Origin and pronunciation of "Thawte"

Question: Working in the IT industry I often have to use the word Thawte - the name of a company and its certificates. What is the origin of this word and its correct pronunciation? Does it have its own meaning or is it just a name? A web search result seems to contain IT security stuff only.
Answer: I believe Thawte constructed its name as a portmanteau of "thought" and "thwart", which would make sense considering their area of expertise. I would imagine that "Thawte" was intended to be pronounced the same way as you would pronounce "thought".
Comment: My South African friend just informed me that Thawte are based in SA, and a lot of South Africans would struggle to pronounce the *thw-* part of "thwart", and would say "thawt" instead.
Comment: @NateEldredge - No, hence my tone - "I believe", "I would imagine".
Comment: @Polynomial, yes that's the initial company of Mark Shuttleworth of Ubuntu/Canical fame. I think he sold it for half a billion usd to Verisign.
Comment: Do you have a source for this?
Answer: I've never heard anyone say it, but all the references I can find say to pronounce the name as "thought".

Origin and pronunciation of "Thawte"


What does [:] mean in python?

Question: e.g. if tableState is a tuple, and we're declaring a variable:
x = tableState[1][:]

What would the [:] mean?
Answer: It takes a copy of the tuple, instead of a reference to the tuple itself.
The [:] syntax is a slice with the default start and end values (0 and the length of the list), returning a new tuple with those indices, so effectively an exact copy of the contents.
For tuples, this doesn't make much sense, because tuples are immutable. You can safely pass around references to a tuple without changing what it's indices refer to.
It works the same for lists, though. You often need to create a copy of a list to be able to modify the contents, and using the default 'all elements' slice is a nice, concise and fast method of doing just that.
Comment: it seems as you are waiting for that Ques. :) too quick.+1
Answer: In general, you're extracting a copy of the tuple.  Keep in mind though that tuples are immutable, so taking a copy of a tuple doesn't really do you much good - it's far more useful with lists.
Answer: [:] it is similer to [0:] which means split from 0 index to the end. it returns a new List .

What does [:] mean in python?


If Animals Drank The Water Post-Netilat Yadayim

Question: Can the tumah water from after netilat yadayim affect animals if they were to drink it?
Answer: The MB 4:20 when commenting on SA 4:9 who says

מים של נט"י שחרית אסור ליהנות מהם ולא ישפכם בבית ולא במקום שעוברים שם בני אדם:

Water which has been used for hand-washing before morning prayers should not be used afterwards for any other purpose. One should not pour it out in a house, nor any place where people pass by

mentions that the problem with giving it to an animal to drink is due to the fact that your gaining benefit from it. Seemingly, the Ruach Ra affecting the animal was not a concern

(כ) מהם - ע"כ לא יתנם לפני בהמת
From them - Therefore, one should not place them before his animal [to
drink from].

When he discusses why not to pour it in a place where people pass by, he says because they can be harmed by the Ruach Ra.
Upon further research, I found that the Dirshu MB understands the issue with giving the water to an animal, that it will be affected by the Ruach Ra, not that it is an issue of having benefit. They quote the Derech Hachaim 1:5 that indicates as such (although in my humble opinion, it isn't clear he's referring to all 3 cases). They also refer to Biur Halacha 338:8 that mentions only the issue of Ruach Ra not assur to have benefit. (Also not entirely sure if this is a good proof)


Disable WP Bakery plugin on specific page

Question: Is it possible to choose not to use WP Bakery on a specific page even if it's used for the rest of the site? Would I be able to upload and use my own template (i.e template-pagename.php) + custom CSS for that one page while leaving the rest of the site intact?
Comment: Yeah, just don't use backend or frontend editor. BTW, support for third-party plugins are offtopic here.
Answer: Yes, it's possible. You can do it with Freesoul Deactivate Plugins.
I mean, use FDP to totally unload it on the frontend, so WPBakery will not load any asset, and will not add any database query on that page.
If you simply want to edit the page without WPBakery, you don't need FDP, just use Gutenberg or the classic editor, but WPBakery will load all on that page in any case if you don't disable it.


Video editing/face replace

Question: I'm new to Blender but want to edit video,I need to replace faces. I will cut face from picture and put there. Found this Overlaying an image to cover a face in a video? but don't get it. Can't found  2D Stabilization
I need to replace and track faces in video.I'm beginner and need explanation step by step.I will cut face from picture and put on actor face in video. It's not that easy,video is long 4min It's fight scene from movie,they jumping ,spinning and I need to track all that.Don't even know how to add image :) I'm new to this and is all complicated :) If somebody can help me step by step I will really appreciate that.  And I hope that is clear now what I want to say.
Comment: Related: [How do I overlay a photo of a face over a character on a video?](https://blender.stackexchange.com/a/36680/1853) and [How would I attach text to a tracked point on video clip](https://blender.stackexchange.com/questions/38549/how-would-i-attach-text-to-a-tracked-point-on-video-clip/38557#38557)
Comment: Please use the [edit] link at the bottom of your question (https://i.stack.imgur.com/lXFuK.png) and add detailed information describing the steps you've taken so far.
Answer:
Open the "Motion Tracking" layout.
Load your video

Track high contrast points (ctrl+LMB to create a tracking point, then press the track forward/backward buttons)

Change the layout to "Video Editing"
Drag in your tracked footage
Drag in your image file
Use the VSE_Transform_Tools addon to position and size your image over the face

Alt+S will rescale an image to it's original aspect ratio FYI

Use the "Transform from 2D Track" function (also part of the VSE_Transform_Tools addon) to pin the image to the face.
Comment: I need explanation step by step :) It's not that easy,video is long 4min
It's fight scene from movie,they jumping ,spinning and I need to track all that. Don't have motion tracking option up there.I can put trackers in movie clip editor. When I press Ctrl+T is very slow then I need to move green bar with mouse. And through the whole video I need to move that tracking square to the face.Don't even know how to add image :) I'm new to this and is all complicated :)
Comment: I will tell you what I know and how I do that. I go to movie clip editor then open video after that turn on AV-sync,adjust Start and End and frame rate. Then go to Tracking settings and change keyframe to previous frame then add marker. I put markers where I want and after that don't now what to do :(

Video editing/face replace


How do I divide taxonomy term pages by content type?

Question: Drupal out of the box lists all of the content tagged with a term in a single list on a terms page. I would like to split up that list into sub pages based on content types tagged with that term. See mockup below. Seattle is the term page and the "Attractions, Museums, Restaurants and Shopping" are content types tagged with "Seattle". To achieve this, i cannot use quicktabs as it requires an admin to create a new quicktab collection everytime a new city is created. Also, panels is not an option on this project either. I am thinking it they are just views pages, with a term id from URL contextual filter, but I am lost on how to add them as secondary tabs on the term page. Unless I am heading in the worng direction. I would love some advice.
Answer: A couple approaches come to mind, I will outline the one that does not use panels.
Start by overriding the default taxonomy page by enabling the one that comes with views.  At this point you will have the same behavior as the default taxonomy pages.
Clone the default taxonomy view and disable the clone (this is case you want to restore the view).
Now back to the taxonomy view
Remove the existing two contextual filters  (not this means the depth feature will no longer be available)
Add a contextual filter on "Content: Has taxonomy term ID"
Add another on "Content: Type".
Change the path to "taxonomy/term/%/page" (for page use the content type machine name you want for this tab)
Change "menu" setting to "default menu tab"
(A) Clone the "Page" display, I gave by clone the name of the content type for the tab
(B) Change the path so "page" is replaced with the next content type you want.
(C) Change "menu" setting to "menu tab"
Repeat (A) (B) and (C) for each content type/tab


Spark Gap in EMP Generator

Question: I recently got into eletronics, and there are some concepts I am having a hard time understanding. I was looking around youtube and saw this video of a small EMP generator, I understand the basics of it, the magnetic field inducts a current thus frying electronics, but what I'm interested in is why there is a spark gap in the schematics. What does it do ?
Comment: Voltage is induced and this voltage may circulate a current.
Answer: The spark gap provides abrupt onset of energy movement; depending on how the spark/plasma extinguishes, you may also get abrupt ending of energy movement.
The abrupt changes in energy into the "coil" implement abrupt changes in magnetic fields.
Abrupt changes in magnetic fields are one form of EMP.
Comment: No. The capacitor will pass charges, using its displacement current, for ANY change in voltage. The spark gap has a "holdoff" voltage, nominally 3,000 volts/millimeter depending on air humidity and sharpness of any non-planar metallic edges. A cap does not provide "holdoff" behavior.
Comment: so could the spark gap be replaced with a capacitor?
Comment: Unlike a capacitor where you don't want the electrons to pass from one plate to another, in a spark gap you want that to happen at a known breakdown voltage. (As analogsystemsrf said, 3kv/mm). If you would put a capacitor instead then you would store a lot of charges in one place with a breakdown voltage that is much less than 3kv/mm, and when the electrons finally break through and form a closed circuit the capacitor would start smoking and possibly start burning. A spark gap is essentially two connectors spaced from each other.
Answer: Presumably the high voltage converter is rectified and put through a multiplier, otherwise this circuit wouldn't work. The capacitors in the multiplier are charged up by the DC and when the voltage becomes high enough to jump the spark gap, all of the energy stored in the capacitor(s) is dumped into the coil, thus producing a powerful EMP. You can think of the setup as building up pressure until it reaches a certain point, and suddenly releases all of that pressure all at once. You can see how that would be much more powerful than simply passing the current through the coil.
Comment: So that means the purpose of the capacitors are to release  all the energy in a short time and the spark gap acts as a trigger for when it reaches a certain voltage?
Comment: Pretty much, yes.

Spark Gap in EMP Generator


Are the plastic covers where the plug is inserted remove able so a different color one can be used?

