Are my half siblings related to my half brother?

Question: My parents Bianca and Ivan are currently married and have always been since before I was born. Both of my parents have had previous relationships in the past. Bianca had a previous relationship with Henry and have a son named John, making John my half brother. Ivan had a previous relationship with Alicia, and have two sons named Frank and Ernest, making Frank and Ernst my half brothers. After that, Ivan met Katy and have a daughter named Pamela, making Pamela my half sister. So basically, I have one brother from my mom's side and two brothers and one sister from my dad's side. John knows who my other half siblings are but he doesn't know them at all and he barely sees them. Is he related to them?Is there a term for this relationship?  I suspect he really isn't but I'm just curious.
Comment: I am at a loss. How is this a question about English?
Comment: @RegDwight I am wanting to know if there is a term for this relationship in English Language.
Answer: According to today's standards, they're not truly related.
However, they are members of the same clan.
Also, less than 500 years ago, if John and Pamela had a relationship, it would have been considered incestuous: a sibling was a true sibling once he or she had been recognized as such. This had to do with the Christian view of the family as a concept, I think (which is why, for instance, Shakespeare's Hamlet views his mother's marriage to his uncle as incestuous).
Comment: @Samuel: Do PLEASE re-read the answer. Goodness gracious.
Comment: It's not incestuous...they're not blood related whatsoever...so they're not really siblings.
Answer: The answer to your question depends on your understanding of the word related.
Oxford defintes related as:

related -
  adjective - Belonging to the same family, group, or type; connected.

In that sense you are absolutely related, but in another sense you might not be.  Some people use the term related to refer to primary familial connections (father, mother, sister, brother, cousin.)  In the eyes of such a person, you wouldn't be related unless you shared familial DNA.
In my opinion that definition is too narrow.  Ultimately, all humans are related, and we are genetically related to other mammals.  The important thing is, are you family?
Comment: I am asking you if my half brother is related to my half siblings?
Comment: When you say "Oxford" what do you mean? There are all kinds of dictionaries some highly regarded, such as the Oxford English Dictionary (27 volumes in print format, also online), some awful, which trade off the name "Oxford". There is no protection for the name as there is for "Champagne" and no guarantee that the publishers have ever been anywhere near Oxford, England.


Enumerating through Turing Machines That Solve Same Problem

Question: Is it possible to enumerate through all the Turing Machines that solve the same given problem? For example, we know that there exists a Turing Machine that finds a satisfying assignment given a 3SAT formula. Therefore there are infinitely many 3SAT assignment finder Turing Machines. Could we enumerate all of them? Intuitively, I would expect to be able to find a function that maps natural numbers to 3SAT assignment finders as 3SAT assignment finders is just a subset of all Turing Machines, and the set of all Turing Machines is countable. However, could we compute this function that enumerates the problem solvers? Intuitively it feels like this should not be possible, but I am not sure.
Answer: Your question is, given a TM $M$, where $L(M) = L$, is it possible to create an enumerator $E_L$ that enumerates every $TM \  M'$, such that $L(M') = L$
The answer to this interesting question is actually no, we prove this by contradiction
First consider the language $ATM = \{<M, w>| M \ is \ a \ TM \ and \ M \ accepts \ w\}$, which we know is undecidable
Our proof will show that if we can construct $E_L$, then $A_{TM}$ is decidable, hence a contradiction
Assume given $TM, M$, where $L(M) = L$ we can construct enumerator $E_L$ enumerating every $TM \ M'$ such that $L(M') = L$
Now we will have two subroutines that we will run in parallel $A$ and $B$
Given $<M,w>$, $A$ halts if $w \in L(M)$, $B$ halts if $w \notin L(M)$, either one of them is the case, so eventually one halts and gives us the answer
First lets explain how $A$ works, given $M,w$, $A$ constructs a new machine $M_w$ which recognises the language $L(M) \cup \{w\}$, $M_w$ just checks if the input is $w$ if so it accepts, otherwise it simulates $M$, now we construct the enumerator $E_{L_{M_w}}$ which enumerates every $TM$ recognising $L(M) \cup \{w\}$, now if $M$ already accepts $w$, then $L(M) \cup \{w\} = L(M)$, and so $E_{L_{M_w}}$ eventually prints the description of $M$ and hence we halt and accept
Next lets go with $B$, given $M,w$, $B$ constructs an new machine $M_{\bar w}$ which recognises the language $L(M) - \{w\}$, so $M_{\bar w}$ just checks if the input is $w$, if so it rejects otherwise it simulates $M$, now we construct the enumerator $E_{L_{M_{\bar w}}}$ which enumerates every $TM$ recognising $L(M) - \{w\}$, if $w \notin L(M)$, then $L(M) - \{w\} = L(M)$ and hence $E_{L_{M_{\bar w}}}$ eventually prints the description of $M$ and hence we halt and reject
Again its important that we run both enumerators $E_{L_{M_{w}}}$ and $E_{L_{M_{\bar w}}}$ from $A$ and $B$ respectively in parallel to guarantee that we don't loop
Using this construction, we can show that $A_{TM}$ is decidable yielding a contradiction, and hence we cannot construct such an Enumerator


SQL developer- the network adapter could not establish the connection

Question: I am new to oracle database and i was trying to set up SQL developer.After installation when I open it and make a new connection it gives me "IO error: the network adapter could not establish the connection".I tried to look up for the solution everywhere but nothing worked.Can someone please explain me in detail hoe to fix this thing?
Comment: if you didn't' install XE, it's not there
Comment: It means server is not reachable at the given address. Is Oracle XE installed on your system?
Comment: I don't think so.Is there any way I can check whether it's there on my system.I use ubuntu 16.04 lts
Answer: You have installed SQL Developer, the client.
It's effectively limited to working with files and offline data models.
If you want to do database work, you need a database.
Here's your options for getting started.
Answer: You have to start the listener with
<code>lsnrctl start
</code>


Is there a difference between Weight and Force of Gravity?

Question: Is there a difference between Weight and Force of Gravity or they just mean the same thing? My textbook does not clarifies this point.
Comment: According to wikipedia,''In science and engineering, the weight of an object is usually taken to be the force on the object due to gravity.''
Answer: Understanding this question already has an accepted answer, I was confused by this as well and did some additional research that I will share.
The first is the definition of weight. I first understood the definition of weight from the textbook I was reading as the gravitational force that exerts on a body. From this definition, there is no difference between ${F_g}$, the gravitational force, and $\vec w$, weight force.
That said, after re-reading and searching all the internet sufficiently, the definition more accurately used for weight is the gravitational force that the earth exerts on the body or "If you are on another planet, your weight
is the gravitational force that planet exerts on you." Young, H. and Freedman, R. (2016). University Physics with Modern Physics (14th ed). Pearson Education, Inc, pp. 114.
With that in mind, typically weight force is a particular type of the gravitational force that refers to the gravitational force on a body (e.g. on the moon, on Mars, on Earth). If you are referring within space such as the gravitational force of Earth on the International Space Station (ISS) or an astronaut on the ISS, they are in constant free-fall, and for sake of clarity, the force causing that free-fall is just called gravitational force since there is the sensation of weightlessness. It would be a misnomer to say how much does an astronaut weigh on the ISS and more accurate to say what is the gravitational force the earth (or the ISS) exerts on the astronaut.
The same can be said of celestial bodies, such as the moon. One would not say, how much does the moon weigh. One would say, what is the gravitational force the earth has on the moon (and so forth for the Earth to the Sun and Mars to the Sun).
When being asked for the weight force, it is generally implicitly understood, it's the gravitational force of an object on the earth (or it will be specifically called out on what body and the acceleration due to gravity on that body, e.g. find the weight force of a person of 68 kg mass on the moon which has an acceleration due to gravity of $1.620 \dfrac {m}{s^2}$). When asked for the gravitational force, the 2 object's mass will be provided or the needed data to calculate their mass.
Here is a comparison at the formula/math definitions.
Weight Force: $$\vec w = m\vec g $$ where m is the mass of the object and $\vec g$ is the acceleration vector due to gravity (e.g. has both magnitude and direction).
Gravitational Force between 2 objects:
$${F_g} = G * \frac {m_1 m_2}{r^2}$$ where G is the gravitational constant $$\frac {6.67384(80) * 10^{-11} m^3}{kg * s^2}$$ and $m_1$ is the mass of object 1 and $m_2$ is the mass object 2 with $r$ being the distance between the 2 objects.
If we were to calculate both values for 150 lb person at sea level, we would find that both equal $667 N$ (rounding to 3 significant figures). To simplify the calculation of gravitational force on the Earth, Newton derived the weight force relationship.
Hope this helps.
Answer: While both are forces, weight is generally specific to any sum of forces you feel reciprocated as a normal force (or tension). I can feel heavy in a centrifuge because of the centrifugal force. When I find myself sitting in my chair (safely away from centrifuges) the astronauts on the International Space Station and I are both are subject to the force of gravity--but only I will feel my weight in my chair as the chair pushes back up against me. The astronauts are in free fall and do not feel the sensation of weight ignoring tidal effects.
Answer: Weight is a subtle concept, because we are so used to it we don't even notice it anymore. You'll find surprising how badly some students grasp the concept of weight, despite the fact they are firmly sitting on a chair in the very same moment.
Anyway, weight is the force an object experiences when inside a gravitational field. That means me, you, StackExchange servers, air, but even ISS, which is orbiting apparently "weightless", experience weight.
You can be tricked to feel less or more heavy by applying other forces, for example in a centrifuge, on a roller-coaster, or when accelerating inside a car.
Even when you are free-falling you are experiencing weight, in fact it's exactly the reason you're falling down.
But weight is not really gravity, because sometimes it doesn't really make sense to speak about weight, even in a gravitational field.
First, whereas you can have gravity without weight (e.g. light is bended by gravitational fields, altough it has not weight, because it is massless), you cannot have weight without gravity.
Second, gravity acts both ways: as Earth is pulling you down on the ground, you are pulling Earth "up" with the same strength. Thus by talking only about your weight you're being a little selfish and hurting Earth's feelings, as well as Newton's third law's.
Comment: I don't agree with your penultimate paragraph. The first sentence should surely read, "...you can have gravity without $mass$..." This is surely equivalent to "You can have weight without mass" and does not in any way imply that you can have gravity without weight.
Comment: Yeah you're probably right, but I was trying to avoid speaking about mass etc. since my goal was to keep it simple and relatable. Or at least I think that's what I was trying to achieve four years ago.
On the other hand, I feel "weight" in more general situations doesn't really apply anymore. It's weird to speak of "Earth weight wrt the Sun" or "light weight". I guess I was trying to convey this in that sentence.
Answer: Physics texts are regrettably nonuniform in their usage of the term "weight." Here's a useful definition of weight. Your weight is numerically equal to the magnitude of the force that gravity exerts on you. But weight and gravity are not synonyms, as is seeming to be implied. Have you ever heard the expression about being weightless in outer space or when you're free falling? That doesn't mean there's no gravity in outer space or that it isn't gravity causing you to fall. Gravity as a vector force points downwards. Your weight is the UPWARDS force that the floor (or a chair) is exerting on you that counteracts gravity and keeps you from falling towards the center of the earth. (Rereading things, I believe I said what Andrew said, just differently.)
Answer: Weight is a pre-science concept which has been retrofitted into the framework of Newtonian mechanics. Not surprisingly, this retrofitting is not always consistent and is sometimes at odds with natural language usage and our intuition. For example, consider the following questions:

Does a spring balance/strain gauge measure weight ? Is it always correct ? Does a beam balance measure weight ?
Does your weight change depending on your location on the Earth e.g. at the poles, at the equator, at the top of Mt Everest, at the bottom of the oceans ?
If it were possible to drill a hole hundreds of km deep, how would your weight change at different depths in the hole ?
What does a parachutist weigh (a) when they step out of the plane, (b) when they reach terminal velocity and (c) when their parachute opens ?
What does a balloon filled with air weigh ? Does its weight change depending on altitude ? What does a balloon filled with helium weigh ?
What do the astronauts in the ISS weigh ?
What would you weigh at the L1 point between the Earth and the Moon ? What would you weigh at the L1 point between the Earth and the Sun ?
Answer: Weight is the force experienced by a body due to the gravity of the earth, a planet, a particle, or another body. The Force of gravity is the force that brings about weight.
Answer: The difference is that weight is a consequence of the Force of gravity. Weight is a quantity that you measure for a particular object, while gravity is a measure of how curved is the spacetime where that object is living. To understand better this difference, think about a light beam traveling along the space. You can't measure the "weight" of the light beam, however, the light beam will not travel in a straight line if the effects of gravity are considerable.
Answer: Weight is the force the earth exerts on the body.
Force of gravity is the force per unit mass exert by earth or gravitational field strength.
Comment: The force per unit mass due to gravity is the gravitational acceleration, not the force of gravity.
Comment: While one can call it the gravitational field strength in the Newtonian sense, the Force per unit mass is not the Force of gravity.


Why do the intake of some helicopters have a bump body?

Question: Not all but the intake of many helicopters have a bump body. Why? e.g.
Answer: I don't know of the Apache, but the Russian helicopters have a dust separator there. This link shows how the dust protection system works on the Mi-17. The Mi-28 and Ka-52 have the same engines, so the system probably works similarly.

The system works by making the air follow a curved path from entry to the first stage of the compressor. Due to inertia, heavier-than-air particles are forced to the outside of the curve, which is the center of the intake protrusion. Air in the separator is forced through baffles to separate the dust from the air, then through a channel that leads overboard. A bleed air nozzle at the end of the channel creates vacuum at the baffle section to aid with removing dust.
The system reduces engine performance as it reduces the compression ratio with bleed air.
Comment: Basically a cyclonic vacuum cleaner lol.
Comment: A giant, 2500 hp vacuum cleaner, yes. I want one.
Comment: Thank you for your answer but I think your answer would be better if add the details of that link here. again thank you


Is there a term that means that the numbers are well spread out?

Question: For example: 1, 12, 34, 41 are well spread-out, but 1, 2, 3, 4 are not well spread-out. I guess spread-out can work, but I am looking for a single-word or a non-composite adjective to say this.
Comment: 1,2,3,4 (each a difference of 1) are as evenly spaced as 1,11,21,31 (each a difference of 10) so I agree that 1,12,34, and 41 are (as Jason suggests) not as evenly spaced (or spread out) as 1,2,3,4
Comment: spread out compared to what?  1, 12, 34, and 41 are very close together if we are talking about numbers that reach into the thousands or more.  In mathematics, integers are adjacent if they are right next to each other, but 1 and 3 are not (however 11 and 13 are adjacent primes)
Comment: On the contrary, at least in terms of a pattern, I would say that 1,2,3,4 is much more evenly spread out than 1, 12, 34, and 41. (If you look at the lowest number and the highest number, and then the distribution of the numbers in between.)
Comment: Maybe "dispersed" or "scattered". You might need to specify the space available for the numbers (such as integers 0 to 100) for any term to have meaning. But if you define terms in what you are writing, you could use anything you want.
Comment: Do you consider {1,2,3,41} to be spread out?
Answer: I would say the first has a larger range than the second.  My second choice is "notnexttoeachother", where the idea of running words together is borrowed from German.  Another more serious choice is disparate.
Comment: An upvote as a thank you for making me laugh! Oh, German...
Answer: After puzzling over this for a good long time, I decided to adapt this question and then ask the experts over at math.stackexchange.com. Looks like the best word for your situation, since you are dealing with sets of numbers, is dispersion. The set {1,2,3,4} is far less dispersed than the set {1,12,34,41}. One way to measure dispersion is range, which can be found by evaluating the highest number in the set minus the lowest number in the set. There are many other more complicated methods of measurement listed on the linked Wikipedia page for dispersion if you are mathematically minded.
Hope this helps!


Best way to share and sell new CVT design?

Question: What is the best way to sell an unpatented CVT design? It is hydraulic/direct drive design, and can function as a clutch mechanism.  I am just one person, and not capable or inclined to build it myself, and i am not interested in filing a provisional patent app myself (at least, not until the design is validated as being desireable and mechanically sound).
It has been sitting in the back of my mind for 15 years, and i have forgotten some of the advanced features.  The basic machine is still there, and i can re-engineer (re-imagine) the whole device if there is a good reason to.
I apologize if this is not the best forum to ask this question.  I've gotten bored with the cryptography board (cryptographic discoveries, totally separate), since those ideas have met resistance.
Thanks.
Comment: It might not be wise to wait for final design to file for patent. Consult a patent lawyer. They can assist for doing search for existing patents and help draft the patent so as to encompass your idea as well as possible improvements (since your design is not final yet) while ensuring that application is not rejected due to prior art.
Comment: With suitable modifications, this questions might be suited for law SE or a business/finance related SE.
Comment: Thanks for advice.  I was thinking more aling the lines of non-disclosure agreement with an interested company, and let them handle patent part.  Only problem is how to get an interested party without showing them something.  May have to do provisional,  in that case.
Comment: @Zekchelovek - also you probably know but just to make sure. Once you file a provisional, at least in the US, you have a fixed 1 year deadline to file the real patent application
Comment: possibly a question for https://freelancing.stackexchange.com/ too. Actually I think it's an interesting subject with a lot to discuss, but is as much about super-early-phase business strategy as it is about the patent-law aspects
Answer: Critical CAVEAT: If you disclose it (without an NDA), or offer to sell it (without an NDA), then you will lose the right to patent it. Furthermore, while this should in theory prevent another party from patenting it, in practice, it might not. So you might get locked out of your own invention. The system is pretty unforgiving in this regard.
Comment: Thank you for feedback.  I do realize the provisional limits, having filed a couple times before.  I may try selling the NDA on ebay, with completion of NDA gaining access to invention for buyer.  That probably is a better question for legal board.


Making a Ubuntu Live USB?

Question: Using the program Universal USB Installer, is it possible to make a Ubuntu Live USB so I can boot the USB, Use Ubuntu until I get bored, shut down my computer, remove the the Live USB and then just use Windows normally?
Comment: Does this answer your question? [How to make a persistent live Ubuntu USB with more than 4GB](https://askubuntu.com/questions/397481/how-to-make-a-persistent-live-ubuntu-usb-with-more-than-4gb)
Answer: Yes, you can do it. If you want to know how to use UUI, then follow these steps:

Select the operating system:
You can select almost any Linux distribution here, you can even select antivirus tools and Windows installers (Windows Vista to Windows 10)
Select the image of the distribution or operating system or antivirus tool you choosed. UUI also offers the original website's link in case you don't have the ISO image.
Select the device you want to install it on. (Be careful, you're better using a USB, not your harddrive!)
Let UUI do the job. After it says you're done, you can reboot and boot to your USB.

Here's a image of the latest UUI version:
Answer: On Ubuntu you can use
<code>usb-creator-gtk
</code>
It should be installed by default (or get it by apt-get).
Or, from Windows, use UUI. Don't use Unetbootin for an Ubuntu 15 stick, because currently it's not working.
Answer: Personally, I've never used  Universal USB installer,so I cannot comment on that. Unetbootin has always met all my needs for creating LiveUSB. I've used it with Puppy Linux and Ubuntu. Very simple and works.
However, if you plan on using Ubuntu without installing, then I'd suggest using Virtual Box or VMWare to create an Ubuntu virtual machine. You can use it from within Windows, and it's a safe way to learn about basic steps needed in creating an actual installation.
Comment: I kinda want to use a Live USB, so i can use it in multiple devices
Comment: @Jordii Well, basic answer is "Yes, you can".  I'd use an external hard drive with full installation, however.  It's performance is a little better than USB jump drive, and jump drives can lag a little bit.
Comment: I know it serves no purpose, seth. @Serg If he wants Ubuntu 14.10, that's not fine, also for newer versions. Also one time Unetbootin completely corrupted my Ubuntu!
Answer: on windows
download the ubuntu iso image you want to try,, download win 32 disk imager, use win 32 disk imager to write the iso image to the usb stick you wish to use, this usb will be overwritten of any info you have on it
turn off computer plug in usb and turn back on, press f2 f12 or during bios load to choose boot from usb if you computer does not automatically, if you want hit f2 during bios load, go to boot options, move usb to top of list, and hdd one below to boot from usb auto any time a usb with os on it is present

Making a Ubuntu Live USB?


Do Hidden-Variable models have a large (computational) complexity?

