Caching proxy for yum and debian repositories

Question:
Does a caching proxy for yum exist, similar to approx for Debian repositories?
Is there a way to have reprepro behave the same as approx? I have heard that approx was not as stable; besides, I would prefer the use of reprepro so that I could use my existing web server to serve the repository.
Answer: The closest thing will probably be mrepo.  It's run out of band from Yum itself, though.  You'd set up local mirrors of your favorite yum repos with mrepo and point your yum clients to that instead.  It handles apt repos also, if that's of any benefit.
Answer: There is also http://pulpproject.org that does similar things as mrepo. Currently it only works for yum, but folks are working hard adding support for other technologies. It supports Puppet today (2014) and the core was refactored so patches for Debian support are possible.


Boot from USB option not avalible Ubuntu 14.10

Question: I am trying to install Windows 7 on my ASUS K55V laptop running UBUNTU 14.10 but I cannot seem to find Boot from USB option in BIOS. There are only two options to boot form, Hard disk and DVD Drive. There is not even an option to Add Bootable device or anything as such.
Help!!
Comment: Many new computers see a USB flash drive as just another hard drive.
Can you set your flash drive as first hard drive in BIOS?
Comment: I cannot see my flash drive anywhere in BIOS. And if I try to make my Hard Drive as the first boot option, still doesn't recognise the flash drive anywhere.
Answer: I had to turn secure boot off before an Asus X200 would boot from USB.  Things worked normally after that.

The secure boot option is in the UEFI settings (BIOS), so if your machine is not a UEFI machine, it does not even exist.
Comment: How can I turn secure Boot Off?


Grammatical structure in "best avoided"

Question: I come across some phrases such as "best avoided," or "better avoided." I understand what it means, but don't know how this phrase was made. What grammatical structure is in this? I thought this phrase is short for "is best (when it is) avoided," but this underatanding is just based on my rudimentary grammar. Could anyone help me with this?
Comment: I would say it relates to constructions like *you'd better go now*. To me at least, *X is best avoided* does not mean *X is best when it is avoided*. It means *it is best to avoid X* / *the best thing you can do is avoid X* / *you'd be better-advised to avoid X* etc. Sometimes there is hardly any difference between this meaning and the meaning *X is best when*, e.g. *pizzas are best cooked in the oven* can mean *the best way to cook pizzas...* or *pizzas come out best when...* Sometimes though it can only really have the *it's best to* meaning.
Comment: For example in *Leicester is best avoided*, Leicester is pretty much the same whether it is avoided or not, so this can only really mean *the best thing to do is...* In fact, on the *X is best when it is avoided* reading, this would mean something like *please don't come to Leicester, we're better off without you*, which can't be the intended meaning.
Answer: In your case 'best' is an adverb form which is used to modify a verb.
Here's an extract from the entry in Merriam-Webster's Dictionary
(https://www.merriam-webster.com/dictionary/best):
best
superlative of WELL
1: in the best way
: to greatest advantage
// Some things are best left unsaid.
The same thing is with 'better':
better
comparative of WELL
1a: in a more excellent manner
// sings better than I do
b: to greater advantage
 :PREFERABLY
// some things are better left unsaid
(https://www.merriam-webster.com/dictionary/better)

Grammatical structure in “best avoided”


Can I migrate my SSL certificate to windows SBS 2008?

Question: I have currently on my windows SBS 2003 box an SSL certificate for www.mydomain.com. I understand that for the 2008 SBS box I need a certificate for remote.mydomain.com. Can I simply export and import the certificate, or must I contact the issuer to get a changed one?
Answer: You would need to get a certificate for remote.mydomain.com. Certificates are specific to the FQDN (with the exceptions of wildcard certs), so you would get errors when you tried to connect with that cert. Although depending on what you are doing a self signed cert might be just fine. Is this just for RDP or Webmail type setups?
EDIT (RE Win Mobile Devices):
You don't have to pay for a cert, You just need to get your root CA's public cert into the certificate store. I used to do this two ways:

Create a simple installer for the cert ( I can dig this up if you want an example) and put it on a public website, then just browse to it and install OTA.
Put the Cert on an microSD card, toss that int he device and when you click on the cert it will prompt to import.
Comment: This is because the "CN" or "Common Name" of the certificate has changed, and no provider will permit you to change the CN. Some will allow you to cancel the cert and submit a new one within 7 days but I'm guessing this has well and truely passed for you now...
Comment: I want to be able to synchronize windows mobile 6.x devices, that demands a trusted certificate if I am not mistaken.
Comment: thanks for your added reply. I am quite a NOOB at server administration and I would need to be taken by the hand to see how the things you describe are done.
Answer: While Zypher's answer is true (I received an email from comodo that they will not edit my old certificate to remote.mydomain.com), it seems that it is possible to change the default remote access url to www.mydomain.com: In the get an internet address wizard at the page where you have to fill in your domain name you can click on advanced options: there you can set the prefix for your domain to "www." in stead of the default "remote." It possibly causes other connectivity problems, but for now I can live with it.


Update kde to newest version

Question: My OS is debian squeeze and I installed kde as graphical interface. My current kde version is 4.4.5. But I want to update it to the newest version (4.10.5). How to do it?
Comment: So this is what you actually wanted to *accomplish* when you asked about [upgrading Debian from squeeze to sid](http://unix.stackexchange.com/q/87312/2465)?
Comment: Yes.. as I said I am a newbie^^
Answer: According to the packages list 4.10.5 havent made into Squeeze yet. But is avaliable in Sid. You can add Sid packages to your sources.list and install the packages from there. The problem is KDE uses a whole bunch of libs which might break when combined with your current setup. As squeeze is really "old" I'm not sure they will backport kde 4.10 to it. According to here:
August 24, 2010
As Squeeze has been frozen, Debian will ship Squeeze with KDE 4.4.5. Unstable repos will have 4.4.5 too until Squeeze release. KDE 4.5.x will be available via other repo some time later.
Seems 4.10 wont make into your release. Hence I suggest you to dist-upgrade.
Comment: I followed this tutorial (digitalocean.com/community/articles/upgrading-debian-to-unstable) to upgrade squeeze to sid. The problem is that I didn't get any questions to answer during dist-upgrade (like he said) and after repeating dist-upgrade I get these errors:
E: Couldn't get lock /var/cache/apt/archives/lock - open (11: The ressource isn't available)
E: The directory /var/cache/apt/archives/ can't get locked ..
My sources.list:

deb http://ftp.de.debian.org/debian sid main

deb http://ftp.de.debian.org/debian squeeze main

deb http://ftp.de.debian.org/debian sid main contrib non-free
Comment: Have you ran the update till the end? Was it successful?
Comment: I don't really know.. I got a really big changelog and didn't saw any errors. Atm KDE still reminds me of 214 updates.. but dist-upgrade isn't working as I said.

Update kde to newest version


How is 痺れた use in this context?

Question:
My understand is that the character is saying because the actor performs the victory pose with ピシッと決まってて he himself is 痺れた by it?
Answer: Yes, the subject of 決まって is 決めポーズ, but the subject of 痺れた is the speaker himself. So an unnecessarily wordy version is 決めポーズはピシッと決まってて俺は痺れたよ.
For the meaning of 痺れる, see the third definition of jisho.org's entry:

to be excited; to be titillated; to be mesmerized; to be enthralled

How is 痺れた use in this context?


How can gravitational forces influence time?

