Tourist visa policies in Dubai

Question: I'm residing in Dubai and my tourist visa will expire by June 24, 2018. Is there any grace period in Dubai, even after the expiry?
Comment: Unless somebody says otherwise, the *general rule* is that countries take dates like that **very** seriously.  Also, a tourist visa is for tourism: unusual for a tourist to *reside*, how do they support themselves without violating visa conditions e.g. taking employment. On your next entry they will look at that and may have questions.  This is all speaking generally, Dubai may differ.
Answer: According to the UAE Goverment, a grace period is not allowed for those on a tourist or visitor visa, only for those who are residents (added emphasis mine):

Overstaying your visa
If a tourist or a visitor overstays, he will be fined with AED 200 for the first day of overstay, followed by AED100 each consecutive day. This is to be paid in addition to AED 100, as service fees at the immigration offices or at the airport when exiting.
In the case of UAE residents, they have 30 days' grace period after visa expiry to either amend their status and get another residence visa or leave the country. Fines do not apply during the grace period.
If they overstay after the grace period, they will be fined with AED 125 for the first day and AED 25 for each subsequent day.
After six months of overstaying, the resident would be fined AED 50 per day.
After one year of overstaying, the resident would be fined AED 100 per day.

Tourist visa policies in Dubai


Scientific Theories for Personal short-range teleportation.

Question: The world I am designing contains several ancient artifacts that among other things, share the common trait of allowing users to short-range teleport (think the Blink ability from Dishonored). The humans of the world are bound by our laws of nature, and are in a 1890s - 1910 level of technology, so they don't believe in magic or witchery. What is a way they can explain their newfound powers? THEORETIC/Strong Hypothetical Concepts are okay, they don't have the means to prove anything yet. My one limitation is that it can't be something we (as in 21st century humans) have disproven.
Comment: There might be a *highly unproven and quite question* theory that's going around about quantum mechanics, but that's well outside 1890s-1910s level of scientific understanding. Besides that I think you're out of luck. Would you be okay with that?
Comment: Are we talking instant teleportation or not? Because how you'd do one or the other is different...
Comment: It doesn't have to be actually instant, it just has to feel instant and not interact with any in-between environment
Comment: Explanations in a world at 1890s-1910 level would invariably include concepts today we would discard as unscientific. Some scientific explanations at that level would border on the supernatural or could invoke the deity. You could be asking for a contradiction. With them knowing what is disproven in the 21st century & without the science to back it up.
Comment: Thanks for accepting my answer. Nice to have it appreciated after three years. It was fun & challenging to work out what would be scientifically plausible in the 1890's. They had ideas that were both sensible & quite odd compared to current science. I hope the answers you got helped your story.
Comment: I was going back through and noticed I had forgotten to accept it. That was an oversight on my part
Answer: My previous answer and most of the others here may have put the cart before the horse.  We've all striven to provide scientifically plausible explanations for how a teleportation device might work.  But that isn't what the OP is asking.  The question is...
How would 1890's scientists "explain their newfound powers", namely their PROVEN ability to teleport short distances.
All of us have attempted to mold the PROVEN FACT THAT TELEPORTATION WORKS in the OP's 1890s world, to our current understanding of science.
That is backwards!  That is not how science works.
Science lives and dies by observations.  Every scientific belief lives with a knife against its throat.  A single repeatable experiment result which contradicts any scientific theory, immediately slaughters it; leaving us in need of a new understanding.
So if teleportation existed and we couldn't empirically figure out how it really works, its existence would open the door to many new possible explanations, regardless of whether those explanations contradict our current understandings or not. Wild ideas would be thrown around and each new possibility would garner advocates to champion it against rival theories.  Meanwhile, cool minds would carefully design experiments to eliminate those proposed theories which can be eliminated.
For example, some might believe that the teleportation artifact accesses a previously undetected axis of space/time.  That on some level, every location is directly connected to all other locations in the universe.  Any two locations are next to each other on this new axis, even if they are extremely distant on all of the other axis-es.  No quantum tunneling or atomic disassembly is needed to traverse the distance via the other three axis-es of height, depth and width.  Instead, you simply move along this fourth axis directly from here to there.
Who knows what other theories might be offered, but it is crucial to understand that it is not the proven fact which would bend to science's current beliefs.  It is science which always must bend around what ever is truly present and can be perceived.
Comment: HG Wells used the 4th dimension is several stories. CH Hinton was an early adopter. Edwin Abbott's FLATLAND: A Romance in many Dimensions (1884). Even Oscar Wilde's "The Canterville Ghost" used the 4th dimension in his hauntings. Higher dimensions were all the rage at that time. Clifford Pickovers's SURFING THROUGH HYPERSPACE (1999) might be a good place to start. The 4th dimension has a long history. Although these days it has been forgotten.
Comment: Thanks for the edits!  You're making me look like I know how to use this language.
Comment: I agree that the object is to figure out what they'd think, however. first we must figure out the method that it's actually using so we know what clues would be there. For example Nightcrawler produces a gas every time he teleports which makes you question where it is coming from which leads to the answer that it must be comes from other world since he's not losing mass himself...
Comment: Congratulations! You've just rediscovered the fourth dimension, though without knowing it was the fourth dimension. A concept well known to late-19th-early-20th century scientifically minded persons. The concept featured in my answer.  A small  knowledge of history helps -- sometimes.
Comment: @a4android!  Thank God it has a name.  It was a b!+ch to describe, and I will probably want to use it again sometime.  Thanks for the history lesson.  BTW... the reason that the phrase "small knowledge" and "history" go so well together, is that there is sooooooo much history!  None of us know it all, but almost always, the answer to every problem (whether practical or speculative, present or future-tense) can be found somewhere in our history.   ...so "sometimes" is too modest a term for so powerful a knowledge.
Answer: The answer is as any history of science buff knows, especially if that person has more than a passing awareness of the 19th science fiction like the Victorian scientific romances, is a theory based on the fourth dimension.
Short-range teleportation by ancient artefact could be explained as an effect of passing through the fourth dimension from one place to another. Essentially this is not too dissimilar to theories involving higher dimensional spaces that are certainly not disproven by 21st century science. Today we wouldn't be able to understand the actual machinery of the ancient artefacts even if we thought we could explain their teleportation.
That's the most plausible explanation a person of science in the late 19th and early 20th centuries would come up with, that the ancient artefacts transported their users through the fourth dimension to accomplish short-range teleportation.
Interestingly Wilhelm Roentgen discovered x-rays in 1895, or as they were initially known roentgen rays. This coincides with with the era the OP is interested in. So possibly a theory could have been devised that the artefacts converted its users into a form of roentgen radiation to pass through intervening matter to arrive at their destination. While this hypothesis contravenes the OP's requirement that explanations shouldn't be disproved in the early 21st century science isn't like that.
Besides teleportation by roentgen radiation sounds like a fun concept. So typical of its era, and yet so wrong. Understanding discredited scientific concepts is an excellent way of understanding how scientists grappled with different ideas to comprehend the laws of nature. Today being turned into x-rays to be teleported sounds downright dangerous and utterly absurd. But not then. The past is a another country, their ideas were different too.
Comment: +1 Fabulous answer!  Especially the roentgen ray based transporter.  That would fit beautifully into some SteamPunk that I've been contemplating.  It is going into my idea journal right now!  I'm off to look for  a source of 19th century scientific romances.  Thanks!
Comment: @HenryTaylor You're welcome! Glad you liked my roentgen ray teleporter. Have fun with it. Michael Moorcock relabelled 'steampunk' as "Steam Opera". This is an improvement. My writers' group loved the idea of steam opera. Most steam punk isn't punk at all. Worth digging into 19th C scientific romances, they have an originality & vitality. The prose can be laboured by modern standards. But for energy & ideas, plus the quirkiness and unexpected they can't be beaten.
Answer: Method 1: Quantum Entanglement. Somehow entangle all the particles in your body with another set of particles. Somehow send the entangled particles forward without sending yourself backwards. Then, flip a switch and instantly move the information from your current particles to the projected forward particles, resulting in "teleportation".
Method 2: Somehow scan all the particles in your body at the precise moment activate the teleport and then use that data to construct a copy of you as you are being destroyed on the other end. If done with a handheld device you'd just have it create a copy of itself based on orientation and such without having to scan and duplicate itself then have the original destroy itself.
Method 3: Nightcrawler's method which is that he simply travels through another dimension (reality which exist in the same space as ours) so it looks like he's teleporting but not.
Method 4: Dimension Shifting. Shift's the user into a different "dimension" where all movement is some multiple of what it feels like. ie Think about how Minecraft works with the Nether. Every step you take in the Nether = 8 steps in the overworld. Same concept.
Method 5. Spacial Folding. Basically you "fold" space, bringing 2 points together so that they overlap. At first you are at point A. You want to go to Point C so you overlap with Point B so that when you step forward you go to point C, because Point B is connected to Point C.
Hypothetically we could do these things... but they'd rely on solving some problems or proving some theories as true such as multiworld theory in the case of Method 3.
Answer: The world is a virtual reality and we are all just constructs within that computer program.
Teleportation is a simple process.  I simply change the values of the X, Y and Z fields in my PhysicalBody.CurrentLocation variable and then wait while the system renders me at my new location.
Comment: The law of conservation of energy is a compiled-in "asserts" check.  Difficult to bypass, but not impossible *if you know the code.*
Answer: You have to invent new physics, or invoke Clarke's Third Law
No, there is no science either in late the 19th century, nor in the 21th century, that can even begin to hypothesize about the mechanics behind that sort of thing.
Physics- and theories-wise it would be like someone finding a radio controlled quadcopter drone in the 1500s, i.e. 300 years before even Maxwell had come up with the theoretical concept of "electromagnetism" which then leads to "radio". In a world where geocentrism is still the predominant model of the universe; where the concept of gas does not even exist yet, they would be hopelessly lost at trying to make sense of any of the physics behind it.

