Can you use spell-like abilities in a grapple?

Question: The rules say you can cast spells as an in-grapple maneuver (subject to some strict limitations), but don't appear to expressly mention spell-like abilities.  Yet in most ways spell-like abilities act and cast as spells without components. Does being in a grapple preclude the use of spell-like abilities?
Comment: Related: [Are Spell-Like Abilities actually Spells?](http://rpg.stackexchange.com/questions/28993/are-spell-like-abilities-actually-spells)
Answer: Yes you can use them, but you would have to make a concentration check or lose the usage.
According to the SRD on SLA:

A spell-like ability has no verbal, somatic, or material component, nor does it require a focus or have an XP cost. The user activates it mentally. Armor never affects a spell-like ability's use, even if the ability resembles an arcane spell with a somatic component.
Using a spell-like ability while threatened provokes attacks of opportunity. It is possible to make a Concentration check to use a spell-like ability defensively and avoid provoking an attack of opportunity. A spell-like ability can be disrupted just as a spell can be. Spell-like abilities are subject to spell resistance and to being dispelled by dispel magic. They do not function in areas where magic is suppressed or negated.

And then under their section for Grappling:

You can attempt to cast a spell while grappling or even while pinned (see below), provided its casting time is no more than 1 standard action, it has no somatic component, and you have in hand any material components or focuses you might need. Any spell that requires precise and careful action is impossible to cast while grappling or being pinned. If the spell is one that you can cast while grappling, you must make a Concentration check (DC 20 + spell level) or lose the spell. You don't have to make a successful grapple check to cast the spell.
Comment: You emphazised the part of text on SLAs that talked about attacks of opportunities and casting defensively, which is not relevant to the question. The sentence I bolded in my edit, though, could be a good reason to ask the concentration check for SLAs too.
Comment: I was initially going to suggest a reroll for grapple control as an AOO but then realized there's no true foundation for it.
Answer: Yes, you can use spell-like abilities in a grapple.
Spell-like abilities, amongst other things, have no somatic, verbal or material components, making them suitable even in situations, such as grapple, where you're prevented from acting freely.
Mechaniclly, my deductions work on three levels:

The list of possible actions that is given for grappling is not an exhaustive one, because it misses the word only. Only spells are hard to cast and SLAs are never mentioned, leading me to think that one can cast them freely.
As @Ernir pointed out, this is not a strong point: WotC is quite infamous for not meaning what they write and the list could have been intended to be an exhaustive one. Again, we're heading into RAI here.
The text describing what a SLA is, quoted in @CatLord's answer, suggests that grapple works when it comes to disrupting SLAs.
Now, disruption is about concentration checks against damage made to the caster during spellcasting, which is not what grappling does but for lack of something specific on grappling could be considered a good analogy.
In his comment to this answer, @GBorreson points out PHB, page 70:

A character with the Combat Casting feat gets a +4 bonus on Concentration checks made to cast a spell or use a spell-like ability while on the defensive (see page 140) or while grappling or pinned.

So, you should treat SLAs as spells without any component for the purpose of grappling.

Glossary:
RAI: read as intended, as contrapposed to RAW - read as written.
SLA: Spell-Like Ability
Comment: The PHB is full of cases establishing this analog. E.g. p.70: *A character with the Combat Casting feat gets a +4 bonus on Concentration checks made to cast a spell or use a spell-like ability while on the defensive (see page 140) or while grappling or pinned.* (That one even refers to grappling.)
Comment: This is similar to other questions we've had on this where the designers sometimes say "spells and spell-likes" and sometimes don't, even conflictingly - like dispel magic doesn't mention spell-likes but the dispelling rules include them explicitly. Curse those game designers for not making legally binding documents!
Comment: My concern is that the rules state that in a grapple you can "perform only the following maneuvers" from a list that includes casting spells but does not mention spell-like abilities.  Generally, I read that as meaning you can't take any action that isn't on the list.  By that logic, if you can analogize a spell-like ability to be included with casting spells, you should be able to do it subject to the same limitations as spellcasting, but if spell-likes are not treated as spellcasting you shouldn't be able to do them at all.  I'm not sure which approach to use, though.
Answer: No, you can't.
This hinges on the actions one can take while grappling being specifically listed. Using a spell-like ability is not among the listed options.
The alternative reading (used in Zachiel's answer) is that the list of options only mentions those standard options it modifies (such as "attack your opponent") and those it adds, but does not exclude others that would be normally available to a character. I find this reading problematic, on account of it allowing actions the rules can't handle ("what happens if a character decides to take a 5' step?" comes to mind). Also, D&D 3.5 very frequently uses this model to determine the scope of the rules - listing what is possible, leaving the undefined actions as impossible.
This is what I believe is the most correct application of the rules. For what I personally feel makes the most sense, I refer the reader to the other answers.


Adding music to the Play Music queue

Question: In "play music" mode must I be using a play list for the 'add to queue' function to work?  Can I create an empty playlist with which to start queuing function? Add to queue does not seem to work when playing off the music library. Why?
Answer: No, you don't need to be using a play list to add stuff to the queue. As soon as you select music to play it adds it to the queue. To add more to the queue, navigate to an artist, album, playlist, or song and there should be an "add to queue" option in the overflow menu.

Adding music to the Play Music queue


Finding the correct FFC Cable (flexible flat cable)

Question: I have this device which has 2 PCBs, they are connected to each other using this slot, i've counted the pins and the number is 70, i want to have the board connected to each other using a cable instead of being stick together over this socket, reason is i want to probe the board and having them stuck together makes it difficult, extending their distance will help alot, your answers are appreciated
Comment: Do you have the manufacturers part number for the socket shown in the picture? With a part number, hopefully will be able to find the datasheet for the socket which will contain dimensions to help finding a suitable FFC cable.
Answer: That is a board-to-board connector. That means its family includes only PCB headers. It does not include any cable-mounted plugs. Therefore, the only way to make a cable that separates the boards is to make a custom FPC (Flexible Printed Circuit) and solder a pair of those connectors onto it. As I am sure you understand, that is not cheap and not straightforward.
Identifying that connector would require two additional pieces of information:

The exact pitch
Pictures of its mate

Even if you do go through all that trouble, I must caution that, if this connector carries high-speed signals, the product may no longer work through an extension cable due to the additional delays, mismatched impedance, waveform deformation from additional reactance, cross talk, and receiving electrical noise from nearby sources.
Comment: Thank you Davide


Why would one ever buy a 12-25 cassette when an 11-25 is available?

Question: I was looking at purchasing a new cassette and chain. Looking at the available cassettes for SRAM components, there is a big variety of sizes available:

11-23: 11-12-13-14-15-16-17-19-21-23
11-25: 11-12-13-14-15-17-19-21-23-25
11-26: 11-12-13-14-15-17-19-21-23-26
11-28: 11-12-13-14-15-17-19-22-25-28
11-32: 11-12-13-15-17-19-22-25-28-32
12-25: 12-13-14-15-16-17-19-21-23-25
12-26: 12-13-14-15-16-17-19-21-23-26
12-27: 12-13-14-15-16-17-19-21-24-27
12-28: 12-13-14-15-16-17-19-22-25-28
12-32: 12-13-14-15-17-19-22-25-28-32

Now I can understand why someone would choose a cassette based off of how many teeth the big gear has. Some people live in hilly or mountainous areas and desire a higher number of teeth. Some people live in flat areas where they simply won't use those cassettes with a lot of teeth on the big gear.
But why would anyone ever choose to buy a cassette with 12 teeth on the small gear instead of 11? 11 teeth = higher maximum speed. I doubt many people buying a nice set of components (Shimano, SRAM etc) would ever say "I don't need to go faster so 12 teeth is fine with me."
What's the point of 12 teeth when you could opt for 11 instead?
Comment: The 12-25 gives you one more cog in the middle of the range, where you'll spend the most time and hence most want to "optimize".
Comment: @Criggie 53x12 gets you 40+ mph at 120 RPM.  What kinda winds you riding in?  ;-)
Comment: @DanielRHicks - exactly right. I have an 11-25, and I find I very often have a "gap" where a 16 fits perfectly. I can find the number of times I've used the 11 on one hand with a couple fingers and thumb left over.
Comment: @nuttyaboutnatty http://www.sram.com/sram/road/products/sram-pg-1070-cassette
Comment: With this many cogs in the back, do you still have a front derailleur?
Comment: I've got an 11-23 and it wouldn't matter if it started at 12...  The 11-12-13 are too crossed over on the small front chainring and on the big front chainring I don't get past 14 or 15 ever anyways.  :-)
Comment: So far I've used [12-26](http://www.sram.com/sram/road/products/pg-850-cassette) (which got me up the steepest Scandinavian mountains with luggage), though I wouldn't have minded an even lower gear. Now that replacement of the cassette is due again: I'm trying to find the 12-27 you quote - but can't. Do you have a link to SRAM or a supplier with that spec?
Comment: @BrianKnoblauch It sure sounds like that 11-23 does not work so well for you in that bike; you might enjoy a set of cogs that in fact tops out at 14.
Comment: Not an answer but a confirmation - I've just taken 11 - 25 OFF my Roubaix Pro for an Ultegra 12 - 25 for the mid range on bike tech advice. Used the 11 half a dozen times in 5 years, and never where I am now (Guernsey)
Comment: I'd rather carry around an 11 tooth cog and rarely use it, than spin out in a decent tailwind.
Comment: @AndrewHenle that'd be awesome - but its 44:11 max gearing which is 35.5 mph at 120 RPM (57 km/h)    and given its a bent, 90RPM.
Answer: If you want to maximize your max. speed, go for an 11 tooth cog. If you want to maximize your average speed, unless you're a pro you probably are better off without it. Even cruising at 40km/h does not require and 11 tooth cog.
For example, take a look at this table, showing cruising1 speeds for a 11- 21 tooth cassette:

And compare to this table for a 12 - 25 tooth cassette:

You can see that the 11 tooth cog is only really useful for cruising speeds that riders at the professional level can maintain, or for short bursts. So, like I said, if you aren't trying to break your own max speed record, you may be better off with a 12 tooth cog.
(Tables screen captured from bikecalc.com. Check it out.)
I remember reading a while back about how most riders can't maintain a high enough wattage output to make an 11 tooth cog worthwhile, but I couldn't turn it up. Maybe another contributor will post it.
1 Cruising here means pedalling at 90 r.p.m.
Comment: "You can see that the 11 tooth cog is only really useful for cruising speeds that riders at the professional level can maintain, or for short bursts." This of course assumes flat terrain. People who live in mildly hilly areas might find themselves frequently cruising at a higher speed. It all depends on where you live and how you ride.
Comment: It's all relative to the wheel size, crank length and front chain ring! I put an 11-28 freewheel on my compact MTB. It has 24" wheels and a 48 tooth front ring. The 13-28 wasn't doing it for me any more (got to the point that I'm climbing some hills using the highest 48/13 combo), but 11-28 is about perfect. The 11 gives that nice impedance when I stand up to pedal, and less spinning on declines. If I build more muscle, I will have to go for a 50+ ring.
Comment: Is the row along the top the number of teeth in the front chain ring?
Comment: Yes, although practically you are very likely to be in a chainring with either 50 (compact crank) or 53 (standard) teeth while using a 12- or 11-tooth cog.
Comment: @user973810, What is the units in the table.  I'm assuming km/h given your usage of it preceding it.
Answer: For me, and for many riders that come through my shop, the 11-25 is missing the critical 16t cog, which (at least for me) is the sweet spot. That is, the gear which I don't tend to spin out of, and that doesn't turn in to a grind fest.
If I'm doing a Euro trip, then I will run an 11-28, with a compact front.  But at home, for daily riding, a standard 53/39 with a 12/25 is perfect.
For what it's worth, the 11t cog was designed to give a compact crank, with its smaller front range, the same or similar top speed as a "standard" setup, which at the time was a 53/12 maximum.
Answer: An 11-tooth cog is significantly less efficient than a 12-tooth one, even without the increased wind resistance at that speed.
See the following in depth article "On the efficiency of bicycle chain drives"
Answer: Some people will never get the chance to use the 11 teeth setting, whether this is through not being fit enough or another reason.
So they can opt for the slightly longer expected lifespan of the 12 (lower wear per tooth) and the slightly narrower gap between ratios which can make gear changing less of a struggle.
Comment: I only switch into my smallest cog when I'm taking off the wheel.
Comment: @Kibbee But the bigger chainring scales up all of the cogs! Your 25 is now faster, too. A chainring swap cannot do exactly that what a switch from 12-25 to 11-25 does.
Comment: You can compensate for the lack of the 11 tooth cog with a bigger chainring on the front as well.
Comment: Your logic is that 12 teeth wears slower than 11 teeth just because there are more teeth to handle the forces from the chain at any given time?
Answer: One thing to ask yourself is "What is the max speed where I'm willing to expend energy, on a continuous basis, to maintain that speed?"
Yes, it's (maybe) nifty to do 60 mph down a hill, but the energy required to maintain that speed on any sort of continuous basis is astronomical.  Most people have a max sustainable speed (on the flat) somewhere between 15 and 25 mph (depending on the individual), and it makes no sense to have gears that permit you to pedal (at a semi-normal cadence) at a speed faster than your max sustainable speed.  It's more valuable to have the "in-between" gears than high-speed gears you will never really use.  At most you might want to "push" the high end ever so slightly to take advantage of that rare day when you have a nice tailwind.
Comment: @Michael - Any momentum you "stored up" on that downhill will be lost to wind resistance in the first 30 seconds of the climb.  In terms of "conservation of energy" it's a very bad deal.
Comment: Right, it really depends on the hill. For my commute, in one direction a certain hill is a 60 second climb on my best day, but going the other way with enough momentum I can clear the next lower hill and still be going 20-25mph at the top.
Comment: Missing from this answer is the fact that it's usually counterproductive to even try pedaling down a hill where you can reach 60 mph/90 kph.  On such really steep grades, if you want to maximize your descent speed it's better to forego pedaling and get into as aerodynamic a tuck as you can - even pulling your knees in tight and close to the frame is going to be beneficial at those speeds. See http://www.roadbikereview.com/reviews/study-reveals-most-aero-position-on-bike. You can try different values at http://bikecalculator.com/veloUS.html Try 400W/drops vs 0W/aerobars on a -10% grade.
Comment: It's nifty to go 60 mph down a hill if its in front of a comparable climb, and you want as much momentum as possible to carry you up.
Answer: Another way to see it is that while crosschaining is not that big of an issue with nowadays components (this has been confirmed to my on this very forum), the extreme cross-chainings are not very pleasant (noise, not completely smooth pedaling and so on,...).
On the other hand, the second-to-last cog is very usable most on most (double) transmissions.
Therefore, with a 11-25 cassette, you can ride on "small-ring"/12 rather than "small-ring"/13 like you can on a 12-25 cassette (regardless of whether the "small ring" is 34, 39 or anything else).
In the same time, the 11 cog is not useless either as it can be used in downhills or sprints.
On the other hand, if you are sure with your extreme gears usage, having the tightest possible cassette is better: I could rephrase your question and say: "why would one buy a 12-25 cassette when you can have a 12-21 which will allow faster speeds and has smaller gaps (actually almost none)?"
The answer to that is actually the only right answer to your initial question and that is that your cassette must reflect what kind of rides you intend to use it for? loaded touring? flat racing? moutain racing?
Answer: 1
Here is an excellent technical reason not to: maybe you simply can't put the 11-* cassette onto your hub.
For instance, if we consider Shimano HyperGlide: the Shimano cassettes which have 11 cogs require the HyperGlide-C (compact) style hub, whose splines do not extend all the way to the edge.  The 11 cog does not actually go onto the splines like the other cogs. It sits on the end of the hub, and partially goes onto the shortened splines.  It requires a special variant of the lock-ring, which comes with the cassette. On the other hand, 12-* cassettes fit these compact hubs. For example, I'm using a 12-23 range CS-HG50-8 on a HyperGlide compact hub that previously had a 11. The shortened splines of the compact hub still adequately grab the 12 cog, so it doesn't rotate freely around the hub. (By the way, there you go: I'm a a live example of someone opting for 12, after using 11! I still just rarely use the 12).
2
Related to point 1, the fact that a special hub is required tells you something: the 11 cog is technically inferior. It is on the specification fringes of what will possibly fit onto the hub, which is a bad place to be. It has to be constructed with partial splines, because if it had full splines to go onto a regular hub then the cog's hub would be too thin and weak. The splines not going all the way through the cog's inner hub allows there to be more steel to hold the entire part together.   There is another way in which the 11 is inferior: you will commonly find, on even a lightly worn cassette, evidence that the chain plates are making contact with the 11T cog's hub! In other words, chains do not sit very well on the teeth of the 11; they ride the inner ring. If not when the cassette is new, then eventually. The 11 will likely be the first gear to start skipping when the chain and cassette wear. Since for many riders that's a big clue to throw out the entire cassette and chain, it may lead to unnecessarily frequent replacements.
3
A cyclist that rarely uses a 12 will use an 11 even more rarely; perhaps never. Any gears you don't use effectively reduce the number of gears in your cassette. If you have a 9 speed cassette but only use 2-8, then you really have a 7 speed cassette, with spacing and padding cogs that make it compatible with your 9 speed shifter.
4
Higher gear does not translate to faster. Your maximum speed over a short distance might not be achievable in the highest gear, in fact. One use for the highest gear is in fact to go slower, with a relaxed, slow cadence.  A car analogy can be made here: it's like an over-drive gear that lets you work with lower RPM on the freeway, saving gas. (Car analogies are good, but they break down in one important way: car engines do not get tired, and do not have to pace themselves with regard to expected distance.)  Just like a car, we can downshift on a bicycle to get more power. Yesterday, to catch a green light, I downshifted from 5 to 4 on my 12-23/8 cassette, accelerated, and outpaced the cars. Also, these downshifts have to be subtle: it helps to have the close gear ratios. To have close gear ratios, don't get a cassette which includes gears that you won't use! I was already pedaling at a decent cadence in 5; too much of an increase in cadence in the downshift would have been counterproductive: I would end up whipping my legs around, going nowhere.
5
The 11 tooth cogs have a purpose: they go with compact drive systems which have a smaller ring in the front, like 48 teeth (or even less), common on mountain bikes. They are also useful for bikes with smaller diameter wheels.  The 11 cog against a 48 ring gives you almost the same gear ratio as 12 against 52.  The 11 cog is thus a useful accessory for converting a mountain bike for commuting use in an inexpensive way (avoiding replacing the front ring). Throw out the 13-34 cassette and put in an 11-25, slap on "road slicks" tires, and maybe some fenders and possibly a rack, and you're good to go. If this is what you're doing, the 11 may be for you.
If you have a road bike with a 52 or 53 front ring, with 700c wheels and average sized pedal cranks, the 11 is probably a bad idea that you will regret, unless perhaps you're an elite cyclist with a "power plant" that works well with higher gearing.
6

Now I can understand why someone would choose a cassette based off of how many teeth the big gear has. Some people live in hilly or mountainous areas and desire a higher number of teeth.