Question: How does it work that gravitational forces can affect time and what usable applications could arise from this?
Comment: +1 good question, can we get Einstein in here?
Comment: You may be interested in the classic experiment that verified the existence of the effect: http://en.wikipedia.org/wiki/Pound-Rebka_experiment It was also one of the effects involved in the memorable Hafele-Keating experiment: http://en.wikipedia.org/wiki/Hafele-Keating_experiment
Comment: Let's see how people feel about my reasoning.The only reason we think there are directions like up down left right are because of reference points and gravity. If you were floating in empty space there are no real directions.Up and down are only intrinsic to us because of the earth's pull on us. We always think that time has an intrinsic direction: up or forward. We've given time a direction, but directions only exist because of gravitational fields. Therefore time does not have a true direction, it is only given a direction when mass bends it a certain way.
Answer: Gravity is currently understood to be curvature of spacetime, so mathematically it's unambiguous why gravity should affect time. But to leave it at that would be cheating, no? So I'll try to give an explanation of why you'd intuitively expect gravity to affect time. This is called the Einstein Tower thought experiment. If you've seen the phenomenon of time dilation in special relativity before, you'll notice that the way time behaves depends a lot on how light behaves. It's not crucial you know this but the spirit of the following explanation is the same.
Let's assume for a moment that gravity doesn't affect light in any way. Suppose you create a photon with energy $E$ on the ground and fire it up to the top of a tower where this photon is converted into an equivalent mass $m=E/c^2$. This mass will fall back to the ground and once it reaches the ground it will have gained extra energy $mgh$ because it fell through the gravitational field. If you started with energy $E$, you end up with energy $$E'=E+mgh=E(1+gh/c^2)$$  So every time you do this, you create energy! Surely something is wrong -- it must've been our assumption that gravity doesn't affect light. The most obvious fix then is to assume that the photon lost energy as it climbed up the gravitational field and that its energy at the top is $$E_{top}=E(1+gh/c^2)^{-1}$$ This is (a first approximation to) the phenomenon of gravitational red shift where photons lose energy as they climb out of a gravitational field.
Now, if you remember that the photon frequency is related to its energy by $E=h\nu$, you'll see that the frequency (~$1/T$ which is the "internal clock" of a photon) obeys the same relation as above. This is indicative of gravity affecting time -- in fact it's immediately obvious that any clock based on the frequency of light will run at a slower rate higher up in the gravitational field.
In reality, the result is far more general, though you'll need the apparatus of general relativity to see this.  See http://en.wikipedia.org/wiki/Gravitational_time_dilation for more.
There's probably no practical application you can milk out of gravitational time dilation (yet) since the effect is weak. But you definitely need to account for these effects in engineering projects such as GPS satellites.
Comment: Since the OP phrased the question in terms of "gravitational forces," it may be worth pointing out explicitly that the effect has absolutely no dependence on gravitational *force*. It depends only on a difference in gravitational *potential*.
Answer: Since your question is from the How Things Work site I guess you're looking for some basic understanding rather than lots of equations. What follows is in that spirit ...
Your question doesn't really have an answer, because it isn't meaningful, or at the least it's misleading, to say that gravitational forces affect time. Mainly that's because, assuming you believe in General Relativity, gravity isn't really a force at all. At least it's not a force in the same way that there's an electric force between two charges or a strong force between two subatomic particles.
General Relativity is based on the idea that mass (and energy and even pressure) cause spacetime to curve. The path that objects moving through spacetime follow is affected by this curvature so objects moving through curved space don't move in straight lines. If you've watched any popular science programmes you've probably seen the analogy of balls rolling on rubber sheets. The key point is that the freely moving object thinks it's moving in a straight line and it doesn't feel any gravitational force.
For example, suppose you leap off a high cliff. As long as nothing is in your way you'll move in a locally straight line and you won't feel any force at all (ignoring wind resistance). That is, you won't experience any gravitational force. The trouble is that the presence of the Earth curves spacetime in your vicinity, and as a result your locally straight line will hit the surface of the earth. Assuming you land with no injury, you'll now find you feel a force holding you to the ground that you (and Newton!) would describe as a gravitational force. But the apparent force is just because you and the Earth are trying to move along different locally straight lines. There isn't really any force there.
So my point is that it isn't meaningful to ask how a gravitational force affects time, because there isn't any such thing as a gravitational force. What does affect time, or more precisely spacetime, is the presence of matter, and that produces the appearance of a gravitation force. Your question should really be "How can (the curvature of) time affect gravity?" i.e. exactly the reverse of what you asked!
So now you're going to ask "How does matter affect time", and that's a good question that doesn't have an easy answer. The Einstein equation tells you how matter affects spacetime, and you can feed in numbers and get the right answers. What it doesn't tell you is why matter affects spacetime. We tend to leave the "why" questions to the philosophers :-)
Answer: The Schwarzschild metric is
$$
ds^2~=~(1~-~2GM/rc^2)(cdt)^2~-~(1~-~2GM/rc^2)^{-1}dr^2~-~r^2d\Omega^2
$$
This has all the constants and the like here to illustrate how the time part of the metric has $O(c^2)$ larger dependency than the spatial part, so $|g_{00}~-~1|~>>$ $|g_{rr}~-~1|$.  So we may approximate this with
$$
ds^2~\simeq~(1~-~2GM/rc^2)(cdt)^2~-~dr^2~-~r^2d\Omega^2
$$
So we may then consider a stationary situation with $dr~=~0$ so the propertime is
$$
d\tau~=~\sqrt{1~-~2GM/rc^2}dt~\simeq~(1~-~GM/rc^2)dt,
$$
which for near Earth surface gravity the $1~-~GM/r~\simeq~1~+~gh/c^2$, $r~=~R~+~h$.  This recovers the dbrane result.  For a moving body $dr~=~vdt$ we may the compute a gamma factor
$$
ds^2~\simeq~(1~-~2GM/rc^2~-~(v/c)^2)dt^2
$$
which can be used to derive modified Lorentz transformations of spacetime.  These then may be used to compute time dilation results for satellites in Earth orbit.
Comment: I changed the last equation.  In looking at it I see I made a small mistake.
Answer: The easy answer is that in day to day life, it can't. And so not any really usable applications.
The hard answer is that in special circumstances it can (see Special relativity), or more accurately the speed you travel at can affect how you experience time. To get a really good understanding of why would require a university degree in both maths and theoretical physics, which I don't have and neither would I have chance to explain in a couple of paragraphs.
Put simply, the closer to the speed of light you travel, the slower you experience time, so that if you could theoretically reach the speed of light (which you can't without an infinite amount of energy, unless you have zero mass, which is a mind bender in its self) time would appear to stop (from your point of view at least).
Consider this (sorry its quoted directly from wikipedia but its illustrates it quite well): Since one can not travel faster than light, one might conclude that a human can never travel further from Earth than 40 light years, if the traveler is active between the age of 20 and 60. One would easily think that a traveller would never be able to reach more than the very few solar systems which exist within the limit of 20-40 light years from the earth. But that would be a mistaken conclusion. Because of time dilation, he can travel thousands of light years during his 40 active years. If the spaceship accelerates at a constant 1G, he will after a little less than a year (mathematically) reach almost the speed of light, but time dilation will increase his life span to thousands of years, seen from the reference system of the Solar System, but his subjective lifespan will not thereby change. If he returns to Earth he will land thousands of years into its future. Even if he should accelerate for a longer period, his speed will not be seen as higher than the speed of light by observers on Earth, and he will not measure his speed as being higher than the speed of light. This is because he will see a length contraction of the universe in his direction of travel. And during the journey, people on Earth will experience much more time than he does. So, although his (ordinary) speed cannot exceed c, his four-velocity (distance as seen by Earth divided by his proper (i.e. subjective) time) can be much greater than c. This is similar to the fact that a muon can travel much further than c times its half-life (when at rest), if it is traveling close to c.
Comment: Note: special relativity specifically does *not* deal with gravity: the special means it applies in inertial reference frames. To answer this question, one must appeal to general relativity.
Comment: "the closer to the speed of light you travel, the slower you experience time" could be misleading. A person moving near the the speed of light will age slower *relative to* someone who is moving slower, but each person will experience time the same way. 40 years would still feel like 40 years to both people. As described in the Wikipedia article, the traveller returning to earth would find that much more time has passed *on earth*, even though the traveller himself has only experienced 40 years of life as a high-speed astronaut.
Comment: That's a mind bender. Not a scientific reference by any means, but the Stargate episode "A Matter of Time" illustrates this theory if you're interested in a less technical explanation.


How to connect a hard drive (with NTFS) to Android phone?

Question: I have a Samsung device and I want to connect an external hard drive to it with OTG but the problem is the hard drive isn't readable om my phone. I searched the internet for a solution and I found a tutorial that says I have to convert the filesystem of the hard drive from NTFS to FAT but the problem is there is no tutorial for converting NTFS to FAT (not FAT32) because FAT32 isn't readable on my Android device either.
So can you please help me to make my external hard drive readable on my Android device?
Comment: Why do you believe your device doesn't support FAT32? I ask because FAT32 is quite old and widely supported at this point.
Comment: This will show you how to convert [NTFS to FAT32](https://www.easeus.com/partition-master/convert-ntfs-to-fat32.html)
Comment: Most of the newer Android devices (and even some older) support NTFS, FAT(32/16), exFAT and vFAT. You can check by 'cat /proc/filesystems' or the *_FS= entries from your kernel source. I have been using Western Digital 512 GB USB hard drive with NTFS on my Android phone.
Comment: Please [edit] to mention device and Android version
Answer: Your device doesn't recognize your hard drive because your hard drive need a electronic power to work not because of your hard drive format.
The only way to use hard drive in your android device is using hard drive with less down 512GB capacity, or using hard drive with separate power wire and data wire.
Comment: Can you add a citation about the 512GB capacity and if the limit is for all Android versions or only some.
Comment: not true. I perfectly read 4Tb external drive via OTG connection without any external power, and my phone was released in 2018, just when you wrote this answer
Answer: Android recently got support for NTFS
Ok, for all my HDD partition work, i use a Windows PC and a free program called AOMI Partition Assistant Standard
Using Part'Assist' is very straight forward and has heaps more control over the ordinary formatting support of Windows.
You can convert, clone, format, move, repair & resize drives & partitions.
How to format using the software.

Install & Open Part'Assist'

Place your HDD into your PC usb port

Select the HDD in Part'Assist'

Select your desired action

Reformatting will be the quicker option, however it'll erase everything.
I personally use exFAT on my HDDs, however i believe it should support FAT or ( VFAT is what terminal emulator throws out )
Android will power your HDD if it is self powered, and doesn't take Two Usb Cables ( 5volt + 5volt = 10v )  .. Androids that support OTG ( On The Go ) provide 5v power to the micro usb port and this is enough to run a very large 5volt portable HDD ( 2 TB Etc... )
You may need an extra power supply if your device doesn't handle OTG properly ( some tablets and older devices ) and requires an adapter to supply the 5 volt power ( can be built by soldering the ground wire to the micro usb sleeve on the jack to provide 5v power on some models ).
Once formatted as vfat ( FAT ) you shoul be able to get it to work just fine.
I'd just like to mention that i think it's amazing how far this hack has come... In the beginning, Android never supported usb devices using the micro usb, some hacker decided to give it a go years back and found out that all it needed was power to run a usb memory stick, mouse or keyboard... or any device with a driver that could be built....
After the hack became a part of many custom ROMs like Cyanogen Mod ( CM ), Manufacturer's and someone at Android HQ noticed !! it soon became known as OTG ( On The Go ) - This hack now has hardware support to supply 5volt power because someone else looked at the micro usb cable diagrams and said hey, let's just ground the shell on the usb and we'll have a 5vlt supply from the battery ... Genius...
Comment: I think Android supports NTFS. It's a part of AOSP now. Check vold source. Also, /system/bin contains fsck, mkfs and mount binaries for NTFS. For r/w access on NTFS, fuseblk device is used because it's not directly supported by Linux kernel so far.
Comment: Your answer is a bit unclear about powering the USB device. I'm sure that most smartphones will not provide more than standard 500 mA to OTG devices, which is NOT sufficient for many older 2.5" HDD to start up, it won't work with 3.5" HDD (maybe it works with USB-SSD). Maybe you edit your answer that the HDD should be self-powered. Alternatively a self-powered OTG-HUB can do the trick also.


Why are so many kids apps are in landscape mode?