The biggest problem with your apparatus is that it (seemingly) violates the law of conservation of energy. Blink a weight 10 meters into the air, attach it to a chain, let it "fall" slowly while the chain turns a cogwheel attached to a generator. Rinse, repeat. Now you have free energy. We have nothing in physics that can start to explain that. Even on metaphysical levels, that should not be possible.
So you have to go the Arthur C. Clarke route and invoke magic: "Any sufficiently advanced technology is indistinguishable from magic", that is to say: some advanced civilization left this artifact here. Physics? No... just, no. You have to invent new physics for this, or quite simply have your scientists shrug and invoke Clarkean Magic by saying "This is way above our heads... we cannot explain it".
Answer: Instead of affecting space, the artifact may affect time. You can move normally, but after each second of movement, you go back one second in time. That is, you have to physically traverse the space through which you "teleport," but for those around you, no time has passed.
Obviously, there are drawbacks. First, you can't move to a place you couldn't normally reach, such as an upper floor. For instance, you can't get from the ground floor to a balcony without something to climb up or a stairway inside. Second, the device only operates for a limited period before it has to recharge, say sixty seconds, which limits the range. Third, you leave behind a series of phantasmal copies, one for each second. They fade instantly, but they leave a clear trail showing where you went. There's also an annoying buzzing sound that the device makes while operating.
Comment: Welcome to Worldbuilding, RalphCrown, your answer is an excellent explanation for short-range teleportation. There is one problem. The OP wants a 19th century style theoretical explanation (but one which isn't disproved by current science) while this explains how it works it isn't a 19th C type explanation. I had once devised a similar mechanism for a FTL drive, so I approve of your idea. Glad to have you on-board. Have fun here!
Answer: Teleport equals :
phase 1 -Kill the person by dismembering it at atomic level.
phase 2 -Rebuild atom by atom the person in another place.
phase 3 -Implant the memories and identity of the killed person in the new builded one.
Not quite a good idea...
You might  prefer super-sonic speed for short ranges, someone moving at this speed would make a big noise that can break crystals and knock down people.
But, someone moving at this speed would be invisible for the human eye, therefore giving the illusion of teleportation.
Another option is creating portals by bending the space around you, but this ability would make anybody a living god.
I don't know how to achieve this two powers through technology,if i knew i would already have invented such things...
Comment: It doesn't have to be Star Trek style teleportation. Any transmission of someone where they are not affected by the matter in between will work.


Display problem in watch dogs 1

Question: The game launches, and everything seems to be ok. However, the screen starts rendering in a pink color. The game starts ok the first time, but when I restart it, it goes like this. I reinstalled the game but the problem persists.
Comment: Do you meet the minimum system requirements for this game? Not meeting minimum specs can cause odd issues like this.
Comment: it not meeting the min but when i start it first time it start correctly without any problem, i wondering the reason
Answer: Your drivers must not be able to run some elements of the game, making the rendering crash when that element is loaded the first time and making it unrecoverable. Guess its something weird because it doesn't crash the UI and doesn't crash the game outright. But at that point to debug I would need to know how deeply how the game is programmed, something that I do not know.
Something like the engine absolutely needs some code to be able to run so it can simulate rain, but since you dont have requirements, that code crashes, and crashes the engine. So you are fine until the engine tries to switch the weather to rain, and then everything goes wrong. (Rain is an exemple, it could be anything, like simulating birds flying or whatever.)
Sadly, there's not much we can do to help. If you do not match the system requirements, usually these are the lowest they can get it before the game just can't run.
What I'm trying to say is there is probably no script that would recover the rendering after it crashed because if such a script existed, it would be packaged in the game so it would be able to run on worse computers.
So sorry if this is a no-answer, but you need to at least have the minimum specs required if you want to run the game. You can still try your luck, but seems luck is not on your side for this instance.
If it can be any help, my guess would be something about textures. You often see, when engines can't load textures, it loads the default texture that is, if I remember right, a pinkish color in both Source and Epic. (I dont know Watch dogs is programmed on what engine)
TLDR: Sorry man, seems you will absolutely need to update your rig to make the game work.

Display problem in watch dogs 1


HO fluorescents not working after switching with power on

Question: I'm curious as to why after replacing T12 HO bulbs they don't come on if power was on when replacing. I come back hours later and they are finally on.
Replace with power off and they work right away. Ideas? Thanks.
Comment: Welcome. Replace _in what_? Please read your post as if you aren't inside your own head and add clarity so we can help.
Answer: Depending on the ballast type the lamps need to go through a "start cycle".
Live swap is not the best thing for a ballast and although not usually dangerous it's never a good idea to change out lamps live.
What is the start cycle, when a ballast is first fired the voltage spikes depending on the type well over 300v until the gas in the tube ionizes and starts to glow, at this point the voltage is quickly reduced to control the current this is why you need to use the correct lamp type for the ballast, wrong lamp type and the lamp life is drastically reduced or the light output is reduced.
Many times the lamps will light on install on mag ballast but solid state need to go through the cycle and may have turned that lamp channel off because of the bad lamp or open socket. The next power bump the ballast goes through the start cycle sees a good lamp and it works.
With electronic ballast I pull the power to that fixture prior to relamping why most ballast I have are electronic and the channel or lamp may be shut down, if not overheated Chanel's need to cool before they will try a restart or strike.
If the lamps don't light up I know the ballast is bad this is quite common with electronic ballast that have been trying to light a bad lamp for months.
Today I convert all my fluorescent lamps to LED and have been doing this for years. My opinion the universal led retrofit lamps are the best light color is up to you but if you want bright work area lighting go 5000k or higher light color 6500k at 1/2 the wattage of a fluorescent will appear 2x the amount of light. If in a area like a living room you want a lower color in most cases 3000k -4000k is usually preferred but you still get the same light feel fro 1/2 the wattage.
Comment: The biggest mistake you can make when evaluating lighting is looking at the light.  Instead, look at the stuff being lit up.  LEDs are notorious for that eyeball searing intensity, and that makes them seem brighter.   But if you ignore the light and actually look at the workspace being lit, I find LED installations are dimly lit.  What really helps is CRI, however, and going from a LOL 20 CRI ratty old green fluorescent to a 75 CRI LED helps. *But going to a 90 CRI modern fluorescent helps a lot more*.


Proof in Bartle's book

Question: I am studying real analysis by my own and stumble into the following theorem, that Bartle's proves in its appendix, however, I do not understand the case 2. Specifically I do not understand why does he define $h_1$, and the induction hypothesis is not supposed to be that there is not induction from $ N_m \rightarrow N_k$, so how does it implies that $h_1$ is not an injection. Can somebody please clarify this part, or explain it thoroughly, for me it is not easily seen as the book states. Thanks
Answer: Here is a few ideas.

$h_1$ is well defined because $h$ is well defined and no element in $\mathbb N_{m-1}$ is being sent to $k+1$.
$h_1$ is not an injection because $m > k + 1\implies \color{red} {m -1 > k}$ and by the induction step $h_1 : \mathbb N _{m-1} \to \mathbb N_k$ can't be an injection, notice in this case we are assuming $h(p) = k+1 $.

Finally, $h$ is not an injection because we have seen that $h_1$ isn't, and we know that $h(p) = k+1$. Notice that $\mathbb N_{m-1} \cup \{p\} = \mathbb N_m$ and $\mathbb N_k \cup \{k+1\} = \mathbb N_{k+1}$.
Answer: Well, the induction hypothesis is actually that there's no injection from $\mathbb{N}_m$ into $\mathbb{N}_k$.

Proof in Bartle's book


How do you think about and architect programs?

Question: I'm a QA guy and designer and i'm coming to development. How do most developers architect programs? With design I build up with a vague idea of what I have in mind and adapt my design to keep in moving forward and looking good. With coding, I'm trying the same methodology. I'm constantly testing and debugging my code and I make forward moving tweaks to my code. The problem is, I dont think this is how it's done. When I look at good Javascript for example, everything is broken out into evenly distributed functions. I don't architect my code in this way. Do you normally have to sit out and draw out your classes and functions before you start writing?
Answer: Some devs architect their designs in UML completely before starting any coding, and others just jump right in. I've seen good designs both ways. The key is, I think, to be open to redesign and refactoring at any stage of development. A beautifully-architected design, conceived in a 300-page requirements document and drawn out with a stack of state and sequence diagrams, can be utter garbage when coded.
Be willing to throw out your work whenever necessary. Have the tests in place to prove that your refactored design works as correctly after changes as before. Having tests that you trust will give you the courage to change.
Answer: The best definition I've come across so far for architecture goes something like this: When you learn how to read the time off a clock you've basically learned about its architecture. That there will be at least two needles -- a fat and short one denoting the hour and another thinner and longer denoting the minutes -- moving in a certain direction.
Design on the other hand is about how the clock actually looks and feels. Does it have all twelve hours etched on? Does it run on quartz or do you have to wind it everyday? Is it 10' tall or is it a wrist watch?
Implementation is about making the parts that make the design tick (pun unintended) that is the design sticks to the fundamental rules that our architecture laid down.
The Wikipedia article aside I suggest you go through the SEI website to learn more about software architecture. This article on IBM is a good start.
On the more practical side of things there are things called architectural patterns that significantly reduce the amount of effort you need to invest on defining an architecture when you start writing a brand new application.
Answer: I think you should start to write code as soon as you have a clear view of how it will eventually be written, be it after 10 minutes of thought or after 10 days. In order to achieve that you should use every tool at your disposal according to it's goal - I find mock-ups to be extremely helpful when I need to understand the reqs., database diagrams for designing the DB structure, and class diagrams for code (although that part I sometimes skip :-)).
Answer: Sometimes a prototype can be a really good way of finding out some possible ways of doing it wrong. Don't get attached to the prototype, don't worry about details unless it is a detail that will effect the overall system, just use it to understand the problem.  Once you've had a good look at the problem you can either start a new prototype or if you think your basic design is right you can start a more detailed design process.


Why couldn't the decay $\pi^- \to e^- + \bar\nu_e$ occur if electrons were massless?

