Cytoskeleton made of only actin?

Question: I am aware that the cytoskeleton has three structural components: actin, microtubules and intermediate filaments. I was wondering if any cell could possess a cytoskeleton made only of actin. Or made only of microtubules, for that matter. Is it possible for actin to perform the functions that microtubules ordinarily perform in a cell? Or vice versa?
Comment: If you are talking about an eukaryotic cell, I'd say no, due to the reason that the three types all have some different, irreplaceable functions. For example, microtubules form the mitotic spindle; actin filaments are greatly used for movement protrusions and cell adhesion; intermediate filaments are what convey the cell its structure, being the strongest. As the cell system is already tuned differently around these 3 types of filaments (proper linking proteins, enzymes, ...), my idea is that taking any out would probably make the cell unviable
Answer: 1) Can cells survive without any of the different cytoskeletal components?
Yes, most certainly. At least for actin and microtubules (MTs) there are plenty of eukaryotic cell types that can survive without them. MTs can be disrupted by cold-shock (see for example here https://www.ncbi.nlm.nih.gov/pubmed/16505977). How well the cell survives depends on the type of cell, but the ability to survive without MTs can range from minutes to hours as far as I'm aware. Once the temperature goes back to normal, the MTs just grow back. Of course, the cells won't behave normally in the meantime, because many processes do depend on MTs. Actin can be disrupted using various drugs or genetic constructs, or they can be cut using femtosecond lasers (see for example https://www.ncbi.nlm.nih.gov/pubmed/28324605). Again, many processes are disrupted, particularly cell motility, but most cells can survive without actin for a while.
I'm not aware whether any eukaryotic cells exist that have no intermediate filaments or can survive at least for some time without them.
2) Could a cell function normally while lacking one type of cytoskeletal component?
First, to my awareness there is no eukaryotic cell without MTs or actin. We do commonly use actin and tubulin promoters for transgenes and assume that all cells will express them. So I'm taking this question hypothetically.
As with every hypothetical question, the answer then purely depends on the restrictions that you define. Can the cell possess arbitrary new proteins that currently don't exist? Then yes, definitely you could get eukaryotic cells with just MTs or just actin or just intermediate filaments. You just have to bend all the other things the cell does to fit with that filament type, and then enjoy arguing whether that's still a eukaryotic cell or not.
But I think actin would find it easier to take over the other filaments' jobs compared to the other way round.
MTs are large and rigid. They can't operate on scales below 25nm like actin can, and the individual tubulin dimers can't do anything useful until a tube of some minimal length has been formed out of many dimers. Intermediate filament monomers are pretty thin, but very long. Actin monomers are small and globular, and a supershort actin filament made of a handful of monomers can already function as a filament, branch out, form networks, pull on things etc. Actin-mediated endocytosis crucially depends on this (https://www.ncbi.nlm.nih.gov/pubmed/25675087 for example). It would be difficult to find workarounds for these small-scale functions of actin if MTs or IFs were to replace it. On the other hand, actin filaments can very easily be made into large, thick, rigid rods like microtubules. Many cell types do this constantly when they form filopodia. Actin meshworks can also provide similar mechanical support (both stable and flexible) as IF meshes. With minor shifts in the regulation of where, when and how to organise filaments, actin could probably take over the other cytoskeletons' functions. It would probably require a quite sophisticated regulatory system though to perform all the different functions at the same time in one cell.
Comment: @EliKorvigo Noted, thanks for the correction.
Answer: I think sperm is only having microtubules (axoneme) in them as a part of the cytoskeleton. Different types of cytoskeletons evolved to perform the different function so generally they will not exchange their function but are precisely evolved to carry out their individual functions.
(From textbook Molecular Biology of the Cell. 4th edition https://www.ncbi.nlm.nih.gov/books/NBK26914/)In tail section of sperm, which is a long flagellum.The core of the flagellum is composed of a structure called an axoneme.The axoneme consists of two central singlet microtubules surrounded by nine evenly spaced microtubule doublets. These dense fibers are stiff and noncontractile, and it is not known what role they have in the active bending of the flagellum, which is caused by the sliding of adjacent microtubule doublets past one another. Flagellar movement is driven by dynein motor proteins, which use the energy of ATP hydrolysis to slide the microtubules.
But I would like to correct my answer, as sperm also contains actin for capacitation and acrosomal reaction.So I think sperm is a eukaryotic cell where you can only see 2 types of the cytoskeleton.Here is the link for the paper https://www.ncbi.nlm.nih.gov/pubmed/15749953
Comment: Welcome. Can you add sources and references to your claims to allow other users to background read on your answer?
Comment: Yes ,see this link please https://www.ncbi.nlm.nih.gov/books/NBK26914/
Comment: Could you add it into the answer proper, please?
Comment: Sperm cells, like all eukaryotes (with some pretty rare exceptions), contain actin. "So I think sperm is a eukaryotic cell where you can only see 2 types of the cytoskeleton" – by virtue of having a nucleus, sperm cells also contain lamins – intermediate filaments.

Cytoskeleton made of only actin?


Designing a Single Board linux computer

Question: I'd like to design a single board Linux computer, maybe something ARM-based but I really don't know that much about the hardware side of computers. Does anyone know where I could get some information to get started? Thnx
Comment: It's the definition of madness to build something like this when there are already 100 to choose from on the market...
Comment: I think it would make a nice learning project... well perhaps at for someone a bit more experienced, at least.
Comment: The best thing is to get a simple development board and study the circuit diagrams, data sheets of the ICs on the board and then the board itself. Reading data sheets will give you an idea what the *questions* are you have to ask.
Comment: check this http://hforsten.com/making-embedded-linux-computer.html
Answer: There are many topics about this, and 99.9% of them say (paraphrased):
"You are not good enough. Unless you have many many years in industrial professional board design for similarly complex embedded systems, start with Arduino and making your own (successfully), and perhaps go get a bachelors in Electronics Engineering and a few years experience at a company that does that sort of thing. THEN you will be successful and have the skills and knowledge to do what you want"
I hope that helps - but do know, it IS possible. Just very hard and you will waste a lot of time and money unless you get the required experience and knowledge first, and honestly for a singleboard computer style architecture similar to the raspberry pi and beaglebones, you really do need all of that under your belt to make it work properly.
Answer: Take a look at the OMAP processor from Texas Instruments. There's quite a lot of data available on those, compared to a lot of the ARM chips from other vendors. Nowadays, also the Broadcom processor which is used in Raspberry Pi has at least some public documentation, much because of Raspberry Pi.
The core design for Cortex A is always similar: the ARM has pads on top of the IC for connecting a multi-die memory chip which has two dies (chips) in the same package: A mobile DDR3 DRAM and a Nand Flash to boot from. This design is fixed, so there's no thinking involved for you to do, a good thing in this respect.
In addition to the main memory, you'll need to provide power and clocking. These should be fairly well explained in the datasheets also. Then you'll need some I/O: bring out USB ports, UART for the console and SD card connection.
Study how the chip is supposed to boot (Linux) from http://processors.wiki.ti.com/index.php/Boot_Sequence or the datasheets and application notes for your processor. You should figure out much of the needed stuff by studying the boot sequence. When you power up the device and get anything from the console, you're much closer to success.
These devices are complex, but the complexity is often exaggerated. Take a look for example at the Raspberry Pi schematic at http://www.raspberrypi.org/wp-content/uploads/2012/04/Raspberry-Pi-Schematics-R1.0.pdf. That's rather simple, I would say; there's mainly just the main CPU and a few external connections. Just the Ethernet looks a bit complex. And you don't need to support every feature of the chip at once. Also, even if you're not successful, you have learned a lot in the process.
Finally, add a video output for a more capable display than the serial console. Add a RCA connector for the Video DAC and HDMI if it's supported by the chip. Find linux distributions which are already targetting your chip, such as Angstrom or others; scout the web pages of already existing single board computers such as the Beagleboard for OMAP or the Raspberry Pi for Broadcom.
One more hint: If you're not accustomed to soldering these BGA beasts with hundreds of balls, find a cell phone repair shop. They'll be able to solder the main chip and the memory for you, no problem.
Good Luck!
Answer: First of all, unless you are willing to spend hundreds of hours and probably a thousand dollars (minimum) on this, it is not a good idea.
Good news, since you won't be selling your board, you can get a hobbyist version of Eagle which is good for up to 6-layer 4" x 6" board for $169.
Bad news, is because of all the surface mount components inclduding BGA, you likely won't be able to assemble your own boards, so each board spin is going to cost perhaps $500 or more -- and I guarantee you're not going to get it right the first time.
Pick an open-source hardware design -- like the BeagleBone Black -- as a starting point.  The Raspberry Pi design is closed source, so avoid that.
Comment: http://hforsten.com/making-embedded-linux-computer.html Check that link. Its not that hard.
Comment: +1 I don't think this is an answer that deserve a downvote. The OP asked for something really beyond his/her abilities, but he/she even can't understand how difficult his/her idea is.

Designing a Single Board linux computer


How to get an actual copy of my eOs configuration in an executable penrdive?

Question: Does anyone knows how to get my current elementary OS 5.1 Hera configuration  to work in an executable usb pendrive?
Answer: I've used Pinguy Builder (https://pinguyos.com/2018/05/pinguy-builder-updated-license-change/) for that exact purpose. While it works nicely, it does has some limitations on the SquashFS size so if your installation is too big, you might not be able to build a working Live Environment.
If that doesn't work, you might Google around for " install linux ubuntu on USB drive". Never attempted that myself though.


Vendor escalated to our Manager

Question: We use a Service vendor to help us with various system issue that arise.  We are the administrators of the system and manage the overall state of it. We occasionally need to work along side with the vendor to make sure they have everything they need like access into the system, and to make sure the system is running A1 so they can run updated scripts/updates against it.  We usually are quite quick in responding to their needs.  We got behind recently and replied back we would look after them as soon as we would and appreciated their patience (twice).  After all we pay them for their service.  They didn't like the second response and went to our manager.  She told us to make sure we got things moving, which we did and looked after them.
There had been times when we needed to wait for them to get back to us on various things in the past, and never escalated. Should a follow up email be in place now to close the case?
Comment: Vendor shouldn't be working with you direct, it should always be going through the manager. So there is a problem there.
Comment: "After all we pay them for their service." No, you don't. Your company pays them. Or your manager makes the decision to pay them, not you. If something doesn't get done in time, your manager could blame them.
Comment: The vendor likely doesn't get paid unless they fully complete what they contracted to do and there may even be a time component involved. They need your "we're all done" email so they can say to your procurement folks that they're done and ready for payment.  There's often a disconnect between people who do the work and those who deal with procurement. It's not always easy, but just try to respond proactively to their constraints regarding "time and done-ness" and things will go MUCH smoother.
Answer: Well, that's annoying behavior from a vendor.
But it is no big deal, not at all.  You said wait, to your boss they said "can't wait." Your boss said "oil this squeaky wheel, willya?" So you did so. All's well that ends well.
No followup needed. No closeout message.
But if it happens again you've got to bring it up with your boss. She needs to go back to them and work out expectations for how they are to make requests to your team.
Answer: Maybe it's possible there's part of the picture we haven't seen (and, to be fair, everyone will be in that position to some extent, irrespective of company size).
If the service provider has been asked - by someone else (possibly your manager) - to provide a particular service, and they are unable to do that without your input, it would be entirely correct for them to make people aware that they are unable to do what they've been asked to do without the information they've requested.
If everyone should be going through you to deal with this supplier, there's a gap that needs to be addressed. This is something for your manager to arrange, so it's good that they've become involved.
I'm seeing this more as the supplier covering their backs rather than escalation.
Comment: I'm pretty much seeing the same thing. Two requests put off with no firm timeframe for resolution or anything but 'be patient'.
Answer: Almost 20 years doing projects in international corporations taught me one thing. If some activity requires several chained actions, it is always better to inform everyone involved about the completion of one task in order to advance to the next.
In your particular case, I would just send a "job done" e-mail, which would act as the "follow-up" e-mail you mentioned.
Benefits:

everyone knows that you did the job;
you do not remind anyone about the hiccup and the escalation.