Question: I'm trying to figure it out for couple of days, google best ux practices for building apps for kids, but none of them says "you should make your app in landscape mode". Tried to search for answers here, but the only thing I have found is that kids seem to prefer positioning devices in landscape mode. Why is that?
Comment: I wont post an answer as I don't have any data to back up my claims. But I will say a couple of obvious reasons are **usability** - small children will find it easier to hold and interact with devices in a landscape orientation. And also **content**, a lot of kids apps are visually driven and will undoubtedly make better use a screen space when in landscape mode - think like why a TV is always landscape.
Answer: I'd say because landscape is likely more appropriate for the content displayed in most apps for kids.
Portrait Mode is generally used to display lists of things, or long text passages, because you can fit many items onto the screen. For example, when browsing Amazon in portrait mode, I can fit ~5 items onto the screen, whereas in landscape mode, I can fit only ~3 items on the screen. In general, most things "adults" do either revolve around lists (social media, shopping, e-mail, etc.) or text (Stack Exchange, Wikipedia, etc.).
Landscape Mode is generally used to display more "visual" or "interactive" content. Most applications for kids are usually going to be interactive or try to present content in a visually engaging way, rather than trying to achieve high information density, and cramming the most information into the smallest space.
Landscape Mode may be seen as "more engaging", because it better matches our natural "screen ratio" of being wider than tall.
As a result, it doesn't make sense to say "Apps for Kids should be in Landscape Mode", because that's simply not true. It's just that Landscape Mode is generally the better choice for the kinds of application marketed towards kids.
Answer:
It is easier to hold a large phone with two hands, especially for the small hands of children.
Many handheld consoles (Nintendo switch, 3DS, PSP) are in a landscape format. Kids might be already familiar with these consoles.
Answer: I assume they may have had a few of these considerations for this.
Familiarity
Most video games are in landscape mode as compared to portrait mode, even in mobile.  Since kids are already playing mobile games they are pretty used to landscape mode than portrait.
Handling
As kid's arms and hands may not be stronger as compared to adults, making the application landscape forces the kids to hold the phone with both hands, reducing the likelihood of dropping it.
Safety
Another positive might be that it's easier for people to walk around while using an app in portrait mode. This can be hazardous especially if the app is more immersive. This can make kids more prone to accidents. When the app is in landscape mode users are less likely to use it while walking or multitasking as holding it takes both hands.


Doing part of my PhD remotely in Europe while working full time?

Question: my US company offered me the prospect of doing my PhD (in public health, public policy, international development or something similar) at a European university while retaining my employment. They would also pay for the PhD. My thesis would be based on a research project I was already going to pursue in my work. I already have a Masters in Economics. Would a university be okay if I only worked out of the university for the first and the 2nd and 3rd year was finishing my research in the USA? Thanks!
Comment: Does the company already have in mind a particular university (and advisor), perhaps in place from on-going joint research? Has somebody from the company done this before at that university?
Comment: I suspect that your company has some specific ideas, although if they didn't bring that up when discussing with you its kind of odd. I would have thought something more like your manager having a meeting with you and saying "Goldy, would you like to go to Oxford to work on a PhD with Prof. BigName?" I would get clarification from management on what the company would, and would not, support.
Comment: The company does have a relationship with a couple of universities there, but I was wondering if I would be able apply to other universities.
Answer: You would need to check that with both the university and with any supervisor/advisor you would have. I'm pretty sure that such relationships do occur, even if not common. But being less the norm, you need to work out the details.
In some ways the supervisor might be the bigger block than the university. It might take a trip to Europe to finalize any such arrangements. But you first need to determine if they would even consider such a situation. The answers will vary.
Comment: Thanks, it seems like you think this is not out of realm of possibility. I am okay with mid-tier universities, so not sure where to start processing of narrowing down list of schools. The process is very different in North America, that I am more aware of.


Most succinct proof of the uniqueness and existence of the Levi-Civita connection.

Question: Seeing as proving the existence and/or uniqueness of the Levi-Civita connection seems to crop up in every single exam in Geometry and General Relativity, what is the most succinct proof of this, to memorize.
Comment: What do you know? I assume you have seen wiki page of [Levi-Civita connection](http://en.wikipedia.org/wiki/Levi-Civita_connection). The proof of uniqueness there is not that bad.
Answer: It's just a matter of remembering the order of things. The most practical way of proving the existence of Levi-Civita connection in a Riemannian manifold $(M,\langle\cdot,\cdot\rangle)$ is using its desirable properties, say:

Symmetry: $\nabla_XY-\nabla_YX=[X,Y]$
Compatibility: $X\langle Y,Z\rangle=\langle\nabla_XY,Z\rangle+\langle Y,\nabla_XZ\rangle$

We construct the connection based on the behavior over the fields: lets $X,Y,Z$ be fields over $M$. By 2. and 1.,
a) $X\langle Y,Z\rangle=\langle\nabla_XY,Z\rangle+\langle Y,\nabla_XZ\rangle=\langle [X,Y],Z\rangle+\langle \nabla_YX,Z\rangle+\langle Y,\nabla_XZ\rangle$
b) $Y\langle Z,X\rangle=\langle\nabla_YZ,X\rangle+\langle Z,\nabla_YX\rangle$
c) $Z\langle X,Y\rangle=\langle\nabla_ZX,Y\rangle+\langle X,\nabla_ZY\rangle$
Notice that in first and second equations above we have $\langle \nabla_YX,Z\rangle$ appearing two times. Calculating "a) $+$ b) $-$ c)" we get, putting similar terms togheter,
\begin{eqnarray}
X\langle Y,Z\rangle+Y\langle Z,X\rangle-Z\langle X,Y\rangle&=&\langle [X,Y],Z\rangle+2\langle \nabla_YX,Z\rangle\\
&+&\langle Y,\nabla_XZ-\nabla_ZX\rangle+\langle\nabla_YZ-\nabla_ZY,X\rangle\\
&=&2\langle\nabla_YX,Z\rangle+\langle [X,Y],Z\rangle+\langle [Y,Z],X\rangle+\langle [X,Z],Y\rangle
\end{eqnarray}
(this equation is known as the Koszul formula) Isolating $\langle\nabla_YX,Z\rangle$, you get a formulae and hence can define point to point the value $\nabla_YX$. You just have to remember the (natural) order of derivations in a), b) and c) and "a) $+$ b) $-$ c)". The rest is straightforward.
Comment: I guess i cannot do any better than this.
Comment: @DanielOfTaebl Also for a connection, we need the target to be a vector field. In this proof, we only define the $D_YX$ point-wisely. How can we guarantee the smoothness?
Comment: I think if you wanna, for instance, remember the proof, you only need to remember that we derived in a mnemonic order and then sum and subtract. The rest is a matter of using identities listed above =)
Comment: @DanielOfTaebl   May I know why Koszul formula can uniquely determine $D_YX$? Does it follow from the inner product structure (since the formula holds for all $Z$)?
Comment: @John Rearranging the terms in the Koszul formula, we get $2\langle\nabla_YX,Z\rangle=K(X,Y,Z)$ where $K(X,Y,Z)$ denotes the remaining terms. Assuming $\nabla_YX$ defines a vector field, one can show with some lengthy but straight forward computations, that $\nabla$ in fact is a metric torsion free connection by using $K(X,Y,Z)$ in the computations. The fact that $\nabla_YX$ is a vector field is more tricky. One can show that $T(Z):=K(X,Y,Z)$ is $C^\infty(M)$-linear in $Z$, and conclude the unique existence of some vector field $X_0$ with $\langle X_0,\cdot\rangle=T$ using coordinate patches.


Nikon D7100 files save as black and white when it is set to standard

Question: Why did some of my Nikon D7100 photos save as black and white when no monochrome settings were selected? I realized later it was shot in "effects" mode but some of the photos saved black and white and some did not. I want them in color. Is there a way to reverse this?
Comment: Which Effects? Manual says Night Vision and Selective Color basically do B&W.  I can't imagine there is any way to reverse them now.
Comment: If you got mono out of the camera there is probably nothing for it, other than to use these photos to experiment with creative post-processing tinting.
Answer: On the D7100, there is many way of influencing color of the photo you take. The 2 main ones are Color Profiles (standard, vivid, neutral...) and Special Effects.
The Special effects can be used by turning the mode dial to 'effects'. Then the desired special effect can be selected by the main command dial. Some special effects can turn the image Black & White such as Night Vision or Selective Color.
When you take a photo the special effect is applied on top of the color profile selected then stored in memory.
That means there is no way to recover the color version of your photos taken in effects mode.
To avoid this, you must not use the 'effects' mode directly. Prefer the green auto mode or P mode. If you like the Special Effects, you can always create a copy of the photo and retouch it in-camera, see Nikon D7100 User Manual page 274.
Even in auto mode, you will still have the color profile automatically applied to your photos among other things like white balance... Once a photo is taken, its colors cannot be changed. You can retouch them lightly in camera. However, you will notice that heavy retouching in-camera can degrade the image quality.
To have a total control on the colors and the quality of your photos, consider shooting RAW or RAW+JPEG (see image quality page 66) and learning to process RAW files on a dedicated photo editor like Lightroom(paid), CaptureOne(paid), Darktable(free), RawTherapee(free)... Choose one and learn it. You will find plenty of resources to learn them online.
Also, processing your photos this way allows you to not think about colors during shooting and concentrate on your subject more or be less hesitant shooting. Later behind the computer, you can have a deeper though about which effect or color you want to achieve.
Comment: Does the D7100 apply special effects to the RAW? Otherwise, RAW+JPEG mode is the perfect backup strategy here....
Comment: Nope, RAW is raw; which is good. That said, some camera models do not save RAW files while in "helper" mode (not PASM). I couldn't find about this one in the user manual. @Annie has to try and confirm that RAW are saved in "helper" modes. In that case, this is the perfect backup indeed.
Comment: Thank you so much for your answer. Unfortuneatly I won't be able to recreate the photos I took because they were of the blizzard that has now melted. I'm not quite sure how my camera was set in effects mode but I am certain I will always check to make sure that it isn't from now on.  What is "helper mode" that you are talking about.
Comment: It is just a word I use to designate all the modes found on entry level camera that helps beginners to shoot what they want (auto, portait, night, action, no flash...) in opposition to 'creative modes' namely P, A, S and M where the photographer has more control over his camera.