Question: If we assume that electrons (just like neutrinos) are massless, why can't the decay $\pi^- \rightarrow e^- + \bar{\nu}_e$ occur under the weak interaction?
Comment: I believe a pion can decay in an electron and an antineutrino check [wikipedia](https://en.wikipedia.org/wiki/Pion#Charged_pion_decays)
Comment: @Pablo Not when the electron is massless.
Answer: Since the spin of the charged $\pi$ is $0$, the spins of the daughter particles need to add up to $0$ as well, i.e., their spins need to be anti-parallel. That's nothing else than the conservation of angular momentum.
Assuming the anti-neutrino to be massless, it is always right-handed. Right-handed means that the momentum vector and the spin vector are parallel, while left-handed means that the momentum vector and the spin vector are anti-parallel. This is well defined for a massless particle, since it travels at the speed of light, and there is no inertial frame in which the momentum vector would switch direction.
Since the anti-neutrino is right-handed, the electron would need to be right-handed as well to conserve linear momentum and angular momentum (spin). But the decay of the $\pi$ happens via the weak interaction, i.e. via the $W$ boson. Since the $W$ boson is known to couple only to left-handed particles, the decay would be forbidden.
Since the electron is not massless, it has a small left-handed component. The decay is suppressed, but not forbidden. The heavier muon has a larger left-handed component, and its decay is less suppressed. Hence, pions usually decay into muons, although they have less phase space available.
Answer: pfnuesel's answer is absolutely correct and very satisfying to understand, and you should read it before this one.
There is, however, a route which would permit $\pi\to e+\nu$ even if the electron were massless.  The conserved quantity which suppresses that decay is not spin, but total angular momentum.  There exists an electron+neutrino wavefunction with spin $S=1$, orbital angular momentum $L=1$, and total angular momentum $\vec J = \vec L + \vec S$ of magnitude $J=0$; this wavefunction is available for pion decay and competes with the $S=0, L=0$ channel described by pfnuesel.
However, like all high-$L$ decays, this one is suppressed because the overlap of a wavefunction with nonzero $L$ and the parent particle with radius $R$ is proportional to $R^L$.


Long term medication and increased risk for CLL?

Question: Is a person on long term medication (aspirin, bisoprolol,vitamin B1/B6/B12, simvastatin and trimetazidine) because of a heart attack 30 years ago (and no positive family history) at increased risk of developing Chronic Lymphocytic Leukaemia (CLL)?
Comment: Ok. I have answered your question. I will also edit a little bit your question. As already suggested in my first comment, the title is inconsistent with your question and can be misleading as you are asking about CLL in particular and not cancer. And as a side note: when asking a question on Health SE, it is better to write the compound name of a drug and not its market name, which can be different from one country to another. Hope this helps. Best regards. M. Arrowsmith
Comment: Hi! Just to be sure that I understood your question correctly: you want to know if a person with a coronary heart disease, under ASA, betablocker, furosemide, statin has an increased risk for developing chronic lymphocytic leukaemia? I am right? May I ask you why you are asking for this typical hematological malignancy? You may also wish considering editing your title which is somehow inconsistent with your question (too broad for a very specific question). Thank you. Best regards. M. Arrowsmith
Comment: Hi, I am asking this question because I know of someone who has a heart condition and been taking these medicines for some years now. The person has now been diagnosed with chronic lymphocytic leukaemia. As mentioned in my earlier post this person has no family history of cancer nor any lifestyle issue that puts the person in the risk category for cancer.
Answer: According to the literature, risk factors for chronic lymphocytic leukaemia (CLL) are:

gender: CLL is more frequent in men than in women
age: CLL is considered to be mainly a disease of older adults, with a
median age at diagnosis of 70 years. Although younger individuals (in their 30s-40s) can develop CLL, the incidence rises dramatically with age
ethnicity: studies have shown that the incidence of CLL varies by
race and geographic location: it is higher in caucasians and lower in
African Americans or Asian Pacific Islanders.
genetic/positive family history: the cytogenetic and molecular genetic characteristics of CLL appear to be similar throughout the world suggesting a common genetic alteration. Also, CLL  occur with higher frequency among first-degree family members of patients with CLL.

Finally, no clear discernible occupational or environmental risk factors that predispose to CLL have been identified yet. Also, no long term medication has been associated with the development of CLL.
Sources:
http://www.uptodate.com/contents/clinical-presentation-pathologic-features-diagnosis-and-differential-diagnosis-of-chronic-lymphocytic-leukemia


Can the G1 garbage collector be used when System.gc() is called

Question: In Hotspot, when System.gc() is invoked, I can have this use the Concurrent-Mark-Sweep collector by adding the -XX:+ExplicitGCInvokesConcurrent option to the command line.
Is there anything equivalent to make the JVM use the G1 collector when System.gc() is invoked? By default, the standard parallel collector appears to be used.
I'm guessing not, but I just wondered if anyone could confirm.
Don't worry! I'm not planning to invoke System.gc() myself, but there are parts of the JVM (direct buffers, RMI) that rely on it being called.
Answer: From this bug post :

G1 now observes ExplicitGCInvokesConcurrent

there is also this link that confirm it.
AFAIK there is no special command, neither the list of Oracle JVM options nor this longer list refer such command option.
Answer: <code>bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
  switch (cause) {
    case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
    case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
    case GCCause::_g1_humongous_allocation: return true;
    default:                                return false;
</code>
}
    }
And
bool ExplicitGCInvokesConcurrent               = false                               {product}


Is this an electric guitar? if so how do i make mine sound like it?

Question:

Eight seconds into this song, there is what I think is an electric guitar.  Does anyone know how to produce that sound?  Is it even an electric guitar?
Comment: this question clearly has a definitive answer. Does not look to broad to me.
Answer: This effect is called volume swell. It's achieved by fading in notes using your volume knob or a volume pedal.
Comment: Just to be clear, it *is* an electric guitar, played with volume swells. And there's a touch of feedback, delay, and reverb.
Comment: You beat me to it was just about to post the same.
Answer: Just a bit more info on cyco130's answer :
'Tis indeed a volume swell effect, and is an electric guitar.
The technique is to pluck the note with the volume turned down, then bring the volume in - either via a volume pedal or using the volume control on the guitar.
Some guitars make this easier because the volume control is easily reachable from where your hand would be when playing. A Fender Stratocaster is the classic example: it's easy to pluck a string then turn the volume up. Mark Knopfler of Dire Straits used this to good effect.
There are also effects which do this automatically. They detect when you have strick a note, and fade the sound in for you with settable speed - of- volume - increase.
If you'd like a cheap-but-effective example, the Zoom 505ii pedal has this built-in.
Answer: Sounds like either a guitar with volume swells, or a electric keyboard. In my experiences sounds more like a keyboard. Or some kind of synth sound (coming from a keyboard)


Can a deleted Gmail message be used as proof?

Question: Suppose I have a message in my email client with full headers, but the message isn't available in Gmail anymore. In a copyright infringement dispute or something similar, can that message be used as some kind of proof? Can headers prove that the message and its content are legitimate?
Comment: @Moo respectful, I disagree, in court, anything that strikes the interest of opposing counsel can be submitted into the record as evidence (Example: opposing counsel, "is it true that on (this date) you sent an email title (something incriminating)". The Defendant, "No, it isn't true". opposing counsel, "Then how is there a record of it in your list of e-mail?").
Comment: No, headers alone cannot prove anything, as they are simply lines of text in a text file - they can be whipped up in any text editor.  What you would need to do is get confirmation from Google that the message is authentic.
Comment: @Moo Copyright infringement cases are governed under common law, which means that copyright infringement cases have the [right to a trial by jury](https://www.rcfp.org/court-finds-right-jury-trial-copyright-damages-claim/). During a jury trial, all pieces of relevant evidence that are damning (makes the Defendant look bad), will be used to discredit the defendant in the eyes of the jury, either that be hearsay or a title recovered during e-discovery.
Comment: @Moo the text of an email alone does not prove anything, but testimony can establish it as a valid copy of a transmission actually sent and received. See my answer..
Comment: @Moo: An exception would be if the message carried a digital signature which validated using an undisputed public key of the alleged sender.  Then the message would contain proof of its own authenticity, since it could only have been prepared by someone possessing the matching.private key.
Answer: YES
Most people overlook the statement "everything on the internet is forever", but in the modern age, this is a reality. During discovery it isn't uncommon for opposing counsel to request large amounts of e-mail documentation, including documentation that has been deleted, but is still stored on the server of the email provider or in the meta-data from the computer being analyzed (email recovery is usually done by a third party, professionals at data recovery).
Under Rule 26 of the Federal rules of civil proceeding, electronic documentation is categorized under the same rules that govern paper documentation during discovery.

Can it be used?

This is a tricky question to answer because the answer is, yes, it CAN be used, but WILL it be used depends on if there was a successful motion filed with the court to suppress this evidence.
Answer: YES
More exactly, it can be offered in evidence. As the answer by @StephanS says, it may well be possible to establish that the email was sent by various recovery methods, which are frequently used in legal cases. But even if it were impossible to establish through third-party sources that the email was authentic, it could be offered based on testimony by the party offering it that it was actually sent. Such testimony might or might not be believed, just like all testimony. But it can be offered. Admissibility would be subject to rulings by the Judge, of course.


Carbon Frame Ding

Question: Today I had my Tarmac propped up against a rock wall and it slid down, scratching the paint/frame on the seat stay. I'm pretty new to carbon frames, and have heard they are relatively sturdy, but wanted to see what some more experienced eyes might think of the ding. I tried the coin test and everything sounded okay, but I'm still paranoid. So, in your opinions, cosmetic or structural?
Comment: My guess is cosmetic, looks like it scraped down to the primer coat but i don't see any actual carbon by the looks of things.
Comment: +1 For posting a good picture, not something to be taken for granted with newcomers
Comment: Keep in mind how the damage occurred.  Damage like that caused by an impact might give one pause, but caused by a much less forceful abrasion (assuming the bike fell with basically it's own relative inconsequential weight), I wouldn't be worried.  Annoyed that my paint was marred, but not worried.
Answer: It may have gone beyond the paint, by the looks of it. But I say keep riding it.
Put a piece of electrical tape (or something similar) over the spot to discourage further aggravation.
For the next couple weeks or so, take care to pound your bike over bumps extra hard, and be very perceptive to creaking or cracking sounds. If your frame accepts a couple weeks of beating with no complaints, don't worry and continue on your merry way.
Comment: +1 For the first two paragraphs. I wouldn't suggest riding it any differently to normal. Just be aware of the normal handling and sounds the bike makes, and be alert for changes. Both of the (non carbon) failures  (fork and handle bar) I've had were detected this way before any catastrophe occurred.

