What is the purpose of this notation that has short lines through the note stems?

Question: Why are these semi quavers written like this?

It is part of a string quartet
Comment: The answers explain *what* they are, but the *reason* for this notation is basically to save space. String players have to stop playing to turn over a page. (But in an orchestra there are two players sharing each copy of the music, so half of them can continue playing through page turns).
Comment: For what instrument is it - violin?  Maybe quavers?
Comment: @alephzero  you Luddite!  :-) .  Get thee to a 12.9-inch iPAD Pro and a foot-pedal.  No more page turns!.
Answer: There are, at least in a way, two answers to this question. This first is that it simply saves some ink and some performer eyestrain because writing it out in full would involve double beams and each note written twice.
The second answer gets at the psychological or interpretive meaning of a notation like this, and is, as such, more subjective. I know that for me, and I think for a lot of other string players, there is a slight difference in stylistic interpretation between notation like that in your question and the expanded version it functions as an abbreviation of. When I play a passage like this, I generally try to have slightly more of a sense that I'm playing a line that is essentially eighth notes, but that each eighth note is just doubled for added volume and intensity. I slightly accent the first of each doubled note and try to think of the line in its more basic, purely eighth note form. Obviously, this is a highly nuanced idea, and may not be especially obvious to a listener, I'm not sure. All I know is that I tend to approach passages like this as an eighth note idea that is simply being doubled, as opposed to a sixteenth note idea. Does that make any sense? At least subjectively, it feels like a relatively strong difference of emphasis.
Answer: It means to play each note twice, as 16ths.  Sort of a Stage 1 tremolo I suppose!  But very specifically just two 16ths for each 8th.  Very common notation from the Baroque era onwards.  Used for all orchestral instruments.
Answer: They look like measured tremolos on a single note. Here's some information:
https://en.m.wikipedia.org/wiki/Tremolo
Mix between Half Notes and Eighth Notes: What Kind of Note is This?
How to interpret half notes combined with thirty-second stems? [This one is mostly about unmeasured tremolos]
Note that those examples mostly show tremolos between two notes, but it's perfectly normal to perform one on the same note. The specific technique that you will need depends on the instrument that you play.

I seem to have attracted a downvote, so perhaps I should be clearer. Tremolo doesn't mean "play as many notes as you can". The number of slashes through the note stem actually means something. The term I've heard used is "measured tremolo", as opposed to an "unmeasured tremolo".
Single slashes are measured tremolos. If they are quavers, play semiquavers. If they are crotchets, play quavers. It gets a little more vague with minims and semibreves, but I'd generally play quavers. If they wanted crotchets or minims, they should just write them out.
Double slashes are also measured tremolos, but at twice the speed.
Triple slashes are your classic "play all the notes" unmeasured tremolos. The exception would be if the tempo is really slow, and the symbol is on semibreves, which can be a little ambiguous.
I'm not claiming this is an authoritative source, but it seems close to what I've heard: https://easymusictheory.wordpress.com/tag/measured-tremolo/.
Also, for what it's worth, Sibelius interprets tremolos in a similar fashion.


Vote count in Users->voters is off

Question: Right now, my MathOverflow user page shows 12,878 votes, but the page with people's overall vote counts shows a mere 8674.  I see similar discrepancies with other people's accounts.  Is there some unorthodox enumeration method at work?
Comment: I _believe_ this is because you're seeing votes on deleted posts in your profile, which is not even considered on the other page. I'm pretty sure that's it but I'll confirm just to be sure.
Comment: @TimPost The summary page of the profile doesn't show deleted votes but does include votes cast on deleted posts. The Voters tab should basically show you the same thing. It is, however, cached. The thing that's puzzling me here is why we don't get an up-to-date value since the site basically just went up. Maybe it has something to do with the pre-migration test instance. Either way, I'd wait a few days to see if the value updates.
Comment: Thanks for looking into it.  My initial impression is that 4204 is a surprisingly large number of deleted posts.
Answer: There are several places where we assume the Community User's creation date is when the site was created - one of those places is on the /users list page for the "all" filters.
For whatever reason*, Community's creation date was incorrect, having a value of 2010-11-10, instead of 2009-09-28, or when Anton's user was created.  This would result in over a year of your votes not being aggregated.
I've updated Community to have the proper date, so everything should be fixed.
* I think it's because the old SE1.0 codebase didn't use this date for anything, so it wasn't imperative for it to be correct.
Comment: Yes, it it seems to be fine now.  Thanks a lot!

Vote count in Users->voters is off


People need to read past the title?

Question: I just asked a question
 with a rhetorical question in the title. If people had read the body of the question they would have noticed the obvious answer to the question in the title. But they have not done so and I have received comments and down votes for that reasons.
Answer: I thought for a second when I saw your original title that you might have been intending it literally. This is a fairly academic site, in which question content rather than expression is important. Therefore questions will tend to be taken literally. That probably explains the comment you got.
I think the problem people are having with your question is that the title "Was Jesus a liar?" obscures the question in your post, which is "Why is it that many Christians firmly believe that the wailing wall was part of the Temple?" People are confused about which question you're asking. That may be the source of the downvotes. Since they're anonymous, and there's no obligation to explain them, we'll never know.
My suggestions are to make sure the question in your title can be taken at face value, and also take care that it matches the question posed in the body of your post.
Comment: The title was related with the body of my post, as I explained the implications of my question
Answer: If I could suggest something for all questions here, it is to add the doctrinal framework you're asking for to the title (i.e. according to Baptist, Evangelicals, Catholics, Orthodox, etc...).  This is the best thing you can to do ensure you get the answer you're looking for.
If you're non-denominational, this is difficult, but you still ought to have some doctrines, so you can say, "according to people who believe X, what is the Biblical basis for Y).  Questions aren't a place for flowerly language, and shouldn't need interpreters to read.  Questions must be utterly straight forward and have answers that may be divergent in conclusion, but must agree in principle.   As in, the theological axioms used to formulate the questions and the answers must be identical.
Not looking for something from Christian doctrine?  Think very, very hard about whether only God can answer your question.  If only God can answer your question, ask Him (i.e. pray about it!)

People need to read past the title?


UIViewcontroller won't rotate

Question: I have a problem with uiviewcontroller rotation.
I have a mapkit view with annotations that when tapped, display a popover. (everything works to this point)
Within that popover there's a button attached to a segue (modal) which transitions to a fullsize view of that popover. The mapkit view rotates fine with the popovers, but the fullsize view (when present), doesn't rotate.
I can see the iPad toolbar rotate, but the fullsize view won't.
Popover presented with
<code>- (void)mapView:(MKMapView *)mapView didSelectAnnotationView:(MKAnnotationView *)view {

//display basic popover on map
if([view.annotation isKindOfClass:[MapAnnotation class]]){

    storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];
    viewController = [storyboard instantiateViewControllerWithIdentifier:@"MapPopover"];

    popOverController = [[UIPopoverController alloc] initWithContentViewController:viewController];

    [popOverController presentPopoverFromRect:view.bounds inView:view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];

    //de-select annotation so the map will detect if you tap it again
    [map deselectAnnotation:view.annotation animated:NO];
}
</code>
Here's a sample project with the problem. https://github.com/nhart/UIViewController-Problem
Answer: you have to override

(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

in your modal viewController and return YES for all orientation you want to rotate to.

UIViewcontroller won't rotate


Are most bikes' paint jobs not as durable as they used to be?

Question: I am asking specifics in a few posts so as to not get into discussions.
Consider this a continuation of bike quality for the price.
I find the paint job on my bike to be nice but very thin and fragile.
It scratches very easily. When I was a kid you would need to use a
jack-knife to scratch the paint. I know there is the rationale that paint weighs and so to eliminate weight they spray the paint on as thinly
as possible. Even the rubbery plastic of my U-lock scuffs it.
Comment: Based on single example and gut feeling, I would argue the other way. I have an Italian road frame from the 1980s that looks nice but gets scratches from everything. My newer Italian frame does much better.
Comment: Today lots of high quality bicycle frames are powder coated which is a very durable type of paint/coat. I have a Focus Mares cyclocross bike which, after years of (ab)use doesn't have a single visible scratch or scuff.
Answer: Price.  A combo undercoat/primer, a top coat, and a lacquer/transparent would be the norm.
In the 80s, a nice bike might have had 10 very thin spray coats with multiple clear coats on top, most of which were over the decals/transfers.  This represents a lot more work, time, and materials.
In addition, the older bikes would have been steel, whereas the newer bikes are possibly aluminium now which doesn't hold paint as well, due to microscopic differences in how the paint keys into the surface.
Comment: On the other hand steel (especially cheap steel) needs better paint to protect it from rust, so you can get away with a cheaper paint job on aluminium.
Comment: Also, many paints and solvents used back in the day would not pass today's regulations. It's far cheaper to powdercoat than to properly protect workers and dispose of waste.
Answer: I really think it depends on the quality of the bike you buy.  Back in the 80's most bikes were of good quality.  Today, you can pay more and buy a bike of good quality or spend less and get...what you pay for.  That's the kind of world we live in right now.  But that being said, there are still some less expensive bikes that have durable paint and durable parts.  You just have to do the research and stay on the lookout for a sweet deal.


How do you beat Belial in Diablo 3 as a Monk?

