$SU(2)$ to $U(1)$ symmetry breaking

Question: Why does electroweak theory have $SU(2) \times U(1)$ to $U(1)$ symmetry breaking. Is it not possible to have simply $SU(2)$ to $U(1)$ symmetry breaking?
Comment: It *is* possible to have $\mathrm{SU}(2) \to \mathrm{U}(1)$ breaking, but the resulting theory will be of course different and no longer match experiment. If you're not concerned about the number of bosons generated (which is the easiest observable consequence), I'm not sure what exactly you're asking for.
Comment: PS. I am not worried about the number of massive bosons generated
Comment: The model @ACuriousMind mentions is the Georgi-Glashow model, failing phenomenology tests. Basically, the weak charged charges as already known before the discovery of neutral currents ***failed*** to close to the EM charge, so *another* neutral charge was all but necessary, and was therefore conjectured by Glashow.
Comment: [Glashow 1961](https://doi.org/10.1016/0029-5582(61)90469-2). You can repeat the commutation of charged current charges yourself, to see the evident point.
Answer: It is technically possible to have a theory where and $SU(2)$ symmetry spontaneously breaks to a $U(1)$ symmetry. The simplest example is when you have a field that transforms in the adjoint (spin-1) representation of $SU(2)$ and it gets a non-zero vacuum expectation value. If the $SU(2)$ symmetry were gauged this would leave you with one massless gauge boson and one charged massive gauge boson.
However, the Standard Model needs spontaneous gauge symmetry breaking for two reasons. The first is to give mass the to the $W$ boson, but the second is to give mass to the fermions. The weak gauge bosons treat left- and right-handed fermions differently, as scattering experiments teach us, but mass terms mix left- and right-handed fermions, so gauge symmetry forbids fermion mass terms. The solution is to have fermions couple to the Higgs field in a gauge-invariant way that then produces an effective mass term after spontaneous symmetry breaking.
The $SU(2)\rightarrow U(1)$ breaking pattern cannot do this without introducing additional fermions. Weak interaction phenomenology suggests that left-handed leptons and neutrinos transform in an $SU(2)$ doublet while right-handed fermions do not transform under $SU(2)$ at all. To have a gauge-invariant Yukawa term we then need the Higgs field to also transform as a doublet.
However, a doublet with a vacuum expectation value breaks $SU(2)$ to the trivial group (no remaining symmetry), leaving us without a massless boson to act as the photon.
The next simplest solution is to increase the symmetry to $SU(2)\times U(1)$. Now the Higgs doublet vacuum expectation value can break $SU(2)\times U(1)$ to $U(1)$ as long as the doublet's $U(1)$ value has the right value.
Answer: For the SU(2) gauge Group you have only 3 Generators of a gauge field. This is because from the 2*2 =4 Matrix entries you remove one due to the condition that the determinant of the Group must be equal to 1. In SU(2) group are encoded the force carriers of the weak interaction; These are $W_+,W_-$ (W-bosons in positive and negative charge) and $Z$ (Z-bosons).
In the Group $SU(2) \times U(1)$ you have also a $U(1)$ symmetry with a single Group generator and therefore you have 3+1=4 gauge fields for this group.
When symmetry is broken, you will get 3 massive weak bosons and the photon.
Comment: Not sure how this answers the question.
Answer: There is the Pati-Salam model that has an electroweak field $SU(2)_L\times SU(2)_R$. With the strong nuclear interactions it is $SU(4)\times SU(2)_L\times SU(2)_R$. There are some problems with the idea of an $SU(4)$ strong nuclear interaction theory. The recent results by the LLNL lattice group might breath some life into this. The $SU(4)$ has $4$ colors with $7$ additional gluons that change color with an additional color neutral gluon. Maybe the additional stuff is associated with dark matter. The symmetry breaking of this theory involves the decomposition of the $SU(2)_R~\rightarrow~U(1)$ that recovers the standard electroweak field theory. The $\sigma_{\pm}$ elements from this broken $SU(2)_R$, which in the $SU(2)_L$ go on to define the $W^{\pm}$, might have some additional physics. These might go into the generation of additional photons or combine to form a sort of $Z_\gamma$. Whether this is the case or bit will ultimately come from experimental data.

$SU(2)$ to $U(1)$ symmetry breaking


What's the best UX option to help users choose between three items

Question: So, I'm trying to use an optimal UX design for three choices that are responses to questions. The three choices are choice 1, choice 2 and "I don't know." Currently, I've been considering using radio buttons with text next to them, but I'm wondering if there is a better option. I've considered making the item choices into button graphics and having them change color when the user clicks, but that process is very time-consuming and inflexible if you wish to change the text. I'm really open to listening for ideas here.
Answer: In what context does this option appear? Is it the only thing on the page or is the UI cluttered with other elements? Or is it somewhere in between?
If the screen is pretty barren, I would use radio buttons. That doesn't prevent you from having a button-like background surround them after you select them. Something like this:

But using buttons as radio buttons can be a little bit confusing.
Comment: I think radio buttons are better for busy screens with other form elements. Otherwise it is just an extra step. (1. select the radio button, 2. click submit)
Comment: Thanks jonshariat, I was not very clear. I meant that I would use "fancy" radio buttons like the above image when there is not much else on the screen (as opposed to using a dropdown or regular radio buttons). Regular radio buttons would probably suffice at other times.
Comment: Lens, thanks so much for that advice. I'll be going with a radio button with a background to contrast, exactly as you said. I also really love the visual appeal of it, which is why I was hesitant on radio buttons to begin with. The only small thing I will add is that clicking anywhere on the image can make the radio button turn on (but not off), since a sizeable part of my target audience may not be technology proficient. No point in penalizing them for a slight misclick since we know their intentions.
Answer: You can do something interesting things with labels and radio buttons; making them stylistically like buttons or image buttons.
I've had good results by using radio buttons in situations like these and styling the parent label to look somewhat like the tags used on this site - except there would be a radio button before the text.
Play around with it, I think you'll find what you're looking for.


What is the best way to use uniswap without router?

Question: I just bought a scam token. The liquidity pool is still there but I couldn't sell because I couldn't approve the token in Uniswap. When I try to approve, the error "execution reverted: ERC20: approve from the zero address" appears on the javascript console. There may be something shady in the approve function. However, I found that a front-running bot was able to sell the token without approval. It seems the bot just calls the swap function and transfers the tokens.
The sell transaction is this.
Can I do the same with Etherscan's writeContract?
Or can I do that with javascript SDK? Or should I deploy a contract like the front-running bot?
Any input would be greatly appreciated.
Answer: You could deploy your own custom router contract. Easily fork one from the original Uniswap Router. Make every write function to be onlyOwner(). Then modify the swap function so instead of sending the token back to the sender wallet. The contract itself will receive and send the token.
Thus when selling you don't need any approval, because the contract is the owner of the token itself. For actual uses, you transfer WETH from your wallet to that contract first. Then use your custom function for swapping tokens. And don't forget to create a withdrawn function so you could call that and let the contract send WETH it has back to your wallet.
This is common practice use by bot. You can completely trade using this contract instead of Uniswap one unless the token only lets a specific address(eg. original router) call transfer.


Quoting/Citing Footnotes in APA

Question: When directly quoting from a footnote, I have sometimes seen authors indicate this by including something along the lines of "n", "fn.", "footnote 2", etc. in their citations, like "(Jones, 2023, p. 160n)" or some such. Is there any standard way of doing this in APA? Also, is there any particular convention for when I want to point to both the body of a particular page, and a particular footnote on that page? For example, if I want to point towards both p. 160 of Jones, 2023, as well as a footnote on that same page, can I say something like "Certain comments in her 2023 (p. 160 and n) make it clear that Jones..."?
Answer: This is partly addressed in the APA Style blog post How to Cite Part of a Work. The example given for a parenthetical in-text citation referencing a footnote is

(Park, Van Bavel, Vasey, & Thayer, 2013, footnote 3)

The page claims that the word 'footnote' should be in lowercase, however that might not be universal as the presumably more recent basic principles page gives as an example

(Garcia et al., 2020, Footnote 2)

Also, is there any particular convention for when I want to point to both the body of a particular page, and a particular footnote on that page?

It is unclear to me why you would need to cite both in that case. Since the page contains the footnote it would seem enough to cite just the page. (Perhaps it's worthwhile if the footnote continues on the next page?) But based on the comments to the blog post I think you can use

(Jones, 2023, p. 160 and footnote 4)

Note that this is different from

(Jones, 2023, footnote 4, p. 160)

which is interpreted as a reference to footnote 4 on page 160. I would tend to avoid using "n" or "fn." in most contexts, as spelling out "footnote" is more clear.
Comment: Thank you! I guess I wanted to cite both the footnote and the page because there are two relevant points, one in the body and one in a footnote, and if the reader looked to the source to see what I'm referring to, they may just see the relevant part of the body and think that's all I'm referring to and not consider the footnote too. (I feel like that's what I'd do if I were such a reader... but maybe that's just me.)

Quoting/Citing Footnotes in APA


Single remote trigger for fifty cameras

Question: I want to assemble several cameras, triggered by a single remote. Is this possible?
The trigger doesn't have to be wireless, because the cameras will be very near to each other. The cameras need to be very cheap, because I'll be needing 50 of them.
Comment: Well... even if you manage to find, let's say a $40 camera (that can be remote-controlled) you're already reaching $2000+ ! Am I correct in thinking about a "bullet-time" effect like in Matrix ?
Comment: for that price, it's reasonable for me.
Comment: The cheap eBay triggers work great.
Answer: I think there is one main problem with what you are asking : a cheap camera probably won't come with an external triggering system.
So you could :

buy a bunch of (not so) cheap cameras (~$100 ?) with an external trigger socket, and for the trigger go the cheaper way : buy the hardware and build it yourself. You need plugs compatible with the (possibly model-specific) sockets, connect them all in parallel with some wires to a single pushbutton (you also need the schematic of the plug to know how to connect...).
buy a bunch of very cheap cameras (~$40-50) without an external trigger and "hack" them : remove the trigger button and solder/attach wires instead, and connect them to a single pushbutton like above.

