Which one is the proper alternative ? niche / field / area / domain

Question: I'm developing software that asks user to specify a niche / field / area / domain of the document he is uploading. It can be business proposal, technical documentation, official stuff, correspondence, complain  whatever. How do I call this field ?  There will be a suggestion form field that will contain the most frequent expressions.
Comment: You might want to try the [User Interface SE](http://ui.stackexchange.com) as well.
Comment: It is a pure english question, I just need the proper "english" expression
Answer: The word most familiar to your users for this function is "category", as in "specify the category for this document". This word, coupled with examples will clearly convey your message.
Another useful word might be "type", but users uploading files might interpret that to mean "which software package created the document" and thus provide answers such as MS Word, Excel, PowerPoint, etc. That is not what you are looking for, as stated in your question.
Comment: The expression Category already occurred to me, but it seems to me that it is used for types of subject that is/are exactly specified ... like categories[blue, red, orange, yellow], but if they are uploading document that can be of hundreds of possible "types" like "living environment" or PR article, the word category is kind of inappropriate.
Comment: @lisak: well, what is the name of the field in the database where this "category" will be saved? Use that. And if you don't have a name for that, either, then just ask yourself what the purpose of that field is. If it's supposed to be a "short description", then use that. If it's supposed to be a "topic" or a "subject", use that. If the field ultimately serves no purpose, just drop it.
Comment: @RegDwight to much IT :-) I'm asking on the English StackExchange because I need the english expression. The purpose of this field is augmenting the system with semantics and categorization. What I need is a native english speaking person that could tell me what is the most appropriate expression. I think I accept the "category"
Answer: It could be difficult to pick the perfect label for this field. But based on your description, and as a programmer, I agree with John Satta, Category is probably the safest bet. But some other words which might work:

Tag
Description
Subject
Topic
Comment: +1 for __Tag,__  it's looser than category and more "Web 2.0" :-) and thanks for the shout out!
Answer: You may be mixing different things together. What you are trying to describe may be an aggregate of:

The document structure, as given by what headings and subheadings it is supposed to contain. This could be called document type. Some examples are Invoice, Memo, Activity Report.
The area of discourse of the document content, i.e. what the document talks about. This could be called document theme. Some examples are Business, Computing, Linguistics.
The audience for which the document is intended (which is linked to the tasks that are expected to be performed with the document); this could be called document usage. Some examples are User Training, Product Testing, Claim Processing.

There could be more aspects. My point is that each aspect describes a different variable, and they have different names. Mixing them together results in confusing semantics and, as one would expect, a confusing name. :-)
Comment: the first is called _genre_ and the second _subject_ and the third _audience_, if single word terms would help.
Comment: what connects them is that they are _facets of document classification_. genre, subject, and audience are complex facets as they require thought to determine (this means that it's harder or impossible to classify by them if the vocabulary or taxonomy of terms is unknown) while author, title, date are simple (they are free) because they come unchanged from the items (there is no need for terms). the values of complex facets are terms defined by taxonomies. (btw i'm an incidental librarian, amidst dozens of other thing, and trying to write.)
Comment: and there are a lot more facets than just these music tracks, and specialized document genres have extended facets like how a patents have additional fields that are helpful because they make the relations between this document and the rest of the world by reference of the names of entities explicit if you understand how to read them the fixed form makes scanning for a field quick and if they are indexed by those fields you can request a list of items with a field with specified values like i want all documents authored by John McCarthy or all the documents that cite a paper authored by him
Comment: documents refer to the world by names, that occur in relations; sentences are complexes of relations. the document can be inverted to turn these relations from contents in English into indexable form, just by recognizing the citing structures that exist in literature. this doesn't need hard tools just facet tagged strings like in Entity Workspace would allow for fast access to names that occur in documents although this can be automated the disambiguation can't be automated due to the requirement for human judgement which can't be automated away


Validating ePub File using selenium webdriver

Question: Is there any way to validate the ePub file using selenium webdriver?
Answer: I haven't done this, but since epubcheck has a CLI & java library, you could incorporate the library with WebDriver & do the validation that way.
The wiki has an example of how to use it as a library.
Answer: epubcheck will assess whether your file conforms to the epub standards. It doesn't care about your content or your formatting, as long as it conforms to the epub standards.
An epub file mostly a static web site compressed into zip format (plus some additional metadata). So:

You could unzip the content in a directory and use Selenium to examine the HTML pages.
Some of the epub metadata files are XML-based (e.g. the NCX and OPF files). You might be able to use Selenium to examine some of those. I haven't used Selenium to validate XML stuff that isn't HTML, so I can't comment on its helpfulness there. epubcheck does a thorough job of validating the structure of those but, again, not the content.

I don't have an opinion about whether this approach is worthwhile. But given that some of the content is plain old HTML, it is possible to check it with Selenium.
Answer: No.  Selenium WebDriver is a tool for operating a browser by remote control.  It is not a tool validating ePub files.
It is conceivable that you could find a web-based tool for validating ePub files, and that you could operate that tool  using Selenium WebDriver, but I would not recommend testing that way.  If you need to validate an ePub file, I recommend finding a CLI that does the job.


Why are journalists covering U.S. executions banned from using photographic equipment?

Question: According to the Wikipedia article on Tom Howard (the photographer who famously took a picture of Ruth Snyder's 1928 execution), photographers are banned from U.S. executions (the state of New York unsuccessfully attempted to prosecute Howard and the newspaper he took the photograph on behalf of); why is this so?
Comment: The last US public hanging (execution) was in 1936 and attracted a huge crowd, Interesting read at https://www.nytimes.com/2001/05/06/weekinreview/the-last-hanging-there-was-a-reason-they-outlawed-public.html . Despite the title the article doesn't really give a specific reason why the KY legislature and the governor passed the law to abandon the practice.  -
Comment: My guess is that some law was passed and upheld under the auspice that it is deleterious to the public to expose them to such events.  And also that to invite them in is to invite them to make a spectacle and public event of it, which is not what the event is supposed to be. But I don't know any facts to back that up.  I'm actually a tad surprised this got migrated from Law.SE, but maybe that's an implicit endorsement of this being a mostly political assertion of moral good rather than anything specifically legal. But that's another uncorroborated guess.
Comment: Because the State doesn't want to show the populous what it is doing in its name.
Answer: In the first half of the 19th century executions were frequently held in public as spectacles. Campaigners such as Charles Dickens protested against this, calling it "inconceivably awful" and noting the "bearing, looks and language of the spectators", and "when the two miserable creatures that had attracted all this ghastly sight about them were turned quivering into the air there was no more emotion, no more pity, no more thought that two immortal souls had gone to judgement, no more restraint in any of the previous obscenities, than if the name of Christ had never been heard in this world."
In short public executions tend to corrupt the public.  And allowing cameras at an execution turns it into a public show that lasts as long as the images are published.
Answer: Existing case law on this issue is readily available via Lawson v Dixon in North Carolina and Garrett v Estelle in Texas. In this case, and in most states, the legal authority lies with the Warden to maintain "the supervision and control" of the prison.

"...plaintiffs David Lawson, Phillip J. Donahue, and James Arnold do not
  have a right under either the First or Fourteenth Amendments to the
  United States Constitution or under Article 1, Section 14 of the North
  Carolina Constitution to audiotape or videotape plaintiff Lawson's
  scheduled execution, see Houchins v. KQED, Inc., 438 U.S. 1, 57
  L.Ed.2d 553 (1978); Pell v. Procunier, 417 U.S. 817, 41 L.Ed.2d 495
  (1974); Saxbe v. Washington Post Co., 417 U.S. 843, 41 L.Ed.2d 514
  (1974); Garrett v. Estelle, 556 F.2d 1274 (5th Cir. 1977); that under
  N.C.G.S. 15-190 the execution is under the supervision and control of
  Warden Dixon; and that, as a matter of law, neither Secretary Freeman
  nor Warden Dixon can be mandamused to permit the requested audiotaping
  or videotaping;"

Lawson v. Dixon, 336 N.C. 312, (N.C. 1994)
As the quote above states, also explore the cited case law:

Houchins v. KQED, Inc;
Pell v. Procunier;
Saxbe v. Washington Post Co.;
Garrett v. Estelle (5th Cir. 1977);
Comment: For the curious, [mandamused](http://legal-dictionary.thefreedictionary.com/mandamused) is an actual (legal) word.
Comment: I'm not a lawyer and don't even play one on the Internet, so thanks for the addition to my limited bank of knowledge on legal terminology!
Comment: This would be a good answer on SE.Law, but the question here is about the political reasons for having those laws.


Screen Capture control

Question: Is there any control (To use in a c# project) to record user activities and then encoding it to a video file?
Answer: as i understand a video file is a collection of static image frames. You can use this tool's api from http://www.vcskicks.com/ScreenShotTaker.zip, which essentially shows you the mechanism of capturing the screen. So what you may have to do is, automatically capture images in a loop according to a set frame rate and then export it to a video. I'm not sure of how to create a media stream, but you have the library to do the screen capture.

Screen Capture control


My HTC One M9 has a pattern lock that I forgot (I know, dumb). Used Android Device Manager. No prompt

Question: So the screen actually appears saying "Locked by Android Device Manager" but I have absolutely no prompt to type or a keyboard or anything. Hitting the home button just brings the pattern back up. I would much prefer not having to factory reset this phone. Any help would be appreciated. Thanks.
Answer: What os version is your phone? If it's kitkat, it should have a Forgot pattern below it if you don't draw the correct one.
Answer: Here is my blog check this out...
https://techicraze.wordpress.com/2015/12/16/hack-android-pattern-or-password/
Helpful if rooted only
You just have to remove "gesture.key" file from your system and then reboot mobile and then any pattern you draw will unlock the mobile.


