Question about cutting gene in Plasmid

Question: I am designing a researching proposal for the class. Because it uses microinjection to up-regulate the gene in C. elegans, the plasmid pCFJ104 - Pmyo-3::mCherry::unc-54 sequences has been chosen. But because the plasmid already has a unc-54, I wonder if there a way that to cut the unc-54 out of the plasmid?
Comment: _unc-54_ encodes the major bodywall muscle myosin. In these plasmids the only portion from _unc-54_ is usually the 3'-UTR and the polyA addition site (AATAAA). _myo-3_ is either another BWM myosin, or a pharyngeal-specific myosin. This is providing the tissue-specific promoter. The expression plasmid drives expression of the mCherry fluorescent reporter in muscle cells.
Comment: Can you give more information on what the unc-54 gene does? Try and be a bit more clear maybe even a picture or link of the plasmid with the unc-54 location, thanks.
Comment: pCFJ104 - Pmyo-3::mCherry::unc-54  is the plasmid I choose, here is the link: https://www.addgene.org/19328/; because the experiment need to up regulate a gene that is also in the muscle, so before doing the microinjection, the unc-54 need to be cut out before insert the gene I use. So I am wondering how to cut the gene out. Thanks!
Answer: Following the link you provided confirms that the C. elegans expression vector will express your insert of choice in the transgenic animals' pharyngeal muscle cells (driven by the myo-3 promoter).
From examining the two images of the plasmid's restriction map on the page you linked to, I infer that a SacI x XbaI double digest should excise the mCherry insert, and be suitable for sub-cloning your fragment of choice.
However you will need to confirm this for yourself. In general, I think it extremely unlikely that you would find an individual on Biology SE who could provide such precise information as "what enzyme sites should I use for my sub cloning experiment."
A general approach would be to

Research to find out if you can obtain a fasta file containing the complete DNA sequence of the starting plasmid.
Search GenBank to see if there is a record containing annotations for the starting plasmid sequence--that will tell you the start points and end points of each functional region.
If the plasmid is not in a sequence database try using the sequence in a BLAST search of a Non-redundant sequence database. In this example you would have retrieved high scoring hits on the unc-54 gene, the myo-3 gene, the mCherry gene, the beta-lactamase gene from pMB9/pBR322/pUC, and the E. coli lacZ gene (among others).
You should also consult the original publication (if there is one) because it may contain additional useful information, including how to contact the authors--who may have sequence files, useful maps, etc.
With the sequence in hand you will be able to create your own restriction map using a suitable software program (there are many commercial ones), e.g. the EMBOSS suite of open source bioinformatics software.

In your case most of this work was done for you because the AddGene site had two annotated restriction maps that showed almost all of the information you needed.  N.B. One map had the locations of the useful restriction enzyme sites, and the other map had the annotations showing the extent and locations of the worm fragments and the reporter gene. It was only by integrating the information from both maps that I was able to suggest one possible solution to your query.

Question about cutting gene in Plasmid


How long can I hold brown rice between boiling and steaming?

Question: I use a technique from Cooks Illustrated for cooking my brown rice. I simmer for 25 minutes and then steam for 10. It gets a nice consistent result. But how long can I hold the rice between simmering and steaming? Does it matter if it sits out for 30 - 45 minutes before finishing? Would I need to increase the steam time? How much? Are there any safety concerns?
Answer: You can wait as long as you need to between pre-cook (that's the simmering) and finish (the steaming), it's how things work in restaurants.
The steaming time will only go up if you let the temperature drop appreciably.  Even so, you shouldn't need more than an extra minute or so.  Steaming is pretty benign to rice.
As far as the safety concerns...if you keep the temperature above 135 F, you are out of the danger zone, and you can hold there forever.  The danger zone is 41 to 135 F, but the goal in cooling foods is to get it from hot to cool in 6 hours...below 70 in two, and then 4 hours to make it below 41 (yes, I'm ServSafe certified).  So your hypothetical 30-45 minutes shouldn't cause you a problem.  But watch it if you start going long.
Comment: @yossarian: Do danger-zone concerns really factor into *rice*?  Unless you had some kind of cross-contamination, it should be bacteria-free to begin with.
Comment: Sorry guys, rice can be a serious problem...the specific bacteria is bacillus cereus.  And the problem isn't that you can't kill the bacteria, it's that the bacteria create toxins that persist after the bacteria is dead.  But again, the times you are talking about aren't going to be a problem.  Just don't let it sit all afternoon, then think the steaming will take care of anything.  It will, indeed, kill the bacteria, but not the toxins.  If you ever want to freak yourself out, take the ServSafe course.  They get your attention up front by telling you everything you want to avoid.
Comment: What I was really wondering about the safety concerns is how much it even matter if it was held in the danger zone? Would 10+ minutes in a steamer kill off anything that may have shown up while it was being held?
Comment: @aaronut, yeah, I kinda figured that it would be ok whatever I did with it since it's rice and I'm steaming it before service, but I'm not positive.


Protecting LAN from remote controlled VMs

Question: I am making a virtual network setup for my high school cybersecurity team to practice. I am connecting all the VMs together through a VPN and then people who are practicing will VPN in and ssh/remote desktop into the different VMs. The problem is that for practicing, they will need root access into the VMs and because the VMs are connecting to my personal network, the VMs pose a security risk to my personal network. Is there any way in either VMWare or VirtualBox or even making an unchangeable iptable (I can make all the windows VMs go thru a linux VM) to prevent people from connecting to my local network via the VM?
Answer: Have you thought about this:

VMacc will be the linux access VM, this one has a public IP I guess? It also has is your VPN access point.
Create a virtual switch in vmware and put all your vulnerable VM's in the same subnet. You can use the let them be on the same subnet your vulnerable VM's will be on.

Now just firewall so that only the openvpn port is open on your Linux machine. People will be able to VPN into your network and access the vulnerable VM's and there is no connection to your normal LAN since they are on their own virtual network.
Answer: You can also:

Put the host of the VMs into a separate VLAN, considering possible
risks already described on StackExchange.
Create a NAT for the VMs on the
host(or the linux box you wrote about) and block access to your personal network via
IPTables like this:
iptables -I FORWARD 1 -d 192.168.0.1 -j ACCEPT
iptables -I FORWARD 2 -d 192.168.0.0/24 -j DROP
Assuming your network address and default gateway.


