Observing visible light itself by our eyes

Question: We know that for any object to be seen by a human eye, the light from any source must be reflected from that object so that it reaches our eye and we can detect it.....but how do we see light itself? Bcoz obviously light can't bounce off light itself, it just pass right through each other, do our eyes absorb the light for it to be detected??
Answer: You do see the light itself. That is what your eyes do - send electrical signals to your brain based on the energy from light hitting cells in your retina. Without getting into wave/particle duality, there are cells which respond to photons at different wavelengths and the signal sent to the brain is proportional to the energy of these photons. Our brains then translate these signals into colours, shapes and so on.
That light all comes from sources - so you are effectively seeing light either directly from a source, or after reflection/refraction etc from other objects. When light bounces off another object (or is absorbed etc) it passes on some of it's energy. When it hits your retina it passes on energy - and this is what you "see"
Answer: The retina in your eye contains light sensitive structures called rods and cones. The light sensitive agent within these is a class of molecules called opsins, and the bit that actually absorbs the light is a chemical called retinaldehyde that is a derivative of vitamin A.
When light is absorbed by retinaldehyde it causes the molecule to change its shape, which in turn causes the opsin to change its shape and this triggers a process called phototransduction that eventually ends up with an electrical signal being sent into the optic nerve. Your brain does the rest.
Answer: We can't actually see light. The reason we can only detect light that strikes our retina and not light that passes us is because we feel light. We have specialized light detectors which react only to specific wavelengths and when they are triggered they send electrochemical impluses to our brains optic center. The brain converts these impulses into a 3 dimensional visual representation of our surroundings. This is what we see. We also see things in our dreams without the involvement of light. Detecting light is part of the visual process but it's not the entire process. Light is what causes our brain to create images. There is no objective brightness caused by light but merely a subjective experience. This might seem counterintuitive after centuries of hearing terms like visible light spectrum, red light, blue light, etc and it's unlikely everyone can grasp this concept, but feeling light makes more sense than seeing light.


Excessive voltage drop from LiPo battery

Question: I am using a 750mAh 25C 3.7v LiPo battery for a custom electronics project which currently draws ~1.5 amps, far below the rated operating current of (0.75 * 25 = ) 18.75 amps. However, at the battery terminals (before any PCB traces) I am noticing a drop from 4.03v to ~2v, below the 3.3v I require for my MCU. Why is this drop so significant? Is the battery bad?
Comment: In a word, yes. Unless (possible facepalm moment here) you are not fully charging the battery. Even when nearly discharged, in general a battery will put out a high voltage with no load applied, so you can't use that as a check on state of charge.
Comment: @WhatRoughBeast that's not really true of this type of lithium cell.  While the voltage drops under load, the unloaded voltage is a rather useful indicator of the state of charge - not a linear one, but the slope is useful.   Much of the usable life, especially in placing something into use is when it reads in the 4.2 down to 3.7 range.  Once it's reading 3.7 volts unloaded, there is still some capacity that can be drawn but in a high load application it would be better to swap it out and recharge.
Answer: Assuming it was fully charged before, either your battery is bad or its rating is hugely overstated.
LiPo batteries should never be discharged below 3V, but for longevity it is best to have cut-off at 3.2-3.5V
Note that 1.5A is relatively high load for only 750 mAh battery of any C rating. I am not saying they shouldn't be used this way (RC toys and electronic cigarettes use same batteries at currents many times more than that) but cell lifetime will be affected.
The usual definition of C rating is "how fast the battery can be discharged safely". The safety bit should be understood as not blowing up or exhibiting immediate drop in performance. This does not mean, however, that discharging at full C rating has no negative effects. In fact, by pushing the cell to its limit you severely reduce its lifelong capacity. I've seen many 400 and 750 mAh cells used in RC helicopters completely giving up after only 50-70 charge-discharge cycles.
Comment: the poor service life in such toys tends to result more from poor charging, and also from failing to cut off the discharge before too low a voltage, than from the actual rate of discharge.
Comment: I did purchase the battery off of eBay. I also decreased the load to 350mA (for testing purposes) and still experienced a voltage drop of over 1v.
Comment: Dispose of it (take it to RadioShack or whatever you have in your area) and ask for refund if seller offers it.


Bash completion dynamic behavior

Question: I would like to have 2 different behavior of "tab" depending of the usage context.
I would like to have the default behavior of bind '"\t":complete' any time except when users are trying to complete arguments of the "mybashfunction" command. In this case I call a special function to generate the completion, but I would like "tab" to work like if bind '"\t":menu-complete' was set.
Answer: I believe that its readline library will only support one kind of tab-completion behaviour at a time.
Answer: Is this what you're looking for? Bash: menu-complete only for few matches
Comment: Nope, that already what I have. I want complete for some command and menu-complete for some others
Answer: You can achieve this by using bash complete rules ...
_myfunc() {
    _opts="zero one two"
    # COMPREPLY is bash built-in for array of possible completions
    COMPREPLY=()
    # cur & prev are current & previous words typed in shell
    cur="${COMP_WORDS[COMP_CWORD]}"
    prev="${COMP_WORDS[COMP_CWORD-1]}"
    COMPREPLY=( $( compgen -W "${_opts}" -- ${cur} ))
    return 0
}
complete -F _myfunc myfunc

This won't touch bash's normal completion but when you tab complete myfunc you'll have "zero one two" as possible completions.
Edit: oh yeah, jam this into your bashrc or similar so it's sourced in new shells.
Comment: That's not what I want, I already have a custom completion function. What I would is to have  acting as menu-complete when completing myfunc. But  acting as complete in all others case.
I have tried changing the binding inside _myfunc() but changing it inside the function is too late to have it working for the first  (but works after but in this case I can't revert to complete)

Bash completion dynamic behavior


Understanding Mixed-Effect Models

Question: I am trying to get my head around exactly how mixed-effect models produce the estimates they produce. Say you have 20 students from 100 classrooms each (200 students altogether) and you're trying to regress minutes spent studying onto GPA. My understanding of the general concept is that the model will estimate "fixed-effects," that is, what the intercept and slope would be if you ran one big regression and ignored the clustering by classroom. Then, it produces "random-effects" that are essentially classroom-specific deviations for the intercept and slope parameters. What I don't understand is how these 40 estimates (20 random intercepts, 20 random slopes) are produced. If they are just assumed to be drawn from a random normal with mean 0, how does that improve anything? Take classroom 1. Compared to classrooms 2 through 39, it has an above-average intercept and a below-average slope. But if the random-effects (deviations from grand-intercept and grand-slope) are both drawn from normals with mean 0, what's preventing the random effects from estimating a below-average intercept and an above-average slope? How does the model fitting find some "medium-ground" (partial pooling) between the grand-intercept/slope and the intercept/slope it would produce if it just ran 20 independent regressions? How does the shrinkage produced by the added mean 0 noise aid inference?
Answer: There are several issues here. First I try to be precise about terminology. The random effect for classroom has only one parameter, namely its variance. Its mean is fixed at zero. Only one parameter is estimated here in the standard statistical sense, although one can, based on this estimate, also predict the specific values taken by the random effect. This is not called "estimation" but "prediction" because these are not model parameters but rather realisations of random variables that are unobserved.
The mean zero assumption for the random effects is an identifiability assumption, meaning that if the mean were something else, you'd have an equivalent model if you'd also change the fixed overall intercept and slope, the parameters would not be identified and could not be estimated. This is not different from if your random effects were modelled as fixed effects. You'd then need an identifiability assumption of the kind that they all sum up to zero (sometimes other identifiability assumptions are used that change the interpretation of the parameters but don't change the overall model).
What is won by using a random effects model is in the first place a reduction of the number of parameters to estimate, leading to more stable estimators and to what some people call "borrowing strength", meaning that if you don't have much data/information for a single effect value (e.g. specific to one classroom), overall distribution information over all values (classrooms) can be used to say something more specific about the one about which you'd otherwise observe very little.
This is good but also to some extent risky, as the "prediction" for this (random) effect relies more on information "elsewhere in the data" than if it were a fixed effect for the specific classroom, and it is usually hard if not impossible to check to what extent this "borrowing" of information is reliable. This is a reason why, in a situation in which (a) you have enough data for every single classroom and (b) you want reliable prediction within that classroom, a fixed effect would usually be preferable. A standard recommendation is that fixed effects are used if the focus of your interest are the specific effects for your factor levels, which may also be relevant for predicting future observations, whereas random effects are typically applied if in future you are interested in new factor levels (i.e., further classrooms, not the ones already in your study), for which a fixed effects model doesn't allow predictions.
The "shrinkage" of random-effect predictions is hard to explain in intuitive terms. What I can say is this:

There are two sources of variation to be taken into account when predicting a random effect, namely the variation in the random effects themselves, and the variation at individual observation level (this is different from fitting 20 different regressions).

Formally, shrinkage does not happen conditionally on the observations; the random effect is predicted as its expected value conditionally on the observations, and this looks like no shrinkage takes place. Shrinkage only happens looking at the unconditional distribution of the predictions.

The way I see it, this shrinkage happens because the assumption that the random effects distribution is normal with mean zero internally translates to additional information that predictions "if in doubt" (i.e., if the predictions are based on not many observations at that factor level) should be chosen closer to zero than what they would seem without that assumption (this bias goes to zero if the number of observations at that factor level grows). If I understand things correctly, this could only be "repaired" at the cost of having a larger mean squared error. The requirement to balance the two different sources of variation renders the situation asymmetric in such a way that either one can choose random effect predictions on average slightly too close to zero, or one reduces their precision so that the expected squared error is ultimately larger, as predictions larger in absolute value come with a bigger potential for imprecision.

Understanding Mixed-Effect Models


Artemis - how to delete all entities from world

Question: I want to delete all entities from world. And if a tag or a group is registered for the entity, I want to remove them too. Like there was no such entity at all. It is much like World.delete function, but you should loop on all entities. I can't find a way. And can't believe the designers didn't prepare such functionality for clearing the world from entities. Do I miss something?
Answer: There's no default way of deleting all entities from the World - typically this is done by disposing and recreating the world - but it can be easily achieved by adding a custom manager:
public final class EntityTracker extends Manager {
    private Bag<Entity> entities = new Bag<Entity>();

    @Override
    public void added(Entity e) {
        entities.add(e);
    }

    @Override
    public void deleted(Entity e) {
        entities.remove(e);
    }

    public void deleteAllEntities() {
        for (Entity e : entities)
            e.deleteFromWorld();
    }
}

In recent versions of artemis-odb it's easier to use the AspectSubscriptionManager:
    IntBag entities = world.getAspectSubscriptionManager()
        .get(Aspect.all())
        .getEntities();

    int[] ids = entities.getData();
    for (int i = 0, s = entities.size(); s > i; i++) {
        world.delete(ids[i]);
    }

edit: The above code assumes artemis-odb; I'm not sure whether vanilla artemis' TagManager and GroupManager automatically removes entities upon deletion.