Actually it may require a "two-level" pushbutton like the original one (actually a double sided temporary flip switch, or two distinct pushbuttons, or...) in order to prefocus, then take the shots.
If the camera model is the same, I don't foresee a problem with connecting all the triggers in parallel. Otherwise some electronics might become necessary (relays/optocouplers/...).
And as a final note : beware that with cheap cameras you'll get... your money's worth : fewer control options, good image quality in good lighting conditions but otherwise "maybe not", etc.
Answer: If cost is a central concern, then you might want to investigate a DIY route. Using a platform such as Arduino, you can purchase basic cameras, and using the Arduino board, trigger them together in a variety of ways...really only your imagination is your limit here. As most of these cameras are very small, it should be easy to pack them together.
I have linked to Adafruit for these items, but there are hundreds of vendors for Arduino or Raspberry Pi products.
Comment: My guess is that this solution you gave probably it's the best.
I'll take a look into it, and let you know my doubts after....
Comment: Arduino is nice solution +1 :)
Comment: Alternatively, a Mega 2560 can simultaneously drive up to 54 output pins.  You could use those to trigger standalone cameras.  Just wire each output to the base of a transistor (or to an optoisolator through an appropriate current-limiting resistor) and wire the other pins on the transistor to the trigger contacts, paying attention to the direction of current flow.  You would likely need to pre-focus and put the cameras into manual focus mode, or else, you'd probably need twice as many outputs to drive the half-press contacts, too.
Answer: This is the product recommended by Chris Breeze and Eric Pare at Xangle amongst others - the Esper Triggerbox https://www.esperhq.com/product/triggerbox/
The ESPER TriggerBox is the world's leading programmable multi-camera shutter release controller. Up to 6 cameras can be connected to each TriggerBox and it allows multiple camera to be fired simultaneously or with programmed sequences and offsets + multiple TriggerBoxes can be linked together to synchronise larger multiple camera setups and they neatly stack together, a bit like LEGO bricks!
Answer: Breeze Systems makes software for controlling multiple cameras at once. It's worth looking at their site if only for inspiration.
Keep in mind that cheap cameras may not have a remote shutter release option; if this is for a one-time event, you might be better off renting a set of more capable cameras.
Comment: it's not for one time use only....
and cause it's a controlled environment regarding light, the cameras don't need to be great...
Answer: It can be done with GoPro cameras, and the GoPro wifi remote. You can pair one remote to multiple cameras, apparently you can control up to 50 cameras at once. See
Controlling Multiple Cameras with One Wi-Fi Remote

Though it wouldn't be cheap, if you need to buy 50 of them. The cheapest current model would be the Hero3 White edition, which has wifi built in. Or you could use an older HD Hero or HD Hero 2 with the wifi bacpac, but these are now discontinued and getting harder to find.
This video is a nice example of using 52 GoPro cameras for a "bullet time" effect. https://www.youtube.com/watch?v=zKtAuflyc5w
Answer: The TriggerTrap mobile app allows configuration of master/slave modes which would do what you want - multiple slave triggers from one master.
Of course you'd still have to find a cheap phone and cable for each camera, so unless you have a ton of old android phones knocking around you're still paying a few $$ per camera to trigger them.
Answer: If you want to go the low cost route Mike's Cool Stuff shows a design for doing this. It is fairly complex and requires detailed elecronics knowledge to create. He avoids using costly modules such as wifi, uses low cost camera modules and tackles subtle issues such as power drain, sequence triggers etc. https://m.youtube.com/watch?v=Lvyslu65V3s

Single remote trigger for fifty cameras


What is the maximum takeoff weight allowed for a part 103 ultralight?

Question: What is the max takeoff weight (MTOW) for a part 103 vertical takeoff (VTOL) ultralight?
And is the value peak or continuous limit?
Answer: 14 CFR 103.1
The FAA currently does not discriminate between "VTOL" and "normal" ultralight aircraft, nor between gas-powered or electric. The aircraft, if powered, cannot weigh more than 254lbs "empty" weight excluding floats and safety equipment that deploys in an emergency situation.
I'm not sure what you mean by "peak limit" or "continuous operation". The aircraft, when weighed without liquid fuel, must be less than 254lbs. It can carry up to 5 US-gallons of fuel (which can add up to 30lbs).
There is no limit to the MTOW for the aircraft though, it can carry a 400lb individual if you can make it fly, but it can't carry more than 1 person. So if the aircraft weighed 253lbs, you were 400, fuel is 30 that is 683lbs and still legal under Part 103. (Depending on how liberally you want to apply the "single occupant" rule, you may try to squeak your 200lb Mastiff aboard as well)
Answer: There is no "gross weight" limit as far as I can find in the regulations.  I think the thing you need to be concerned about is Power off stall speed.  The regulations do state a 25 knot limit on power off stall which has to do with wing loading.  If you have a high wing loading (high weight to wing area ratio) then your stall speed will be higher.
So the question is what is YOUR Gross Weight based on your wing area, weight and lift coefficient and air density.  So you need to "work backwards" with the stall speed formula to determine the gross weight for your aircraft.
SkyClimber


Making uibarbuttonitems fade

Question: I have a navigation bar that is set up and controlled completely with code. So it does not show up in IB. I have a button appear by "self.navigationitem.rightbarbutton = myButton;"
An I make it go away by setting it equal to NIL. What I am wondering is how could I make it fade in and out?
Answer: I found what worked best for me
[self.navigationItem setRightBarButtonItem:myButton animated:YES];

And then
[self.navigationItem setRightBarButtonItem:nil animated:YES];

To make it fade out.
Answer: Swift version
fade in: navigationItem.setRightBarButtonItem(myButton, animated: true)
fade out: navigationItem.setRightBarButtonItem(nil, animated: true)
Answer: Unfortunately there is no built in way to animate this for bar button items in a navigation bar. UIBarButtonItem is not a view or a control so it does not have animatable properties like alpha.
For bar button items in a UIToolbar, there is a way to animate. See this answer for details:
Is it possible to use Core Animation to fade out a UIBarButtonItem?

Making uibarbuttonitems fade


How can I use jQuery to show and hide DIVs based on checkboxes in a submitted form from a different page?

Question: I need to submit a form on one page, and show and hide DIVs on the receiving page based on what checkboxes were checked. The script also needs to display different messages for no checkboxes being checked, some checkboxes being checked, or all checkboxes being checked. Both pages are static HTML.
Answer: The form would need to use the GET action so it passes the values on the querystring.  Then from Javascript, you need to look at the QueryString to evaluate what was checked.  Details of doing than are explained in this question on SO:
get querystring with jQuery
Answer: If you were displaying both pages within a single page by using frames or iframes, then you could traverse the DOM to get to whatever elements you wanted to in order to change what's being rendered (I think).  In this case, both pages would need to be on the same server (or some domain anyway) to avoid being blocked for cross-site scripting.
Another option would be to embed both "pages" in the same HTML document, have one in a hidden div, which you then show when the user clicks submit.
Hope this helps.


Arduino Wire Types?

Question: I don't know what wires to get for my first Arduino project. I am planning on getting a pre-made light strip that I would control with an Arduino from across my room. Is there any specific type of wire to get? It needs to be about 15 feet. There are so many choices, but I don't know what I need. Does anyone else know?
Comment: What light strip? How long do you want the wire to be? What are your needs? Do you have an unusually hot/cold room? (Kidding with the last question :D)
Answer: Choosing wire all depends on what you're going to do with it, and most of the choice is based on how much current it will carry and how durable it needs to be. Generally, you're going to use insulated copper wire - aside from that, your answers are mostly here: https://electronics.stackexchange.com/questions/16948/choosing-the-right-type-of-wire
For experimentation - which you will need to do a lot of before attempting your goal project - you can use the little wires which come in the Arduino starter kit. They are "jumper wires" designed for use on a bread board - they can not carry large amounts of electricity.
This product here: https://www.sparkfun.com/products/8431 - these have "male" ends designed to be stuck into the holes in the breadboard, and connect to the holes on the headers of the Arduino.
Here's an example of a project laid out on a breadboard:

None of those wires carry a lot of current. If you're hooking up 50 LEDs that might be almost a full 1-AMP of current, so I would use thicker wire. Do yourself a favor and start with a kit like in this video, learn the basics, then attempt a 'real' project. Every Arduino user should be able to do all the experiments in the training book and understand them. You will be lost if you jump in deep right away...
https://www.youtube.com/watch?v=pf4qosqpv3A
Comment: While you can indeed use these stranded wires with solid ends, they may tend to break at the junction.  Plain 22 gauge solid wire works too, and is cheaper.  High power loads should not be drawing their power *through* the arduino board anyway.
Comment: Thanks Chris. Yes that's very important. It's covered in the video how to do that. Shows how to run the lights and the Arduino on two different power sources.

Arduino Wire Types?


Where does the parallel universe in the Penrose diagram come from?

Question:
In this diagram, as well as our universe, you have a parallel universe.
Where does this come from? Is this just a artifact of the diagram, or is it predicted by the maths in some sort.
Comment: the diagram you show depends on wormholes, which are not really mainstream physics, althouigh they are studied mathematically https://en.wikipedia.org/wiki/Penrose_diagram#Black_holes
Answer: This is the 'maximal extension' of the Schwarzchild metric - the solution of the field equations for a point mass that exists eternally, both in the future and in the past. It doesn't describe our universe, or real astrophysical black holes, because they don't extend forever into the past. (Our universe started with the big bang, and black holes started with a collapsing star.)
Schwarzchild's original black hole solution only described the right-hand and top quadrants. You have the outside universe, and the inside of the black hole that things fall into. If you start with a freely-falling particle with a given position and velocity, you can trace its trajectory forwards in time and see it fall into the black hole.
But you can also trace the trajectories backwards in time, too. The equations are time-symmetric, so any solution can be time-reversed and yield another equally valid solution. However, if we trace the trajectories backwards in Schwarzchild's right-upper diagram, we run into the diagonal line on the edge of the diagram, where it stops. What then?
Likewise, for locations inside the horizon, for a given velocity you can trace the free-fall trajectory back in time to this 'edge'. Spacetime is smooth there, there doesn't seem to be anything special or extreme going on there (unlike the singularity at $r=0$). So what happens? Is there really an 'edge' to space and time there? Or is it just a coordinate-system thing, and spacetime carries on?
The maximal extension is what we get if we assume spacetime carries on. It's like the way Eratosthenes observed that the Earth was curved in the neighbourhood around Egypt, and extended that to work out the circumference of the world. We use the fact that General Relativity is time-symmetric, turn the diagram upside-down, and glue the two halves together. The result is a full solution to the equations of General Relativity that is time-symmetric - it extends forever both forwards and backwards, and looks the same both forwards and with time in reverse. All geodesics (freefall trajectories) end either at singularities or infinity.
It answers the previously-awkward questions about why the diagram is not time-symmetric, and what you would see if you sat at a point and looked in that direction. (We can only see events along the past light cone, pointing downwards on the diagram. We have to trace trajectories of light rays back in time.)
--
Another useful way of looking at the diagram is to consider the analogy between black holes and uniform acceleration. Rindler noted that the diagram for a maximally extended Schwarzchild black hole looked a lot like the diagram for a uniformly accelerating reference frame. (This is to be expected by the equivalence principle.)
(I should emphasise, they're not actually the same metric, just similar-looking.)
A uniformly accelerating particle follows a hyperbolic trajectory when drawn on a spacetime diagram. This looks very much like the hyperbolic trajectories of particles hovering at a constant radius outside a black hole. Its past and future approach two light rays. The accelerating particle can never see any event that occurs after the futurewards light ray - it acts like an event horizon to the accelerating observer. If it ever crosses the line, it can never escape back to its home quadrant. And similarly, it can never influence any event before the pastwards light-ray - it acts like the anti-horizon in the eternal black hole.
So, we can take any patch of empty space, draw the spactime diagram for it, and draw an analogy with a black hole using accelerated observers. A uniformly accelerating observer constrained to stay within the right-hand quadrant sees the two light rays emanating from the centre as event horizons. They can see events in the past light cone, the bottom quadrant. And they can send messages to observers in the future light cone, the upper quadrant. But they can neither see nor be seen by observers in the left-hand quadrant. It is forever 'elsewhere'.
The accelerating observer can deduce it's there by tracing trajectories in the top quadrant backwards, or the bottom quadrant forwards. But no communication is possible. You can't get there without going faster than light, and they can't get to you.
So, a uniformly accelerating observer could deduce the existence of a part of the universe they can never see or influence, by considering what free-fall observers beyond their event horizons could see or be seen by. You just take the part of the universe you can see, and extend it using the same laws of physics as far as it will go.
--
Edit:
Because the problem seems to be trying to visualise how this geometry connects together when we add more dimensions, I'm going to attempt to draw some pictures!
First, get two sheets of paper and sketch on them both something like the following:

