Nexus 10 - Android 5.0.1 OTA upgrade, "no command" and suggested steps failed

Question: I was trying to install the OTA upgrade on my Nexus 10 running Lollipop 5.0.1. Got the "no command" problem. I tried the steps below from this link.

I suggest you try the following:
Press and hold Power button until your device powers off (it could take 30 seconds).

Press and hold Power and Volume Down buttons simultaneously until you see something other than Google on the screen.
You should see a large arrow at the top of the screen.
Tap Volume Down repeatedly until you see Recovery in the arrow. Then tap the Power button
You should see an android on his back, chest open with a red triangle and exclamation mark.
While holding Power button tap Volume Up once then release Power.
You should now see a list of items at top of screen.
Tap Power Down until the item to erase or wipe the cache partition is highlighted. Then tap Power button to initiate.
Status messages will appear at ths bottom of the screen. Be patient - it can take 10-15 minutes to complete. When done restart the Nexus.

Wiping the cache partition does not impact any of your data, but it may take a while before your apps repopulate their cache values. During this time some may appear a bit slower than previously.

I can't get past step 1, as when I do that, it keeps saying, "download in progress. do not close target ( or similar)".
I tried the Power + Volume up + Volume down buttons, and get the menu, but don't see as below.
I also tried Nexus Root Toolkit flash + restock, and that also shows "finished", but reboot goes back to "no command".

What to do?
Answer: Problem solved.  Called google support.  Had to press Power + volume UP to get to second level menu, then select clear cache option.  Re-booted and 5.0.1 upgrade continued.
Answer: Was using Nexus 10 and stuck at "No command.." message. Had to use "Power+ volume down" buttons simultaneously to Stock Recovery mode.

Power + Volume-up = Downloading mode
  Power + Volume-down = Recovery mode


Show the vibrational frequency of fluorine molecule anion is much lower than that of fluorine molecule

Question: Basically I need to draw the molecular orbital for $\ce{F2}$ and then answer a bunch of questions about it. I have drawn it correctly, as far as I know, but I don't know how to use it to show that the vibrational frequency of $\ce{F2-}$ is lower than $\ce{F2}$.
I worked out the bond order for $\ce{F2-}= 0.5$  and for $\ce{F2}= 1$. Is this what you use to find it out, or is it something to do with the HOMO-LUMO?
Comment: Want to bust out some electronic structure theory? *raises and lowers eyebrows rapidly*
Comment: My answer is intended to be some sort of interactive guide to the solution. So, when you have looked at my hints so far and they aren't enough to get you to the solution simply notify me, tell me what points are unclear and I will add something to my answer that should get you back on track.
Answer: You should definitely post the MO diagram of $\ce{F2}$ that you worked out. When trying to solve such a problem you should try to analyse the question as thoroughly as possible to make sure that you collect all the information available to you beforehand. Especially important here is that the question already tells you that the vibrational frequency of $\ce{F2^{-}}$ is lower than that of $\ce{F2}$. So the first question you should ask yourself is: Under what circumstances is a vibrational frequency lowered and which relation do I know that links the vibrational frequency to some variable that is connected to the MO diagram of $\ce{F2}$? I give you a hint: You will need the equation of a harmonic oscillator
\begin{equation}
 \omega = \sqrt{\frac{k}{m}}
\end{equation}
where $\omega = 2 \pi f$ is the angular frequency, $f$ is the frequency, $k$ is the force constant (in your case of the bond and thus its a measure of the bond strength) and $m$ is the reduced mass of the oscillating system. (The harmonic oscillator is one of those simple model systems that can help you quite often when you want a starting point for the investigation of much more complicated ones.) Now ask yourself: Which of the variables $k$ or $m$ might have a relation to the MO diagram and how will they be related?


What kind of pie is this?

Question: So over the thanks giving holiday my wife asked me to go get the apple pie out of the chill chest.  However there were three different pies in there and they all looked alike, and neither of us knew which was which.  We ended up cutting all of them to find the right pie, and made the blueberry pie we took to my parents house look really bad. I was wondering how can I determine what type of pie is in the refrigerator without breaking the structural integrity of the crust? Because I'm sure I'll do it again in the future.
Comment: Do you not have even tiny holes for ventilation you could sample through? And do you regard a toothpick hole as looking really bad?
Answer: If you do this often I would make a little pastry cut out of the fruit type of the pie and use some egg wash to stick it onto the pie - it looks good and eases identification.
Comment: Anyone who bakes pies regularly should get in to this habit, edible labels make sense, pretty too.
Answer: Label them before you put them away.
Use pictures of the filling in pastry on the top crust.
X-Ray machine?
Comment: How would you be able to identify the pies with an X-Ray machine? Would this defrost the pie?
Answer: If you properly vent your pies, you should be able to determine the difference by the color you see through the vent for fruit pies with two crusts.  You can make some very pretty pies with large vents that look quite attractive.  Even pies with a crumble or crisp topping should show a bit of their fillings in parts.
Answer: As with everything you put in the refrigerator and freezer, label and date it.
Comment: Agreed on the date -- and I've even gotten into the habit on some dishes of listing ingredients (was helpful for the meals I gave my sister-in-law when she was pregnant, as she started having issues with some things, so could tell what stuff to save 'til later)
Answer: If it's a two-crust pie, you should be able to flip it over, and cut a small hole in the center, take out a core sample, and examine the interior.
Flipping them over is also one of the best ways of cutting many pies, since it will cause less damage to the sides, and thus a more visually appealing slice.

What kind of pie is this?


Do I need Phantom Power?

Question: I wanted to ask that I want to buy a condenser mic, I know it needs phantom power to work. So my question is will it work if i will connect it to a 3.5mm jack to my amp.
Answer: 3.5mm mic jacks might (sometimes supported by a jumper or different sound card setting) provide "plugin power".  It can power electret condenser capsules with the typical single-FET preamplifier and works, for example, for the surprisingly good stereo clip microphones that were available for Minidisc players.
Regular phantom power, however, is 40V to 48V and is never provided on 3.5mm jacks.  You'll primarily find it on XLR sockets.
There may be electret condensers with 6.3mm jacks that can alternatively use plugin power or a single 1.5V battery inside.  You'll probably fare better with clip-on mics for wireless setups (mini-XLR or similar) but you'll have to make sure the pinout is compatible.
Any mic advertised to be using "regular" phantom power will not work.
Answer: Not all condenser mics need phantom power. Not all amps/mixers provide it. If the mic in question needs it, and the amp doesn't provide it, then it won't work. Usually phantom power is provided through the XLR (Cannon) plug/socket. By using an XLR-jack adapter, the power may well be lost through the connection.
Answer: A microphone that requires phantom power will not work without it.  Phantom power is a method to feed 48v to the microphone through the 3-connector XLR plug.  You'll need to plug that mic into a preamp or mixer input that provides phantom, or alternatively various companies make a DI box that provides phantom power.

Do I need Phantom Power?


Nail through ceiling

Question: We live in Northern Illinois. Five or six years ago we had the roof replaced on our detached, single family house. The job seemed to be well done and we had no complaints. This afternoon, however, as I lay down on my bed for a moment, and, looking straight up, noticed a nail protruding through the white, finished ceiling directly above me.  I look at that spot in the ceiling multiple times a day, and there is no way that the nail was protruding before this afternoon.  The house has two stories, and a 16 foot ceiling in that room. No one, to my knowledge has been on that part of the roof since the new roof was put on.
So, is it normal for a nail to come through so long after the new roof was put on? In any case, what dangers/issues are there with this situation, and what steps might I take to correct the problem? Picture attached.
Answer: Looks to me like a drywall screw or nail has "bubbled out". It happens sometimes due to wall movement, especially with weather swings (like a real wet winter or a long drought). It also happens when moisture gets to a nail or screw and causes it to corrode. Hopefully your kinda new roof is not leaking. I don't see any signs of plaster discoloration indicating a leak.
Get a ladder and bang the nail back in (or give the screw a turn) and spackle over it.
Comment: I would actually remove the nail and drive a new screw in a few inches away. Banging it back in the same spot will just end with it popping again.
Answer: Unless the gypsum board is attached directly to the underside of the roof sheathing, it is not a roofing nail. If the gypsum board is attached directly to the underside of the roof sheathing, then there are larger quality of construction issues than a protruding nail.

Nail through ceiling


Exporting XML EDL from Premiere to Davinci Resolve

Question: What is the best way to successfully export an EDL from Premiere to Davinci Resolve?
Currently I export a Final Cut Pro XML, but whenever I import into Davinci, there are often errors with scale and speed, if any changes have been made to the size of the source footage.. What's the right way to do this?
Answer: Fcp .xml  is limited in features. Although more powerful than other EDL types, most of Premiere's transformation and animation properties are not supported. You can read more about its capabilities here. However it appears Premiere CC neither exports the xml file as recommended by Apple nor in its latest version.
I'd suggest collapse your timeline and make sure there are no nested clips. Then save your timeline as .xml (at least for reference) and replace all faulty shots in Resolve, if required. Alternatively you can export the whole clip from Premiere via any production codec or ideally as image sequence (.exr, .dpx, whatever you like depending on your color management workflow) and use Resolve`s Scene Cut Detection function to chop the imported clip into multiple shots automatically.