Mobile Push Opt-out status update per deviceid

Question: Let me quickly describe, what issue we are facing.
The push notification messages delivery rate for our clients is currently 67%, which means that 33 % have bounced or are undeliverable due to various reasons. Either the client uninstalled the app or disabled push etc. Since we are going to be sending more and more push notifications, the total amount of bounced push notifications will rise and we don't want to rely on the automatic opt-out functionality in MC anymore (it's not reliable). Therefore, we have to optimize this.
I was thinking of deactivating push notifications on a device ID level. If the push notification bounces only once, I want to stop sending push notifications to this specific device. In other words, the idea is to opt-out device IDs under the _PushAddress data view. The problem is that it didn't work for me when I was testing it out.
I found a related documentation

LINK

This article describes how to import users into MobilePush (I believe _PushAddress data view) and it also mentions the following:
"Import doesn't allow users to set the opt-out status of a device. But you can change the Marketer Status by mapping to the _Status field (either Active or Inactive)."
Do I understand correctly that it is actually possible to inactivate/opt out a certain device ID for a user (client/contact key) who has more devices?
If yes, how does it work? What is the "Marketer Status", and what is the name of the _Status field inside the _PushAddress data view? Based on the actual data view, it's a numeric value.
I was trying to find any option that would help to optimize this process, therefore I also posted a question on the possibility of targeting only specific devices based on certain criteria (Link).
Thanks for your help.
Answer: I found the answer. The "Status" attribute value should be "Active" or "Inactive", but the result value in the _PushAddress data view for the status attribute will be "1" indicating "active" or "2" inactive.
I also tested it out with some push send-outs. When the status is inactive (2), the device is not used in push notification sends. When the status is active  (1), the push is successfully sent.


How exactly does vapor pressure relate to saturation pressure?

Question: I'm confused as to what exactly is vapor pressure and saturation pressure. From what I understand, vapor pressure is just the equilibrium pressure of a vapor above a liquid at some temperature. Is this not also the definition of the saturation pressure (ie. an equilibrium pressure at some temperature)? Does a system always tend towards its saturation pressure? Or is it that there is one saturation pressure at some specific temperature, and that upon increasing the temperature, the vapor pressure will eventually reach the saturation pressure? Is the saturation pressure dependent on overall pressure?
Comment: According to [Wikipedia](https://en.m.wikipedia.org/wiki/Vapor_pressure#Meaning_in_meteorology) they are the same
Answer: You can have vapour when there is no liquid present and that vapour would exert a vapour pressure.
If however you have liquid and vapour present in dynamic equilibrium with one another then the pressure exerted by the vapour is the saturated vapour pressure.
So start off with a container with only vapour in it.
The vapour exerts a vapour pressure.
Now do something eg add liquid, cool the vapour, reduce the volume of the container, etc, so that there is also liquid in the container.
Then the pressure exerted by the vapour is the saturated vapour pressure.


How to serve multiple domains from the same code base in Play Framework 2.1 (Scala)

Question: Using Scala under Play Framework 2.1 I want to serve multiple domains using the same code base and database. Can't find anything on this for the latest version under Scala.
I'm building a multi-site CMS sort of like Magento and need to be able to detect the domain/hostname and pull a different entry from the database based on the domain being requested.
How do I detect which domain is being requested within Scala so I can serve the proper content?
I was thinking something like this in Global.scala could work:
import play.api._

object Global extends GlobalSettings {

  override def onStart(app: Application) {
    //detect domain host here
    //set global variable for which domain to use when interacting with the DB
  }

}

Or would this be something that needs to be handled in the routes file?
Answer: You can use the play.api.mvc.Call.absoluteURL method to retrieve the full URL of a controller.
As example:
val url = controllers.routes.Index.view().absoluteURL()

You need a implicit RequestHeader in scope for this call. I think the best solution to detect the URL globally, is to use the filter API.


SharePoint Foundation 2013, branding search results page?

Question: How I can brand search results page in SharePoint Foundation 2013?
I have brand other sites using custom.css file, however it dosen't work in search result page at all. What am I missing here? How I can change background etc?
Answer: The search results page exist in a search template/web part. You can edit these and even create your own based on the standard templates.
To see all the default search display templates, go to Site settings --> Master pages and page layouts. In the Master Page Gallery, click Display Templates --> Search.
The following diagram is how it all hangs together.

The following blog post explains it all in full detail. The 2nd link is how to specifically create your own.
Understanding how search results are displayed in SharePoint Server 2013
Customizing SharePoint 2013 Search Display Templates
Comment: This is does not work in Foundation, only Server.
Answer: Make sure your css is loaded by the master page. You might have to set it again if your search is hosted in a sub site.
The search page layout can differ a lot from the default SharePoint layout. You might need to redo a bunch of the styling.


Are there any Monero devs involved with the LOKI project?

Question: The Loki project is pretty new, but who is really behind it? Who are the main devs to be able to just fork monero code and build out their own software. The Monero software is pretty complicated, I'd imagine there are Monero devs behind this new system.
Comment: This question seems offtopic for the Monero StackExchange, Please go to one of Loki's social media channels to ask this question
Comment: For better or worse, this site does allow for other cryptonote/fork questions. See https://area51.meta.stackexchange.com/questions/23731/are-questions-about-other-cryptonote-coins-on-topic
Answer: Not to my knowledge. However, tewinget is a former Monero contributor, and a current (or recent past) contributor to Loki.


Once a surgebinder drains a sphere, can it be recharged?

Question: I had a hard time understanding this but I've not yet finished book 2 (maybe 75% of the way through). Seems like Kaladin was constantly finding new spheres as opposed to just recharging what he had.
Answer: Spheres recharge when they are left out in a Highstorm.  They pick up and store Stormlight from the storm.  Since Highstorms occur every couple of days, it's not hard to recharge spheres, but Kaladin is a fairly active fellow, with not a lot of spheres, so it's not surprising he needs to scrounge Stormlight where he can.
Adding to this, towards the end of Words of Radiance...

 ...they are entering the period of the season called the Weeping, where Highstorms slow then stop altogether.  This is what Dalinar's military plan is relying on, that the army can reach the Parshendi and end the war before the Highstorms resume, and not have his people exposed on the Shattered Plains with no shelter from the storms.  So if you're in that portion of the plot, Kaladin is looking for more spheres because there's been nothing to recharge them lately, and he's not the only one doing so.
Answer: IIRC its stated in the first book that if you leave a dimmed sphere outside during one of the surge storms (or whatever they were called) it would brighten again
The bright spheres are the ones that have usable power in it so a sphere that has been left in a storm is recharged so to speak unless I am mis remembering


How to install libtheora for MacOSX (ffmpeg)

Question: My ffmpeg version is missing 'libtheora' codec and I downloaded this version of 'libtheora' to make it work. http://www.theora.org/downloads/
The problem is that after extracting the zip file, I dont know how to install it. The README file does not give a lot of details. Do I just run make?
Anyone that did this before?
Answer: It is very simple with Homebrew:
brew install ffmpeg2theora

But actually it does not allow you to convert to OGG/OGV format after this. What actually helped me to convert MP4 to OGV format in the end was compiling ffmpeg with libtheora support. Detailed explanation could be found here ffmpeg Mac OSX compilation guide. And after this I finally was able to run the following command:
ffmpeg -i input.mkv -codec:v libtheora -qscale:v 7 -codec:a libvorbis -qscale:a 5 output.ogv

Comment: Hi there with `ffmpeg2theora ` this command is not correct! This is most simply and correct one:

```shell
ffmpeg2theora  --videoquality 7 --audioquality 4 --output
```

Regards
Comment: Hire you have how to add this feature to OSX actions submenu

https://github.com/klich3/OSX-Automator-custom-actions
Answer: You can install libtheora for ffmpeg with brew
brew install theora

To use it in ffmpeg you should recompile ffmpeg. Source of solution: https://trac.ffmpeg.org/wiki/CompilationGuide/MacOSX
brew install automake fdk-aac git lame libass libtool libvorbis libvpx opus sdl shtool texi2html theora wget x264 xvid yasm

git clone git://source.ffmpeg.org/ffmpeg.git ffmpeg
cd ffmpeg
./configure  --prefix=/usr/local --enable-gpl --enable-nonfree --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid
make && sudo make install

as for me it works like magic.
Answer: after reading a long mailinglist and getting sad because people are rude i finally solved this problem for me. it seems to be necessary to specify the lib paths with --extra-ldflags and --extra-cflags. so in my case it looked like this:
./configure  --prefix=/usr/local --enable-gpl --enable-nonfree \
--enable-libass --enable-libfdk-aac --enable-libfreetype \
--enable-libopus --enable-libtheora --enable-libvorbis \
--enable-libvpx --enable-libx264 --enable-libxvid
--extra-ldflags="-L/usr/local/Cellar/lame/3.99.5/lib \
-L/usr/local/Cellar/libogg/1.3.2/lib \
-L/usr/local/Cellar/theora/1.1.1/lib \
-L/usr/local/Cellar/libvorbis/1.3.5/lib \
-L/usr/local/Cellar/xvid/1.3.4/lib" \
--extra-cflags="-I/usr/local/Cellar/lame/3.99.5/include \
-I/usr/local/Cellar/libogg/1.3.2/include \
-I/usr/local/Cellar/theora/1.1.1/include \
-I/usr/local/Cellar/libvorbis/1.3.5/include \
-I/usr/local/Cellar/xvid/1.3.4/include"

depending on your required libs and versions this may be different of course.
Answer: Have you tried Macports (http://www.macports.org/) to install ffmped or libtheora?
If you don't have it ...download an install it.
then go into your console and execute this:
sudo port install libtheora

Comment: can I do the same with brew?
Comment: Nope, brew doesn't have a repo for libtheora.