Question: Belial is the guy at the end of act 2, and the last part is really hard.  I never seem to get his life very low.  How do you beat him as a monk?
Answer: Stage 1
Kill all the worms which is trivial.
Stage 2
Focus on Belial and let your companions handle the little guys for the most part.  Make sure at the end of this round you are full on spirit or else you'll be in much worse shape.
Stage 3
From what I can tell, Belial has 3 main abilities:

Whack you
Spit green stuff in sweeping motion
Green exploding void zones

It requires a little concentration, but if you counter each one individually, it's much easier.
When he whacks you, you are in his melee range and it doesn't hit very hard, so you can basically ignore it.
When he spews green stuff, make sure you 300 life and you should live through it.
The green exploding void zones are the hard part.  These will tag you for bleeding damage while you are standing in them and then they pop you for 500-600 when they explode.  The only real strategy for these is to run away from them.  I have found that running around the outer edge of his zone gives you the most room to work with and tends to be a lot less busy so you can see yourself the whole time.
This is not a DPS fight!  Focus on keeping yourself at full life.  I used the aura that heals you when you use spirit and the one that gives you 100 extra spirit.  I don't think the mantras I had at this point are particularly useful for this fight, but I used the one that increases dodge to help with the first 2 stages.  I also used the aura companion spell and the heal party spell.  I had the enchantress follower with me.
The basic strategy is to keep your spirit capped off, and as soon as you take damage, blow some spirit.   During the slow parts, run up to him and build your spirit back up.  Don't forget to use your potion if you get into trouble and don't worry about your companions, they will figure it out.  The last piece of advice is to not go crazy and blow all your heals when you take damage.  If he hits you with a whack as you are lighting up your spirit orb or you take a green spit, just cast a single damage spell that uses spirit and save the big cool downs for when you are running away from the green voids.
Lastly, health globes do pop up in melee range quite often.  It's more important to keep yourself topped off than it is to DPS.
Comment: DPS = "Damage Per Second". I had to look it up, so hopefully it helps someone else.
Comment: I had a tough time beating Belial (3rd stage) with my WD (lvl 22) last night.

My biggest advice to WDs is: enable Spirit walk! Most other abilities don't do much damage, frogs, etc. can't even touch him in 3rd stage, literally.

Spirit walk though let me avoid his last attack (green circles of death EVERYWHERE) with relative ease.

Just play it smart. The trick is merely staying out of his line of fire.
Comment: +1 Total pro. This worked a treat. I had to turn on 'Elective mode' in the options to be able to bind two defensive skills, but cracked it first time with this setup, after 3 failed tries. This answer should be accepted.
Comment: "I used the aura that heals you when you use spirit and the one that gives you 100 extra spirit." I did the same and it was the key for beating it Belial at second attempt. Good one!
Comment: I died about 10-12 times with a lvl 24 wizard on this. I gain one level just by fighting his minions over and over again. Finally, I learned that when the entire screen is exploding, don't try to sneak in even one attack - just focus on running away.
Answer: Nick's answer about how the fight works is awesome, but to add to it here are some of the specific spells I found useful during the fight

Equip both heals (Breath of Heaven and Serenity with the Peaceful Repose rune), and alternate between them as needed. If both are on CD, use a potion or the skill listed below
Seven-Sided Strike - I usually save this one for when he gets all angry-mode and starts dropping the green exploding void zones. It removes you from the area for a few seconds and has saved my life at least once when both heals and my health potion were on cooldown
Transcendence - This passive makes it so you almost always full-heal with any of the 3 skills listed above

The important bit was to save your spirit for heals, and just auto-attack for damage and spirit generation.
And a side note, be sure your best quality health potion is equipped in your Q slot. I didn't notice at first that it doesn't automatically use the best health potion when you hit Q, and you have to actually change which health potion to use by dragging the one you want onto your skill bar.
Comment: Sweeping Wind and Way of the Hundred Fists are key to maintaining damage in this fight.  Healing will keep you in the fight, but you still need the fight to end.
Comment: I tanked this alone after my 2 buddies died by using Mantra of Healing on cooldown to stay alive (with Transcendence as well) and  Serenity with Peaceful Repose to live through void zones.  My only damage was Crippling Wave + the Bell, so it took a while, but I was more or less unkillable (at about 4K HP vs the Nightmare 3-person version of Belial)
Answer: Inferno mode is a bit problematic, since you have 4 minutes in phase 3.
With adequate gear (800+ loh, 900+ all res, 20k+hp and 5k+ armor, at least 14-ish k unbuffed dps), and with this setup you should have little problems.
Phase 1&2:
Just stand in a corner and spam thousand fists, using other skills as needed.
The huge knockback of the 3rd hit will migitate a lot of dmg. With above stated stats u shouldn't have to move from anything belial/trash throws at you in phase 1 & 2.
Phase3:
You should be able to survive a hit or two from belials slam and be healed to full by the loh in almost no time. If you see you wont use breath of life, or a potion. If none is available, don't use serenity, just move a bit to the side and continue dpsing.
During the voidzone part, stop dpsing and move out of the pools. If you get cornered in pop serenity and move to a safe spot. After, just continue to dps following all stated above.
Also, during the 3rd phase, it is imperative you keep the sweeping wind up at all times, use blinding flash whenever it's up and pop the mantra whenever you can. And keep the dmg buff from breath up, although it last preety long and probability is you wont even have to look at it.
Comment: Pretty sure the enrage timer hits at the three minute mark in the third phase, but otherwise, that's pretty close to what I do.
Comment: Just checked the patch notes, you are correct. Belial's enrage timer is indeed 3 minutes, not 4.
Answer: After dying a couple of times in this fight, I finally went with the passives Exhalted Soul and Transcendence.  Keeping a large Sprit pool available (and a couple of health potions) was the key for me to keep alive in this fight! DPS and keep out of the bad stuff.
Answer: I soloed him in a party of 3 because the other 2 died. Use serenity with the rune that makes it heal you and you win


Backup MBR , boot loaders etc for trouble free OS installing/uninstalling?

Question: First I installed xp , then xp64 , then windows 8 developer preview , now I wish to install a linux flavor. This is all easy.
Some months later I may want to uninstall windows 8 preview and install its beta. OR I may want to remove linux without reinstalling windows. Now the problem with MBR and bootloaders begins. In my experience , sometimes here something  goes wrong at this point and I end up in an unbootable state.
Is there a way to 'manage' all bootloaders(second stage)/MBR , so that they can be simply restored to a particular state after a OS is removed/added? I know MBR can be backed up easy(dd command,hirens boot cd), but that doesn't seem to be enough..
Thanks
Answer: Start with this GHacks How to:

How To Backup And Restore The MBR In Windows


RRD Performance reporting with GSA/OpenVAS

Question: I'm running Greenbone Security Assistant 7.0.2 (on Kali Linux) and the default performance reporting currently goes a "Fallback Report" which only dumps /proc/meminfo to the screen. A note on the page implies that there's more rich reporting but I haven't been able to find anything documented for setting up or enabling it. I'm assuming it's more or less standard RRD reporting. Anyone know how to configure this?
Answer: Quoting the relevant part of the source code documentation:

Prerequisites for generating system reports:

A program in the PATH, with usage "openvasmr seconds type", where
seconds is the number of seconds before now that the report covers,
and type is the type of report.  When called with type "titles" the
script must print a list of possible types, where the name of the
type is everything up to the first space and everything else is a
title for the report.  When called with one of these types openvasmr
must print a PNG in base64 encoding.  When called with the special
type "blank", openvasmr must print a PNG in base64 for the Manager to
use when a request for one of the titled types fails.  openvasmr may
indicate failure by simply refraining from printing.

Disclaimer: Answer of a NVT Dev @ Greenbone


2002 Saturn SL2 Stalls After Warmup No Spark

Question: My SL2 stalls (it just cuts out, no warning) shortly after warmup (this all started right after I topped off the coolant after a low coolant light came on, although I don't know if they are related).  After the stall there is no spark but all other electronics work and I need to wait at least 20 minutes before the car will start again.  I replaced the ignition module, but this did not fix the problem.
Comment: I have to wait for it to cool down, normally at least 20 minutes.
Comment: Does the vehicle start right back up after it dies? Or do you have to wait until it cools off before it will start again?
Answer: It is possible that it is the crank position sensor. My friends trunk had the same problem. It would start and run for maybe 10 minutes then sputter out and die and not be able start again for hours.
Turned out to be a crank position sensor.
Answer: After you stated that you have to wait for it cool before it will run again is an indication that the crankshaft position sensor has failed. You should have a look at how to replace it on your vehicle. It's usually found on either the transmission bell housing (reading off of the flywheel as it rotates) or near the crank pulley at the lower front of the engine.
If you want to be 100% sure (I already am), then you could remove the sensor, and hook up an ohm meter and check resistance in the sensor. While watching the reading get a blow dryer and heat the sensor (don't melt it). While heating it, you'll notice the resistance begin to increase. This is normal since adding head to a circuit will increase resistance. Watch the meter's output closely. It will eventually show OPEN. It may only just flash OPEN for a second but at this point, the vehicle has stalled. With the crank sensor signal lost the engine's control systems have lost it's idea of where the engine is in it's "timing" (there's much more to it, just trying to explain it a simple as possible).
Comment: After reading this thread, which well describes my own car's misbehaviors, I've just verified that a new crank sensor fixes it, and dipping the old sensor in a cup of hot water results in ohmmeter reading going from 550 ohms (normal) to 'OL' whiich indicates resistance  of many megohms.   The test is spot on (but the sensor is inside a casting, and takes hours to replace, I couldn't test with just a 'blow dryer').
Answer: Change the coolant temperature sensor
 When they get hot they expand (copper sensor head) and it loses signal and stalls. This will look exactly like slipped timing when hot and stalled. It is located under the upper coolant hose on the cylinder head. Pinch The two wire connector end to get it off. 13 mm long socket works perfectly with 3 inch extension. It may even be visibly cracked on the head of the sensor


Is it possible to find / estimate the volatility surface of non-listed index options?