Actually, the desire for more teeth in the cassette is only understandable if the cyclist has no front derailleur. Or, say, only two rings in the front. Otherwise, the desire is, well, still understandable as a desire, but not all that rationally founded. If you have three rings, there is no need for anything larger than a 23 cog in the cassette. With the small ring engaged in the front and the 23 in the back, you have a ridiculously low gear that feels akin to riding a five-year-old's tricycle. If there is a section of road you can't climb with that, just get off and walk. The only cyclists who need anything lower are athletes who do mountain cycling as a sport, involving ridiculous feats like climbing very steep sections of a rough trail. (They must stay on the bike, because that's the sport; a "normal person" either wouldn't go there with a bike at all, or would just carry it up that section of trail).
Bicycles marketed at the mass consumer market often come with ridiculously fat cassettes combined with three speeds in the front, which reinforces the consumer belief that these are good and necessary. It's not clear why this is, but it's probably for two or three reasons. It simplifies the use of the bike: the user can find every gear they need using the front derailleur only. Secondly, the number of speeds is often touted as a selling point to the general public. What happens when you put an 11-34 "Mega Range" cassette (say 9 speeds) into a mountain bike with three rings in the front is that the user ends up with effectively a 9 speed bike, with 18 additional gears that are either redundant or uselessly low. However it can be marketed in the flyer as a 27 speed bike. The large cassette also looks impressive, and consumers like words like "mega"; they think they are getting something special, or more for the money.
Comment: "... only understandable if the cyclist has no front derailleur. Or, say, only two rings in the front." You say that as if having two chain rings is some sort of weird affliction that's relevant to almost nobody. Pretty much every road bike made has two chain rings.
Comment: @DavidRicherby Thanks for the heads up; that is not very well worded there. There are some subtle issues as well. Road bikes sometimes have a second ring that is still a pretty high gear, like 52-42. Someone with a narrow-range cassette could struggle on hills with that 42.
Answer: The simple answer is that people (racers especially) like closely spaced gears so they pedal as closely as possible to their optimum cadence.
Comment: And of course they know their optimum cadence down to three significant figures.
Comment: It's not about knowing, but the feeling "I need to shift slightly up / down but next gear is too high / low"
Answer: In addition to the other answers, there's also cyclocross. People don't typically ride as fast in cyclocross as they do on the open road, thus lower gears might be better.
Answer: Different strokes for different folks is all. Guys with arms like legs and legs like people have no need for a stump puller or even a 25 sometimes and are wishing for a 10 until they discover what a Campy set up costs while in my world of recreation and fitness a 12-28 seems almost perfect most of the time and I've even considered a 13 or even 14-27 from the 6600 junior cassettes. My first road bike was a '73 Fuji S10S 10 speed with a 14-17-20-24-28 and it seemed to be all I really needed (at the time) but now, at almost 70 yrs, bigger gears are my friend.
Answer: I hesitate to dig up an old question, but there is one answer missing.
Maximum Gear ratio restrictions in Junior racing. That's why you'll also see 14-25 cassettes.
USA Cycling rules on junior gearing
It is almost impossible to get a crankset that meets the regs with an 11 tooth cog.( Generally max is 52/14 w/700c wheels and 23-25mm tires ). With an 11t, you have a most 40t in front and lower high gear. 12 isn't a lot better, but 44t is at least possible and is closer to 52/14.
Answer: I personally never use my 12 cog: even sprinting I can go faster in the cog maybe one or two down.  I tend to naturally ride at quite a high cadence (often over 100 rpm) even when cruising, live in a fairly flat area, and I'm just an average rider who isn't going to do an average speed faster than 30kph over any reasonable distance.  For me, filling in gaps in the gear range is more important than having top end speed.  Even when I've ridden in hillier areas I find bike handling is more of a limitation on descending speed than my gear ratios.
Answer: This might not be welcomed but Michele Ferrari has a website http://53x12.com. The idea is to use smaller gear and higher cadence because using 11 cog requires tremendous amount of torque that makes it hard to pedal efficiently.
With 11 speed cassette now available, tighter spacing between cogs is achievable with 11 cog. But use 12 if you want to be efficient.


How can I display contents of trash using terminal?

Question: How can I display contents of trash using terminal?
Comment: You had two questions in here. This site works better when there is only one question per question. That way, it's easier for other people to find solutions if they have the same problem. I've edited out your second question. As AskDifferent is focused on end-user problems, it would be off-topic here anyway (StackOverflow.com might be the better place for that).
Answer: You can run
ls -al ~/.Trash

to show the content of the Trash of the current user.
To see the content of all Trashes, use
sudo ls -al /Users/*/.Trash

from an admin account.
And if you also want to include the content of the Trash on external volumes, use
sudo sh -c 'ls -al /Volumes/*/.Trashes/*/'

Comment: Ahh, of course, the second `*` gets expanded too early, thanks. Fixed.
Answer: Your Trash is a unison of the directory ~/.Trash and the .Trashes directory on any other mounted file systems. To view the contents of the GUI Trash in your shell
    ls ~/.Trash /Volumes/*/.Trashes/$(id -u) 2>/dev/null


Peace Lily damage! Please help!

Question: I received this plant after a family members funeral service. I placed the plant in my vehicle and it was rather hot out, around 85 degrees. The plant was left in my car for a few hours before I was able to get it home. On the side that was closest to the window a bunch of the leaves had turned to brownish black and were droopy. I do not want to loose my lily, unfortunately I do not have a green thumb so Any advise would be quite helpfu!
Comment: Diagnosis and prognosis is easier to make when a picture is provided
Answer: These are very resilient plants and this one should bounce back and be back to normal health soon.  They dislike direct sun and what i believe happened is some of the leaves were burned.
Plants like the peace lily are strong determined things that prefer to be left alone in their ideal conditions. The best thing you can do is place the peace lily in it's ideal environment, water it when it needs water and let the lily do the rest.
Ideal environment includes minimum bright light.  They like to see light but not feel light, so keep it away from direct sun.  Keep the plant watered but do not over water.  The leaves will tell you when to water, they will start to droop a little.  Over time you will get used to a schedule maybe once a week, or 10 days depending on the size of the plant, its root structure and size of the pot.
The plant will let you know if it is getting to much water/sun etc.  Right now it is just upset it received too much sun, but it should be fine.
Answer: Just cut the dead leaves back and provide water.  This is one of those plants that look good with enough water and wilt and look dead when dry.  See my answer here and here for more details.  A one time incident with hot temperatures and not enough water will not cause lasting damage.
I used to take care of these on a commercial basis when they were in 12" diameter pots.  Water them once every two weeks with three or four litres of water...no problems in low light.

Peace Lily damage! Please help!


How to convert a latex folder(including multiple tex files, sty, cls files) to PDF using python?

Question: I am creating a web-app using Python(Flask), the app will have multiple latex templates, based on the user's input, changes will be made to a template and the final file needs to be exported in PDF. I used pdflatex package in python and it does the job on a single tex file, but most templates have other files as dependencies, how can these be converted to PDFs?
I found a repo: https://github.com/aslushnikov/latex-online that converts files with dependencies, but it does so on the terminal, I need to do it programmatically, anyway I can achieve that?
Answer: From the way the question is asked, I guess you have multiple independent .tex files.
I wouldn't use LaTeX code here - you are using a programming language.
Loop over all .tex files and look into them. Loop over the lines. Look at each line. Remove spaces at the start of the line. If it now starts with a %, go to next line. If it starts with \documentclass, exit the line-loop and run it through pdflatex. If it starts with anything else, go to next file.
You could e.g. do
<code>import glob
for file in glob.glob("/home/me/*.tex): #You need to edit the path here.
  f=open("file", "r") # open the file in read mode
  while True:
    line=f.readline()
    if line.startswith("%") :
      #we want to skip these lines
      continue
    elif line.startswith("\documentclass") :
      # tex-commands here
    else :
      #we are done with this file, its used as an \input or \include somewhere
      break
</code>
Comment: Hey, no the files are not independent, there are multiple templates but every single template has the main tex file and several dependencies(sty, cls, and other tex files as well), think of it as the zip file you'll get if you download the source code of any template from overleaf, how do you convert that source having multiple files into one PDF, like overleaf does, through python(or some API)
Comment: Like template1.tex, template2.tex, ... and the content is
\documentclass{something}
\input{main}

?
If yes, the answer works.


I've deleted my /var/lib/dpkg/status and status old files

Question: I run Deepin, I've been trying to install the necessary compenents to run a LAMP server on my machine for web development. As the title says I've somehow deleted my status files. I'm not sure how, I'm a student with a decent understanding of linux but when I went to apt-get something I was met with a 'bad address' error. On investigating that I discovered the missing status file. I tried to copy the status-old file to a new file named status, but the permissions made it difficult, even in super user mode and I accidentally deleted the status-old file, my own fault. Very frustrating. Anyway, I can't download the necessary files to create a bootable usb etc. to install ubuntu (been meaning to switch) as my apt-get is broken. How can I fix my computer?
Answer: There should have been backups at <code>/var/backups/dpkg.*</code>.


Can i use A1278 screen to replace with my A1502 screen

Question: I've a A1502 macbook pro late 2013 with damaged 13" retina display. There is another A1278 macbook pro with 13" display. I am getting this laptop way cheaper than the screen replacement. I was wondering if i could use an A1278 screen to replace with my A1502 screen. Is it possible? Are there any hardware differences? Maybe difference in the wire connector on board? Or any compatibility issues?
Answer: This has been answered for 'the other way round': putting a Retina screen in an older MBP, and I'd suggest many of the answers there apply here.
The screens are different dimensions, and use different connectors. The firmware expects the original screen resolution.


vmware player fails to install but no errors given

Question: I am trying to install VMware player onto my workstation (Ubuntu 18.04.3 LTS).  I've followed the instructions for installing from a bundle (download, chmod and sudo ./bundle_file) after which the installation process goes through a number of steps and finishes without any obvious errors.  Despite there being no errors, closer scrutiny of the output seems to suggest that the installation did not actually install.
command ran as follows:
sudo ./VMware-Player-15.5.0-14665864.x86_64.bundle

Extracting VMware Installer...done.
Installing VMware Player Setup 15.5.0
Copying files...
Rolling back VMware Player Setup 15.5.0
Removing files...
Deconfiguring...