Can I fly a UAS that weighs more than 55lbs if I'm on private property?

Question: Can I fly a UAS that weighs more than 55 pounds within my own private property if I stay below say, 200 feet? I do not have 333 exemption
Comment: It may help to list (generally) where you are. Airspace regulations extend to the surface and the type of airspace you are in may effect the answer.
Comment: The FAA regulates the airspace from the surface to 60,000 feet regardless who owns the land property beneath it.
Comment: Even on your own property, a UAV can lose the control signal, or malfunction, and travel well outside of your property before impacting heaven knows what. The larger the UAV, the more damage from the impact, the propellers, or the resulting fire if the liquid fuel ignites or the li-ion batteries short circuit and ignite. I believe that's the FAA's concern over large UAV's... not like a hobby quad copter that will just bounce off of a building or a car, and not like a land based vehicle that usually won't go far before impacting something in an uncontrolled situation.
Answer: TL;DR
According to the FAA Part 333 rules, all UA aircraft (> 55 lbs) must register with the FAA with an N-number before flight. As far as I can tell, the rules don't specify zones or altitudes where the regulations aren't in effect, so I think it is highly advisable to register.
My personal rationale
Being safe just in case is far better, at least in my mind, than choosing to avoid registration. I know people in my RC Quadcopter possee that fly sUAS aircraft but don't have Part 107 licenses. I have one, (I would rather be safe than sorry) but I could see how as long as you are careful, flying a small sUAS without a Part 107 license isn't such a terrible option.
In my mind, UA aircraft are an entirely different story, as they are inherently significantly larger than sUAS aircraft, and if something does go wrong, damages would be more severe. The risks (not to mention the responsibility) involved are far more substantial, and I would never consider flying a UA aircraft without a license even if I was only flying on my own property.
Comment: I think you mean "never consider flying a UA aircraft wit no liscence" at the end, but didn't want to suggest edit for something potentially involving meaning.
Comment: @starweaver yes. Thanks for the suggestion!
Answer: Flying over your own property doesn't matter.  As soon as you leave the blade of grass, whether at 1 inch or 1 mile, you are under FAA domain.
Therefore in your case, you would need to comply with appropriate regulations.
If you have a special application, or you are doing some specialized development, you might look in to a waiver.  But in general, expect that all the rules apply to you even if you are over your property.  This includes prohibitions about flying over people, night operations, etc.
Comment: No one considers "flying while touching the ground somehow" to be flying, so the opening soulds contradictory.
Comment: @StarWeaver, good point on English usage, and I have edited the answer per your point.
Comment: IDK about that 1 inch.  I mean, if I imported a Flymo https://en.wikipedia.org/wiki/Flymo would I have to register it with the FAA?
Comment: @jamesqf: The Flymo (my dad had one) is connected to the ground by the pilot, if that makes any difference. Now a ride-on Flymo ... Do hovercraft fall under FAA in the USA? I was intrigued on a jetfoil journey between Ostende, Belgium and Dover, Britain, many years ago to have a pre "take-off" briefing by the cabin crew.
Comment: @Transistor: Well, how about a remote-controlled Flymo, then?  Or one that's purely robotic?
Answer: Sure.  In the eyes of the FAA, a UAS over 55lbs is no different from any other aircraft operating in the national airspace system and subject to the regulations under Title 14 CFR.


Templates and Rich Text Editor properties

Question: I have a field called "description" but I want to use different Rich Text editors with it.  Can I do this with the same template, or do I have to make different templates with the same field name?
Answer: You just put the path to the editor in the datasource for the Rich Text field. Path you see here is in the core database. You can just copy an existing profile rename it.
If you want one field to the OOTB editor and one to use you custom, yes you need two templates with two different rich text fields. One with datasource set and one not.
Answer: The RTE definition is put in the source field of your field definition. If you inherit  a template with such a field you cannot change that property in the new template as you don't have access to the inherited field definitions. So: yes, you will need separate fields if you want other RTE profiles.
There could be a way to achieve this with custom code - there usually is in Sitecore ;) But in this case I don't think you would want to go that way. It will overcomplicate things.


$i,j,k$ Values of the $\Theta$ Matrix in Neural Networks

Question: SO I'm looking at these two neural networks and walking through how the $ijk$ values of $\Theta$ correspond to the layer, the node number.
Either there are redundant values or I'm missing how the subscripts actually map from node to node.
$\Theta^i_{jk}$ ... where this is read as " Theta superscript i subscript jk "
As shown here:

It looks like the $\Theta$ value corresponding to the node circled in teal would be $\Theta^2_{12}$ ... where:

superscript $i=2$ ( layer 2 )
$j=1$ ( node number within the subsequent layer ? )
$k=2$ ( node number within the current layer ? )

If I'm matching the pattern correctly I think the $j$ value is the node to the right of the red circled node ... and the $k$ value is the teal node...
Am I getting this right?
Because between the above image and this one:

That seems to be the case ... can I get a confirmation on this?
Answer: Yes, $\Theta^i_{jk}$ is the weight that the activation of node $j$ has in the previous input layer $j - 1$ in computing the activation of node $k$ in layer $i$.
Comment: "Previous input layer j-1" I think this should be i-1?


Is elementary OS performance suitable for Games and Steam?

Question: I googled it and did my search well but I still wanted to ask people to hear some thoughts and opinions. I got an MSI laptop now and like most, I use Windows for a long time. But I'm bored a lot of using the same OS. I've been searching which Linux OS I could use and found eOS and thought that's it. I love it. I'm a intermediate programmer and coder but I'm not a pro, but I'm working on it. And I actually play hundreds of games on Steam, both old and new and keep buying. So I may call myself a gamer easily. I found out some old and new games doesn't support Linux and I'm not sure if they ever will. I also installed eOS on VirtualBox but I couldn't completely feel its sensation, its stabilization, you know what I mean? It was slow and unstable. I know it won't be the same when/if I would install it directly on my SSD. Someday soon I'll test eOS on my partitioned SSD to see its real performance. I really, really want to install it in place of Windows but I sadly got doubts. I'm sure I can get used to it but should I? How's its gaming and daily performance. Will I always have to deal with some problems or will there be so many troubles that will make my day awful and let me search codes online for hours and ask here questions? Will all of my drivers work (GTX 950M - i5 4210U - Intel HD 4600 etc. [MSI GP62-2QE])? How will I make unsupported softwares work, such as SteelSeries Engine 3 and some not-well-known, made in PRC keyboard's software etc.? Please let me hear what you people think. What would you do? Thank you already!
Comment: Lots of questions here, but they mostly rely on opinion. We cover focused Q&A best here. The discussion questions are better brought to the elementary Reddit.
Answer: Because this is a subjective question I'm sure you will get different opinions here (especially as it is an elementary OS User forum).  Firstly elementary is stable (I have similar specifications to you) and the drivers are supported.
I spend much of my time helping Windows user transition to Linux (specifically elementary) and there are clues in your question that you might not be ready.  Steam OS will work great with your GTX but will not play your old Windows catalogue.  Do some additional research and check out linux applications like "Wine" and "Play on Linux" to confirm your older games will play.
If there is other Windows software your rely on I also suggest you check out alternativeto.net to see if there is a Linux equivalent.  If it was not for your legacy software my suggestion would have been to jump right in especially with your programming skills.  I made the decision 9 years ago, I use elementary OS everyday and my kids use Steam on it.
Comment: Thank you for sharing your experiences. I somehow feel like I'll not regret. Anyway, it's not end of the world, I can go back to Windows anytime but this isn't what I want. I want to push the limits to get used to using eOS and being part of this community. I believe it's time but what makes me actually worry about is that unsupported games/softwares that I can't give up so easily. As you just said, I might not be ready. But if I'm not, how will I? I'll be hearing more opinions about it!
Answer: I suggest reading these two articles since I can't be any better in stating my point of view. (I will put a extract of them for those who want to decide if the articles are worth reading):

"A couple of years ago, gaming on Linux was a joke. There were a few open source games that, while fun, were nothing compared to the Call of Dutys, Battlefields, Skyrims, and Grand Theft Autos of the day. Yes, there were a handful of people that they got their game working on Wine by spending 3 days configuring it and accepting defeat on certain features. But serious gamers never bothered to go through all that work.
  Today, things are definitely better. Ubuntu, Steam, and others are working hard on making gaming not only possible, but decent on Linux. Unfortunately though, it still has a long way to go before contending with Windows. A serious gamer could not live on Linux."