This shows the lightcones pointing out of the singularity in the bottom half, crossing the event horizon and progressing up the sheet, and then diving back in to the singularity. Fold the sheet at right angles along the event horizon.
Next make a cut in each sheet from the singularity to the event horizon, and tape them together in the following shape.

Note that each sheet joins on to one sigularity in the top half, and the other singularity in the bottom half.
Now, if you take this model and give one of the sheets a twist through $180^\circ$, you get the Penrose diagram you showed above. Try to flex it so all the lightcones point up. (You really do have to make one out of paper and try it to get the idea!) This is effectively taking a copy of the Schwarzchild solution, time-reversing it, and gluing the two together, as mentioned above.
Finally, to appreciate what happens in 2+1D, we take one of the sheets and rotate it about the singularity like this:

The top half of each sheet spins around one $r=0$ singularity, which we can imagine being the equatorial plane of the black hole in our universe. The bottom half of each sheet connects to the singularity from the other time-reversed universe.
And then you have to imagine adding the other sheet, spun around its own singularity, joining up continuously.
Thus there are two whole external universes, joined together inside the black hole.
That's a pretty crude way of visualising the geometry, and we're still missing a dimension! It's hard to cram multisheet 4D spacetime wormhole geometry into our 3D imaginations, which is why we generally stick to the simple, flat Penrose diagram.
I doubt that helps much, but it's the best I can do right now.
Comment: But is the paraller universe simply an artifact of the diagram, or does it show up somehow via the maths. And if you diagram was "3D" would that make the parallel universe quadrant disappear?
Comment: It shows up via the maths. If the diagram was 3D (actually it would have to be a 4D hypersurface embedded in an even higher-dimensional space) then it would still be there.
Comment: In a 3-d diagram wouldn't the black hole/ white hole each be a cone?
Comment: @blademan9999 No, you thinking of making the diagram 3D by rotating it around the axis of $r=0$. You can do this with the diagram of an astrophysical black hole where the vertical line on the left is $r=0$, so you end up with the horizon being a cone. The reason you can do this is that the space is spherically symmetric, so you can rotate around $r=0$. You cannot do the same with the diagram above, because the vertical line in the middle is not  $r=0$, but is a timeline of the wormhole called the Einstein-Rosen bridge. Making this diagram 3D would be a bit more complex.
Comment: Assuming you are talking about a cross-section with 2 space dimensions and 1 time dimension, yes. But there are still two separate universes attached to them. It's hard to visualise. But the coordinate in the diagram shown is the radius $r$, and so each point on the right represents an entire sphere. (Or circle, in your 2+1D slice). And each point over on the left represents a sphere (circle) in the other universe. They're not the same. The other side of the diagram is not simply around the other side of the black hole. The left+top quadrants map to one entire 2+1D universe.
Comment: Actually, I'll revise that, because it's a bit misleading. The horizons are 'light cones' in the sense of being the paths rays of light follow, but mapped another way they're shaped more like cylinders. The question doesn't exactly make sense in this highly-distorted, curved space. I would need to think about this some more to come up with a reasonable way to visualise it.
Comment: "*they're shaped more like cylinders*" - A Schwarzschild timeslice inside the horizon is shaped as a spherinder - a 3D hyper-surface of a 4D hyper-cylinder of the spherical type: http://hi.gher.space/wiki/Spherinder


Can I make a closed-source game if part of it utilizes a EUPL-licenced code?

Question: I want to make an app game in which I make use of a code that is licensed under the EUPL. The code will probably make up about 10 to 20 percent of the game's entire code (the rest will be original work). Will I be required to make the whole game open-sourced if I use that EUPL code? Are there any factors that would limit my ownership rights?
Answer: If your game is a derivative work (which it likely is unless you're very sure it isn't) of the EUPL software it will also have to be released under the EUPL. See section 5 in the license text:

Copyleft clause: If the Licensee distributes and/or communicates copies of the Original Works or Derivative Works based upon the Original Work, this Distribution and/or Communication will be done under the terms of this Licence or of a later version of this Licence unless the Original Work is expressly distributed only under this version of the Licence. The Licensee (becoming Licensor) cannot offer or impose any additional terms or conditions on the Work or Derivative Work that alter or restrict the terms of the Licence.


Kolmogorov inequality for Bernoulli random variables

Question: This question is also asked on math stackexchange. The question is about one inequality which shows in Kolmogorov's paper (inequality (3.1)) but is not proved. The inequality says that, if we assume $Y_1,Y_2,\ldots$ are i.i.d. Bernoulli random variables with expectation $p$, then the following inequality holds
$$\mathbb{P} \left( \sup_{k\ge n} |\overline{Y}_k - p|\ge \varepsilon \right) \le 2 e^{-2 n \varepsilon^2 (1 - \varepsilon)} \qquad \text{for any $\varepsilon>0$,}$$
where $\overline{Y}_k = \sum_{j=1}^k Y_j / k = S_k / k$.
To prove and improve this inequality, several people made contributions. However, I found I got lost when reading several steps in the proofs of these literature.

Paper 1 discusses a general case where Bernoulli random variables are independent but not identical. However, in the 9th line of the proof of the Lemma 1 (key lemma), it seems that the inequality is contrary to the assumption ($\phi_i^\varepsilon (t) \ge 1$). Without Lemma 1, we cannot get the inequality we want.
Paper 2 improves the inequality proposed by Kolmogorov. However, Lemma 1 is also weird. First it cites Lemma 3 in paper 3, but the definition of $\phi_\varepsilon (\lambda)$ (paper 2) and $\varphi_\varepsilon (\lambda)$ (paper 3) are different, with opposite sign before $\lambda$. Despite this fact, both these two lemmas are strange. They say that: let $\varepsilon\ge 0$, if there exists a $\lambda>0$ s.t. $\phi_\varepsilon (\lambda) = \mathbb{E} (e^{\lambda (X_i - \varepsilon)}) \le 1$, then
$$ \mathbb{P} \left( \sup_{k\ge n} \frac{\sum_{i=1}^k Y_i}{k} \ge \varepsilon \right) \le \left[ \phi_\varepsilon(\lambda) \right]^n. $$
It is strange that the inequality is also true (trivial) if $\phi_\varepsilon (\lambda) > 1$. We only needs to find that minimum of $\phi_\varepsilon(\lambda)$ when we fix an $\varepsilon$.
Then I checked the proof in paper 3, especially the proof of Lemma 2. I did not find mistakes except one citation in the first line of the proof. It is a Russian book and we need theorem in page 183. In the proof, it defines a random variable $\eta (x) = \inf \{ i: 0\le i\le n, S_i \ge x \}$. However, I did not understand the following inequality.
$$ \mathbb{E} (e^{t S_n} \mid \eta(x) = k) \ge e^{tx} \mathbb{E}(e^{t S_{n-k}}). $$
I guess it uses the independence of $Y_i$, but I think here we need conditional independence, and it is not true since $\eta(x)$ is defined by $Y_1,\ldots,Y_n$.

I truly wish you can give me some hints, no matter on whether this inequality is true, or on where I can find the correct proof, or on whether the ''mistakes'' I found is right. Thank you. Any comments help.
Answer: We will use (3). $\eta(x)=k$ means that $S_1,\dots,S_{k-1}<x$ and $S_k=Y_1+\dots+Y_k\ge x$. In particular, it means that the event $\{\eta(x)=k\}$ and $Y_{k+1},\dots,Y_n$ are independent. Hence $\{\eta(x)=k\}$ is independent of $Y_{k+1}+\dots+Y_n=S_n-S_k$.
Therefore,
\begin{align*}
\mathbb{E} (e^{t S_n} \mid \eta(x) = k)&=
\mathbb{E} (e^{t (S_n-S_k)} e^{t S_k} \mid \eta(x) = k)=
\mathbb{E} (e^{t (S_n-S_k)})\cdot  \mathbb{E}(e^{t S_k} \mid \eta(x) = k)
\\ &
\ge  \mathbb{E} (e^{t (S_n-S_k)})\cdot  e^{tx}
 =  \mathbb{E}(e^{t S_{n-k}})\cdot e^{tx}.
\end{align*}
since $S_{n-k}$ has the same distribution as $S_n-S_k$, and on $\{\eta(x)=k\}$ we have $S_k\ge x$.