The attempted installation takes approx 9 seconds.
The complete installation log is as follows:
/tmp/vmware-root/vmware-vmis-20775.log
2019-09-23T13:13:06.271+09:30| host-20775| I125: The process is 64-bit.
2019-09-23T13:13:06.271+09:30| host-20775| I125: Host codepage=UTF-8 encoding=UTF-8
2019-09-23T13:13:06.271+09:30| host-20775| I125: Host is Linux 4.15.0-64-generic Ubuntu 18.04.3 LTS
2019-09-23T13:13:06.270+09:30| host-20775| I125: DictionaryLoad: Cannot open file "/usr/lib/vmware/settings": No such file or directory.
2019-09-23T13:13:06.270+09:30| host-20775| I125: [msg.dictionary.load.openFailed] Cannot open file "/usr/lib/vmware/settings": No such file or directory.
2019-09-23T13:13:06.270+09:30| host-20775| I125: PREF Optional preferences file not found at /usr/lib/vmware/settings. Using default values.

No vmplayer command is created anywhere that I can find.
I've also tried downloading and running the full workstation bundle (VMware-Workstation-Full-15.5.0-14665864.x86_64.bundle).  Output of the run attempt is nearly identical (only the name changes).
I've spent many hours crawling through Q&A forums and cannot find a similar case.  Anyone know how to fix this?  I need the vmplayer working asap.
Comment: Same problem in Linux Mint (Tina). And really don't see the point in downvoting.
Comment: Same problem in Ubuntu 18.04.4 LTS with VMware Workstation 15.5.2, here I have Rolling back VMware Installer 3.0.0 and I don't find useful logfiles with it.
Answer: Besides doing a complete manual reinstall as described here, consider checking if you've disabled all other hypervisor kernel modules such as
$ lsmod | grep vm
kvm_intel             217088  0
kvm                   610304  1 kvm_intel

and removing them (with sudo)
modprobe -r kvm_intel
modprobe -r kvm


Trace of raman tensors

Question: A raman tensor $\gamma_m$ is defined as the derivative of the polarizability tensor $\alpha$ with respect to a raman mode $Q_m$, so
$$
\gamma_m =\frac{\partial\alpha}{\partial Q_m}
$$
$\gamma_m$ will show certain symmetry properties which depend on the point group of the material (e.g C2v, Td etc.) and irreducible representation of the respective raman mode (e.g. Ag, B2g etc.). I have recognized that the trace of $\gamma_m$ is only non zero if the raman mode has $A_g$ symmetry, so
$$
\text{Tr}(\gamma_m) = 0 \quad \text{if} \quad\text{Irrep}(m) \neq A_g
$$
Is this always true and is there a rigorous proof for this?
Answer: This is a general aspect of representation theory. The polarizability tensor $\alpha$ is rank (1,1), and is acted on by a group of transformations $G$. The class of all possible polarization tensors forms a vector space, that decomposes into mutually orthogonal representations of $G$. One of these representations is the 'trivial' representation, invariant under the group action. Since $\alpha$ is an element of $V\otimes \bar V$ for some vector space $V$ (e.g. the vector space of spherical harmonics, acted on by the group $G=SO(3)$), elements $\alpha$ transform under $G$ as $g(\alpha)=g\alpha g^{-1}$. Since the trace is cyclic, $\text{tr}(g(\alpha))=\text{tr}(g\alpha g^{-1})=\text{tr}(g^{-1}g\alpha)=\text{tr}(\alpha)$, so the trace operation projects $V\otimes \bar V$ to the trivial subrepresentation. By orthogonality, all non-trivial representations therefore have zero trace.
Comment: Thanks for the very nice answer. Could you explain the effect of the derivative with respect to $Q_m$ and how the symmetry of $Q_m$ comes into play?
Comment: As I read your question, I interpreted the $Q_m$ as coefficients for $\alpha$ in a basis of irreducible tensors.  If we write $\alpha = \sum_{m} Q_m \gamma_m$, where $\gamma_m$ are the basis elements, then $\frac{\partial\alpha}{\partial Q_m}=\gamma_m$.  The 'symmetry of $Q_m$' comes into play when I discuss the transformation rule of $\alpha$: if $Q_m$ is a coefficient for a copy of the trivial representation, then  it is invariant under the group action.  If not, then it will transform in some finite dimensional irreducible vector subspace of coefficients for other basis elements.

Trace of raman tensors


Since the gravitational force is only attractive, why does matter not just concentrate into a small sphere?

Question: This doubt has been wandering in my head for a long time. The gravitational force is only attractive force not a repulsive force. Since gravitational force is only attractive force, why not the universe is concentrated as a small sphere. All the stars would be attracting each other and hence the would stick to each to attain equilibrium. Why doesn't this happen? Is it because we consider gravitational force to be only attractive not repulsive?
Comment: There are other repulsive forces and other mechanisms that keep matter from collecting into one big lump. Additionally, the expansion of the universe makes most matter move away from other matter
Comment: maybe it *will* happen: http://en.wikipedia.org/wiki/Big_Crunch
Comment: For one thing, the universe is not a sphere. That's just a very poor illustration they keep showing (for no good reason other than the limited attention span of the audience) on tv. For another, the "size" of the universe may be quite small at all times, we simply don't know what the relevant size scale for its evolution is.
Comment: Somewhat related: http://physics.stackexchange.com/q/182679/
Comment: @ACuriouaJim I just wanted what these repulsive forces were.
Comment: @Aditya Kumar: E.g. the centrifugal force.
Comment: Related: http://physics.stackexchange.com/q/12140/2451 and links therein.
Answer:
All the stars would be attracting each other and hence they would stick to each to attain equilibrium. Why doesn't this happen?

This is an old question. Even Newton himself had thought about this question. His idea was that in long distances or separations (say, inter-galactic distances) the force of gravity might appear to be repulsive. That's why not

the universe is concentrated as a small sphere.

There were also many contemporary thoughts on this topic.
But this idea does not work at present day. We have got some new view about the gravitational force itself. The gravitation is not considered to be a force anymore. Today physicists believe that gravitation is a manifestation of space-time curvature or the space-time curvature or distortion creates gravity, you can read about this in the following site http://www.einstein-online.info/spotlights/geometry_force
If any doubt remains then you can ask. So gravity is not a force rather it is the effect of space-time geometry (you can say "Gravity is Geometry"). Now the question is what determines the geometry of space-time. The answer is the distribution of matter and energy (electromagnetic fields also) in the space-time determines its geometry. Therefore, the universe will be contracted or not depends upon the matter distribution or the distribution of stars, galaxies etc. For different distributions of matter there are three possibilities about the fate of the universe, shown as models of universe and known as Friedman models of universe, which are: the universe may always be expanding with acceleration, the universe may stop accelerating but may expand with something like uniform velocity or the universe may stop expanding at some critical point and start to contract to end up as a concentrated small sphere and known as Big Crunch. (Note: I am avoiding technicalities as much as possible). Recently it has been proved that the first model is correct. Now why the universe does not contract rather it expands. The physicist wish to explain it in terms of Dark Energy (read: http://en.wikipedia.org/wiki/Dark_energy). Physicists hope that the dark energy opposes gravity (in common language) and far more stronger than gravity that's why the net effect is against gravity and the universe is expanding rather being contracted. The energy is Dark because not more is known about this. Hope this answers your question. In case of doubt you can ask another question.
Answer:
All the stars would be attracting each other and hence the would stick to each to attain equilibrium. Why doesn't this happen?

You are forgetting angular momentum. Consider a binary star pair. Ignoring the expansion of spacetime, and in the absence of some mechanism that removes angular momentum from the system, those stars will orbit one another forever. The distance between the stars will vary between some fixed minimum and maximum values. While gravitation holds the system together, gravitation (from a Newtonian perspective) cannot make the two stars collide.
There is a mechanism in general relativity that can remove angular momentum from the system, but this is rather small in most cases. This answer ignores gravitational waves; that's a separate question.
One of the key subjects investigated in astrophysics is the formation of galaxies, black holes, and stars. One of the key challenges is explaining how they can form at all. The formation of galaxies, black holes, and stars has a common problem: Angular momentum. The collapse of gas clouds into stars, stars and gas clouds into galaxies cannot take place unless there are mechanisms that somehow remove angular momentum from the gravitationally collapsing system. Without such mechanisms, the collapse just stops, and it would stop well before a star (or black hole, or galaxy) could form.
A lot of progress has been made in addressing the angular momentum problem, but it still remains an unsolved problem to some extent.
Comment: If gravitational force of repulsion doesn't exist then how could the universe expand?
Answer: If there would be initial rotation(as we see most of all objects today are rotating around another) gravitational force is accounting for the centripetal force. I'm new here so, I don't know how to type the equations, but I hope you get my point. Further many objects are there which have many other forces, like Coulombic force(when charged bodies are involved). All objects have charges, but they are neutralized due to proper distribution, incase something erratic occurred, that could be another form of attractive and repulsive force causing new equilibrium.
Comment: the gravitational force creates centripetal force
Comment: See [Using MathJax on Physics Stack Exchange](http://physics.stackexchange.com/help/notation) for typing beautiful equations.


Aptana Ctrl + Left/Right

Question: I just started using the Aptana 3 plugin for Eclipse Indigo. When I use the Aptana editor in some contexts it changes the behavior of CtrlLeft/Right. So say I'm editing some JavaScript
<code>function foo() {
    alert('bar');
}
</code>
If the cursor is left of the 'f' in function, CtrlLeft does nothing, rather than going to the begging of the line, then end of previous line, etc. as it does normally in eclipse. If the cursor is right of the 'o' in foo, CtrlRight does nothing, rather than jumping to the curly brace.
I use CtrlLeft/Right to move around often and this is incredibly annoying. I'm not finding any settings relevant to key bindings in the options. Does anyone know how to change this behavior?
Update: I just tried Aptana on Windows and do not have this issue, it appears to only happen on Linux. I submitted a bug report to Aptana.
Comment: I don't think it's Aptana - it happens to me in all perspectives / editors.
Answer: It is a known bug in Eclipse 3.7: https://bugs.eclipse.org/bugs/show_bug.cgi?id=350362. There are no known workarounds to date, except for to downgrade to Eclipse 3.6.