Open iMovie with alt down from AppleScript

Question: How to open iMovie with alt from keyboard with AppleScript?
Comment: Please be clearer: what are you hoping to accomplish? What does iMovie do when opened while the `alt` key is held down?
Comment: The dialog for choosing an iMovie-Library.
Answer: Here is a script by maeks84 which does the same for iPhoto that might help you with accomplishing the same for iMovie (need to post as answer due to the length).
Code inserted in case it ever goes down..
--email@example.com
--http://maeks84.wordpress.com

property libraryPath : "Macintosh HD:Users:Path:to:iPhoto Library"

--Determine if iPhoto is open and needs to be quit
--Will only bring iPhoto to the front if the correct library is already open
tell application "System Events"
    if exists process "iPhoto" then --Only worries about the current user
        tell application "iPhoto"
            if image path of photo 1 does not contain POSIX path of libraryPath then
                activate
                beep
                display dialog "About to quit iPhoto!" giving up after 300 --Gives a chance to cancel otherwise continues on
                quit
                tell application "System Events"
                    repeat while exists process "iPhoto"
                        delay 3
                    end repeat
                end tell
                my launch_library()
            else
                activate
            end if
        end tell
    else --iPhoto is not currently running
        my launch_library()
    end if
end tell

on launch_library()
    do shell script "defaults write com.apple.iPhoto RootDirectory " & quoted form of POSIX path of libraryPath
    tell application "iPhoto" to activate
    tell application "System Events"
        repeat while (exists process "iPhoto") is false --Delay until iPhoto is launched
            delay 5
        end repeat
    end tell
    do shell script "defaults remove com.apple.iPhoto RootDirectory" --Restore the default library
end launch_library

Answer: --here's an applescript to copy/paste that might work (unless I misunderstood the question...)
display dialog "would you like to open imovie?"
tell application "finder"
open "imovie"
end tell
--p.s. I havn't tested this, so i'm not sure whether it will work


Georeferencing set of historical maps to each other then georeferencing set to current map using ArcGIS Pro

Question: I have a set of 10 hand-drawn maps from the 1930's that all appear to have the same carbon-copied basemap (the streets and shorelines look identical). They were scanned from Arch D size linen paper so I'm not expecting them to line up perfectly but I should be able to georeference them all to each other (without too much distortion) to compare the data on each.
Then I'd like to georeference the entire group to a current OpenStreetMap. I don't have the projection or scale they're drawn to (there is a bar but I only have the scanned copies) but its really more important that I compare them to one another than to the current map.
I'm using ArcGIS Pro Georeferencing tools but it might be more effective to leave geography out of the mix altogether and just match them on street intersections (there are 50+ clean, right angle intersections) before bringing them into the GIS (not sure if this is even possible).
Any thoughts on how to accomplish this?
Answer: I would suggest doing it the other way around. If you're going to align them to each other then pick the best one and georeference that first, then georeference the rest to that.


Reading ePub format

Question: I am trying to develop an iPhone application to read ePub files.  Is there any framework available to develop this?  I have no idea about how to read this file format.  I tried to parse a sample file with .epub extension using NSXML Parser, but that fails.
Answer: The EPUB format brings together a bunch of different specifications / formats:

one to say what the content of the book should look like (a subset of XHTML 1.1 + CSS)
one to define a "manifest" that lists all of the files that make up that content (OPF, which is an XML file)
one to define how everything is packaged up (OEBPS: a zip file of everything in the manifest plus a few extra files)

The specs look a bit daunting but actually once you've got the basics (unzipping, parsing XML) down it's not particularly difficult or complex.
You'll need to work out how to download the EPUB, to unzip it somewhere, to parse the manifest and then to display the relevant content.
Some pointers if you're just starting out:

parse xml
unzip

To display content just use a UIWebView for now.
Here's a high level step by step for your code:
1) create a view with a UIWebView
2) download the EPUB file
3) unzip it to a subdirectory in your app's documents folder using the zip library, linked above
4) parse the XML file at META-INF/container.xml (if this file doesn't exist the EPUB is invalid) using TBXML, linked above
5) In this XML, find the first "rootfile" with media-type application/oebps-package+xml. This is the OPF file for the book.
6) parse the OPF file (also XML)
7) now you need to know what the first chapter of the book is.
a) each <item> in the <manifest> element has an id and an href. Store these in an NSDictionary where the key is the id and the object is the href.
b) Look at the first <itemref> in the <spine>. It has an idref attribute which corresponds to one of the ids in (a). Look up that id in the NSDictionary and you'll get an href.
c) this is the the file of the first chapter to show the user. Work out what the full path is (hint: it's wherever you unzipped the zip file to in (3) plus the base directory of the OPF file in (6))
8) create an NSURL using fileURLWithPath:, where the path is the full path from (7c). Load this request using the UIWebView you created in (1).
You'll need to implement forward / backward buttons or swipes or something so that users can move from one chapter to another. Use the <spine> to work out which file to show next - the <itemrefs> in the XML are in the order they should appear to the reader.
Comment: Thanks a lot Euan ...For all those who are still searching for a solution,i have created a sample and posted in http://ideveloperworld.blogspot.com/2011/02/epub-reader.html
Comment: I have already done this part . I am not able to implement highlight and bookmark functionality like ibook. Any suggestion
Comment: Note that there's no particular need "to unzip it somewhere" if by that you mean creating separate new files that are the unpacked contents of the ZIP archive. ZIP is a pretty simple format, and it should be fairly easy to create libraries that give you input streams for the various files in the archive that read directly from the archive on the fly, if you don't already have such libraries. One example of such a library, with full source available, is RubyZip (http://rubyzip.sourceforge.net/).
Comment: I will show list of epub files from webservice to user which he can download and read in my reader app for ipad. How to download a file into my app from internet or website and save locally with progress bar which he can stop in between or restore. But my priority is atleast epub file can able to download from website to app

I tried this but not download my file.

http://stackoverflow.com/a/8677389/846372

I dont know what i am doing wrong.

Thanks in advance
Answer: Apparently EPUB is "just" an XML format, so if you have an xml parser and the spec it should be okay.
Plus a little tuto? Have fun!
EDIT: you could also read some code here, this is for generating epub, not reading them but the code may be useful.
EDIT again: And see links to related question in the right sidebar, there are some links in the answers to free ebook reader which support ePub.

EDIT 3: You should add a comment when you edit your question so people who answer you can continue the discussion (if you don't comment we're not noticed of your edit).
So, The parsing fail because you didn't read the spec or related questions on Stack Overflow... *.epub file are a zipped folder containing XML file(s), not plain xml.
Answer: I read through this tutorial once (free registration required, sorry) and it gave me a great introduction to ePub. deverloperWorks tutorial here
I highly suggest you look at some of the XML processing libraries. If you just want to get specific information out of the XML file, then you can pick the right parsing strategy.
Comment: This tutorial is excellent and is written by the person who authored many of the standard open source ePub tools available.  It's a quick read and gives a perfect working intro to the ePub format.
Answer: there is an open source project fbreader,
it also support iphone
http://www.fbreader.org/about.php
Comment: or there is also futurepress/epub.js (it reads epub and annotation through a web browner)
Answer: I'm playing arround to create an epub-framework for iphone apps.
At the moment (I really just startet) i can generate a title page with links to the chapters.
My approach is

Use quickconnect iphone framework as
a layer (maybe i change to phonegap)
which basically allows for javascript
apps as iphone apps
Add the UNZIPed epub as a ressource to the project
Parse the whole thing with a customized version of the epub.js (somewhere on google-code)

Right now I'm looking into pageflip, some kind of gui and minor usability issues (save the current page beingviewed)
I hope that give's you an idea on how to start
Comment: i have used the epub.js what i got an error as *XML Parsing Error: no element found* location line number1 column number 1.can u hel me by providing some links
Comment: whats up with your framework? have you published it somewhere?
Answer: Jonathan Wight (schwa) has developed a ObjC solution for parsing and displaying ePub documents on the iPhone. It's part of his TouchCode open source repository.
Comment: please give me link of TouchCode open source
Comment: http://code.google.com/p/touchcode/source/browse/Experimental/?r=e621eadd838d7733f5025e16733fccb967eb2325#Experimental%2FTouchBook

Reading ePub format


Explaining small sample size---influencing stakeholders

Question: I am new to the user experience world. Based on some references I've read and threads here,  it's Ok to determine statistical significance and compare means for  a small sample size of 11 (7 users in group A and 4 users in group B). How do I influence stakeholders, peers that my sample size is acceptable to do stats in the first place? Is there a more specific statement or explanation that will catch their attention. It seems that although there are experts opinion that says "it's enough sample size", most experienced usability professionals do not agree.
Answer: I know people quote Nielsen a lot here and some love him and some hate, but in any case, Nielsen has a lot to say about the benefits you can get from testing with a very small sample size. He also has some interesting points on why a small amount of data is better than guessing, which is what usually happens if no testing is done at all.
The theory, I think, goes along the lines of: humans are much more alike in their behaviours to stimuli than you would realise and so testing with a small sample size still gives you a lot of useful results. Further more, testing with larger samples hits a level point in usefulness very quickly because you are simply getting more subjects that are likely to behave very much the same or in a narrow range.
Nielsen quotes the numbers 5 as being the point at which you start to get proportionally less new information for additional subjects, and 15 as the point where it pretty much levels off.
I don't know if these numbers are right, but your question was not asking for what those numbers were, but rather for something to show the stakeholders to convince them that your small sample size is still worth it. I should think that showing them the pages I have referenced here and then getting them to Google Jacob Nielsen (>1.25 M results) should do it ;)
Comment: p.s. don't tell the muggles about this site.
Comment: I don't know where I found it (what a pity), But there was a statement or study that to gain tangible more information you have to tenfold your sample size. i.e. large sample sizes *do* reveal much more, but only when they are really large. The reason - as you say - is this: http://www.google.com/search?q=gaussian+distribution&tbm=isch
Comment: A comment on the first link: Thomas Landauer (the other guy in the Nielsen & Landauer duo) also touches the subject in *The Trouble with Computers* (ch. 13, *User-Centered Development*). It is worth a read (and covers much more than this issue). Google Books [provides a preview](http://books.google.com/books?id=h0iKRZunOaYC&lpg=PP1&pg=PA301#v=onepage&q&f=false).
Answer: This topic comes up quite regularly:
A quick search on here finds:
When does statistical significance matter?
Ideal number of candidates for user-testing
Personally I wouldn't even mention 'statistical significance'.
Usability testing is a form of qualitative market research, rather than being quantitative scientific research.   We're not doing a scientific experiment: we're looking for meanings.
You don't just want to know how many 'observed behaviours' there were - you want to know 'why?'.  And often lots of little 'whys' turn out to just part of one big user misconception.
Answer: Steve Krug's book 'Rocket Surgery Made Easy' is a very relevant book here. (Steve Krug's site - http://www.sensible.com/rocketsurgery/index.html - easy to find on amazon which has inside preview)
Quoting a few sections of the book which I thoroughly recommend reading.

