Zakat payment inquire

Question: I purchase land for resale in future by 10-15 years and every year value of land is increasing...  for example: last year if the value of land is Rupees 500000/- which paid zakat @ 2.5%  and this year it is increase to rupees 600000/-
So please advise me shall I pay zakat in rupees 600000/- or increase in the value of land by rupees 100000/-
Comment: I think its today's price
Answer: In the Name of Allah, The Most Gracious, The Most Merciful.
When you pay zakat, you have to pay 2.5% of that which you own. So if you have 100,000 dollars, you have to pay 2,500 dollars AT LEAST. You can pay more if you want, but the extra you give is considered as "sadaqa", not as zakat.
As for your question; you have to give 2.5% of all your wealth the moment you give zakat. So if you decided to give zakat tomorrow, and everything you own is worth one million (right now), then you have to give 2.5% of what it's worth now, so 25 Thousand (of one million).
In your case, you have to pay 2.5% of 600k Rupees. So yeah, you always have to take today's price.
I'm not a scholar, so if someone disagrees with me, and comes with proof that I'm wrong, please share it, so that we may benefit.
Allah knows best.

Zakat payment inquire


Partial travel insurance

Question: Are there insurances available that can be tailored to cover specific needs. E.g. my luggage is already insured through my credit card provider, health insurance is provided through my employment insurance, but my electronics are not covered (also missed flights are not covered). Are there insurance companies that allow me to tailor insurance to "fill the gaps", or is it cheaper to get default insurance (despite the fact that I'm overinsured)? Any information on saving possibilites?
Comment: There are insurance policies that are available to fill various gaps.  You might want to clarify which gaps.  In the US "gap insurance" usually refers insurance for what's not going to be covered by your regular auto policy usually on leased vehicles.  Plus you may want to check what's covered under your employment medical policy when it comes to travel.
Answer: The best and cheapest option is not to get these insurances (with the exception of health insurance, which you already have - but make really sure it actually covers travel).
One thing you have to understand is that on average, buying insurance is always a net loss for you. The expected value (probability of the insured risk occurring multiplied by the payout sum) is always considerably smaller than what you pay in premiums, since otherwise the insurance companies would not earn money. They have the world's topmost experts on statistics working for them as actuaries to ensure that insurances are always a net loss for the customer.
If an insurance seems "cheap", it's because either

The insured risk does not occur as often as you think
It does not cover as many cases as you think (e.g. most luggage insurances will deny your claim in cases of theft if you so much as set down the luggage for a second without looking at it.
or it does not pay out as much as you think (e.g. electronics may be only covered for their current used value, not the price of a similar new item).

So why buy insurance at all? Because there are some risks that can completely bankrupt you and which you therefore cannot bear; chief of these are medical treatments, disability and liability. Insuring against these is important.
Other insurances are a waste of money; people buy them basically for peace of mind and might argue that this has a value of its own, but I submit that this value disappears once you consider the factors described above and the fact that even if your claim is approved, all you get is money, not e.g. your luggage back, and only after you jump through a lot of bureaucratic hoops.
You're much better off not buying them and instead putting the money into an "emergency account" where you keep few thousand dollars to cover, well, emergencies. This is much more flexible and actually saves you a lot of money (you don't have to pay for the insurance companies' expenses and profits).
Comment: +1, although I remember reading once that the actual underwriting often ends up being zero profit/loss, and the money comes from having that big pile of premiums lying around to invest with...
Comment: @AakashM: depends on the kind of insurance. In the case of travel insurance, I doubt that's a factor. And in any case, their investment gain is your investment loss.
Comment: @MichaelBorgwardt : I find your advice quite dangerous. Yes, in some cases insurances are irrelevant because the risk is very low. But do you really want to travel to dangerous countries (i.e. all across latin america) with valuables (i.e. camera, laptop, cash, credit cards, passport, driving license, & more) and just hope for the best!? Not me. I know that my chances of getting robbed or mugged would be high, hence I'd be more than happy to pay a reasonable monthly fee to insure my valuables.
Comment: @AdrienBe: I find your beliefs quite irrational. First of all, it's not as if the insurance will prevent the loss. You'd still have exactly the same bad experience, hassle of having the stuff replaced and loss of intangibles (such as pictures). You will merely get reimbursed for the *used* value of the items, *if* the insurance company doesn't find a reason to deny coverage (which they are very good at). Also, you do *not* know the chances of getting robbed or mugged as well as the insurance company - they are making a healthy profit by knowing it better than you.
Comment: @MichaelBorgwardt : I know what I pay the insurance for, that is, to give me back part of the value of what was stolen. I understand what you mean by having the same bad experience, unfortunately, that you cannot always avoid. Yes, insurances will try not to pay you back and you'll probably have to chase them, that's quite typical. Let's not go into too much debate, the main point is, do you want to have the peace of mind that if you get your stuff stolen or broken an insurance will give you back its value? If yes, then pay for it. If not, just don't take it.

Partial travel insurance


FAQ Schema Markup

Question: All of my website service pages have a FAQ section with different questions and answers for each page. Would the FAQ schema markup be eligible here? Or does it need to be a single FAQ page?
Comment: Which type do you mean with "an FAQ schema"? Did you check its definition?
Answer: Based on schema.org FAQpage definition A FAQPage is a WebPage presenting one or more "Frequently asked questions" so there is no mention that the FAQ page must be a dedicated page, separated from the content it provides answers for.
On top of that, you can (and most sites do) use multiple schemas in the same page to describe the different data that are presented on it, so it is safe to use the FAQpage schema alongside any other schema that page already has, without worrying that the FAQ section should be in a separate page.
Answer: Schema.org doesn't make suggestions, how to design your internal architecture. But it supports any architecture.
I would design FAQ sectors so, as it is easier to your visitors to get their info. Let usability guide your design. Schema.org allows pretty everything.

FAQ Schema Markup


Momentum Operator in curved spacetime (QFT)

Question: In flat space we have $$\hat{p}_\mu=-i\hbar \partial_\mu . $$ Does this still hold in a curved spacetime (particularly Schwarzschild space)?
Answer: In the paper [1], p.111, it is said that the operator of the square of momentum on a curved $n$-dimensional pseudo-Riemannian manifold is:
$$
P^2 = -\hbar^2 \left( \square - \frac{n-2}{4(n-1)}R \right)
$$
Here, $R$ is the scalar curvature.
This $P^2$ is the analog of the classical one $g^{\alpha\beta}p_\alpha p_\beta = m^2 c^2$.
The inclusion of the scalar curvature $R$ is required by conformal invariance of zero mass scalar field. In the case where $n=4$, we have the analog of the Klein-Gordon equation on a curved space-time:
$$
\left(\square - \frac16 R\right) \varphi + \left(\frac{mc}{\hbar}\right)^2\varphi = 0
$$
They say that this equation was considered by Penrose [3] in 1964.
The "non-relativistic" limit of this should be Schrödinger equation where $R$ appears
:
$$
\hat{H}\psi = -\frac{\hbar^2}{2m} \left(\Delta - \frac16 R\right)\psi
$$
This equation can also be found via geometric quantization of the hamiltonian responsible of the geodesic flow, see [2], eq. (7.114).
Now, what is $\hat{p}_i$ on a curved space ? According to geometric quantization (see again [2], eq. (7.42) (7.82)) it is given, at least in the non-relativistic limit, by:
$$
\hat{p}_i = -i\hbar \left(\partial_i + \frac12 \mathrm{Div}(\partial_i)\right)
$$
Here, $\partial_i := \partial/\partial q^i$ and $\mathrm{Div}(\partial_i)=|\det[g]|^{-1/2}\partial_i(|\det[g]|^{1/2})=\Gamma^k_{ik}$ is the covariant divergence of the vector field $\partial_i$.
Now, what is $\hat{p}_\mu$ ? I guess it would be $-i\hbar \left(\partial_\mu + \frac12 \mathrm{Div}(\partial_\mu)\right)$, but I'm not sure.
So, to answer your question : Does $\hat{p}_\mu = -i\hbar\partial_\mu$ still hold in a curved spacetime? I would say no. There should be at least some divergence term $\mathrm{Div}(\partial_\mu)$ somewhere.

Remark :
According to the Wikipedia sign convention :
$$
\Gamma^k_{ij} := \frac12 g^{km}(\partial_i g_{jm} + \partial_j g_{im} - \partial_m g_{ij})
$$
$$
R^l_{kij} := \partial_i\Gamma^l_{jk} - \partial_j\Gamma^l_{ik} + \Gamma^l_{im}\Gamma^m_{jk} - \Gamma^l_{jm}\Gamma^m_{ik}
$$
$$
R_{ij} := R^k_{ikj} = \partial_k \Gamma^k_{ij} - \partial_j \Gamma^k_{ik} + \Gamma^l_{ij}\Gamma^k_{kl} - \Gamma^l_{ik}\Gamma^k_{jl}
$$
$$
R := g^{ij} R_{ij}
$$
the "good" sign is $\square - R/6$ as in [2], p.180, and not $\square + R/6$ as in [1] and [3]. Also, even if [2], p.133, has a different definition of the Riemann curvature and scalar curvature, at the end of the day the scalar curvature according to [2] is the same as the one written here.