Frost prevention for indoor router and cable modem

Question: I'm working on a community wifi project for an impoverished settlement. We have a router and a cable modem installed in a container house, sometimes without heating for days. Both are designed for indoor use. (Wifi coverage is provided by outdoor APs.) What should I do to protect the indoor equipment from frost? Outdoor temperatures sometimes reach -15 °C (5 °F), the container is made of metal. We would need the cheapest workable and safe solution. The cable modem is provided by the ISP and they offer no outdoor equipment (but we may be able to convince them to let us use our own one).
Comment: Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
Answer: Whenever I am deploying something outside in an enclosure, this is the procedure I use.  First, make sure you start with the proper enclosure (for example NEMA 3 or 4).  If you penetrate the enclosure, make sure the penetrations are properly sealed to maintain the rating.  (I assume this would be the case as you need electricity and because you mention that the enclosure is made of metal and no one wants their antennas inside a metal box, right?)
Since your enclosure is going to be restricting air from flowing into/out of the enclosure, you now only need to contend with any moisture that is trapped within the enclosure with your devices.
Your next step is to reduce the moisture in the trapped air. Low moisture means less chance of condensation and with no condensation, you get no frost.  For this, I prefer to use silica packs.  You can buy these cheaply, but even better they come in the packaging with many items (shoes, clothes, electronics, and so on).  Most people throw them away, but I recommend saving them as they have many uses.
Before you close you enclosure, add some silica packs.  However, before you do that, make sure the packs are "fresh" by heating them.  Heating them (120-150C/250-300F) will cause them to "release" the moisture they have gathered.  For this, I use either an oven (longer, but you can easily set the temperature) or microwave on 1-2 minute cycles (faster, but you need to figure out a way to determine if you have heated them enough and some outside packages won't do as well).
Now, silica packs will not remove all the moisture from the air, but you don't really need to remove all the moisture.  The waste heat from your electronic devices will help to prevent the moisture from condensing on them and most of the condensation (if you have any) would be on the inside of the enclosure itself (which will tend to be colder).  Make sure you account for this by not setting any electronics or power cords directly on the bottom of the enclosure.
Comment: Thank you! So basically you're saying I don't need to meet the operating temperature requirements (above 0C/32F)as long as I get rid of the humidity? The mentioned metallic container house is not an enclosure - it's an actual building of about 20m2 (~200 sq feet) area. (Antennas are placed outside, attached to proper outdoor APs, connected with ethernet cables.) As there is no rain inside, do you think we are OK with a simple enclosure without NEMA3?
Comment: You need an enclosure (or something) that will prevent the free flow of air.  If you have free flow of air, that air will bring more moisture into the environment and you won't be able to prevent condensation/frost from forming.  As for the temperature requirements, most devices will operate outside of those ranges but it can shorten the life of the product or cause problems.  The enclosure will help to contain some of the waste heat produced, maintaining a higher ambient temperature inside the enclosure than exists in the surrounding environment.  Dealing with the heat is a separate issue.
Answer: Buy an inexpensive cooler -- a big plastic or styrofoam one like you'd use for a picnic -- remove the lid, place it open side down over the equipment. As long as there's no drafts in the container/house-unit, the heat from the equipment will stay up inside the cooler. If it's really cold, move the wall-wart power supply/ies inside the cooler too.
Comment: If you do this, you'll need to be careful that when the ambient temperature changes, the equipment doesn't overheat.
Comment: @alx9r, that is true, but it also works both ways.  It can actually protect from excess heat in the enclosure, especially if in direct sunlight.  The bottom of the enclosure itself may be enough surface area to radiate excess head depending on how much is produced while the cooler protects the electronics from the air being heated by the other surfaces of the enclosure.
Comment: @ylearn I don't understand your argument.  The property relied upon to increase the temperature of the device is the insulation of the cooler.  The waste heat of the router passing through the cooler creates a [temperature differential relative to ambient temperature](http://en.m.wikipedia.org/wiki/Heat_transfer_coefficient).  For example, the combination of router and cooler might result in a measured temperature differential of 20C.  No matter the ambient temperature, the inside of cooler will always be 20C higher.  So if it's 40C ambient, it'll be 60C inside the cooler which is now too hot.
Comment: @alx9r, you are not accounting for two things.  First, there is no "cooler" or insulation between the equipment and the bottom of the enclosure, which will make it free to radiate out waste heat.  Second, I said this is especially true if in direct sunlight.  The bottom (protected from direct sunlight) will be significantly cooler than the surfaces in direct sunlight.  Those surfaces in direct sunlight may radiate more heat into the enclosure than the router produces, meaning that the cooler will insulate the router from the surrounding hotter air.
Comment: Thanks! It's fully OK for us if we have to remove the cooler at the beginning of spring and put it back again before the winter freeze kicks in.


Provision to allocate multiple Roles to single User

Question: Just want to know, is there any work around to allocate multiple Roles to a user. The user with multiple roles should able to handle all assigned role's responsibilities.
Answer: There is no functionality to allow assignments of multiple Roles in the way that a Permission Set allows extension of the Profile's system permissions.
To allow access to records in other parts of a Role Hierarchy you can use Sharing Rules or Apex sharing based on either the user's current Role or another part of their profile.
Another option is to use Public Groups for the users to allow access to records without being part of the same Role hierarchy.


Freestyle "Material Boundary" not working?

Question:
I am trying to add an outline around this geometry, that is overlapping a plane. This is not the result I was hoping for. I thought the checkbox "Material Boundary" would solve my problem but it doesn´t really seem to do anything. Please help D: (using the newest version of blender)
Answer: This is not an error. Unfortunately, freestyle cannot detect face intersections, even if they have different materials. You can use inset face or a loop cut and slide to try and put an edge there for freestyle to use, but unless there is an edge there or an outline, there will be no freestyle.


How to use Google Font in Draw.io?

Question: Is it possible to use Google Fonts (https://www.google.com/fonts) in Draw.io?
Answer: While draw.io does not to the best of my knowledge allow importing fonts, I wanted to post what works for me. You have to use a extension capable browser such as Chrome or Firefox (I'm using Chrome for screenshots).
To start get the "Stylish" extension for your browser (Chrome, Firefox). Next open the extension options and click the "Write New Style" button.

From here you'll need:

Enter a name for your style (I used Draw IO, but anything is fine).
Enter the Google Font url in the text box. I wanted to import Google Material Icons to draw.io so my example uses:

@import url('https://fonts.googleapis.com/icon?family=Material+Icons');

Note: You will probably want to set your "Keymap" (bottom left in image) to "basic" if it is not already. This makes copy / pasting simpler.

Ensure the "Applies to field" (Under text box) is set to "URLs on the domain" and the value is "draw.io". This will ensure the import is applied to the draw.io web application. You could use this same technique for any web app which supports custom fonts.
Now hit "Save" button under the title you originally set. When you open draw.io the font will be properly imported.
Open your draw.io and click on a shape.
In your format panel (Default panel on the right side) click on the "Text" tab.
Under the font drop down select "Custom" and insert your font (Mine was "Material Icons") and click apply.
You are now all set to choose this font.

Example with Icon Font:

Note on Icon Font: Since I'm using Material Icons in this instance I used the name of the icon as text (font ligature). E.g. For the star I inserted a text box, and inserted "star" (per the name from Material Icon Page ) and ensured the font was set to "Material Icons". For names with spaces make sure to use underscores (e.g. "star_border").
Example with Text Font:

@import url('https://fonts.googleapis.com/css?family=Indie+Flower');

Comment: Awesome hack! I'll be using this a ton in the future
Answer: I somewhat tried the guides above but couldn't get them to work. I then asked the question on draw.io's google groups page, and was informed that the custom field is for locally installed fonts on your system.
Wrote the following which might help someone else who came across this post via google:

Find the font you want on Google Fonts
Download the zip of the font
Follow https://www.google.com/get/noto/help/install/ on how to install the font on your system
Restart Chrome or your browser of choice (so the fonts can be loaded in).

Click on the Custom font field, and write the name of the font you've installed (There's no need to put it in quotes or underscores etc).
See an example I've attached to https://groups.google.com/d/msg/drawio/mjJR6pRVTmo/T0Lrhr45AgAJ
Answer: Stumbled upon this while facing difficulty to add Custom Font(specifically a Google Font) to draw.io(desktop version).
Turned out I was using 12.1.7 - which has a less simple way to add custom font.
Found the following link after a google search - post dated Dec 2, 2019 - but no mention of version in it. Checked for the upgrade and it upgraded draw.io to 13.0.1, there you have it:
https://drawio-app.com/external-fonts-in-draw-io/
This is the feature request on GitHub:
https://github.com/jgraph/drawio/issues/577
Comment: System Fonts work seamlessly too.
Installed `Quicksand` fonts by downloading from Google Fonts.
Used `System Fonts` option to set - e.g. `Quicksand-Thin`
Answer: I haven't been able to figure out a way to use some of the newer Google fonts, but you can use some of the more common/popular ones by selecting "custom" under the fonts section, and typing the name of the font (e.g. "Avenir Next", "Oswald", etc) and it will then use that font.  On the bright side, it also seems to recognize certain popular fonts that are not on Google fonts and would be costly to purchase (e.g. Myriad Pro).
Answer: You can add the full link, so instead of just typing 'Heebo' in the custom field, you can type <\link href="https://fonts.googleapis.com/css?family=Heebo:500" rel="stylesheet"\>. It still works a little buggy when changing fonts afterward, but it got me further.
Or.. just go to the 'style' tab and click 'edit' style. Add the link above and change the font-family.

How to use Google Font in Draw.io?


An electrostatic problem for two disks in $\mathbb{R}^2$ - how can the solution be represented?

Question: The electrostatic Laplace problem for the exterior of a disk can be solved in a straightforward manner using separation of variables. Suppose we have a unit disk $\Omega$ with a charge density of $f$ on the boundary. Then the solution to the exterior problem,
\begin{align}
& \Delta v(x) = 0 \quad \quad  x\in \mathbb{R}^2\setminus \overline{\Omega}, \\
& v |_{\partial D}(x) = f,
\end{align}
is given through separation of variables as
$$
v(x) = v(r,\theta) = \sum_{n=0}^\infty r^{-n}(a_n \cos(n\theta)+b_n \sin(n\theta)),
$$
where
$$
a_n = \frac{1}{2\pi}\int_0^{2\pi} f(\theta)\cos(n\theta) d\theta, \\
b_n = \frac{1}{2\pi}\int_0^{2\pi} f(\theta)\sin(n\theta) d\theta.
$$
But what about the case where we have two disks $\Omega_1$ and $\Omega_2$, and we want to determine the solution to the exterior Laplace problem for a charge density $f$, with $f$ defined on the union of the disks $D=\Omega_1\cup \Omega_2$? Say for example the disks both have radius $1$ and are symmetric on the $x_1$ axis with a distance of $6$ between them.
Can we just take define two new origins $O_1$ and $O_2$ at the center of the disks, with associated polar coordinates $(r_1,\theta_1)$ and $(r_2,\theta_2)$, and then say the following:
$$
v(x) = \sum_{n=0}^\infty r_1^{-n}(a_n \cos(n\theta_1)+b_n \sin(n\theta_1)) + \sum_{n=0}^\infty r_2^{-n}(a_n \cos(n\theta_2)+b_n \sin(n\theta_2)).
$$
Is this a valid solution? If not, why not?
Answer: This is indeed a solution due to the linearity of the Lapacian. If I have 2 charge distributions $\rho_1$ and $\rho_2$ and
\begin{align}
\nabla^2 v_1 &= \rho_1\\
\nabla^2 v_2 &= \rho_2
\end{align}
then we have that
\begin{align}
\nabla^2 v_1 + \nabla^2 v_2 &= \rho_1 + \rho_2\\
&= \nabla^2( v_1 + v_2)\;.
\end{align}
This is known as the principle of superposition.


