Why does the Symbiote need a host?

Question: I'm not aware of a time limit to how long the Symbiote can live without bonding with a human, what does it gain from doing so?
Comment: Birds gotta fly, fish gotta swim, symbiotes gotta symbiote.
Comment: Comics-wise or all-scope wise?
Comment: @Jenayah- comics wise for now.
Comment: Well in the movie they mentioned, That for the symbiote to live in a rich oxygen enviroment, they need a host.
Comment: according to the wiki https://marvel.wikia.com/wiki/Klyntar_(Race) they where once part of a hive mind and thus require a connection to another being to give their lives meaning. That being said i'm not an expert on the comics so can't confirm the validity of that and this doesn't explain why they'd die without a host so i'm not going to count it as an answer.
Answer: TL;DR: The Symbiotes used to absolutely need a host because they were adrenaline junkies. Nowadays, they don't need a host (whether it be human or something else) for survival, but they need it to reach their species' purpose. Having a host helps:

To help people out
For communication
For food
For food of the mind and self-definition
For self-control
For vesseling and environment awareness

Previous version: Galaxy's bane
Back in the day, the Symbiotes used to be addicted to the emotions of the host creatures, as they did not have feelings of their own. The result would be Symbiotes wiping out whole species as they pushed the hosts to lethal exhaustion. Thus, hosts had a "limited term of utility" (panel is mildly NSFW: corpses).
The Venom Symbiote was an aberration among its race, as he explains to Eddie in Venom Super Special (1995).

In Venom: Along came a Spider #1 (1996), we meet the Hybrid Symbiote, which is formed by four Symbiotes which were being experimented on. This Symbiote escapes and seeks a host (Scott Washington); the terms it uses imply there is indeed a need, without much explanation given, though.

Starving, alone, together but alone; need Other, kind one, Scott, need Scott and Scott needs us...

However, this same Symbiote is featured in Venom: The Hunted (later in the year 1996). At this point, Scott states that the Hybrid Symbiote needed a host "to survive". Since the wording implies said host had to be human, it's possible however than this very condition is only applicable to Hybrid (maybe due to the fact it used to be experimented on).

Current version: Galaxy's saviours
Nowadays' Symbiotes, however, are not the mindless junkie conquerors they used to be presented as - or at least, that is not how they behave. De facto, having a host helps...
To help other people out
Yes, the Klyntar may be a species of monstruous-looking black goo aliens seemingly parasiting bodies, but apart from the appearances and the dozens of Symbiotes which eventually turned into rogue psychopaths, the Symbiotes want to bring peace and fight for the greater good.
Problem being, it's not exactly easy to do when you're a black goo thingy, so while they are "the mind and soul of the warrior", they also need "a form to act out what they know to be the true ways of a noble and virtuous galaxy".
In Guardians of the Galaxy #23 (2015), the Guardians reach the planet of the Symbiotes, and this is pretty much what they tell them, while also explaining how the numerous rogue Symbiotes can be explained by the delicate balance needed between the host and the Symbiote to reach the aforementioned goal.

For communication
When your goal is to travel the galaxy and help other people out, you might want to communicate a bit. Especially when your Symbiote form looks like a drugs-induced nightmare with several teeth rows: being able to speak out your noble intentions helps people seeing you as a friend, not a foe.
Then again, verbal communication can only be achieved by bonding to a host, as shown in the same issue, where they need the Guardians to bond with them.

For food
Symbiotes thrive on phenethylamine, a chemical found in chocolate and brains. Some Symbiotes don't mind consuming people, too. Access to these things is made easier when you live in a fauna, or a big city with people and supermarkets; I have yet to find any mention of a Walmart in their home planet.
For more details on what Symbiotes feed on, I shall redirect you to What does the Venom symbiote subsist on? (disclaimer: one of the answers there is mine)
Food of the mind, and self-definition
Klyntar planet seriously lacks art, music, literature, in a word, culture. All the Symbiotes have is their hosts, and as such, the relation between a Klyntar and its host is sacred because it shapes their history; even more so when you know that Symbiotes retain memories of their previous hosts. That defines them.
Panel below is taken from Venom #3 (2017).

For self-control
For all their powers, Klyntar also have their fair share of weaknesses, the main ones being fire and some sonic frequencies. When faced with one of these, they're not good at self-control. Think freaked-out dog. They will not think straight, they might attack those around, and hurt innocents - which is the very thing they try not to do. As such, the host is there to keep things in charge.
Panel below is also from Venom #3 (2017).

For vesseling and environment awareness
Knull, who is basically a deity and the origin of all Symbiotes, describe his origin in Venom #4 (2018) (nb: that's not the same series as above). After being beaten up and stranded on a desert-like planet, he discovered he could bond with the "lesser creatures" that were there, and that such symbiosis could be of use to gather information around. This was the first instance of symbiosis.

Worth to notice anyway, that most of the things above apply for "good" Symbiotes. Rogue ones (some incarnations of Carnage come to mind) tend to be a bit more on the "just want to kill and it's easier with a host" vibe. Then again, one does not simply try to understand why those would do the things they do; sometimes you need a monstruous-looking alien to do what's expected of it, meaning go around and mindlessly kill people.
Answer: When the Venom symbiote was healed by his people, we got the following explanation of why the Klyntar seek to bond with others:

So, apparently, Klyntar bond to hosts not purely for survival, but to become cosmic do-gooders (or, as stated in the Venom: Space Knight series that followed this event, "Agents of the Cosmos".
Or, for shorter term reasons like communication (as happened immediately before the scene above; the Guardians allowed Klyntar to bond to them, because that was the only way the Klyntar could fill them in).
We saw some support of this idea (that the Klyntar as a rule don't require a bond for survival) in the recent Venomverse / Poison-X / Venomized trilogy; the Poisons (some sort of extradimensional race that can take over other bodies if the others are bonded to a symbiote, killing the symbiote and the other's mind in the process) kidnapped basically the entire Klyntar race from their homeworld, performed some sort of genetic modification to make it practically impossible for a human and to separate once joined, and forced them to bond to humans with powers. At the end, the KLyntar (as a race) were perfectly happy to be separated from their forced bondings, and go back to their homeworld (as seen at the end of Venomized #5).
So, to answer your question - a symbiote doesn't need to bond to a host; normally, they can survive indefinitely without bonding to anyone.

Why does the Symbiote need a host?


RPi2 Windows IoT and UWP

Question: I've been working on FTP server for RPi but Windowss UWP sandbox is a real nightmare for me. I need full privilages to the file system on RPi which sandbox doesn't want to accept. Can I build app for RPi without UWP? I know I'll probably lose GPIO support but FTP doesn't need GPIO anyway...
Answer: Since I don't need to have access to gpio with this app, I can create a Win32 project, add ARM platform to it, compile and then copy it to RPi via built in Win 10 IoT FTP. You can then start your app using SSH (PowerShell or cmd).
Comment: Yeah you can't run Universal Apps that way.. But you can register them as default app so they will start when RPi starts..
Comment: Oh very nice solution (if you dont need GPIO) can you please update your answer with the command you used to start the app from cmd? (Also, please mark it as accepted if it worked for you)
Comment: @ppumkin use any SSH (like putty for example), write .exe path ("C:\IoTApps\YourApp.exe" for example) and press enter. From PowerShell use: & "C:\IoTApps\YourApp.exe" PS.: sorry for delay
Comment: Ohh right, I thought I tried that and didnt work, but I suppose it was a Universal App and not a Win32 App. Cool

RPi2 Windows IoT and UWP


Hollywood movie that took longest to create

Question: What Hollywood movie did take longest to create? By 'the longest' I mean full production until it made it to the theaters.
Comment: I'm sure _Boyhood_ took a while.
Comment: That would be my winner, as it was designed from the start to be in continuous production for so long, it wasn't an accident of scheduling.
Answer: If the John Carter (2012) answer from Dr R Dizzle isn't what you are looking for this it's this:
It's a box office & Yahoo offer the answer.
The Thief and the Cobbler
The animated movie The Thief And The Cobbler holds the record for a movie to be in production for the longest time. It was in production stage for 31 years. (1964-1995)
Then there's Love & God (1986) directed by K.Asif. He started the film in color after Mughal-E-Azam casting Guru Dutt & Nimmi. Guru Dutt died in 1964, shooting came to a halt. Then, Sanjeev Kumar was taken in the place of Dutt, but Asif himself died in 1971. The film was left incomplete. Later in 1986, Asif's wife revived the film & released it in the incomplete form. Sadly, one year before it's release, even Sanjeev Kumar died.
Comment: I think Pakeezah took longer to complete. Work was started in 1956, after which Meena Kumari and Kamaal Amrohi seperated, It was started in B/W and then Kamaal Amrohi restarted the project when color technology arrived on the scene. The film was finally released in 1972. The song Inhin logon ne was shot on July 16, 1956.
Answer: Although this might not be exactly what you are looking for, John Carter (2012) first entered production in 1935 as a hand drawn animated film, which means John Carter was in production for nearly 80 years before it was eventually released.
Comment: But can this really tracked down to ultimately be the same project developed over all this time? Or was it just someone starting a new John Carter project now end then, dropping it again and then someone else making a new try years after that?


When Should I Stop/Start an IIS Application Pool?

Question: I was told that every time I refresh our web site, either individual pages or the entire site, I should first stop the application pool, update my website file or files, then start the application pool. My web site files consists, of HTML, JS, ASPX, INC, GIF, JPEG, CONFIG, etcetera. I'm asking because I believe I have updated my site without stopping the application pool and starting it, and also by stopping and starting it, just trying to find out what the correct approach should be.
Answer: It really depends on what changes you're making. If you're just updating a config file then often you don't even need to recycle the app pool, let alone stopping and starting it. Whereas if you've changed some asp.net stuff, then recycling the app pool is usually required, but once again, a stop and start is not usually required.
Here is a good explanation of exactly what happens when you recycle an app pool and/or reset IIS. Give it a read and you should get a better understanding of when a stop/start is required.
http://fullsocrates.wordpress.com/2012/07/25/iisreset-vs-recycling-application-pools/
Comment: I looked at the linked article and it was very informative. Thanks for your help and quick response.
Answer: You don't have to recycle or re-start your application pool when you update your site. Neither for adding/updating files nor for updating your web.config.
IIS picks up all changes automatically.
Reasons for why you may want to recycle include:

The application pool hangs and no longer serves requests.
The application pool uses too much memory or your app has a memory
leak.