At-will Spellcasting in 3.5

Question: My gaming group is currently playing a game in 3.5e, but I have done some of the DnDnext playtests and find myself very intrigued by the wizard class' at-will cantrips, and I was wondering if there was a way to build a 3.5 character with at-will spells.  I've toyed around with some Sorcerer powers that increase spell slots, but I haven't come up with anything that truly allows for at-will spells.
Comment: You might want to look at Pathfinder, which is similar to 3.5. In that game, all classes with access to 0-level spells can cast them at will, though preparation-based spellcasters still have to choose which 0-level spells they have available on any given day. It was also a popular houserule for 3.5 among certain groups I played with before Pathfinder was developed.
Comment: Was it Complete Mage that had the feats that allowed spellcasters to perform certain spell-like abilities at-will so long as they had a particular (more powerful) spell prepared?
Comment: That does sound like a pretty good house rule to throw in.  I can't see getting all our people to buy new rulebooks and learning a new system, but next time I DM I'll probably house rule that in.  Thanks!
Comment: @GMJoe: There's also prestige classes for that, but they lave a limit of X/day, usually 1-3/day.
Answer: Complete Mage has a set of feats that provide, as long as you have certain spells memorized, you can do at will magical tricks based on the spell memorized.  These feats relate to various keywords, such as fire, electricity, or teleportation.  For instance, if you take the fire related feat, you get the at will ability to conjure a burst of flame that does 1d6 damage per level of the highest level fire spell memorized.  For the electricity feat, it does 1d6 damage per level of the highest level electricity spell memorized.  May want to look into that.
Comment: Hi, thanks for your answer, and welcome to the site! Please read the faq, and when you have 20+ reputation, feel free to join the chat!
Comment: Ah, forgot the Reserve feats. For the record, most of them aren't very good (or, the active effect isn't; the Caster Level bonus can definitely be), though Summon Elemental is awesome. Good addition.
Comment: Excellent! This is more along the lines of what I was looking for, though the Warlock looks good, too, KRyan.
Answer: Complete Arcane has the Warlock
The Warlock from Complete Arcane is basically the at-will version of the Sorcerer. You get a ray that deals damage sort of comparable to Sneak Attack (i.e. 1d6 every other level, except at high levels it slows down for no apparent reason), as well as a dozen "invocations," which are at-will arcane spell-like abilities.
Ultimately, the Warlock was badly over-charged for the privilege of having things at will. Most of the invocations aren't especially awesome to be able to do constantly (though the flight, invisibility, and teleportation ones are pretty sweet), and in combat actions are usually a much tighter limit than spells per day. And invocations are much weaker than spells, at the same class level. But you can still do some pretty neat things and it does make you pretty independent and reliable.
As a side-note, the Dragonfire Adept from Dragon Magic uses similar mechanics, though he's less "magely," and some other alternative magic systems (meldshaping, pact magic, truenaming) are at least sort-of at-will, though again they differ quite a bit from your typical mage.
Lastly, there is a grossly-overpriced feat that can allow high-level regular spellcasters to use a select, low-level spell at will. I cannot recommend it.
Comment: @acolyte Touch-attacks are dead-easy to make; a Warlock doesn't even particularly need much Strength to hit them. They do gain only medium BAB in-class, so the second attack is at 8th and the third at 15th. Careful prestige classing can improve that, though. I suggest if you wish to know more, though, you start your own question on the subject.
Comment: What is the name of that horrible, horrible feat?  :-)
Comment: @ilinamorato I believe it's Innate Spell; there are a couple of different printings of it (3.0 and 3.5). Both are badly overpriced.
Comment: Oh, I hadn't seen that one...but yeah, it looks like it costs a lot for the little bit it gives you.  And it isn't even really at-will spellcasting, just additional casting.  I shall take your recommendation, thank you.
Comment: Warlocks get some really good invocations - one allows him to never be caught flat-footed and the other good one is the infamous eldritch glaive. Not so mage-y but they deserve mentioning I think since they make up for the lack of other good things.
Comment: @Zachiel eldritch glaive?  i don't remember that from Complete Arcane.
Comment: @acolyte It's from *Dragon Magic*. Full-round action, make a melee touch attack that deals *eldritch blast* damage at 10 ft. range, plus an additional attack for any iteratives you may have for high BAB. The *glaive* also remains until your next turn so you can make AoOs with it. It's a Blast Shape, but you can still apply Eldritch Essences to it.
Comment: @KRyan ineresting.  when does Warlock gain bonus attacks from BAB?  I mean, unless you kit yourself out specifically to take advantage of that invocation, i don't see you hitting things all that easily or it really becoming super strong.
Comment: @KRyan oh, wait, i see the benefit.  instead of the massive range from eldritch spear, you're getting the ability to use any additional attacks you might have (though at a shorter range).
Answer: Being able to actually cast an unlimited number of spells is--barring excessive shenanigans via things like using plane shift to go to planes wherein time passes at a far faster rate so you can rest in the middle of an encounter--impossible. Having a character with a host of at-will spell-like abilities is possible with some effort.
Templates
If the character starts as a humanoid, he can take the templates half-fey (Fiend Folio 96) with at-will charm person for LA +2, half-rakshasa (Dragon #313 96) with at-will empathy (Dragon #313 94) for LA +3, and katane (Dragon #313 64) with at-will spider climb for LA +4, then top off with either half-celestial (MM 144) with at-will daylight for LA +4 or saint (BE 184) with at will bless, guidance, resistance, and virtue for LA +2. The character'll have 1 HD when he takes his 1st class level and count as a level 12 or level 14 character, but his ability scores will be amazing.
Also, this assumes reflavoring the names so the character isn't 3/2+ something.
Races
Play a monster. All of the following monsters get at least a few spell-like abilities at will: the ECL 20 astra deva (MM 11) and trumpet archon (MM 17); the ECL 19 hezrou (MM 44); the ECL 18 vrock (MM 48); the ECL 16 couatl (MM 37) and erinyes (MM 54); the ECL 11 hound archon (MM 16); the ECL 12 succubus (MM 47); the ECL 10 drider (MM 89). You can probably tell where I stopped going through the Monster Manual, but picking a monster is almost always suboptimal to picking an actual non-LA, non-ECL character.
Classes
The warlock from Complete Arcane's been suggested, but I also recommend Tome of Magic's binder, whose vestiges can grant spell-like abilities at will, like the Acererak vestige which grants at-will use of detect undead and speak with dead. The bound vestige persists for 24 hours after which it must be bound again, so it's not technically inherent-forever spell-like abilities. (Thus foiling your scheme to create a perpetual motion machine via an enslaved creature with an at-will spell-like ability.)
A 5th-level spellthief can steal another's at-will spell-like abilities all day long. The spellthief only gets one use of it before he must steal it again, but if the source is limitless so is the spellthief's ability to steal. Improved familiars make good targets.
Feats
Other than Complete Arcane's feat Innate Spell--which lets you trade mind blank or polymorph any object once per day for mage hand at will--getting at-will spell-like abilities via feats looks impossible.
However, like everything in D&D 3.X, being a caster and ruthlessly pushing the limits of the feat Craft Wondrous Item (PH 92-3) pretty much lets you make anything your DM allows. With the core rules setting a precedent with hand of the mage (DMG 258), convincing your DM to allow crafting other comparable at-will items should be trivial.
There's one feat, though, that I mention here because it's the Feats section: Fiendish Summoning Specialist (PlH 39). You needn't take it; just know it exists.
Spells
Depending on the errata the campaign uses the spell polymorph any object might be used to just become a creature with spell-like abilities, but neither magic jar nor shapechange grants access to a creature's spell-like abilities.
What does explicitly grant access to a creature's spell-like abilities is the 5th-level Sor/Wiz spell fiendform (SpC 90). It reads, "[Y]ou can take the form of any fiendish creature, demon, or devil that can be summoned by a summon monster I, II, III, IV spell..." (emphasis mine). So if the Fiendish Summoning Specialist feat exists in the campaign, by a strict reading, other folks have added to the summon monster lists, and those can be accessed by anyone who casts fiendform. The fiendform spell only lasts 1 minute per caster level and has as an unpriced but weird material component, and you've to convince your DM that other people totally put the demon, devil, or fiendish creature you want to change into on their summon monster list via the Fiendish Summoning Specialist feat, but if those obstacles are overcome--and you don't mind that sick feeling you get after having so much cheese--, have fun with your demonic and devilish at-will spell-like abilities. If being such a creature all day is required the fiendform spell is a valid target for the Persistent Spell feat (CAr 81) and multiple ways exist to reduce what would otherwise be an 11th-level spell to something that can be cast pre-epic.
There is not, to my knowledge, an identical opposite celestialform spell.
Comment: +1 for binder, the only class that I'm still willing to play in 3.5
Comment: Wow, this is amazing.  Far more detailed than I expected!  Thank you!
Comment: Och, don't forget 'bout MoI book - some of the soulmelds are working exactly spell-like AND the character may just refuse to reshape 'em for his entire life. They're not as flavorfull as Binders, but still pretty neat 8)
Comment: I'm AFB, so I cannot double-check, but vestiges typically grant Su abilities; does Acererak really have an Su ability that grants Sp abilities? Not impossible, but seems weird.
Comment: @KRyan It doesn't; they're still Su. My bad. But I think it was close enough for this question (which asks more for at-will abilities than spell-likes, really) despite its technical inaccuracy.
Comment: Agreed, was just surprised to see that.
Answer: I believe there was a add-on class called the "Hedge Wizard" which specialized in cantrips.  I would recommend looking into it.  Sadly, I do not have the pdf on hand, but it might be something worth looking into for you.
Comment: I believe the Hedge Wizard is in Power Classes. It's 3rd party if that makes a difference.
Answer: If your character has written scrolls for all known spells, you achieve the same effect: being able to cast any spell you know at will, without having to bend the rules and without having to be a special class.
But it costs XP and GP to do so; plus you need the Scribe Scroll feat.

At-will Spellcasting in 3.5


What is the correct tag to use when asking which dialects use a specific word?

Question: Which tag should be used for a question that asks if a word is used only in a specific English dialect?
Answer: If a question is about a specific dialect then a tag corresponding to that dialect should be used, e.g. american-english, british-english, canadian-english, austrailian-english, etc. If the user wants to be more specific, then they should tag the question with the broad dialect and specify the more specific dialect in the question.
For example, if a user is specifically asking about any dialect spoken in the British isles, they should tag the question british-english and specify the more specific dialect in the text of the question.
If the user is trying to find out which dialect a specific word or phrase is in, then perhaps they should tag the question with dialects.
Comment: A very helpful answer (+1), but your [tag:australian-english] tag has a typo and should be edited.
Answer: Although I disagree with FumbleFingers that we should only teach Standard English - there are cases for example where answering in Standard English is not appropriate, for example where different idioms are used in BE versus AE, pronunciation of "tomato" or whether the use of the royal "we" is valid - I do agree that in general we should teach Standard (by which I mean "universal") English first and foremost.
For example,

I've never had no money

is perfectly valid colloquial English, but an English learner would be better advised to learn the Standard English equivalent:

I've never had any money

This form is more useful to most English learners, since it is the form that is more common, more understood, better for use in writing formal letters, novels (outside of quoted speech), business speech and making themselves generally understood in the English speaking world. It's also less likely to cause offense and is more likely to get them marks in English exams or tests.
For this reason, I think ELL should encourage answers to be in Standard English first and foremost, but we shouldn't discriminate against non Standard English forms, particularly when the question directly relates to it. For example:

What does "I've never had no money" mean? Shouldn't it be "I've never had any money"?

To which a good answer might be:

They are both equivalent. The former is a colloquial form of the latter - particularly as used in the African American Vernacular.
Generally for formal writing you should prefer the Standard English form "I've never had any money" in non-quoted formal writing and business speech.

This is certainly a much better answer than

Yes. The first one is not Standard English. Always use the latter.