Vendor escalated to our Manager


Flow of pressure in water bottle

Question: Say you would have a plastic bottle partially containing water that is laying on its side. How would applying external pressure through a weight on the side affect the internal pressure. In other words, how well does the pressure transfer from outside to inside the system?
Comment: Do you have any thoughts on what to expect?  This sounds a bit like a homework-type question.  Generally you're more likely to get the answers you want if you provide all the thought you put into it.
Comment: Yeah sorry you're right. From previously seen formulas I have established that the pressure would definately be higher, but this is based upon the gas laws. If there would there be any possibility to combine the gas and fluid laws the question would be much easier.
Comment: The pressure won't "definitely be higher."  If you apply clamping force to the right places on a container of the right shape, you can actually _decrease_ the pressure inside the container by _increasing_ the clamping force.
Answer: Based on your comments I'd say you're on the right path on your own.
You already mentioned using the (ideal) gas laws.  Beyond that there isn't a whole lot to consider in this problem.  (assuming you want to do a cursory analysis of this situation, and not find exact pressure values or anything like that)
It's worth noting that water is approximately incompressible, so it doesn't build pressure quite like the gas does, but as long as the gas is pressurized the water will be at that pressure (and a bit higher the deeper you go, see hydrostatic pressure).
So the basic concept is apply a weight > deform the container > reduced air volume means increased pressure in the bottle due to ideal gas law.
Your rewording of the question is a bit more complicated.  The effectiveness of transferring pressure between outside and inside depends quite a bit on the material of the bottle.  Depending on the material, it will deform more or less when you apply a force to it.
A weak material, like a balloon very easily deforms, so it's very easy to apply a force to the outside and increase the pressure inside.  Something like a steel container doesn't work as well.  When you apply a force it does deform a bit, which would increase the pressure; but it barely deforms, so the volume barely changes and pressure barely increases.
Comment: Yes this is basically what I meant. Now though I am looking for a precise way of knowing by exactly how much the internal pressure will be changed. I have previously found the following formula: Qm = C * A * sqrt((2* Delta(Pressure))/diameter of hole) here [link] (http://physics.stackexchange.com/questions/80277/flow-rate-and-orifice-diameter). Therefore I would expect to be able to find the internal pressure by finding the Qm, right? Not sure about how well this works.
Comment: @AdrianSie I wouldn't do it that way, that's for sure.  Personally it would depend on what I'm doing and what I might know.  For example, if you had a good way to determine the volume change, that would help.  You could definitely measure the flow through an orifice, but you would need to know about the orifice.  There would also be issues with how that would change things compared to having a fully sealed container (as the pressure builds it actually resists more, having an opening to alleviate pressure buildup might make those results irrelevant).
Comment: This is indeed true and what I'm looking for, though would there be a controlled way of finding/formula between external pressure exerted, the amount of stress the bottle can handle and the addition of the internal pressure? The relationship is clear but I might need more precision than a statement :/ Couldn't find too much on internet
Answer: Pressure is $\frac{F}{m^2}$. If we apply a force $W$ on one side, we must apply an equal and opposite force on the other side of the bottle. Therefore, the increase in pressure in the bottle when the weight is applied is $\frac{2W}{\text{Surface Area Of Bottle}}$. If you increase the surface area of the bottle, the increase in pressure will be lower.
Comment: I'm pretty sure it wouldn't increase the pressure in the bottle that simply.  A force on the outside of the bottle would cause a deformation to the inside of the bottle, changing the air volume and increasing the pressure.  This will be proportional to the force and bottle geometry, but not as directly as you show.  The bottle will resist deformation.
Comment: Equal and opposite force? It sounds like you're trying to use Newton's Third Law of Motion. However, that law specifies an action-reaction pair, i.e., the forces that are equal and opposite are for two interacting objects, not both for the same object. The "inside" and "outside" (walls?) of the bottle are not an action-reaction pair, they are the same object. Unless you're talking about an area on one side of the bottle, and an area 180 degrees from it. Either way so, I don't think that analysis is appropriate.
Comment: My analysis is fine. If there is a force acting on one side of the bottle and no net force acting on the bottle(it isn't accelerating), then we can assume there is an equal and opposite force acting on the bottle as well. Since both forces of magnitude $W$ are acting on the bottle, the net amount of force pushing inward on the bottle is $2W$.
Comment: I disagree. I think only one "side" of the bottle needs to be considered (a half-cylinder), and the equal force opposing W is the "tension" of the plastic around the point of depression. I'm not an engineer, but a force of 2W contributing to the pressure seems wrong to me. Perhaps a third party can verify.
Answer: It's not so simple. For example, try to open such a bottle and place something light (e.g. coin) on it. Obviously you will have no pressure transfer at all (pressure inside and outside will be the same), but the bottle will not collapse.
Comment: I disagree that the coin wouldn't affect the pressure of the bottle.
Comment: @electronpusher Deformation is generally continuous on these scales.  Many materials have an "elastic" region where there is a linear relationship between stress and deformation.  I'm not aware of some lower limit where this fails to be continuous; any weird effects would likely require even far less force than a small coin.  A plastic bottle is thin and has very little deformation resistance.
Comment: JMac, for an object (coin) so light relative to the "deformability" of the material (plastic), don't you think we can reasonably approximate the bottle as fully rigid and unperturbed by the weight of the coin? Perhaps this may even be better than mere approximation; is deformation continuous with respect to applied force or is there a certain minimum weight that must be applied before a material begins to deform? (I suspect there are various classes of materials, if so let's take the class containing this plastic).

Flow of pressure in water bottle


Heisenberg uncertainty from estimation in Fourier transform

Question: The Heisenberg uncertainty principle $\Delta x \Delta \nu \geq \frac{c}{4\pi},$ seems to be the foundation of all quantum mechanics.  However, as far as I'm aware, this uncertainty arises (at least in part) from estimation and measurement limitations associated with the Fourier Transform (Gabor limit looks like $\Delta x \Delta \nu \geq \frac{1}{4\pi}$ ). I would interpret this as a limitation to what we can actually probe from the quantum world, and how we percieve it. However, there are quantum phenomena that appear to arise from an intrinsic notion of uncertainty, like quantum tunneling, election-proton stability within an atom, etc.. I'm wondering first if my view holds to one of the more subjectivity centered interpretations of QM, and if so, how to interpret quantum-tunneling and atomic stability in that view. Second, are there other details or views that would help me align to a more Copenhagian interpretation here?
Comment: The uncertainty principle isn't a statement about waves we send out to probe a system. It's a statement about the waves that *make up* that system.
Comment: How do you make a distinction between the two?
Answer: Found an answer here. The Fourier transform fits the mathematics, but it is not the "true" reason for the uncertainty, which is derived from the canonical commutation relation.
Comment: https://physics.stackexchange.com/questions/720811/confusion-regarding-heisenberg-uncertainty-principle

I posted a question a while ago about the uncertainty principle, you might be interested in the discussion we had. I've gained some new insights about this over the time period that has passed, let me know if you would like me to give my take.


Install Python for Windows

Question: What is the best way to install Python for Windows?
Answer: Download the executable ("Windows Installer") from python.org and install it.
Answer: For an IDE based full package install for Scientific computing I have used Python-x,y and it comes with the kitchen sink.
Answer: Active Python

ActivePython is the industry-standard Python distribution, available for Windows, Linux, Mac OS X, Solaris, AIX and HP-UX.
Comment: Active Python is a CPython package
Comment: You comment that "Active Python is a CPython package"  <-- can you elaborate on the relevance of that? particularly as the OP's question is a newbie type question so many people reading this QnA might not know the implications of whatever that is, are..
Comment: @barlop - 6 years after posting and question moved to another site, I agree that the comment is irrelevant to a newbie.
Comment: -1 the standard cpython distribution for windows or linux, is from python.org, not ActivePython.
Comment: And I think you are wrong again to use the term cpython package, Python has packages you can import in, but CPython is not a package it is an implementation. (And AFAIK packages aren't really dependent on implementation, they are code). And ActivePython is a distribution not  a package.
Comment: You are misleading saying 6 years. It is not that your answer has gone out of date since after you posted it 6 years ago. A python distribution was available from python.org even in 2001 (and yeah, cpython implementation, as they do)  web.archive.org/web/20020602032836/python.org/ftp… And more importantly, I think maybe that quote that you have about ActivePython is marketing. Most people on windows either use Python for windows, that is available on python.org or perhaps if they're scientists, apparently these two are quite good, enthought canopy, anaconda
Comment: And the Python releases on python.org are so standard they aren't even considered distributions. And you quoted from a page where just aboev the line you quoted from, it says "World's best python distribution" so you should've known it was just marketting. Very misleading.
Answer: This is the best install guide I've ever seen. Don't forget Part 2 to get easy_install working, as well.
Answer: In this article, I will explain how to install Python using the steps mentioned above. First of all, I want to say that Python is an open source project, which means that it is available to everyone for anyone to use and modify. For that reason, there are many tutorials on the web, which can help you install Python using the steps mentioned below.
To start off, first of all, get the program called Python Installer. To install python, all you need to do is run an executable file named install python (wherever you obtained the program) and it will install the necessary modules and files needed by your Python interpreter to run properly. But be sure you download the most recent release of the Python interpreter, because the older ones can break your computer., but don't worry - this is very rare. Usually, the standard library for Python is included in the program when you install it. If not, you can search online for an updated list of the available standard library for your operating system. need to be in a directory that contains Python installation files, such as C:/ python. Once you've found the right place to store the files, run the following command to install the required modules:
In order to successfully install Python on Windows, you first need to be able to run Python from your command line prompt. To start Python, you need to open up a command line window. To do that, click Start, then Run, on the menu at the left of the screen. When the command line prompt appears, type "pip." It's likely that you'll be prompted to key in your user name and password, so be sure to always remember those!
Finally, if you don't have a recent version of Python installed, you also have two options. You can download and install the latest official release of Python, or you can use a homebrew package manager to install Python. Although the installation process is typically straightforward, it can get a bit complicated if you're not familiar with working with programs like Homebrew. If you're running into problems, or if you aren't comfortable working with the command line at all, it may be easiest just to use a homebrew package manager to get Python running on your computer.
Comment: Welcome to Super User! There are other answers (and a accepted one) that provide the OP's question, and they were posted some time ago. When posting an answer (see: [answer]), please make sure you add either a new solution, or a as short as possible and substantially better explanation, especially when answering older questions. Please take the [tour] and read through the [help] center.
Answer: Get ActivePython for Windows.
See here for installation instructions.
In addition to the installer at python.org, ActivePython includes pywin32 (Windows API extensions) and several unofficial documentation including tutorials to learn Python.
Answer: Download Python.exe from the Python website. Then, install IDLE or PyCharm or any other Python editing software and set the interpreter as your Python.exe file. You should be set.