By default an application pool is recycled every 29 hours, so usually you'll never have to recycle an app pool manually.
Comment: Thanks Peter very helpful! This will save me some unnecessary work I was doing.


Installing OpenERP on Ubuntu

Question: Is there anything better than the official documentation for installing OpenERP on Ubuntu?
Answer: The Open Sourcerer described all the steps for installing manually from source, and Iñaki Fernández published a script for doing it all automatically.
I've used the script for several releases now, and it handles updates well. It just grabs the new revisions from a Launchpad branch.
I haven't tried the Open Sourcerer instructions, but I didn't notice anything obviously wrong when I read through them.

Installing OpenERP on Ubuntu


Still waiting for prospective PhD to reply to my email after sending the provisional research title!

Question: I am still waiting to get an answer from my prospective Ph.D. supervisor.
On July 15, 2019, I have sent my master transcript and initial statement of research upon his request, and a week after I sent him another e-mail in a very polite manner to make sure that he could open my file without difficulty, but there was no reply. As the university located in New Zealand I am sure they are not in the mid-semester break, I told them that I am going to apply for July 2020, I do not know what to do now. Should I dismiss this case and go for another supervisor, or send him another email to see what is going on? or should wait a little bit longer? At first, he showed his eagerness and told me that he had to talked to his colleagues about my research proposal and interest and then let me know about the outcome. Thank you guys for your answer.
Comment: Welcome to the site!
Comment: What action are you looking for?  A statement that says "If you apply, and you get accepted, I can take you on as a student"?
Answer: Remember your prospective supervisor is only human, with their own personal life, obligations, and work load. Semester 2 started in New Zealand around 22 July and I imagine it is a very busy time for whoever you contacted. They likely have a very full inbox.
It's been long enough for a polite email asking if they saw your previous message and if they would like any further information from you.
Comment: Thank you for your answer.
Answer: Academics tend to get a ton of email, and their attention tends to be split lots of different ways. My guess is that the supervisor plans to read your email carefully and then reply, and hasn't done so yet. Alternatively, the outcome might depend on external factors (e.g. availability of funding), and the professor might be waiting on that.
If the application deadline is soon, or for some other reason you need a reply soon, then you could send an email asking about the status. Otherwise, I would recommend waiting a bit longer.
Comment: Thank you very much, yes, , yes, he asked me before if I need scholarship or not. Maybe he is looking for this.


Storage DNA Condition

Question: It is possible to store a digestion of cells with lysis buffer several days at -20 degrees and then proceed with the phenol chloroform isoamyl purification?
Comment: Strictly speaking your answer will depend on what you want from the sample and QA requirements etc - can you elaborate a bit?
Answer: Should be fine, but if I were you, I'd spare a few more minutes and carry on until ethanol precipitation (15 min of work at worst). Here's the protocol:
https://www.thermofisher.com/pl/en/home/references/protocols/nucleic-acid-purification-and-analysis/dna-extraction-protocols/phenol-chloroform-extraction.html
You can store it in -20 degrees for several days (extend the overnight incubation, that is the second step of ethanol precipitation) and you'll have the certainty that it will stay ok. In fact, freezing in most buffers, whether lysis buffers or extraction buffers shouldn't significantly hurt any nucleic acids. From my personal experience: I've frozen plant material in extraction buffer for RNA isolation (TRI-zol method) in -80 for a few days and got very high concentrations in most samples in the end. I was told freezing in -20 would impact quality but RNA is generally less stable than DNA.
If you had little to none material, you're better of doing the precipitation procedure and then freezing it. If those are minuscule amounts and/or you work with something sensitive like forensic evidence, following through with the procedure will be the most reasonable solution.

Storage DNA Condition


Understanding "V'haya"

Question: Being that the Medrash Rabba (Vayikra 11:7) explains every mention of the word "v'haya" refers to simcha, how can we understand Bereshis (12:12) where the pasuk begins with v'haya yet continues with a discussion of the dangerous fate of Avraham and Sara entering Mitzrayim?
Answer: The Midrash Vayikra Rabbah 11:7 says the following:
(Sources provided by Sefaria.org)

.אתא ר' ישמעאל: עבדה פלגא, כל מקום שנאמר ויהי אין שמחה, והיה אין צרה
Rabbi Yishmael came (and said): Do half 1, any place where it says ויהי there is not Joy, (and here it says) והיה there isn't suffering

(The following is my humble opinion, please take it with a grain of salt)
It is to be noted that by the Akeda, Rashi comments on the verse (22:5)

וַיֹּ֨אמֶר אַבְרָהָ֜ם אֶל־נְעָרָ֗יו שְׁבוּ־לָכֶ֥ם פֹּה֙ עִֽם־הַחֲמ֔וֹר וַאֲנִ֣י וְהַנַּ֔עַר נֵלְכָ֖ה עַד־כֹּ֑ה וְנִֽשְׁתַּחֲוֶ֖ה וְנָשׁ֥וּבָה אֲלֵיכֶֽם׃
Then Abraham said to his servants, "You stay here with the donkey and I and the lad wil go up there and we will worship and return to you"

the following:

ונשובה: נִתְנַבֵּא שֶׁיָּשׁוּבוּ שְׁנֵיהֶם
ונשובה AND WE WILL COME BACK — He prophesied that they would both return (Genesis Rabbah 56).

It could be also here that Avram also prophesied that they would both be safe and benefit from this venture.
By 12:12, though it was dangerous for both Avram and Sarai, the result of the venture ultimately lead to Avram amassing much wealth (as demonstrated in 12:16) without Sarai or him being harmed in the venture (see 12:17-20 with Rashi and the Chizkuni on 12:17). That being said, it could be reasonable why the word "והיה" is used.
Hope this is insightful.
1 See context discussed there.

Understanding "V'haya"


high resolution (< 1.24km/pixel) physical map with global coverage?

Question: I find ESRI's World Physical Basemap very good because you can see 1) topography, and 2) habitat. However, the problem is that it isn't very fine resolution (1.24 km/pixel outside the US), so it's only really useful for broader scale maps.
Does anyone know any high-resolution (<1.24km/pixel) physical map with global coverage?
Comment: I don't think that exists.  Global land coverage, perhaps, but global coverage, probably not.
Comment: "Blue Marble" is down to 250m / pixel. Otherwise some of the Natural Earth stuff might be useful, although it shows physical rather than cultural. How fine do you need?
Comment: 250m / pixel might be good enough, and it's certainly better than 1.24km / pixel. I haven't looked at Blue Marble for years - I'll go back and have another look at it. Thanks.
Answer: I think that the EarthEnv project (http://www.earthenv.org/) might have a lot of what you need. While most of the non-elevation data is at the 1km resolution, the reprocessed DEM available there is at a 90m resolution.
Another potential source of data is from government agencies themselves (one such listing of most available government data is here: http://www.opengeocode.org/opendata/). If there is a place in particular that you're looking into, the respective government agencies might have something available.


How to use alphabetical autocomplete?

Question: Mathematica maintains a file with the history of commands input by the user (under <code>$UserBaseDirectory/.Mathematica/SystemFiles/FrontEnd/SystemResources/FunctionalFrequency/</code>), so as to provide better suggestions in autocomplete. However I personally prefer a more consitent experience, where I always get suggestions in alphabetical order. Is there a way to configure autocomplete so that suggestions are always listed in alphabetical order, instead of using cues from my history?
Comment: See also: http://community.wolfram.com/groups/-/m/t/806341
Answer: Not currently.  You should understand though that data from your autocompletion history is just one factor that determines the order of completions.  There are other terms in the weighting equation which come from other sources of usage data in a given context.  Strictly alphabetical ordering can be problematic too, and you may wind up typing more characters to narrow things down.
Comment: Would you be willing to complete the missing information [here](http://mathematica.stackexchange.com/a/129910/12)?  What I want specifically is to be able to autocomplete something else than a simple string in an argument.  Example: one of the completions offered in `GraphData` is `{"Knight", {2, 3}}`, which is a list, not a string.  Is this possible without using `.trie` files?  If not, do we users have access to tools to create such `.trie` files?
Comment: Another question: can we set up auto-completion for option values for user-defined functions?  [Here's the question](http://mathematica.stackexchange.com/q/78935/12), but the existing answer is about modifying the Mathematica installation.  I am not interested in doing that.  All I want is some option value suggestions for certain options/functions I defined in my own package.  It's to make the package more user-friendly.

How to use alphabetical autocomplete?


Contractor v homeowner. Disparagement clause

Question: My husband and I would like to complete a remodeling job on our home. The relationship between us and the contractor has gotten tense as there are many errors that need correction. We have sought estimates for repairs from other contractors. Before the original contractor will approve the estimates to be deducted from our final payment the original contractor is trying to force us to sign a non disparagement contract. Can they do this legally?
Comment: FYI. We are in California. I thought California does not allow no disparagement clauses on consumer exchanges.
Answer:
the original contractor is trying to force us to sign a non disparagement contract. Can they do this legally?