Often it is the case where an answerer is not aware of the fact that their answer is local to their region. In these cases, the answer should not be discouraged or removed, but a commenter may wish to point out that the answer is not valid in all regions or is not Standard English.
Answer: I think this site should address the various English dialects. I'm a non-native speaker learning US English. I'm having a lot of trouble understanding UK English (written and conversation). Anyone speaking the UK English will understand this simple sentence, "let's ring her up". This sentence has no meaning to me. Since I'm not at all familiar with the UK English dialect, I'm unable to form any thought in my head. Now, after knowing a little bit about the UK dialect, I'm able to at least understand how it's being used.
Answer: I don't think ELL should directly concern itself with dialectal variation.
It's no purpose of the site to teach learners how to use Australian, or Indian English. Nor even American or British English, come to that. We're here to help people learn and understand standard English (however that may be defined).
So if someone asks about the meaning or origin of Dingo's breakfast - a yawn, a leak and a good look round (i.e. no breakfast), I don't want ELL to tag it Australian English - I want to close it as either Too Localised, or Off Topic.
On the other hand, I notice that arvo - afternoon is starting to be used quite a bit in the UK. Probably because, as with 2moz - tomorrow, it's a useful short form for txting what would otherwise be quite a long word. So that one I wouldn't closevote, but I still don't see a lot of point in tagging it "dialectal" - which might have been how it started, but isn't where it seems to be ending up.
Comment: It's true that there's no dialect that is universally perceived as standard across the world.  It's usually more useful to refer to a construct as standard or non-standard, and one construct may be standard in e.g. British English and non-standard in American English. "Standard English", then, is shorthand for the dialect which contains the features that are standard in the relevant context, so a British speaker likely speaks a different Standard English than an American speaker does. Therefore, kiamlaluno is correct that there "isn't a Standard English", but there are many Standard Englishes.
Comment: I think whether or not ELL should handle dialectal variation should be its own question.
Comment: There is no standard English. Everybody speak an English dialect, and everybody is taught an English dialect. In Italy, they teach British English at every level of public school. If you are going to say that learners don't know if they are learning British English or another language, that is wrong. I had an American friend, and it has been not difficult for me that the English word that was taught me for _gasoline_ was not a word she understood.
Comment: No offence, @kiamlaluno, but the fact that British cars normally run on *petrol*, whereas Americans ones run on *gas*, is hardly worth knowing until you get used to "standard" English. For example, *everyone **speaks***, not *speak*. For a non-native speaker you obviously know quite a bit *about* English, but you don't really *know* it. It doesn't bother me that this answer gets downvoted - people are free to fail to learn in whatever way they choose - but I will continue to present what I see as the *basics*, that will avoid people advertising their "non-native-speaker" status too bluntly.
Comment: Well, at least I don't speak of Standard English, when there isn't a Standard English. Point me where I said I know everything about English, or that I don't make typos.
Comment: @snailplane, kiamlaluno: I put "standard" in quotes, and didn't capitalise it. It's no more a single "dialect" than Joe Public is a specific individual. But we're not so much concerned here with identifying exactly what aspects of English are (more or less) universally known and accepted as "correct". We're talking about whether a *specific interest in "non-standard" dialectal usages* is appropriate on an ***English** Language Learners* site. You might well find such issues interesting, but I think they should be aired elsewhere. Even if downvoters (currently 3) disagree, my opinion stands.
Comment: @Andrew Grimm: I'd have thought votes/comments against this answer address that issue well enough. Even if I'm right, not everyone agrees, obviously!


Problem with MS Excel 2007

Question: I get an error dialog that states "this workbook contains no unbount sheets".  It then freezes my session of excel.  I cannot find a help topic that relates to this problem.  Has anyone seen this before?
Update
This error occurred when I attempted to open a workbook that is dependent upon several others. I have set the workbook up to return values from other workbooks to get a current view of the status of several items as they transition from production to ready-to-ship. There is no VBA coding involved, all the returned values are the results of MATCH or VLOOKUP functions. My workstation computer has only Office 2007 resident, and it none of my colleagues seem to ever have had this error in their collective experience.
To clarify - the dialog box has the message: "workbook has no bound sheets.". The only option is to click "OK" (or to close the box with the red X). Either action freezes that session of Excel.
Thanks for your attention to my plight.
Comment: @warren Your dad will have to register both his SU and SO accounts to regain ownership of this question
Answer: I suggest you to try to save the workbook in an older Excel version (say XP, 2003) and try to reopen it.

Problem with MS Excel 2007


Li-Ion protection

Question: I have a couple of Li-Ion batteries I made up for a particular application.
They each consist of four 18650 cells in series along with a 4S battery protection board.
I have been using these two batteries in series to give me an 8S configuration without any problems.
My question regards re-purposing these batteries.
I'd like to use these batteries to make up a 2P4S battery but I don't want to strip the cells out of these batteries and reconfigure them. What would be the down-side(s) of putting these two batteries in parallel (effectively paralleling-up the two 4S protections boards)?
Answer: If by 'paralleling up' you mean just paralleling the battery + and - leads then it will be fine.
The protection circuit in each pack works independently of the other, so in a fault condition (over/under voltage, over current) one pack may disconnect first but the second one will follow shortly afterwards.
Comment: I'd connect them via a resistor initially, because if you directly connect them the voltages are going to be minimally different, leading to a high current to equalize them. After they are at the same level, connect them directly and keep them connected -- repeat the bit with the resistor when they have been disconnected for some time.
Comment: That's exactly what I was hoping for Bruce. Thanks for your input.
Comment: Thanks Simon. I built a board that permits me to bottom balance all eight cells in situ via the balance ports, and I plan to run all cells down to the same low voltage before connecting the batteries in parallel. Then I'll supply 16V across the entire pack to charge it up via a 6V lamp (current limiter and charging indicator) before checking the voltages on each individual cell.
Comment: If the batteries had previously been used in series then they _should_ have the same charge. I wouldn't bother discharging them, just measure the cell voltages and equalize if necessary (>0.05V variation). If one battery has markedly lower voltage than the other then charge it to the same voltage before connecting them together.
Comment: I'd be more comfortable playing it safe with Lithium cells Bruce, which means connecting them in parallel when fully discharged. Since I intend to never top-balance, I think it would be good for the cells to begin their life in this new configuration in a bottom balanced state. Maybe overkill, but peace of mind too.
Answer: You will definitely want to be sure the cells in parallel have a voltage close to each other before connecting them, otherwise you will get fairly large currents trying to balance the cells as they even out. Other than that there should be no issues.  Side note: If you use cells of similar capacity in parallel it helps boost life and efficiency.  We started capacity matching cells in one of our batteries that uses cells in parallel and it boosted the specs a fair bit.
Comment: Thanks Jared. See my reply to Simon above and I'd be interested to hear if you have any advice on that procedure.
Comment: It appears to be a reasonable procedure, although you need to be sure that the voltages on specific cells don't go too high when charging the string. Even though you may be charging the string to only 10V, assumption based on 16V minus the 6V lamp, it is very easy for an individual cell to charge much faster than the faster than the rest which could lead to an unsafe condition.  Also, what voltage are you planning on balancing down to?  I would recommend staying above at least 2V to avoid plating lithium.
Comment: The 4S string charges from the 16V supply via the lamp. As the string voltage approaches the supply voltage of 16V, the voltage drop across the lamp will approach zero, so the lamp will eventually extinguish when the string is fully charged. Using identical cells, so I'm assuming they'll charge fairly evenly though I will keep a check on that. I'm using TP056 boards that cut out when the cell voltage drops to 2.5V. I would have preferred 3.0V cut-out but can't find anything to do that job. I'm not overly concerned about this since bottom-balancing is not frequently performed.
Comment: I would not recommend charging them that way as it is almost certain they will not charge equally.  All it takes is one cell to go to far and then they all "rapidly disassemble".  Lithium batteries are not something to be taken lightly, you need to keep careful track of them and don't let them go too high.  Some 18650s come with protection circuitry built in, if you have those you should be fine, otherwise I would be very cautious charging them that high with that method.
Comment: Thanks for your concern Jared. I used to give my lithium cells a top-balancing charge cycle, but I've been swayed by the people that promote an occasional bottom-balancing discharge cycle and whole-pack charging on the grounds that all cells reach the same low voltage together during a normal discharge. I use a cell logger to give me a visual indication of how much the cell voltages have diverged after a full-pack charge, and somewhat surprisingly I've never found a significant deviation (I suspect I'll see that when one of the cells is failing and needs replacing anyway).

Li-Ion protection


Is amount transferred by third party to savings account considered as income?

Question: If my friend transfers (using Third Party Transfer or NEFT) some money to my savings account, does that amount count as my transfer income and do I have to pay tax on it?
Comment: Unless it is for work you have done, then NO.
Answer: The purpose of the transfer determines the taxability. If this is happening to frequent, it is advisable to keep proper records of the transaction so that if there is an enquiry from Tax authorities you can explain.
Unless you explain the why the transfer is being made, I have put out some broad categories.

Transfering the Money to you as Loan with expectation of repayment in future date. This is not taxable to you. When you transfer back the money to your friend the interest will be taxed to him as income. Proper paperwork required to be maintained with you to answer any queries to Tax Authorities.
Transfering the Moeny to you as repayment of Loan. I.E. Your friend had borrowed from you and is repaying you. The interest is taxable to you. Proper paperwork required to be maintained with you to answer any queries to Tax Authorities.
Sharing of Expense. i.e. you have both out of dinner / movie / renting an apartment and he is transfering his share of Expenses. No Tax obligation. Paper work required to justify that it was an shared expense. Receipts etc.
In absence of any of the above, the transfer will be termed as GIFT from you friend. There is an yearly limit of Rs 50,000/- as Gift from Unrelated persons. Anything above that would have Gift Tax
As Victor pointed out in comment, if its in return for work, then its definately your income and taxable.
Answer: As per Indian tax laws; income, expense, gain and loss constitute the basic pillars of every individual's economic life. There are very few cases under which this new 'income' is non taxable. Based on the circumstances, you might have to pay capital gains tax.
Comment: **Capital gains** tax? Where is the investment that produced the capital gain?