Carbon Frame Ding


UK business visa - Marital status is married but spouse does not have passport

Question: I am applying for UK Business Visa. I am married and I have to travel alone. While applying for Visa I need to fill the marital status, I am choosing married but there it is asking for passport no. of my wife.
My wife doesn't have passport. What to fill in that field as it is a mandatory field.
Answer: You can write "not applicable" or "none."
Comment: Can you please share me any official document where it is mentioned to write 'Not applicable or None'.
Comment: @Sumit I cannot.  But what else would you put?  Also, there is no UK visa called a "business visa."  What kind of visa are you actually applying for?  Is it a *Standard Visitor visa?*  What web site are you using to apply?
Comment: I am using www.visa4uk.fco.gov.uk.
Comment: Visa type - Visit - business - 6 months.


Should the Multicast source in an ASM network be a member of the Multicast group?

Question: What happens if traffic is sent to a multicast group from a host which is not a member of that multicast group ? Does the router keep any information for a valid Multicast source and discard this traffic ? I could not get a clear picture of (*, G) vs (S, G) entry. Will the packet be forwarded since there is a (*, G) entry ?
Comment: Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
Answer: Multicast senders are not generally part of the multicast group they are sending to, since they already have the information they are sending to the group.
Depending on your multicast configuration the router could take the new multicast packet and forward to a known rendezvous point and the RP will forward towards interested receivers. This would create an (S,G) entry, if you want to control who is sending to your multicast groups you need to limit the sender source address.
Other configurations could have different forwarding decisions.
Comment: "Multicast senders are not generally part of the multicast group they are sending to, since they already have the information they are sending to the group." - Is it possible to create a multicast group where everyone can send/receive to/from other members ? (In which case everyone in the group is a sender as well as receiver.)
Comment: Sure, the multicast 'sender' and 'receiver' role are completely separate.  Multicast senders send traffic to the multicast group address, multicast receivers send requests to be joined to the multicast group. Each role is independent of each other.
Answer: Multicast sources register with the RP (rendezvous point) through their local first-hop routers (DR - designated router) and the receivers "join" the shared tree rooted to the RP via their own local first hop DR. Now (in sparse mode) the receivers join the shared tree (*,G) via IGMP messages indicating they wish to receive the multicast, and then the (S,G) (shortest path) state is built from RP towards source's DR. Once this connection is realized, the multicast traffic is sent down the shared tree. However, once the receiver's DR sees the multicast's source IP in the first few packets down the shared tree (*,G) , it switches over to use the shortest path (S,G) and the shortest path tree means it uses the unicast routing shortest path back to the source.
To answer the first part of your question "What happens if traffic is sent to a multicast group from a host which is not a member of that multicast group ?"  If you do not have any security built into your multicast configurations, traffic can be delivered to a multicast group from a rouge source.
The second part of your question "Does the router keep any information for a valid Multicast source and discard this traffic ?" Again, if you had no security, yes the DR routers accepts this as a valid source and retains it's (S,G) state, which will also send a PIM source message to the RP, which maps it to the source.
And the third part of your question "I could not get a clear picture of (*, G) vs (S, G) entry. Will the packet be forwarded since there is a (*, G) entry ?" Again, if you had no security, the rogue multicast source can and would send traffic to all requesting receivers. The rogue builds a valid, but unauthorized shared tree (*,G) to the receivers and once the receiver's DR receives the first few multicast packets from the unauthorized source, the DR will switch to the unicast routing distribution scheme, meaning it will use the shortest path to the source (S,G).
So in your case, for "rogue source security", which is a very common best practice, you can use the "pim accept-register" on the RP and all DR's and then this is tied to an ACL permitting all valid multicast sources.
"ip pim accept register list valid_sources"
"ip access-list extended valid_sources"
"permit ip 220.127.116.11 0.0.0.15 239.x.0.0 0.0.255.255
Comment: Now I can understand a multicast group will have a shared and sourced based tree. Now, assume a receiver R wants to send a message to the multicast group. Initially there will not be a (S,G) entry for this source. So, the the packet will be transferred to RP. R (which is now also a sender) is a part of shared tree rooted at RP. Now, my doubt is, since the link from R to its DR is a part of the shared tree, will R be able to hear the same message that it sent, as there is only (*,G) entry in the DR??
Comment: Check out bidirectional multicasting for many-to-many interactive applications http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfbipim.html
Comment: Because I'm not a multicast guru... multicast should never switch to a 'unicast distribution scheme', it should switch to a shortest path?
Comment: I meant to type multicast! (should have added mroute actually) It was a long day/night. :-)


Why the natural log is there in MLE?

Question: Why do we use natural log for MLE?
Answer: Likelihood function is generally ratio of two densities. Since working with ratios is not convenient when taking max, one normally takes the logs. This is most effective when densities involve exponential functions and is extremely convenient in the case of normal (Gaussian) densities.
Taking logs does not always help. In fact if the underlying densities are uniform, then logs actually make it worse, not better.
Added based on comments
Say you want to take the derivative of ratio $N/D$ to find the maximum. Then the derivative would be $\frac{N'D - N D'}{D^2}$. This could be difficult to manage. Suppose $L_N = \log(N)$ and $L_D = \log(D)$. Then taking the log of the ratio we get
$$
\log\left(\frac{N}{D}\right) = \log(N)-\log(D) = L_N - L_D
$$
maximizing a positive functio is same as maximizing the log. So
$$
\log\left(\frac{N}{D}\right)' = = L_N'- L_D' \tag1
$$
If $L_N$ and $L_D$ are simple, then the above derivative is simpler to work with.
Note one can obtain the same anser by looking at
$$
\frac{D}{N}  \left(\frac{N}{D}\right)' \tag2
$$
called the Logarithmic derivative and is obtained from (1). It is not difficult to show that (1) and (2) give the same right hand side.
Comment: I try to understand what you have told me but it is still far too abstract. I feel that I kind of understand and at the same time I feel that I am not really understanding what you are telling me... hope you can explain it with a numerical example. Thanks in advance.
Answer: The fundamental reason for the presence of log, the Kullback-Liebler divergence. That is why MLE is consistent, among other things. Pointing out trivial consequences like "log turns product into sum..." is very misleading.
Answer: Since natural log is a strictly increasing function, the max of the density in question will be the same as the max of the natural log transformation, given that it exists.  The natural log simplifies densities that involve exponentials.  Also since densities usually involve products, the transformation will simplify all that potentially messy calculation.
Answer: Sometimes we don't use the log (natural or otherwise).
Mostly it's a matter of convenience - taking logs in many cases makes it simpler to find the argmax. However, results like Wilks' theorem may make it more convenient to work with logs in more situations than might otherwise be apparent.
Taking logs is not so much help with the triangular distribution, for example.
Answer: I would disagree with Michael's statement that
"Pointing out trivial consequences like "log turns product into sum..." is very misleading."
In fact, those consequences are precisely WHY the logs are used when finding the MLE for a parameter. The MLE has the value that it has in order to minimize the Kullback-Liebler divergence. However, I think this question was more about why we USE logs to find the value of the MLE. The answer to that question is what most of the above answers are suggesting - most of the time, the utilization of logarithms (which fortunately do not affect the logic involved in the process) make the calculus and resulting algebra easier. They are a convenience in this setting, not a necessity.

Why the natural log is there in MLE?


Is it legal to make false advertising claims but give the correct info in small print?

Question: 2 Terabyte Solid State Drive - only $20!
(product is actually a 100 gigabyte hard disk drive)

Would that ad be legal?
Comment: My gut says no, as your well under an order of magnitude under; that said, I have seen a "terabyte" drive that was 1000 gigabytes, rather than 1024, as it should be. (It's binary, not metric, darn it!).
Comment: @sharur That's common. The capacity of almost all physical drives is given with a metric size, not a binary (it's declared in the fine print). Not so with modern SSD drives, because apparently those chips really come in binary sizes.
Comment: @sharur Usually, due to simplicity, it's not even 1024^4 byte but 1000^4 Byte, which only amounts to 909 494 MB (and some) instead of 1 099 511 627 776 bytes - a loss of about 190 GB.
Comment: Kilo-, mega-, giga-, and tera- should always refer to powers of 10: 1,000, 1,000,000, 1,000,000,000, and 1,000,000,000,000. The correct prefixes for powers of 2 (1,024, 1,048,576, 1,073,741,824, and 1,099,511,627,776) are kibi-, mebi, gibi-, and tebi-. They're commonly mixed up, and many people would expect a gigabyte to be 1,073,741,824 bytes, but it is actually 1,000,000,000 bytes. 1,073,741,824 bytes is a gibibyte.
Answer: Hypo
A quick factual analysis: You don't mistype 200 gigabytes to 2 terabytes. That needs a "mistyping" of 200 to 2 and the words "gigs" to "tera". No typo, that's obvious.
A reasonable person wouldn't put the incorrect data quantity there in an honest mistake either since every reasonable person has a within -50% to + 100% sense of the price of things. One intending to sell and cognizing a difference in excess of that would do a double take on the price in such a case. Even if the price increase is not linear with the storage capacity of a hard drive, we are still talking about 2 and a half 3 times the price difference at best. It cannot happen in negligence. It might happen in reckless disregard, but knowing and intentional action appears more likely than not putting the onus on the advertiser to prove that is not the case affirmatively.
Law
In any case, the scope of uniform false advertising and unfair business practices acts of U.S. states typically require good faith actions and reasonableness in that they punish those not only who knew their advertisement is false, but those who should have known by the exercise of reasonable care, one summary example from California:

