how many outlets can you put on a 15amp breaker?

Question: how many outlets can you put on a 15amp breaker
?
Comment: [How many receptacles can I place on a 20 ampere 120 volt breaker?](http://diy.stackexchange.com/q/63324/33) has also been asked before.
Comment: An anecdotal experience here: I put in a new 15-amp breaker in my basement, which is dedicated to controlling wall and ceiling outlets. This has 16 double receptacles in total, and the city's electrical inspector didn't seem to have any problems with the number.
Answer: It depends on your local Building Codes, Local Electricians, what you think might end up using the circuit & if there's carpet...An average Upright Vacuum Cleaner sucks up (pun intended) most of the 15-amps. But, some used to say 6, then 8 then 10 & now I'm hearing 12. Some go with a "Rule of Thumb" being 1.5 Amps per outlet to arrive at the 10 number.
I prefer to do Home-Runs for each average sized room & might hit 8 which includes a single light. But, I also use 12-gauge regardless of whether I'm doing 15 or 20-amps on both ends, in case a 15 needs to have both ends bumped up to 20's in the future.
Comment: +1 But I try to keep the light separate from the outlets. If using the vacuum and leaf blower blows (pun intended) the circuit, you wont be sweeping in the dark.
Comment: And I understand the benefits of 12 everywhere, cost is small, flexibility, but box fill and wire handling keep pushing me back to 14 in most cases.
Comment: I used to agree with both of your comments & did it because that's what people said. But, I never found an extension corded light to be a hassle & maybe 1 room in my project buildings had a light separated. I like the 1 breaker switch to kill the entire room idea a lot. Yeah, 12's wear you out but the back insert screw-down clamping outlets got rid of that. Plus, I'm not an electrician doing it daily & I use only Commercial Grade.
Answer: According to the National Electrical Code, there is no limit on receptacles in residential occupancies. Limits on commercial occupancies do not apply to dwelling units.
You are free to decide how many receptacles you want on each circuit.
The only caveat is, if you are putting 15 amp receptacles on a 20 amp circuit then you must have a minimum of 2 receptacles but there is no maximum.
Good luck!


R-matrix for spin chains

Question: In algebraic Bethe ansatz procedure, one of the central objects is the R-matrix satisfying the Yang-Baxter equation, but all the papers/books give directly its expression without deriving it, so my question is How can i derive the R-matrix for XYZ/XXZ Heisenberg model?
Answer: This is essentially an answer to your questions R-matrix for spin chains, Elliptic R-matrix and Yang Baxter solution for XYZ model, $R$ matrix for XYZ spin chain, Algebraic Bethe Ansatz and $R$-matrices, which all basically ask the same question anyway.

In short: to the best of my knowlegde, coming up with an R-matrix is an art, not a derivation. (Cf. the notion of a Lax pair in classical integrability.)
The quantum inverse-scattering method (QISM) was developed as a synthesis of the classical ISM, spin chains and lattice models. The best way to understand it is from this multi-topic point of view, rather than focussing just on spin chains. Faddeev's How Algebraic Bethe Ansatz works for integrable model [arXiv:hep-th/9605187] focusses on spin chains mostly, which makes several constructions --- such as the introduction of an auxiliary space --- appear somewhat ad hoc; at least it certainly felt so to me when I first read them. The vertex-model point of view makes these constructions much more natural; this is also why I organized my lecture notes A pedagogical introduction to quantum integrability, with a view towards theoretical high-energy physics, [arXiv:1501.06805] in the way I did.
Some more comments:

Once you know the Lax matrix (containing the vertex weights) of the six- or eight-vertex model you can solve for the R-matrix (solving the "RTT-relation" with $T=L$ for the case of one site), see e.g. Sections 9.6 and 10.4 in Baxter, Exactly solved models in statistical mechanics (or Appendix C in my lecture notes mentioned above).
Alternatively, you can look for solutions of the Yang--Baxter equation, and then interpret each R-matrix you get as a vertex model or see which spin chain it yields by computing the logarithmic derivative of the associated transfer matrix.
It might be instructive to read up on another example: Shastry's R-matrix for the Hubbard model. See e.g. Section 12.2 in Essler, Frahm, Göhmann, Klümper,
Korepin, The one-dimensional Hubbard model [e-print].
Comment: Thank you for your answer ! i understand what you're telling me, and i've seen your notes which seems very interesting, But : suppose that you don't know that XYZ model is integrable, so it's contradictory to find its R-matrix by using the "RTT" relation because the "RTT" is valid only if your model is integrable. In another hand if you look for solutions of Yang-Baxter equation directly, you can not  know for which model you're solving. What i was thinking  was : In order to find R-matrix for XYZ you have to find $Z_2 $ solutions of YBE, but i don't know if it's possible to do?
Comment: @Giuseppe You're welcome. I don't know of examples of models that were found to have an *R*-matrix without already expecting (or constructing) them to be quantum integrable. Here hints for the integrability (loosely: the existence of many conserved quantities) may for example come from  factorized scattering in a Bethe-ansatz type of solution.
Comment: @JulesLamers Yang-Baxter eq (YBE) seems to be a sufficient condition, i.e. if you have an R-matrix satisfying YBE, then the model is integrable. But how about the reverse? Do all 1+1d integrable spin-chain models have an R-matrix satisfying YBE? For example, spin-chain models having _discrete_ (say $\mathbb{Z}_2$) on-site symmetry, do these models have an R-matrix satisfying YBE?
Comment: @QGravity: That is a good question, but really beyond the OP. If you ask it as a separate question I'd be happy to write an answer. This will make it easier to find, which I think will be more useful for others
Comment: @JulesLamers thank you. I just did.
Comment: For easy reference: that question is https://physics.stackexchange.com/q/780311/

R-matrix for spin chains


Why are all Starfleet ships commanded by Captains?

Question: To my knowledge every Starfleet ship we see is commanded by a Captain. From what I know of modern navies: Lieutenants, Lieutenant Commanders, and Commanders can also command ships. I'm just curious as to why, in starfleet, we never see this.
EDIT: I was obviously a little hasty in saying 'all' but what I meant was ships like USS Brattain and USS Lantree, Both have crews of less than 50 which seems very small for a captain to command.
Comment: I can't think of any TNG counterexamples, so not posting as an answer, but in DS9 the Defiant is usually commanded by Sisko, who is a Commander at first and only promoted to Captain later in the series. It's also commanded by Commander Dax a few times. One of those times someone even explained to a cadet that they're supposed to address Dax as Captain in spite of her actual rank.
Comment: Two words: Commodore Decker.
Comment: In regards to TNG, there are a several instances where ships are temporarily given to commanding officers below the rank of Captain. In fact, there's an [episode](http://memory-alpha.wikia.com/wiki/Redemption_II_%28episode%29) where Lt. Cmdr. Data and his ability to command a ship is a pivotal ethical concern for some human officers who don't know him personally.
Comment: I downvoted this question because the cases of non-Captain rank holders commanding ships is nearly too numerous to count, and thus demonstrates lack of research.
Comment: I thought my answer to this one was pretty comprehensive. Is there anything else you think I should address before considering an acceptance?
Comment: Re your edit, if you're in command of a ship, you're the captain, regardless of rank.
Comment: As Valorum mentioned I know of the navy tradition of anyone in command was called 'Captain' as Data was when given temporary command of the Sutherland. However in Night Terrors we see that the commanding officer is Captain by rank and she is commanding a ship with about 35 crew.
Answer: The Memory Alpha article on Starfleet Captains makes several references to Junior Captains, those who've commanded a Starfleet vessel but don't yet hold the rank of 'Captain'.

Commander Riker, William T. (USS Hathaway, USS Excalibur, and USS Enterprise-D)
Lieutenant Commander Data (USS Sutherland and USS Enterprise-D)
Lieutenant Commander Jadzia Dax  (USS Defiant)
Lieutenant Commander Piersall (USS Prometheus)
Lieutenant Commander James T. Kirk (USS Enterprise)
Cadet Tim Watters (USS Valiant)

In short, you don't have to be a captain to captain a vessel, but when you do, you're referred to as "captain" regardless of rank. On top of that, most captains are ranked as captains as a recognition of their status within Starfleet and in general recognition that they're competent to lead a large team, head up an important project or be in charge of a vessel.

On a similar note, there are also Senior Captains, those of flag rank who choose to take over a single vessel. Again, these individuals are referred to as "captain" for the duration of their command.