Question: I have 3 QNET options (european, 2 puts, 1 call, all same expiry, different strikes) that the broker is pricing clearly off a volatility surface. Bloomberg only carries historical volatility and I assume the broker is pricing this off quotes.
Answer: Yes, your broker could have used one or combination of many factors: estimated volatility surface from historical returns of your target index, historical returns of similar indexes, implied volatility of similar indexes, existing inventory,etc. Check out these two approaches to deriving surfaces from returns   starting slide 14


Will increasing samples reduce fireflies?

Question: Will increasing the samples eliminate fireflies? I know that the question of reducing fireflies has been already asked, but i want a straight answer on whether it will help or not.
Comment: BlenderGuru has a nice article about how to get rid of fireflies [here](https://www.blenderguru.com/articles/7-ways-get-rid-fireflies)
Answer: Just posting for empirical data:

These renders are at 2000 samples with a Sun Lamp pointed at an Icosphere with 100% glossy shader... just to demonstrate differences between firefly reduction techniques:

For noise reduction, see this answer: https://blender.stackexchange.com/a/84326/38953
Comment: Love the crystal ball example - that really shows the difference the number of samples makes. It also shows just how high it needs to be to produce nice caustics.
Comment: @RichSedman - Yes, it took my three GPUs 3.5 hours to render the million sample frame.
Answer: Short answer: No.
Long Answer: As far as I know, not always; there is a point where more samples will do you no good for fireflies.
Increasing the number of samples will more often then not reduce noise in your scene, generally to a point where it is acceptable for the final result, at the expense of render time. The higher the sample count the less noise you should get.
Similarly, increasing samples will also more often then not reduce the amount of fireflies in your image. However there is an undefined point where increasing the amount of samples will no longer reduce the amount of fireflies.
Cycles being a physically based render will in theory converge to a physically correct and accurate representation of your scene.
Rays are cast, they bounce around the scene, and yield a result. More samples for the same pixel will average out the result and smooth any irregularities reducing noise and fireflies, the more samples are calculated the smoother the result.
However in some cases the scene converges poorly and the math averages slowly to a point where churning more and more samples will only converge to a same physically correct solution that still suffers from some bright spots (fireflies).
At this point more and more samples will no longer solve that problem and will only refine and confirm the already obtained result that includes some undesired bright spots, which are unacceptable from an artistic point of view, despite being accurate from a mathematical interpretation.
In this commentary by Brecht, the author of Cycles Render engine, the linked scene shows a common culprit, caustics, where he states that increasing samples will actually produce more fireflies.
Suggested solutions are changing seeds, clamping, post production, blurring samples, turning on Filter Glossy, noise reduction or any other of the well known methods will alleviate the problem.
Comment: I'm not convinced that there's a point where fireflies won't be resolved by more samples - artifacts from inacuracies in the calculation should not occur unless you're running to extremes... eg, very large scene far from the origin with very small details with small (or distant), bright light sources - generally more samples will resolve fireflies in all but the most extreme cases but may require an extremely large number of samples to become unnoticeable (which might be impractical). Are there any solid examples of more samples not resolving fireflies?
Comment: I have a faint recollection of reading something about it somewhere, written by Brecht Van Lommel himself, (if I recall correctly) the original creator of Cycles. Unfortunately in my admittedly superficial search I could not find the original again. I'll try searching a bit harder.
Comment: Maybe @brecht can barge in and demystify the issue. Please correct me If I'm wrong.
Comment: @RichSedman Late to the party, but found comment by Brecht about a scene that converges poorly where more samples will not reduce fireflies https://developer.blender.org/T52313#450602
Answer: There are numerous ways of reducing fireflies and increasing the number of samples is the simplest, most generic, and also typically the most expensive (in CPU time). Usually you would want to try all other methods first and only resort to increasing the samples as a last resort.
Answer: I am a beginner in Blender, and what I found to reduce noise has nothing to do with the number of samples, blurring, or clamp setting.
Below is an image with only 50 samples. You reduce noise by using mesh objects as emitters.

Here, I consider the 'size of the mesh emitter[4*4]' and 'strength of li8' which is 5, based on the room size, and I enclose the emitter with a diffuse object in order to reduce the bounces on the ceiling i.e to reduce the fireflies.
If you want the emitters on the ceiling, follow the above method with only 50 samples.
Another way to reduce fireflies is to move the emitter away from the ceiling and reduce the size of the emitter by double[2*2], with the same strength of li8 from above case which is 5. No enclosing is needed and only 50 samples.
If you want the emitters a little bit under the ceiling, follow the 2nd method.
Here, my uploaded image is based on the 1st method.
I hope my suggestion might help you.
If you have found out a good method to remove fireflies better than mine, please let me know.


The relation between the roots of a polynomial equation and a matrix equation

Question: (I call matrix equation for example this $X^2-X+1=0$. Does it mean so?)
When a polynomial equation is solved for $x$, we get a complex number.
If we solve the "same" equation (same coeficients), such that the unknown is inside a matrix, is there any relation between the matrix and the roots?
Maybe I have not expressed it well, so I'll put an example:
$$ { x }^{ 2 }-x-1=0 $$
So
$$ x=\frac { 1\pm \sqrt { 5 }  }{ 2 }  $$
Now the unknown $x$ is inside a matrix and $\alpha,\gamma,\zeta$ are known numbers:
$$ X=\left[\begin{array}{cc}x & \gamma\\\alpha&\zeta\end{array} \right]$$
$$ X^2-X-I =0$$
If it can be solved, is there any relation between $x$ and $X$ ?
Comment: This isn't really valid to have a single unknown in the matrix, because you get inconsistent results. For instance, if you compute the left hand side, in the (1,2) position you get $x\gamma+\gamma\zeta-\gamma = 0$, and in the (2,1) position you get $\alpha x + \alpha\zeta - \alpha = 0$. These are both linear equations for $x$, which may lead to two different answers.
Comment: @EdGorcenski: In that case, the equation simply has no solution.
Comment: Which is it, $-1$ or $+1$?
Answer: First, note that a "polynomial matrix equation" may have more solutions than its degree! For example, the equation $X^2-1=0$ has only two complex solutions, $x=-1$ and $x=1$, but it has many matrix solutions, among them:
$$\left(\begin{array}{cc}
1 & 0 \\
0 & 1
\end{array}\right),\quad \left(\begin{array}{rr}-1&0\\0&-1\end{array}\right),\quad \left(\begin{array}{rr}1&0\\0&-1\end{array}\right),\quad \left(\begin{array}{rc}-1 & 0\\0&1
\end{array}\right),$$
and more. In fact, there are infinitely many solutions: for any $a,b,c,d$ such that $ad-bc\neq 0$, we have that
$$\left(\begin{array}{rr}
\frac{ad}{ad-bc} & \frac{bd}{ad-bc}\\
-\frac{ac}{ad-bc} & -\frac{bc}{ad-bc}
\end{array}\right)$$
is a solution. And there are plenty more!
That said, if $\alpha$ is a complex solution to $p(x)=0$, then $\alpha I$ is a matrix solution to $p(X)=0$. Moreover, if $M$ is a matrix solution to $p(X)=0$, then the minimal polynomial of $M$ is a divisor of $p(x)$, and this means that every eigenvalue of $M$ must be a root of $p(x)$. Thus, the roots of $p(x)=0$ in $\mathbb{C}$ give you the possible eigenvalues of any solution to the matrix polynomial equation $p(X)=0$. In particular, any diagonal matrix whose diagonal entries are chosen from among the roots of $p(x)$ will satisfy the equation.
Also, if $M$ is any solution and $Q$ is any invertible matrix, then $QMQ^{-1}$ is also a solution (this is the source of my "infinite family of examples" above; but note that none of the examples in the first displayed equation line are related in this way). Conversely, a diagonalizable matrix is a solution to $p(X)=0$ if and only if the eigenvalues of $X$ are roots of $p(x)=0$.
Added. None of which directly addresses your question, on second reading, since you are asking about the unknown being in the matrix, rather than being the matrix. But you can do a bit with the information above.
For example, consider the situation you describe. We know that if $X$ is a solution to $p(X)=0$, then the eigenvalues of $X$ must be either $\frac{1+\sqrt{5}}{2}$ or $\frac{1-\sqrt{5}}{2}$. That means that the characteristic polynomial of $X$, which is
$$(t-x)(t-\zeta)-\alpha\gamma$$
must either be equal to $t^2+t+1$, to $(t-\phi)^2$, or to $(t-\psi)^2$, where $\phi=\frac{1+\sqrt{5}}{2}$ and $\psi=\frac{1-\sqrt{5}}{2}$. This allows us to solve for $x$: we must have either:
$$\begin{align*}
x\zeta - \alpha\gamma &= 1\\
x+\zeta &= -1
\end{align*}$$
(if the characteristic polynomial is $t^2+t+1$); or
$$\begin{align*}
x\zeta - \alpha\gamma &= \frac{3+\sqrt{5}}{2}\\
x+\zeta &= -1-\sqrt{5}
\end{align*}$$
(if the characteristic polynomial is $(t-\phi)^2$); or
$$\begin{align*}
x\zeta - \alpha\gamma &= \frac{3-\sqrt{5}}{2}\\
x+\zeta &= -1+\sqrt{5}
\end{align*}$$
(if the characteristic polynomial is $(t-\psi)^2$). This gives you three possible values of $x$ (if the system is consistent).
If the first system is consistent, then the Cayley-Hamilton theorem guarantees that the resulting matrix is a solution to the original polynomial. The other systems are more difficult: it turns out that the only way they can be solutions to the original $p(X)=0$ is if $\alpha=\gamma=0$ and $\zeta=\phi$ or $\psi$, respectively; this follows from the theory of minimal polynomials: we would necessarily have that the minimal polynomial of the matrix is either $t-\phi$ or $t-\psi$, but this would force $X$ to be a scalar multiple of the identity.
I think this kind of question is better approached from the point of view of the minimal polynomial; a bit of theory can simplify the search (as in the previous paragraph) or even determine that no search is necessary (because no solution is possible).  I didn't make use the trace, for example, which also gives you information about the eigenvalues.
(I guess the very short answer is "yes, there is a relation, through the eigenvalues and minimal polynomial")
Comment: @N.S. I just noticed that I wasn't actually addressing the question asked directly, so I've added a bunch of stuff. I'll add that as well.
Comment: @qbt937: I think that was supposed to have a $-1$ in the upper left corner...
Comment: Might also be worth noting explicitely (it is actually hidden in your answer) that a diagonalizable matrix is a solution to $P(x)=0$ if and only if its eigenvalues are roots of $p(x)$.
Comment: I don't think $X = \left(\begin{array}{cc}0 & 0\\0&1\end{array}\right)$ is a solution to $X^2 - 1 = 0$, since $X^2 = X \neq 1$.
Answer: Just as with scalar quadratic equations, you can complete the square:
$$X^2 - X - I = \left(X - \frac{I}{2}\right)^2 - \frac{5}{4} I$$
Thus any solution $\pmatrix{x & \gamma \cr \alpha & \zeta\cr}$ to $X^2 - X - I = 0$
must have $x = 1/2 + \sqrt{5/4}\, x'$, $\zeta = 1/2 + \sqrt{5/4}\, \zeta'$ ,$\alpha =  \sqrt{5/4}\, \alpha'$, $\gamma =  \sqrt{5/4}\, \gamma'$ where $\pmatrix{x' & \gamma'\cr \alpha' & \zeta'\cr}$ is a square root of $I$.  The square roots of $I$ consist of the following classes:
$$ \pmatrix{s & \dfrac{1-s^2}{t}\cr t & -s\cr} (\text{where}\ t \ne 0), \ \pmatrix{\pm 1 & 0 \cr t & \mp 1\cr}, \
\pmatrix{\pm 1 & t\cr 0 & \mp 1\cr}, \  \pmatrix{1 & 0\cr 0 & 1\cr}, \ \pmatrix{-1 & 0\cr 0 & -1\cr}$$