"It is unlawful for any person, firm, corporation or association, or any employee thereof with intent directly or indirectly to dispose of […] personal property […] or anything of any nature whatsoever or to induce the public to enter into any obligation relating thereto, to make or disseminate or cause to be made or disseminated […] from this state before the public in any state [including this state], […] in any … manner or means whatever, including over the Internet, any statement, concerning that […] personal property […] or concerning any circumstance or matter of fact connected with the proposed […] disposition thereof, which is untrue or misleading, and which […] by the exercise of reasonable care should be known, to be untrue […] or for any[one] to so make or disseminate or cause to be so made or disseminated any such statement as part of a plan or scheme with the intent not to sell that personal property […] so advertised at the price stated therein, or as so advertised. Any violation of the provisions of this section is a misdemeanor punishable by imprisonment in the county jail not exceeding six months, or by a fine not exceeding two thousand five hundred dollars ($2,500), or by both that imprisonment and fine." (Cal. Bus. & Prof., § 17500)

EDIT 1 — Not 200 gigs to 2 terabytes, but 100 to 2
I just noticed we're not even talking about 200 GB "mistaken" to 2 TB, but 100 GB to 2 TB. It's not apples to oranges, but an apple to soccer balls. Good luck to whoever wants to get on to the lower end of § 17500 claiming no knowledge, but reckless disregard.
EDIT 2 — Hypo of disclaimer elsewhere
In case where the correct information somewhere else is included in the advertisement, that both give rise to the presumption that actual knowledge of the untrue or misleading nature of the advertisement existed in the advertisers mind. On another note, in case a buyer's exclusive decision metrics relate to the storage capacity and the price, the statement of the storage capacity also creates both an implied warranty of fitness and an express warranty. (Lane v. C.A. Swanson Sons, 130 Cal.App.2d 210, 278 P.2d 723 (Cal. Ct. App. 1955) ["the label on the can coupled with the representation in the newspaper ads that the contents contained no bones, constituted an express warranty"], (Cal. Civ. Code §§ 1791.1, 1791.2, et seq.; U.C.C. (UCC § 2-313(1)(b)) ["[a]ny description of the goods which is made part of the basis of the bargain creates an express warranty that the goods shall conform to the description."])
In other words, the buyer is not imposed any statutory or common-law duty to read further in the advertisement unless a reasonably cognizable indication is made that the storage-capacity statement is, well, false. For example, an internationally well-understood indication of the incompleteness of the a statement is the inclusion of an asterisk (less often a footnote number) behind the specific information or statement that needs further relating.
Other than common sense, Brady v. Bayer Corp., 26 Cal.App.5th 1156, 1172 (Cal. Ct. App. 2018) provides the same:

"Nothing in law or logic suggests consumers will take such a belt and suspenders approach[]: You cannot take away in the back fine print what you gave on the front in large conspicuous print[; in fact,] Under Commercial Code section 2316[,] any disclaimer ha[s] to be conspicuous."

Accordingly, even asterisk may not be sufficient as a matter of law, and an action based on an asterisk notice of disclaimer may potentially proceed to trial for the factfinder to decide if they would be put on reasonable notice that, as a matter of their good-faith duty, would have to look further on an advertisement to find that the storage capacity information was simply false.
Answer: It could be legal. Both products actually exist (can be ordered on Amazon, from different vendors), so both are reasonable prices for the product. A vendor might have mistakenly put the wrong drive information in the headline, but the correct information in the body of the ad. Errors do not give rise to false advertising claims, but one they have been alerted to this situation, they have to fix the ad. (Or, if this is a misplaced shelf tag in the store, put the correct tag on the shelf).
A deliberate ploy to attract customers via a "great deal" headline would be illegal "bait and switch". If the ad does not at all indicate that the product is a 100 GB HDD, which is what they shipped, then that is a breach of contract. The most likely remedy would be cancelling the contract (refunding the money), which is a typical "term of use" condition for online sales.
Comment: Good faith "errors" and "mistakes" don't, but an advertising seller is imposed not only the duty of acting in good faith as a requisite to the contract, but also to act with reasonable care. A reckless mistake *does*, indeed, give rise specifically to a false advertising claim.


What's the most poetic way to translate this song line?

Question: "Ground control to Major Tom...". It's a very pressing matter, in that it relates to my own amusement. I hope I have met Stack Exchange's quality question guideline rules. Thank you.
Comment: The answer to this question is very much up to taste. How to translate a line in a song is a bit too subjective a matter to have a satisfactory answer.
Answer: "Ground control" is (sur)tera direktejo and "(military) major" is majoro, and in both, the j is pronounced like the y in yes. However, it is better if the name Major Tom is pronounced as in English.
So the translation is Direktej' al Major Tom. ("dee-reck-tay al Major Tom")
If you want it entirely in Esperanto, use Direktej' al la Major'. The stress is normally on the second-last syllable of a word, but it doesn't move if the ending -o is dropped: major'.
Answer: Bazo al Majoro Tom
Terbazo al Major' Tom
Comparable - in a wide sence - with "base camp."
If you merge "zo-al" you get an interesting sound, just as "ground control" has interesting r-s. You could elide the final o in Majoro: Major' Tom.
Comment: Oni devus fuŝi la akcenton por kanti la duan version, ĉu ne?
Answer: The most poetic way to translate a poem is to translate the whole poem. When you look at it this ways, the possibilities open up a bit. For example, since the first two lines are identical, you could take two lines to get the idea out.

Vokas vin la ter-staci'
Ni vokas nun al la Major'

My understanding is that Major Tom is not a real person so there's no reason you couldn't change the name to get it to work out.

Ter-staci' al la major'
Ni vokas al Majoro Tom

You could really call him anything you want.
I'm personally partial to Ter-Staci' - which is what I came up with after reading a few national language translations of the song.


Zebra Striped vs Line Separator vs Plain for a list of items?

Question: I am designing a news site the is will list a lot of news articles in a compact space. I have tried the following 3 ways to separate the articles, and I'm wondering which is the best from a UX perspective?
Zebra:

Lines:

Plain:
Comment: I don't think that there is a 'best' answer here, but the decision could be based on a number of different considerations such as the general look & feel of the website, the amount of space available, the suitability of applying the same styling similar content on other pages, etc.
Comment: If you were to give the primary criteria that you're using to determine which is "best", the question may be answerable.  However, right now it's primarily opinion based.
Answer: Of the options you show I would go with the 'plain'. The distinctive image in each row is likely enough to visually separate rows. The striping and lines only add noise.
(Always good to test though …)
Answer: The stripes are more for data tables when you have to follow top to bottom.  Also, if not lines there needs to be clear separation between each result.
Comment: Yes, zebra striping helps you read across long rows in a data table. That's not necessary here.


Fluid doesn't react on wind force field

Question: I baked fluid domain with wind force field inside it but it seems that the wind has no impact on fluid. What did I do wrong or there is supposed to be no result at all? in this case how to simulate the wind on the top of the water surface in particular spot? For example, I wanna turbulence on the water caused by helicopter.
Comment: As a tutorial link to the dynamic paint method mentioned below [Blind Illusionist](https://www.youtube.com/watch?v=smArCTzxGpE) put together a good step by step.
Answer: The Elbeem fluid simulator in Blender (fluid sim for 2.79 and earlier) doesn't support force fields.
You can use a particle system with Fluid physics and force fields but the challenge is getting a good surface.

Metaballs is one approach - see Is there a way to render particles as if they were a single liquid?
The Cubesurfer addon (example here) was looking pretty good a few years ago but the development doesn't seem to have moved on from Beta.

If you need to stay with the Elbeem simulator another option is to use dynamic paint to displace the surface by turning the fluid domain into a "canvas" and rig a object as a "brush" to follow the movement of the helicopter. I've made a very quick proof of concept and you can see it here. Note - very rough just to prove it could be done.
Finally, it looks like Mantaflow (the new Fluid simulator being developed) does support force fields. There are custom Mantaflow Blender builds for versions 2.79 and 2.8 that you can download. My experience from a small amount of playing with 2.79 is that Mantaflow was not very stable. I haven't tried the 2.8 version yet... use at own risk!

Fluid doesn't react on wind force field


Should I be worried about brown spots on my mint leaves?

Question: Found some brown spots on the old mint leaves on my new planted cuttings. Is this normal or a sign of disease? They're planted indoors at around 70°
Answer: I'm going to stick my neck out here and say no- pick off affected leaves if your worried and keep the soil clean, pop outside as soon as possible and plant in a large pot with ordinary garden soil- nothing special/fancy. If you plant directly into the soil, you will regret it for the entire lifetime of the garden whilst your there- it suckers every where and comes up where you don't want it to! so never plant it directly into your garden! big pots only! take cuttings next time from the roots and do it every few years or so to keep it healthy- old plants don't make good plants when it comes to mint. The plants in the photos look very good and could even be split apart into separate pots- being outside will harden them off and increase ventilation thus avoiding any fungus's, keep the soil clean by removing any dead leaves and remove any other weeds that might spring up- other than that, they are completely hardy and regrow again next year with fresh new growth(die down during the winter)and live for years and years! hope it helps


Do grave sinners attain moksha if they remember Lord Vishnu?

