Would it be problematic to have only on/off throttle control?

Question: On a remote controlled airplane, would it be a problem to only have on/off throttle control and not be able to set a particular throttle level? Would landing be possible?
Comment: The general answer is going to be yes it's possible.  Lots of planes are relatively easy to set up final approach and landing power-off.  Takeoff would be more of an issue, it's nice not to just suddenly go to full blast, but not a huge issue if the power is modest enough *or* if you are hand-launching.  Or if it's design with no P-factor etc issues (examples: counter-rotating props, electric ducted fans, etc,).  I'll take a look at Drone SE if you post it there or it migrates.
Comment: @quietflyer would it be feasible to manually "PWM" the throttle by quickly turning it on and off if it was controlled by a button? Would it solve the problem caused by suddenly going full blast? (What is the problem?)
Comment: Actually I believe some of the rc racing planes (google Quickie racer?) are started on ground, tuned for full power before takeoff, may not even have throttle at all except for an emergency kill fuel shut-off system (if that), helper releases tail when plane is pointing straight down runway, and off you go, fly till fuel runs out, deadstick land.  Rather similar to what is done with control-line models.  Anyway, better stop here w/ this, we're not supposed to use comments for discussion--
Comment: @quietflyer I hazily recall something similar to that event, except that it was not racing but endurance - models had a limited amount of fuel (or a similar constraint) and they would briefly climb very rapidly then attempt to catch thermals.
Comment: @kj7rrv -- for "discussion"-oriented questions consider also joining some forums such as rcgroups.com -- the "modelling science" sub-forum there might be of special interest -- maybe some other sub-forums there would also be well suited for practical design questions--
Answer: I have tried this, when I was experimenting with a pan-and-tilt FPV camera controlled by the left stick of the transmitter, on a multiplex Easy Star. That resulted in either a gentle climb or a gentle glide. It was quite manageable, although the constantly changing altitude wasn't much fun. I also tried a 3 position switch, which was better but the middle position was never quite right for a steady cruise, and a rotary knob, which was too fiddly when you can't see it.
Some models are flown as if they have a binary throttle. Electric gliders typically climb at full power then cut power and fold their prop for more efficient gliding. Pylon racers fly at full power during the race and then land. Some vintage models didn't have a throttle and just flew until their fuel ran out. And there's always that one guy at the club who only ever flies at full power...
However most electric models have more power than they need, and a full power flight will run the battery down quite quickly. It's nice to have a good strong climb, and adjustable cruise power.
Most models are landed with the power off. The exception being some heavy planes where the sink rate in the glide is too fast for a smooth landing. These need a small amount of power for a smooth landing.


Pull up problem, left side pulls towards right

Question: video of my pull ups
I feel some sort of movement restriction or problem on my left shoulder but not sure if that is the source of the problem...
Comment: If you perform a banded pull-up, does the imbalance go away? Try filming it.
Comment: I have tried also with a band and it feels easier but after recording the same imbalance is replicated. The thing is, a lot of the times, my left shoulder clicks often when i go up or down in the movement or even when I lift my left arm straight up it clicks (but doesn't hurt) this may be restricting my movement.
Answer:
See a qualified sports physician if you are unsure wether both arms and shoulders move in the same way and to the same extent. If your imbalance is not caused by a mere difference in strength (see point 2), but by a medical condition, you may require physiotherapy or some other intervention before you begin or continue with strength training. It is always a good idea to see a doctor before you begin a sport, and it is the common recommendation in all sports. You may be unaware of a condition that can cause injury and possibly permanent damage.

If your arms or legs are different in strength and the stronger limb carries more weight in an exercise (thus preventing the weaker limb to be exercised equally), find a variation of the exercise that you can perform with one arm or leg. In this case, find or create a one-armed pull-down machine, e.g. fix a weight to a rope that you run over the pull-up bar.

Do your exercises with less weight to gain more control over the accurate execution. In the video, you look like you are at the limit of your strength and your body is compensating by moving your arms and shoulders in a way that reduces the strain to the overloaded muscles.

A movement is performed by a group of muscles, some of with are stronger than others when you begin a sport or exercise. For everyday movements, the strong muscles are sufficient to compensate for the weaker muscles in the group, but when you go to the limit, the weak muscles fail before the strong muscles, and this can cause imbalances as in your example and injury. Often the weak muscles are not those that move the weight (such as the bicep) but those that stabilize the movement. Which is why you need to focus specifically on strengthening the stabilizing muscles so you don't build up the weight-carrying muscles beyond your stability. The stabilizing muscles are more difficult to train, because they often need exercises that aren't straightforward such as pull-ups and require specific care in their proper execution. If you begin to train beyond an everyday level, it is a good idea to see a phyisotherapist or training specialist who will help you with developping exercises adapted to your physique.
Comment: I think there is definitely better activation on my right side when I do pull ups which might be why I veer towards my right side so much... I think I will go back to Ring rows to try and get better form with my left arm first. Thank you for your reply and experience


How to Make two different frequency outptups with Arduino for SMPS inverter?

Question: i am triying to make a SMPS inverter with Two different chips (TL494), one controlling the low side at 50Khz and one controlling the high side at 50hz. This task is getting difficult because the frequency of one chip affects the other and is not something that results in stable output.
So i want to use Arduino (am new at Arduino), i just want to know if IT IS possible to have One pair of the pwm outputs with 50Khz frequency (one being phase shifted respect to the other to drive a pair of mosfets in totem pole configuration) and another pair outputs running at 50hz (again phase shifted).
Can Arduino do that without problems? The range of frequencys is too different to make that possible? I would like to use an Arduino Nano because it is chepaer.
Comment: No. You need to access the AVR at a lower level to do that.
Comment: How accurately must the PWM signals be 50Hz and 50kHz? Do they need to be adjusted, and if so, roughly how much and what level of precision? Do you need the Arduino to do anything else other than generate the two pairs of PWM signals?
Comment: Not too accurately, in fact i don't plan (at first at least) to have some kind of feedback (for pwm and have a regulated supply). Only that the 50hz stays at 50+-3Hz i'll be fine. The low side (the one with 50khz) doen't need that much precision, the transformers i use seem to be quite independt of frequency as long as i stay in the Khz region. And they do not have to be adjusted, i need them at those values all the time.
Answer: The Arduino Nano/UNO hardware could generate two PWM signals, with their complements, at 50Hz and 50kHz. The ATmeg328 contains three hardware timers, which can autonomously produce PWM signals over a reasonably wide range of frequencies.
However, the standard Arduino library does not provide any way to control the frequency of the timers, so you will need to understand how to use them directly. That involves reading the ATmega328 datasheet, and maybe asking questions if you have problems.
The ATmega328's timers are not ideal for this task, but there several practical approaches.
A timer has several parts (simplified a bit):

'Prescaler' divides the MCU clock to produce the basic 'tick' rate
Counter which , in combination with the prescaler, sets the fundamental frequency of the PWM signal. Ideally the counter can be
reset at any count value so that, in combination with the prescaler,
it can generate any frequency.
Compare/Match register which sets the PWM signals ratio of High to Low, and so produces the signal for the Waveform Generator
Waveform Generator which interprets the Compare/Match signal to set an output pin High or Low, and hence whether the output follows the Compare/Match signal, or is instead its complement.

The ATmega328's timers are not ideal. Either they can

generate complementary outputs, but only for disjoint frequencies,
i.e. it can't produce every possible frequency, there are
'holes' in the frequency range, or
generate a better (smaller holes) range of frequencies, but for only
one output pin.

As long as their isn't much else happening, issue 2 can be overcome by using interrupts to trigger software to set the complementary output pins. The amount of error ('jitter') can be removed when their is no other (interrupt driven) processing. The disadvantage of this approach is, if you want to add extra processing, or even just debugging messages, the jitter may increase significantly. My interpretation of your acceptable levels of drift or jitter is that this should still be okay as long as you don't rely on debugging messages.
If you have familiarity with MCUs and C/C++ programming in general, and are only new to Arduino, then you might want to get a better MCU, with better timers for the job. If this is the case, and you want a small form factor, I'd recommend looking at mbed compatible MCU development boards. Mbed has a harder-to-use IDE and library than Arduino. However, it gives much better access to the hardware of much better MCUs.
As a concrete example, look at ST Micro Nucleo-32. They can do everything you can do with Arduino Nano hardware, and much more. They are longer than an Arduino Nano, but have a very similar pin-out. ST Nucleo-32 are ARM CPUs, and have much better timers, which should not only be able to generate those PWM signals with a small error (better than +/- 0.1% for 50kHz) but will be autonomous, so no jitter. Some ST parts have timers which can generate 'dead' time between the complementary signals, which may be useful. All have ADC about 100x faster, or better, than an Arduino Nano (Nano is worse than 10k samples/second). Some also have several analogue comparators and DACs, so generating a feedback signal may be much easier too.
Comment: Wow that was really helpful. I will try to get that ST Nucleo you recomended, and try the arduino since i don't need any debugging messages or so, so thank you very much.


What counts towards the dryads corruption status?

Question: I have gotten a world to 1% corrupt and have been hunting down small bits of corruption for a while now, and I'm wondering if demon alters or demonite count towards the dryads calculations and if anything else does that I might be missing.
Answer: As far as I can tell altars (both crimson and corruption) do not count as corrupt (or crimson). However, any time an altar is broken, there is a 66% chance that a single random tile in the rock layer will become ebonstone or crimstone (depending on the world) or pearlstone. These tiles can create an entire biome if left unchecked (which might be your problem).
As for demonite (and its counterpart, crimtane), I think it is not counted as corruption (or crimson) as it does not spread any corruption (or crimson).
Corrupt thorny bushes do spread corruption and must be destroyed as well (another possible problem). Other corrupt plants do not spread corruption as far as I can tell, but the block they rest on might.
To make clearing things out easier, try investing in the Clentaminator.
Comment: I have been using the clentaminator, I have not broken any alters.
Answer: Tiles that count towards the total corrupt count include: Ebonsand, Ebonstone, Corruption Thorny Bushes, Purple Ice Blocks, and Corrupt Grass. Look for these; I also suggest drilling holes every 40 or so tiles, going straight down to the Underworld. Then, use the Clentaminator in both directions when falling down the holes (go slowly!). If you are pre-1.2.3, I suggest removing any Red Stucco from the world. I'm not sure if this counted towards corruption counts, but it used to (pre-1.2.3) spread corruption.