Question: I need to know if I can replace the plug cover not the plate, to change the color without having to remove the entire box?
Comment: Plug Cover - AC Outlet Plug ? Interior exterior, Plug Cover or Receptacle Cover Plate ?
Answer: There are cover plates which cover the receptacle and not just the surrounding space. I don't know if there are problems with them or not. They do cost more than a standard cover plate. There are different shapes of receptacles and one might have to get a cover which fits the type of receptacle one has.
In any case one never has to "change the entire box". The box is not visible when a cover plate is in place. The box is fastened to framing in the wall. What one might have to change is the receptacle inside the box. The receptacle is screwed to the box and has the wires attached to it.
The usual procedure for changing the color exposed to the room is to change the receptacle and its cover plate together. This may be what you meant by changing the entire box. If so, one shuts off the breaker to that circuit, removes the cover plate, unscrews the two screws holding the receptacle in the box, pulls out the receptacle, detaches the wires from the receptacle (usually by loosening screws) and the receptacle is free. Installing the new receptacle is just the reverse. This is a simple and straightforward procedure for an experienced DIYer, but for someone who has never done it it has pitfalls.
Comment: Example https://www.youtube.com/watch?v=vfZAE1VQPEY  But breaking off the connecting tab is **not** done unless the two receptacles are powered by different lines. Normally both receptacles of the standard duplex receptacle are powered by the same line so this tab is left in place.
Answer: Receptacles and trim plates are two separate components, so if you want to change the color completely you have to change both. Changing the receptacle is not difficult, but it does require turning off the power -- it's one of the most basic electrical tasks you can do.
Here's a couple pictures to give you an idea of the parts involved:

When you do this, you also get the option of going to a different style (eg "decora") or installing outlets with USB power, if you want that.
Code compliance
As of the NEC 2011 (which applies to basically everywhere in Canada/USA), there are additional requirements to comply with code if you replace outlets, which essentially boil down to:

You have to maintain grounding if the previous outlet was grounded
You have to install a GFCI and/or AFCI (arc-fault) protection if required under current code
You have to install tamper-resistant and/or weather-resistant receptacles when required by current code

These are explicitly not grandfathered in.
Full NEC excerpt:

NEC 406.4 General Installation Requirements
Receptacle outlets shall be located in branch circuits in accordance with Part III of Article 210. General installation requirements shall be in accordance with 406.4(A) through (F).
(D) Replacements.
Replacement of receptacles shall comply with 406.4(D)(1) through (D)(6), as applicable. Arc-fault circuit-interrupter type and ground-fault circuit-interrupter type receptacles shall be installed in a readily accessible location.
(1)Grounding-Type Receptacles.
Where a grounding means exists in the receptacle enclosure or an equipment grounding conductor is installed in accordance with 250.130(C), grounding-type receptacles shall be used and shall be connected to the equipment grounding conductor in accordance with 406.4(C) or 250.130(C).
(2)Non–Grounding-Type Receptacles.
Where attachment to an equipment grounding conductor does not exist in the receptacle enclosure, the installation shall comply with (D)(2)(a), (D)(2)(b), or (D)(2)(c).

(a) A non–grounding-type receptacle(s) shall be permitted to be replaced with another non–grounding-type receptacle(s). A non–grounding-type receptacle(s) shall be permitted to be replaced with a ground-fault circuit interrupter-type of receptacle(s). These receptacles shall be marked "No Equipment Ground."
(b) An equipment grounding conductor shall not be connected from the ground-fault circuit-interrupter-type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle.
(c) A non–grounding-type receptacle(s) shall be permitted to be replaced with a grounding-type receptacle(s) where supplied through a ground-fault circuit interrupter. Grounding-type receptacles supplied through the ground-fault circuit interrupter shall be marked "GFCI Protected" and "No Equipment Ground." An equipment grounding conductor shall not be connected between the grounding-type receptacles.

(3)Ground-Fault Circuit Interrupters.
Ground-fault circuit-interrupter protected receptacles shall be provided where replacements are made at receptacle outlets that are required to be so protected elsewhere in this Code.
  Exception: Where replacement of the receptacle type is impracticable, such as where the outlet box size will not permit the installation of the GFCI receptacle, the receptacle shall be permitted to be replaced with a new receptacle of the existing type, where GFCI protection is provided and the receptacle is marked "GFCI protected" and "no equipment ground," in accordance with 406.4(D)(2)(a), (b), or (c)
(4)Arc-Fault Circuit-Interrupter Protection.
Where a receptacle outlet is supplied by a branch circuit that requires arc-fault circuit-interrupter protection as specified elsewhere in this Code, a replacement receptacle at this outlet shall be one of the following:

A listed outlet branch-circuit type arc-fault circuit-interrupter receptacle
A receptacle protected by a listed outlet branch-circuit type arc-fault circuit-interrupter type receptacle
A receptacle protected by a listed combination type arc-fault circuit-interrupter type circuit breaker

(5)Tamper-Resistant Receptacles.
Listed tamper-resistant receptacles shall be provided where replacements are made at receptacle outlets that are required to be tamper-resistant elsewhere in this Code.
(6)Weather-Resistant Receptacles.
Weather-resistant receptacles shall be provided where replacements are made at receptacle outlets that are required to be so protected elsewhere in this Code.
Answer: If you are referring to the AC Outlet Receptacle Cover plate - they come in several different colors and styles.
White, Bone, Black, Brown.
Your hardware stores or even online search for AC Receptacle Covers. As for replacing it - there is usually one screw in the middle of the plate that allows you to remove it and replace it.
Now if you are talking about the AC receptacles themselves - the answer is replace the AC receptacle, they come in different colors as well.


Should there be additional parallel boards?

Question: Meta will go a long way to remove such discussion from Stack Overflow proper.  A site like fun.stackoverflow.com, or similar, could do likewise -- keep the main board pure, and provide an outlet for those who just can't ask a straight question today.
Answer: I think you just want to keep it straight forward and utilize tagging. Forking things too much makes things to complex to use.
Comment: I'd have to disagree there, I have developed an utter hate for forums. Too much over head, too much complexity, its just a nightmare for anyone with OCD because the nature of them requires you to basically work yourself into a state where you are manually monitoring all threads, and threads grow vs time, etc etc. Utter calamity.
Comment: If search worked much, much better, I would agree.  But I think forums make for a nice, clean, well-organized separation of major topics.  Would really like to see it happen.
Answer: I was under the impression that SuperUser is going to cater for the 'fun' questions?
Comment: depends on your definition of "fun"
Comment: Yes, hence using the quotes. I'm sure there will be some form of definition once the site goes live.
Answer: The site is prompting me to select an answer to my question.  I don't like any of those posted so far, so my self-answer follows.
There's a reason one always finds the Wendy's in town right across from the McDonald's, which is right down the street from the BK, which is across the corner from the Subway and KFC.  The reason is that the businesses co-locate intentionally, and the reason they do it is they know it's good for business.  If your first thought for fast food is to head their direction, then they've already won your money.  Even further, if they can get you to just think "fast food" when you're hungry, they've made you think so much less about the whole thing that they've won even more of your money.  If those places were scattered all over town, you would have to first decide exactly what you wanted, and consequently where you wanted to go, then go there, without the opportunity to change your mind at the last minute and go next door instead.  That's a harder prospect to think about, and might just stop you from going out to eat altogether. ("Don't Make Me Think", anyone?)
Likewise with SO, SF, SU.  Each board does serve a specific kind of fare, and works hard to differentiate itself; and the purity of the board matters.  It is important to know what's on the menu before you go, and to know that they serve consistent, high-quality fare.
But in a larger sense, what the SO sites really serve is not coders, or unix SAs, or spreadsheet jocks, but a huge population of tech-savvy tinkerers and professionals.  That group has other interests, too.  If you want to draw them and keep them, then in addition to having a forum for their individual, specific interests, you should also be catering to their other, known, common interests.
The obvious ones, that have already been identified, here and on other posts/locations, are:  technical books, subjective (on-topic) discussion, humor, and wholly-off-topic.  (In truth, the decision about how many related forums to have should be driven by traffic metrics -- when traffic gets too heavy, meiosis takes place.  But classification must of course be done carefully.)
The SO sites collectively will do themselves a huge favor by (1) creating forums for discussion of these related topics, (2) making navigation from forum to forum seamless, so that the user effectively feels like he's at the same site, and (3) strengthening the moderator organizational structure, so that some mods have strong authority over individual boards, and others have broader, cross-board power.
Rep, user details, even URL are all manageable details.  It is the intuitively obvious, effortless navigation from one forum to another that creates the cross-feeding of visitors and the sense for the visitor that these boards, collectively, are a web "destination."
If the links to related forums aren't directly on the banner, then they should be at the top of the right sidebar.  Anywhere less prominent consigns each separate site to a more solitary existence, increasing the likelihood that a visitor never finds the material that really grabs him, and moves on, never thinking of the SO family of sites as a place to come back to often.
Comment: Can't say I didn't expect a downvote, but a remark would be appreciated
Comment: we need to disable that accept nudge for meta.. don't take it as a requirement
Comment: Fair enough, unaccepted
Answer: I think the "fun" board you're referring to would house things like "Favorite Programming Cartoon" and "Favorite Coding Music" and "Favorite Coding Beverage" and things like that.
I don't think these questions get asked at a very high rate on SO anymore, and tend to be shot down when they're tried.  Providing an outlet for them is a reasonable hope, but frankly, I don't see much value in it.  Sure, I may want to get some ideas for new music to listen to while coding.  But I can use Pandora.  And as much as I enjoy reading Jeff's blog posts, I don't really care about what food gets him in the mind for coding.
The resources, in terms of equipment, time investment, and support don't justify it in my opinion.