What strategies assist in destroying a team's nexus?

Question: I have been playing LoL for a little over a month, and I thought that the strategy of the game was to destroy the other team's nexus without losing yours. However, I've been watching league games, and they hide in bushes and take golems from across the river and the announcers are always talking about gold. Why? Am I wrong about LoL? Is there really more to it than just destroying the enemy nexus? Is League of Legends really an in-depth strategy game, or do they hide and take golems to just have more fun?
Comment: That's like saying Chess is nothing more than taking the enemy King. Yeah, that, and how to get to that point
Comment: Hi @conjim, unfortunately I'm voting to close your question as Not A Real Question because of its very broad and also very subjective. This is a question better asked on a discussion forum, not our site, as we focus on Q&A that can be directly answered. What your question as stated asks is basically "What is the point?" which is something that will be very subjective to each player. We cannot provide a definitive answer to this.
Comment: The game is vastly more complex than you may think it is. The golems provides buffs for your champion that can greatly influence the game, depending on who they're on and how they use them. Gold is a great indicator of how many items you'll be able to buy, and so usually, the team with more gold wins the game. When you hide in a bush, the other team can't see you, so it's usually a good way of ganking someone (that is, catching them off guard, and killing them).
Comment: @FAE is there a way I could alter the question to allow it to stay up? and I dont find the question to broad its basically whats the point.
Answer: The game is very much about gold. Gold, experience, buffs (from minions) and team work.
There are lots of elements in LoL which make it a fantastic game: jungling, ganking, getting dragon and baron, backdooring, team comp.
Destroying the enemy nexus is the main objective and the only way to win, but an enormous amount of events and variable go into destroying the other teams nexus.
Answer: Well, destroying the Nexus isn't really a strategy, it's a goal. You use your strategy to achieve that goal. Several strats that come to mind:
1) Buff control. Controlling the neutral buffs is essential to winning the game. Blue and red buff are great for AP and AD champs respectively.
2) Dragon/Baron control. Try to control Baron/Dragon. Baron gives you a massive buff, drag gives you a nice global gold bonus, which leads me into the next strategy:
3) Gold and last hitting. Making sure you get the last hit on minions in lane will get you that gold. More gold = more items. More items = more pwnage.
Those are the main strategies. Obviously, LoL is a very complicated game and there are several factors and subtle things that go on in every game, but those are three big ones.


Convert SharePoint 2013 Intranet site collection to Internet

Question: How to make my SharePoint 2013 intranet (Host named site collection) to be accessible from internet. I will implement 2FA with the help of any 3rd party and will take care of authentication. Can i just create an alternate access mapping keeping the same windows claims authentication and move forward.
Answer: You should set up a ReverseProxy with Preauthentication in front of your SharePoint Farm like WebApplicationProxy.
WAP provides a lot of useful stuff:

Security is increased, because only authenticated users can communicate with SharePoint
You can pass one authentication to multiple backend-applications (SharePoint Portal, MySites, Provider Hosted Apps, ...). You can choose between Kerberos and Claims-Tokens. This feature has been improved on Windows Server 2016.
MultiFactorAuthentication is an optional feature
Integration to Office client apps can be improved by using persistent cookies (no login required when opening a document)

Implementing ADFS+WAP is not the easiest task, but it's absolutely worth it.
Comment: Hi, Thank you so much for your valuable suggestion on enhancing security to the application. It was really worth to understand these things. Can you also help me with a high level idea of how to enable my intranet to be accessed from outside the network (Same set of users as in intranet , same domain users).
Comment: This can also be achieved with WebApplicationProxy with Kerberos-Authentication. But you have to think about your existing AlternateAccessMappings. If they are "internal" (e.g. sharepoint.company.local), you have to get an public URL linke sharepoint.company.com. My recommendation: Get rid of your "local" URL and only use public Domain. Makes more migration-work, as users have to change all URLs. But it's worth the effort in the long term.
Answer: At the WebApp level you will need to edit your authentication settings to enable Anonymous authentication.
Then, set the Anonymous Access Policy for the web app to define what anonymous permissions are available.
Finally, in the site collection itself, grant the required permissions to the anonymous user (it's in the ribbon when on the permissions page).
Comment: I don't require anonymous access. Users would be given login page and they will be authenticated using 2FA. What should i do in this case. (I know about extending the web application to internet zone , but then it will be 2 set of user tokens for the same user, & 2 set of permissions . That will not work)
Comment: Then you should edit your question to remove the "made public" and "public facing" wording.  What you're describing is either an Extranet or still an Intranet, just accessible from the outside but not "publicly" accessible.
Comment: Sorry Greg for the confusion. It's like my intranet users have to access the site from outside the network. Yes you are right. How can i do it. Can i use windows claims for authentication as well.


Structure of a profinite group as a condensed set with an action of an open subgroup

Question: Let $G$ be a profinite group and $H$ be an open subgroup. As a continuous $H$-topological space, we have $G=\coprod_{G/H} H$. Does this also hold as condensed sets, i.e. do we have an identification of $\underline{H}$-condensed sets $\underline{G}= \coprod_{G/H} \underline{H}$ ? If not, what can we say about the structure of $\underline{G}$ as an $\underline{H}$-condensed set ?
More generally, can we say something about the structure of a compactly generated topological group as a condensed set with an action of (the condensed group associated to) an open subgroup of finite index ?
Comment: I think that the functor $X\mapsto\underline X$ from T1 topological spaces to condensed sets preserves coproducts. Filtered colimits of condensed sets could be computed pointwisely w.r.t. extremally disconnected sets, thus it suffices to show that this functor preserves finite coproducts. Finite coproducts of condensed sets is the sheafification of finite coproducts of presheaves on the site of extremally disconnected sets, and the result follows from unrolling the definitions (and the compactness, in general topology, of extremally disconnected sets).
Comment: I think I don't understand how one computes the sheafification in this case, can you say something about that ? Also, extremally disconnected sets are not compact objects in the categorical sense so I don't follow your argument of reduction to finite coproducts (it doesn't matter though as I am only interested in the commutation with finite coproducts anyway).
Comment: Ok, I understood the sheafification argument, the point is to show that the sheafification of a finite coproduct presheaf $\coprod \underline{X_i}$ is $S\mapsto \mathrm{Cont}(S,\coprod X_i)$ by showing that the latter satisfies the universal property. This comes from the fact that for a map  $f:S\to \coprod X_i$ we can write $S=\coprod f^{-1}(X_i)$, a finite disjoint union of extremally disconnected sets; $f$ is then uniquely determined by the maps $f_i : f^{-1}(X_i)\to X_i$
Comment: The reduction to finite is argued in the same way. I do not claim that they are compact objects. The disjoint union of the target gives rise to an open cover on the extremally disconnected source. I am not commuting it with arbitrary filtered colimits or so.
Answer: Yes, that is true. I'm not sure I'm explaining the step that's confusing you, but you are asking about a special case of the statement that the functor $S\mapsto\underline{S}$ from profinite sets to condensed sets commutes with finite coproducts. This is a formal consequence of the fact that the Grothendieck topology on profinite sets used in the definition of condensed sets allows such finite disjoint unions as covers.
Even more generally, if $G$ is any condensed group (for example $\underline{G}$ for a topological group $G$) and $H\subset G$ is a subgroup that is open (in the sense that for any profinite set $S$ with a map $S\to G$, the pullback $S\times_H G\subset S$ is an open subset of $S$ -- this is satisfied for $\underline{H}\subset \underline{G}$ for an open subgroup $H$ of a topological group $G$), then as a condensed $H$-set, one has $G\cong \bigsqcup_{G/H} gH$, where the index set $G/H$ is a discrete condensed set (i.e. just a set). Indeed, it is clear that $\bigsqcup_{G/H} gH$ injects into $G$ (on the level of presheaves, and thus after sheafification). But for any map $S\to G$ from a profinite set $S$, one has, set-theoretically, $S=\bigsqcup_{G/H} S\times_G gH$, and each term $S\times_G gH\subset S$ is open. Thus, this gives an open cover over which one gets a map to $\bigsqcup_{G/H} gH$, as desired.


Adding items from the bottom up in listview

Question: I've currently got two lists I'm working with. One filled with items and the other one is empty. When the user double-clicks an item in the filled list it's supposed to add that item to the empty/second list, but instead of adding it to the top of that list I want the newly added item at the bottom. So the items should be added from the bottom up.
I'm working with a datagridview, but am willing to use listview/listbox as long as it gets the job done.
Answer: I added two list boxes to a windows form. listBox1 and listBox2
I added Seven Items to the first list box {One,Two,Three...}
I added the double click event handler where I
<code>  listBox2.Items.Add(listBox1.SelectedItem);
</code>
The new Item added to the bottom of the list, which is what it sounds like you want.  I know the same thing works with a DataGridView.
Do you want them to be added physically to the bottom of the box leaving whitespace at the top until it is filled?  Is that what you are trying to do?
Sorry this isn't really an answer, I guess I don't have enough rep to reply as a comment.

