelson's "Foundations of Economic Analysis" (1947), the scholars may have envisioned an exact social science at the end of the road, social engineering reigning supreme.
We soon learned how implausible such a goal was, while also understanding what this mathematization really offered instead :
A) Sanity-check of economic theorizing to a degree not permitted when this theorizing swims in the moving waters of human language
B) The ability to obtain new economic insights unattainable by human reasoning phrased in human language
c) Greater degree of re-usability of the work of others, thus accelerating research
...and I may think of a few more.
In another comment, the OP seems pre-occupied with the relation between  forecasting performance and complex mathematics. Two remarks here:
No forecasting method, complex or naive, does well in the face of structural breaks, we are not there yet. Second, the combination "sophisticated forecasting model + experienced forecaster" most of the times performs better than "simple model".
This is not news: 30 years ago, in Granger & Newbold (1986) "Forecasting Economic Time Series" book, in the relevant sub-chapter on evaluating macroeconomic forecasts, the authors reviewed the literature in a very balanced and detached way, and found just that: since this is not social engineering, tools should be handled by humans (like complex models that are handled by their creators), not left alone (as simple models are, by their nature).
In a more recent paper
Dovern, J., & Weisser, J. (2011). Accuracy, unbiasedness and efficiency of professional macroeconomic forecasts: An empirical comparison for the G7. International Journal of Forecasting, 27(2), 452-465.
the overall evaluation of professional forecasters (which certainly use complex models alongside their experience) appears to be improving.


Youtube's Picture-in-Picture (PIP), but more options/features?

Question: I really love the new PIP for youtube vids. I had been using VLC for youtube and other videos to date and setting it up like in the screenshot. But you are stuck with those giant ugly title bars, windows 10 lets u kill the side padding but that doesn't fix the problem. So the PIP is really wonderful in that respect, however it's really limited in what u can do with it atm.
Is there anything out there right now that mimicks what youtube has achieved in terms of just having a free floating picture without menu's clogging up the screen? I guess a media player in general would be the desired, but something to make windows not put a giant ugly titlebar on things would work, or extensions for existing players would be good too. The desire is to use a single monitor.
Answer: I suggest taking a look at VLC Skins you can either find a minimal one that you like or design your own using the Skin Editor.
Note that Skins do not work on OS-X


Why do we say "I am in a good mood" and not just "I am in good mood"?

Question: I'm just curious to know, why do we say "I am in a good mood"
not "I am in good mood"? Is there any grammatical rule for that?
Comment: Related: [Are they "in a good mood" or "in good moods"?](http://english.stackexchange.com/questions/250702/are-they-in-a-good-mood-or-in-good-moods)
Comment: Thank you all for answering my question! That was my first question I've ever posted here. Thanks!!!
Answer: Folks are discussing "a good mood" versus "good spirits" and I think that points to the answer.  It's the fact that 'spirits' is plural.
It's the same as "I'm with a good friend" versus "I'm with good friends".
Comment: Sure, but that doesn't really explain why we say *in a good mood* as opposed to *in good mood*. (Cf. *in good company*, *in good standing*, *in good time*, *in good conscience*, *in good condition*, *in good stead*.)
Answer: I believe the reason why one uses the determiner 'a' is without it your sentence becomes grammatically incorrect.
In the phrase 'in good spirits' one uses the undetermined plural which in English doesn't have an article. In other words the sense of the phrase can be rewritten as 'in any good spirits', not 'in certain good spirits'. This the same reason why you say 'in a good mood', not 'in the good mood'.
'In fine fiddle' was grammatically misused by the lower class of the past to such an extent it became a saying which is used until today, or at least that is my theory.
Everything I wrote has no evidence to support it and is only a linguistical theory.
I hope this helps you.
Comment: Your (unsupported) theory, such as it is, seems to hinge on the notion that "mood" is countable here — but is it? You can certainly say "in good ___" with non-count nouns; e.g., "in good company," "in good time," "soaked in good wine" or "cooked in melted butter."
Comment: I believe 'mood' is countable because one of its definitions is 'a temporary state of mind or feeling'. You can count 'states of minds' (e.g. 'What are the ten states of minds which oppose Buddhism?'), so you can also say 'What are the ten different moods which oppose Buddhism?' So if mood has a plural and a singular, it can be counted. Also, 'in a good mood' means that you have a good one, not one in general, thus you're counting it. Your examples with 'in good company' or 'in good time' are incountable, as you say, thus you can't use the determiner 'a' even if you mean a certain kind of ...
Comment: ...company. (My message was four characters too long)
Answer: I am in good mood would really be grammatically wrong because it lacks a determiner. Determiner, which is often describe as demonstrative and possessive adjectives, often serves as a distinction. For more information regarding the determiner kindly click  here.
Comment: Then how come we say "I am in good spirits" and "I am in fine fettle"?  By the way, I am not the downvoter.
Comment: Would you really use "in bad spirits" here? Remember, good here describes the word "mood". I could say that I am in a bad mood, but I wouldn't dare to say "I am in bad spirits."
Comment: @deadrat I think, your examples contain compound words. Kindly correct me if I'm wrong because I am also confused. thanks
Comment: A brief look with the google finds the use of "in bad spirits" by Willaim James, so I think we're both free to use that phrase.  I'm not sure what you mean by *compound words*, so I can't tell whether you're correct or not.  What are compound words and which words of my example do you think are compound?