[1] : Quantum theory of scalar field in de Sitter space-time, N. A. Chernikov and E. A. Tagirov, 1968
[2] : Geometric quantization and quantum mechanics, J. Sniatycki, 1980.
[3] : Conformal treatment of infinity, R. Penrose, 1964.
Answer: A short-ish answer to this : $\hat{p}_a = -i\hbar \partial_a$ is not appropriate for the momentum operator due to the fact that it is not self-adjoint. As a reminder, $\hat{p}$ is hermitian if
$$\langle \psi, \hat{p}_a \phi \rangle = \langle \hat{p}_a\psi, \phi \rangle$$
In a curved space, that will be
$$\langle \psi, \hat{p}_a \phi \rangle = \int \psi^* (-i\hbar \partial_a \phi) \sqrt{g}\ d^3 x$$
Integrating it by parts,
\begin{eqnarray}
\langle \psi, \hat{p}_a \phi \rangle &=& -i\hbar [\psi^* \phi ] + i\hbar \int \partial_a (\psi^* \sqrt{g})  \phi d^3x\\
&=& -i\hbar [\psi^* \phi ] + i\hbar \int \left[ \sqrt{g} \partial_a (\psi^*) + \psi^* \partial_a (\sqrt{g}) \right]  \phi d^3x\\
&=& -i\hbar [\psi^* \phi ] + i\hbar \int (-i\hbar (\partial_a + \frac{\partial_a \sqrt{g}}{\sqrt{g}}) \psi)^* \phi d^3x\\
\end{eqnarray}
It's not actually true that wavefunctions tend to 0 at infinity, but the boundary term can be neglected. We still have an extra term, though, which can be gotten rid of by using
$$\hat{p}_a = -i\hbar(\partial_a + \frac{1}{2} \frac{\partial_a \sqrt{g}}{\sqrt{g}})$$
From differential geometry, we also have that
$$\frac{\partial_a \sqrt{g}}{\sqrt{g}} = {\Gamma^b}_{ab} = \Gamma_a$$
so
$$\hat{p}_a = -i\hbar(\partial_a + \frac{1}{2} \Gamma_a)$$
This is both self-adjoint and obeys the canonical commutation relations.
Comment: I ended up figuring this out independantly. But I sincerely appreciate this write up for future students! One thing to remember is the $\sqrt(g)$ is the determinant of the spacial metric, not the whole spacetime metric
Answer: This operator exists in flat spacetime because one has translational symmetry $x^\mu \to x^\mu + a^\mu$. This is no longer true in generic curved spacetimes. So no, there is no momentum operator in curved spacetimes.
That being said, quantum mechanics/field theory is well-defined only in spacetimes which are globally hyperbolic, i.e. those that have a globally time-like Killing vector $\xi$ (with $\xi^2 < 0$). In such spacetimes, there is a time-translation symmetry so there exists a Hamiltonian operator ${\hat H} = - i \hbar \xi^\mu \partial_\mu$. In Schwarzschild spacetime, $\xi = \partial_t$.
Comment: The existence of a unitary operator does not imply the existence of a symmetry. It is only a symmetry if it preserves the Hamiltonian. The absence of translational invariance does not mean that momentum doesn't exist, just that it isn't conserved.
Comment: I don't know why you say the momentum operator cannot apply in curved spacetime. You can write the full energy-momentum relation as in context with a Dirac Hamiltonian in curved spacetimes. Such things can exist.
Comment: Existence of a Hermitian operator such as ${\hat p}$ implies (via exponentiation) existence of a unitary operator ${\hat U} = \exp ( i a {\hat p} )$ and existence of such a unitary operator implies a symmetry (since we can transform all operators via the unitary transformations $O \to O' = U O U^{-1}$ and unitary transformations preserves correlation functions). In the case of the momentum operator the corresponding symmetry is space or time translations. In a generic curved background such symmetries simply do not exist!
Comment: @GarethMeredith - In any local quantum field theory on a curved background, there continues to exist a local energy-momentum tensor $T_{\mu\nu}$ which is covariantly conserved $\nabla^\mu T_{\mu\nu} = 0$. This does not however imply existence of a translation generator $p_\mu$.
Comment: The Dirac equation and the Dirac Lagrangian/Hamiltonian CAN be written down in curved spacetimes. What I do not understand is what that has to do with the momentum operator. There EXISTS a covariant derivative $\nabla_\mu$ which acts on field operators, $\Psi(x) \to \nabla_\mu \Psi(x)$. However, note that $\nabla_\mu$ is acting on the fields, NOT on wave-functions in a Hilbert space. There DOES NOT - in general - exist a momentum operator that acts on wavefunctions on a Hilbert space.
Comment: So explain why we can construct the Dirac Hamiltonian on curved spacetimes? That involves an energy and momentum operator.
Comment: @GarethMeredith I have explained this in my answer already - Quantum theories are defined on globally hyperbolic spacetimes which have the special property that they have time translation invariance (for a particular definition of time). Since we have a time translation symmetry the corresponding Hermitian operator - namely the Hamiltonian - does exist! So to be clear, if the spacetime is globally hyperbolic (which is almost always the case), one CAN define a Hamiltonian operator. However, one CANNOT - in general - define a full MOMENTUM operator.
Comment: No you haven't explained anything. I keep asking you how a Dirac equation can be modeled on curved spacetime, and you keep hitting out with this time translation invariance, which is really not the point here. I am asking a direct question, if there is no such thing as a momentum operator in curved spacetime, how can you have a curved Dirac equation, its a simple question which should have a simple answer.
Comment: And I'll assume you know the Dirac equation...? It too has a momentum operator after second quantization and curved models of this equation are well known to exist.
Comment: Right, so what is the Dirac Hamiltonian, do you know it off by heart? Not the quantized version, to keep this simple.
Comment: Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/91973/discussion-between-prahar-and-gareth-meredith).


How do I get my USB keyboard to not freeze up in the recovery menu?

Question: I am using Ubuntu 11.10, and whenever I enter the recovery menu, my keyboard freezes and I can't make any selections. I have tried using GRUB_PRELOAD_MODULES="usb usb_keyboard" but this doesn't help at all.
The keyboard works in the BIOS screen and in Grub (i can select an OS, write to the command line, etc.) but as soon as i get to the recovery menu it stops working. If i had the numlock on it will stay lit and i cannot turn it off, if that helps
Comment: I have the same problem with my Apple USB keyboard. There is a bug report in Launchpad about this problem: https://bugs.launchpad.net/ubuntu/+source/friendly-recovery/+bug/203385
Comment: This question should instead be filed as a bug report, thanks! [Instructions here](http://askubuntu.com/questions/5121/how-do-i-report-a-bug).
Answer: I had the same issue and finally got it resolved.
I had to unplug all my usb devices besides the keyboard (maybe there was just one that caused the issue, but I didn't want to try all possibilities). I also had to add 'acpi=off nohz=off' to my boot line in grub (hit 'e' in grub while the recovery mode is selected to change the boot line).
Comment: I tried only the code and it didn't fix it for me (I didn't try removing all of my other USB cords - maybe that would have solved it)
Answer: I had the same issue today, and with Johannes' answer was able to solve it - unplugging all USB devices except the keyboard worked.
Note though - when I first tried adding the suggested 'acpi=off nohz=off' to the boot line in grub, the keyboard was still non-responsive in recovery mode.
Trying again but NOT adding 'acpi=off nohz=off' did work.
Also, tried various combinations of USB devices (mouse, keyboard, external USB HD, ext USB hub on monitor), and the only combination that worked was "keyboard only".
Also tried adding/removing devices when the Recovery Menu was 'frozen' and it displayed alerts that devices were added or removed (always device 2 though).


Identification of a transfer function

Question: Can you obtain a transfer function in frequency domain with a bode plot form given by this function:
$$ S=k_1 \sqrt{1+\frac{k_2}{f}} $$
I did not managed it because actually in the lowest part of frequencies decreases with 10dB/dec. So is not a simple pole (20dB/dec) and zero function.
Maybe it is possible to obtain such function by adding many low pass filters.
Any idea?
Comment: These questions are related and may be helpful: [Q1](https://dsp.stackexchange.com/q/27520/4298), [Q2](https://dsp.stackexchange.com/q/28514/4298), [Q3](https://dsp.stackexchange.com/q/46705/4298)
Comment: I think maybe you are confused it's already in frequency domain please check it out.
Comment: @Ch.SivaRamKishore The purpouse is to obtain a transfer function with a form similar to the plot of S(f). Off course, the S is dependent by the frequency but not expressed in term of s.
Answer: The objective is to produce noise, presumably Gaussian distributed, that has both white and 1/f components. This is evident from the desired power transfer function, i.e., the square of the OP's "S" expression, which would be used to convert input white noise to output white plus 1/f noise. The  OP does not state whether the PSD should be unilateral or bilateral, so it will be assumed, without loss of generality, to be unilateral. Hence the unilateral noise PSD is
$$\mathrm{S^2 = k_1^2(1+k_2/f)} \tag{1}$$
where $\mathrm{k_1^2}$ is the unilateral noise PSD of white noise only, with units of $\mathrm{V^2/Hz}$ and $\mathrm{k_2}$ is the noise corner frequency, with units of $\mathrm{Hz}$. In a digital simulation,
$$\mathrm{k_1^2} = 2\sigma^2 /f_s = \sigma^2 /f_{nyquist} = 2\sigma^2 \times \Delta t    \tag{2}$$
where $\sigma$ is the standard deviation of the Gaussian white noise (units: V), $\mathrm {f_s}$ is the constant sampling frequency (units: Hz), $\mathrm {f_{nyquist}}$ is the Nyquist frequency (units: Hz), and $\mathrm {\Delta t}$ is the constant sample time spacing (units: s).
To generate the noise, first select parameters in accordance with equation 2. For example, if it is desired to have $\mathrm{k_1^2} = 5.00 \times 10^{-8}$ $\mathrm{V^2/Hz}$ and $\mathrm {f_s} = 1$ $\mathrm{kHz}$, then $\sigma = 0.005$ $\mathrm{V}$. This is the standard deviation entered into the Gaussian white noise generator in the figure below:

The second step is to specify $\mathrm{k_2}$. Using the noise generator described previously here, it is not feasible to directly enter a noise corner frequency into the non-white noise generator code. However, it is necessary to enter the desired low limit and high limit for the non-white noise, as shown in the dialog box in the figure, so the high limit can be adjusted empirically to obtain the desired noise corner frequency. Note that $\gamma = 1$ generates $\mathrm{1/f}$ noise and there is an optional gain adjustment as well.
The next figure shows a temporal trace of the noise produced with $\mathrm{k_1^2} = 5.00 \times 10^{-8}$ $\mathrm{V^2/Hz}$, $\mathrm {f_s} = 1$ $\mathrm{kHz}$, $\sigma = 0.005$ $\mathrm{V}$ and the non-white noise parameters shown in the first figure:

Then the third figure shows the average of 1000 32k FFT PSDs:

The noise corner frequency is where $\mathrm{f = k_2}$. From the plot, this is about 1.6 Hz or so.
If this noise was the dominant one in an experiment, and if the signal was baseband, then the measurement would be afflicted with $\mathrm{1/f}$ noise and all the annoying consequences that entails. But if it was feasible to modulate production of the signal, before the signal encountered the noise, then the signal could be deliberately located in the white noise 'flats' and a lock-in amplifier could perform the customary demodulation.