What CDNs can I connect to with SDL Media Manager

Question: I have a requirement to support multiple CDNs for different asset types (due to cost/volume consumption/politics) - I am assuming (as I cannot see any documentation) that SDL Media Manager will allow me to easily define a separate CDN target for the different MIME types?
Comment: Hi, it would help you to get more meaningful answers if you clarify whether this is a Tridion integration or not. In it's current form your question could be viewed as off topic.
Comment: It is a Tridion integration indeed!
Answer: This is probably the wrong place to ask about core SDL Media Manager features.
Assuming you are referring to a Tridion integration with SDL Media Manager Connector (since this is the Tridion stackexchange site) and if SDL Media Manager can't do what you need it would technically be possible to do the following:
Write a custom TBB that uses the Media Manager Connector API (for 2011SP1, for 2013 this would be the ECL API - same thing, new name) to retrieve a link to the published images or files. Then copy them to your CDN of choice and insert the updated link in the template. I would not try to do anything with videos - the link you can retrieve is not to the video file directly, but to a player that access the video.
The main drawback is obviously that you now have to (re)publish the item through Tridion before it is available.
Notice as mentioned this is technically possible. Whether you should do it is another issue altogether which I won't make any comments on (although I did make this comment which might be seen as a hint). :)
Comment: If your question doesn't have anything to do with Tridion, then I would say it is out of scope of this stack exchange site.
Comment: Thanks for the reply - I can only find (through a Google search) references to the AKAMAI network - I cannot find anywhere in the docs on sdllivecontent that this can be swapped out.  I don't want to (nor should I have to) develop anything Tridion side to do this, it should be the domain of the DAM system.
Answer: As far as I understand it, Media Manager is only provided as a SAAS solution, so the assets are not hosted on your server, and you do not have any control over how they are provisioned (via CDN etc.). Therefore I dont think you have control over what CDN to use, unless you want to build something like Lars says to pull the assets from Media manager, and publish them to a CDN. That seems to destroy half the point of the SAAS offering though...
Comment: Exactly, it's actually a completely useless system for anyone who has contracts with CDN providers in place.  I'll be looking for an alternative.
Comment: If you are on Tridion 2013, you can probably use ECL to integrate with whatever solution you come up with.
Comment: @mpaton: CDN is included in the Media Manager price, would it in your case be cheaper to bring your own CDN contracts? Or are you forced to keep and use your current CDN contract?
Answer: SDL Media Manager comes with a CDN as it is a hosted service/SAAS. The CDN is included in the price and there is no need to bring your own CDN. If you want to have your data one particular CDN, I think Media Manager does support other CDNs on request by a CDN connector. Separating CDN targets for different MIME types is not supported.
Media Manager is a MAM, it focusses on the delivery of video and image assets. It's much more than a CDN, I think it cannot be replaced with a CDN + ECL connector. You would miss a lot of features, like localization with       subtitles and audio tracks, screen grabbing, multi chapter video's, the encoding for various formats and devices, the video player and so on. Only if you need a CDN to host some static images, then indeed you can use a CDN and ECL, but you probably choose Media Manager for a reason.


Autoincrement a field based on ID

Question: So I'm trying to autoincrement a field on a list item.
First i tried using a calculated value field "=[ID]" which works the first time, but after saving a new item to the list the "[]" are gone and, the calculation is dropped.
I also tried using a workflow like "when item is created, set my_id = ID" but I got type errors, as ID is a double, and Sharepoint(as far as I've found) cannot handle conversion on the fly(?)
I have to say, that I have not tried to code this into an event receiver, it seems like the only way, unless any of you have any ideas.
Thanks for reading my question.
Answer: Alexandar,
To answer all your questions/doubts..

ID Column in Calculated Column
Excerpt from Microsoft documentation

You cannot reference the ID of a row for a newly inserted row. The ID
  does not yet exist when the calculation is performed.

Using SharePoint Designer Workflow
There are many posts which show solution to this problem using SharePoint Designer Workflows or other workarounds (using extra list and so on).. Please have a look at:
Add a Unique Auto-Incrementing Column to a SharePoint List
Screenshots of Workflow used in above post
Using the Row ID value in a calculated column
Using SP ID in Calculated Field No Code
Event Receiver
Of course for developers the first thing that comes to mind is writing an Event Receiver for the List. On ItemAdded you can retrieve ID of the item.

I hope this helps
Answer: You can use WorkFlow for this. Create another list, use your WorkFlow to create a new blank item on this list and get ID of this new item for your incremental column. ID values on list are incremental, so you dont need to do anything except create and get ID value. If you want to reset the ID value, you need to drop and re-create this value list.

Autoincrement a field based on ID


How can I export civicrm contribution along with its price set fields?

Question: I want to export the civicrm contributions. I want the priceset fields to be included in the report. I am trying to export them in Contributions->Find Contributions->Export Contributions
While selecting the fields I want all the priceset fields in the option. How can I achieve this? Any help would be appreciable. Thanks in advance.
Answer: Have a look at eileen's Extended Report Extension which includes

Extended Report - Contributions with Price Set data
Extended Report - Price Set Line Items
Answer: Currently, contribution level searches and reports will only show you the contribution level information, not the line item detail (a.k.a. the price field options selected on the contribution). Take a look at Reports > Contribution Reports > Bookkeeping Transaction report - this report will show you the financial type of each price field option selected.
Hope this helps,
Tamar


Tool to automate login and workflow inside desktop application

Question: My project is into inventory domain, once order is created on the web/URL , need to login the desktop application to complete and fulfill the order.
I am using selenium web driver to create order on the Web.
What tool can i use to automate a desktop application? All inputs are greatly appreciated.
Comment: Steps involved are:
1. To create an order on the web
2. To login a desktop application and complete the order.
Comment: Please write a better title, that reflects your needs.
Comment: Also, please read http://meta.softwarerecs.stackexchange.com/questions/336/what-is-required-for-a-question-to-contain-enough-information
Answer: You can use powershell to create an automation script. One possibility (but not the only one, Google is your friend here) is the UIAutomation library, for which I found an example here.
I remember doing some simple automation without this library, so you might be able to find other approaches, but in any case: this can be done with powershell.
Answer: For a few decades now, I have been using Autoit, and can't recommend it enough for automating WIdnwos tasks. See, for instance my answer to How to automatically input text to the window program's text field and search this site further for `autoit/
To quote that answer:
Personally, I always use AutoIt to automate any Windows tasks

AutoIt v3 is a freeware BASIC-like scripting language designed for automating the Windows GUI and general scripting. It uses a combination of simulated keystrokes, mouse movement and window/control manipulation in order to automate tasks in a way not possible or reliable with other languages.

I am not sure about AutoHotKey, but one big feature of AutoIt is that it will locate a window, or wait for it to become active. It doesn't rely on X/Y coordinates, you can resize, move, or even minimize or hide  a program and your script will still run.
Here's a simple script which opens Notepad, writes to its input and saves the file:
<code>Run("notepad.exe")
WinWaitActive("Untitled - Notepad")
Send("This is some text.")
WinClose("Untitled - Notepad")
WinWaitActive("Notepad", "Save")
;WinWaitActive("Notepad", "Do you want to save") ; When running under Windows XP
Send("!n")
</code>
Comment: Five years later, and I am using AutoHotKey, which is a fork of AutoIt. Be sure to use v2, not v1. If your app uses WFP, then you need anotehr solution


Fuzzing in OWASP ZAP through the command line

Question: First of all, I'm running ZAP in a Docker container and will automate ZAP scans using Jenkins.
The official docker image seems to have a script that performs spidering and active scans but does not do any fuzzing. Is there a way to fuzz through the command line? I can't do the manual way of going to the GUI and running a fuzz since everything needs to be automated.
Answer: No, fuzzing is currently a manual only process. We do plan to add an API but have not had the chance yet.
Its worth noting that even if we do add an API it will still be tricky to automate. In ZAP when you're fuzzing you have to specify exactly what you want to fuzz (per request), what you want to fuzz it with and analyse the results.
In general the active scanner is a better bet in automation.
Having said that, what are you expecting to be able to do with ZAP fuzzing?


How do I find expiration date of my misplaced US ham license?

Question: I can't find my general class license. I want to apply for a vanity call sign (my call sign when I was 16 years old) but I don't know the expiration date of my current license. Is there some way to find the expiration date online?
Comment: I assume you're in the United States because you say "General Class". Please make sure to mention that when asking licensing questions.
Comment: When did you last renew the license? Within a few years would help. If you never renewed, then what year were you 16?
Comment: Quick way: google your call sign
Answer: Go to the FCC Universal Licensing System (ULS) web site and search for your license. You can search by call sign, name (in lastname, firstname initial order), or address (in the advanced search form). It will show you the expiration date and current status.
If your license has already expired, you can submit a renewal up to two years afterward. From a review of the form, it looks like you can combine a renewal with a vanity call sign application, but I'm not sure.
If two years has passed since the expiration of your license, you will have to take the Technician exam over again, but you can get exam credit for your previous General license.
Note that there is a very good chance that "your call sign when you were 16" has already been claimed by someone else if it is shorter than modern sequential call signs; short vanity call signs are in high demand. The first thing you should do is search for that call sign in the ULS, even though it's not the one you currently hold, to check if it is available.
Comment: @FredMarlin Hello, and welcome to this site! Can we help you with something?
Comment: Did not help me at all. This page is useless. Needs to be better
Answer: For licenses in the USA you can go to this site
FCC ULS
Scroll down the page to the entry for entering your call sign, then scroll to the bottom and click search.  It should find your license no matter if it is current or already expired.  You can click the call sign it finds to see all of the detail including your FRN number you can use to attempt to renew the license.  The license should be good for ten years and you have a two year grace period after that for renewal.  Renewal can be done online and costs nothing.
Comment: I see that Kevin typed faster than I did.   :-)
Answer: You should be able to search for it via the FCC's licensing database.  Might also try Googling your callsign, many times that can take you right to the licensing page for your sign.


EC Public key encryption scheme where Alice does not know Bob's public key

Question: I've found ECDH and ECIES, but those both require Alice to know Bob's public key and Bob to know Alice's public key in order to derive a shared secret.
Now assume Bob knows Alice's public key $A$, but Alice does not know Bob's public key $B$. Is there an Elliptic Curve encryption scheme where Bob can encrypt a message for Alice using just their public key $A$ which Alice can then decrypt without needing Bob's public key? (The reverse is not necessary, Alice does not need to send any encrypted messages to Bob)
Answer: ECIES does not require the sender to publish their own permanent public key. Instead, they can just create an anonymous ephemeral key pair, and publish the ephemeral public key along with the ciphertext. The sender can discard the ephemeral private key as soon as the encryption has been completed. Alternatively, the private key can be retained so that the sender can provide a signature at a later time to prove that they were the sender.
Comment: Exactly what I was looking for, thank you!
Answer: You might be looking for anonymous messaging in which the sender hides their identity from the receiver. The Libsodium has one specially designed for this sealed_box

Only the recipient can decrypt these messages, using its private key. While the recipient can verify the integrity of the message, it cannot verify the identity of the sender.