Does the Rybczynski theorem also hold in modern trade theory models?

Question: Does the Rybczynski theorem also hold for modern Melitz (2003) type trade models?
Answer: The Rybczynski theorem is not directly applicable to the Melitz (2003) model, because the model the Rybczynski theorem is originating from, the Heckscher-Ohlin model, is built on different assumptions and focuses on different aspects of trade. The Heckscher-Ohlin model assumes that firms are identical within an industry and that there are constant returns to scale. In contrast, the Melitz model emphasizes firm heterogeneity and incorporates increasing returns to scale.
Comment: Thanks! In case you know, what would be the effect of an increase in the number of workers for melitz-type models?


Run/Debug Maven JavaFX 2 in Netbeans

Question: I setup a Maven project for a JavaFX 2 application, which uses javafxpackager threw exec-maven-plugin to build a runnable jar. This build process works fine and the application can be started from the commandline.
Does anyone know how to modify nbactions to run and debug this jar from within the IDE?
The command to execute the jar on the commandline is:
<code>java -Djavafx.runtime.path=$JAVAFX_HOME/rt -jar ./target/MyApp.jar
</code>
Answer: The modification it's, for every "action" tag, change the  tag as follows:
<code> <exec.args>-classpath %classpath  -Xbootclasspath/a:"C:/Program Files/Oracle/JavaFX 2.2 SDK/rt/lib/jfxrt.jar"  ${packageClassName}</exec.args>
</code>
Of course, change "C:/Program..." to fit your setup.

Run/Debug Maven JavaFX 2 in Netbeans


Read MIDI data from Akai MPK mini mkII USB MIDI controller to AVR

Question: I have experience with AVR controllers and now I am developing analog synth like sound module. I would like to be able to connect a USB midi controller to my sound box. I would like to use an AVR microcontroller and I think my option is either to buy a USB to MIDI adapter for the keyboard and build an AVR MIDI interface or use something like an FT232RL chip for USB and code for reading MIDI commands. I would like to hear suggestions from more experienced engineers.
Comment: While English may not be your first language, please try to spell check and use proper capitalization to the best of your ability. It greatly increases readability.
Answer: USB MIDI is a different protocol that is not supported by the FT232R.
You would need to use a general-purpose microcontroller with USB support.
Furthermore, USB makes a strict distinction between hosts and devices, and your controller is a USB device, which can be connected only to a USB host.
So you would need to use a board with a USB host (or OTG) controller, such as the Raspberry Pi. Alternatively, pay for the Kenton USB MIDI Host, or connect both the controller and your AVR board to your PC.
Answer: To add to CL.'s excellent answer: Creating a USB host that supports USB MIDI is not trivial. Either use a computer in between, or get a keyboard that supports "real" (hardware) MIDI output, which is very easy to interface with the microcontroller of your choice. The Akai MPK 25 would be an excellent choice, for instance.
Edit: after further research for another project, I've realized that creating a USB MIDI host device may be easier than I thought. A MAX3421E can be used to implement a fairly inexpensive USB MIDI host. For a "just add water"-product, get yourself the USB Host Shield for your Arduino, which has a MAX3421E. You should be able to find a library supporting USB MIDI, and you can relatively easily build a USB-MIDI to hardware MIDI converter.
Comment: MAX3421E  looks like a good option. It would help implement my AVR as USB host device to read MIDI notes from USB midi device?
Comment: Yes, it should.
Comment: What if I don't have possibility to buy another keyboard? Maybe usb to midi adapter would do?
Comment: Yes, you can go keyboard to computer via USB, and computer to Arduino via USB-MIDI cable, if you're OK with the computer in the middle.
Comment: This options is viable for me, but how will USB Midi keyboard passthrough computer to my AVR MIDI device?
Comment: You simply need a piece of software that can route a MIDI input (your keyboard) to a MIDI output (the USB-MIDI cable). Numerous pieces of software exist for your operating system of choice.
Comment: @user112290 See my edit, I've changed my answer after some research.


Mirroring sql server , how to change the port?

Question: I have two servers on the same cluster, in fact my goal is to set up "high availability", but the databases that I have integrated are not synchronized, so I think it is " mirroring "that I created but the port on which the two servers is not the same, I have a 1433 on the other and a 5022 on the other. what should i do ?
Comment: 1433 is the default port used by SQL Server's client connection TCP endpoint, and 5022 is the default port used by SQL Server's mirroring/Always On endpoint. Can you provide more information about how you configured mirroring, what version you're running and what your actual problem is?
Answer: Just specify the port when you set it up
<code>ALTER DATABASE <DBNAME> SET PARTNER = 'TCP://<ServerName>.<Domain>.com:5022'
</code>


combobox change back SelectedIndex C#

Question: in my comboBox2_SelectedIndexChanged event i do some processing and in certain cases i want to change the SelectedIndex back to what it was before i change it. I see that sender.selectedIndex is the last index i used however i cant access that var. How do i tell the combobox to go back to w/e it was?
Answer: See the code below. If the case satisfies you set the selected index to the lastIndex, while setting lastIndex, you make sure to unsubscribe the selection event, set and resubscribe. Track the lastIndex each time by setting it to the selectedIndex.
<code>    int lastIndex=0;
    void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (isItTheCase)
        {
            comboBox2.SelectedIndexChanged -= new EventHandler(comboBox2_SelectedIndexChanged);
            comboBox2.SelectedIndex = lastIndex;
            comboBox2.SelectedIndexChanged += new EventHandler(comboBox2_SelectedIndexChanged);
        }
        lastIndex = comboBox2.SelectedIndex;
    }
</code>
Answer: Please check anywhere you are registering the SelectedIndexChanged more than once. It generally happens that you register events at design time which goes in Initilizecomponent() method and then register it in the constructor.
Thanks

combobox change back SelectedIndex C#


Pathfinder Post-processing incorrectly- Data severely shifted

Question: I'm new to Pathfinder (just transferred our license over to my computer). I post-processed my data and exported to ESRI shapefile. My data from the east end of Long Island, New York displays off the coast of Africa. I've tried post processing a few different files, ones that post-processed fine on my coworkers computer, and all have the same issue. I can't seem to find any settings or help documents that address the issue. Any suggestions?
Answer: I'm not sure what exactly you mean by "set a projection to create the .prj file but I did solve my problem. After reading your comment I looked around for the .prj file
I followed the steps I found here:
https://mapsupport.seilerinst.com/2012/06/07/where-to-find-the-projection-files-for-coordinate-systems-to-use-for-trimble-gps-pathfinder-office-export/
All seems to work now. Thanks so much!
Answer: It sounds projection related. What projection was the data taken in and what is the coordinate system in ArcMap? My experience with Pathfinder is that you have to "set projection" to create the .prj file for ArcGIS.


How to close apps from Mission Control on macOS Sierra?

Question: I'm used to being able to close my apps from the mission control view by clicking on an X sign in the upper left corner - I don't have this feature in Sierra. How can I turn it back on or do it in a similar way from Mission Control?
Comment: You said, "X sign in the upper left corner", where exactly is this and what OS were you running that you saw this in Mission Control? I'm asking because I do not see that on any window when in Mission Control in OS X 10.11.6. Nor can I click anything to close a window when in Mission Control, even if when using standard modifier keys. Now in a normal Desktop view if I mouse-over the red close button it changes from solid red to a black x on a red circle but it doesn't do this when in Mission Control, when there it stays solid red on only the front most window prior to going to Mission Control.
Comment: [http://apple.stackexchange.com/questions/231154/how-to-close-windows-in-mission-control-of-el-capitan] here's a link to a question that has a graphic representation of it - I had this X sign on El Capitan, except that it was black and on the individual apps, not workspaces.
Comment: The image referenced in the link of your comment is to the virtual Desktops **not** applications and I can close additional virtual Desktops from Mission Control in macOS Sierra just like I can in OS X El Capitan. When I click on the The (x) in the upper left corner of the icon for the virtual Desktop it is closed and the apps on that Desktop are moved to another Desktop in either version of the Mac OS. So it is still unclear what your issue is as you've obviously not described it correctly in your original post.
Comment: I have described it correctly - I want to be able to close apps from Mission Control. Not workspaces, apps. What's wrong with this description? I've had this feature OOTB on El Capitan and I don't have it on Sierra, I want to have it back.
Answer: I have recently bought a new MacBook Pro after 4 years of using Windows, and I really missed the ability of directly closing windows in Mission Control, as I used to do in my good old Mac OS X Snow Leopard.
I have searched around the web and in macOS Sierra settings, but I didn't found a OS native way of achieving it.
So I installed this little tool (I also used it in the old days) called Better Touch Tool. It allows you to set customised keyboard and gesture shortcuts.
I use a 3 finger tap to close windows directly bellow the cursor (which works anywhere, even in Mission Control). You can set up any shortcut you want. I find using it very convenient, I hope you do also.
Comment: Nice tip!
Anyway it has one caveat/error. It closes app. Not quits.
Comment: Yup, but in previous OSX versions it would also just close the app. I also have a gesture shortcut for quitting, but the app needs to be in focus. In Mission Control it doesn't work.