Identification of a transfer function


Do I need anything over the wall board around wood trimmed garage door openings?

Question: I am replacing all the wood trim around my garage door openings. The trim butts to vinyl siding with j-channel. The siding at the top of the doors had no flashing or trim cap and that is where the water got in. I am installing flashing above the door trim. The wall itself only has chip board (I guess it is really called OSB) behind the siding. Should I install some sort of tarpaper or plastic behind the siding a few inches along the top and sides of the opening before putting up the new wood trim? Seems like another disaster waiting to happen with just bare chip board behind the siding. I pulled out a bunch of soggy chip board where the leak occurred at the top. The chip board had soaked up the water like a sponge! North facing wall which gets snow and ice in winter. Moss growing in J-channel above door due to lingering moisture.
Comment: User last seen September 29, 2014. Mods, close?
Answer: I would put some flashing there. I was just doing some work on my back door and while it leads directly to the house not the garage. There was some flashing that went under the siding and over the trim. (For the horizontal piece) You're right OSB does soak up water pretty well. Once wet it doesn't stay together very well either.
Answer: This is one of the drawbacks to what I refer to as "the caulkless era" of exterior construction, before housewrap and other drain-plane measures were written into code. All those channel joints with no protection from driven rain (and your header trim sans flashing to boot).
Consider the drain route for water coming off the flashing you're installing. Unless it has a positive slope forward, much of it's likely to run to the ends and down the side trim. Do what you can to properly lap a water barrier behind the flashing and down beyond the sensitive materials on the wall.
For more help, please post a photo.


Hanging Large Framed Prints on Plaster

Question: What REALLY works for hanging pictures on old plaster walls--the kind with cement not too far beneath a skim coat of the white stuff (technical term).  I bent four nails "specifically designed" to hang pictures on such a structure--even after drilling pilot holes; + broke a drill bit in the process!
Comment: Walls are not made out of cement. Choices are: (1) lathe and plaster, (2) gypsum drywall, (3) fiber board, (4) cinder block, (5) brick, (6) stone, (7) concrete (if you live in a parking garage), (8) logs
Answer: The best bet is to find a stud and use a heavy nail or screw.
If that isn't an option for the print's sake, I've had luck in such walls with toggle bolts before. It can be hit or miss with screws and even mollies and screws in tandem because behind the plaster and cement are 3/8" thick by 1 3/8" wide strips of wood spaced 3/8" apart called lath, which is what the gray cement (the "scratch" coat) squishes into when wet and locks into once dry. You'll drill a hole and you might hit wood (lath), or you might hit air, and which you hit will affect a fasteners ability to hold in the hole, and it's often a crap shoot on the first hole or two going in blind. A toggle bolt works well in these walls because the "wings" of the bolt have a good chance of catching the back of at least one strip of lath and hopefully more, no matter where a hole is drilled, giving it a good purchase and a high chance of success on the first try.
Don't even bother with nails in these walls unless your certain you're driving one into a stud. You're liable to break loose burgs of cement and plaster, and yes, bend nails, because the elasticity and memory of the wall across open space is high and the energy of your hammer blow will be mostly directed back at you and the nail itself.
You'll want to use masonry drill bits for any drilling in these walls. The cement beneath the skim coat of plaster will chew up any others almost immediately.

Hanging Large Framed Prints on Plaster


Where are my barrel adjusters for my shifting cables?

Question: I have a Devinci Caribou I and I was trying to adjust the front derailleur. I got the top and bottom stops adjusted right, but it seems that it doesn't downshift correctly from the biggest cog to the intermediate cog.  From reading on the internet, I've seen recommendations to adjust the barrel adjustment to fine tune the derailer. Only problem is I can't find the barrel adjustment.  The shifter cables come right out the side of the brifters, and there's no adjustment there. They go through the frame, and come out near the bottom bracket.  On the cable housing there's something that can be turned that seems like it could be a barrel adjuster, but turning it creates no changes in derailleur position.  This turnable part of the cable housing is present on both shifter cable. There is functioning barrel adjuster for my rear brakes, but this is quite different then the possible barrel adjustment for the shifter cables (and it actually works).  Can anybody help me out finding my barrel adjuster?  Here is a picture of the model that I have, although it's hard to see any of the cabling in this picture.
Comment: If all else fails, take it to the shop where you bought it and ask them to show you the barrel adjusters.
Answer: Looks like there's an adjuster in-line, right before the cable enters the down tube.
Comment: Looking at the picture, I assume you mean the black piece about 2 inches from where it enters the down tube. This picture is different then mine, because mine is from the previous year, but that appears to be the same mechanism I have on my bike, that doesn't actually do anything.  Not sure if you can tell from the picture, but that mechanism is a different shape than the barrel adjuster on the brake cable that you see a little bit above that when you zoom in on the picture.  On my bike the "barrel adjuster" you see is actually located about 3 inches from where it comes out of the brifter arm.
Comment: That gizmo must be there for some reason.
Answer: It is  the black piece about 2 inches from where it enters the down tube.
That is the barrel adjuster, but in line adjusters can be difficult get started adjusting, as often they come from the factory with the 2 halves of the barrel adjuster turned tightly against each other.
That makes it appear to do nothing, when in fact the reason it is doing nothing is because it is rotating around the cable housing, rather than activating the adjustment.
Try to hold one half still, while rotating the barrel. Once it is broken free it should work normally. If not, then take it back to your LBS, and ask them to do it, as you will likely have to remove it from the bike to get it free.
Comment: Thanks for the tip. It was indeed the barrel adjuster, but it was hard to get it going. There wasn't much to hold on to on the one side, but after some fiddling, I got it started. Fixed my problem.
Answer: You shouldn't need too much adjustment in your FD via barrel adjustments. If your cable is stretched or your not getting clean shifting just readjust your FD, it doesn't take that long and there are a lot of tutorials out there:
http://www.parktool.com/blog/repair-help/front-derailleur-adjustments
Comment: You need barrel adjusters because of cable stretch.  A brand new cable will need adjustment within a few days, and it's a royal PITA to try to reset the cable (exactly!) to get proper adjustment.  To quote the site you linked "To reduce gap, increase inner wire tension by turning *barrel adjuster* counter-clockwise."
Comment: i realize you need barrel adjusters, that's why i said "you shouldn't need MUCH adjustment". Additionally, adjusting a FD is not a royal PITA. I've adjusted mine over a lunch break from work. Anyway...all this is moot since his question has been answered above. They are right there above where his cables enter the frame. Most modern road setups don't have anything but a micro adjust barrel adjuster because you don't need anything else.


What are the "tails"?

Question: While reading an article on home brewing the article said to keep the tails, what does it mean by tails? What are the tails?
Comment: Can you post a quote where it is used? Without context - I have no idea.
Comment: Are you sure it was homebrewing and not an article related to distillation?
Comment: @brewchez that makes sense, but I can't figure a use for distillation tails, maybe as a fuel or solvent?
Comment: Can't find the article I read it on to save my life, I have gone through my search history but no luck, but Evil Zymurgist nailed the question.
Comment: I've heard the term used in moonshine distilling.  The tails is the last of the liquid you get from the distillation process. It's a mix of good ethanol and harmful  alcohols, so you don't want to drink it. However, it can be thrown into your next batch to boost the quantity of ethanol you get in your next batch.
Answer: Tails or Tailings is what's left of a material after it has been processes and something more valuable has been removed. Though a term used in mining more than homebrewing.
In brewing this will refer to making use of...
1) Second runnings from a mash, parti-gyle. Great for a second a batch of a smaller beer or for yeast starter wort.
2) Making use of spent grain for baking or compost
3) Yeast trub. The gunk on the bottom of the fermentor. This is mostly yeast, hops, etc. Use this to grow more yeast, or even pitch a seconds batch of wort right on top.
Comment: Yes using this in context with what I remember reading makes very good sense.

What are the "tails"?


Can I host wordpress separately on one hosting account?

Question: I have a client who would like an auction site. I have decided to use Wordpress for this and found proper hosting and what not and thought I was set. Then the client asked if I could save time and money on their part by hosting this event site on their main site as well as their domain. IE: www.123.com/auction. The main site was not created by me and is not powered by WordPress. It is also hosted by some sort of "school community" website platform. Is it even possible, If I can access the file manager in the first place, to host a wordpress database and CMS separately on one hosting account for what is pretty much an entire different web page. Is this even practical?
Answer: Assuming that the hosting account is capable of meeting the minimum requirements, yes, you can install WordPress in a subdirectory of an existing site.
See more info here:
https://codex.wordpress.org/Giving_WordPress_Its_Own_Directory


How would I develop AGFA Moviechrome 40 film?

Question: I recently was crawling through old boxes and came across my grandfather's old Canon Zoom 518-2 Super 8 video camera. Inside was a cartridge of AGFA Moviechrome 40 film. I'm wondering where/how I'd go about getting this developed and was wondering if anyone had any suggestions?
Answer: You could try giving Film Rescue International a go. Their FAQ predicts the results of Moviechrome to be on "poor" quality level, and  people seem to agree.
There's also Rocky Mountain in US; Process C-22 and FotoStation in UK.
Comment: Thanks four your answer, Imre. I got in touch with Film Rescue International. Their prices seem pretty reasonable. Have you had any first-hand expereience with them?
Answer: AGFA 40 film is from the 70's and film processing has changed a huge amount since then, and I don't think the old processing even exist anymore (in shops or repo centers) Instead of trying to replicae the old proceess the developers will just process as they would B&W film.
If they do this (which is very likely) then you will end up with very flat and grainy images that unless they have some value wont be worth looking at.
However as with this type of thing curiosity is a very funny thing and i'm sure I would just give it a go to see what comes out.
(p.s this question is slightly off topic as it is about videography)


Is vitamin D a very passive xenogenic factor to major depressive disorder?