Bob can decrypt the incoming message from Alice, however, they cannot verify the identity of the sender. Also, there is no way Eve can determine the sender, too. This scheme uses an ephemeral private and public key pair (generated and used once) is generated and later the ephemeral private key is destroyed. As long as the sender IP etc. is hidden from the observers, there is no way to determine the sender.
Note 1:  this is an existing and well-maintained library that you don't need to implement anything to achieve your target.
Note 2: ElGamal Encryption (1985) , on the other hand, is exactly designed in this manner. Alice doesn't need to set up a public-private key pair to send a message to Bob. ElGamal Encryption is used to encrypt the symmetric key ( or one can transmit the key material and derive the key with a good KDF like HKDF).
Comment: Both ECIES/sealed_box and EC ElGamal are essentially creating an ephemeral key pair in order to then perform an ECDH step. Then they differ slightly according to whether a symmetric key is derived from this ECDH shared secret, or whether in the case of El Gamal the shared secret is encrypted with the ECDH shared secret.
Comment: @knaccc It is here to show the first one ( DLIES 1999). sealed_box is intended to be like this ( provides only integrity) in contrast to crypto_box which has authentication, too ( the libsodium is the library to be used IMHO ). Yes, DLIES( ECIES) is also designed in this way, too.
Comment: Ah interesting, that's a good point, I see what you're saying now. The authentication would be unnecessary overhead when the key pair is ephemeral.


Is there a way to post the images on google+ wall using my ios app?

Question: I have checked the API but it allows to post the URL not the image?
Answer: From what I've read on the internet the Google+ API (https://developers.google.com/+/mobile/ios/) currently does not allow for an upload like that.
Instead some people have been using the Picasa Web SDK (https://developers.google.com/picasa-web/) since it is what powers Google+'s images.
Answer: Currently, it is not possible to write to a user's Stream in any form. However, you can make this feature request in our Issue Tracker, which you can find at https://developers.google.com/+/support.
Answer: Edit: Google+ History was deprecated on February 26, 2013
Checkout the Google+ History developer preview.
The History API allows you to record different types (docs) of user interactions.
For now these interactions only show up in the History tab (along with all other Google activities for that account). From there the user is able to share to it's timeline.
This is a developer preview, and it's probably not a good idea to go live with an app that uses this. But it gives you the opportunity to start developing for the future. I can imagine a user has a future option to autopost certain types of history to it's timeline.


Raspberry Pi configuration is not opening when connected via Windows remote desktop connection

Question: Raspberry Pi configuration is not opening while connected using windows remote desktop connection or VNC. I'm trying to open it from the main menu. It's opening if I connect RPI to a monitor.
Comment: Are you using the latest Raspbian Stretch with Desktop ?
Comment: I'd be tempted to re-flash the latest Raspbian Stretch image to your sd card.
Comment: Yes. Also I tried to update GUI of the RPi config.
Comment: Open a terminal and type sudo raspi-config
Comment: Could this possibly be a security feature?  I know that there is a GPIO setting which forbids manipulating the GPIOs remotely.  I'm wondering if this is an extension of that.
Comment: If I opens it in terminal it shows. Seems a security feature.
Comment: for me configuration was not opening when using tightvnc-server, configuration open after using realVNC-server
Answer: If you're using tightvncserver this might help you.
I had VNC enabled in the RPI Configuration (uses realvnc) and installed tightvncserver after that on the RPI. Before that installation it told me that it will remove realvnc. So I guess RPI Configuration got confused with VNC enabled while realvnc had been removed.
Simply removing tightvncserver from the RPI, setting VNC to disable, and installing tightvncserver again did the trick for me.
I probably just could have disabled the realvnc in the RPI configuration via the terminal
sudo raspi-config > Interfacing Options > P3 VNC > No (to disable realvnc server)
Or maybe you overruled another setting in the RPI Configuration.
Hope that helps


If induced voltage (back-emf) is equal and opposite to applied voltage, what drives the current?

Question: Suppose we have a circuit with a voltage source, a switch open and an inductor all in series. If we close the switch, the potential difference of the voltage source is instantaneously applied to the inductor. As the current starts to build up, induced voltage from the inductance opposes it. If the induced voltage (back-emf) is equal and opposite to the applied voltage, and the net voltage is zero, what drives the current then?
Comment: The source drives the current, by virtue of applying a voltage across the inductor. The current is initally zero, but it has a gradient, hence \$L\frac{di}{dt}\$ is generated to match the source voltage. The current continues with the same gradient as long as the source is connected.
Comment: This will be interesting to read especially if someone can answer it assuming that the inductor's internal resistance or losses is zero.
Comment: Consider that the back EMF doesn't exist if there is no current.
Comment: Nice question... IMO the induced voltage is absolutely equal only in the first moment after closing the switch so the net voltage and current are zero. Then it begins gradually decreasing... the net voltage and accordingly the current, gradually increase. So the inductor forms the increasing current by adjusting its opposing voltage. Indeed, it is difficult to imagine this without some internal resistance (just as it is difficult to imagine what happens at the first moment when a perfect voltage source is connected to a capacitor without any resistance).
Comment: ... So both inductor and capacitor can be considered as "dynamic opposing voltage sources" - the inductor fully opposes the input source in the beginning while the capacitor fully opposes it at the end.
Comment: @Circuitfantasist you said " the induced voltage is absolutely equal only in the first moment after closing the switch so the net voltage and current are zero. Then it begins gradually decreasing... " just tell me why it begins gradually decreasing in answers and i will be very much grateful to you.
Comment: Or consider another analogy. I want to lift a weight. If the force the weight exerts on my hands is equal to the force I exert on the weight, how can the weight move? (Point being, the question doesn't make any sense. The weight moves because I apply a force to lift it, and the current flows into the inductor because we apply a voltage. The fact that I experience a reaction force and the voltage source sees a back-EMF doesn't change that)
Comment: @Alex, since my answer is still hidden, here is a simple intuitive explanation by using the mechanical property of "inertness".

Imagine you want to move a car... so you press it firmly from behind (apply "input voltage"). At first the car does not move at all (the "current" is zero)... since it fully opposes your force (full "opposing voltage"). Then it begins slowly moving and  accelerating (the net "voltage" and "current" are gradually increasing). After a long enough time, you do not experience any opposition from the car.
Comment: analogy is correct but the question is still there. what makes the back emf decrease with time ?
Comment: Maybe the reason is that some kind of potential energy (voltage) gradually converts to the dual kinetic energy (current); that is why the voltage decreases and the current increases. In contrast, in the case of a charging capacitor, a kind of kinetic energy (current) gradually converts to the dual potential energy (voltage); that is why the current decreases and the voltage increases...
Comment: see my comments  .........
https://electronics.stackexchange.com/questions/572096/transient-analysis-of-inductor-circuit-and-back-emf/572131#572131
Answer: The seemingly paradoxical image of "a current that is flowing despite nothing is driving it" stems from the misconception that you always need a force to move charges. You don't!
Just think about those old-fashioned cathode ray tubes, where you accelerate electrons inside a highly charged capacitor, and the electrons exit the capacitor through a small hole at the end with a certain velocity. Even in the absence of any electric field they will keep this velocity (current!) right until they hit the opposite phosphorescent side of the screen where they get decelerated abruptly and get their energy converted into visible light (and some X-ray!). This lack of resistance is all because these electrons move in vacuum and they move almost in the same direction, so they don't collide with each other.
This is very different from a solid state conductor, where electrons get scattered at the atom bodies, ie. the crystal structure of the solid, and thus constantly lose energy. This is similar to the molecules in a gas that will eventually lose any initially coordinated movement direction, and showing their undirected internal energy as temperature. In order to refuel the charge carriers in a solid resistive conductor (ie. non-superconductor), a persisting electric field is needed.
In an ideal inductor there is no resistance. Think of a coil shaped cathode ray tube as an approximate mental picture. Then what governs electron movement are the law of induction and Ampere's law:
$$\nabla \times E = -\frac{\partial B}{\partial t}$$
$$\nabla \times B = j$$
the latter of which is the simplified version for slowly varying fields (no EM waves).
So the only thing the laws of nature require for the existence of a current is a magnetic field with non-vanishing curl (second equation). If there is no magnetic field (i.e. in the beginning right after pulling a huge Frankenstein switch), there is certainly no current. Moreover, the shape of the current determines the shape of the magnetic field and vice versa. If the shape of the currents is given for all times (because we squeeze the charge carriers through the windings of a coil), the only thing that can vary about the magnetic field is its magnitude with time.
On the other hand, from the law of induction (first equation) we learn, that if the shape of the magnetic field is constant and only its magnitude changes with time, it will be the source of a rotational (closed) electric field of a given shape. In a coil the induction voltages along the individual windings (multiple rotations around an axis) add up to the total inductor voltage. Again, vice versa, any electric field with non-vanishing curl will give rise to a magnetic field changing in time.
Finally we can combine both equations into one by forming the curl of the law of induction and substituting Ampere's law into it:
$$\frac{\partial j}{\partial t}=-\nabla\times\nabla\times E$$
What we see here is the mathematical way of saying that a change of current in time is caused by (the second curl derivative of) a circular electric field. The remaining steps towards U=-L*dI/dt is just geometry applied to the specific inductor under consideration, and the boundary conditions it is subject to.
Conclusion: since there is no resistance, we don't need any voltage driving the current according to Ohm's law. Rather the current change rate is driven by the rotational electric field represented by the constant external voltage that is guided through the coil windings (as soon as the switch has been actuated). Most importantly the "net voltage" is not at all zero, but rather it is the external voltage that is defined by the given boundary conditions.
Comment: Yes, it is actually Newton's first law (inertia) that comes into play here. The reason why we are so familiar with intertia in everyday life, but we don't usually encounter it in electrical engineering, is because electrons are so tiny and sensitive to random disturbance. Everyone will agree that a train is very inert once it is rolling, but already for dust particles submerged in the air inertia doesn't play that much of a role (whereas viscous forces do).  Macroscopically resistance shares some similarity with viscosity, but on the quantum mechanical level it is a little more complicated.
Comment: It seems the general property of some "inertness" can explain the phenomenon of "current without voltage" ("movement without force"). Indeed, there is always a need for initial voltage (force) as a kind of potential energy. But in such elements it is converted and accumulated in a form of some kinetic energy… and they can produce current without voltage... movement without force...
Comment: Well, what do you call a "true current source"? Normally the notion of a technical source (voltage or current) also includes control, i.e. if a load is connected, the controller restores its setpoint from a reservoir behind the scenes. But if you leave control out of the discussion, then an inductor could be considered a current source (in the sense that it maintains the present current to some extent). Likewise a capacitor is a voltage source because it maintains the present voltage. But any inductor and capacitor is not ideal in that they have some resistance (+inductance +capacitance).
Comment: This belief may be due to a capacitor requiring an *open* circuit to maintain its voltage (so nobody will notice its series resistance without load). Whereas an inductor requires a *closed* circuit to maintain its current. But as soon as you have a closed circuit, everyday experience tells us that there will be some resistance in this circuit, which then inevitably links the current to a voltage (and thus seemingly defying "current without voltage"). If superconductivity were a more everyday phenomenon, people would probably be more inclined to accepting an inductor as a current source.
Comment: @Alex: as you can see, the current is not determined by the applied voltage but by the curl of the magnetic field. What you call back EMF is somehow similar to a ficticious force in mechanics: if you accelerate a steel ball on an inclined plane, the inertial force seems to balance the external force (gravity). In your logic, the ball should not move because the "net force" is zero. But the inertial force is a fictitious force that just expresses change of motion. Likewise, the back EMF is a "ficticious voltage", that just expresses the change of current due to the increasing magnetic field.
Comment: So the charged inductor can be considered as a "true current source" (current "battery") that produces current without voltage? Only it has to be periodically charged… Another idea would be to assemble a current source by two inductors that work alternatively - while the one produces current, the other is charged and v.v. Maybe this idea is exploited in step-up DC-DC converters. This topic is interesting to me since I have been convinced in many web discussions that such a true current source cannot exist in this world...
Comment: My observations are that people accept the capacitor as a kind of voltage source but do not accept the inductor as a current source since, they think, it is impossible to produce current without applying voltage. I also think there is a need of voltage but not necessarily at the moment... it can be applied before to charge the inductor... and then there will be only current without exciting voltage...
Comment: IMO they mean rather some exciting voltage (emf) than the voltage drop across the inductor ohmic resistance...
Comment: Thanks alot for your answer. Actually i m not familiar with maxwell equation that is why its hard to get the concept of current without voltage. @oliver
Comment: You said "Most importantly the "net voltage" is not at all zero, but rather it is the external voltage that is defined by the given boundary conditions." can you please explain this to me in laymans vocublary? I shall be so much grateful to you.
Answer: We don't generally refer to it as "back EMF" when we're driving the coil, that term is more popular when we stop driving it.
The voltage across the coil is proportional to the rate at which the amplitude of the magnetic field is changing.  When we put a fixed DC voltage across a coil (and yes, it can be superconducting) the current (and thus the magnetic field) increase at a constant rate proportional to the voltage across it, which we control.
Back EMF generally refers to the effect of not driving it once the field is established.  If you open that switch, you're no longer driving it and the magnetic field collapses at the speed of light.  This attempts to continue driving a current through the coil in the same direction, and since there's no current path available, a large reverse voltage will be seen across the inductor until such time as current flows...which it will take the first opportunity to do without regard for the damage done.  This is why you often see diodes across relay coils, the current spike flows through the diode rather than damaging the driving circuit.
Comment: It does not attempt to drive current in the opposite direction. It seeks to maintain the current in the same direction.
Comment: Thanks, fixed it.  I was thinking of reverse voltage.  Good check.