Install Python for Windows


Work out 5 times a week, out of breath

Question: So I exercise 5 times a week by lifting weights as well as 30 mins of cardio and some stretching every day. I still find myself running out of breath when walking uphill during my daily commute, for example, even though I'm in fairly good shape. My resting bpm is 57, for example, which is fairly low for a 205 lb 6 ft 1, 20 year old male. I'm a pretty big guy. Any suggestions for what the reason might be for running out of breath?
Comment: Resting BPM isn't that useful for determining fitness level as different people have different sized hearts. I'm about your size, 20 pounds lighter, and a resting BPM of 60 would mean I'm quite out of shape.
Comment: Your best bet, if you haven't done so already, is to visit your personal physician.  From your description, you are active and should not be out of breath.
Comment: How big is the hill, and how hard do you work during your cardio? If you aren't pushing hard when you do cardio you won't see benefits.
Comment: Judging by your low resting heart rate, it could possibly be hypotension. I would get your blood pressure checked (preferably at the doctor's office so that you don't self-diagnose yourself). If that's the case, it could simply be an issue of malnutrition, or an underactive thyroid.
Comment: @mufasa56 - Can you define a bit more what your workouts look like? 30 minutes of cardio could be walking on a treadmill or high intensity interval training. Likewise with weights, what kind of program are you on?
Answer: All I can wonder is how your diet is compared to how much exercise you do. You seem to be working out a lot and may not be supplying your body with what it needs. It is more important that you check why your heart rate is low, that in itself will make anyone more sluggish because your heart is not supplying your body with the necessary oxygen levels it needs.
Answer: It all depends on your training methodology. I can train my biceps 5 times a week, and that would not have any benefit in my hill climbing.
I presume you get my point :)
Comment: By your definition, a runner can still be an elite runner by only doing biking; since "cardio is cardio". You are wrong and confused. Please read "Body by Science" by Doug McGuff. For a non-professional it is irrelevant. But for a professional, it is not cardio, it is a skill, and it needs to be trained.
Comment: And you you call your bicep training "30 mins of cardio"?
Comment: A regardless comment. My point was clear. If you want to get better in hill climbs, do hill climbs for cardio. An elite endurance cyclist is not an elite endurance runner, and he/she would not be even if he had the skillset of a runner. (e.g. knowledge of running mechanics)
Comment: Cardio is cardio - the heart.  Elite athletes cross trail all the time.  An injured runner will often bike to keep in cardio condition.
Comment: @TuğberkKocatekin Even though I get your point and see where you're coming from with this response, you are misunderstanding him. He isn't saying you can be a elite runner simply by riding a bicycle. He is just saying you can keep your cardio endurance in tact by doing so. You will still need to train your legs by running since you use your leg muscles in a different way while running compared to while riding a bike. The cardio is just a part of being a runner.

Work out 5 times a week, out of breath


What proof is there in pudding?

Question: Yesterday I heard an English baker on a cooking show say that "the proof is in the pudding."  I've heard the expression before but I can't imagine how pudding would prove anything.  How did the idiom start, what did it mean originally, and how is it correctly used today?
Comment: If you make it with alcohol, there could be quite a lot.
Comment: The proof [that the pudding tastes good] is in the pudding (eat it and taste!).  The original phrase was "The proof of the pudding is in the eating", but has just been changed over the years.
Comment: Here's one bit of stuff: http://en.wiktionary.org/wiki/the_proof_of_the_pudding_is_in_the_eating
Comment: [This video may explain it perfectly.](https://www.youtube.com/watch?v=TVApHh5Rax4)
Answer: The proof of the pudding is in the eating has mutated over the years. As you mention, some of the current versions of the phrase lack apparent meaning.
Answer: William Camden, Remains Concerning Britain: Their Language, Names, Surnames, Allusions, Anagramms, &c. &c. &c. (1674) has this formulation

The proof of a pudding is in the eating.

which means simply that a pudding is as good as it tastes—or conversely, that if it doesn't taste good, no amount of justification offered on behalf of its other merits or initial disadvantages really matters.
Oswald Dykes, English Proverbs, with Moral Reflexions (1713) offers this moral reflection on the proverb:

In fine, the best Way of judging of Things beyond Mistake, is by the Issue, or the Event of them ; for as we say commonly, The Proof of the Pudding is in the eating, so we ought to speak as we find only upon the last Tryal and Experience, either of its Goodness, or its Distaste.

Charles H. Spurgeon, The Salt-Cellars (1889) frames the test—and the proverb—as a negative:

The proof of the pudding is not in chewing the bag.

after which he draws a religious analogy:

No ; nor does the proof of soundness in the faith lie in using the phrases of orthodoxy, and harping on mere words.

So if true faith is the pudding, "the phrases of orthodoxy" are the bag.
Answer: To prove in this context means to test (cf. Danish 'prøve', German 'probieren', 'to try', 'to sample', 'to try out'). Although it is almost obsolete in normal usage today, this less common application of the verb 'prove' is still current in certain familiar collocations, e.g. 'to prove [= test] the suitability' of someone or something, 'to prove [= test] ore', and in the term 'proving ground'.
The same sense of the word is the one being invoked in it's the exception that proves the rule. (If you substitute test, the proverb actually makes sense: it's the exception that tests the rule.)
Comment: The exception and proof is about 'rules' like this: if I say `you cannot park here on sundays`, this is the exception that proofs the  (unmentioned) rule "you are allewed to park here" (on any other day).
Comment: You might want to double-check your understanding of exceptions testing rules.  There's [good evidence (see final entry)](http://www.straightdope.com/columns/read/731/whats-the-meaning-of-the-expression-thats-the-exception-that-proves-the-rule) that the phrase uses "proof" in the usual sense of implication, but is only sensibly applicable to a somewhat narrow range of situations.
Comment: @blahdiblah - Did *you* understand your comment? I certainly didn't. It also turns out that even Cecil Adams (whose discussion you linked to) had to eat his own words under the cover of a flurry of incomprehensible verbiage, and arrived at something like my interpretation.
Comment: @ErikKowal Sorry you didn't understand my comment.

What proof is there in pudding?


Consistent black horizontal lines on colour negatives

Question: I just received negatives back, and on the last 10 or so exposures there is a constant black horizontal line on the bottom left of the image. Does anyone know what it is? Thanks in advance!
Answer: A hair.  Looks sharp enough that it could be on the film side of the shutter in which case getting it out should be easy.  If it is on the other side of the shutter and your camera has an interchangeable lens, you should be able to get at it with removing the lens and putting up the mirror.  If you don't have an interchangeable lens, it might require convincing the camera to open shutter while the back is open.  Don't prod the shutter itself: it's easy to bend the blades and that is bad news.
If you already reloaded the camera, you can either pray or rewind the film.  It's not likely to be a problem of development: if this happened while scanning the negative, the hair would show as white.
Comment: I'm seeing something a little thicker than a hair. Maybe a bristle from a cheap cleaning brush?
Comment: More worrying, if the shutter is made of cloth... What is the make/model of the camera?
Comment: @MichaelC The full image height is just 24mm and a hair is 20–50µm.  I find that relation plausible.  Also a "bristle" is more likely than a hair to follow gravity rather than sticking around obnoxiously.  So I would really suggest looking carefully and not expecting some thick and obvious obstruction.
Comment: I've had experience with both back in the 1980s-2000s when I shot plenty of film. It looks larger than a normal human hair to me. *Maybe* a fake eyelash with mascara caked on would be that large, or hair from an elephant (4X as thick as average human hair) or other animal with hair that is a lot thicker than human hair.


Quantum Gate - Negating qubit whose state is known to lie in the equatorial x-y plane

Question: Given a qubit whose state is known to lie in the equatorial x–y plane in the
Bloch sphere is it possible to find a quantum gate that will always negate this qubit?
If so, exhibit such a gate. If not, explain why it is impossible.
Answer: Assuming that you are talking about a pure state, simply apply the $Z$ gate.
If you have a state $|\psi\rangle=|0\rangle+e^{i\phi}|1\rangle$ then let $|\phi\rangle=Z|\psi\rangle=|0\rangle-e^{i\phi}|1\rangle$. We have that
$$
\langle\psi|\phi\rangle=(\langle 0|+e^{-i\phi}\langle 1|)(|0\rangle-e^{i\phi}|1\rangle)=1-1=0,
$$
so they are orthogonal.
For a bit more insight about how to come with this: any state on the equator of the Bloch Sphere has a Bloch vector that comprises $X$ and $Y$ components but not $Z$ components. So, you're looking for something that anti-commutes with both $X$ and $Y$ (because that will introduce a minus sign, reversing the direction of the Bloch vector, giving the orthogonal state). That's the $Z$ operator.


Definable relations in given structure (first order logic)

Question: I'm bothering with this problem. I'm given a first order predicate language with only one ternary predicate symbol $p$ (no equality sign). Also there is structure for the language $\mathcal{A}$ over $\mathbb{N}$ ($0 \in \mathbb{N}$), where $p(x,y,z) \leftrightarrow x+y+1 = z$. The problem is to prove that the set $M = \{ (a,b) \in \mathbb{N} \times \mathbb{N} : a \leq b\}$ is definable in $\mathcal{A}$. I feel that the set $N = \{(a, b) \in \mathbb{N} \times \mathbb{N} : a < b\}$ is definable by the formula $\psi = \exists x \ p(x,y,z)$. However I don't know how to prove it and how to switch to the set $M$. I was thinking of $\neg \psi$, but I guess it will define the set $\{(a,b) \in \mathbb{N} \times \mathbb{N} : a \geq b\}$. Any help?
Answer: You are correct that $\exists x: p(x,y,z)$ defines $N = \{(a,b): a < b\}$, since $0 \in \Bbb N$. In order to prove this, you demonstrate (to a satisfactory level of detail) that the conditions $\exists x: p(x, a, b)$ and $a < b$ are equivalent.
Now what do you know about $a, b \in \Bbb N$ if $a \not< b$ and $b \not< a$?
Comment: Ah you mean that I can simulate the equality like this $\neg \exists x \ p(x, y, z) \wedge \neg \exists x \ p(x, z, y)$ ?
Comment: @brick Yes, presuming you meant to write $\neg \exists x: p(x,y,z) \lor p(x,z,y)$ or $\neg \exists x: p(x,y,z) \land \neg \exists x: p(x,z,y)$.
Comment: OK, thanks a lot! One more question. If $\psi = \neg \exists x : p(x,y,z)$ defines $\{ (a, b) : a < b\}$ can I use the same formula for defining $\{ (a, b) : a > b \}$. I mean that it is the same formula except that the variables are taken in the other order. Or it is the case that $1$ formula defines only one set?
Comment: @brick Interchanging the variables gives a different formula, which indeed has the desired property for defining $a > b$. So $\neg \exists x: p(x,b,a)$ works for $M$ as well.
Comment: Oh, looks great! (I like simple formulas) Thanks!