Viewport Display Glitch

Question: I started having this issue with image display. It looks the same in render view, but not in actual render or through camera lens.
Comment: Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
Comment: maybe try to play with the viewport's start/end clip values
Comment: Maybe try updating your GPU drivers?
Comment: I'm experiencing a similar issue on macOS m1 max with blender 3.2.2. Additionally the problem disappears if I disable the perspective. Also in camera view it usually looks fine, only the standard 3d viewport is very glitchy.
Answer: It is just lots of intersecting geometry (Probably).
When multiple faces exist at the same location this is exactly how the faces will be visible in the viewport.
Just for example open a new file and add another cube at the default location. You will see the same thing.
This glitchy looking thing will disappear while rendering.
But if you want the thing to go away then make sure that the geometry doesn't intersect. Try scaling or moving one of the e intersecting meshes.If intersecting geometry is the problem then scaling or moving should solve the problem. If that doesn't work, then either it is some other problem or it is a bug.

Viewport Display Glitch


question about z-stabalizer

Question: I'm learning quantum error correction. I also had a hard time understanding the following stabilizer form. I read this paper, which gives two circuits for Z-Stabilizer, I can understand a but I don't know why b can achieve the same effect: use ancilla qubits to control the original state will that change the state of original qubit?
Answer: This follows easily from the observation that $$(I\otimes H)CZ(I\otimes H)=CNOT$$ see for instance this post and the answers within. Then, since $H^2=I$ simply put an $H\cdot H$ in between all the CZ (controlled-$Z$) gates to turn them into CNOTs, so (b) and (a) are equivalent circuits.

question about z-stabalizer


Very detailed Tellraw command that i need help with

Question: Okay so im making an adventure map and i have a command block that will say when someone has found mining supplies and then you will have to click where it says here to receive some of it. The thing is it just says like error on line 323 unterminated character or something. Also i cant type the command cuz i broke to block so here is a picture of the text
Comment: In the future it would be helpful to copy/paste the text directly instead of taking a screenshot.
Comment: Possible duplicate of [How do I fix 'Invalid JSON' errors?](https://gaming.stackexchange.com/questions/304990/how-do-i-fix-invalid-json-errors)
Comment: I don't believe you can run two commands at once in a run_command. Instead, you can place a redstone block somewhere or change a scoreboard objective that will activate both commands separately (the answer below has a good solution as well, but if you want a single clickable word that does everything, try this).
Answer: All of the problems I noted with your code:

You didn't escape ", causing the problem you're gettingFix this by escaping quotes within quotes, like so: /"
You have multiple commands in one run statement.Fix this by having multiple clicks.
You didn't separate your text elementsFix this by having each text element in its own dictionary.
Your command in the runCommand value is too long.

Here is an expanded (and corrected) JSON view of your code:
[
    "",
    {
        "selector": "@p",
        "color": "dark_purple",
        "bold": true,
        "italic": true
    },
    {
        "text": " has found mining supplies! Click ",
        "color": "aqua",
        "bold": true,
        "italic": false
    },
    {
        "text": "here for Torches",
        "color": "dark_red",
        "italic": true,
        "underlined": true,
        "clickEvent": {
            "action": "run_command",
            "value": "/give @p torch 10"
        },
        "bold": false
    },
    {
        "text": " and ",
        "color": "aqua",
        "italic": true,
        "underlined": false
    },
    {
        "text": "Here for a Pickaxe",
        "color": "dark_red",
        "italic": true,
        "underlined": true,
        "clickEvent": {
            "action": "run_command",
            "value": "/give @p iron_pickaxe 1 249 {display:{Name:\"Dull Pickaxe\",Lore:[\"This pickaxe is very worn out\",\"can only be used for fighting\",\"and mining weak stone\"]}}"
        }
    }
]

A minified Command Block friendly version of this code is this:
/tellraw @a ["",{"selector":"@p","color":"dark_purple","bold":true,"italic":true},{"text":" has found mining supplies! Click ","color":"aqua","bold":true,"italic":false},{"text":"here for Torches","color":"dark_red","italic":true,"underlined":true,"clickEvent":{"action":"run_command","value":"/give @p torch 10"},"bold":false},{"text":" and ","color":"aqua","italic":true,"underlined":false},{"text":"Here for a Pickaxe","color":"dark_red","italic":true,"underlined":true,"clickEvent":{"action":"run_command","value":"/give @p iron_pickaxe 1 249 {display:{Name:\"Dull Pickaxe\",Lore:[\"This pickaxe is very worn out\",\"can only be used for fighting\",\"and mining weak stone\"]}}"}}]

In the future, you should use generators to do this for you.

Note: The Pickaxe command may be too long to actually run. You might want to make it act as a "trigger" command that causes other command blocks to run. You can do this using the aptly-named /trigger command. From there, have a bunch of command blocks give the items to everyone with that scoreboard value set to 1.
To do this, create a Scoreboard objective with some unique name, like NeedsItemPack83028. Then, make it a valid Trigger by running /scoreboard players enable @a NeedsItemPack83028. Your command block would have the command set to /trigger NeedsItemPack83028. From there, you have a bunch of command blocks on a tick clock checking for NeedsItemPack83028. Apply the items to everyone who has it, and clear the flag.
Now, this opens the trigger command up to abuse. You can have a second Scoreboard item (ItemPack83028Redeemed) that can not be set by triggers. Ensure that that is false before giving items (!=).
Comment: You don't need the trigger, unless you want the player to be able to change the objective. Otherwise, you can use /scoreboard objectives set    [datatag (not required)], which command blocks have permission to use
Comment: @DanielG Thanks for the correction. It's been a while since I worked with scoreboards ^^
Comment: @DanielG That is not correct in this case. When players run a `/tellraw` command's click event, they are running the command as though they typed it in the chat themselves. This means the command is subject to standard chat limitations, being the requirement of a high enough OP level to run `/scoreboard`. The `/trigger` command is *supposed* to be used in cases like these, unless only OP'd players are meant to run the command.
Comment: @Skylinerw Thanks, I never realized that. All the examples I've seen have cheats enabled. Thanks!


How exploitable is a QR code in a login system?

Question: I'm taking a CTF challenge on a web service. The goal is to gather the most information possible of a user. I have access to it's login and password, but password is expired and the account must be recovered by uploading a QR code to the website. No other file extensions besides JPEG are allowed for upload. Given that, I tried to generate a QR code with the provided login info, with no results. Please notice that my understanding on this matter is very bad. So I was wondering if exploiting a QR code would a good attack vector. But I'm starting to realize that might not be a practical/executable way. Am I going in the right direction?
Comment: Do you have any information on what parser is used for the QR code reading and what version? Did you find a local file include bug that could execute a script you uploaded with a jpeg extension?
Comment: @SmokeDispenser no I don't have any info on QRcode parser. Is there any way to get it?
Answer: Instead of uploading user info to QR code try to upload a malicious script to bypass the login. If you found the uploads directory, you can run your script and get more access.
Comment: As I mentioned before the upload only allows `.jpeg/.jpg` extensions. How could I find the uploads directory? I tried to use dotdotpwn in order to know about vulnerable directories but this don't have a module for https
Comment: I think I misunderstood you. Were you suggesting to "disguise" malicious code on QRcode and then submit it to the website? Will this trigger a script by simply doing that?
Comment: use a directory brute force to know the upload directory,, then upload a malicious script disguised in QR image .jpeg/.jpg , then from the upload page you found trigger the script.
Comment: @fish202 What I think is wanted here is for you to try to upload something else other than a JPEG file. It's likely that the server is only checking the file extension rather than the content, so you can upload something else by changing the file extension. What needs to go in the specially-crafted file I have no idea, I imagine the idea would be to trigger some kind of injection or buffer overflow attack.


Is it possible to append the same type of shapefile captured on two different Trimble Juno 3b's with ArcPad 10?

Question: I will soon have access to two Trimble Juno 3b's which will both have ArcPad 10. I have done some practice with one Juno 3b and I am very confident with my ability to use them. All I need to know is that if I have the same type of shapefiles, in this case points, and load them into each on of the Trimble Juno's, can I combine them?
I plan to hand one to another person and use the other myself to collect points on different areas of a field. Can I run some sort of tool or even a Python script in ArcMap 10.2.2 to combine both shapefiles so that it creates a single shapefile with the same attributes and spatial extent? I will need them to be combined so that I can use them all in Kriging interpolation.
I believe the union tool is a possibility, but can it be used with points collected in this manner?
Answer: You might look at creating a point feature class with the field structure that you require in ArcGIS, and then checking-out the schema of that fc (or the data, if you plan to carry out field edits to exisiting points) to both the Junos, using the Arcpad Data Manager toolbar. Do the data capture, and then check the data back in to ArcGIS. This will populate your fc with both sets of field data. This can be done with any number of field devices. There is no need for unions/merges etc.
Answer: As long as the units are set up the same and produce identical files (same attributes, field names, coordinate systems, etc.) then yes, there are several simple ways to combine the data from the two units. The Merge tool can combine them to a new file. The Append tool can add one file's points to the other. You could also use a copy/paste operation in an edit session to accomplish the same thing.
Union would not work, primarily because it only functions with polygons. It's an analysis tool more aimed at combining overlapping features to new features with the attributes of all the source features.


Why is the harmonic series presented as a succession rather than a chord? And has it been definitely proven that all partials sound at once?

Question: It is my understanding from so far limited research that all whole number integer ratios sound simultaneously with the fundamental, but has this been proven beyond all doubt?
Is it possible that the partials sound in succession even if it so rapid that to the human ear it sounds as a chord rather than an arpeggio? Are there any ways to measure this?
Comment: I believe musical acoustics should be on topic here, if they aren't already. Perhaps a meta post is in order.
Comment: I'm voting to close this question because this is better asked on a physics.SE.
Comment: I have answered this in from what I thought was a similar perspective to user77599, but I now see that  Michael Curtis has answered from (I think?) a slightly different perspective, so perhaps the question could do with clarifying. @Aaron despite those concerns, I can't see anything here that isn't solidly relevant to music?
Comment: @Aaron, I agree with topo Reinstate Monica and think harmonics are usually very on topic here. I think the question about "proof" seeks to ask if this has been verified experimentally. User77573, it's not required for all harmonics to be present in all contexts. In fact, it depends on the shape of the guitar string when plucked (or piano string when hit). The volume/amplitude of the harmonics depends on that initial shape. Check out the answers to [this question](https://music.stackexchange.com/questions/60833/what-determines-the-relative-volumes-of-the-harmonics-when-plucking-a-guitar-str).
Comment: There is no such "proof" , and even if there were, it would fail in the presence of physical instruments which have limited capability (e.g., vibrational range of a string).
Comment: Perhaps the OP was fumbling with the concept of "start-up transition" when a string, or a wind, instrument transitions from silence to the full set of harmonics.  dispersive wave propagation speeds and the like could theoretically lead to FFTs calculated in the first few percentages of the fundamental period (1/frequency) might show a build-up of the harmonics in some instances.   Or not.
Answer:
It is my understanding from so far limited research that all whole number integer ratios sound simultaneously with the fundamental

It depends on exactly what situation/instrument you're talking about. With many acoustic instruments, you often see an initial 'chaotic' part of the sound that quickly turns into a pitched sound as the energy driving the sound becomes subject to the resonances of the system. It's entirely possible that one partial might reach some threshold of audibility before another, so I don't think your statement is necessarily true.