Source: http://downtoearthlinux.com/posts/11-reasons-to-avoid-linux/
Since the above article can be perceived as a hard critic against Linux there are many truths in it. On the other hand the author "John Morris" describes himself as a passionate Linux enthusiast.
Another article, less polemical, I hope, concludes:

"I would advise you to dual boot Linux with Windows . Use Linux as your main desktop and if you want to play games, boot into Windows. This could be a compromised solution."

Source: https://itsfoss.com/linux-gaming-guide/
Hope it helps.
Comment: Thank you! That's exactly what I did today. With dual boot, I use Linux and Windows together. I only boot Windows when I want to play games. Though it's an amazing feeling to use eOS, I'm trying to fix some bugs, such as my Wingpanel disappeared and I did everything to get it back but didn't work. Searched everywhere but nothing. I think I'll ask here to get a help and will keep checking this thread if anyone shares their opinions. See you!
Comment: @mawendir. If you are satisfied with any of these answers (and do not expect more opinions). I beg you mark your question as answered. Doing it so it's more useful for others. If you consider both answers helpful you should decide which one helped you more as it's not possible to choose more than an answer. Thank you.
Comment: Hello. I'll mark my question as answered when I'm satisfied but I still don't feel like I get the answer I'm looking for. Thank you for your help again.


Instead of using flexible mirrors, could software be used for adaptive optics?

Question: Telescopes that use adaptive optics now use flexible mirrors to adjust for distortions in the atmosphere.  The mirrors are flexed in real time to account for the distortions.  I am wondering if it would be feasible to instead use fixed mirrors and use software to make the needed corrections to the image?
Answer: Short answer: no.
Why not?  because the mirror is placed at a position in the optical train such that it controls the wavefront phase and tilt of each subsection, "subaperture" of the incoming beam.  Once an optical system has formed an image, all phase information is lost.  There  are some software methods which can correct for simple aberrations such as astigmatism or coma, but those require a near-constant type of error across the input field.  The problem with atmospheric turbulence is that the errors are essentially of a localized and random nature.
Note that even a plenoptic camera which, by tricky use of sublenses at the focal plane, record enough information to change focus, cannot correct for general phase aberrations.
Comment: The reverse of this answer also holds: You can do software adaptive optics if you can capture the phase of incoming light. And according to [this answer](https://astronomy.stackexchange.com/a/13967/18324) that is regularly done for radio telescopes. Unfortunately phase information cannot be captured for infrared and shorter wavelengths (in practice at least. No idea if the latest experimental tech can do better).
Comment: @uhoh,  Lytro **is** a plenoptic camera :-) .  And, yes, you're right - even some astronomy observation involves local interferometry tricks.  You should see the spatial filters used, too: there's one which removes the bright center of stars (zero-order) so we can look at coronas, planets, etc. (at least in theory)
Comment: ...is on its way to being lost at least. Once you go ahead and record the image with film or a CCD, or otherwise *intercept the image* with something that converts the electric field irreparably to intensity, then it's completely lost. In some imaging applications (mostly outside of astronomy) people play with various tricks, like white-light interferometry, or the cool [Lytro](https://www.lytro.com/imaging) camera that didn't really sell but attracted a lot of venture capital so they could make [this stuff](http://blog.lytro.com/light_field_production_methodology/).
Comment: Do you think this particular [demonstration coronograph](http://astronomy.stackexchange.com/q/18726/7982) will work, or will the technology need more time to mature? This reminds me I have a follow-up question in the oven as well.


Error when working on project from windows 10 laptop

Question: Good morning, I have a rather large project that I've been working on without any problems on my mac desktop, but I'm having a problem preventing me from building anything when I attempt to work on the project from a windows machine.
My shared project contains code like:
<code> if(Device.RuntimePlatform == Device.iOS)
{

        // Create base Alert Controller
        UIAlertController alertController = UIAlertController.Create("", null, UIAlertControllerStyle.Alert);
...
</code>
Which needs a reference to Xamarin.iOS, but when attempting to add that reference under a clean install, I get an error

"'CSHarpAddImportCodeFixProvider' has encountered an error and has
  been disabled"
System.AggregateException : One or more errors occurred. ---> Unable
  to find a type of reference that is appropriate for this file:
  "C:\Program Files (x86)\Microsoft Visual
  Studio\2017\Enterprise\Common7\IDE\ReferenceAssemblies\Microsoft\Framework\Xamarin.iOS\v1.0\Xamarin.iOS.dll".

Anyone come across this before?
Answer: I found a workaround by replacing those statements with
<code>    #if __IOS__
 #endif
...
    #if__ANDROID__
...
#endif
</code>
and then removing the IOS macro from the args, which causes the statement to act as a comment, and allows me to work on and build the android app on my PC, while ignoring the iOS specific code.
Not sure if it's exactly a smart method, but no problems so far.


"A patients guide" or "A patient's guide"?

Question: I am working on one of my employer's websites, and we have a video guide up for patients of how a particular procedure works. The guide was previously titled "A patients guide to [X]", but I have corrected it to "A patient's guide to [X]" as I initially felt that that was correct, and Grammarly also agreed. However, now I'm not so sure. Which do I go for?
Comment: I've seen book titles similar to that one, like *A Student's Guide to....*, so I assume the same goes with *patient*.
Answer: You need an apostrophe to mark a possessive case here. However, the possessive case doesn't refer to ownership in such examples, instead it refers to the meaning "is intended for":

A patient's guide to [X]
A student's guide to [X]
A teacher's guide to [X]

This means that this guide is intended for students, teachers or patients.
Example "The Hitchhiker's Guide to the Galaxy", "The Student's Guide to Becoming a Nurse", "The Teacher's Guides To Technology And Learning".

An edit based on FranklinCovey Style Guide: For Business and Technical Communication by Stephen R. Covey:
Possessive case vs Descriptive nouns.
First of all let's distinguish the difference between the possessive case and the descriptive uses of nouns:

The Teacher's Guide (or Teachers' Guide) - Possessive case
The Teacher Guide (or Teachers Guide) - Descriptive nouns

The traditional use of the possessive (with an apostrophe) is less common today, especially with corporate names. The name for a guide for teachers is open to all sorts of possibilities. In The Teacher Guide, the noun "teacher" functions as an adjective and not a possessive. This form, without the apostrophe, would appear in titles and in news headlines (which often omit apostrophes). But notice that other options are possible (and correct).
  The best advice is to decide for a single document whether you want to use a descriptive or a possessive. Then be consistent throughout that document.
Answer: If you use the S, it must be "A patient's guide", which implies that the guide is possessed by a specific patient, or "Patients' guide", which implies that the guide is for multiple patients.  I would argue the latter is more grammatical, although the first seems more common.  I think one could justify both.  The first could be justified as being specifically for the reader, who is a patient.
Alternatively, one could call it "A Patient Guide", although this risks being confused with the adjective "patient", which would describe someone or something that is tolerant and will wait without complaint.  With some contexts (e.g. "A doctor guide") this would be fine.  Here, I think it's slightly ambiguous and best avoided.
Comment: @SovereignSun I'm not saying one *should*, merely that one *could*.  I would call it "A Doctor's Guide..." or "Doctors' Guide..." myself.
Comment: @SovereignSun "doctor" acts as an adjective in the first use. It's a "noun adjunct," just like in "chicken soup."
Comment: A doctor guide? Seriously? Never heard of! Should be "A Doctor's guide" instead.
Comment: +1 for the first paragraph, and -1 for the second; none of the versions with no `s` sound appropriate.
Comment: @TonyK So tone-deaf, this link http://www.classroomengineers.org/media/engineer-guide/ uses the same construction: "Engineer Guide".  I'm not the only one, evidently.
Comment: Downvoted because of "A doctor guide", which is completely tone-deaf.
Comment: A "doctor guide" could be a patient's guide to choosing a doctor, or a doctor's guide to handling awkward patients.
Comment: You could say "**Doctoring guide**" - A guide on how to doctor *(change the content or appearance of (a document or picture) in order to deceive; falsify)*
Comment: A patient guide could also be a guide who is a patient. Perhaps he conducts tours of the hospital.
Answer: I haven't gotten a single example of "A patients  guide " over searching on Google, so "A patient 's guide " is appropriate here. It's also same for "A parent's guide " and "A student's guide " .
Comment: Google searches don't define grammar.  You should have an actual reason, like the other answers.
Comment: @MatthewRead Usage defines grammar, and Google searches tell a lot more about what people actually use than many of the seemingly arbitrary reasons given in other answers.
Comment: But you can really get a number of good  sources which are trustworthy.
Comment: Hm. I think "Texas drivers license" is the canonical spelling, at least in Texas ;-). Event though it's rather a (i.e. one, singular) "driver's license", logically: after all, each one is issued to a specific individual, not to the collective. That would be an even stronger case than in the "patients guide", which actually *is* issued to the collective. *Addendum:* The Texans are not consistent. The DMV's [page](https://www.dps.texas.gov/DriverLicense/) title is "Your Texas Drivers License", but the text uses "driver license" (note: no apostrophe). Natural languages are a mess, aren't they?
Comment: Expanding on the driver['][s]['] license issue, after some googling: The Texas license proper says "Driver License", nominative singular. Minnesota and some other states write "Driver's License". I could not find an image of a license saying "Drivers License" (nominative plural) or "Drivers' License" (genitive plural).
Answer: Merriam-Webster's Manual for Writers and Editors says:

No apostrophe is generally used today [1998. -p.a.s] with plural nouns that are more descriptive than possessive.