Question: Taking hidden variables to mean an underlying dynamics characterised by some hidden variable $\lambda$, which characterises a definite state of a system at any given time, whilst reproducing the statistical predictions of a quantum mechanics. Since such a model is, by construction, classical does that necessarily mean problems that are soluble by a quantum computer in polynomial time would, in practice, have a large complexity should Hidden-Variables be true as it cannot take advantage of superposition and interference? For example should a large scale quantum computer be developed, tasked, using Shor's algorithm, with factorising large primes actually find the problem as difficult as a classical computer?
Comment: If QM is correct, then if there are  hidden variables, the hidden variable theory  has to be non-local. All the weirdness of QM will still be there, regardless of the hidden variables, because QM will remain unmodified. Now, if QM is inaccurate, then the story will be different.
Comment: I agree that a valid hidden variable theory would have to reproduce the observed quantum weirdness. But, take for example n entangled Qubits this corresponds to a state characterised by 2^n complex numbers, surely an algorithm designed to take advantage of interference due to superposition, would in practice have on the order  2^n more calculations to do if in actuality hidden variables were specifying a single state for the Qbits?
Answer: It depends what you define as a computation. It will certainly not work as Turing machine (or a modern computer), because a Turing machine is local, in the same way that a cellular automata. If you define a cellular automaton with nonlocal rules, then it will be much faster than a turing machine, in the sense that many NP problems will become polynomial in time. I do not think the speed up is specific to QM, but to many other non-local rules too.
For instance, you can define quantum cellular automata that do have an exponential speed up. But even if they claim to have local rules, the computation is nonlocal: because of the conservation of the total probability for each time step, information of the global array spread out over generally nonlocal distances must be conveyed for each time step to each local site via the normalization procedure (see here).
I do not have knowledge of non-local cellular automata that could have more power than a Turing machine (not just a speedup), but I would not be surprised if somebody finds one (well, perhaps there is some theorem that does not allow it).
Other extensions of Turing machines, local but that can run on ordinal time do have super Turing power.
I wonder if a cellular automata based on Newtonian mechanics could result in exponential speedups due to the fact that Newtonian mechanics is nonlocal (my guess is no, but I hope somebody here knows better).


Launch window from NSView subclass in cocoa

Question: Is it possible to launch a window in an NSView subclass by clicking a NSRect? I have tried makeKeyAndOrderFront but this doesn't work.
Comment: How are you creating the window? It would help if you showed the relevant code.
Answer: You can't click on a rectangle. A rectangle is just four numbers.
You can have an NSView that responds to clicks, but you should consider using NSButton instead. If you really want a custom view, you can both create the button and add it as a subview of your view programmatically. Then, set the button's target to yourself and its action to the selector of a message you'll respond to by opening the window.
One more thing: You don't launch a window. Windows aren't applications and applications aren't windows. On Mac OS X, applications have windows—always more than one (counting at least the About panel). So, you'll load the window from a nib, then make it key (respond to events) and order it front.
On that point: You probably should not have your view owning a window. Consider making a controller object to own the window instead, and having your view simply forward the message to the controller object (or even hook the button up to the controller directly).


New PC, New Operating System. Can I transfer my Steam games and data?

Question: I used to use a Mac with some Steam games like CS:GO, I'm gonna build my gaming PC soon (on Windows 10). Is transferring Steam games possible to another computer with another operating system possible. And if, how? Do I just log in and install the games or is the process different?
Comment: it may not be necessary for you to completely re-download all your games, if you transfer your steam library, you can then install steam, point to the library location, and then tell steam to check the local game files. I am sure some might not work this way, but many games are going to share the same art & assets (the massive data) even if they need different binaries
Comment: Thank you guys for all the answers, figured out I already had Steamplay on the only games I had, since most of the games that supported Mac also had Steamplay. All I cared about was CS:GO anyways :P
Answer: If the games have Steamplay, then yes, games that you have on your Mac will be able to be played on your Windows machine.
If they do not have Steamplay, you will have to buy the Windows version even if you already have the Mac version.
From the Steamplay Documentation:

Steam Play allows you to purchase your games once and play anywhere. Whether you have purchased your Steam Play enabled game on a Mac or PC (both Windows and Linux), you will be able to play on the other platform free of charge.
Comment: Just to add to this, Steam has cloud saves on many games so that when you install it elsewhere you can continue your game as if nothing happened. However, some games don't offer cloud saves so it might be good to check the important games if you want to make sure you'll be able to continue where you were at last.
Comment: Just too add too, I am pretty sure you'll be in safe hands downloading your games from your Mac to PC, since there are pretty much no Mac exclusive games so I am pretty sure everything you own will transfer properly to your PC.
Comment: To tell if a game has steam play, see the link in the answer.  There will be a steam play icon on the games main page in Steam.  It doesn't look like CS:GO has Steam Play.
Comment: @TimmyJim I think that link may be a bit outdated I think the store page changed and just having the icon for both mac and pc means it has steam play. I was checking games that I **knew** had steamplay and I didn't see that icon anywhere. I am not 100% sure though
Comment: @Ramirez Steam ought to update their page then ;).  I was looking for games that had the icon as well and I wasn't able to find any.  CS:GO and LFD1 didn't have that symbol at least.  I would think that those two games would be on Steam Play, otherwise, Steam is pretty greedy!
Comment: I was looking at Portal 2 which was kind of touted as the first game with steam play.
Answer: You can copy over your Steam folder (by default C:\Program Files\Steam) from one Windows computer to another and as long as you copy over everything and you don't change any paths, and then you re-install Steam on the new computer with the same paths as you had on the old one (and yes, you will need to re-install the Steam client), you'll have minimal work that needs to be done on the new computer.
Paths can be altered as well, but then things get more complicated -- keeping paths the same is the easiest way to make this work.
You can also just copy over the Steam steamapps directory without the rest of the Steam client and as long as the Steam client on the new computer knows of that directory, it won't have to download games again on the new computer, though you will have to "install" each one, but in that case "install" will mean "verify that everything is valid, and maybe do some minor setup work" rather than "download all 50 GB of stuff again".
If by "different operating system" you don't mean Windows 7 -> Windows 10, but instead "Windows 7 -> Mac or Linux", then this isn't going to work, but do be aware that in the vast majority of cases, if a game on Steam is available on Windows and also on Mac or Linux, if you bought one version you'll have access to the other OS versions as well for free.
That said, there are a few exceptions -- "Call of Duty Black Ops" and "Call of Duty Black Ops Mac Edition" comes to mind.
Comment: They specifically state they used a Mac and will be using Windows so this won't help at all.
Comment: While I have not tried it between the various OSes I would expect that even if it wasn't 100% that copying over the steamapps directory would go a long way towards cutting the downloads as a lot of assets should be the same even if there are some differences.
Comment: The question wasn't entirely unambiguous, so I covered several possible scenarios, including the "completely different OS to completely different OS" one.

And yes, Loren is correct -- the more the directory that's copied over matches what needs to be there, the more you'll save in bytes downloaded as it fixes the directory up.


Data from DetailViewController not displaying

Question: I'm making a chemistry calculator segment in an app I'm working on, and I cannot get the data and I cannot get the information to correctly populate the screen. There is a secondary issue, the alignment, and if someone can help me with that I'd greatly appreciate it, but it isn't the primary focus of this question - I'll make a dedicated topic for it.
So I'll go over what I want to do, and what I've tried. What I'm trying to do is make a chemistry calculator where depending on what equation is selected, a UIStepper max/min.Value is modified to include all possible derivations of that equation, as well as certain UILabels and UITextFields shown/hidden.
I have confirmed that I have data passed down from the MasterViewController as I've set the data to an NSString called _equation, and successfully used _equation to modify the title of the DetailViewController under self.title in viewDidLoad.
I have tried placing and initializing all UIStepper properties appropriately under a if/if else nest under viewDidLoad (which also quantizes the _equationName possible values to an integer (eqNum) so that it can be used in a switch statement). I have also tried placing the UITextField hidden properties under viewDidLoad, to no avail.
So without further ado, let's get to the code. I've truncated the code down to one equation so you can see what's going on here easier - note that this is nested under the IBAction for the Calculate button:
<code>// Take _equationName quantization and use it in a switch case to determine the formula that IBAction will use:
if (dflt)
{
    switch (eqNum)
    {
        case 1:
            if ((stepper.value = 1))
            {
                // Change deriv_units appropriately:
                deriv_units.text = @"Energy (Joules)";
                // This is a Planck's constant calculation, we hide the second variable as the constant
                // is stored:
                value2.hidden = YES;
                value2_type.hidden = YES;
                // Now we set up the parameters of the first entry variable:
                value1_type.text = @"Frequency (in Hz)";
                double frequency = [value1.text doubleValue];
                double Planck = 6.626069e-34;
                double energy = Planck * frequency;
                // Now we set up the return field to return results:
                NSString* resultIntermediate = [NSString stringWithFormat:@"%f", energy];
                result.text = resultIntermediate;
                units.text = @"J";
            }
</code>
and the subsequent code under viewDidLoad:
<code>- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self configureView];
    self.title = _equationName;
int eqNum;
if ((_equationName = @"Energy-Frequency Relation"))
{
    eqNum = 1;
    // Set stepper bounds for derivation:
    [stepper setMinimumValue:1];
    [stepper setMaximumValue:3];
    self.stepper.stepValue = 1;
    self.stepper.wraps = NO;
    self.stepper.autorepeat = NO;
    self.stepper.continuous = YES;
    // This is primarily a two-variable equation, so hide UITextView and UILabel #3:
    value3.hidden = YES;
    value3_type.hidden = YES;
}
</code>
(Props to anyone who recognizes this - it's Planck's relation! :D)
Here is what the GUI is supposed to look like (as it appears in Storyboard):

Here is what it comes out looking like in the iOS Simulator:

Note the misalignment issue, which isn't the principle issue in play here.
Also note that right now, the switch statement for equation parameters is under an if tree that checks to see if dflt (a Boolean variable assigned to UISwitch) returns true for double-precision calculations. However, upon toggling the switch ON, the issue does not correct.
Here's an even more complete explanation:

value#.text is the number entered in one of the three UITextFields, from top to bottom.
value#_type is the text to be displayed in the corresponding UILabel.
deriv_units is the UILabel below the one marked "Derivation Units", and is used to display which derivation of the equation has been selected using the UIStepper.
At bottom: The rightmost UILabel is the result label, whereas the leftmost is the units label.