Is it possible that the partials sound in succession even if it so rapid that to the human ear it sounds as a chord rather than an arpeggio?

Do you mean such that each partial stops before the next starts, or just that they start in succession? Either is possible, but both are probably easier to achieve with electronic than acoustic instruments.

Are there any ways to measure this?

The fourier transform is the most usual way to see where in the frequency spectrum the energy in an audio signal is.
Answer: Sound consists of individual sine waves, meaning that any waveform that occurs in the physical world can be decomposed into a number of single-frequency waves.
A sound can consist of only a single frequency. For example, a sine wave produced by a synthesizer's sine oscillator is like that. In that case there are no overtones, there are no partials. Only a fundamental.
If there are overtones in addition to a fundamental in an instrument's sound, then the overtones do sound simultaneously together with the fundamental.
This can be seen in a spectrum analyzer. And it can be heard by the human ear https://en.wikipedia.org/wiki/Hearing#Inner_ear The ear contains small hairs which react to the incoming sound, and different areas or cells are sensitive to different frequencies.
Whatever kind of sound waveform you produce, say, by playing an instrument, using a synthesizer, or by drawing a waveform (that you could store in a WAV file) in an audio application and playing it back with your computer, the sound output will "contain" one or more partials, sine waves. This can be "proven" in many ways. You could for example filter the sound with very narrow band filters and notice that more than one of the filters lets something through it. Or you could have resonators that resonate at different frequencies, and you would see that a sound with overtones excites several of them, not just one. Or you could use a spectrum analyzer, if you believe what it's showing to you.
Let's take a square wave as an example
https://en.wikipedia.org/wiki/Square_wave

(Picture from Wikipedia https://en.wikipedia.org/wiki/Square_wave#/media/File:Fourier_series_for_square_wave.gif)
A perfect square wave has infinitely sharp edges, the corners of the squares. Such a sound cannot "exist" in the real world - any observer with finite resolution would perceive it as consisting of a number of sine waves, without being able to tell if the sound was really a square, or if the non-squareness is just beyond their capabilities to perceive. In the above picture, a square wave (blue curve) is synthesized by adding more and sine partials with different frequencies, and as more and more partials are added, the sum of the partials gets closer and closer to a theoretical square. Or as Wikipedia puts it, "An ideal mathematical square wave changes between the high and the low state instantaneously, and without under- or over-shooting. This is impossible to achieve in physical systems, as it would require infinite bandwidth."
Comment: Most sound actually consists of a pretty complex waveform.  The fact that Fourier Analysis can describe it as the sum of many sine waves doesn't mean that's what it IS.
Comment: @LaurencePayne  Your comment has veered into the philosophical.  The waveform is the waveform is the waveform.  It can be parametrized by decomposition into sines, or into Zernickes, or lots of other complete function sets.
Comment: I tried to avoid the word "is" in the first paragraph. Consists of ... and then a sentence about what I mean with that consisting. The message did not get through. Maybe I should have added: in the sense that the individual waves, when combined, would produce an identical waveform. If someone wants to find a definition saying what something "is", without opening that up in terms of behaviors or actions or however it could be explicated from other perspectives, then it's going to be a useless dead-end. I wonder how Laurence would have translated his remark into a language without the word "is".
Answer: I don't think it's always presented that way. The Wikipedia page has three different graphical representations.
Of those representations the one in staff notation presents it like a series I think to simply allow space for labeling. I know that I don't read it and think it's literally presenting pitches in time, like it was a melody.


Exception handling with phpunit and Silex

Question: I am using a route in Silex to delete an object from the database. If an object does not exist, a 404 error should be thrown. This works fine in the browser, and the response is received accordingly.
This is my source:
<code>$app->delete("/{entity}/{id}", function(\Silex\Application $app, HttpFoundation\Request $request, $entity, $id) {
    // some prep code is here
    $deleteObject = $this->em->getRepository($entityClass)->find($id);
    if (empty($deleteObject))
        $app->abort(404, "$ucEntity with ID $id not found");
    // other code comes here...
}
</code>
This is my test case:
<code>// deleting the same object again should not work
$client->request("DELETE", "/ccrud/channel/$id");
$this->assertTrue($response->getStatusCode() == 404);
</code>
Now phpunit fails with the following error:
    1) CrudEntityTest::testDelete
    Symfony\Component\HttpKernel\Exception\HttpException: Channel with ID 93 not found
I can see from the message that the 404 was thrown, but I cannot test the response object as planned. I know that in theory I could assert for the exception itself, but that is not what I want to do, I want to get the response (as a browser would do as well) and test for the status code itself.
Anybody any ideas how to reach that or if there is a better way to test this?
Thanks,
Daniel
Answer: This is how it is being done in the tests of Silex itself (see here):
<code>public function testErrorHandlerNotFoundNoDebug()
{
    $app = new Application();
    $app['debug'] = false;

    $request = Request::create('/foo');
    $response = $app->handle($request);
    $this->assertContains('<title>Sorry, the page you are looking for could not be found.</title>', $response->getContent());
    $this->assertEquals(404, $response->getStatusCode());
}
</code>


retrofit an installed HVAC system

Question: My day care center, located in a 100+ year old house and only licensed for 28 kids, had an HVAC system installed about 15 years ago.  Can it be set to vent ALL indoor air and send only cooled outdoor air throughout the house?  I am trying to remove any airborne COVID particulate. I'm willing to give up comfort for safety during this COVID pandemic.
Answer: Yes, of course that could be done but you'll likely be looking at some significant ducting work.  The air return, that normally comes from the living space will need to be re-routed and brought in from outside.  Since that will create back pressure on the air handler blower, you will also need to duct the living space to the outside.
Often air-to-air heat exchangers are used in cases like to to minimize losses.
But to your point, I don't believe this is going to be in any way effective in removing COVID-19 virus particles from your space.
Comment: Why not? The CDC is saying that circulating clean outdoor air is crucial.
Comment: Not meaning to be argumentative but strictly curious and wanting to discuss options. Do you have an idea that WOULD help my problem?
Comment: 2 suggestions:  HRV (heat recovery ventilation) can be used to bring in outside air without having to re-condition it. Second:  In my home I have a highly efficient filter and UV lamps in the air handler that traps very tiny particles as well as kills germs.
Comment: HRV (or ERV) is not 100% efficient - it reduces, does not eliminate, the need to condition outside air - somewhere in the 60-70% range seems to be a typical efficiency rating - HRVs are optimized for heating, ERVs (Energy recovery ventilator) for heating and cooling, from what I understand so far in my shopping process looking into getting one or the other for a project that's a "tight" building where mechanical ventilation is advisable.

retrofit an installed HVAC system


Problem saving a new item to custom SharePoint 2007 list using Silverlight 4 UI control

Question: I am hoping someone might be able to help me. I'm working on a Contact Manager built using a custom SharePoint 2007 list with a Silverlight 4 UI embedded in a content editor web part.
I am currently able to retrieve the data from the list and display it in a datagrid on the UI and everything works well.
Now I am trying to add the the ability to add new items to the list using the following code but the items do not save.
I've remotely debugged the following code using the Debug -> Attach to Process option and everything seems to execute successful without any errors but it does not save the item to SharePoint.
In order to simplify and get a working insert function I changed all the SharePoint fieds to single line text with the exception of the notes (multiline) and none of the fileds are required.
The sharepoint site does require Windows authentication but it seems to be working correctly as I am able to display it as well as add new items manually using the standard SharePoint forms.
Lastly, I have added the xml for the Batch element at the bottom which I copied as output while debuging.
Please let me know if there is any additional information I might be missing.
Thanks in advance for any assistance you might be willing to provide.
Charles
<code>public string sharepoint_soap_namespace = "http://schemas.microsoft.com/sharepoint/soap/";
public string sharepoint_rowset_namespace = "#RowsetSchema";
public string service_lists_url = "http://myDomain/_vti_bin/lists.asmx";
public string listName = "MyContacts";

 public void TestCreateContact()
{
  Uri serviceUri = new Uri(service_lists_url);
  BasicHttpBinding binding = new BasicHttpBinding(BasicHttpSecurityMode.None);
  binding.MaxReceivedMessageSize = 2147483647; // This has to be the same as in the ServiceReferences.ClientConfig file.
  EndpointAddress endpoint = new EndpointAddress(serviceUri);
  ListsSoapClient testCreateClient = new ListsSoapClient(binding, endpoint);

XElement batch = new XElement("batch",
  new XElement("Method",
  new XAttribute("ID", "1"),
  new XAttribute("Cmd", "New"),
  CreateFieldElement("ows_ID", "New"),
  CreateFieldElement("ows_Title", "John"),
  CreateFieldElement("ows_SupportFor","USA"),
  CreateFieldElement("ows_LastName","Doe")
));

testCreateClient.UpdateListItemsCompleted +=
      new EventHandler<UpdateListItemsCompletedEventArgs>(createSoapClient_UpdateListItemsCompletedEventArgs);

testCreateClient.UpdateListItemsAsync(listName, batch);
testCreateClient.CloseAsync();

}

private XElement CreateFieldElement(string fieldName, string fieldValue)
{
  XElement element = new XElement("Field",
  new XAttribute("Name", fieldName),
  fieldValue);
  return element;
}
</code>
Answer: Just a quick update to let everyone know I was able to answer my own question.
It seems that in the batch XElement I was using the wrong field names.

CreateFieldElement("ows_SupportFor","USA"),

I was using "ows_SupportFor" instead of "SupportFor" without the "ows_" prefix.
Cheers,
Charles


Single word for something that is 'sound producing'

Question: I need a single word for "sound producing".
What do you call something that produces sound?
Example: Radio is ___________ (sound producing) but I need a single word.
Comment: Audible? Or its synonyms.
Comment: Why not simply "audio"? Radio is (or *has*) audio.
Comment: "sound producible" means that it can be produced by sound, not that it produces sound. You want to say "sound producing" instead.
Comment: Elements of some kind vibrating in air produce what we call sound, so how about *vibrelement*? Radios and other sources of sound contain *vibrelements*. It's one "word". :-)
Comment: @curiousdannii Yes
Answer: If you think of television as a visual medium, then the obvious equivalent word would be aural.  The word is often used in educational contexts but may be less familiar more widely.  You could otherwise speak of a sound medium.  You would, I think, be forgiven by the possible ambiguity.   Aural is better.
Answer: Your other apparent option would be sonic
From M-W:   capable of uttering sounds; utilizing, produced by, or relating to sound waves
Answer: Soniferous is what you're looking for.