Question: Are the biosynthesis, utilisation and catabolism systems of vitamin D, especially the pathways of neural cells' vitamin D response, altered by the pathophysiological condition of major depressive disorder? If so, can antidepressant drugs restore that? (Assume the dietary uptake and ultraviolet exposure are normal.)
Comment: What makes you think it is?
Answer: As someone who has been diagnosed with severe vitamin D deficiency, I can tell you from my personal experience that low vitamin D levels almost always makes you feel sad and depressed (we are talking about the chronic type). And since the levels take a lot of months to rise to normal, this lower mood levels start to become a part of your life.
The vitamin D receptors are linked to the areas of the brain associated with depression.
There have been many studies to prove this is true. A quick google search will point you to many more studies.
Anti-depressant drugs help in most cases, although the doctor should decide more on this. Almost always as the vitamin D level starts to rise, it does take care of this.


Facebook: How to hide 'Work and Education' from specific people?

Question: In Facebook how to hide my "Work and Education" or "About You" details from specific people? Is there a way to hide from specific people?
Answer: If you want hide any section from your few friends from your timeline, just set audience as Custom.

Go to your timeline.
Click on About.
Click on the section you want to edit from left hand side and select the subsection from right hand side, click on pencil symbol to edit.
Now select audience as Custom and then Specific People or Lists...
You will see Don't share this with These people or lists option, write your friend's names (or lists) with whom you don't want share information about you.


Preparing for a throw, when forwarding ether to another contract?

Question: If a contract has a payable function, which forwards ether to another contract, but the second contract throws, how can you properly prepare for a throw in the first contract? Will the throw leave the money in the first contract, and if so can you return this money to the initial msg.sender?
Answer: Very important to follow a safe three-step process.

Optimistic accounting (counter-intuitive but correct to do it first)
Try the send() and check the result (true or false).
On fail, either revert the accounting step-by-step, or throw (which reverts state changes including the account, returns the ETH and destroys the gas in one move.).

Example (Simplest interpretation I know with a full stop):
function forwardFunds(address recipient) payable returns(bool success) {
  LogForwarded(msg.sender, msg.value, recipient);
  if(!recipient.send(msg.value)) throw;
  return true; // doesn't make it this far in case of trouble
}

If the receiver throws, this function will throw as well, the event (i called it LogForwarded) that represents the "accounting" step will not occur and the received msg.value will be returned to msg.sender. Nevermind that the accounting event appears to come first, because throw will reliably revert that state change.
Check out "Reentrancy" and other stuff here: https://github.com/ConsenSys/smart-contract-best-practices. The three-step process above covers your concern and also synthesizes the know-how described (in the link) into a pattern I find easy to remember and apply consistently.
Hope it helps.


What kind of rock could I use in my mountains?

Question: in my world there is a mountain system where most of the rock is some kind of material or mineral that conducts heat very well. So much so that there is no snow on the peaks as it melts quite quickly if it falls. I would also like to take advantage of these properties so that the civilizations that settle there can use the geothermal energy of the mountain system as their main source of energy. Is there any mineral or rock type that exists that could have these properties? Also, if this mountain system were huge, for example as large as the Alps, what consequences would it have for the climate?
Comment: I'm not 100% sure, but isn't it more about having a very hot mountain rather than having a heat conductive mountain? If it is the latter, you'll get something akin to a sand desert, where temperature rises and drops very quickly as heat sources come and go.
Comment: If it conducts heat well, that means it'll conduct cold as well. Snow could still cool the top of the mountain.
Comment: What is the link between "rock which is a good thermal conductor" and "use the geothermal energy"? Why would the snow melt when it falls on a good thermal conductor? Anyway, the point is that the thermal conductivity of minerals varies extremely widely, with diamond being thousands of times better than limestone at conducting heat. (Some widespread minerals, such as pyrite or haematite, have thermal conductivities comparable to steel.)
Comment: I think you have a misunderstanding WRT geothermal energy.  Unless the mountains are volcanic, you're not going to find geothermal sources IN the mountains.  They'll be along the edge of the mountains, where uplift & active faults are located.  Take for example the Sierra Nevada, which is a block being uplifted on the east.  That eastern edge has many hot springs & at least one large geothermal plant, but there are few if any in the mountains to the west.  You have to go nearly to the coast (near Clear Lake & the San Andreas fault) to find California's major geothermal plants.
Answer: Diamond!
I recycled this answer of mine from here:  How would a 30-kilometer tall mountain on an Earthlike planet look?
These folks want a tall mountain but as a bonus it was a hot mountain too because of the thermal conductivity of diamond.

A mountain of diamond seems so trite, but really it would be better in many respects.  Lets get it over with.
So diamond: density of 3.5 and compressive strength of 60 GPA;  maximum mountain height is 196 km
These diamonds would have been formed in the atmosphere of a ancient gas giant and then incorporated in the crust of this Earthlike world.  I envision this huge, partly fused mountain of diamond extending farther down below the surface than it does above.  Despite the huge mass balanced on one point, it does not sink further down because the bottom of the mountain is floating in denser, partly metallic molten materials.  The diamond mountain is essentially an iceberg in the crust.
This also gives insight into how this diamond iceberg mountain would look.  There would be no plants on it and no ice or snow.  Diamond is one of the best thermal conductors there is.  With its big bottom side down into the mantle, the entire thing would be very hot.

my own assembly.  mount hood with uncut diamond
.
Comment: @Tortliena - maybe you could have nondiamond inclusions in the big diamond, that were more amenable to tunnelling.
Comment: And now you've brought down the value of diamonds to the one of dirt :D. I guess you'd need to dig down or a little to avoid the cold air and get the most temperature of it. I recall that diamonds are extremely hard but easily breakable; How easy do you think it'd be easy to dig a tunnel inside?
Answer: The remains of coal mining
In regions where coal mining was predominant, it was common to put the waste of mining aside, shaping a cone, usually dark in color. Over time, they form spoil tips, which easily reach 150 m in height, but I guess it could go further and higher if people continued to look for coal.

A "terril" or Spoil tip at Loos-en-Gohelle, North of France1
As far as I am aware, this composition has a triple effect to heat : First it's black, so any ray of sun will get absorbed, increasing its temperature. Then, it is often subject to internal combustion, increasing the temperature increase. Finally, because of various chemical elements, plant life has a much harder time growing on it, giving less freshness and therefore more heat.
Things to take into account
Unless your world is able to directly transfer "low" heat (as in under water ebullition point) into mechanical energy, you'll probably will never get what you wish.
Indeed, it's already hard to get a whole place to burn over long period of times. Yes, there are "red" volcanoes, but high temperatures are reached only in places where you don't want to put a long term-infrastructures, such as a power plant :p. Moreover, even if you do find a place with a high-enough temperature, you'll only be able to build on its surface without killing your workers, which drastically reduces the power output and maneuverability in and out of your mountain. Recall : If the heat of your mountain is high and easily transmitted, then any of your power-plant operators will quickly suffocate, even if they're equipped with protective equipments.
My suggestion isn't perfect either, as the coal remains are quite unstable by nature, due to the way it has been formed or/and by the explosive components inside. You should expect explosions and possibly landslides from time to time.
Still, given the Steampunk tag you've put on your question, I guess it's quite in sync with what nearby populations could have done over a very long time :).

1 : Picture courtesy of Wikimedia Commons, Author : Sylvain Beucler, CCA 3.0
Comment: You don't have to justify when it's easily seen in nature. Cotopaxi in Ecuador is a volcano that is largely formed out of basaltic andesite, which is black to very dark gray to dark brown in composition, and is actually darker than that pictured waste pile. It sits on the equator, so maximum year-round exposure to sunlight. It also has a permanent snowcap (except for the parts that melt when it erupts).
Comment: black and lifeless will make it colder not hotter at mountain altitudes.
Comment: @John Lifeless, perhaps, but black? Black objects absorb all energy, as opposed to white ones which reflects everything (on the visible scale, at least). This energy shakes up the molecules, increasing therefore warmth. It's also the reason why you should wear sunglasses when you go skiing, as you take on all UVs from the snow that acts like a mirror because it's white. You should explain why it acts differently at high altitudes.
Comment: @KeithMorrison That doesn't mean that black color makes an object colder than grey or white at high-altitudes, which is -I remind you- the affirmation. Watch out for logic shortcuts here!
Comment: It's... hmm... like you're trying to prove that a specific car is broken because it doesn't have fuel by sinking it deep in water. Yes, of course the car won't move, but does that mean the lack of fuel is the fault? For the mountain sake, there is a limit to the efficiency of one component, you have to play with others to increase the height you have no snow cap.
Answer: Its impossible without handwavium.
No matter how good a thermal conductor you make it that will just result in the rock being colder not hotter. Even active volcanoes develop snow on their peaks. All you are doing is cooling your heat source faster. Note the peaks of mountains often have little to no snow just because they are steep, most of the snow is in the valleys.

Good news geothermal energy is completely usable without any magic properties.
If the mountain range is mildly volcanic it will supply plenty of energy. volcanic geothermal can be used for dry steam power generation which is very efficient and cheap to boot. Hot wet rock geothermal is even better and you actually want snow for that because you need a lot of water in the rock.
Comment: Oh I understand your comment now, when you thought about mountains, you went with the biggest ones XD. Do you your answer still applies for mountains at around 800-1200 m? Or should I better ask : at which point do you think volcanoes would overcome snow?
Answer: Well, if this is science fiction, then good news -- you make the rules!
Why not just create your own special type of rock? It can have all the properties you need. As far as geothermal energy goes...you could say that the mountains contain a lot of thermal springs, and that your special rock conducts the heat very well. Maybe steam from the streams can be used. Or maybe the civilizations have found ways to magnify the heat from the rocks for energy. IDK, I wouldn't think too hard about it. Just do what's necessary for your story :-)
As for the mountains affecting climate...I'm no expert. But I think usually mountains tend to absorb weather fronts, creating more or less peaceful valleys. Could be wrong though. I would simply research different geographical areas like the one you wish to create so you can make an informed decision.
Best wishes!
Answer: If you want to have a dry mountain range you may have to replicate the environmental conditions associated with the Atacama Desert in south America.
Failing that, the mountain range may need to be a constantly active volcanic gash that brings hot magma to the surface to erupt as lava. It's also how the inhabitants can utilize geothermal energy.