Many thanks to anyone who can help this beginning developer along the path of programming righteousness.
Comment: Try using breakpoints to make sure your ifs and switches do what you expect them to do.
Answer: <code>- (void) viewDidAppear: (BOOL) animated{
    [super viewDidAppear: animated];
    // some rude NSAsserts, but let's be sure
    NSAssert(value1_type != nil, @"Your control element is nil, it might not be hooked up");
    // you should now see this text in the textfield
    value1_type.text = @"Frequency (in Hz)";

    NSAssert(result != nil, @"Your control element is nil, it might not be hooked up");
    result.text = @"some test text";

    NSAssert(units != nil, @"Your control element is nil, it might not be hooked up");
    units.text = @"J";
}
</code>
Comment: How do you declare the selector? It throws me "No visible @interface for UIViewController declares the selector 'viewDidAppear'
Comment: Excuse me, I made a mistake in the method name.
Comment: I added it and it gives me two things: a warning at the function declaration telling me that there's a conflicting return "void vs. id", secondly upon simulating when I enter the DetailViewController it throws an error. It doesn't seem to like the first NSAssert in particular.
Answer: About your alignment issue: it looks as though you are creating the storyboard for 4" screen, while running it on a 3.5" screen. In the storyboard onnthe lower right there are some small buttons, one of thise allows you to change instantly between the display for either 4" or 3.5".
Have you made sure your controls are connected to your code?
Comment: Great; fixed! I'm assuming that's the difference between the 3/3GS/4/4S and iPhone 5 screen sizes. Any ideas on the main issue?
Comment: Yep (if that were it, I'd bow my head and run away in shame). Now that I think about it, there's a possibility that I might have erroneously hooked up the UISwitch or UIStepper to an IBOutlet, which obviously won't make the _dflt_ statement true and do anything. Let me check that; I'll keep you posted.
Comment: Right now it's connected to IBOutlet. Does it need to be linked to IBAction?
Comment: A IBOutlet gives you access from your code to the object in IB; an IBaction gives an object in IB the ability to call code in your source. Put differently: an IBOutlet allows you to change the object fro within code (set it hidden, change its frame or color, remove it from superview etc), an IBaction is simply a method that will be shown in IB and  might (not necessarily) be executed as a consequence of an action on the control in IB. So I think you would want your value3 be connected to an IBOutlet, and the calculate btn to an IBAction.
Comment: The Calculate button and double-precision switch are routed to IBActions, whereas everything else is IBOutlet.
Comment: Just to rule out the obvious: have you tried setting some text in the labels in -viewDidAppear?
Comment: No, and I checked my hierarchy - the project did not add viewDidAppear automatically, how would I go about setting text there manually?
Comment: I don't know how to format code in a comment, so I put it in an answer


Michelson-Morley Experiment Why 90-degree rotation

Question: Why the apparatus is rotated by 90 degree? If it is not rotated, there is still path difference between two lights. So why it is rotated?
Comment: Please can you provide a reference which states that the apparatus must be rotated?
Answer: Superfrankie,  You were right about the first part. It doesn't matter what direction the arms of the experiment go as long as they are the same length. For many experiments like gravitational waves it's better to cover the full 90°. That way when you rotate experiment you will have a full range or a full contrast to compare the two readings.
Answer: I believe there was no such rotation by 90 degrees of the experimental setup, relative to the floor at least. The aim of the experiment was to measure the influence of moving through the hypothetical Aether, a substance which was hypothesized to be the medium in which light-waves travel.
The original measurement took place at two different times in the year, in which the Earth would be moving in different directions with respect to this elusive Aether. This movement of the medium should then be measurable in the speed of light, in the framework of Galilean relativity. In the end, they weren't able to find any such difference, concluding that light is not traveling in such an Aether material!
Check out the Wikipedia, especially the diagram! https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment
Comment: The first picture on that page shows the experiment sitting on a mercury trough.  The purpose of that trough was to allow the experiment to be easily rotated.
Answer: Simply to account for the case where they might be measuring perpendicular to the flow of the postulated ether, which was assumed to be the medium that the light "waves" were "oscillating in.


What can I do to maximize the efficiency of the defogger?

Question: As I understand the 'defogger' for the windscreen consists of blowing hot air up from the bottom of the windscreen. There are claims that rolling the windows a crack speeds up the defogging - how does that work? What can be done when the windows have to be all the way up; e.g. in case of rain, snow or strong winds?
Comment: Take a look at [this question](http://mechanics.stackexchange.com/questions/39997/does-putting-down-the-visors-help-defogging-the-windshield/39999#39999) which came up yesterday, must be that season, and see if it answers your question. If it doesn't perhaps you can refine this one to clarify where it falls short.
Comment: Rolling down the window an inch gets you rid quicker of the vapour saturated air in the car. Fresh unsaturated air absorbs more (and quicker) vapour, resulting in quicker windshield defog.
Comment: @dlu The other question was specifically about the visors' effect on defogging. My question was more on the lines of: For any [generic] car, what steps can reduce/prevent fogging?
Comment: Yes, but it also included a set of, generally good, steps. The one thing to add would be to turn on a/c if you have it.
Answer: Turning on the air conditioner helps dry out the air. It seems counter-intuitive to have both the heat and the air conditioning running at the same time, but I personally have found that it works far better than rolling down a window or using the heat on the defog setting alone. I've also heard that running the AC in the winter time is good to help keep the seals from drying out.
To be clear, I'm saying to turn the heat all the way to the hottest setting, turn the air deflector to the "defogger" setting so that the hot air blows up along the windshield, and then also turn on the air conditioning.
Answer: The only way I know as to each of the hundreds of brands, models and years of cars is to read the owner's manual and to follow instructions. All cars are not sealed but have a designed rate of air exchange even when the A/C is off. If all is working there is no way to improve. If you are having issues with this feature, it is best to have a mechanic check the car. For example, allcars from 15 years ago +- have a cabin air filter. If clogged the volume of air could be less than optimum. To defog the A/C compressor must be in operating order as it takes moisture out. The A/C is very complex and each tech must be certified to repair.
Comment: Welcome to the site and thanks for stepping up to help with this question! I'm wondering if you can focus this to some tips that a driver might use to get the more effective defogging – for example, make sure cabin air filter isn't clogged, turn on A/C, check owner's manual for tips.


What are these plants? Please help identify

Question: I bought Gladiolus (sword lily) bulbs from an e-commerce site. But the plants which have grown from the bulbs I received do not seem to be Gladiolus. I would appreciate any help in identifying what these plants actually are. The leaves are long grass-like but smooth and somewhat waxy, and the flowers are white as shown in the pictures.
Answer: Having difficulty recognising this - it might be one of the Tritonia - there is one called Tritonia gladiolaris with a synonym name of Gladiolus lineatus, which might explain why you haven't got the true Gladioli you expected, but the foliage looks a bit too narrow to definitely be that. Some images here  https://keyserver.lucidcentral.org/weeds/data/media/Html/tritonia_gladiolaris.htm.  When you ordered, was there a Latin or botanical name for the bulbs?
Comment: Thanks for replying, @Bamboo. But the leaves of the Tritonia gladiolaris in your link appears flat, blade-like. However, my plants have nearly cylindrical long leaves, which are also somewhat waxy. Unfortunately, no Latin name was there in the e-commerce page. It was only mentioned as Gladiolus and sword lily.
Comment: Well how odd - I'm not sure where you are, but rain lilies usually bud in August, so I wouldn't expect it to be in flower now in June..... it definitely  does look like Zephyranthes though, but I did not consider it because its June, not late summer...my oversight, given I don't know where you are
Answer: Found it from a reddit answer. The plants I received are actually white rain lily rather than sword lily which I ordered.
Comment: That would have been my first guess; native pink ones are somewhat common here . They bloom fast but then fade fast . More a novelty than a flower for a bed.


Christ as primordial sacrament

Question: The theologian Edward  Schillebeeckx described Christ as the primordial sacrament.  What does that mean?
Answer: Edward Schillebeeckx was a Dominican priest, born in Belgium in 1914, taught theology  at the  University of Nijmegen in the Netherlands, and was influential at the Vatican Council. He was a very prolific writer. He expired in 2009.
William J Hill OP, a fellow Dominican, wrote a "non-technical" summary of Schillebeeckx work in this field called "Christ, the Sacrament of the Encounter with God". Google William J Hill Christ Sacrament Encounter
Fundamental is the concept of Encounter.
An Encounter with God is always sacramental, in that it must involve some visibility or physical expression, capable of human perception; and yet that this must point to, signify, and be, a reality beyond our conception. Encounter as a human confrontation can only happen through physical expression.
Jesus, when on Earth, was a human being, outwardly and visibly, and truly. Yet He was also the Manifestation of God, His hidden Reality as the Express Image of the Father. HIs Redemptive Incarnation was a sign, and an instrument of God's love for mankind, delivering God's grace.
The very existence of Christ makes possible encounter with God. This applies to every detail of His life, but most particularly to His Passion and Death. This revealed both God's will to save, and Christ's love for His Father. The Death of Our Lord Jesus Christ both signifies and causes, is sign and effect, of the Reconciliation of Man to God.
Now that Christ is in Glory, His continuing action in the World demands a tangible prolongation of His Incarnation.  This is the Church,  and Christ acts, through the Church, in and by the Sacraments. The Sacraments signify what they effect, and effect what they signify, but more importantly they are Acts of Christ. Though done at one time and in one place, they transcend both time and place.
Christ is the greatest and original Sacrament, so primordial; and also primordial in that all other sacraments  derive from His actions and so from Him.
Comment: Found the William Hill's article here: https://ejournals.bc.edu/ojs/index.php/ctsa/article/viewFile/2572/2209, which confirms davidlol's answer.

Christ as primordial sacrament


How should I select which antivirus software to install on my new laptop?

Question: I'm in a bit of a dilemma here. I have bought a new laptop with no antivirus installed. I'm wondering how to choose an appropriate antivirus software to install.
Comment: Install ***GNU/Linux***!
Comment: The best antivir to date is CommonSense 2015 !
Answer: What you want for software in general is that it:

does the job;
is easy to install and manage;
is cheap.