Soniferous: Producing or conducting sound.
Example: Soniferous marine animals — M-W

How I found it:
I combined soni and ferous to make an adjective:
Soni of sonication + (-iferous) → Soniferous.
Sonication is a noun which means relating to sound. It's derived from sonic.
Sonic is an adjective which means:

Denoting, relating to, or of the nature of sound or sound waves.
Example: The whales emit sonic pulse systems — Lexico

-Ferous is a suffix which is defined by Lexico as:

-ferous (also -iferous): Having, bearing, or containing (a specified thing)
Examples: Carboniferous, pestiferous.
Origin:
From French -fère or Latin -fer 'producing', from ferre 'to bear'.

First I combined sono of sonography and some adjective forming suffixes like ful, ive, ic etc and googled them but did not find any useful results. But googled sonoferous, the second result was 'soniferous' so I then googled soniferous and found its definition.
Quote from IBT UK:

The most common sources of marine biological sounds are snapping shrimp snaps, sea urchin raspings and fish vocalisations. Snapping shrimp (family Alpheidae), are the most ubiquitous and noisy soniferous animals in coastal ecosystems.
Comment: @Decapitated Nice etymological sleuthing!
Answer: My suggestion is:

Radio is/has sound

If you're talking about something that's more than sound, you need to use the verb has:

TV has sound

Why would I suggest this? Because it's extremely natural and it works in virtually any context. (You might say it's so natural that it seems silly to even suggest this as an answer!) It's neutral in connotation and formality. I offer no definitions because it can be used to communicate with anyone of any level of English fluency.
Here are some examples in use:

Live radio is sound transmitted by radio waves, as the sound happens. (Wikipedia)

Even though radio is sound only, nonverbal communication is still important. (Speaking via Electronic Media)

Radio has sound, but no text or visuals. Television has sound, video and, theoretically, it can also display text. (Teens and the Media)

You can also sometimes use "audio" instead of "sound", with the difference being that "audio" is usually used only for sound that came from somewhere else (e.g. it's a recording or a speaker that you're hearing). For example:

Radio is audio and audio is sound. Voice is sound and sound is audio. (How Technology Helps Radio and Its Listeners)

(Also that last source shows us another example of flexibility here with the expressions "audio medium", "audio technology", etc.: noun adjuncts!)
Answer: Not very descriptive so, here's what a radio is, what radio is, and what radio does.
A transistor radio is an electroacoustic device used to reproduce sound via an integral speaker(s) or an ear piece(s).
"Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz)."
"Radio broadcasting is transmission of audio (sometimes with related metadata) by radio waves intended to reach a wide audience."

I realize I'm way to caught up on radio, but it's the only thing we have to go on for "sound producible", as it's all dependent on how the thing is capable of making sound. If it's percussive you have to hit it. If it requires electrical energy it's electroacoustic. If it relies solely on vibration and does not require electrical energy nor percussive force, it needs a resonance chamber or body, which is called acoustic.
Comment: What's the hypernym for a string, a reed, and the simple hole in the mouth of a flute? That should go after "resonance chamber or body" with another *or*.


Unattended linux installation (Debian/Ubuntu)

Question: I want to make an Debian or Ubuntu unattended ISO, for my FOG server - to boot up system installation via LAN. I've searched over the internet but I didn't found nothing, which will be adequate for me.
Answer: Creating an unattended Ubuntu install consists of the following steps:

Create a configuration file, ks.cfg, using the GUI Kickstart tool.
Extract the files from the Ubuntu install ISO.
Add the ks.cfg file to the install disk and alter the boot menu to add automatic install as an install option.
Reconstitute the ISO file.

See http://www.linuxuser.co.uk/tutorials/unattended-ubuntu-installations for more details.
Answer: See here: https://github.com/core-process/linux-unattended-installation/
This project provides all you need to create an unattended installation of a minimal setup of Linux, whereas minimal translates to the most lightweight setup - including an OpenSSH service and Python - which you can derive from the standard installer of a Linux distribution. The idea is, you will do all further deployment of your configurations and services with the help of Ansible or similar tools once you completed the minimal setup.
Comment: Niklas, if this is your project your really need to disclose that.


How do I get responses in Google Forms to automatically be updated when updating the spreadsheet?

Question: I'm in a situation, where I have been given a source of information, with all sorts of people. And with that, I wish to insert all this inside of Google Forms, in the response section. And so I was wondering, if I could simply insert all this inside of the spreadsheet, for the response destination.
Is this possible, and how could I do it?
Comment: Welcome. Please see if you can edit your answer and provide a link to a sample spreadsheet or/and form. Your question is quite vague. Also please read [ask] and [About asking](https://webapps.stackexchange.com/help/asking)
Comment: not possible...
Answer: i know this is an old post but this answer is for anyone else looking for the same solution to a similar problem quite recently.
I did something similar recently- auto populating & auto updating a google form with data values from the google sheet after a response has been submitted, here is the working live sample form:


Can a city police officer leave the city to pursue someone who commits a traffic offense within city limits?

Question: If I commit a traffic offense in the city and a city cop observes this, and I then leave the city, can the city officer continue the pursuit, or must they terminate the pursuit at the city limits?
Comment: All the definitions I could find of "police pursuit" indicate that you are fleeing from the police and they are chasing you. You left that part out of your story. Are you talking about eluding or just crossing the city limits?
Comment: @segnerd just leaving city limits
Answer: There should be a policy, following GA Code § 35-1-14 (2020) which requires there to be a written pursuit policy (if they don't have a policy, they can lose funding). So you would have to look at the particular jurisdiction. The Georgia Dept. of Public Safety (i.e. State Patrol) has this policy, Atlanta has this policy, and so on. I'll ignore the state patrol given their state-wide jurisdiction, but it would apply to interstate pursuit. It specifically says:

4.1.1 Pursuits are prohibited for the following types of offenses: ...3. Traffic offenses

Athens-Clarke County requires (§6.08.04) that

Pursuits are permitted under the following circumstances: [CLE 41.2.2
a-b]

When an officer has reasonable grounds to believe the suspect has committed, or is attempting to commit, one of the following felonies:
murder; rape or other felonious sex offense; abduction; robbery;
felonious assault; arson involving death or serious injury;
When an officer has reasonable grounds to believe the suspect has committed, or is attempting to commit, a crime which involves the
display or use of a firearm, even if such crime is classified as a
misdemeanor.

The point is that this is a matter of policy determined by each department, and not situation with a universal answer. In Zilke v. Georgia, the Georgia Supreme Court overturned a traffic conviction because the arresting officer "had no authority to arrest appellant because, at the time of arrest, Officer Mason was outside his statutorily-designated territorial jurisdiction". That case involves a DUI not a speeding ticket and also involved campus police not city police, so different conclusions are still possible for citations rather than arrests. It does however indicate that there are jurisdictional limits to police actions within the state of Georgia.


Installing a dimmer switch to multiple lights

Question: I have read the wiring configuration for a regular switch. Is this the same configuration for a dimmer switch? One switch, several lights. I don't need a three way switch do I?
Comment: If you have only 1 switch on the lights a standard dimmer is all that is needed. (SPST) Single pole single throw.
Answer: A dimmer switch can replace a regular switch as long as the lights/light bulbs are dimmable.
A three way switch is a way to have two switches control one light.


chmod: cannot access 'file' : No such file or directory error when the file exists

Question: I downloaded and saved 2 files on Linux tails live os. I have set the appropriate permissions on those 2 files to allow them as executable. This is the command I used.
sudo chmod 777 home/amnesia/Desktop/file
sudo chmod 777 file

However, when I try to access these 2 files, both the files yield me an error as cannot access.
I am not sure why it isn't recognizing the file permissions correctly.
Answer: this to:
sudo chmod 777 home/amnesia/Desktop/file

this:
sudo chmod 777 /home/amnesia/Desktop/file

you left a '/' slash
better to use will be:
sudo chmod 777 ~/Desktop/file

Comment: Doesn't seem to work
Comment: @hodurrr whats the output of `echo $HOME`. tell me
Comment: what is the location of file, if you download it may be in download folder instead of Desktop
Comment: The output is /home/amnesia and the location of the file is also /home/amnesia
Comment: @hodurrr then do this `sudo chmod 777 ~/file`
Comment: I did that and I didn't get any output (no error message, nothing). Does that mean it worked?
Comment: yes it worked not error , if you give `ls -l file`, you will get `-rwx-rwx-rwx` in begning. it worked you can accept my solution


Which current Macs have an infrared receiver

Question: I have an Apple Remote that I used with a white plastic MacBook. I no longer have the MacBook, but still have the remote. What current Macs have an infrared receiver and can work with the Apple Remote? What current Macs do not have an infrared receiver and cannot work with the Apple Remote?
Answer: Currently (March 2012) the MacBook Air and the Mac Pro are the only generally available macs that lack a built-in infrared receiver.
The white polycarbonate MacBook that is still available as a refurbished product and from educational sales channels also lacks an infrared receiver.
Comment: The Mid 2009 non-unibody MacBook was the last. The late 2009 unibody model (first polycarbonate unibody) lacked it as well as the follow on 2010 model.
Comment: Interesting... I wonder which model of white polycarbonate MacBook lost the receiver.
Answer: The only current* model of Mac with an infrared sensor is the Mac Mini. Other than Mac Mini and Apple TV, no Apple products have included a sensor since 2012. Here's a list of models from each line of Mac computers which can receive input from an infrared Apple Remote:

MacBook Pro — non-Retina, Mid 2012 and earlier
MacBook Air — Mid 2009 and earlier
MacBook — Mid 2009 and earlier
iMac — Mid 2011 and earlier**

Finally, except for the 4th generation Apple TV, all Apple devices with infrared sensors can only be used with infrared Apple Remotes, and not with any other IR devices.
(Source: Mactracker)
* Most recent version of a product still sold by Apple in May 2017
** Only since the iMac G5 with iSight (from 2005), and with the somewhat surprising lone exception of the 20-inch, Mid 2009 model.