Windows IIS: Show files in public directory?

Question: I made a directory called /Files and I want it to show the files when somebody goes to mydomain.com/Files but all I get is permission denied. How can I make the folder show the files when person goes to mydomain.com/Files ? Site is hosted on IIS 6.0 and Win Server 2008
Answer: You can't be hosting a site on IIS 6 under Windows Server 2008 because IIS 6 only installs on Windows Server 2003.
In IIS 6 on Windows Server 2003 just tick the "Directory Browsing" box in the properties for the "Files" directory.
The procedure for IIS 7 is a bit more involved, but will accomplish the same result.


Paypal API MassPay for 1 user

Question: Any problem in use MassPay to pay 1 user payment? Any disavantage about that? What should i use instead mass pay for single payments?
I see that paypal forum is dead so im aking here.
Answer: MassPay is fine. If you're already using Adaptive Payments, you could also use Implicit Payments. But if you're not, MassPay suits just fine.
Comment: Thanks thats all i need to know :)
Answer: MassPay works fine with single or multiple payments.  It makes payment more flexible.
Comment: Thanks thats all i need to know :)
Answer: In simple terms Masspay allows you to make multiple payments to multiple people in a single shot using xls or csv files.
If you are just paying a single user:
PayPal provides various payment related operations using the /payment resource and related sub-resources. Use /payment for direct credit card payments and PayPal account payments.
URI: https://api.paypal.com/v1/payments/payment
Create a payment: POST /v1/payments/payment
For more information, refer:
https://developer.paypal.com/webapps/developer/docs/api/#create-a-payment

Paypal API MassPay for 1 user


Losing your portion in the world to come and Elisha ben Avuha

Question: I don't remember which mishna it is, however there is a mishna that lists certain ways a person loses their portion in the world to come. However in the case of Elisha ben Avuha, he thought he lost his portion in the world to come because a "bat kol" told him so. In the end the Gemara explains that he was eligible to repent. However, how does that fit in with the mishna that lists certain ways a person CAN lose their portion in the world to come? I'm sure Elisha ben Avuha knew which things affect whether you are/not eligible
Comment: Anyone can repent if they are on that list in the Mishna, and then get it back. The Mishna (11th chapter of Sanhedrin, 10th in some versions) is only talking about a person dying without repenting.
Answer: Firstly, if one hears something directly from a heavenly source, one can reasonably believe that it's an exception.
But more to the point, Elisha had reason to believe that he qualified anyways.
The Mishna in Shanhedrin Daf 90a states that one of the categories of people who lose their portion in the world to is  one who reads literature categorized as Sifrei Chitzonim.

ר''ע אומר אף הקורא בספרים החיצונים

The Gemara (Daf 100b) defines ספרים החיצונים as ספרי מינים.
In Chagiga Daf 15B we learn "אמרו עליו על אחר בשעה שהיה עומד מבית המדרש הרבה ספרי מינין נושרין מחיקו" Elisha - before he went off [Rashi] - already was so engrossed in Sifrei Minim  that he used to bring them with to the Beth HaMidrash.
So he was already disqualified according to the Mishna in Sanhedrin.
Comment: נושרין מחיקו Means that the books fell out of his lap.  Not that he brought them with him.
Answer: The Bas Kol was about not accepting his repentance not about his losing Olam Haba. As @Yishai pointed out, as long as a person is alive and he repents he goes off that list.
Teshuva is a special benefit, which is sort of undeserved. It is a gift. The Baal Shem Tov explained that when a Bas Kol calls out every day to do Teshuva, we hear that in our hearts in the form of a sudden pang of guilt, or introspection. It is not from within but it can be cashed in.
There is a separate list of those from whom Teshuva is withheld. Most famously is the one who says that he'll first sin and then repent.
A careful look at Rashi in Va'era died that Hashem didn't actually take away Paroah's Bechira, but rather his ability to repent. Since the sudden, implanted introspective moment is a gift from above it is withheld from certain individuals. This is what happened to Acher.
If you enjoy non-literal, rational, explanations we can say that it was this lack of any moment of regret that the Gemara is referring to as his Bas Kol. But even a straightforward understanding is that in contrast to everyone's Teshuva broadcast, he got a non-Teshuva broadcast.


Should I authenticate user on every request?