Evaluate $\lim_{n\to\infty}\left(\sqrt{\frac{9^n}{n^2}+\frac{3^n}{5n}+2}-\frac{3^n}{n}\right)$

Question: Find, if it exists, the following limit: $\displaystyle\lim_{n\to\infty}\left(\sqrt{\frac{9^n}{n^2}+\frac{3^n}{5n}+2}-\frac{3^n}{n}\right)$.
Comment: @AlexM. For your information, it's okay to post questions and their answers so that other people or myself can find it and learn from it. See: https://blog.stackexchange.com/2011/07/its-ok-to-ask-and-answer-your-own-questions/ So consider things more carefully before voting.
Comment: What are you doing here? Asking questions and then immediately posting their answers? Not nice, please stop doing this.
Comment: @DanielW.Farlow It seems so... what a shame... this site is to help people learn math, after all.
Comment: @Cristopher That is nice when one really faces an obstacle then finds the answer himself so he can clear up the train of thought. However, as things are now, it seems like it's writing a solution manual, which is not really good.
Comment: @Cristopher For what it's worth, I think questions like the one you just asked are not worth posting Q&A for (in my humble opinion). Why? It seems to be something you could simply feed into W|A and have an answer churned out with what value? One of the main issues, I believe, is the extremely high volume of questions MSE gets on a daily basis, making more or less "not special" questions like this one of less value. Don't know if that makes sense, but I imagine that is how some other users feel. I'd encourage a Q&A when facing something extra challenging or unique.
Comment: @DanielW.Farlow As far as I know, W|A just gives you the result, it doesn't tell you _how_ to arrive at it. I only wanted to help...
Comment: @Cristopher W|A will give you full solutions if you have Mathematica 9 or greater or Wolfram Alpha Pro, a complete waste of resources and just a money-grabbing douche move by Wolfram. It's just the *nature* of the problem that I am talking about. For an instance of where Q&A is actually a good thing, I'd recommend reading [this post](http://math.stackexchange.com/questions/1196303/fake-induction-proofs) from a while back. Those are the kind of problems more appropriate for the Q&A style in my opinion.
Comment: @DanielW.Farlow I see. I guess that's one way of seeing it. I still think it should be fine. I would like to read some moderator's opinions, though.
Comment: As a side note, I have Mathematica 10, and I just asked it to compute the limit. It says: "step-by-step solution unavailable".
Answer: There is a more efficient way than the approach posted as an answer by the OP.  Here, we simply note that
$$\begin{align}
\left(y^2+\frac15 y+2\right)^{1/2}&=y\left(1+\frac{1}{10}y^{-1}+O\left(y^{-2}\right)\right)\\\\
&=y+\frac{1}{10}+O\left(y^{-1}\right)
\end{align}$$
so that we have immediately
$$\begin{align}
\left(y^2+\frac15 y+2\right)^{1/2}-y&=\frac{1}{10}+O\left(y^{-1}\right)\\\\
&\to \frac{1}{10}\,\,\text{as}\,\,y\to \infty
\end{align}$$
Answer: $\displaystyle\lim_{n\to\infty}\left(\sqrt{\frac{9^n}{n^2}+\frac{3^n}{5n}+2}-\frac{3^n}{n}\right)=L$
Let $y=\dfrac{3^n}{n}$. If $n\to\infty$ then $y\to\infty$. Also, note that $\left(\dfrac{3^n}{n}\right)^2=\dfrac{9^n}{n^2}=y^2$. Hence:
\begin{align}
L &= \displaystyle\lim_{y\to\infty}\left(\sqrt{y^2+\frac{1}{5}y+2}-y\right) \\
&=\lim_{y\to\infty}\left[\left(\sqrt{y^2+ \frac{1}{5}y+2}-y\right)\cdot\frac{\sqrt{y^2+\frac{1}{5}y+2}+y}{\sqrt{y^2+\frac{1}{5}y+2}+y}\right] \\
&=\lim_{y\to\infty}\frac{y^2+\frac{1}{5}y+2-y^2}{\sqrt{y^2+\frac{1}{5}y+2}+y} \\
&=\lim_{y\to\infty}\frac{\frac{1}{5}y+2}{\sqrt{y^2(1+\frac{1}{5y}+ \frac{2}{y^2})}+y} \\
&=\lim_{y\to\infty}\frac{\frac{1}{5}y+2}{y\sqrt{1+\frac{1}{5y}+\frac{2}{y^2}}+y} \\
&=\lim_{y\to\infty}\frac{y(\frac{1}{5}+\frac{2}{y})}{y\left(\sqrt{1+\frac{1}{5y}+\frac{2}{y^2}}+1\right)} \\
&= \lim_{y\to\infty}\frac{\frac{1}{5}+\frac{2}{y}}{\sqrt{1+\frac{1}{5y}+\frac{2}{y^2}}+1}=\frac{\frac{1}{5}}{2} \\
&=\frac{1}{10}
\end{align}


Smaller font size for appendix

Question: Because of the large amount of appendix pages, I am looking to change the font size of my appendix text. Google'ing returns lots of links on how to change the title of sections, but I am talking specifically about the content text (paragraphs), the title size can remain the same. Any ideas? I am using scrbook and the appendix package.
Comment: just use `\small` ?
Comment: @DavidCarlisle Yes, that is it! Thank you. Is there any way to make the section and subsection text one 'size' smaller as well?
Answer: Are you looking to change some definition in your preamble?  If you just need it for a specific set of paragraphs, you can just use \small or a similar command like David suggests (with or without {}).
\documentclass{article}
    \usepackage{sectsty}
\begin{document}
    \scriptsize This is text in script size.

    \tiny This is a different paragraph in {\small tiny size}, with a different sized section in the middle.
    \section{First Section}
    \sectionfont{\small}
    \section{Second Section}
\end{document}

For what the actual sizes are, have a look at this good answer here.  I believe a section header is normally \Large, a subsection is normally \large, and a subsubsection is normally \normalsize so that might give you some perspective.  A command like \sectionfont{\large} or \subsectionfont{\normalsize} should change the size of all the applicable headers after it.
For a more in depth answer, check out what Gonzalo had to say.
Comment: Thank you for your answer. I'm basically looking to change the text size of one or multiple appendix files (they are all separate .tex files, so I don't mind putting '\small' at the start of these files). Also I would like to turn down the size of the section and subsections heading for these appendix files.
Comment: @WalterB i added section/subsection headings to my answer.  does that do what you wanted?

Smaller font size for appendix


Domain of log function having fractional base.

Question: Find the domain of the function $${\sqrt{\log_{0.4} (x-x^2)}}$$
Where $0.4$ is the base
$0.5$ is the power on the whole bracket.
Comment: @lulu Your expression is also hard to read.
Comment: @callculus   Indeed it was.  Let me try again:  $\sqrt {{\log_{.4} (x-x^2)}}$
Answer: First, we want to make sure that the term inside the logarithm is always positive, as $\log{x}$ is defined only for $x > 0$.
$$x-x^2 = x(1-x) > 0 \implies 0 < x < 1$$
Next, we need the term inside the square root to be positive or equal to 0, so we get:
$$\begin{align*} \log_{0.4}(x-x^2) &\geq 0\iff\\\frac{\ln(x-x^2)}{\ln{0.4}} &\geq 0\iff\\\ln(x-x^2) &\leq 0\iff \\x-x^2 &\leq 1 \iff \\x^2 - x + 1 &\geq 0 \iff \\ \left(x-\frac12\right)^2 + \frac34 &\geq 0\end{align*}$$
And this statement is always true. Hence, our domain is $$0<x<1$$
We have used:

$(x-a)(x-b) < 0,\, a < b,\,\implies a < x < b$ and
  $\log_{a}x = \frac{\ln{x}}{\ln{a}} $
Answer: You have here two conditions on the domain:
$$ x-x^2 >0 \tag{1}$$
because $\log_{0.4}(t)$ is defined only for $t>0$, and
$$\log_{0.4}(x-x^2)\geq 0 \tag{2}$$
because $\sqrt{t}$ is defined only for $t\geq 0$.
From $(1)$ we want that $x>x^2$ and so $x\in (0,1)$ because $x^2 \geq 0$ and $x^2\geq x$ for $x\geq 1$.
For condition $(2)$, we know that for $s\in (0,1)$ we have $\log_{s}(x)\geq 0$ if and only if $x\leq 1$ so we want that $x-x^2\leq 1$ which is true whenever $x\leq x^2+1$. This is satisfied for every $x\in (0,1)$.
It follows that the domain is $(0,1)$.


Working with multiple environments and vNext best practice

Question: The new ASP.NET documentation under Fundamentals/Working with Multiple Environments it has a detailed description of how to handle multiple environments (surprise surprise) in code.
I was wondering if this is the "best practice" when dealing with multiple environments or should it be handled by something other than code like the tool that is doing the deployment for example?
Answer: At my workplace we have many test environments to manage, and we generally run a .NET stack for websites. We currently use Octopus Deploy which, for each environment, will configure applications at deploy time. Our apps are built and packaged up with replaceable variables which Octopus fills in on deployment.
Even if you don't use such a tool I would recommend configuration at deployment time. Your application that you package up (in your CI tool of choice) for deployment should be the same repeatable package that goes into dev, test and prod. We use Team City which builds our deployment packages, and another tool which is a package repository to store all the build artefacts.
Having code paths that are special for an environment potentially makes testing harder since your application is behaving differently.
Comment: We have a similar stack, using Octopus and Team City and we are currently on the path to replace variables with Octopus as you suggest above. The only thing that gives me pause is the idea that it would be clearer to keep all the **test**, **staging**, **live** (or insert environment names here) values in the same place.
Answer:
Continuous integration which compiles all code as it checks in and runs unit tests.
As in point 1 plus variant or parameterized builds. Build for windows server. Build for linux server. Etc.
For internal components or shared assemblies one or multiple private nuget feeds may be desirable.
A devops culture may be useful.
A strategy for continuous deployment of systems composed of subcomponents often tagged as microservices may be useful for asp.net webapi services.
Blue/green deployment may be useful. See http://martinfowler.com/bliki/BlueGreenDeployment.html