How do i get concurrent asp.net on linux?

Question: -edit2- It turns out asp.net (i dont know if its mono specific) blocks if the url and ip address are the same. Its nonblocking if i run it from my local machine and server at the same time.
I have nginx setup using mono's fastcgi server (fastcgi-mono-server2.exe) on debian linux.
Below is a sample of my config file. I modified the page to sleep for 5seconds and opened up two tabs and visited the page. The 2nd took 10seconds to load (the first waits for 5seconds, loaded while i was looking at the 2nd page which then loaded 5seconds later)
How do i get concurrent request on the same website?
-edit- it seems to be concurrent across different domains/app since my other pages load while that test page blocks however the test pages are serial. I would like all pages on all domains concurrent.
<code>server {
    server_name    box.com;

    root /var/www/WebApplication1/WebApplication1;
    index Default.aspx default.aspx;

    location ~ \.(aspx|asmx|ashx|asax|ascx|soap|rem|axd|cs|config|dll)$ {
        fastcgi_pass   unix:/srv/mono/monoserve.pid;
        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
        include        fastcgi_params;
    }
}
</code>
Answer: Without knowing anything about mono asp.net, try disabling cookies when testing. It might be your application is locking session storage to keep things serial, thus consistent, per-user. Without cookies (also across domains), your tabs get unique sessions each.


Help defining architecture - async messaging; web app as portal in web page

Question: I don't know if this is a legitimate architecture that I've been playing with.  It consists of nodejs servers for services and to create web app front ends.  And it is using async messaging (Redis) to communicate between services.  And socket.io to implement full duplex comms between server and web apps.
So far in my example "stock portfolio" app this is working as desired (simple implementation with contrived data).
The goal of this architecture is to be fully decoupled through the use of messaging.  The services follow some API / Protocol and can publish and subscribe to desired channels.  Then this leads to alternative implementations of services and there will be some kind of broker to manage these situations.  I'm not up to that.
I'm stuck on having multiple web apps that exist inside or alongside each other.  For example there is one that is for managing the portfolio where users can enter in stocks they own.  And another that manages funds.  And another that displays data for all these.  And another for graphs.  The intention being that these are also loosely coupled.
At the moment I have one React app that displays graphs from contrived data (updated dynamically and redraw via socket.io).
How do I create such embedded web apps that need to be dynamic?  If the web app server was known about before hand then you could add the url in an <iframe.  But the intention is that some service would be providing the web app and it should send a message saying 'here is the url for my web app' that I want to display.
Does this sound sensible?  What is the best way to achieve the multiple web apps?  Are there any examples of this?
What about security issues (I've only thought about defining my own services and not allowing it open to the internet; but I might want to allow a more flexibly generalised approach)?
Answer: I had no traction on this question here so I asked the pure technical one at https://stackoverflow.com/questions/51172037/dynamic-portals-in-react-web-app and received an accepted reply to that - https://stackoverflow.com/a/51174869/1019307.
render() {
   const { iFrameSrc } = this.state
   // if You have the source, return the iframe
   if (iFrameSrc) return

   // if you dont have the source, render default
   return null;
}

I was also hoping for some comments on the architecture.  I'll work on it a bit more first.


Is Heady Topper by The Alchemist worth it?

Question: I have heard a lot about Heady Topper, the Double IPA by The Alchemist brewery, and how it is a fantastic beer. Online reviews always rank it exceptionally high and everyone I have asked that has tried it has said it was good. However, I have also been told that it is fairly pricey; due to name, renown, and the exclusivity of it. Would it be worth trying to get or order some?
Comment: Where are you located? If it's hard to obtain where you are, Reddit's [beer trade](http://www.reddit.com/r/beertrade/search?q=alchemist+heady+topper&restrict_sr=on&sort=relevance&t=all) regularly has an FT (For Trade) posting for Heady Topper. If there's a unique beer you can provide from your own region, maybe you can close a deal on it.
Comment: I am from Virginia, so there is a fair amount of breweries that are relatively close to me. Off the top of my head, I am not sure if there would be anything unique enough.
Thank you, though. I will try and see if there is anything I can manage from that site.
Answer: I've had it and I would say it's not really worth going out of your way for it. It's been overhyped, in my opinion, and while it's a good beer I don't think it's really as mind-breakingly good as many others seem to think.
I believe this discrepancy arises from the fact that Heady Topper is a relatively well balanced IPA. It has the hops bitterness to it that IPAs do, and the high alcohol content of a double, however it also has more of a malty body to it that most people are unused to when drinking IPAs. So lots of people are shocked when drinking it that it actually has some balance between the body and the aftertaste, so that's part of what leads to the high reviews (in my opinion).
So if the opportunity comes up to try it, sure, go for it. But I wouldn't really go out of my way to chase after it - there are other well balanced IPAs out there that are more readily available.
Comment: I figured as much. I'll take your advice and just not bother with it unless the opportunity presents itself. It's probably a good idea anyway since it is pretty out of the way for me and it's not like Heady Topper is on the cheap side.
Answer: I live in Vermont and I've had quite a few cans of Heady Topper and some from cask. I really love Heady Topper and I haven't yet had another DIPA that tastes similar. First, it's not that expensive. It's $3.75 for a 16 oz can. $14 for a 4-pack. You can get it at local bars, pubs, and restaurants for $5/can. Around $78 for a case (24 x 16oz cans). Compared to other DIPA of similar quality, it's not that expensive (sure if you compared it to macro lagers...)
It's produced by a small family owned brewery that's went through 2 expansions which doubled their brewery in size each time over the last 2 years (cannery has only existed for 2 years, before that they brewed it at a brewpub until the brewpub was destroyed by Hurricane Irene). They are currently getting their paperwork finalized for construction of a second brewery which will expand their production even more than before.
For locals, it's not that difficult to acquire. If you visit Vermont and plan ahead, then you're sure to leave with a case or two.
I think it's worth trading for, but just remember that there's no beer that's life changing. Just a lot of really good tasting beer.
Answer: I was recently in Burlington and picked up a couple of cases.
Yes, it's a good beer.
No, it's not as good as the hype suggests.
One of the previous posts hit the nail on the head.  Heady Topper has a good balance between the strength and the hoppiness.  It has what I call smooth strength.
But is it worth driving up from Pennsylvania and following the delivery truck around - probably not
Answer: Being in California, I have only been able to get my hands on one can. I did enjoy it, however I found it to be very common. In California we are bombarded with IPAs of this same ilk. High alcohol, created by adding sugar to lighten the body, and huge amounts of hops. Call me old school but I prefer IPAs that have about 7 ABV. and about as much hops as the average Pale Ale these days. Lagunitas just put out a beer that is 4.75 ABV with a bunch of hops. Maybe I can have two!


How can I configure my server so that my domain points to it?

Question: I have bought a domain name (without hosting), and at home I have a static ip address on Ubuntu server 11.04. How can I redirect users to my web server at home? What configuration needs to be done?
Answer: If your registrar has DNS, you just need to create an A Record in your DNS entries for your domain. This A record would point to your static IP address. Consult your registrar documentation on how to do this.
If it is not the case, you will have to setup a nameserver, or have to use a 3 a DNS service like dnsexit
Comment: My provider has but costs, i want a DNS for free, can i take for example http://freedns.afraid.org/ or http://dyn.com/dns/dyndns-free/. Thanks.
Answer: I don't know about purchasing a domain name that you can't point to an IP address so I can't help there (does this mean there are no configuration options for it) but I can suggest what needs to be done on your side of the net.