Question: I'm working on a social network using Vue.js on frontend, and Node/Express on backend. To store user sessions I'm using Redis. I'm wondering if I should hit Redis everytime user requests content, or maybe there is a way to reduce the load?
Comment: I think this is a great question. Security is absolutely part of programming, sys admin and network engineering. Oh and policy and hr...
Comment: Are you sure this is necessary? Redis should be pretty fast, have you done performance tests?
Comment: Application login session management is NOT a security question, it is more like a programming question. (I didn't downvote)
Answer: You should be using session management to handle information transfer between clients and servers.
Session management essentially involves authenticating  a user to initially perform a privileged action, with all subsequent activities being authenticated via 'shared' information eg: cookies.
Asking users to authenticate for each and every action might be considered more secure but will heavily reduce platform usability and overall user satisfaction as a  result.
With regards to database load, without seeing the specific application I can't be 100% however I would advise as long as you are logging the last time the session was used, you don't need to write much other information to the database.
Comment: Just to elaborate... one of the ways sessions can be authenticated is with a digitally-signed cookie. Most frameworks have something like this built in. Verification that the session is authentic can be done with crypto up-front, saving a database (or cache) hit. You'll still want a session store in the database or some other server-side store to keep internal secrets and details from leaking into the browser's cookie storage.
Answer: Claim-based identity is a good way to reduce the load of authenticating a user.
The simplest way to implement that is to have a first authentication portal that generate signed tokens containing the necessary claims for the user and then have the subsequent call require that token, verify the signature and, trust the claims.
See JWT for a practical implementation.
Comment: It should be noted that this makes it impossible to force session expiration while a JWT is still valid.
Comment: Correct. There are ways to mitigate this (adding an ID to the token and propagating a list of invalidated tickets to all system that will need to validate) but it's something that adds complexity and potentially lowers perfs.
Comment: Indeed, if you're checking redis for a blacklist on every connection, you might as well just do sessions the normal way. You could propagate the blacklist to each system, but that's more complex.
Comment: Ah no: authenticating the user is really NOT the same as checking if the session is part of a specific set of expired sessions. First, if you store your credentials properly, it is likely to be waaay faster and cheaper. And even if you don't, it can be optimized in many different ways (because it's a dataset of limited size, doesn't contain any confidential data, only needs to be propagated once per record and in one direction and each record has a very limited lifetime). It's really not that hard to implement in a secure and efficient way even for larger systems.
Comment: Hmm, yes, that is a bit of a weak argument isn't it? I'm not arguing for authenticating the user's credentials on every request though, just for using a central storage for standard sessions.
Answer: This is really somewhat off-topic here. We don't know what your application is/does/looks like - so we can't answer the question you asked beyond saying that the functional relevance usually overrides the performance consideration. However since others have already started answering....
Traditionally, http sessions use a random identifier sent to the client which is a key to data on the server. Each time a request requires session data, this is read from the storage. And in most implementations it is subsequently written back to the storage on or before completion of the request. The latter is important to update the timestamp on the session so it can be garbage collected later. Now you definitely want to write the data back to storage when it has changed, but writes are at least 3 times as expensive as reads. So even though you can implement this without impacting delivery of content to the client, not writing unchanged session data back to the storage with every request can have a big impact on capacity.
Using a faster storage substrate can help too.
Then there's the possibility of caching content. Some content needs to be generated afresh each time its accessed. Some content will be near static for a given user, and some content will be the same for all users. HTTP provides mechanisms for advertising this fact to the client and to a reverse proxy. For example, for content cacheable by a specific user, you could incorporate the user id in the Etag - but remember to add a cache-control:private header at the point where it leaves the reverse proxy.
Although you generally can't trust content sent from the client, you could encrypt the data in cookies and use the client for storage - and check for tampering when you decrypt it. Again, this is about capacity rather than performance. And some thought needs to be applied to persistence of the data on the client, even if it is encrypted.
But, except in a very few cases, the performance overhead of sessions, relative to everything else going on in a web page is very, VERY small.
Answer: It looks like you are rolling your own authentication or at least a part of it.

I'm wondering if I should hit Redis everytime user requests content,

Yes you have to check the user session against your backend storage on each http request, this a how web servers and web frameworks deal with user sessions, some of them use filesystem to store sessions like Apache and others use relational DB like Django Framework does by default.
In-memory storage like Redis and Memcached is de facto the right choice for such case.
However you can still increase the performance by reducing the number of roundtrips between the client and your server this can be achieved by aggregating data to smaller numbers of request which will decrease in hit frequency on Redis.
Answer: No, you don't need to hit Redis on every request is the answer, as you can manage sessions from your backend by issuing a secure cookie. Imagine what would happen if facebook or twitter would hit their db on every request user makes? Additionally to this it would slow down users request.
Comment: The cookie provides the means to authenticate/authorize; whether or not you need to check against the back-end's system of truth depends on the scenario. A secure system *does* need to check to see if the user's auth is still valid, e.g., if I terminate an employee, they should no longer have access to company systems: I cannot rely on the *client's* (e.g., browser) version of truth to secure my system. In general, DBs (or a caching layer) *are* hit on every request, that's how the back end knows what to send back.


Is an air gun allowed on the flight to Australia?

Question: I bought an air gun in Visakhapatnam and I was wondering if I could take an air gun to home to Australia in my checked-in baggage?
Comment: There are different types of "air guns", notably spring-loaded and gas loaded. Those may very well be covered by different regulations for air transport, so it may help if you specify as much about the item you bought as reasonably possible. (Import regulations once it *arrives* in Australia are an entirely different issue, but not less important.)
Answer: Airlines may permit you to carry an air gun as checked baggage, but policies may differ from airline to airline.  For example, Qantas permits firearms (including airsoft guns) to be carried under certain conditions.
However, an air gun is classified as a firearm for the purposes of the Customs (Prohibited Imports) Regulations 1956.  You will not be able to import the item without the appropriate gun licence, acquisition permit and police certification.


What is the difference between ARINC 429 labels 025 and 102 for Selected Altitude?

Question: What is the difference between ARINC 429 labels 025 and 102 for Selected Altitude?
Answer: According to A429, the difference is the type of data coding. Label 025 is BCD. Label 102 is BNR.
Label 025 by being a Binary Coded Decimal codes each character of the altitude value in binary. With a range of 0 to 50000 feet, the first digit uses 3 bits and the remaining use 4 bits each for total of 19 data bits.
Label 102 is a Binary number. The range is 0 to 65535. There are 16 data bits (2^16 = 65536).
Both are transmitted. Receivers will use the version most appropriate for the application.  BCD is normally used for display. BNR is normally used in computations.


How to use a realized kernel?

Question: I've read that realized kernels are the thing to use for calculating daily volatility from high-frequency data. So I've got minute data, how do I actually use such a kernel? Will it give me minute-ly volatility, do I have to normalize it somehow? Also, what data do I feed it - minute data since the start of the trading day, one day's worth of data, all historical data I have until this point, or something else?
Answer: The use of kernels to estimate volatility using intraday data is "nothing more" than combining:

intraday volatility estimation
kernel smoothing

Thus you have to take care about the "usual pits" of these two approaches.
Intraday volatility estimation. I hope you know the "signature plot" effect. Of course if you use the proper estimation method, it should take care of if, but just in case you should check that you do not suffer from it.
Kernel smoothing. You will have to tune the time scale of your kernel. Of course theoretical papers like Designing Realized Kernels to Measure the ex post Variation of Equity Prices in the Presence of Noise do not really have to do it since their results are asymptotic but real life is not.
Moreover you may know that since you will have at date $t$ information of previous dates in your estimator $\hat\sigma_t$, if you multiply it by a statistic from the past $X_{t-\delta t}$ you will obtain a "trace" of the correlation between $X$ and $\sigma$ (i.e. somewhere inside $\mathbb{E}(\hat\sigma_t \cdot X_{t-\delta t})$ you have a term in $\mathbb{E}(K(\delta t) \cdot \sigma_{t-\delta t} \cdot X_{t-\delta t})$, where $K$ is your kernel). It may add biais if you use your kernel volatility estimate to build other estimators. And not only for multiplications.
Comment: Very detailed insight; do you have an article that expands on the bias problem when using realized kernel to build other estimator? thanks.
Answer: Using a realized kernel for calculating volatility will give you results in the same resolution as the data you feed them. So if you feed them minute-by-minute data, then the volatility will be calculated minute-by-minute. What that really means is that only once per minute will you have a good estimate of the volatility of whatever asset you're looking at. The other 99.99% of the the time, the market might introduce changes which may throw that estimate out of the window.
If you're not interested in high-frequency volatility estimates, then it's a completely different matter. You'd be better off trying to pre-filter your data before feeding it to the realized kernel. The goal there is to reduce the noise so that the remaining signal matches up to the frequency you wish to use. So if you want to have a day-by-day estimate based on minute-by-minute data, you can probably get a pretty good result by boiling down the minute-by-minute event data into a hour-by-hour events.
I'm not familiar with such algorithms that give weight to temporal heuristics such as day-of-week or month-in-year or year-by-year cycles. Unless you know you're using such an algorithm, then there's no reason to feed more than a just today's data if you want an estimate for the current day. If anything, adding more data only causes the estimate to become duller, giving you only week- or month-accurate estimates.
If you don't weight your data at all, then feeding in all your historical data might give you a volatility estimate for the next decade, but it will be off by a mile in the short term.
Comment: I may have misunderstood you, when you say realized kernel is estimating same resolution as data, that sounds different to what's described in the accepted answer... and to what I have understood as well. i.e. Realized Kernel is a combination of intraday estimation plus kernel smoothing; I agree that the intraday estimation can provide same resolution estimates, but the kernel smoothing step is surely doing "smoothing": most of the time we are using RKV to estimate today's vol, and that's a different resolution.

How to use a realized kernel?


corsa 1.2 2007 drain battery

Question: I have corsa 1.2 2007 keep losing charge. in the morning start normal. but in the evening not start I try with new battery same things when I plog off the battery wire on the evening car start normal in the morning. I really don't know where the problem
Comment: Welcome to StackExchange! I noticed a typo on your post. What does "plog" mean? Please edit your post for clarity, and provide any other details you might have which could help us help you!
Comment: Did you add any extra equipment to the car?
Comment: I mean when I disconnect the battery on the evening and but it back in the morning the car start fine
Comment: yes I added some internal bulbs
Answer: Sounds like you have a battery drain, but the fact that it starts in the morning is abit strange though, normally battery drain will cause the battery to run flat over a period of time, ie; have to jump start in the mornings, and will be fine driving around through the rest of the day, next morning, same problem. you can check the drain with a multi-meter, switch it to the 10A range, move your one multi-meter cable to the 10A plug on the multi-meter (not the com/comm one, that stays where it is) disconnect the negative terminal at your cars battery and connect one lead from the meter to the negative pole of your battery and the other lead to the negative terminal on the car side battery cable, does not really matter which way around the red and black leads are, reading amount will be the same either way (bare in mind, do this with the ignition off, doors closed and lights etc off, as if you had just parked and closed the car, KEEP KEYS IN YOUR POCKET, or you might end up with the keys locked in the car).
You should get a reading of 0.07A or less, preferably less than 0.05A though, if its higher than 0.07A, check that no lights are on, boot lights can sometime be the culprit, an incorrectly connected radio as well. if you see no obvious items staying on (give it 5mins if you do have a reading over 0.07 to make sure there isnt anything on a time delay) you may want to take it in to a shop to have it checked, trackers are a prime cause of drain and are sometimes hard to find and disconnect or replace the battery, there are multiple other things that could cause it, but its best to let a professional check it

corsa 1.2 2007 drain battery


Using one Raspberry Pi as the Interface to trigger a camera on another Raspberry Pi zero