Aptana Ctrl + Left/Right


Can Veracode detect vulnerabilities in jsp files?

Question: We have chosen Veracode to perform security assessment of our JavaEE code. We have been performing white-box security testing using Veracode. As I am quite new to Veracode, I was surprised to find no results for our imperfect jsp files. All the results were around a few servelets. Also we did not find any results in our Manager classes and Service Classes (backend code). Please guide. What am I missing here?
Comment: There in an answer from Veracode or the question.https://getsatisfaction.com/veracode/topics/veracode_support_for_jsp_files
Answer: Hi and thanks for your feedback. I can offer you some general information here and provide suggestions about how we can dig into your specific application.
First, Veracode does have support for JSPs. We generally precompile the JSPs upon your submission so that we can ensure we have all the necessary supporting pieces, then we analyze the resulting bytecode alongside the rest of your compiled Java code.
There are a few things that can go wrong when a customer uploads JSPs:

JSPs cannot be compiled. This happens when either a supporting
library required by the JSP is not present in the upload, or the JSP
is in an uncompilable state. We report back any JSP compilation
failures in the prescan report, so if you see these it's generally a
sign that we won't be able to analyze the content of the JSPs. If
you see these warnings, check to see if you are missing a class
dependency and see if you can upload it so we can get a good
compiled version of your JSP.
There's a packaging issue. While we can handle a few different ways to package your application, the Veracode service gets best
results if you upload a web application as a properly packaged WAR
file, including the web.xml. If you upload the application packaged
in a different way we may not be able to put the JSPs in their
proper context for analysis. This is an area we're working on,
because we realize that not every Java application server requires
WARs, and you may be deploying using a different model.
We don't support one of your frameworks. Because Veracode does a full data- and control-flow analysis of the application, we need to
have an understanding of everything that might impact the control
flow, including frameworks. We typically try to call out unsupported
frameworks at upload time as well; obviously that's not something
you'll be able to address with a quick fix, but we try to be as
transparent as we can about what we can analyze and what we can't.

All of that aside, we may simply have an issue in our engine when it comes to your application. The best thing to do is to schedule a readout with our service team so we can look at your results with you and offer you advice for your specific application. Depending on your subscription, you may have a "Request a Readout" button directly in the UI; if you don't, please contact us at support at veracode.com and we'll see what we can do to answer your concerns.


How to see replies to your comments on YouTube?

Question: When I accidentally opened the notification window two times the replies there disappeared.
Answer: If you want to check replies to your comments, just got to the YouTube channel that posted the video, find your comment, and open replies. If you saw replies before and they are no longer there than its possible that the people who replied deleted their comments (reply to your comment). You can also try a different browser which sometimes can fix problems like that.
Answer: You can see your own comments by clicking on History in the left menu, then Comments in the right menu. Then you can open each comment in a new tab and look at them and their replies.
Note that if your comment was a reply to a top-level comment it will always appear to be the last one in the thread, so you will have to click the "3 replies" link to see if there were any replies after your comment.
You may want to check your YouTube settings for Notifications to see if notifications for replies to your comments are turned off, as this is the easiest way to see them.
Answer: I also have this problem. From what I've read, this often happens if YouTube detects the comment to be spam. Basically the comments are automatically deleted, but it doesn't remove the "reply".
Comment: This is a different problem, and it's also not an answer to the question.


Does using magick to reversing aging accrue permanent paradox?

Question: Reversing aging is a vulgar effect(Page 509 MtA 20th Anniversary Edition) and it has a permanent effect. Considering both of these is similar to using enhancement to get an attribute past five dots, would reversing aging cause permanent paradox as well?
Answer: There's a fine line between reversing age and just halting aging or considerably slowing it to extend the lifetime.
Aging backward
Aging backward is a Time-Life-Magick effect and is very vulgar. This can very much incur permanent paradox if the Storyteller wills it, especially if it becomes easily apparent: a 50-year-old person simply doesn't look 21. But someone 21 to 25 might still convince people that he just has a case of babyface to appear about 17-ish.
Only if you manage to make Leónisation something mainstream people totally accept, you can repeatedly jump into the fountain of youth and extend your life indefinitely and without paradox. Way to get a goal in the war for reality!
Slowing Aging
A less intrusive way is to do the 'ageless monk' way of just slowing down the own body's aging. There's a sweetspot for old age, where there is little to no age that can be attributed to a person - somewhere in the 50s, it's really hard to guess the age of people. Extending the own age by just slowing the process of physical decay with Life-Magick while retaining a fitting look shouldn't incur a permanent paradox.  The number of centenarians is steadily increasing, so the ageless person isn't breaking the wall of paradox... until they are way too old. The current limit when you might incur permanent paradox from overstepping the capacity of human possibility is about 120 years - the record is 122.
Afterward, you might accumulate permanent paradox at a Storyteller's fiat. That is, unless you manage to convince reality that humans don't die from age... or to make reality forget that you have an age in the first place.
Answer: Yes, once you start to exceed a human lifespan.
Simply put, yes, magick that allows you to exceed a human lifespan causes you to begin accruing Permanent Paradox once you start exceeding a human lifespan. This is why all the centuries-old Arch-Mages live out in the Umbra, where they don't need to worry about this.
A possible exception would be various forms of reincarnation or cloning magick, since your original body does, in fact, grow old and die.
Comment: it's less the exceeding human lifetime but that reverse aging is vulgar to the sky and back
Comment: @Trish Reversing aging is vulgar, but the Paradox it generates isn't permanent until you start exceeding a normal human lifespan.
Answer: You haven't altered yourself beyond human limits, so no permanent paradox involved
I don't have MtA: 20th Anniversary Edition, but in the earlier editions, they make it clear for the Life 3 effect "Better Body" that permanent Paradox is a result of "changing a Pattern beyond normal limits" (where increasing attributes to six or more, adding inhuman features, or fortifying to soak aggravated wounds all count as such). By that definition, I don't see any reason why changing your age would involve permanent Paradox.
Being strong enough to lift a car at all times is an ongoing violation of reality, same goes for growing gills or having skin as tough as Kevlar; it doesn't matter if no one sees you change, you're violating reality just by existing. By contrast, your age at any given point in time is not an ongoing violation of reality. Sure, you'd get whacked by Paradox if you deaged in front of a crowd of Sleepers, and even without witnesses the actual deaging process itself is vulgar, but once it's done, merely "being 20" is not an obvious and ongoing violation of reality; permanent Paradox should not be involved.
Comment: Isn't going over ones lifespan going over normal limits considering humans aren't meant to live a hundred and fifty years?
Comment: @MaikoChikyu: It's going to be a Storyteller judgment call, but in general, I'd say no. It's like using magic to heal; someone healing a fatal wound in front of witnesses is vulgar as hell, but once they're healed, they're just a healthy person. Reversing your age is vulgar as hell, but once it's done, you're just a person of that age, there's nothing inherently supernatural about your new state. People aren't meant to live that long, but people don't come with tags that state their real age (or at least, mages learn to get fake IDs pretty quick).


What is considered now over astronomical distances?

Question: For the sake of discussion, let's say that Mars is exactly 5 light-minutes away and that Earth and Mars are moving with the exact same velocity so that special relativistic effects are irrelevant. Let's also assume that clocks on Earth and Mars are synchronized so that if a laser is pulsed on Mars towards Earth at 4:00 it is detected on Earth at 4:05. Would a person on Earth at 4:05 say that a laser is pulsing on Mars now, or that it pulsed on Mars 5 minutes ago? When speaking about Mars in the real world it seems that people would say "a laser pulsed on mars five minutes ago." However, it's also clear that if our senses were finely attuned enough to detect things over astronomical distances, it would appear that the laser is pulsing on Mars at 4:05 on Earth, at 4:05 a Earthling would say "a laser is pulsing on mars now." So which interpretation of now is correct?
Comment: There is no fact of the matter about 'now.' Simultaneity is not preserved under Lorentz boost. Things that happen at the same 'now' in one frame, happen at different 'nows' in another. The more precise statement that the Earthling could make is that in a certain reference frame, the state of the electromagnetic field (AKA the laser light) at some point (t,x) is [....]
Comment: Let's rephrase this as a Galilean question, then, where the speed of light in the relevant reference frame is c.
Comment: You could then try and calculate what the state of the field was at point(t', x') some time in the past, say on Mars 5 minutes ago. It can be true both that the state at (t, x) is [....] and the state at (t', x') is [.....]. There is no disagreement about 'now' in this picture.
Answer: A physicist, me for example, identifies events by choosing a set of coordinates. For example I have a clock that I use to record time and a ruler that I can choose to measure distance. This allows me to set up some coordinates $(t, x, y, z)$ so I can assign every event to some point in my coordinate system.
If I received a laser pulse from Mars at 16:05 then I assign my reception of the laser to the event (4:05, 0, 0, 0). By inference (since I can't measure it) I assign the transmission of the pulse to (4:00, 5 light minutes, 0, 0). This makes the proper time between the two events zero, which is consistent with my knowledge of relativity.
So, assuming I'm a reasonably typical Earthling, an Earthling would not say a laser is pulsing on Mars now at 4:05.
While this is a somewhat facile argument, it does illustrate an important point. Any observer can set up a coordinate system of whatever form they find convenient, then they can use this coordinate system to identify hypersurfaces with constant time (technically this is known as foliation). Events can be identified as simultaneous if they lie on the same hypersurface.
But, and it's a very very important but, this foliation is observer dependant. A different observer using a different coordinate system would not foliate spacetime in the same way and events that are simultaneous in my coordinate system will (in general) not be simultaneous in other coordinate systems. This makes the word now less than useful in relativity. The only way all observers everywhere will agree that two events are simultaneous is if they happen at the same spacetime point i.e. at the same time in the same place.
Comment: Is it philosophically uncontroversial to say things like "that star has probably already gone supernova, but the light hasn't yet reached us". I mean, can we really assert that it already happened, or do things rather unfold when we get informed about them? Is there any sense in saying that "it's already this or that way and the light is on its way, but we don't know what happened yet"?
Comment: @isarandi: yes. The supernova won't unexplode because I didn't detect it.
Comment: I don't mean it that way of course. I don't mean things changing retroactively. But before having even the theoretical access to the fact whether the supernova exploded or not, can we say it already "happened"? In what sense has it happened if no possible implications (but *really* absolutely none) of that fact have reached us thus far?
Answer: A space train leaves Mars at 14:00pm and arrives on Earth at 19:45. The train moves at 0.001C and has 40Km of length. How long will it take for the whole train to arrive on Earth?
 - Disregard re-entry and friction.
Nobody on Earth will say the train is leaving mars now. Same thing with the light, just it moves faster and is smaller than the train above.
We see the laser arriving on Earth at 4:05, but since we know it is 5 light-minutes away, we know it pulsed from mars 5 minutes ago.
An analogous thing would happen if the sun were to go supernova at once (lets say the romulans from 2009's Star Treck arrived just a couple hours ago). We would only see it 8 minutes later, but we know the sun is 8 light minutes away. So our last thought would not be:

The sun is going supernova right now.
Comment: @JohnKugelman It was an assumption. you are right, removed.