Examples they give are "steelworkers union", "managers meeting" and "singles bar". I think patients guide fits in that group nicely: After all, the patients indeed do not actually own it.
Comment: @AndyT But the cited manual says that it is more a descriptive plural than a possessive case, so an apostrophe would not be any more correct.
Comment: This is a good point. The apostrophe is grammatically correct, but it wouldn't be thought of as unusual if it wasn't there.
Answer: "A patients guide" would be a guide about patients.
"A patient's guide" would be a guide FOR a patient.
Comment: _'"A patients guide" would be a guide about patients.'_ This would be my intuition, too, but is there an actual example of a similar title?
Comment: It seems other answers were not able to find an example. You could imagine an example such as 'A cars guide' - though typically we'd see that as 'A guide to cars'. So it's more likely to find 'A guide to patients'. Googling 'A guide to patients' returns many results and also suggests searching for 'A guide to educating patients' which are both more along the lines of my interpretation. To me this says that we don't see 'A patients guide' (sans apostrophe) because it would be more common to say (and see) 'A guide to patients'.
Answer: Part of the issue is that you have an "A" at the beginning of your title.  Such titles, as pointed out by others, feature singular nouns -- you might have a book about insurance called "A Patient's Guide to Patience."
However, there are other publications whose titles start with "The" -- and these can go either way.  "The Boy's Guide to Greatness" or "The Boys' Book Of Survival" are two examples.  When these "The" titles are singular, there is usually an adjective included: "The Young Person's Guide to the Orchestra" or "The Married Man's Guide to Adultery" or combined forms like "The Gentleman's Guide to Vice and Virtue."
Titles like these sound a bit traditional or even old-timey.  No surprise, then, that "Ladies' Home Journal" dropped its "The" a while ago.
Comment: Where did you pick up those book titles?
Comment: Googled stuff like "boy's guide".  "Patient's Guide to Patience" I made up, of course.

Also, apparently LHJ has ceased publication.
Answer: The key in this case is that Teachers Guide is Plural Possessive.
Proper form is "Teachers' Guide". The apostrophe goes at the end.
Check out this "Advanced (plural) possession" video from the Khan Academy.
Comment: If you are going to link to another site, you should include the relevant information in your answer. Links can become obsolete. See [Your answer is in another castle: when is an answer not an answer?](http://meta.stackexchange.com/q/225370/) for more information.
Comment: **Teachers Guide** as is isn't the *Plural Possessive*; it's the *Descriptive noun* - **Teachers.** However, if we add the **apostrophe** then it becomes a **plural possessive**.


The Role of Sound Design in Post Production

Question: Could someone please help me with defining what it means to be a sound designer/ mixing artist working on a feature film as well as what the role is of the sound designer, his/her responsibilities, the working environment and employment conditions, entry level conditions with the potential of growth and the pros and cons of working in this field.
Answer: First, welcome!
Second, this is an exceedingly broad question (or series of related questions tied together).
Sound designer can mean one of two roles:  the more or less 'incorrect' usage of the term is an individual either doing all or multiple sound editorial roles on a show (e.g. if you're the only one doing post on the film, you may go credited as Sound Designer instead of Supervising Sound Editor, etc)
The more accurate definition is that they are someone who is charged with designing and creating never-before-heard (usually) concrete sounds (and/or an expressive library of these sounds), as well as creating conceptual and subjective (think whooshes, stings, transitions and all those) signature sound textures for a show (or a series, if we're talking episodic TV).
For the purpose of answering your question, I'll go with the latter definition.
Their responsibility is to ultimately develop the sound signature of a show, creating all of the non-Hard FX effects elements (and sometimes Hard FX-related elements) and in many cases nowadays, also required to edit those together for the show in question.  Sometimes this involves creating specialized, literal computer sounds for a high-tech system (think Minority Report), other times it's creature development (think Super 8), sometimes it's sweetening combat with larger-than-life, in-your-face ballsy sound textures.  And other times it's creating scare moments, stings, transitions, whooshes, swishes, booms, speed ramps, flashes, whip pans, snap zooms, suck outs, swells, drones, bumps and other tasty elements to work cohesively to drive/reinforce the story and visual where appropriate and where requested by the client.
As far as entry-level goes, my best understanding and from my own experience, is that it requires some background experience in cutting sound effects and working your way up.  It's not one of the walk-in entry level roles (in the feature world at least, as per your question).  It's a considerably demanding role and comes with a large responsibility.  Sound Designer sits in a gray area between Sound Effects editors and the Supervising Sound Editor - as what they are doing is sound effects related, but they are charged with making sweeping creative and aesthetic decisions in tandem with the supervisor.  It's a pay your dues type of role that some individuals grow into by chance or by choice.  But usually you have to show that you can deliver solid tracks in regular sound effects editorial for some time and the like in order to be provided more opportunities to instill creative freedoms and subsequently ease into a role of a Sound Designer (that's been my own experience).
As for pros and cons, I can't really answer that because the scope and esteem of a Sound Designers role changes on a show by show basis and it's one of those "to each their own" opinions - which too change on a show by show basis.
The working environment also depends too.  I work from a home studio, as do a lot of other sound editors I work along with and/or know personally.  That seems to be the paradigm today.  On major Union shows, depending upon how classified/big the show is, you might be working on a studio lot in an edit/design suite.  Again, it all depends, so there's no definitive answer to this question.  Employment environment and conditions are transient in nature.
Hopefully that helps!  Again, only my opinion.


What is the relationship between regression and linear discriminant analysis (LDA)?

Question: Is there a relationship between regression and linear discriminant analysis (LDA)? What are their similarities and differences? Does it make any difference if there are two classes or more than two classes?
Comment: A note for the reader: the question is ambiguous, it can be understood as asking about **logistic regression** or about **linear regression**. The OP seems to have been interested in both aspects (see comments). The accepted answer is about linear regression, but some other answers  focus on logistic regression instead.
Answer: I take it that the question is about LDA and linear (not logistic) regression.
There is a considerable and meaningful relation between linear regression and linear discriminant analysis. In case the dependent variable (DV) consists just of 2 groups the two analyses are actually identical. Despite that computations are different and the results - regression and discriminant coefficients - are not the same, they are exactly proportional to each other.
Now for the more-than-two-groups situation. First, let us state that LDA (its extraction, not classification stage) is equivalent (linearly related results) to canonical correlation analysis if you turn the grouping DV into a set of dummy variables (with one redundant of them dropped out) and do canonical analysis with sets "IVs" and "dummies". Canonical variates on the side of "IVs" set that you obtain are what LDA calls "discriminant functions" or "discriminants".
So, then how canonical analysis is related to linear regression? Canonical analysis is in essence a MANOVA (in the sense "Multivariate Multiple linear regression" or "Multivariate general linear model") deepened into latent structure of relationships between the DVs and the IVs. These two variations are decomposed in their inter-relations into latent "canonical variates". Let us take the simplest example, Y vs X1 X2 X3. Maximization of correlation between the two sides is linear regression (if you predict Y by Xs) or - which is the same thing - is MANOVA (if you predict Xs by Y). The correlation is unidimensional (with magnitude R^2 = Pillai's trace) because the lesser set, Y, consists just of one variable. Now let's take these two sets: Y1 Y2 vs X1 x2 x3. The correlation being maximized here is 2-dimensional because the lesser set contains 2 variables. The first and stronger latent dimension of the correlation is called the 1st canonical correlation, and the remaining part, orthogonal to it, the 2nd canonical correlation. So, MANOVA (or linear regression) just asks what are partial roles (the coefficients) of variables in the whole 2-dimensional correlation of sets; while canonical analysis just goes below to ask what are partial roles of variables in the 1st correlational dimension, and in the 2nd.
Thus, canonical correlation analysis is multivariate linear regression deepened into latent structure of relationship between the DVs and IVs. Discriminant analysis is a particular case of canonical correlation analysis (see exactly how). So, here was the answer about the relation of LDA to linear regression in a general case of more-than-two-groups.
Note that my answer does not at all see LDA as classification technique. I was discussing LDA only as extraction-of-latents technique. Classification is the second and stand-alone stage of LDA (I described it here). @Michael Chernick was focusing on it in his answers.
Comment: Mmm.. Just a couple of papers coming to mind quickly: `Harry Clahn. Canonical Correlation and Its Relationship to Discriminant
Analysis and Multiple Regression`. `W. Stuetzle. Connections between Canonical Correlation Analysis,
Linear Discriminant Analysis, and Optimal Scaling`. `Olcay Kursun et al. Canonical correlation analysis using within-class coupling`. If you can't find them in the internet I can send you. If you find more and better sources - please let us know.
Comment: +1 (long time ago). Do you know of any references that discuss (in some detail) this connection between MANOVA/CCA/regression between X and the matrix of group dummies Y, and LDA (for the general case of more than two groups)? I am now studying this topic, and I think I have more or less figured it out already, but when I search for `regression formulation of LDA` it's surprisingly difficult to find something -- there are multiple research papers published after 2000 saying that such a formulation does not exist or trying to suggest one. Is there perhaps a good [old] reference?
Comment: My passage did not at all imply that you can obtain CCA coefficients having just the regression (the MANOVA) results at hand. I was saying that MANOVA is "surface" and CCA is more "deep" layers of the same analytical enterprise. I did not say they are synonyms or that one is a plain specific case of the other.
Comment: I see. I decided to post another answer here, providing the mathematical details of LDA/regression equivalence.
Comment: Why do I need "canonical correlation analysis" and what does it do here? Thanks.
Comment: Uhm, don't unserstand you. Did you read the answer? Canonical analysis was necessary in order to clarify how LDA is related to linear regression; this relation appears quite complex in general case of more than 2 groups.
Comment: So, having a good understanding of MANOVA might be helpful for us to understand LDA at feature extraction, right?
Comment: Thanks! I am reading all that, but here is what I am confused about in your answer. In the general case of two multivariate datasets $X$ and $Y$, CCA is not equivalent to the regression $Y=XB+\mathrm{noise}$. If we solve for $B$ using the usual regression formula, I don't think there is a way to recover CCA solution from it. The regression formulation of CCA exists, but is more complicated. Therefore I am not sure I understand your point when you write that `canonical correlation analysis is multivariate linear regression deepened into latent structure of relationship between the DVs and IVs`.
Answer: Here is a reference to one of Efron's papers: The Efficiency of Logistic Regression Compared to Normal Discriminant Analysis, 1975.
Another relevant paper is Ng & Jordan, 2001, On Discriminative vs. Generative classifierers: A comparison of logistic regression and naive Bayes. And here is an abstract of a comment on it by Xue & Titterington, 2008, that mentions O'Neill's papers related to his PhD dissertation:

Comparison of generative and discriminative classifiers is an
  ever-lasting topic. As an important contribution to this topic, based
  on their theoretical and empirical comparisons between the naïve Bayes
  classifier and linear logistic regression, Ng and Jordan (NIPS
  841---848, 2001) claimed that there exist two distinct regimes of
  performance between the generative and discriminative classifiers with
  regard to the training-set size. In this paper, our empirical and
  simulation studies, as a complement of their work, however, suggest
  that the existence of the two distinct regimes may not be so reliable.
  In addition, for real world datasets, so far there is no theoretically
  correct, general criterion for choosing between the discriminative and
  the generative approaches to classification of an observation $x$ into
  a class $y$; the choice depends on the relative confidence we have in
  the correctness of the specification of either $p(y|x)$ or $p(x, y)$
  for the data. This can be to some extent a demonstration of why Efron
  (J Am Stat Assoc 70(352):892---898, 1975) and O'Neill (J Am Stat Assoc
  75(369):154---160, 1980) prefer normal-based linear discriminant
  analysis (LDA) when no model mis-specification occurs but other
  empirical studies may prefer linear logistic regression instead.
  Furthermore, we suggest that pairing of either LDA assuming a common
  diagonal covariance matrix (LDA) or the naïve Bayes classifier and
  linear logistic regression may not be perfect, and hence it may not be
  reliable for any claim that was derived from the comparison between
  LDA or the naïve Bayes classifier and linear logistic regression to be
  generalised to all generative and discriminative classifiers.

There are a lot of other references on this that you can find online.
Comment: Here's another comparison of generative and discriminative classifiers by Yaroslav Bulatov on Quora: http://www.quora.com/What-are-some-benefits-and-drawbacks-of-discriminative-and-generative-models/answer/Yaroslav-Bulatov
Comment: +1 for the many well placed references on the (now clarified by the OP) subject of logistic regression vs. LDA.
Comment: Also a related topic, http://stats.stackexchange.com/q/95247/3277
Answer: The purpose of this answer is to explain the exact mathematical relationship between linear discriminant analysis (LDA) and multivariate linear regression (MLR). It will turn out that the correct framework is provided by reduced rank regression (RRR).
We will show that LDA is equivalent to RRR of the whitened class indicator matrix on the data matrix.

Notation
Let $\newcommand{\X}{\mathbf X}\X$ be the $n\times d$ matrix with data points $\newcommand{\x}{\mathbf x}\x_i$ in rows and variables in columns. Each point belongs to one of the $k$ classes, or groups. Point $\x_i$ belongs to class number $g(i)$.
Let $\newcommand{\G}{\mathbf G}\G$ be the $n \times k$ indicator matrix encoding group membership as follows: $G_{ij}=1$ if $\x_i$ belongs to class $j$, and $G_{ij}=0$ otherwise. There are $n_j$ data points in class $j$; of course $\sum n_j = n$.
We assume that the data are centered and so the global mean is equal to zero, $\newcommand{\bmu}{\boldsymbol \mu}\bmu=0$. Let $\bmu_j$ be the mean of class $j$.
LDA
The total scatter matrix $\newcommand{\C}{\mathbf C}\C=\X^\top \X$ can be decomposed into the sum of between-class and within-class scatter matrices defined as follows:
\begin{align}
\C_b &= \sum_j n_j \bmu_j \bmu_j^\top \\
\C_w &= \sum(\x_i - \bmu_{g(i)})(\x_i - \bmu_{g(i)})^\top.
\end{align}
One can verify that $\C = \C_b + \C_w$. LDA searches for discriminant axes that have maximal between-group variance and minimal within-group variance of the projection. Specifically, first discriminant axis is the unit vector $\newcommand{\w}{\mathbf w}\w$ maximizing $\w^\top \C_b \w / (\w^\top \C_w \w)$, and the first $p$ discriminant axes stacked together into a matrix $\newcommand{\W}{\mathbf W}\W$ should maximize the trace $$\DeclareMathOperator{\tr}{tr} L_\mathrm{LDA}=\tr\left(\W^\top \C_b \W (\W^\top \C_w \W)^{-1}\right).$$
Assuming that $\C_w$ is full rank, LDA solution $\W_\mathrm{LDA}$ is the matrix of eigenvectors of $\C_w^{-1} \C_b$ (ordered by the eigenvalues in the decreasing order).
This was the usual story. Now let us make two important observations.
First, within-class scatter matrix can be replaced by the total scatter matrix (ultimately because maximizing $b/w$ is equivalent to maximizing $b/(b+w)$), and indeed, it is easy to see that $\C^{-1} \C_b$ has the same eigenvectors.
Second, the between-class scatter matrix can be expressed via the group membership matrix defined above. Indeed, $\G^\top \X$ is the matrix of group sums. To get the matrix of group means, it should be multiplied by a diagonal matrix with $n_j$ on the diagonal; it's given by $\G^\top \G$. Hence, the matrix of group means is $(\G^\top \G)^{-1}\G^\top \X$ (sapienti will notice that it's a regression formula). To get $\C_b$ we need to take its scatter matrix, weighted by the same diagonal matrix, obtaining $$\C_b = \X^\top \G (\G^\top \G)^{-1}\G^\top \X.$$  If all $n_j$ are identical and equal to $m$ ("balanced dataset"), then this expression simplifies to $\X^\top \G \G^\top \X / m$.
We can define normalized indicator matrix $\newcommand{\tG}{\widetilde {\mathbf G}}\tG$ as having $1/\sqrt{n_j}$ where $\G$ has $1$. Then for both, balanced and unbalanced datasets, the expression is simply $\C_b = \X^\top \tG \tG^\top \X$. Note that $\tG$ is, up to a constant factor, the whitened indicator matrix: $\tG = \G(\G^\top \G)^{-1/2}$.
Regression
For simplicity, we will start with the case of a balanced dataset.
Consider linear regression of $\G$ on $\X$. It finds $\newcommand{\B}{\mathbf B}\B$ minimizing $\| \G - \X \B\|^2$. Reduced rank regression does the same under the constraint that $\B$ should be of the given rank $p$. If so, then $\B$ can be written as $\newcommand{\D}{\mathbf D} \newcommand{\F}{\mathbf F} \B=\D\F^\top$ with both $\D$ and $\F$ having $p$ columns. One can show that the rank two solution can be obtained from the rank solution by keeping the first column and adding an extra column, etc.
To establish the connection between LDA and linear regression, we will prove that $\D$ coincides with $\W_\mathrm{LDA}$.
The proof is straightforward. For the given $\D$, optimal $\F$ can be found via regression: $\F^\top = (\D^\top \X^\top \X \D)^{-1} \D^\top \X^\top \G$. Plugging this into the loss function, we get $$\| \G - \X \D (\D^\top \X^\top \X \D)^{-1} \D^\top \X^\top \G\|^2,$$ which can be written as trace using the identity $\|\mathbf A\|^2=\mathrm{tr}(\mathbf A \mathbf A^\top)$. After easy manipulations we get that the regression is equivalent to maximizing (!) the following scary trace: $$\tr\left(\D^\top \X^\top \G \G^\top \X \D (\D^\top \X^\top \X \D)^{-1}\right),$$ which is actually nothing else than $$\ldots = \tr\left(\D^\top \C_b \D (\D^\top \C \D)^{-1}\right)/m \sim L_\mathrm{LDA}.$$
This finishes the proof. For unbalanced datasets we need to replace $\G$ with $\tG$.
One can similarly show that adding ridge regularization to the reduced rank regression is equivalent to the regularized LDA.
Relationship between LDA, CCA, and RRR
In his answer, @ttnphns made a connection to canonical correlation analysis (CCA). Indeed, LDA can be shown to be equivalent to CCA between $\X$ and $\G$. In addition, CCA between any $\newcommand{\Y}{\mathbf Y}\Y$ and $\X$ can be written as RRR predicting whitened $\Y$ from $\X$. The rest follows from this.
Bibliography
It is hard to say who deserves the credit for what is presented above.
There is a recent conference paper by Cai et al. (2013) On The Equivalent of Low-Rank Regressions and Linear Discriminant Analysis Based Regressions that presents exactly the same proof as above but creates the impression that they invented this approach. This is definitely not the case. Torre wrote a detailed treatment of how most of the common linear multivariate methods can be seen as reduced rank regression, see A Least-Squares Framework for Component Analysis, 2009, and a later book chapter A unification of component analysis methods, 2013; he presents the same argument but does not give any references either. This material is also covered in the textbook Modern Multivariate Statistical Techniques (2008) by Izenman, who introduced RRR back in 1975.
The relationship between LDA and CCA apparently goes back to Bartlett, 1938, Further aspects of the theory of multiple regression -- that's the reference I often encounter (but did not verify). The relationship between CCA and RRR is described in the Izenman, 1975, Reduced-rank regression for the multivariate linear model. So all of these ideas have been around for a while.
Comment: +1 from me for the particulars and for referring to my answer and for introducing the RRR here (upvoting in advance because it will pass some unknown time before I sit down to tear through all that magnificent/formidable algebra!).
Answer: Linear regression and linear discriminant analysis are very different.  Linear regression relates a dependent variable to a set of independent predictor variables.  The idea is to find a function linear in the parameters that best fits the data.  It does not even have to be linear in the covariates.  Linear discriminant analysis on the other hand is a procedure for classifying objects into categories. For the two-class problem it seeks to find the best separating hyperplane for dividing the groups into two catgories.  Here best means that it minimizes a loss function that is a linear combination of the error rates.  For three or more groups it finds the best set of hyperplanes (k-1 for the k class problem).  In discriminant analysis the hypoerplanes are linear in the feature variables.
The main similarity between the two is term linear in the titles.
Comment: Here is a related question and answers on CV. http://stats.stackexchange.com/questions/14697/are-fisher-linear-discriminant-and-logistic-regression-classifier-related
Comment: Yes there is a relationship between logistic regression and linear discriminant analysis.  Efron and his student Terry O'Neilll wrote about this in the late 1970s.  I will try to find a link to a reference.
Comment: Sorry, I wrote wrong. Should be regression and LDA. I saw some articles about linear discriminants via regression, but I don't know how it works. I think LDA and logistic regression for two classes have some relations but cannot tell very clearly what they are. And for more than two classes, I don't know if there are any relations.
Comment: -1 because actually there is a deep relation between LDA and regression, as both @ttnphns and myself explain in our answers.