Rear Admiral James T. Kirk, (USS Enterprise)
Commodore Matt Decker, (USS Constellation)
Commodore Robert Wesley, (USS Lexington)
Fleet Captain Garth of Izar. (Unnamed Federation starship)
Comment: this is true for our RN, RAN, and RNZN - Commanders are titled Captain when on board the vessel they command. i think this is also true of the USN, where Roddenberry served, but not 100%
Comment: I'd add that there's a distinct absence of Star Trek episodes (or TV/movies/fiction novels) about the boring day-to-day routine of the ordinary people who command cargo ships and construction vessels and border patrol boats. The stories about the adventure of the more interesting people commanding bigger ships in no way implies that the rank of the guy in charge of any ship should be the same across the board.
Comment: @HorudKol Yes, also true in USN. See [title v. rank](https://en.m.wikipedia.org/wiki/Captain_(naval)#Etiquette)
Comment: Did or did not Commodore Decker captain both Starships in the *Doomsday Machine*?
Comment: @MajorStackings - Damn. I need to add a section for Senior Captains like Decker and Admiral Kirk.
Comment: @HopelessN00b I somehow believe to remember an episode where a guy in charge of such a small vessel and his hey-so-we're-both-captains attitude plays a role ... (might be TNG or ENT)
Comment: @HagenvonEitzen - [The Outrageous Okona](https://en.wikipedia.org/wiki/The_Outrageous_Okona)?
Comment: I'm the original poster. Thank you for your replies. I am aware of the examples above, with Data and Dax, but they tend to be temporary not they're actual assignment. I'm thinking about ships like USS Brattain. A crew of 35 - we see the captain and she has four pips.
Comment: Lieutenant Commander Worf regularly commanded USS Defiant (NX-74205) whilst posted on Deep Space 9
Comment: In the Caine Mutiny, the captain of the ship, played by Bogart, is a Lt. Commander.
Comment: @releseabe - Which was not at all unusual for the times, then or now.
Comment: @Valorum: but to me surprising. I knew someone who held that rank and had not thought much about what it meant until seeing the Caine Mutiny and realizing it meant, for example, that he could have commanded a ship.
Answer: The ranks in Star Trek are taken from the Navy ranks.  In the Navy a Captain is not only a rank but also a title.  Someone does not have to be a Captain to command a naval ship.  But any officer commanding a naval ship is considered the Captain of that ship regardless of their rank. That's why a Commander can be considered a Captain if they command a ship.  While on that ship you would be accurate to refer to that commanding officer as "Captain" when addressing them.  But on land you would refer to them by their rank.
Comment: @Aegon I don't see why not, and even if not something similar would be in place. OOC of course an explanation is simply that the authors used the terminology they're familiar with, which is to describe anyone commanding a vessel as its captain, whether they hold that military rank or not (and that includes civilians with no rank).
Comment: For other media that somewhat uses this convention, see Mass Effect. The Quarians refer to Commander Shepard as Captain, as in their culture anyone who commands a ship is a Captain regardless of rank.
Comment: Possibly correct IRL. But Do Star Trek Military traditions inherit from ours?\
Comment: @jwenting It wasn't meant as critique. I was genuinely asking that as I know nothing about the Franchise :P :D
Comment: Is it true that in the USN, there can only be one Captain of a ship, so if a another person with the rank of Captain boards, they are temporarily promoted to the next rank?
Comment: I was just watching S6E26 (Descent 1), and there is an exchange that excellently illustrates that whoever in command is _the Captain_.
    `    BEVERLY
    Any last orders?

    PICARD

    BEVERLY
    Got it.

    BEVERLY
    Good luck, Jean-Luc.

    PICARD
    Good luck... *Captain*.

Comment: @nb - wrap one star for *italics*, two stars for **bold** and three stars for ***bold italics***.
Comment: @Aegon Here's the link to the our ranks vs thier ranks question: http://scifi.stackexchange.com/questions/22151/are-the-star-trek-next-generation-rank-pips-based-on-anything-from-real-life
Comment: @MajorStackings Awesome. Many Thanks!
Comment: @HateSockPuppets - Whose sockpuppets do we hate now?
Comment: A possible explanation - but among the captains we *see*, does anyone sport anything other than four pips on their uniform collar?
Comment: @PhasedOut I have come accross the story several times, especially in older fiction, where a ranking captain or higher on a vessel commanded by someone else is referred to / addressed as commodore instead and they state that it is a USN tradition. On the flip side, someone of higher rank in command of a ship is still addressed  as captain - the captain is the highest authority on the ship
Answer: The other answers address officers below the rank of Captain commanding ships. We can also go the other way, though: James T. Kirk was an Admiral when he commanded the Enterprise in Wrath of Khan.
Comment: And Riker was an Admiral in charge of the Enterprise during 'All Good Things'
Answer: I vaguely remember an episode of TNG where a Starfleet ship was hailed and that person addressed himself as the captain of that vessel, however, the rank on his collar was that of a commander. I'm not quiet sure which episode it was but I'm 75% positive I saw it. Now, whether or not he was the highest senior officer or just filling in for him, I don't know, but all I remember is that he addressed himself as the captain and no person of captain rank was mentioned. From what I remember the part was really small, a single 20-second conversation between the Enterprise and some random other vessel.
Despite there being no proof to actually back this up, the scene stuck in my mind because it made me think of the USN where people who hold the rank of commander are captains of some vessels. However, maybe this is proof that this tradition does exist in star trek. Also if you recall in DS9, Sisqo held the rank of Commander for a while. It would be interesting if Star Trek ever actually adopted this tradition because it would open up a whole new type of command structure concerning vessels deemed less important by the federation.
Comment: Welcome to SciFi.SE! I think I might be worth you posting an episode-identification question to see whether anyone can track down the episode you're vaguely remembering. If it exists, and your memory is correct, it would make a strong answer.
Comment: And then there's the issue when marines are aboard a navy vessel. A marine captain (allegedly) has to be addressed as Major until he leaves the ship, there can only be one person of authority with the title 'Captain' - I don't know if this is actually true, I just heard it somewhere


Can I limit content scrapers by counting the number of hits from an IP?

Question: I would like to ban aggressive scrapers that access x number of pages in an hour, say 1000. I plan to implement such a check via fail2ban and count the hits from the same ip via access logs. Should I be looking for other clues as well? I would whitelist the biggest scrapers like Google, Bing and ban the rest. I understand there may be some casualties if hundreds of users are behind an IP, but the ban would be temporary.
Answer: Yes. You can. I do not know the tool you are using, but here are some clues.

Not a search engine (duh!).
High number of requests over a longer period of time- more than a
user.
Does not request an image, CSS, or JS (some do, most don't).
Changes agent name and OS over a longer period of time.
Comes from a web-hosting IP address block/range.

Check for access over various periods of time; one hour, one day, one week, one month. The reason for this is that stealth bots will make a high number of requests over a longer period of time. If the number of requests are higher than that of a user, then block them. Bots will stick out big-time. There will be no confusion on this one.
Some bots will request images to escape automated blocking, but may or may not request CSS and JS (javascript). Some will. If you have a request for a page but none of the above, it is a bot. If you have a request for a page and only one or two of the three, then it is a bot. Create a bogus JS (with virtually do nothing code) file and request it in your page. Keep it very small so that you are not effecting download speeds. You just want to see if it is requested.
Some bots will change the user agent (browser) and OS, some won't. If over a longer period of time these elements change, it is a bot.
Bots sometimes can come from subscriber lines (telcos) but most will not. If you check the IP address and it belongs to a web hosting company, then it is a bot. Subscriber lines are also used. Over a period of time, you will learn where bots come from. It will become a no-brainer for the most part.
If you are not sure if an IP address or access is a bot, come back here and ask making sure to post the original request. I should be able to help. I do this all day every day.
I have a much longer list of criteria, but those determinations get complicated and are protected processes. Sorry. But the list above should be more than enough for anyone to determine a bot %99 of the time.
Comment: Oh excellent response. Been thinking about creating some open source initiative for this. I notced for example that Gutenberg.org blocks access from non residential ips straight away. So either such an open source db, or rules like the ones you mentioned could be maintained on github perhaps,
Comment: @giorgio79 Go for it! I used to have a PERL script called tinyTrap that worked very well, but rolled that into a variety of other highly detailed mechanisms that run live on my site. In my case, I do not block access, but change the content and report on these bots (hackers too). I could do a better job of course. It is a work in progress. I do research for others so I cannot give it all away. But the list I gave is strong enough to really do a good job blocking bots. Let me know what you come up with! If you have questions, I am here every day- but not all day- mid-day and evenings mostly.
Answer: Alas if your data is worth getting it will be gotten.
When we decided to handle IP addresses, the scrapers went horizontal on us and came back with thousands of IP addresses, each accessing us well under the limit we set.
I am myself hunting for the newest hints on how to stop robots that do not respect any protection.
Comment: Great if it works for you. Our robots came in the hundred thousand unique IPs in no particular range and made one or two requests per IP. Only visible as robots after the fact. To block them would be useless and slow every future request from legitimate users down.
Comment: Were you blocking IP address with your firewall or something of the sort?
Comment: Something if the sort. But if an address never returns it is just a waste of processing to block it.
Comment: Well... I have seen many bots hitting my websites hundred of times. So blocking is really cheap in comparison to regenerate a full request in Apache, and then my code...


Why "I already said" is correct? I am confused with using past perfect and already

Question: I have to improve my English, and I live in the USA.
I am confused with using past perfect and past simple after "already".
Is past simple correct after "already"?
I know, some people say it, but is this correct to say and write at work or university?
Comment: For learning English, you might want to ask over at [ell.se]
Answer:
"Already" is usually used with the (1) Present Perfect and (2) Past
Perfect. However, we can also use "already" with the (3) Simple
Present, (4) Present Continuous and (5) Simple Past Tense.
Examples:

Have you already registered?
She had already read the news.
I already miss you.
We are already working on it.
They already left the city.

[EnglishStudyPage, adjusted.]
I'd add the caveats that
(a) using the simple present will involve a continuing state or iterative process, not a punctive event

I already take vitamin supplements.
*I already take the penalty.

(b) especially in the UK, the simple past is far less commonly used than the present perfect for a completed action / event

They have already eaten / arrived / gone home.

?/??/*They already ate / arrived / went home.