Why categorical cross entropy loss is not correlated with NLP scores?

Question: I'm training a deep network for image captioning which is consist of one CNN and three GRUs. During training epoch by epoch model loss (categorical cross entropy) decreases but when I'm measuring bleu,METEOR,ROUGE,CIDEr and SPICE scores,I get best ones in the first epoch that has worst loss. I don't get why this is happening? And if categorical cross entropy is not a suitable loss function for autoencoder then what should I use instead?
Answer: There may be no mathematical linkage between categorical cross entropy and BLEU. BLEU if i remember correctly is probably a distance based measure of computer output to human judgement - there's no loss variable anywhere. This is unlike the perplexity score which IS derivable from the categorical cross entropy.
Loss function really depends on what you're comparing against your labels. Categorical cross entropy gives a way to compare the distributions of the prediction and truth labels and calculate an error based on the 'distance' between the distributions. Categorical cross entropy really works well to model the distributions of discrete vector labels, common in NLP.


2012: Is there some astronomical event happening?

Question: The news media has publicized that 2012 is the end of the Mayan calendar, and that all the planets will be aligned.  Is there any truth to this?
Comment: Since this subject has been extremely mixed up with a lot of misinformation and fearmongerin which doesn't seem to be going out before we arrive at 2013, you may find it worthwhile to consult this site: http://www.2012hoax.org/ You would do well to approach claims from mainstream media with a (very large) grain of salt.
Comment: There is a reason why the Maya aren't around anymore...
Comment: By reflex I thought this should be closed, but the tints of voodoo don't taint the underlying, very answerable question regarding planetary alignment; with consideration, I also think it is a valuable example that the community can approach and address these questions (where they are fundamentally legitimate and not venturing into the pseudo-scientific) pragmatically and tolerantly. Not least, should I need to mention, is the responsibility to provide the science!
Comment: @BenjaminHorowitz :Some of them are still around in Yucatan, but they never predicted the end of the world. I heard on the (French) radio a mayanist explaining that the very concept of "end of the world" is antinomic with Mayan religion, which is based on a cyclic idea of the time.
Answer: The answer is absolutely not.  There is nothing interesting/important/rare/weird/abnormal/whatever astronomically happening in December 2012.  I have written at length on this topic and a year ago summarized my posts on the subject.  In those, I've covered the vast majority of 2012 doomsday or whatever claims.  Besides that, though, 2012 is likely not the start of the next baktun in the Mayan long count calendar.
With that stated, one astronomical event that is rare that is occurring in June of 2012 is a Venus transit of the sun.  This happens in pairs of 8 years separation with gaps of 121.5 and 105.5 years between those pairs.  The last transit was in 2004, the next in 2012, the one after that in 2117.
Comment: Can't edit my comment, so I'll just add -- people on this site will usually vote down a question/statement on pseudoscience topics, so that was probably why it was downvoted.  I've actually only downvoted one person's post before, I think because it was completely illegible.
Comment: Not that a transit of Venus means anything at all in the apocalyptic sense. The last pair of transits (or was it the pair before that?) enabled some interesting science to be done for the first time, but there's not much that another transit can reveal to modern astronomy.
Comment: And I just posted a small correction (not relevant to the current point) on your [blog post](http://pseudoastro.wordpress.com/2010/11/06/planet-x-and-2012-my-posts-so-far/).
Comment: Thank you for the clarification.  Did I get a -1 because I didn't read your blog post before asking the question?
Comment: I didn't down-vote your question.
Comment: Correction, my comment was on [this blog post](http://pseudoastro.wordpress.com/2010/10/31/planet-x-and-2012-when-is-2012-anyway/) (regarding Julian vs. Gregorian calendars).
Answer: I have thought for many years that the current transit of Venus, mentioned above, is the reason why the Mayan calendar "ends" this year. On the multi-decade or multi-century scale, this time is singled out by the equinoctial precession having placed the solstice sun in proximity to the center of the Milky Way bulge, and the precise year is singled out by the second transit of Venus. This refines John Major Jenkins' idea that this is the year in which the solstice sun comes closest to the "galactic center", as seen from earth. That's not true and the exact center doesn't stand out to the naked eye anyway, but the general precessional trend and the timing of the transits were both accessible to Mayan observers.
Comment: There is no historical evidence to suggest the Mayans knew anything about the transit of Venus (it is a very rare event that is difficult to see by the naked eye). Also the skills required to calculate the intervals of Venus's transit were, in all likelihood, well beyond the ability of Mayan astrometers.
Comment: Calculations were widespread (see: Xultun) and the best records were destroyed (see: Diego de Landa). All they had to do was figure out the motions of Sun and Venus on the celestial sphere, extrapolate, and take note of when the paths coincide.


Call setTimeout without delay

Question: Quite often see in JavaScript libraries code like this:
setTimeout(function() {
    ...
}, 0);

I would like to know why use such a wrapper code.
Comment: **PRO TIP:** You don't need the `,0` at the end.
Answer: Very simplified:
Browsers are single threaded and this single thread (The UI thread) is shared between the rendering engine and the js engine.
If the thing you want to do takes a lot of time (we talking cycles here but still) it could halt (pause) the rendering (flow and paint).
In browsers there also exists "The bucket" where all events are first put in wait for the UI thread to be done with whatever it's doing. As soon as the thread is done, it looks in the bucket and picks the task first in line.
Using setTimeout you create a new task in the bucket after the delay and let the thread deal with it as soon as it's available for more work.
A story:

After 0 ms delay create a new task of the function
and put it in the bucket. At that exact moment the UI thread is busy
doing something else, and there is another tasks in the bucket
already. After 6ms the thread is available and gets the task in front
of yours, good, you're next. But what? That was one huge thing! It has
been like foreeeeeever (30ms)!!
At last, now the thread is done with that and comes and gets your
task.

Most browsers have a minimum delay that is more than 0 so putting 0 as delay means: Put this task in the basket ASAP. But telling the UA to put it in the bucket ASAP is no guarantee it will execute at that moment. The bucket is like the post office, it could be that there is a long queue of other tasks. Post offices are also single threaded with only one person helping all the task... sorry customers with their tasks. Your task has to get in the line as everyone else.
If the browser doesn't implement its own ticker, it uses the tick cycles of the OS. Older browsers had minimum delays between 10-15ms. HTML5 specifies that if delay is less then 4ms the UA should increase it to 4ms. This is said to be consistent across browsers released in 2010 and onward.
See How JavaScript Timers Work by John Resig for more detail.
Edit: Also see What the heck is the event loop anyway? by Philip Roberts from JSConf EU 2014. This is mandatory viewing for all people touching front-end code.
Answer: There are a couple of reasons why you would do this

There is an action you don't want to run immediately but do want to run at some near future time period.
You want to allow other previously registered handlers from a setTimeout or setInterval to run
Answer: When you want to execute rest of your code without waiting previous one to finish you need to add it in anonymous method passed to setTimeout function. Otherwise your code will wait until previous is done
Example:
function callMe()
{
   for(var i = 0; i < 100000; i++)
     {
       document.title = i;
     }
}

var x = 10;
setTimeout(callMe, 0);

var el = document.getElementById('test-id');
el.innerHTML = 'Im done before callMe method';

That is the reason I use it.
Answer: Apart from previous answers I'd like to add another useful scenario I can think of: to "escape" from a try-catch block. A setTimeout-delay from within a try-catch block will be executed outside the block and any exception will propagate in the global scope instead.
Perhaps best example scenario: In today's JavaScript, with the more common use of so called Deferreds/Promises for asynchronous callbacks you are (often) actually running inside a try-catch.
Deferreds/Promises wrap the callback in a try-catch to be able to detect and propagate an exception as an error in the async-chain. This is all good for functions that need to be in the chain, but sooner or later you're "done" (i.e fetched all your ajax) and want to run plain non-async code where you Don't want exceptions to be "hidden" anymore.
AFAIK Dojo, Kris Kowal's Q, MochiKit and Google Closure lib use try-catch wrapping (Not jQuery though).
(On couple of odd occasions I've also used the technique to restart singleton-style code without causing recursion. I.e doing a teardown-restart in same loop).
Answer: To allow any previously set timeouts to execute.

Call setTimeout without delay


Virtual machine protection

Question: Let's say I have VirtualBox or Vmware Workstation on a Windows 10 Pro host, hosting Windows or a Linux distribution such as Ubuntu or CentoS). If I have an antivirus or Internet Security software on the Windows host, could it protect Windows or Linux VM's?
Can any consumer, SOHO, or small business version of Norton, Avast, BitDefender, Kaspersky, McAfee, or other security software, protect virtual machines while the security software is on the host operating system?
Comment: An AV on the host cannot access the memory or filesystem in a VM
Answer: The answer is bit of yes and no, but in some cases, it is a definite no.  It really depends on what security software you are using, and what type of virtualization software you are using.
A traditional antivirus program that just scans a host computer cannot protect your VM.  The reason being as @schroeder said, "An AV on the host cannot access the memory or filesystem in a VM."
If you are using an internet security software that has a HIPS (Host Intrusion Prevention System) feature that acts like a network firewall, the answer is bit of yes and no.  The yes part is if the VM program tries to send a request (considering that you are using a browser inside a VM, like VirtualBox), thru the host to access a website.  In the scenario that the HIPS detects the destination of the request or source address of the data received listed in a global or local blacklist, the HIPS would drop the data.  In that case, the VM would not receive anything.  The no part is related to the fact that the security software would not be able to access the memory or the filesystem of the VM to scan for viruses.
Comment: This is a big corner case and not really helpful. Web filtering by destination can also be done on the router or the ISP. At that point, it's not about the host's AV. So, ***if*** the host's AV has HIPS, and ***if*** that HIPS will read the traffic coming from the VM (which requires the HIPS has access to the networking stack), then ***maybe*** traffic might be blocked.
Comment: In my opinion, many modern day AV software comes with HIPS, in fact even consumer versions come with it as well.  To name a few, ESET, Norton, McAfee.  It even says it on their website under the features.  It may not say HIPS clearly, but it would state something along the lines of what an HIPS would do.  Under a basic scenario how would a HIPS with a IP bock list work with web browsers if it does not have to the network stack?
Comment: I used the word "HIPS" because you did, but don't lose sight of what you are talking about. You are talking about IP block lists. And that feature would need to be deployed at such a deep level in the stack to be able to inspect traffic coming from the VM. And, don't lose sight of the bigger topic: if it did work, this is hardly worth mentioning when the topic is protecting a VM from viruses and this feature isn't really about AV.