What do I tell people who say, "But if you're only testing three people at a time, it can't be statistically valid. You can't prove anything that way"? Here's what you should say to them: "You're absolutely right. Testing with so few people can't possibly produce statistically valid results. The samples are way too small to even bother with statistics. But the point of this kind of testing isn't to prove anything; the point is to identify major problems and make the thing better by fixing them. It just works, because most of the kinds of problems that need to be fixed are so obvious that there's no need for 'proof.' "
Try to say it with a lot of conviction and a friendly smile.

Three is enough
The debate over how many test participants you need has raged for a long time in the usability community, like one of those coal mine fires that burn underground for decades. Almost everyone agrees that there are diminishing returns from having more users do the same tasks: the more users you watch, the fewer new problems you see. Most of the research that's been done—and the arguing—is about how many users will uncover most of the usability problems in what you're testing. For instance, "Testing with five users will find 85 percent of the problems." But that's the wrong argument for you, the do-it-yourselfer. You're not interested in what it takes to uncover most of the problems; you only care about what it takes to uncover as many problems as you can fix. After many years, I've settled on three users in each round of testing for a number of reasons:

The first three users are very likely
to encounter many of the most
significant problems related to the
tasks you're testing.
Finding three
participants is less work than
finding more.
It's much more
important to do more rounds of
testing than to wring everything you
can out of each round.
Testing with
just a few users makes it easier to
do more rounds.
Testing with three
users makes it possible to test and
debrief in the same day.
With only a
few users, it's easier to encourage
people to come and observe.
In
addition to diminishing returns,
there's the tedium factor—for you as
facilitator and for the observers.
Starting with the fourth user of the
day, there's usually a lot more snack
eating, checking of voice mail, and
side conversations.
When you test
with more than three at a time, you
often end up with more notes than
anyone has time to process—many of
them about things that are really
"nits." This can make it harder to
see the most serious problems—the
"can't see the forest for the trees"
effect.
Testing with a lot of users
can uncover an overwhelming and
dispiriting amount of problems.
Prioritizing and triaging them
becomes a problem in itself, another
process to manage.
Answer: I'm puzzled myself by this notion some people have that sample sizes can be too small for inferential statistics. Unless you literally get divide-by-zero, there is simply no such thing. I would explain to anyone who questions using statistics that the whole purpose of calculating the p-value is to determine if the sample size, however small it is, is large enough to draw a reasonable conclusion. Refusing to do statistics but using the results anyway does not solve the problem of having a small sample size. Saying a sample is too small to bother with statistics is like saying a boat is too small to worry about overloading it.
As for getting your team and stakeholders to accept your statistical results from a small sample size, UX peers shouldn't be a problem because they should have at least a rudimentary statistics background and understand that the p-value is what's important, not the sample size. If they don't understand that, then feel free to direct them to my Stat 101 article.
For stakeholders, assuming they have any quantitative sense at all, try to report the p-value in terms they understand. For example, for a p of 0.018 when comparing completion times, try something like "I've done the probability calculations, and even with this small sample size, we can be 98.2% sure that Design A is faster to use on average than Design B for users in general." I would use 3 decimal places. Saying "I'm 95% sure" or "99% sure" sounds like you're making up numbers. Emphasize that your calculations take into account the sample size. It's literally in the equation.
I would report the p-value (or one-minus-the-p-value), not whether it's "statistically significant" or not, because "significance" takes some mental gymnastics involving null hypotheses that makes it harder to grasp. Stakeholders may confuse statistical significance with business significance. Reporting the p-values instead makes it clearer what stakeholders are choosing to do. It may encourage stakeholders to embrace your findings even when they are not technically significant, but I would argue that may be legitimate to do outside of academic research. For example "89.1% sure A out performs B" sounds like a pretty good bet for a business. It really depends on how comfortable your stakeholders are with an 11% chance of being wrong (of making Type I error). Giving the p-value let's them make an informed decision.
For stakeholders that aren't so quantitative, but still don't trust small sample sizes, try to give them an intuition of the role of the magnitude of the effect. With small sample sizes, you're going to observe a dramatic difference in A and B if you're going to have anything like a small p-value. Say something like, "Look, Design A was completed in about half the time of Design B on average. Now with this small sample size, I can't say exactly how much better Design A is (at this point you could give confidence intervals), but it's really unlikely that A and B are actually same on average when you're seeing this kind of difference."
If that doesn't work, show a video of one average user from each group. Seeing one user thrash around on B and another breeze through A will hit home for some stakeholders far better than all the numbers in the world.
BTW if you can get closer to equal numbers in each of your groups (i.e., 6 and 5, rather than 7 and 4) you'll get more statistical power. Power depends more on the size of the smaller group than the larger one.
Answer: It's a qualitative vs. quantitative issue. Both are important, both can produce slightly different data. You really want both whenever you can get it. In the past we've done on-site observed user testing of 7-10 people and then may do an online test of 30-100 people.
If stakeholders are concerned about low sample sizes, then they need to up the budget and staff so you can do more testing.


Evolution through unfavourable conditions or domestication

Question: What is the minimum time taken by a species to evolve? Let the evolution not be completely advantageous to the species, but still, even a little evolution which can be seen or proved should be okay.
Comment: Evolution is a continuous process - there is no end point or finished product. As such, the idea of a "time taken" rather misses the point.
Comment: It depends what you mean by "evolve". Many changes in characteristics of a population like colour changes in moths can occur very rapidly (decades). Although this is really just the natural selection between characteristics that are already present to some extent. True evolutionary change is very slow and gradual, but can be seen over almost any time scale if you are willing to look at very small changes. It would normally take millions of years for such small changes to build up sufficiently to create a new species.
Answer: You can prove evolution by analyzing the genome after only a couple of generations.
Evolution is a process, not an event, and every new specimen will have different DNA than his predecessors. Some of the changes give it an advantage, others a disadvantage, or no changes occur.
You will always need a point of origin for your analysis, so a specimen that came a couple of generations before the current. Only this way you can detect changes and analyze their impact on the fitness.
In some cases you might even be able to tell when a specimen has lived according to historic extinction events that greatly influenced the fitness function.


Do guitar endpins get damaged?

Question: My guitar is already more than 5 years old. It has an endpin which I have never actually used. I bought audio jack and connected it to pc via microphone output. Sound is so unstable that I gave up on this idea quickly. So I was wondering, what is causing this problem, cables, pc output or guitar endpin. If I buy guitar combo is it possible that there still will be a problem with sound? Or most likely directly connecting it to combo will fix the problem.
Comment: Can you add some more details on what you mean by 'unstable'?
Comment: Simply saying sound is unclear, distant and lagging
Answer: It sounds to me like the most efficient way to find the defective component is to figure out a process of elimination by substituting out each component starting with your connecting cable, then try plugging into an amp. If it works fine there then suspect the interface or computer. If it still doesn't work right then suspect the guitar and its parts, depending on your skill level, you may choose to continue the process of elimination by attempting to bypass each component in your guitar, or you may choose to take it in and have a repairman fix it for you.
Comment: I have 2 cables, one with noth sides thicc jack, and other to guitar jack to computer jack, i also have small output changers or whatever its called. I tried what you said with my pc. It had no sound, but when i tried with laptop it had some sound but the sound was very distant and unclear. So this really got me confused
Comment: @Saba- If you plug your guitar into an amp and it works ok, then you'll know that the problem exists in either the interface or the computer, but first you need to determine that in fact the pickup and components in the guitar are functioning properly. Then you'll need to determine if the signal from the guitar is high level enough to drive the input of the interface, which possibly requires a line level signal to drive it to full output. Guitar level signals are usually much lower level signals. A preamp can boost this signal for you if you need it.

Do guitar endpins get damaged?


How do I hide these visible paths on my artwork on illustrator?

Question:
If you look closely, you can see the paths of my art even after saving the artwork to my computer! How do I fix this?
Answer:
Select all the shapes which comprise one of the letters
Open the Pathfinder Panel (Window > Pathfinder)
Hit the Unite button on the Panel (top left button)

This will combine all the little pieces into one single shape.

Repeat for each letter

Then re-save.
If saving for web, for the Anti-Aliasing method, be certain to choose Art Optimized.


Fill about a 2.5" gap between drywall frame and and brick

Question: In the basement, we got done getting drywall up, but there is a gap between the frame and the brick wall. In addition, Perma-seal put there cover up the wall.
Eventually, the window will completely replaced and a frame will be installed.
For now, I would like to fill the gap between the brick wall and the wood frame. Insulation was installed, however I don't want to fill it with that as I have a cat who likes to look out the window and don't want that getting on her.
What can I easily put in there that's not too costly? Appearance is not a large concern.
Here is a picture of the gap.
Answer: What about just drywalling the faces of the 2x4s and letting it hang off, to fill that 2.5" gap? E.g., use a 6" wide strip. You should probably plywood the bottom sill for safety (yours and the cat's) before you drywall it.
Use corner bead and mud it for a 'temporary-permanent' solution, after you do shove a little more insulation back there.
Comment: Could work, except we don't have any extra insulation or left over mud to use and I'm not the one funding this. Might have to be just drywall...


What are the soak, armor, and health levels for vehicles in cWoD or V20?