He'd only been gone two days, and I missed him already. [ongoing state]

?? I already missed the last post. [referencing a {notionally} fixed point in time]
Comment: Thank you for your answer. And it's grammatically correct to use  (3) Simple Present, (4) Present Continuous, and (5) Simple Past Tense?
Comment: I heard in the USA "she don't" but it does not mean I can write it in an essay or at work, or "ain't". Just I do not want to look silly at work when I use "I already helped"
Comment: Yes, with the provisos given for the present simple and the past simple. // 'I already helped Jane with the dishes' is something I'd consider many Americans would use without batting an eyelid, at least in conversation. It's probably used in writing, too, but would not be considered best practice in the UK.


How to burn a .mp4 to DVD+R

Question: I have the osx version 10.9.2
I can't find any way to burn my .mp4 file to a DVD+R.
Can anyone recommend a way to do this?
Comment: What hardware are you using?
Answer: There is a freeware software called Burn:

Made your own movies and want to share them with family and friends? No problem. Burn can create a wide range of video discs. From VideoCD to DVD-Video discs. And DivX discs to fit more of your videos on a disc.

I use it all the time for burning mp4s to DVDs, the finished product will also work with DVD Players too.
Answer: A lot of what you are trying to do depends on what you plan on doing with the resultant DVD. If you just want to play that file on a Mac than all you have to do is put it in a folder, right-click and select the option for burning the folder to disk (sorry, it's been a while since I did this and don't have a current Mac to reference at work for the exact procedure.)
However if you then want to play the DVD in a DVD player hooked up to a TV you may have issues with that. Look at the manual for the DVD player (or find it online) and see what disk formats it supports. Some do support movie files of various types burned to a CD or DVD (note that DVD+R is a newer format designed to avoid licensing the original [now called DVD-R] format and not all players play both kinds of discs.)
Also burning a DVD+R in the Finder will give you a Mac formatted disc that will not play on a PC and MAY not play on a DVD or Blu-Ray player. Check the specs on the DVD player for that as well.
If I need to burn an actual DVD (like you get movies and TV shows on commercially) I use Toast which can transcode the MP4 file into a format any standard DVD player will understand. I haven't done that in a number of years as I just play those files using Plex on a Mac Mini plugged into my TV.
Toast is a commercial product that you'll have to purchase. There may be shareware/freeware programs that do this but I don't know what they are.
Comment: All DVD and Blu-Ray players will read UDF format discs. Reading the content is another story, some newer BD players will read raw MP4 video or .mov/.avi files etc.
Answer: Apple has removed iDVD from their suite. You will need to use a tool like iMovie (which is no longer free), or a 3rd party utility like burn
Answer: There are a few articles listing 3rd-party options; the top free one seems to be Disco, which was originally a commercial app.
miDVD is available in the Mac App Store.
Answer: While iDVD is no longer included in Mac OS releases or in the App Store, it is still available from the Apple Website.
Comment: Are you sure that these upgrade versions will also work if no previous installation of iDVD is found on the Mac in question?
Answer: UFUSoft Blu-ray Creator for Mac is reputed to be the most professional Blu-ray burning software for Mac users. The best Mac Blu-ray burning software enables you to make DVD folder/DVD disc (DVD-5/DVD-9), Blu-ray folder /Blu-ray disc (BD-25/BD-50), as well as ISO Image File out of various videos in a super easy way. To get individualized DVD and Blu-ray disc, this program allows you to design menu with customized theme, background picture, background music, button, caption and more. On top of this, the internal impressive video editing features will make it a piece of cake for you to personalize videos via options like Trim, Crop, Rotate, Effect, and Watermark. Apart from this, the powerful 2D to 3D video conversion function will enable you to obtain vivid 3D DVD/Blu-ray disc on Mac with ease.

How to burn a .mp4 to DVD+R


Which attributes of a X509v3 certificate are never really used?

Question: Are there any extensions/extended key usage attributes of a X.509Certificate that are rarely or never used in practice?
Either due to never being part of an issued certificate or because they are skipped during validation for some reason (e.g. obscurity in the RFC on the usage of the attribute)?
A  documentation of the opposite (i.e. list of attributes extensions/extended key usage that are known to be used in the field) if available would be also of interest to me.
Answer: Take care that the set of possible extensions is, by definition, not bounded (at least not practically; there is an internal limit a bit of about 1282255). There are standard extensions which are described in the X.509 standard, but there could be a lot more elsewhere. In particular, Microsoft's implementations (e.g. AD Certificate Services) tend to use a few Microsoft-specific extensions (such as an extension which designates the "certificate template" which was used to issue a given certificate).
Among the extensions described in RFC 5280 (which is the standard for "X.509 on the Internet"), the following are rarely used in practice:

Policy Mappings: people rarely get policies right anyway, and to use mappings meaningfully you have to understand how certificate policies work.

Issuer Alternative Names: this is not a very useful extension, since name chaining in a certificate path uses Distinguished Names, so there is little reason to give extra names to the issuer (if extra names are needed for an entity, they will be as Subject Alternative Names in the certificate for that entity).

Name Constraints: support from existing implementations is, let's say, a bit lacking in reliability. Also, the semantics are convoluted and contrived, so even if someone says that they implemented it, you cannot be sure that they implemented it properly and it is hard to test. Thus, nobody really uses them.

Policy Constraints and Inhibit anyPolicy: same reasons as for policy mappings.

Subject Directory Attributes: too new, too broad in scope.

All other standard extensions are commonly used (not always used, but common enough). However, some features of these extensions are rarely used, including indirect CRL (where the CRL issuer is not the CA), CRL scopes which do not cover all revocation reasons, X.400 addresses,...
Comment: So I understand that an organization can create its own "custom" extensions?Is this what you mean with the example of Microsoft?But in this case how are clients supposed to take these into account?Or are they for MS client implementations as well?
Comment: Every extension can be marked as "critical" or "non critical". Systems which encounter extensions that they do not understand can ignore them if they are marked non-critical, and must reject the certificate altogether if one of these unknown extensions is marked "critical". Thus, non-standard extensions can be embedded in certificates.


Why we need an egg cell donor and a surrogate mother in an organism cloning process?

Question: Could a whole set of artificial organism-cloning process only be operated on the  somatic nuclear donor ,which means for example ,can we extract the somatic nuclear from animal "A" and put it into the egg cell plasma also from animal "A"  then implant it into the animal"A"'s uterus to clone "A" ?
Answer:
Could a whole set of artificial organism-cloning process only be
  operated on a somatic nuclear donor?

No, this would not be possible. Single-cell reprogramming would enable you to reset the potency status of that cell up, yielding an embryonic stem cell (ESC). However, ESC do not have the ability to generate extra-embryonic structures (e.g. placenta), which are known to be required for providing oxygen and nutrients to the embryo, amongst other relevant functions.
Theoretically, it could be possible to replicate the embryological environment, and I think this is the second part of your statement. Nevertheless, in practice this is not possible... the amount of signals and parameters that one would need to control simultaneously is far too extensive.
I don't quite see the point of having an enucleated egg and performing somatic cell transfer, when you're not really interested in implantation in utero. Somatic cell reprogramming would be sufficient (see iPSC)
Comment: @Snake From your comment and your newly edited question I see what you mean. You are wondering whether it is possible to clone an animal by using its own somatic cells AND eggs.

I do not have extensive experience with transgenic production, but I have a hypothesis on why the same female is not used as a donor and for implantation: oocyte extraction is an invasive method that may be destructive (i.e. the donor female dies). Therefore, it is not possible to use the same female and a foster mother is required.
Comment: thanks ! Now I gain some new knowledge now , but there is a little bit misunderstood , what I mean is that ,for example ,if we get a somatic cell from animal "A" , can we just transfer that cell to animal A's uterus to clone animal"A",instead of finding another surrogate mother or egg cell donor?
Answer: the trick is ovum come with a whole package of signal pathways built in before fertilization that you need to trigger implantation and embryonic development. In theory you could engineer these (search artificial ovum)  but it is drastically easier and less expensive to just use existing ovum organisms produce for essentially free.
could you use ovum and somatic components from the same organism that is the surrogate mother, sure, but there is not much reason to do so. You still need a donor egg and surrogate mother they just all happen to be the same individual.


Where is the Data Import Wizard Error Log

Question: I am using Salesforce Professional Edition.  I am trying to locate the data import wizard log file.  Can someone point me in the right direction?  I have import errors and want to see what they are.
Answer: This is from one of the documentations on Data Import Wizard:

When we finish importing your data, we notify you by email. Review the results and resolve any errors that occurred.

You should check your email to see those results/errors. It will contain link to the result file.
Additionally you can access this file from navigating to Setup --> Bulk Data Load Jobs to view and download the results which will consist of success/errors
Comment: Thank you.  The errors came to me via email.  I don't seem to have the Bulk Data Load Jobs option.


Barbell exercises to undo damage of sitting?