(Topological) Superconductor is an Insulator

Question:
Superconductor may be viewed as an Insulator, if the Superconductor is formed by the BCS pairing where the excitations around the Fermi surface are gaped everywhere. However, superconductor also superconducts. So how can a superconductor be both an Insulator, as well as a superconductor?
Topological Superconductor may be viewed as an Insulator, if the Superconductor is formed by the BCS pairing where the excitations around the Fermi surface are gaped everywhere. However, Topological superconductor also superconducts. So how can a Topological superconductor be both an Insulator, as well as a superconductor?
The classifications of Topological Superconductor requires the assumption that the phases of matter to be gapped in the energy spectrum between ground state and 1st excited states, such as the work of Kitaev and Ryu et all. If Topological superconductor also superconducts, it should be gapless, should the classifications fail when Topological Superconductor becomes gapless and superconduct?
Comment: First and second questions are the same aren't they ? The only requirement for the classification is the presence of a gap, hence it works for superconductvity as well. In fact superconductivity enlarges the classification by adding a few extra groups (the one you can reach by requiring particle-hole symmetry), as found by Altland and Zirnbauer in 96. A gapless state would not superconduct, because the gapless state would be influenced by impurities. All states (superconductor, topological insulator and topological superconductors), have edge states which conduct, though of different origins.
Comment: @FraSchelle, thanks However, for superconductor, at DC limit of conductivity $\sigma(\omega)= \infty$ as $\omega \to 0$ . So other than the gap, there is a density at $E=0$ that looks like to be gapless?
Comment: A superconductor is gapped. There is no excitation (i.e. no state) below the gap. Still the DC conductivity is theoretically infinite (in fact it's not because a current generates a magnetic field which destroys the superconductivity if too strong ; it's called the critical current of a bulk superconductor). To reconcile all the ideas, the supercurrent has to be on the edge, see the book by London on Superfluids. This edge state are not of the same origin than the bulk-boundary correspondence in topological systems.
Answer: 1. Answer to questions 1 and 2:
The energy gap that is most commonly referred to in a superconductor is the gap in the dispersion of Bogoliubov quasiparticles. These quasiparticles do not contribute to superconductivity. The supercurrent, which is composed of Cooper pairs, is responsible for superconductivity. For any non-zero temperature below the critical temperature ($T_{\rm c}$), the conduction electrons in a metal (which now superconducts) contribute to the formation of two types of quasiparticles:

Cooper pairs (bound state of two electrons), or
Bogoliubov quasiparticles (superposition of electron and hole)

It is the Cooper pairs that flow without any resistance. Despite the existence of a non-zero density of (non-superconducting) Bogoliubov quasiparticles at finite temperatures, the reason the resistance remains zero below $T_{\rm c}$ is that the Cooper pair condensate "shorts out" the Bogoliubov quasiparticles. In other words, in terms of a circuit diagram, you have a finite resistor (Bogoliubov quasiparticles) in parallel with a zero resistor (Cooper pair condensate).
Ironically, the energy gap helps in maintaining superconductivity. Here's why: below $T_{\rm c}$, when we break a Cooper pair, by supplying an energy equal to the energy gap, we get a pair of Bogoliubov quasiparticles (not electrons). If the gap were zero (everywhere in the Brillouin zone) we would not have Cooper pairs, thus no supercurrent, and thus no superconductivity!
2. Answer to question 3:
No, it is still possible to classify gapless or nodal superconductors in terms of the Altland-Zirnbauer symmetry classes. Note that these systems only have gap vanishing in certain regions (points or lines) in the Brillouin zone; these regions are called nodes.
The classification of nodal systems, however, differs from the original work of Kitaev, Ryu et al. from ~2008-2010, which does indeed limit itself to fully gapped systems. Nonetheless, Ryu, Schnyder et al. later on extended this classification to nodal systems in 2013. This work can be found in the following paper:

S. Matsuura, P. Y. Chang, A. P. Schnyder, S. Ryu. "Protected boundary states in gapless topological phases." New Journal of Physics. 2013 Jun 3;15(6):065001. (arXiv)

If you're interested, you can find the aforementioned work on classification of nodal systems recently (Aug 2016) contextualized in the review article:

C. K. Chiu, J. C. Teo, A. P. Schnyder, S. Ryu. "Classification of topological quantum matter with symmetries." Reviews of Modern Physics. 2016 Aug 31;88(3):035005. (arXiv)


Email Notification not delivered to customers in Magento

Question: I am new to Magento. As an admin i am getting email notifications on orders. But customer doesn't get any email notification on orders, password reset, etc. Is there any settings to be enabled it for customers?
Answer: Finally i traced the problem. Its just because of the version 1.9.1. It queues the mails to cron. I just commented the queue syntax in email template. Now It started working. You can refer Magento 1.9.1 Email Queue not working/buggy - how to troubleshoot and what is considered the best patch?.
But this is just a workaround. The right way is of course to enable the Magento cronjob
in shell (SSH):
$ crontab -e

Add this line to execute the Magento cron queue every 5 minutes:
*/5 * * * *  php /absolute/path/to/magento/cron.php -mdefault
*/5 * * * *  php /absolute/path/to/magento/cron.php -malways

You might need to replace php with the absolute path to your php-cli binary. Ask your hoster if it doesn't work and you don't know the path.
Answer: Use this free extension to set up SMTP on your store. Recommended by most people.
http://www.magentocommerce.com/magento-connect/smtp-pro-email-free-custom-smtp-email.html
There may be several reasons why your mail is not getting sent. Maybe you are working on localhost. Or your server doesn't allow sending mails. Checking if mail() function is working would be a good start.
Answer: It sounds like there may be some misconfiguration with your server.
I agree with Hashid that you should consider the SMTP Pro Email extension by Ashley Schroder: http://www.magentocommerce.com/magento-connect/smtp-pro-email-free-custom-smtp-email.html
Besides that, I highly recommend you to consider pairing Mandrill with the SMTP extension: http://www.mandrill.com/
Mandrill is a transactional email provider and you will improve your email delivery rate if you use their service instead of your own server's mail service.
The first 12,000 emails for Mandrill is FREE every month so you don't have to pay a thing if you are not sending more than 12,000 emails to your customers every month.
UPDATE (JULY 28, 2016): Mandrill stopped offering their free service but there are still other providers offering similar service, like SendGrid and Mailgun.
Comment: Unfortunately, Mandrill has stopped this free service.
Comment: Yes, that is correct but there are a few other providers offering this including SendGrid and Mailgun.
Comment: I would suggest Sparkpost if you were using Mandrill for free. Sparkpost offers 100k emails per month for free.


Why is offspring of identical twins not identical?

Question: When identical twins marry identical twins, the children of the couples will be full genetic siblings but why are they not genetically identical?
Comment: I think we need more information. What is the evidence for your assertion?
Comment: Apparently this phenomenon (twins marrying twins) is called "quaternary marriage." Useful to know because (1) you can change the title of your question to be more precise (and maybe get better answers to your question); and (2) you now have a starting point to dig around to find answers.
Answer: They are not identical for the same reason full siblings are not identical.
A simplistic Mendelian setup would be the following:
X1/X2 = Mothers
X3/Y = Fathers
That means the children could be:
X1/X3
X1/Y
X2/X3
X2/Y
So children born to two married couples composed of identical twins only have a 50/50 shot at being the same gender, much less have the exact same set of genes and express them in the same way.
Now, the simplistic view above only concerns 4 alleles - but the human genome is composed of thousands. By the end, the chances of genetically identical offspring from a set of identical twins is still very, very low.
And you haven't even began to include epigenetic variations, which often arise as a response to the environment! One cousin might be shorter due to their diet as an infant, one might have allergies the other does not depending on if they played outside as a child, and for non-Mendelian traits (incomplete dominance, co-dominance, phenotypes that rely on more than one allele [especially hair, eye, and skin color]) there's even more opportunity to introduce differences!
Comment: Exactly. And then there is crossing over that will produce even more variability.
Comment: Let's not forget possible environmental influences on development.
Answer: There was actually a 1960s TV sitcom based on the notion of identical cousins. It was called the Patty Duke show. In reality the only way to have cousins that look alike would be through a quaternary marriage. That is when twins marry other twins. The children from the two marriages would technically be 1st cousins yet genetically they would be siblings as well. In other words, it would be impossible to figure out who the biological parents are based on the DNA alone since the parents (being identical twins) would share the exact same genetic material. The truth is the Patty Duke show scenario is highly unlikely. Patty and Cathy could not be identical cousins because the only way we get identical offspring is when a fertilised egg splits into two cells. Those identical cells grow into identical twins. So there would be a strong resemblance between Patty and Cathy but the odds of them looking like identical cousins is unlikely. More likely they would look like fraternal twins. Patty would indeed look like Cathy but you could tell the difference between them just as you could between any pair of sisters. The cousins wouldn't look identical but they wouldn't look like cousins. They would look like sisters.
Comment: Hi Toussaint, welcome to Biology.SE! Nice anecdote! It would be useful to add reference for the "scientific" part of your answer and improve the formatting for better reading.


What Is This Quotient Space?

Question: Let $X$ be a finite CW-complex with only even cells $x_1,\ldots, x_k$ and let $Y$ be the complex obtained by attaching one more even cell to $X$, call it $y$.  Assume both $X$ and $Y$ are connected.  The quotient complex $Y^n/X^n$ has the cell structure with one cell for each product of cells $e_1\times\cdots\times e_n$ where the $e_i$ are either equal to $x_i$ or $y$ and at least one $e_i$ is equal to $y$.  I want to say that this amounts to a wedge of products of spheres each product of spheres depending on how many copies of $y$ there is in that cell.  Is this correct?
Answer: Suppose Y is obtained by attaching a zero-cell, so $Y = X \cup \{\ast\}$.  Then $Y^2$ is $$(X \times X) \cup (X \times \{\ast\}) \cup (\{\ast\} \times X) \cup (\{\ast\} \times \{\ast\})$$
and so $Y^2/X^2$ is homeomorphic to
$$
\{\ast\} \cup X \cup X \cup \{\ast\}.
$$
This can be arbitrarily complicated depending on X.
ADDENDUM: By request, a connected example is the inclusion $\mathbb{CP}^1 \subset \mathbb{CP}^2$.  The quotient $Y^2/X^2$, in this case, has a nonzero cohomology operation $Sq^2$ from H6 to H8 with ℤ/2-coefficients, and there is no wedge of products of spheres that can have this cohomology.  (You should work out the details.)
Comment: What if I assume that both $X$ and $Y$ are connected?
Comment: @Richard: I think you get the same problem if you attach something other than a 0-cell. If $y$ is the new cell, the quotient looks like $\{\ast\}\cup (X\times y)\cup (y\times X)\cup (y\times y)$.
Comment: @Anton: Exactly.  The sets $(X \times y)$ etc produce suspensions of X sitting inside this quotient space.  Unfortunately in order to show that these don't decompose, up to homotopy equivalence, as wedges of products of spheres you need at least a little machinery.