EDIT:
ok I think I have your answer now
Add a list box with your items, it doesn't have to be a list box your Datagridview would work fine.
Try using a FlowControlPanel and change alignment to bottom up, sounds easy, well it is.
Add labels to it, like this
<code>//add a label to the flow control panel when you double click on an item
private void listBox1_DoubleClick(object sender, EventArgs e)
    {
        Label label = new Label();
        label.Text = listBox1.SelectedItem.ToString();
        label.Click += new EventHandler(label_Click);
        label.AutoSize = true;
        flowLayoutPanel1.Controls.Add(label);
        label.BringToFront();
    }
    //Will remove the label if you click on it.
    void label_Click(object sender, EventArgs e)
    {
        ((Label)sender).Click -= new EventHandler(label_Click);
        ((Label)sender).Dispose();
    }
</code>
brining the label to the front puts the new one at the bottom.
Comment: yeah I want to add them at the bottom of the list with whitespace at the top, kind of like vertically aligning it to the bottom of the listbox
Comment: FlowControlPanel and FlowDirection=BottomUp fixed my problem.
Answer: I think I understand what you want to do and the only way I know of is to fake it by pre-filling your second list / datagridview with with empty items so the user doesn't see anything. Then as your user makes selections from your first box you will replace the bottom most empty item with your new real item.
Comment: I was hoping to avoid that, but if there's no other way I guess I'm forced to do it that way. Thanks
Answer: Try my code. I am using C# 3.5
<code>    private void listBox1_DoubleClick(object sender, EventArgs e)
    {
        if (listBox1.SelectedItem != null)
        {
            int index = listBox2.Items.Count>0?listBox2.Items.Count:0;
            listBox2.Items.Insert(index, listBox1.SelectedItem);
            listBox1.Items.Remove(listBox1.SelectedItem);
        }
    }
</code>


Parametrization of a line segment using angle as parameter

Question: I know this is probably elementary level for most people here, but I've been stuck on this problem for no less than 4 hours and I am completely clueless as to how to figure this out. Is it possible for anyone to point me to an explanation made for idiots?
Answer: First you want a $y=m_1x+b_1$ equation for your line segment. Then a $y=m_2x+b_2$ equation for the line out from the origin. The second will be a function of $\theta$. Then you solve the simultaneous equations for $\theta$ and $y$ (eliminating $x$) and then for $\theta$ and $x$ (eliminating $y$).
Answer: OK, clearly $\theta$ will range from $0^\circ$ to $90^\circ$ because at the one end you have to point to $(12,0)$ on the $X$ axis and on the other end to $(6,0)$ on the $Y$ axis.
Now let's take some arbitrary value of $\theta$ in that range, and say the line at angle $\theta$ meets the line segment in blue at some point $P$ with coordinates $(x,y)$.  Drop a perpendicular line from $P$ to the $X$ axis, meeting the $X$ axis at $A$ which has coordinates  $(x,0)$.  If we call the origin of the coordinate system $O$, then we have created right triangle
$OAP$.
In that right triangle, side $AP$ over side $AO$ is opposite over adjacent for angle $\theta$; therefore $\frac y x = \tan \theta$.  And since $P$ is on the blue line, which can be described as $y = 6 - \frac12 x$, we have two simultaneous equations:
$$
y = x \tan \theta//
y = 6 - \frac12 x
$$
To solve these, eliminate $y$ to find $x$, then plug $x$ back into either equation to find $y$.
$$
x \tan \theta =  6 - \frac12 x \implies x = \frac{12}{2\tan\theta + 1} \\
y = 6 - \frac{6}{2\tan\theta + 1}
$$
And this is the parameterization:

$$
x = \frac{12}{2\tan\theta + 1} \\
y = 6 - \frac{6}{2\tan\theta + 1} \\
0^\circ \leq \theta \leq 90^\circ
$$
Comment: Thanks to everyone for answering but you are the f***ing man for breaking it down like that. Exactly what I needed....now let's hope the next problem makes sense. :\
Answer: $x$ and $y$ satisfies both
$$\frac x{12}+\frac y6 = 1\quad \wedge\quad \frac yx = \tan \theta$$
So e.g. to represent $x$ in terms of $\theta$, eliminate $y$:
$$\begin{align*}
y &= -\frac x2 + 6\\
\tan\theta &= \frac{-\frac x2 + 6}{x}\\
x\tan\theta &= -\frac x2+ 6\\
x &= \frac 6{\tan\theta + \frac12}\\
&= \frac{12}{2\tan\theta + 1}
\end{align*}$$
Answer: Use polar coordinates
$$x=r\cos\theta\ ,\quad y=r\sin\theta\ .$$
You need formulae in terms of $\theta$ only, so you want to find $r$ in terms of $\theta$.  To do this, find the equation of the line interms of $x$ and $y$, substitute the above into this equation, solve for $r$ in terms of $\theta$.
Don't forget that for a parametrisation you also need to specify the range of values of $\theta$.  This should be easy from the diagram.


Track field dependency with features

Question: I modified a field dependency on my Call content type. Features did not track the change automatically. I cannot figure out how to manually add it to features.
Answer: This is a way to it:

Add the feature exportable manually to the module.info.
You can check the available features with the drush features-list command. You have to find the field dependency format within that list, it could be a variable that looks like your field name.
If you module.info has the new field dependency, you can update the feature drush fu myfeature_module
Then review the generated files, maybe with git diff. You should see the change.

I am not sure what an exported field dependency looks like, there are different formats, these are examples so that you have an idea of what it would look like:
features[ctools][] = field_group:field_group:1

features[ctools][] = strongarm:strongarm:1

features[features_api][] = api:2

features[field_base][] = field_image

features[field_group][] = group_teaser|node

features[field_instance][] = node-about_page-field_image

features[node][] = about_page

features[variable][] = comment_about_page

Comment: I think you're talking about module dependencies. I'm asking about field dependencies on a content type (the field dependency determines when the field is visible to a user).

Track field dependency with features


What is the main difference between an Emperor, a King, a Char, a Sultan, a Dictator, a Dynast and a Tyrant?

Question: They all look the same to me. Monarchies with a different name according to time and place.
Comment: @Demis I know that wikipedia may not be the perfect source but it can be starting point for further research. Your question is very broad and generic, this makes very hard to answer precisely and dimostrate no initial research on the subject.
Comment: I think this question will be closed as too basic but have you tried reading the wikipedia page regarding Imperial, royal and noble ranks? You can also find equivalent ranks outside the classic european. https://en.wikipedia.org/wiki/Imperial,_royal_and_noble_ranks
Comment: If they all walk into a bar, you have the makings of a great joke...
Comment: I'm voting to close this question because it appears to be about comparing dictionary definitions rather than about history.
Comment: Basic or not I don't think the StackExchange forums where meant for only expert people to ask questions. Wikipedia is never deemed professional. And someone else could have the same trouble differentiating between these terms. Anyway I wouldn't mind if someone with administration privileges closed the topic, but pointing it out like this could draw some negative bias towards it.
Comment: @Meir OMG you're right ! now i'm excited to know about the rest of the joke !
Answer: Let's start with the oldest one.
Tyrant comes from ancient greek τύραννος, tyrannos. It means an absolut ruler that s unbound by law. An Absolute Ruler. The word is connotated negatively since Plato. A tyrant is always an autocrat, a ruler that holds all powers, but not all autocrats are tyrants. Generally, a Tyrant usurped his power in some way or another. Peisistratos wasn't bad but he made a power grabby paying his brutes to enforce his rule, making him a tyrant. His sons were tyrants because Peisestratos was.
Dictator started as a Roman military rank: dictator comes from dictare, to rule/govern/dictate. It was an emergency rank where one person was given the supreme rulership for 6 months. Gaius Iulius Caesar was given this power repeatedly, he handed it back again and again. Shortly after senate voted to grant it to him for life, he was stabbed to death. The term became connotated negatively only during the decades after this. A dictator is an Autocrat.
Next is a czar, char and so on. Or in Latin: CAESAR. These are variants of the cognomen of Gaius Iulius Caesar. In Roman imperial times the word became a title, and that title was adapted by various empires for their supreme rulers. The term is not negatively connotated. The German Word Kaiser comes from this and means emperor.
Emperor. This stems from Imperator - the power that a Roman Dictator was granted in an emergency, and that usually was handled by the two consoles in Roman Republican times. In imperial times, every imperator was a caesar: the official title was Imperator Caesar.
King. King is of anglo-saxon origin as cyning. It means something like hailing from a noble family. It is equivalent to roman Rex, which means ruler. Since the classic Roman times had typically people of the rank of a rex bending the knee to the imperium (empire) and its leadership, be them the two elected consuls or a single imperator caesar, or be an independant leader. As an example, Gaius Iulius said, that Ariovistus was Rex Germanorum - A/The king of Germanic People.
Leaves us with Dynast. A Dynast is generally any ruler that stems from a Dynasty. As a modern example, any Japanese tenno (~emperor) is from the same Dynasty, and the acting tenno is as a result a dynast. Queen Elisabeth II is a member of the Windsor dynasty, which branched from Saxe-Coburg and Gotha and via a few other corners can trace lineage back to William the Bastard, and so she is a dynast. Friedrich Wilhelm Viktor Albert was the King of Prussia and Emperor of the German Kaiserreich from 1888 to 1918 - and so was in that time the Dynast of the Hohenzollern.
Comment: Thank you ! This was so informative. I never thought a Czar could be related to ancient Rome. Too bad the question was closed.
Comment: @Trish Great answer, although my understanding of *Dynast* actually includes anyone who is in the line of succession to a title - generally royal/princely - by blood, not by marriage. So Princesses Beatrice and Eugenie are *dynasts*, although highly unlikely ever to be queens. The Duchess of Cambridge, OTOH, whilst she almost certainly will be Queen Consort, is **not** a dynast.


gnome-shell-extensions-user-theme won't install due to unmet dependencies

Question: I have gnome-tweak-tool install and use it regulary. I cannot however install the gnome-shell-extensions-user-theme to change the shell.
I already have the ppa but when it put
sudo apt-get install gnome-shell-extensions-user-theme
into the terminal i get this output.
dvorak@dvorak-g51vx:~$ sudo apt-get install gnome-shell-extensions-user-theme
[sudo] password for dvorak:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have requested an
impossible situation or if you are using the unstable distribution that some
required packages have not yet been created or been moved out of Incoming.

The following information may help to resolve the situation:

The following packages have unmet dependencies:
gnome-shell-extensions-user-theme : Depends: gnome-shell-extensions-common
but it is not going to be installed

E: Unable to correct problems, you have held broken packages.

Can anyone elaborate on what I am doing wrong? I have tried to both install and remove both the unmet dependencies with the same error.
Answer: Try ;
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install -f

Then try installing gnome-shell-extensions-user-theme again
sudo apt-get install gnome-shell-extensions-user-theme

If you get any error message with those first 3 commands, post back or use pastebin
Answer: I was having a similar problem. gnome-shell-extensions-user-theme is 3.2 whereas the shell is 3.4. Shell extensions seem to be handled by installing from https://extensions.gnome.org/ rather than yourself via package manager.
Answer: Installing from here: https://extensions.gnome.org/extension/19/user-themes/ ended up working for me. Had the exact same error msg.
Notes
ubuntu precise -> gnome3 shell
64bit


How can I buy apps from unsupported countries?