EOL conversion in notepad ++

Question: For some reason, when I open files from a unix server on my windows machine, they occasionally have Macintosh EOL conversion, and when I edit/save them again they don't work properly on the unix server.  I only use notepad ++ to edit files from this unix server, so is there a way to create a macro that automatically converts EOL to Unix format whenever I open a file?
Comment: Your issue may be with whatever FTP program you are using. For example, I use WinSCP to remote into a Unix server, Notepad++ is set as my default editor, but I had to go into WinSCP's settings and set the transfer mode to `Binary` in order to keep line endings preserved. So, you may be able to reconfigure your FTP/SCP/etc program to transfer the files in a different manner.
Comment: possible duplicate of [Change EOL on multiple files in one go](http://stackoverflow.com/questions/11341660/change-eol-on-multiple-files-in-one-go)
Answer: That functionality is already built into Notepad++.  From the "Edit" menu, select "EOL Conversion" -> "UNIX/OSX Format".
screenshot of the option for even quicker finding (or different language versions)
You can also set the default EOL in notepad++ via "Settings" -> "Preferences" -> "New Document/Default Directory" then select "Unix/OSX" under the Format box.
Comment: I know about the conversion in the edit menu, and the settings you mentioned are only for new documents.  I want to automatically make the conversion for every file I open (or every file I save)
Comment: @OffTheGold The UNIX EOL option is greyed out because it is the current selection.
Comment: The problem is when I open an existing Unix file, the "EOL Conversion" --> UNIX/OSX Format is greyed out. Notepad++ is to frustrating to use with UNIX files, so I use Notetab Lite which allows me to save All files as UNIX, not just new ones.
Comment: RIght on.  Thank you from November 2017 via Google.
Comment: This is no working for me. I keep selecting "EOL Conversion -> Unix", but it does nothing. I go back into the menu and see that Windows is the greyed out (therefore selected?) option, so I click Unix again. I even tried to select-all my text first in case it only works on selection, then selected Unix again. Still it does nothing.
Comment: … and now I figured out why. The file had its read-only flag set (not to be confused with a lack of write permission). In Notepad++ I had to go to the Edit menu and first select "Clear Read-Only Flag", then I could make an EOL Conversion selection and it worked.
Answer: In Notepad++, use replace all with regular expression. This has advantage over conversion command in menu that you can operate on entire folder w/o having to open each file or drag n drop (on several hundred files it will noticeably become slower) plus you can also set filename wildcard filter.
<code>(\r?\n)|(\r\n?)
</code>
to
<code>\n
</code>
This will match every possible line ending pattern (single \r, \n or \r\n) back to \n. (Or \r\n if you are converting to windows-style)
To operate on multiple files, either:

Use "Replace All in all opened document" in "Replace" tab. You will have to drag and drop all files into Notepad++ first. It's good that you will have control over which file to operate on but can be slow if there several hundreds or thousands files.
"Replace in files" in "Find in files" tab, by file filter of you choice, e.g., *.cpp *.cs under one specified directory.
Comment: This can cause loss of EOLs due to replacing a \r\n\r\n with a single \n. I think.
Comment: Confirm worked in Notepad++ 6.9.1. It will search forward, therefore not recursively replace those are behind.
Comment: In replying to: "This can cause loss of EOLs due to replacing a \r\n\r\n with a single \n" >> It will not, as it uses | (or) operator between 2 possible group.
Answer: I open files "directly" from WinSCP which opens the files in Notepad++
I had a php files on my linux server which always opened in Mac format no matter what I did :-(
If I downloaded the file and then opened it from local (windows) it was open as Dos/Windows....hmmm
The solution was to EOL-convert the local file to "UNIX/OSX Format", save it and then upload it.
Now when I open the file directly from the server it's open as "Dos/Windows" :-)
Answer: Depending on your project, you might want to consider using EditorConfig (https://editorconfig.org/). There's a Notepad++ plugin which will load an .editorconfig where you can specify "lf" as the mandatory line ending.
I've only started using it, but it's nice so far, and open source projects I've worked on have included .editorconfig files for years. The "EOL Conversion" setting isn't changed, so it can be a bit confusing, but if you "View > Show Symbol > Show End of Line", you can see that it's adding LF instead of CRLF, even when "EOL Conversion" and the lower bottom corner shows something else (e.g. Windows (CR LF)).

EOL conversion in notepad ++


How to show additional fields from InfoPath in Document Library?

Question: I have a document library of type InfoPath Forms.
Currently the columns in the list (Library) only showing some of the InfoPath Fields.
I'd like to add the rest of them so they are visible in the library.
Basically so then I can manipulate them with a workflow. I can't seem to remember where I allowed which columns are visible outside of infopath.
Answer: Duh!...
Here it is.
Infopath File > Form Options > Property Promotion


Simulate a double balanced coil for a metal detector on PROTEUS

Question: I am trying to build a metal detector with double balanced coil, (the scheme source is the french magazine : L'ELECTRONIC POUR TOUS project: EN1465 Un détecteur de métaux très sensible, the magazine available on the internet), I had a problem with simulating the double balanced coil on PROTEUS marked by the red circle in the attached image. What electronic components should I use (only inductors) to simulate the receiver and sender coils? I saw some metal detector project they use an RLC circuit.
Any ideas?
Comment: Consider adding a screenshot of the Proteus circuit and any error message that application provided or any waveforms which indicates the problem that you are facing.
Answer: The leftmost oscillator coil induces hopefully the same signal to the mid and rightmost (=R) coils. The mid and R coils are in series so that the caught sum signal is zero if there's no metal. If someone brings a piece of metal near the coils, it very unlikely affects (via eddy currents) identically to what's caught by mid and R coils. The balance vanishes and the detector line starts to get signal from the mid and R coil combination.
You can simulate the detector (a synchronous one) system simply by feeding the 5500 Hz oscillator signal to the +input of IC2-A. Do not cut its dc-path, R5 is a must.
To simulate the coil system you must know the coil inductances and their mutual inductances - total 6 different inductance values. I'm afraid that a direct measurement needs advanced instruments and calculating it needs  advanced math knowledge, both beyond what I have. But if you know those inductances you simply change for ex the mutual inductance between the leftmost and mid coil.
You can measure from a built practical circuit how much mid and R coils catch.
How much a given piece of metal can cause mutual inductance imbalance at the operating frequency - it can be measured. It can be also calculated numerically with full 3D electromagnetic field simulation system. Again something quite advanced.
Not asked: There's many other metal detection systems. Some of them need only one coil.


What is the source for bowing during 'zeh el zeh v'amar"?

Question: I have searched, and seen some type of questions related to this. However, I have seen no sources. I figured I would ask: does anyone know of any sources for bowing during 'zeh el zeh v'amar"?  Why do we do it?
Comment: I have looked for a source as well, with no success. I figured it's just "something that people do" without a source.
Answer: An answer is provided here:

Hatefilah Vhilchoteha 2:314 quotes Rav Ovadia Yosef and Rav Chaim Kanievsky that there's no basis for the minhag to bow during vkara zeh el zeh v'amar. Az Nidbaru 13:32:3 agrees. He says for those who do it can bow either to the right first or left first but what is important is to pay attention to the words. Shivat Tzion Shabbat 7:106 v. 2 p. 117 writes based on the zohar that the angels when praising Hashem turn to the right first and then to their left and in kedusha we're mimicking the angels. He explains that it isn't similar to Yoma 53b where we're leaving Hashem's presence.1 Rivevot Efraim 5:103:2 writes that one should turn to the right first and the left. Hatefilah Vehilchoteha ask quotes the Mayim Chaim 2:7 who writes that one should first turn to the right since one isn't taking leave of Hashem.
Comment: Whenever you don't know which way to go you go right (RAMBAM
Comment: I always went to the left first and I thought that was the rule -- until I read the above!
Comment: I'm pretty sure Rav Ovadiah has a tshuva where he says to get left first . Can't find it
Answer: There are a few more reasons cited here
They seem to centre around requesting permission from the angels to praise Hashem:

The Siddur Tefila L'David of the Lelover Chassidim says that when one is reciting the "V'kara Zeh el Zeh V'amar" one should bow to the right and then to the left as if one is taking permission. [Cited in Minhag Yisrael Torah O.C. 125:2]
The "permission" in this context is open to a number of different interpretations. One will note that the opening line of the Kedusha is a declaration of our desire to praise God just like the angels do. We are told that when the angels praise God with the thrice "Kadosh", they first call out to each other in order to organize themselves to praise Him in unison. We can suggest therefore that our bowing to the right and left is intended to humble ourselves and request permission from these angels, often depicted as standing on either side of God, to praise Him as they do. [Yeshayahu 6:3]
Another cited source for the "V'kara Zeh El Zeh V'amar" movements is a reference to the piyut "Amitzei Shechakim" that is recited on Yom Kippur which makes mention of angels turning to "every side" to recite the "Kadosh". Again, it would appear that the desire to imitate the angels at this time is seen as a commendable act which likely fueled the "V'kara Zeh El Zeh V'amar" customs. There is also a basis for the practice based on the Zohar [Parshat Noach, cited in Minhag Yisrael Torah O.C. 125:2] which relates the bowing to the right and left to the rainbow. [Cited in Minhag Yisrael Torah O.C. 125:2]

It is also worth noting this here which reiterates the above.
Answer: I beleive that this started as a 'reenactment' of how kedusha is said by the melachim - i.e. "and they call one to another and say..." so you would turn to your neigbouring angels in turn and say 'Kodosh'.
This then morphed into people assuming that 'Oseh Sholom' movements is on the program.


In Neverwinter Nights: Enhanced edition do the inflict wounds spells do critical damage?

Question: Do the inflict wounds series of spells cause critical damage on a critical hit?
I've tried to test this but am unsure about the results? Is there a way for me to test this to get a clear answer? If the answer is "No" then is this a bug?
Answer: All the Spells that have a Touch Attack can critical strike.
With some Spells, instaed of have more damage you can have some scripted unique results.
Neverwinter Nights Wiki - Critical Hit
Comment: I've discovered that inflict wound touch attack spells are scripted to not do critical damage.
Comment: Hi Rick.
I found some extra information as well. Should I just adjust my question or add to it in the comment section?
Comment: Depends if the anserw remains the same or if it change the subject. In the latter case, it's better to create a new post, otherwise you can adjust your question with extra information.


What is the pressure and density of a neutron star?