Virtual machine protection


How to remove access to all files or attachments from a user

Question: Just like I can remove access to a particular object, how can I remove the user's access to Files or Attachments? Right now they can still access it if they use the global search function. I think there is no way to disable the global search function too. Any ideas?
Answer: Who Can See My File?
Your files in Salesforce can be private to you, privately shared, or visible to your entire company. Learn how to identify a file's sharing settings and how to change them. Check this doc for details
Make a File Private
You can restrict access to shared files that you own by making them private.Details here
Steps

From the file detail page, click either Share File Share File | Sharing Settings or Show All on the Shared With list.

In the Sharing Settings dialog box, click Make private (or Restrict access if the file originated in a Salesforce CRM Content library).

In the confirmation dialog box, click Make private (or Restrict access).

View Where a File Is Shared
Find out who can see a file and their level of access. From the File Detail page, you can access a full list of every person or object the file is shared with.
The Shared With list on a file detail page shows you who the file is shared with and their level of access. Check details here
Global Search
Yes, unfortunately global search can't be disable for particular user or profile. Check this idea


How do you get the AB Destroyer in Saints Row IV?

Question: I looked all over the Airport but couldn't find it. Are there any prerequisites?
Answer: In my game, the AB Destroyer is parked in front of one of the hangars. If you look at the runway that goes east to west, north of this runway is a set of 5 buildings visible on your map.
The western building is the control tower, and there are 4 hangers to the east.  The AB Destroyer was parked in front of the first hanger east of the control tower.
I'm not aware of any prerequisites, although in my game I do have 100% completion.  The game is pretty liberal about giving out powerful vehicles, though.  Normally, if there is an unlock condition, the vehicle will be given to you in a pack and immediately summonable via your phone.
You might have to destroy the Zinyak statue on top of the terminal (near the Snipes 57) to unlock it.
Comment: Found it! The weird thing, though, is that I didn't see it the first time (or any of the other times I flew past the place). I looked in the same place, gave up and destroyed the nearby Zinyak statue, and came back to take a screenshot to make sure it was the right place - and that's when I saw it.
Comment: @ARADPLAUG, that might be it, but I'd be willing to bet it just sometimes doesn't spawn there.  I found it on the first try, though, so maybe I just got lucky :)


Are these two semidirect products isomorphic?

Question: Let $p$ be a prime. Then there is a nonabelian semidirect product of $\mathbb{Z}_{p^2}$ and $\mathbb{Z}_p$. There is also a nonabelian semidirect product of $\mathbb{Z}_p\oplus\mathbb{Z}_p$ and $\mathbb{Z}_p$. Since there are only two nonabelian groups of order $p^3$, are these groups isomorphic?
Comment: Exponents${{}}$?
Answer: They are not.  The second of your examples, but not the first, has all nontrivial elements having order p.  This is because for any nontrivial element z of the acting subgroup, there is a base x,y for the normal subgroup for which the action maps x to x and y to x+y (or xy in multiplicative notation).  Raising any $x^iy^jz$ to the pth power then introduces $jp(p-1)/2$ more x's when you collect terms and move z's past y's that many times.  Since p is odd, this is divisible by p, and since x has order p, this means it's the same as raising everything else to the p and introducing no additional x's, which obviously gives the identity.


Craft Commerce - More detailed reporting

Question: I'm looking to get more detailed reporting from craft commerce. I would like to be able to see a breakdown of what we've sold in a set period of time (week, month etc) which details out products, revenue, and quantities. Right now I only have the option to see total revenue or top products
Answer: Select the date range of your orders:

Then export the line items to csv and open in excel:

You can then use excel to create sums/grouping and charts etc.
Comment: Just found that product description and SKU are not in those exports (only purchasableId) I have added those to the export for the next commerce release.


How do I retain my photo edits when opening the files in other apps?

Question: I just got back from our first family road trip vacation. I took about 1000 pictures and edited them each night and as we drove to our next location.
Today, when I tried to open them in other apps, the edits were gone. They still show in the Albums, but when the file is transferred, the original one is sent. All my work was for naught! Unless you know of somehow to have the edits stay? I'm really hoping you know of a fix for the issue. When I tried to look up a fix, I just found sites of others complaining. I'm on the latest iOS (I think is 6.0.3 or something like that). Can you help? :)
Comment: What app did you use to make edits?
Answer: Assuming you're using iPhoto for iOS (please clarify):
Applications can only access photos stored in your iOS device's Camera Roll. When you edit a photo in iPhoto (and likely in other, similar applications), the app creates a copy of the photo and stores it within its own storage area, where other apps can't see it. In order to make the edited photos available to other apps, iPhoto lets you export one or more of your Edited photos in a variety of ways: select one or more photos and tap the Share button to see the options, which include sending the photo to your Camera Roll (where other apps can see it) and Open In... which lets you send the photo to a specific app.
I'll admit, this is somewhat inconvenient when you have a large number of photos, as even when selecting multiple, iPhoto limits you to selecting 100 at a time.
Answer: Since we do not know what application did you use to do your EDITS, it is difficult to help you.
Unfortunately there are to many photo applications out there.
The problem is that you can make edits in some but the edits are application specific and mostly not transferable to other photo app.
In simple terms, when you make an edit in one application, others my not be able to read them, but they are not lost, just have to use the original application.
To overcome some of the problem in the future do not use albums, instead use saving a single photo. The reason is the albums are made specific to a photo software and not transferable.
So to fix your problem, open the albums in the application you made the edits and save the individual photos.


What is the suggested way to pass in large amounts of data into solidity contract?

Question: If a Member(struct) has 10 fields, the contract stores an array of Members, how would I pass 100 Members worth of data into the contract?
Answer: It's not recommended to keep a lot of data on the blockchain, rather you can use some storage solutions like IPFS or Swarm. By this, you can store the data on one of them and the hash of the files/attributes can be stored on the smart contract.
So basically using IPFS/Swarm is a smarter way of storage, you can store the data on blockchain as well, but in that case storing data would cost you more gas in comparison to storing the hash(pointing to your data).
Blockchain and IPFS/Swarm can be a really good combination, as it becomes more secure because your data is not on blockchain network.
Comment: you don't explain why he should use swarm or ipfs? why not a simple contract storage?
Comment: Updated my answer.


.NET Jump List

Question: Is there a .NET library/tutorial available that will let me show me how to customize the Windows 7 Jump List for my application?
Answer: channel9.msdn.com did a series of discussions covering the new taskbar, including the jumplist.
Jump Into Windows 7 Taskbar Jump Lists
Additionally, The Windows 7 Blog started a series of posts that covering developing the task-bar, including how to work with jump-lists. You can view their initial post at http://blogs.msdn.com/yochay/archive/2009/01/06/windows-7-taskbar-part-1-the-basics.aspx
Comment: Just FYI, full task bar support, including jump lists, progress bar, and thumbnail customization, was added in .NET 4.0 under the [System.Windows.Shell](http://msdn.microsoft.com/en-us/library/system.windows.shell.aspx) namespace.
Answer: Windows 7 API Code Pack contains the official implementation for .NET, see http://code.msdn.microsoft.com/WindowsAPICodePack
Answer: Also it looks like this question has already been answered:
Another Article
And here is the simplest way to fill your jump list with the contents of your app's recent files list (Thanks Code Project!:
<code>    void AddFileToRecentFilesList(string fileName)
    {
        SHAddToRecentDocs((uint)ShellAddRecentDocs.SHARD_PATHW, fileName);
    }

    /// <summary>
    /// Native call to add the file to windows' recent file list
    /// </summary>
    /// <param name="uFlags">Always use (uint)ShellAddRecentDocs.SHARD_PATHW</param>
    /// <param name="pv">path to file</param>
    [DllImport("shell32.dll")]
    public static extern void SHAddToRecentDocs(UInt32 uFlags,
        [MarshalAs(UnmanagedType.LPWStr)] String pv);

    enum ShellAddRecentDocs
    {
        SHARD_PIDL = 0x00000001,
        SHARD_PATHA = 0x00000002,
        SHARD_PATHW = 0x00000003
    }
</code>
Answer: See here Windows Team Blog. Microsoft are working on .Net wrappers for a lot of the new Windows 7 features.
Answer: Starting from .NET 4.0 JumpLists can be used easily with System.Windows.Shell namespace.
See reference and code examples at Microsoft's official JumpList Class documentation.

.NET Jump List


Issue with locks opening on both sides

Question: I got a lot of locks for a new hotel (bungalows), and I want to make one side of the locks inaccessible to any key.  (They have 3 doors so only one needs a key for both sides).   Is there some way to make the exterior lock hole to not work but allow people to unlock from inside?
Comment: @AloysiusDefenestrate, I  think its the reverse. Howvever, its also offtopic because its not a home but a motel.
Comment: As we can't see what type of locks you mean, we can't say. Pictures always help.
Comment: This is a confusing question: are you actually proposing to have doors that lock people inside where they need a key to get out? Have you looked into fire/egress regulations in your area?
Answer: You can use a "Killer Key" to permanently block the key slot. Either buy one or cut your own as shown below. Once you insert the key, the deep square cut catches on the pins and it can not be removed. Snap off the key at the weakened point and you're done.

Photo credit
Answer: Easiest thing to do is simply use a deadbolt...
Comment: I dont the Op is looking to replace that many locks.
Answer: If I understand your question, you're looking for a single sided deadbolt.  It has a knob to lock or unlock on one side and nothing on the other.  Here's a link to an example.  Many others can be found by searching for "single sided deadbolt" or "one sided deadbolt".