Apparently not (see here). But even if it were lawful for the contractor to pursue a non-disparagement contract, that does not mean you are required to enter it.
Entering a non-disparagement contract (assuming it were valid at all) would put you in a risky position, since you inevitably will have to talk with others (e.g., other contractors) about this contractor's flawed job. This contractor might opt to (ab-)use his awareness of those communications as an excuse to disavow the agreed deductions; namely, by alleging that your portrayals of his job are tantamount to disparagement.
Instead, it is in the contractor's best interest not to oppose your attempts to remedy the situation (i.e., by approaching other contractors and deducting from the final payment to him). That is because the repairs you are pursuing were caused by this contractor's poor performance. That poor performance might constitute breach of contract on this contractor's part.
As for trying to "force" you to sign a contract, it should be pointed out that contracts entered by coercion are null and void. However, it will be difficult for you to prove that you were forced or coerced to sign the contract. Although one can imagine the contractor being pushy on this issue and you might feel forced or overwhelmed, your description does not reflect that the circumstances or this contractor's method(s) amount to coercion.
Comment: @ScottDunnington The clause certainly *is* a form of settlement agreement, but it would not be cognizable as "independent" of the original/consumer transaction. Otherwise, all suppliers would defeat legislative intent by offering their products & services at an excessive price together with an optional non-disparagement clause disguised as condition for "discount" (so as to bring the price down to an acceptable level). A contractor who truly intends to avoid a lawsuit for breach would not attempt to subject the customer to the heightened risk outlined in the 2nd paragraph of this answer.
Comment: Could the clause be considered a settlement agreement and not a consumer transaction?  Essentially it's a tactic in negotiations to avoid a lawsuit for breach.


Office 365 Groups vs MS Teams

Question: Major differences between Office 365 groups, Team sites. As I referred some links which are saying both are same. Both will create the SharePoint modern site. Then why we need both?
Answer: They are both exactly the same.
MS teams is just another front from which you can create Office 365 group enabled modern team site.
You can create these sites from multiple point of contacts like SharePoint, Teams, Outlook , Admin center etc.
MS has just provided multiple fronts from which you can create these. The end-result is exactly the same i.e Office 365 group enabled Modern team site with associated baggage of Outlook mailbox, planner, Teams, Stream, OneNote etc.
The only minor difference I found was that, whenever we create it via Teams, it is by default associated to a Team. But if created via SharePoint, we need to manually associate the Office 365 group to a Team. Other than that, it provisions all the same artefacts.
Answer: Here are two great articles on groups, and the last one is a video of a comparison of the two features of Office 365 and more what I think you are looking for:
Office 365 Groups – What You Get and What to Use:
https://en.share-gate.com/blog/groups-for-office-365
Office 365 Groups Explained:
https://en.share-gate.com/blog/office-365-groups-explained
Office 365 Groups vs SharePoint Team Sites:
https://en.share-gate.com/blog/microsoft-modern-workplace
I hope the last one, the video helps!
Happy SharePoint-ing!
Answer: Microsoft Teams and Office 365 Groups both provide collaboration services for groups of people.
Teams and Groups isn't oranges to apples but yin to yang, two halves forming the full picture; Groups is how you share your resources, and Teams is how you talk about what's being shared.
The most notable difference between the two is the chat feature in Teams.

Office 365 Groups vs MS Teams


Schedule a powershell script

Question: I have a powershell script to delete a list . I want to schedule it to run once a year . Is there a way to schedule a powershell script ?
Comment: Why don't you write a C# Console Application and use Task Scheduler to schedule it yearly ?
Comment: i have powershell script ready , dont wnt to write code again .
Answer: Use Windows Task Scheduler. I sometimes use it for console applications. You can schedule the .ps1 file to run at yearly intervals.
http://windows.microsoft.com/en-ca/windows/schedule-task#1TC=windows-7
Answer: You can run this as a Windows Schedule task to run once a year.

load Task Scheduler from Start > All Programs > Accessories > System Tools
create a new scheduled task, click Create Task from the right-hand "Actions" panel. At a minimum, you should fill out the following information:

General Tab

Name of the task – e.g., Intranet Backup. A description is also
useful, but not mandatory
Ensure the user account running the task has the following
permissions:
Log on as a batch job rights in the User Rights Assignment section of
the server Local Security Policy. These rights could be set on the
server itself or by Group Policy if managed from Active Directory –
see http://technet.microsoft.com/en-us/library/dd277404.aspx for
details
Permissions to use PowerShell on the SharePoint farm. You can add
these for a new user by running Add-SPShellAdmin –UserName
domain\username in the SharePoint 2010 Management Shell console as a
current administrator – see
http://technet.microsoft.com/en-us/library/ff607596.aspx for details
Permissions to be able to perform the script operation in SharePoint.
For example, for the site collection backup in this example, the
account used in the scheduled task required:
dbo access in SQL to the database hosting the site collection
Membership of the local Administrators group on the server – you may
be able to experiment with fewer permissions than this, but this was
required on my development server, which is also a domain controller
Select Run whether the user is logged in or not and tick the Do not
store password checkbox
For certain operations, you may also need to enable the Run with
highest privileges option. As this should only be enabled when
necessary, I would recommend testing the script from Task Scheduler
with the option disabled and only enable if the script does not work
without it

Triggers Tab
Click New and add your schedule, as required. In the example below I am going for daily at 2:00AM
Actions Tab
Click New. Ensure the action is set to Start a program and type Powershell.exe in the "Program/Script" box. In the "Add arguments (optional)" box, type &'c:\scripts\script.ps1' replacing the path and name with the details for your script. Wrapping the file path and name in single quotation marks allows you to specify spaces in the text.
When you click OK to confirm task creation, you will be prompted to enter the password for the account you selected to run the script. Enter the password and click OK.
You should now see your script in the Task Scheduler Library (if not, click Refresh in the right-hand panel). To test the script, highlight it in the console and click Run from the right-hand panel.
Check that the changes required are performed (for this example it was checking to ensure the backup file was being created in the folder when the task ran) and leave it to run on the schedule. Don't forget to perform regular checks in the future to test the script continues to run as expected
http://get-spscripts.com/2011/01/running-sharepoint-powershell-script.html
Comment: Since i do not have arguments . I did set the "Program/Script" box directly to script : powershell -file "C:\NIKHIL\Powershell Scripts\ArchieveSitelistToNewList.ps1" . I can directly type in run and make the script work . So this also work . http://blogs.technet.com/b/heyscriptingguy/archive/2012/08/11/weekend-scripter-use-the-windows-task-scheduler-to-run-a-windows-powershell-script.aspx

Schedule a powershell script


Visa for traveling to Italy

Question: My visa will expire on 10 February. Can I still travel to Italy and come back before my visa expires?
Answer: You can use the visa until the very last day of its validity, provided you also fulfill all other conditions (including the number of entries, maximum stay in the Schengen area, having a valid purpose, financial means, etc.)
Do note that in the Schengen area, your visa must also be valid until the last day of your stay. Consequently, if the visa is set to expire in the next few days, you might be asked about your plans.
If your visa is a short-stay Schengen visa, you should be prepared to explain how you plan to leave the country in time (ideally show a return ticket) or somehow switch to another status (apply for a residence permit, get a new citizenship, etc.). If it looks like you actually intend to stay longer without proper documentation, you could be denied entry or even see your visa revoked.
Unlike the visa, your passport (or travel document) must be valid for three months after your intended departure date (so if your passport also expires on February 10 then you cannot go to Italy without getting a new one).
Answer: Very much like in this question your visa is valid from 00:00 on its start date, to 23:59 on the date of expiry. So yes you can travel to the Schengen area, as long as you leave before the visa expires.
Having said this, you might have exceeded the maximum number of entries allowed on a single visa. Your visa might in fact be either single-entry, or multiple-entry. It's up to you to check which one applies to your specific case.
Comment: A Schengen visa can also have two entries.

Visa for traveling to Italy


Truncate Custom Attribute Label/Options using SQL Query

Question: I am using Magento 1.9.x.
I have created several custom attributes in Magento project. They all have thousands of labels or options. I don't want to remove custom attribute just want to delete all their values only.
For example I have one attribute as Manufacturer and 1200 options for that attribute now I want to delete all values of Manufacturer Attribute.
How can I do this using SQL queries?
I am following below process

Get attribute_id from Table: eav_attribute by searching attribute_code (In my case it is "manufacturer" and attribute_id is 81)
In table eav_attribute_option, searching 81 under attribute_id field will get us all option_ids
By taking all id's in eav_attribute_option_value, I am searching under option_id and getting value field and removing.

Final Query would be like:
DELETE eav_attribute_option , eav_attribute_option_value  FROM eav_attribute_option  INNER JOIN eav_attribute_option_value
WHERE eav_attribute_option.option_id= eav_attribute_option_value.option_id and eav_attribute_option.attribute_id = 81

To perform such action for multiple Custom Attributes I need to run this query for multiple time.
Any specific solution??
Comment: http://stackoverflow.com/a/14252142/7089203
Comment: Thanks @GopalPatel I don't want to do it using Magento Programming. I want to achieve this using SQL Queries.
Answer: Find Below Query
To view Options
SELECT `option`.`attribute_id`, `option`.`option_id`,
        `attribute`.`attribute_code`, `value`.`value`
    FROM `eav_attribute_option` AS `option`
    INNER JOIN `eav_attribute` AS `attribute`
        ON `attribute`.`attribute_id` = `option`.`attribute_id`
    INNER JOIN `eav_attribute_option_value` AS `value`
        ON `value`.`option_id` = `option`.`option_id`
        WHERE `attribute`.`attribute_id`=81

To Delete Options
DELETE `value`,`option`
    FROM `eav_attribute_option` AS `option`
    INNER JOIN `eav_attribute` AS `attribute`
        ON `attribute`.`attribute_id` = `option`.`attribute_id`
    INNER JOIN `eav_attribute_option_value` AS `value`
        ON `value`.`option_id` = `option`.`option_id`
        WHERE `attribute`.`attribute_id`=81


Making circular actions without inserting keyframes manually?

Question: I want to move my bone in a simple circular motion in the xz-plane in an action. I have tried to insert my keyframes manually to move in a circle, but it is always bumpy and I have a hard time making it loop. Is there a way to get it to loop in a circular motion in an action without "drawing" it with your own manual keyframes? I'm already bad at drawing circles. Or is there another way to go about it?

Thanks a bunch!
Answer: Method for a primarily 2D context.

 RMB select the foot bone and go into edit mode of the armature. ↹ Tab
Create a parent bone at the position, you wish to rotate the foot around. ⇧ ShiftA Bone.   RMB select the foot, then ⇧ Shift RMB select the parent, and parent them with an offset. ⎈ CtrlP > Keep Offset.