Spaces don't work as expected in isearch

Question: I recently installed a new major mode for something I'm working on, and suddenly spaces in expressions I'm searching for don't work as expected. Help!
Comment: Care to tell us in which way they don't work as expected?
Comment: The question is unclear. Please state (1) what behavior you see, that you didn't expect, and (2) what you expected instead. And then say what your question is, given that information. I expected to see a train. I saw a plane instead. My question is ____.
Answer: Anything that makes changes to your ~/.emacs/~/.emacs.d/init.el initialisation file may, for various reasons, tinker with the emacs variables isearch-regexp-lax-whitespace and search-whitespace-regexp. This may lead to behaviour other than what most emacs users are used to, that is, a single space character standing for an arbitrary number of whitespace characters. Thus, the fix would involve restoring these variables to their defaults, by adding the following lines at the end of the initialisation file.
(setq isearch-regexp-lax-whitespace t)
(setq search-whitespace-regexp "\\s-+")


EE update 2.6 to 2.9 : during update cannot select language

Question: I am trying to update from 2.6. to 2.9 and when asked to select the language the select menu is empty.
Answer: Did you copy the languages folders from your old to your new system/expressionengine/language folder?
Edit: to make this a more complete answer- The Expression Engine docs on languages http://ellislab.com/expressionengine/user-guide/general/languages.html
Comment: Good chance it "just" works. If it doesn't work i'd try smaller steps. Upgrade to 2.7 first, then 2.7.3 etc.
Comment: I treid to use the language folder from the new zip as well as my old folder.  neither worked.  I ended up reverting back to my last backup.  I will attempt it again and hopefully not get this issue


How to legally distribute the data of all Internet websites?

Question: We are a humble startup that's very good at Internet crawling and data mining. Unfortunately after 2 years of struggling, we may soon fail.
We have lots of data and we want to release them free before we go under. However as our data collections are so massive, downloading from our servers won't be a good option. Even P2P downloading would cost massive amount of bandwidth and time. It's much more efficient to just send the data in storage devices such as USB drives or discs to the users.
As you can see from here, we currently have 1,287 web sites crawled and mined with all their data semantically extracted and constantly updated in our cloud. An example data set from one of the sites is like this, well structured with both texts and images.
Eventually we would have hundreds of thousands or even millions of websites collected. We would have PBs of data in our cloud which we will need to distribute to the fellow users.
We have to charge for a fee for this, e.g. for the storage devices and shipping, etc.
We are not merchandising the data which are not copyrighted by us, of course, but we have to charge a fee for all other things that went into it. And we will properly attribute each data set to the original website.
My question is can we do this legally? Is it possible at all to distribute all the data of the Internet this way?
Comment: We can't give legal advice on specific situations,which includes "can we do this legally".  You'll need to hire a lawyer who knows the laws in your jurisdiction and can advise you on the specific risks here.
Comment: You need to make this question less about your own situation and more about the legal pillars under it. Like _"Is it legal to distribute publicly available content?"_ and _"Is it legal to distribute content that once was publicly available?"_ And I guess the answers will depend on what the content was and under what licence it was published.
Answer: You want to sell or distribute Intellectual Property owned by other entities?  Depending on the jurisdiction it's likely that you will need permission from the IP owner.