Issue with locks opening on both sides


Loan Interest Discrepancy

Question: Suppose that I have a loan value $x$ and interest rate $r$. The simple interest is then $x\cdot(1+r)$. If I take out a loan compounded annually and paid monthly for $12$ months the amount at the end of the year would be the same. Why is it then that loan calculators give a different value? For example, if I were to borrow $100$ at $10\%$ I would owe $110$ in simple interest and so $110/12$ each month, yet using an online calculator I get that I owe $5.48$ in interest for a total of $105.48$. Why the discrepancy?
Comment: You pay interest only on the portion not yet repaid.  So each payment consists of: whatever interest is owed for that month, plus an installment on the principal.  The next month, the principal is smaller, so the interest is smaller, and the payment toward the principal is larger.
Answer: The reason you are getting a discrepancy is because you are using compound interest calculators to calculate something that is NOT compound interest. You are saying if I divide the total amount by 12, and then add all 12 of them back together, it should be the same as not breaking it apart:
$$x(1+r) = 12 \left(\dfrac{  x(1+r)}{12}\right)$$ Which is clearly true. But compounding annually and breaking apart into 12 payments is very different from compounding monthly.
Consider the formula you provided alongside the formula for compound interest: $$\underbrace{x(1+r)}_{\text{simple}} \neq \underbrace{x\left(1+\tfrac{r}{n}\right)}_{\text{compound}} \biggr|_{n=12,\ 0<r<1,\ 0<x}$$
These are clearly unequal. That is because with compound interest, you are paying a fraction of the annual interest on the currently remaining balance.
Comment: So normally if I were compounding I would expect the compounded amount be greater than 110 because I'm not paying anything and it continues to accumulate.  However, since I am paying off an amount each period and compounding the total interest accumulating is decreasing, so it lowers the total paid to 105.48?  Is this the amount that is meant when the term 'APR' is used?
Comment: You must have been using an APR calculator and not a compound interest calculator. If you used compound interest, the total amount paid would be $110.47. APR is a similar but different beast and has a much different formula, which is why the total paid is less than the simple interest. The wikipedia page is insightful, though this is definitely a more advanced topic in interest theory compared to compound interest. I would also check out Khan Academy for visual explanations.
Comment: Thanks.  So APR is different from simple interest and compound interest?  Why do so many sites describe it as simple interest then (APR) and then define compound as APY?
Comment: @user195519 APY is annual percentage yield. Informally, it is a way of comparing compound interest wih different parameters. If bank A compounds quarterly at a rate of 2% and bank B compounds monthly at a rate of 1.9, who has the better deal? 2%>1.9% but maybe compounding more often off sets this? APY helps us compare the two. If you just compare rates, it's like telling someone they are tall. If you compare APY its similar to saying you are tall for your age.

Loan Interest Discrepancy


What would be the best thing to do when you post a question and then realize it's already been asked

Question: I just asked a question and find out its a duplicate, now what should be the best thing to do, as If you delete your question, I think SE keeps a track and after a certain amount it bans you from asking questions.
Answer: Well, if you don't delete it, someone else likely will.
I suppose as an alternative you could flag your own post and mark it as a duplicate, but this is just adding noise to the moderators' queues.
I think your best bet is just to delete the post (or use that little box in the corner that says "search" before you post a question).
Comment: I usually use google: blah blah blah site:sharepoint.stackexchange.com
Comment: @rjcup3 - I don't know... I only know that everytime some vampir.. new user post on meta cryin.. asking why he can't ask questions some one points out that deleted questions that aren't 30 or more days old count for the auto-ban. If this means that deleting a question with less that 30 days age gives you a +1 or that you won't erase any bad effect of the question if you delete it before six month.... only staff knows.
Comment: I tried searching it using the "search" box but sometimes if keywords are different then search results won't gonna show you the exact similar posts.
Comment: Lol, Nice 1 but I wonder if there is any difference between Google and SE search as they both work same ways, they use keywords to perform searches and if keywords doesn't match it will not gonna come back with all expected results.
Comment: little notice: AFAIK deleting your question will add a nice +1 on your question ban point card, so take that in account, too.
Comment: @SPArchaeologist, how many points gets you banned from asking questions?
Comment: Anyway, If I should place my bet - I would go for the first option: the system gives you a +1 elixir of ban if you delete a question. I also belive it could work on a % of deleted question vs the total: if it is the case, and if Jeff never forgets his towell, I declare that the magic percentage is 42.


What is $\Delta(1)$ for $1$ in $U(\mathfrak{g})$?

Question: Let $\mathfrak{g}$ be a semisimple Lie algebra and $U(\mathfrak{g})$ its universal enveloping algebra. Then $U(\mathfrak{g})$ is a hopf algebra. Is $\Delta(1) = 1 \otimes 1$ or $\Delta(1) = 1 \otimes 1 + 1 \otimes 1$? Here $1$ is the identity in $U(\mathfrak{g})$. Thank you very much.
Comment: By definition of a Hopf algebra, the comultiplication map is an algebra homomorphism, so $\Delta(1)=1\otimes 1$. This is not to be confused with the comultiplication of Frobenius algebras, which are not algebra homomorphisms.
Comment: @Hanno, thank you very much. Yes, I think we have $\Delta(1) = 1 \otimes 1$ since $1 \otimes 1$ is the identity of $U(\mathfrak{g}) \otimes U(\mathfrak{g})$ and $\Delta$ is a homomorphism of algebras.
Answer: One of the axioms of a bialgebra $B$ (in particular a Hopf algebra) is:

(taken from Wikipedia: in their notation $K$ is the base field and $B$ is the bialgebra).
Here $\eta$ is the unit and $\Delta$ is coproduct. In plain words, $\eta(\lambda \in K) = \lambda 1_B$. By the commutativity of the diagram, $$\Delta(1_B) = \Delta(\eta(1_K)) = (\eta \otimes \eta)(1_K \otimes 1_K) = 1_B \otimes 1_B.$$
As Hanno says you can interpret that by remembering that $\Delta$ is a algebra homomorphism in a bialgebra, so it has to preserve the unit.
The equation $\Delta(x) = 1 \otimes x + x \otimes 1$ is only valid for the elements of $\mathfrak{g}$ in $U(\mathfrak{g})$. Such an element is called a primitive element. You should be very careful when computing the coproduct in $U(\mathfrak{g})$, because it's tempting to believe that since $\Delta(x) = 1 \otimes x + x \otimes 1$ on generators, the same holds true for every element. That's not the case. The rule to use is again that $\Delta$ is a algebra homomorphism, so for example if $x, y \in \mathfrak{g}$,
$$\Delta(xy) = \Delta(x) \Delta(y) = (1 \otimes x + x \otimes 1) (1 \otimes y + y \otimes 1) = 1 \otimes xy + x \otimes y + y \otimes x + xy \otimes 1.$$
And a similar pattern holds true for products with more terms.
Answer: On my master thesis two year ago, i think i used  $\Delta(1) = 1 \otimes 1 + 1 \otimes 1$. By a fast googling, i found the same on wiki.
I hope that helps.
Comment: The equality $\Delta(X) = X\otimes 1 + 1\otimes X$ holds for $X\in {\mathfrak g}\subset{\mathscr U}{\mathfrak g}$, but not for the unit $1$ of ${\mathscr U}{\mathfrak g}$. As said in the comments, the unit has to be preserved under comultiplication, and the unit of ${\mathscr U}{\mathfrak g}\otimes{\mathscr U}{\mathfrak g}$ is $1\otimes 1$.
Comment: Hi Giannis. Nice to see you here! Btw: I am sure you have used the correct expression $\Delta(1) = 1 \otimes 1 $ in your master thesis. (I verified this by looking at the bottom of p. 40 of your thesis as this is posted in the arXiv) ;)


Transfer .cn domain to another registrar

Question: I have to transfer domains hosted by a deficient local ISP in China. Can I transfer my domain registration without my current ISP's cooperation?
Comment: If your registrar is uncooperative, there is not much you can do. You may be able to file a complaint with the entity that handles the ccTLD or gTLD assignments. Otherwise, maybe any new registrar can help though that may be difficult. I am sure that many registrars deal with this everyday. I would assume that GoDaddy can give pointers and help you to transfer the site. They are large enough and the have some real experts though they are not generally answering the phone. You may have to ask for a supervisor if you contact any registrar. Be patient and explain your issue carefully.
Answer: .cn domain transfers generally work about the same as transfers of any other domain name. You obtain an authorization code from the old registrar, and have the domain unlocked. Then you provide the authorization code to the new registrar and wait up to 5 days.
There is a restriction that .cn domain names registered with a registrar in China cannot be transferred to a registrar outside China, and vice versa. So if your current registrar is a Chinese company, you can only transfer to another Chinese registrar.
Under CNNIC rules, the old registrar can take up to three days to give you the authorization code to transfer the domain, but in practice this should happen within minutes. Check with the old registrar to confirm what they may require to initiate the transfer process, such as submitting proof of identity.
If the old registrar is refusing to give you an authorization code, I would suggest contacting CNNIC directly for advice, as this is a very unusual situation. I was not able to find any mentions on the Internet of anyone who had suffered it.


Ok to paint exterior trim of leased building?

Question: I have a club that leases a space including a street-facing exterior. There is a small flat awning over the entrance way which is bordered by a metal channel which is about 4 inches square. The paint on this metal trim is flaking off. Am I within my rights to repaint this without the landlord's permission? There is nothing in the lease one way or another about painting the exterior trim or other surfaces. I assume having the "full use" of the property means I can repaint the trim. Is that right?
Answer: No, you cannot do this without permission. Ask for permission, you will almost certainly get it.


FSK Modulation using I/Q

Question: Is it possible to do FSK with I/Q data? If I/Q only shows amplitude and phase changes is there anyway I can use it to generate a frequency f1 to represent binary 1 and f2 to represent binary 0?
Comment: Do you have access to Matlab? I have a pretty straightforward simulation of an FSK system using I/Q data I would be happy to share if it would be useful to you
Answer: Yes. Set your local oscillator halfway between f1 and f2 i.e. (f1+f2)/2. As your I/Q data, make a sine/cosine wave (i.e. a complex sine wave i.e. a point going around in a circle) with a frequency of either + or - (f1-f2)/2 (i.e. same frequency, different direction).
In one direction the frequency will add, and after the mixer you'll have a frequency of (f1+f2)/2 + (f1-f2)/2 = f1. In the other direction it will subtract and you'll have a frequency of (f1+f2)/2 - (f1-f2)/2 = f2.
Any RF signal that's limited within a band near the local oscillator frequency - and I do mean any - can be represented by I/Q data below a certain maximum frequency. That's the advantage of I/Q mixing and that's why it's used in SDR. The higher-frequency you allow the I/Q signal to be, the wider the band you get. If your local oscillator is e.g. 300MHz and your SDR has a 30MHz bandwidth, it can process I/Q signals up to 15MHz and it you can make any RF signal you like, so long as it only contains frequencies between 285MHz and 315MHz. (I think. Not sure how SDR bandwidth is specified. It might be double that.)
Note: when changing from 1 to 0 or 0 to 1, avoid phase discontinuities, i.e. your wave should continue from the last point but go in the opposite direction - it shouldn't jump to another point such as the mirror image of the last point.
Comment: @PrematureCorn how much do you know about I/Q modulation?
Comment: @PrematureCorn have you seen I/Q points plotted on a chart?
Comment: @PrematureCorn a circle going one way is a frequency lower than the LO, and a circle going the other way is a frequency higher than the LO
Comment: I don't totally understand the setup your describing. So the LO input to the mixer should have a frequency halfway between f1 and f2? And how does this generate a complex sine wave?
Comment: Yes I've seen them plotted and how they trace out a circle from the two quadrature waves varying
Comment: Are you saying once I add or recombine the outputs of the two mixers then I'll have the complex sine wave?
Comment: Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/142735/discussion-between-prematurecorn-and-user253751).
Answer: Yes, you can use an I/Q system to do FSK. The quadrature receiver can be beneficial, especially in a setup like the one described by @user253751 where the LO frequency is halfway between the bit 1 frequency and the bit 0 frequency. \$ f_1 = \$ frequency for bit 1, \$ f_0 = \$frequency bit 0 and \$ f_{LO} = \dfrac{f_1+f_0}{2} = \$ frequency local oscillator. Below I attached a schematic for an IQ receiver