Question: What can you do if you are located in a country that still does not support paid apps?  Please include solutions for non-rooted users as well.
Comment: This doesn't help you right now, but it looks like Paypal might be integrated into Android Market: http://www.downloadsquad.com/2010/08/18/paypal-rushes-in-to-save-android-market/
Comment: See also: [How can I circumvent regional restrictions in the Android Market?](http://android.stackexchange.com/questions/12538/how-can-i-circumvent-regional-restrictions-in-the-android-market)
Answer: Requirements

a google checkout account with valid credit card (this has no country limitations)
pre-paid SIM card from supported country (for me pre-paid Three UK SIM worked just fine)

Steps for purchasing

insert the pre-paid SIM
enter google account that is associated with google checkout (account will be asked because of SIM change)
connect over Wi-Fi
purchase the wished application
just download and install

Questions
What about roaming charges? As a rule pre-paid SIMs do not work in other countries, so the only way to browse the market and download applications is connecting over Wi-Fi.
Why is a SIM required? Market detects Your location by SIM cards home country. By using a SIM from supported country You are effectively faking Your location.
Isn't it required for Google Checkout account or credit card used to be in supported country? It seems that not. For me these were both located in Estonia and everything went without problems.
What if application is using some weird copy protection that locks it to a specific SIM card? Would the app not stop working when real SIM is swapped in? To prevent this kind of copy protection on locking to the incorrect SIM the easiest option is to cancel the download after purchase has been complete. Swap the real SIM in and complete the download. If there is some kind of SIM check, it can be only done after installation has been complete.
Where can I get a pre-paid SIM card? Check eBay :) There is no actual credit required on the SIM, so these should be pretty cheap.
--credit: the poster himself (JaanusSiim)
Comment: This answer is many years old. Can anyone confirm if it still works?
Answer: For rooted phones:
There is an app called Market Enabler that allows you to fake which country and carrier you're on when you're browsing the market so that you can easily browse markets from other countries or carriers. using this you should be able to connect to other European markets (I don't know which country you're in but many European markets such as UK do allow paid apps, you don't have to go to the US for them).
Comment: You can't sell apps on an Android phone anyway.
Comment: For Market Enabler phone must be rooted and this only works for buying apps not selling them
Answer: I think you'd need to have a credit card that has a billing address in the US (or other supported country).
In Europe apps can be bought by users in Austria, France, Germany, Italy, Netherlands, Spain, the UK, and Switzerland.
Hopefully the number of supported countries will be increased when Google announces its apparently imminent Market improvements.  The recent change to the terms and conditions to allow for carrier billing and rumours of Paypal support suggest that there will be new payment options in the near future, potentially for countries where Google Checkout is not currently available.
If you can't use the official market you could use AndAppStore, SlideME or one of the other third party app stores.  The app selection and user base is considerably reduced however.
Comment: The billing address doesn't make any difference.  I have a German credit card (in euros), but my Google Play store is set to the US.  Some German (and Swiss) apps are Play-store-region locked and won't work for me.  I strongly suspect the real issue is that developers think this allows them to geographically restrict their apps without having to demand location permissions.  They seem to have the misconception that one's Google Play store region and one's geographic region are the same.  They're not.
Answer: You could also use Entropay for obtaining a Virtual Card to make payments in Google Play Store wherever you are. I was able to buy games and apps for my Moto X using the Virtual Card from Entropay as I live in India and Google Play Store doesn't accept my debit card.
Thanks to Mr. Narendran for sharing this info.
https://android.stackexchange.com/a/65739/77738


Why does the US keep survey miles and feet?

Question: The United States adopted the international mile and foot in 1959, but for some reason they decided to keep alongside the older units as survey mile and survey foot. These units are almost equal to the first two, but "almost" means "problem" when it comes to measuring large distances, or areas (when the units are squared), and comparing measurements. I understand that some people did not want to bother with conversion of old measurements, but that was sixty years ago and the National Geodetic Survey wasn't sleeping since then. So why do they keep both units?
Answer: Back in 1959, it was because the US had accumulated a lot of survey data using the older definition of the foot.
For most people, the 2 PPM discrepancy between the two types of "foot" went unnoticed; AFAIK, no suburban homeowner ever put up a fight over losing ~100 µm of their lawn.  But if you're making a detailed coast-to-coast map of the US, the discrepancy adds up to 9 m or so, which was enough to concern the mapmakers.  So the geodetic surveyors were temporarily granted permission to use the old definition.  However,

It was furthermore mandated that the U.S. survey foot be replaced by the international foot upon readjustment of the geodetic control networks of the United States. Although such a readjustment was completed in 1986, use of the U.S. survey foot persisted. This situation has led to confusion and errors that continue to this day, and it is at odds with the intent of uniform standards. (Source: NIST)

So, the original reason for retaining the survey foot ended 35 years ago, but the typically slow-to-react US government just didn't bother taking the old standard off the books.  Finally, in 2019 (after the OP asked the question), NIST announced the deprecation of  "survey" measure, effective December 31, 2022.
Answer: This is more of a political question than scientific, I fear.   The USA is really bad at standardization.  The US Navy, for example, still insists on knots,  fathoms, nautical miles, etc., even though their hardware is mostly full of metric fasteners and dimensions.
So far as survey-X units go, I wouldn't be surprised to find that they are in use so that all the previous benchmarks (stones hammered into the ground, mostly) don't need to be moved.  ... Peeking around, there's the "acre" and then there's the "acre (Cheshire)" which are radically different.  And hectares, and rods, and furlongs....
Rather as the UK is officially on kg but people still use "stone" , I fear no culture ever gives up its semitraditional units.
Comment: EVERY navy uses knots and nautical miles. This has nothing to do with US.
Comment: "I fear no culture ever gives up its semitraditional units" isn't exact. But it takes time (in France, although the metric system was imposed around 1800, it has taken more than a hundred years to forget all the old units).


Can I block users from my chat room?

Question: I currently do not have a chat room, but I was wondering, could I block annoying users from my chat room?
Answer: Yes, as a room owner you'll have the ability to kick/mute users from your room.
For a full list of chat-related abilities and privileges, refer to this answer on meta.
Answer: To elaborate on what gandalf3 said, no you can not just block a user from your chat room.
Chat room are set up to be public, and in normal rooms there is no mechanism to banish a user from just that room.
The "kick-mute" feature will last (depending on how frequently the user has been kicked) 1, 5, or 30 minutes. So it is not permanent.

Now you can create a restricted room where only people that you let in can talk. That type of room is called a "gallery," only the people you have on the room's access list (and mods) will be able to talk; however anyone can view it.
Those are the only two ways a room owner can control who talks in their room. But there is no way to just block a user from talking.

Can I block users from my chat room?


Controlling number range in a colour scale matplotlib

Question: I have done a Graph using matplotlib and I would like to know how to control the scale in the colour bar and how to use just two numbers...
I am creating something like:

However I would like to have a scale bar from 0 to 2.5 using just the values [0.0, 0.5, 1.0, 1.5, 2.0, 2.5] and I would like to have just one decimal number like 2.5 and not 2.500 as it been used in the example above.
The source code to create this graph:
v = np.linspace(-0.001, 2.5, 15, endpoint=True)
plt.contour(xi, yi, zi, v, linewidths=0.5, colors='k')
plt.contourf(xi, yi, zi, v, cmap=plt.cm.jet)
plt.xlabel("x (cm)")
plt.ylabel("z (cm)")
plt.colorbar()

plt.show()

P.s.: Even using from 0 to 2.5 in v doesn't solve my problem.
Thanks for helping
Comment: Did you try to use `plt.yticks()`? Example: http://matplotlib.org/api/pyplot_api.html#matplotlib.pyplot.yticks
Answer: Capture the colorbar object and then set the ticks to be what you want:
cb = plt.colorbar(...)
cb.set_ticks(tick_list)


How to authenticate with node.js Passport through a get-request?

Question: I am using Passport-Local (https://github.com/jaredhanson/passport-local) to authenticate with node.js. So far this example works like a charm, since the users are logging in thorugh a post-webform:
app.post('/login',
    passport.authenticate('local', { failureRedirect: '/login', failureFlash: true }),
    function(req, res) {
        res.redirect('/');
});

Now, however, I want to code up a JSON-based API to authenticate users by calling a particular URL. Modifying the code block to app.get(… doesn't work though.
Any advice?
Comment: Update: Seems passport is using `req.body` for username/password. If I hack passport-local to use `req.query` it works. Not my preferred method of doing it though…
Answer: I ran into this same problem, and solved it by adding this to my route handler for login:
req.body = req.query;

Maybe not the perfect solution, but it's certainly better than hacking passport. ;)
Also note that there's a pending request in passport-local to fix this problem: https://github.com/jaredhanson/passport-local/pull/12
Answer: Maybe https://github.com/yarax/passport-url strategy will be useful for you
It allows to authenticate users with a token giving by GET request
var url = new UrlStrategy({
    failRedirect : "/login",
    varName : "secret"
}, function (secret, done) { // put your check logic here
    if (secret == 'foo') done(null, {id:'bar'});
    else done("wrong");
});

passport.use(url);

Comment: This question is rather outdated, given it is about to have its third anniversary :-) Thanks for your reply anyways!


Which punctuation should be used for spelling out acronyms?

Question: Is "COPD (Chronic Obstructive Pulmonary Disease)" more correct, or would "COPD [Chronic Obstructive Pulmonary Disease]" be right?
Answer: Preference for the use of parentheses or brackets or some other punctuation, such as commas, would be a matter of style for a particular publication and governed by a style guide, such as the Associated Press Stylebook, the Chicago Manual of Style, the MLA Style Manual and Guide to Scholarly Publishing, or other style guides.
However, in most style guides that I'm familiar with the full name is provided on the first reference with the abbreviation in parentheses. For example:

Chronic Obstructive Pulmonary Disease (COPD)

After the first such reference in the article/document, the abbreviation can be used without need to reference the full term.
Comment: (+1) Just so---except that, unless writing for young children, I would not capitalize the words. People of even marginal literacy are exposed to numerous initialisms and well understand the principle of them. For such people, you don't need to capitalize the first letter of a word to draw attention to the fact that it is the first letter of the word. There is a tendency for too many capitals to creep into text, for many reasons, good and bad, so we should enthusiastically banish the unnecessary ones.
Answer: Your second example would be correct if you were quoting from some source that didn't explain the meaning of the initialism; in that case you'd be introducing words not present in the source and square brackets would be used for that.