How to transfer BTC from desktop wallet to mobile wallet (without fees), say using Electrum or Bitcoin Core

Question: I have both Bitcoin Core & Electrum wallets installed on both my desktop & mobile.  How do I transfer BTCs from respective desktop to mobile wallets (& vice-versa) directly (i.e., not thru the blockchain) to avoid fees?
Comment: By exporting and importing the WIF private key?
Answer: To accomplish this you will not 'transfer the bitcoin', you will just import the keys that can spend your bitcoin, into a new wallet.
Not all wallet software will support importing/exporting keys in every format, so you'll need to ensure that your current wallet software is capable of exporting keys in a format the the new wallet will accept. There are several formats for private keys, as well as other standards for backing up/recreating wallets, such as BIP32/39/44/84, etc. Be sure to familiarize yourself with these formats, and know which ones you'll need to use in order to accomplish your goal. Any wallet software worth using will allow you to export keys in some way or another, and hopefully provide some sort of documentation to help with this.
Very importantly, you need to understand that the private keys (or mnemonic seed phrase) that you'll be handling is the literal key to your bitcoin. If you store it on, or enter it into a compromised device, your bitcoin could be stolen.
Once you have the keys that control your bitcoins exported, you can import them to the new wallet, and (potentially after a rescan of the blockchain to locate your funds), your funds should appear in the new wallet.
Answer:
I have both Bitcoin Core & Electrum wallets installed on both my desktop & mobile

Not sure what are you using for Bitcoin Core on mobile. Recently a pull request was merged to use Bitcoin-QT on Android: https://github.com/bitcoin/bitcoin/pull/17227 and two other projects exist that allow using Bitcoin Core on Android: ABCore and Nayuta Core

How do I transfer BTCs from respective desktop to mobile wallets (& vice-versa) directly (i.e., not thru the blockchain) to avoid fees?

I will share the steps to use the same wallet in Electrum(Desktop) and Electrum(Mobile). This is not transfer of BTC but importing the wallet.
Desktop to Mobile:
Open Electrum on desktop -> Wallet -> Seed
Write this seed on a paper and keep it safe as backup information which can be used later to access your bitcoin.

Create new wallet, select "standard" wallet and enter the seed you got from Electrum(Desktop)

Mobile to Desktop:
Enter the seed from paper which has backup information saved.

Bitcoin Core to Electrum or Bitcoin Core to Bitcoin Core:
https://bitcoin.stackexchange.com/a/102908/
Electrum to Bitcoin Core will require copying private key for an address(right click on any address to get private key) and importing it in Core using importprivkey: How can I import a private key into a pruned node?


Can I disable product reviews in Google Structured Search?

Question: I am getting annoying warning messages from Google Structured Search about not supplying product reviews under offers. We don't have product reviews as it doesn't fit our target customer base. Is there a way of disabling it?  If there isn't, does it negatively effect our search visibility?
Comment: With "Google Structured Search", do you mean the Search Console or the Structured Data Testing Tool? And to keep the question for the future, can you please include the warning in the question?
Answer: It's only a warning. Ignore it if you have no reviews. It has no effect on search visibility beyond you can't get review stars without reviews.
Comment: Thanks for your answer.  It us already scary how Google tyrannizes online commerce and content through its search monopoly. To add insult to injury, they arbitrarily flag "warnings" based their own overly generalized ideas on what information is important to businesses and customers. While not an error per se, flagging a warning for not including reviews (as opposed to other microdata) clearly shows what bits of data is most important to them. In this case, they value highly gamable, crowd generated data.


Can we just go ahead and start a topic of the week?