Select the child and in the Properties context, in the bone tab, in the Relations section, uncheck Inherit Rotation.

Go into Pose Mode ⎈ Ctrl↹ Tab. Select the parent, key the parent at a rotation of 0°, then at a rotation of 360° a few frame later. Locate the keys in the dopesheet and select them. Press ⇧ ShiftE > Make Cyclic, to make the rotation action loop. Press T > linear, to transform it into a linear motion.

Alternatively to the cyclic repetition, you could press ⇧ ShiftE > Linear Extrapolation.
Comment: Thanks for the great, easy to understand method. This should work perfectly. :D
Comment: I tried it and it didn't work, but then I realized it because I was in quaternion mode so I changed it to XYZ Euler mode and that made all the difference. I have no idea what in the world those modes are, but it works now, so I'm happy. Thanks again. :)


Get Google Backup and Sync to only sync one file at a time instead of three?

Question: I have Google Backup and Sync set to upload all files in a folder to Google Drive. The default behavior seems to sync 3 files simultaneously. Is there any way to set it to sync only one file at a time?
Answer: I am having this exact issue.
The files are 360 video files, about 4 GB each, and an hours recording can produce 6-10 of them. Backing up the videos can take DAYS...even if leaving the computer on overnight!
I suspect that if only a percentage of the file is backed up before I need to shut down, that is lost and the process starts over from scratch when the computer is turned on again.
I just hit on a potential workaround this morning.
Copy (or move) one file at a time into the synced folder, which forces Backup and Sync to work on only one file at a time.
Tedious? YES!
But the files do eventually get completely saved in a reasonable amount of time as opposed to three files that only ever get to 15-20% because I needed to shut down and go to work.


Query on Guillotine press

Question: I have been doing the guillotine press for two weeks due to the unavailability of an incline bench at my gym. I heard that it can cause serious rotator cuff injury when used long term. I wanted to know the method to perform this exercise safely and some rotator cuff exercises that can help mitigate rotator cuff injuries caused by guillotine press.
Comment: Do you currently have rotator cuff issues?
Comment: I never had a rotator cuff injury. Four years back I had an anterior shoulder dislocation. That's the only injury I had in the past.
Answer: It is safe to assume that any exercise invented by the bodybuilder Vince Gironda is just risking one's joint health in futility, many people got injured because of the  ignorance spread by that guy, he literally took normal exercises and transformed them into joint destroying ones.

Query on Guillotine press


Malware spreading via installation media

Question: Imagine user downloads and burns installation USB stick on their compromised Linux system. Are there any known malware that is capable of spreading via Linux distributions installation media so that after reinstallation system is still compromised through installation media? Or it is hard to automate and rather subject of targeted attack?
Answer: I am not aware of anything that would compromise a installation media while the user is writing it. It's possible to do something like that, but it would be a very focused attack.
An attacker would need to know the installation file and the burning software. There are a lot of ways to create a installation USB media (dd, unetbootin, USB Image Writer, for example), so the attacker would need to monitor all of them, intercept the read or write, and compromise the request.
Possible, but it's easier to change the DNS and direct the user to a rogue download site.
Comment: Why can't it just detect media containing boot records and try to put malware there? Is it too much there to keep this kind of attack generic to certain degree?
Comment: It's complicated. If you have root access on a Linux system, compromising the DNS servers is way easier and faster than to monitor every read and write operation.
Comment: You wouldn't need root access.  The malware would just check mounted drives for a folder structure resembling install media for a popular distro (Ubuntu) and attempt to replace some of the binaries on that drive (sudo, or another executable which runs as root), then any system installed via that media would be compromised.
Comment: To create a USB install media, you need root. You don't `fdisk` as normal user. Nor you `dd of=/dev/sdb` as well.
Answer: This question, like many others, falls under the category "yes, it is possible, but not widely seen in practice".

Is there known malware that spreads via Linux distribution installation media?

I didn't find anything exactly like this after performing a quick Google search. So it seems like not much is out there.

Or it is hard to automate and rather subject of targeted attack?

Not really. I have some scripts lying around that make changes to the distribution's installer image, given an ISO file. Once you know how to correctly unpack and pack different installers from their ISOs, it's not too hard to automate whatever changes you want to make. It also wouldn't be too hard to periodically scan for ISO files and infect them when found.


Notation for blind people?

Question: Let's assume a person can no longer see, but he can play a musical instrument. He wants to read notes and learn new pieces. Is there any kind of notation system for such blind people?
Comment: There is definitely a braille system for music. The Spanish composer Joaquín Rodrigo was blind and composed the famous *Concierto de Aranjuez* in braille.
Answer: There is a braille system for music that uses the same 2X3 configuration of dots as literary braille, but ascribes different meaning to the patterns. The Wikipedia page about musical braille lists the most common symbols.
The National Federation of the Blind maintains a page dedicated to braille music resources.
Here is a link to a non-profit project to provide braille sheet music for visually impaired musicians. Braille sheet music can be downloaded for free here, or printed copies can be requested for those who don't have access to a braille printer.
Answer: Yes.  Blind musicians can use Braille to learn new pieces, but there is only a limited amount of music available in this form.  Learning by ear is an important method too of course.

Notation for blind people?


Are there any tutorials on Bayesian probability theory or graphical models by example?

Question: I've seen references to learning Bayesian probability theory in R, and I was wondering if there is more like this, perhaps specifically in Python?  Geared towards learning Bayesian probability theory, inference, maximum likelihood estimation, graphical models and the sort?
Comment: Is Bayesian **probability theory** any different from regular probability theory?  I agree that Bayesian _decision theory_, Bayesian _inference_,  Bayesian _estimation theory_ etc. do differ significantly from the frequentist versions of these two topics, but probability theory is the same for both camps, no?
Comment: Thanks, poor use of terminology :) What word would I use to encompass those topics?
Comment: Are you interested in coding or math?  If the former, how about "programming Bayesian estimation procedures..."?  Also, maximum likelihood estimation isn't Bayesian, except asymptotically in almost all cases.
Comment: Really both.  I want to really understand the math, but I've found that methods shown by coding seem to solidify understanding, kind of like the 'Think Stats' series for basic statistics in python :)
Answer: Starting late January 2012, a 10 weeks course on the topic of Probabilistic Graphical Models will be held online for free by the Stanford Professor Daphne Koller. It's considered a natural continuation of Andrew NG's ML course, and if it's anywhere near Andrew's, it's going to be of exquisite quality.
There is also mathematicalmonk's - free youtube videos covering many topics like MLE, Bayes networks, they are more math heavy.
ai-class course units 3.x Probability in AI and 4.x Probabilistic Inference (if you create an account on http://www.ai-class.com you may see them in a nice ordered interface)
More:
http://www.cs.ubc.ca/~murphyk/Bayes/bnintro.html
http://mtnwestrubyconf2007.confreaks.com/session03.html
Answer: Great use of ipython notebook and learning Bayesian methods is Probabilistic Programming and Bayesian Methods for Hackers. If you are using the Ipython /Scipy stack, you can download the notebook and run the example code locally; it's interactive console is great for learning, testing, and writing Python.
Ipython: http://ipython.org/
Comment: Very Python indeed.
Answer: If you really want to learn fundamental concept of Bayesian statistics, definitely you should read Bayesian data analysis written by Andrew Gelman. I encourage you do the exercise. You will learn much from it. Doing the math of Bayesian statistics is an important step for you to learn Probabilistic Graphical Models. It seems you are freshman to Bayesian concept. DO NOT read Probabilistic Graphical Models hastily if you have not learnt any basic concept and not familiar with the Bayesian mathematical calculation. you know my suggestion If you have read the video lectures from Stanford provided by Andrew Ng.
Answer: Just came across this MOOC "Autonomous Navigation of Flying Robots" (https://www.edx.org/course/autonomous-navigation-flying-robots-tumx-autonavx-0). In the course the instructors teach participants how to programme (in python) a flying robot for autonomous navigation, exploiting Bayesian statistics for states estimation and other useful techniques (e.g. Kalman filtering of noisy sensor input). The nice thing is that the code that one writes in class is usable for some commercially available flying robots, so one can later play more around with this and seek possibilities how to improve Bayesian state estimation.
For the Ipython Notebook "Probabilisic Programming & Bayesian Methods for Hackers", I can also highly recommend it. Haven't come across such a well accessible and comprehensive hands on introduction before and really learned a lot within a relatively short time!
Comment: Please clearly explain the connection between your first link and the question. Your second link is already covered in another answer.


Stuck tub drain

Question: I am having trouble removing a tub. Specifically, I cannot seem to loosen the drain. I've tried a proper tub drain wrench, but it still won't budge. Any ideas how I can get this thing to loosen?
Answer: I presume these are normal threads and you are trying to turn the wrench counter-clockwise to loosen, right?  :-)
It sounds like there may be corrosion involved, which will make it difficult to loosen. It could also be good old-fashioned pipe-dope that is thoroughly set and hardened.
A longer handle on that wrench might help (Archimedes, levers, etc.).
Also, impact can help a lot. Tapping it with a hammer while trying to turn it might do the trick. Or pounding the handle with a hammer in a counter-clockwise direction might do it.
Once you get it to start turning, the rest should be easier.
Of course, depending on your tolerance for replacing part of your plumbing if it breaks, enough raw physical force can solve a surprising number of problems...
Comment: You could try heating it up a bit, sometimes that will soften old plumber's putty and pipe dope. And like @Craig mentioned, try harder! I sometimes use the handles of my Channellock pliers to grab the "cross" strainer, and turn it with another large wrench.
Comment: FWIW, "raw physical force" was the solution. Took a big pipe wrench to turn the drain wrench, but it eventually loosened up. Thanks!