Question: I was wondering if someone can tell me the basic concept of how I can accomplish this. I want to use a Raspberry Pi Zero with a camera module mounted on a drone to take a series of pictures using a script that takes a picture every x seconds (I have that script working). The challenge is that, seeing that the Pi Zero is attached to a drone, there is no monitor, keyboard, etc. to start and stop the script or adjust the settings. I would like to make an interface with a touch screen mounted to a separate Raspberry Pi that I could connect (via cable or wifi, etc.) to the Pi Zero in order to adjust the settings and then trigger it to start. The idea being that, in the field, I would just fire up both Pi's, connect them, configure the photo session, start it, disconnect them, and then fly the drone. I am new to scripting. I don't care if I connect wirelessly or have to plug/unplug a cable. What would be the best/easiest way to make this happen?
Comment: Are you able to edit your question to include the approximate range of your drone, and which country you're in? There may be some suitable radio options, but they're not all legal everywhere.
Comment: The range of the drone is only about 150-200 feet. I am located in the United States (and the drone is FAA registered). I'm not really concerned about controlling the camera while in flight (though that wouldn't be a bad thing). I just want to be able to configure the script to take pictures at certain intervals for a certain amount of time, and then start the script. It would also be nice to confirm the PiZero is operating and the script is running. I also want to keep the weight the drone is carrying to as minimal as possible.
Answer: A RaspberryPi is a Linux computer.  If all you need is to configure the RaspberryPi while connected to it on the ground you can use a dumb terminal connected to the RaspberryPi over a TTY serial port running a getty program.  At which point you simply log in, perhaps configure a file with interval and time information and start your script.  Then log-out, disconnect the cable and fly.
Answer: I'd use some decent router, USB WiFi adapter for Rpi Zero and setup WiFi network, so RPi Zero could connect and stay in the range while airborne. It should work out of the box, but in case of problems, you can use better antenna (maybe directional one) on the router side.
Then you can control your Rpi remotely, through SSH console or using any other interface (write simple webserver, maybe setup some web sockets, there are many options - just choose what suits you best). What is better, you can have (almost) live feed from the camera, so taking pictures when you want is possible. Maybe it's better than scripting it remotely?
Comment: Are there going to be powering issues - as the distance between the WiFi transceivers increases the power needed to maintain the link will increase and (I'm not up on this) will the PiZero be able to provide all the current needed to a plugged in WiFI dongle?
Comment: It's not the Pi0 that provides the energy but the USB power supply (or any other 5V source that you connect). Power consumption should not rise above maximum USB value (500mA), with increasing range data transfer speed might be limited (e.g. from 56Mbit to even 2Mbit). Have a look on the power consumption test: http://raspi.tv/2014/pihut-wifi-dongle-vs-edimax-power-usage
Comment: As I see it the dongle is plugged (possible via a plain adapter lead) into the RPiZero and both get their power from (presumably in this case a battery pack + voltage converter) connected to the power input on the zero.  However as your WIfI dongle gets further away from the other device it is in contact with  it must increase it's transmission power in order to maintain the link - given that it uses a nominally omnidirectional antenna I think the relationship between distance and power level is a squared one (double the distance needs four times the power) but it _might_ be a cube one...
Comment: It still should not get over USB specification limit (500mA) so I don't think this matters how much energy would it draw.


When and how will the Chinese spacestation reenter?

Question: China's first space station Tiangong-1 is expected to deorbit in late 2017. Are NASA or others tracking it? What is its position and condition at present time?
Comment: Related: http://space.stackexchange.com/questions/15218/do-we-have-any-idea-when-tiangong-1-will-deorbit
Answer: It is absolutely being tracked, as everything in space large enough to do so, by JSPOC. They release all non-classified spacecraft locations as well.
When it will reenter, and even better, where, are much more difficult questions.
The exact time of it's reentry can't be accurately predicted in advance. Right now it is just under 400 km, which, while it will have a short lifespan, likely be less than a year, it won't reenter in the next month. So I predict between 6 months and a year to reenter, at a location that will only be known a few days in advance, if we are lucky. The exact orbit in which a satellite will reenter is very difficult to determine ahead of time, and even just 1 orbit difference could mean thousands of km difference in it's landing position.
At this time, it is believed that there is no control authority at all with the space station.
Answer: For your viewing pleasure, the current position of Tiangong 1:
http://www.n2yo.com/satellite/?s=37820
Answer: If you live more than 43 degrees north or south of the equator you won't get hit by it, it'll be constrained to somewhere within that band.


Closing out an in-the-money equity option spreadtrade

Question: I put on a debit weekly diagonal ITM put spread trade on stock A selling at $45 : I Buy back week put strike 55 sell front week put strike 50.  I am assigned overnight and have to purchase 100 shares of Stock A for $50 ($5000 debit that creates a money due in my account).  The next morning, my broker pre-empts me from exercising my put to sell the stock at $55, by selling the stock in my account for $42, creating a loss of $800.  Is that legal ?  The broker negated my spread trade!
Answer: If you did not have the margin requirement (cash or marginable securities) to buy the stock then the broker had every right to liquidate your newly purchased long stock.
On face value, it's not a disaster unless after closing the stock position, the stock rose and you gave back paper gains on your long put.
What broker was this?
Comment: I get it.  Because the short put is at a lower strike, it's covered and once assigned, the downside risk is also covered.  The only question mark is whether you had sufficient margin to carry it.  Schwab isn't designed for traders nor is it their interest and I've read a lot of complaints about how they handle various issues like this as well as non options positions.  I hope that their management of this didn't cost you.
Comment: Broker was Schwab.  The spread trade was accepted - the long side was put on to limit any loss and guarantee a cash out of $500 if the front leg exercised.
Answer: Was $42 the fair market value of the stock when the broker sold it? If so, then you didn't really lose anything significant. At that point you were free to sell your long put in the market and end up about the same as if you had exercised it instead. Better, in fact, if there was any time value remaining. The broker certainly didn't cost you the difference between $42 and $55, because they left you still owning a long put worth at least $13.
Comment: Forced buy-ins from assignment and short covering (and sell-outs) are done by the broker during after hours (pre and post).  They're not going to work the trade for the best possible fill.  They trade at the market which during after hours is wide, costing additional B/A spread.  For illiquid stocks, that can be  painful.  Then on top of that, there's the market risk of a directional position which as you said, could be favorable or unfavorable.   A good rule of thumb is that you never want your broker closing your positions.
Comment: You have several incorrect assumptions. As long as both legs are deep ITM, underlying share price change is offset. The OCC handles exercise after the market closes and assignment notification occurs in the morning. The broker usually buys in positions in the pre market. Even if the OP got timely assignment notice, he'd have to be available to trade early in the AM as soon as notified. And there's also the market of the stock rising sharply before he can trade, causing his long $55 put to lose money. So it's possible that the broker could indeed cost some of the difference between $42 and $55.
Comment: @BobBaerker If indeed the assigned stock is sold in premarket when options cannot be traded, you are right that risk is increased -- it could be favorable or unfavorable. However, I thought OP was concerned that the broker simply cost him the difference outright. OP didn't seem to be accounting for *any* value in the long put.


How to progress in calisthenics?

Question: In the past two years I have been doing basic calisthenics(Push-ups,Pull-ups, Chin-ups, Squats). I do 1500 push-ups one day and a total of 600 chin-ups and pull-ups the other day, and 250 squats everyday.. I have decided it is time to progress to more difficult body weight exercises such as planche, muscle up, flag pole etc..
I don't know where to fit the training for them into my workout routine. I workout M-Saturday and Sunday off. After I am done with my workout I am too exhausted to train for them, and I need advice on when to do them and significantly progress in them.
Comment: What are you goals? If you want to be able to do lots of pushups, pull ups, chins and bodyweight squats, I'd say you have achieved that.
Answer: It sounds like you've built up enough strength to be able to start moving onto some more advanced moves.
I'd say If you want to learn new movements, just start learning, training, building, improving as you did with your current exercises.
I'm guessing you didn't start out one day and do 1500 pushups without training!?
You just need to incorporate these new advanced movements into your current normal routine.
Also check YouTube for instructions/advice on proper form to prevent injury.
For example...
On your pull up day swap a few sets of pullups for muscle ups,
(before moving straight to muscle ups you may need to work on dips as you don't mention how many bodyweight dips you can do)
Also training to get more explosive at your pullups will help. so you can let go of the bar at the top and clap etc.
On your squats day throw in a few sets of alternating pistol squats, or bench lunges.
On push up day try handstand pushups or jumping/clapping pushups, wide grip, narrow grip, diamond grip... there's lots of pushup variations to make it more difficult.
I'd also suggest looking at core, and lower back training as doing more advanced static hold moves like flagpole planche etc. you're going to need to be able to recruit good balance and stabilization skills.
Get a couple of bricks or pushup bars and start trying to planche, see how much you can do and go from there... 5 seconds one day, 10 seconds the next and so on.
Also exercising in a weighted vest or with a heavy backpack will give you a jump in strength.
And if you're saying you're exhausted check that you're eating enough You don't want to burn out. especially if you're training 6 day splits!
But keep up the good work!
Sounds like your progressing well!

How to progress in calisthenics?


Restoring user data to os10.7

Question: My computer crashed and I made a copy of the entire hard disk by drag and drop on an external hard drive in target mode. Can I restore everything from this drive to the computer now that is 10.7 has been installed. Migration assistant does not see the drive. Help?
Answer: Migration assistant doesn't work with individual users data unless it's backed up by Time Machine AFAIK.
If you just copied the user folder over to the other drive, you should be able to create the new user and then copy the contents of the old user folder to the new one.
It sounds like there's something wrong with the external drive.  Try using Disk Utility to scan and fix it.  If that doesn't work, post back here with details of what happened.

Restoring user data to os10.7