Question: I know doing a topic of the week has been discussed before. What I'm suggesting is that even with out a reward we just start a topic of the week to generate more questions on this site during Beta. I also think that a general topic will generate more questions. Such as Classic TV Sitcoms would generate more questions then Sanford & Son. So should we go ahead and start a topic of the week?
Comment: I upvoted this, but just wanted to toss out a concern. If we create a topic of the week, will that encourage more frivolous questions from users trying to meet the theme?
Comment: @Nobby At the same time, anything we do that might be promotional, whether it be topic of the week, contests, etc are bound to have people just wanting to write w/e to participate.  That's what the quality control is for.  If we see them result into utter chaos, then a re-evaluation of the idea will have to be done, or just tossed out the window completely.
Comment: Point taken. I've no idea why I'm so twitchy today.
Comment: @Nobby better to be twitchy today rather than regretful tomorrow :)
Answer: I think that as long as we can build a list of topics that is long enough that we can be confident that the idea will not just die off, then I think that would be a good idea.
If this question gets enough support, then we could open another community-wiki question to collate and order the list of topics.
I think that people should upvote / downvote your question to register support or not. (also if people have points to make, other answers would also be welcome).


How can I move the position of a cue for the second shot in a pool game

Question: I am trying to build a pool game but having difficulty with the position of the cue after the break shot. I can get the cue to move in a number of ways but none of them face the cue in the right direction. Please can anyone suggest a simple way to do this.
Answer: Maybe something like this:

A very simple rig: The bone that controls the cue is parented to another bone that represents the cue's target. You can move and rotate the parent bone to match the position of the target, and rotate it to the angle you want to strike from; the cue will revolve around the target accordingly. Then you can control the movement of the cue toward the target by moving its bone along the local Y axis.


Switching sides

Question: I'm writing a drama and need some help. Can a criminal lawyer in a rape case switch sides from the person they are representing to the victim if they have been fired by their client?
Comment: Note that there have been cases where a prosecutor (or someone then employed in the prosecutor's office) subsequently represented a defendant on appeal - but I understand that this would normally be spotted by the opposing party.
Answer: No.  As the defendant's lawyer, they will have been privy to privileged communications.  As such, it would be unfair to the defendant if they now started prosecuting.
Also note that a victim very rarely has their own lawyer in a criminal case.  The prosecution lawyer is acting for "the Crown" (essentially, "society as a whole").  (There are exceptions, if the victim is bringing a private prosecution - but this is very rare for serious cases such as rape).
Comment: @Ayeesha you might also consider whether a civil action would fit your purpose better than a criminal trial, since both parties in a civil action would be represented by lawyers in private practice. The principle identified in this answer would still apply, however, so the lawyer would not be able to represent the former client's victim. Whether civil or criminal, though, there could be other kinds of relationships that might arise between the accused's former attorney and the victim or the victim's attorney. Some such relationships might be improper, but that might be fruitful in a drama.
Comment: Thanks Martin. I'll amend my tags but this is really useful. Thank you.

Switching sides


Is it possible to swap the items you're holding?

Question: It's now possible to hold onto two items at once in the Deluxe version of Mario Kart 8. One in the hand of the driver and one in the reserve. Is it possible to swap the items you're holding on your hand with the item you have on the reserve? Or do you always have to use the item on your hand first?
Answer: I would look at your controls menu to see if there is a specific button because I haven't found anything that labels what exactly could swap two items, but there was this info from Polygon.

In the original Mario Kart 8, holding an item behind your kart
  wouldn't remove it from your currently held arsenal. That has not
  changed in Mario Kart 8 Deluxe, but there are now two active item
  slots, so you have more wiggle room and can make more liberal use of
  your items regardless of your current standing.
One of the oldest Mario Kart tricks is to hold an item like a shell or
  banana behind you to block shots or automatically hit someone who's
  tailgating you. Upon impact, the item will be consumed — its job is
  done, and you can grab a new item. Get in the habit of cycling through
  objects or putting them in situations where you can use them instead
  of hoarding them.