Question: Apparently sitting for long periods leads to muscle imbalances. Due to my current situation, it is something I have to do. Hence I'd like to ask what would be some good barbell exercises to work against the negative effects of sitting?
Comment: "Apparently sitting for long periods leads to muscle imbalances." No. Just stop listening to whoever told you this nonsense.
Comment: Adding a hat imbalances  might help.
Comment: Overhead press and bent over rows.  However the idea that you can undo damage from sitting for a lot of hours every week by doing barbell exercises for a few minutes every week is probably both wrong and dangerous. As mentioned get up from your chair and move  as often as you can.
Answer: Just exercise.
All the risks of a sedentary lifestyle can be mitigated by, well, not living a sedentary lifestyle. When we talk about deleterious health effects of sitting all day, we're talking about people who sit all day, and do nothing else, for years. Just exercise regularly (a combination of resistance and aerobic training), and you've mitigated all the risk of a sedentary lifestyle simply by not having one.
Comment: Even getting up every hour, and walking a quick lap around your office, or the lower floor of your house, does a lot.
Answer: do some squats, deadlifts and bent over rows to strengthen your core, lower back and legs which is weakened from sitting all day long/


Common side bar for multiple websites

Question: I have 5 WordPress sites and each site should have the same sidebar content. It is dynamically posted from userend and it should be common to all my WordPress sites. Without using iframe, how can I repost the same content that is in the right sidebar?
Answer: The short answer is you can't.
The long answer is that there are plenty of options to do so, but they're all extremely convoluted, bug-prone, and most assuredly not anything you want to be looking into if you're not a sophisticated PHP hacker who can gore through the WP code base blind-folded.
If you are, one option is to dodge the WP widget API through the use of a sidebar.php file in your themes instead of dynamic_sidebar() calls.
If you mean to make it work on themes you don't control, note the get_sidebar() function to that effect. It has two calls of potential interest:
    do_action( 'get_sidebar', $name )
    locate_template($templates, true)

But even then, not all themes call it, which brings us to dynamic_sidebar() and widgets.
Those are even trickier to hack in my experience. There are places like 'sidebars_widgets' or 'register_sidebar' or 'widgets_init' that you can try to hook into to "import" something in there that masquerades as a genuine widget area without actually being one.
Note, however, that even then your sidebar params would remain site-specific when dynamic_sidebar() gets called. The latter includes things like the following to potentially override things:
apply_filters( 'dynamic_sidebar_params', $params )
do_action( 'dynamic_sidebar', $wp_registered_widgets[$id] )

And there are heaps of other hooks and private APIs, tied to the sidebars themselves or widget configuration, that you need to monitor. No amount of asking WPSE will spare you the need to have a cold hard look at the WP code base.
I'd like to stress that last bit: you must read and understand the WP Widgets-related spaghetti code to make the slightest sense of the above. Moreover, it's extremely important to monitor any change to it in the foreseeable future if you proceed.
Failing to do either is a recipe for having your site blow up in your face or worse, because hacking into WP private APIs is prone to introducing buggy side effects, and subjected to frequent API changes. (The next of which, incidentally, is hot on the WP todo list.)

Common side bar for multiple websites


Inheritance of child behavior based on daily life experiences of the parent

Question: Our brain is a large network of neurons connected with each other.Our daily experiences change how  our neurons are connected.Some experiences create better connections between two neurons A and B and worse connections betweens neurons A and C.When someone makes children of his own ,does the experiences in the life of the parent influence the behavior of his child for example if the parent has experienced some very traumatic situations will the child be more distant or less sociable?
Answer: Children inherit DNA from their parents, which in turn was inherited by their parents from their grandparents, and so on. Only modifications to the DNA in the germ-line cells (those producing eggs and sperm) are heritable; changes in brain cells are not heritable, because those do not involve the DNA of the eggs and sperm.
Everything else that influences a child is environmental. The nature-nurture debate involves discussion of how much genetics versus experience influences development of different traits and characteristics.
Part of the difficulty in measuring the relative contribution of genes and environment is that parents are often important contributors to the environment as well as genetics of their children. Environment starts in the womb, so some of the mother's behaviors and experiences can influence the developing fetus. After birth, a child will continue to be influenced by their environment. Their parents' presence or absence will be part of this environment.
A child will only be influenced by traumatic experiences of their parents to the degree that those experiences influence the parent's behavior around the child.
Comment: @anongoodnurse You'll note the article you link has quite a bit of skepticism, too; I certainly believe epigenetic inheritance exists, but this is really just an extension of the genome beyond nucleotide sequence. The examples given like famine in the Netherlands involve exposure to a stressed maternal environment.
Comment: Do you feel that scientists who seem to have demonstrated generational epigenic modification are in error? E.g. [mice and cherry blossoms](https://www.nature.com/articles/nature.2013.14272.pdf).
Comment: I agree there is uncertainty (I wouldn't say there was quite a bit), but the evidence is compelling; in vitro fertilization still produced mice who, without ever meeting their parents, were afraid of the scent. "A child will only be influenced by traumatic experiences of their parents to the degree that those experiences influence the parent's behavior around the child." this statement does not support generational epigenetic modification...
Comment: ... In that respect, the child may well behave differently "if the parent has experienced some very traumatic situations..." I don't say it's highly likely, but it's not impossible.


Problem With Custom Scrollbar Text Cutoff

Question: I am currently working on making a photography website for my good friend. I have employed the custom jScrollPane scrollbars from Kelvin Luck over at www.kelvinluck.com.
However, I am having some problems.
The temporary website is hosted here: http://phr-clan.com/nikka/index.php  You'll see the lovely scrollbars in action.  But, there's a problem. Scroll down all the way to the bottom and you'll see that the text is being cutoff before you can scroll all the way to the bottom.  It turns out that there is actually around a full couple paragraphs that aren't being displayed.  And the ironic thing is that it displays correctly in IE6 (Isn't it usually the other way around?)
Anyway, what am I doing wrong?  Here is my CSS file: http://phr-clan.com/nikka/styles.css
Help is greatly appreciated.  I have been pulling my hair wondering why it doesn't work.
Thanks.
Answer: Just add
<code>p.text {
  text-align: left;
  font-family: 'DISCORegular';
  font-size: 19px;
  padding: 3px;
  margin-left: 10px;
  margin-right: 10px;
  display: block;
}
</code>


Determining inverses when verying if a set of matrices is a group

Question: I am trying to determine whether or not the set of all n x n diagonal matrices under matrix multiplication is a group.  I can show that the set is closed and associative under the operation, but I am confused on how to show that every element of the set has an inverse in the set.  I understand that since the determinant of any element of the set is nonzero each element has an inverse, but why must that inverse belong to the set?
Answer: you seem to have neglected the "the determinant of the matrix is non-zero" from the beginning of the question. If you are considering the collection of diagonal matrices, then it is not a group. But the collection of invertible diagonal (i.e., those diagonal matrices with non-zero determinant), then it is indeed a group. To see that this collection is closed under inverses, take an arbitrary diagonal matrix $diag(d_1,\ldots, d_n)$ with non-zero determinant. What does that tell you about each $d_i$? Can you now explicitly describe the inverse matrix and see that it too is diagonal?
Comment: The definition of a diagonal matrix I was given was that each diagonal entry must be nonzero and every other entry must be zero.  Is this incorrect?  Is it correct to say that under this definition every diagonal matrix is invertible?
Comment: this is not the standard definition. A diagonal matrix (the way is commonly defined) is a square matrix all of whose off-diagonal entries are $0$. According to the non-standard definition you quote it is indeed the case that every diagonal matrix is invertible. Needless to say, you should adhere to the standard uses!


How to Permanently Delete Photos from iPhone

Question: I have so many photos on the iPhone. And my iPhone's internal space is not enough now.
Comment: Let's see if anyone has a ready answer. If not, we can help you edit your question to provide more details on what you've tried, what exactly you don't get. See the guides on [about] and [ask] if you don't get an answer and decide to edit your question. They are often helpful in refining / reframing your query.
Comment: If you want to delete photos on your phone to recover space - try this app http://getflic.com/ helps a lot
Answer: Presuming you're not looking to securely delete these photos, just recover space that they're consuming, as suggested by your original question, let's just start simply...
Aside from the suggestions by superriku11, including using iPhoto to transfer them off with the delete option and Image Capture, you do realize that you can, in Photos in your Camera Roll select Edit and then proceed to select a series of photos and then Delete them. This is time consuming for lots of photos, but does allow you directly on the iPhone to get rid of images you may no longer want to keep. This is the obvious solution to getting rid of multiple images at once but some people forget about it. Realize that if you delete a photo in the Camera Roll that's in an Album it goes away there too. You can delete albums using the Edit button, but this keeps images in the Camera Roll.
If you want to get rid of all the photos in your Camera Roll all at once, go into Settings > General > Usage under Storage click Photos & Camera and the right swipe Camera Roll to bring up a Delete button. Give it some time and it will delete all your photos in the Camera Roll. Likewise you could delete all the photos in your Photo Library and/or Photo Stream the same way.
Answer: Must they be permanently (securely) deleted? If not, simply deleting them regularly should suffice. There's a delete option while viewing the picture. That's pretty slow though, so here's some faster options:

There's an option in iPhoto (if you use that) to delete photos after transferring.
If you're able to access the iPhone photos through another method that allows you to delete photos (such as the fact that an iPhone presents a USB interface on other systems than OS X) you can delete them much more quickly and easily too.
I haven't used it in a while, but I think Image Capture on OS X may provide a way to delete pictures from the camera (your iPhone) as well. If so, it may provide an option to bulk delete.

If the photos must indeed be securely deleted, the question is how secure. Tests on Solid State Drives (SSDs) have shown that even with standard deletion, the data is almost entirely irrecoverable afterwards. The NAND storage that iPhones use is likely similar.
If you absolutely need a secure delete though, it may be possible through running a secure delete tool such as srm (OS X) or shred (nearly the same thing, for Linux systems) on the photos if you can connect to the iPhone via USB interface. To be more sure, you should run a secure erase command from the phone itself, which would probably require it to be jailbroken and you to SSH into the phone or use a terminal program.
Answer: please only do this, if you know what you are doing!
Under Linux:
Plug your iPhone via USB.
Open your file explorer (I used Nautilus) and navigate to your iPhone -> DCIM.
Right-click the folder 100APPLE -> "open terminal".
In the Shell, delete photos using the rm command.
Answer: If deleting them from Image capture or the device itself doesn't work, make a backup and then consider restoring.