Question: I am interested in finding pressure of neutron star!  So. Please could any tell me how to choose central density for the inner and outer core of neutron Star. What numeric value should me in both core. Also what should be the polytropic index gamma for outer core.
Comment: How can you have a "central density" for an "outer core"?
Answer: The central density of a neutron star is unknown, but probably lies in the region of $\sim 10^{18}$ kg/m$^3$, depending on the details of the composition, the equation of state and of course the mass of the neutron star.
As an order of magnitude estimate, at these densities, the pressure approaches the maximum for a relativistically degenerate ideal fermion gas of $P \simeq \rho c^2/3 = 3\times10^{34}$ Pa.
By "outer core" I assume you mean the neutron fluid region. Here the density could reach somewhere between $3\times 10^{17}$ and $\sim 10^{18}$ kg/m$^3$ before something may (or may not) cause a phase change (hyperons, quark matter etc.). The pressure at the upper end of this range would approach that which I gave above. A more formal calculation could calculate the equilibrium composition of an n,p,e gas and then use the appropriate formula for an ideal Fermi gas to estimate the total pressure. Such a calculation, at a range of densities, also gives you an estimate of the adiabatic index. I find that the pressure of an ideal n,p,e gas is $7\times 10^{32}$ Pa at $3\times 10^{17}$ kg/m$^3$ (completely dominanted by non-relativistic neutrons), rising to $5\times 10^{33}$ Pa at $10^{18}$ kg/m$^3$. The adiabatic index $\gamma$, (where I define $\gamma$ in terms of $P \propto \rho^{\gamma}$), is approximately 1.6 over this range.
You have to realise though that this is an unrealistic equation of state at these densities. As the neutrons get closer together ($\leq 10^{-15}$ m) they must interact and this hardens the equation of state such that $\gamma \geq 2$, otherwise neutron stars of mass up to $2M_{\odot}$ couldn't exist! Indeed, one definition of the "inner core" might be where this hardening happens.
A recent paper by Hebeler et al. (2013) includes the following plot (in cgs units) which reviews the many possible equations of state in the density range I have discussed above. For reasons discussed in that paper, the authors favour the AP3 or AP4 equations of state which give higher pressures tan the simple n,p,e approximation. The slope of these graphs gives the the value of $\gamma \simeq 3.3$ for AP3 and AP4 for $\rho > 5 \times 10^{17}$ kg/m$^3$.
Comment: Hmm yes siR thanks!   well what dou you think so if I take central density = 9. 99*10^14,  central pressure 1. 385*10^35 , polytropic index gamma as 2. 8535 and integrate T. O. V EQUATION for presssure. Will its describe the outer core state which is mainly composition of  neutron-protron fermi liquid + few% of electron fermi gas.
Comment: @umarkhan It will give you a result, but the outer parts of a neutron star would *not* be well characterised by such an equation of state. $\gamma$ is smaller in the n,p,e fluid below nuclear densities and in the crust.


Does applying $5\mathrm{N}$ force on a object for $2$ seconds mean applying $10\mathrm{N}$ force on that object?

Question: If I apply $5\mathrm{N}$ force on a object for $2$ seconds, can I say that I applied $10\mathrm{N}$ force?
Comment: If I have 10 dollars for 2 days, can I say I have 20 dollars? :)
Answer: No, because the force was 5 N the entire time.
You can say that the object (provided there are no other forces acting on it) received an impulse of $\Delta p = 10 \rm\,N\cdot s$ due to the force you provided.
The relationship you are looking for is between momentum, force, and time:
$$ F = \frac{\Delta p}{\Delta t}. $$
Answer: No, not at all.  When a constant force $F$ of $5\mathrm{N}$ is applied for a time duration $t$ of $2\mathrm{s}$, it imparts an impulse $F\cdot t=5\cdot 2=10\mathrm{Ns}$ to an object which causes the change in linear momentum $\Delta p=\Delta (mv)=10\mathrm{kgm/s}$ of that object.


How to evaluate social/emotional development?

Question: I know there are many books on evaluating academic success and deficits, but how do you evaluate social/emotional learning?  Are there studies to help with this? What milestones should a parent look for?  Should the amount of schooling in the younger years be factored into the evaluation as the child started learning social skills at a younger age?
Comment: What do you mean what is the point @tomjedrz ?  Social/emotional is just as important as academic development and some would say more important.  Ensuring that my kids are on track is extremely important to ensuring a happy well adjusted child.
Comment: What is the point? What changes would less than stellar results lead you to make?  Perhaps you should just make those changes ...
Comment: @tomjedrz:  I assumed when I was answering the question that morah was using this as a way to determine areas of "need" for her children (as I periodically do) so that she can make a gameplan to work on these areas with her kids.  However, it helps to know what is socially/emotionally expected out of a kid before you start being concerned about it.  For example, we are currently working on sharing and using our words--perfectly acceptable expectations for my 4 year old, not so much for my 1 year old.  Please feel free to correct me if I misinterpreted any of this, morah.
Comment: @morahhochman:  I would +100 that if I could.  I think sometimes parents tend to overlook social/emotional development assuming that kids will just figure it out for themselves.
Comment: @all "It helps to know what is socially/emotionally expected ... " is the problem. How can it be measured?  If the goal is a "happy well adjusted child", then evaluate if your child is happy and well adjusted. If not, find out what and help your child. If yes, then who cares if the child has fewer friends than peers, or doesn't text message 100x/day, or only gets 1 birthday party invitation a month, or whatever measure some academic comes up with. This is one area where you should TRUST YOUR INSTINCTS.
Comment: I abhor the "Stepford child" attitude I see so frequently. On no, my child isn't "normal". There is no "normal", just as there is no "average". We spend far too much time and effort applying standards to our kids and then worrying about differences.
Answer: I don't know if this will help you, but I found a study published online from January 2011 for the Raikes Foundation entitled "Social-Emotional Learning Assessment Measures for Middle School Youth".  I know it seems to focus primarily on middle school ages, but it seems to have some information in it that talks a little bit about social-emotional assessment in younger ages, and it includes several samples of assessments towards the end.  The reference page is a solid two pages, so there might be some literature in there that would help you some.  Fair warning:  It's about 50 pages long so you might want to settle in with a big cup of coffee after the kids have gone to bed :-D


Resonance- sound

Question: Can someone please explain resonance to me? I thought it was when an external object has the same frequency as an object, so through constructive interference, the amplitude is intensified. And maybe this has something to do with standing waves, I don't know. But can someone please further explain this? Thanks.
Comment: Hi Renee If you read this first, and then come back with any points you don' t follow, that might help you ( I hope its at the right level for you) http://www.physicsclassroom.com/class/sound/Lesson-5/Resonance
Comment: Okay, I think I understand this in terms of a tuning fork: you force one into vibration, causing the other to vibrate also without having to hit it. Can you explain how resonance plays a role in the example of pushing a swing, or the collapse of the tacoma bridge if soldiers don't break their step? I think I understand resonance in terms of its definition, I am still just a little fuzzy on how to apply it. Thanks!
Comment: The Tacoma bridge collapse is always thought of being due to resonance, I used to quote that myself, but it was something else (that I hope you don't need to worry about)  called **aeroelastic flutter** that is now thought to have caused it to fall. https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)  I will do an answer , or a comment re resonance  in a few minutes
Comment: links re resonance, will you see is this a duplicate of what you want to know, but I have no problem writing an answer.  John Rennie in his answer covers the swing part, I think: http://physics.stackexchange.com/questions/90497/an-analogy-for-resonance?rq=1. The other example is the soprano breaking the glass with the pitch (that is the  frequency)  of her voice, I always wanted to know if that is true.
Comment: Just wanted to say thanks for all the help! I aced my test yesterday :)
Answer: Resonance is a property that some systems exhibit due to their specific structure, but fundamentally involves the trapping and a structural means by which energy can flow within the system between different states of energy.
The trapping of energy means that the system structure enables the system to admit at least as much energy as what energy is lost by the system. And the flow between internal states means that energy at some times may exist as potential energy and at other times as kinetic energy, or in other types of systems as electrical and magnetic fields.
Resonant systems are defined as having modes or natural frequencies and these are states of internal energy flow at which there is little energy loss relative to energy intake. Some resonant systems reach an equilibrium of energy flow and maintain a steady resonant state, but others may take in more energy than what can be lost, and in this case may reach a structural limit with regards to how much energy they can contain which can cause the system to break. A classic example is the Tacoma Narrows bridge collapse which was a mechanical resonance of the bridge structure driven by aeroelastic flutter.
Resonance exists in all types of systems, mechanical electrical, geophysical, etc., natural as well as man made systems and at all scales from within the nucleus of the atom to galactic structures. At human scales resonance can be used to our advantage or can lead to destructive events. Resonance is all around us.

Resonance- sound


Optimistic vs. Pessimistic Burndown Lines - just a Project smell?

Question: Not been here for a while but thought I would jump back with an interesting question.
Are optimistic and pessimistic chart lines on a burnup/down genuinely useful or just a project smell imported to an Agile chart?
Comment: Can you explain what you mean by `Optimistic/Pessimistic Burndown Lines`. Do you have two esimates in time (min/max) instead of story points?
Comment: I'd think that a *range* for release planning would be useful, but not for a sprint. Since a sprint's burn-down chart reflects work done or not-done, I don't really understand the use case for forecasting within a sprint. Maybe you can expand on that a bit.
Answer: They are genuinely useful, but there are a few factors that can really skew them to be wary of.
For those not familiar, when we use a burn-up chart to track work toward some scope marker, like a release, on a project, we can take the average velocity and plot a line forecasting when the total amount of work complete will meet expected scope (when it'll be done).
We can also plot lines assuming every future sprint is as good as our best sprint and one assuming every future sprint is as bad as our worst sprint. This gives us a window of when I'll reach an expected scope. I am very unlikely to be done by my optimistic date and very unlikely not to be done by my pessimistic date.