Solar powered mini water pump: how to turn it on/off automatically

Question: I have acquired a mini water pump (5V 1.0A) and several solar panels (each: 5V 200mA). What I try to achieve is to pump water from a container above a vertical hydroponic system and let it flow down back to the container while watering the plants inside. I want to pump the water only for ca. 3-5 minutes each hour during the day. Pumping non-stop during the whole day is not good for plants and unnecessarily wear out the pump. What is the simplest/cheapest way to interrupt the pump most of the time and power it only for 3-5 minutes during the daylight?
Comment: I have several such panels, if one is not enough...
Comment: correct, edited.
Comment: Diy microcontroller timer or buy a pre made one.
Answer: You don't really need multiple solar panels, I would add a small battery, Perhaps lead acid for durability, and a solar charge controller to keep it at the proper charge level. You should be able to get all of this off-the-shelf.
After that, just get an Arduino or a PI zero, and a relay shield or hat, the code to start once an hour run for a few minutes and then put the processor to sleep is relatively straight forward. And, although this is overkill and simpler circuitry could be designed to do this, it would require more experience that what you seem to have, it's not necessary unless you are designing a sellable product, and it would save you a lot of aggravation later on. Particularly if you feel compelled to modify the behavior in the future.
What you would need if you want to put together a circuit from scratch:

A solar charge controller. An IC such as this one, its purpose is to optimize power extraction from the solar panel.
A battery or super capacitor. To store the necessary power to drive the pump and the rest of the circuitry.
a small switching regulator for the circuitry power.
A power switch, relay, or transistor to drive the pump. You might want to regulate the voltage to it unless you can directly power it from the battery. You can do this via simple pen and an LC filter, ourjust a simple switching regulator.
A reasonably stable oscillator. A cheap circuit would just use an RC, a less cheap one a ceramic resonator, but a crystal oscillator takes all the guess work out of it.
A set of counters and flip flops to put together a state machine with the desired duty cycle of 3mins per hour (a purely analog oscillator with such a duty cycle would be very hard to pull off). This is where I would use a timer counter IC, which are being discontinued.

Such a system would be very hard to modify once put together unless the changes are designed from the beginning.
Or for less hassle and money you can use a simple 8-pin microcontroller (e.g., a PIC or a tinyAVR) with its built-in RC oscillator and program it to generate the duty cycle, the pump PWM, and even a heartbeat LED so you know it's working, and go to sleep to conserve power. The same thing you would do with an Arduino, harder to program, but with no unnecessary parts and perhaps more satisfying.
Comment: @user1876484 in more than one occasion I have gone the route of designing that "simpler circuit" and regretted not having just used a microcontroller at the end. I'll edit the question later to add some suggestions, but a microcontroller is nowadays the cheaper/simpler route (the type of timer IC I would have used for this (CD4541) I have recently found to be obsolete).
Comment: @EdgarBrown: you've convinced me and I will go the Arduino NANO + relay route. Could you, please, explain or schematically show how do I connect all the 5 parts: Arduino NANO , relay, solar panel, solar charge controller and the battery? Are you aware of solar charge controller/battery with  suitable parameters on Aliexpress?
Comment: I have already used Arduino for this type of things. So I actually wanted to know what are those more simple circuits in order to decide whether my experience is enough to build them or not. Thanks!
Comment: @user1876484 I can envision a solution that uses two ICs (a PIC12HV615 8-pin microcontroller and the above solar charge controller) a couple of transistors and diodes, a couple inductors, a few passives, and a very large capacitor (to store power for the pump). A nifty little project that could teach you a lot, as the PIC would be doing both the high-voltage storage and voltage regulation for the pump. The most expensive part of this would be the PCB.
Comment: An Asian sourced Arduino for a few $ US is a very flexible and capable solution. You could perform your basic task with a  package of hex Schmitt triggers acting as a delay and timer (which is the sort of solution I used to use long before Arduinos existed) - but if you want to change any parameters or add complexity the Arduino wins hands down on flexibility.
Answer: Just usa an arduino with a relay. You just need a simple code like this-
<code>void setup{
pinMode(13, INPUT);
}
void loop{
digitalWrite(13, HIGH);
delay(180000);
digitalWrite(13, LOW);
delay(3420000);
}
</code>
Answer: If you're looking for "simpler" than an arduio, you could probably accomplish this with a 555 timer. The accuracy won't be good but I assume the plants won't care if their water comes 2 minutes late on warmer days or however the temperature would mess with it.
To implement with a 555, set it up in the astable pulse configuration with a large capacitor that charges and discharges with your 8% duty cycle and a period of 1 hr. Since you'll probably end up using an electrolytic capacitor which, by it's nature is a little bit leaky, you'll have to adjust the resistor values experimentally to get the timing you want. As you create your design I'd look up how much leakage you should expect and compensate your charge/discharge resistors accordingly. Ultimately you'll need a transistor/FET driver stage to drive your pump motor and don't forget the flyback diode! This should come out to about 4 resistors, a big capacitor, a small capacitor, the 555, transistor/FET and a diode or two depending on your 555 setup.
Comment: All that being said, if you have the Arduino working already, stick with that. It's cheap enough and will cause less frustration than trying to tune the 555 circuit. Also, it gives you the option to add features, for example you could add a photoresistor and resistor voltage divider to an Analog input pin to only pump during the daylight hours.
Comment: Would you mind to add a picture of the circuit and approximate values for all the different parts? This will help me to understand whether I want to try to build it or better stay with Arduino. And yes, precision is not that important in this case. Thanks.
Comment: A frequency of 277uHz is nearly impossible to achieve with such analog circuit. The behavior would be completely unpredictable and controlled by system noise. A problem when the we te is a pump attached.
Comment: As a disclaimer I have never designed a 1hr period circuit with a 555 timer, but if the capacitor were low leakage, say a 1uF polystyrene cap, don't you think this could work?


Developing for IIS and IBM Websphere

Question: My company is looking to develop a web product that will need to run on both Websphere and IIS.  Ideally, we would like to use the same framework for both, but I am currently ignorant of the options, if there are any.  On IIS, we would most likely use ASP MVC, and JSP on Websphere.  Is there some common technology we could use on both platforms?
Answer: IIS is a web server. Websphere (or what just the term Websphere commonly refers to) is an application server, Websphere Application Server (WAS). IIS would be more comparable to IHS (IBM HTTP Server) or Apache HTTP Server.
So the answer to "Is there some common technology we could use on both platforms" is probably JSP since WAS is mostly just a Java application server.
A reference for running JSP on IIS Lightweight servlet engine for serving java application via IIS
Here is a more detailed discussion on application vs web servers
What is the difference between application server and web server?
A more general note: Getting the same application to run exactly the same in both environments will likely be a difficult task for any moderately interesting application.
Answer: What would be truly common to both is HTML, CSS, and JavaScript. That is, client-side technologies rather than server frameworks. So I'd recommend at least considering one of the JavaScript MVC frameworks. TodoMVC.com compares several of them.

Developing for IIS and IBM Websphere


How to remove stuck glass bowls? (Square bowl in a cylindrical glass bowl)

Question: Currently facing a situation where a square-ish glass bowl is stuck in a cylindrical bowl in a weird angle. Tried the ice in the inner one and immersing the outer one in hot water but it still wouldn't budge. Any help would be appreciated.
Comment: As a general comment for all the solutions below: the **thermal expansion coefficient of glass is low**, so for heating the outside glass and cooling the inside glass to work, you may need to heat/cool quite a bit. Rapid changes in temperature however may instantly fracture either of these (and possibly produce sharp shards), so please be careful.
Answer: I can only make a suggestion.
You need more ice in the inner bowl, so it fills it. The outer bowl should be standing in a bucket of hot water, at the same time. Prop it so that the ice in the inner bowl is level, to its brim. The space between them should have no water or ice.
You could also drip some oil around the corners of the inner square bowl to provide lubrication.
Then, stay on the case as the outer bowl expands and the inner bowl contracts (hopefully). It may need some help at the right moment, such as under the highest corner of the trapped square bowl, which isn't level.
Perhaps you can contrive some kind of lever that goes through the gap between the square inner bowl and curved outer bowl, that tries to gently pry up the highest corner from underneath. For example, a metal fork or spoon: or a pair of such implements, one helping the other.
Comment: An especially valid consideration here is that some form of upward pressure should be applied. As the inner shrinks and the outer expands, one does not want the pieces to drop deeper and jam more tightly!
Comment: @fred_dot_u the answer does say that. *to gently pry up the highest corner from underneath*.
Comment: You actually need to lever the *far* corner… which you can't actually see because of the distortion. By extrapolation, as we can see the two near left corners are touching the side, the 'trapper' must be opposite, and at the top. See https://i.imgur.com/psjsdGY.jpg
Answer: Topsy-Turvey Lifehack:
Turn the two pieces over so that the stuck piece can fall out.

Put a small folded dish towel under the small stuck piece to cushion it when it drops out.

Lift the edge of the cylinder a bit and let the cylinder edge drop to 'jar' the stuck piece loose as it hits the counter top.
(Let the weight of the stuck piece help to dislodge it.)

Experiment with lifting different places around the edge of the cylinder and different 'drop' distance to the counter.

Gravity always wins.
Good Luck
At the very least, DON'T store the jars upright which increases the problem.
Answer: Disclaimer: this method is a bit more aggressive, so damage (breaking) might occur !
Put the entire thing in the freezer (-18 C), without anything inside or outside for a few hours - to get the inner thingie as small as possible. Take it out, and place the outer bowl in water (room temperature). The outer bowl should grow in size, while the inner "remains" small.
If nothing happens in one to two min, start heating the water - slowly. The outer bowl will expand at a higher rate, releasing the inner one.

Maybe spraying some WD-40 would help - but it might help crack the glass in combination with extreme temperatures.


Using other's contents in your website

Question: How can I use someone other's article/post on my own website? What is the legal way of doing this? Usually what I do is that I mention the source from where I got that post. Is there any other way? What ways do you follow to prevent yourself from copyright issues? Can I just use their content and not mention their name? Can I use a hidden HTML link of the source?
Comment: What exactly are you trying to do? The fact you're even asking about attributing via a hidden link(effectively pointless) sounds questionable to say the least.
Comment: Using other's content is a tricky area of law.  It may be worthwhile to research a firm's actions with respect to enforcing their client's copyrights.  Righthaven has been aggressively pursing many web sites for "fair use" of copyrighted material. Arstechnica.com has done extensive reporting on this topic ( http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=site%3A+arstechnica.com+righthaven).  The search should get you going.
Answer: Assume that you can't reuse content unless told otherwise.
Unless the page specifically states that the content is licensed for reuse under a Creative Commons licence or similar, or the work is in the public domain, you should assume that content is not licensed for reuse, and not reuse it in any way.
You can find content that is licensed for reuse with Google's Advanced Search. From their page on usage rights:

"The usage rights filter on the Advanced Search page shows you pages
  that are either labeled with a Creative Commons license or labeled as
  being in the public domain."