Stuck tub drain


HHL Algorithm: Relation between Eigenvalues and condition number

Question: I have been going through the original HHL paper (2009), and I see that they call a linear system of equations "well behaved" / "well-conditioned", if
$$ |\lambda| \in \left[\frac{1}{\kappa}, 1\right]$$
where $\kappa$ is the condition number. I am not that strong in Linear Algebra, but it is very obscure to me why they are combining eigenvalues and singular values. Could someone explain why this is being done either in the context of this particular algorithm, or in general?
Answer: In the HHL algorithm, they are solving a linear system $Ax=b$. This is achieved by embedding $A$ into a Hermitian matrix such as
$$
H=\left(\begin{array}{cc} 0 & A \\ A^\dagger & 0 \end{array}\right).
$$
If $A$ has singular values $\lambda$, then $H$ has eigenvalues $\pm\lambda$. So to all intents and purposes, they are the same thing in this context.
For a bit more context, there's basically two things that you need to know about for the algorithm: the spread of the eigenvalues, and how close to 0 the eigenvalues get. The spread is so that you can pick a $t$ such that $e^{iHt}$ has eigenvalues (to be determined by phase estimation) that do not loop past any $2\pi$ boundaries so there's never any ambiguity. i.e. you want $0<t\lambda<\pi$ for all singular values $\lambda$. The second issue is that the main part of the algorithm essentially calculates $1/\lambda$, which is bad news if we've identified $\lambda=0$, so we want to ensure that our phase estimation procedure is accurate enough to be able to detect that the eigenvalues are not 0.
Comment: Could you point me out to a pedagogical resource that captures the nuances of HHL? I've been going at it for a month now, and the semantics are not at all clear.


Analytical Calculation of the Impulse Response of an Arbitrary Filter

Question: This is a rather general question.  Suppose I have an arbitrary filter, $F$, defined in the Laplace domain;
$$
F=k\frac{\prod_i (s+z_i)}{\prod_j(s+p_j)}.
$$
How do I calculate the impulse response of this filter analytically?  As a specific simple example, consider the first order low pass filter
$$
F_0=\frac{1}{s+p}.
$$
To be clear, what I want to get from this transformation is a function which describes the delta function response from $t=0$ to $t\rightarrow\infty$ where the delta function is applied at $t=0$.
Comment: Lookup partial fraction expansion and inverse laplace transform tables.
Comment: @porten That makes sense, rather obvious in retrospect.  Perhaps you could expand your comment into a full answer for posterity?
Answer: Your expression is the Laplace transform of the exponential function $e^{-pt}$. The Laplace transform of the dirac unit is $1$. So the inverse Laplace transform is exactly $e^{-pt}$. Maybe the fact that this function is noncausal adds a little complexity here.


Minecraft 1.7.10 launcher won't launch mac osx maverix

Question: My minecraft lagged so i put the java in the trash and i restarted my macbook pro
after that I got it out the trash and didn't know where to place the file. When later i just put it in the minecraft folder. and i launched minecraft but it did not work so i deleted everything what has to do with minecraft on my mac even the minecraft folder at application support. I re-downloaded minecraft from the website. and it did not start. then I downloaded the newest java and it did not work. does anyone know. what to do because I bought the game and now I can't play.
Answer: Please uninstall your current java, which includes removing ALL files related to it, such as the part that you put in your Minecraft folder (Which you weren't supposed to do, as it probably messed up the path).
Then install java again from the Java website
Answer: Try uninstalling and reinstalling your Java. If that doesn't work, then try removing all things related to Java SE Binary and Java. Then reinstall Java.


How is a finish sander different than an orbital sander?

Question: Other than an orbital sander being circular and a finish being square, I was wondering if there are any other differences.  If I already own an orbital one, does it make sense to add a finish one to the portfolio?  I am currently doing some antique doorway and window trim restoration, I chemically removed the paint and now doing final polishes before I stain and lacquer.
Comment: antique doorway and window molding? i presume that means very few flat surfaces, in which case you will ruin the profiles with any electric sander.  all your sanding will need to be done by hand.
Answer: Anything that sands across the grain on wood puts scratches in the growth rings that can be hard to remove.
Orbital sanders are good for removing homogenous materials like paint where you don't want a pattern to the marks left by the sand paper. As you use finer paper, the random action leaves finer scratches till the surface is smooth.
Finish sanding on wood is a bit different, you want a straight line sander so the abrasive cuts parallel to the wood grain so you can get a smoother surface.
Also, Finish Sanders are available with Random Orbital Action. If you've ever been in a car paint shop, you know it as a DA or Dual Action Sander. The pad is loosely coupled to the orbital mechanism so it doesn't produce spiral cuts in the finish but has a random combination of straight and orbital motion.
Comment: The wood grain may seem irregular, but scratches across the grain are more visible to the eye than scratches that run nearly parallel. At least that's what I've noticed. It's similar to why you plane with the grain and not across it. You get wood tearout going cross grain.
Comment: "parallel to the wood grain" -- but the wood grain is highly irregular in shape.
Comment: so for this application, would you use an orbital or a finish sander?
Comment: @FiascoLabs describes the differences between random orbital and straight line sanders well. This answer, however, may seem to imply that finish sanders are straight line sanders. Some, but not all finish sanders are straight line sanders. There are orbital action sanders sold as finish sanders as well.
Comment: Make sure it says Random Orbital Action for your finish sander, standard Orbital Action leaves small round spirals. As to the application, I would use the orbital action sander to remove the finish and a finish sander during the last fine sanding operations and inspect the surface for marring scratches. Rub it down with a tack rag to remove the dust and give it a visual inspection. Sometimes the scratches show up only after finish is applied, so choose an inconspicuous test piece to get your technique down.


Is the covariance or contravariance of vectors/tensors something that can be "visualized"?

Question: I'm taking an undergrad GR course, and our text (Lambourne) mentions covariant and contravariant vectors and tensors ad-nauseum, but never really gives a formal definition for what they are, and how they are unique from each other in any physical sense (other than their difference in transformations).  Is there any physical intuition behind these two labels?  There should be, right?  If they differ in how they transform with transformation of coordinates, doesnt that indicate that there has to be some way of visualizing their difference, since coordinate transformations are easily visualized?
Answer: This whole business of covariant vs contravariant is very old school. Some very old texts go into ways of visualizing this. I would suggest instead learning about tangent vectors (contravariant) and 1-forms (covariant) and the equivalence between tangent vectors and directional derivatives.
Associate the vector $\vec{v}$ with the derivative operator $\vec{\frac{d}{d\lambda}}$ by saying that there is a curve parameterized by $\lambda$ that has $\vec{v}$ as it's tangent vector.
Similarly, associate to the function $f$ the 1-form $df$. A 1-form is a linear map from tangent vectors onto real numbers. A 1-form $df$ maps a tangent vector $\vec{\frac{d}{d\lambda}}$ to the real number $df \left( \vec{\frac{d}{d\lambda}} \right) \equiv \frac{df}{d\lambda}$.
Once you are comfortable with this idea, you will notice that we can introduce a coordinate system $x^i$ and tangent vectors $\frac{\partial}{\partial x^i}$ and one-forms $dx^i$. Note that from our rule, $dx^i \left( \vec{\frac{\partial}{\partial x^j} }  \right) = \delta^i_j$.
You can then parameterize your curve with the functions $x^i(\lambda)$. Note that from the chain rule
$\vec{ \frac{d}{d\lambda} } = \frac{\partial x^i}{\partial \lambda} \vec{\frac{\partial}{\partial x^i}}$
and you can use what we've produced so far to show that
$df = \frac{\partial f}{\partial x^i} dx^i$.
When all is said and done, you can prove that
$df \left( \vec{\frac{d}{d\lambda}} \right) = \frac{\partial x^i}{\partial \lambda} \frac{\partial f}{\partial x^j} \delta_i^j = \frac{df}{d\lambda}$
is coordinate independent, as it should be.
From there on, you can define arbitrary tensors as multilinear maps taking $n$ 1-forms and $m$ vectors onto real numbers. The utility of this construction is that it is very geometrical and at the same time not tied to coordinates (abstract). You also never have to wonder which way a thing transforms, because it's always the natural way.
I recommend you pick up a good book on differential geometry for physicists. Geometrical Methods of Mathematical Physics by Schutz is OK, his GR book is probably more useful. The bible by Misner, Thorne and Wheeler goes into great depth into this business and has handy visualizations of n-forms if you are so inclined.
Comment: Lionel and Sigma: I'm not sure that Schutz's GR book is as good a reference for geometry as it used to be. True, it does still include the discussion of the one form as you and Mark's answer describe them, but stuff like the Lie derivative and much of the other geometrical discussion that used to be in his book has had to make way for expanded chapters of GR experimental evidence and issues. I think Schutz even says something about using his geometry book together with a second reading of his "first course on GR" in the latter's preface.
Comment: True, I used both simultaneously.
Answer: Here is a visualization from Geometrical Methods of Mathematical Physics by Schutz. The co-vector is here called a "one form". His notation $\langle \tilde{\omega} , \bar{V} \rangle$ is equivalent to $\omega_\alpha V^\alpha$, which you might be used to seeing.