Question: I searched though the V20 PDF but couldn't find any advanced statistics (anything beyond maneuverability) for vehicles in V20. I'd like to have some armed players participate in a car chase and I'm wondering a) what kind of soak common vehicles have b) how many health levels different vehicles might have. This would be just for targeting the vehicle, not called shots at the tires/attempting to blow out windows, or targeting NPCs inside the opposing car (which I am assuming I would treat as behind cover)
Comment: Please note that invisible does not equal behind cover. It is a common movie trope to have a character kneel behind car's door, but unless the car is armored this is about as effective as hiding behind a wooden table - not very much. Even a handgun penetrates thin sheet metal with enough force to kill people on the other side. To be honest I'm beginning to think unless you specifically call shots to **avoid** hitting people inside, they would be dead long before the vehicle starts malfunctioning.
Answer: Vehicles Stats for the 20th-anniversary edition only came with M20 in 2014/15, page 458 onwards.
Each vehicle is given with Safe/ Max. Speed (which translates to movement in combat), Maneuverability (which is a dice pool maximum to handle it), Crew & passengers (required and non-required people on board), Durability (which is the car's armor), and Structure (which are its health levels). There's also a weapon entry for some. Some lists of vehicles can be found later in the chapter, as can be rules for targeting weak points.
Depending on the vehicle type, the vehicle can offer each enclosed passenger its durability and structure as protection.
Of the 50 different vehicles, I offer the following 4 as exemplary vehicles:

Vehicle
Speed (safe/max)
Maneuver
Crew
Durability
Structure

Compact Car
70/130
6
1 (1 pass.)
3
3

Cop Car
80/200
7
1 (3 pass.)
5
5

Bus
60/100
3
1 (20+ pass.)
4
8

Hummer
80/120
5
1 (1-5 pass.)
5
8

Compared to the old WoD Combat Structure was roughly divided by 3. In turn, Durability is not rolled but directly substracts from all damage inflicted on the car, or other items, as the rules explain.1 The example makes maybe most clear:

Based on six successes scored on the Enlightenment roll, plus
one automatic success for using the Forces Sphere, the kick itself
inflicts 14 health levels of damage on the pillar. Use of the Matter
Sphere reduces the pillar's Durability to 4, so that kick deals out ten
health levels against the pillar's Structure of 6.2

14 levels damage - 4 Durability = 10, 10 > 6, so the pillar was destroyed.

1 - Mage the Ascension, 20th Anniversary edition, p.439.
2 - Mage the Ascension, 20th Anniversary edition, p.440.
Answer: Note that this is probably not THE answer, but AN answer.
I looked through some books but the only book I have been able to find any kind of information is World of Darkness: Armory. Unfortunately this is for the New World of Darkness, so it's not really what you are looking for. However, AFAIK the damage levels for humans and object didn't really change that much between cwod and nwod, so it might at least get your bearing.

Durability: This is the vehicle's material hardness. Any attack
  against the vehicle has the vehicle's Durability subtracted from its
  successes before damage is applied.
  (...)
  Structure: This is the amount of damage the vehicle's body and frame can endure.

World of Darkness: Armory, p.132

Type - Durability - Structure
  Subcompact Car 2 10
  Compact Car 3 12
  Mid-Size Car 3 15
  Performance Mid-Size 3 15
  Full-Size Car 3 17
  Limousine 3 22
  Police Car 3 17
  Sports Car 2 12
  Muscle Car 3 15
  Sport Compact 3 12
  Supercar 2 12

WoD: Armory, p. 135
So, for a regular car, you could say that it takes about 15 damage to render it destroyed, you can find more examples in that book - trucks, vans, bikes, even heavy duty construction vehicles. They follow a similar progression.
However, I'd like to leave a comment that it should be taken with a pinch of salt. These are all stats measured as if you were unloading on an empty car expecting to destroy it. During a car chase these would actually be rendered moot, as a seemingly innocent amount of damage (smashing front window or activating airbags) can cause the driver to lose control over the vehicle and do the extra 10+ levels of damage in a resulting car crash. Think of it this way: just as a human suffers losses to his Dice Pool when injured, the car would be progressively harder to control when driven in a banged-up state.
Also, do not confuse Durability with Armor. Just because the engine is tough enough to make most handgun bullets ricochet off its surface (durability 3 perhaps?) does not mean the characters inside are similarly protected. I'd say that a regular car from the table has indeed 3 Durability, but only 1 Armor. Sheet metal could at best redirect some glancing blows.
Remember, that being concealment does not equal cover. See TVTropes.
The shooter will know where the driver is and there is little apart from some rebars that could stop the bullet flying at him. So if you play any kind of semi-realistic game, do not treat people inside a car as in cover.
Of course, if your campaign is less about simulationism and more about gamism, this might be acceptable, but make a conscious break from reality rather than unintended misinterpretation.


"Compare with / Latest from repository" color change

Question: I installed Aptana Studio 3 eclipse plugin which totaly changed all default colors. After uninstalation of the plugin, in view for comparing changes from files on SVN - "Compare with / Latest from repository" still remains black background for sections which are different, comments and line numbers. Restoring setting and colors to default in "window / preferences / general" does not work. I tried also to manualy delete all folders containing "aptana" in the name from workspace. This also did not help. Thanks in advance for your ideas.
Answer: I just went through the same issue.  You have to reinstall Aptana, go to Preferences -> Aptana  Studio (or whatever it is) -> Themes and pick Aptana Studio 2.x, which uses a white background and black foreground.
That preference pane goes away once you uninstall it unfortunately.  Kind of a stupid thing for them to change in that plugin, but I guess being edgy is more important than being consistent :)


How is 'flash fiction' a distinctive genre?

Question: "Flash Fiction" is an umbrella term used to describe any fictional work of extreme brevity, including the Six-Word Story, 140-character stories (also known as 'twitterature'), the dribble (50 words), the drabble (100 words), and sudden fiction (750 words).  Is the genre significantly different from poetry and short stories, and, if so, what are its distinctive attributes?
Comment: The *dribble*! I wasn't familiar with that one. I've heard of the *double-drabble* (200 words), and the BBC Sherlock fandom also has "221B fics," which are stories of exactly 221 words and the last one must start with the letter B.
Comment: I don't really see how it compares to poetry. Part of poetry is form and meter... and I'm pretty sure that's not part of this.
Comment: @Catija Some modern poetry also eschews or actively opposes form and meter, like slam poetry. I'm not overwhelmingly familiar with slam poetry but what I have heard was very informal and not too different from prose.
Answer: You might think of flash fiction as a very short story (it is sometimes also referred to as a short short story). Most magazines that specialize solely in flash fiction don't accept fiction that is above, say, 1000 words or 1500 words, maybe as much as 2000 words at most. Flash Fiction Magazine and Flash Fiction Online both have a maximum word count of 1000 words, for example. By contrast, some (though not all) magazines that specialize in traditional short stories require a minimum word count of around 2000-3000 words. Some magazines also accept both flash fiction and more traditional short stories.
It differs from poetry in that poetry typically puts a stronger emphasis on the aesthetic qualities of language such as rhythm, rhyme, alliteration, metaphor, simile, etc to create layers of meaning on top of the literal text. Most (though not all) poetry is written in verse. That being said, there probably is a certain degree of overlap between what is known as a prose poem (a poem written in prose as opposed to verse) and a piece of flash fiction that uses very lyrical language.
The other forms that you've mentioned (twitterature, dribble, drabble, and sudden fiction) all sound like specialized forms of flash fiction. I know that the drabble, for example, is a concept that originates in fandom and is traditionally a story that is exactly 100 words, though some people don't use this strict of a definition for it.


What is the recommended way to get nmap on OSX?

Question: Can I just use apt-get, or should I use some Mac tool?
Comment: By default there is no `apt-get` on OS X. So the question is, do you already have `apt-get` installed (probably by installing FINK) and now you are unsure if you can install `nmap` with it? Or are you completely unsure about how to install `nmap` or other such packages and just chose `apt-get` as an example?
Answer: First Option
Nmap's Official Website

Download the latest official installer here:
https://nmap.org/download.html#macosx
Check this out for additional information:
https://nmap.org/book/inst-macosx.html
Alternative versions can be found here:
https://nmap.org/dist/

Second Option
Homebrew Package Manager

Install Homebrew
$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Install Nmap
$ brew install nmap

Optional
$ brew search nmap
$ brew info nmap

Third Option
MacPorts Package Manager

Install MacPorts
$ bash -c "$(curl -fsSL https://raw.githubusercontent.com/tjt263/macports-installer/master/macports-installer.sh)"

Install Nmap
$ sudo port install nmap

Optional
$ sudo port search nmap
$ sudo port info nmap

Comment: WARNING: this post gives commands to execute remote code on your machine! Do Not run anything from "raw.githubusercontent.com" as it can change and is not the official method.
Comment: @MichaelOzeryansky True for MacPorts, but for Homebrew that *is* the official way.
Comment: Third option is my favourite.
Comment: anyone concerned about executing code is expected to vet it first.
Answer: The  package manager for MacOS that  apple mention https://developer.apple.com/opensource/  is MacPorts. And the nmap website mentions MacPorts.
A package manager that people often use with MacOS, is Homebrew. To install nmap, using Homebrew- http://brewformulas.org/Nmap brew install nmap. Though another answer mentions that brew has an issue installing nmap as of 2020, and the nmap website mentions Macports and doesn't mention brew.
Additional notes
Your question is largely answered at this unix.stackexchange link.  https://unix.stackexchange.com/questions/80711/how-to-install-apt-get-or-yum-on-mac-os-x  So, apt-get is not really recommended as a package manager for MacOS, it's for Debian(so, e.g. Ubuntu is debian based hence Ubuntu uses apt-get). Homebrew is one for Mac OS.. and another one called macports. ..Apparently you can get apt-get on macOS but getting it to work is, they say here, a bit advanced.
I suggest you learn your package manager, e.g. in the case of MacOS, macports or homebrew, learn how to get a list of packages, or search for a package e.g. search for nmap, see the command to search or list packages and to install a package. (besides googling can show what package managers apply for your OS and then what command to install the package.. sometimes the programs website can mention it)
added
this link https://ports.macports.org/port/nmap/  mentions clearly how to install nmap with the MacPorts package manager sudo port install nmap
Installing nmap with MacPorts, or with the Fink package manager, are mentioned on the nmap site https://nmap.org/book/inst-macosx.html
Comment: It's a little bold to say "The package manager for MacOS is homebrew", it's just as official as Mac Ports.
Comment: @MichaelOzeryansky thanks, i've corrected my statement
Comment: Apple Inc. officially recognize and acknowledge MacPorts but not Homebrew: https://developer.apple.com/opensource/
Answer: As of May 20, 2020, the homebrew installer fails to install something called nmap-scripts. This means nmap will work for some scans, but as you start to go deeper, you may see error messages like this:
nmap -p 1-65535 -T4 -A -v example.com
Starting Nmap 7.70 ( https://nmap.org ) at 2020-05-20 13:25 JST
Unable to find nmap-services!  Resorting to /etc/services
NSE: failed to initialize the script engine:
could not locate nse_main.lua
stack traceback:
    [C]: in ?

QUITTING!

This Link explains what is missing. Unfortunately that package is not available through homebrew at the moment.
The most foolproof way at the moment is to either use a different package manager (both fink and macports are endorsed by nmap.org), build it from source, or download the installer from nmap.org. All methods are explained here.