You can also use the Creative Commons search tool to find works that are licensed for reuse.
It's important to respect people's rights on this one; publishing content on the Internet does not transfer any rights to people who can access that content, nor does it put content into the public domain in the legal sense. The copyright automatically belongs to the content's author, be it a person or a company, and they alone can license its reuse.
If you can't see a licence and you want to reuse content, contact the author to ask if it's OK. If they don't reply, assume that you cannot use it. Contacting them does not transfer any rights to you. You need a reply in writing approving reuse.
If you are currently reusing content, and the original author has not provided a licence on the page to do that or otherwise given you permission in writing, you should stop stealing their content. Write your own, hire writers, or use Creative Commons -licensed work instead.
Finally, even if content's licensed for reuse, there may be provisos attached to its reuse. The standard Creative Commons Licence, for example, requires that you attribute the work to its original author in whatever manner they ask you to, often with a simple link, but sometimes with a specific paragraph of text. This text should be visible. It is not OK to hide attribution text with CSS, JavaScript, or any other method.
Comment: ...the general exception to the above, at least in the US, being that you're allowed to use a reasonable excerpt. You may want to check if that works differently in your particular country. For the most part, though, nobody's going to come after you if you re-post a snippet and link through– **visibly** –to the original document.
Comment: @DisgruntledGoat Yes, they can. See the @Mike Chess comment on question. What you mean is that they're (almost certainly) wrong and won't win a legal challenge. That hasn't stopped some companies from trying anyway and getting their result through simple fear. Further, Fair Use(with that name) is largely a United States concept. OP is in India. Other countries have different qualifications, and in some, eg. South Korea, the concept doesn't even really exist.
Comment: @Nick:  This is a well stated answer.  Agree that if the content isn't your original work, assume it cannot be used unless granted permission.  Many websites will post a copyright notice somewhere on their site.  That copyright notice will often spell out the legal terms for reuse or syndication of content from that site.
Comment: @Su: no one *can* come after you if you quote snippets. That falls under fair use. See http://www.templetons.com/brad/copymyths.html
Answer: In addition to Nick's answer, if you're going to reproduce the content from another website, you should use canonical URLs referring to the original source so search engines know which content is the original work.
Also, from an seo point of view, reproducing another website's content will have no SEO value to you as it will be filtered out as duplicate content.
Answer: Is it mandatory that you use the entire article or post? You should be fine so long you only reproduce part of the content and invite your visitors to read the rest of it in the original website.
It's not a copyright infringiment if you're just mentioning it, think of it as a quote. To avoid losing visitors to the sites you link, it's important you describe the content with your own words and, of course, produce content of your own.

Using other's contents in your website


How to calculate this congruency?

Question: Let's say I have this linear congruency: $2x + 1234 = 7 \mod 17$.
Without "$+1234$" I would've used the following formulas: $x = x_0 + k(\dfrac{m}{gcd(a, m)})$, whereas $ax_0 + my_0 = b$. But I don't know what to do with $1234$? Thank you in advance.
Answer: No worries, just solve it like you would solve a normal equation.
$$2x+1234=7$$
$$2x=7-1234$$
and then apply your usual method.
Answer: I would calculate everything mod. $17$: $\;1234\equiv 10\mod 17$, so the equation becomes
$$2x+10\equiv 7\mod17\iff 2x\equiv-3\equiv14\mod 17. $$
Now as $2$ is a unit mod. $17$, we may apply the cancellation law:
$$2x\equiv 14=2\cdot 7\mod17\iff x\equiv 7\mod 17.$$

How to calculate this congruency?


how to make a socket server for multiple clients

Question: I have seen a lot of tutorials on client/server chat rooms using sockets, I am trying to create a instant messenger which will allow users (stored in a sql db) to chat with there contacts and groups(also stored on sql db). now I am really puzzled where to start. how would i go about creating a server which can handle peer to peer chat and group chat. I am using a mysql database which will store the user data and contacts list.
Answer: To get you started on ServerSocket and ClientSockets for multiple clients you can refer to the below post.
Two Socket sharing a port
Ideally every client would have only 1 socket connection to the server. To differentiate between your chats you can very simply use a unique identifier which will help differentiate between the different chat types.
Comment: thanks for the reply, so do you mean that ever client would have a socket each which would connect to ONE socket in the server or will the server have to have a socket for each client socket.
Comment: The Server would have 1 `ServerSocket`. Multiple clients (each with a `Socket` of their own) would connect to the same `ServerSocket` in the server.
Answer: You will need to create a multi-threaded socket server, this will accept incoming connections on a loop, and then pass off all operation between that instance of the socket and the client into a separate thread. This will allow you to run multiple client connections at once. This Page goes into great detail about creating both single and multi-threaded chat servers.


How to hide desktop icons on a single desktop

Question: I'm a big fan of multiple desktop spaces on OS X 10.7 (see image).

I'm wondering if you can hide desktop icons on just one of the 4 spaces I have setup. Is that possible?
Answer: This free app may be useful to you. It does not exactly do what you ask, but it comes close, and there may be ways to further automate it to get even closer.
http://www.shirt-ediss.me/clarity/
When this is installed as directed, a couple of simple terminal commands, e.g.:
$ sw 0
$ sw 1

let you empty the desktop of icons (except for mounted drives, if you have your desktop configured to show them) and then switch back to your standard desktop.
In my initial testing (I just installed it tonight) it takes about 2 seconds to clear the desktop and about 4 seconds to restore it.
Clarity has the added advantage of letting you save various desktop configurations to switch back and forth among, identified by either number or a text name. In the above commands, you could also type
$ sw home

which may be more mnemonic if you have saved dozens of desktop configurations.
If you want to have the Clarity commands automatically invoked to change the icons when you move between desktop workspaces, as in the OP, I believe you can achieve that using the free Mac program CurrentKey Stats (https://currentkey.com/). The latest version (12/2020) adds the feature of "Bi-directional AppleScript support". As described on the CurrentKey web page:

CurrentKey can also notify your own custom AppleScript every time you switch between Rooms. This enables you to trigger Room-specific functionality outside of the app.

While I have not tested that feature of CurrentKey, I've corresponeded with the developer and I use it for switching between workspace desktops constantly.
It seems like it would be a straighforward task to have CurrentKey trigger an AppleScript function that runs sw 0 when you enter a specific workspace and then run sw 1 when you leave it. If I were more facile with AppleScript, I would knock one up right now to try it and complete this answer.
Another technique for clearing and restoring the desktop icons is described at Hide files/icons on the desktop but not in finder. While Clarity (above) empties the Desktop folder and then restores it from saved snapshots, the technique on that thread addresses the need to have the contents of the Desktop folder stay intact. It turns off or on a Finder default setting and then kills the Finder app so that it restarts.
When I tried it, the icons went away instantly, but so did my Finder windows, which then took about 12 seconds to be automatically restarted. When restoring the desktop, the Finder windows were again restored in about 12 seconds with the desktop icons following a few seconds later. Personally, I would find it disturbing to have that automatically happen whenever I changed desktop workspaces. If you absolutely need to access the contents of your Desktop directory while the icons are hidden, that delay may be worth it to you.
I hope this helps.


Change font color when posting new iCal events

Question: I have an iMac with OS X version 10.9.4. When using the iCal application I cannot change the color of a new event I post to match the color I've  chosen for the event.  Example: If I post a Red color coded event the lettering for my description is black.  I want the description I type for my Red event to be Red, not Black.  It would stand out as what color code the event is. Currently if I post a new Calendar event and choose a color for it just a small dot appears next to black font description of my event.  I want colored font to match the colored dot on my calendar.  Additionally there is a Gray Birthday event option but I cannot place any personalized  Gray color coded birthday events. I want the typing font color to match the event color for new iCal events I add and I want to be able to post Birthdays using the Gray color set up on my iCal menu.
Comment: Could you edit if you are using iCal on Mac or the web or iOS? Adding versions for the software helps us help you.
Answer:
The calendar app doesn't give you that level of flexibility. Apple has designed it to look a certain way, and that's the way it's going to look, bar some pretty serious hacking. Busycal is a calendar app that does use the calendar's color for the text, not just for the dot.
The "Birthdays" calendar is a special one automatically generated based on the birthday info you enter for your contacts. You can't edit it directly.


How common are recruitment fellowships for students accepted to PhD programs?

Question: When I was applying for PhD programs, only one offered a recruitment fellowship, a small (but more than $1,000) fellowship to be disbursed in the August before the initial semester began. This turned out to be the program I joined, and as I now am beginning to look for positions, I realized this could perhaps be listed as a fellowship on my CV.
How common are recruitment fellowships for students accepted to PhD programs? Would it be appropriate to list on one's CV as "[University] Fellowship" or something to that effect?
Comment: It's pretty common in my field, amounts of $2000-5000 are generally given as fellowships for dissertation completion for top students.
Answer: You could, without any ethical pangs, but please realize that it will not carry much weight with hiring committees. Overall, it's a feather in the cap, as they say.


Can we use Conga Composer Application with Force.com sites?

Question: I am having a requirement of sending Conga generated document to Force.com sites.
Is it possible?
Can someone pls share a link of any documentation,so that it would be helpful for me to fulfill my requirement.
Answer: Conga Composer requires an authenticated user as it is a named user license model.  Some clients have setup solutions using Force.com Sites where the sites user could invoke a workflow rule, then Conga Composer would be initiated through an outbound message action tied to a Salesforce Workflow rule.


How to make transition from trade school to graduate degree?

Question: This question is asking how to bridge the gap between knowing programming to research.
I'm an undergraduate in a decent BA computer science program at a college with a decent-to-low reputation. Most of the professors here aren't PhDs. I can't transfer to another college, because a close relative of mine is at a prominent member of this college's staff and all eyes are on me. I've taken data structures, architecture, etc but it's much more of a trade school than a rigorous theoretical foundation.
After reading a few advanced data structure books, I've become very interested in certain theoretical computer science topics. If I want to do research after undergrad, how should I go about it? I'm a pretty motivated person and I am good at self studying. Should I try to create interesting projects? work on open-source? work at a prestigious company?
Thanks for any advice.
Comment: Are you working on a bachelor's or an associate degree?
Comment: Fixed in question.
Answer: A common piece of advice for situations like this is to apply to master's programs.
This will give you time to catch up on any background that you may be lacking and give you the chance to become more competitive for PhD programs by getting letters of rec, good grades, and research experience.
Answer: perhaps look into publication options? Grad schools often look at whether the person can do research, which will work against a trade school background because it is more hands-on. However, there is nothing to stop you from writing up articles on the areas that interest you. It wont be easy, at all, but if you can get published in a peer reviewed journal--or at least a trade publication--that should help. See if you can get a professor to work with you, if you aren't sure. If there aren't any professors at your school willing to help, network out with professors at other universities if at all possible. Also, see if you can be a research assistant to a professor (preferably one who has a PhD).
I would also directly address this in any grad school applications through the essay. You can focus your essay on your passion for research and how you went above and beyond to find research options. That will show commitment that committees will like.