What is the difference between numpy.array([]) and numpy.array([[]])?

Question: Why can't I get the transpose when of alpha but I can get it for beta? What do the additional [] do?
alpha = np.array([1,2,3,4])
alpha.shape
alpha.T.shape

beta = np.array([[1,2,3,4]])
beta.shape
beta.T.shape

Comment: The [] add a dimension.  Transpose does not.
Answer: From the documention (link):

Transposing a 1-D array returns an unchanged view of the original array.

The array [1,2,3,4] is 1-D while the array [[1,2,3,4]] is a 1x4 2-D array.
Answer: The second pair of bracket indicates that it is a 2D array, so with such and array the transposed array is different from the first array (since the transpose switches the 2 dimensions). However if the array is only 1D the transpose doesn't change anything and the resulting array is equal to the starting one.
Answer: alpha is a 1D array, the transpose is itself.
beta is a 2D array, so you can transform (1,n) to (n,1).
To do the same with alpha, you need to add a dimension, you don't need to transpose it:
alpha[:, None]

Answer: alpha is a 1D array with shape (4,). The transpose is just alpha again, i.e. alpha == alpha.T.
beta is a 2D array with shape (1,4). It's a single row, but it has two dimensions. Its transpose looks like a single column with shape (4,1).
Answer: When I arrived at the programming language world, having come from the "math side of the business" this also seemed strange to me. After giving some thought to it I realized that from a programming perspective they are different. Have a look at the following list:
a = [1,2,3,4,5]

This is a 1D structure. This is so, because to get back the values 1,2,3,4 and 5 you just need to assign one address value. 3 would be returned if you issued the command a[2] for instance.
Now take a look at this list:
b = [[ 1,  2,  3,  4,  5],
     [11, 22, 33, 44, 55]]

To get back the 11 for instance you would need two positional numbers, 1 because 11 is located in the 2nd list and 0 because in the second list it is located in the first position. In other words b[1,0] gives back to you 11.
Now comes the trick part. Look at this third list:
c = [ [ 100, 200, 300, 400, 500] ]

If you look carefully each number requires 2 positional numbers to be taken back from the list. 300 for instance requires 0 because it is located in the first (and only) list and 2 because it is the third element of the first list. c[0,2] gets you back 300.
This list can be transposed because it has two dimensions and the transposition operation is something that switches the positional arguments. So c.T would give you back a list whose shape would be [5,1], since c has a [1,5] shape.
Get back to list a. There you have a list with only one positional number. That list has a shape of [5] only, so there´s no second positional argument to the transposition operation to work with. Therefore it remains [5] and if you try a.T you get back a.
Got it?
Best regards,
Gustavo,


Can we have the Ubuntu emoticons in the chat room?

Question: Can we have the Ubuntu emoticons on the general chat room?
Comment: I have a sneaking suspicion this one will be met with why not a userscript instead of an infrastructure change...
Comment: There is historical precedent for this sort of thing: RPG chat has an awesome dice emulator, and Arqade has a game in its chat. I think Super User has a clippy thingy.
Answer: Let's not. Please. Personally, I find the colored smileys that so many services insert awful:

They break the flow of text.
They tend to be larger than normal characters, making the line they are in taller and so inserting spaces between lines.
Unnecessary overhead (OK, extremely minor issue).
Ugly (very personal choice of course but there you go).

If we're going to add something to chat let's make it useful, something like having code blocks displayed with a different background like this so we could easily paste commands in chat. As it stands, we just get a fixed width font, no background and it is easy to get confused.
Comment: Exactly.
Answer: My initial thought would be to just upload individual images from this lot of reasonably sized set of PNG emoticons - example:

The problem here is, I think because of the way the chat system works (I don't often use it, so correct me if I am wrong), is that it uploads a new image each time. I already have accidentally done two:
 +  = :D
So the image servers might just fill up with AskUbuntu smileys
I also remember from the million edits of my post here pointed me in the direction of this: Do we have a policy on smileys?
Though this will probably be considered differently on chat - and perhaps even Meta...
Comment: We have a shortcut URL that's somewhat configurable at hostmar.co, it's how we do the software icons. While it's not a small URL you could do something like `![](http://hostmar.co/software-small)` in chat. Ideally a userscript that rewrites :) :D :( etc in to an image is the best way to go.


What are the Types of Validation Testing?

Question: I just need to know the answer to "What are the Types of Validation Testing?"
Comment: Siddheshwar, could you expand on this a little? What drives your need to know the four types? Is this prep for an interview, or perhaps a case to stakeholders?
Comment: this should be answered by Google
Comment: Why do you think there is more than one?
Answer: This question is not so easy to answer, since there are several sources and they distinguish between validation and verification and types and levels.
So in an interview question, it's important to listen closely to find out what exactly is asked. Terminology and context is important.
Verification vs. validation
A main point is to distinguish between validation and verification.
According to ISTQB: what is verification:

Verification is the check of the product against the specification ("Am I building the product right?")

and ISTQB: What is validation:

Validation is the check of the specification against the user's needs ("Am I building the right product?")

Then, there is CMMI - Verification (emphasis mine)

Verification in CMMi is a Software Quality Control (SQC) process that addresses the question: Are we building the product correctly?
This process looks at specifications, standards and guidelines to ensure that they have been correctly applied.

and CMMI - Validation (emphasis mine)

Validation in CMMi is a Software Quality Control (SQC) process that addresses the question: Are we building the correct product?
[...] the essence of the question is, when this software product is placed in its proper environment does it fulfill the goals and needs of the end user, as expressed in the requirements.

ISO 9000 also defines verification (emphasis mine)

Verification is a process. It uses objective evidence to confirm
  that specified requirements have been met. Whenever specified
  requirements have been met, a verified status is achieved.
There are many ways to verify that requirements have been met.
  For example you could inspect something, you could do tests,
  you could carry out alternative calculations, or you could
  examine documents before you issue them.

and validation:

Validation is a process. It uses objective evidence to confirm that the
  requirements which define an intended use or application have been
  met. Whenever all requirements have been met, a validated status is
  established. Validation can be carried out under realistic use
  conditions or within a simulated use environment.
There are several ways to confirm that the requirements which define
  an intended use or application have been met. For example you could
  do tests, you could carry out alternative calculations, or you could
  examine documents before you issue them.

Note that in ISO 9000, the practical way of performing verification and validation overlaps ("for example you could do tests").
Four types of verification
According to Toolbox.com, the four levels are

Component Testing, verifying a software element (unit)
Integration Testing, verifying if the units work together
System Testing, verifying that the system meets the requirements
Acceptance Testing, verifying that the system satisfies accepance criteria

and the four types are

Inspection (reviews)
Analysis (mathematical verification)
Testing (white-box testing)
Demonstration (black box testing)

In comparison, ISTQB lists 8 testing levels:

Unit testing
Component testing
Integration testing
Component integration testing
System integration testing
System testing
Alpha testing
Beta testing

so it's not 100% clear if there are really only four types.
Coley Consulting thinks there are five types:

Component testing
Interface testing
System testing
Acceptance testing
Release testing

Four types of validation
According to Tutorialspoint, validation testing in the V model has the four activities:

Unit Testing, validating the program
Integration Testing, validating the design
System Testing, validating the system / architecture
User Acceptance Testing, validating against requirements

Note how this overlaps the four levels of verification defined by Toolbox.com. It seems that the terminology is not used consistently.
An acceptable answer in an interview
In an interview, you could have answered as follows:

explain what validation and verification are, since this this is the part with least ambiguousity
reassure whether you understood the question correctly. Let confirm that the term is really "validation testing".
explain that this term is only defined vaguely / differently by different sources
explain which definition(s) you know
ask which definition should be used in this interview question
if you know that definition: answer the question; if you don't: state that you assume the definitions shouldn't be too different and give a definition you know
Comment: Thaks for answer and I also given this answer in interview but, interviewer said these are Levels of Testing. So, can stay constant on this answer in future?
Comment: @SiddheshwarM. I have updated my answer


Approximate compass bearing of a normal

Question: Let's say I have a 3D model that represents a small real-world space; it could be bounded by a 10" by 10" by 10" box. I know the real-world compass bearing for an observer in the center of the box looking down the X axis. How can I estimate the bearings of other vectors in this space?
Answer: So there are an infinite number of vectors that satisfy this. Here are 3 ways to find some solutions:

Use the swap and negate method similar to that from 2D.
Given a vector $(x, y, z)$ orthogonal vectors are $(-y, x, 0)$, or $(-z, 0, x)$ or $(0, -z, y)$ ie set 1 component to zero then swap the other two and negate one of them(usually the first).

Solve for the dot product. The dot product of two orthogonal vectors would be equal to zero. So just pick two values and solve for third. ie given a vector $(1,2,3)$ the dot product of an orthogonal vector would be $1x+2y+3z=0$. Use some method to pick $x,y$, or just pick them randomly, and solve for $z$. This is nice if you have just a little extra info but not all of it.

Similar to number 2. Solve the cross product for a vector that is orthogonal.