What Is This Quotient Space?


Ola Scripts installation in "Multi-server" Jobs Folder

Question: I am installing the Ola scripts on a Central Management Server for multi-server administration. How can I get the jobs to show up under "Multi-server" Jobs Folder instead of the "Local Jobs" folder?
Answer: The first part is to understand that a Central Management Server and a Master Job Server are not the same. CMS is used to centrally manage instances, the master job server is used to deploy standardised jobs across mutiple servers. These two can be linked but are not directly related.
To have the jobs appear in Multi-Server Jobs, the jobs need to be configured as multi-server jobs. To do this, open the job and navigate to the Targets page. Select "Target Multiple Servers" and then select the target job servers to which you wish to deploy the job.
See this link for more info.
If you're deploying Ola's maintenance jobs on a Master Job Server, there are several considerations you should make before deploying:

All jobs have the same configuration, so your output file path must be accessible or identical on all servers. If it varies, you will get errors on the servers that don't match. NOTE: in later versions (2014+) of SQL, you can use the Agent macro SQLLOGDIR to use a local path for output log files that vary between servers in a master job server.
Backup jobs must be configured to backup to an identical path, either a local path that exists on all servers or a shared path that all servers can access.
Exclusions for databases, tables etc must be applied to all servers, as the jobs cannot be individually modified on servers.
Schedules are identical across servers, so if you're backing up to a shared location, you may encounter performance issues due to increased write activity at the same time.


Why is the atmospheric pressure on Venus so high?

Question: The pressure on Venus is 1334 PSI (9.1976 MPa) or 92 times the pressure at sea level on Earth, which is 14.5 PSI (99.9734 kPa). Now, in our oceans the pressure increases by 14.5 PSI (99.9734 kPa) every 33 feet (10.058 m), or 9997.734 kPa every meter. So, we're told that the atmospheric pressure on Venus is equal to the pressure on Earth at 3036 feet (925 m) under the ocean? Do I have this right? If so what is causing that much pressure in a gas?
Comment: The pressure is caused by the gravity of Venus and the amount of gas around venus. Gravity of Venus is 90 % of Earth. The mass of the whole atmosphere of Venus is about 93 times the mass of the Earth atmosphere, see https://en.wikipedia.org/wiki/Venus#Atmosphere_and_climate
Comment: Sorry, but most of Earth's original CO2 was converted to various calcites (CaCo3, mostly limestone) long before photosynthesis started. Water mixed with CO2 to form carbonic acid, which reacted with calcium minerals to form calcites.
Comment: Given that the atmosphere on Venus is 95% CO2, the CO2 most likely originates from the volcanic activity on Venus, the same way the Earth's early atmosphere was mostly CO2 because of early volcanic activity. If it wasn't for ancient microbes using the carbon in CO2 & releasing the oxygen back into the atmosphere, Earth's atmosphere would still largely be composed of CO2.
Comment: Yeah, but I'm going to find out where all that gas comes from. Maybe it's the nearness to the sun.
Comment: @RichardWales Please clarify the title and text of your queston to properly reflect that you are indeed interested in **how** venus *acquired* such a heavy/dense atmosphere. Currently, your question (What causes so much pressure) and what you ask in your comment are two different things.
Comment: Something something a your mom joke.
Answer: The pressure exerted on a surface area under the ideal gas law is $P = \frac{\rho k_B T}{\mu}$ with the following notation:

$\rho$ being the volume mass density (or simply density)
$k_B$ is the Boltzmann constant
$T$ is the temperature in Kelvin
$\mu$ is the mean molecular mass in g/mol

On Earth $\mu_E \approx 29$, while on Venus it is $\mu_V \approx 44$. Furthermore $T_E \approx 300$ and $T_V \approx 750$, so the factor of $\frac{T}{\mu}$ accounts for only a factor of $1.76$ between those pressures.
The main difference here comes from the density: $\rho_E = 1.2 kg/m^3$ while $\rho_V=67 kg/m^3$.
Together you get $P_V = P_E \cdot 1.76 \cdot 55.8 \approx 98 \cdot P_E$. The difference from this calculation compared with the factor of $92$ that is actually true, come from the fact that Venus atmosphere on the surface mostly is in a state of supercriticality, which means it is somewhere between the state of gas and fluid. This makes it necessary to apply corrections to the ideal gas law which I've not used above, for simplicity.
So the main difference in pressure comes from the higher density of Venus atmosphere. What does that mean?
There is simply so much more 'stuff' in Venus' atmosphere. Earth's total atmosphere has a mass of around $5 \cdot 10^{18}$kg, while the Venusian one has $5 \cdot 10^{20}$kg, so this is 100 times more than what Earth has.
How could this happen?
Or you could ask "How can a planet nearly the same mass as Earth have an atmosphere 100 times more massive?". This is one of the big mysteries of Planet formation & evolution. There are two halfway compelling scenarios that come to my head now, both involve Earth and Venus having similar atmospheres at a relatively young age of $\sim 100$ Million years.

Venus might have gotten less accretional heat in the phase as the solar system formed. Together with it's smaller size, it was able to radiate this heat away even faster than Earth was. Also smaller size implies less radiogenic heat production throughout the ages.
All those factors might have conspired to make plate tectonics much weaker/nonexistent on Venus. This prevents burying of the atmosphere, as it happens in Earth's mantle. But it is hard / impossible to estimate how strong this effect was in the past.
Venus went early into a stage of runaway greenhouse effect. We know this, because we find it today in this state. Somehow this protected the atmosphere from escaping (I don't want to specify any mechanism, as there are many possibilities), while Earth lost a significant portion of its atmosphere over time.

If you're more interested in this topic I recommend as introductory read Imke de Pater and Jack Lissauer's book "Planetary Science".
Comment: `+1` This is a very helpful answer as it addresses what I think the OP is actually asking about, and what I think many people would like to know; **How could this happen?**
Comment: @MagicOctopusUrn I would absolutely recommend this review article http://adsabs.harvard.edu/abs/2018A%26ARv..26....2L by H. Lammer et al. from last year (2018) that summarizes all the most recent understanding in a detailed manner. The article also goes into issues of solar activity with time, atmospheric escape, first accreted atmospheres, outgassed secondary atmospheres, etc.
Comment: @Uwe: You're right in saying that this is the ideal gas law for a constant volume. But you have to check which volume you're talking about. The way the gas law is derived it is locally valid for all individual test volumes on which the density $\rho$ is defined, thus it is valid everywhere in the atmosphere. Only when phase-changes become involved it's not fully correct anymore, but I've pointed that out in my answer.
Comment: In a constant volume, increasing temperature increases pressure. But the atmosphere of a planet is not a constant volume. If the temperature rises, the atmosphere gets higher, but the mass of the atmosphere over a given area does not change and pressure does not change. There are areas of lower and higher pressure on earth, but this is caused by temperature differences. But we assume here a constant temperature at the surface of the planet.
Comment: @Uwe: What are you trying to say? Argue math and physics, not semantics. Also weather on Earth is not the same as the average state of the atmosphere on Venus.
Comment: @AtmosphericPrisonEscape What I want to say: Are you sure that the formula for the pressure you wrote in the first line is applicable to the atmosphere of Venus or Earth? It seems to be the ideal gas law for a constant volume, but an atmosphere of a planet is not a constant volume. Temperature does not change the gravity of the planet and the mass of its atmosphere, so temperature can not change the mean pressure at the surface of the planet. By the way, I did argue mathematical and physical.
Comment: Thank you very much. Yes you are right, I very much would like to know how such a situation came to pass. It's interesting that the answer is that we don't really know. Amazing.
Comment: Awesome answer, do you have any additional reading on this topic to suggest?
Answer: The question you did ask:
Why is the atmospheric pressure on Venus so high?
The answer is that the mass of the atmosphere of Venus is very high compared to that of the Earth, by almost a factor of 100. On the other hand, the two planets have similar surface areas and similar gravitational accelerations at the surface. Since surface pressure is approximately the weight (mass times gravitational acceleration) of the atmosphere divided by the surface area, this means that surface pressure on Venus is very high compared to that of the Earth, by almost a factor of 100.