Localization of roots of complex quadratic equations

Question: Let $a,b,c\in\mathbb C\setminus\{0\}$ be complex numbers such that
$$b^2-4ac \neq 0.$$
We consider the equation
$$ax^2+bx+c=0.$$
I am interested in general statements about the roots of this equation from the geometric point of view and how they are located in the complex plane. In particular, I seak sufficient conditions on $a,b,c$ to obtain roots whose imaginary parts have opposite signs.
For instance, if $a=1,\mathrm{Im}b>0,c=1,$ then this is true. Indeed,if $x_1,x_2$ are the two solutions of
$$x^2+bx+1,$$
then
$$x_1x_2=1$$
and thus
$$\mathrm{Im}x_1=\mathrm{Im}\frac{1}{x_2}.$$
Answer: The conjecture about imaginary parts is certainly false, for the equation
$$
P(x) = (x - i) (x - (1+i))
$$
has roots $i$ and $1 + i$, whose imaginary parts have the same sign.
In general, there are two roots, and just as in the real case, the sum of the roots is $-\frac{b}{2a}$, while the product of the roots is $c/a$. Other than that, there's not a lot to say.
Answer: A general quadratic polynomial over $\mathbb C$ has the form $a(z-w_1)(z-w_2)$, where the roots $w_1, w_2 \in \mathbb C$ are arbitrary. So, there isn't much more to say about their nature and location.
The restriction $b^2-4ac \neq 0$ says that $w_1 \ne w_2$.
The restriction $b \neq 0$ says that $w_1 \ne -w_2$.
The restriction $c \neq 0$ says that $w_1 \ne 0$ and $w_2 \ne 0$.
The roots have imaginary parts of opposite signs iff $b/a$ is real.
Answer: It's not true that the imaginary parts of the two roots will be conjugates of each other. In fact, for real numbers $a$ and $b$,
$$(z - (a+bi))(z-(a-bi)) = z^2-2az+(a^2+b^2)$$
So a quadratic polynomial has this property if and only if it has real coefficients. In fact, you can make the roots of a complex quadratic polynomial anything you want; just pick two complex numbers $z_1$ and $z_2$. Then the polynomial
$$(z-z_1)(z-z_2)$$
will have $z_1$ and $z_2$ as roots.


Turkey to Europe by car

Question: I'm looking to travel across Europe by car, like a crazy road trip with some friends. I'd like to start from Turkey. What is it like to drive from Turkey into Europe because that's where I would like to start the journey from.
Comment: Welcome to Travel.SE. I'm not quite sure your question is [on-topic](http://travel.stackexchange.com/help/on-topic) here and it seems _really_ subjective. Can you please be more specific about your question? You can read [FAQ] and [ask] as a start..
Answer: It's perfectly possible, but right now it's really not sensible - due to the ongoing situation with refugees and illegal immigrants, many of the borders in the south-east of Europe are much more restricted than usual, and you'd have to go through migrant camps to get to them.
I'd recommend that you either wait for the current situation to stabilise, or choose a different route.
Comment: If starting from Turkey is the goal, he could go the long way through Caucasus countries and Russia. Or take a ferry between Turkey and Greece.
Comment: What is the source of your information?

Turkey to Europe by car


Availability Group with log backups to NUL

Question: We currently have a database in SIMPLE recovery and are planing on setting up an Availability Group for reporting purposes (Enterprise SQL 2016).  My understanding is that this will require moving the database to FULL recovery.  We have no need of the log backups and no interest in storing them so I was thinking about setting up the log backups to NUL (bit bucket).  Nothing I've read has said I'll have any problems with this but I wanted to make sure I'm not missing anything.
Comment: ✋ I've done this. Works just fine.
Comment: How does an AG enable reporting?
Comment: You make a secondary that you use as a read only location for reporting.
Answer: No, you aren't missing anything except the opportunity to do a point in time recovery of the database.  AG's protect you from MOST hardware failures but they don't protect from user errors that drop a table or truncate data. Even if the business didn't have a SLA for RPO I would have log backups running as a DBA just to cover things, but you can backup to DISK='NUL' and the log will clear just like you backed up to a regular disk file.
Comment: We aren't even using the AG for HA. Just for reporting.  The business has literally said "We don't care about point in time, last nights backups are good enough".  We even have it in writing :)
Comment: Replication to Standard Edition would be much cheaper in licensing costs and wouldn't require FULL recovery for the database if it is just for reporting purposes.
Comment: Because we are a large enterprise we have special licensing and believe it or not currently Enterprise licensing is actually cheaper than new standard licenses.
Answer: I would still suggest to take log backups (not to NUL) and have a delete process to delete then after x hours.
If for some reason, your both servers are down & your primary backup is corrupted. So in this worst case, you will have a possibility of restoring the db  provided you have preserved the log backups.
If the db can be recreated and is not that critical, go for discarding the log backups to NUL.
See this : http://sqlinthewild.co.za/index.php/2009/08/31/backing-up-to-nul-vs-backup-with-truncate-only/
Comment: Make them in writing .. when business says so ... Go for it once you have a written proof :-)
Comment: We will absolutely still be taking regular FULL and DIFF backups and making sure to keep them.  It's just the LOG backups I don't feel like we need.  The business is good without point in time recovery currently and I don't see that changing.
Comment: @KennethFisher If you're using Ola's scripts, just set the delete time to the space between Diffs. That way you're only keeping as much as you'd theoretically need if anyone changes their mind. How often are you planning on taking log backups on this thing, anyway?
Comment: It's a long standing DB and we do have in writing that last nights backups are good enough (even farther back at need).  We'll probably be taking the log backups every 15 minutes and then may make it more often depending on how things work out.


Soundness Theorem in reverse mathematics

Question: STPL  :=  soundness theorem for predicate logic

(see this)

When trying to figure out the strength of the STPL in reverse mathematics, I managed to convince myself of the following:

a)  ACA0 has a (provably) $\Delta_1^1$ pair of formulas, which it proves enough about to consider them as defining in it the truth predicate for first-order structures.

b)  ACA0 does not prove the STPL using the truth predicate as defined in (a).

c)  [ACA0 + [$\Delta_1^1$ induction]]  does prove the STPL as given in (b).

(EDIT: Based on François's answer, I now believe that I was wrong about (a).  First, the two formulas I was thinking of aren't provably equivalent; second, the $\Sigma_1^1$ formula, which comes closer to working, does not provably satisfy ($\operatorname{True}(\lnot p) \leftrightarrow \lnot \operatorname{True}(p))$).

So, my questions are:

1.  Are my understandings correct?

2.  Does ACA0 + STPL prove $\Delta_1^1$ induction?

3.  Is anything else known about the positions of STPL and $\Delta_1^1$ induction in the reverse mathematics hierarchy?  (For example, where would they go on the list on page 4 here?)
Comment: Would you need the truth predicate for arithmetic? I haven't thought carefully about what STPL would really look like in the language of second-order arithmetic, but aren't the extralogic symbols given as sets? I.e it only needs a truth predicate for logical symbols plus some extra symbols, not successor, addition, multiplication. This sounds like it ought to be simpler than Delta-1-1.
Comment: Excellent point re arithmetic.  (fixing that now)
Comment: Somewhat along the lines of Daniel's comment: some forms of STPL, at least, are provable already in RCA0 (as in II.8 of Simpson's _SOSOA_).
Comment: About the rest of Daniel's comment, a truth predicate has to be for all (codes of) first-order formulas, not just atomic formulas.
Comment: I don't think STPL proves $\Delta^1_1$-induction, since it looks like STPL is provable in $ACA_0^+$. (Because $ACA_0^+$ is strong enough to comprehend the truth predicate for a model.)
Comment: I think your point is that $ACA_0^+$ is strong enough to *form the truth set* for the model, because I think $ACA_0$ can "comprehend the truth predicate" for the model.  Furthermore, it's not obvious (to me) that $ACA_0^+$ doesn't prove $\Delta_1^1$ induction.  Is there an online reference?
Answer: First, a caveat: Simpson treats the Soundness Theorem in SOSOA, but not in the way you intend it. Simpson defines (II.8.3) a model $M$ as having a truth valuation for all sentences in the language of $M$ augmented with a constant for each element of $M$. When models are defined in this way, the Soundness Theorem is provable in RCA0 (II.8.8).
Now, you probably define a model in the usual manner: a set of elements together with an interpretation for each function symbol and relation symbol of the language. This is much weaker and it requires some work to go from such a traditional model to a full model in Simpson's sense. The fact that every traditional model can be extended to a full model is equivalent to ACA0+ (ACA0 plus the assertion that every set has an ω-th Turing jump). Thus the Soundness Theorem (for traditional models) is provable in ACA0+.
That said, ACA0' (ACA0 plus the assertion that every set has a $n$-th Turing jump for every internal number $n$) proves that partial truth valuations exist: for every (internal code for a) formula $\sigma$ there is a truth valuation for all substitution instances of subformulas of $\sigma$. (ACA0 only proves this for every standard formula $\sigma$.) So the Soundness Theorem for traditional models is actually provable in ACA0'.
In fact, the Soundness Theorem for traditional models is precisely equivalent to ACA0' over ACA0. First observe that ACA0 is strong enough to prove the uniqueness (but not the existence) of partial truth valuations as described above. So it is reasonable to define the satisfaction relation for a traditional model $M$ as usual: $M \vDash \sigma$ iff there is a partial truth valuation for $\sigma$ that assigns value true to $\sigma$. The fact that this relation satisfies $M \vDash \sigma\lor\lnot\sigma$ for every $\sigma$ is then precisely equivalent to the existence of partial truth valuations for every $\sigma$. In turn, the existence of such partial truth valuations for the first-order part of a model of ACA0 augmented with a predicate for the set $X$ is precisely equivalent to the existence of the $n$-th Turing jump of $X$ for every internal number $n$. Note that this reversal is a little weak since it relies on a particular definition of the satisfaction relation, but I can't think of any other reasonable definition.


Custom sort of search results

Question: I have a site with 4 lists, with the same column names, each list has over 4,000 items. Need to search all lists and display result sorted by column called CaseNumber in descending order. Is there a way to do that? Thank you.
Answer: This can be done using content search webpart, your can write a query to limit your search result from the 4 lists only, this will be done by providing the URL's of the lists, content search webpart has sorting option as well, you should be able to see"CaseNumber" column in the list of fields, if you don't see your column, you have to create a managedfiled for that.
more detail can be found here

Custom sort of search results


Where is netherite?