The receiver has a few parts. Primarily there is the mixer which (ideally) multiplies the LO and the received signal together. Using the product rule for sinusoids gives that. The output signal for the 0-bit and 1-bit cases are going to be
\$ cos(2 \pi f_1t) cos(2 \pi f_{LO} t) = \dfrac{1}{2} [cos(2 \pi (f_1-f_{LO}) t) + cos(2 \pi (f_1+f_{LO})t)]  \$
\$ cos(2 \pi f_0t) cos(2 \pi f_{LO} t) = \dfrac{1}{2} [cos(2 \pi (f_0-f_{LO}) t) + cos(2 \pi (f_0+f_{LO})t)]  \$
Usually following the mixing of the signal, there is an LPF to remove the high-frequency components, which are \$ cos(2 \pi (f_0+f_{LO})t) \$ and \$ cos(2 \pi (f_1+f_{LO})t) \$
So based on the image schematic of the IQ receiver belo,w the received signal at the \$y_I(t) \$ is
\$
y_I(t) =
\begin{cases}
     \dfrac{1}{2} cos(2 \pi (f_1-f_{LO}) t) & \text{for bit 1} \\
     \dfrac{1}{2} cos(2 \pi (f_0-f_{LO}) t) & \text{for bit 0}
\end{cases}
\$
There is a problem with this because of how \$ f_1 f_0, f_{LO} \$ were chosen. In the scenario above, define
\$ f_{b1} = (f_1-f_{LO}) \$
\$ f_{b0} = (f_0-f_{LO}) \$
Then based on the definitions for \$ f_1 f_0, f_{LO} \$ I can say that \$ f_{b1} = - f_{b0} \$. Furthermore, since we are measuring real signals, the Fourier transform of these signals will have symmetric and identical magnitude spectrums in the Fourier domain.
This is where IQ sampling comes in. It allows us to differentiate these signals by essentially making them complex signals. This is done by adding a phase shift of 90° before mixing in the quadrature (Q) channel. Following the same analysis as above, it is possible to derive that.
\$
y_Q(t) =
\begin{cases}
     \dfrac{1}{2} cos(2 \pi (f_1-f_{LO}) t) =  \dfrac{1}{2} cos(2 \pi (f_{b1}-\dfrac{\pi}{2}) t) = \dfrac{1}{2} sin( 2\pi f_{b1} t) & \text{for bit 1} \\
     \dfrac{1}{2} cos(2 \pi (f_0-f_{LO}) t)=  \dfrac{1}{2} cos(2 \pi (f_{b0}-\dfrac{\pi}{2}) t) = \dfrac{1}{2} sin( 2\pi f_{b0} t) & \text{for bit 0}
\end{cases}
\$
Now if I define my final signal as \$ y_1(t) = y_{I1}(t)+jy_{Q1}(t) = e^{j 2\pi f_{b1} t} \$. Now because my signal is complex, I can differentiate \$ f_{b1} \$ and \$ f_{b0} \$ in the frequency domain. From this point on, I can do my matched filtering/detection however I want.
To help illustrate the entire process, I wrote a MATLAB script to detect if a 0 or 1 is being transmitted using an IQ receiver.
First is an image of the transmit signal for bit 1, along with the local oscillator and mixed signals for bit 1. Notice how in the mixed signal, there are fast oscillations from the summation of the local oscillator and bit 1 frequencies and slow oscillations from the difference in the local oscillator and bit 1 frequencies.

In the script, I apply an IIR filter to remove high-frequency oscillations. The mixed signal before and after the filter is shown below.

Likewise, the FFTs of the transmit signal, complex mixed signal, and filtered complex mixed signal are shown below. Note that the transmit signal, which is real, has a symmetric FFT, while the complex mixed signals are asymmetric in the frequency domain. Before the filter, there is a peak at 0.4 GHz. This peak is really at a higher frequency, but I am undersampling, causing it to alias to 0.4 GHz.

The script also includes a simulation of a matched filter and the ability to transmit multiple bits. For example, a script for transmitting 10 random bits is shown below. The bits transmitted are [0, 0, 1, 0, 1, 0, 1, 0, 1, 1].

Later in the script, I employ a matched filter to detect the signal. The whole script can be found below
<code>clc
clear
close all

f0 = 1.0e9;        %Frequency to send a 0
f1 = 1.05e9;     %Frequency to send a 1
LOf = (f0+f1)/2; % Local oscillator frequency

% Note. Recall that the fft resolution is determined by the length of time
% that is observed. So by using longer pulses we can use a smaller
% bandwidth to transmit the signal. The trade off is (bandwidth vs bitrate)
% (i.e the frequency used for 1 and the frequency used for 0 may be closer
% together)
Tp = 100e-9; % length of the pulse
Fsim = 2.5e9; % Sampling rate for the simulation (not for ADC)
Tsim = 1/Fsim;

tsp = 0:Tsim:Tp; %Time for a single pulse
Tp0 = cos(f0*2*pi*tsp);  % A single pulse for bit 0
Tp1 = cos(f1*2*pi*tsp);  % A single pulse for bit 1
LOI_s = cos(LOf*2*pi*tsp); % The in-phase local oscillator signal for 1 pulse
LOQ_s = cos(LOf*2*pi*tsp+pi/2); % The quadrature " "

figure(1)
subplot(3,1,1)
plot(tsp,Tp0,'linewidth',2);xlabel('time (s)');ylabel('wave voltage')
subplot(3,1,2)
plot(tsp,Tp1,'linewidth',2);xlabel('time (s)');ylabel('wave voltage')
subplot(3,1,3)
plot(tsp,LOI_s,'linewidth',2);xlabel('time (s)');ylabel('wave voltage')

%% Generates random bits and then combines them into a single transmit Signal
bTran = 10; % The number of bits to transfer
txSig = []; % Initialize the transmit signal
startPhase = 0; % The starting phase
bits = [];

% signal
for i=1:bTran
    r=randi(2,1,1)-1;
    if r == 1
        txNext = cos(f1*2*pi*tsp+startPhase);
        startPhase = startPhase+f1*2*pi*tsp(end);
    elseif r == 0
        txNext = cos(f0*2*pi*tsp+startPhase);
        startPhase = startPhase+f0*2*pi*tsp(end);
    end
    txSig = [txSig,txNext(1:(end-1))];
    bits = [bits,r];
end
t = 0:Tsim:(bTran*Tp-Tsim); % Signal transmit time
LOI = cos(LOf*2*pi*t); % Local oscillator signal in-phase
LOQ = cos(LOf*2*pi*t+pi/2); % Local oscillator signal quadrature
%% Simulate Mixing Signals
mixSigI = LOI.*txSig; % Mixes the signal with the LO
mixSigQ = LOQ.*txSig; % Mixes the signal with the LO
mixSig = mixSigI+1i*mixSigQ; % Mixed signal is the combination of LO and
figure(2)
set(gca,'fontsize',18)
subplot(3,1,1);plot(t,txSig,'b','LineWidth',2);xlabel('time');ylabel('volt');title('Transmit')
subplot(3,1,2);plot(t,LOI,'r','Linewidth',2);xlabel('time');ylabel('volt');title('LO')
subplot(3,1,3);plot(t,mixSig,'g','Linewidth',2);xlabel('time');ylabel('volt');title('Mixed')
%% Low Pass Filters the Signal (Part of Mixing
% Design the filter
fp = 2*(f1-LOf); %filter pass frequency
fs = 8*(f1-LOf); %filter stop frequency
rpDB = 0.25; %passband ripple (dB)
rsAt = 40; %Stopband attenuation
[n,wn]=ellipord(fp/Fsim,fs/Fsim,rpDB,rsAt);
[b,a]=ellip(n,rpDB,rsAt,wn,'low');

% Show the filter performance
[H,w]=freqz(b,a,2^13);
maxH = max(abs(H));
figure(3);subplot(2,1,1);plot(w/pi,20*log10(abs(H)/maxH));grid
xlabel('Normalized Frequency');ylabel('Magnitude dB')
subplot(2,1,2);plot(w/pi,angle(H));grid
xlabel('Normalized Frequency');ylabel('Magnitude Squared')

% Apply the filter to the signal
a = a(2:end);
zeroPadMixSig = [zeros(1,length(b)-1),mixSig,zeros(1,length(a))];
mixSigFilt = zeros(1,length(mixSig)+length(a));
for i = (length(a)+1):length(mixSigFilt)
    xinS = i-length(b)+1;
    xinE = i;
    yinS = i-length(a);
    yinE = i-1;
    mixSigFilt(i) = sum(fliplr(b).*zeroPadMixSig(xinS:xinE))-...
                    sum(fliplr(a).*mixSigFilt(yinS:yinE));
end
%% Take FFT of signal
N = 2^10;
mixSigFiltfft = fftshift(fft(mixSigFilt,N));
mixSigfft = fftshift(fft(mixSig,N));
txSigfft = fftshift(fft(txSig,N));
f = ((0:(N-1))/N-1/2)*Fsim;
figure(3)
subplot(3,1,1);plot(f/1e9,abs(txSigfft),'linewidth',2);xlabel('Freq (GHz)');ylabel('Mag');title('FFT transmit signal')
set(gca,'fontsize',18)
subplot(3,1,2);plot(f/1e9,abs(mixSigfft),'linewidth',2);xlabel('Freq (GHz)');ylabel('Mag');title('FFT mixed IQ signal')
set(gca,'fontsize',18)
subplot(3,1,3);plot(f/1e9,abs(mixSigFiltfft),'linewidth',2);xlabel('Freq (GHz)');ylabel('Mag');title('Filtered mixed IQ signal')
set(gca,'fontsize',18)

% Show unfiltered and filtered signal in time and frequency
figure(4)
subplot(2,1,1);plot(t,real(mixSig),'b','linewidth',2);xlabel('time');ylabel('volts');title('Before Filter');set(gca,'fontsize',18)
subplot(2,1,2);plot(t,real(mixSigFilt((length(a)+1):end)),'r','linewidth',2)
xlabel('time');ylabel('volts');title('Before Filter');set(gca,'fontsize',18)

%% Take a Short Time Fourier Transform of the Filtered Signal
winL = ceil(length(Tp0)/4);
[s_stft,f_stft,t_stft] = stft(mixSigFilt,Fsim,'FFTLength',N,'Window',ones(winL,1));
figure(5),pcolor(repmat(t_stft.',size(s_stft,1),1),repmat(f_stft/1e6,1,size(s_stft,2)),abs(s_stft));xlabel('time');ylabel('frequency')
set(gca,'fontsize',18);xlabel('time');ylabel('frequency(MHz)')
ylim([-200 200])

%% Sample Using the ADC
Fbmax = f1-LOf; % The maximum beat frequency (difference in local oscillator and transmit frequency)
Fadc = 3*Fbmax; % I only need to do 2*Fbmax (according to nyquist) but do to
Tadc = 1/Fadc; % The sampling period of the adc
tadc = 0:Tadc:t(end); % Times that the adc is sampled
mixSigFiltADC = interp1(t,mixSigFilt((length(a)+1):end),tadc); % Interpolates to get sampled value by adc