This leads to the question you didn't ask:
Why is the atmosphere of Venus so massive (and why is it almost all CO2)?
The answer to this question is that the Earth has water on the surface, plate tectonics, and abundant life. Venus has none of these.
The combination of the above means that Earth has a vigorous carbonate-silicate cycle that sequesters vast amounts of carbon underground. This cycle does not exist on Venus. Venus has instead expelled a large amount of its crustal carbon into its atmosphere, mostly in the form of carbon dioxide.
Comment: @ApurvaSingh Citation needed for your claim. The general consensus is that the primary reason Mars's atmosphere is so thin is that Mars isn't quite massive enough to hold onto a thick atmosphere. However, Venus also doesn't have much a magnetic field, receives a lot more solar heating than does the Earth, and yet its atmosphere is much thicker than is the Earth's. Magnetism is not the answer.
Comment: Interesting answer. Does the argument apply to Mars as well? Mars does not have a crushing CO2 atmosphere because it (once) had a carbonate-silicate cycle? Let's give this hypothesis a test drive.
Comment: It's pretty amazing that Venus can have 100 x Earth atmosphere but Mars only 0.01 x Earth atmosphere just because of the size difference. Also I thought Mars' problem was the lack of magnetic field?
Comment: Carbonate cycle is all well and good, but is this mechanism able to bury 91 atmospheres of material? Would also be interested in references for this.
Comment: @uhoh - Mars is too small to hold onto a substantial atmosphere.
Comment: On Earth there is not only the carbonate-silicate cycle, there is also the https://en.wikipedia.org/wiki/Carbon_cycle, both are removing carbon dioxide from the atmosphere. But both cycles are not possible on Venus due to the high temperature and the lack of  photosynthesis. On Earth, a lot of oxygen removed by photosynthesis from carbon dioxide was bound in metall oxides long ago, for instance iron ore.
Answer: Atmospheric pressure (or water pressure, for that matter) is simply the weight of the atmosphere that one square inch (or any square unit) supports. The atmospheric pressure on earth is, for the sake of argument, 14.5 PSI. That simply means that there is 14.5 pounds of atmosphere above one square inch of surface at sea level on Earth. (To calculate the pressure at a given depth in the ocean, you only need to calculate the weight of the ocean above that depth.) As @Uwe pointed out in comments, the mass of the atmosphere on Venus is 93 times that of Earth's, so one would expect that the surface pressure would be that much greater, as well.
Answer: Answer: No oceans, no life … so no CO2 sequestration.
previous answers provided an insightful answer by pointing out it is the mass of the atmosphere which provides pressure. But this begs the question of why Venus's atmosphere is so much more massive than Earth's (Venus's sister planet). Or, conversely, why Earth's is so much less massive.
Most of the difference is due to CO2. Venus's surface pressure is 93 bar. If CO2 were removed, the remaining atmosphere would be almost pure nitrogen. Other gasses would be measured in parts per thousand. Surface pressure would be just over 2 bar.
Earth's early atmosphere (after the collision which formed the moon) was similar to today's Venus atmosphere. https://www.anl.gov/article/unlocking-the-secrets-of-earths-early-atmosphere#:~:text=The%20energy%20from%20this%20catastrophic,the%20one%20we%20have%20today
The CO2 in the Earth's early atmosphere was drawn down as CO2 was absorbed by water in the oceans and sequestered by marine organisms. The White Cliffs of Dover are a visible example. Venus is too close to the sun for liquid water oceans, and Mars is too far away.
Comment: this is the same argument as [David Hammen's answer](https://space.stackexchange.com/a/22874), isn't it?
Comment: @ErinAnne ... dang, you're right. I originally wrote this answer for a similar question in SE Astronomy and migrated it here because it was listed as a "related question". Apologies to David.
Comment: Actually we're lucky that a huge collision created the earth and moon, which likely keeps plate tectonics more active.  Metals welling up from the mantle, such as sodium, magnesium, aluminum, calcium, and iron sequester huge amounts of CO2.  To this day earth's ocean pH is more than 8!  Yes, ocean life evolved to make their own shells too.  Venus has no  oceans and no moon.  One may wonder is the continents "floating" around over the mantle aren't actually originally pieces of the moon.
Answer: The atmosphere of Venus up to 48 km comprises high velocity jetting of sulfur (SN) gas through over 1,000,000 'small domes' imaged by Soviet and NASA Magellan radar. SN gas, the normal form of sulfur at the temperature in the lower atmosphere, jets at high speed until it reaches the altitude (temperature) at which it crystallizes to form a monoclinic crystal and due to the heat released rises a few km to the temperature level where it changes to a rhombic crystal. The denser rhombic crystals fall downward and revert to the monoclinic form which, the change of which is completely reversible. This produces the the thin roiling lower cloud layer, the mass of which, along with the jetting SN and CS  produce the high pressure at the surface.
The Lower Cloud Layer (LCL)forms the boundary between the two modes of Venus' bi-modal atmosphere, where different molecular species and pressure altitude relationships attain.
Changes in molecular species with elevation can only occur in such a 'mass flow' environment. The original Pioneer Venus figure showed the physical layers and temperatures of each as a function of altitude, but the chemical composition above and below the LCL were not be determined.
A three order-of-magnitude drop in the Pioneer Venus CO2 mass spec channel at the LCL altitude was interpreted as a clogging of the inlet leaks (there were two at the time).  The mass 44 counts remained low until PV descended to 31 km, the bottom of the red-haze layer, where the channel 44 counts recovered. This was attributed to the evaporation of the occluding droplets and the counts below 31-km were assumed to be CO2. The crystallization temperatures of monoclinic and orthorhombic S8 correspond exactly with the temperature at the LCL. The mass spectrometer not detect the S8 because the mass of the S8 molecule, 256.47 amu is beyond the range of the mass spectrometer instrument, 208 amu.
Carbon Sulfide, CS, occupies the entire lower atmosphere of Venus along with S8. What scientists expected to be CO2 below 31 km is actually CS (carbon sulfide), 'masquerading' as CO2. CS and CO2 have very similar masses – 44.0686 and 44.0096 amu, respectively. The evidence indicating CS in the lower atmosphere is present in the form of the red haze observed from 31 km up to the LCL. Again, a simple look-up of the temperature at which rising hot CS gas would form small red crystals (200 C) coincides exactly with the lower level of the red haze.

ref: http://firmament-chaos.com/papers/Venus-Paper-2018.pdf
Comment: *Thanks for the link!*
Comment: *Welcome to Space!* This is a really interesting answer to read. I'd like to make a few recommendations for how to make this a better Stack Exchange answer. 1) please include some supporting links, references or citations. Without those, there is no way for future readers to judge how accurate this information is. 2) Make sure that you clearly mark which part of the answer directly addresses the question as asked: "**Why** is the atmospheric pressure on Venus **so high?**" and " **...what is causing** that much pressure in a gas?" Thanks!
Comment: This is utter nonsense claiming that Venus is 6000 years old. The linked paper is by the poster. " As clearly expressed in the Rigveda, Egyptian, Greek, Roman, and Biblical sources,
Venus was born some six thousand years Before the Present (BP), when a large dark body
struck Jupiter on the sun side." You upvoters should be ashamed and this drivel should be deleted.
Answer: Yes you are right. There is a lot more and heavier gas on Venus than on Earth, and since Venus is smaller than Earth, the pressure that the gas exerts per square inch is much higher.
Here is a good comparison between the two planets. Notice that according to Dr Soper's table, there are 66 molecules per square meter on Venus, versus only 1 on Earth.
Comment: "since Venus is smaller than Earth, the pressure that the gas exerts per square inch is much higher" What does that mean?
Comment: There are much more molecules per square meter than only 66. Carefully read the explanation of Dr. Soper's table.


Distorted and weak sound on some backing tracks

Question: When I plug my stereo backing tracks into dual mono or stereo inputs on my desk, some of them sound very tinny and quiet until I unplug one side. Any ideas? Thanks. Mick
Comment: this is called phase cancellation, check your input settings (look for a button with a symbol that looks like  "0" combined with a "/" . And check with another pair of cables..
Answer: The issue you are facing might be caused by a phase inversion between your two stereo channels.
This phase inversion might occur at various points in the chain :

The recorded backing track might have a phase inversion
The cable used to connect the player to the desk input
A phase inversion switch activated on one channel in the desk


What is the purpose of Jews going into exile?

Question: What are the main reasons we are in exile?
I recall some reasons but I can't remember all of them.
Comment: Please add what you already know so no one duplicates your efforts.
Comment: To make gerim. So says the Talmud.
Answer: On page 12 of Rabbi Menachem Mendel Schneerson's (the Lubavitcher Rebbe) book "Torah Studies a parsha anthology", he cites a Midrash (Bereishit Rabbah 39:2) about Abraham's journeys and writes,

"The Midrash compares his many journeyings to the way a spice box must
be shaken about to spread its aroma to all corners of a room."

A few pages later (p.14) the Rebbe writes about exile saying,

"Exile, then, is an integral part of spiritual progress; it allows us to sanctify  the whole world by our actions, and not simply a small corner of it."

(see @Shmuel's link in the comments for an on-line version of the Rebbe's words)
In my mind, when I read these passages I like to think that Israel is the spice box and by scattering Jews (exile) into the four corners of the world we bring G-d's light to the darkest fringes so that others may see it and be guided by it, and thereby hasten the appearance of the Messiah.
Comment: @יהושעק Rabbi Menachem Mendel Schneerson
Comment: Viewable here, under paragraph 5: https://www.chabad.org/therebbe/article_cdo/aid/110320/jewish/Torah-Studies-Lech-Lecha.htm
Answer: The Gemara Pesachim 87B:

וְאָמַר רַבִּי אֶלְעָזָר: לֹא הִגְלָה הַקָּדוֹשׁ בָּרוּךְ הוּא אֶת יִשְׂרָאֵל לְבֵין הָאוּמּוֹת אֶלָּא כְּדֵי שֶׁיִּתּוֹסְפוּ עֲלֵיהֶם גֵּרִים, שֶׁנֶּאֱמַר: ״וּזְרַעְתִּיהָ לִי בָּאָרֶץ״. כְּלוּם אָדָם זוֹרֵעַ סְאָה אֶלָּא לְהַכְנִיס כַּמָּה כּוֹרִין.

And Rabbi Elazar said: The Holy One, Blessed be He, exiled Israel among the nations only so that converts would join them, as it is stated: "And I will sow her to Me in the land" (Hosea 2:25). Does a person sow a se'a of grain for any reason other than to bring in several kor of grain during the harvest? So too, the exile is to enable converts from the nations to join the Jewish people
Answer: I mean the Torah clearly illustrates the connection between the Jews and the land of Israel- when we sin and don't follow in the ways of G-d, the land will kick us out. So galus is our punishment for not following the Torah, and it gives us a chance to repent and think about what we've done and better ourselves
Answer: Ezekiel 20:34-38

והוצאתי אתכם מן העמים וקבצתי אתכם מן הארצות אשר נפוצותם בם ביד חזקה
ובזרוע נטויה ובחמה שפוכה. והבאתי אתכם אל מדבר העמים ונשפטתי אתכם שם
פנים אל פנים. כאשר נשפטתי את אבותיכם במדבר ארץ מצרים כן אשפט אתכם נאום
אדני ה'. והעברתי אתכם תחת השבט והבאתי אתכם במסרת הברית. וברותי מכם
המרדים והפושעים בי מארץ מגוריהם אוציא אותם ואל אדמת ישראל לא יבוא
וידעתם כי אני ה
And I will bring you out from the peoples, and will gather you out of
the countries wherein ye are scattered, with a mighty hand, and with
an outstretched arm, and with fury poured out; and I will bring you
into the wilderness of the peoples, and there will I plead with you
face to face. Like as I pleaded with your fathers in the wilderness of
the land of Egypt, so will I plead with you, saith the Lord GOD. And I
will cause you to pass under the rod, and I will bring you into the
bond of the covenant; and I will purge out from among you the rebels,
and them that transgress against Me; I will bring them forth out of
the land where they sojourn, but they shall not enter into the land of
Israel; and ye shall know that I am the LORD.


how to define the top dir in automake system?