Windows 8 comes with Microsoft's antivirus already included (it is called "Windows Defender"), which fulfills point 3 (you already paid for it, so it is technically "cheap") and point 2 (the software which is easiest to install is the software which is already installed). As far as I know, it also does the job, and since it is backed by a big company (Microsoft) which has a vested interest into this antivirus keeping on doing its job properly, I tend to think that it is a reasonable choice.
For previous versions of Windows, the same antivirus is known as "Security Essentials" and can be downloaded and installed for free. It is also a reasonable choice.
(I have used other antivirus in the past, but most had some irksome feature, such as "nagging" the user with ads for the full, non-cheap version. Also, this is only for Windows; the main OS on my laptop happens to be a Linux, which can safely operate without any antivirus.)
Answer: Measuring real-world antivirus performance is difficult to do because malware risk is hard to quantify.
AV-Comparatives and AV-Test are two independent Antivirus testing organizations. They perform periodic tests from multiple features such as detection, performance, enterprise functionality, etc.
Here is a summary report of AV performance for 2012 split into categories so you can chose what is best suited for you.
Free AVs are good choices too because they provide all the basic features and the same signature database as the premium version. They lack extra features such as SPAM and phishing protection, firewall or parental controls.
Comment: I personally don't recommend free antivirus. Keeping signatures up to date is very costly for antivirus companies and imho not the right place to safe money. Plus there are tons of bad free av solutions and picking out the good ones can be quite hard. Getting a paid version almost always gives you faster update servers on top of other pro features. Also keep an eye out for performance and and usability. Nothing worse than "having" to turn of av to be able to play a game or having to turn of notification because you're getting spammed with popups
Answer: AVG Free 2013 has received positive reviews and rankings on independent lab tests. The latest Webroot and Norton(I suppose) has also scored well but are around $40 per year. If you're trying to avoid firewalls, stay away from 'Internet Security Suite' software and look specifically for Anti-Virus.
The latest Bit-Defender scores were pretty good according to AV-TEST.
http://www.av-test.org/en/tests/home-user/producer/bitdefender/
The most effective thing you can do is keep your software, especially web browers+plugins(java, adobe *, etc) up to date and be mindful of the sites that you visit. Try running firefox, adblock, and NoScript if you're really concerned.
Answer: You can try http://www.av-comparatives.org/ .
I really can't vouch that they aren't paid to make certain companies look good, however they have comprehensive reports that show which AV's picked up on what. Seems bias-free.
Some basic ones that might help:
-Microsoft Security Essentials
-MalwareBytes
-AVG
All free, and will certainly get the job done!
Answer: It doesn't matter which antivirus software will you by, but which package.
So It all depends what is the type of work that you gonna do on your laptop.
If you just going to surf on the Internet and such stuff then you can install some free antivirus software like Avast or AVG.
But if you are going to work on your laptop and other important things then I recommend to you that you use some professional  Antivirus Package or maybe Internet Security (or some Total Protection or how it is called).
So it all depends on your type of work.
Oh and by the way I recommend to you that you choose some antivirus like : Kaspersky, Norton, AVG, Avast, BitDefender, G-Data or McAfee.
Answer: Antivirus software should be one layer among many in your computer defense kit.
You will want to search out reviews and keep an eye out for the following criteria:

Cost (fixed vs subscription)
How many devices can yo install it on for that cost?
Does it work on all of your devices? (Laptop, desktop, Apple, tablet, phone, etc...)
Current reputation of the company (not the past; a lot of AV software has stuck around long past the hero time and become the villain, at least in some peoples minds. Movie quote)
Does the software require an internet connection?
Is the software a suite, or a single purpose software: firewall, registry cleaner, hard drive cleaner, secure delete, etc...

Some reputable websites to gather information about software, including security/AV software:

Lifehacker
Ars Technica
Maximum PC
GHacks
XDA developers
EFF.org (Electronic Frontier Foundation)
Answer: Antivirus is fine but not too good when it comes to prevent security the right way.
Install a good antivirus (Personally I like Kaspersky, and that is what I am using), and monitor what you really is doing considering there are many 0Day exploits coming which no Antivirus provider would be able to detect early unless it goes into wild.
So :

Install a good antivirus (Kaspersky, or Mcafee)
Monitor your activity on internet. Dont just feel too free to click on anything.
Comment: I will probably use my old laptop for suspicious internet activities. So I need just antivirus for checking mails, usb's and so on.
Comment: Essentially you dont need an antivirus. But a antivirus + firewall thing. I use Kaspersky Internet security and its pretty good. Though for nasty things i just use VM (In your case old laptop)


Can the API Key on a MobileConnect message be changed?

Question: Any insight would be helpful if this is possible through the UI or through an API call. The purpose of changing this is so that the API key is the same across business units (qa/prod environments) - thank you!
Answer: The API keys change hourly (clientID/Secret) are unique and linked to an account. More info on SE.  The MessageIDs are unique, static and cannot be changed.
Comment: Sorry, perhaps I was not clear. I am speaking towards the external key (API key) for an outbound SMS message not the clientID/secret for the REST services.
Answer: At the time the MobileConnect message is created, it's assigned an API identifier, and as far as I know, there is no way to change it.
You would need to assign some sort of variable for the key to switch between your environments.
Comment: OK - thanks for confirming. This is in line with what I'm finding.


Calculate The Minimum Distance from Polygon Centroid to Edge

Question: I am looking to calculate the minimum distance from the Center of a polygon (A crescent shaped polygon would have a center inside the polygon) to its edge. I have parcel data and I am trying to calculate in my model I created how tall I can build a cell tower on that parcel. The maximum height that I can build the tower is equal to the minimum distance from the center of the parcel to its edge. Is their a simple way to calculate this? Once I have the minimum distance calculated I can complete my query for my model.
Comment: There's a number of possible definitions of "center" and/or "centroid"; please **edit** the question to specify which particular "center of parcel" you want -- would the "center" of a crescent-shaped parcel be inside or outside the polygon?
Comment: I think by centroid in the contex of his question he means center of gravity point. He has a parcel, and in the center of gravity of that parcel a cell tower will be raised. It doesn't really mater though the question is valid for any point.
Comment: Have a look http://gis.stackexchange.com/questions/166230/deleting-polygons-smaller-than-certain-dimension-using-arcgis-for-desktop/166253#166253
Comment: @nickves You can't erect a tower on a parcel you don't own to service the one you do without special arrangements.  There are also potential propagation issues (direct line of sight) which would invalidate a center of mass centroid, even if it is located in a regular polygon (at which point visibility analysis may be necessary)
Answer: The following approach requires you to have an Advance license:

Convert your polygons to lines using the Feature To Line tool
Identify the distance from your centroid point to the line using the Generate Near Table tool

These two steps can be wrapped up in a model.
Comment: Python and `arcpy`. In 10.3 the Polyline object has a method [queryPointAndDistance](http://desktop.arcgis.com/en/desktop/latest/analyze/arcpy-classes/polyline.htm#M1_GUID-FC2C3085-2C89-4CDB-985B-DFE78118B603) which can be used to extract the information you require. You could expose it as a Script tool and then embed it in to a large workflow model. So you would need to get your GIS developer to write this for you or employ someone who can.
Comment: Is there a way to achieve this with a Standard License?
Comment: Not if you want to use model builder..
Comment: How would you accomplish this outside of Model Building with the Standard License?


Resize texture to fit minimum rectangle

Question: I just UV unwrapped an icosphere to the default 1024x1024 texture, and the uv map has a lot of wasted space. I want to cut this texture to the minimum rectangle containing the uv map, essentially cutting at least half of the texture.
Answer: There doesn't seem to be a way of doing this automatically, unless someone makes a plugin. This is how I did it with external image manipulation programs.

This is the current UV unwrap

To save the image from Blender, open it in the UV Editor and press Shift+Alt+S to Save As. Then use an external image editor to crop the image. Note the factor you are cropping by. If you crop it down by 1/2, note down 2. 1/3 is 3, 3/4 is 1.333... etc.  Go back to the UV Editor, click on Image > Replace. Find and select the cropped image. It should look like this:

Now in the UV Editor, press N to bring up the sidebar if it isn't up already. Click View, then set the 2D Cursor to 0,0.

Select all the vertices in the UV Editor with A. Press S then Y to Scale on the Y axis. Then enter your factor I mentioned before. I cropped the image by a half so I'll enter 2. Left click to finish scale.
Comment: Hello @Benus, thanks for your input. I'm very disappointed this isn't a feature. It's not practical to do this manually with dozens of textures, and more importantly, how do I find the exact amount to crop?

Resize texture to fit minimum rectangle


Tips for defeating Benezia and her commandos at Noveria

Question: With less than a year to finish Mass Effect and ME2, I've been grinding my way through.  Right now, though, I'm having some trouble with Benezia.  What are some strategies and associated tactics that should I be using?
Answer: I usually just ignored her (e.g. let the party handle her), and ran around killing commandos. If you let them set up or split up, they can be a real problem, but if you get them while they're grouped around the door, you can turn them into mush without losing your shields. Typically I'd hunker down and pare their numbers with the sniper rifle, then charge in and finish them off at close range.
The only trouble I ever had was that occasionally I'd get knocked off the walkways and be unable to complete the effing mission.
Answer: I've managed to make it through intact.  Standard use of cover and good position saw me through.
Comment: 90% of the battles in Mass Effect 1 can be won with patience. The other 10% are when Rachni sneak up behind you and 1HKO you through your shields.
Comment: The low platform sort of under where she hangs out was one of my favourite places to take cover the first time I fought her (from the door where you enter turn right and it is the first left).
Comment: Benezia was the boss that gave me the most trouble.  Use cover constantly and always have a place to fall back to.