Access Custom Object from Managed Package

Question: I have a question . Let's say that i have a controller and a visualforce page in a Managed package . Can I make the controller so that it accesses the Custom object in the Org ( in which the package has been installed ) without exposing the controller at all ?
Comment: What do you mean by access? if that is query or dml data - you can do via dynamic query by fetching required sobjects and dml on it. Please, update your question according to site rules - http://stackoverflow.com/help/how-to-ask
Answer: The controller in the managed package can have custom settings also in the managed package that nominates custom objects and custom fields that are not in the managed package to be queried/displayed/updated. (Describe calls can also be made to get more information.)
Dynamic SOQL has to be used for the querying and the get/put methods of the SObject base type used to access the data in Apex code. In Visualforce
the map-like syntax then has to be used to identify a field:
<code><apex:repeat var="field" value="{! fields }">
    <apex:inputField value="{! sob[field] }"/>
</apex:repeat>
</code>
This only works if you know in advance what you want your controller to do with the custom object e.g. just display it and allow it to be edited so that the code can all pre-exist in the managed package.
Comment: Thanks for the info . I have one another question . I got the Dynamic SOQL part . But if my visualforce page has to be included in a Custom object's page layout then it's standard controller should match with the object . So how can i come over this situation ? I have to display one VF page in the page layouts of all custom objects .
Comment: @PruthviRaj The `standardController` attribute of an `apex:page` can't be an expression so the best you could do is include a component in your package that then has to be wrapped in a page that nominates the object.


If statements in equations?

Question: When creating an equation is there any way to let someone know that if this number doesn't fit into this then use this other equation? Ex: $x>1$ then use $x+y$, or if $x<1$ then use $x-y$.  Or do you just have to find an equation that works for both probability?
Comment: here is another example, this is an equation i created to find how many square in the square aren't touching other squares Example: 2*2*2 square only has 4 sqaures that have two sides not touching another block and 8 squares that have 3 sides not touching a block. Equation: for 0sides
Answer: Like this:
$$ f(x,y)=\begin{cases} x+y & X>1 \\
x-y & X<1 \end{cases} $$
Answer: Yes, you can set up a function like this. For example, like this:
$f(x,y) =\,$ for $x>1\,$ use $x+y\,$ and for $x<1\,$ use $x-y$
Answer: A good example is the Kronecker delta.
Answer: You could also say $f(x,y) = x + \frac{x-1}{|x-1|}y$ for your particular example.

If statements in equations?


Qatar Airways Eco Power Outlet A350

Question: I recently booked an itinerary, containing a leg on Qatar's A350. I found an image on seatguru showing power outlets.
Did somebody fly the A350 in eco and can tell me if I can use a standard German laptop charger (230V, 50Hz) or do I need an adapter?
Comment: Are you sure your laptop charger is 230/50 only? Most are happy with 110-240
Comment: I can't find a reference, but I'm pretty confident it will. That looks like a standard generic international socket, designed to take European, UK, US, and probably Aus/NZ plugs. You see them a lot these days in planes, international hotels, etc.
Comment: yes, sure, 100-240 will work. I'm just not sure if it will work physically for the german plugs: http://www.tuxgraphics.org/electronics/powersockets/power_plug_frde.jpg
Answer: Yes, the German type plug will fit in there, if you look closely you will notice a curved notch in the outlet made for round pins. Check the end of the arrow:

Actually, plugs with round pins are the standard in Qatar the country, along with the UK type.
Answer: Based on the logo on the socket, this is an "EmPower" socket - which isn't surprising as they are the most common type of these sockets on airplanes.
You can find a datasheet for these types of sockets here, that claims they are "Compatible with plugs from over 170 countries", and then specifically shows compatibility with multiple forms of 2-plug European power sockets (earthed and unearthed)
So yes, this socket will accept your German power plug, along with plug from most other countries, without an adapter.

Qatar Airways Eco Power Outlet A350


Html 'Select' control always returnh selected index as 0

Question: I have placed HTML 'Select' control on aspx page and it's items(options) are loaded dynamically using javasvript. The items in dropdown appear properly on web page. But when I select any item from dropdown, it's selected index is not returned in aspx.cs file. In fact, it shows selected index as 0 and size of 'Select' html control as -1.
I have inserted the javascript(which inserts items in dropdown) in body tag. I also tried by calling javascript function on Body onload. But it didn't help.
Please advice.
Answer: Because you populated the list via javascript, the values aren't in ViewState. So, when it posts back, the code behind isn't aware of the values that are on the list.
You could use Request.Form["ddWhatever"] to get the value of the selected item, but you lost the server side capabilities when you populated it on the client.
Answer: That's a normal behavior.
Why not bind the values from the server side? Use an <asp:DropDownList> instead of <select>, give it an ID, and populate it from your .NET code before returning it to the client (Possibly on Page_Load, and make sure you check for !IsPostBack before binding)


Downgrade SharePoint 2010 from Enterprise to Standard

Question: Is there a way to downgrade a SharePoint 2010 Server from Enterprise to Standard version, preserving all contents and profiles?
Answer: From everything I've read, it is not possible to downgrade a farm.  You can, however turn off any Enterprise features that you do not wish to use.
If that is not a solution then you will need to build a new farm using Standard and then copy your existing Content Databases to that farm and attach them to web applications there.
Comment: If you go do reinstall standard make sure to deactivate all the enterprise features before you shut down the old farm before migrating the content database. If you had used enterprise features and try and move it to a standard install items could possibly break.


Alien planet concept: could a completely misty, dark atmosphere be possible?

Question: I was thinking of creating an alien planet that orbits a star slightly past the habitable zone, but is kept warm by an extremely dense atmosphere, made primarily of a black gas, but still contains oxygen, nitrogen, and other gasses that support life on earth. If this is plausible, what gas could be the cause?
Comment: *"Kept warm by an extremely dense atmosphere, made primarily of a black gas":* that is **not** how the greenhouse effect works. For the planet to be kept warm by its atmosphere, the atmosphere must let visible light in to warm the ground / ocean, but be opaque to infrared so that the re-radiated heat cannot escape. Basically, the atmosphere must be transparent to light coming from the star but opaque to thermal infrared.
Comment: @Double_S  I think you should read some or all of the scientific papers that discuss the inner and/or outer limits of the habitable zone of the Sun, listed here:  https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates  - If you want the planet to be habitable for humans & oxygen breathing life it will have to do without any of the greenhouse gases that would combine with oxygen and remove it from the atmosphere, which is a big limitation.
Answer: Nitrogen dioxide is a brown colored gas that seems to fit your scope.

However mind that a dark gas would stop light coming from the star, while to increase the planet temperature you want to stop the energy leaving the planet, creating the so called greenhouse effect.
Effective greenhouse gases are CO2, water and methane, which are transparent in the visible part of the EM spectrum while are opaque in the infrared.
Comment: If it stops light coming in, it stops photosynthesis, so any life has to be chemosynthetic.  Or possibly floating "plants" in the upper atmosphere, with surface life surviving on what falls down from them - rather like deep ocean life.
Comment: Nitrogen dioxide is not a very stable gas - it react (often violently) with many compounds).
Answer: Cosmic soot.

http://www.billcaid.com/2003/Fire2003/CedarFire2003l.html
During the 2003 wildfires in Southern California, you could look right at the sun and see sunspots.  People were calling radio stations to ask what was wrong with the sun.  Not a "black gas" but airborne solid carbon particles that filled the air.
In your world, these particles descend from space.  Like tholins that form in the upper atmosphere of Titan and rain down on it, giving it an orange atmosphere, your planet is moving through great clouds of carbon monoxide and methanol that rain down and recombine as their enter your planet's atmosphere, mostly as tiny black carbon particulates of soot.  Even in broad daylights the sun is dimmed by black clouds.
Soot is compatible with Earth-type life.  Aquatic life would not care.  Air breathers would need ways to avoid inhaling it, but that is not a big ask.
Answer: Rather than the atmosphere being a dark gas, you could have a dense, moist atmosphere that houses a lot of airborne microalgae. Earth's atmosphere contains some microalgae, at low as wellas high altitudes and in dry as well as wet climates, but not enough to visibly dim the sunlight. A thicker atmosphere could naturally hold more, especially if it has a high concentration of water vapor (which is an excellent greenhouse gas). This might imply that the surface on average is warmer than Earth's (15 C), but with less variation due to the thich atmosphere.
There could be several permanent cloud layers, each hosting their own species of microalgae, and each absorbing their own share of sunlight (microalgae are photosynthetic). The light on the surface would be murky, and the high temperature and moisture would make mist very likely.
Algae might fall to the surface during rainfall, making the rain a slightly nutritious soup that could be filtered for nourishment. The dark, warm, moist surface would be perfect for fungus.
It is not true what other have said that a black atmosphere would prevent the planet from absorbing sunlight. In fact, it will absorb all the sunlight, whereas Earth reflects about one-third of the sunlight it receives back into space. The atmosphere will transmit some energy to the surface as infrared light, but some will also radiate into space as infrared. In an equilibrium state, the planet will radiate as much energy into space as it receives. How much solar energy makes it to the ground is difficult to say.
Perhaps more importantly, a dense, dark atmosphere will limit how much heat from the planet's interior is lost into space. This helps keep the surface warm, sort of how a tea cosy keeps a teapot warm. This factor of course depends on the planet's interior temperature.


What is the difference between key types and value types in solidity? and how do you differentiate the two?

Question: So I've been learning solidity for the past month through an online course. The bad thing is there are some basic things I just cant get the hang on like in Mapping the difference between keys and values. Also what does mapping even do? I dont understand the core of what its used for. I know this question may be ridiculous to advanced programmers but help a girl out pls...
Answer: Mapping works as Dictionary, the key is the unique value which you want to access its related data later. For example if you want to keep a balance for an address that means you will search later in this dictionary by key = address and you will get the value = uin256.
<code>mapping (address => uint256) private balances;

function set(address user, uint256 balance) public returns (bool) {
    balances[user] = balance;
}

function get(address user) public view returns (uint256) {
    return balances[user];
}
</code>


Using different Ethereum network in Metamask in different tabs

Question: Is there any way to have Metamask use, for instance, the mainnet in one Chrome tab and Kovan in another? Thanks!
Answer: No, this is not possible, unfortunately.
The way I debug is to use MetaMask on the main network in a normal Chrome tab, and use a local Parity node on a testing chain in a Chrome Incognito tab.
This way you can still have two Chrome tabs on different Ethereum chains.
I hope this helps :-)
Answer: In the short term, there's no way to do this, in the long term, MetaMask is interested in doing this, but it's probably going to be a while, I wouldn't be surprised if it was more than a year out.
One way you can work around this in the meanwhile is to use multiple Chrome profiles, and you can have a different instance of MetaMask on each profile, even a different seed phrase, which can be very nice for using multiple networks at once.