Question: How to surrender to god? For attaining moksha.in kaliyuga?
Comment: Getting rid of sin doesn't imply getting Moksha. Once you realize your true nature, that is Moksha or as Rohit said, surrender to Lord not just remember, that is also a path to the ultimate reality.
Comment: Is the person known to you? And surrender is "giving up fully without even thinking what God will do to him, if you expect something better after surrender it is not surrender". Don't even expect whether you will be saved by the God. In surrender there is no expectation, only love. Love God, nothing more. Develop some good virtues. Purity chitta. If you are capable to purify chitta before death, nothing wrong will happen to you.
Comment: Anyone who realizes his/her mistake, and surrenders to the Lotus Feet of Shriman Narayana will get moksha because Bhagwan promised this in BG18.66 aka Charama Shloka(Sri Vaishnava notation).
Comment: @Rishabh you should ask this as a question so that many are benefited. :)
Comment: @RohitSinghRathore Questions has been posted. Please do check and inform us about it so that we can get our afterlife journey peaceful :)
Comment: @RohitSinghRathore Great message/teaching, but can you please explain what is chitta? and how can we purify it?
Comment: Seen @Rishabh , Will answer sooner or later. Meanwhile other users might help you.
Comment: Truth_finder Your Question title is about Grave sinners and their moksha, and your Question body has entirely different topic about performance of Sharanagati to attain moksha.You should rephrase the question. Question title summarizes the content in Question body, title and body must be synchronized. If you want to change the question you should Change Title as well.
Comment: @ChinmaySarupria "Getting rid of sin doesn't imply getting Moksha". You have either  misinterpreted Sin(s) or Concept of Sharanagati. If you have no Sin(s) left in your Karma balance sheet, there is only Punya and you can exhaust it by surrendering leftover Punya to Bhagwan. The main reason for Ajnana is Sin(s) and if you exaust them somehow(either by Sharanagati or by Bhakti Yoga) then true Janana is attained(whether Atma Jnana or Bramhajnana). So whether you go by Sharanagati or by Yoga you have to clear karma Balance sheet, and thus it implies Moksha.
Answer: If someone wants to surrender to Lord Vishnu then he must have left off all his desires first. Means his/her all expectations, desires, wishes also need to be surrendered to Lord. In order to surrender he must do the following:
You should gift all good deeds (Punya karma phal) to Lord Vishnu:
Means, in our life we all do some good deeds. And in return of our good deeds we get returns/gifts from Lord in form of money, fame, peace etc. This is our divine income that we can only earn from the Lord after doing good deeds. If someone wants to surrender to the Lord then he should gift away all his divine income (punya phal) back to Lord Vishnu. Why should we do that? This implies that you don't want fame, money and other good things that we can get in this world anymore. We pray "that's why (because I do not want the worldly items) I am gifting all my divine income back to you, my Lord!".
NOTE:
If while gifting all your divine (income) you have any kind of greed/attachment in your heart  except Moksha then Lord Vishnu won't accept this gift. If there is some feeling in your heart that if I gift away all my divine income to the Lord then I am left with no fame, respect and other good things of life for myself. Because of such thinking Lord will never accept my gift to Him because, Lord Vishnu only accepts if someone really wants to give with all his/her heart.
You should gift away all your sins to Lord Vishnu
After giving all divine income (punya phal) to the Lord one should also give all sin income (papa phal, that we get by doing bad deeds ) also to Lord vishnu. This can be accepted by God only when you have full faith in the Lord and you are determined about not doing any more sins in future. One should tell the Lord " If you want to forgive me about my sins then I will be grateful to you, but, if you want to punish me for my sins then also I accept  that punishment with all my heart". After seeing your faith and determination Lord Vishnu will accept all your sins.. meaning he will make you fully pure (sinless).
You should have left all worries
The humans always worry about their present, future etc. If you have surrendered to Lord vishnu then you have no need to take on those worries. And why so? Because if you already have surrendered yourself to Lord then how you can worry about yourself? You can only worry about your Lord now. If your Lord want you to suffer then you must accept all suffering given by your Lord and if your Lord wants you to enjoy then you should do that also. You have to obey whatever your Lord commands. The commands come to you through good incidents or bad ones in your lifetime... means if something bad  happens to you then you should accept it by thinking it's your Lord's wish.
Keep thinking about your lord Vishnu
One thing that should keep in your mind foremost is Lord vishnu. While you are thinking (Chinta) about your Lord then don't let anything else distract you. You should forget the whole world and only one thing should remain in your mind and that is Lord Vishnu, nothing else. Your whole mind must be full with Lord vishnu's thoughts so that no other thought can enter in your mind.
NOTE:
Lord Vishnu also tests (Pariksha) of his devotee to check how much they are determined on their words of surrender and how much real faith they have in Him. For that He will put obstacles in your way and also might impose lots of suffering on you to check how much faith/respect you have in Lord Vishnu. So be prepared for that examination to prove that your surrender is not going to break that easily. Lord's examination is not going be that easy. He will test your surrender in all ways possible.
Another important thing is, it is not necessary that you have to make this kind of surrender to Lord Vishnu only to get Moksha. If you are a devotee of Lord Shiv then you should surrender to Lord Shiv and if you are Devotee of Mata Durga/Kali or Devi Lakshmi then you can surrender to them also.
Only Lord Vishnu, Lord Shiva and their wives have power to give Moksha. So to get Moksha you have to surrender to one of them only. But do surrender to one only so that your surrender won't get distracted by diluting your faith in different Gods.
Answer: In Chapter 9 of the Gita Krishna says (Swami Nikhilananda translator):

I am the same towards all beings; to Me there is none hateful or dear. But those who worship Me with devotion--they are in Me, and I too am in them.
Even the most sinful man, if he worships Me with with unswerving devotion, must be regarded as righteous; for he has formed the right resolution.
He soon becomes righteous and attains eternal peace. Proclaim it boldly, O son of Kunti, that My devotee never perishes.
For those who take refuge in Me, O Partha, though they be of sinful birth--women, vaisyas, and sudras--even they attain the Supreme Goal.
Fix your mind on Me, be devoted to me, sacrifice to Me, bow down to Me. Having thus disciplined yourself, and regarding Me as the Supreme Goal, you will come to Me.

and in Chapter 18, He says:

Take refuge in Him alone with all your soul, O Bharata. By His grace will you gain Supreme peace and the Everlasting Abode.
Fix your heart on Me, give your love to Me, worship Me, bow down before Me; so shall you come to Me. This is My pledge to you, for you are dear to Me.
Abandon all dharmas and come to Me alone for shelter. I will deliver you from all sins; do not grieve.
Answer: At the time of death, we attain to the abode of whichever god we were thinking of. Krishna tells Arjuna that people go to the abode of the gods that they think of.
https://www.sacred-texts.com/hin/m06/m06034.htm

Whichever form (of godhead) one remembereth when one casteth off, at the end, (his) body, unto that one he goeth, O son of Kunti, having habitually meditated on it always. Therefore, think of me at all times, and engage in battle. Fixing thy mind and understanding on me, thou wilt, without doubt, come even to me. Thinking (of the Supreme) with a mind not running to other objects and endued with abstraction in the form of uninterrupted application, one goeth, O son of Pritha, unto the Divine and Supreme male Being.

Even if you are a sinner, at the time of your death, if you think of Krishna, you go to his abode.Krishna tells about his supreme seat.

hey who know a day of Brahman to end after a thousand Yugas, and a night (of his) to terminate after a thousand Yugas are persons that know day and night. On the advent of (Brahman's) day everything that is manifest springeth from the unmanifest; and when (his) night cometh, into that same which is called unmanifest all things disappear. That same assemblage of creatures, springing forth again and again, dissolveth on the advent of night, and springeth forth (again), O son of Pritha, when day cometh, constrained (by the force of action, etc.) 4. There is, however, another entity, unmanifest and eternal, which is beyond that unmanifest, and which is not destroyed when all the entities are destroyed. It is said to be unmanifest and indestructible. They call it the highest goal, attaining which no one hath to come back. That is my Supreme seat

"The Holy One said, 'Once more still, O mighty-armed one, listen to my supernal words which, from desire of (thy) good, I say unto thee that wouldst be pleased (therewith). 2 The hosts of gods know not my origin, nor the great Rishis, since I am, in every way, the source of the gods and the great Rishis. 3 He that knoweth me as the Supreme Lord of the worlds, without birth and beginning, (he), undeluded among mortals, is free from all sins. Intelligence, knowledge, the absence of delusion, forgiveness, truth, self-restraint, and tranquillity, pleasure, pain, birth, death, fear, and also security, abstention from harm, evenness of mind, contentment, ascetic austerities, gift, fame, infamy, these several attributes of creatures arise from me. The Seven great Rishis, the four Maharishis before (them), and the Manus, partaking of my nature, were born from my mind, of whom in this world are these offsprings.


Sketch symbol undeline link

Question: Is it possible to create a symbol for underline link so when the text changes the line width changes as well?
Answer: Use the built-in text underline rather than drawing the line yourself?
I imagine that you...

knew about this and wanted a line you could style yourself?
completely missed the Options button (in which case, you're welcome!) :D
Comment: Thank you for your answer. I knew about options button :) I didn't want to use it because the line is too close to the text.
Comment: Thought that might be the case :(  Unfortunately I don't think there's another way to do cleanly.

Best solution I can think of is to pin the line to the bottom left/right of the symbol and manually set the width of the symbol for each instance — but that's pretty messy too :(

Sketch symbol undeline link


bird set bgp next hop self in filter

Question: I'm trying to set the next hop of a BGP route to "self" in a export filter, but I can't seem to figure it out. Here's a sample of what I have setup:
filter BGP_EXPORT_POLICY {
    if ( source = RTS_INHERIT ) then {
        gw = 192.168.1.1;
        accept;
    }
accept;
}

protocol bgp SomeRouteReflectorClient {
        direct;
        local as 65000;
        passive on;
        neighbor 192.168.1.2 as 65000;
        rr client;
        export filter BGP_EXPORT_POLICY;
        import all;
}

The filter appears to be working correctly (it's matching the routes I expect). However, the gw = 192.168.1.1; does not work. I've set it to the address of the interface I would like the next hop to be set to, however, I get the following error:
<ERR> filters, line XX: Invalid gw address

Ideally, I 192.168.1.1 would be a keyword for "self" (or there would be some other key word). I'm coming from a Cisco world, so I'm trying to lift and replace an existing setup wherein the next hop of locally originated routes by the route reflector are set to the BGP peer ip of the route reflector.
I don't think I can use next hop self; at the BGP peer level because then all routes get next hop self. The goal is that client to client routes do not get the next hop updated by the route reflector, only routes originated by the route reflector.
Answer: You can't use the gw parameter in export filters as it is only valid in import.

bird set bgp next hop self in filter


do wood chips insulate better for cold than heat?