Protonation of ketone and ester

Question: If there is a ketone and ester functional group in the same compound and I want to protonate with $\ce{HCl}$, which one will protonate first? Is it the carbonyl group in the ketone or the carbonyl group in the ester and why? Is it related to the $\mathrm{p}K_\mathrm{a}$ of the functional group?
Comment: The $\mathrm{p}K_\mathrm{a}$ values of protonated esters, protonated ketones and hydrochloric acid are close to each other (-7 to -6 according to  http://www2.onu.edu/~b-myers/organic/2511_Files/pKa%20table.pdf), so $\ce{HCl}$ will protonate both groups, perhaps with a slight preference for the ketone.
Answer: As was mentioned in the comments, with reference to the Myers $\mathrm{p}K_{\mathrm{a}}$ table, the $\mathrm{p}K_{\mathrm{a}}$ values of a protonated ester and a protonated ketone are largely similar (in the region of $-7$ to $-6$).
Therefore, it will likely depend on external factors, which group is protonated first. Are there electron withdrawing or electron donating groups in the vicinity of either? Can the proton on either maybe intramolecularly hydrogen bond to something?
All these effects will also slightly modify the $\mathrm{p}K_{\mathrm{a}}$ of the functional group you're observing. The one with the higher $\mathrm{p}K_{\mathrm{a}}$ will be protonated first. Thus, it is impossible to give a general answer here, it depends on which molecule you have and which groups are where.
Side fact: $\ce{HCl}$ has almost the same $\mathrm{p}K_{\mathrm{a}}$, so the protonation will be very close to equilibrated between all three components.
Answer: Has nothing to do with pKA tables or external factors. pKa values are determined for a singular compound acting as a Bronsted acid.  When two similar species compete you can have behavior divergent from simple pKa analysis.
If you protonate the sp2-lone pair of a ketone, you are protonating a lone pair close to the nucleus which is less basic. No further stabilization occurs.
If you protonate the sp2-lone pair of an ester carbonyl oxygen, the conjugate acid is stabilized by resonance.  The resulting positive charge can be drawn on both the carbonyl oxygen and the alkoxy oxygen, which is a stabilizing factor.

Protonation of ketone and ester


What are the hardware requirements for Battery monitoring?

Question: I looked at the hardware compatibility list, but there is no mention for a requirement of a battery monitoring functionality in the hardware. But, all phones display the battery level with the BatteryManager API.
Comment: Why are you asking this question? Are you planning to create a hardware (or a custom ROM) that doesn't show battery information?
Answer: As far as I know, there is no particular requirement.
You will get battery monitoring details when you send particular commands to the battery.
That is, the battery itself will have hardware for that.


Why is an Alcubierre drive shaped like it is

Question: When I look up the Alcubierre drive I keep seeing that the drive powering the bubble is shaped like a circle - is this necessary for the creating of the "warp bubble" that travels forward? Does the theory say anything about what happens if you do not shape it like a circle? Is it possible to have it warp spacetime in one 'direction' (i.e. it contracts space in one direction (--->) but does not expand space in the other direction (<---))? Or will there always be created a uniform bubble around whatever exotic matter is used for the drive?
Answer: Einstein's equation is:
$$ G_{\alpha\beta} = 8\pi T_{\alpha\beta} $$
In this equation $G_{\alpha\beta}$ describes the curvature of spacetime and $T_{\alpha\beta}$ describes the mass/energy distribution, so the equation relates curvature to mass/energy. Solving this equation is the basic task in general relativity.
There are two ways to look at the equation. The most obvious is to start with some known distribution of mass/energy $T_{\alpha\beta}$ and solve the equation to get the spacetime geometry. This is how Schwarzschild worked out the geometry of a black hole, and Friedmann et al worked out the geometry of an expanding universe. However you can reverse the process i.e. start by deciding what geometry you want and then work out the corresponding mass/energy distribution $T_{\alpha\beta}$. This is what Alcubierre did.
Alcubierre started with the spacetime geometry he needed for his FTL drive, then solved for the corresponding mass/energy distribution. The result turned out to be a ring of exotic matter, which is why the Alcubierre drive uses a ring - it wasn't designed that way in advance, that's just the way it worked out.
You ask what happens if we use different shapes, but that question is far easier to ask than to answer. Calculating $T_{\alpha\beta}$ from a known $G_{\alpha\beta}$, as Alcubierre did, isn't that hard to do. However the more conventional calculation i.e. starting with $T_{\alpha\beta}$ and calculating $G_{\alpha\beta}$ is a formidable problem, and indeed can only be done precisely for a few special cases. In the vast majority of cases we have to resort to numerical methods and an extremely large computer.
So there isn't a simple answer to what happens when we change the shape of the ring. Very small changes could probably be tackled using a perturbative approach, but in general you'd need to reach for your (super)computer.
Answer: Since you don't locally travel faster than light it is hard to call what you are doing FTL if you don't contract on one side and expand on the other.
That said, you don't have to contract space in front of you. The Natario drive is claimed to pancake the space in front of you, thus reducing the distance to your destination but without contracting space in front. (Thank you to diffeomorphism for correcting my poor citation.)
For instance if you are in a big crunch scenario with a globally uniform contracting spacetime then it hardly makes sense to call sitting around not moving being a warp drive even if the comoving proper distance between you and a distant place is decreasing at FTL speeds.
It doesn't require exotic matter so doesn't seem exotic.
What is the difference between contracting and pancaking?
Contract is a standard term meant to oppose expand. Like when the universe expands or contracts. They give a definition of contracting/expanding or lack thereof in the Natario paper but I'm not sure how physically meaningful the distinction is, which is why I merely said they claim.
The term pancake is my own. If you'd rather you could pretend I said the region in front of you contracts in the forward direction and expands in the sidewise directions. (But all of that is happening in the region in front of you.) So the idea is that you aren't destroying space in front of you in any sense.  So I imagine a sphere in front of you becoming a pancake just like squishing a ball of dough. Similarly you can set it up to not create space behind you. Then connect them all up.
The Alcubierre drive sort of piles things up in front of you which is quite destructive for anything in front of you if you managed to slow down because you have lots of space debris you've carried with you that shoots off.
The Natario drive might be safer for the people in front of you when you break if it acts more like a two sided snow plow and let's thing go around you rather than pile up in front of you.
But I'm not sure if it safer by an important amount, I haven't seen anyone write a paper on that.
Comment: I think you meant the Natario drive, Naruto is a character from an anime :-)
Comment: What is the difference between "contract space in front of you" vs "pancake space in front of you"?
Comment: @mbeckish edited


A MAP sensor small piece of plastic and a nipple fell into intake

Question: I tried to remove the MAP sensor (the car is Clio 3 1.6 16v k4m engine) and it was moving very easily and just tried a little bit to pull it out and a small piece of plastic with an oring was just fallen out in the intake...
Comment: Welcome to Motor Vehicle Maintenance & Repair!
Answer: You definitely need to retrieve that part out of the intake of your engine.  One way or the other it's going to get into the valves or all the way into the combustion chamber and there is a distinct possibility that it may cause catastrophic damage.
While it may be a bit of work to pull the intake manifold off the engine to get at it, you don't want to risk the damage it can easily cause.


Enable Hebrew Swipe Input

Question: I noticed I can use (with my out of the box Nexus 4) swipe for.input in English but there does not seem to be a way to use swipe for Hebrew input.
Am I missing a configuration option that enable this?
I know there are 3rd party applications that does Hebrew swipe input but I prefer not to use them if the OS provides me that functionality.
Comment: Today (almost a year after my initial post) I tried using swipe on the Hebrew keyboard and now it works.
Answer: Did you activate the Hebrew language pack in the Settings/Language & Input/Android Keyboard Settings/Input Languages? Hebrew is listed there. Check the box.
I don't know if that will give support for swiping but it will at least add the language dictionary.
Comment: Yes, Hebrew is activated. I can write (Hebrew keyboard) in Hebrew just not using swipe.
Comment: You may have to go with a 3rd party app like Swype Beta SwiftKey to get Hebrew swiping. I believe Swype supports Hebrew. Not sure about SwiftKey.
Answer: This worked for me: uninstall your current google keyboard (it will ask you if you're sure you want to uninstall updates as you can't really uninstall the keyboard), then reinstall it.
If you're having trouble finding it in the play store here's a link to open from your phone:
https://play.google.com/store/apps/details?id=com.google.android.inputmethod.latin
Comment: Tried it but that did not work for me.
Comment: This worked for me. I didn't have gesture support for Croatian. After reinstalling, when I switched to the Croatian language, a toast message applied saying something like "Downloading, gestures will be soon available for Croatian". It sucks that there's no way to trigger this manually.

Enable Hebrew Swipe Input


How to zoom into a video inside of a mask?

Question: So I am trying to make a small clip wherein I have a solid black layer masked on top of a video to give it a film bar. Now at one point I want to zoom into the video without zooming into the solid layer. You can see my screen below. I am pretty new to AE. Any idea how I can go about doing this?
Answer: You can do this by selecting every layer except the solid (your letterbox) and precomping it. Then, you can switch into your precomp and do as much zooming as you like. If you then render the composition with your precomp plus the solid layer on top, your solid will be unaffected by the keyframing going on inside the precomp.
Comment: How do I zoom into into all those layers at once after pre comping it? I am sorry if this sounds too amateur.
Answer: I would make a black solid layer above all the others with your mask (as you have I think).
Then make a Null layer.
Parent all of the other layers to your Null layer.
See parenting tutorial here
Then adjust the scale of the Null and all the other layers will follow it.
Alternatively you could pre-comp all your other layers, but you will lose resolution on them as they scale unless you do some other things...
Comment: Yeah this is what I did. Thanks!


Checkers games with computer random movement

Question: Im studying Java OOP, and I have to make first assignment about making checkers board game. I have to get input from user if he plays, and than when his turn is over the computer will play. Computer's movement is random but if he has the opportunity to "eat" his rival, he has to do this and if not than making random move.
Can someone help me with the coding?
Comment: What have you tried so far? It could be even written as one-liner such as `tokens.stream().collect(Collectors.collectingAndThen(Collectors.toList(), list -> Collections.shuffle(list).stream())).findFirst(token -> token.canMove())`.
Comment: On which part are you stuck exactly right now?
Comment: Computer turn, how can I write the code of selection random cell from line 2, for the first movement
Comment: @wondra That is terrifying and exciting at the same time. Congrats
Comment: hey, I have learned only Java and C programs. Have no idea what does it means. Thanks anyway!
Answer: The most straightforward way would be to build a list of all possible moves and then randomly select from them.

Initialize two empty lists, eatMoves and nonEatMoves
For each rival token:

For each possible move of that token:

if the move involves eating an opponent:

Add move to eatMoves

else:

Add move to nonEatMoves

Choose one of the moves:

If eatMoves is not empty:

Randomly choose from eatMoves list

else:

Randomly choose from nonEatMoves list

Return the random move selection

Actually choosing a random number is straightforward: https://docs.oracle.com/javase/8/docs/api/java/util/Random.html
Comment: Hey, I've made it already, but Im strugeling to find the right code for the random. I know that this is the best way to 'start' computer first move. After using random, I'll use IF loops and FOR .