Finding the sum of the cubes of the first n odd natural numbers.

Question: I know that the sum of the cubes of the first $n$ natural numbers is $({\frac{n(n+1)}{2}})^2$, which in expanded form is $(1)^3+(2)^3+(3)^3+...+(n)^3$. Multiplying by $2^3$ on both sides gives $2(n(n+1))^2$, which I can see is the sum of cube of first $n$ even natural numbers. But my question is why do we take the difference between the sum of cubes of all $2n$ (i.e. $({\frac{2n(2n+1)}{2}})^2$)  numbers and sum of cubes of first $n$ even numbers (i.e. $2n^2(n+1)^2$) to obtain the odd sum? How would you distinguish between the two?
Comment: Hint: Try grouping the even terms and taking someting common out.
Answer: Use a specific example.
Let $A = 1^3 + 3^3 + 5^3 + 7^3 + 9^3.$
Let $B = 2^3 + 4^3 + 6^3 + 8^3.$
Let $C = 1^3 + 2^3 + 3^3 + 4^3.$
Assume that you want to evaluate $A$.
You can use the formula to evaluate $(A + B)$, so the problem is reduced to evaluating $B$.
This can be done by using the formula to evaluate $C$, and then reasoning that $8C = B$.


What is the purpose of this patent WO 2015160373 A1 (GAME MODIFICATION)

Question: Does this patent stop anyone modifying board games?.
Answer: First, this is a patent application, not a patent.
The objective of the patent is described in the Background section, specifically, paragraph 5 and 6:

[0005] Sometimes a game becomes less interesting and less enjoyable to
  a player as it becomes more familiar to that player…
[0006] However, game modification apparatus and processes disclosed
  herein can help make familiar games more interesting, …

The scope of the application is specified in the claims. Again, this is a patent application, so the claims may change during the examination process, but generally the claims cannot be expanded beyond what's originally written.
The application has three independent claims. Each claims began with the preamble

Game modification equipment for modifying how a variety of preexisting
  games are played by modifying aspects of play which are shared by
  various games,…

We should reasonably assume that means the board by design allows you to play more than one game with it.
Each independent claim also includes reference to a "modification instruction". So it is quite apparent that the claims are intended to cover boards as manufactured, not any personal modification by individual persons.


Vim: remap 'D' modifier on linux

Question: I'm using Mac-oriented vimfiles with linux. In this config modifier D (Cmd key on Mac) is intensively used. I don't want to change every D to M, but I want to remap D to something like Meta or Alt. Is it possible?
Answer: D is the "Apple/Cmd" key. The only version of Vim that understands it is MacVim and only in its GUI incarnation: D is simply a non-existing key for CLI Vim in any terminal emulator and GVim on any platform.
The immediate consequence is that you'll actually need to replace/duplicate all the <D- mappings in your config if you want it to be portable across environments.
Another somewhat softer way to deal with this issue is to branch your ~/.vimrc. Here is how I do it, there might be better ways:
let os=substitute(system('uname'), '\n', '', '')

if has('gui_running')
    if os == 'Darwin' || os == 'Mac'
        " GUI-only stuff for Mac OS X
    elseif os == 'Linux'
        " GUI-only stuff for Linux
    endif
else
    if os == 'Darwin' || os == 'Mac'
        " CLI-only stuff for Mac OS X
    elseif os == 'Linux'
        " CLI-only stuff for Linux
    endif
endif

Considering the unnecessary mess introduced by splitting an honest ~/.vimrc into many vimrc.after and plugin_name.vim, I'll let you find the correct location for that block of code on your own.
Vim's ubiquity is a strong plus: using and maintaining platform-specific mappings is both impractical and counter-productive. I strongly suggest you choose a better, more portable, strategy for your custom mappings: use the "Control" key or even better the <leader> key. See :h mapleader.
Also, using someone else's config is a very bad idea. You should drop that "package" and take care of your own config yourself.
Comment: New vim users need to do that as part of the learning process: using a distribution only hides things, create bad habits and generally prevent proper learning. Unfortunately, they often want the bells and whistles without having to put any effort in it, hence the success of YADR/SPF13/JANUS among newbies
Comment: I'd like to inject a touch of moderation here: it's not necessary simply to junk the dotfile package you're using, but it would be advisable to review each file in it and construct your own dotfiles from just the bits you find worthwhile (i.e., understandable and applicable to your situation). This still counts as maintaining your own configuration, but doesn't imply that you have to ditch everything you're using and start from scratch -- because who wants, or needs, to do that?
Comment: I don't disagree; the same problem exists among Emacs users, but tends to be even worse because newbies find elisp so intimidating. Fortunately (?), Emacs is nigh-impossible to use until you've thoroughly customized it, so the problem tends to limit itself.
Comment: Thanks for your advice. It isn't a first vim config for me. So I try to understand what is under the hood :)

Vim: remap 'D' modifier on linux


Would you recommend internship, or more courses, for preparing for a PhD in Applied Math?

Question: For a math student, does an industrial internship, where you use the applications of the mathematics you learned in courses, give a better preparation for a PhD in Applied Math, or taking more advanced courses? How about taking courses on other topics (not math), which are skill-based or otherwise practical with a lot of applications in applied math, such as high-performance computing, statistical learning, numerical modeling, etc.?
Comment: I would recommend getting some research experience rather than taking courses.
Comment: I could make strong arguments for all of the options that you've mentioned depending on your circumstances and the institutions that you're interested in applying to.  I've voted to close on the grounds that the answer depends too much on particular circumstances.
Comment: I would strongly recommend getting some research experience over taking more courses (except for courses with a significant research component) or an industrial internship (unless the internship has a significant research component).
Comment: I think that the answer may vary accordingly with the country.
Comment: PhD applied math is not necessarily math you already learned in courses applied to various things. To see this, go to an 'applied math' department's page and look at their phd students. So, courses and research!
Answer: First of all, you should narrow down which applied mathematics are you applying. I know people in that area that don't know how to code, and people that use high performance computing. The same applies to almost all non-basic math skills. Applied maths is way too wide to just ask for a general skill.
In my opinion, just general coding knowledge should be fine, you will have time to learn anything you need on the way, that's part of the Ph.D. and, if you follow academia, the rest of your life; you just need to be able to learn new things.
I just would discourage an industry internship if you can use that time for something better (with respect to applied maths).
Answer: Having been on the grad student selection committee of the departments I was in for the past 4 or 5 years, and having read hundreds of applications, here are the things that really make an application stick out (in roughly this order):

Having research experience
Doing well in senior-level and graduate-level courses in the area you
are applying for
Experience applying your knowledge outside an academic setting.

So, if you have the opportunity to do an industrial internship, then you're satisfying the last point and, if you get the internship in the right environment, then also the first point. If that means dropping one of 5 senior/graduate-level math courses (or a non-math course) you were going to take before applying for grad school, then that's a worthwhile trade off. On the other hand, if that means that you're not going to take any advanced courses, then that's not a worthwhile trade off.


Global Variables and Functions in Headers

Question: I'm trying to separate my code into headers and cpps
I made a .h and .cpp for every class I had
but I have no idea where to put the functions (that aren't in classes) and the global variables
I tried putting them in main but it didn't work
I also tried putting them in every cpp that needed them but I got the error of (Multiple Definition of the variable)
What to do?
Answer: In the .h:
extern int myGlobal;
int myFunction(int arg);

In one of the .cpp files:
int myGlobal;

int myFunction(int arg)
{
    return arg + 5;
}

You can split stuff across multiple .cpp files, just don't define anything in more than one place. If you put a definition in a .h file, and include it multiple times, you get multiple (conflicting) definitions.


Can "This edit will be visible only to you until it is peer reviewed" link you to the review page?

Question: When I make an edit and then get the text "This edit will be visible only to you until it is peer reviewed" am I just supposed to guess the URL for the peer review page? Can't you just link me there direct from the question? Am I missing something?
Comment: It should, it was already asked. Vote up and wait for the team. :)
Comment: This is now `status-completed` :D
Answer: This is suggested once, but it is not (yet) implemented.
However, you don't have to guess the URL for the peer review page: go to your profile, then go to the 'activity' tab, and then you see your activity: including your suggested edits!
If you only want to see your suggestions, select "suggestions". If an item of your activity is a suggested edit, then "suggested edit" is linkified: this link goes to the peer review page.
Comment: Implemented as at Sep 30 2014 :)


Insert date in MSaccess database.