Oh...I guess it goes without saying since I forgot to say it...
The last vector is the cross product of the compass heading, and the "made up" vector.

Approximate compass bearing of a normal


How do you calculate the Attack and damage workspace?

Question: I am relatively new to D&D, and there has been one question about the character sheet of 4th edition. How do you calculate the attack and damage workspace on the character sheet? So far, I've haven't been using it in my games, also, what is it exactly? I've read the players handbook over and over, but I haven't found anything about it?
Comment: @Purple Monkey Yes, I do
Answer: The attack and damage workspaces are there for use as a quick reference when you need to know your total attack and damage bonuses for frequently used attacks without constantly having to recalculate it.
You calculate it as you normally would for an attack or damage roll (half level, proficiency, etc.) and write the appropriate numbers in the appropriate boxes.

The first box (from left to right) is for the total bonus.
The second is for half your level, rounded down.
The third is for the ability modifier used by the power you choose to write in. I.E. if you write in a melee basic attack the ability modifier would be strength, a ranged basic attack would be dexterity.
The forth is for any class bonuses that might apply to the power. So something like the Fighter's Fighter Weapon Talent could be written here.
The fifth is for bonuses to attack or damage you gained from feats.
The sixth is for enhancement bonuses from magic items.
The seventh and final is for any other bonuses.

Here's a snapshot of what it might look like for a level 2 druid (you can put in specific names for powers or whatever you like).

It's a handy thing to fill out as it helps combat move a lot faster since you can just quickly glance at your character sheet and the only calculations you'll really have to make are situational things like flanking or bonuses/penalties from (de)buffs. Obviously you'll also have to recalculate a few things whenever you gain a couple of levels, gain new feats, pick up magic items, or what-have-you.
Comment: What ability do you use in the Abil section?
Comment: @ThatlonelyEladrin That should really be another question. In short: whatever you use for attacks. It might be Str for basic melee attacks, Dex for basic ranged attacks and, say, Wis for your cleric powers. Choose which you want to have a quick reference to.


How to fix roller shade that pulled out of top window frame

Question: My roller shade is mounted in the top inside of the window frame. The shades were here when we moved in. One of the plastic anchor screws broke off in the drywall, and the bracket pulled out of the ceiling. My question is, can I replace the old screws with Twist-N-Lock 50 lb. Self-Drilling Drywall Anchors with Screws (1-1/4 in. pan-head philips screws from Home Depot) without repairing the drywall? Or will it just pull out again? The old anchors were just straight plastic anchors with a 1/2" screw.
Comment: Some photos would help!
Answer: Those anchors should work for you. Remove the old anchors so you just have the small hole in the drywall. Since you're using 1-1/4" screws, stick a small screwdriver into the holes and make sure you've got enough space up there to accommodate the anchors and screws. Follow the directions and snug those anchors pretty tight.


Reasons for not using IFrame?

Question: are there any reasons not to use iframes at all? I currently use it to load a page from a different server (a sign up page - part of a distributed application) to provide a seamless experience. Is using iframes considered bad practice or is its use OK?
Comment: FYI: Multiple answers are great. Check out all of them, not just the accepted one.
Comment: See this question: http://stackoverflow.com/questions/362730/are-iframes-considered-bad-practice
Comment: [This](http://stackoverflow.com/a/362752/1257607) may help
Comment: ⚠ ALL answers below are from 2009. There are many reasons **against** iframes, e. g. Security Risks (clickjacking vulnerability), Usability Issues (too small mobile screens), and SEO issues.
Answer: The iframe is a great tool. It enjoys near-universal browser support, it's easy to implement and has a number of useful functions. As with any other HTML element, it can be abused, but wielded intelligently it can play a part in a solid UI.
Some developers might argue to use AJAX instead, and in some situations that may be the more appropriate approach, but AJAX is not a panacea and iframes can be a far simpler implementation which has the same end-result for your users. Do whatever is simplest first, and only change that when you can verify how and why that is not working.
Comment: @Alex you can always get around the cross-domain problem by writing your own web service which fetches and re-displays data from other domains, and call *that* from your AJAX code instead. However, as I said in my answer, if an iframe already accomplishes what you need, don't over-engineer it or spend more time than necessary.
Comment: I wanted to do AJAX but as the mentioned sign up page is coming from a different subdomain I couldn't do it (cross domain problem)
Answer: Keep using iframes.  Here's an example of why:
The whole Verified By Visa thing really annoys me.  I'm happily shopping at some site that I trust, when I'm redirected to some site I've never heard of (not visa.com) and I have to fill in some other form and hope that I get redirected correctly back to the shopping site.
Then recently I was shopping at the John Lewis website, and they brought up the Verified By Visa page in an iframe - wonderful!  I'm still looking at the John Lewis site, and all that's happening is I'm being asked for my Verified By Visa password - no problem.
Although as a web developer I know that there's no technical difference between that and a plain old redirect-there-redirect-back, the user experience is so much better!
Comment: that's a point, but I would say the opposite, when entering credit card data I would rathre prefer to be entirely in the Verified By Visa (Paypal) webpage (with the url easily visible in the address bar) rather that entring my credit card data in an iframe of someone's website.
Comment: @Marco Demaio: The Verified By Visa page includes a security phrase that I entered when I registered with the scheme, so I know it's real.  Yes, in theory someone at John Lewis could be proxying the Verified By Visa content and sniffing my results, but that's why I said "I'm happily shopping at some site that I trust" - I trust John Lewis not to do that.  And the URL for Verified By Visa is for some address that you've never heard of anyway, so seeing it actually *reduces* your trust.
Answer: Pros:

Helps with slow third-party content like badges and ads
Security sandbox
Download scripts in parallel

Cons:

Costly even if blank
Blocks page onload
Non-semantic

Source: Best Practices for Speeding Up Your Web Site
Comment: Any resource on your page can block page onload, like pictures and videos. More modern approach is always use DOMContentLoaded, which iframe would not block. And I don't understand what non-sematic means here. For Costly if blank, is there reference for that?
Comment: The link you provided as source is really helpful :)
Answer: iframes have access to certain properties of the parent document, e.g. redirect the parent frame to a new location using parent.location.href or parent.window.location (IE allows to restrict that).
This is great for phishing attacks when embedding content from other servers (even if you trust that server it might be compromised).
iframes can also be used for a variety of other attacks: IFrames security summary.
Answer: With HTML 5 you'll be able to use the cross document messaging API to send messages from window to window, but for now the iFrame is the most viable alternative to any sort of AJAX that requires styling and scripting to load with the data.
If you're looking to just use text data in the iFrame, use AJAX instead. If you want external CSS or JavaScript to work in a protected environment, want styling to start from scratch, or need to access cross domain documents, use the iFrame.
Cons are that the accessibility of iFrames generally sucks, although you can prevent this by making sure that you proceed the iFrame with a notice of external content for screenreaders. Also check the HTML specifications for other ways to make the iFrame more accessible. Other than that and the obvious limitations scripting wise, the iFrame is a great tool is used responsibly and sparsely.
One last note, piling a page full of iFrames is definitely not a good idea, as remember that for each loaded iFrame, a DOM is created, HTML requests are made and document wrappers are instantiated, eating memory and bandwidth in the process. Keep iFrame's to a minimum on the page, and you'll avoid misuing a powerful tool in the HTML aresenal.
Answer: IFrames are a great way to "include" external content in a web page. However, there are a couple of (small) drawbacks:

Security sandboxing will cause problems with JavaScript if the IFrame does not originate from the same domain.
You cannot get CSS to co-operate between the IFrame and the parent page, unless you control the stylesheets themselves.
From an indexing point of view, the IFrame's content doesn't exist.
Screen readers might not like the IFrame, for the same reason. Or they won't be able to properly indicate the relative meaning of an IFrame's contents.

Apart from that, they're great! The points I mentioned might even be considered advantages, if you think about it (except the screen reader one): in principle, an IFrame can't influence its parent page's layout, and it isn't influenced itself by its parent either.
Answer: As a general rule, iframes are a bad experience for SEO reasons.  So, you ask is there any reason not to use iframes?  Yes, if you use iframes you are losing some organic placement in the search engines.
Of course, there are usability concerns which can (and should) trump SEO value of pages.

Reasons for not using IFrame?


What's the difference between datetime in ISO 8601 and UTC formats in javascript?

Question: I pick some date and time in javascript and then want to store it on server (.NET). Dates are supposed to be in future from the current moment (so they won't be before 1970).
Having read topics here on SO I learnt it's better to store date as a string and people suggest using Date.prototype.toISOString() or Date.prototype.toUTCString().
I've read that toISOString() is not available in IE 7. And I'd like to know other differences, when I should choose one or another function.
Answer: They're for different purposes.

UTC is the primary time standard by which the world regulates clocks and time.
ISO is standard format time. ISO also supports ms in its format.