How to deal with sitting next to an alcoholic colleague

Question: I have a work colleague I sit next to whom I suspect to be an alcoholic. Certainly other colleagues have expressed this opinion. It used to be that occasionally he would come in smelling of stale beer from the night before, but recently it has been every day. The smell is unpleasant and sometimes makes me feel ill. Should I approach someone at work about this? I have nothing personal against the guy and find he is a useful to talk to and I wouldn't want to get him into trouble, but the smell is becoming difficult to put up with.
Comment: If your assumption on his condition is based on the smell only, I'd like to point out that diabetes results in a similar smell. Clarify that before you make any irreversible accusations.
Comment: Just for clarity: is it only the smell or do you suspect he's actually drunk on the job? If it's the former, I think it's a duplicate to the linked question.
Comment: @JohnHC and others the linked question is from a manager's perspective.  It's different if it's just a colleague and not someone you are responsible for, so I wouldn't call it a duplicate.
Comment: Not sure it's quite an exact duplicate @JohnHC, however the advice provided in the answer does equally apply. I'm not casting my VTC, but will not cast my vote to keep it open as I'm torn. See what others think of it.
Answer: If you aren't willing to take action that might get him in trouble, I see three options:

Talk to him about it.  Mention to him privately that the odor is bothering you and makes it hard to concentrate on your work.  This can be quite a difficult conversation to have, but many people would be appreciative to know the problem.
Put up with it.
Try to get moved to another location. You could ask to sit somewhere else.  This might not be possible, and it might cause suspicion about your co-worker (or someone else you sit near) unless you can think of a plausible excuse for wanting to move.

The next level of action beyond this would be talking to either your manager or HR.  It would be better to simply mention the odor, rather than the suspected alcoholism.  But I think you should talk to him first, before escalating the issue.  If you aren't willing to talk to him, then just ignore or avoid the problem.
Answer: Sorry to hear that, that is a tough situation.
If he is truly an alcoholic, nothing you can say will make a difference. It is a severe addiction and there will be no change without significant therapy and/or intervention. Chances are its going to get worse. I've seen it happen and it's not pretty.
You need to decide how much you want to get involved. Doing nothing, is probably not the right thing. As I said, it's likely to get worse and if, for example, he starts driving drunk he is danger to himself and to other people. Work will suffer as well. You can try to remove yourself from the situation as much as possible but it's better if something happens.
You don't do him any favors by protecting him. He won't get out of this without external help and without some drastic intervention. I'd recommend bringing HR into the loop, if you have someone decent in there. They are better trained for this type of situation.
Answer: Tell him he stinks in whatever fashion you deem best. He'd much prefer a heads up from a colleague than a reprimand from management. Only if that doesn't work should you escalate.
I'd say something like 'Mate, you stink of booze, you need to brush your teeth or something.'
But judgement call on the wording, not everyone is as straightforward.
Comment: Wow, this seems very unprofessional. I don't think talking to him in that way will result in any change, just in an angry colleague.
Comment: @SimonHoubracken if someone is making me want to puke all day every day, I couldn't care less if they get angry when I confront them about it.


Average share price question

Question: I have 6000 shares of stock priced at 1.34/share. I want to how many shares I'll need to purchase at 0.87/share to get an average share price of 1.00/share.
Comment: What have you tried?  If you buy $N$ shares at $.87$, what is your average (as a function of $N$)?
Answer: Let's talk a little abstractly. You have $S$ shares bought at $P$ dollars each. Then the value of your portfolio is $SP$.
If you buy another $S'$ shares at $P'$ dollars each, the value of those shares would be $S'P'$
A portfolio with an average price per share of $P_A$ is worth $P_AS_T$ where $S_T$ is the total number of shares.
So you want the sum of your two purchases to equal the average portfolio identified, so that $PS+P'S'=P_AS_T$. Finally, you know that $S_T=S+S'$ since $S_T$ is the total number of shares in your portfolio. Do you see how to use the equation $PS+P'S'=P_A(S+S')$ to answer your question?
Comment: Trying to figure out how to use the equation.  My algebra is so lacking!
Answer: We want buy $N$ shares such that the average price will be
$$
\frac{6000\times 1.34+N\times 0.87}{6000+N}=1
$$
that is
$$
6000\times 0.34=N\times 0.13\quad \Longrightarrow\quad N=\frac{6000\times 0.34}{0.13}=15,692
$$

Average share price question


Inverse of a certain block matrix

Question: So I'm trying to compute the inverse of a block matrix that's a subset of a larger consideration I was attempting (this particular matrix comes from the normal and orthogonal equations for least squares). Let $A$ be an $m\times n$ matrix with full column rank, and I'm trying to compute the inverse of this guy:
$$\begin{bmatrix}
A^* & A^*A\\
I+AA^* & A
\end{bmatrix}$$
Following through straightforward Gaussian elimination and augmenting by the identity, I right multiply $A^*$ with its right inverse (which exists since it has full row rank), and then I zero out the bottom left corner by $\text{new_row}_2=-(I+AA^*)\text{row}_1+\text{row}_2$.
$$\left[\begin{array}{cc|cc}
A^*    & A^*A   & I & 0\\
I+AA^* & A      & 0 & I
\end{array}\right]
\to
\left[\begin{array}{cc|cc}
I    & A^*A(A^*)^{-1}   & (A^*)^{-1} & 0\\
0 & -(I+AA^*)A^*A(A^*)^{-1}+A      & -(I+AA^*)(A^*)^{-1} & I
\end{array}\right]$$
However, here's where I'm stuck. The bottom-right entry is far too convoluted for me to find an inverse and get an identity matrix out of. Also, the $A^*)A^*$ part of the term doesn't even make any sense, as this is multiplying $n\times m$ with $n\times m$ (and likely true for the $A(A^*)^{-1}$ as well). I assume I can't just right-multiply like that and follow through. Is there a way to simplify this?
Answer: \begin{align*}
\begin{bmatrix}
A^\ast & A^\ast A\\
I_m+AA^\ast & A
\end{bmatrix}^{-1}
&=
\left(\begin{bmatrix}
A^\ast A&A^\ast\\
A&I_m+AA^\ast
\end{bmatrix}
\begin{bmatrix}
0&I_n\\
I_m&0
\end{bmatrix}\right)^{-1}\\
&=
\begin{bmatrix}
0&I_m\\
I_n&0
\end{bmatrix}
\color{red}{\begin{bmatrix}
A^\ast A&A^\ast\\
A&I_m+AA^\ast
\end{bmatrix}}^{-1}.
\end{align*}
Since both $A^\ast A$ and the Schur complement $S=I_m + AA^\ast - A(A^\ast A)^{-1}A^\ast$ are invertible, you can compute the inverse on the last line by the matrix inversion formula
$$
\begin{bmatrix}A&B\\ C&D\end{bmatrix}^{-1}
= \begin{bmatrix}A^{-1}+A^{-1}BS^{-1}CA^{-1} & -A^{-1}BS^{-1}\\ -S^{-1}CA^{-1} & S^{-1} \end{bmatrix}
$$
where $S=D-CA^{-1}B$ (to apply this formula, you should replace $A$ by $A^\ast A$ and $B$ by $A^\ast$ etc.).
Alternatively, if you perform a singular value decomposition $A=U_{m\times m}\begin{bmatrix}\Sigma_{n\times n}\\ 0_{(m-n)\times n}\end{bmatrix}V_{n\times n}^\ast$, where $U$ and $V$ are unitary, it is easy to see that
$$
\color{red}{\begin{bmatrix}
A^\ast A&A^\ast\\
A&I_m+AA^\ast
\end{bmatrix}}
=
\begin{bmatrix}V\\ &U\end{bmatrix}
\begin{bmatrix}\Sigma^2&\Sigma&0\\ \Sigma&I_n+\Sigma^2&0\\ 0&0&I_{m-n}\end{bmatrix}
\begin{bmatrix}V^\ast\\ &U^\ast\end{bmatrix}
$$
and hence
$$
\color{red}{\begin{bmatrix}
A^\ast A&A^\ast\\
A&I_m+AA^\ast
\end{bmatrix}}^{-1}
=
\begin{bmatrix}V\\ &U\end{bmatrix}
\begin{bmatrix}\Sigma^{-2}+\Sigma^{-4}&-\Sigma^{-3}&0\\ -\Sigma^{-3}&\Sigma^{-2}&0\\ 0&0&I_{m-n}\end{bmatrix}
\begin{bmatrix}V^\ast\\ &U^\ast\end{bmatrix}.
$$
Comment: Hi thank you for the answer! The Schur complement approach makes a lot of sense. As for the SVD, how do we know that the matrix multiplication achieves that matrix (and consequently, what the inverse of the 3x3 block matrix is)?
Comment: I guess I'm having trouble making sure the dimensions here are fine. As I'm interpreting this, don't $\Sigma_{m\times m}$ and $0_{(m-n)\times n}$ have a different # of columns?
Comment: @potionboy I don't understand what your first question means. As for the second question, there was a typo. $\Sigma$ should be an $n\times n$ invertible diagonal matrix.
Comment: @potionboy Huh? No, Some authors use the notation $\Sigma$ to denote the rectangular diagonal matrix in the SVD (so that it is $m\times n$), but the $\Sigma^2$ in my answer means $\Sigma_{n\times n}^2$, which is still $n\times n$. I simply dropped the dimension subscript.
Comment: Oh, sorry that makes more sense. (I realized this and deleted the comment when multiplying through $A^*A$.) Thanks again!

Inverse of a certain block matrix


hot water, baseboard oil boiler - bleeding at boiler site possibility?

Question: I may replace my current oil, baseboard boiler but would prefer bleeding the system at the boiler site (if it's possible) vs at every room separately. Is it possible to bleed air out at the boiler, without doing so at every baseboard? If so, what should I ask for when I talk to a potential installer?
Comment: There are multiple possible set ups and each has their own way of bleeding. If you can take a picture of your system, a radiator and what you currently do to bleed it out, we can better answer your question.
Answer: To answer your question, you can have the installer install a purge/drain valve assembly.I installed this type purge many times. It will remove most of the air from a finned tube baseboard  heating systems, but cannot be used on any other type of radiation. He installs 2 ball valves in series on the return line with a drain valve in between the ball valves. You hook a short garden hose to the drain and close one ball valve, then you open the drain valve and push the water and air thru the system to the drain expelling the air. You alternate opening and closing each ball valve to push the water one way then the other expelling the air. You may still have to vent a small fraction of the air at the vents on the baseboard radiation. Ask the installer if he knows how to install this system.