What Content-Type value should I send for my XML sitemap?

Question: I thought I should send "text/xml", but then I read that I should send "application/xml". Does it matter? Can someone explain the difference?
Answer: The difference between text/xml and application/xml is the default character encoding if the charset parameter is omitted:

Text/xml and application/xml behave differently when the charset
parameter is not explicitly specified.  If the default charset (i.e.,
US-ASCII) for text/xml is inconvenient for some reason (e.g., bad web
servers), application/xml provides an alternative (see "Optional
parameters" of application/xml registration in Section 3.2).

For text/xml:

Conformant with [RFC2046], if a text/xml entity is received with
the charset parameter omitted, MIME processors and XML processors
MUST use the default charset value of "us-ascii"[ASCII].  In cases
where the XML MIME entity is transmitted via HTTP, the default
charset value is still "us-ascii".

For application/xml:

If an application/xml entity is received where the charset
parameter is omitted, no information is being provided about the
charset by the MIME Content-Type header.  Conforming XML
processors MUST follow the requirements in section 4.3.3 of [XML]
that directly address this contingency.  However, MIME processors
that are not XML processors SHOULD NOT assume a default charset if
the charset parameter is omitted from an application/xml entity.

So if the charset parameter is omitted, the character encoding of text/xml is US-ASCII while with application/xml the character encoding can be specified in the document itself.
Now a rule of thumb on the internet is: "Be strict with the output but be tolerant with the input." That means make sure to meet the standards as much as possible when delivering data over the internet. But build in some mechanisms to overlook faults or to guess when receiving and interpreting data over the internet.
So in your case just pick one of the two types (I recommend application/xml) and make sure to specify the used character encoding properly (I recommend to use the respective default character encoding to play safe, so in case of application/xml use UTF-8 or UTF-16).
Answer: As a rule of thumb, the safest bet towards making your document be treated properly by all web servers, proxies, and client browsers, is probably the following:

Use the application/xml content type
Include a character encoding in the content type, probably UTF-8
Include a matching character encoding in the encoding attribute of the XML document itself.

In terms of the RFC 3023 spec, which some browsers fail to implement properly, the  major difference in the content types is in how clients are supposed to treat the character encoding, as follows:
For application/xml, application/xml-dtd, application/xml-external-parsed-entity, or any one of the subtypes of application/xml such as application/atom+xml, application/rss+xml or application/rdf+xml, the character encoding is determined in this order:

the encoding given in the charset parameter of the Content-Type HTTP header
the encoding given in the encoding attribute of the XML declaration within the document,
utf-8.

For text/xml, text/xml-external-parsed-entity, or a subtype like text/foo+xml, the encoding attribute of the XML declaration within the document is ignored, and the character encoding is:

the encoding given in the charset parameter of the Content-Type HTTP header, or
us-ascii.

Most parsers don't implement the spec; they ignore the HTTP Context-Type and just use the encoding in the document. With so many ill-formed documents out there, that's unlikely to change any time soon.
Answer: both are fine.
text/xxx means that in case the program does not understand xxx it makes sense to show the file to the user as plain text. application/xxx means that it is pointless to show it.
Please note that those content-types were originally defined for E-Mail attachment before they got later used in Web world.
Answer: text/xml is for documents that would be meaningful to a human if presented as text without further processing, application/xml is for everything else

Every XML entity is suitable for use with the application/xml media
    type without modification.  But this does not exploit the fact that
    XML can be treated as plain text in many cases.  MIME user agents
    (and web user agents) that do not have explicit support for
    application/xml will treat it as application/octet-stream, for
    example, by offering to save it to a file.
To indicate that an XML entity should be treated as plain text by
    default, use the text/xml media type.  This restricts the encoding
    used in the XML entity to those that are compatible with the
    requirements for text media types as described in [RFC-2045] and
    [RFC-2046], e.g., UTF-8, but not UTF-16 (except for HTTP).

— http://www.ietf.org/rfc/rfc2376.txt
Comment: Not really. `text/html` has been around for a very long time, and it was a bit late to change it.
Comment: Still, it's funny that the preferred HTML MIME type is `text/html` and the preferred XHTML MIME type is `application/xhtml+xml`.
Answer: Other answers here address the general question of what the proper Content-Type for an XML response is, and conclude (as with What's the difference between text/xml vs application/xml for webservice response) that both text/xml and application/xml are permissible. However, none address whether there are any rules specific to sitemaps.
Answer: there aren't. The sitemap spec is https://www.sitemaps.org, and using Google site: searches you can confirm that it does not contain the words or phrases mime, mimetype, content-type, application/xml, or text/xml anywhere. In other words, it is entirely silent on the topic of what Content-Type should be used for serving sitemaps.
In the absence of any commentary in the sitemap spec directly addressing this question, we can safely assume that the same rules apply as when choosing the Content-Type of any other XML document - i.e. that it may be either text/xml or application/xml.