Decimal to Fixed Point Conversion

Question: I am having trouble to get the intuition behind the following approach:
We take the fraction point (say: .642) and continuously multiply by 2,
taking whatever ends up right of the point as our next number (either 0 or 1) after the fixed point in the binary number. Then we take whatever is left after the decimal point and repeat.
Comment: Have you tried working through an example to see what happens?  I'd suggest picking a simpler number: say, 0.75, or something like that.  And then try a few more examples and see if you can start to spot a pattern.
Comment: This seems somewhat more appropriate for math.se.
Answer: Let $x$ be the real number you wish to convert. We will assume without loss of generality that $0 \le x < 1$. Form the Dedekind-completeness of the order on $\mathbb{R}$, it follows that $x$ can be (almost) uniquely written as
$$
x = \sum_{h=1}^{\infty} 2^{-h} \alpha_h
$$
where $a_h \in \{ 0, 1\}$ for all $h$. Now observe that:
$$
2x = \sum_{h=1}^{\infty} 2^{-h+1} \alpha_h = \alpha_1 +\sum_{h=1}^{\infty} 2^{-h} \alpha_{h+1}
$$
where the rightmost sum is nonnegative and less than $1$. Multiplying by $2$, therefore, allowed us to discover a single binary digit of $x$, namely $\alpha_1$. The same procedure can be iterated to yield as many digits as you wish.
Answer: Complementing quicksort's answer.
Your implementation will take a decimal number and convert to it's $(0.d_0d_1\ldots d_n \ldots)_2$ binary representation. Your example would work like this:
Step 1:
\begin{align*}
x_0 &= 0.624\\
2 \times x_0 &= 1.284
\end{align*}
Is $2 \times x_0 \geq 1$? If so, $d_0 = 1$, otherwise $d_0 = 0$.
Step 2:
\begin{align*}
x_{1} &= 2\times x_0 - d_0\\
x_1 &= 0.284\\
2 \times x_1 &= 0.568
\end{align*}
Is $2 \times x_1 \geq  1$? If so, $d_1 = 1$, otherwise $d_1 = 0$.
Step 3:
\begin{align*}
x_{2} &= 2\times x_1 - d_1\\
x_2 &= 0.568\\
2 \times x_2 &= 1.136
\end{align*}
Is $2 \times x_2 \geq  1$? If so, $d_2 = 1$, otherwise $d_2 = 0$.
And so on...
As you can see this looks like a loop, you may want to try to implement it in your favorite programming language. Notice, however, that some finite decimal representations may have infinite representation in binary.

Decimal to Fixed Point Conversion


Using pogo pins in a commercial product as contacts

Question: I've a question about possible usage of pogo pins in a commercial product. I've seen they have simply working principle and are easy to integrate in a case, some of that also have current rating up to 2-3Amps and gold finish. Is it possible to use them in this context? For example in an expansion board that don't require particular connection.
Comment: Yes, though expensive. Use compatible finish on the matching PCB pads, and check their ratings (life, insertion cycles etc) meet your needs.
Answer: It's possible to use them, but it may not be a good idea in terms of reliability. I've used them on production test stands to connect to devices as they get built and they were one of the biggest maintenance issues. Pins would get bent, they'd bind and get stuck in the compressed position, something would loosen so they'd make intermittent contact and so on.
On the other hand, Apple uses a similar component in their MagSafe power connector for charging MacBooks.
Answer: You can personally I'd use something like one of these from Samtec rather than a random pogo pin mfg :).
I'd want to use hard gold on the contacts on the mating board surface unless maybe it was a one time insertion (but I would not plate the whole thing as hard gold).  This will add an extra step and a little cost to the bare pcb but will protect against wear and oxidation.  I'd also think about doing this of the product was going to be subject to any shocks or vibration.
Lastly single pogos would be a pain to line up in mfg without some kind if jig or holder so if you chose them I would pick the multi ones in plastic with guide posts that you show above.


Syntax highlighting and indentation not working at the end of a specific file in python-mode

Question: At the end of one of my files for loops stop being highlighted, aren't automatically indented when I enter them, and TAB won't indent four spaces either. I don't have this issue in any other of my python buffers.  How do I figure out what's wrong, and how do I fix it?
Comment: Comment out or remove  everything but the offending lines.  If the problem goes away, recursively bisect the rest of the file to isolate the problem.
Comment: I finally spotted a syntax error in the previous line. Please post your comment in answer form so I can accept it; I would like to know more about how you would recursively bisect a file in Emacs.
Answer: If syntax highlighting or indentation suddenly stops working as
expected at some point in your buffer/file, there's a very good
chance you have a syntax error somewhere above it.
In these situations, the most straightforward way to identify the
offending lines is to bisect your buffer/file recursively.  What
that means is to comment out all the material above the lines that
are giving you problems.  Uncomment one half.  If the problem
comes back, the error is probably somewhere in that half.  Repeat
the procedure in the offending half by uncommenting one half of
the half until you isolate the error.
Note that this procedure is a common remedy for a problems in your
init file, but the principle is similar for any source code.


What are the benefits of a national cryptocurrency?

Question: I have read about the Marshall Islands partnering with the company Algorand to produce their own cryptocurrency that will act as the nation's official currency. Is there any special benefit from having a nation's official currency being a cryptocurrency that nations working with traditional currencies would not have?
Answer: Cryptocurrencies have long been promoted as an escape from traditional, government-backed currencies, so the proposal of the Marshall Islands to create an official state cryptocurrency seems fairly odd at first. However, some research has been undertaken into how a nationally backed cryptocurrency could work - along with analyses of the associated positives and negatives.
Firstly, in chapter 4 of his book "Handbook of Digital Currencies" (2014) [1], Andras Kristof discusses existing attempts to produce a national cryptocurrency. While all the examples at that time were all set up by individuals, rather than being officially sanctioned by governments, some of the conclusions drawn are still useful. In particular, Kristof concludes that necessary preparations and precautions must be taken, including official backing from government, a robust "Know Your Customer" (KYC) system, and retained control of monetary policy - that is to say that coin creation should be controlled by the government, as opposed to miners.
If the above conditions are met, Kristof predicts that a national cryptocurrency could realise its full potential, by being accepted by the banking industry, making taxation automatic, and also facilitating uses such as smart contracts that we have seen for example with Ethereum. This could be used to replace paper contracts as proof of ownership - things like property deeds or vehicle titles could all be baked into a national blockchain. He goes even further, predicting that an international cryptocurrency recognised by the International Monetary Fund could lead to frictionless global trade.
More recently, in their publication "The wider impact of a national cryptocurrency" (2018) [2], Dennis Ng & Paul Griffin explore the effect that a national cryptocurrency could have on the major players in an an economy - consumers, merchants, banks, payment providers, international money transfer operators and central banks.
While generally, they found that a national cryptocurrency could provide a range of benefits, including reduced transfer fees for consumers, merchants and corporations, easier and more efficient intra-bank transfers, and the ability to  prevent money laundering given the innate transparency of transactions - as well as positioning the adopting nation at the bleeding edge of technological and financial reform - they also urge caution, pointing out that national governments could become responsible for consumers financial losses. They suggest a "sandboxed" approach to mitigate this. In this approach, a financial tech company could apply to test the new currency and their applications in a sandbox arena, allowing issues to be identified and resolved, before a full-scale national rollout.
In conclusion, then, there have been many proposed advantages to a state-backed cryptocurrency, however researchers acknowledge that there is a vast difference between theoretical benefits, and the actual circumstances that will manifest when the policy is tried for real. It is important to recognise that these are predicted benefits - this has never been tried on a large scale before.

[1]: Kristof, Andras. "National cryptocurrencies." Handbook of digital currency. Academic Press, 2015. 67-80.
[2]: Ng, Dennis, and Paul Griffin. "The wider impact of a national cryptocurrency." Global Policy (2018): 1.
Comment: Not to mention that, to date, holdings in cryptocurrency have had depressingly frequent occurrences of [theft, embezzlement and disappearances](https://vancouversun.com/news/local-news/troubled-bitcoin-trader-quadrigacx-takes-another-bizarre-turn).  Combine that with potentially less than ideal governance practice by a minor 3rd world country and... devil's in the details.  Perhaps, learning from past experience, this cryptocurrency design will be secure enough, perhaps not.
Comment: Yes, my own analysis of the situation shows that despite the open source nature of these projects, they are still closed in the sense that very few people understand the complete picture of how these things work. Newcomers continue to discover holes and weaknesses in the systems, and they either claim bug bounties or they just exploit the weakness themselves. I believe a sandpit approach as described above, in collaboration with a state, would turbo-charge the development, attract many new developers, and would be of benefit mainly to the crypto platform itself, ultimately to that state.
Answer: Existing cryptocurrencies have many problems, among them the fact that they are not really currencies for many legal purposes. Having a recognized, sovereign nation lend to legitimacy might help a bit.
Cryptocurrencies are just as faith-based as most other currencies, so moving early and establishing a name (and an unique selling point, see above) might establish the Marshalls SOV as a household name.
The RMI expected income from the initial coin offering and from administrating the currency.
Comment: This answer explains how this move could be beneficial to cryptocurrencies as a whole. But I think what the question author actually wanted to know was how the Marshall Islands benefit from this move.
Comment: @Philipp, I added a sentence at the end. Cryptocurrencies are business, not charity, involving lots of money.
Answer: This very much depends on the architecture proposed and what the political drivers are.
A national consumer cryptocurrency intended to substitute cash operations while at the same time offering smart contract functionaltiy would need to solve the same problems that, for example, Ethereum 2.0 is still researching. Namely, scalability (number and frequency of transactions) while maintaining security, with complex on-chain contracts.
A consumer cryptocurrency must rely on a 'large number' of nodes in a peer to peer network to maintain security. If on the other hand the architecture involves a centralised system that guarantees security through central control, a more efficient system would be available through traditional application+database type architectures like Visa for example. A centralised architecture is better achieved through "standard" 'non-crypto'currency. In other words, a central bank that controls M4 money.
Still on the topic of consumer-grade money, it may be that the particular government in question has a problem with local financial entities, money laundering, poor relations with the banks, or some such,  so one could speculate that an advantage of introducing any state currency, crypto or not, would be to solve those particular problems.
Further, one possible architecture could involve the 'standard' decentralised p2p network approach, but with state mandates and laws on software client usage. For example, if the developers of the crypto-system could work in tandem with the government on legislation, on arrangements, such as for example "it will become law for users of this system to maintain a node on their computer, but all taxation will be automatic and heavily discounted". This could be a monumental, "epic" achievement of huge benefit both to the cryptosystem and to the state. Cryptosystem developers could work with guarantees of hundreds of thousands of nodes, which would not only help guarantee security but transaction throughput.
Moving away from consumer transactions, the present smart contract cryptosystems suffer from scalability problems. In terms of transaction volume they cannot compete yet with the likes of Visa. If, for example, Ethereum 2.0 delivers on its expectations, the impact will be revolutionary in every sense of the word. Payment infrastructure, settlement infrastructure, and various types of legal and financial institution would likely become obsolete. (It is also conceivable that a state controlled cryptosystem network would be an attractive move for a smaller state trying to shield its own finanical services relevance, for example, from the effects of this upcoming decentralised free-reign global network).
Until then, however, these cryptosystems could only deal with low transaction volume, such as aggregate settlements, land registry transactions and the like. Note, by 'transaction' in crypto terminology when smart contracts are involved, we just mean the signal for a general state transition which could mean anything from an account balance change, to the state of an online contract or video game.
The advantages there are manifold. These include removal of legal infrastructure around land registry. Sales of works of art. Settlement of securities transactions , perhaps of certain types only. Private consensus networks can be established that bond the corporate and state elements of the establishment into a trust-less infrastructure. The fact that adoption is still low is just testament, in my opinion, to the fact that the development groups behind these crypto-systems still can't fully get out of the research and development phases. Projects like Ethereum, Tron, Cardano and so are still either 'unfinished' or in one way or another unable to offer the assurances that you could replace the global financial and legal system with them.
It also occurs to me that in the Marshall Islands it would be interesting to know what the relationship is between Algorand and the govt. If the govt has direct or backhander investment in that firm, this might simply be a way of perfecting a highly scalable proof of stake system that Algorand can take global, with Marshall Islands as the test bed and a stake in future profits.
So in summary, on the whole I think it would be interesting to try and understand what the fundamental political drivers are, and then see what architecture is chosen. For example as I mentioned above, it could simply be that that particulare State is worried about losing control of financial services to some outside entity and wants to take control of the financial services sector. Or it could be that the country wants to appear progressive, and attract young technical talent for some reason. Or they have a direct investment in a commercial development company. Once we have the architecture and the drivers we can list what the actual advantages would be.