The parts I bolded suggests you can swap between the two active item slots, but no indication as to what button(s) perform that action.
However; as GarrettJ pointed out (which is much more likely the case), cycling through them most likely means consuming the items to get through them.
HOWEVER, this thread, suggests you cannot, unlike in the game double dash - whatever is your first held item seems to go into your back (2nd) slot and stays until the 1st is gone.
Comment: I disagree that it sounds like you can swap between them. When they say "cycle" they are clearly referring to consuming items to cycle through
Comment: Note the info menu doesn't have a controller mapping and it does not say how to swap items.
Comment: Yeah it seems as though this update just allows you to *automatically* store that second item, even if it isn't one that can be held behind you.
Comment: Sounds like the answer is no, then. I'll look back tomorrow and if nobody has figured out a way to do it yet, I'll accept this.
Comment: @GarrettJ I think you're right, but I'll let that remain as your comment and bump that up 1, unless someone wants it added to the answer (open to edits etc).


Important Concepts In Project Management

Question: What are the most important concepts that should be added (as notes on ms project)? for example: Defining the project scope, risk management .. what others?
Comment: Hi. The question sounds too broad, and, in addition, "most important" things differ from methodology to methodology, and a particular selection is, likely, opinion-based. Instead, try to narrow down your question to be more specific (if you have chosen particular approach, mention it as well). Otherwise, you can find more or less suitable answers to your question just by searching the web or reading Wikipedia.
Answer: I have formulated and defined the following view over many years and now use it quite successfully when I am at an interview seeking a role, and of course in real life when managing projects.
Successful delivery (Waterfall method) comprises the following key elements to the Five-point Plan (MarvTM)

Know your requirements in clear, accurate and unambiguous detail - You must know what it is you are delivering else how will you know when you have achieved it.
Get the "right" team - You must have a team comprised of competent people who have expertise in the specific technical areas required by the project
Work out the most accurate estimates you can - We all know the limitations of estimation, but do the best you can with what you have got, taking into account the views of the people who are well-versed in actually doing it
Develop a detailed plan - Descend in the plan to as low a level of detail as required for you (i.e. the PM) to be able to map activities with a reasonable degree of accuracy. This level will be different for different projects. Don't keep the plan too high-level and don't make it too-low. Herein lies one of the black arts of the seasoned PM :)
Manage the hell out of the project - I don't mean micromanagement, I mean:

active risk and issues management on a frequent basis (daily if appropriate)
continuous tracking of actuals against plan
continuous re-planning as you move towards completion and new things become known and old things get finished late, early or on time
open, transparent and regular communications with the team, with the sponsors and with the stakeholders as often as they need (not when you need it)
regular progress reporting at the level of detail right for the project

It works for me, YMMV, and different methodologies, frameworks, manifestos and mindsets all have different (and probably equally valid) points of view!
Comment: Thank you, always learning on this site! Is it possible for me to obtain five minutes of your time?  Preferably over email? I have a few queries related to a project I am constructing, and would love, and almost need, your expert advice.
Comment: Sorry no. I suggest that if you have specific problems or questions you post them on this site, where they may be answered to the benefit of all visitors. In addition there are many resources on the internet that provide information that will be useful to you, such as http://www.projectsmart.co.uk/


Is host advantage real?

Question: I'm sure many of you have heard the term host advantage through out your time playing action video games.  However, I was curious if this was a real studied and proven concept in game design, computer science, and network programming?  I tried looking it up on Google, but all I saw was just some gamers ranting back and forth on a forum (none of them even seem to bring up client-server concepts in their babbling...).
Comment: The obvious, general answer is that it depends on the game and a lot of other factors.  Of course, this is a concept that ranting gamers miss quite frequently.  The point of view of developers is more nuanced, for example [Respawn's decision to lean on Microsoft's services for Titanfall](http://www.respawn.com/news/lets-talk-about-the-xbox-live-cloud/)
Comment: I think this could be a good question -- it can be generalized to ask "When would a host have the advantage?". And these factors can be generalized.
Comment: It would depend on how the game is programmed.  If commands are executed as soon as they are received the host gets an advantage.  If commands work on ticks and both host and remote commands have the same tick delay then there's no host advantage.
Answer: The essence of the "host advantage" is having a low ping (round trip time to the server). If you are the server, you'd have no ping time, but even being really close to the server would result in a small ping and still have a large "host advantage", so I'm just going to call it a "low ping advantage" instead.
It really depends on the game and how the networking code is written. Some games/engines will publish this information, but many more won't, so I'll take a few examples:
First person shooters (FPS) are likely where the vast majority of low ping complaints come from because you always shoot first, right? Valve describes how the Source Engine handles networking (Counter-Strike:Source, Left 4 Dead, Titan Fall, etc.). The article goes into great depth, so I will attempt to gloss over some of the details:

Entity interpolation causes a constant view "lag" of 100 milliseconds by default

and

Command Execution Time = Current Server Time - Packet Latency - Client View Interpolation

In effect, all clients are looking slightly into the past in order to help compensate for reasonable ping times. In theory, if clients are looking 100ms into the past, and if all players can get their actions to the server & other players within that time frame, then everyone should be looking at the same picture of the world at all times and everyone will be happy. But what happens when two players shoot within 100ms of each other? It will still take time for the shot information to reach the other clients, so both players may still see themselves shoot, even though there can only be one survivor. This likely creates a lot of false-positives. Since ping times aren't going anywhere anytime soon, there will always be "who shot first" arguments.
This still leaves the question: is it better to have a low ping? In the case of the Source Engine, I would argue that there's no advantage to have pings lower than ~50ms (about half of the interpolation time with default settings), but it will vary by game and can be affected by many external factors like packet jitter.
The answer gets a bit fuzzy when you start to consider high pings though. Those high ping players may not have an accurate view of the world, AND the other players may not have an accurate picture of the high-ping player. This can cause a variety of issues for everyone. Games handle this situation in various ways, and there is no clear solution. You can increase the interpolation time to make it more fluid for high-ping players, but then there will be more situations where one player thinks they did something before another. Decreasing the interpolation time will make it worse for high-pings, but fewer Hans shot first situations. Until ping times are non-existent, there will always real-time communication issues.
Age of Empires uses a what I'll dub a "buffered lock-step approach" as described in this article. There is some debate, but StarCraft and other modern strategy games likely use a similar method. Again, it's quite detailed and technical, so I'll gloss over it.

The game would tend to pause or slow only at the very worst spikes- command latency would go up but would stay smooth

There is no advantage for a low ping in games that use this method because each block of commands is executed in-order, at the same time, on all machines. You can read the article for more details on how.
Only real-time games are affected by a low ping advantage, and most real-time games will fall into one of the two categories above, which leads me to conclude that extremely low pings are no better off than medium to low pings.
Comment: +1. There are limits to cognition and reaction time, which is probably why dropping below the 50ms threshold doesn't much improve success statistics.
Comment: I should add: you know in BF3/4 when you die "behind cover". The reason is that someone else is far enough back in time to shoot and kill you on THEIR screen before you get the message. I suspect the interpolation time is more like 100-200ms, which would lead to 200-400ms message times.

Is host advantage real?


Why won't primer adhere to my walls?