Music for the entire New Year

Question: I know about this disk jockey, J. Jason. He plays same track every year, over and over again and just started his play list again. He never plays venues. His music can only be listened to on the radio, both on FM and on AM as well. Can you guess the play list?
Answer: This playlist must be:

 the months of the year.

Since...

 J JASON DJ FM AM (all elements from the text, since 'DJ' is an abbreviation for 'disc jockey') represents the initial letters of the English months in order, starting from June: June, July, August, September, October, November, December, January, February, March, April, May.

This explains why his playlist just started again:

 It's January 1 - a new year has begun and the cycle of months has begun again!
Comment: @oAlt I believe that's purely set-up for the FM/AM quip, no further significance of its own
Comment: ROT13 Lrnu, gung'f jung V gubhtug gbb ohg V fgvyy qba'g frr gur pbaarpgvba jvgu "Ur arire cynlf irahrf." vs rire gurer vf bar...
Comment: @Stiv you are quite right. As an afterthought, I could have obscured it a bit more by replacing FM/AM with the corresponding wave bands but nevertheless you've already answered it.

Music for the entire New Year


Is $k[x][[h]]$ finitely generated as $k[[h]]$-algebra?

Question: Is $k[x][[h]]$ finitely generated as an algebra over $k[[h]]$, where $k$ is a field, and $xh=hx$.
Comment: It seems that in general people don't think this is the right level for this site... However, these sort of issues can be confusing at first (e.g. that k[x][[h]] \neq k[[h]][x]). In brief I believe the answer to your question is "no." If you have trouble working out a proof I'd try to prove that k[[x]] is not finitely generated over k (hint consider cardinality as vector space over k) and then adapt an argument from that case...
Comment: I'm not sure, @user36931, that your proposed strategy is the right one, but that may be the kind of approach for OP to use.
Answer: Let $F_1, \ldots, F_m \in K[x][[h]]$. Let $d_j$ be the maximum $x$-degree of the coefficient of $h^j$ in $F_1, \ldots, F_m$ and let $\delta_n = \max \{d_0,\ldots, d_n\}$. In any term $f F_1^{a_1}\ldots, F_m^{a_m}$ where $f \in k[[h]]$, the $x$-degree of the coefficient of $h^n$ is at most $(a_1+\cdots+a_m)\delta_n$. Let  $\epsilon_n = (n+\delta_n)^2$. Given any $a \in \mathbb{N}$, we have $\epsilon_n > a \delta_n$ for all $n$ sufficiently large. Hence
$$x^{\epsilon_0} + x^{\epsilon_1}h + \cdots + x^{\epsilon_n}h^n + \cdots $$
is not in the $k[[h]]$ algebra generated by $F_1, \ldots, F_m$.
Comment: Much shorter than the labored proof I was trying to construct.


Using Count function in SOQL and If condition

Question: I am updating a value on related record based on the count of another record. The condition is say A is lookup to B record. So, if there is only one B record then certain Value of a field say C on B record will be populated to a new field in A record.
Comment: Was trying to check condition directly using COUNT(), but that's wrong. So, I am storing the count in a variable and trying to check with that variable
Answer: There are no conditional statements (such as IF()) in SOQL, and you can't put an aggregate function like COUNT() in the WHERE clause, so you'll need to do at least some of the processing in Apex.
I don't think the Declarative Lookup Rollup Summary Tool is a fit for you in this case, because I don't know if it allows you to restrict the 'rollup' based on a count.
That aside, there are a couple of queries that can accomplish what you want.
First, using aggregate functions:
[SELECT Object_A__c, Field_C__c, COUNT(Id) number_of_B_records FROM Object_B__c GROUP BY Object_A__c, Field_C__c]

Second, using Parent-Child subquery:
[SELECT Id, (SELECT Id, Field_C__c FROM Object_B__r) FROM Object_A__c]

In the end, there's not much of a difference between these two queries. The only appreciable difference is in the Apex to process each query.
For the first query (n.b. You'll need to manually cast the value from ar.get('Field_C__c')):
List<Object_A__c> recordsToUpdate = new List<Object_A__c>();
for(AggregateResult ar :[SELECT Object_A__c, Field_C__c, COUNT(Id) number_of_B_records FROM Object_B__c GROUP BY Object_A__c, Field_C__c]){
    if((Integer)ar.get('number_of_B_records') == 1){
        recordsToUpdate.add(new Object_A__c(
            Id = (Id)ar.get('Object_A__c'),
            Field_To_Update__c = ar.get('Field_C__c')
        );
    }
}

For the second query:
List<Object_A__c> recordsToUpdate = new List<Object_A__c>();
for(Object_A__c a_rec :[SELECT Id, (SELECT Id, Field_C__c FROM Object_B__r) FROM Object_A__c]){
    if(a_rec.Object_B__r.size() == 1){
        recordsToUpdate.add(new Object_A__c(
            Id = a_rec.Id,
            Field_To_Update__c = a_rec.Object_B__r[0].Field_C__c
        );
    }
}

Either one could be used in a trigger for either object, or in a separate Apex class.
If you do use this as a base for a trigger on Object_A__c, you'd want to have this snippet execute Before Update. You'd also want to modify the snippet to make use of Trigger.new or Trigger.newMap to avoid using a DML statement.


Is there a difference between "Frenchmen" and "French men"?

Question: I was just reading a news article about a couple of French men and was wondering what (if any) the difference between that and Frenchmen is?
Answer: "Frenchmen" could refer to French people collectively, including French women. For example:

National Stereotypes in Perspective:
  Americans in France, Frenchmen in
  America [1]
It seems that many lower-class Englishmen still harbour a Napoleonic dislike of Frenchmen  [2]

It can, of course, also refer to any smaller group of French persons:

Where would you take a couple of
  Frenchmen [in L.A. area]? [3]

"French men" refers just to men from France (all of them or a specific group, depending on context), but not women. Example:

French men are three times more likely than French women to kill themselves [4]

I think that is the principal difference.
So, in the context of a news article about a couple of people, using "French men" at least makes it clear right away that all of them were men. Using "Frenchmen" would have left that unspecified.
Comment: I would also offer some synonyms of Frenchmen — "The French", "Frenchies", "Frogs" (the last one is offensive).
Answer: Frenchman means a person, especially a man, who is French by birth or descent (New Oxford American Dictionary); a French man is a man who is from France.
Answer: A Frenchman could mean a French ship. That seems an odd usage since ships are usually referred to as 'she', but there you are.
Comment: Wiktionary says it also means "A home-made tool used by bricklayers to cut excess mortar from newly pointed brickwork" but doesn't mention the ship definition.
Comment: And a red-legged partridge, too. You learn something new every day. Thanks for the suggestion, Shinto; I've bookmarked Wiktionary now.
Answer: Basically a French man is a Frenchman and vice-versa, so the meaning is the same. Stylistically the word Frenchman seems a little old-fashioned. It's something I would avoid using, perhaps because it is associated with unacceptable terms like Chinaman for Chinese man.
Comment: I think this is more of a square/rectangle situation: All French men are Frenchmen, but not all Frenchmen are French men. I do, however, agree with your point about the subtle insult that could be implied by using the term *Frenchmen*.
Comment: _Chinaman_ seems to me different from _Frenchmen_. The exact comparison would be between _Chinaman_ and _Franceman_.


Does dark matter in the universe acts as a pulling force or a pushing force?

Question: Scientists have claimed that in this world there are two kinds of forces which help in keeping everything in its place called dark matter and dark energy. But are these two forces act as a pulling force which pulls the universe or pushing force which pushes the universe.Also lights bend when it passes through these forces so is pushing this light beam away or pulling this light beam near itself.
Answer: Which scientists have called dark matter and dark energy forces? Dark matter is a form of matter that doesn't feel any force other than gravity (so far as we have observed). It's true that dark matter bends light because it has mass and it makes up about $5/6$ of all the mass in the universe. The gravity from this mass is what bends light through gravitational lensing (like a magnifying glass made of gravity and without a focal point). So in a way, this gravity from dark matter acts as a pulling force; dark matter itself though is not a force.
That said, nothing is keeping everything in its place; things are constantly moving around and (usually) flying away from everything else. Dark energy is also not a force, it is an unattributed type of energy that happens to have a negative pressure and so it drives accelerated expansion of the universe. But it is not a pushing force and in a flat universe, it does not bend light.
Comment: What kind of acceleration is it and is there any mathematical model for it
Comment: @sayanchattopadhyay there are many complex models for it and it is asymptotically exponential acceleration


Can DHIS2 be used for other development programs besides health?

Question: Can DHIS2 be used for other development programs besides health? For example: education or economic development?
Comment: Why don't you use their contact form and ask them? https://www.dhis2.org/contact
Answer: Yes. While DHIS2 was primarily designed for HIS use, its development has shifted towards a flexible meta-data approach.
There's a beautiful guide available here:
How to Set-up DHIS2 in a New Context?
https://www.mn.uio.no/ifi/english/research/networks/hisp/integrated-health-information-architecture/ch-07.pdf
Answer: Yes it can definitely be used outside the health domain. The system is designed to be generic and domain-agnostic. Successful implementations have been done within logistics, forestry, facility registry, surveys, education, food security, water and sanitation and social franchising.


Calendar Event Color

Question: I want to arrange different calendar events with different colors. I work on several projects, and use different colors to identify with calendar event corresponds to which project. My company uses Google calendar, but I use the Mac Calendar. I can not find a method to change specific events to the color I want.
Answer: The colors are set in your Google calender (the Google web site).
There you can set the individual colors for the events.