Note that when the magnitude of $\bar{V}$ increases, the arrow gets longer. When the magnitude of $\tilde{\omega}$ increases, the parallel surfaces get closer together.
Physically, vectors and covectors are not meaningfully differet from each other. Mathematically, either can be defined as the dual space of the original, so they have all the same properties. You could switch which one is the arrow and which one the set of parallel lines in that picture. If you choose displacements to be prototypical vectors, then other quantities will be either vectors or covectors depending on how they're related to displacements. For example, velocities are just derivatives of displacements, so they are also vectors. Gradients act on displacements to produce scalars, so they are co-vectors.
Answer: Tensors (or rather tensor fields in case of differential geometry) are very generic and not particularly intuitive objects that can fill a lot of roles - volume elements, endomorphisms, Riemannian metrics are just a few things you can describe with tensors.
However, to get an intuition about co- and contravariance, it's enough to look at tangent vectors and covectors, which can be visualized and are the building blocks of higher-rank tensors.
In differential geometry as traditionally taught in physics courses (mathematicians stopped doing it this way some decades ago), we always work in charts (ie local coordinates).
A vector would be a column vector
$$
\begin{pmatrix}
v^1\\\vdots\\v^n
\end{pmatrix}
= (v^i)_{i=1}^n=v^i
$$
and a covector a row vector
$$
\begin{pmatrix}
w_1&\cdots&w_n
\end{pmatrix}
= (w_i)_{i=1}^n=w_i
$$
with duality pairing
$$
\begin{pmatrix}
w^1&\cdots&w^n
\end{pmatrix}
\begin{pmatrix}
v^1\\\vdots\\v^n
\end{pmatrix}
=\sum_{i=1}^n w_iv^i = w_iv^i
$$
As there is in general no global chart, we need to specify transformation laws and make our vectors and covectors equivalence classes with respect to these transformations.
The tranformations are given by the Jacobi matrix of the coordinate switchover and its inverse, which is obviously necessary to keep pairings invariant.
Now, the coordinates of vectors transform opposite to basis vectors - they are contravariant - whereas the components of covectors transform the same way as basis vectors - they are covariant.
You may encounter the opinion that the difference between vectors and covectors doesn't really matter as in general relativity, you can raise and lower indices as you see fit, which culminates in the idea that there's only a single geometric object - the vector - with co- and contravariant components.
That is in my opinion a pretty bad idea: It only works if there is a distinguished non-degenerate bilinear form available and normally, there's a 'natural' placement of indices due to geometry which might even be relevant to model physical concepts (eg velocity vs momentum in context of Lagrangian and Hamiltonian mechanics).
Besides these technical definitions of vectors and covectors (which do make some sense geometrically once you introduce principal bundles and associated vector bundles, but that's not something typically done in physics courses), there are of course more geometric ones:
We can consider a vector an equivalence class of curves through the same point with first order contact. Similarly, a covector would an equivalence class of real-valued functions at a given point with first order contact.
If we compose representatives of a covector and a vector, we get a function $\mathbb R\to\mathbb R$ and evaluating its derivative gives us the natural pairing.
There are also abstract definitions available: We can identify vectors with their directional derivatives, ie a vector is a linear functional on the space of real-valued functions that respects the Leibniz rule. For covectors, there's an algebraic definition as the ideal of real-valued functions vanishing at a point factored by the ideal generated by product of such functions.
Instead of coming up with definitions for both vectors and covectors, it's enough to define one of those manually (typically vectors) and define the other one by duality, ie as real-valued linear maps.
Now, if you actually want to visualize these objects (as in draw meaningful pictures), the obvious representation for vectors is as little arrows in coordinate space. Now, if there's a distinguished non-degenerate bilinear form available, you can represent covectors via their associated vectors (raising its index) and pairing will just be the Euclidean scalar product.
A second way to visualize covectors would be as (oriented) hyperplane fields, with the pairing as described in Mark's answer. This also does not work for arbitrary manifolds - you need a volume form to do so (this is basically a variant of the Hodge dual with the last step from the Wikipedia explanation omitted).
(If you do not have a bilinear or volume form available, you could of course chose an arbitray local one).
Answer: Although this is saying the same thing as Lionel's answer and Mark's answer from a different standpoint, another idea that I like in describing the tangent space is to think of the one dimensional $C^1$ space curve (or spacetime curve) within the manifold $M$ as a grounding concept. So our fundamental idea is some function ("A Path" or "A Trail") through the manifold $M$ and centred on some point $p\in M$ which is constant for the present:
$$\sigma:(-\epsilon,\epsilon) \subset \mathbb{R}\to M$$
such that  ${\rm d}_t \sigma(t)$ also exists in the same interval $(-\epsilon,\epsilon)$ and such that $\sigma(0) = p\in M$ and $\sigma(\epsilon)\neq p$.
After all one dimensional paths, even if very windy, have made sense to us human and related animals ever since we've needed to find water, food and the way back to our cave!
Then, the tangent space $T_p M$ at point $p\in M$ is the set of equivalence classes of such paths, where we define two such paths $\sigma_1: (-\epsilon,\epsilon)\to M$ and $\sigma_2: (-\epsilon,\epsilon)\to M$ as "equivalent" if their "tangents" are the same at $p$, i.e. if : $\left.{\rm d}_t \sigma_1(t)\right|_{t=0} = \left.{\rm d}_t \sigma_2(t)\right|_{t=0}$. We can then readily define scalar multiples of tangents and additions of tangents: here we must be a little careful because what we are doing of course is implicitly labelling $M$ with one of its atlas's charts so that we are implicity thinking about paths as functions $\sigma:(-\epsilon,\epsilon) \to \mathbb{R}^m$ and their "tangents" ${\rm d}_t \sigma:(-\epsilon,\epsilon) \to \mathbb{R}^m$, where $m$ is the manifold's dimension and this is how we compare paths and declare them to be "equivalent" in the above way. Otherwise, in general, there is of course no notion of the linear operations of scaling and addition in the manifold itself $M$.
So now "contravariant" vectors (or simply plain vectors) are objects that live in such tangent spaces.
Okay, all this is long winded, but my point is that I actually thing of wiggly, squirmy "threads" in families (the latter defined by this equivalence) when I think of tangent vectors and not little arrows. This is something I personally find very helpful as one can imagine something "real" within the manifold itself (and, implicitly through a chart, within our homely and wonted friend $\mathbb{R}^m$) and not simply some idea of "arrows" stuck all over the manifold by some graffiti vandal!
So now, with this concept, we take up Mark's Answer to imagine the one form - or what you're calling a covariant vector (or sometimes covector). Actually, I find the idea of a dual vector space pretty neat, so I generally sit with the mathematician's idea of the one-form. In finite dimensional $\mathbb{R}^m$, a dual vector - a linear functional $\mathbb{R}^m\to\mathbb{R}$ is always an inner product as in Mark's answer (this assertion is the same as saying that $\mathbb{R}^m$ is a complete metric space) and indeed can be represented by its "components" - the values of the functional for the basis vectors of $T_p M$, with all values in $T_p M$ then following from linearity. So this (co)vector (one form) uniquely defines the vector orthogonal to it (modulo a multiplicative constant). The spacing between the level planes of this linear functional defines the "length" of the covector.

if you want to get heavy handed, this is where the Riesz Representation Theorem comes on stage - although you don't need anything like the full strength of this theorem to discuss the ideas here.

Now, if your background is optics like me, you've got a very strong and concrete example of the one form. Namely, the wave vector $\tilde{k}$. This beast forms inner products $\left<\tilde{k},\,\underset{\sim}{r}\right>$ with position vectors $\underset{\sim}{r}$ to give you the local phase of the plane wave component it represents. The maximum rate of change of phase in radians per metre is the length of the covector $\tilde{k}$.
Indeed, in Minkowsky spacetime, the four-wavevector is a one-form - a covector:
$$\tilde{k} = (\omega,-k_x,-k_t,-k_z);\qquad \omega = \sqrt{k_x^2+k_y^2+k_z^2}\,c$$
Now, to go to arbitrary valence tensors, if you haven't got some of the references in Lionel's or Mark's answers, a great introductory discussion is given in the first chapter of Kip Thorne's physics 136 course which is downloadable from here. He talks about all these ideas in terms linear functionals and "slots" for components, rather like you would go about representing and storing these ideas in computer memory (with a countably infinite word size, of course, to represent real numbers exactly!).
An aside about references: I'm not altogether sure that Schutz's GR book is as good a reference for geometry as it used to be (as Lionel makes out). True, it does still include the discussion of the one form as you and Mark's answer describe them, but stuff like the Lie derivative and much of the other geometrical discussion that used to be in his book has had to make way for expanded chapters of GR experimental evidence and issues. I think Schutz even says something about using his geometry book together with a second reading of his "first course on GR" in the latter's preface. So have a browse carefully at the contents of any book you might be thinking of buying - an older copy of Schutz may fit better with you.


What is a Mining Pool, what is it good for?

Question: What advantages / disadvantages does it offer over solo mining?
Answer: A Mining Pool is a protocol for a group of miners to work together, in order to smooth out their mined coins. A miner working alone would generate a block (= 50 Bitcoin) whenever he is the first to find a correct hash. In practice, this happens quite rarely for a single miner.
When several miners are working together in a pool, their earnings are split among all miners (with the pool usually taking some commission). This guarantees an even spread of earnings over time instead of "all or nothing" in solo mining.
One disadvantage of a mining pool is its centralicity - most pools today have central nodes that can be DDOSed, and if not configured accordingly when a DDOS happens the miner will just sit idly instead of reverting to a different pool or to solo mining.
Comment: Exactly. It's just like a lottery pool. Your odds of winning a lottery are very low, so you team up with a bunch of other people and agree to split the winning. This makes your odds of winning much higher, but the amount you win much lower.
Comment: Is there some sort of system that guarantees the owner of the mining pool will redistribute equally the gains if a block is successfully mined ? What prevents the pool owner to claim the entire reward of a block for himself without letting know the contributors of that pool ?


GFCI breaker trips

Question: My 20 amp breaker in my basement to my unattached garage works fine, but when I put in a gfci breaker, it pops as soon as I flip it on, two different breakers. The only thing that is plugged into my garage outlet is my garage opener, and all the wiring is new underground in sealed conduit and 20 amp, frustrating. about ready to put all gfci outlets in the garage.
Answer: Your devices are NEVER broken
Let's be clear about this.  GFCI is a fault-detection device.  It detects ground faults, mainly in appliances, but it can happen in wiring too.  However, ground faults in appliances only happen to other people. YOUR appliances never ground-fault!
So definitely leave everything in the garage plugged in, and don't go unplugging anything to troubleshoot.
Narrow it down
What's left? It could be a hardwired appliance like a lamp, but it would have to go to a neighbor's house, because your lamps don't fail!
It could also be a fault in the wiring.
A hot-ground hard fault would trip a regular breaker.  A soft fault (leakage) might not, but would surely trip a GFCI.  This might happen if a box was getting wet, or if outdoor wiring was leaking (perhaps because it is not rated for outdoor use, e.g. NM "Romex" outside or buried).
A neutral-ground fault will not trip a breaker, but will trip a GFCI.  This could be a bootlegged ground, or a neutral screw touching a ground wire at a receptacle.
Look at the cable to the garage.  Is it /3 cable with a black, red and white wire? That's the problem right there: This type of wiring* is incompatible with single-pole GFCI breakers.  First, the black and red wires need to be on a 2-pole breaker with common shutoff, regardless, for safety - they must shut off together.  Then, you need to use a 2-pole GFCI breaker, because it need to measure all 3 wires - both hots and the neutral.
Another potential problem is if two separate circuits (not MWBCs) unintentionally mix their neutral wires.  That's a perception problem among installers: you should intermix all grounds from multiple circuits, and some people think they should intermix neutrals too.  Or they need a neutral wire, so they grab one from another circuit. That's very common with smart switches and in boxes with 3-ways.  (Thanks DoxyLover).
All these problems should be observable by opening up the junction boxes (with power off and tested to confirm off, obviously).