Question: I usually use a typical steps to generate the makefile, and firstly I use the "build.sh init" to generate the configure file, and then I use "configure" to generate the makefile with makefile.am file. Now I want to estiminate the "../../" in some include file like include "../../dirA/dirB/C.h", just write it as include "dirA/dirB/C.h", so the settings of configure.ac or makefile.am must be modified. Who can help to solve this?
Answer: The first thing to note, is that the configure system has two top_dir's. A top directory for where the source code resides, and a top directory for where the code gets built. Often these two directories are the same. But there are situations where the source code resides say on a read-only file system, so you need to build the software somewhere else. Below I am going to use the the top build directory, again noting that this may be the same as the top source directory.
autoconf already defines a couple of variables for the top build directory. One of them is called "abs_top_builddir".
Let's say the include file you want to use  "abs_top_builddir" is called x.h. You would create a file called x.h.in The way you refer to this variable in that file is to surround it with '@'.  So you might have:
#include "@abs_top_builddir@/A/dirB/C.h"

The other thing you need to do is tell the configure script to create header file x.h from x.h.in. You do this by adding
AC_CONFIG_FILES([x.h])
AC_OUTPUT

to the end of configure.ac. You only need one AC_OUTPUT so if that line is already there, then you don't need to add it again. Now run autoconf to create the configure script and when you run configure you should see
configure: creating x.h

Check x.h and make sure the include line is what you expect.

And having written all of the above, I should also point out this this is what is not what is usually done. Instead, on in CFLAGS or some similarly named variable, you just include the directory. For example a Makefile.am might have:
AM_CPPFLAGS = -I$(top_srcdir)

Here I am switching to srcdir because I don't have to create the header like I did before. And you probably won't have to add additional lines to configure.ac because those lines will probably already be there.


How much does google know about me if I visit a website with Analytics?

Question: If I visit a website that contains Google Analytics, information about my visit is sent to Google, which is used to provide the website's owner with demographic and other statistics about his/her site visitors. However, I'm wondering if and how my visit will affect Google's knowledge about me, specifically. For example, will it affect the parameters that are used for Google's personalized search results that are presented to me? And is Google able to tell that it was me who visited a website (i.e. attribute that visit to my Google account) that has Analytics enabled, even if I didn't access the website via a Google search?
And does the answer differ depending on whether I'm logged in to a Google account on the computer I'm using to access the website, and whether I'm browsing in private mode?
Answer: Google will know nothing about you (or at least it should not) as it would go against their privacy policy about collecting any information that could personally identify you and other visitors. Of course, that does not mean that the site itself won't prompt you for some personal information, for example if you fill out a form, and if the site administrator inadvertently collects information about you and sends it to GA, then that is another issue (also one that goes against Google's privacy policies). You can read more about this in section 7 here: http://www.google.ca/analytics/terms/us.html.
Google Analytics alone does not do remarketing, so it won't be able to target you with specific ads or content. There may be some other tools used alongside GA, but I don't think GA by itself has that ability.
Additionally, I don't believe GA data has any bearing on searches done with Google search engine, whether you are logged in to your Google Account or not.
Comment: Thanks for your answer!
Just to be clear, does that also mean that the data collected by Google Analytics will have no effect whatsoever on my personal 'filter bubble' (i.e. my personalized search results) when I use Google search?


How to add an uploaded image to my own ImgUr Album

Question: I have created an application on ImgUr and recieved the ClientID and ClientSecret.

I know my album id for example: xbvhXo(not a real id)
I want to upload an image to my album.
What I have done:
I installed imgur npm package for my TypeScript Next.js project.
Here is the code for uploading images to ImgUr:
const albumID = 'xbvhXo';
const client = new ImgurClient({
    clientId: process.env.IMGUR_CLIENT_ID,
    clientSecret: process.env.IMGUR_CLIENT_SECRET,
 });
export async function uploadToImgUr(imgData: APImageData | Buffer[]): Promise<string[]> {
    let files: Buffer[];
    let album: string | undefined = albumID;
    let name: string | undefined;
    let title: string | undefined;
    let description: string | undefined;

    if(Array.isArray(imgData)) {
        files = imgData;
    } else {
        files = imgData.files;
        album = imgData.album ? imgData.album : albumID;
        name = imgData.name;
        title = imgData.title;
        description = imgData.description;
    }

    const uploadPromises = files.map(async (file) => {
        const response = await client.upload({
            image: file,
            type: 'stream',
            album: album,
            name: name,
            title: title,
            description: description,
        });

        return response.data.link;
    });

    return Promise.all(uploadPromises);
}

when trying to add the image to my Album, it errors out:
You are not the owner of album 'xbvhXo', which means you can't add images to it. For anonymous albums, use the album deletehash.

This is not true, as I am clearly the owner of this album.
How can I fix this?
Answer: Figured out that I need to

call the ImgUr authorize endpoint with the client id and client secret to
get refresh token and access token. ( This is a manual work, I access this [url](https://api.imgur.com/oauth2/authorize?client_id=response_type=token&state=, then manually clicked 'Allow'.
It then redirected me to the callback url which I set up during the creation of my application in ImgUr Settings -> Application.

Once got these 2 tokens, I added the following code:
const client = new ImgurClient({
clientId: process.env.IMGUR_CLIENT_ID,
clientSecret: process.env.IMGUR_CLIENT_SECRET,
accessToken: process.env.IMGUR_ACCESS_TOKEN,
refreshToken: process.env.IMGUR_REFRESH_TOKEN,
});

Then the rest code remains the same and it starts to working.


Do I need a heat sink for small voltage regulator?

Question: I'm using a 7808 voltage regulator in to-220 package. Vin is 12V, Vout is 8V. Expected max current should be in the range of 10mA, let's say 50mA at most. Circuit is to be encased. Do I need to add a heat sink to the 7808, or that power will dissipate correctly without?
Comment: That depends on how well the 7808 will be (thermally) isolated from the surroundings. With good isolation you can still cook it to death, even at a lowly 0.05 * 4 = 0.2W.
Answer: Do the math.  The regulator will drop 4 V with 10 mA thru it.  (4 V)(10 mA) = 40 mW.  That's not much at all, and even a small package like a SOT-23 can safely dissipate that when mounted normally on a board.
However, you mentioned this will be encased.  That changes the thermal resistance from junctions to ambient.  Ultimately its about keeping the junctions below some maximum temperature.
A typical junction to ambient resistance for a SOT-23 is about 360 °C/W.  At 40 mW that means the junction would be 15°C above ambient.  If the part can operate at up to 120°C junction temperature, for example, and ambient is 25°C, then the device could dissipate up to 260 mW.
The calculations are the same with a potted circuit, except that the junction to ambient thermal resistance will be different.  It can be both higher or lower, depending on the nature of the potting compound and its depth.  This is something you have to look into by carefully examining the potting compound datasheet, and possibly talking to the manufacturer and maybe running your own experiments.
One strategy is to grossly over-spec it.  For example, if you get a 7808 in a TO-220 package, then it's hard to imagine there will be a problem except for some extreme potting situations.
Comment: Thx for the explanation. The 7808 is in a TO-220 package, so I guess I'm ok without heat sink.
Comment: @Ant: Probably, but guessing is no way to do a design.  Read the datasheets and do the math.
Answer: My rule of thumb (conservative in most situations) is that 600mW is acceptable for a TO-220 without a heat sink. (at a typically stated \$R_{\theta JA}\$ of 65°C/W, that's a rise of 39°C, so in a 70°C environment the junction would be at 109°C).
Your maximum dissipation is (12-8)*50mA + 5mA*12 = 0.26W (5mA is roughly the current the regulator uses itself).
So it appears it will be just fine. However if you happened to omit that it must operate at an ambient of 100°C, or in a vacuum, or some other important 'detail' it may not last long. It gets a bit more complex with SMT parts that have heat spreaders such as copper patches on the board- the stated \$R_{\theta JA}\$ is only valid for a very specific test PCB situation and attempts to apply it to a very different situation may end in tears.
If the calculated dissipation approached my rule of thumb or if the operating conditions were unusual (eg. vacuum or high ambient) I would do the calculations from scratch.


QField auto-numbering

Question: A simple need but no success in default auto-numbering an integer type field in QField.  Have tried $id, $row_number, etc., but no default value is entered on point digitization. An expression such as maximum("id") + 1 requires "apply default value on update" which appears to sometimes overwrite values on synchronization in QGIS - which is detrimental to 'permanently' indexing points in the data-collection/synchronization process. Have searched these posting and other on-line sources and tried all options found.
Answer: You said:

An expression such as maximum("id") + 1 requires "apply default value
on update"

Although there is a caution that states:

"Using fields in a default value expression only works if 'Apply default value on update' is checked"

...this is NOT the case. I number sequentially across 3 layers (a point layer, a line layer and a polygon layer, with the following expression, and 'Apply default value on update' is NOT checked and it works.
<code>Max(
    aggregate('tree_pt','max', "num"),
    aggregate('tree_ln','max', num"),
    aggregate('tree_ar','max', "num"),
    0)
+1
</code>
I use the Max() funtion with an argument = 0 to account for an empty dataset.
But, if you are using this sequence as a primary key in a multi-user environment, or will upload the data to a database elsewhere, you may wish to consider using a uuid; Set default = uuid().

QField auto-numbering


Is there a meaning of why does the wire in a Cat6 or Cat5e cable colored differently?

Question: like for example: does the green wire mean something in a Cat6/Cat5e cable?
Answer: The Cat5e/Cat6/Cat7 cables are colored differently, because a technician for example should know how correctly set the connectors on the cable. Imagine if you have to put a connector on 30m cable, when the cords inside are with the same color?
There are also different type of cable termination, depending on what devices you're going to use (although nowadays most of the devices support  Auto MDI-X).
Most common is the twisted pair cable. There are two (widely used) standards for it - TIA/EIA-568-B.1-2001 T568A Wiring and TIA/EIA-568-B.1-2001 T568B Wiring (commonly referred as A and B). They are used when you have to create a straight (twisted pair) cable. You connect pin 1,2,3,6 on side1 to pins 1,2,3,6 on side two (depending on the standard, you use orange&white, orange, green&white, green for respectively 1,2,3,6, or you start with green&white for 1 and end with orange for 6)
So, to create a crossover cable you need to connect:
Side 1
- pin 1 (green&white - it's `transmit +` signal)
- pin 2 (green - it's `transmit -` signal)
- pin 3 (orange&white - it's `receive +` signal)
- pin 6 (orange - it's `receive -` signal)

Side 2
 - pin 1 (orange&white - it's `transmit +` signal)
 - pin 2 (orange - it's `transmit -`)
 - pin 3 (green&white - `receive +`)
 - pin 6 (green - `receive -`)

You see - you can't do all this with the same color.
Comment: 1 Gbit/s cable uses four pairs, that is eight pins. There isn't a 1000gb ethernet cable yet.
Comment: Actually, the standard calls for all four pairs to be connected for a single WAO connection. That is actually required for 1000BASE-T (1 Gbps on UTP) to connect. Also, ANSI/TIA/EIA define the cable categories, and they have refused to recognize or certify a Category-7, so there are no specifications or test suite for such a cable category. ISO/IEC does have a Class F cable that seems to be about what most people are calling Category-7. The only recognized cable categories are 3, 5e, 6, and 6a. See the latest ANSI/TIA/EIA 568 standard.
Comment: So in a 1000gb ethernet cable,do they only use 4 pins or 8 pins?
Comment: ohh I misspelled, i meant 1000base t


SQL Sever Alwayson - Increase the WSFC failover threshold

Question: Im trying to simulate the Failover in my SQL server 2017 alwayson by stopping and starting the SQL server service.
It worked 2 times, but after that, the failover is not happening, It showing an error like,

Clustered role 'sqlag' has exceeded its failover threshold.  It has exhausted the configured number of failover attempts within the failover period of time allotted to it and will be left in a failed state.
No additional attempts will be made to bring the role online or fail it over to another node in the cluster.  Please check the events associated with the failure.  After the issues causing the failure are resolved the role can be brought online manually or the cluster may attempt to bring it online again after the restart delay period.