The Mac Calender is using the Google calender settings, but you can not change the colors in your Mac Calender.
UPDATE
If you really want to use the Apple Calender there is a somewhat initially complicated process to set it up, but easy to use afterward.
You would in Google Calender make new Calenders (name them to your liking) like Events A ect.. then assign a color to it.
Now they will show in your Apple calender with the assigned color.

and you will see them in your calendar list
Comment: That's what I was afraid of. Thanks, I suppose, for confirming my fear.
Comment: Nice one - thanks for this clever solution !
Answer: On OSX the Calendar app uses different colors to distinguish between different calendars being displayed in the app. Eg. any events added to my personal Calendar are green, but events added to my work calendar are blue.

Calendar Event Color


Does anyone know a quote, from an opponent of MLK (e.g. a sheriff) which presents him as radical?

Question: This is for some research I am doing about the life of Martin Luther King.
Comment: Presumably, the 'him' refers to MLK and not the opponent?
Comment: What research have you done?  As I recall his radicalism was pretty obvious - kind of like asking for a quote identifying him as bipedal.  And why from an opponent? Why not from an ally identifying him as a radical? or from a newspaper?
Answer: The FBI under J. Edgar Hoover spent a great deal of effort trying to tie MLK to Communism or otherwise discredit him. They even tried to blackmail him into committing suicide (though that is outside the scope of this question).
In a DOJ memorandum on July 6, 1965, Hoover discussed whether "there [had] been any hard Communist Party line tying together [opposition to] Vietnam and the civil rights movement," he wrote:

I stated there was no doubt in my mind from information we have had in the past few months that King, Levison and Jones in New York have been having these huddles together meeting at the Kennedy Airport motor inn...Stanley Levison is a member of the Communist Party and Clarence Jones also.

https://alphahistory.com/coldwar/j-edgar-hoover-martin-luther-king-1965/
At the time, of course, Communism was the ultimate expression of radicalism in the USA.
Answer:
While not the instigator, and presently unable to direct or control the coming Negro August 28 March on Washington, D.C., communist officials are planning to do all possible to advance communist aims in a supporting role. Martin Luther King, a key figure in the March, does have as an advisor, Stanley Levinson, a secret Communist Party member King himself has been reported to be a Marxist.
It should be very clear to all of us that Martin Luther King· must, at some propitious point in the future, be revealed to the people of this country and to his Negro followers as being what he actually is: a fraud, demagogue, and moral scoundrel.
We do not have, and no Government agency or private organization has, any yardstick which can accurately measure "influence", in this particular context; even when we know it does exist such as Levinson over Martin Luther King and King's influence over other Negro leaders. Personally, I believe in the light of of King's powerful demagogic speech yesterday he stands head and shoulders over all other Negro leaders put together when it comes to influencing great masses of Negroes.
We must mark him new, if we have not done so before, as the most dangerous Negro of the future in this Nation from the standpoint of communism, the Negro and national security.
–– FBI Documents Related to its Plans to "Neutralize" Martin Luther King
  by U.S. Federal Bureau of Investigation (FBI)

In this case William Sullivan, the FBI's director of intelligence wrote that.
The demagogic speech was "I have a dream".
Answer: If by as a radical, you mean as someone who declares himself of the left, as the term is generally understood, King, himself was not; he had, as the King Institute at Stanford University points out:

to defend himself against allegations of being a Communist, though his view that "Communism and Christianity are fundamentally incompatible" did not change.

Given Marxism was predicated on a materialist philosophy on the nature and progress of history and he was a Christian, it's hard to see how anyone could mistake him for a communist. His 'radicalism' came from taking his Christianity seriously. Nevertheless, given his commitment to speaking up against injustice, he was sympathetic towards it, decrying:

America's "morbid fear of Communism," [and argued] that it prevented people from embracing a "revolutionary spirit and … declaring eternal opposition to poverty, racism, and militarism"

One need not, after all, share all the commitments of a philosophy, to find something to admire in it, if there are other important points on which one could agree, and King found plenty to admire in the then communisms revolutionary commitment towards changing working conditions in favour of those who were oppressed by them.  It's his commitment to these values that most likely led to his slurs and slanders that the newspapers and media were only too happy to amplify. For example:
The New American has, by its own admission, published many articles on King's 'communist connections' and in its predecessor magazine, American Opinion, and the monthly bulletins of The John Birch Society, the parent organization of both publications. In fact, in this article they point out that the book It's Very Simple: The True Story of Civil Rights, by Alan Stang, who was a member and writer for the John Birch Society) wrote:

Through Levison's influence, other subversives were attracted to SCLC [The Southern Christian Leadership Conference, which King helped found]. Hunter Pitts O'Dell, former National Committee member of the CPUSA, was employed by SCLC. In 1962, when King mentioned to Levinson that he was thinking of adding an administrative assistant to his staff, Levinson recommended O'Dell, who was then head of SCLC's New York office. King said he liked the idea. At that time, King was well aware of Levison's and O'Dell's communist affiliations.

Also, Robert Welch, the founder of The John Birch Society, was keen on 'exposing' King's communist connections. He wrote the following words for May 1968 John Birch Society Bulletin.

During this career of a brief dozen years, [King] was constantly surrounded by, and associated with, Communists. He "employed" such Communists as Bayard Rustin and Hunter Pitts O'Dell; and he worked closely with Carl Braden and James Dumbrowski.

All of these quotes present MLK as a communist radical by association (despite what he himself had to say about it) and it's also remarkable that they say nothing about what these communists had done that constitutes a crime! It seems rather like the John Birch Society thinks that merely being a communist, or being friends with a communist, or associating yourself with one, is a crime in itself: strange in a country that prides itself on free thinking and free speech.


How to understand wedge?

Question: It is heard that trading wedges (cap/floor straddle - swaption) is actually trading the correlation btw forward rates. How to understand this? Either swaption or cap/floor seem to be insensitive to the correlation and that's one reason it is often suggested to calibrate correlation structure of LMM/HJM to CMS spread options. Pls let me know if I missed sth.
Answer: A 'wedge' as understood by interest rate options traders is a structure of the form : long a cap/floor straddle struck ATM for a period of 1 yr starting in N years / short a N year into 1 year swaption straddle also struck ATM. Usually the cap/floor underlying is 3mo Libor but nowadays it can be daily SOFR.
This transaction has two principal exposures (a) it is short the correlation between the short term rates (either quarterly Libor or daily SOFR ) and (b) it is long volatility , specifically the forward vols of the short term rates that remain after swaption has expired.
'Wedge' is indeed a term recognized by the trading community.  If you draw a diagram of forward vol vs calendar vol , the region of exposure of this trade is represented by a triangle that looks like a 'wedge'.
To answer the comment of @JUW: yes this is well expressed in HJM framework.  In that model, correlations are defined as between pairs of short term rates.  Therefore as you say , (a) comes only from the swaption.   However (b) is the net exposure (eg cap/floor is long 120 units of Vega/ swaption is short 100 units).
Comment: Thanks for your insights! So can we say that (a) comes from the swaption component and (b) comes from the cap/floor part? And which part plays the dominant role? Also, shall we expect the wedge price should be close to zero?
Comment: I like your diagram argument. Now I understand why the product is called as wedge. It seems that you are an HJM/LMM user. lol
Answer: I have never seen the wedge term in the literature, where do you get it from?
Caps and floors are indeed insensitive to correlation, since they are baskets of options (caplets/floorlets), but this is not the case of swaptions. Indeed, their single payoff at $T_\text{expiry}$ is
$$
\left[\sum\limits_{i = 1}{P \left(T_\text{expiry}, T_i\right) \left[F \left(T_\text{expiry}, T_{i - 1}, T_i\right) - K\right]}\right]^+
$$
Because they are options on a basket, they are sensitive to the correlation between the components of the underlying basket, which are the forward rates $F \left(\cdot, T_{i - 1}, T_i\right)$.
Comment: Thanks for your answer! Yes, in theory swaptions shall have sensitivity to correlation. But it is an empirical observation that they are less sensitive to correlations compared with CMS spread options and mid-curve options. So it is suggested in the literature that one shall calibrate the correlation structure of fwd rates in a term-structure-model (like HJM, LMM) to the spread options.

How to understand wedge?


Does Metropolis advocate for Social Democracy?

Question: Metropolis (1927) talks about the importance of a mediator between the hand and the head. In the movie the head is the capitalists and the hand is the workers. A core aspect of Social Democracy and the Nordic model in Scandinavian countries is the importance of dialogue between trade unions and employees organizations, a mediator of sorts. So does Metropolis advocate for Social Democracy?
Metropolis Restored
Comment: Welcome to Movies & TV. Nice question, seeing the time period and cultural/political backdrop it was made in, that interpretation isn't too unlikely afterall.
Comment: @Catija I thought that they had done a [near complete reconstruction in 2010](http://en.wikipedia.org/wiki/Metropolis_%281927_film%29#Restorations), I actually watched it on TV this way. Is there anything significant lacking in that version?
Comment: It's too bad that the full film isn't available any more.  I wonder if this would be easier to intuit if the original cut were still available.
Comment: @NapoleonWilson I actually just saw that... I graduated from Film school in 2010, so the last time I thought about *Metropolis* was before they did the newest reconstruction.  The Wiki does say that there are still a couple of scenes missing because even the newly discovered film was very badly damaged. I wonder if many people have seen the newer reconstruction.
Answer: No, not particularly regarding a mediator. A mediator between the working class and the capital is not an exclusive feature of social democracy and the scandinavian model is a sub category of social democracy. There's rather a strong reference to Marx regarding the revolte. The movie is rather slightly adovcating left-winged politics in general. He might have been favoring social democracy over marxism regarding the outcome of the revolte. This might have been an indirect comment on Marx.


Does wearing a disguise affect armor rating

Question: In ESO you can pick up different disguises and some of them look really nice. You wear them as a separate piece, so I wonder if they affect your armor rating.
Answer: Disguises and costumes (as well as the upcoming guild tabbards) are all cosmetics only (i.e. they don't have any influence on your stats), with slightly different behavior:

Tabbards are permanent (till you unequip them) and help you showing your membership in a guild (will be introduced with version 1.3 some time soon).
Disguises allow you to make some hostile NPCs neutral towards you and they might allow you to use passages otherwise locked, e.g. to sneak into bandit camps and similar. Whenever you receive any damage, they're removed (and the equipped item is destroyed).
Costumes work similar to disguises, but they won't disappear if you're hit, meaning that you're able to keep them equipped while in combat.