So if you want to send data to the server, send the ISO, because ISO is the standard format:
var date = new Date();
sendDate(date.toISOString());

You can also use toISOString in IE7 polyfill.
Comment: You'll likely want to use UTC too to ensure a consistent time standard for your back-end.
Answer: I hope it will helpful to you.
Summary About toISOString() :-
The toISOString() method returns a string in ISO format (ISO 8601 Extended Format), which can be described as follows: YYYY-MM-DDTHH:mm:ss.sssZ. The timezone is always UTC as denoted by the suffix "Z".
Refer Below link for more information about toISOString().
Date.prototype.toISOString()
Summary About toUTCString() :-
The toUTCString() method converts a date to a string, using the UTC time zone.
Refer Below link for more information about toUTCString()
Date.prototype.toUTCString()
Comment: Which provides the exact time, with milli seconds. Since C# and javascripte Date time is different so, which is better to use?
Answer: Always use .toISOString()
They give almost the same information, but in different formats. Here is what I get on my machine.
new Date().toISOString()
"2019-10-11T18:56:08.984Z"

new Date().toUTCString()
"Fri, 11 Oct 2019 18:56:08 GMT"

There are 4 reasons .toISOString() is more often what you want than .toUTCString().
A. More convenient sorting
When you sort alphabetically, the "2019-10-11T18:56:08.984Z" pattern of .toISOString() gives you the correct date order.
B. Millisecond precision
.toISOString() provides millisecond values, whereas .toUTCString() does not.
C. Any user can interpret correctly
The .toUTCString() value may be more familiar to human end-users, but only if the language settings are suitable for them. In contrast, the .toISOString() is the same regardless of language settings.
D. Reproducibly regeneratable by software
You can easily convert the ISO date string to a Javascript Date object, and then back again, regenerating exactly the same string. This is regardless of who gave you the ISO date string, where the server is, and where you are.
This is not automatically true for the UTC string. For example, if a second instance of your app system is running in a different time zone, or language, it's .toUTCstring() may use different numbers or words (respectively) to represent the same instant in time. It will be difficult for it to create a UTCString that matches what was made by the first instance of the app, since in general it will not know the language or timezone in which the first UTC string was produced.
I think nobody needs .toUTCString()
I don't know why `.toUTCString()` exists. Its word-heavy format makes it useless for internal storage of dates in your program, because it varies depending on your language and timezone setting etc.
So maybe it is to produce something nice to display externally for the user to see? Well, not really. Anyone who is not in the London time zone will not find it very helpful.
I live in London. And even I, even if I was writing an app purely for use by me, solely on my system, and only in my home, would still not want to use .toUTCString(). Because it is showing UTC (also known as GMT). London is not always on GMT. In summer, we move to GMT+1, so the .toUTCString() result would mislead anyone who didn't notice the "GMT" and do the time adjustment in their head.
If I wanted a natural-language time, to make non-computer literate users comfortable, I would construct it manually from parts, using a library like moment.js. If I wanted a quick-and-dirty solution, I would use .toString() which at least will move to Summer time when appropriate.


Flex component visibility on application

Question: Is there a way to tell at runtime if a flex UIComponent is in the user's view or not.
For example, if I have a tabNavigator with a combobox on each tab, is there a property of the comboBox that will tell me if it is visible to the user or not when I switch from one tab to another?
I know it is not the comboBox.visible property. That is set to "true" for both comboboxes. I want a property that will change when I switch from one tab to another making the comboBox visible to the user. I don't know what that property is.
Answer: I am a bit confused about the question. Do you want to know if the combobox visible property is true or if the user can actually see it (which would be false if the user had scrolled away from the combobox and it was not currently on the screen although the visible property is true).  For the most control over the visibility of the comboboxes I would bind the visible property to a global variable. You can then change these to be whatever you want when the user clicks a tab.
Answer: What you actually need to do to determine if a UIComponent / DisplayObject truly visible is to check the "visible" property for that object AND the visible property of all its parents.  Please see my answer to a related question here (includes code):
Flex: Determine if a component is showing


Does the existence of one angle in a triangle imply the triangle inequality?

Question: It seems intuitive that, given three lengths of $a,b$ and $c$ and given that an angle opposite the side $c$ of $C$ exists such that $-1 \leq \cos(C)\leq 1 \implies -1\leq \dfrac{a^2+b^2-c^2}{2ab} \leq 1$, we should be able to prove that these lengths obey the triangle inequality. I have also graphed this function $(\cos(C))$ to find that whenever it is within these bounds it obeys the triangle inequality at least for a finite range of inputs. Of course this is not a proof, so I have also attempted to prove this, but after going through the algebra, I find $(a-b)^2 \leq c^2 \leq (a+b)^2$. Now, I have always struggled with understanding how to manipulate inequalities, so I am unsure how to proceed here. What exactly do these two inequalities imply about the square roots of each side? When you take the square root of both sides of an inequality, you obviously can not treat it like you would with equality, as in that there are two solutions of $LHS \leq \pm{RHS}$ as this is self contradictory. How would I get all the solutions required for the triangle inequality then? As in: $a\leq b+c, b\leq a+c$ and $c\leq a+b$. What are the logical steps in solving for the square roots of inequalities?
Answer: From $(a-b)^2 \leq c^2 \leq (a+b)^2$, we can deduce that $|a-b|\leq |c|\leq |a+b|$ by taking positive square roots (taking negative square roots would reverse order). Since $c,a+b\geq 0$, it follows that $c\leq a+b$ and $|a-b|\leq c$. The latter gives $a-b\leq c \implies a\leq b+c$ and $b-a\leq c \implies b\leq a+c$ as required.
Comment: We always have $a-b\leq |a-b|$ and $b-a \leq |a-b|$, so both $a-b\leq c$ and $b-a\leq c$ hold regardless of whether $a\geq b$ or not. As to the second question, you are correct. For a concrete example, note that I can say $4<9$ so $2<3$, but I cannot also say that $-2<-3$.
Comment: Don't we need to assume that $a \geq b$ for  $a \leq b+c$ from $|a-b| \leq c$ and that $b > a$ for $b \leq a+c$? But then they can't simultaneously be true as you can't assume both $a \geq b$  and $b > a$ right? And we require that they are simultaneously true. Also, I am still unsure as to what you mean by taking the negative square root reverses order. Does this mean that we have both $|a-b| \leq|c|$ and $-|a-b| \geq|c|$ or $-|a-b| \geq-|c|$?
Comment: $|a-b|\leq c$ if and only if both $a-b\leq c$ and $b-a \leq c$ hold. No assumptions are made on $a,b,c$ other than that they are real numbers. By reversing order I mean $-|a-b|\geq -|c|$
Comment: But $|a-b| = a-b$ if $a-b\geq 0 \implies a \geq b$ and $|a-b| = b-a$ if $a-b<0 \implies b>a$ by the properties of absolute value. Do both $a-b \leq c \text { and } b-a \leq c \text { hold }$ by some other rule? Also, by your second remark, $-|a-b| \geq-|c|$ can be rearranged to the original $|a-b| \leq|c|$ so does this mean taking the square root of an inequality does not lead to two 'sets' of solutions as it does for equalities?


What should I do to maintain a long-distance relationship?

Question: I am a 17 years old boy. On my last holiday I met a girl one year older than me. We talked for like 5 min and I really liked it. She is working in the hotel which I was guest in. We exchanged our facebook profiles because we wanted to maintain some sort of connection. For now we are only texting and sending photos. I know that it's not enough. The distance between me and her is 4-5 hours by car. Can you give me any advice on how to improve our realtionship? Thank you in advance.
Comment: Hi! Questions asking 'what should I do' or 'what can I do' tend to be very broad, and are also off-topic on this site. We can't decide for you what you should do to maintain your relationship. What do you mean by 'it's not enough'? What parts of your relationship are bad right now, and need improving? What would 'improve' be, what's the goal you're aiming towards? Would you qualify your relationship as romantic, or friendship?
Answer: I have been in a long distance relationship for 5 years (my husband and I are married now, but still living apart due to immigration stuff).
What we found worked was making sure we made time for each other. We text, we make sure we talk to each other every day (like a phone call or Skype call or something), that sort of thing. Knowing that we will hear each other's voices, even for a bit (and see each others faces, if we do a video call) helps the distance seem shorter.
Other than that, find ways you can be together even with the kilometres between. For my husband and I, this means we play a lot of video games together, because that's what we like doing. There are sites you can use to watch the same movie together (or you get really good at going "okay press play in 3,2,1,go"),stuff like that.
Basically, it's like any other relationship, except you have to work a little harder to be present in each other's lives, because you can't just hang out in the same space when you want to. Make sure you make time to visit each other when you can, because nothing replaces that face to face time when you can actually touch each other and do "normal couple stuff" (you never realize how nice it is to just sit snuggled up to someone quietly reading or something until you can't do it).
Good luck!
Comment: Thank you! I really appreciate your help. But in my situation it is impossible to play video games together. She is not that type of person but I will find something else.


Why does my cat only bite me?

Question: I live with my mom and we have a one year old cat. The cat only ever bites me and she bites me repeatedly. They're gentle unprovoked bites. I'll be laying down and she'll start biting me repeatedly, my feet, my legs, my butt, my arms, my hands, and even my head. They're not aggressive but she does this often, I raise my voice and tell her to stop but she doesn't. Why does she do this to me only?
Comment: Welcome to pets.SE! How much hours of the day do you both spend at home with the cat? Could be the cat has different relationship to your mum, than to you?
Comment: Probably because you let her. You "raise (your) voice and tell her to stop," but without details I can only assume you're not actually doing something to discourage the behavior, which becomes more ingrained the longer it goes on.
Answer: Are you her favorite person? If so, she may be bored and trying to get you to play with her!
Soft bites, called nips, are one of the ways cats initiate play with each other. It's soft enough that the other cat knows that no real harm is intended, but it's still enough to get their play/hunt/fight instincts to kick in.
Cats often pick one specific human as "theirs", which explains why she doesn't do it to other family members: you're the only one she wants to play with.
In the short term, you can try playing more with her before she nips you. But if she is just too active for you to keep up with, getting a second cat may be the best solution because they'll have more similar daily sleep/play cycles.
Answer: This could be a sign of favor, actually.
Cats have scent glands inside their mouths, and sometimes use nipping or licking or even teeth-rubbing (my personal favorite) as a lesser-known way to get you to smell like them and therefore to belong to them. Cats rub their chins or heads on us for the same reason, but the inside of the mouth also works.
My cat nips me a bunch when I get back from a long time away. It doesn't hurt and it's not an issue. She just wants to get me smelling "right" as quickly as possible.