Question: Alright so...
I cannot find netherite on Xbox One or Xbox 360. I have done all the updates and it still not up to date. I have a friend with Minecraft and he has netherite and more updated stuff. Im wondering if my Xbox is broken, or netherite is only supported on certain platforms. If so, which ones?
Answer: Netherite is actually an unreleased update. I don't know about Xbox but it is a snapshot. You have to use experimental gameplay and if on PC java edition, it is easier. So far, on your edition, which is the most current one, it is normal to not have netherite. Don't worry, and hope for Mojang to release their update sooner.
Answer: Netherite is already available and you can find it around y = 15. Best you can use to find netherite faster is explosives.
The best explosive for the nether are beds. Very cheap, and makes a huge explosion, giving you a higher chance of finding ancient debris. You also need to mine gold and smelt the debris for netherite scraps.
Make the netherite ingots and get a smithing table, then start upgrading your diamond items. Now you have netherite!

Where is netherite?


Space of differential operators

Question: Let $A$, $B$ be two smooth vector bundles of finite rank over a smooth manifold $M$. Let $Diff(A,B)$ be the space of differential operators from $A$ to $B$. Can I talk about "the space of smooth maps from $[0,1]$ to $Diff(A,B)$?
Answer: You could use the bijective correspondence between differential operators $L: \Gamma(A) \to \Gamma(B)$ and vector bundle homomorphisms $\tilde{L}: J^k A \to B$ to topologize your space $Diff(A,B)$. Then $C^1$-curves in $Diff(A,B)$ are defined as usual, that is, the differential quotient has to exist and be continuous. Iterating yields the notion of smooth curves.
Comment: If the order of operators in $Diff(A,B)$ is not a priori bounded (and in particular not bounded by $k$), one should use the infinite jet bundle $J^\infty A$ instead of $J^k A$.
Comment: I was hoping to get an answer which would in the end match with differential operators $Diff(p^*A,p^*B)$ that are linear in the $[0,1]$ direction where $p: M\times [0,1]\rightarrow M$ is the projection map. Is this intuition correct, with your topology?
Answer: One way to introduce the space you are interested in is:
$$
\widetilde{\textrm{Diff}}(A,B):=C^\infty([0,1])\otimes_{\mathbb{R}}\textrm{Diff}(A,B).
$$
I'm sure this approach is equivalent to the topological one, suggested by @Tobias, at least for operators of bounded order.
You can also characterize it as a distinguished subspace
$$
\widetilde{\textrm{Diff}}(A,B)\subseteq \textrm{Diff}(p^*A,p^*B).\quad\quad\quad (*)
$$
Indeed, if $\{\alpha^i\}$ (resp., $\{b_j\}$) is a basis of $\Gamma(A)^*$ (resp., $\Gamma(B)$), then
$$
L=L_{i\, I\, l}^j\cdot b_j\otimes \frac{\partial^{|I|+l}}{\partial x^I\partial t^l}\circ \alpha^i
$$
is the local expression of a generic element $L$ belonging to the right--hand side of $(*)$, which sits in the left--hand side if and only if $L_{i\, I\, l}^j=0$ for $l>0$, i.e., as you said, $L$ is of order 0 along the fibers of $p$.
P.S. I used coordinates $x^i$ on $M$ and $t$ on $[0,1]$; $I$ is a multi-index of length $|I|\leq k$, and $L_{i\, I\, l}^j\in C^\infty(M\times [0,1])$; I tacitly used the same bases for $A$ and $B$ and their pull-backs (it is only the algebra of scalars which grows bigger).
Comment: Just noticed a minor bug in my answer: $\widetilde{\mathrm{Diff}}(A,B)$ should be defined as $C^\infty(M\times[0,1])\otimes_{C^\infty(M)}\mathrm{Diff}(A,B)$. The rest is unaltered.
Comment: Is $Diff(A,B)$ a Frechet space? Because then your first tensor product would make sense.

Space of differential operators


second order direction field in matlab

Question: I am trying to plot a second order direction field in MATLAB.  The equation is $$LQ'' + RQ' + (1/C)Q = E(t)$$ where Q is the total charge on the capacitor at time t in coulombs, L is inductance in henrys, R is resistance in ohms, and E is impressed voltage in volts.  If possible, I want to plot the particular solution, $$Q'' + 40Q' + 625Q = 100\cos(10t)$$ on top of the direction field.  I don't really understand MATLAB, so I really appreciate any help anyone can offer here.
Answer: In order to get a plottable solution your first need to specify initial conditions for $Q$ and $\dot{Q}$. I assumed them to be $Q_0=1$ and $\dot{Q}_0=0$.
First rewrite the ODE as a first order system. Introduce the substitution $Q = q_1$ and $q_2 = \dot{q}_1$. This will transform the equation into:
$$ \dot{q}_1 = q_2$$
$$ \dot{q}_2 = -625q_1-40q_2+100\cos(10t).$$
Now create a function in MATLAB and save it as electric.m in your current folder:
<code>function Dq = electric(t,q)
%q(1),q(2) are the states
%Dq(i) is the derivative of the ith state
Dq = zeros(2,1);
Dq(1) = q(2);
Dq(2) = -625*q(1)-40*q(2)+100*cos(10*t);
end
</code>
You should now be able to run the following lines from your command window:
<code>% [0,10] time interval; [1;0] initial conditions for q1 and q2
[t,q] = ode45(@electric,[0,10],[1;0]);
plot(t,q(:,1)); % plot q1=Q
</code>

second order direction field in matlab


Hurrah or Hooray?

Question: I have been using 'Hurrah/Hurray', but when I recently saw google spam box it says 'Hooray'. Which word actually suits or which one to use?
Comment: When I want to be intentionally .. quirky, I use the slightly archaic synonym "huzzah".
Answer: The first two are commonly used in British English, and the latter is used in American English. They'd all be understood completely fine, though - there's no difference in the meanings.
Answer: NOAD lists the terms this way:

hooray exclamation
  another term for hurrah
hurrah (also hooray, hurray |-ˈrā|) exclamation
  used to express joy or approval:   Hurrah! She's here at last!

Meaningwise, there's no difference between the terms. As for which one you should use, that depends on how you envision the last syllable pronounced. If you want the reader to mentally end the word with a -rah, use hurrah; if you want them to end it with -ray, use hooray (or hurray).

Hurrah or Hooray?


fixed position div freezes on page (iPad)

Question: I have an asp.net web site I am building to be supported on ipad.  When I focus on an input element and the keyboard pops up, the position fixed header div(which normally scrolls along with the page) will pop up the page a distance equivalent to the amount the keyboard takes up and freeze there for the duration of the input process.  Once the keyboard is dropped back down, the div snaps back into place and behaves normally again. I am testing on iOS5 so position: fixed should be supported.
Is this a known issue?  Has someone come across this and dealt with it before? I can't seem to find anything on this.
Answer: Fixed positioning is broken on iOS5/iOS6/iOS7.
Edit 3: See link to a working fix near end of this answer for iOS8.
Position:fixed is broken when either:
a) the page is zoomed
or
b) the keyboard shows on the iPad/iPhone (due to an input getting focus).
You can view the bugs yourself in jsbin.com/icibaz/3 by opening the link and zooming, or giving the input focus. You can edit the edit the html yourself.
Notes about bugs (a) and (b):

A fixed div with top: 0px; left: 0px; will show in the wrong position (above or below the top of the screen) when an input gets focus and the keyboard shows.

The problem seems to have something to do with the auto-centering of the input on the screen (changing window.pageYOffset).

It appears to be a calculation fault, and not a redraw fault: if you force the top: to change (e.g. switching between 0px and 1px) on the onScroll event, you can see the fixed div move by a pixel, but it remains in the wrong place.

One solution I used previously is to hide the fixed div when an input gets focus - see the other Answer I wrote.

The fixed div seems to becomes stuck at the same absolute position on the page it was at at the time when the keyboard opened.

So perhaps change the div to absolute positioning when an input has focus? Edit 3: see comment at bottom using this solution. Or perhaps save the pageXOffset/pageYOffset values before the keyboard is opened, and in an onScroll event calculate the difference between those values and the current pageXOffset/pageYOffset values (current once the keyboard is opened), and offset the fixed div by that difference.

There appears to be a different problem with fixed positioning if the page is zoomed - try it here (Also good information here about Android support for fixed in comments).

Edit 1: To reproduce use jsbin (not jsfiddle) and use the fullscreen view of jsbin (not the edit page). Avoid jsfiddle (and edit view of jsbin) because they put the code inside an iframe which causes interference with fixed positioning and pageYOffset.
Edit 2: iOS 6 and iOS 7 Mobile Safari position:fixed; still has the same issues - presumably they are by design!.
Edit 3: A working solution for (b) is when the input get focus, change the header to absolute positioning and then set the header top on the page scroll event for example. This solution:

Uses fixed positioning when input not focused (using window.onscroll has terrible jitter).
Don't allow pinch-zoom (avoid bug (a) above).
Uses absolute positioning and window.pageYOffset once an input gets focus (so header is correctly positioned).
If scrolled while input has focus, set style.top to equal pageYOffset (header will jitter somewhat due to onscroll event delay even on iOS8).
If using UIWebView within an App on iOS8, or using <=iOS7, if scrolling when input has focus, header will be super jittery because onscroll is not fired till scroll finishes.
Go back to fixed position header once input loses focus (Example uses input.onblur, but probably tider to use
document.body.onfocus).
Beware usability fail that if header too large, the input can be occluded/covered.
I couldn't get to work for a footer due to bugs in iOS page/viewport height when the keyboard is showing.
Edit example using http://jsbin.com/xujofoze/4/edit and view using http://output.jsbin.com/xujofoze/4/quiet
Comment: it turns out this is an iOS bug, I will be leaving this issue for now, but your suggestions are valid so I will mark this answer correct
Comment: jas, is it possible to give the link for the iOS bug issue url?
Comment: I haven't looked at what has been fixed in iOS6, but at least one extra bug has been added: http://igstudio.blogspot.com/2012/09/positionfixed-in-ios-6.html (I also suspect giving the fixed div a CSS property that forces it to have Hardware accelerated compositing might also fix it).
Comment: IOS 8 The bug is still here but now acts different. When changing the position to absolute the DIVs dont stay at the same positioning.
Comment: @nicolas The example for iOS8 referenced above seems to work fine. Try it here: http://output.jsbin.com/xujofoze/4/quiet
Answer: For my needs, I found it easier to use an absolute positioned header, hide it before scroll and show it when finish scroll (I need the same code to support iOS4 and Android).
For my purposes, I hide the header on a touchstart event, and show it again on touchend or scroll event (plus some timers to improve responsiveness/reduce flickering). It flashes, but is the best compromise I could find. One can detect the start of scrolling using the touchmove event (jQuery does this), but I found touchmove didn't work as well for me because:

regularly the iPad fails to do a repaint before scrolling (i.e. the absolute header remains stuck - even though the top was changed before scrolling started).
when an input element gets focus, the iPad auto-centres the element, but the scrollstart event doesn't get fired (because no touchmove if just clicking an input).