Note that the naming ingame isn't very consistent. Most quest disguises will disappear once you're hit in combat, while some of those are permanent (e.g. the disguise obtained on Stros M'Kai).
Comment: Thanks for the answer. I am using medium armor in the game, but all the pieces have different styles, which makes my character look all messy. I made a lot of in-game pictures, and I have a costume that looks quite nice. So until I can make my own set of armor, I'd like to have my costume equipped, but like to have the benefits of my medium armor.
Comment: All your armor effects (stat changes as well as set bonuses) are always active, even if you can't see the armor (either due to a costume or due to the helmet being hidden).
Answer: No. Disguise items' only gameplay effect, aside from the obvious change to your appearance, is the pseudo-stealth effect they grant in certain areas during quests. No disguise provides any stat bonuses.


What exactly happened to the guys in Scenic Route movie?

Question: Sorry, I didn't get what really happened to the guys in Scenic Route. Did they die, dream or really escape from the desert?
Comment: i think if we try to put a final ending of what happened were missing the point of the movie. its left questionable for a reason.
Comment: I think the point is what happened to them =)
Answer: I watched Scenic Route last night just to answer this question. It appears that the ending is purposefully ambiguous. I think that enough data was given for someone to make a call in either direction. Let's go over what I came up with
They lived

They both heard the phone ring. Normally one person will hallucinate and trigger another person to also hallucinate the same thing, but in this case they both heard the phone at the same time.
An ambulance came to get them instead of a helicopter. If you were hallucinating, you would most likely think about a faster way to get saved
There were a lot of scenes after they left the desert. These scenes were not flashes, but played out scenes with both happy and sad emotions which might be expected after a traumatic event
We see Mitchell being unhappy at his wife's parents house. He is sitting in the hallway and his son comes up to him and they go into the dining room with everyone else. If you were hallucinating about escaping hell, why hallucinate about sadness?
It's common for PTSD to occur after a traumatic event which explains Mitchell's  concerns about not actually leaving the desert.

They died

They drank washer fluid from the truck which contains methanol. Methanol if highly toxic in small amounts.
They were dehydrated for 3 days that we saw.
Subjected to major temperature swings for 3 days
A lot of blood loss
The phone rang when they were in the ghost town. If the phone had no signal near the road, why would they have it even further into the desert.
When Mitchell called Carter toward the end, Carter started to say, "It's funny you say that" and the line went dead. Mitchell got mad and threw the phone. When he picked it up, it was cracked just like it had been cracked out in the desert.
Mitchell still had a scab line where is nose was broken. Broken noses can heal within 3 weeks so this means that within 3 weeks of leaving the desert, Mitchell convinced his wife to let Carter move in with them, Mitchell quit his job to become a rock star, Carter finished a book and Mitchell and his wife decided to just pickup and travel the world. Not only that, but within 3 weeks, Carter got a new car (be it, a used one) but he had no money as made clear during the first half of the movie.

The kicker is the very last part where Mitchell has a flashback of them being in the hole and then crying. This is the reason I say the ending is ambiguous. Does it mean that he was flashing back to them being in the hole and he is sad that it happened and happy he survived or does it mean that the "flashback" is actually showing reality of them dead in the hole and he is crying because he knows he has died?
I'm sure my points can be argued, but it's mostly to show that there is no definitive answer from what I saw and I was watching specifically to answer this question.
Comment: I think that's the great idea to create another movie, where guys died in the desert but their souls live happily, but some evidences (like broken phone iin this movie) say different. And in the end they came to the place in the desert where they died... or smthng like this =)
Comment: I think the most sertaingly they died in this movie.
Comment: @EL I believe they died as well, but as I mentioned, you make your own conclusions. If you want a movie like you describe, try Dream House http://www.imdb.com/title/tt1462041/?ref_=nm_flmg_act_10
Comment: Just watched it. Great movie. The last time I watched a movie with opened mouth was several years ago and it was the `Skeleton key`. `Dream house` seems not worse than that.
Answer: I really enjoyed that movie, you see after they fought, Mitchell doped his phone,when he thought that Carter is dead there is a camera rapprochement on his broken phone lying on the ground. I don't think that he ever picked it up! (unless it's not shown)
Comment: good notice ...
Comment: So I guess it is obvious then? They died ...
Comment: dont think so..
Comment: ...I mean, they could be dreaming or something
Answer: Its obvious, and yet so sad. And Mitchel got the blunt of it. These two life long friends, at the edge of death, desperately search for water to survive. Sure they find it, but it was only the beginning of their and they're families death, because they did make it out alive.
But they brought the demon of they're friendship along with them. It shows Mitchel crying at the end and in the hospital because he knows that they are all slowly dying of a deadly parasite that made cozy in that warm rusty water tank at the end. He cries as he knows now where he had obtained it in the flash backs and cries for mercy for his family and himself.
They made it out alive. But only to live life possibly hurting the ones they love and slowly suffering while holding on to the last pieces of they're lives.
Comment: parasite? don't remember any recalls of this.
Answer: This movie does pose a lot of interesting questions and i also noticed the phone wasn't
cracked during the conversation with carter but yet it appeared again when mitch throws the phone onto the sink. It also leaves the question were they already dead when mitch tried to say "were here" to the tow truck driver as at the end they are lying in the hole the same as they were then leaving the viewer to think "did anything after the driver actually happen?" however the ambulance vs imagining a helicopter and the not imagining sadness thing mentioned earlier leads me to believe they actually are alive just suffering PTSD. Very good movie it really makes you think.
Answer: I believe it is up to the viewer to come to a conclusion on how they ended up. For me a weird sort of way I took from the ending was that in some sort of twisted way what they went through in the desert was the first time in their lives they really felt alive and the true reality in their lives was spent in the desert. Almost as if he was more comfortable re-living those days over and over rather than being in the real world.
Answer: Kinda seemed like at the end there, he was realizing they're dieing & never got out the hole. The broken phone and flashbacks (plus the whole convo) lead me to think Mitchel realized what was going on while dreaming..(or dieing).


Why do objects burn when they enter earth's atmosphere?

Question: Why do all objects burn when they enter our atmosphere? is this because of our atmosphere composition? and does this happen on other planets as well?
Comment: Maybe you should better post two separate questions.
Comment: Please close this question and make two separate questions.
Comment: Already separated by the OP :)
Answer: You'll often hear that it's because of friction, but that's often not the main factor. For larger objects it's more likely the pressure they create.
In both cases the reason is the enormous speed, often tens of kilometers per second. When a larger object enters the atmosphere at these speed the air in front of it gets compressed so much that it becomes extremely hot. (Think of pumping up a tire; you're also compressing air and you can feel the valve becoming hot.) The compressed air will often disintegrate the object in the air, and then the debris may burn because of the heat. This is exactly what happened to the asteroid above Russia last year: it exploded with an enormous flash in the air, and left little traces on the ground.
This happens on other planets as well, if they have a sufficiently dense atmosphere. In 1994 the comet Shoemaker-Levy crashed into Jupiter. It disintegrated before entering Jupiter's atmosphere due to the strong gravitation, but when the fragments entered the atmosphere they could easily be seen lighting up as they burned up.
edit
Remember the Space Shuttle? It had heat resistant tiles on the bottom of the craft to protect it from burning when it entered the atmosphere, even though its speed is only a fraction of a meteorite's speed when that enters the atmosphere.
During the last launch of the Space Shuttle Columbia some material from the external fuel tank damaged this heat shield, and upon re-entry the heat and the highly pressurized air under the craft could enter it, causing the craft to disintegrate and kill all crew.
Comment: So if the speed and the air's pressure are the reason, such a thing won't happen in space itself where there is a vacuum right?
Comment: @stevenvh it doesn't necessarily have to be 'this is exactly where I got my knowledge from' as much as its good to have a source to say 'here is verification that this isn't just speculation on my behalf'. For example, is there any source somewhere that agrees with you on it being based more on pressure than friction? ect, hope this helps!
Comment: @stevenvh: Sorry, but your answer is wrong. That's why I downvoted it. See http://astronomy.stackexchange.com/questions/14712/why-do-meteorites-explode/
Comment: @A.K - Right. Comets move at speeds of hundreds of kilometers per second without having any medium in which they would heat up. Note that comets may evaporate very slowly due to the sun's *radiation* though, but this is nothing mechanical.
Comment: Good answer, any chance of getting some sources in there too?
Comment: @RhysW - 'fraid not. This is knowledge I collected over several decades through several sources, including courses. I read in meta that there seems to be a need for references for some people, but I disagree (as I pointed out there).
Comment: @RhysW - I didn't make this up; I definitely have heard this elsewhere, otherwise I wouldn't post it. I found [this video](http://www.youtube.com/watch?v=NFPXRnfrNSQ), which doesn't refer to the pressure per se, but talks about meteorites exploding above ground, like Tunguska. I'm also thinking about the meteorite above Russia last year. I think these can be explained easier by the pressure hypothesis than pure friction. Also see my edit on the Columbia shuttle, where speed (and pressure) were much lower than those of a meteorite. I'll try to find more material.
Comment: @stevenvh, are you sure it isn't the friction of the air going through the rubber tire pump that causes the heat instead of the pressure?
Answer: An object hitting the Earth at high speed has a lot of kinetic energy, \begin{align}
  \frac{1}{2}mv^2
\end{align}
where m is the object's mass and v is it's velocity. If the velocity goes from lots to nothing relative to the Earth, that kinetic energy has to go somewhere. That somewhere ends up as heat.


Modelling Ice cream/pop

Question: i'm having difficulty modeling this icecream. for previous iterations of this, I could get away with making a basic modified circle and using a simple deform twist modifier but this is slightly more complex. Does anyone know how I could go about modeling this? Thank you :)
Answer: Create a torus, in Edit mode rotate it on Y, move it away from its origin on Y:

Create an empty at the same location as the torus origin, give an Array modifier to the torus with the Object Offset option, choose the empty as Object Offset:

Rotate the empty on Z, choose a Count of 8 for the torus Array, in Edit mode rotate and fatten the torus as needed:

Give it a second Array, this time in Relative Offset mode, on Z:

Modelling Ice cream/pop