What is the normal operating temperature for the MacBook (2016 generation)?

Question: My MacBook sometimes becomes hot when I'm using it, and I want to make sure it is operating within normal temperature. What's the operating temperature for the MacBook that was released in May 2016 normally?
Comment: You can install a Dashboard widget or an app that reports the temperature sensors in the Mac. But temperatures of a single computer will range wildly depending on what is going on, if a rogue CPU process is running too much or something is using WiFi too much it will be hot, if you watch a lot of movies or play games it will be hot. I would expect typically it to be warm to the touch in light usage when not charging but not hot, but you have to ask those with that specific MacBook to give you their readings.
Answer: You can find your processor model by entering the following into a terminal:
sysctl -n machdep.cpu.brand_string

which will return a string, for example, like this:
Intel(R) Core(TM) i5-5287U CPU @ 2.90GHz

You can then search for your processor on the intel product specifications page, by pasting for example i5-5287U into the search box.
On the resulting page you will see something called TJUNCTION ...

This is the maximum temperature recommended for that processor. You can monitor this with htop.
Comment: This is a useful answer, but it only tells us the max temperature the process should be able to withstand. In contrast, e.g.: would regular spikes to, say, 97° be considered normal?
Comment: @FabienSnauwaert it's difficult to say what 'normal' is without any indication of what your workflow might be. If the laptop is idling without any cpu-intensive processes running (top or activity monitor can identify these), then there should be no reason for spikes to such high temperatures. If you have something periodically requiring high cpu usage however, then this might be 'normal' - Hope that helps to clarify.
Answer: Internally, the processor is rated to run up to 100°C and since this model has no blower or fans, that heat will be conducted out to the frame. The nature of conductive heat transfer is that the case itself won't get that hot unless it's insulated to near perfection.

The system will slow down the processor to keep the internal thermal temperatures in line, but most modern cell phones, tablets and computers will get warmer than most people feel is proper and run just fine for extended periods of time. If a store is close, you might make an appointment and have them run diagnostics - just because they are designed to be within the specs - failures can happen on the chips and on the sensors to make yours painfully hot. I would always have someone trained look over something you feel could be a fire risk or dangerous no matter what I say is normal.
Answer: The aluminum chassis of the MacBook works as a heat sink itself. Translates the internal heat to the outside. It's normal that the housing is quite hot, always within a limit. Unless the temperature exceeds 80 ºC, I wouldn't worry at all.
Answer: Considering that the entire line of MacBooks have no fans, I wouldn't be surprised if it got to the range of 50°C while idle.
Apple only supplies minimum and maximum ambient temperatures; the specified ambient temperature range for your MacBook 50° to 95° F (10° to 35° C) (source). Unless you're using your MacBook in an abnormally warm environment (i.e. direct sunlight in a tropical country), your MacBook shouldn't get too much hotter than its regular idle temperatures.
My 13" Retina MacBook Pro, mid-2014 version can get rather warm when idle (~50°C-60°C) especially if placed on a non-heat conducive surface like a mattress or my legs. I don't mean to get too technical, but you can think of the entire unibody as a rather large heatsink that conducts heat away from your Mac (another reason why sometimes the entire computer feels warm and not just one region). It's also important to remember that OS X will shut your computer down if it gets too hot (>100°C IIRC).
Unless the MacBook in question is exceeding 80°C while idle with no absurd CPU usage or rogue processes (check with Activity Monitor for process CPU usage), I wouldn't see any cause for concern about the temperature of your MacBook.
Answer: To follow up on comments relating to fans, I am unsure why posters are stating that "entire line of MacBooks have no fans," because they do have fans. All of them. It is true that they use their cases as heat sinks, but they also all utilize fans. You can monitor your internal temps with apps such as smc fan control. That particular app will also allow you to set manual fan speeds and create specific profiles that you could select based off of what type of processing you are using you computer for.
Comment: The 2016 MacBook (12-inch) is fanless. You must be thinking of MacBook Pro's, which is a different product line.


Why are there some really young professors and other much older lecturers without professor status?

Question: I was just wondering how this is possible, there are some 50+ year old people who are 'Dr. X Y', and others who are maybe "only" 40 years old , but they are 'Professor Dr. X Y'.
Comment: Because these job titles are awarded based on a person's career choices and accomplishments, not based on the year of their birth.
Comment: ... because being a professor is not just a function of age ???
Comment: @NateEldredge: _"Because these job titles are awarded based on a person's career choices and accomplishments, not based on the year of their birth."_ Well, to be honest also **a lot** on the base of the luck to be at the right time in the right place with the right topic.
Answer: Academia, like any other organized human profession, has a system of ranks and advancement on which those particularly talented or ambitious tend to rise quickly, while others may rise much more slowly or eventually stop.
Comment: @Chris: "Professor" means something different in the UK than it does in the US (and many other countries).  In the UK there are three different classes of permanent faculty who fully contribute to the department, including supervising PhD students: lecturer, reader and professor.  In the US we have assistant professor, associate professor and professor, but in the US system seniority automatically makes you an associate professor (or out of a job) within 7 years, and at many places if you're one step above adequacy you'll get promoted to professor sooner or later.....
Comment: ....However in the UK all three classes are what we would call "tenured professors" in the US, and one does not automatically rise from one to another.  In the UK, "professor" is being singled out for distinction among other permanent faculty.  (Whereas in my department in the US, at any time more than half the permanent faculty are "professors.")  In the US we have "named professors" and/or "endowed chairs" which is generally 5-20% of the permanent faculty.  This is probably the closest US analogue to a UK professor.
Comment: What country's system are you discussing?  The meaning of "professor" varies.
Comment: @ChrisDoyle no, assuming it is research supervision, look at their research output (especially their last 5-10 years) and look at the outcomes of their other recent supervisions (or ask their current students).
Comment: how does this work then? And is it advisable then to avoid some 50 year old Dr. X Y as one's supervisor if he or she is not a professor yet?
Comment: UK. But I have also seen these things in other countries like the US.
Answer: In a colloquial sense, may simply refer to a group of educators/teachers at a university/colleges. However, in more strict sense, the formal designation of Professor is generally obtained by rising through the ranks. You can find lots of details regarding how this system works out, and even some technicalities, in this link. (N.B. US-specific, but generalizable to some extent.) Quoting verbatim from the article:

Educators who hold a formal title of "Professor" (referred to as tenured/tenure-track faculty) typically begin their careers as assistant professors, (or "lecturers" and "senior lecturers") with subsequent promotions to the ranks of associate professor and finally professor. The titles are historical traditions; for example, it is not implied that an assistant professor "assists" more senior faculty. There is often a strict timeline for application for promotion from assistant to associate professor, most often 5 or 6 years following the initial appointment. Applicants are evaluated based on their contributions to research, teaching, and administration. The relative weightings of these contributions differ by institution, with PhD-granting universities usually placing more emphasis on research and liberal arts colleges placing more emphasis on teaching.

Now, until one has risen through the ranks to formally hold this title of professor, technically that guy can't/shouldn't use the title "Prof." in front of his/her name. But, if he/she holds a Ph.D. (i.e. Doctor of Philosophy) degree, "Dr." can be used as a prefix before the name. Later in the career, when this person becomes a formal Professor, he is free to replace that "Dr." by "Prof." (or rarely, even use both at once.)
Also, while there may be correlations between age and rank, there is absolutely no reason why a more aged person can not be academically junior to a younger person who might have made it further in the hierarchy. It all depends on satisfying the requisite criterion (see linked article). This explains you observation:

there are some 50+ year old people who are 'Dr. X Y', and others who are maybe "only" 40 years old , but they are 'Professor Dr. X Y'

Hope that helps :)
Answer: It is possible that some older Drs may not want to be profs.  As an academic rises through the ranks, their duties tend to migrate from active teaching and research into more of a managerial role, which doesn't suit everybody (and the activities that merit your promotion do not necessarily imply you have the abilities required to flourish in the role into which you find yourself promoted).