List of possible image features for content based image retrieval

Question: I am trying to find a list of possible image features like color, oriented edges and so on for measuring their usability in case of finding same/similar objects in images. Does anyone know such a list or at least some features?
Comment: This is out of the topic but, is CBIR can extract feature from Open Image dataset? Is that possible to extract feature of an image even though the image is not saved in local disk?
Answer: The field itself is too vast. So i doubt you can have a fully exhaustive list here.
However, MPEG 7 is one of the primary effort in standardizing this area. So what is included here is not universal - but at least the most primary.
Here are some key feature set which are identified in MPEG7 ( I can really talk only about Visual Descriptors not others see this for full scope).
There are 4 catagory of Visual Descriptors:
1. Color Descriptors which includes :
Dominant color,
Color Layout (essentially Primary color on block-by-block basis)
Scalable Color (essentially Color histogram),
Color Structure (essentially local Color histogram),
and Color spaces to make things interoperable.
2. Texture Descriptors (see also this) which includes :
Texture Browsing Descriptor - which defines granularity/coarseness, regularity,and direction.
Homogeneous Texture Descriptor - which is based on Gabor filter bank.
and
Edge Histogram
3. Shape Descriptors which includes :
Region based descriptors are scalar attributes of shape under consideration - such as area, ecentricities etc.
Contour based which captures actual characteristic shape features and
3D descriptors
4. Motion Descriptors for Video
Camera Motion (3-D camera motion parameters)
Motion Trajectory (of objects in the scene) [e.g. extracted by tracking algorithms]
Parametric Motion  (e.g. motion vectors, which allows description of motion of scene. But it can be more complex models on various objects).
Activity which is more of a semantic descriptor.

MPEG 7 doesn't define "How these are extracted" - it only defines what they mean and how to represent/store them. So research does exists on how to extract and use them.
Here is another good paper that gives insight in this subject.
But yes, many of these features are rather basic and may be more research will create more sophisticated (and complex) feature set.
Answer: Ok I think I found a suitable list by just searching a bit more. There is a paper by Deselaers etc al. which seams to be what I was looking for!
Answer: There is also a book that bundles a set of papers related to this topic. It's called Principles of Visual information Retrieval.
Comment: Googleing about the books doesn't reveal many positive reviews. More complaints than positives actually. Do you still think it is a good reference, and if so, maybe you could tell us when it was useful to you? :)
Comment: Main reason to put it here is not that I used it much, but my teacher recommended it (and I value his opinion). Googleing about it shows that it's really a bundle of papers, and not really a book. It also shows its quite old, but yet one of the few books on the topic. Therefore, I think my answer is still appropriate.
Answer: @Dipan Mehta covered the feature descriptors that can be used. Let me now try and cover the other side of the coin by mentioning some feature detection methods that extract features good for CBIR.
My reference for my CBIR research were the papers by Sivic, Zisserman and Nister, Stewenius. There are more current papers from these authors, but these present all of the relevant ideas.
They argue that to implement an efficient CBIR methods, features of complementary properties should be used:

Shape Adapted regions - tend to be centered at corner-like features
examples:
Harris corners, multi-scale Harris, DoG (Difference of Gaussians - but also responds to edges!)
Maximally Stable regions - tend to be centered at blob-like features
examples:
MSER  (Maximally Stable Extermal Regions), DoG

Suprisingly, Wikipedia also offers a good classification of feature (detector) types, stating the type of interest regions they detect for most of the current widely used features:

edge detectors
corner detectors
blob detectors
ridge detectors

Most current articles I have read swear that SIFT (Scale-invariant feature transform) descriptors rock and are sufficiently robust to use in the combination with chosen feature detectors. References include:

already provided links
Mikolajczyk, Schmid deals with comparison of local descriptors
Dahl evaluates detector-descriptor combinations

Note! that these papers do not deal strictly with CBIR but are used as references in CBIR-related works.
Finally, it is wort mentioning that successful CBIR methods do not depend only on feature detectors and descriptors used, but also:

an efficient search structure (quantisation of visual features)
way for constructing image descriptors -- either based on the common visual features (local descriptors), or by comparing global image descriptors (this is a very new idea, so no references currently)
distance measure between image descriptors

Also, I have already answered some questions concerning CBIR on DSP and stackoverflow, both are accompanied with references and explanation and I think they might be relevant, so you might want to take a look:

DSP: 1
stackoverflow: 1, 2


What is the life expectancy of a geosynchronous satellite dependent on?

Question: When a geosynchronous/geostationary satellite is launched, how do its designers calculate its life expectancy? A random sampling of some communication satellites suggest that ~ten years might be the norm. How is this figure arrived at? Is it simply a question of propellant required for orbital corrections and eventual retirement to a graveyard orbit?
Comment: Once upon a time it was due to solar panel lifetime. Now, you have to account for technical progress - you don't want to overinvest in durability if something better can be launched in several years.
Answer: Propellant
Typically propellant consumables for station keeping were the limiting factor.  Once a Geosat reaches near the end of its propellant life, they need to maneuver it out of GEO so as to free up the slot for its replacement.
This has been mitigated somewhat by the use of electric propulsion, where Xenon or the like is used as propellant after being accelerated electrically for thrust.  The propellant in that case is much smaller in quantity due to the higher ISP but lower thrust.  I.e. If you use a low thrust very high ISP system, and have lots of time, it is more efficient long term.
Solar Panels
Solar panels used to degrade and power was thus reduced to the point where it could no longer function. (Or conversely, knowing how fast the panels would degrade, they would launch oversized panels, so that in 10 years, degraded it would still have enough power to operate).  Better panels have mitigated that somewhat.
Reaction Wheels
If there are strong pointing requirement, reaction control wheels (gyros) are well known failure points, since by definition they are moving parts.  (Kepler, Hubble, ISS, etc are examples where issues have come up).
Electronics
Electronics exposure to radiation in space, outside the Van Allen belts can degrade the electronics, but mostly this has been mitigated with better shielding and electronics.
Answer: To calculate life expectancy, there are a few things to consider. The first is to determine how long we want it to last, as this is going to drive other considerations. As the launch cost is a considerable part of the investment, one aims to maximize the lifetime, taking all other considerations into account. To be sure the satellite lives as long as we want it to, a reliability analysis is performed, taking into account everything that can fail. From that the amount of spare units to fly (doubling essential units, flying 5 amplifiers when 3 are used for normal operation etc, etc).
The second important element is the fuel budget. At launch, about half the satellite mass is fuel, considering a chemical propulsion system. Of this by far the biggest part is used to bring the satellite from its transfer orbit (which is achieved by the launch vehicle) to the geostationary orbit. The fuel budget covers a number of uncertainties (accuracy of the transfer orbit, efficiency of orbit raising maneuvers). If the fuel allocated for these uncertainties is not used, it becomes available for all other tasks and typically extends the useful lifetime beyond the design life of the satellite.


Finger picking on a acoustic steel string

Question: I recently bought a steel string and was wondering what would be the type of strings you should buy for finger picking. The strings that where on the guitar when I bought it was rather harsh on my fingers. I really want to finger pick and not chicken pick
Comment: Have you already built up callouses? As far as I know, steel strings are steel strings and will definitely cause discomfort until you have callouses.
Comment: Ok not yet. so your fingers are in for some punishment either way
Answer: Whilst lighter strings are generally thought to be better for chicken pickin', they also work for ordinary finger picking - especially on electric. If your guitar has something like .013s, you will benefit from putting .010s, or even .009s to start with. Maybe you'll get so happy with them, they'll stay on! I'm not a strong believer in having callouses - I used to do a lot of finger picking - both on acoustic and electric, and never had callouses. If you're plucking too hard, they'll probably appear. God's way of saying be more gentle...
You could also try tuning what you have (or what you replace with) down a little. The lower tension will help, as long as they don't buzz.
Another solution is finger and thumb picks. Try them, it's a Marmite thing.
Answer: As Tim mentioned in his answer, you could try finger and thumb picks.  I personally prefer the tactile sensation and control afforded by finger picking with bare fingertips.
If you are like me and prefer to eschew the use of finger and thumb picks, I would recommend trying a set of silk and steel strings.  These strings have a wrap of silk like polyester between the steel core and the metal windings that act as a padding of sorts. They also tune up with less tension. You can mix these with some lighter unwound strings from a set of extra light acoustic strings if you prefer less tension on the high e and b strings.
Here is a quote from a review of Martin M130 Silk and Steel strings.

The feel is soft and easy on the fingers, strings bend with more ease, extending the time you can physically spend with your guitar (especially important for beginners who usually complain a lot of finger fatigue, or older musicians with arthritis, or nerve damage like I have).

Here is a link to a description of silk and steel acoustic strings.  Martin Silk and Steel Strings on line
These strings do have a more mellow tone but many guitarist prefer the tone of silk and steel.  You can find them by Martin, D'Addario, Ernie Ball, John Pearse, GHS and other manufacturers and the tone may vary somewhat between brands.  If you prefer the brighter sound of 80/20 bronze then you can switch back to those when your callouses have developed more.
If you do use regular bronze acoustic strings, the lighter the gauge, the less tension required to tune to pitch.  So lighter gauge strings will be a tad friendlier on the finger tips.  But of course you will get a tad less volume as well - unless your acoustic is amplified with some type of built in pickup.
Good luck and have fun fingerpicking.