Tag discussion: arthritis and other wrist problems?

Question: Thus far there are no tags for "arthritis", "carpal tunnel", or any other common wrist problems. What is the proposed tagging system here? A general 'catch-all' tag for "wrist problems"? Catch-all tag for "auto-immune" and "nerve problems"? Or individual tags for individual conditions?
Comment: (I added an RSI tag.)
Answer: I don't think catch-all tags are good in most cases. Obviously it depends on how broad the bigger tag is. For example, the milk tag was removed as the dairy tag (its parent) was not very broad. The general rule for tags is that they should be able to be used alone. I think for many medical conditions, this will be the case, even though you probably will add extra tags to go along. For example, carpal-tunnel-syndrome could probably be used alone, but you would still add in other "helper" tags. Same thing with an arthritis tag. We can see examples of this in many successful SE communities, like SO. StackOverflow has a python, but it also has more specialized tags like python-2.7 and python-3.x.
As long as the parent tag is broad enough and the specialized tag could stand alone, then it is fine to create them. In fact, the specialized tags could help with SEO (search engine optimization).
Answer: I would disagree on a general catch all tag as they make it hard to get the information you need. Is your wrist problem a strain? is it broken? is it carpel tunnel? I think they would be better served by a combination of tags that help describe the problem. Could use wrist and arthritis for example or wrist and strain to accurately describe the problem.


Is there a way to quickly swap active images for UV maps?

Question: I have been looking around for this and haven't really been able to find a definitive answer. I just finished unwrapping a model and am getting ready to bake the Masks and an ambient occlusion map. This model has a lot of different objects a modifiers so I can't exactly combine them into one mesh. Is there a way I can take all the different objects and change the active image for baking on all of them simultaneously?
Answer: Maybe Texture Atlas can be of help enter link description here


kneading vs. stretch and fold with pizza

Question: I've read in another answer, that for bread stretch and fold and kneading is more or less the same. On the other hand, almost all of the pizza recipes say kneading and almost all of the bread recipes have stretch and fold. Is there a reason for this, or more of a tradition sort of thing or is just my sample of recipes very bad?
Comment: Does this answer your question? [Why stretch and fold vs traditional kneading of bread dough?](https://cooking.stackexchange.com/questions/21675/why-stretch-and-fold-vs-traditional-kneading-of-bread-dough)
Comment: I would doubt the "almost all of the bread recipes have stretch and fold" statement. You may be misled by a recent trend of "no knead bread" and similar.
Comment: Hmm. So, kneading is faster (if you are good?), but you need drier dough for it, which pizza dough is, compared to bread dough?
Comment: I wouldn't say my pizza dough is drier.  Hydration will certainly depend on your style of pizza.  Remember both kneading and stretch and fold are about creating a gluten structure...and they both accomplish that.  Time also helps this process.  So, how long are you fermenting your dough?  I think, in the end, you will find that the answer you cite answers your question.
Answer: It is just a matter of your sample. "Kneading" and "stretch and fold" are not really the same thing - the actual relationship is that stretch and fold is a subtype of kneading. In some cases (mostly very high hydration), it is more comfortable than other subtypes, in others, any subtype will do. So, if a recipe directs the baker to just "knead", the baker will use their preferred technique, which might be stretch and fold. On the other hand, if a recipe author very much likes stretch and fold, they may write it into the recipe even if there is no technical need to prefer it over another technique. The baker may follow it, or decide to deviate.
So in the end, what gets written into the recipe is mostly a personal preference of the recipe author. And what gets done during baking is influenced by both the recipe and the baker. So the word choice is a bit random, and there is no reason to have one more commonly used in bread than in pizza or the other way round. If you noticed such clustering (and just "noticing" is actually not enough due to confirmation bias) then it is likely you got an unbalanced sample, which is a very common thing to happen.


Pythagorean Theorem on Spiral of Theodorus Triangles

Question: I have 1 right triangle of dimensions $\sqrt75$$, 11, 14$. I'd like to know how to quickly obtain the other right triangles with $\sqrt75$ as a leg, and two integers as the hypotenuse and the other leg (as per the Pythagorean theorem). It is to my understanding that these triangles are all connected somehow geometrically and, consequently, algebraically.  Are the necessary techniques for quickly obtaining them related to: https://en.wikipedia.org/wiki/Spiral_of_Theodorus and/or the proof using differential techniques shown here: https://en.wikipedia.org/wiki/Pythagorean_theorem ?
Comment: I don't see how this may be related to Theodorus' spiral. Anyway, using Pithagoras' theorem you can prove (see my answer) that there exist exactly 3 such right triangles.
Comment: Got it, thanks!  I just thought there might be a way figure out the other sides without having to determine the divisors of the common side.
Answer: Factor $75=3 \cdot 5^2$. This implies that $75$ has 6 divisors, namely $1,3,5,15,25,75$.
Your problem is equivalent on looking for all integer solution to
$$x^2+75=y^2$$
Now, write this equation as
$$(y+x)(y-x)=75$$
so that you have to solve 6 different linear systems
$$\left\{ \begin{matrix} y &+&x& =& a \\ y&-&x&=& 75/a\end{matrix} \right.$$
where $a$ is a divisor of $75$. For example, for $a=25$ you get the solution $x=11, y=14$.
The other solutions are $(37,38)$ and $(5,10)$ (and other 3 negative solutions, which must be discarded).
Comment: Ah but one has to find the divisors of a number first?
Comment: Since you want $x,y$ to be integers, it is necessary to consider only divisors of $75$ ($a=x+y$ must be an integer, and the same for $75/a=x-y$). If you are not interested in having sides with integer measure, then every possible value of $a$ is allowed, giving you infinitely many systems, hence infinitely many solutions. But these three are the unique ones with $x,y$ integers.


two boson gravitational interaction

Question: If two bosons (or photons) posess energy and momentum, then they will interact gravitationally.  If they approach each other to within a distance r, and r is small compared to their positional uncertainty then they can be considered to partially overlap. The gravitational interaction should then be estimated by the average over all relative distances and will certainly contain infinities due to the (1/r) nature of the gravitational potential. How are such infinities dealt with?  Or did I get their occurence all wrong?
Answer: In the case of photons, you will just add up the energies to obtain the total energy. This total energy will curve space according to Einstein's general relativity theory.
In the case of bosons, the gravitational energy scale is much smaller than the energy scale of the electro-magnetic and the strong force. Hence, your consideration becomes purely hypothetical and nobody will be able to answer that.
QM does not incorporate gravity. Hence, you can't just apply concepts from quantum mechanics to calculate gravitational potentials. You must dig deeper using theories which combine these two worlds. Good luck!

two boson gravitational interaction


How can I phrase questions to user tests to not give away the solution?

Question: For a site project I'm designing, I want to make sure people know where to find what they need so names of main sections must be clear. I want to test with a couple users, as many as I can perhaps. When phrasing a list of tasks for users to complete, what are some good methods to do so? (Without giving away so obviously which section contains what information)... As a rule, should I always avoid using the words of each category/section on my site in my phrasing of each task to do?
Comment: I'd test with more than a couple of users.  As to how many:  see other answers on here.
Answer: Say if it's a travel site, tell them to book a flight and a hotel.
Just give them the final objectives.
And then tell them to "think aloud" ( not what they think about xyz, but "I am pressing the red button")
If you want to ask questions as you go along  you end up asking mangled English "why did you press the 'thing,' you just pressed"
You can't call the thing by what it does because that gives the game away.
Answer: As a general rule, try to avoid using the labels for your sections. I've found that testers use your wording as a guide and focus on searching that word in the labels instead of doing the mental work of guessing where to find it.
To avoid this, describe things you can do inside the section, or content it might contain that would be beneficial for the user to find. Don't use synonyms since users can quickly figure those out as well.
Answer: Start by asking them to think out loud.
Then keep the monologue going:

Tell me what you are seeing on the screen
Tell me what do you think that thing that you are seeing does etc.

You can find out more here.
Answer: Phrase tasks from the participants perspective not knowing about the IA of the application/site.
From https://www.nngroup.com/articles/better-usability-tasks/:

Task goal: Use the location finder tool (labeled Find a Branch)
Leading user task: Find a branch near you and see when it is open tomorrow.
Improvement: When is the bank location that's most convenient to you open tomorrow?

When it is difficult find good tasks, create a story for each task that deals with the reason why the feature exists:

You need to open a new account for your business tomorrow and don't want to invest too much time in that. When is the bank location that's most convenient to you open tomorrow?
Answer: You want to phrase the question in relationship to accomplishing the end-value, to the user.  This is often not directly related (by name) to the labels of sections. e.g.

aim: see how the user does a transfer or withdrawal
Q: "How would you get your money out?"

The wording is in the focus what what they want to do, and is in the most simple and self-aware terms.
This can be hard to do when the informal way to referring to a thing is also the canonical way. With consideration to your audience, there's almost always a key.


Sentence Transformation: ... enough ... to ..... so ... that

Question:
Tu Pee was hungry enough to eat a horse.
  Tu Pee was so hungry that he could eat a horse.

I'd like to know whether the two sentences are exactly the same. Thanks a lot.
Comment: The second sentence talks about Tu Pee's *extended* capacity to eat something as big as a horse. The reason is Tu Pee's isn't hungry, he is *famished*.
Answer: Because this is a common idiom, I don't think anybody would have trouble recognizing them as the same thing. They both mean "Tu Pee was very hungry".
I may be wrong, but I can't see any difference in the literal interpretations either. In either case, we're saying Tu Pee's great hunger enables him to "eat a horse".
However, I could imagine scenarios where they are different.

Tu Pee was hungry enough that he ate a horse.
  Tu Pee was so hungry that he ate a horse.

"Hungry enough" says he could eat a horse, as in your first example. But I don't think my first example sounds very natural. My second example sounds much better to me.
I can't think of an example where this would make sense, but there is a way to interpret your second example differently.

Tu Pee was happy enough to eat a horse.
  Tu Pee was so happy that he could eat a horse.