% Displays the ADC data
figure(6)
plot(tadc,real(mixSigFiltADC),tadc,imag(mixSigFiltADC),'linewidth',2)

% Takes the STFT of the ADC data and plots it
figure(7)

%% Creates a matched filter to determine frequency
mix0 = LOI_s.*Tp0+1i*LOQ_s.*Tp0; % The mixed signal for bit 0
mix1 = LOI_s.*Tp1+1i*LOQ_s.*Tp1; % The mixed signal for bit 1

%
zeroPadMix0 = [zeros(1,length(b)-1),mix0,zeros(1,length(a))]; % Zero pads the mix filters prior to filtering
zeroPadMix1 = [zeros(1,length(b)-1),mix1,zeros(1,length(a))];

filt0 = zeros(1,length(mix0)+length(a)); % Holds the matched filters
filt1 = zeros(1,length(mix1)+length(a)); %

% Applies filter to expected signal
for i = (length(a)+1):length(filt0)
    xinS = i-length(b)+1;
    xinE = i;
    yinS = i-length(a);
    yinE = i-1;
    filt0(i) = sum(fliplr(b).*zeroPadMix0(xinS:xinE))-...
                    sum(fliplr(a).*filt0(yinS:yinE));
    filt1(i) = sum(fliplr(b).*zeroPadMix1(xinS:xinE))-...
                    sum(fliplr(a).*filt1(yinS:yinE));
end

matchFilt0 = fliplr(filt0);
matchFilt1 = fliplr(filt1);

% Sample the matchFilter using the ADC
tadcMF = 0:Tadc:Tp;
matchFilt0_ADC = interp1(tsp,matchFilt0((length(a)+1):end),tadcMF);
matchFilt1_ADC = interp1(tsp,matchFilt1((length(a)+1):end),tadcMF);

%% Apply Matched Filter to Determine Frequency
% Zero pads the received signal
is0 = conv(mixSigFiltADC,matchFilt0_ADC,'valid');
is1 = conv(mixSigFiltADC,matchFilt1_ADC,'valid');

figure(8)
subplot(2,1,1);plot(abs(is0),'r','linewidth',2)
subplot(2,1,2);plot(abs(is1),'b','linewidth',2)
grid on
</code>
Answer: Sure, phase is the integral of the frequency, so to generate a FSK signal, you need to generate the I/Q signal from a constant amplitude and the numerical integration of the frequency.

FSK Modulation using I/Q


What does Heidegger mean "the closedness of earth"?

Question:
What does Heidegger mean "the closedness of earth" in 'the origin of the work of art' aka 'Der Ursprung des Kunstwerkes'?
Comment: What is the citation for the quote?
Comment: It could mean earth is topologically *complete and closed* in the sense of containing all the necessary natural laws or whatever for its own evolution as Heidegger hinted later to achieve so it *strives to entrust everything to its law*. With such closedness it contains its own power within itself as an *inseparable unity* and thus contestants as a part of it should not strive for rift of a cleft but for the *intimate* dependent arising to be able to achieve *Dasein* as being there, otherwise it is immoral and being not...
Comment: It's the only game in town.
Answer: First of all, this is an awful translation IMHO. It even omits whole sentences and loses a lot of the obviously intended connotations. The German original (as pointed out in Mr. White's answer, can be found in Holzwege (Gesamtausgabe, Band 5), Klostermann 1977, pp. 50-51) reads:

Indem aber eine Welt sich öffnet, kommt die Erde zum Ragen. Sie zeigt sich als das alles Tragende, als das in sein Gesetz Geborgene und ständig Sichverschließende. Welt verlangt
ihre Entschiedenheit und ihr Maß und läßt das Seiende in das
Offene ihrer Bahnen gelangen. Erde trachtet, tragend-aufragend sich verschlossen zu halten und alles ihrem Gesetz anzuvertrauen. Der Streit ist kein Riß als das Aufreißen einer bloßen Kluft, sondern der Streit ist die Innigkeit des Sichzugehörens der Streitenden. Dieser Riß reißt die Gegenwendigen in die Herkunft ihrer Einheit aus dem einigen Grunde zusammen. Er ist Grundriß. Er ist Auf-riß, der die Grundzüge des Aufgehens der Lichtung des Seienden zeichnet. Dieser Riß läßt die Gegenwendigen nicht auseinanderbersten, er bringt das Gegenwendige von Maß und Grenze in den einigen Umriß.

My translation would be:

But as a world opens itself up, earth starts to tower. It shows itself as that which carries everything, that which shelters all being in its own law and is ever enclosing itself. The world demands its determination and measure and lets that which is into the openness of its ways. Earth strives, carrying and towering, to keep itself closed and entrust everything to its laws. The strife is not a rip [Riss] as the ripping open [Aufreißen] of a mere gap, the strife is the intimacy of a belonging together of contestants. This rip rips those which turn away from another back together, into the source of their unity. It is the primordial rip [Grundriss]. It is a ripping open [Aufriss] that outlines the rise of the illumination of being. This rip does not let those who turn away from one another rip apart, it brings the measure and boundary of them into a unified shape [Umriss].

Other than in the surrounding text, Heidegger makes a more fundamental point here. He speaks generally about the problems of extracting truth from the world as there is a fundamental tension between the world as an object that is the original, self-sustained being and a subject that tries to get a perspective on that all-encompassing being, from the outside, as it were.
Art is, according to Heidegger, about how the world can be formed so that it is depicted (or, more generally, represented) with the very substance that makes it up. That is closely linked to phenomenology, but also about technique of art. This is why he uses word plays like "Riss", which means both sketch (literally the first few lines drawn) and chasm/rift/tear, "Grundriss", which means both the ground plan of an object (the drawing perspective from above) and the basic structure of something, "Aufriss" which means both the frontal view of an object in drawing and the process of tearing apart/opening a rift, and "Umriss" which means the outline in terms of drawing, concepts, and phenomenologically.
Now on to the phenomenological context. In phenomenology, the closedness of reality is the default state. It is generally shut away from us, and only in the phenomenon "opens itself up" to us, shows itself to us in certain ways that depend both on the object and us, the subject. Heidegger again plays with words when he says that the way earth opens itself up is as a closed entity, something that wants "to preserve its closedness" (or, as I put it, "keep itself closed") and thus, in opening itself up, is closed: The world discloses itself as all-encompassing, as that which can have nothing beyond itself, so that everything has to follow its laws since it is a closed system that contains everything.
Therefore, when the artist tries to take a standpoint in relation to the world, a perspective onto the world, they have to tear themself apart from the world, open a rift, try to set themselves apart from it while the world does not allow for it according to the internal logic of it as a phenomenon. As that means a complete severance is impossible, we end up with this "intimacy of the mutual dependence of the contestants" and a work of art that is a result of the being ripped together again, of mutual aspects of both artist and substance.
Hope that helps.


How is a svarabhakti different from a vowel

Question: I recently came across the concept of "svarabhakti" in the context of the Gaelic word "Alba" (pronounced with a vowel between l and b). What I'm confused about is why this is considered a svarabhakti rather than the word simply being "Alaba"?
Answer: "Svarabhakti" is from a Sanskrit grammatical terms referring to a rule of pronunciation promulgated in the Prātiçākhyas that inserts a "brief" vowel between r and a nasal, see Whitney's Sanskrit Grammar, 230(c). In contemporary terms, this is not a full vowel, this is a vowel-like concomitant of /r/ in a certain context, part of phonetic implementation. Sometimes such vowel-like sounds are called "epenthetic" vowels, if the vowel that is inserted is the same as some phonemic vowel (apparently not the case with Sanskrit). Sometimes, such articulatorily-driven vowels are called "excrescent" vowels.
There isn't a particularly good reason to use the word "svarabhakti", but there might be a real linguistic question at stake. There is discussion of this issue in Bosch & De John 1997. One question is whether what is inserted is a full vowel as opposed to being a simple "vocalic release". IMO the evidence is good enough that it is not a "mere release gesture". The epenthetic vowel is an exceptionally-stressed non-initial vowel (any vowel quality can be inserted, whereas unstressed vowels are drawn from a restricted inventory). The fact that intervening consonant palatality determines frontness argues that there is a phonological process (this is not phonetic implementation), as does the fact that the inserted vowel is phonetically not a micro-vowel of e.g. 40 msc, it is a full vowel.
However, that does not address the question of claiming that the underlying and surface forms are different: why not just say that [dɔrɔγ] is /dɔrɔγ/ rather than /dɔrγ/. The rationale is that there are phonetic details that force such an analysis, e.g. that with non-epenthetic /a/ an intervocalic consonant is syllabified in the coda ([ar.an] "bread") but with an epenthetic vowel the intervocalic consonant is in the onset ([a.ram] "army"). This is not a particularly compelling argument. Bosch has another paper, "The syllable in Scottish Gaelic dialect studies", Scottish Gaelic Studies XVIII, 1-22, which is said to go deeper into the question. It is important to note (as Bosch does) that not all Gaelic dialects are identical: she is reporting a famous fact from Barra Gaelic, which crucially depends on a particular interpretation of a transcription.
Answer: Svarabhakti, or anaptyxis, or, in more common sense, epenthesis can't be different from the vowel because of the different nature of them: a vowel is the vowel, but svarabhakti is the process of the insertion of vowels into clusters of consonants.
Also svarabhakti is related with the phonotactics:
the word 'Alba' can't be simple 'Alaba'  because Contemporary Gaelic 'Alba' /'aLVBa/ (L, B - different allophones, V - inserted vowel) comes from Old Irish 'Albu' /'albu/ where there no need epenthesis too much.
And also svarabhakti is related with the orthography:
before the recognizing of such type of vowels, they comes from sporadic processes of pronunciation, but then the pronunciation can be influenced by the new spelling, i.e. 'Alaba'.
Comment: I don't find any of this answer persuasive. The arguments seem to be 1) it's different because there's a process with a name; 2) it's different because Old Irish; and 3) it's different because it doesn't appear in the spelling. It mentions phonotactics but then proceeds to ignore it.
Comment: Then I tried to answer to the question inside: why inserted vowel in the 'Alba' is considered as svarabhakti, not just it is crypto-'Alaba'-word: because of the history of the word and phonotactics of the languages - firstly it was 'Albu' in the Old Irish, where it was easily pronounced without any epenthetic vowel, or only some people inserted it. Then it becomes 'Alba', and more peoples start to insert the vowels. The different vowels in the different languages: a or ə. This is related to phonotactics of the language. But also we have the literary tradition, where word is still 'Alba'.
Comment: This is my fault, I did type "considered", but I mean "related".
Comment: And first part was as answer to the topic's headline. Question was incorrect because of the different nature of the 'svarabhakti' and 'vowel'.
Comment: So until there is 'Alba' spelling in the languages, we say that there is process of inserting of the epenthetic vowel. And even we would write it as 'Alaba' some people would say it as 'Alba', there is still the process inside. But when most of the people become to pronounce it as 'Alaba' it seems to be new statement.