How do I to access a deceased family member's Hotmail or Outlook.com account?

Question: I can not access my deceased wife's Hotmail account.  I do not know password or have access to the phone number to get the pass code. The phone number that was used when account was sent up says the phone number can not be completed as dialed.
Comment: Only Microsoft can help you.
Answer: First let us express our condolences for your loss.
Outlook.com, Hotmail, Live, and MSN email accounts are dealt with on one website.
Microsoft recently changed their website invalidating older links. Currently the information is available at: "Next-of-kin process for Outlook.com" (previously available at http://windows.microsoft.com/en-us/outlook/next-of-kin but that now redirects to a webpage where the information isn't shown).
Other references showing similar advice: "I need to get into a persons account that passed away" or "How to Contact Different Digital Services".
You will need to contact Microsoft's "Custodian of Records". The information provided on their website regarding this is:

If a family member has passed away or become medically incapacitated, we're here to help. We have a dedicated team that can release Outlook.com content belonging to the family member—including all emails and their attachments, address book, and contact lists—to a next-of-kin or guardian.
To help safeguard the privacy and security of all Outlook.com customers, we cannot provide you with or change the password to the account, or transfer ownership of the account. Nor are we able to assist you with password resets, account recovery, or any other support for your own account.
The content will be transferred to a DVD, which will be shipped to you. To request the release of content and to close the family member's account, please contact the Microsoft Custodian of Records by emailing firstname.lastname@example.com.
In the email, please include the following info:

Your first and last name.

Your phone number.

Your Email address.

The full name of the deceased or incapacitated family member.

To the best of your knowledge, the Outlook.com accounts belonging to the family member.

Our team will reach out to you with details and specific documentation requirements.
Note
If you have the family member's sign-in info (e.g. email address and password), and you can sign in to the account or accounts, there's no need to go through the next-of-kin process. You already have access to all the info we would compile on the DVD.

Even though the advice appears to refer to outlook.com this is where you end up if you visit https://www.hotmail.com/ and use the "Contact Us" link in the footer.
A similar question Logging into a deceased relative's Facebook account for Facebook users has been asked on SE's WebApps site (here). For Stack Exchange users we have this Q&A on Meta: How should a user's death be handled?. It is OK to ask this question here, but you will need to go to Microsoft for further assistance.
Comment: Hotmail has officially been retired, but the existing email addresses have all been aliased to Outlook.com addresses, so this advice definitely applies.  Good find!
Comment: 2021 update: I tried to sending an email to that address and I got `550 5.4.1 Recipient address rejected: Access denied`
Comment: @razpeitia visiting Hotmail redirects to: https://outlook.live.com/owa/ and searching for the email address leads here: https://answers.microsoft.com/en-us/outlook_com/forum/all/microsofts-next-of-kin-process-accessing-emails/c848d768-58e8-428f-b10a-4fcd1f95c8d8 - perhaps the problem is local.


A Java programmer has questions regarding C header files

Question: I have a fair amount of practice with Java as a programming language, but I am completely new to C. I understand that a header file contains forward declarations for methods and variables. How is this different from an abstract class in Java?
Comment: Edited out the trolling question.
Answer: The short answer:
Abstract classes are a concept of object oriented programming. Header files are a necessity due to the way that the C language is constructed. It cannot be compared in any way
The long answer
To understand the header file, and the need for header files, you must understand the concepts of "declaration" and "definition". In C and C++, a declaration means, that you declare that something exists somewhere, for example a function.
void Test(int i);

We have now declared, that somewhere in the program, there exists a function Test, that takes a single int parameter. When you have a definition, you define what it is:
void Test(int i)
{
    ...
}

Here we have defined what the function void Test(int) actually is.
Global variables are declared using the extern keyword
extern int i;

They are defined without the extern keyword
int i;

When you compile a C program, you compile each source file (.c file) into an .obj file. Definitions will be compiled into the .obj file as actual code. When all these have been compiled, they are linked to the final executable. Therefore, a function should only be defined on one .c file, otherwise, the same function will end up multiple times in the executable. This is not really critical if the function definitions are identical. It is more problematic if a global variable is linked into the same executable twice. That will leave half the code to use the one instance, and the other half of the code to use the other instance.
But functions defined in one .c file cannot see functions defined in another .c files. So if from file1.c file you need to access function Test(int) defined in file2.c, you need to have a declaration of Test(int) present when compiling file1.c. When file1.c is compiled into file1.obj, the resulting .obj file will contain information that it needs Test(int) to be defined somewhere. When the program is linked, the linker will identify that file2.obj contains the function that file1.obj depends on.
If there is no .obj file containing the definition for this function, you will get a linker error, not a compiler error (linker errors are considerably more difficult to find and correct that compiler errors because you get no filename and line number for the resulting file)
So you use the header file to store declarations for the definitions stored in the corresponding source file.
Answer:
IMO it's mainly because many C programmers seem to think that Java programmers don't know how to program "for real", e.g. handling pointers, memory and so on.
I would rather compare headers to Java interfaces, in the sense that they generally define how the API must be used.
Headers are basically just a way to avoid copy-pasting: the preprocessor simply includes the content of the header in the source file when encounters an #include directive.
You put in a header every declaration that the user will commonly use.
Comment: explaining what something is and does, is not the same as explaining why.
Answer: Here's the answers:

Java has had a bad reputation among some hardcore C programmers mainly because they think:

it's "too easy" (no memory-management, segfaults)
"can't be used for serious work"
"just for the web" or,
"slow".

Java is hardly the easiest language in the world these days, compared to some lanmguages like Python, etc.
It is used in many desktop apps - applets aren't even used that often. Finally, Java will always be slower than C, because it is not compiled directly to machine code. Sometimes, though, extreme speed isn't needed. Anyway, the JVM isn't the slowest language VM ever.
When you're working in C, there aren't abstract classes.
All a header file does is contain code which is pasted into other files. The main reason you put it in a header file is so that it is at the top of the file - this way, you don't need to care where you put your functions in the actual implementation file.
While you can kind-of use OO concepts in C, it doesn't have built-in support for classes and similar fundamentals of OO. It is nigh-impossible to implement inheritance in plain C, therefore there can never actually have OO, or abstract classes for that matter. I would suggest sticking to plain old structs.
If it makes it easier for you to learn, by all means think of them as abstract classes (with the implementation file being the inheriting class) - but IMHO it is a difficult mindset to use when for working in a language without explicit support of said features.
I'm not sure if Java has them, but I think a closer analogue could be partial classes in C#.
Comment: Subjectively what I've experienced is that the tradition of hard-core old timers is that Java is surely a baby-talk language.
Comment: Even if C doesn't support OO programming directly, OO programming is more than just language support. OO programming is also about design (class hierarchies). Besides, many OO practices can be applied in procedural languages.
Comment: I don't know C, I don't know Java, but I know enough of them to know this is a crappy answer.....
Comment: I don't see anything shocking here.
Comment: In what way is that a crappy answer? :) I'm perfectly ready to accept that it's crap and remove it from the interwebs forever, but I'd like to know what's wrong with it.
Comment: OK, I'll change that bit. Also, @Neil: it has bad history with relatively few C programmers. I'll edit that as well. Thanks for the feedback!
Comment: I hope the answer is a bit less, shall we say, offensive. Let's see if we can calm the ranting a bit now. :)
Comment: Java is definitively slow for GUI Desktop Applications. Maybe thats why most people coming from other languages say its slow, they're trying it for the wrong propose.
Comment: A) java does not have a bad history B) just because you are using alanguage like C that does not natively support classes, there is no reason at all to forget the concept
Comment: The line "basically forget all about classes" is what strikes me as wrong. C is OO isn't it? THe fact that there are no abstract classes doesn't mean there is NO OO does it? If I code a class names Car it can still have a collection of type Wheels can't it?
Comment: The answer not THAT crappy... +1
Comment: @Colin: no, C isn't OO. (http://userpage.fu-berlin.de/~ram/pub/pub_jf47ht81Ht/doc_kay_oop_en).
Answer: If you forward declare something, you have to actually deliver and implement it, else the compiler will complain. The header allows you to display a "module"'s public API and make the declarations available (for type checking and so) to other parts of the program.
Comment: Wrong: it is not the compiler that will complain. It is the LINKER that will complain.
Comment: Sure, to be exact it's the linker. I wanted to say "C will complain"; I mean it is not going to work.
Comment: @kaizer.se: it might still link, if you provide the implementation elsewhere.
Answer: Comprehensive reading: Learning C from Java. Recommended reading for developers who are coming from Java to C.
Answer:
I think that there is much derision (mockery, laughter, contempt, ridicule) for Java simply because it's popular.
Abstract classes and interfaces specify a contract or a set of functions that can be invoked on an object of a certain type. Function prototypes in C only really do compile time type checking of function arguments/return values.
Answer: While your first question seems subjective to me, I will answer to the second one:
A header file contains the declarations which are then made available to other files via #inclusion by the preprocessor.
For instance you will declare in a header a function, and you will implement in a .c file. Other files will be able to use the function so long they can see the declaration (by including the header file).
At linking time the linker will look among the object files, or the various libraries linked, for some object which provides the code for the function.
A typical pattern is: you distribute the header files for your library, and a dll (for instance) which contains the object code. Then in your application you include the header, and the compiler will be able to compile because it will find the declaration in the header. No need to provide the actual implementation of the code, which will be available for the linker through the dll.
Answer:
C programs run directy, while Java programs run inside the JVM, so a common belief is that Java programs are slow. Also in Java you are hidden from some low level constructs (pointer, direct memory access), memory management, etc...

In C the declaration and definition of a function is separated. Declaration "declares" that there exists a function that called by those arguments returns something. Definition "defines" what the function actually does. The former is done in header files, the latter in the actual code. When you are compiling your code, you must use the header files to tell your compiler that there is such a function, and link in a binary that contains the binary code for the function.
In Java, the binary code itself also contains the declaration of the functions, so it is enough for the compiler to look at the class files to get both the definition and declaration of the available functions.