2009 Toyota Camry.. ABS light comes on occasionally.

Question: There doesn't seem to be any pattern to it coming on.  The only way to turn it off is to
kill the engine, and restart it.  Brakes seem to work alright when the light is on.
How do I test it to see what is causing this light to come on?
Answer: Without an ABS capable scan tool you would be guessing. Since the problem is intermittent a scan tool is really required since you need to retrieve any stored codes. It could be a sensor, a wiring issue or a wheel bearing allowing enough play to occasionally miss the timing ring.


Reference request : an elementary product-sum formula for binomial coefficients

Question: I apologize if this is too elementary. The following identity arises in cluster algebra, where  I'm trying to find an expression for cluster variables. Let $a,b$ be any nonnegative integers. Then there are nonnegative integers $d_0,...,d_{a+b}$ (depending on $a,b$, but not $X$) such that
$$
{X\choose a} {X\choose b} = \sum_{i=0}^{a+b} d_i{X\choose i}
$$for all large enough integers $X\gg 0$. I could prove this, but I'm pretty sure this must be well-known. I just want to get a reference. Or very short proofs (less than five lines) are welcome, too. Thank you.
Answer: $\binom{X}{a}\binom{X}{b}$ is the number of ways to choose a subset of size $a$ and a subset of size $b$ from a set of size $X$. The union of these two subsets is a subset of size anywhere from $\text{max}(a, b)$ to $a + b$, so $d_i$ is the number of different ways a subset of size $i$ can be realized as the union of a subset of size $a$ and a subset of size $b$. Whatever this number is it manifestly does not depend on $X$, and the conclusion follows.
Comment: Which implies $d_i = \binom{i}{a}\binom{a}{b-i+a}$, I think.  But the limits are not $\min(a,b)$ to $\max(a,b)$, they are $\max(a,b)$ to $a+b$.
Comment: @Brendan: ah yes, you're right.
Answer: Another very short proof: the left side is a polynomial in $X$ of degree $a+b$ that takes integer values when $X$ is an integer, so it can be expressed in the form of the right side.
The identity is equivalent to Vandermonde's theorem.
Comment: This doesn't prove that the $d_i$ are non-negative.


Is Photoshop possible on Ubuntu Touch

Question: Is it possible to run a full version of Photoshop on Ubuntu Touch.  I'm thinking about switching my wife from a standard laptop to a tablet (Nexus 10), but she does a lot of photo editing and I don't want her to be stuck with the limited Photoshop touch version.  Has anyone managed to use the full version on a tablet yet?
Comment: No, but the good news is, you don't need Photoshop to do photo editing.
Comment: The full version of adobe photoshop is really not that easy to handle without a mouse, be aware of that.
Answer: At this time Ubuntu Touch is only available as Developer Preview.
Many things do not work yet as they will be on a finalized version. This might be earliest end of 2013 or beginning of 2014.
Till that time it is just meant to give a preview for Developers. They can work on the first apps and on the core system itself to make it work well and to make it look beautifully.
You will have to wait or you will have to check for a device with a different operating system.
Additionally you should try it out before you buy - My personal opinion is, that the use of phontoshop or any other similar program will be completely different on a desktop pc with mouse or graphic tablet than on a tablet computer itself. This is a decision that neets a lot of research.

Is Photoshop possible on Ubuntu Touch


Why can't alcohols turn blue litmus red?

Question: I came across the fact that alcohols cannot turn blue litmus red. The fact confuses me as they are acidic and acids do turn blue litmus solution red. What prevents alcohols from turning blue litmus solution red?
Comment: I'm not sure but I think because of two reasons: 1- Aqua in aqueous solution (the solution I assume you mean) is amphoteric. 2- Alcohols aren't very strong acids.
Answer: Litmus is a weak acid, with a $\mathrm{p}K_\mathrm{a}$ of about 6.5.
Alcohols are extremely weak acids, with $\mathrm{p}K_\mathrm{a}$'s (typically) around 17.
The litmus itself is a much stronger acid than the alcohol. Dissociation of the alcohol won't produce enough protons to shift the equilibrium between the two colored forms of the indicator, so you'll see no color change.
Answer: Alcohol in water solution is not acidic enough to change the solution pH. So, it doesn't turn blue litmus red.
Answer: The pH of ethanol ($\ce{C2H5OH}$) or pure alcohol is $7.33$. This means that ethanol is slightly basic. And the colour of litmus paper change at $\mathrm{pH} =7$.
Consider the ionization of indicator  in solution represented by this equation:
$$\ce{HIn  <-->  H+    +   In-}$$
And the acidic  colour  of  $\ce{HIn}$ is red, the basic colour of $\ce{In-}$ is blue.
According to Le Chatelier's principle, if we put indicator in basic solution, $\ce{H+}$ reacts with base, more $\ce{HIn}$ ionized, more $\ce{In-}$ formed, so the colour of blue litmus unchanged.


Make code to wait before executing click() command

Question: I have a Java code that populates all the text fields automatically.
Before executing click() command for Submit button, I need to enter the Captcha manually. So I would like to make the code to wait for a few seconds so that I can enter the captcha.
Comment: If this is a website you control you're trying to test, you might want to mock out the Captcha (i.e. something like https://github.com/anhskohbo/no-captcha or http://stackoverflow.com/questions/4819902/mocking-away-captcha-field-when-testing-zend-form) so you can fully automate the check.
Answer: Waiting for few seconds is fragile.
Your Java code is running in some terminal. Make it to prompt for for text input and wait. Entered input will be the solution of the CAPTCHA, which your code then enters to the page. Voila, you have as much time as you need to solve the CAPTCHA!
Of course even better solution would be to have special test instance of your system where CAPTCHA is disabled. But you already know that.
Answer: You need to ask developer to display value in "Alt" attribute for testing purpose only. After testing is completed, we can remove value from alt.
You can automate captcha only using display captcha value in alt attribute.

Get the WebElement of captcha image
Fetch the value of alt attribute
Send alt value in text field
Answer: To handle CAPTCHA field in automation is extremely difficult and in some cases not possible. You can try one of the following to try and make your tests work,

Ask your dev team to set up a test environment where CAPTCHA is removed from the module you are testing, so that your tests can continue running without any problem.
Some CAPTCHA have a limited database and each image or text value has a unique ID. You can get the list of the IDs can match that to enter CAPTCHA value in the form.
Since you are using Java, you can use Thread.sleep() method to make the form wait for suffecient time before submitting the form so that you may enter the CAPTCHA code manually. But for this you will have to constantly examine the execution of your tests.
You can ask your dev team to add a hidden field with the available CAPTCHA value (Only for testing purpose, remove it before going live), which you can get in your script and have it inserted in CAPTCHA field.

Hope this helps!


what are the other tools available for editing eps files other than Illustrator?

Question: I made a vector logo using Illustrator cs6 in my office, but when I returned back to my home to work on it on Inkscape, it shows nothing, showing the error-- the file is not supported!

to solve this problem, I need Illustrator, but I don't have money to buy it.
I want to use Inkscape or similar products which are open source.
so, my question is:

what are the other tools available for editing eps files other than  Illustrator?
Comment: Just save your file as an AI8 eps and Inkscape should open it. (You'll lose some more advanced editing features though).
Comment: Save as PDF, ai, SVG depending on how "vector" is your file... and sometimes it helps to save in lower versions than your Illustrator CS6. Also this: https://inkscape.org/en/learn/faq/#How_to_open_EPS_files_in_Windows and this http://clownfishcafe.blogspot.ca/2014/05/importing-eps-files-into-inkscape.html
Comment: is there not another program which can copy all the metadata of a CS6 ,ai file & produce it exactly when needed ?plz answer with good references..thanking Scott, go-me
Comment: You can edit them on Corel. Its a little cheaer and also has a subscription plan.
Answer: Following vector drawing applications should have pretty good EPS support:

Adobe Illustrator
Corel Draw
Xara Designer Pro
Affinity Designer

Some vector drawing apps with adequate EPS support

AutoCAD
Inkscape

Of these Xara can open atleast v8 ai files with metadata. Unfortunately newer AI files are in a undocumented, possibly encrypted container, inside a PDF file. So while you can get the graphics you lose all illustrator specific stuff.
There has been some attempt in reverse engineering the container. But this is preempted by adobe as they reserve right to changes. I havent tested Xara in a long time, they might have actually reverse engineered the  ai file to some degree.
Answer: A 1-month subscription to Illustrator through the Creative Cloud is $29.99. It's not free, but it's not the hundreds of dollars it used to cost. Might be worth it when compared to the time spent trying to find a work-around.