Implementing a fixed header on iOS5 could be improved by using a hybrid approach of fixed and absolute positioning:

used fixed positioning for iOS5 until an input gets focus.
when an input gets focus (keyboard showing), change to the iOS4 absolute positioning code.
when the keyboard is closed, change back to fixed positioning.

Code to detect when keyboard is closed (e.g. using keyboard hide key) is to register the DOMFocusOut event on the document element and do something like the following code. The timeout is needed because the DOMFocusOut event can fire between when one element gets the focus and another loses it.
function document_DOMFocusOut() {
    clearTimeout(touchBlurTimer);
    touchBlurTimer = setTimeout(function() {
        if (document.activeElement == document.body) {
            handleKeyboardHide();
        }
    }.bind(this), 400);
}

My fixed header code is something like:
{
    setup: function() {
        observe(window, 'scroll', this, 'onWinScroll');
        observe(document, 'touchstart', this, 'onTouchStart');
        observe(document, 'touchend', this, 'onTouchEnd');
        if (isMobile) {
            observe(document, 'DOMFocusOut', this, 'docBlurTouch');
        } else if (isIE) {
        // see http://ajaxian.com/archives/fixing-loss-of-focus-on-ie for code to go into this.docBlurIe()
            observe(document, 'focusout', this, 'docBlurIe');
        } else {
            observe(isFirefox ? document : window, 'blur', this, 'docBlur');
        }
    },

    onWinScroll: function() {
        clearTimeout(this.scrollTimer);
        this.scrolling = false;
        this.rehomeAll();
    },

    rehomeAll: function() {
        if ((isIOS5 && this.scrolling) || isIOS4 || isAndroid) {
            this.useAbsolutePositioning();
        } else {
            this.useFixedPositioning();
        }
    },

    // Important side effect that this event registered on document on iOs. Without it event.touches.length is incorrect for any elements in the document using the touchstart event!!!
    onTouchStart: function(event) {
        clearTimeout(this.scrollTimer);
        if (!this.scrolling && event.touches.length == 1) {
            this.scrolling = true;
            this.touchStartTime = inputOrOtherKeyboardShowingElement(event.target) ? 0 : (new Date).getTime();
            // Needs to be in touchStart so happens before iPad automatic scrolling to input, also not reliable using touchMove (although jQuery touch uses touchMove to unreliably detect scrolling).
            this.rehomeAll();
        }
    },

    onTouchEnd: function(event) {
        clearTimeout(this.scrollTimer);
        if (this.scrolling && !event.touches.length) {
            var touchedDuration = (new Date).getTime() - this.touchStartTime;
            // Need delay so iPad can scroll to the input before we reshow the header.
            var showQuick = this.touchStartTime && touchedDuration < 400;
            this.scrollTimer = setTimeout(function() {
                if (this.scrolling) {
                    this.scrolling = false;
                    this.rehomeAll();
                }
            }.bind(this), showQuick ? 0 : 400);
        }
    },

    // ... more code
}

jQuery mobile supports scrollstart and scrollstop events:
var supportTouch = $.support.touch,
    scrollEvent = "touchmove scroll",
    touchStartEvent = supportTouch ? "touchstart" : "mousedown",
    touchStopEvent = supportTouch ? "touchend" : "mouseup",
    touchMoveEvent = supportTouch ? "touchmove" : "mousemove";

function triggerCustomEvent( obj, eventType, event ) {
    var originalType = event.type;
    event.type = eventType;
    $.event.handle.call( obj, event );
    event.type = originalType;
}

// also handles scrollstop
$.event.special.scrollstart = {

    enabled: true,

    setup: function() {

        var thisObject = this,
            $this = $( thisObject ),
            scrolling,
            timer;

        function trigger( event, state ) {
            scrolling = state;
            triggerCustomEvent( thisObject, scrolling ? "scrollstart" : "scrollstop", event );
        }

        // iPhone triggers scroll after a small delay; use touchmove instead
        $this.bind( scrollEvent, function( event ) {

            if ( !$.event.special.scrollstart.enabled ) {
                return;
            }

            if ( !scrolling ) {
                trigger( event, true );
            }

            clearTimeout( timer );
            timer = setTimeout(function() {
                trigger( event, false );
            }, 50 );
        });
    }
};

Answer: This is somewhat still a problem in iOS13 (when a long text gets deleted in the 'textarea' field, fixed header jumps to the start of that 'textarea' field, obstructing the view), therefore, I thought I share my quick fix:
Since my footer is rather large, I went about without any JS and just adding a greater z-index to the footer than what the fixed header has. Out of sight, out of mind.


Is it possible to prove copyright infringement when artificial intelligence is used?

Question: If there are two significantly similar pieces of fiction, but no word to word sentences, is it possible to use artificial intelligence to prove the similarities ( or reverse engineer in the case artificial intelligence was used to write one, when the other has been used as a prompt to train the program) ? What is the law concerning non consenting parties whose work was used to "teach" the machine?
Comment: AFAICT, the use of copyrighted materials in training AI's is legally a bit ambiguous, where I'm tending to the "it's allowed since it's not forbidden, and it's not forbidden since it wasn't foreseen".
Answer: In such a case, a court would generally look at the result. If the later work is found to have "substantial similarity" to the earlier work, or to be a derivative work of the earlier work, and if fair use (in a US court) or another exception to copyright (elsewhere, including fair dealing in the UK) is not found, then the court might well find that there  was an infringement of copyright.
Note, both "substantial similarity" and "derivative work " are intentionally somewhat vague terms in copyright law, allowing case-by-case decision and flexibility.
The court will probably care little about whether or how an AI was used. It is the output, not the input, that will be the issue, I think. I do not know of a case with exactly this fact pattern, however.
Comment: An independently created work where the author had no access to the original is not copying. If an AI program or an un-artificial intelligence created a very similar poem having no access to the original it is not copying. The input matters.
Comment: @George White It is true that creating a work that is very similar, even perhaps identical, to an earlier work without any use of that work is not copying. It is also true that wHere the similarity is substantial, a court will usually find *PRIMA FACIE* copying, and leave it to the defendant to prove lack of access. Therehave been cases of in infringement found with no proof of access.. But in the scenario here, there was access, so the detailed nature of the access and the use or non-use of an AI will probably weigh little with the court
Comment: I generally agree with your point about AI. But it is not true that the input doesn't matter. In the case of alleged copying by a person it is hard to establish one way or the other that they were or were not exposed to the original. In the case of a program it could be provable that inputing *only* poems A-G will output poem Z. Then input matters more than output.
Comment: @GeorgeWhite So if that roomful of monkeys banging away at keyboards (https://en.wikipedia.org/wiki/Infinite_monkey_theorem) finishes my novel before I do, I'm hosed?
Comment: Change the ending
Answer: There seem to be a number of questions here. One is, suppose a program actually generates a literary text, which happens to be sufficiently like another human-created text. Then who holds copyright? The human-created text is protected by copyright, the machine-created text is not in the US, until the courts say that computer-generated text is copyrightable (unlikely, without an act of Congress). The monkey-selfie case clarified that only human outputs are protected.
The second question is whether a program could be used to address the question of whether there was copying. Logically, it it seems that two works are similar, the similarity could be a coincidence, A might have copied from B (or the opposite). This is a factual question which ideally involve expert testimony (which incidentally can only be provided by a human). The expert can and really should rely on some computer program that instantiates scientific knowledge about the structure of texts. The expert could testify that it is highly probable that certain similarities are coincidental (the presence of the sentence "Well, then, let's go!") or that it is highly improbable that the texts arose independently (the text "It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to Heaven, we were all going direct the other way—in short, the period was so far like the present period, that some of its noisiest authorities insisted on its being received, for good or for evil, in the superlative degree of comparison only"). Scientific evidence in copyright infringement cases is no more legally obligatory than DNA is required in criminal cases, it's just harder to disagree with a one-sided cold-hard scientific argument. Instead, courts may rely on ideas like "striking similarity", "probative similarity" or "substantial similarity" as a subjective standard for determining whether copying took place. A program would instead give you a number, such as a p-value.
Such expert testimony would be subject to an admissibility challenge, where the opposing side would argue that the supposedly scientific methodology was no better that entrail-divination. So far, no court has allowed ChatGPT dialogues to be admitted as expert testimony. Courts routinely allow experts to base their testimony on the output of statistical programs, because they are reliable at that. Ultimately, any computer-assisted testifying requires the expert to understand the logical basis for asserting "this was copied" vs. "this is just a coincidence".