Give your webserver a static IP address on its local network.
Set your modem to forward incomming traffic to your webservers IP
Configure your firewall.
Make sure you have apache2 installed and dump your site under /var/www/

Step 1 can be done by taking the IP, netmask and gateway that your currently using and adding it into the IPv4 Settings of the network adapter you use to connect to the net.
To find your current settings use connection info under network settings in the top panel (by the time), and you can configure your adapter from there too. NOTE: This isn't the static IP that you bought from your ISP.
Step 2 will require logging into the modems web interface and trawling around until you find settings for Port Forwarding (somewhere around NAT or Address Translation). Add an entry to set port 80 (TCP protocol) (if given the option use 80 for public and local ports) to point to your IP that you set in Step 1 and apply the settings.
For step 3 I use firestarter but you can also use ufw (uncomplicated firewall) which is installed by default on Ubuntu (I haven't used it but here is a guide to setting up ufw). If you install it (available from Software Centre), open it and click the policy tab. Add a new service policy, select HTTP for the name, 80 for the port and the source is 'Anyone'. Click add and then apply the settings with the tick icon.
Your modem should also tell you what your WAN address is if you don't know it (or find your IP online. That's the address you want to point your domain name to (not the IP you gave your webserver in step 2). Also, you should be able to check that your webserver is accessible to the world by entering your webserver's WAN address directly in a browser address bar (you must either by outside of your home network, or use a free proxy server (which you can find at proxy.org) to break out of your network).
Answer: If your domain name provider provides DNS servers too, you should only add A record with your IP to it.
Else, you should install DNS server(i.e bind9) on your computer, add zone - your domain here and after that use it as DNS server on your domain provider
Answer: Well! Your static IP will pointed to your domain when you make changes in DNA record.It probably requires registrar advice.First of all you should note all the DNS records and informations before moving for registrar suggestions. To know the DNS record details make a DNS look up at WhoisXY.com website where i had checked my DNS information and further did the configuration.


Print long JPG onto multiple pages OSX

Question: I have a really long jpg comp I want to print out and annotate. My print options are to scale or fit to page, but I want it to print it to multiple pages, the cutoff points aren't important. I want it to fit the width and whatever is cut off, print to the next page. Is there a setting in OSX print options for this?!
Answer: I think there are settings for this sort of thing in Photoshop.
Otherwise, you might want to check into a tool that is meant to take images and make them span multiple pages, like Rasterbator.

Print long JPG onto multiple pages OSX


Applied for a job without attaching resume

Question: Is there any way to view an application and edit it after the fact? I was so focused on the cover letter part that I clicked "Apply" as soon as I finished writing it but by the time I realized my mistake it was too late. I know that SO uploads a PDF copy of your developer story if you don't upload a resume, but I feel like there should be at least a prompt to make sure that's what you want to do if you click "Apply" without uploading a resume.
Comment: The question title reminds me [this](https://cdn.meme.am/instances/500x/76195696/profound-advice-applied-for-job-without-attaching-resume.jpg)
Answer: Thank you for your feedback.
We're aware that the user experience around application could be better, and we are considering some ideas to improve it that may help the concern you raise.  Also, a few minutes ago we launched a new feature: when you upload a resume and submit the job application, the resume you uploaded is saved for the next application.  That way, you have one fewer thing to remember in your later job applications if you want to keep reusing the same resume.
I know none of this helps your immediate problem, and I'm sorry you experienced it.  Our intent is to make the Developer Story a great replacement for your resume, so if you have completed your Story, we hope it will impress the employer you contacted regardless.
Comment: Awesome! That sounds like a great addition.

As it turns out, I was able to find an email address to send the resume to directly, so no harm done :) Thanks for the quick reply!
Comment: Actually, how difficult would it be to have a prompt to remind a user that he/she has not attached a resume? What is your point of view behind not being ready to make this modification. Actually, you could have a checklist somewhere showing what user has/doesn't have. When any items are absent, you could provide a prompt.
Comment: @ParagS.Chandakkar That's probably not the modification we will make, to start.  We already validate required fields on the application form.  However, because we automatically attach the Developer-Story-generated resume for users who have a minimum-complete Developer Story, failure to attach a resume in this case does not cause a validation error.  Of the two approaches we might take to fix the problem -- neither of which is a prompt -- the cheaper one still requires _some_ design and development effort, and there are other competing priorities.


Correlating a sequence or a code with itself at QPSK symbol rate

Question: I am sending a QPSK signal that represents a certain sequence or code and  that needs to be correlated with itself on the receiver (there are other sequences/codes in the system, and they are all orthogonal). The result of the correlation should  indicate which code was sent . Suppose an AWGN channel, and at the output of the I and Q matched filters on the receiver  I have one sample/symbol that is a 'sufficient statistic" , so one sample on I and one sample on Q , and suppose timing synchronization is perfect and no other impairments besides AWGN (SNR is high enough), my question is the following:  Can correlation take place at the symbol rate ? or does one need more than one complex sample/ symbol in order to do the correlation?
Comment: It is unclear to me what the problem is. You can correlate any two sequences. Do you need it to happen in real time?
Comment: What I am asking is one sample /symbol enough for correlation?
Answer: The answer is yes, absolutely 1 sample per symbol is sufficient if your symbol timing and frequency offsets are sufficiently accurate (they need not be perfect).
Regarding frequency accuracy: The magnitude of correlation vs frequency offset is a Sinc function with first null at 1/T where T is the length of the sequence being correlated.
I started to develop this point in another recent post (Derivation of the Optimal Matched Filter - Convolution vs. Correlation) showing the first three samples of a correlation when a frequency offset exists. The results in this post showing correlation without a frequency offset should make it very clear why 1 sample (the correct sample) per symbol is sufficient.  In the plot we see the resulting Sinc response of correlation vs frequency offset with the first null at 1/T = 1 Hz. If we needed a wider tolerance to frequency offset, we could easily correlation over 100 samples in the case to then push the null out to 1/.1 = 10 Hz. Of course we would lose 10 dB in processing gain (see prior post referenced) so we see the trade of SNR needed versus the frequency inaccuracy that can be tolerated.

This next graphic continues that example to show the case of a correlation over 1000 samples vs frequency offset when the sampling rate is 1 KHz. This means that T = 1 second in this case, and we see that if we considered correlating a 3 Hz signal to a 4 Hz signal, that after summing 1000 products, the summation will be back at the origin (correlation null).

The exact relationship for the correlation versus timing offset depends very much on the pulse shape of each chip in your signal (the change in magnitude for each sample due to timing offset), and the concern therefore would be both with a timing offset in time, and a timing offset in frequency (this is different from the frequency offset above in that an offset in frequency of the timing clock will cause it's sample position within the symbol to roll, while a frequency offset in the carrier will cause the complex IQ correlation to rotate on the IQ plane.).
Both cases are easily computed by knowing that correlation is a sum of products, and correlation sequences typically have the same number of 1's and 0's (or close to the same number, often they are an odd number so in that case would have one greater 1 than 0 or vice versa).
Answer: just as a simple example.
let's say we want to find the sequence h in data
let's make
h = [ 1 2 3 4 5 ];

now we got data with h in it and we want to find where h starts
let's make data
data = [ 0 0 0 0 0 1 2 3 4 5 0 0 0 0 0 0 0 0 0 0];

to find where h is we can use convn
hfind = conj(  h(end:-1:1)  );

hdetect = convn(data,hfind,'same');

[maxnumber,index] = max(abs(hdetect));

index will be 8
so h starts at  index - (5/2) = 8 - 2
so h starts at sample 6 in the data set
hope this helps


Do I use SO to ask for code sample/solutions?

Question: Would I use SO to ask a question about looking for code samples or solutions that can read/write a standardised file format? [e.g. Australian Payments Clearing Association's Direct Entry file specification, used by all Australian banks].
Comment: There also [the Software Recommendations sister site](http://softwarerecs.stackexchange.com/).  You couldn't ask for sample code there, but you could ask for a library that performs the task (and its documentation should have usage samples)
Comment: @BenVoigt Please be aware of the strict rules over on SR. I've added your suggestion to my answer.
Answer: No, those type of questions fall in Some questions are still off-topic category:

Questions asking us to recommend or find a book, tool, software library, tutorial or other off-site resource are off-topic for Stack Overflow as they tend to attract opinionated answers and spam. Instead, describe the problem and what has been done so far to solve it.

Instead you could start on your own, implementing a reader or writer for that format and ask a question when you are stuck. Good chance someone answers, maybe with a link to more material.
As  Ben stated in a comment you could ask for a library on SoftRec. But if you do please take note of the following rules.
tl;dr don't post I search for a library to do X on SR because it will fail miserably

If you visit Software Recommendations you'll find this text on their on-topic page:

Good software recommendation requests have two components:

A purpose — a task to accomplish, a user story
Some objective requirements — a minimum set of features

Beyond this they have a post with quality guidelines that require you to post the correct content in the correct format.
On content expect to provide at least: the kind of application you're looking for; the operating system to be used; your budget; needs and features of the application
For formatting you have to make sure that your post has a clear title and it's features should be listed in order of importance.
Visit their meta for extra guidance.

Adapted from my own answer on MSE
Comment: Thanks. I've certainly made a start and am porting our old code to new, but it's a shame there's only a loose collection of blog posts and very little guidance beyond the spec. (I'm sure I could do it much better). I will look at Ben Voigt's suggestion about Software Recommendations too.
Comment: @PeterX please check my additional edit before you go the SR route!