Some Things That Throw Them Off
Predictability: If your team's velocity isn't fairly consistent, your window will be so wide that it'll be useless. Two things to help with this are to use the last few sprints and to throw out understood outliers (like sprints with a week out for Christmas).
Multiple Projects: I've seen teams add stories done for work outside of the project into their burnup, but leave the scope line the same. For obvious reasons, it messes up your chart. Either increase your scope line when you add extra stuff in or don't include it in your burn-up line.
Poor Definition of Done: If you don't have a strong Definition of Done, you don't know if you're really done or if you're piling up technical debt. If you leave a lot of testing, release, or other work until the end of the project, your forecasts will be meaningless.
Some Great Uses
Obviously being able to give the PO and stakeholders some idea of how the overall project is awesome, but there are some other things it's great for too.
Yes/No/Maybe Scope questions: It's easy to plat a particular amount of work or particular feature on this chart and say that it will, will not, or might be done by a certain time.
Prioritization: Let's say something is lower on the backlog and I don't need it done right now, but I need it done before New Years. I can use these lines to know how far up the backlog it needs to be in order to be certain it's done in time without having to throw it to the front.
Optimistic / Pessimistic line shows behaviors (you might say this is just team/project smell): Different trends may mean different things. A large cone of uncertainly (difference between Opt and Pes lines) with the average near the middle suggests that the team has a fairly even number of highs and lows and probably carries a lot of work between sprints. If there's a large cone of uncertainty with the average closer to the Opt line, something is occasionally sabotaging or crashing sprints. Maybe business is changing it's mind mid-sprint or they're being plagued with environment problems. If the reverse is true (average is near Pes line) then the team is occasionally having amazing sprints. The team is probably capable of a lot more, but something slows them down most sprints. You should target those opportunities.
Comment: How does this take in to account scope change as a result of feedback at the end of each sprint? It seems to rely on the scope being known in advance.
Comment: @Barnaby: That scope will often change withe the inclusion of feedback or removal of items from the scope. I've updated the image to show that more accurately. Thanks for pointing that out!
Comment: Great response Daniel - like it a lot.  Marked as answered.
Answer: There is a great video that shows how to use variance in trend lines in an agile project. This video is a standard part of my two day Scrum Master training class because Henrik does such an amazing job of giving a total overview of scrum and by doing it from the PO perspective, helps to pull in the most skeptical of students (the product manager).
The Optimistic/Pessimistic Burnchart conversation starts about 12:20.


Can Higgs potential provide a cosmological constant?

Question: Usually, in particle physics, people do not care about a constant term in scalar field potential. Rather, attentions are paid to the local profile at the minimum. But in the context of cosmology, the absolute value of the potential has a physical meaning; it is a cosmological constant and can cause the Universe to accelerate or decelerate. My impression is that the naive potential for the Higgs field has a negative value at the minima. Do people take it seriously as a negative cosmological constant? Is the dynamical change in the value of the potential at the minimum during EWSB taken into account?
Comment: Well, a contribution to the CC is generated spontaneously when the Higgs obtains a VEV. But it can always be cancelled by a CC is the Lagrangian.
Comment: @innisfree Sure, but the CC in the Lagranian is fixed once given while the Higgs potential is dynamical durning the evolution of the Universe. I want to know whether or not people seriously consider the corresponding gravitaional effects for this dynamical change. Or it is just too small that can be neglected?
Comment: This is an interesting question. My suspicion is that any such changes are too small to have an effect on cosmological evolution, provided that you fix the vacuum energy _after_ all phase transitions, etc. complete. For instance, naively the electroweak phase transition changes the vacuum energy density by order $m_W^4$. But it takes place at temperature $T \sim m_W$ where the energy density is already $T^4 \sim m_W^4$ anyway.
Comment: So any effect will change the expansion rate a little around that phase transition, but will have little effect if one goes more than an $e$-fold before it. Of course, such gigantic changes in the cosmological constant occurring early in the universe do make it mysterious how the final value is so small -- but that's precisely why the cosmological constant problem is so hard.
Comment: @WeinEld I get it, i have added a sentence to your question, if it's OK
Answer: There are two things to consider here: the late-time accelerated expansion, often discussed within the context of the cosmological constant, $\Lambda$, and primordial inflation.  Let's take the latter first.
In primordial inflation, one has a field initially evolving in the false vacuum of some potential energy function.  The false vacuum must be very flat in order to get enough inflation and generate the right spectrum of density perturbations. For example,

Cosmologists early on hoped that the SM Higgs, or perhaps a GUT Higgs, might have been what drove primordial inflation but the trouble was that the false vacuum wasn't flat enough.  In recent years, this idea has been regained momentum when it was realized that if one coupled the Higgs to gravity (as a non-minimal coupling with the scalar curvature), then one could flatten this region and obtain successful inflation, see https://arxiv.org/abs/0710.3755.
Once the Higgs decays to the true vacuum, primordial inflation ends.  If the true vacuum, however, has a nonzero vacuum energy, then it's possible that the Higgs field could contribute to the observed late-time accelerated expansion.  As you note, the classical vacuum energy of the Higgs is negative, $\rho_{\rm Higgs, \,vacuum} < 0$, and this is not what we observe.  Therefore, it's possible that the effective cosmological constant is something like $\Lambda_{eff} = \Lambda + \rho_{\rm Higgs,\,vacuum}$, but this subtraction would need to be fine tuned to get our tiny observed amount of cosmological constant.
(Image from: https://indico.cern.ch/event/180122/attachments/239069/334713/NExT_2012_Atkins.pdf)
Comment: Thanks a lot for your answer. Although this is not strictly speaking the answer I expected but it provides useful information. What I would like to know is actually not about the cosmological constant per se but rather the discussion of the gravitational effects (at least from the change of the effective cosmological constant) during the electroweak phase transition happened in the early Universe.
Comment: As the Higgs decays, its vacuum energy drops, and so the expression I wrote above for the effective CC applies, but with $\rho_{\rm Higgs,\, vacuum}$ replaced by the time-varying vacuum energy density.  Since the universe was radiation dominated during the EW transition with the vacuum making up only a tiny proportion of the energy budge, the effect of this is tiny.
Comment: Also, in the case of Higgs inflation, then the change in vacuum during the EW transition has a huge effect, namely it causes the inflationary epoch to transition into the radiation dominated phase.
Answer: The cosmological constant is part of the mathematical framework of General Relativity.
The Higgs field is part of the mathematical framework of quantum field theory and particle physics .
At the moment there is only effective quantization of gravity, used in cosmological models , and yes, if you google higgs field and the cosmological constant a number of publications come up, so people are examining the  possible relation.
A real proof will come only when/if a unifying theory of everything embedding the standard model of particle physics and gravity is found.
In this answer I give a link to a related question, on how string theories, which include both the standard model and quantization of gravity may deal with the problem.
Comment: Thanks for your answer. As I commented above, I did not mean to ask about the cosmological constant problem and not quantum gravity, but actually the gravitational effects from the change of the absolute value of the Higgs potential at the minimum. It is a classical effect, i.e. with the spacetime or graity treated as classical.


difference kill -9 pid and kill pid command

Question: what is the difference between kill -9 pid and kill pid command ?
Do they have different behavior ?
i know that -9 is for "SIGKILL" signal
Comment: If you don't specify a signal it will send SIGTERM (giving the process a chance to close itself down gracefully)
Answer: kill pid (which sends signal 15 (SIGTERM)) tells pid to terminate, but said program can execute some code first or even ignore the signal. kill -9 pid, on the other hand, forces the program to immediately terminate (it cannot be ignored).
You should always try kill pid first, as it allows the program to do things like saving/closing open files before exiting. Only use kill -9 when you need the program to close and it won't respond to a simple kill pid.


How accurate is facial reconstruction in forensics?

Question: I've seen on tv where they reconstruct heads and faces from the remains of ancient people and I was wondering if anyone had a source that has pictures of maybe side by side of a facial reconstruction Vs. a picture of the actual person being reconstructed. I know it takes a long time to fully decompose but surely there's been a reconstruction done of a recent person who's been photographed
Comment: So, it isn't accurate at all then. Eyes, hair, nose and mouth are the things that make a person identifiable, not just the shape of his head with some imagined details.
If you just make all those details up, you may end up with a totally different looking person. You may also get a result that is somewhat similar but that's by pure chance.
So the rest of it is just art, not science.
Comment: I'm voting to close this question because it is about forensics rather than biology.
Answer: okkkk. I did a big project on this... and here's some of my research... let's hope it answers your question