Export only selected and reordered columns to Excel

Question: I am using QGIS 3.12. I want to export my attribute table to an exciting EXCEL table but I want to arrange the columns in a different order and also to select which columns to export and which not. Is it possible?
Answer: I think the best way is to use the "Refactor fields" tool from the processing toolbox.
This tool let you reorder field, drop field, rename field and even using expression to change field value. You can then save the result in many different format including .xlsx
From the tool help :

Refactor fields :
This algorithm allows editing the structure of the attributes table of
  a vector layer. Fields can be modified in their type and name, using a
  fields mapping. The original layer is not modified. A new layer is
  generated, which contains a modified attribute table, according to the
  provided fields mapping.
Comment: Cool..I'll try.Thank you!
Comment: You can also create a virtual layer if you know how to write sql and then save the output to any format you need


Dynamic Symbols

Question: Is there a dynamic symbol (preferably a numbered circle or square) in ArcMap that is symbolized uniquely to each feature?  For example, I have 150 features that I would like to symbolize with a circle and the number 1 - 150 in the center.  Is this possible?
Answer: This can be achieved by going to the Labels section within Layer Properties, choose Symbol, then Edit Symbol. In the editor go to the Advanced Text tab, and choose Text Background. Click Properties and then choose Marker Text Background from the type drop down. Check the scale marker to fit text box, and choose a symbol from the Symbol... option, a circle for instance.
Comment: That worked perfectly.  Now is there a way to create a legend with the newly created labels associated to each feature?
Comment: Please mark this as answered.  There is no way to create a dynamic legend from labels in ArcMap. You will need to build a static legend or you will need to create 150 symbols in symbology categories then create the legend.
Comment: You can create such 'legend'. Have a look at http://gis.stackexchange.com/questions/170707/adding-labels-with-symbols-to-legend-in-arcmap/170763#170763
Answer: Yes there is.
You need to label the feature class.
Here is a tutorial: https://www.youtube.com/watch?v=RU6kxi-q_oA

Dynamic Symbols


Homework - Young's Double Slit Experiment

Question:
I have attached the question as a picture. I simply don't understand where to begin this question. It is given that $l \gg d$. Why shouldn't the phase difference at $O$ be zero? What exactly is different about this set-up as compared to the 'normal' set-up of Young's Double Slit experiment?
Comment: That's not how the diagram is drawn, but you are right, that's what the text says. I hate it when questions are deliberately obfuscated like that. It doesn't aid in understanding.
Comment: Which makes the height offset $\frac{d}{2}$
Comment: Nothing in the question suggests that the phase difference at $O$ is anything but zero... just follow the physics you know. Note that if there is a medium with refractive index >1 between the slits and the screen, the wavelength of the light becomes shorter. That's all you need to know...
Comment: @Floris Well nothing except the answer... The answer given isn't zero.
Comment: Ah - I just noticed that the source is not centered on the line. But the height of the source (offset) is not given...
Comment: @Floris The height offset would be zero, I presume? As the source is *directly behind* $S_1$?
Answer: The drawing is a little bit confusing - but the key is that the source $S$ is a relatively long way from the slits (compared to their spacing), and at a height of $\frac{d}{2}$ (from "directly behind $S_1$"). This means you can draw a diagram to calculate the relative path distance between S and each of the two slits. The difference in path length results in a phase difference before the light arrives at the slits - and that phase difference is maintained as you travel from slits to screen.
One way to look at it is to say that the "zero" of the diffraction pattern will be directly in line with the line connecting $S$ to the middle of the slits. If there was just a single large hole between the slits, you would have no problem seeing that this is the case:

When you add a refractive index, the wavelength of the light is shorter (by a factor $\frac{1}{n}$). It's interesting to note that you can find the "zero" of the diffraction pattern (regardless of whether the refractive medium is in front of the slits or behind) by repeating the above argument: pretend there are no slits but just a single hole, and imagine where the light would go. Snell's law will quickly give you the answer.

I will leave the rest up to you - our homework policy asks us not to give complete answers to this kind of question, but just to explain some of the principles.
Comment: Well won't the path difference simply be $\sqrt{l^2 + d^2} - l$? But unfortunately, that's not the answer given... Or am I doing something wrong?
Comment: If the light arriving at a distance $h$ below $O$ has zero phase difference, then the path length difference $\Delta$ at $O$ (for small angles $\theta$) is found from (similar triangles) $\frac{\Delta}{d} = \frac{h}{D} = \frac{d}{2\ell}$. In this, I assume that $\sin\theta = \tan\theta$ which is an OK assumption for small angles. Note that your expression simplifies to the same thing if you do an expansion (noting that $d\ll l$, write $\ell\left(\sqrt{1+\frac{d^2}{\ell^2}}-1\right)\approx \ell(1+\frac{d^2}{2\ell^2} - 1) = \frac{d^2}{2\ell}$ which is what I got the other way...
Comment: I'm not seeing it... Which two triangles are we talking about?
Comment: Triangle made by $h$ and $D$, triangle made by $\frac{d}{2}$ and $\ell$, and triangle made by path difference $\Delta$ and the slit spacing $d$ all have the same angle $\theta$.
Comment: Aha... Now I see it... yes...  Thanks for the help! And sorry for being so stupid :)
Answer:
A phase difference may also be zero.
Whenever the difference of the distances the beams travel is not a multiple of the wavelength, there is a non-zero phase difference - as simple as that. So if the source is not equidistant from both slits, and the point of measurement is equidistant from the slits, mean you already have a pretty good chance of non-zero phase difference.
Answer: The text states that the source $S$ is placed just behind the slit $S_1$, so it looks to me that the sources $S_1$ and $S_2$ already are out of phase by a factor $\exp(i k d)$. Thus the phase difference in $O$ is $\Phi_O = k d$.
This is different from the usual experiment where $S$ is placed at equal distance from $S_1$ and $S_2$.
Comment: @D.Labat be careful not to give away too much.  We don't want to answer the question for him.
Comment: What is $k$? And where did you get this answer?
Comment: $k$ is the wavevector : $k = \frac{2 \pi}{\lambda}$, $\lambda$ being the wavelenght of the source. Assume $S$ is at the same position as $S_1$ (as it is directly behind it). If we set the original phase of the light in $S$ to be zero, the phase in $S_1$ is thus zero as well, and the phase in $S_2$ is $k*d$, as the light travelled on a distance $d$ from $S_1$ to $S_2$.


Page doesn't fill window in Tor Browser

Question: When I resize the Tor Browser window the webpage doesn't fill the entire screen. I think that this is a problem with Firefox. How do I fix this?
Comment: Does this answer your question? [How can I disable the grey border?](https://tor.stackexchange.com/questions/20691/how-can-i-disable-the-grey-border)
Comment: Does this answer your question? [NEW TOR VERSION problem](https://tor.stackexchange.com/questions/20681/new-tor-version-problem)
Comment: Go to about:config and change the privacy.resistFingerprinting.letterboxing to false.
Answer: This is intentional as it is a way to protect against finger printing your browser window based on the dimensions of going full screen.  It reduces the websites ability to track you based on the window dimensions.
Answer:
Know and understand the security-related implications of making this change
In the Tor Browser address bar, type in about:config and press enter
Search for privacy.resistFingerprinting.letterboxing
Set the option to False
Restart the browser for changes to take effect

Letterboxing

Tor Browser 9.0 is configured to use letterboxing by default. The
technique adds white margins to the browser's frame to let users
resize the browser window while still prevent fingerprinting using
screen dimensions.
It will mask the window's actual dimensions by adding space to width and height at
multiples of 200px and 100px while resizing. So the gray space will be
added at the top, bottom, left, or right of the current web page.
Since advertising codes listen to window resize events to gather this
info, Firefox 67 will provide a generic dimension to such trackers and
bring back the window to its actual size milliseconds later.
So basically, letterboxing delays the loading of actual page content
on the newly-resized window; long enough to trick the tracker codes or
scripts to read the incorrect window dimensions.
Letterboxing isn't a new technique since it was originally developed
by Tor Browser in 2015 coming from experiments that the developers of the
Tor browser conducted and is part of the Tor Uplift project that
introduces improvements in the Tor browser to Firefox (Tor browser is
based on Firefox code).
Answer:
What are grey bars on resized Tor Browser window?

Tor Browser in its default mode is starting with a content window rounded to a multiple of 200px x 100px to prevent fingerprinting the screen dimensions. The strategy here is to put all users in a couple of buckets to make it harder to single them out. That works so far until users start to resize their windows (e.g. by maximizing them or going into fullscreen mode). Tor Browser ships with a fingerprinting defense for those scenarios as well, which is called Letterboxing, a technique developed by Mozilla and presented in 2019. It works by adding white margins to a browser window so that the window is as close as possible to the desired size while users are still in a couple of screen size buckets that prevent singling them out with the help of screen dimensions.
In simple words, this technique makes groups of users of certain screen sizes and this makes it harder to single out users on basis of screen size, as many users will have same screen size.
But still I didn't understand 100% of this!
for more info

Page doesn't fill window in Tor Browser


How to handle requests that will be picked up by a person and responded to within 5 minutes

Question: I'm currently designing a voucher/discount journey.
Due to system constraints, this is the scenario
User needs to request a voucher.
The request then goes to a crm that is managed by individuals.
Individuals will respond with voucher number within 5 minutes of the request coming into the CRM.
Once the voucher/discount is sent to the user, they only have 2 minutes within which to use it on the platform. If they don't it will expire and they need to request another voucher/discount.
I've thought of in-app notifications to let the user know that the voucher is ready, but since the voucher is only valid for 2 minutes, I'm not sure if there's a better way?
Comment: Can you clarify why you're looking for a better way? What's the problem with the current approach? Do you have screenshots/mockups etc. to share?
Comment: @jazZRo I can't share the details but a qualifying customer will receive an offer of being able to apply for a discounted voucher. Once they apply for the voucher, they will receive a response (discount due to the voucher) within anywhere from 30 seconds to 5 minutes.
Thereafter the customer needs to make payment for the goods within 2 minutes or else the voucher/discount expires
Answer: To handle requests for vouchers that need a quick response within 5 minutes and have a short validity period of 2 minutes, You can use notifications, displaying timers, and some other ways:

Real-time Notifications: Send in-app notifications to inform users
that their voucher request has been processed and the voucher number
is available. Ensure the notifications are delivered instantly to
minimize delays.
Push Notifications: Use push notifications, if possible, to deliver
immediate alerts to the user's device, ensuring they are promptly
notified about the voucher availability.
Countdown Timer: Display a visible countdown timer within the app,
showing the remaining time for voucher utilization. This creates
urgency for users to act quickly.
Simple Voucher Redemption: Enable users to redeem their vouchers with
a single click or tap, minimizing steps and simplifying the
redemption process.
Support Channel: Provide clear instructions for requesting a new
voucher if the previous one expires. Offer a support channel for
quick assistance if needed.

By implementing these strategies, users will be promptly notified about their vouchers, reminded of the expiration timeframe, and able to quickly redeem them within the given validity period.
Hope this help.
Comment: Thanks Ali but chatGPT gave me these exact answeres already. Hopefully someone has encountered a similar scenario previously or can point me to something they have seen in the past
Answer: I would probably create a socket server, and connect it with an interface on the receiver's end (the responder) who then is getting some kind of notification through that interface.
That could be push notifications or simply redirect to a page where the information is present for the responder to accept the request.
You could also send an SMS with the above, so the chances for seeing the request is higher :)