* It's called a Multi-wire branch circuit and there's nothing wrong with it, however it does require knowledge and special handling, GFCIs being one such case.
Comment: Or someone mixed neutrals between circuits or connected neutrals for two circuits together. That will trip a GFCI.
Comment: Also, hire a certified electrician to make sure it's done properly.
Answer: Have you tried to unplug the garage door opener? Since that is the only thing plugged in try that first, then if it still trips you will need to check every switch & junction box. This can even happen to pros, not long ago my apprentice wired up some lights , they did work at first but he skinned the hot in a metal box and the next day shorted. So wiring faults happen even to pros, you will need to check each branch of the circuit. And possibly the feed even in conduit.
 If the circuit comes in and branches going to outlets and some to lights pull the splice and see if the half that is still connected trips if no trip you would know the feed is good and the problem is someplace in the side that was disconnected you get the idea try cutting the problem in half first with the 1 device that is plugged in then to the branches or if all daisy chained disconnect it 1/2 way and see if it still trips you should have it narrowed down in 5 or 6 try's since is is only a 20 amp circuit.
Comment: All receptacles in a garage require GFCI protection there are no exceptions in the 2017 NEC (local ahj May have exceptions).
Comment: Apprentices aren't pros yet, that's why a certified professional tradesman is supposed to be supervising and approving their work.
Comment: You are so right but as a 4th year can work on their own you know nothing. Even I have had a few of the same since the 70's so get a "grounding" in reality it happens but you are uninformed in most of the states I have worked, so you are just a hack that thinks the code is simple it happens get a life
Comment: Does a garage door opener need to be GF protected? If the opener is causing the GF, you could install the GFCI receptacles so that each receptacle is independent. The opener would not be GF protected and would not trip the GFCI receptacles.

GFCI breaker trips


User interface Scripting Issue Rigify Multiple Rigs Appended

Question: So I have created two characters in two separate blender documents. I used rigify to create a rig for both of them. I then appended both characters into the same blender document. The first character appended worked properly.  The user interface for rigify was complete with all of the animation tools built into rigify. Then I appended the second character.  The user interface script didn't work properly as the controls for the tools built into rigify were missing. How do I bring in multiple characters and have each of them have their user interface intact? There is a rig_ui.py script that was appended with each character. It seems the script runs once for the first character, then on the second append the script can't handle a second rig. How can I solve this problem?
Answer: I asked this same question on blender artist and got an answer that worked. Here is the link to that forum thread. Blender Artists Forum Solution


How to obtain a parametric equation out of a part designed in Autodesk Inventor?

Question: Whenever you make a part in inventor, the software calculates de properties of the whole body given a constant density. Then, automatically,  it shows the inertial tensor. As you can recall from math, the inertia equation is $I_x= \rho\int(y^2+z^2)dV$
for the x axis. So, clearing rho, how can I get the right hand of the equation that is been solved in the underlying algorithm without doing any hand calculations?
Answer: I guess your question is how to compute the inertia tensor automatically. A parametric equation may not be always possible, but we could write a program to avoid hand calculations as much as possible.
The inertia tensor $\mathbf{I}$ is defined as an integral over the object domain $\Omega$ (see Inertia tensor):
$$
\newcommand{\V}[1]{\mathbf{#1}}
\begin{align}
\V{I} &= \int_\Omega \rho (\V{r}\cdot\V{r} \delta - \V{r}\V{r}^T)\,dV
\end{align}
$$
where $\V{r}$ is the position relative to the center of mass (COM),$\rho$ is the density, and $\delta$ is the identity matrix.
Note that $\text{tr}(\V{r}\V{r}^T) = \V{r}\cdot \V{r}$, the above definition  can be rearranged as
$$
\begin{align}
\V{T} &= \V{r}\V{r}^T \\
\V{I} &= \int_\Omega \rho (\text{tr} \V{T} \delta - \V{T})\,dV
\end{align}
$$
Analytic object
For analytic objects you can substitute their equations into the integral and do symbolic integration. This step can be automated with any symbolic computing software.
Object in tetrahedral mesh
We assume the object is simple and has a closed boundary.
An analytic solution is not possible in this case because we do not have an explicit equation for the object. But we could compute the inertia tensor numerically.
The only integral we have to compute is
$$
\begin{align}
\V{C} &=
\int_\Omega \rho \V{r}\V{r}^T\,dV
\end{align}
$$
To compute this integral, this paper could be helpful.
The general idea is to compute $\V{C}_t$ for each tetrahedron $t$, and sum $\V{C}_t$ to get $\V{C}$.
We first compute the integral for a canonical tetrahedron $t0$ whose vertices are
$(0,0,0)$, $(1,0,0)$, $(0,1,0)$, and $(0,0,1)$.
In maple, this canonical integral $\V{C}_{t0}$ is (assume $\rho$ constant)
<code>r:=<x,y,z>;
                                                    [x]
                                                    [ ]
                                               r := [y]
                                                    [ ]
                                                    [z]

with(LinearAlgebra):
rrt:=r.Transpose(r);
                                             [ 2               ]
                                             [x      x y    x z]
                                             [                 ]
                                      rrt := [        2        ]
                                             [x y    y      y z]
                                             [                 ]
                                             [               2 ]
                                             [x z    y z    z  ]

seq(seq(int(int(int(rrt[i,j],x=0..1-y-z),y=0..1-z),z=0..1),i=1..3),j=1..3);
                      1/60, 1/120, 1/120, 1/120, 1/60, 1/120, 1/120, 1/120, 1/60
</code>
Then the integral $\V{C}_t$ can be computed by a change of variable.
Assume the coordinates of a world space tetrahedron can be represented as $\V{r}=\V{F}\V{r}_0 + \V{x}$, where $\V{F}$ and $\V{x}$ are constant.
We have
$$
\begin{align}
\V{C}_t &= \rho \int_{\Omega_t} \V{r}\V{r}^T\,dV \\
&= \rho \int_{\Omega_{t0}} (\V{F}\V{r}_0 + \V{x})(\V{F}\V{r}_0+\V{x})^T \det \V{F} \,dV_0 \\
&= \rho \int_{\Omega_{t0}} (\V{F}\V{r}_0\V{r}_0^T\V{F}^T + \V{x}\V{x}^T + \V{F}\V{r}_0\V{x}^T + \V{x}\V{r}_0^T\V{F}^T) \det \V{F} \,dV_0 \\
&= \det(\V{F}) \V{F}\V{C}_{t0}\V{F}^T + \det(\V{F}) m \V{x}\V{x}^T + \det(\V{F}) m \V{\bar{r}}\V{x}^T + \det(\V{F}) m \V{x}\V{\bar{r}}^T
\end{align}
$$
where $\V{\bar{r}}$ is the COM and $m$ is the mass.
Objects in other form
I did not use Inventor before but I suspect the part produced by it may have other formats, such as Bezier surface. For now I would suggest tetrahedralize the object and apply the above method.


How can Smoker hold Sea Stone as a Devil Fruit user?

Question: Do anyone know how can Smoker hold Sea Stone when he himself a devil fruit user?
Comment: If you mean his [Jitte](https://onepiece.fandom.com/wiki/Nanashaku_Jitte) only the tip is made out of seastone allowing him to hold it while still using his powers.
Comment: Oh , i have to take a relook at that
Answer: Only the tip of his Jitte is made of sea stone. The rest is made of a substance he can hold.
Answer: To expand on the current answers a bit, seastone is a mysterious substance that apparently has the same "wavelength as the sea" which we famously know to be the weakness of any devil fruit user, sapping them of their energy, powers and costing their ability to swim. The minutia of the effects of seastone are somewhat vague but a few things are quite concrete. One must be in direct contact with the seastone for it to have an effect, Luffy loses his abilities and becomes very tired when smoker pins him with the end of his jitte which is where the seastone is, the rest of the jitte is safe to the touch. Another example is that marine warship hulls are covered in seastones to ward off neptunians but people with devil fruit powers are unaffected by being in such close proximity to so much seastone such as when Hancock and Luffy rode one to Impel down. Seastone has varying levels of effectiveness which might have to do with how much of it is present, note the marines have seastone handcuffs which sap devil fruit users of their powers but doesn't seem to apply the strong lethargy something more substantial like Smoker's jitte does.