Why does my cat only bite me?


is there a word to describe someone who is running out of time to complete a task?

Question: Specifically, I'm looking for an adjective that describes someone who is aging and realizes there are more days behind them than in front of them.  Ideally, the adjective would have a positive connotation to it rather than a negative one. Maybe I'm asking too much?  lol
Comment: You might get better results if you gave an example sentence that shows how you want to use the word. In particular, we can't tell whether you want a noun or an adjective, and so you have gotten some of each.
Comment: Out to pasture, long in the tooth, autumnal, in the golden years
Comment: The poor soul is *up against the clock*, and *time is running out*.
Comment: Seems like the question in the title is about a task, but the question body is about a person ageing. I don't really understand what you are after here.
Answer: "a word that describes someone who is aging and realizes there are more days behind them than in front of them"
I suggest you use "over-the-hill" or "past one's prime". -   These are phrasesl, though.

over-the-hill

"no longer able to do something at an acceptable level because of age" TFD
old and no longer in the best part of your life" IM

past one's prime

"beyond the most useful or productive period" TFD
"no longer as good at something as one once was" MW

examples

Once you turn 60, you are over the hill. It's all aches and pains.
Barbra was a wonderful singer, but she's past her prime now.
Your car is past its prime. It's hight time you bought a new one.
She was a great actress once, but she is past her prime now.

As single-word adjectives: aged, retired, declining, etc.
Comment: ouch!! @Centaurus
Comment: one downvote. It would help if you explained why.  I would try to improve the answer.
Answer: The first word that comes to my mind is senescence, or, its adjective form, senescent:

the state of being old; the process of becoming old (http://www.merriam-webster.com/dictionary/senescence)

Wikipedia has a more technical definition:

Senescence (/sɪˈnɛsəns/) (from Latin: senescere, meaning "to grow old," from senex) or biological aging (also spelled biological ageing) is the gradual deterioration of function characteristic of most complex lifeforms, arguably found in all biological kingdoms, that on the level of the organism increases mortality after maturation. (https://en.m.wikipedia.org/wiki/Senescence)

You could perhaps also use the related term senile:

showing a loss of mental ability (such as memory) in old age (http://www.merriam-webster.com/dictionary/senile)

Finally, you could also consider that this person is aware of their own mortality:

the quality or state of being a person or thing that is alive and therefore certain to die; the quality or state of being mortal (http://www.merriam-webster.com/dictionary/mortality)

I hope this is helpful for you!
Answer: The Oxford dictionary of American English defines short-timer as

A person nearing the end of their period of military service.

In my experience, this is routinely used in the civilian world as well,
to refer to somebody who has submitted a resignation
(or announced a retirement date), but who is still at work
(for a last few days).
The Cambridge English Dictionary defines lame duck as

a person who still has time to serve in an elected position
  despite not being elected again in a recent election,
  with the result that the person has no real power

Of course there are many terms for an old person
(politically correct: senior citizen / slang: geezer).
I can't think of a word that encompasses both concepts.
You might want to look up bucket list and last gasp
and see whether they lead you anywhere.
Answer: Perhaps waning or the phrase on the wane

to draw near the end.
The year is waning, and what have we accomplished?
His childhood was waning; he would soon become an adolescent.

Wordsmyth.net
Answer: The OP prefers a word with a positive connotation.  The positive word that is associated with aging is wiser, as in older and wiser.
See The Science of Older and Wiser

Vivian Clayton, a geriatric neuropsychologist in Orinda, Calif.,
  developed a definition of wisdom in the 1970s, when she was a graduate
  student, that has served as a foundation for research on the subject
  ever since. After scouring ancient texts for evocations of wisdom, she
  found that most people described as wise were decision makers. So she
  asked a group of law students, law professors and retired judges to
  name the characteristics of a wise person. Based on an analysis of
  their answers, she determined that wisdom consists of three key
  components: cognition, reflection and compassion.

The article goes on to discuss how these three components change with age.   Although cognitive functioning slows with age, the quality of information in the older brain is more nuanced.  This can form the basis for wise behavior.
The article concludes with a paragraph that directly addresses the OP's question:

Dr. Clayton says there's a point in life when a fundamental shift
  occurs, and people start thinking about how much time they have left
  rather than how long they have lived. Reflecting on the meaning and
  structure of their lives, she said, can help people thrive after the
  balance shifts and there is much less time left than has gone before.

As for the aspect of running out of time to complete a task, which was in the OP's title, the older and wiser person will realize that many tasks are  unimportant, and will focus on essential tasks.
Answer: The one I am guilty of:
procrastinator
Seeing further clarification of the question brings to mind this: See lyrics to Pink Floyd's "Time"


SharePoint 2010 SDK

Question: Anyone know where I can download the SharePoint 2010 SDK. I'm particularly after the SharePoint 2010 Microsoft.SharePoint.Client.Search.dll. Looks like Microsoft have removed downloads for it. Thanks
Answer: SharePoint 2010 Client object model SDK only has 2 dlls , it deos not have support for search. To access search functionality of SP 2010 from client application you have to rely on search.asmx service.
Microsoft.SharePoint.Client.dll
Microsoft.SharePoint.Client.Runtime.dll
You can download it from here..
https://www.nuget.org/packages/Microsoft.SharePoint.Client/
Microsoft.SharePoint.Client.Search.dll is supported only from SP 2013
you can download that SP2013 version from below.
https://www.nuget.org/packages/SharePoint.Client.Search/

SharePoint 2010 SDK


Connecting one Interface Builder view to multiple variables / dynamic creation

Question: I have created a custom view with Interface Builder and defined its IBOutlet variable within my ViewController.
Now I would like to instantiate multiple variables of this view, without duplicating the view in Interface Builder and creating its respective IBOutlets.
When I connect the view in Interface Builder to multiple reference outlets they all instantiate the same view, but I would like to place multiple views at different positions as subviews.
What is the right way to do this ?
Answer: This is very similar to my question Reusable Bits of Interface Designed in IB, which contains working code.
You might not like that solution, though, because it still requires that you place "placeholder" views in the appropriate locations and connect them up (even though their content is copied automatically). In most circumstances, this makes perfect sense: you need to tell your app where to place the views and what outlets they're connected to anyway at some point.
If manually specifying location and outlets seems "wrong" to you, then perhaps your situation would be better addressed by something like an NSCollectionView or an NSMatrix, which will handle placement and organization for you.


Use of undeclared identifier NSLinkAttributeName

Question: I'm trying to add a link to an NSAttributedString via the NSLinkAttributeName function, and I keep getting the undeclared identifier error.  I have imported the Foundation.framework and I still get this error.  Here's the code where the error appears:
<code> NSAttributedString *string = [[NSAttributedString alloc] initWithString:nonAttrString
                                                              attributes:[NSDictionary dictionaryWithObjectsAndKeys:NSLinkAttributeName, @"http://www.google.com", nil];
</code>
Any idea what the problem is?
Thanks,
Pete
EDIT: Clarifictation, the NSLinkAttributeName is the unidentified part.
EDIT EDIT: Okay, silly mistake, the answer is that NSLinkAttributeName isn't in the standard libraries or the CoreText library, so I had to import AppKit/AppKit.h in order to get rid of the error.
That being said, AppKit requires the NSGeometry library which I don't have, where can I find this or is NSLinkAttributeName impossible on ios?
Comment: Which part is undeclared exactly?
Answer: NSAttributedString and Links on iOS this question was already answered, didn't realize it was iOS specific.


Where to Apply for International Relations?

Question: I'm having some trouble figuring out what schools to apply to for a Masters in International Relations. There are a number of lists I've seen but many of the schools are very focused on the practical side for mid-career people. I'm interested in eventually getting a PhD and being an academic. Also most lists are only of the top 5 or 10 schools so it's hard to tell how good other schools are. My application is a little mixed, some strong parts some weak parts, so I was thinking of applying to a wide range of schools but I could really use some advice in what schools to look at. My undergrad GPA isn't good, 3.14 (3.5 in the major), but my GRE scores are good, 170V 168Q 4.5. I've been living in China for the past 5 years, but only speak a tiny bit of Chinese. I'd love some advice about where to apply or any rankings to look at. Thanks.
Answer: International relations at the University of St Andrews are quite highly ranked. They definitely give you the option of eventually moving on to a PhD. I don't know much about their entry requirements though; I'd suggest that you contact them and ask.
Answer: International relations is a famous major at American University in Washington DC.
The School of International Relations is the speciality of American University.
For a nice historical background, it was at American University where JFK spoke:

Ask not what your country can do for you....
Comment: Hi user3953, and welcome to Academia Stack Exchange! We tend to avoid one-sentence one-link answers… Could you elaborate on what makes your answer a good fit for the original poster's specific case? Otherwise, this would be more fitting as a comment below the question.