Facial reconstruction (also known as craniofacial identification) is a method used in the forensic field.  Many people view facial reconstruction as an art instead of science.  Art is commonly portrayed as the expression or application of human creative skill and imagination, typically in a visual form such as painting or sculpture, producing works to be appreciated primarily for their beauty or emotional power.  Science is thought of as the intellectual and practical activity encompassing the systematic study of the structure and behavior of the physical and natural world through observation and experiment.  But where do science and art blur the lines?
WHAT CAN WE TELL FROM THE SKULL:
The skull provides clues to personal appearance. The brow ridge, the distance between the eye orbits (sockets), the shape of the nasal chamber, the shape and projection of the nasal bones, the chin's form, and the overall profile of the facial bones all influence facial features in life. Using these bones, artists and forensic anthropologists work together to reconstruct facial appearance through the process of forensic facial reconstruction.  There are many ways of telling both the approximate age, and the approximate ethnic background of the victim.  To find age, you can pay attention to the cranial suture (or the place where the cranium fuses to other bones of the skull), the size of the skull can help, as well as the teeth and the formation of the bottom jaw.  When looking for the birth gender of the victim, scientists often pay attention to the brow ridge, eye sockets, mandible, and the slant of the jaw.  Sometimes, it is impossible to tell by looking at the skull what birth gender the victim was.  In cases like this, people look to the pelvis to tell if the human has given birth, and if not, males do not have a ventral arc.  It is often very difficult to find the race of a victim if they are mixed race, or if the skull is very worn out.  However, to find the ethnic background scientists will look at the shape of the skull, the nazel root, and the space between eye orbits.
WHAT ARE THE PROCESSES OF FACIAL RECONSTRUCTION AND ARE THEY ACCURATE:
Facial reconstruction is an exacting process. The finished product approximates the actual appearance, because the skull does not reflect the details of soft tissues-eye, hair, and skin color; facial hair; the shape of the lips; or how much fat tissue covers the bone. Yet, facial reconstruction can put a name on an unidentified body in a modern forensic case, or, in an archaeological investigation, a face on history.
Today, many forensic facial reconstruction techniques are in use, including two-dimensional (drawn), three-dimensional manual and three-dimensional computer-based.  In the manual techniques, including two dimensional a cast of the skull is required, so the facial markers do not become an anomaly when analyzing the skull.  Although all of these methods are used, it is most common that a trained sculptor, who is familiar with facial anatomy, works with a forensic anthropologist and uses clay to build the facial features. The forensic anthropologist interprets skeletal features such as the subject's age, sex, and ancestry, and anatomical characteristics such as facial asymmetry, evidence of injuries (a broken nose, for example), and loss of teeth before death.
Facial reconstruction is used when the victims dental records fail to identify them, and there is no dna to pull from the body.  The process of reconstruction starts with making a mold of the unknown skull with the jaw attached and false eyes in place.  Depth markers are placed on 21 different "landmark" areas of the mold of the skull to approximate the facial tissue thickness that lay on the skull.  These tissue thicknesses are approximated from averages of other people of the same age, sex, and race as the skull is assumed to be.  Facial muscles are placed on the mold next and then the face is built up with clay to within a millimeter of the depth markers as tissue.  The nose and eye setting are very difficult to estimate due to the enormous amount of variation possible, mathematical models are used to make the approximations, the mouth is assumed to be the same width as the distance between the pupils. In facial reconstruction the eyes, nose, and mouth are mostly guess work.  Characteristics such as birthmarks, wrinkles, scars, and such are guesses at best and cannot actually be determined from the skull.  Facial reconstruction is accurate because it has been using mathematics, and calculations as such, in order to determine spaces, amounts, as well as the shapes of the face themselves.
WHY IS FACIAL RECONSTRUCTION IMPORTANT:
Facial recognition, as well as facial reconstruction is very important in the forensic field.  Both have a very important role in catching murderers, and investigating crime.  Without having a facial reconstruction, often times, you cannot identify victims.  Assuming the body is historical and for museum purposes, then without an identity it becomes very difficult to fill in large gaps of information, and time that can be crucial to history.  Also, if you can't identify a murder victim then scientists could only look into cause of death.  Learning the identity of a deceased victim is as important to crime investigations as learning the identity of the suspect. When human remains are found, then the top priority is often to find the identity of the victim.  Police often also will look for an identity out of respect, for both the victim and the victim's loved ones if any.  Facial reconstruction has been used ever since 1890.  Before 1890, people mostly used few facial indicators such as the shape of the frontal bone, and the remains of flesh to help identify the victim.  Facial reconstructions, can also show what injuries were sustained previous to death.
WHAT CAN WE LEARN FROM FACIAL RECONSTRUCTIONS:
Our skeleton is an extensive record of our lives. The food we eat, the rate at which we grow as a child, the injuries we sustain, whether we have given birth; all can be determined from our bones. Experts can determine sex, age, and ethnicity, relatively easily from the skeleton, with the skull and pelvis playing pivotal roles in this analysis. Later this week, we'll be taking a more detailed look at how to determine sex and ethnicity from a skull.Teeth can reveal information about diet and a comparison between dental records of the deceased and the recovered skull is often the primary method of identification.  By looking at the scull (or any bones in fact,) you can tell childhood injuries from injuries that might have been fatal.  You can also look at bone density and other factors to tell if the victim was suffering from any diseases.  People look for the sagittal suture – the squiggly line that runs the length of the skull – If it is fully fused, the remains are likely to be of someone older than 35. After that professionals look for a second line at the front of the skull -- the coronal suture – which fully fuses by age 40. Teeth are also looked at. If they're worn down it could be a sign of a poor diet. If they're well-maintained and/or have good dental work such as fillings, they were able to afford proper dental care—another clue as to the identity of your skeleton. Oftentimes professionals consult a scientist who specializes in teeth, known as an odontologist. They can determine how old a person was at death, what kind of health they were in and what kind of diet they had.
Baby's bones begin to grow in the womb. At birth, the skeleton is partially formed. Many bones are still in "parts." The ends (epiphyses) and bony shafts (diaphyses) of long bones form separately in the womb. At birth, the ends of the long bones are mainly cartilage, with centers of bone beginning to form inside. As a child grows, the shafts get longer, and bone gradually replaces the cartilage epiphyses. Through the growing years, a layer of cartilage (the growth plate) separates each epiphyses from the bone shaft.  By paying attention to this, it is easier to tell age, and follow growth patterns to have a successful reconstruction.
Between 17 and 25 years, normal growth stops. The development and union of separate bone parts is complete. At this point, you and your skeleton are as tall as you are going to get - with many fewer bone parts than you started with.  The bones that enclose the brain grow together during childhood along lines called cranial sutures. During adulthood, bone "remodeling" may gradually erase these lines, at variable rates. Closure of cranial sutures gives general information about a person's age. It is best used with additional indicators to estimate age, or when other age indicators are unavailable.
WHAT ARE THE LIMITATIONS:
It is very hard to estimate a person's weight and represent that with facial markers.  Since a chart of average thickness of soft tissue is used to estimate the way a person looked, if you were on the skinnier side, your head might appear a lot more overweight than usual and or skinnier.  To help determine weight, scientists look at the rest of the remains for a height.  Facial reconstruction relies on the relationships between the facial features, subcutaneous soft tissues and underlying bony structure of the skull. If there is no clue for potential identity because of impossibility to compare questioned remains with possible familiar material, in such cases one of the last chances is to recreate ante mortem appearance by face reconstruction. Many of the soft tissue thickness values are significantly different from those reported for comparable groups, suggesting that individuals from different geographical areas have unique facial features thus requiring population-specific values. This literature review attempts to throw some light on the important aspects that has to be taken into consideration while setting norms of soft tissue thickness among various populations.
Studying the unknown skeletal remains mostly becomes the only way to find out more information about individual characteristics, which could lead to identification of potential victim. If there is no clue for potential identity the most precise comparative techniques fail, because of impossibility to compare questioned remains with possible familiar material. In such cases one of the last options is to recreate ante mortem appearance by face reconstruction. Following the first introduction of reconstruction in the late 19th century, other techniques have been developed including radiography, 3D statistical model, ultrasound, MRI, CT and Cone Beam Computed Tomography (CBCT).  Facial contours were traditionally considered to be the result of positioning of underlying hard tissue followed by the soft tissue. However, current trend shows a paradigm shift from the conventional hard tissue analysis to also include both hard- and soft-tissue analysis.
IS FACIAL RECONSTRUCTION AN INTERDISCIPLINARY ART:
The skull is made up of 22 bones, 14 of those are facial and eight are cranial bones; it is a complex structure, and small variations during development and growth, together with soft tissue differences, create the enormous facial variation seen in the human population.  Artists have long been interested in the direct anatomical relationship between the skull and facial appearance.
Artist, Gaetano Guilio Zumbo (1656-1701), used facial reconstruction as an art because he believed that math and science are both forms of art.  His work can be found in the Wax Anatomical Collection at La Specola Museum, Florence, became famous for his macabre scenes depicting various stages of decomposition of the human body.  One of his most famous pieces is the head of a dead man, with facial muscles recreated in wax over a real skull.
This is the earliest surviving anatomical wax model created for didactic purposes and exhibits extraordinary anatomical precision alongside an artistic sense of horror and decay. Although we assume that Zumbo was less concerned with facial appearance than anatomical detail, he pioneered the development of scientific art and this work ranks as one of the finest examples of three-dimensional facial reconstruction.
By definition, an interdisciplinary art is relating to more than one branch of knowledge.  Facial reconstruction is often categorized as both a science and a mathematical equation.  Both science, math and art are human attempts to understand and describe the world around us. The subjects and methods have different traditions, and the intended audiences are different, think the motivations and goals, specifically for this purpose is fundamentally the same.
Comment: Welcome. Can you add sources?
Comment: Interesting essay about forensic facial reconstruction. I've noticed that forensic depictions of people from archaeological remains tend to be flattering, depicting the individual as facially attractive, whether male or female. This tendency most certainly reflects the artistic side of reconstruction.
Comment: @CaryCotterman that may have more to do with reconstructed faces always being symmetric and free of small scale flaws, which would not show up on bone. They are not going to add flaws willy nilly because it would adding things they have no evidence of, but completely lacking them makes for a more attractive face. it is the same reason a touched up photo of a model is often more attractive, touching it up is  often just removing small flaws.


Wpf inkcanvas Save and Retrieve text

Question: Hi I am trying to implement a mspaint like application in wpf.I have successfully implemented most of the basic drawing functionalities by implementing a custom stroke class.Now I am trying to implement the Text inserting option from mspaint.I have tried to implement using DrawingContext.DrawText,it is working alright but when I save the strokes to an isf file and reloading the drawing,all the drawing is loaded but the text is not restored.Please help me on the same.
Answer: I'm afraid the Text is a member of the Children collection.  Your StrokeCollection, which is what you're asking to do the serializing and deserializing, doesn't know anything about it.  You're going to have to build serialization logic yourself, or go through a DataContractFormatter, or whatever permutation of same you prefer.
Comment: Thanks Chris..any way i used an alternative approach

Wpf inkcanvas Save and Retrieve text


Calendar overlay or metadata

Question: I have a lot of calendars. I would like to create a new one which aggregate contents from all of them.
Do you know how?
Answer: You need to create one "parent" calendar to which you overlay the other calendars.
"The following procedure describes how to overlay one SharePoint calendar onto another SharePoint calendar. After you overlay the calendar, you can use this calendar to create a special calendar view.
To overlay a SharePoint calendar with another SharePoint calendar, follow these steps:

In a SharePoint calendar, choose the Calendar tab and then select
Calendar Overlays.
In the Calendar Overlay Settings page, choose New Calendar.
In the Name and Type section, type the Calendar Name and then select
SharePoint.
In the Calendar Overlay Settings section, type a Description for the
calendar (optional), and change the Color theme for the calendar
(optional).
TIP    Selecting different colors for different calendars makes it
easier to distinguish which calendar an event is from.
Type the Web URL for the SharePoint site that the calendar is in,
such as https://contoso.com/TWGroupWorkSite/calendar, and then
select Resolve. If the calendar is in the same site as the group
calendar, Web URL will already be populated accurately.
Select the List drop-down arrow and then select the calendar that
you want to add to the calendar.
Select the view that you want to use from the List View options.
If you want the overlaid SharePoint calendar to always display in
the SharePoint group calendar, select Always Show.
Click OK to accept the overlay specification, and then click OK to
complete the process."