I tried to change the Alwayson group resource restart timeout values like this. But still the failover is not happening, can someone help me where to increase this failover threshold?

And I tried even the max allowed values, but getting error like this.

Cluster resource 'sqlag' of type 'SQL Server Availability Group' in clustered role 'sqlag' failed.

Based on the failure policies for the resource and role, the cluster service may try to bring the resource online on this node or move the group to another node of the cluster and then restart it.  Check the resource and group state using Failover Cluster Manager or the Get-ClusterResource Windows PowerShell cmdlet.
Answer: Go to your Roles, click on AG and on the bottom you have resources - click on it.
Then open properties of Other resource - Your AG and go to Policies and play with those values.


Which preposition should we use in this sentence?

Question: We arrived (at/in) our village (on/in/at) a lovely night in October.
Comment: You have two questions here really - these two other questions may help: [Should I say "She is in the park" or "She is at the park"?](http://ell.stackexchange.com/q/40439/) and [Rules for "on", "at", and "in": preposition of time](http://ell.stackexchange.com/q/54364/9161)
Comment: What specific issues are you having? What do you think is right, or why are you unsure?
Comment: I don't know much about using preposition. In some case, I think I can use all of the choices in the question, but I must chose one choice to be my answer like this case.
Answer: The most common form would be We arrived at our village on a lovely night in October, but there's nothing inherently "incorrect" about using in for the first one.
For the second preposition, we usually use on in respect of days or nights (He'll come on Tuesday, We work on alternate nights). We tend to use in (or during) if the word day or night primarily means "daytime" as opposed to "nighttime" (or vice-versa) - but in that case we'd use the definite article, and it would be odd to include a modifier like lovely (We arrived in / during the night of October 12th).
You can also say We arrived at night (i.e. - at nighttime), but not ...at a night.
Answer: Your question is not an easy one to answer as English prepositions are tricky and difficult to distinguish.
Here are some rules of thumb.

Arrive can take both "at" and "in". The main difference is whether your designation is a specific and rather small place such as village or airport. You use "at" in such cases. You use "in" for big places such as city or country. But it is not wrong to use "at" before a city. There are some grey areas. But "arrive in London" is far more broadly used than "arrive at London".
At night and in the night are used to mean during the night. However, you have to use "on a lovely night" when you have an adjective or attributive noun before night. For example, "on Tuesday night" instead of "at / in Tuesday night".
Comment: @NguyễnQuốcViệt You are welcome. Next time you ask a question, please include what you understand and what you don't understand with your own research included in your question. Your question as it is, it is not an ideal question.


How to delete unused file parts that are not used in the FCPX timeline?

Question: I want to clean up my hard disk and delete large unused GB files on my macbook. In the FCPX timeline I have  several hours of footage cut down into a 3-minute movie, with all short 2-second pieces.
I want to delete the folder with unused long hours files from my disk. How do I save the new short files that I want to keep into a folder?
So the old folder is filled with useless long hour files that I want to delete, and the new folder is filled with short good files that I want to keep.
Comment: Answer your own question so that others may learn.
Comment: i found the answer , it is not possible , how do i delete this question ?
Comment: it is possible , but not how i hoped with 1 menu click ,
Comment: You might want to look at this technique: https://larryjordan.com/articles/fcp-x-media-manage-your-projects/
Answer: As you already know you can't easily export just the used parts of your clips. But given FCPX uses XML there must be utilities to do that.
You can get something like clipexporter that will do it automatically.
However you can "share" your final project and then slice that up into shots -- I don't know why you want to do that slicing. AVcutty will slice AVI's automatically (windows OS only).
If disk space is a real problem and you don't mind losing your original footage, just share your final timeline.
Personally I buy an external HDD every two years (whatever $200 gets me) and archive all my personal projects to that. I then copy all the old projects from the old HDD to the new HDD.


Ghost Town - Do abilities of the characters still count?

Question: Claus the Saint can draw! 5 cards. He dies. When the Ghost Town is in effect, is he still allowed to come back and use his ability?
Answer: Yes he can use his ability.
For reference the Ghost Town card reads:

During their turns, eliminated players return to the game as ghosts.
They draw 3 cards  instead of 2, and cannot die. At the end of their
turn, they are eliminated again.

Note that it states that they are to draw cards, so the ghost's will enter at phase 1, the draw phase.
Clause "The Saint"'s special abillity is:

He draws one card more than the number of players, keeps 2 for
himself, then gives 1 to each player.

From the answer to Q14 on the FAQ for the High Noon from the publisher dV Giochi:

Q14. How many cards Bill Noface and Pixie Pete draw when they enter in play as ghosts  thanks to the Ghost
Town?
A. Bill Noface enters in play with 5 cards, Pixie Pete with 3 cards.

We can see that a players special ability does not suffer from the Ghost Town card being put into play.
However as Claus "The Saint" is not specified in any FAQ that I could find, we do not know if he should have gotten the advantage that the Ghost Town card gives ("adding an extra card to the ghost", and thus giving him 6 cards to draw. So that he would end up with 3 cards for himself.), but seeing that Pixie Pete starts with 3 cards and not 4 (His special ability +1 (for the "extra card" from the Ghost Town), we have to assume that Claus "The Saint" get neither benefits or drawbacks from the the Ghost Town card.
Comment: Here, have an upvote to drop your new user restrictions. I've integrated your links, except for the ghost town link which was broken.
Comment: Problem is the FAQ and cards frequently contradict each other. For example Q8 from the same FAQ says during ghost town you draw 3 cards. The ghost town card itself says you draw 3 cards both of which contradict what is on the character card. In this case if you have two different cards telling you what to draw, it should be the most related card, ghost town in this case, which determines the card draw. Otherwise it gets to the point where you don't know which cards to follow and which cards to not follow. The FAQ only looks at cards in a narrow fashion.
Comment: I do see how one can conclude that they contradict each other, but the cards especially and FAQ answers can't have all exceptions listed.
For that reason the normal ruling is displayed on the card, and in the answers.
The exceptions are listed separate, this is to make it easier to read and understand.

So the answer in **Q08** is how most players should play their card when Ghost Town is in play.
However there are some characters that should be played different. This is clarified in **Q14**, it is not a contradiction, but a specification on how some specific characters should be played.
Comment: So for those two characters you follow, **Q14**, ie. the Ghost Town card and **Q08** does not overrule the characters special abilities.
The reason for Clause "The Saint" not being mentioned in **Q14** is that he is not part of that expansion.

Note that the FAQ does answer questions on how to play specific characters when a specific card have come in to play.
Answer: It depends on the character ability and in the case of Claus the Saint and other characters with beginning of turn draw abilities those abilities will not work.

Ghost Town: during their turn, killed characters return in play as ghosts, with 3 cards. They cannot be killed but they leave the game immediately after their turn.

The Ghost Town card specifies that the player returns with 3 cards which overwrites Claus the Saint's ability (and any other character with a beginning of turn draw ability)
There are characters that can use their ability during Ghost Town and here is an example.

Suzy Lafayette = As soon as she has no cards in her hand, she draws a card from the draw pile. (4 life points)
Comment: So in effect we should actually discard the ability cards when the characters die, because they cannot be played?
Comment: @leon No, some characters still have abilities that can be used, such as Rose Doolan, Slab the Killer, Suzy Lafayette, Vulture Sam and Willy the Kid. Plus there are more if you count in the expansions. Think of it as some characters are better during ghost town then others.


MiKTeX crashed on Ubuntu 20.04 (Focal Fossa)

Question: I installed MikTeX from their official website on my Ubuntu 20.04 using shared settings and auto-installation. After opening the console for updates my system turned off due to a power failure and the next time I tried to open the MiKTeX console an error mentioning "File is empty" was displayed with details telling that ****.fndb-5 file is empty. As I wanted to use MiKTeX for writing article I was confused as what to do. If anyone finds a solution, kindly let me know.
Comment: Clearly it's supposed to work, but why miktex? Almost everyone using linux will be using texlive.
Answer: I am providing an answer to this query in case anyone else has a similar problem in future. After reading similar posts I found out that going to the var/...../data/le folder I can find the ****.fndb-5 file mentioned in the error which can be removed and in case other errors pop-up with other ****.fndb-5 files they also can be removed until MiKTeX console starts working again.
Answer: Only answering because of the "power failure" mention. I do not have Windows. But something similar happened to me with Linux. Apparently the system UUID and handshake is not foolproof. Solution is to remove then reinstall.


Is this phrase correct? "Got it, thanks!"

Question: I received this regularly from my colleagues but not sure if this is grammatically correct
Comment: What are your doubts?  It's not a complete sentence, but people often don't speak or write entirely in complete sentences.
Comment: Define "grammatically correct". It's a perfectly natural usage, which you could understand to be a "reduced" form of something like *I have **got it**, for which I convey my **thanks** to you,* but of course we don't often use such verbose phrasing.
Comment: It is the way everyone says it. It's not something Jane Austen would write, or what a copy editor would accept for a news article, but it is exactly how one of many ways there are to say 'I understand"  to another person.
Answer: Yes, it's grammatically correct in informal language.
Strictly speaking, it's not grammatical (it should be I've got it in active or I got it in passive), but it's well established among native speakers and only prescriptivists might claim it shouldn't be used. As far as the rest of the world and linguistic usus is concerned, there's nothing wrong with this sentence in an informal setting.
It's fine to write it to your colleagues, but might not be fine to write it to your supervisor or boss, depends on the company and whether it's American English or European English (EuEn tends to be more formal).