Question: I want to perform an insert query to insert some set of values which include dates also. I am getting Data type mismatch error.
In My access database i have set Ass_date(as Short date(Format 4/13/2012)(i.e MM/dd/yyyy)) and Ass_Time(as Long Time(Format 5:13:00PM(i.e hh:mm:ss tt)) and same goes for Sch_Date and Sch_Time.
I am making user enter a value from DojoDateTextBox for date and DojoTimeTextBox for Time And when user enters a value i get them in the form of String In this format Date (2012-04-13) and Time(T17:45:00)( which is 5:45:00PM). I retrieve these values using ::
String assdate = request.getParameter("assigneddatename");
String asstime = request.getParameter("assignedtimename");

And them i am inserting it into database using Query ::
String sql2= "insert into ATT_Table(Assigned_To_ID,Assigned_By_ID,Env_ID,Product_ID,Project_ID,Act_Number,Act_Type,Status,Sch_Date,Sch_Time,Ass_Date,Ass_Time,Percent_Complete,Description,Comments) values('"+var1+"','"+var2+"',"+var3+","+var4+","+var5+","+actnum+",'"+acttype+"','"+status+"',#"+schdate+"#,"+schtime+",#"+assdate+"#,"+asstime+","+percent+",'"+descr+"','"+comm+"')";

Please help me out as to how to insert the value of a date in database. Thanks .
Answer: Time is also a date datatype. You'll need to wrap the times in '#' symbols as you have done for the dates.

Insert date in MSaccess database.


how to create simple website using php,mysql,css,jquery and html?

Question: I am new to php. I want to develop a website for some electronic company using php, mysql, jquery, css and html.
Anybody guide me how to start with it? Please give me some examples of website developing using php.
Comment: http://php.net/manual/en/getting-started.php
Comment: No offense, but I don't think a beginner should be making websites for Utilities.. not if it's in any way connected to the Utility's network, anyways.
Comment: @jnpcl Exactly my point. Though I think a beginner should not make a website for any company. Learn the profession first and accept jobs afterwards.
Answer: Website development is a profession. It is not something you learn in a day. Your question is like: "I want to build a car. Please tell me how can I build a car. Give me an example please.".
If you are really interested in learning webprogramming, forget about "developing" a website for any company (for the sake of all Internet users, please), and give yourself a few months of intensive training.
If you want to start, search SO, it has loads of links to great tutorials. You can also search Google (and please avoid w3schools).
Learn building a simple website using HTML and CSS only first. And I don't mean spending an hour on it and finding out how to turn a word green. Later you can start learning how to output HTML using a programming language (like PHP). Your question have not clarified if you have ever programmed or not, if not, you need to take your time on this. And this is just a quick outline.
Answer: Not sure how advanced you're looking for...
http://php.net/manual/en/tutorial.php
http://www.tizag.com/phpT/
http://devzone.zend.com/article/627
If you really want to learn PHP, get a good IDE (Eclipse or NetBeans would work), and just start googling "PHP Tutorial".
Shortly you'll find yourself googling more specific things, like "PHP Session Variables", or "PHP Date Addition", etc.  It really is self guiding as to your specific needs.  I would start with the third link in the list above.


Geometry Nodes: How to begin countdown from any frame with a click?

Question: This is going to be a very specific question, about a very specific problem.
I am trying to make an interactive game, similar to Who wants to be a Millionaire, where I want to have Blender run constantly for a couple of hours as a background and interactive menu to show questions and different actions. There I also want to have a countdown timer, which I can start at any time during the game with a boolean switch or something as simple, basically just a click of a button in the modifier panel.
I found this tutorial for a simple countdown timer, Make a Countdown Timer Node in Blender Geometry Nodes! by Johnny Matthews, which I converted to show minutes, seconds and hundredths of seconds, and to have specific timer active or a custom time limit active.
My node tree:

Countdown

Numbers

Output text

But the problem is, it can countdown only from the first frame, and I don't want to constantly restart it.
I tried to use Capture Attribute node before geometry output and add the attribute to countdown, but anyhow I do it, the timer goes ether to 0. I don't know how to program either, so if the solution is as simple as a couple lines of code, I don't know what to write there.
Blend file used:
Answer: if you add this to your subtract node:

you get this if you click on restart:
Comment: I see, thank you so much! I would also ask on how to make it restart on only True output, but if it works why fix it. XD
Comment: I got it now, when I removed nodes for restart and put the switch into first Capture attribute, it turned into a start countdown switch, which is even better to be honest. XDDD


How do you set up headset/mike communications for GTA V online with ps3?

Question: I have a PS3 and would like to communicate with other online GTA V players. How does this work? Can I use a Bluetooth headset with mike? do I need special software?
Answer: PS3 natively supports bluetooth.
Before you can use the Bluetooth headset with any device, such as the PS3 or a mobile phone, the headset must be paired to the desired device.
You can pair the headset in two ways:
Automatic mode (using the supplied USB cable) - Enables the headset's advanced features for the PS3. Using automatic mode, you can pair the headset with any PS3, but only the most recently paired PS3 will be saved in the headset's list of paired devices.
Click here for more information on the advanced features of the Bluetooth headset.
Bluetooth discovery mode - Sets up the headset as a standard Bluetooth headset. By using Bluetooth discovery mode you can pair the headset with many other Bluetooth devices.
https://support.us.playstation.com/app/answers/detail/a_id/1226
Answer: To communicate with others for PSN just go to Accessory setting -> Manage Bluetooth Devices and scan your headset type. Then go back to Accessory Settings -> Audio Device Settings. Make sure that the microphone level is at 5 and the input and output settings match the type of your headset.


How to use condition that adjacent elements are not acceptable for iterations

Question: I'm trying to figure out how to create a matrix in mathematica, since I'm just starting working with the program to get a feel before I start graduate school. I'm working through a book problem where I have a 50x50 matrix with each entry being 0, but I need to randomly select an entry and randomly generate either a 1 or 0. After that I need to check if there are any adjacent 1s anywhere in the matrix (if there is a 1 to the left, right, above, or below on the matrix). There obviously won't be any adjacent 1s after the first generation and check, but I need to iterate those two steps, and when there are adjacent 1s, to not update the matrix and instead generate a random entry again. How would I do this?
Comment: Welcome to MSE. What have you tried? Have you checked the documentation? e.g. [this](https://reference.wolfram.com/language/howto/CreateAMatrix.html).
Comment: Another useful command might be RandomInteger.
Answer: You could do this the conventional way where you have a loop, generate random coordinates, see if the nearby entries are 1, retry and so on. However this is awkward because as the matrix is populated more, the random coordinate selection will waste time on entries with 1s in the neighbourhood. It will be very slow.
If instead we convolve the matrix first with a radius 1 cross kernel, this tells us how many 1s there are in the neighbourhood of every entry. We can easily pick out random positions we know will work by finding positions of zeros in the filtered matrix. You can write all of this extremely compactly:
cx = CrossMatrix[1];
m = ConstantArray[0, {50, 50}];
While[MemberQ[(af = ListConvolve[cx, m, 2]), 0, 2],
 {r, c} = RandomChoice@Position[af, 0];
 m[[r, c]] = 1;
];
MatrixPlot[m]

Update:
In the case where you can pick 1 entries and flip them if there are no 1s in the neighbourhood, then I don't think it will terminate but you could cap the number of iterations and use the same method. The only difference is we want the cross kernel to not count the entry it is centered on:
cx = CrossMatrix[1];
cx[[2, 2]] = 0; (* set center kernel cell to zero *)

m = ConstantArray[0, {50, 50}];
iterations = 0;
While[iterations < 10000 &&
  MemberQ[(af = ListConvolve[cx, m, 2]), 0, 2],
  {r, c} = RandomChoice@Position[af, 0];
  m[[r, c]] = Min[RandomInteger[1], 1 - m[[r, c]]];
 ++iterations;
 ]; MatrixPlot[m]

Comment: @mathfanatic33 are you sure, in that case it would never terminate.
Comment: I forgot to mention that if the randomly selected entry is already a 1, it is changed back to a 0. But this is still very helpful thank you!
Comment: yes because the the question asks for the probability that M(25,25)=1 and when some expression with n going to infinity (not quite there on the math yet), it will converge to the invariant probability


IPython notebook shortcut to run

Question: I am currious if there is a shortcut for runing the  selected cell in IPython notebook such as alt+F5 or ctrl+f5 or something simmiliar  that is present in Visual Studio (I don't recall exactly now ) , cause I found it annoing to go with  the mouse on  the run  button every  time I need to run a cell?
Comment: Try shift+enter.
Answer: IPython notebook Keyboard shortcuts:

Shift-Enter: run cell
Ctrl-Enter: run cell in-place
Alt-Enter: run cell, insert below
Ctrl-m: This is the prefix for all other shortcuts, which consist of Ctrl-m followed by a single letter or character. For example, if you type Ctrl-m h (that is, the sole letter h after Ctrl-m), IPython will show you all the available keyboard shortcuts.
Answer: IPython notebook Keyboard shortcuts
![Option the options [2:4] i think is the answer to your question.]
Comment: That is great , tnks!

IPython notebook shortcut to run


Do products of a build process belong in a repository?

Question: For example:

we don't put python compilation files (.pyc's) into the repo, probably because python generates them automatically.
In a java house, do they commit the .jars to their repos?
Traditionally, I believe, C source went into the repo with headers, link libraries? or whatever it took to do a compile, but never output of the build, like the executable itself.