Traveling to Australia with an expired Australian passport

Question: I am traveling to Australia and I am a dual citizen (Maltese and Australian). As my Australian passport is expired, can I travel to Australia with my Maltese passport? What should I show the immigration in Australia on my arrival to show them that I am Australian?
Answer:
What documents do Australian citizens need to return to
  Australia?
If you are an Australian citizen, you:
<code>do not need a visa to enter Australia
must have a valid Australian passport or other acceptable travel document
will need a completed and signed Incoming Passenger Card.
</code>
If you are an Australian citizen and you hold dual or multiple
  nationalities, you should use your Australian passport to enter or
  leave Australia, even if you use a foreign passport when you are
  outside Australia. The only exception is if you have been issued with
  an Australian Declaratory Visa.

It would be best to contact the Australian consulate to get your passport renewed, or to obtain a travel document if you need to travel more quickly than they can process the renewal. This is backed up by Timatic, the database used by airlines for immigration information, which says:

Dual nationals of Australia must enter and depart using their Australian passport.

While some countries will allow you to travel home on an expired passport, Australia is not one of them:

Passports and other documents accepted for entry must be
  valid on arrival.
Comment: Note that technically you cannot be refused entry to Australia once you get in front of an Australian immigration agent with an expired passport. Only issue is getting to Australian soil in the first place.


Why does subprocess use a list instead of a string with spaces by default?

Question: Why does Python's subprocess module expect the arguments as a list by default? Why isn't a string with spaces (similar to what you type into a terminal when running the command normally) the default input? There are plenty of sources explaining how to pass in the space delimited string of the command into subprocess, but it's less clear as to why the default isn't the other way around.
Answer: TL;DR Using the list bypasses the shell so that you don't need to worry about the shell interpreting a dynamically constructed command line in ways you did not intend.

Suppose you have a really simple command: echo foo. Here it is, using both a string and a list:
Popen("echo foo", shell=True)
Popen(["echo", "foo"])

Not much difference yet. Now suppose the argument contains quotes to protect whitespace and/or a shell pattern, echo "foo   *    bar":
Popen("echo \"foo   *    bar\"", shell=True)
Popen(["echo", "foo   *    bar"])

Yes, I could have used single quotes to avoid needing to escape the double quotes, but you can see the list form is starting to have an advantage. Now imagine I don't have a literal argument for the command, but that it is stored in a variable. Now which do you want to use...
This?
Popen('echo "%s"' % (x,), shell=True)

or this?
Popen(["echo", x])

If you answered "the first one", here's the value of x:
x = "\";rm -rf \""

The command you just executed was echo ""; rm -rf/"". You needed to make sure any special characters in the value of x were first escaped before incorporating it into the string you are building to pass to the shell.
Or you just use a list and avoid the shell altogether.
Comment: That's a reason why you or I should prefer the no-shell list version, but not exactly an answer as to why that's the default.
Comment: More efficient (no shell process is started) and more secure isn't enough?
Comment: An additional moral of this story is that echoing strings containing `rm -rf` is probably a bad idea, even when you think you're being careful.
Answer: Forget all that I wrote - just read the relevant PEP yourself
https://www.python.org/dev/peps/pep-0324/
===============
My short guess - the no-shell list version is closer to the format that is eventually passed to the POSIX forking commands.  It requires less manipulation.  The shell string approach is something of a Windows legacy.
=====================
So you are asking why the shell=False case is the default?

On POSIX, with shell=False (default): In this case, the Popen class
  uses os.execvp() to execute the child program.  args should normally
  be a sequence.  A string will be treated as a sequence with the string
  as the only item (the program to execute).
On POSIX, with shell=True: If args is a string, it specifies the
  command string to execute through the shell.  If args is a sequence,
  the first item specifies the command string, and any additional items
  will be treated as additional shell arguments.

'why' questions tend to be closed because they rarely have definitive answers, or they involve opinions, or history.
I'd suggest studying the subprocess.py code.  I see for example a lot of calls to:
Popen(*popenargs, **kwargs)

It's init is:
def __init__(self, args, bufsize=-1, executable=None,
                 stdin=None, stdout=None, stderr=None,
                 preexec_fn=None, close_fds=_PLATFORM_DEFAULT_CLOSE_FDS,
                 shell=False, cwd=None, env=None, universal_newlines=False,
                 startupinfo=None, creationflags=0,
                 restore_signals=True, start_new_session=False,
                 pass_fds=()):

As a keyword arg, shell has to have some default value; why not False?
I suspect that in the shell case it passes a whole string to some code that calls the shell.  In the no-shell case it must pass a list.  But we have to find that code.
There are 2 methods of call the subprocess, one for POSIX and the other Windows.   In the POSIX case it appears to convert the string list, regardless whether shell is True or not  It may be more nuanced than that, but this is the relevant code:
        """Execute program (POSIX version)"""

        if isinstance(args, (str, bytes)):
            args = [args]
        else:
            args = list(args)

        if shell:
            args = ["/bin/sh", "-c"] + args
            if executable:
                args[0] = executable
     ....
     self.pid = _posixsubprocess.fork_exec(
                        args, executable_list,...

In the windows shell case the args string is combined with cmd info:
    if shell:
            ....
            comspec = os.environ.get("COMSPEC", "cmd.exe")
            args = '{} /c "{}"'.format (comspec, args)
     hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
                                     # no special security
                                     ....

Comment: No, it's more complicated than this.  `shell=True` can be a security hazard.
Comment: And making it non-default reduces that hazard? Who does it protect, the beginner or the expert?


Help with undergrad econometric project

Question: I am working on undergrad research in econometrics and am seeking some advice/help in terms of finding data sets and picking variables. I have an idea chosen for my topic, but I need to make a official proposal including a rough linear regression equation to turn in to my teacher soon.
My topic idea is to observe the causes for recent decline in female labor force participation in the US. I am hoping this topic is not too broad. Initially, I was going to look at whether campaign spending impacted voter share in Senate races from 2012 data sets, but I find this idea a tad boring and would like to make my new idea work if possible.
My ideas for variables include the obvious: age & teen participation rates (16-24), race/ethnicity, educational attainment, children, martial status, avg weekly hours worked, etc. However, I wanted to also see if the increase in opioid addiction in the US could also be having an impact on labor force participation specifically for women, as well as paid family leave benefits in the US vs other countries and labor force participation of immigrant women.
So with all said, does anyone have any suggestions for me both as to whether this topic is viable as a project in my course, as well as where I could find the data for such a topic? I have been reading a lot of literature on the topic, but having a hard time finding actual data sets that I could use for regression.
Thanks!
Answer: Can you provide your research question in one concise sentence? It seems like you've proposed half a dozen topics some of which are peripherally related. You need a quantifiable dependent and independent variable as well as essential control variables.
The question needs to be quantifiable and have a wealth of data already available. I'd highly recommend for your undergraduate paper instead of asking a question and then searching for the data to back up the answer, you instead peruse some interesting data sources and ask a question based on what is available.
Check out sites like https://www.data.gov/open-gov/ which have a wealth of easily downloadable datasets that you can explore. Find datasets related to topics that you find interesting and go through the available data and begin to think of what can act as an independent or dependent variable. Base your question so that the dataset you have already found and think is interesting perfectly fits instead of the other way around.
Unless you plan to do original research it will be quite difficult to simply find data to fit your question unless you already knows it exists.
Comment: +1, a very short statement of the thesis of the paper and preferably a form for the regression would be appropriate to lay out for us @Haley

Help with undergrad econometric project


Use of stock image on book cover

Question: My book was published by a now defunct publisher.  They returned my records to me (locked, and I could not open any of the documents) and I've since re-published my title under my own name.  However, my question is ... can I still use the same cover?  The image on my cover is appropriate for the material, but I assume it was a stock image the initial publisher paid a "right to use" fee for.  Thanks for your assistance.
Comment: That is a difficult question to answer without knowing the details of the license issued for the use of the image.  I think it would be best to contact the copyright holder for information and advice.
Comment: I would go with a new cover. You don't have the rights to the artwork. You will need a new ISBN and other changes to show that you are the publisher now. Give your book a fresh start!
Comment: You might be able to find out who the copyright holder for the picture is by using Google Images' reverse image search.  Go to google images at https://images.google.com and click the camera icon.  Then upload the image in question.  Google will search the web for similar images  and in the process probably locate one or more instances of your exact image.  One of the links associated with one of those exact matches may lead you to the owner of the image.
Answer: Definitely commission or make a new cover.
If you are going to self-pub on Amazon, simply use THEIR cover-maker, a link to it will come up when you go through the publishing process.
Comment: I wouldn't use Amazon's cover creator since it's not professionally designed, but yes I'd agree with a new cover image for sure!

Use of stock image on book cover


How to cook rice with fish without overcooking the fish

Question: How can I cook rice with fish so that the fish is not over cooked or breaks into smaller pieces? Fish meat cooks quickly, in much less time than rice. Would anyone like to share tricks or tips for this?
Answer: While boiling/cooking rice and fish is safe for consumption, the cooking method gives the rice an extremely fishy taste. If you crave that flavour, go ahead with cooking the two things together.
However, if you wish to retain the individual flavours of the food, par boil the rice while you can pan fry the fish pieces in a separate utensil (to get rid of the excessive sweet/salty fishy flavour). Add the fish to the rice at a later stage. By doing this, not only will the fish pieces retain their shape and form after frying, but your rice would remain fragrant on its own as well.
Comment: I feel like you haven't really addressed the question, which was about preventing overcooking, not taste.
Comment: As stated by Stephie, cooking time of fish varies due to the type of fish and its cut. A simple test would be to use a fork to check it the fish is flaky. A time period would be misleading to stated in this case. Basically, rice takes longer to cook than fish. Thus, the fish can be introduced to the rice at a much later point, depending on the texture of fish one wants. Besides, frying the fish would be a good way of controlling the overcooking - again depending on whether one is shallow frying or deep frying.
Answer: This problem can be solved with a bit of kitchen maths:
You noticed already that

your rice takes X minutes unti fully cooked and
your fish takes Y minutes.