Question: I noticed that my wood chip compost pile that I never turned has ice still about 1" below the surface, so that got me to wonder if wood chips are better cold insulators than heat insulators.
Comment: Like a thermos bottle ; the wood chips don't know if the are keeping something hot or cold.
Comment: The insulating properties of *woodchips* are irrelevant. What you have, apparently, is woodchips embedded in a block of ice. That is something completely different! To thaw 1 gallon of ice takes about the same amount of heat as to warm 4 gallons of water from freezing up to 70F.
Answer: Anything which absorbs water becomes less inaulating. Here is an example:
http://www.city-data.com/forum/house/717131-foam-insulation-installed-wet-wood.html
The hot summer desiccates the woodchips. Water is taken-over by air that fills the pores. Air is a better insulator. It is very important, however, that a dry summer should help the chips to dry faster than a moist one. In addition, hot air rises. The hot woodchips should lose heat by convection faster than cold chips getting a warm-up. The cold air does not rise and remains above the wood chips for longer.
Comment: will this bother thawing  of the soil if the area was covered since last summer?
Comment: Mulch is an extra-layer, so basically will delay heat exchange between soil and the air. It is simply less prone to temperature fluctuations. Average temperatures will simply lag behind seasonal changes while keeping same average. The mulch decays more quickly in the summer, and is vital to the nutrients cycle. I advise you to keep mulching anyway.
Comment: the mulching is to kill off grass, and get a nice area to walk as it's always warmer in that area than the surrounding ground once things warm up
Answer: You can get an awful lot of heat out of compost heaps, the bigger the better, we used to heat an entire garden centre, 7 smaller business's and a busy cafe + 2 sets of offices with the heat given off by several hundred tons of mostly grass cuttings but with plenty of general gardening waste, even at edges, it would get so hot that Wellington boots just melted away.
Piles turned with an old Ferguson tractor with front end loader, it ate the kleats off the tires
We bought a big load of scrap steel pipe and fittings for a few hundred pounds, a high temperature pump for a bit more, and employed a plumber for a week in the winter. It worked so well, none of the old systems ever came on automatically so every now and then, they had to be turned on by hand.. Saved lots of money back then(1990's) now, with the price of energy for business, we would be saving probably well over £150-200.000 per year.
Answer: The composting process creates heat if it is done properly. It can create a lot of heat, like over 150 Fahrenheit (65 celsius).
For composting you need:

a mix of nitrogen sources and carbon sources, chopped into small chunks
a healthy mix of microbial (micro digesters) and insect/bugs (macro digesters) - generally these will show up with dirt as long as you have throw in some handfuls of local soil and you use some natural materials like leaves (which have bugs on them)
mixed thoroughly - like, really really thoroughly
and moist - enough that if you pick up a handful and squeeze it then a little bit of water might drip out or be visible on your hand afterward
oxygen, from weekly mixing or just a pile design that provides aeration
depending on your environment you might want some walls to help keep in moisture (in a dessert) or a roof (to prevent steady rain from soaking the pile) or some insulation like an enclosed box or old scrap of rug or black plastic tarp to help it heat up.

If you did all that in a way that's appropriate for your environment, then the middle of the pile should start heating up within a day. It should get above 100 degrees Fahrenheit (30 celsius) within a week.  The outsides of the pile might not ever get warm, which is why you need to mix the whole pile periodically to let the outsides get mixed into the middle.
If your pile is literally frozen in the middle then some key condition is missing and you can start over trying to build the pile and paying more attention to all the details to figure out what was missing.
Comment: the middle is soft, there is about a 1' hard shell still on it from the hard winter


Can we let the system automatically remove comments that are short and contain "+1"?

Question: I saw a comment on an answer on SO that was made by the answerer. The comment was "if useful +1". I flagged it for removal and it got removed about a minute later. Can we prevent such useless comments by blacklisting short "+1" comments?
Comment: Sometimes it's useful to explain -1 in comments. (If this comment would be auto blocked, I wouldn't be able to explain, and would be discouraged from even trying further)
Comment: Similar goals: https://meta.stackexchange.com/q/257769/282094  https://meta.stackexchange.com/q/139795/282094
Comment: An alternative: each user that finds those comments, flag them to be deleted. I can't remember where I read this, but, when a comment "and this applies to questions" has more than 5 downvotes/flags, the comment is deleted (or, in the case of questions, the question itself is closed as off-topic).
Comment: This has actually been implemented!  I tried to send a comment starting with "-1" on SO but it wouldn't let me.
Answer: Plus one!
Blacklisting specific words from posts or comments to a point where they can not be posted or will be automatically deleted after posting will only 'move the problem', people will only get more creative in their ways to still post their one-up comments.*
A system-level blacklist will only make people write more creative comments trying to circumvent it. There's no easy fix for this, people will also abuse comments to make remarks like 'good answer', 'I agree'...
Any comment that's not doing what comments are for (request clarification, leave constructive criticism for improving the post, add relevant but minor/transient information) can be flagged as 'no longer needed'. It is suspected that short +1 comments already require less of those flags to be deleted, which will help a little in keeping at least those comments under control.
Blacklisting '+1' entirely will probably get a few false positives, e.g. when mathematical formulas are involved, and some creative (but barely legible) ways to still circumvent not being able to post 'pl0s 0n3'. So, it's probably better to not let the system prevent or automatically delete them, but have some human oversight. Just enjoy your helpful comment flag count going up :)
 * I seem to remember a meta post on how people would replace characters when words are blacklisted somewhere already but I can't find it


How could colonists living above Venus lower the temperature at 1 bar atmosphere to 70-80 Fahrenheit?

Question: In the book I am writing, I am going for a a partially terraformed Venus setting. I like the concept of floating cities, but I want to be able to make it a little easier to live up there. If colonist had around sixty years or so, could they lower the temperature at 1 bar down to 80 Fahrenheit? How would they do this?
Comment: @AndrewZacharyForeman Wikipedia is more credibleanthe a source that exists only in your memory. Can you provide a reference to what you think the temperature profile on Venus is, or, preferably, a paper describing how to calculate ourselves?
Comment: At 1 bar pressure the temperature is lower than 80 Fahrenheit, not generally higher https://en.wikipedia.org/wiki/Atmosphere_of_Venus
Comment: That wiki needs to be updated. The temperature is actually quite higher.
Comment: What is the temperature? Your question doesn't include it. Can you please provide a source for the temperature as now known?
Comment: I actually don't remember, but the source I read was far more credible than wiki
Comment: @AndrewZacharyForeman Wikipedia isn't a source.
Answer: Wikipedia has compiled many of the leading proposals in an article on the topic. The table of contents to it lays them out nicely:

1   Solar shades
1.1   Space-based
1.2   Atmospheric or surface-based
2   Eliminating the dense carbon dioxide atmosphere
2.1   Biological approaches
2.2   Introduction of hydrogen
2.3   Capture in carbonates
2.4   Direct liquefaction and sequestration
2.5   Removing atmosphere
3   Day–night cycle
3.1   Space mirrors
3.2   Changing Rotation speed.

The mostly likely of the proposals to work on the desired time frame would probably be to impact the surface of Venus with about 2000 large asteroids.
Comment: How expensive would something like that be?
Comment: OP already dismissed Wikipedia in the comments to the question, so I'm not sure this is any better...
Comment: @ Andrew Zachary Foreman: Wickedly expensive. Moving even one large asteroid slightly (a la movies in the genre of Deep Impact) is an epic engineering feat. But, since there aren't a lot of asteroids near Venus you'd need to move them a great distance from the nearest asteroid belt (or blow up Earth's moon in a manner that would send the fragments in the right general direction) and you'd also have to aim them much more precisely than when simply trying to prevent them from hitting a planet. If it cost 1 to 10 billion bucks each (probably low), you'd be talking about up to 20 trillion dollars.
Comment: So that's just an all around bad idea. Thanks. I wonder if bioterraforming would be too much of a cop out
Answer: The temperature of the Venusian atmosphere is 72 C at an altitude of 50 kilometres (km) where the pressure is 1 bar. This could be an uncomfortable altitude for floating cities. However, the simplest solution for colonists in the floating habitats to enjoy cooler temperatures is go higher.

Height (km)             Temp. (°C)                Atmospheric pressure (atm)
<code> 0                 462                     92.10

 5                 424                     66.65

10                 385                     47.39

15                 348                     33.04

20                 306                     22.52

25                 264                     14.93

30                 222                      9.851

35                 180                      5.917

40                 143                      3.501

45                 110                      1.979

50                  75                      1.066

55                  27                      0.5314

60                 −10                      0.2357
</code>

Sorry about the formatting glitch. All attempts to rectify it have failed. Go to the source enter link description here and check out the table with the heading Atmosphere alongside the section on Troposphere.
At 50 km, the temperature is 75 C and the pressure is 1.066 bar, while at 55 km, the temperature is now 27 C and the pressure is 0.5314 bar. This is a comfortable temperature, though the atmospheric pressure is lower and this means the flotation mechanism will be correspondingly larger for floating habitats. It should be easier to go higher than attempt complex, costly and unnecessary methods to lower the atmospheric temperature.
Essentially the Venusian atmosphere does it for you with increasing height and corresponding falling temperatures.
Comment: @MichaelKjörling The OP may have dismissed Wikipedia, but its information on the Venusian atmosphere falls into line with the results from the Magellan and Venus Express missions. It seems credible enough in that case. Besides its temperatures do correspond to the OP's own comments about troposphere temperatures.
Comment: OP already dismissed Wikipedia as not trustworthy, and that particular table is even tagged *citation needed*. So I suspect that won't do.
Comment: You can use [MathJax arrays](http://meta.math.stackexchange.com/a/5044/53424) for this type of data.
Comment: @MichaelKjörling Thank you for the information. Never used MathJax before, so more stuff to learn.