In this specific instance I'm thinking of the web scenario, if we build stuff with nodejs, does the output of that process belong in the repo, or just the sources?  Do we commit just the stuff that is necessary to make the build, or do we commit what we need to do the deploy (thus avoiding all the tooling).
In the absence of in-house rules, what is the guiding principle?
Answer: No. The binaries generated do not belong in your repository. You need to keep them in some kind of store, but committing them to your history is a bad idea.
All VCS systems I'm aware of have some kind of issue with storing the resulting binaries, although the particular problems will differ depending on the implementation. Some are common to both systems though.
Centralized systems, like TFS, need to frequently compare the files on your local system to the latest version on the server. They have a harder time comparing binaries than than regular text files, so making it constantly check those binaries for changes will slow down your development environment.
Git, on the other hand, uses hashes of the repositories content to determine if a file has changed. (Fun fact: The sha is actually the resulting hash of the entire repo.) That makes the check very quick, but because Git stores the entire file at every commit, instead of just the delta, storing slightly different binaries will bloat the size of your repository greatly.
All systems fall to the same flaw when it comes to storing build outputs in your repository though. Its an utter PITA to have your VCS think something has changed just because you built the solution.
Imagine this scenario happening a dozen times a day:
You pull down the latest source code. You're paranoid, so before changing anything, you build the project to make sure your environment is set up correctly and the last guy to commit didn't break the build. Your VCS now thinks something has changed, even though nothing has.
So, you ignore those pending changes and go on with your work. You're a good developer, so you commit a half dozen small changes and submit them for review. When your coworkers go to review the changes, all they see is a dozen changed binaries. They have to sift through all those files in order to find the one line change you made.
Does this sound efficient to you?
Comment: `(Fun fact: The sha is actually the resulting hash of the entire repo.)` Kinda - that's really oversimplying it.
Comment: Yeah, it really is over simplifying it @Qix, but at the end of the day, yeah. That's basically what it is.
Answer: I realize you meant a source code repository, but it's interesting that you just said "a repository," because many organizations do store their binaries in a different kind of repository called an artifact repository, especially companies with microservices architectures or other highly componentized architectures.
This allows you to just compile the microservice you're working on and pull in already compiled binaries for the rest of the system for local integration testing.  Tools like maven or gradle can do dependency resolution of your company's libraries in your local repo and third party libraries in repositories on the internet.
But no, in source control you want to only store the preferred form for making modifications.
Answer: This is just to add on to RubberDuck's answer.
Everything he said is true. But there's another reason binary files don't play with with a VCS. VCSs are designed with programming in mind, and the fundamental file type that programmers work with are source files. Source files are text-based, meaning they're structured as a sequence of lines (which are themselves sequences of characters) separated by the newline-character. The other common file types that programmers work with, such as setting and configuration files, are also usually text-based.
Thus, with this format in mind, the VCS compares files line-by-line (although some will work at an even finer granularity). This technique fails utterly for non-text (binary) files. Of course, binary is a large category; any binary format will of course have its own internal format (jpg, mp3, rdb, etc), but these differ wildly, and they aren't line-based.
For a VCS to work with any file type, it has to understand its structure. You could conceivably create a VCS that understands the binary format of some database dump, and can compare databases table-by-table or even row-by-row. But this is infeasible to do for every file type, and the ROI is low anyhow. That's why we stick to text files.
Comment: A VCS doesn't have to *understand* the structure of the files it stores. The point is that by using line-based diffs, it can store N different versions of a file using storage *much* less that N times the size of a single version. This happens to be impractical for (most) binary files. On the other hand, if changes in a binary file are sufficiently localized and the VCS is able to use a binary diff algorithm (they do exist), then it might not be a problem. On the other other hand, changes to binary files, especially generated ones, tend not to be localized.


Executing 2 commands in 2 different Terminal windows

Question: I want to execute 2 python programs(both run flask servers on different ports) in 2 different terminal windows, from a single bash script.
Python files: a.py and b.py
Bash Script: runner.sh
This is my current bash script, runner.sh:
a.py
b.py

So when I say,
./runner.sh
It should execute a.py and b.py in 2 separate terminal windows.
Answer: You can launch a terminal via a command; this should include an option to execute a command inside the terminal as well.
There are various GUI terminal applications available on GNU/Linux.  They are usually paired with the DE (desktop environment).  The default DE on Raspbian ("the DE formerly known as PIXEL", for lack of a better name1) is derived from LXDE, whose terminal app is lxterminal.  You can read the documentation for that with man lxterminal. The execute option is -e, so:
lxterminal -e "/usr/bin/python /home/pi/myscript.py"

Using quotes here is required if the command contains whitespace. Beware that the terminal will close when myscript.py ends, which can make it hard to determine what went wrong if it doesn't work properly.
To get around that what should work (I'm not an LXDE user, but I tested it with another terminal app) is to wrap it in a shell script:
#!/bin/sh
/usr/bin/python /home/pi/myscript.py
$SHELL

This will open a shell (ie., your normal command line) after myscript.py exits.  So to use this, lxterminal -e "/path/to/that/script".  The script must be executable (chmod a+x whatever.sh).

Why they decided the DE should not have a name I don't know. It seems the opposite of user friendly, but perhaps that depends which way your head is on.
Comment: Thanks for the answer, works well.
Answer: Your files a.py and b.py should have "hash-bang"-lines at the top, to tell the environment how to execute them. They look similar to:
#!/usr/bin/python

There is a good chance they are already there, but check to make sure.
Once that is done, your runner.sh, placed and executed in the same directory, should look like so:
#!/bin/sh
lxterminal -e ./a.py &
lxterminal -e ./b.py &

The trailing & of the lxterminal-lines makes sure that this process is executed in the background, and that the script continues to execute.
Comment: works really well. Thanks for the answer.


Make MySql Accessible from Outside (Windows)

Question: I have a Mysql instance installed (not as a service) on a WinXP virtual machine (VirtualBox). I installed it from the installer with GUI on the MySql site. Everything works perfectly, but the MySql connection refuses external connections. What are the simplest steps to be able to connect to this MySql instance from outside? I use a user called 'root'...
Answer: You have to explicitly grant access from external hosts to the user
http://dev.mysql.com/doc/refman/5.1/en/adding-users.html
it is generally best not to use root externally
Answer: I think the default root user only has access on the local machine. This offers some sort of protection since the 'root' account in many cases has no password by default. Only users who can access the machine can administer as root (by default).
You need to create another user who can access MySql remotely. See the Adding Users page for more details on this. It is well explained there.
Note that you should be logged into Windows and MySql running.
If you will wish to access MySql when you are logged out, then you will need to install it as a service.
Answer: Using @Adam and @codinguser's answers, and assuming that VirtualBox host is 192.168.57.1:
<code>CREATE USER 'root'@'192.168.57.1' IDENTIFIED BY 'pass';
GRANT ALL PRIVILEGES ON *.* TO 'root'@'192.168.57.1' with grant option;
</code>
Note:

Assuming the machine (or virtual machine) is not accessible from the outside, you can use root with no problems.
It helps if the DB has NO vulnerable/interesting data.


Motivation to run full nodes

Question: I'm sorry if I ask a stupid question. Bitcoin network was conceived by Satoshi Nakamoto as a decentralized network, but now we are seeing the full centralization of nodes in the United States.
The user lacks motivation for hosting the full node as it requires financial costs but it does not pay off.
I have a question. Does the bitcoin network protocol display address when requesting a useragent. Now we can see only the version and ip address. To anyone could donate a certain amount of coins for those who start a full node in the network.
The ideal option proposed by the bitcoin core developer Jeff Garzik  would be to make a commission for that unit is now fully take miners to share with all the owners of the full nodes.
Sorry for my English.
Comment: 'now we are seeing the full centralization of nodes in the United States.' That's a huge exaggeration.
Comment: A correction in your question: the article doesn't say it is Garzik who is proposing to reward people who run a full node, it just says it is "an idea that has been floated".
Comment: Incentivising nodes is an issue. But it depends on how that is handled. Are there other duties that a machine running a full node could perform, and, for example, benefit from by the inclusion of a small payment?
Comment: From a pragmatic standpoint nodes *are* an issue in the Bitcoin network. There is a lot of centralisation since CPU mining was traded for ASICs. Personally, I run a node because I want to learn how the network works. There is incentives to run nodes, nonfinancial incentives too, I'm sure.
Answer: I'm not sure I understand your question, but: No, Bitcoin nodes do not announce their own Bitcoin addresses as part of the network protocol.
One could imagine modifying the protocol so that they did, but it would raise anonymity concerns: currently, by design, it is difficult to match an address with its owner's IP address.  If you knew at least one address that belonged to a particular node, you  might be able to look at other transactions in the block chain and deduce other addresses belonging to that node.  And ISPs usually have records that determine the identity of a user from their IP address.

Motivation to run full nodes


Is the Galactic Federation a multi-dimensional organization?

Question: At the beginning of season 3, Rick teleports the Council of Ricks into the middle of the headquarters of the Galactic Federation. Was the organization he destroyed in this way the Galactic Federation of a singular dimension, (the one they fled to after leaving C-137 to the Cronenbergs) or a multi-dimensional entity?
Answer: No, although they are the primary controller of the Interdimensional Customs
The Federation has appeared a few times. First in the Pilot, when Rick and Morty travel through the Interdimensional customs which is primarily controlled by the Galactic Federation. (click to embiggen)

Although called the Interdimensional Customs, it seems to be more of a high speed way of travelling by using other dimensions to travel through. Nothing yet has suggested that the Galactic Federation from the Cronenberg dimension is the same as the Galactic Federation from the "new" dimensions. Or that they're aware of their co-existence. This is supported by the fact that in Season 3 Episode 1, The Rickshank Rickdemption, we find out that blue portals are only for regular travel and green portals are for interdimensional travel.
From the end of the below clip of the pilot, we see the Rick hacked the blue portal and turned it green.

More evidence is given in The Rickshank Rickdemption when the blue and green portals are clarified as seen below:

(ignore the ending I think it's some promotional nonsense)
Comment: So interdimensional customs isn't, in fact, interdimensional?
Comment: @DanielB everything points to "Rick made it up" usually related to convincing Jerry and Beth that he's teaching Morty valuable skills
Comment: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/65898/discussion-between-edlothiad-and-flater).
Answer: While we have not seen any evidence my guess is they are not.  The reason is in The Rickshank Rickdemption one of the major plot points is the Federation going through great risk to get their hands on Rick's portal gun.  While it may be just better than their technology, most likely they need it because they do not have interdimensional travel.
Otherwise why go to this Rick?  Just find one in some other reality that is more agreeable.
I am also assuming there there are many Federations, one in each dimension, they just can't work with each other
Comment: Supporting my answer! Glad someone agrees :)