You also noted correctly that usually X > Y.
The best time to add the fish to the rice would therefore be after (X-Y) minutes.
But I guess you want a slightly more practical answer?

Well, X will depend on the type of rice you are using - white rice will need somewhere around 20-25 minutes, perhaps 30 if you like it very soft, while whole grain may need up to 45 minutes.
The cooking time of the fish will depend on the kind of fish and the thickness of the fish pieces, a few minutes will be enough for a thin fillet.

Assuming that you have used both ingredients before, you should have at least a rough idea on the timing already.
Additional hints:

Cooked fish will break apart easily when done, so ideally you simply put the fish on top of the rice and serve it like that or, if your dish needs stirring, stir once, briefly and carefully when adding the fish, then leave the pot alone.
Of your two ingredients, the fish is by far the more critical one. A bit too long, and you have exactly the over cooked state you wanted to avoid. So if you are unsure about when to add the fish, pick the later time and cook the rice longer.


Docking of CSM with LM

Question: After separation from the SLA (by about 50-100 feet), the CSM "turned around" and docked with the LM to pull it out. This turning around was done by a 180 degree change in orientation. This could have been done by using the "YAW" or the "PITCH" function. I understand this was done by change in "PITCH" and not YAW. Is there any specific reason for using the PITCH function or it was left to crew?
Answer: The book "Lost Moon" by Lovell and Kluger talks about this, but I don't have a technical reference handy:
The guidance platform used on the CSM would go into gimbal lock at +/- 90 degrees yaw, so yawing would cause loss of attitude information.
Comment: @Niranjan It's not that they *can't* yaw, it's that it would cause the guidance platform -- and therefore, the whole guidance system -- to lose track of where they are pointing.  Not a good situation when you need precise pointing to get to where you need to go.
Comment: Great research and answer!
Comment: @Tristan. Hi Tristan, thanks for the answer. But then what if the craft need to change the YAW beyond 90 degree? I feel, once in space, the YAW, PITCH and ROLL functions are carried out using RCS (reaction Control System) - 4 set of 4thrusters each are mounted on diagonaly opposite corners of the craft. The RCS does not have a gimbal, instead, using two thrusters located on opposite ends, and pointing in opposite directions create the required moment. Please correct me if I am wrong.
Comment: @Tristan: I am somewhat confused. 1- Whether YAW or PITCH, the orientation needs to be changed (to capture LM from SLA), and this (LM)will be the new target. 2 - Do you think / know that RCS is not used for such purpose? This is similar to minor mid-course corrections required by the craft.
Comment: @Niranjan They always rotated 180 degrees in pitch for Turnaround, Docking, and Extraction.  Performing the same rotation in yaw would have them pass through either +90 degrees or -90 degrees yaw, which would create a gimbal lock singularity, causing the guidance system to lose all pointing information.  Of course they used RCS to perform the maneuver -- it's the only way they could adjust the spacecraft attitude.
Answer: Initially, I could not find a source for the selection of pitch over yaw, though I did note that the pilots preferred to start the pitch up manually before engaging autopilot, because autopilot would pick pitch up or down depending on what was shorter--the procedure was to pitch up. So it sounds like the pilots were pretty consistent about following the procedure.
[EDIT: Removed speculation.]
After Tristan's answer, I was able to track down the original explanation of the problem with a yaw maneuver:

For a vehicle that needed to refine its trajectory by fractions of a degree on the quarter-million-mile coast to the moon, the system worked exceptionally well, with one small exception. If the spacecraft inadvertently moved to a full right or full left yaw position, the gimbals had a nasty habit of lining up with one another and locking in that configuration, instantly wiping out whatever knowledge the computer had of the ship's attitude.

From Apollo 13 by Jim Lovell and Jeffrey Kluger
In more technical detail:

The third effect - that due to outer gimbal inertia - comes into play only with large middle gimbal angles away from the zero orientation shown in Figure 1. In the extreme, large middle gimbal angles cause an effect called "gimbal lock". Gimbal lock occurs when the outer gimbal axis is carried around by vehicle motion to be parallel to the inner gimbal axis. At this trivial point the three gimbal axes lie in a single plane. No gimbal freedom now exists to "unwind" base motion about an axis normal to this plane. Even though any vehicle orientation with respect to the stable member can be accommodated by particular sets of the three gimbal angles the condition at gimbal lock prevents accommodation of a particular orientation change from the locked condition.
Transient loss of attitude due to gimbal lock effects, or any other disturbance, does not necessarily mean a permanent loss of orientation unless the gyro gimbal limit stops are reached. Within the integration range of the gyro the attitude is recovered as the gyro error is brought back to zero.
Firm groundrules on how close to gimbal lock the Apollo IMU could operate satisfactorily depend upon experimental results with the actual flight configuration IMU. Within the last month these data have started to be collected using IMU #3 with breadboard electronics. It appears that gimbal lock can be approached as close as 10 degrees without risk and even much closer with some possibility of loss of stable member attitude. Stated more dramatically, the inner axis of the system was aligned within 10 degrees of a base motion axis perpendicular to the output axis.

From "Apollo Guidance and Navigation Considerations of Apollo IMU Gimbal Lock" by David Hoag
Figure 1

References:

Apollo 11 Mission Report - NASA
Transposition, docking, and extraction - Wikipedia
Apollo transposition and docking maneuver - collectSpace
Apollo 13 - Lovell and Kluger (Alternate title for Lost Moon)
Apollo Guidance and Navigation Considerations of Apollo IMU Gimbal Lock - David Hoag (MIT Instrumentation Laboratory Document E-1344)

Docking of CSM with LM


How do I install Citrix ICA Client (Receiver) 13 on Debian 64-bit Linux?

Question: The Citrix ICA Client (Receiver) 13 has many i386 dependencies, so I cannot install on my amd64 (64-bit) Debian Linux.  How can I make this work?
Answer: This was very difficult to fix, so I am answering my own question.  Much debt is owed to the others who have blogged about the various components of this fix!
This answer assumes you are running Debian amd64 architecture.  It also assumes your Debian installation is already multiarch-aware.  (That is beyond this question.)

Get the Citrix ICA Client (Receive) 13 installer: http://www.citrix.com/downloads/citrix-receiver/linux/

Be sure to select the 64-bit .deb installer
Example filename: icaclient_22.214.171.1246735_amd64.deb

dpkg --add-architecture i386
apt-get install ia32-libs ia32-libs-i386 libglib2.0-0:i386 libgtk2.0-0:i386

This will install almost two hundred dependent packages.  Be very patient.

dpkg --force-all --install icaclient_220.127.116.116735_amd64.deb

Ignore the warnings about missing dependencies: lib32asound2 and nspluginwrapper.  The installation will work without these libraries.

Check there are no missing dependencies: ldd /opt/Citrix/ICAClient/wfica

If you see not found in the output:

Uninstall the Citrix ICA Client: apt-get remove icaclient
Install the missing packages.  (This can be a bit tricky as Debian does not always have a 1:1 relationship between names in the ldd output and package names.)
Reinstall the Citrix ICA Client: dpkg --force-all --install icaclient_220.127.116.116735_amd64.deb

Don't forget to copy the CACerts from Mozilla.  The default collection from Citrix is pathetic.

cp --verbose /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts/

If you are using KDE, edit the file association application/x-ica.

Add a new application: /opt/Citrix/ICAClient/wfica.sh

At the moment, it is better to use Firefox/Iceweasel to login into remote Citrix servers.  Google Chrome requires the launch.ica to be downloaded first, then run.  For Firefox/Iceweasel, this is seamless, and these applications automatically respect KDE's file associations.

Each time you need to add unrelated Debian packages in the future, you will be forced to:

Uninstall package icaclient: apt-get remove icaclient
Install other packages
Reinstall package icaclient (using the .deb file from Citrix)

dpkg --force-all --install icaclient_18.104.22.1686735_amd64.deb

Recopy the CACerts from Mozilla.

cp --verbose /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts/

What a pain.
Finally, you can make permanent changes to your .deb package.  Read more here: How do I fix a bad commercial deb package?
Comment: If you have `dpkg-add-architecture` you cannot have `ia32-libs-*` -- these are different solutions.  On legacy Debian, you could install `ia32-libs` on amd64 for 32-bit support; from Wheezy onwards, the superseding -- and much superior, much more general -- solution is `dpkg-add-architecture i386`.  See also https://wiki.debian.org/Multiarch
Comment: @tripleee: I suggest you expand your comment into a separate answer.
Comment: I don't have the knowledge of Citrix etc to answer the actual question.  Please feel free to update your answer instead.  The gist of it is that there are two different methods, the older of which only works on Debian-based platforms from before the introduction of general *multiarch* support; if you can only describe one method, I suggest you describe the new one instead of the old one (the support has been there for several years already, so even Debian *oldstable* is covered, IIRC).
Comment: Before *multiarch* there were ad-hoc dedicated packages for supporting `i386` on `amd64` with different names than the regular packages for `libc6` etc; with *multiarch,* you can say I want *this* package for *that* architecture and you can have packages with the same name for multiple architectures installed at the same time.
Answer: I as well had some trouble with missing dependencies, however the solution I found is a bit simpler than yours ( Thanks to linuxquestions.org ):

Download the squeezy nspluginwrapper at the link:
https://packages.debian.org/squeeze/...apper/download

Download the Citrix icaclient at the link:
http://www.citrix.com/downloads/citrix-receiver/linux

Add the 32-bit architecture option

$ sudo dpkg --add-architecture i386
$ sudo apt-get update

Install the nspluginwrapper downloaded in step 1

$ sudo dpkg -i nspluginwrapper_1.3.0-1_amd64.deb
$ sudo apt-get -f install

install the Citrix ica client

$ sudo dpkg -i icaclient_184.108.40.2066735_amd64.deb

Trigger another apt-get -f install in order to get the last missing libs and finally install the client

$ sudo apt-get -f install

When you start citrix, an error about missing certificates will pop up. If using firefox(iceweasel) you can make citrix happy by adding a symlink to the firefox certificates:

$ sudo ln -s /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts

Answer: I followed your instructions to the point of installing the icaclient_188.8.131.526735_amd64.deb file. Instead of using terminal, I opened the deb file using gdebi and it worked from there. I didn't have to force it to ignore missing dependencies.