Why is Premartial Sex punished in Islam?

Question: My question is that why premartial sex is punished by the state in Islam? I mean, it is entirely the personal matter of two individuals, regardless of their faith. If two muslims commit premartial sex, God would punish them in afterlife. And if two non muslims commit it, they are not bounded by Islam so they shouldn't be punished. But why does the state punish them? Specially if its done in private? Its a non violent act. I mean its not like robbery, murder or other crimes that affect other people.
Answer: The main reason for the prohibition of pre-marital or extra-marital sex is to safeguard the family as an institution. Islam like other religions, recognizes family as the main building block of human societies.
The importance of living together as a family can be understood by looking at the life cycle of a human being. When he is born he is weak and is capable of doing nothing by himself. He needs care and proper guidance until he matures into adulthood. In his adulthood he is finally able to contribute constructively to the society. And his strengths get gradually reduced as he becomes older. Without a strong family unit, it would be impossible for him to get through the stages in his life when he is weak.
A strong family needs a mother and a father; to care and to provide. The absence of trust or the absence of a full commitment between these two to each other, would result in a disrupted family life. This in turns leads to the creation of human beings who are incapable of contributing positively to the society.
Islam wants to prepare human being and wants him to adopt a lifestyle that would help him avoid all the things that might lead to a dysfunctional family. These includes pre- and extra-marital sex. They both have a very strong potential of disrupting a family life to say the least. Pre-marital sex makes him prone to a lack of commitment and orients him toward seeing this relationship as merely sexual. Where as extra-marital sex leads to the destruction of trust.
To avoid values such as open sexual relationships creeping into societies, Islam sanctions punishments for individuals who act utterly irresponsibly and break down these boundaries. It doesn't concern itself very much with what individuals do in private, but if their actions are so brazen that they engage in such acts openly and could careless even if a group of adults witness them doing the act, it draws the line and wants to put a stop to it.

I'll refine and rephrase the answer soon
Answer: Because it is a rule set down by Allah. It is zinah, and zinah is forbidden, because it could only bring us into difficulty. This law is for the better of a society, because if people committed premarital sex like it's normal, women would suffer badly if not the men. There would be marital problems, and a high divorce rate, like in the U.S. And one reason is that it sets us apart from other animals. Allah is the Most Wise, the Eternal. He set these rules to guide us to the straight path. Imagine if your daughter or sister were involved in such an act. Disobeying Allah's laws for a moment of pleasure would only result in a lifetime of regret and shame.
Answer: Although is a personal matter, liberalising such behaviour does inevitably lead to worse situations. Consider the fact that such behaviour is perfectly fine in western countries and as as result you have high number of abortions, females with no husbands and looking after their newborns because they decided not to abort, diseases as a result of being careless and so on.


What differences are there (if any) between building a world for rpg-gaming and building a world for story-writing?

Question: From my own perspective I don't necessarily see any immediate differences, but I'm newish to the field. What differences have you come across in regard to building for these two different scenarios (an rpg world and a story world), and should a builder consider what the world will be used for before beginning their building?
Comment: @CalWest From the perspective of RPG-gaming, do you mean designing for an existing system (e.g. create a world to play Dungeons and Dragons in) or designing a world to be the setting for a new system (e.g. designing system and world in parallel)?
Comment: @KRyan I meant the latter. Designing system and world in parallel.
Comment: So you're looking at this from the perspective of "I want to build a world, then I'll see what it might be useful for" rather than "I want to tell a story this way, and I need a world to set it in"?
Comment: Yes, using a builder's perspective, not a DM or author's perspective. The person building the world may not be the same person who writes the stories about it.
Answer: There is a little bit of subtlety I want to clear up in your question before answering.  There are two ways to build a world independent of its use:

Build a world then select a use for it based on its characteristics
Build a world expecting that it can be use for any use

From your comments it sounds like you lean towards the first but I will try to discuss both.
The first idea is very similar to story creation when deciding what media it will be portrayed in.  If your story has a lot of action sequences, you may lean towards a movie, a lot of dialogue may lean towards live play, a lot of psychological ideas may lend itself towards a novel.  Anyone who works with stories knows that some stories are better suited for different media.
It is very similar for world building.  For a world you have created you would look at different characteristics such as how well defined are the physics, how many minute details are included, and the events that go on in it.  A small, very detailed world with well defined physics may lend itself toward video games or a tabletop RPG.  If it lacks the physics definitions, it may be more suited to being paired with an existing tabletop RPG system.  A loosely defined world with large events happening may work better for story-telling (novel, etc.).  But there is no reason this has to be decided before you make the world.  Build the world you want to build, and likely before you finish, you will understand what uses would best fit it.
The second bullet above, however, is the trickier of the two.  If you want to build a world that someone else can pick up and say "I want to use this as a setting for a novel" and someone else says "I want to make a video game here" and yet another "I'm going to write the next script for a James Bond movie in this world", you are setting a very tall order.  This sort of world almost requires a top down design process.  You can't possibly design all the details for it, some of it has to fall to the individual authors.  Therefore it must be designed to detail the parts of the world that would impose consistency between the different author's creation.  Physics, political maps, geography would all be required.  Detailed demographics would also be very important.  It would need to be detailed enough to provide consistency without being so complex that the authors can't possible get it right.
This is also much more difficult to do if you plan on it being paired with a generic tabletop RPG system.  An RPG system, by definition applies rules to the world.  You would likely need to have the system in mind before designing the world to ensure that the rules the world makes is consistent with the rules of the RPG system.  With a little work you could even make it compatible with multiple systems, assuming the systems themselves are consistent with each other.  I don't think it would be possible to design a world that would work with any RPG system, however.
Comment: Note that, based on comments, @CalWest means a tabletop game, a la Dungeons and Dragons, and not a video game, when he says RPG. There are similarities, of course, and I've upvoted your answer since it's not major, just a thing to be aware of.
Comment: @zoltan yes, somewhat.  For example, a world for an animated series will need to have the architecture and clothing much more developed than a world made for a novel
Comment: Yes, I understood that, I just pulled a couple examples.  I will look for a way to include a tabletop example in the discussion.  It is just a tricky thing to do since table tops are usually more difficult to build worlds for than other media.
Comment: @GodricSeer if a world is specialized for storytelling, do you think it matters whether it'll be the base of a video game, an animational series, a comic or a novel?
Comment: "*I don't think it would be possible to design a world that would work with any RPG system, however.*" - assuming someone(s) had the time and patience to design a world as full and complex as our own (*including our entire history*), I think it's possible - you'd just have to be careful about using a suitable rpg system for a suitable piece of the world/time. So while I'd consider it possible, it certainly wouldn't be practical.
Answer: Note: since you mentioned DM in your comment, not Game Designer most of my answer will consider rpg world to be D and D like instead of Skyrimish.
The main difference is purpose.  An rpg world is typically designed to allow multiple people to play characters in the world over a long period of time several times, such as D and D.  Even a game like Skyrim gives a player multiple ways to build their character and explore the world.  A story is written once, by you, under your complete control.  That means an rpg world must be balanced and open ended.  Everyone needs to have fun and should be able to reach the same level of inworld power.  In a story you can have the prophecied one, someone with extreme or unique abilities.  That doesn't work as well when multiple people are involved.
All this means that your first consideration when designing an rpg world is balance, you are creating a world for other people to tell stories in.  Each person needs to have multiple choices available to them that allow them to have as much fun and impact in the story as anyone else.  Since you hope the world will be used multiple times, you need a large world to give players plenty of area to explore.  Mechanics need to be simple and well defined.
For an actual story, you only need to create as much of a world as your characters will interact with.  Mechanics can be bent to fit the needs of the story.  Since you control the story, you can have a much narrower focus.  I think of it as, building a world for others to tell a story requires a telescope, a long range overview that gives plenty of room for exploration.  A story is a microscope, a narrow focus on particular characters on part of your world.
Answer: As others have said, the differences are fairly subtle.  In both cases you need a world that's well-enough developed to be plausible and interesting to the people consuming it (readers or players).  But there's an important difference: RPGs have players.
Well duh, you're probably saying.  Let me unpack that.
A work of fiction like a novel is controlled by one person (absent unusual situations like shared-world collaborations), who is usually the world-builder.  You build the world for the purposes of your story, revealing its characteristics in the telling, and if you need to adjust something while you're writing, you do that.
An RPG has players who interact with your world.  In the course of doing that they may bump into problems you don't want your world to have (such as inconsistencies) that you wouldn't have found on your own.  You might decide to fix those issues rather than living with them.  If you fix them, you have to decide whether to do so in-game ("you've just discovered a new magic manual and it says...") or in consultation with your players ("look guys, I didn't mean to make it impossible for you to create simple healing potions; forget that thing I said about needing unobtanium").
And sometimes, as the players discuss what they're experiencing, they'll speculate about your world and you might hear something that you like even better than what you were doing, so you might want to incorporate it.  This happened to me once in a game I was running and I found myself rewriting the explanation for an important artifact in real time because a player had said something that sounded way better than what I'd done and I wanted to run with it.  This can be exciting (you're now part of the collaborative story-telling just like your players) but also nerve-wracking (you need to not mess up any of your other secret information, and you need to be good at thinking on your feet in multiple dimensions).  I don't recommend doing this often, but in an RPG setting you have the option in a way that doesn't come up as much with fiction where, at best, you can address complaints in reviews in a later episode.
Bottom line, an RPG gives you the opportunity for more collaborative world-building even if you aren't explicitly inviting your players to the design table.  Depending on how rich your world is and how story-focused your game is, your world-development and progressive-revelation processes could be very different from those you'd use in a story.  Here are some links from the Worldbuilding blog that discuss these issues in more detail:
RPGs (these are all by me):

Revelation for RPGs I: Setting the Stage
Revelation for RPGs II: The Written Word
Revelation for RPGs III: Your World is Made of People
Revelation for RPGs IV: I Can See Clearly Now

"Behind the scenes" fiction (various authors, related to stories posted on the blog):

Artificial Stupidity: Behind the Story
Sisters: The Story Behind the Story
Worldbuilding 101: On Suspension of Disbelief (could apply to either form but is mainly about writing)
Answer: There are a number of good answers, but I'm hoping to condense and shorten the ideas presented:

a RPG-world includes "empty spaces" for the player to take actions and define themselves or their world.
a Story-world includes "empty spaces" which are open to interpretation and guessing, but knowing what happens during these spaces does not affect what will happen for the remainder of the known story.