Source
Answer: Remember, the max calendars limits in SharePoint overlay is hard coded to be 10 and cannot be modified, if there are over 10 calendars, additional group calendar would be suggested, the following thread shows the similar issue, please refer to it for more information:
http://social.msdn.microsoft.com/Forums/sr-sp-latn/sharepoint2010general/thread/a8d2ef90-f893-44aa-80fb-e680f46f62ce

Calendar overlay or metadata


Advanced Probability Question - Chance of Not Picking an Object with 10 Trys and no Replacement, then replacing all objects and repeating.

Question: In my AP Government class in preparation of a quiz we are given an unlimited amount of attempts at a practice quiz. There is a bank of 40 questions. Each practice quiz consists of 10 random questions (no repeats) drawn from this question bank. The real quiz is just like a practice quiz and takes 10 random questions (again, no repeats) from the bank. If I take, say, 14 practice quizes, what is the probability that on the 15th real quiz I would receive a question I have not seen before (one that has never been on a previous practice quiz)?
Comment: What have you tried? Certainly you're also taking AP Statistics concurrently?
Comment: @ParclyTaxel  I am actually not taking AP stats. I asked my calc teacher and he gave some advice but no solution. I wrote a computer program that simulates this senario which allowed me to experimentally find the probability, which was about 17% taking 14 practice quizzes and about 2.5% taking 20 practice quizzes. Do these numbers seem reasonable?
Comment: Looks reasonable; see my answer.
Answer: This answer is adapted from the first part of this other answer.
Without loss of generality, fix the 10 real questions that appear on the real quiz. The probability that $j$ specific real questions have not been seen after $k$ practices ($1\le j\le10$) is
$$S_j=\binom{10}j\left(\frac{\binom{40-j}{10}}{\binom{40}{10}}\right)^k$$
Then by inclusion/exclusion the probability that at least one real question has been seen is
$$\sum_{j=1}^{10}(-1)^{j+1}S_j$$
For $k=14$ the probability is $0.165970\dots$, and for $k=20$ it is $0.031333\dots$


Should a post be flagged if the OP does not remember the code owner and adds the code without attribution?

Question: Should a post be flagged as "plagiarism" if the OP does not remember the original code creator and adds the code to the question without attribution? What should be done?
Comment: If you don't know for sure that something is plagiarized and can point to the source, then you should definitely not flag it as plagiarized. Unless you know where the code came from, it is impossible to tell under which license to original was.
Comment: Do you know the code owner? Then add the reference. If you don't, then how do you know it is plagiarized? There was a [very similar question](https://meta.stackoverflow.com/questions/380687/is-your-code-really-yours) some hours ago.
Comment: @BDL This didn't happened. I am assuming if something like this happened and the OP forgot the code owner.
Answer: Flag for plagiarism if you know what has been plagiarized and can point the mod to the plagiarized content.
If you suspect a post to be plagiarized, do your research and find exactly the URL of the original content. Preferrably, include the appropriate attribution by editing the post.
But if you can't find it, how are you going to include the URL in your flag? Do you expect the mod to do this research for you?
Do not flag on hunches or hearsay.
Comment: _"Flag for plagiarism if you know what has been plagiarized and can point the mod to the plagiarized content."._ If you know what has been plagiarized and can point to it, do so.
Comment: What if the code owner forgot the code creator but you know the code creator?


Is it worth changing external outbound links from http to https if the other site redirects properly?

Question: Many of the outbound links on my site have changed but only from 'http' to 'https'. Do I need to add the 's' to all the links if they 301 redirect to HTTPS?
Comment: One problem we ran into, was that HTTPS -> HTTP does not carry referrer information. We had a client who for all intents and purposes thought we stopped sending them traffic as we slowly disappeared from their GA reports. After we updated their url to HTTPS, things returned to normal.
Comment: You tagged this as [tag:seo] but I doubt there are SEO benefits for your site of implementing the changes.  Are you interested only in SEO benefits, or do you also want to know about security and usability reasons to make the change?
Comment: How difficult it is to do this using your CMS will probably determine whether it is worth it.  If it's easy, it's definitely worth it. If it's not easy, it might not be worth it.
Comment: @StephenOstermiller tiny heads up, your edit introduced a typo into the title
Comment: Actually, I would have to change each link separately  so, if it doesn't matter, I won't worry about it. Thanks.
Comment: @StephenOstermiller What are the security and usability reasons in making the change?
Answer: Security
Changing the links to HTTPS prevents a class of attacks against your users.   When a user clicks off your site with a HTTP link, that request could easily be intercepted and changed.   Instead of getting a 301 redirect to HTTPS, the attacker could instead feed malicious content to the user.    Linking directly to the HTTPS site prevents that type of attack.
Speed
Clicking on HTTP links that redirect to HTTPS is slower.  Because HTTP is on a separate port from HTTPS, it is necessary to create two different sockets.  One for the HTTP request and then when redirected, one for the HTTPS request.  That adds 100ms to 500ms of overhead to each and every click off your site via one of these links.  Your users will have a faster experience if you link directly to HTTPS.
Referrer data
When you link from your HTTPS site via HTTP, browsers strip the referrer from the request.  That means that the sites you link to won't see that you are linking to them.   Linking directly to the HTTPS versions of the URLs will preserve the referrer and allow the other sites to give you credit for the links.
Browser warnings
Browsers are starting to show warnings when users visit HTTP URLs.   While no browsers show warnings now when you link to HTTP sites that subsequently redirect to HTTPS, they may in the future.  Changing the links to HTTPS now would prevent it from suddenly becoming a problem later.
SEO
It is possible that Google prefers sites that take care of the external links.   Although I haven't seen any hard evidence for it, it is plausible that Google would ding sites that don't pay attention as their outbound links get stale.   Even worse than URLs that redirect would be ones that have 404 errors.
Is it worth updating?
While there are benefits to changing the URLs, the benefits are relatively minor.     The security attacks are rare, the speed increase in modest, the SEO benefits are speculative, and the referral data may not be important.
I recommend changing the URLs, but there is no need to rush and do so.  You can change them a few at a time as you edit pages for other reasons if it is difficult to change them all at once.
It is more important to change outbound external links that are truly broken.   You should periodically crawl your site and its external links to find any dead or redirected links.  I try to do so with my sites once a year.
Comment: Thanks! That's excellent!


Simplicial polytope in $\mathbb{R}^n$ with $n+2$ vertices

Question: I am interested in simplicial polytopes of dimension $n$ with exactly $n+2$ vertices. Is there a nice characterization of those? For $n=2$ there is of course only the quadrilateral but what about in arbitrary dimensions? Are the $f$-vectors known?
Answer: Those are the bipyramids on the n-1-dimensional simplices.
From that fact then you can deduce the f-vectors directly.
--- rk
Comment: I don't think that this answer is correct. For example the convex hull of the six points $(0,0,0,0),(-1,0,0,0),(0,-1,0,0),(0,0,1,0),(0,0,0,1),(1,1,1,1)$ in $\mathbb{R}^4$ has $9$ facets whereas the bipyramid on the $3$-simplex has only $8$ facets.


UDP listening socket stops listening after network configuration changes

Question: I have a UDP socket listening in a port for broadcast transmissions and it is working fine.
However, when I hibernate and resume the OS (Windows 7), the socket just stops receving data (and I can see that there is data arriving using Wireshark).
This also happens if I change any network settings like, change my IP address, disable and enable the network adapter.
The OS seems to disable all network adapters when hibernating and to re-enable them when it is resumed.
select just returns 0 (timeout) which is no different than when I'm not receiving any data. I could not find any references to this behavior anywhere.
If I close the socket and recreate it, it starts to work again.
My TCP listening sockets still working fine after resuming the OS.
Any ideas on how detect and correct this situation?
EDIT: It still receiving directly addresses data just fine, it just does not receive brodcast transmissions anymore.
EDIT2: Just discovered that if I write to the socket (send a dummy packet to anywhere)  it starts to work again...
Comment: you might want to add tag(s) with the related windows versions
Comment: what is the address the socket is bound to?
Answer: I think your code does not explicitly binds the socket to "0.0.0.0" address. So when you do sentto it binds the interface IP which is available at that time. When this IP is changed or interface is disabled, this socket will be reset by the TCP/IP stack. In your TCP socket, you should have bound to "0.0.0.0" address so it will always listen for connection independent of any IP/interface changes. You can make your udp socket also bound to "0.0.0.0" before sending any data on it. This will make it work even after hibernation or IP changes.