Facebook like gate not revealing content

Question: I'm trying to add a like gate to a facebook app. I am using the most recent facebook PHP SDK, but even when the page is liked, the gated content is now being shown. Code below:
<?php

require 'facebook.php';

$app_id = "xxxxxx";
$app_secret = "xxxxxxxxxx";
$loginNextPage = 'http://www.facebook.com/KillegarStables/'.'?sk=app_'.$app_id;

$facebook = new Facebook(array(
        'appId' => $app_id,
        'secret' => $app_secret,
        'cookie' => true
));

$signed_request = $facebook->getSignedRequest();

$page_id = $signed_request["page"]["id"];
$like_status = $signed_request["page"]["liked"];

if ($like_status) {
// FOR FANS
$session = $facebook->getSession();
    $loginUrl = $facebook->getLoginUrl(
            array(
            'canvas' => 1,
            'fbconnect' => 0,
'next' => $loginNextPage,
            'req_perms' => 'publish_stream,photo_upload,user_photos,user_photo_video_tags'
            )
    );

    $fbme = null;

if (!$session) {
echo "";
        exit;
}
else {

try {
            $access_token = $facebook->getAccessToken();
            $fbme = $facebook->api('/me');
$user = $facebook->getUser();

$url = "https://graph.facebook.com/".$user;
$info = file_get_contents($url);
$info = json_decode($info);
$vars = "id=$user&first_name=$info->first_name&last_name=$info->last_name&access_token=$access_token&pathToServer=$pathToServer&appName=$appName";

        } catch (FacebookApiException $e) {
            echo "";
            exit;
        }

// Begin Like Gated Content.
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<link rel="stylesheet" href="style.css" type="text/css" charset="utf-8" />

Answer the following question to be in with a chance of winning a voucher for 2 riding lessions at the lovely Killegar Stables. The lucky winner will be announced on Christmas Eve, and notified by e-mail.

What Animal Pulls Santa's Sleigh?

<form method='post' action='update.php' onSubmit="return formCheck(this);">

  <input type='radio'& name='animal' value='Donkey'gt; />Donkey

  <input type='radio'& name='animal' value='Horse'gt; />Horse

  <input type='radio'& name='animal' value='Reindeer'gt; />Reindear

  E-mail
  <input type='text' name='email' id='email' size="50"/>

  Name
  <input type='text' name='name' id='name' size="50"/>

<a href="javascript: alert('1. Acceptance of these terms and conditions is a condition of entry and the entry instructions form part of these terms and conditions. By entering into the competition you agree to be legally bound by these terms and conditions. Killegar Stables reserve the right, at their discretion, to exclude entrants and/or any winner if she/he does not comply with any of these terms and conditions. \n
2.  No purchase is necessary for entry. Competition entry is via the Killegar Stables Facebook page. The Christmas competition involves answering a simple questions of what animal pulls Santas sleigh. There are 3 answers to choose from. Users are asked for email address and their name to enter the competition. \n
3.  The competition will run from the 16th November until the 24th December, Monday to Sunday inclusive. All daily entrants will go into the draw. \n
4.  A panel of judges will choose the winner on the 24th and contact the winner by email. This will be announced on Facebook oon the Killegar page. Killegar Stables reserve the right to judge the correct answer with regard to the skills test element to the competition.
5.  There will be one winner of the competition. All entrants will automatically be entered into the draw for the prize.\n
6.  There will be one overall prize winner. \n
7.  The lessons which are the prize must be taken as part of a group lesson in Killegar Stables. \n
8.  The winner is not entitled to use these lessons in relation to any pther product offering from Killegar stables or as a private lesson.
9.  The prize may not be exchanged for a cash value. \n
10. Entry to the competition will close on Friday 23rd December at 10.30am. The overall winner to be announced between Saturday 24th between 5pm and 12 midnight \n
11. The winners will be contacted via the email address provided at entry. In the event any prize winner does not communicate his/her acceptance of the prize within 24 hours of notification or cannot be located within this period, Killegar Stables reserve the right to select an alternative prize winner(s) (and the person not responding will waive his/her rights to the prize or forfeit the prize). \n

12. The email address provided by entrants will only be used for communication purposes by Killegar Stables and winners of the competition. All entries email addresses will be added to an email newsletter for sole use by killegar Stables and no pother parties. \n
13. Any delay in waiting for acceptance from winners (within the stated 24 hour period) may affect the announcing of the winners. Killegar Stables can accept no responsibility for this delay. \n
14. The finalists may be required to participate in publicity arising from this promotion including their name & profile picture being featured on the Killegar Stables Facebook wall. \n
15. No applications from agents, third parties, organised groups or applications automatically generated by computer will be accepted. Entries not in accordance with the entry instructions will not be accepted. \n
16. The Facebook competition is open to all registered Facebook users, resident in the Island of Ireland over the age of 6 except employees of Killegar Stables, their families and anyone professionally involved with this competition. \n
17. The decision made in relation to the prize winner will be final and binding on the entrants and no correspondence will be entered into.  Killegar Stables  accept no responsibility for any disappointment incurred or suffered as a result of any entrant entering the competition or accepting a prize. \n
18. In the event of any dispute the decision of Killegar Stables is final. In the event of unforeseen circumstances Killegar Stables reserves the right to substitute the prize for an alternative of equal or greater value. No correspondence will be entered into.\n
19. Killegar Stables reserve the right to change, alter or withdraw the promotion at any time. Acceptance of the rules is a condition of entry and the entry instructions form part of the rules. \n
20. Responsibility is not accepted for entries lost, damaged or delayed as a result of any network, computer hardware or software failure of any kind. \n
21. To the maximum extent permitted by the law, Killegar Stables shall not be liable for any claims or actions of any kind whatsoever for damages or losses to persons and property which may be sustained in connection with the receipt, ownership and/or use of the prize. \n
22. Killegar Stables shall not be liable for any loss, damage or consequential damage of any nature in contract, tort (including negligence) or otherwise caused by acceptance of the terms and conditions or in connection with the Prize (to the extent permissible by law). \n
23. By entering the promotion, all entrants will be deemed to have accepted and be bound by the rules and consent to the transfer of their personal data to Killegar Stables for the purposes of the administration of this promotion and any other purposes to which the entrant has consented. All entry instructions form part of the rules. If any of these terms and conditions are found by a competent court or other competent authority to be void or unenforceable, that term or condition shall be deemed to be deleted and the remaining terms and conditions shall continue in full force and effect. \n
24. These terms and conditions shall be governed by Irish law and the courts of Republic of Ireland shall have exclusive jurisdiction. \n
25. This promotion is in no way sponsored, endorsed or administered by, or associated with, Facebook. You are providing your information to Killegar Stables and not to Facebook. The information you provide will only be used on within our Facebook page.\n
             Promoter and Data Controller: Killegar Stables, The Scalp, Enniskerry Village, Co. Wicklow.
')">Terms and Conditions. Tick here to confirm you agree

  <input type='checkbox' name='terms' id='terms' />

<input name='enter' type='submit' value='Enter' />

</form>

<?
}
}
else {
// FOR NON FANS
?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<?
}
?>

I am baffled as to what the issue with this is. I have seen mention of .htaccess causing problems, but no solutions mentioned.
Answer: FB's docs say getSignedRequest returns a string, not an array.
http://developers.facebook.com/docs/reference/php/facebook-getSignedRequest/
More info here:
http://developers.facebook.com/docs/authentication/signed_request/
As the second link suggests, it's really pretty easy to do this part (decoding the request) without using FB's php sdk at all.


Confusion regarding the terms in the covariant derivative of a Tensor

Question: I am learning General Relativity from Leonard Susskind's Lectures. In Lecture three, he introduces to covariant derivatives, and I understood it's meaning. But when he applies it to a Tensor, I am having some confusion. If we consider the Tensor  $T_{mn}$ , it's covariant derivative  $D_sT_{mn}$  , he says is given as
$$D_sT_{mn}=\partial_sT_{mn}-\Gamma^t_{ms}T_{tn}-\Gamma^t_{ns}T_{tm}$$
Where  $\partial_sT_{mn}$   represents the derivative of the Tensor with respect to  $x^s$, while the Gamma's are the Christoffel Symbols. My question is that why are the contravariant indices of both the Christoffel symbols (The index t in this case) the same.
Comment: It's a dummy index. You can rename them if it confuses you.
Comment: @ApolloRa I know that it is a dummy index, but the equation won't remain the same if the said indices were different. If they were different, say t and u, then the sum (the above represents sums of equations) would contain terms like t=0 with u=1, but if there were only t, it wouldn't have such terms
Answer: The left hand side has three indices: $m,n,s$. These are free indices. In order for this equation to be correct the right hand side must have the same $m,n,s$ free indices. Indeed it does. The $t's$ are dummy indices. It doesn't matter how you name them. You can change the $t's$ (of course both $t's$ of each term or else they will not mean summation) to whatever you like. Examples:
$$D_sT_{mn}=\partial_sT_{mn}-\Gamma^u_{ms}T_{un}-\Gamma^t_{ns}T_{mt}$$
$$D_sT_{mn}=\partial_sT_{mn}-\Gamma^u_{ms}T_{un}-\Gamma^u_{ns}T_{mu}$$
$$D_sT_{mn}=\partial_sT_{mn}-\Gamma^a_{ms}T_{an}-\Gamma^b_{ns}T_{mb}$$
All the above equations are the same.
Comment: Although, shouldn't the last term have $T_{mt}$ instead of $T_{tm}$, for the covariant derivative to be correct?
Comment: @Elias Riedel Gårding Indeed yes! I didnt check the equation in the question! Thanks for pointing it out! For an arbitary tensor $T_{mn} !=T_{nm}$
Comment: I would still take my stand, this is because, the dummy indices are summed over, so if we had separate variables, in this case a and b, we sum over a separately and b separately, so there are cases in which a is not the same as b, but if they had the same  contravariant indices, there wouldn't be any cross terms, a and b must be the same.
Comment: a and b are summed over the same "numbers". Consider a four dimensional spacetime, then a = 0,1,2,3 and b =0,1,2,3. Does this makes things clearer???
Comment: Hmm okay I got the point you are trying to make, thank you