Both cases do not necessarily require previous knowledge of which you are going for, before creating the world. However, it may require more world-building in some areas, and less in other areas, depending on what you eventually decide to do with it.
So, you could create your world, leaving more specific parts blank for whether you go for a story or rpg.
Or, you could create your world, and flesh out everything for both the story and the rpg, knowing that some of that information may get thrown away later.
If you want to do both story and RPGs in the same "universe", you could look at which pieces of your world are more relevant to a story. (Probably pieces of the world's history and major events). As well as look at the events and places that are not as defined - and allow your RPG game to take place where the players would have more influence.
An example might be the Lord of the Rings universe. The story of Frodo and the Ring is defined, but many RPG games focus on the doings on what some other person (the player) is doing somewhere else, or even at, some of the major events of the story.
Answer: The difference lies in the relative scope and detail levels; the world of a novel has less scope but more detail than the world of a RPG. Novels follow set lines created by the author so they only ever use a small part of the world they are set in but they use those areas very heavily so they have to have really full and lush details. RPGs have a planned outline but Player Characters (PCs) will go off and do unpredictable things in unpredictable places so the world has to be mapped completely because you don't know what you may need but PCs also don't tend to spend too long in one place so they can be kind of shallow in their details except where the GM needs them for the overarching campaign.
Answer: I think the differences are fairly subtle if you want to do a good job with either.  The main difference in my mind is how apparent the different aspects are to your target audience.
In either case you are creating the settings for a story.  You need to figure out the nature of the environment (climate, geography, resources, etc.), the form of the society(s) (population density, main pass times, cultural rules, technology level, etc.), and at least an outline of how things got to be the way they are (historical events, migration paths, wars, etc.).  A key point is making sure you have internal consistency.
For example, having a major city on top of a mountain or in the middle of a desert wasteland doesn't make a lot of sense on the surface. What brought people there in the first place? Why do they stay? What resources support them? How have the above influenced their culture?  Crafting your world to provide reasonable and reinforcing answers to those questions makes a big difference in how immersed people become in the stories.
The difference between building for a story and a game is in how you present things.  In a book you have all of this framework that you hang your story on, but none of it may be apparent to the reader if it doesn't advance the plot.  It should however be apparent to you that the assumptions and actions of the characters fit with living in this setting and their individual backgrounds.  Which brings up the point of character development, in a book type environment, it is all on you to figure out the traits, background, and motivations for each character the reader sees.  In some ways each character that comes to the foreground is a world building exercise in itself.  One major advantage of the book type setting is that it supports an iterative approach, you can go back and adjust and revise things until you have a cohesive whole.
In a game setting the perspective changes.  The audience is not passive and focused by the scope of vision you have presented to them (or at least not in most good games).  Instead you have to split the load and let the players help shape the plot as the story progresses.  You as the world creator need to give them enough background to know how their characters fit into the setting, while allowing them to discover the rest as they move through the world.  This is a difficult line to walk. Giving the players too much kills alot of the mystery and discovery that can keep a game interesting.  Not enough information makes the game feel disjointed and contrived.  And it is almost guaranteed that at some point your players will take off and run in some direction you were not expecting.  The more complete your view and understanding of the world is, the easier it is to figure out what the outcomes of such actions should be.


Can I get smaller tires without changing my rims?

Question: I currently ride a hybrid that came with 700x32c tires. Can I swap out a narrower tire without changing the rims, or do rims only fit a specific size of tire?   How small can I go before I have to buy new rims?  I hear having narrower tires makes you go quite a bit faster.  Does it really help that much?
Answer: Most 700c rims will work with essentially any size of tire. Yes, smaller tires generally reduce rolling resistance a little, but unless you're road racing, it's rarely worth going below about 700x23c, IMO. Also note that just being smaller doesn't necessarily mean lower rolling resistance -- one brand of 700x19c might have higher rolling resistance than another brand of 700x20c, for example.
The big change (if any) happens when you switch to slick tires (and most 700x32c tires have fairly substantial tread if not outright knobs).
Comment: @Kibbee: You *will* gain a little -- but with smaller tires, it's also easier to get snakebite (pinch) flats.
Comment: I replaced my rear tire last year with a slick tire, from a tire with a fairly flat tread.  It's about time I switched out the front tire as well,  I was wondering if I could go narrower as well as more slick to get even more performance.
Comment: I would also note that if you want to get better performance, make sure that your tires are always pumped to the max.  The harder your tire is the faster you will go.
Comment: "essentially any size" is a bit of an exaggeration:
http://www.sheldonbrown.com/tire-sizing.html#width

Also, all other things being equal, a fatter tyre has _less_ rolling resistance. But (i) thinner tyres have less aerodynamic resistance which matters more to racers, and (ii) all other things aren't equal, because a narrow tyre can be run at a higher pressure with the same tyre construction.
Answer: For smooth tires, rolling resistance is a relatively small factor in terms of your overall performance.  The optimal tire depends on your riding conditions and personal riding style.  Narrower does not automatically equate to faster - there are both terrible narrow tires and excellent wide tires available today.  If a tire otherwise possesses the characteristics you desire - such as grip, flat resistance, cost, handling - you'll probably be just fine riding it from a pure performance perspective.
It's also categorically false that maximizing the pressure in your tires will make you faster.  There is a "sweet spot" in inflation where the tire is stiff enough to roll smoothly but still able to smooth out road vibrations that lead to fatigue.  Bicycle Quarterly tested and published a handy inflation cheat sheet that may help you dial in your optimal riding pressure.
As far as rim compatibility, the width of you rim will affect the shape of the tire; if you plan on running any tire narrower than 28mm you should measure your rim and consult this handy chart.  It's overly-cautious but a useful rule of thumb for the new mechanic.


Why are the episodes "Crocodile" and "Hang the DJ" named that way?

Question: In Black Mirror season 4 there are 2 episodes named Crocodile and Hang the DJ. These are the only two episodes that don't have an obvious explanation for their name. Why are they named this way?
Comment: @Fogmeister But they could use any other song and give any other name to the episode. There might me a meaning
Comment: Hang the DJ is the name of the song playing in the pub at the end of the show.
Comment: I haven't watched either episode yet but, Hang the DJ seems conceptual to the idea of 'blaming the orchestrator' [when things go wrong] -- and may have themes about playing God vs having freedom to make one's own decisions.  Crocodiles are usually symbolic to primal instict, fertility, and strength. The episode's trailer seems very pyschological thriller to me, so I suspect that survival or preservation of the self coud be a theme? I'll come back after I watched the episodes though, if I think I have a better understanding.
Comment: @Fogmeister Hang the DJ  is not the name of the song, Song name is "Panic"
Comment: @Fabich that's true.
Comment: I'm watching the Crocodile episode now and so far I think every answer on here is accurate or valid, along with my initial thought of self preservation as a theme--the insurence tech def has croc mouth motif, croco-tears is def an analogy  (mia in front of the rain on water digital art motif)-- so is the the idea of struggling makes it harder to survive (because the 'deeper' water one is in). One building has something that might be comparable to scales/skin cells as a kind of croco-motif and there is this character looking out/next to window motif (eye of the croco-idea)...
Comment: I believe it has to do with crocodiles having amazing memories and since this whole episode was about memories it made sense.
Comment: I think that Mia becomes addicted to killing, she had other ways of solving her problems, but instead she always opts on killing. So it may have something to do with the most addictive drug known, "Crocodile".
Answer: "Hang the DJ" is the chorus of the song "Panic" by the Smiths, which is played at the end of the episode. The gist of it is that the songs on the radio are meaningless to the singer and don't describe his life. My guess is that the various relationships they go through without each other were meaningless to them, hence they ended up with their 99.8% rating in the end.