Boundedness of solutions to a semilinear PDE

Question: Let $D$ be the unit disk in $\mathbb R^2$ centered at the origin. Given any $\lambda \in \mathbb R$, let $u_\lambda$ be the unique solution to the semilinear elliptic equation
$$ -\Delta u + u^3=0 \quad \text{on $D$},$$
subject to the constant Dirichlet data $u|_{\partial D} =\lambda$.
Prove that $u(0)$ is uniformly bounded in $|\lambda|$ and that more generally given any $h\in (0,1)$, the solution $u(x)$, with $|x|<h$ is uniformly bounded in $|\lambda|$.
Comment: I just checked the details...maybe I should write an answer, it seems to work in any dimension
Comment: I think this is true (maybe you already know it) since the radial ODE (with $u'(0)=0$, I guess) explodes for $u(0)$ large before reaching $r=1$. Do you have the same feeling? By the way, where does it come from?
Comment: That's exactly my intuition for this problem. As for where it comes from I remember reading this in a paper but can not locate it anymore.
Comment: does maximum not show that the maximum is on the boundary?
Answer: Let me give a positive answer perhaps omitting some details.
Fact 1. Let  $u'' \geq ku^\alpha$ in $[c,\ell[$  with $k>0, \alpha>1$ and $u,u' \geq 0$. Let $A=u(c)$, then $ \ell \to c$ as $A \to \infty$.
This follows by multiplying by $u'$ and integrating. One obtains $$u' \geq k \sqrt{u^{\alpha+1}-A^{\alpha+1}} \geq k \sqrt{(u-A)u^\alpha}$$ and integrating again
$$
\ell-c \leq k^{-1}\int_A^\infty \frac{ds}{\sqrt{(s-A)s^\alpha}} =k^{-1} \int_0^\infty \frac{dt}{(t+A)^{\frac \alpha 2}\sqrt t} \to 0
$$
as $A \to \infty$.
Assume now that $u''+\frac{N-1}{r}u'=u^3$ with $u'(0)=0$ and $u(1)=\lambda >0$. The maximum principle yields $u \geq 0$ and $r^{1-N} (r^{N-1} u')'=u^3$ with $u'(0)=0$ also $u' \geq 0$. Multiplying the equation by $u'$ and integrating
$$
\frac 12 u'^2(r)+(N-1)\int_0^r \frac{u'^2}{t} dt= \frac 14 (u^4(r)-u(0)^4)
$$
and then $u'^2 \leq \frac 12 u^4$. If $A=u(0)$ is sufficiently large, then $u(r) \geq A$ gives $u'' \geq \frac 12 u^3$ for $r \geq \frac 12$ and one concludes by Fact 1 with initial point $\frac 12$ that the solution explodes before reaching $r=1$.


Access Violation when running C++ desktop application on Citrix Metaframe

Question: I have made a Windows application using C++ which runs with no error connecting to an Oracle database when installed in a real computer. When it runs on Citrix Metaframe it sometimes raises an "Access Violation" exception. Is there any rule or any special security action to be made for running a Windows C++ application on Citrix Metaframe ?
Comment: This is a topic for Stack Overflow. It's time to properly debug your application and find out where and why it's failing. The language the app is written in is irrelevant.
Answer: Access Violation usually means that an area of memory is accessed that may not be used. Citrix uses some special version of core dlls so bugs that are unnoticed in a normal environment may surface there.
The Access Violation error has addition information that is important and can be used to trace the bug.
Comment: That's a massive over simplification. Access Violation is a generic term which describes ALL access denied issues, not just memory related.
Comment: It says Access Denied on missing file system permissions.
Answer: Run Sysinternals Process Monitor and look for any "Access Denied" messages when the error pops up.  It sounds like the user is missing appropriate file permissions.


Huge Web App With Memory Leak in IE 6

Question: I have a huge web app that is having issues with memory leak in IE 6.
Fixing a memory leak in a 5 line code sample that demonstrates the problem is easy.
But if I have a very huge application, where should a start from?
Answer: Check out Drip.  That usually takes the guesswork out of IE memory leaks.
If for some reason Drip doesn't find it, take a close look at any JavaScript code that works with events.  That is almost always the source of any significant memory leak in a browser.
Destroying a DOM element with handlers attached to it, without removing those handlers first, will prevent the memory associated with those handlers from being recovered.
Answer: Does the application use a lot of JavaScript?
If it does, then one thing I've found that helps for avoiding memory leaks is to make sure you're using a JavaScript framework such as Prototype or jQuery because they have tried and tested event-handling code that doesn't leak memory.

IE6 can also leak memory if you have circular references to DOM objects
Also try this JavaScript Memory Leak Detector and see if you can diagnose where the problem is
Answer: Here is how I solved the memory leak problem in IE7. The idea is to dispose/set to null all expando-properties on all DOM nodes at unloading the page. This worked for me. You may find it useful.
<code><!--[if lt IE 8]>
<script type="text/javascript">

function disposeAll() {
    if (window.document.all) {
        for (var index = 0; index < window.document.all.length; index++) {
            try { dispose(window.document.all[index], []); } catch (e) { debugger; }
        }
    }
    dispose(window.document.body, []);
    dispose(window.document, []);
    dispose(window, []);
    window.disposeAll = null;
    window.dispose = null;
    window.onunload = null;
}

function dispose(something, map) {
    if (something == null) return;
    if (something.dispose && typeof (something.dispose) == 'function') {
        try { something.dispose(); } catch (e) { debugger; }
    }
    map.push(something);
    for (var key in something) {
        var value = null;
        try { value = something[key]; } catch (e) { };
        if (value == null || value == dispose || value == disposeAll) continue;

        var processed = null;
        for (var index = 0; index < map.length; index++) {
            if (map[index] === value) {
                processed = value;
                break;
            }
        }
        if (processed != null) continue;
        var constructor = value.constructor;
        if (constructor == Object || constructor == Array) {
            try { dispose(value, map); } catch (e) { debugger; }
        }
        if (constructor == Object || constructor == Array || constructor == Function) {
            try { something[key] = null; } catch (e) { debugger; }
        }
    }
    map.pop();
}

(function() {
    var previousUnloadHandler = window.onunload;
    if (previousUnloadHandler == null) {
        window.onunload = disposeAll;
    } else {
        window.onunload = function() {
            previousUnloadHandler.apply(this, arguments); // <== HERE YOU MAY WANT TO HAVE AN "IF" TO MAKE SURE THE ORIGINAL UNLOAD EVENT WASN'T CANCELLED
            disposeAll();
            previousUnloadHandler = null;
        };
    }
}());

</script>
<![endif]-->
</code>
You may want to remove all "debugger;" statements if you don't feel like dealing with some occasional exceptions.

Huge Web App With Memory Leak in IE 6


Automatic factors of braid groups

Question: Consider the braid group $B_n$ presented in terms of the usual Artin generators $\sigma_1,\ldots,\sigma_{n-1}$. Now add the additional relations $\sigma_i^k = 1$ for $i=1,\ldots,n-1$. For lack of a better name, I'll call the resulting group $B_n^{(k)}$. $B_n^{(2)}$ is just the symmetric group $S_n$. As discussed in this mathoverflow thread, $B_n^{(k)}$ is infinite unless $\frac{1}{n}+\frac{1}{k} > \frac{1}{2}$. $B_n$ is an automatic group and thus any word $w$ in the Artin generators can be reduced to a normal form that depends only on the group element in $O(|w|^2)$ time. My question is, for fixed $k > 2$, can one reduce a word $w$ in the generators of $B_n^{(k)}$ to a normal form in $\mathrm{poly}(n,|w|)$ time, too? (It appears to me that direct simpleminded adaptation of the algorithm for braid group normal form fails.)
Answer: The groups you are considering are a special class of Shephard groups, which are obtained from Artin groups by adding relators $\sigma_i^{k_i}=1$, $0\le k_i<\infty$ for every Artin generator.
Biautomaticity of some of all these groups is conjectured in http://arxiv.org/abs/0901.0094
and this conjecture is verified in some cases. Unfortunately for you, the results in this paper require that the Artin graph contains no triangles with label 2, which will exclude quotients of classical braid groups. Nevertheless, you may want to read the paper to see if the methods could be useful in the context of your question.
Answer: Correction: The original answer was incorrect, since non-uniform complex hyperbolic lattices are not automatic
There are analogous groups where this does not hold. Thurston has examples of quotients of mapping class groups of the punctured sphere which are non-uniform complex hyperbolic orbifolds (I think with up to 12 punctures) where the braid generators have finite order. These groups are not automatic, since they are the fundamental groups of non-uniform complex hyperbolic lattices by a result of Farb. I'm not sure to what extent his examples generalize though.
Comment: Fundamental groups of complex-hyperbolic orbifold examples of Deligne-Mostow-Thurston-Hirzebruch-... are indeed quotients of braid groups by adding the relators of the type $\sigma_i^{k_k}=1$. However, in these examples you add other relators as well, so they do not answer OP's question. Incidentally, groups in OP's question are called "Shepherd groups".
Comment: Ok, I thought the only relators came from powers of the generators, since one partially compactifies the moduli space of the n-punctured sphere by lower dimensional moduli where pairs of points collide, which is the 2-codim. strata. I'm not sure where the other relators come from.

Automatic factors of braid groups


Bank payments are made on the blockchain

Question: I am thinking about making a service in which my customers can pay for me via bank accounts, credit cards, paypal or whatever. But the point is that the payment process will be made on the blockchain. Here's what I thought: I would make a mobile app in which when a new person A registers to use my service, he has to give the information about his bank accounts (bank numbers, passwords,..). This information will not be stored on my server, instead, it will be stored somewhere on the blockchain. When A wants to pay, he will send something (like a private key) to my app. The app should use that information to call a smartcontract to get access to the bank information of A that was stored somewhere on the blockchain. Then the smartcontract will handle the bank payment process via the information of A's bank account. I am a programmer and relatively new to blockchain and I don't really know if the idea could work. The point is that all the  infomation like bank numbers, passwords should be stored in blockchain and the only thing my app server does is getting something (or an authorization) of users that allow my smartcontract to access these information. Does anyone know if this idea can be applied? If yes, is there any concrete solution for this idea?
Answer: This won't work for multiple reasons.

In blockchains, all data is public. It is not a place to store passwords or banking info.
This will cost you and users a lot-storage on Ethereum or any other smart contract chain is expensive.
You don't really utilize smart contracts here-you just store data.

End result: either make payments over the blockchain instead of storing people's banking information there, or just store your information on a server.
Comment: Thanks for your answer!! How about I store my customer's bank account in a NFT and give it to the customer, whenever they want to pay, I just simply ask them to give me permission to access information on that token?? Will this work in this way?? Thanks a lot.
Comment: All of my points will still be valid concerns. It is still 100% public information-NFTs are just contracts that also live on the blockchain and it has not much special compared to just using a straightforward contract.