Decomposition of a Jacobi field along a lightlike geodesic

Question: Consider a Lorentzian manifold of dimension $1+n$ (with $n\geq1$) and a lightlike geodesic $\gamma(t)$ on it.
One can define a Jacobi field $J(t)$ along $\gamma$ in the usual way without issues.
In Riemannian geometry one can decompose the Jacobi field into two components:
The one parallel to $\dot\gamma$ and the one normal to it.
A Jacobi field that starts (to zeroth and first order) parallel/normal stays parallel/normal.
Is there a similar decomposition for a lightlike geodesic on a Lorentzian manifold?
Of course one can say that a vector $v\in T_{\gamma(t)}M$ is parallel to $\gamma$ if it is a scalar multiple of $\dot\gamma(t)$ and normal if $\langle v,\dot\gamma(t)\rangle=0$.
When $\dot\gamma$ is lightlike, the problem is that the parallel direction is normal.
If $n=1$, "parallel" and "normal" are in fact equivalent.
It would be convenient if I could somehow naturally extract the part of $J$ which is not parallel so that this part still satisfies the Jacobi equation or something similar enough.
The best I can think of is to take $n$ lightlike vectors $u_1,\dots,u_n$ so that the set $\{\dot\gamma(0),u_1,\dots,u_n\}$ is linearly independent and parallel transport this frame along $\gamma$.
Then I can express a Jacobi field $J$ in this basis.
This feels clumsy in comparison to the Riemannian version and is less invariant in nature as I need to fix a frame.
Is there something better?
It is still true in Lorentzian geometry that $\partial_t^2\langle J(t),\dot\gamma(t)\rangle=0$.
This identity underlies the decoupling of parallel and normal Jacobi fields in Riemannian geometry, but I can't seem to be able to project the parallel component of a Jacobi field because $\langle\dot\gamma,\dot\gamma\rangle=0$.
Answer: Have a look at how Harris does it in §2 in
Harris, Steven G., A triangle comparison theorem for Lorentz manifolds, Indiana Univ. Math. J. 31, 289-308 (1982). ZBL0496.53042.


What methods are there for storing electrical potential energy in water vapor?

Question: for an engineering class I had to create an electrical energy storage device and I began thinking about  thunderstorms (I think it was a cloudy day) and how they create lighting. I know it's not feasible, but would it be possible to store a charge in water vapor (maybe like a capacitor). Could that water vapor then be stored in a container and be discharged whenever you connect the container (I am thinking like a metal lead coming out of a soda bottle) to a ground? The thought of a thunderstorm in a bottle seems like a very dangerous but cool idea (not that I would use it for my project, I was just wondering if this would be possible).
Comment: google `leyden jar`
Comment: No, this would not be possible.
Comment: Not possible on a human scale.
Comment: On a dry day charge builds up between the clouds and the ground.  Water conducts so there can be different charges in each forming a charged capacitance between the two.  When it starts to rain it is easier for this charge to form a current and we get arcing or as its known in weather 'lightning'.  This is not practical for a design however.  I am therefore voting to close.
Comment: I'm voting to close this question as off-topic because besides leading to opinion-based answers, it's a question better suited for a different physics, general engineering, or even meteorology site.
Answer: A "bottle capacitor" is called a Leyden Jar.   The original one was full of wine, and held in a damp human hand.  The wine is one capacitor-plate, the hand is the other.
Thunderstorms themselves are storing charge on their raindrops.  Not on vapor.
That way, if all the raindrops get charged the same, they can't zoom rapidly outwards from repulsion (because they're large heavy objects, not tiny molecules.)
And, if they did start repelling outwards, well, the region of falling rain might be a half-mile wide.  The drops won't be repelled apart significantly, compared to a half mile.
Inside a tiny bottle, any charged droplets (or vapors) will repel outwards within about a second or two.  They end up stuck against the glass.  You'll have a charged bottle surface, with neutral gas inside.
What solves this problem?   CAPACITORS!   If you put any region of negative charge right next to a region of positive charge, then insert a barrier so they cannot attract together and cancel  ...then you can store some electrical energy (stored in the barrier, stored in the strong e-fields between the two.)
Thunderstorms do this by having positive charge on small droplets, and negative charge on larger drops, then letting the positive droplets lag behind as they're falling.  Gravity and air friction acts as the "virtual barrier" between the two regions of falling, opposite-charged drops.
Answer:
Thoughts on storing electricity in water vapor

If that read storing electrical energy in water vapor, it would have been a viable concept. Because vapor of a few hundred degrees Celsius can store tremendous amounts of energy. It's also cheap and reasonably safe, and easy to turn back into electricity. The technology already exists, too.
Answer: No, you can't capture lightning in a bottle.
Comment: if only he could discharge 1.21 gigawatts from his Leyden jar
Comment: [Benjamin Franklin](https://www.fi.edu/benjamin-franklin/kite-key-experiment) was a liar!
Comment: The question is about creating, not capturing.


Why don't quaternions have an overall phase?

Question: The product of a quaternion multiplied by a real number is a quaternion, but the product of a quaternion multiplied by a complex number is not in general a quaternion.  Why are the quaternions defined so narrowly?  What was gained by banning zq=q' where z is complex and q and q' are quaternions?
Comment: I'm afraid that I do not understand the question as stated either. On the one hand, Hamilton's quaternions are an R-algebra, not a C-algebra (by definition; also, there are no finite dimensional complex division algebras). On the other hand, there are numerous embeddings of C into the quaternions... Could you clarify your question please?
Comment: (I would imagine a quarternion's *phase* to be an element of $S^3$...)
Comment: That should read «as being contained in $\mathbb H$», not in $\mathbb C$. I hope editable comments are not long in their coming!
Comment: What do you mean by "multiplying a quaternion by a complex number"? If your quaternions are the elements of usual, $\mathbb R$-algebra $\mathbb H$ then it does not make sense to multiply them by elements of $\mathbb C$. Now, there are ways in which one can make sense of your question (e.g., extend scalars to $\mathbb C\otimes_{\mathbb R}\mathbb H$, consider $\mathbb C$ as being contained in $\mathbb C$ (in one of the many ways you can do this)), but if we pick one of this interpretations, then it is no longer true that you do not get a quaternion when you multiply one by a complex number...
Answer: The question is a little ambiguous.  However, maybe you are asking why don't people work with
quaternions having complex coefficients as opposed to real coefficients.
The answer is that as an algebra, complex quaternions are isomorphic to the algebra of 2x2 matrices with complex entries, so there is nothing gained by using the quaternion notation, that isn't already available in a simpler form.  You can find a proof in "Spin Geometry" by Lawson and Michelson.
There is still some fun to be had though. For instance, the group SU(2) is the set of real quaternions so that $q\overline{q}=1$ under quaternionic multiplication.  We can define $\overline{q}$ for complex quaternions in analogy to the real quaternions so that it is complex linear,  That is if $q=a+bi+cj+dk$ then $\overline{q}=a-bi-cj-dk$. The set of complex quaternions with $q\overline{q}=1$ under quaternionic multiplication is SL(2,C).
Comment: Just a shout-out for Lawson and Michelson's book "Spin Geometry" http://books.google.com/books?id=3d9JkN8w3X8C: it's great!
Answer: There is a unique copy of $\mathbb R$ in $\mathbb H$ and it is the center.
On the other hand, for every quaternion $q$ not in $\mathbb R$, the generated $\mathbb R$-algebra with unit is a copy of $\mathbb C$, but none is central.
I like to view quaternions as $q=(x,X)\in \mathbb R\times \mathbb R^3$ with multiplication
$$
(x,X).(y,Y) = (x.y - \langle X,Y\rangle, X \times Y + x.Y + y.X)
$$
This uses oriented Euclidean $\mathbb R^3$, and it turns
http://en.wikipedia.org/wiki/Quaternion#Quaternions_and_the_geometry_of_R3
into a definition.
One can then take any oriented orthonormal basis $i,j,k$ for the basic imaginary quaternions.
Edit: Note that $X\times Y$ is a Lie bracket and $-\langle X,Y\rangle$ the corresponding Killing form ($\mathfrak s\mathfrak o(3,\mathbb R)$ up to a constant), one can repeat this construction for every real Lie algebra. Only for 3 of them one obtains an associative algebra.
Second edit: The reference for the first edit is:
Peter W. Michor, Wolfgang Ruppert, Klaus Wegenkittl: A connection between Lie algebras and general algebras. Rendiconti Circolo Matematico di Palermo, Serie II, Suppl. 21 265--274, (1989)(pdf)
Moreover, a similar construction as the above on $\mathbb C\times \mathbb C^3$ using also complex conjugation (see "Greub: Multilinear algebra, 2n ed. 1978" page 289) leads to octonians.
Answer: This is sort of implicit in  Ben Linowitz's answer, but if you allow complex scalars then you get zero divisors, so that $x \cdot y = 0$ does not imply that one of $x$ or $y$ be zero.  To be explicit, look at the product $$(I + i J) \cdot (-i I + J) = i - i + K - K = 0$$
where $i$ is the complex scalar and $I, J, K$ are the quaternion generators.  So these complexified quaternions don't have the same nice algebraic properties that the quaternions do.
That said, these things aren't "banned" --- they are studied under the name "biquaternions" and, while less useful than proper quaternions, still show up occasionally.  I've had a brush with them while studying the differential geometry of plain old surfaces, for example.
Answer: I do not understand Your question. Here You may find that quaternion may be concerned as pair of complex numbers: http://en.wikipedia.org/wiki/Quaternion#Quaternions_as_pairs_of_complex_numbers. So If You proper define quaternion coefficients it may represent every complex number. As quaternions are algebra, so You may multiply one quaternion by other, so whole complex algebra is within quaternion algebra ( You may say it is isomorphic to subalgebra generated by c=0, d=0 in quaternion definition)! From the other side: if You see quaternions as abstract objects outside real numbers, then multiply quaternion by real number have to be defined! It is the same natural/unnatural embedding for real number within quaternions as for complex numbers within quaternions!
It is the same as with complex numbers. You may multiply complex number by real number and You obtain complex number, because You do not go out complex numbers indeed.
Please: explain what You are asking about?