Panic on the streets of London
Panic on the streets of Birmingham
I wonder to myself
could life ever be sane again?
the leeds side-streets that you slip down
i wonder to myself
hopes may rise on the grasmere
but honey pie, you're not safe here
so you run down
to the safety of the town
but there's panic on the streets of carlisle
dublin, dundee, humberside
i wonder to myself
Burn down the disco
hang the blessed dj
because the music that they constantly play
it says nothing to me about my life
hang the blessed dj
because the music they constantly play
on the leeds side-streets that you slip down
provincial towns you jog 'round
hang the dj, hang the dj, hang the dj
  hang the dj, hang the dj, hang the dj
  hang the dj, hang the dj, hang the dj
  hang the dj, hang the dj
  hang the dj, hang the dj
  hang the dj, hang the dj, hang the dj
  hang the dj, hang the dj
  hang the dj, hang the dj
  hang the dj, hang the dj, hang the dj
  hang the dj, hang the dj
  hang the dj, hang the dj
  hang the dj, hang the dj, hang the dj
  hang the dj
Answer: I think that "Crocodile" refers to the Crocodile tears :

The expression comes from an ancient anecdote that crocodiles weep for the victims they are eating. A collection of proverbs [...] suggests that the phrase "crocodile tears" was well known in antiquity: comparing the crocodile's behaviour to people who desire or cause the death of someone, but then publicly lament for them.
  (Wikipedia)

I think this represents Mia who 'needs' to kill people to protect her secret but then cry and lament for what she did
Comment: That doesn't sound right to me. Crocodile tears means its fake tears. Her tears were real. She was genuinely remorseful and didn't want to kill those people.
Comment: @DavidGrinberg: Mia's tears are fake, to some extent. They are only real when she believes what she's telling herself (that it needed to be done - which is not true but she makes herself believe it as a coping mechanism). Killing the child seals that suggestion: she quickly decided to kill the child, when she should've quickly been able to spot that it was blind and therefore did not need to die _even by her delusional standards_. When arrested (after the episode), she'll likely still claim that she's a victim of circumstances => those are self-delusional crocodile tears.
Comment: It's unclear if she's really remorseful, because she doesn't show any other emotions (it's quick & over quickly) and because she continues to go beyond the pale, showing how cold/calculating she can be. It's also unclear if she is doing it protect her family vs herself, given she was a more moral person before having a family, as she wanted to call the cops in the opening scene. However, I think the other character seemed "unprotective" and without instinct alltogether,so there may be an argument about what "fake" emotions really are when contrasting the two female leads.
Comment: I think its quite obvious she is remorseful.... this clearly isn't something she wants to do. She isn't a serial killer, she just wants to keep her life. Calling the cops after the fact wasn't an option anymore because it would open her up to the past crimes. Honestly I think this answer makes no sense and I downvoted it
Answer: My best guess is it's a homage to the pilot episode of Fargo, The Crocodile's Dilemma, which has some similar thematic elements:

...crashes a car at night on a wintry rural highway outside Bemidji,
Minnesota, after hitting a deer

and a series of ever complicating mishaps, including

Lester... hits her with a hammer and kills her.

Googling "black mirror fargo" does pull up some other sources that note the similarity:

"Crocodile" contains numerous echoes of Fargo and A Simple Plan, similar morality tales set against similar desolate landscapes, and both stories of the totality of desperation and the futility of fate. Vox
Once you understand where "Crocodile" is heading, it's already too late. The bleakness of its ever tightening spiral has already sucked you in, and you're just left to reckon with it and its high body count. The knee-jerk reaction would be to say that this "Fargo in Iceland" vignette is dark for darkness' sake — and that's not necessarily an incorrect assessment — but buried beneath the bleak is a message about the unexpected ramifications of our increasingly connected society. Entertainment Weekly

"Hang the DJ" is definitely named after the song, as others have noted.
Comment: This sounds like a good reason. If you can find a citation I'll accept your answer
Comment: Why the downvotes here?
Comment: I don't know--you def found Fargo evidence, which I think adds a layer to the answer for that episode, but I think the poblem lies in that being influecned by something is only part of an answer--one has to get into what 'crocodiles' generally tend to symbolize (or croco analogies in pop culture) and/or how that symbolism is applied to the story/stories.
Answer: First let's talk about Hang the DJ:
Here you have to go through 1000 simulations to check compatibility but the twist is that the system will always try to separate you in one way or another and the right way to rebel against system is to prove your compatibility which Frank and Amy did 998 times out of 1000, making their compatibility level 99.8%.
Only time we hear the words Hang the DJ is in the end of episode where we hear The Smiths's song Panic, you can refer whole song's lyrics here, relevant part of lyrics goes as :

Burn down the disco
Hang the blessed DJ
Because the music that they constantly play
It says nothing to me about my life
Hang the blessed DJ
Because the music they constantly play
On the Leeds side-streets that you slip down
The provincial towns you jog 'round
Hang the DJ, hang the DJ, hang the DJ

Which shows the rebellion of the singer to the the DJ who is playing something which cannot be related to the singer. There are claims that this song was targeting a real DJ:

Legend has it that Morrissey and Johnny Marr wrote the lyric "Hang the DJ," as a protest against a specific DJ named Steve Wright, whom they despised because of his insipid taste and adherence to a kind of corporate approach to music. So, the idea of singing "hang the DJ," was about rejecting the music being played for you, to think for yourself, to rebel. - Source

Same applies for the episode where they have to rebel against the system to prove their compatibility.  So Hang the DJ subtly hint on that real aim is not to make system do your match but to rebel against it like singer is rebelling against the DJ.

Now my take on Crocodile:
As Fabich's answer compared it to Crocodile Tear, which is not really wrong, her tear didn't appear that fake to me but looks more like psychotic tears. I don't see much of remorse as she was fine with killing as many people as she can to save herself. She is just being a psychotic selfish bitch who doesn't care about others if they come in her way, her tears have no meaning as she did nothing in her remorse like surrendering or anything like that, she played it like a pro. If there was no guinea pig she could have survived easily.
But there can be another angle too which is presented in Darth Locke's answer. I remember a famous animal fable from Panchatantra called The Monkey and The Crocodile.
It's a story of how crocodile was fine with sacrificing his best friend a monkey for his wife because she thinks monkey will be so tasty because he ate lots of red apples. It shows clear selfish motives of crocodile and this is not the only story/fable where crocodiles are represented in negative light. From Wikipedia page about Panchatantra:

The names connote the character observable in nature but also map a human personality that a reader can readily identify. For example, the deer characters are presented as a metaphor for charming, innocent, peaceful and tranquil personality who is a target for those who seek a prey to exploit, while crocodiles are presented as a symbolism for those with dangerous intent hiding beneath welcoming ambiance (waters of a lotus flower-laden pond)

So the episode title refers to the Mia's character who is selfish and ruthless while showing crocodile tears after doing a horrific act.
Comment: I think you make a good point about the croco-tear allusion being psychotic--I rewatched the episode and kind of thought maybe, that the insurence agent was actually less sensative in some respects (her husband had to convince her about the hampster being good for their son). It could just be me, but I just felt like she had no intincts and was unpreppaired for a job that I could easily see going south.
Answer: Crocodile Symbolism:

(Above: Sobek)
Crocodiles are featured across many religions and belief systems. Generally, crocodiles are often symbols of strength, fertility, and primal instincts and therefor can be symbols or metaphors for the concept of "self preservation". However in some religions, such as Christianity for instance, crocodiles can have an association with chaos and the devil with the idea being, one is destroyed from within.
(Leviathan: Serpant, Dragons, Etc)

In Bible crocodile is mentioned as one of the monsters of chaos.
  Because of this fact crocodile was later associated with the Devil in
  Christian symbolism. His natural enemy hydra kills him from inside
  like Jesus Christ destroyed Hell after having descended there for
  three days. Hydra represents Christ and crocodile stands for Hell. The
  hydra rolls itself into damp mud till its look is indistinguishable,
  and then makes its way into the mouth of the crocodile, which swallows
  it unawares, and instantly bursts asunder. During the Middle Ages
  stuffed crocodiles were chained on the walls of the churches. They
  represented chained Devil. http://symbols.ehibou.com/crocodile/

So how does this relate to the episode?
Crocodile is specifically about two woman, both MOTHERS, whose paths become intwined, with one women's abilty to do what she BELIEVES she needs to do, in order to survive (ie: not be held accountable, not be caught), but ironically, one accidentally becomes on the hunt for the other. It's a disturbing tale of misfortune by one women for people that are innocent.
It's a pyschological thriller & crime drama with one women almost uncautiously or complacently doing her job, with another relentless of being caught or trapped. Of course this is also personified through the episode's memory-sensory technology (Recaller), which furthers the pyschological aspect, because of the idea of accuracy of memory (which in itself can be subjective) vs if one can actively manipulate one's memory to produce major falshood?, which is distrubanly answered.
There are motifs and allusions pertianing to things one might characterisically associate with a crocodile throughout the episode, especially relating to the character Mia, but the crocodile is not the only animal featured, as there are allusions and reference to other animals, which then furthers the scope that this is about survival of fittest with people behaving like animals (Not unlike Thomas Harris' Hannibal Lector series).
Some Crocodile Motifs

Iceland as a primary location gives us a sense of "coldness" playing to the idea of being characteristically cold-hearted/cold-natured: detached, unfeeling, distant.
A building that Mia gives a conference in. The windows have a plant cell or "scale" motif, but it also could be compared to a crocodile eye, which is highly advanced being able to see several tragectories or targets, are retractable, and nocturnal, giving it a great tactical advantage.
Windows - Many characters are seen next to or looking out of windows. Windows are then used like "eyes" looking into other "eyes", shown through the memory sensory tech, as means for the insurance agent to follow the trail...
The memory sensory technology. The Recaller machine that conects to the chip, opens like a crocodile's mouth would.
Character Mia in partiuclar comes off with a crocodile-like dispostion, incuding a scene with an allusion to Crocodile Tears (fake sympothy), which is furthered by other scenes where the character only sheds tears as opposed to showing any other emotional response. There are also shots of the character's black "leather" shoes and it becomes clear that she is willing to go great distances to protect herself.
Insurance Company Costumer's Apartment with Animal Motif. Plants on shelves, large cat statue, zebra print throw-over, ect.
Comment: Nice answer but Why only answer half the question
Comment: Fair enough, I did liked your answer and kind of borrowed teh angle in my own answer too, +1
Comment: @AnkitSharma because I haven't seen the other episode, Hang the DJ, yet to better determine the meaning of it's title and/or how to apply the song it's in reference to!
Answer: Crocodile is likely named after the technology used; the memory monitor opens a bit like a crocodile's mouth
Comment: Do you have any reference for that? That machine was used in a few episodes I think, but no other was called crocodile.