Privacy/ Private Property

Question: I recently shopped at a large international clothes store with a premises in the UK. When I bought some clothes I was asked by an employee if she could take my photo for Research purposes as Head Office had asked for photos of this specific stores customers, I assumed that to be true. I agreed. The next day my photo was published on facebook on someones private account, someone I knew, knew the person who posted and showed me, It was there without any consent from myself. And while some of the comments are flattering the context and some of the comments are just plain creepy. Where do I stand!? I am not happy about this. Do you think I could get a free three piece suit out of the company for this blatant misuse!?
Comment: @J.Walker: There is no Legal.SE yet. There appears to be a proposal for one Area51, but it is not out of committment yet. Legal questions related to photography are entirely on topic here, as well.
Comment: Try posting this on a legal SE.
Comment: @Alex: It sounds like you might have a legitimate legal issue on your hands. First, I would contact Facebook and see if they can get the photo taken down. Next, if you are truly disturbed by the unauthorized use of your photo, you might want to contact a real lawyer. Internet-based legal advice is tough, as there are so many differing laws across a large and disparate group of regions. Not sure you can get anything from the company, let alone a free suit, but at the very least, you should be able to get your photo taken off of facebook.
Comment: Yeah, even if the legal SE is still in area 51, you could probably still ask your question there.
Comment: @J.Walker: You can't ask questions on Area51...that is a site solely for the purpose of proposing new sites, the listing for Legal there is simply a proposal, it is not a stand-in for an actual site where someone could get actual answers to an actual question.
Comment: Oops... sorry. I'm not extremely familiar with all aspects of SEs
Answer: For a situation like this you are better off consulting a legal expert in your area than relying on advise from the Internet. Where I am there is not a lot of recourse. You were on private property and there is an implied consent.
I would start first by contacting the company and asking them to remove the picture. Starting the conversation by trying to solve the problem rather than being confrontational will usually work better.
Answer: As I understand it (as a photographer, not a lawyer), if the photographer has the permission of the landowner to take a photo, they can; However, I would ave thought that under data protection legislation, your personally identifiable information can only be used for the purpose that was disclosed at the time (and this is why photographers liek models to sign legal releases to consent to their use); so they may have done something they shouldn't have, but you should consult a qualified lawyer if you wanted to take it further with them
There is advice specific to the UK, that was written by people with a better understanding of the law than me over on sirimo.co.uk
Answer: Facebook are reasonably responsive to privacy issues which have the potential to cause them legal woes. If you complain to Facebook with a statement that the photo is of you and that it is being used in a manner that you did not authorise and that it was NOT taken in a public place then they will almost certainly remove it.
If you contact the original photographer and suggest that a complaint to her employer may cause 'problems' she will very likely arrange to have it removed from Facebook.

Privacy/ Private Property


Does the TSA allow liquids based on the US or Metric measurements?

Question: I have a bottle of hair styling gel that says is it 3.59 oz (100 ml). The TSA allows you to have 3.4 oz (100 ml) liquid containers.  The people who made my gel incorrectly converted one way or the other. Will they allow it since it is 100 ml or disallow it since it says 3.59 oz?
Comment: Put a sticker over the "3.59" so that only "100 ml" is visible. Sorted.
Comment: It could go either way. If you don't want to risk losing it, check it or leave it at home.
Comment: Bear in mind that the US [uses a different size fluid ounce from everyone else](https://en.wikipedia.org/wiki/Fluid_ounce).  That given, I submit it is even more likely that as long as the container is clearly labelled as 100ml or less, and otherwise compliant, it will pass inspection.
Answer: There's no way of telling really. If the bottle looks too big, they'll discard it. If it looks like around 100 ml, the official will look at the contents labeled on the container.
My metric European mind says they'll look at the 100 ml (easier to distinguish) but when you've lived with US fluid ounces all your life you might as well have 3.4 burned into your mind (not the 3.59 imperial fluid ounce). So in that case seeing 3.59 will be reason for dismissal.
Once a TSA officer has made a decision they generally don't bargain. Specifically not about containers not being full. They may be sensible to that, but don't count on it.
So, as Michael hampton commented:Put a sticker over the "3.59" so that only "100 ml" is visible. Sorted.
Or leave the container at home.
Or take a smaller travel bottle and put in what you expect to use.
Answer: Well TSA is a US agency so they'll be going my Imperial sizing. But they're not SUPER crazy checking the exact volume of bottles. My rule of thumb is basically is it bigger than a bottle of hotel shampoo? Anything about that size is A-OK. Yes its smaller than 100mL usually but its a safe bet it will travel. Also if it's sold in the travel section of a drug store, it's a good bet it will travel.
Also helpful tip, put all those liquids and gels into a clear ziplock back and put it through separately at security. Makes it easier for them and they get less picky. The easier you make their job the easier they are on you... generally.
Comment: Also, **not** Imperial sizing at all: see my comment above, the US fluid ounce is a different size from the Imperial one!


2009 Dogde Grand Caravan Coolant Fluid leak

Question: Today while driving for about 20 minutes I noticed white smoke coming from the drivers side under the hood.  I pulled into a parking lot and popped the hood and their is coolant everywhere on the drivers side. Literally it looks like the fluid shot up and hit the underside of the hood. Yes the underside of the hood is wet with coolant.  The temp gauge on my dash never went out of the normal range but with fluid everywhere I can't find where it came from.  I checked the reservoir tank and it is now empty.  Any ideas as to what might have caused this?
Comment: You mentioned white smoke, was it actually smoke, or was it steam? Steam would be expected with a coolant leak, not smoke.
Answer: It sounds like you have a leak in the engine radiator or the coolant piping. You can try filling the coolant fluid to max level, turning on the car and looking under the hood. Try to visually find where the leak is. You might need to warm up the engine to develop sufficient coolant pressure to "open up" the leak. Please wear protective eyewear. Coolant in a normally warm engine is under pressure (it is hot too) and it can jettison into your face. Once you've located the leak, you can then proceed to fix the issue yourself or take the car to a repairshop. Repair difficulty and/or methods will depend on where the leak is.
Comment: The vehicle has been turned off for a little over 2 hours. once I add coolant and turn it on to find the leak will this do any unnecessary damage to the vehicle?
Comment: As long there is coolant in the system you should be fine.
Comment: Thank you, leak has been located! It is coming from the connection of the Y shaped house next the engine. Thank you for the warning of possible spray cause it is spraying forward and up, so now I know why there is fluid on the underside of the hood.


Vim immediately sent to background

Question: Whenever I call Vim from the CLI, either to edit a file (vim idk.tex) or without arguments, or run a command (vim +help), it gets sent to the background, as if I had pressed Ctrl+Z.
In order to use it, I always have to send the job to foreground, either to wait for it to finish or to begin working in Vim.
I've tried this on Zsh, bash, fish and tmux (with each shell), and it's always the same behavior.
I can't reproduce it with minivimrc, so I don't know if I should report it as an Airline bug or not.
I have hacked up an alias (vim="vim;fg") so that it won't bug me daily, but it's not feasible when I have other background jobs or when vim fails to start for whatever reason (besides, it's just a hack).
Any pointers as to where I should look or ask are welcome.
I'm running Vim (GVim package) on Termite (v12) on Arch (fully up to date)
My vimrc is:
" for when using elsewhere
set fsync backspace=indent,eol,start updatetime=1500
set shell=bash\ -i
" search candy
set incsearch nohlsearch ignorecase smartcase

" useful shiz
set number hidden cursorline cursorcolumn
set splitright
set mouse=a mousefocus clipboard=unnamedplus
set smarttab autoindent copyindent
set scrolloff=2   " 2 lines of context when scrolling
syntax enable
set history=1000 undolevels=1000
" non-printable and double-width chars
set list listchars=tab:>-,trail:·,extends:#,nbsp:·
set ambiwidth=single
" tab -> 2 spaces, autoindent when pasting
set expandtab tabstop=2
" default tab->2 spaces, use multiples of 2 when autoindenting
set softtabstop=2 shiftwidth=2 shiftround
" wrap shiz
set wrap linebreak nolist
set directory=/tmp   " store swap files here
filetype on
filetype indent plugin on
set ttimeoutlen=10
set noshowmode
set showcmd
set colorcolumn=80
hi ColorColumn ctermbg=7

Answer: I shouldn't have set the shell as interactive. Somehow it pauses the main Vim process.
So:
set shell=bash\ -i

Should be:
set shell=bash

Vim immediately sent to background


Can a pet dog be a carrier of chickenpox?

Question: Can a pet dog be a carrier of chickenpox after contact with a person who has currently suffered chickenpox?
Answer: From Chickenpox:

Other animals
Humans are the only known animal that the disease affects naturally. However, chickenpox has been caused in other primates, including chimpanzees and gorillas.

The varicella zoster virus cannot infect dogs.
Answer: No,dogs cannot get chicken pox. you must first know what an anthroponotic disease is. It means that it is a contagious disease wherein a pathogen found in humans is transmitted to animal species. Once a pathogen transfers to animals, at times it may result to the same disease found in humans with a few significant differences in presentation. Chicken pox not being an anthroponotic disease means that it is not transmissible to your pets.
Comment: Welcome to health SE :-). We require that all answers are backed up with reliable references, since they are the only way for the community to assess the merit of an answer regardless of the reader's background. You can always [edit] your answer to add some. For more information on site policies, please take our [tour] or visit the [help] and [meta]. Thanks!


Can I keep my cat in his Thundershirt for a 5-6 hour car trip?

Question: Can I keep my cat in his Thundershirt for a 5-6 hour car trip? I've tried it on him a few times, and he seems ok with it. He sort of rolls over and becomes quite docile.
Comment: Are you sure the cat is okay with it?  A common response in cats when you put clothes on them, and they don't like it, is for them to freeze up and flop on the ground.  A cat that doesn't mind the clothes will behave like normal.
Answer: Hello and welcome to Pet Exchange :)
I have never heard of Thunder Shirt before but I looked into it.
I am not a fan of putting clothing on animals but this is for certain occasions as I understand and if it helps your pet be more relaxed and calmly learn about new things I think it is worth it.
Most pet owners give very positive reviews.
Their website claims that you can leave it on for up to 10 hours, but especially with the warm weather (assuming it is summer where you are or a hot car atleast) you should be aware that temperatures over 30°C can make it very uncomfortable and too hot for the pet. They also recommend removing it every couple of hours to check it still is in a comfortable position. On a car trip you could check on your cat whenever you take a break too.
Now to the flopping over.
Their Q&A says that it sure can happen and it can mean that the cat is scared. But with some training and encouraging the cat to move around can make the cat get used to it.
The Q&A with lots of interesting info
http://www.thunderworks.com/thunderu/faq/#faq-thundershirt
Comment: There are several questions on Pets involving the "Thundershirt" (one word, no space) product.  I have one for my dog and it does a good job reducing anxiety.