Question: We are finally (after 12 years!) getting to painting the last room in our home.  It was originally painted with builder's paint, but being a "spare" room, we weren't in a rush to repaint.  The room is on the 2nd floor, as are the other bedrooms, and there has never been any moisture or leakage problems.  We purchased Kilz primer and it won't adhere to the ceiling or walls!  It peels off as you apply it!  What do you suggest?  This is getting expensive and very frustrating.  We had no issues with any of the other rooms.
Comment: What is peeling off? the old paint? Did you try scrubbing the walls first?
Comment: Are you using latex or oil based Kilz?
Comment: We had to apply a plaster compound and sand it smooth - making it a professional project.
Answer: Both answers so far are correct to a point. Older oil based enamels can be very difficult to cover. NOTE OF CAUTION, many older enamels contain LEAD and should not be sanded without first testing for lead and if positive,  proper precautions taken. Lead testing kits can be purchased at most paint departments. Read the directions carefully, but they are really quite easy to use and are very accurate if used properly.
As mentioned, cleaning the walls is very important. Use TSP and scrub with something like Scotchbrite pads or green scrubbies. Use an oil based primer or sometimes pigmented shellac (Bulls Eye Primer) works well. If you still have an adhesion problem, there are liquid sandpaper prep liquids available that are good to use if you have lead based paint or high gloss finishes. They are kinda nasty to use, stink and are caustic, so follow the directions carefully and wear protective eye wear and gloves.  If the surface tests negative for lead, sanding may be the best way to prep the surface. Using a DA sander with 100 to 150 grit paper, then cleaning the surface should do the trick.  Be careful and Good luck.
Comment: That is why I suggested an oil based primer.  What do you do if there is lead?   It poses no harm if you don't sand it - well unless you naw on your walls.
Comment: Note for Brits: TSP -> "[sugar soap](http://en.wikipedia.org/wiki/Sugar_soap)".
Comment: @DMoore. You noticed I was very explicit about not sanding lead paint. I have encountered old enamel that even oil based primers will not stick to and have had to degloss the finish before priming. When lead is present and primers won't stick, you have to use non mechanical methods like liquid sandpaper or some other wet method to prep the surface. The danger is in the dust.
Answer: You said you skim coated the surface and sanded.  I assume you used joint compound because you sanded it. You need to get rid of the dust on the surface: So take a wet sponge mop and mop the surface, not too wet.  Then I would rent a sprayer and spray the primer coat on.
Answer: Before applying any new paint on the walls it would be a good idea to wash down the walls with a hot water solution with TSP (tri-sodium phosphate) which should be available at your local hardware store. This will help remove any old oily grime and dirt on the walls that can keep paint from adhering. The TSP wash also helps remove some of the gloss surface of old paint which can also help with new paint adhesion.
To save effort initially you can try a small area before committing to the whole paint job. If you find that the TSP scrub down is not enough to fully solve the problem then you may want to lightly sand the old surface to roughen it up. I would sand before the TSP wash as the this will help to remove any remaining sanding residue from the wall.
Note that TSP solution is fairly caustic and can be quite hard on your hands and skin. Make sure to use some good quality "rubber" gloves that have cuffs that cover well up past your wrists.
Answer: I am going to throw this out there because I have run into it more than a few times with older homes.  If you previous paint was an oil based paint then you need to get an oil based primer.  You can go kilz or latex over that but you will need the first coat to be oil based primer.

Why won't primer adhere to my walls?


Floating values from GPIO pin

Question: I'm controlling a stepper motor through a stepper driver that is connected to the raspberry pi. Before I run a script to move the motor, the pi's  pins have a  "floating" value causing the motor to move randomly as soon as I boot up the pi. I have noticed that "grounding" (not sure if that's the correct term) the pi, either by touching it or connecting a cat5 cable from the pi to my pc will stop this behavior, but I would like a more permanent solution. Any ideas?
Comment: This would be pretty difficult to diagnose without some additional information, such as a wiring diagram, which stepper motor and driver you are using, etc.
Answer: It sounds like you need to add a pull up or pull down resistor to the cable causing your floating value.  See http://en.wikipedia.org/wiki/Pull-up_resistor for more information.
Comment: You can, just make sure that the resistor value is high enough that it will not influence that circuit once the Pi starts driving it.
Comment: Would this work for pins that will become outputs? All I've read on pull-up/pull down resistors seem to point to pins used as inputs.
Comment: @Andres Yes, you can use pull up/pull downs for outputs too, but like Marco said, it should be high, somewhere on the magnatude of 10K should have little effect on the performance of the circuit, but pull the voltage up/down once the value starts floating.
Answer: Since I don't have a reputation on here yet, I can't comment on Butters' answer, so I'll have to post my own answer. The GPIO of the Raspberry Pi includes pull-up and pull-down resistors that reach from 50kOhm to 65kOhm for the pull-up and 60 kOhm for the pull-down resistor. More information and code can be found in the wiki.
Comment: You can only it set once the kernel has finished loading and init starts running usermode programs. That will be a few seconds after power on.
Comment: Would I set these when the pi boots up? That would mean they would still float while while it's booting, no?

Floating values from GPIO pin