The new metaphor makes little sense, but the literal meaning of the first example means his great happiness enables him to eat a horse. The second example could easily mean the same thing. But it could also mean Tu Pee is capable of eating a horse, and that capacity makes him happy.

Tu Pee was so happy because he knew he could eat a horse.

So applying the same grammar to your second example, we could interpret it as being hungry because of his capacity to eat a horse.

Thinking about his ability to eat a horse caused Tu Pee's stomach to rumble with hunger.
Answer: I don't think there's any significant difference in meaning between these sentences.  Both the sentences are indicative that Tu Pee, because of its hunger, was able to eat a horse.
The only subtle diffetence in meaning is that the phrase 'enough hungry' indicates that Tu Pee was as hungry as is necessary to eat a horse. On the other hand, the phrase 'so hungry' means that Tu Pee was very hungry or hungry to such a great extent that it could eat a horse.
In other words, Tu Pee's hunger shown in the latter sentence is more intense than that in the former.
Answer: I see no appreciable difference in their ultimate meaning. With  could {verb}  capacity-to-do is explicit.  With to {verb}, capacity-to-do is implicit in the pattern.

hungry enough to eat...
so hungry (that) he could eat...

The word "that" is in parentheses to show it's optional.
The complement to the "{modifier} enough" pattern is usually a to-infinitive phrase (to eat) but some speakers will supply a that-clause there (that he could eat).
The complement to the "so {modifier}" pattern  is a that-clause or a reduced clause (but not a to-infinitive phrase).
Whether it is a to-infinitive phrase or a that-clause, the pattern indicates a sufficient degree of the property expressed by {modifier} to do the thing expressed by the verb-phrase in the complement.
He was so tall that he could dunk the basketball without leaping.
He was tall enough to dunk the basketball without leaping.


Negative sign on Coriolis acceleration not necessary?

Question: Why is the Coriolis acceleration often written as $-2({\bf \Omega \times v})$, (for example Wikipedia)? Why is it not written $2({\bf v \times \Omega)}$ which means the negative sign is not needed? For example, the Lorentz force on a charge moving in a magnetic field is not written as ${\bf F} = - q({\bf B \times v}).$
Comment: To-may-to, to-mah-to...
Answer: The Coriolis acceleration is the Coriolis force divided by the mass. It has the negative sign because the Coriolis force appears as an additional force to the real forces to describe the acceleration in the non-inertial frame: $$(1) \enspace m{d^{*2}\vec r \over dt^2} = \vec F -2m\vec \Omega \times {d^*\vec r \over dt}$$  The starred time derivatives are with respect to the non-inertial frame.  The left side of (1) gives the motion in the non-inertial frame; that is, the acceleration in the non-inertial frame. The right side of (1) includes all the forces that dictate this motion in the non-inertial frame: both the net external force $\vec F$ and the fictitious Coriolis force.  Since the Coriolis force has the negative sign, so does the Coriolis acceleration.
Similarly, other fictitious forces, such as the centrifugal force, also appear on the right side of (1).
Your Wikipedia reference also discusses (1).
The Lorentz force is a real force and as such is part of $\vec F$ when it is present.
Answer: It shows direction, but you're already familiar with that.
It's a matter of set up. The Coriolis force/acceleration is derived from Euler's approach/philosophy to mechanics, as it occurs in a non-inertial frame of reference. As such, similarly to the derivation of the normal acceleration, it uses polar coordinates/spherical in most set ups. It's a matter of choice of a certain coordinate system which you'll use when tackling a problem. Note that if you choose such a coordinate system in which the Coriolis acceleration points in the positive direction, so will Euler force and the centrifugal force (with respects to their vectors)


Wordpress MU LDAP connection failures

Question: I'm using Wordpress 3.8.1,  WPMU Ldap Authentication plugin 4.0.2 (This site fixes the deprecated WordPress functions ), and Linode Hosting with Linux CentOS 6 and I'm still having problems connecting LDAP. When I test the connection it takes a long time and comes back a "Connection: Failed". Is there a way to look at a LDAP Debug file so I can check for errors?
Answer: I have my LDAP issues as well. Can you check and see if its not a firewall issue? Usually LDAP directories are behind firewalls and you need to make sure that the connection between your WP and the LDAP directory is open. Also check for if the ldap directory needs to be connected over SSL.
Comment: I do know it's over SSL and where using port 3269 has instructed by the plugin.
Comment: Try pinging your LDAP server from your Wordpress server. If it connects, you might have to use a different LDAP plugin.
Comment: Found the problem. The LDAP server for "Search User DN" needed a password in "Search User Password" and it needed a the address name of the server and not the IP address.  Some of the other plugins don't have a that option when I looked.

Wordpress MU LDAP connection failures


Custom CRS settings disappears after file reloading

Question: I have create custom CRS for my project. That's one of local CRS for Russia - MSK-72 / zone 1. Parameters are: +proj=tmerc +lat_0=0 +lon_0=66.08333333 +k=1 +x_0=1500000 +y_0=-6000000 +ellps=krass +towgs84=23.57,-140.95,-79.8,0,0.35,0.79,-0.22 +units=m +no_defs.
After switching project CRS to this one custom, all layers on my map are located on correct places. I've also reprojected layers to custom CRS. After reloading the project, layers still in correct position, but CRS both for project and for all layers is indicated as UNKNOWN. How can I fix this error?
Comment: Is the custom CRS saved as a Custom Projection in QGIS or how did you create the custom CRS?
Comment: Hi, Gabriel De Luca! I've created it in Settings - Custom Projections and after that have seen it listed as Recently Used CRS. Suppose, that after 'dancing with tambourine' I've managed to fix this error. Solution is to set parameters not in Proj String as before but in WKT...
Comment: Hi, I'm glad you found the solution. Also that you wrote the answer! I did not know that the string could bring that problem.
Answer: My own solution for this problem was:
- Set custom CRS with parameters given in Proj String;

- reload file and get an Unknown CRS in project or layer properties;
- make sure parameters of this Unknown CRS are given in WKT;

- copy WKT parameters and past it while creating new custom CRS;
This new one CRS with parameters given in WKT works good and not disappearing after reloading the priject.


How to only perform LTS upgrades?

Question: I know I've seen this documented somewhere before, but what's the option to keep update-manager from prompting for updates except for LTS-to-LTS releases?
Answer: If you go to Ubuntu > System > Administration > Update Manager, you'll see a Settings... button at the bottom left of the dialog. In the dialog, switch to the Updates tab and uncheck the updates checkboxes and set Release Upgrade to "Long Term Support Releases Only".
It should look something like:

See the community docs for more information.
Comment: Is there a way to do this without the GUI? I have an Ubuntu VPS that keeps pestering me to upgrade to 12.10.
Comment: @dgw You'll probably want to check out /etc/update-manager/release-upgrades. You can set Prompt to lts instead of normal and that should help. Run 'do-release-upgrade' to check if it finds a new release.
Comment: The given picture is misleading: "Release upgrade" is set to "Normal Releases", where it should be "LTS Releases"
Answer: Posting as an answer what @flickerfly said in a comment: the way to do it without a GUI is to change the value of Prompt in /etc/update-manager/release-upgrades.
[DEFAULT]
Prompt=lts

The possible values are (copied from the file itself):

never: Never check for a new release.
normal: Check to see if a new release is available.  If more than one new
release is found, the release upgrader will attempt to upgrade to
the release that immediately succeeds the currently-running
release.
lts: Check to see if a new LTS release is available.  The upgrader
will attempt to upgrade to the first LTS release available after
the currently-running one.  Note that this option should not be
used if the currently-running release is not itself an LTS
release, since in that case the upgrader won't be able to
determine if a newer release is available.
Comment: Why can't the non-LTS updater determine when there is a new LTS version available?
Comment: Thanks, this works for running the update in the terminal via ̣´sudo do-release-upgrade´

How to only perform LTS upgrades?


First Order Linear PDE with Boundary Value Conditions

Question: I have encountered a problem here.
Solve the partial differential equation,
$$\frac{\partial u(t,x)}{\partial t}+\frac{\partial u(t,x)}{\partial x}+u(t,x)=1$$
with the inflow boundary value
$$u(0,t)=t^2$$
I know how to solve this with an initial condition, just don't know how to implement the boundary condition.
Answer: Hint: method of characteristics.
EDIT: Using the method of characteristics, you get a formula for $u(t,x)$ on every characteristic curve $x-t=c$, involving an arbitrary constant. Substitute
the boundary condition to find that arbitrary constant.
You may be confused because of an unfortunate notational conflict.  In the PDE your function is given as $u(t,x)$, but in the boundary value the second variable is given as $t$ instead of $x$.  Since you call this a "boundary value" rather
than "initial condition", I assume that this $t$ is supposed to be the "time" variable.  So either replace $u(t,x)$ by $u(x,t)$ in the PDE, or replace $u(0,t)$ by $u(t,0)$ in the boundary condition.
$u(t,0)$.
Comment: I don't know why this was downvoted, it was posted before the OP edited his post to include the last sentence.. +1 from me.
Comment: Thank you for your answer. I know it's the method of characteristics, I just don't know how to implement the boundary condition.
Comment: Thank you, Dr. Israel. I still have to look into that. My textbook does not have a similar example.


What security vulnerabilities does macOS Sierra fix?

Question: I am still not sure If I wish to upgrade to macOS Sierra, If I will upgrade it will be caused only by the fact that macOS Sierra should fix some security vulnerabilities , therefore I would like to understand more deeply what type of security vulnerabilities does it fix?
Answer: All security fixes in Sierra 10.12.0 compared to the latest El Capitan release 10.11.6 are available here:
About the security content of macOS Sierra 10.12.
As far as I know most or all of the vulnerabilities are still unfixed in El Capitan and Yosemite. Usually a Security Update for the prior two systems is released at the same time as the new system comes out - not this time.

To get an impression of the severity of the vulnerability you can look up the CVE-number in different databases like CVE Details, National Vulnerability Database or Common Vulnerabilities and Exposures.
IMHO the former are more informative for laypersons because they provide a vulnerability scoring (CVSS3/CVSS2) (like a traffic light food labeling system) and vulnerability types. The first one also lists already available MetaSploit modules.
Example: apache_mod_php.so CVE-2016-6290

Explaining each vulnerability in detail is far beyond the scope of an answer here.